Food Waste to Valuable Resources: Applications and Management 9780128183533, 1561571571, 1891891901, 0128183535

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Food Waste to Valuable Resources Applications and Management

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Food Waste to Valuable Resources Applications and Management

Edited by J. Rajesh Banu Department of Life Sciences, Central University of Tamil Nadu, Neelakudy, India

Gopalakrishnan Kumar Institute of Chemistry, Bioscience and Environmental Engineering, Faculty of Science and Technology, University of Stavanger, Stavanger, Norway; and Specially Appointed School of Civil and Environmental Engineering, Yonsei University, Seoul, South Korea

M. Gunasekaran Department of Physics, Anna University Regional Campus, Tirunelveli, India

S. Kavitha Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, Tamil Nadu, India

Academic Press is an imprint of Elsevier 125 London Wall, London EC2Y 5AS, United Kingdom 525 B Street, Suite 1650, San Diego, CA 92101, United States 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom Copyright © 2020 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www. elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 978-0-12-818353-3 For Information on all Academic Press publications visit our website at https://www.elsevier.com/books-and-journals

Publisher: Stacy Masucci Acquisition Editor: Megan Ball Editorial Project Manager: Sara Valentino Production Project Manager: Paul Prasad Chandramohan Cover Designer: Charlotte Cockle Typeset by MPS Limited, Chennai, India

Contents List of contributors Author biographies

xiii xv

1. Introduction: sources and characterization of food waste and food industry wastes

1

S. Kavitha, R. Yukesh Kannah, Gopalakrishnan Kumar, M. Gunasekaran and J. Rajesh Banu 1.1 1.2 1.3 1.4 1.5 1.6

Food waste and food loss Food supply chain waste characterization Sources and origins of food waste Food waste generation Food waste quantification Types of food waste and food processing wastes 1.7 Food waste hierarchy 1.8 Management and valorization of food waste 1.8.1 Animal feed 1.8.2 Landfill 1.8.3 Bioenergy and biofuel conversion approaches 1.8.4 Composting 1.8.5 Value-added products recovery 1.9 Conclusion References

1 2 3 4 6 6 7 7 8 8 9 10 11 11 11

2. Valorization of food waste for biogas, biohydrogen, and biohythane generation 15 T.M. Mohamed Usman, S. Kavitha, J. Rajesh Banu and S. Kaliappan 2.1 Introduction 2.2 Anaerobic digestion of food waste 2.2.1 Pretreatments employed 2.3 Factors affecting anaerobic digestion of food waste 2.3.1 pH 2.3.2 Temperature 2.3.3 Hydraulic retention time 2.3.4 Organic loading rate

2.3.5 Micronutrients 2.3.6 Foaming 2.4 Process configuration 2.4.1 Single-stage digestion 2.4.2 Two-stage digestion 2.4.3 Multistage digestion 2.4.4 Codigestion 2.5 Reactor configuration 2.6 Hydrogen production: dark fermentation 2.6.1 Biohydrogen production from food waste 2.6.2 Biohydrogen production from food industry waste 2.7 Factors affecting biohydrogen production 2.7.1 Components/composition of food waste 2.7.2 Pretreatments 2.7.3 Volatile fatty acids 2.8 Biohythane production from food waste 2.8.1 Process description 2.9 Enhancement strategies of biohythane production 2.10 Applications of biohythane 2.11 Challenges in the commercialization of biofuel from food waste 2.12 Future perspectives 2.13 Conclusion References

3. Valorization of food waste for bioethanol and biobutanol production

19 20 20 20 21 21 22 22 22 23 24 24 24 25 26 26 27 28 28 29 29 32 32

39

R. Yukesh Kannah, P. Sivashanmugham, S. Kavitha and J. Rajesh Banu 15 15 17 18 18 18 19 19

3.1 Introduction 3.2 Bioalcohol production from food waste 3.2.1 Bioethanol 3.2.2 Biobutanol 3.2.3 Comparison of bioalcohol properties and their applications 3.3 Bioalcohol production processes 3.3.1 Upstream process

39 40 40 40 40 41 41

v

vi

Contents

3.3.2 Midstream process 3.3.3 Downstream process 3.4 Various bioalcohol fermentation methods 3.4.1 Separate hydrolysis and fermentation 3.4.2 Simultaneous saccharification and fermentation 3.4.3 Simultaneous saccharification and cofermentation 3.4.4 Consolidated bioprocessing 3.5 Other strategies to increase the bioalcohol yield 3.6 Conclusion References

4. Valorization of food waste for biodiesel production

52 58 61 61 62 66 66 67 67 67

75

M. Dinesh Kumar, S. Kavitha and J. Rajesh Banu 4.1 Introduction 4.2 Various food waste pretreatments for biodiesel production 4.2.1 Physical pretreatment 4.2.2 Chemical pretreatment 4.2.3 Mechanical pretreatment 4.2.4 Biological pretreatment 4.2.5 Combined pretreatment 4.3 Lipids to biodiesel conversion 4.4 Transesterification process 4.4.1 Acid-catalyzed transesterification 4.4.2 Alkaline-catalyzed transesterification 4.4.3 Enzyme-catalyzed transesterification 4.5 Reactors involved in biodiesel production 4.6 Scalability of biodiesel production 4.7 Future prospects and conclusion References Further reading

75 75 76 76 78 78 78 78 79 79 81 83 87 91 91 92 96

5. Thermochemical conversion of food waste for bioenergy generation 97 R. Uma Rani, J. Rajesh Banu, Daniel C.W. Tsang and Chyi-How Lay 5.1 Introduction 5.2 Thermochemical routes for bioenergy generation 5.2.1 Incineration 5.2.2 Combustion 5.2.3 Cofiring 5.2.4 Cocombustion 5.2.5 Pyrolysis 5.2.6 Gasification 5.2.7 Hydrothermal carbonization

97 97 97 99 100 102 103 104 108

5.3 Scalability of thermochemical conversion of food waste 110 5.3.1 Incineration 110 5.3.2 Combustion/cofiring 111 5.3.3 Gasification 111 5.3.4 Pyrolysis 111 5.3.5 Hydrothermal carbonization 112 5.4 Concluding remarks, challenges, and future prospects 113 References 114 Further reading 118

6. Production of organic acids and enzymes/biocatalysts from food waste

119

J. Merrylin, R. Yukesh Kannah, J. Rajesh Banu and Ick Tae Yeom 6.1 Introduction 6.2 Production of organic acid from food waste 6.2.1 Citric acid 6.2.2 2,3-Butanediol 6.2.3 Succinic acid 6.2.4 3-Hydroxypropionic acid 6.2.5 1,3-Propanediol 6.2.6 Lactic acid 6.2.7 Volatile fatty acids 6.3 Production of enzymes 6.4 Extraction and purification 6.4.1 Dialysis 6.4.2 Microwave-assisted extraction 6.4.3 Ultrasonication-assisted extraction 6.4.4 Supercritical fluid extraction 6.4.5 Enzyme purification by chromatography 6.5 Downstream processing 6.6 Recovery 6.7 Conclusion References

7. Production of biopolymers and feed protein from food wastes

119 119 119 121 121 122 123 123 125 126 128 128 129 132 132 133 133 134 134 134

143

J. Merrylin, Preethi, Ganesh Dattatraya Saratale and J. Rajesh Banu 7.1 Introduction 7.2 Food waste as a valuable resource 7.2.1 Biopolymers 7.2.2 Single-cell oil 7.2.3 Baker’s yeast 7.2.4 Single-cell protein 7.2.5 Polysaccharides

143 143 144 146 146 147 149

7.3 Reactors used for the production of biopolymers and feed proteins 7.4 Economic aspects and commercialization of biopolymer and protein feed production 7.5 Conclusion References Further reading

8. Production of fine chemicals from food wastes

152

156 157 157 161

163

V. Godvin Sharmila, S. Kavitha, Parthiba Karthikeyan Obulisamy and J. Rajesh Banu 8.1 Introduction 8.2 Food waste as a valuable source of bioactive chemicals 8.2.1 Aromatic compounds 8.2.2 Pigments 8.2.3 Antibiotics 8.2.4 Essential oils 8.3 Bioreactors used for fine chemical production 8.4 Various methods of extraction and purification of chemicals 8.4.1 Microwave-assisted extraction 8.4.2 Ionic liquid extraction techniques 8.4.3 Ultrasound-assisted extraction 8.4.4 High-voltage electric discharge 8.4.5 Pulsed electric field extraction 8.4.6 Supercritical fluid extraction 8.5 Economic consideration 8.6 Scale up and commercialization 8.7 Applications, limitations, and challenges during chemical recovery 8.8 Future perspectives and conclusions References Further reading

163 163 163 172 173 174 175 176 176 177 178 178 178 179 180 180 181 181 183 188

9. Specialty chemicals and nutraceuticals production from food industry wastes 189 T. Poornima Devi, S. Kavitha, R. Yukesh Kannah, M. Rajkumar and J. Rajesh Banu 9.1 Introduction 9.2 Bioactive compounds 9.2.1 Phenolic compounds from food waste 9.2.2 Carotenoids 9.2.3 Bioactive peptides 9.2.4 Dietary fiber 9.3 Biosurfactants

189 189 190 192 192 193 193

Contents

vii

9.4 Fermentation methods 9.5 Various extraction techniques for nutraceuticals recovery 9.5.1 Solvent extraction technique 9.5.2 Microwave-assisted extraction 9.5.3 Enzyme-assisted extraction 9.5.4 Supercritical fluid extraction 9.5.5 Subcritical water extraction 9.5.6 Ultrasound-assisted extraction 9.5.7 Pulsed electric field 9.5.8 High hydrostatic pressure extraction 9.6 Potential applications of food waste-derived nutraceuticals in the food, pharmaceuticals, and cosmeceuticals industries 9.6.1 Use as food additives 9.6.2 Use as nutraceuticals 9.6.3 Use as cosmeceuticals 9.7 Challenges and future prospects 9.8 Conclusion References

194 194 194 197 198 198 199 199 200 201

202 202 202 203 203 203 204

10. Enzymes/biocatalysts and bioreactors for valorization of food wastes 211 U. Ushani, A.R. Sumayya, G. Archana, J. Rajesh Banu and Jinjin Dai 10.1 Introduction 10.2 Enzymatic valorization of food waste for fermentative polyhydroxybutyrate production 10.2.1 Mechanism of polyhydroxybutyrate synthesis 10.2.2 Production of polyhydroxybutyrate 10.3 Enzymatic valorization of food waste for biodiesel production 10.3.1 Mechanism of biodiesel synthesis 10.3.2 Production of biodiesel 10.4 Enzymatic valorization of food waste for bioethanol production 10.4.1 Mechanism of bioethanol synthesis 10.4.2 Production of bioethanol 10.5 Enzymes involved, their roles, and applications 10.5.1 Fermentation of food waste 10.5.2 Types of fermenter 10.5.3 Scaling up of the fermentation process 10.5.4 Application of enzymes 10.6 Immobilized biocatalysts and their applications in food waste valorization

211

211 214 214 215 215 215 216 216 216 217 218 218 221 221 222

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Contents

10.6.1 10.6.2 10.6.3 10.6.4 10.6.5 10.6.6

Carbohydrates Proteins Lipids Organic acids Biofuel Bioreactors with immobilized cells/enzymes 10.6.7 Kinetic aspects of immobilized cells or enzymes 10.7 Conclusion References Further reading

11. Aerobic biodegradation of food wastes

223 223 223 224 224 224 227 228 228 232

235

S. Gopikumar, R. Tharanyalakshmi, R. Yukesh Kannah, Ammaiyappan Selvam and J. Rajesh Banu 11.1 Introduction 235 11.2 Aerobic digestion of food waste and their types 236 11.3 Roles of microbes in composting 236 11.4 Four phases of the compost process 240 11.4.1 Mesophilic phase 240 11.4.2 Thermophilic phase 241 11.4.3 Cooling phase 241 11.4.4 Remedial phase 241 11.5 Types of composting 241 11.5.1 Windrow 242 11.5.2 Static pile 242 11.5.3 In-vessel 242 11.5.4 Vermicomposting 242 11.5.5 Gore cover system 242 11.6 Factors affecting composting of food waste 243 11.6.1 Temperature 243 11.6.2 pH 243 11.6.3 Aeration 243 11.6.4 Porosity 243 11.6.5 C:N ratio 244 11.6.6 Moisture 244 11.6.7 Particle size 244 11.6.8 Feedstock 244 11.6.9 Nutrient balance (micro and macro) 244 11.6.10 Oxygen uptake 244 11.6.11 Microbial growth 244 11.6.12 Odor and color 245 11.7 Advantages and disadvantages of composting 245 11.7.1 Advantages 245 11.7.2 Disadvantages 245

11.8 Current scenario of food waste composting 11.8.1 Developed countries 11.8.2 Developing countries 11.9 Sustainable compost and its application in the global market 11.10 Conclusion References

12. Bioenergy recovery from food processing wastewater—Microbial fuel cell

245 245 246 246 246 246

251

C. Subha, M. Dinesh Kumar, R. Yukesh Kannah, S. Kavitha, M. Gunasekaran and J. Rajesh Banu 12.1 Introduction 12.2 Food processing industries and their effluent characteristics 12.2.1 Dairy industry 12.2.2 Beverage industry 12.2.3 Cassava mill processing 12.2.4 Potato processing wastewater 12.2.5 Meat processing wastewater 12.2.6 Seafood processing wastewater 12.2.7 Cereal processing 12.2.8 Cheese whey processing 12.3 General components of microbial fuel cells 12.3.1 Anode 12.3.2 Cathodes 12.3.3 Membrane separator 12.4 Various configurations of microbial fuel cells 12.4.1 Dual chamber 12.4.2 Single chambered 12.4.3 Stacked microbial fuel cell 12.4.4 Membraneless 12.5 Reactor design and performance 12.6 Anodic biofilm 12.6.1 Factors influencing biofilm formation and performance 12.7 Energy recovery from food waste using microbial electrolysis cell 12.8 Microbial fuel cell coupled with anaerobic digestion of food waste 12.9 Current status of pilot microbial fuel cell 12.10 Conclusions and future directions References Further Reading

251 252 252 252 252 253 253 253 254 254 254 254 256 257 258 259 260 261 262 262 262 266 267 267 270 270 271 274

Contents

13. Integrated biorefineries of food waste

275

14. State of the art of food waste management in various countries

ix

299

G. Ginni, S. Adish Kumar, T.M. Mohamed Usman, Peter Pakonyi and J. Rajesh Banu

A. Vimala Ebenezer, M. Dinesh Kumar, S. Kavitha, Do Khac Uan and J. Rajesh Banu

13.1 Introduction 13.2 Food waste integrated biorefineries: an overview 13.3 Integrated two-stage processes 13.3.1 Methane
lactic acid production 13.3.2 Hydrogen
methane production 13.3.3 Ethanol
methane production 13.3.4 Biolipid
methane production 13.3.5 Methane
biofertilizer 13.3.6 Volatile fatty acids
PHA 13.3.7 Volatile fatty acids
bioenergy 13.4 Liquefied food waste for biomass cultivation and multiproduct recovery 13.4.1 Cultivation of microalgae: biodiesel 13.4.2 Cultivation of microalgae: valueadded products recovery 13.4.3 Cultivation of yeast: biodiesel, biogas recovery, and biofertilizer production 13.5 Electrofermentation process: multiple value-added products recovery 13.5.1 Bioethanol fermentation: microbial electrolysis cell system 13.5.2 Hydrogen fermentation: microbial electrolysis cell system 13.6 Integrated biorefineries of different food wastes 13.6.1 Plant-derived food waste (fruit and vegetable waste) 13.6.2 Food processing industrial waste 13.7 Integrated biorefineries in various sectors 13.8 Integrated biorefineries: techno-economic analysis 13.9 Integrated biorefineries: policies and regulations 13.10 Conclusions: remarks and future perspectives References Further Reading

14.1 Introduction 14.2 Climate change and economic impact 14.3 Current scenario and development of food waste management in various countries 14.3.1 Developed countries 14.3.2 Developing countries 14.3.3 Underdeveloped countries 14.4 Treatment strategies and product recovery 14.4.1 Animal feed 14.4.2 Composting 14.4.3 Anaerobic digestion 14.4.4 Fermentation 14.4.5 Physicochemical methods 14.4.6 Landfilling 14.5 Valorization of food waste around the globe 14.6 Legislation in various countries 14.6.1 United States 14.6.2 European Union 14.6.3 Japan 14.6.4 South Korea 14.6.5 France 14.6.6 Italy 14.6.7 Malaysia 14.6.8 Brazil 14.6.9 India 14.7 Technical challenges, emerging trends, and conclusions References Further reading

275 275 276 276 279 279 281 282 282 283 283 283 283

284 284

284

285 285 285

Mohit Singh Rana, Shashi Bhushan, Sanjeev Kumar Prajapati, Preethi and S. Kavitha

291

15.1 Introduction 15.2 Technical challenges in food waste management 15.3 Commercial scale-up of food waste valorization technology 15.4 Cost estimation of different food waste valorization techniques 15.4.1 Transesterification 15.4.2 Dark fermentation

292 293 293 298

300 300 301 302 302 303 304 305 308 309 311 311 314 314 314 314 314 315 315 315 315 315 315 319 323

15. Techno-economic analysis and environmental aspects of food waste management 325

289

292

299 300

325 326 328 330 330 331

x

Contents

15.4.3 Anaerobic digestion 332 15.4.4 Solid-state fermentation 332 15.5 Cost-competitive food waste biorefinery development 332 15.6 Techno-economic analysis of a food waste biorefinery 333 15.6.1 Techno-economic analysis framework 334 15.6.2 Techno-economic analysis methodology 334 15.7 Case studies on food waste biorefineries 336 15.7.1 Integrated mango biorefinery in an Indian context 336 15.7.2 Food waste biorefinery in a European context 337 15.7.3 Biofuel production from food waste 338 15.8 Conclusion 338 References 338 Further reading 342

16. Problems and issues of food waste-based biorefineries

343

Jaskiran Kaur, Gini Rani and K.N. Yogalakshmi 16.1 Introduction 343 16.2 Issues associated with food waste 344 16.3 Valorization of food waste 345 16.3.1 Techniques used for recovery of bioactive components from food waste 346 16.4 Techniques for the conversion of food waste into valuable products 347 16.4.1 Biological conversion 348 16.4.2 Thermochemical conversion 348 16.5 Impact assessment of food waste valorization technologies 349 16.5.1 Issues in relation to valorization of food waste to compost 349 16.5.2 Issues in relation to valorization of food waste to biogas 351 16.6 Preventive measures taken during food waste valorization 352 16.7 Planning strategies and new innovative plans for food waste valorization 352 16.8 Conclusions 353 References 353

17. Environmental impacts and sustainability assessment of food loss and waste valorization: value chain analysis of food consumption 359 Preethi, S. Kavitha, J. Rajesh Banu, P. Arulazhagan and M. Gunasekaran 17.1 Introduction 359 17.2 Life cycle analysis (LCA) of food waste: an overview 359 17.2.1 LCA methodologies or approaches 360 17.3 LCA analysis of various biological food waste valorization processes 363 17.3.1 Anaerobic digestion: biogas recovery 363 17.3.2 Fermentation technologies: bioethanol recovery 364 17.3.3 Transesterification: biodiesel production 364 17.3.4 Composting: compost and fertilizer recovery 368 17.4 LCA analysis of various nonbiological food waste valorization processes 371 17.4.1 Combustion and energy recovery 371 17.4.2 Landfill disposal 371 17.5 Life cycle costing approaches to food waste and its valorization 371 17.5.1 Functional unit 374 17.5.2 System boundaries 374 17.5.3 Modeling approaches of cost 374 17.5.4 Cut-off and externalities 374 17.5.5 Environmental impact assessment 375 17.5.6 Analysis of results and interpretation 375 17.6 LCA of the food supply chain 375 17.6.1 Limited or full food supply chain stages in LCA 375 17.6.2 Food waste disposal LCA 375 17.7 Current efforts on LCA 375 17.8 LCA analysis with a case study 376 17.9 Exergetic indicators in the food industry 376 17.9.1 Exergy analysis 376 17.9.2 Use of exergetic indicators 377 17.9.3 Construction of a Grassmann diagram 378

Contents

17.10 Mass and energy flow balance in the process 17.10.1 Mass flow balance in process streams 17.10.2 Energy flow balance in process streams 17.10.3 Energy life cycle analysis and a case study 17.11 Food loss and LCA applications: an overview 17.11.1 Types of food loss 17.11.2 Food loss in LCA (different stages) 17.11.3 Modeling approaches to food loss in LCA 17.11.4 Food losses and waste, their implications on water and land: a case study 17.11.5 Benefits of food donation 17.12 Current challenges and future trends in designing sustainable food chains 17.13 Conclusion References Further reading

18. Analysis and regulation policies of food waste based on circular bioeconomies

378 378 379 379 379 379 380 381

382 383 383 383 384 388

389

S. Logakanthi, R. Yukesh Kannah and J. Rajesh Banu 18.1 Introduction 18.2 Circular economic approach 18.3 Circular economy approach to food waste 18.4 Bioeconomic approach 18.5 Bioeconomic application to food waste management 18.6 A circular bioeconomy for food waste management 18.7 Challenges in food waste management 18.8 International approaches to food waste management 18.9 Conclusions and future of food waste management References

389 390 391 392 393 394 395 396 397 398

19. Scaling up of food waste valorization market outlooks: key concerns 401 R.A.A. Meena, Arpan Ghosh, Palanivel Sathishkumar and R. Jayabalan 19.1 Introduction 401 19.2 Institutions and enterprises in food waste management 402

19.3 19.4 19.5 19.6

Production guidelines standards Financial measures Market-based products Food waste management and valorization 19.6.1 Food waste valorization 19.6.2 Biorefinery approach 19.6.3 Up-scaling 19.7 Market value of food waste valorization products 19.7.1 Factors influencing the market value of valorized food waste products 19.7.2 Challenges for attaining the commercial valorization of food waste 19.7.3 Policy framework for commercial valorization of food waste 19.7.4 Factors contributing to the uncertainties for the market value 19.8 Conclusions References Further reading

xi

402 403 403 404 404 404 404 406

409

409 409 410 410 411 414

20. New business and marketing concepts for cross-sector valorization of food waste 417 A. Parvathy Eswari*, V. Godvin Sharmila*, M. Gunasekaran and J. Rajesh Banu* 20.1 Introduction 417 20.2 Commercialized and patented applications of food waste biorefineries 418 20.2.1 Intellectual property protection 418 20.2.2 Commercialization and scale-up issues 419 20.2.3 Patents and their requirements 419 20.2.4 Patented methodologies 420 20.3 Policy options and their implications 420 20.3.1 Social innovation and food waste 420 20.3.2 Policy measures promoting social innovation 420 20.3.3 Policies and regulations 423 20.3.4 Resolving challenges into opportunities 423 20.4 Applications and marketability of food waste-based biorefinery products 423 20.4.1 Fruit and vegetable waste 424 20.4.2 Coffee waste 424 20.4.3 Dairy product waste 424 20.4.4 Animal by-products 424 20.4.5 Seafood waste 425

xii

Contents

20.4.6 Emerging innovative marketing technologies 425 20.5 Need for new marketing approaches 425 20.5.1 Cost and safety issues of emerging technologies compared with conventional techniques 425 20.6 Business models 426 20.6.1 Triple-layered business model 426 20.6.2 Purchase incidence model 427 20.6.3 Order size model 427 20.7 Marketing strategies and practices 428 20.7.1 Food distribution 428 20.7.2 Communication strategy 428 20.7.3 Products and processes 429 20.7.4 Packaging and its types 429 20.7.5 Selling price 429 20.7.6 Promoting sales 429

20.8 Developing unique selling points 20.8.1 Date labeling 20.8.2 Retailer options 20.8.3 Mobile applications 20.9 Contracts and public procurement of biorefinery products 20.10 Food waste and the transition toward sustainable development 20.10.1 Food waste dynamics 20.10.2 Multilevel perspective framework 20.11 Conclusions References Further reading Index

429 429 429 429 430 430 430 431 431 431 433 435

List of contributors G. Archana Department of Biotechnology, Karpagam Academy of Higher Education, Coimbatore, India

S. Kaliappan Department of Civil Engineering, Anna University, Chennai, India

P. Arulazhagan Centre of Excellence in Environmental Studies, King Abdulaziz University, Jeddah, Saudi Arabia

R. Yukesh Kannah Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India

J. Rajesh Banu Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India Shashi Bhushan Environment and Biofuel Research Lab (EBRL), Hydro and Renewable Energy Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, India Jinjin Dai School of Ecological and Environmental Sciences, East China Normal University, Shanghai, P.R. China T. Poornima Devi Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India A. Vimala Ebenezer Department of Civil Engineering, V V College of Engineering, Tirunelveli, India A. Parvathy Eswari Department of Civil Engineering, Anna University Regional Campus Tirunelveli, Tirunelveli, India Arpan Ghosh Food Microbiology and Bioprocess Laboratory, Department of Life Science, National Institute of Technology, Rourkela, India G. Ginni Department of Civil Engineering, Amrita College of Engineering and Technology, Amritagiri, Nagercoil, India S. Gopikumar Department of Civil Engineering, SCAD College of Engineering and Technology, Tirunelveli, India M.

Gunasekaran Department of Physics, Anna University Regional Campus Tirunelveli, Tirunelveli, India

R.

Jayabalan Food Microbiology and Bioprocess Laboratory, Department of Life Science, National Institute of Technology, Rourkela, India

Jaskiran Kaur Department of Environmental Science and Technology, School of Environment and Earth Sciences, Central University of Punjab, Bathinda, Punjab, India S. Kavitha Department of Civil Engineering, Anna University Regional Campus Tirunelveli, Tirunelveli, India Gopalakrishnan Kumar Institute of Chemistry, Bioscience and Environmental Engineering, Faculty of Science and Technology, University of Stavanger, Stavanger, Norway M. Dinesh Kumar Department of Civil Engineering, Anna University Regional Campus Tirunelveli, Tirunelveli, India S. Adish Kumar Department of Civil Engineering, University V.O.C College of Engineering, Anna University, Thoothukudi Campus, Thoothukudi, India Chyi-How Lay Master’s Program of Green Energy Science and Technology, Feng Chia University, Taichung, Taiwan ROC S.

Logakanthi St. Francis College for Women Autonomous and Affiliated to Osmania University, Hyderabad, India

R.A.A. Meena Department of Environmental Sciences, Bharathiar University, Coimbatore, India J. Merrylin Department of Food Science and Nutrition, Sarah Tucker College, Tirunelveli, India Parthiba Karthikeyan Obulisamy Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI, United States Peter Pakonyi Research Institute on Bioengineering, Membrane Technology and Energetics, University of Pannonia, Veszpre´m, Hungary

xiii

xiv

List of contributors

Sanjeev Kumar Prajapati Environment and Biofuel Research Lab (EBRL), Hydro and Renewable Energy Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, India Preethi Department of Physics, Anna University Regional Campus Tirunelveli, Tirunelveli, India; Department of Civil Engineering, Anna University Regional Campus Tirunelveli, Tirunelveli, India M. Rajkumar Department of Environmental Science, Bharathiyar University, Coimbatore, India Mohit Singh Rana Environment and Biofuel Research Lab (EBRL), Hydro and Renewable Energy Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee, India Gini Rani Department of Environmental Science and Technology, School of Environment and Earth Sciences, Central University of Punjab, Bathinda, Punjab, India

V. Godvin Sharmila Department of Civil Engineering, Anna University Regional campus, Tirunelveli, India P.

Sivashanmugham Department Engineering, National Institute Tiruchirappalli, India

of Chemical of Technology,

C. Subha Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India A.R. Sumayya Department of Biotechnology, Karpagam Academy of Higher Education, Coimbatore, India R. Tharanyalakshmi Department of Civil Engineering, Anna University Regional Campus Tirunelveli, India Daniel C.W. Tsang Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, P.R. China Do

Khac Uan Department of Environmental Engineering, Hanoi University of Science and Technology, Hanoi, Vietnam

R. Uma Rani Department of Civil Engineering, Ponjesly College of Engineering, Nagercoil, India

U. Ushani Department of Biotechnology, Karpagam Academy of Higher Education, Coimbatore, India

Ganesh Dattatraya Saratale Department of Food Science and Biotechnology, Dongguk University, Seoul, Republic of Korea

T.M. Mohamed Usman Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India

Palanivel Sathishkumar Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education; School of Chemistry and Environment, South China Normal University, Guangzhou, P.R. China

Ick Tae Yeom Graduate School of Water Resources, Sungkyunkwan University, Suwon, South Korea

Ammaiyappan Selvam Department of Plant Science, Manonmaniam Sundaranar University, Tirunelveli, India

K.N. Yogalakshmi Department of Environmental Science and Technology, School of Environment and Earth Sciences, Central University of Punjab, Bathinda, Punjab, India

Author biographies Dr. J. Rajesh Banu, Associate Professor, Department of Life Sciences, Central University of Tamil Nadu, Neelakudy, Tamil Nadu, India, was formerly Assistant Professor in Anna University Regional Campus, Tirunelveli, India, and Post-Doctoral Fellow and Lecturer in Sungkyunkwan University, South Korea. He is also a visiting researcher in East China Normal University, China. He is the author of 180 publications in SCI and SCIE journals with a cumulative impact factor of 691.38. His publications have achieved more than 4000 citations. He has authored 2 books and published 22 book chapters and 14 conference proceedings. He obtained five major grants from the Government of India and two consultancy from industries. He has guided 14 PhD students and 70 postgraduate engineering students in the discipline of environmental engineering and science. He was awarded with the Think of Ecology award by Hiyoshi Japan for the year 2018. His research centers on biological wastewater treatment, nutrient removal, membrane bioreactors, microbial fuel cells, energy recovery from microand macroalgae biorefinery, and lignin valorization. Affiliations and Expertise Associate Professor, Department of Life Sciences, Central University of Tamil Nadu, Neelakudy, India

Dr. Gopalakrishnan Kumar serves as Associate Professor in the Institute of Chemistry, Bioscience and Environmental Engineering, Faculty of Science and Technology, University of Stavanger, Stavanger, Norway. Additionally, he plays the role of “specially appointed Associate Professor,” concentrating on research in the School of Civil and Environmental Engineering, Yonsei University, South Korea. His major research interests include biofuel/biochemical production from lignocellulose/ waste/wastewater and algal biomass via biorefinery and valorization schemes and microbial fuel/electrolysis cell (MFC and MEC) technologies. He has published extensively, with more than 205 SCI papers in highly prestigious journals (including two cover image articles, seven highly cited/hot articles, and one key scientific article), with total citations of 5000 and an h-index of 37. He has also contributed to more than 15 book chapters and edited/editing 2 books. Affiliations and Expertise Associate Professor, Institute of Chemistry, Bioscience and Environmental Engineering, Faculty of Science and Technology, University of Stavanger, Stavanger, Norway and specially appointed Associate Professor, School of Civil and Environmental Engineering, Yonsei University, South Korea

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Author biographies

Dr. M. Gunasekaran, Assistant Professor, Department of Physics, Anna University Regional Campus, Tirunelveli, India, was formerly Post-Doctoral Fellow in the Department of Information and Communication Engineering, Sungkyunkwan University, South Korea. He was awarded a Japanese Government (Monbukagakusho) Scholarship as a Research Student at the graduate school of Nagoya Institute of Technology, Nagoya, Japan. He received his PhD from the Department of Physics, Anna University, India, in the year 2007 in the field of renewable energy. He is a reviewer of international journals. He is the author of more than 30 publications in SCI and SCIE journals. His publications have achieved more than 595 citations and he has authored 2 books and completed 2 PhD students. He obtained a major grant from DST, Government of India, under the young scientist scheme. Dr. Gunasekaran’s research interest focuses are on effective and environmental-friendly material for solar cell research, oxide metal/semiconductor material for wastewater treatment, sludge reduction under photo-irradiation, and energy recovery from waste and biomass. Affiliations and Expertise Assistant Professor, Department of Physics, Anna University Regional Campus, Tirunelveli, India

Dr. S. Kavitha completed her PhD at the Department of Civil Engineering, Regional Campus, Anna University, Tirunelveli, India. She received her Bachelor degree in Microbiology, and Masters in Biotechnology at Manonmaniam Sundaranar University, Tirunelveli, Tamil Nadu, India. She is a reviewer in various international journals. She has authored about 50 articles in SCI and SCIE journals with a cumulative impact factor of 250. Her publications have achieved 1000 citations. She has authored one reference book and four book chapters. She received the best poster award for the work entitled “Recovery of volatile fatty acids from marine macroalgae hydrolysate using energy efficient thermo-acidic coupled ultrasonic homogenization” at the eighth Global Conference on Global Warming—2019 (GCGW-2019) in April 2019 in Doha, Qatar. Her major research areas include generation of energy from biomass, micro- and macroalgae biorefinery, lignin valorization, and microbial fuel cells. Affiliations and Expertise Former Researcher, Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, Tamil Nadu, India

Chapter 1

Introduction: sources and characterization of food waste and food industry wastes S. Kavitha1, R. Yukesh Kannah1, Gopalakrishnan Kumar2, M. Gunasekaran3 and J. Rajesh Banu4 1

Department of Civil Engineering, Anna University Regional Campus Tirunelveli, Tirunelveli, India, 2Institute of Chemistry, Bioscience and

Environmental Engineering, Faculty of Science and Technology, University of Stavanger, Stavanger, Norway, 3Department of Physics, Anna University Regional Campus Tirunelveli, Tirunelveli, India, 4Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India

1.1

Food waste and food loss

Food waste (FW) have been defined as the byproducts or wastes originating from houses, canteens, hotels, restaurants, catering services, and several food-based industries, etc. FW are considered as the nonproduct streams of constituents where their economic worth is below the collection and retrieval cost, and hence they are thrown away as waste (United Nations Industrial Development Organization, 2012). About 89 million tons of FW are produced annually in the EU-27 (European Commission, 2010). Of this total, 80% has been recorded, with 38% created by the manufacturing sector and 42% by the household sector, emphasizing the generation of FW at each phase in the food supply chain (FSC). Generally, household FW generated by people at their homes signifies an issue from the logistics perspective. “Food loss” is defined as food which accidentally deteriorates either qualitatively or quantitatively due to food spillage, spoilage, and/or drooping. Destruction is also caused by organization boundaries at the manufacturing, storing, handling, and circulation stages of the FSC. FW refers to any foodstuff and uneatable portions of food wasted from the FSC that can be recuperated or discarded. This comprises FW which is to be sent to landfill, managed via anaerobic digestion (AD), incinerated for bioenergy production, combusted, discarded to drainage, disposed to landfill, put in open dumps, or disposed of to water bodies. Food losses can happen during the generation, packing, handling, distribution, and marketing phases, in addition to prior to or at the time or later stages of food preparation (Bio Intelligence Service et al., 2011). Food residuals include inevitably uneatable and partially unwanted products such as hides, stems, and foliage (Bio Intelligence Service et al., 2011; Foresight, 2010; WRAP, 2009). In addition, it comprises remains generated in eateries, hostelries, cafes, and some food facilities that do not plan for social utilization. A byproduct is a beneficial and saleable product or facility arising from a production stage which is not the main one generated (EEA, 2013). The eatable derivatives of food generated in the preparation and processing stages are usually taken from the human FSC and used as animal feed (Foresight, 2010). Food derivatives which are of animal origin include all organs or portions of animal bodies. FW comes under the heading of unnecessary waste. Disposed food, however, has worth and is very appropriate for utilization. Food products which are dropped, decayed, bruised, or crushed are referred to as FW. This comprises complete or sealed packets or separate foodstuffs that are not consumed (WRAP, 2008). In the FSC, FW cane be generated at any stage (Foresight, 2010) due to insufficient performance of food chain players (e.g., manufacturers, sellers, the food service sector, customers). The European Commission (2014) released goals for the bioeconomy and FW handling in July 2014. They defined “food waste” as food products (as well as uneatable portions) lost from the FSC. This does not include food removed to value-added biomaterials, for example, biological materials, food for animals, or that directed for resupply. In addition, the member states of the European Union (EU) plan to launch agendas to assemble and provide reports about the FW Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00001-8 Copyright © 2020 Elsevier Inc. All rights reserved.

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2

Food Waste to Valuable Resources

level in every sectors. Up-to-date records are required to progress FW prevention strategies. These plans are intended to achieve the goal of decreasing FMW by nearly 30% from January 1, 2017, to December 31, 2025. The European Commission (EC) intends to approve executing directives by December 31, 2017, so as to launch perpetual circumstances for observing the execution of FW-preventive processes implemented by EU member states. The Commission has withdrawn the circular economy rules established from the EC’s program on December 16, 2014. This package discussed the strategy and future directions including FW reuse, combustion, and landfilling. The Food and Agricultural Organization (FAO, 2014) issued a worldwide intended agenda demarcating “food loss” as the reduction of food quantitatively or qualitatively, which is initiated mostly by food generation and supply system operation. Thus “food loss” happens during the FSC. In addition, the FAO differentiates “FW” as an essential portion of “loss of food,” that denotes the exclusion of food appropriate for utilization from the FSC from foodstuffs which have been left for spoilage or decay due to failings by the ultimate consumer at the household level. According to the European Commission (2014), FW has been categorized into three groups: “(1) Loss of food: foodstuffs that are lost at the production stage; (2) inevitable FW: foodstuffs that are lost at the consumption stage (e.g., peels of banana, cores of fruits); (3) unnecessary FW: foodstuffs that are not consumed, but lost at the consumption stage.” Based on every stage of the FSC, Gustavsson et al. (2011) divided the generation of FW into the following production stages: agro-based FW generation, postharvest treatment and storing, handling, supply, and consumption. Parfitt et al. (2010) described FW as the loss of food during the absolute stage of FSC (marketing and ultimate consumption), that relates to seller and consumer behavior. Lipinski et al. (2013) defined FW as food products which possess better value and are appropriate for human utilization, that however are not utilized as they are disposed of prior to or after spoilage.

1.2

Food supply chain waste characterization

Food supply chain waste (FSCW) is product rich in organics generated for human utilization which is thrown away, subjected to loss, or decomposed chiefly at the production and marketing phases, comprising waste generated from pest-degraded food or spoiled food. FW is generated during all stages of the FSC, and is mainly apparent at the merchandizing and customer stages. The FAO has reported that nearly 51% of food generated is thrown away or unused prior to and after it reaches the customer (Parfitt et al., 2010). Nearly 1300 million tonnes of food is generated annually worldwide. This clearly illustrates a foremost socioeconomic and ecological issue (Gustavsson et al., 2011). The agribased FSC includes a wide range of production processes that produce incremental amounts of diverse FW, particularly organic residues. The escalating requirement for value-added products and biofuels, along with additional drivers, is inspiring the reutilization and proficient biorefineries of organics from the FSC for the generation of new biomaterials, fine chemicals, and biofuels, as a harmonizing method to the traditional approaches (i.e., incineration, composting, animal feed, and landfill). Industries move in the direction of greater sustainability to decrease costs and increase the effectiveness of processes to make innovative strategies economically sound for reutilization of FW. The progressively stringent European rules and principles and the expenses linked with their compliance (Landfill Directive in Europe) are the main drivers for the utilization of FSCW as a substrate to produce value-added products. Numerous methods can be considered to progress cutting-edge valorization approaches for the remains and derivatives of FW. This includes substantial amounts of biomolecules (i.e., proteins, polysaccharides, triglycerols, lipids, phenolic compounds), which are ample, easily obtainable, reutilized, and renewable. Numerous FW pools have value-added products that can be recuperated, resolved, and reutilized as useful foods, oils, and flavoring compounds. The expansion of valorization methods can solve the chief problems of the food industry, directing progress to more viable FSC and FW treatment schemes. They can resolve both the source and FW treatment issues, as the concerns linked with agro-based FW are significant, and include: G G G G

reducing landfill; reducing greenhouse gas emissions; reducing water supply contamination through inorganic material leaching; and enhancing the effectiveness of traditional FW treatment approaches (i.e., composting and incineration).

The best examples of these systems include expansion of closed-loop models with regard to the supply chain (World Economic Forum, 2010). These models explain that every type of FW can be recycled in the FSC (e.g., packed FW can be reutilized). FSC originate from an agricultural stage, continue through various industries and trades, and end with domiciliary consumption. Throughout this chain, food is wasted or lost due to technical, financial, and/or social causes. Scientist

Introduction: sources and characterization of food waste and food industry wastes Chapter | 1

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have disagreements about the descriptions of “food waste” and “food loss” in FSC. As stated by the Foresight Project report organized through the Government Bureau of Science (Foresight, 2011), FW is demarcated as “eatable product planned for societal utilization which are thrown away, lost, decomposed, or used by nuisances when foodstuff are taken from farms to buyer.” FSC and postharvest schemes are two other definitions under dispute in various reports. Postharvest loss is usually defined as “loss of food” and “spoilage of food.” “Loss of food” is defined as decrements in the volume and worth of food both quantitatively and qualitatively (Premanandh, 2011). Qualitative loss refers to a reduction in the calorific and nutritious value, with a reduction in quality that renders the product inedible (Kader, 2009). Loss of quantity is defined as a reduction in the eatable mass of food during the FSC.

1.3

Sources and origins of food waste

FW is generated mostly, but not absolutely, during the final consumer stage of the FSC (e.g., household waste). Food loss occurs at the processing, delivery, marketing, ultimate utilization, and postconsumption phases (FAO, 2014; Parfitt et al., 2010). Loss of food at the processing stage is typically caused by mechanical damage and/or spilling at harvesting (e.g., separating, fruitlet gathering, or crop categorization). Environmental factors such as changes in climate, for instance, temperature fluctuations and climate change and, in addition, financial issues such as rules, policies, and private or public principles for qualitative characteristics and look are key reasons for the loss of food (Kader, 2009). The stages during which loss of food occurs are postharvest, management, storing, handling, and distribution. Loss of food during the postharvesting stage happens because of leakage and decomposition, lack of storing amenities, and conveyance from the farm (Kader, 2009). A substantial quantity of foodstuff is lost during storage and this largely occurs due to insects and microbes. Conversely, FW at processing occurs due to leakages or decomposition (for instance, juice preparation and canning). During the processing stage, generation of FW may also happen at cleaning, shredding, cutting, steaming, etc. During the distribution stage, FW occurs because of inappropriate conveyance, unsuitable packing, time limitations, and dealer/ purchaser relations and poor organization. During the retailer stage, loss of food is typically denoted as FW as it is chiefly produced because of cognizant resolution to waste food. Such wasted food is however considered nontoxic and nutritive for human use, as stated by the Department of Environment Food & Rural Affairs (Defra, 2009). FW during the retailer stage occurs because of poor claim estimation, record mishandling, temperature changes, climate conditions during conveyance, discarding of unretailed food, unsuitable packing, and food guidelines and their lack of clarification. Venders dispose of substantial amounts of food which have expired in periods with subsequent labels: “best before,” “sell by,” or “use by.” Some sellers unite with charities and redistribution bodies (for instance, food banks) to distribute unretailed food or to guide customers on how to avoid food wastage. FW occurs during the consumption stage because of single shopping practices, absence of cognizance, absence of awareness of effective food utilization, social problems, lack of awareness of suitable shopping estimation, packing, and other issues (Defra, 2009). Rules at the global level take decisions that aim to decrease food wastage by averting waste from landfill via directives, tax policies, and community awareness. During the postconsumer phase, FW has been categorized into three kinds (WRAP, 2009): 1. avoidable FW (food that is wasted as it is not needed or has reached its expiry date); 2. probably avoidable FW (some foods that will be eaten by some people but not others); and 3. unavoidable FW (food wasted during the preparation of food which is not eatable in any condition). Loss of food that occurs from the manufacturer to the supplier stage is calculated to being sufficient to provide food for 1 billion people (Tomlinson, 2013). Loss of food is considered as the wastage of food arising due to human inputs, farm efforts, incomes, money inputs, and limited natural sources, for example, water. FW and loss of food are mainly linked with upstream FSC (manufacture to delivery) in low-income nations. The loss of food and FW in developed countries are highly associated with the downstream FSC. For example, minimizing loss of food in Africa is utmost of significance because of the organization of the FSC. In these places, loss of food originates from extensive technological and decision-making boundaries in harvesting, storage, conveyance, handling, cooling amenities, infrastructure, packing, and selling. Efforts have been taken to calculate FW and loss of food globally. However, because of differences in practices, evaluation extent, and foodstuffs, it is problematic in calculating definitive records (Premanandh, 2011). The loss of food and FW are mainly derived from the manufacturing and marketing stages in the developed nations of Europe. Consumer-stage FW and loss of food are chiefly problems in Oceania, Europe, North America, and industrialized Asia. The minimum FW occurs at the consumer stage and major loss of food occurs during the manufacturing to marketing

4

Food Waste to Valuable Resources

stages in South Asia, Southeast Asia, and sub-Saharan Africa. In developed countries, loss of food and FW occur through the FSC. This can be initiated by poor decision-making, market indications, inappropriate technologies, governing outlines and their miscomprehension, social standards, and unsuitable FW management approaches.

1.4

Food waste generation

In 2009 the United Nations FAO calculated and reported that 32% of generated foodstuffs were wasted or lost globally (Gustavsson et al., 2011). Fig. 1.1 represents the quantity of worldwide FW generation, contrasting sharply with the 0.87 billion persons described as recurrently malnourished. Roughly 1300 million tonnes annually that is, one-third of the food generated for consumption, is unexploited worldwide. In the United States, approximately 0.061 billion tonnes of FW is produced annually (GMA, 2012). Dee (2013) quantified the rate of FW generation in Australia as approximately 4 million tons annually. FW generation records in 2010 showed that South Korea generated 0.00624 billion tonnes, with 0.0924 billion tonnes of FW generated in China (Lin et al., 2011), and 0.021 billion tonnes generated annually in Japan. The generation of FW in Europe is calculated to be 0.09 billion tonnes annually (European Commission, 2013). Reports showed that in Europe, the amount of FW generation was found to be more than 0.014 billion tonnes in 2013 (WRAP, 2013). Quested et al. (2013) estimated that, in the United Kingdom, FW generation was 160 kg per household annually, implying that 12% of food and drink arriving at homes and 30% of overall domiciliary food in the United Kingdom was wasted. Nellemann et al. (2009) implied that 25%
50% of food prepared is lost through the FSC. The scale and extent of FW production is constant and is not restricted to industrialized nations. Gustavsson et al. (2011) documented records of FW production in various regions, illustrating that production of FW showed an analogous directive of extent in developed and emerging nations. However, developed and emerging nations varied considerably. More than 40% of food was lost during the postharvest and processing stages in developed countries, whereas in developing countries nearly 40% of food was lost during the marketing and consumption stages. Based on per capita income, much more food is lost in developed countries than developing countries (Gustavsson et al., 2011). The reasons for loss and wastage of food in underdeveloped countries are mostly associated with technical, economical, and managerial limits in harvesting, packing, and chilling services. Numerous small agronomists in emerging nations survive on the boundaries of food uncertainty, and a decrease in the amount of food loss can have an instant and considerable effect on their quality of life. FSCs in developing countries must be supported, boosting small agriculturalists to establish, expand, and upscale their manufacture and selling of foods. The reasons for food loss and wastage in

85 kg /capita / year 155 kg /capita / year 120 kg /capita / year

17 %

100 kg /capita / year

175 kg /capita / year 180 kg /capita / year

46 % Industrialized 23% Asia

23%

52 %

Europe

11 %

2%

11%

17%

5% 6% North America & Oceania 9 %

15 kg /capita / year

9%

110 kg /capita / year

61 %

175 kg /capita / year

35 kg /capita / year

7%

13 % 23% 34 % North Africa, West & Central Asia

South and South East Asia 4%

21%

25 kg /capita / year

200 kg /capita / year

18 %

32%

15 %

37%

4%

28%

28 %

Latin America

10 kg /capita / year 22%

17 %

150 kg/capita / year

6% 5% 13 % 39% 7%

Production Handling and storage Processing Distribution and market Consumption

FIGURE 1.1 Quantity of worldwide food waste generation.

Sub-Sahara Africa

37%

Retailer

Consumer

Introduction: sources and characterization of food waste and food industry wastes Chapter | 1

5

average/high-income countries are related primarily to customer activities in addition to an absence of harmonization among the numerous players in the FSC. The sales agreement among farmers and buyers could contribute en route to farm crop wastage. Food wastage can also occur because of a lack of value standards (foodstuffs which lack appropriate shape or form would be excluded). At the consumer stage, insufficient scheduling and expiration of “best before date” also create an enormous quantity of FW. This occurs due to the careless attitudes of consumers. FW in developed countries could be minimized by increasing awareness among sellers, food processing industries, and customers. This infers the redundant utilization of enormous quantity of sources utilized in the production of food, and the subsequent upsurge in greenhouse gas emissions (Gustavsson et al., 2011). Generation of FW is articulated using, for instance, the total quantity of FW generated annually (tonnes per year) and per capita (kilograms per year or kilograms per day). The FW generated by buyers per capita in the United States and Europe was estimated to be 95
115 kg/year, and 6
11 kg/year in Asia and Africa (Gustavsson et al., 2011). Dung et al. (2014) estimated that FW in industrialized and developing nations per capita were 107 and 57 kg/year, respectively. These data illustrated that the generation of FW among industrialized and developing countries is reasonably tied to advanced livelihood standards causing elevated FW production (Lipinski et al., 2013). This has resulted in enormous quantities of FW production to meet food value requirements, for example, enormous amounts of constituents are required to prepare better value food. In addition, buyers might impact the quantity of FW generated by sellers. FW is foodstuffs which are not retailed or products that reach their expiry date and are discarded in preference to contributing it to food stores or charities (European Commission, 2014). Societies with poor hygiene values have low requirements for food preparation, and hence, the associated generation of FW per capita is less. However, due to the impact of increasing populations and growing financial restraints, it is anticipated that overall wasted foodstuff quantities in emerging nations is less than in industrialized countries. The Agriculture Organization of the United Nations (2014) has documented that yearly overall quantities of FW generated worldwide are about 1300 million tonnes/year. These data do not showed noticeable variations when comparing industrialized (0.67 billion tonnes) and emerging (0.63 billion tonnes) nations. These data are due to the greater populations and greater number of developing nations (hypothesizing that there is poorly developed financial prudence in developing nations). Presently, the global population in highly industrialized countries is 1.2 billion, with 6 billion in poorly developed nations. At a global level, about 137 countries are developing and 49 are industrialized nations. Among the developing nations, 37% of the overall global population is in China and India. Fig. 1.2A and B illustrates the populations, FW, and different types of FW generated by various countries (developed and developing) around the world. The generation of FW in emerging nations is lesser and those requires a smaller amount food for utilization. However, overall generation of FW in emerging nations is almost equivalent to that generated in industrialized nations. FW in emerging countries is estimated to be 55% of municipal waste. Among the total municipal solid waste, the percentages of FW in Malaysia, India, Mexico, and Brazil were estimated to be 55%, 51%, 52%, and 54.9%, respectively. The greater fraction of organics illustrates the great accessibility of composting, an FW management practice in emerging countries. Furthermore, municipal FW worldwide is anticipated to increase by 44% between 2005 and 2025. Because of the rapid economic growth which is anticipated in Asia, it is expected that there will be a drastic increase in the generation of FW from 0.278 to 0.416 billion tonnes. This could lead to worldwide environmental pollutant emissions increasing by 8%
10%. The generation of FW takes place at different stages in the FSC, beginning at the farm itself even prior to product entering the market (WRAP, 2008). Preharvest losses occur because of great climate impacts (e.g., water scarcity) or pest incursions. FSC wastes are produced during the harvesting stage and are usually exposed to technological changes comprising augmented modernization, equipment faults, and new treatment approaches. Economic factors, which disturb manufacturers’ readiness to take their products to market, are also a general root of FSC waste generation. Food is also exposed to extra losses when it departs the farm for the market. Instances of comparable losses comprise bread, meat, and other associated related foodstuffs manufactured by eateries or caterers that are never distributed, along with the discarding of stained, poorly labeled/packed, improperly stored/conveyed, or overripened foodstuffs that are not able to be sold but remain nutritious and safe for consumption. An essential element of food loss during the retail stage of FSC is stock cleared from markets when the commodity reaches its “expiry” date (WRAP, 2008). Dairy products which are manufactured freshly and extra unpreserved products frame a major portion of marketing food loss. Kader calculated that nearly one-third of all fruit and vegetables which are generated globally are lost prior to reaching the consumer (Kader, 2009). These data have been calculated to constitute 9% in the United Kingdom. FW is also an essential constituent of domestic waste, covering an estimated 20% of total domestic waste (WRAP, 2009).

Food Waste to Valuable Resources

390

1400 60.8

195

40

200 71.9

75 20

12.3

14.3

0.8

1.9

50

33.5

8.8 2.3

6.2 2.3

0.8

12.4

25

19.9 5.5

0

0.9 3.6

9

9.3 0.9

0.4 4.4

5.7

25

Developing countries 1350 1300 1250

Ukraine Nigeria

India Vietnam

Belarus China Thailand Jamaica

Mexico Costa Rica

Brazil Turkey Malaysia

UK

Taiwan

South Korea

USA

Germany

Netherlands

300

Sweden

Australia

0

Romania South Africa

330

225

1200 200

60

150

Population (106)

Food waste (Ton/year)

360

Population (106)

250

60

Food waste (Ton/year)

Developed countries

Denmark

(A)

Singapore

6

FIGURE 1.2 (A) Population and food waste generation in developed and developing countries. (B) Different types of food waste generated in various countries.

100

30

50

India

Vietnam

Nigeria

Ukraine

Jamaica

China

Thailand

250

10

1.5

Japan

Malaysia

Indonesia

Cambodia

Australia

Cereal Rice Sugar Pulses Oil crops Vegetable oil Vegetables Beans Onions Peas Tomatoes Potatoes Fruits Apples Bananas Coconuts Pineapples Coffee Milk Cream Butter Animal fats Meat Offal Poultry meat

China

Asia

SE Asia

0

2

Vietnam

0

50

4

Thailand

20

6

S. Korea

Waste (MT)

100

40

8

Waste (MT)

150

60

Philippines

80

N. Korea

Poultry meat Offal Meat Animal fats Butter Cream Milk Coffee Pineapples Coconuts Bananas Apples Fruits Potatoes Tomatoes Peas Onions Beans Vegetables Vegetable oil Oil crops Pulses Sugar Rice Cereal

200

Waste (MT)

Belarus

Romania

South Africa

Mexico

Costa Rica

Malaysia

Brazil

Turkey

Taiwan

South Korea

United Kingdom

Germany

Netherlands

United States

Sweden

Singapore

0

NZ

(B)

Denmark

Australia

0

0

Food waste quantification

Quantifying the extent of FW is crucial for the progression of active, well-organized FW treatment strategies. This could be employed to decide if future FW recovery and preventive measures significantly modify the remaining leftover materials. Knowledge about the amount of FW could afford motivation for societies to modify their outlooks and possibly their activities toward FW. On the other hand, descriptional problems, the lack of complete quantifying approaches, and an overall lack of imperious or governmental drive have paved the way for substantial records gaps concerning FW quantification (Parfitt et al., 2010). A variety of approaches have been employed for quantifying FW. Some of these have some disadvantages. Some methodologies, which include sorting based on waste characterization and modeling of material flow analysis, have attempted to calculate the quantity of FW mixed with municipal solid waste (i.e., wastes generated from marketable, household, and official divisions). Other approaches, such as food records, quality level analyses/meetings, and FSC and food statistics evaluation place an emphasis on overall FW quantities produced from particular divisions (for instance, residential and eateries) or target related disposal quantities with social activities. Few investigations emphasize simply official waste and reject waste that are discharged via routes other than the conventional FW treatments (e.g., FW sent to landfill, FW which is composted at home, and FW used as animal feed).

1.6

Types of food waste and food processing wastes

Bioenergy and biofuel production from FW mainly utilize mixed/domestic FW but the recovery of value-added products is dependent on the particular FW type. The valorization of both FW and food processing wastes are described below. PURAC (2015) reported the utilization of colorful fruits, olive leaves, and tomatoes for the generation of polyphenols, phenols, fibers, carotenoids, and antioxidants. Likewise, waste originating from dairy processing food industries and slaughter houses was used as a substrate in the production of lactic acid and the abstraction of proteins. Generally, fruits contain high amount of vitamins, fibers, and different bioactive components. A huge amount of wastes are generated from fruit processing industries, including peelings, kernels, cores, and flesh. These can be valuable products in larger amounts.

Introduction: sources and characterization of food waste and food industry wastes Chapter | 1

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Extraction of pectin from fruit processing industrial waste, recovery of phenolics and organic acids from kernels of mango and pigments such as carotenoids, polyphenolic compounds, vitamins, dietary fibers, and enzymes from peels of mango; extraction of biocompounds such as bromelain from the stem of pineapple; extraction of protein powder from coconut processing industrial waste, etc. have been investigated widely. Likewise, a food additive, pectin, which is primarily utilized in chemical, pharmaceutical, and food industries is chiefly extracted from FW which includes pomace of apples, orange peel, and sugar beet pulp waste. It has been found that dried peels of lemon, grapes, and oranges contain 20%
30% pectin. Apple pomace has 10%
15% pectin on a dry weight basis.

1.7

Food waste hierarchy

The major principles of FW hierarchy have been linked to European policies in the early 1970s, and the 1975 rules on waste (European Parliament Council, 1975), and to the EU’s second environment action program in 1977 (European Commission, 1977). In 1989 the FW hierarchy was clearly described in the European regulation’s public policy for the treatment of waste (European Parliament Council, 1989). In the meantime, the FW pyramid was implemented globally as the chief waste managing agenda. Other agendas supported by many Asian countries and Japan include the “3Rs,” which affords a comparable method for managing waste by highlighting the possibilities of reducing, reusing, and recycling FW. The objective of the FW hierarchy is to find the best probable routes to provide eminent and complete favorable ecological consequences. Fig. 1.3 shows the FW hierarchy. As shown in Fig. 1.3, the most appropriate choice is “prevention,” and the least appropriate choice is “disposal,” which is presented at the bottom of the upturned hierarchy pyramid.

1.8

Management and valorization of food waste

FWs have varying chemical compositions based on their generation and origin. Thus, FWs contain a mixture of proteins, carbohydrates, and lipids. If the FW is produced from particular agro-based industries, then it will be rich in one of the above-mentioned components. Various biofuels are thus generated from FW either biologically or thermochemically based on their composition. In addition, FW valorization pathways involve both extraction of value-added products from FW. Fig. 1.4 illustrates the types of FW, their valorization routes, and applications. The management of FW and food industry waste includes various treatments such as chemical, physical, mechanical, and biological techniques, which have numerous benefits and drawbacks. For example, valorizing food processing industry waste as animal feed is the most conventional technique. Proteinaceous and lipid-rich FW is appropriate for animal feed, while FW rich in cellulosic composition can be appropriate for cattle feed. On the other hand, the possible occurrence of toxic products that Most preferable option

01

Prevention Waste of raw materials Waste of raw Ingredients

Optimization

02

Redistribution to people Send to animal feed

03

04 Recycling Waste to anaerobic digestion process Waste to composting

05 Recovery Incineration of waste without energy

Waste

Disposal Waste to landfill Waste incinerated without energy recovery

Least preferable option

FIGURE 1.3 Food waste hierarchy.

8

Food Waste to Valuable Resources

• • •

• • • • •

• •

Biogas Electricity Nutrients recovery

Biohythane Biohydrogen-biomethane VFA-PHA (or) CH4 Microalgae cultivation CH4 Yeast cultivation – CH4

• • • • • •

Integrated biorefinery

Organic acids Hydrogen Enzymes Bio-alcohols Antibiotics Antioxidants

Food processing waste

Microbial fuel cell Microbial electrochemical cell Biohydrogen Bio-electricity

Flesh Head Skin Bones Tail

• • •

Lipids recovery Glycerine Biodiesel

Potato processing waste Cassava processing waste Pulp processing waste Oil seed processing waste

Meat processing waste

• • •

Remaining dishes Cooking oil

• • • • •

• • • •

• • • •

Dairy waste

Catering waste Fish processing waste

• •

Polyhydroxyalkanoates (PHA) Polyhydroxybutyrate (PHB) Biopolymers Polyphenols Fine chemicals Essential oils Bioactive peptides

Transesterification

Fruits & vegetable waste

Peels Leaves Kernel Seeds Pomace Wine lees

• • • • • • •

Fuel cells

Fermentation

Composting

Compost Bio-fertilizer

• • • • • •

Value added product recovery

Anaerobic digestion

• • • • • •

Milk processing waste Curd processing waste Butter processing waste

Liver Heart Skin Bones Lungs Feathers & hair

FIGURE 1.4 Types of food waste and valorization route.

have antinutritious influence and instable compositions of nutrients might threaten the health of both humans and animals (Murugan and Ramasamy, 2013). The conveyance price (because of the distance of the FW generating site and consumption site) regularly makes this source of feed as expensive as traditional animal feed. The various FW management practices are valorizing FW as animal feed, composting, incineration, landfill, and biofuel production (Banu et al., 2018a,b,c, 2019; Kannah et al., 2017a,b, 2019).

1.8.1 Animal feed Animal feed is commonly the best inexpensive valorization route for FSCW, on the other hand, in some cases, it is restricted by governing problems besides the characteristics of byproducts produced in the process. Composting is referred to as a general land spreading or injection process and is a promising and long-term approach. It is an ecofriendly process and it diverts FW from landfill and decreases planters’ requirements (e.g., for fertilizers).

1.8.2 Landfill Strategies for the management of FW raise considerable ecological issues. Discarding of FW to landfill creates influences both economically and environmentally through greenhouse gas emissions (methane and carbon dioxide) directly and indirectly. For instance, 4.2 tonnes of carbon dioxide are released during FSC from 1 tonne of FW produced. This includes emissions to air, water, and soil (World Economic Forum, 2010). Recovery of heat energy via incineration is not economically viable. This is usually due to the loss of energy to vaporize the higher water content of FW. However,

Introduction: sources and characterization of food waste and food industry wastes Chapter | 1

9

in recent years, the utilization of FW as a compost or soil enhancer has emerged. Tuck et al. (2012) validated the economic benefit related to FW valorization to fine products. The typical cost of FW conversion to fine chemicals and biofuels was calculated to be approximately 1000 and 200
400 USD/tonne FW, respectively. Relatively, the animal feed and power were calculated to be in the range of 70
200 and 60
150 USD/tonne FW, respectively. A typical waste disposal approach is the landfill as it is a cost-effective treatment route. Landfill is described as the dumping, solidity, and spreading of FW at suitable locations and comprises four general phases, namely, hydrolysis or aerobic digestion, hydrolysis and fermentation, acidogenic, and methanogenic phases. During this process, the organic matter in FW is oxidized and decomposed, ultimately causing methane production and pollution of groundwater. This could be mainly because of organic matter and metal ions. Various policies have focused on FW treatment approaches to divert FW from landfill. Directives have attempted to flourish in this objective via rules, taxes, and communal alertness. In relation to the EU waste scheme, the amount of FW sent to landfill has been calculated as: G G G

25% decrease in FW sent to landfill was achieved in 2010 in comparison to 2006; 60% decrease in FW sent to landfill was achieved in 2013 in comparison to 2006; and 90% decrease in FW sent to landfill will be achieved in 2020 in comparison to 2006 (European Commission, 2010).

Likewise, the FW regulations of the United Kingdom aim at nearly 85% of waste originating from food processing industries to be spread on land (Sanders and Crosby, 2004). Generally, the best strategies aim to shift FW management from landfill to avoidance, reutilization, and recovery. Thus, a stable strategy comprises joint actions, for example, (1) FW landfilling is banned, (2) taxes on landfilling boost diversion and enhance the use of alternate managements, (3) expansion of composting or AD options, (4) expansion of the requisite setup, and (5) establishing an inclusive management system.

1.8.3 Bioenergy and biofuel conversion approaches Wastes generated from food processing industries consist of an enormous amount of organic matter that can be transformed into energy. This energy then can be used for heat or electrical energy. AD and thermal practices (e.g., incineration, ignition, and pyrolysis) are considered as the chief bioenergy-generating processes (Murugan et al., 2013). FW with a moisture content below 50% is appropriate for thermochemical processes, which transform the organic-rich content of FW into gas or liquid. For example, incineration is a heat-based process which involves oxidization of ignitable components of FW for heat energy generation. Incineration is a feasible process for FW with comparatively less moisture (,50% by quantity). On the other hand, these processes have certain environmental impacts such as greenhouse gas emissions, severe ecological effects, and elevated cost (Murugan et al., 2013). AD is an extensively employed approach (Kavitha et al., 2014, 2015, 2019) for treating FW which has higher moisture content and organic content in excess of 50%. In AD, diverse groups of microbes are involved in treating and stabilizing the FW in an anaerobic environment. Simultaneously, biogas is generated. Biogas is a blend of CH4, carbon dioxide, and water with H2S or H2. Biogas is utilized to produce electricity through the heat generated and is currently decreasing the utilization of fossil fuels and the release of carbon dioxide. Numerous feedstocks have been assessed as possibly appropriate substrates for production of biohydrogen via a dark fermentative process. Among the above-mentioned substrates, FW may be a comparatively cheap and suitable choice of decomposable organics for biohydrogen generation, chiefly owing to its high amount of sugar and abundant nature. This process can be integrated into various biological practices resulting in bioenergy production. The potential of biohydrogen production is influenced by numerous factors such as the type of inoculum treatment, fermenter type, substrate loading, fermentation time, temperature, and medium pH. FW can be utilized as an inexpensive, renewable, and extensively available substrate for bioethanol production. Pretreatments are commonly employed to increase the hydrolysis of sugar-enriched FW (Kannah et al., 2018; Kavitha et al., 2017), as the yeast biomass lack the potential to hydrolyze and ferment complex starch or cellulosic molecules into bioalcohol. Cekmecelioglu and Uncu (2013) established the viability of dropping the cost of ethanol recovery by using household FW as feedstock, without using the carbon sources that are conventionally utilized in the fermentation process. Pretreatment is not needed before enzymatic hydrolysis to obtain more glucose from household FW as the carbon and sugar contents in FW afford an adequately nutritious medium for the inoculum to yield more ethanol (Cekmecelioglu and Uncu, 2013). Kim et al. (2011) have obtained enhanced bioethanol production by utilizing carbohydrates containing FW in which the yield ranged from 300 to 400 mg ethanol/1000 mg total solids. Fruits waste have also been considered as a suitable feedstock for production of bioalcohol. For instance, waste from bananas or spoiled bananas, peelings, and poor-value berries have been widely considered as feedstocks for

10

Food Waste to Valuable Resources

bioethanol. Another biofuel, biodiesel, is defined as the alkyl esters (methyl/ethyl esters) of long-chain fatty acids and short-chain alcohols. This could be obtained from natural lipid-rich FW, such as plant-based oils or fats from animalbased origins, through a process called transesterification. This biodiesel is suitable for application in traditional diesel appliances and circulated via available energy infrastructure. Any FW rich in fatty acids could be used as a feedstock in the production of biodiesel.

1.8.4 Composting Composting is an effective approach in treating FW in emerging nations. In India, presently, over 70 composting treatment amenities are handling mixed municipal solid waste, and reprocess nearly 5.9% of the total FW to produce around 0.0043 billion tonnes of compost annually. Mostly composting amenities treat a mixture of wastes, except the facilities in Vijayawada and Suryapet. These facilities treat FWs which are source separated. This practice is generally employed

Aerobic digestion

Regulation policies & CBE

Role of microbes Composting types Factors affecting Current scenario Compost application

Bioelectricity Chapter - 18

Problems in FW biorefinery

Circular economy CE approach to FW Bioeconomy approach Bioeconomy application Challenges in FWM

Chapter - 16

Issues of FW composting Issues of biogas production from FW Preventive measures Planning strategies Innovative plans

Enzymes biocatalysts

Chapter - 11

Techno economic analysis

Chapter - 10

Enzyme in PHA Enzymes in biodiesel Enzymes in bioethanol Immobilized biocatalysts Immobilized cell bioreactors

Chapter - 12

Food processing industries Fuel cell performance Anodic biofilm formation Role of bioelectrogenesis Application of MFC + AD

Biopolymers & Feed proteins Speciality chemicals & Nutraceuticals

Fine chemicals

Chapter - 7 FWM in various countries

Chapter - 15

Polysaccharides Polyhydroxyalkanoates (PHA) Beaker`s yeast Single cell protein and oil Bioreactors

Technical challenges Commercial scale up Economic aspects Case studies Cost estimation

Value chain analysis

Chapter - 14

Current Scenario FSC- different region Developed countries Developing countries Treatment strategies

Organic acids & enzymes

Chapter - 9

Chapter - 8

Antibiotics Aroma compounds Pigments Extraction and purification Commercial scale up

Phenolic compounds Antioxidants Flavonoids Biosurfactant Commercial scale up

Biodiesel

Thermochemical Chapter - 17

Mass and energy flow Exergy analysis Life cycle assessment Life cycle inventory System boundary

Integrated biorefineries

Scaling Up Chapter - 13

FW to algae production VFA to PHA production VFA to different biofuel FW to yeast production AD + ABE fermentation

Chapter -4

Chapter -6

Fatty acid Latic acid Succinic acid Amylase Lipases

Chapter -5

Incineration Combustion Pyrolysis Gasification Hydrothermal carbonization

Lipid bioconversion Lipase mediated process Transesterification Acid & alkali catalysis Bioreactors employed

New business & marketing concepts

Bio-alcohols

Introduction

Chapter - 19

Institution and enterprises Production guidelines standards Market based products Financial measures Scaling up

Biogas Chapter -3

Chapter - 20

Commercialization Patented methodology Intellectual property protect Policy option Business model

Chapter - 1

Food Waste Food Loss Food supply chain waste Source and origin Characterization Valorization route

Chapter -2

FW Pretreatment Hydrolysis Detoxification ABE Fermentation Alcohol Recovery

Pretreatment Bioreactor CH4 - Anaerobic digestion H2 - Dark fermentation H2 + CH4 - Two stage

FIGURE 1.5 Overall concept diagram for chapters in this book (food waste to valuable resources: applications and management).

Introduction: sources and characterization of food waste and food industry wastes Chapter | 1

11

for the treatment of sugar-rich wastes in Thailand. Presently, as per Pollution Control Department and Ministry of Natural Resources and Environment (2010), exploitation approaches reprocess around 0.00059 billion tons of FW which has been composted to biofertilizers and biomethane. Nationwide 3Rs approaches implement AD and composting to enhance utilization of FW. In Malaysia, the government has implemented a prime initial plan to generate biofertilizer utilizing FW. In contrast, in most developing countries, there are issues with composting due to impure wastes which are the byproducts of source-segregated FW. Thus, the marketing of composting has dropped and FW composts which compete with chemical-based fertilizers create problems for the processes and investments of composting amenities. Global NGOs have provided plans to support the economical needs by implementing small-scale composting in emerging countries. Though steps have been taken to improve the awareness of FW reutilization in some African and Asian nations, the value of compost has not been enhanced.

1.8.5 Value-added products recovery Household or domestic FWs can be used as substrate to recover value-added products. These value-added products include fine chemicals, nutraceuticals, biopolymers, biopeptides, antibiotics, high-fructose syrup, levulinic acid, bionanocomposites, single-cell proteins, polysaccharides, activated carbon adsorbent, chitosan, antioxidants, bioactives, corrosion inhibitors, industrial enzymes, films, vermicompost, mushroom cultivation, organic acids, pigments extraction, sugars, wax esters, and xanthan gum. This book covers in depth the recovery of valuable resources, their applications, and management. An overall concept diagram for this book and the topics covered is presented in Fig. 1.5.

1.9

Conclusion

The expansion of viable resolutions for managing FW is a foremost issue for the general public. These resolutions must be proficient for utilizing the valuable resources signified in FW to accomplish communal, economic, and ecological advantages. Perfect and commonly recognized descriptions of FW and associated definitions are not yet completed, and approximations on the produced quantities are not still finalized. The production of FW can be preferably be achieved with an appropriate balance between the generation and utilization of FW. However, optimal organization remains distant. A viable managing practice for the surplus generation of eatable food could be its redistribution to food banks. The food donation approach aims at provision from directives to ease the acquisition by food banks or societal amenities. Food processing residuals and domestic FW are not appropriate for social utilization and could be employed as a substrate for biopolymer and bioenergy recovery, along with the abstraction of value-added products. This necessitates a lively contribution from the scientific community to finalize appropriate source-separated FW to be converted into reserves.

References Agriculture Organization of the United Nations, 2014. Global initiative on food loss and waste reduction. ,http://www.fao.org/save-food/keyfindings/en. (accessed 20.08.14.). Banu, J.R., Kannah, R.Y., Kavitha, S., Gunasekaran, M., Kumar, G., 2018a. Novel insights into scalability of biosurfactant combined microwave disintegration of sludge at alkali pH for achieving profitable bioenergy recovery and net profit. Bioresour. Technol. 267, 281
290. Banu, J.R., Kannah, R.Y., Kavitha, S., Gunasekaran, M., Yeom, I.T., Kumar, G., 2018b. Disperser-induced bacterial disintegration of partially digested anaerobic sludge for efficient biomethane recovery. Chem. Eng. J. 347, 165
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Sanders, B., Crosby, K.S., 2004. Waste legislation and its impact on the food industry. In: Waldron, K., Faulds, C., Smith, A. (Eds.), BT - Total Food Exploiting Co-Products
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Chapter 2

Valorization of food waste for biogas, biohydrogen, and biohythane generation T.M. Mohamed Usman1, S. Kavitha1, J. Rajesh Banu2 and S. Kaliappan3 1

Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India, 2Department of Life Sciences, Central University of

Tamil Nadu, Neelakudi, Thiruvarur, Tamil Nadu, India, 3Department of Civil Engineering, Anna University, Chennai, India

2.1

Introduction

Food waste (FW) is considered to be a valuable substrate with increased potential to recover bioenergy. FW is mainly generated from homes, restaurants, and the food industry, and includes cereals, milk, fruits, meat, oilseed, vegetables, and seafood that are rich in nutrients such as carbohydrates (starch, cellulose, and hemicelluloses), proteins, lipids, organic acids, and lignin. The high organic matter, high moisture content, and biodegradability potential of FW make it a suitable candidate for bioenergy recovery (Zhang et al., 2011). FW is generally disposed of in landfill sites. Fig. 2.1 shows the most popular practices for FW management. Improper disposal or stacking of FW in landfills can cause serious health-related issues as well as other environmental problems such as odor, emissions of greenhouse gases like methane, and groundwater pollution (Kim and Shin, 2008; Kim et al., 2009; Lee et al., 2010a). A study by the United States Environmental Protection Agency (EPA) revealed that manmade emissions of methane were calculated as 282.6 million tons during the year 2000, where 13% of emissions were from landfills (Ren et al., 2018). On other hand, proper landfill disposal requires a larger area and high capital investment. In general, food production requires energy and nutrients, which makes these processes uneconomical and inappropriate (Uc¸kun Kiran and Liu, 2015). In addition to landfills, conventional treatment methods such as incineration or combustion are practiced to treat FW and to generate energy and heat. During combustion, the high moisture content of FW may lead to the generation of toxic compounds such as dioxin. FW incineration also can induce air pollution and, as a result, the chemical assets of FW may be lost. This turns the research focus into appropriate FW reduction and valorization. In this context, several studies have been conducted on the conversion of food to bioenergy, value-added products, and fine chemicals. Life cycle assessment of FW carried out by Schott and Andersson (2015) shows that an alternative FW management to replace incineration and landfill is anaerobic digestion (AD). AD could greatly reduce the global warming problem. Dark fermentation and AD were widely studied technologies for bioenergy production from FW (Sen et al., 2016). A number of studies have been conducted on the production of methane, which pushes this concept into an industrial-scale application. In addition, biohydrogen-based studies are slowly evolving (Girotto et al., 2015). Also, a blend of hydrogen and methane (biohythane) can be produced from various organic wastes (e.g., FW) through a two-stage sequential digestion process, that is, a first step of a dark fermentation process is followed by a second step of AD for hydrogen and methane yield (Algapani et al., 2018). Thus, this biological process provides an effective pathway to recover energy and nutrients from FW which compensates for early invested energy in food production. This chapter provides an overview of energy recovery (biogas, biohydrogen, and biohythane) from FW, factors affecting the bioenergy recovery, and the challenges affecting commercialization.

2.2

Anaerobic digestion of food waste

FW is rich in nutrients such as proteins, carbohydrates, and lipids. Organic-rich FW can be used as a suitable substrate for AD (Lee et al., 2019). AD is a biological treatment commonly adopted for FW treatment in many developed countries since 2006 (Abbasi et al., 2012b), yet developing countries remain unable to adopt this technique widely. During Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00002-X Copyright © 2020 Elsevier Inc. All rights reserved.

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Food Waste to Valuable Resources

FIGURE 2.1 Commonly practiced food waste disposal methods.

FIGURE 2.2 Anaerobic digestion process dynamics.

AD the complex waste material can be biodegraded into simpler compounds to produce rich calorific biogas as the end product. The AD process is illustrated in Fig. 2.2 (Chinellato et al., 2013). AD is a perfect choice of process for treating high moisture feedstock (up to 90%) such as FW (Brennan and Owende, 2010). AD demands less energy compared with other biological process and also has less of an atmospheric effect compared with other processes such as incineration and pyrolysis. The AD process involves various biochemical reactions mediated by diverse group of microbes. The biochemical reactions involved in AD are commonly divided into four stages: hydrolysis, acidogenesis, acetogenesis, and methanogenesis (Krishna and Kalamdhad, 2014). The first stage, hydrolysis, is mediated by fermentative bacteria, which convert macromolecules such as proteins, fats, and polysaccharides into smaller compounds such as peptides, fatty acids, and monosaccharides or simple sugars. Hydrolysis is followed by the second stage, acidogenesis, during which the hydrolyzed simpler compounds are converted into volatile fatty acids (VFAs) by acidogenic microbes (Kumar et al., 2016). The third step in AD is acetogenesis, during which acetogens convert the VFAs into acetic acid, hydrogen, and carbon dioxide. At the end of this stage the methanogenic process occurs, during which the acetic acid is converted into methane and carbon dioxide. The energy-rich biogas produced at the end of AD mainly contains methane, carbon dioxide, and a small amount of hydrogen sulfide (H2S). Methane is one of the best-known bioenergies

Valorization of food waste for biogas, biohydrogen, and biohythane generation Chapter | 2

17

produced in-house. Household production of methane using kitchen waste (FW) has been studied intensively for the last few decades. Studies on AD shows that parameters such as temperature, pH, C/N ratio (Zeshan et al., 2012), VFA (Xu et al., 2014), organic loading rate (OLR), reactor design (Krishna and Kalamdhad, 2014), and inoculum type (Deepanraj et al., 2017) affect the process dynamics, as discussed in detail in the forthcoming sections. Based on various studies, it is noted that FW would be an appropriate choice of substrate as compared with agricultural residues for production of biofuels such as biohydrogen and biomethane (Dung et al., 2014). A study conducted on cafeteria FW by Chen et al. (2010) showed 0.61 Nm3/kg volatile solids (VS) of specific biogas yield. The results also clearly showed that biogas generated from these feedstocks contains a maximum 59% methane content and the remaining portion was carbon dioxide. The various benefits obtained through biological degradation of FW are volume reduction in organic matter, biogas production, water recovery, and valuable end products such as soil conditioner. Methane is the main component of biogas which has commercial value (Dahiya et al., 2018).

2.2.1 Pretreatments employed During AD of FW, hydrolysis is considered to be the rate-limiting step due to the presence of complex macromolecules which take more time to biodegrade or resist biodegradation. Pretreatment helps to improve the biodegradability and positively improves biogas production. Chemical, thermal, ultrasonic, and microwave pretreatments are commonly adopted for the enhancement of FW solubilization and biomethane production. The effect of pretreatment can be evaluated by its mode of mechanism on FW and its composition (Krishna and Kalamdhad, 2014). Ultrasonic pretreatment mainly reduces the particle size in FW through the cavitation effect and microbubble expansion. Thermal pretreatments have been reported widely for hydrolyzing macromolecular components in various FW (Papadimitriou, 2010). Thermal pretreatment breaks the chemicals bonds in FW through the thermal effect and induces solubilization (Krishna and Kalamdhad, 2014). A study by Ma et al. (2011) clearly showed that macromolecules in FW can be disintegrated after thermal hydrolysis, which improves solubilization, however biodegradability may be limited. Thermochemical pretreatment achieved a maximum of 615 mL/g VS where thermal treatment achieves 602 mL/g VS biogas production (Prabhudessai et al., 2009). Chemical pretreatment recorded the lowest biogas production rate of 410 mL/g VS (Prabhudessai et al., 2009). Combining thermal pretreatment with chemicals could efficiently enhance the biodegradability of substrate and biogas production. For example, Chandra et al. (2012) showed an improved maximum of 441 mL/g VS biogas production through combined thermal-chemical pretreatment of FW, compared with sole thermal pretreatment (357 mL/g VS) and chemical pretreatment (293 mL/g VS). A similar increment in biogas production (441 mL/g VS) was obtained through thermochemical pretreatment of cottage cheese waste (Chandra et al., 2012). Hydrothermal pretreatment is another effective physical pretreatment which results in enhanced solubilization of FW. Qiao et al. (2011) obtained 0.67 Nm3/kg VS specific biogas yield after pretreating FW with a hydrothermal pretreatment. In another study, Salminen et al. (2003) combined thermal with enzymatic treatment so that the methane yield improved from 37% to 51%, whereas the individual enzymatic pretreatment achieved only 32% of the maximum methane production (Salminen et al., 2003; Qiao et al., 2011). Ariunbaatar et al. (2014) worked on low-temperature thermal pretreatment (80 C for 1.5 h) of FW. The authors obtained a higher methane production of 52% than untreated food. Li and Jin (2015) reported that the biogas production rate was increased from 50.88% to 147% after pretreating FW with an elevated temperature. FW normally contains highly biodegradable, and easily volatile carbohydrates. However, studies have highlighted that long-chain fatty acids present in the lipid compounds of FW increase the lag period for methane production. Yet, it is a temporary problem as evolving microbes in the anaerobic process can consume longchain fatty acids (Cirne et al., 2007; Li and Jin, 2015). The negative impacts of thermal pretreatment of FW include the caramelization of fermentable sugars due to extended treatment time. Therefore, to obtain better biomethane production, balance should be maintained between degrading compounds of substrate (carbohydrate, protein, and lipid) (Vavilin et al., 2008; Ariunbaatar et al., 2014). In addition, thermal and chemical pretreatment was not appropriate for pretreating slaughterhouse waste due to the highly biodegradable nature of the substrate. In contrast, Salminen et al. (2003) reported a significant improvement in chemical oxygen demand (COD) solubilization of meat waste after chemical, ultrasonic, and low thermal pretreatment. However, the study showed mixed results as some of the meat industrial effluents showed improved biodegradability after pretreatment and others showed reduced biodegradability due to the intermediate formation of inhibitory compounds, which require further treatment. Ratanatamskul et al. (2015) ran an on-site single-stage anaerobic digester for biogas production. An experiment conducted for different hydraulic retention time (HRT) and OLR was carried out to determine its effect. At minimal HRT of 19 days, maximum biogas production was achieved with a 70% reduction in total volatile solids (Ratanatamskul et al., 2015). Grimberg et al. (2015) compared a pilot-scale study for mesophilic digestion with single- and two-stage

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Food Waste to Valuable Resources

reactors for kitchen waste. The study showed that two-stage mesophilic digestion performed better for methane production than a single-stage digester (Grimberg et al., 2015). Similarly, Kim et al. (2014b) investigated the utilization of FW leachate as the substrate in a two-phase anaerobic digester and achieved a maximum methane yield of 0.85 Nm3/kg of reduced VS. Ahamed et al. (2015) conducted a study on a multiphased anaerobic baffled pilot-scale reactor (MP-ABR) with FW as the substrate to produce biogas. In this study, the authors achieved a biogas yield of 215.57 mL/g VS removed per day (Kim et al., 2014b; Ahamed et al., 2015).

2.3

Factors affecting anaerobic digestion of food waste

A number of environmental factors are known to influence AD, through improving or obstructing operational parameters such as growth of microbes, death rate, biogas generation, utilization of substrate, and start-up. These factors could significantly improve biomethane production (Fig. 2.3). Some of these factors are described below.

2.3.1 pH pH is an important parameter to be optimized in an anaerobic digester and its value and stability are essential because methanogenic processes continue at a considerable extent only at a neutral range of pH. The AD process deteriorates at elevated (values greater than 8.2) and lower pHs (values below 6.5). The efficient methanogenic microbes are active at pH ranges from 7.2 to 8.5. A pH value of 5.5 was found to hinder methane generation in reactors. This could be due to VFA accumulation in the reactors. Lower pH and extreme generation and accumulation of VFA lead to displacement of the neutral pH
carbonate buffer system and methanogenic activity. Operational parameters such as pH also affect methane production. At pH 7, methane production is improved compared to pH 8, at the same time applying thermal pretreatment improves hydrogen production by restricting methane fermentation. Due to this methane yield dropped to 0.385 from 0.446 Nm3/kg VS.

2.3.2 Temperature To ensure maximum growth of methanogens in reactors it is necessary to maintain optimum temperature conditions. Temperature ranges of 25 C
450 C, that is mesophilic temperature, are normally maintained in AD systems as the presence of the thermophilic microbial population is greatly reduced. The optimum range of temperature for AD is 30 C
400 C and when the employed temperature is below or above this optimal level, the AD process is hindered for each level of decrement in temperature. The biodegradation potential of AD is reported to be higher in thermophilic conditions as compared to mesophilic conditions. The benefits of thermophilic AD are improved destruction of FIGURE 2.3 Factors affecting the anaerobic process.

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pathogenic microbes and enhanced substrate biodegradation. Methanogenic bacteria are more highly sensitive to alterations in temperature than other microbes. AD is usually inappropriate for diluted wastewater treatment and at lower temperatures.

2.3.3 Hydraulic retention time HRT is one of the most important processing parameters affecting the process efficiency. Shi et al. (2017) showed that stable performance occurred at higher HRT than lower HRT; however, reduced methane yield was reported in this study at increasing HRT due to substrate reduction. Lafitte-Trouque´ and Forster (2000) conducted an experiment on a two-stage anaerobic codigester with confectionery waste combined with sewage sludge. The study showed maximum performance at 12 days HRT, which produced a better specific methane yield as 82% in biogas. Reduced HRT leads to a reduction in methane formation due to less methanogenic bacteria. In a single-stage digester system less than 20 days of HRT washed out methanogenic bacteria, reducing methane yield. Liu et al. (2018) stated that higher HRT at the initial stage accelerated the microorganism activity and produced a better biogas yield. At the same time, excess HRT could adversely affect the system due to a reduction in the microorganism population in the reactor concentration. This study also stated that higher HRT produced higher VFA and ammonic nitrogen which accumulated in the system, and which could affect the reactor performance. Shorter HRT reduces the production of methane as the growth of methanogenic bacteria was affected (Lafitte-Trouque´ and Forster, 2000; Hawkes et al., 2007; Shi et al., 2017; Liu et al., 2018). Many studies have reported that by maintaining HRT between 2 and 10 h methane production was controlled significantly. However, optimal HRT can be defined only based on the substrate composition, OLR, reactor type, and the type of microorganism employed. Thus, HRT needs to be carefully maintained based on the specific conditions.

2.3.4 Organic loading rate OLR is organic dry solids fed to a digester per day per unit volume of the digester. It is a critical parameter that when exceeding the limit leads to the accumulation of fatty acids and other inhibitory compounds. Accumulation of these compounds suppresses methane production, as the acidic nature harms methanogenic bacteria. Thus, OLR directly affects the methane production rate, which needs to be optimized for better production (Pramanik et al., 2019). Several studies have been conducted for determining the effect of OLR. Liu et al. (2017) studied the effect of OLR in both mesophilic and thermophilic digestion of FW. The study revealed that the optimal OLR for mesophilic digestion was 1.5 g VS/L/day, whereas for thermophilic digestion, the optimal OLR was found to be 2.5 g VS/L/day. Hu et al. (2018) ran a self-agitated anaerobic digester both at mesophilic and thermophilic conditions. In this study, the authors found that the optimal OLR for thermophilic digestion lies in the range of 3.0
14.4 kg COD/m3/day, whereas for mesophilic digestion it lies in the range of 3.0
7.3 kg COD/m3/day. Leung and Wang (2016) investigated the effect of different OLRs on digestion. The authors reported that at high OLR with short HRT, methane production was reduced greatly. This could be due to washout of excess biomass from the system.

2.3.5 Micronutrients Micronutrients are the essential elements required for an effective AD process which may alter environmental conditions and affect the functions of the enzyme system of anaerobic microbes, leading to a digester failure. Trace elements such as nickel (Ni), iron (Fe), cobalt (Co), tungsten (W), molybdenum (Mo), and selenium (Se) enhance the growth and activity of methanogenic bacteria, whereas copper (Cu), manganese (Mn), and zinc (Zn) affect the hydrolysis of bacteria. For example, the excess accumulation of VFAs and ammonia reduces the oxidative potential, causing system failure. In general, micronutrients are severely reduced in FW and can be added through animal manure or sewage sludge (Xu et al., 2018). Thus, micronutrients need to be added manually if FW is used as the sole substrate. Ni, Co, and Fe are the cofactors of carbon monoxide dehydrogenase enzyme, whereas Ni is also needed for activity of enzymes such as methyltransferases and hydrogenases. Thus, these micronutrients are required for the growth and activity of both fermentative and methanogenic microorganisms (Karlsson et al., 2012). Similarly, Mo improves reactor performance, while the addition of Co, Ni, Fe, and Se reduces hydrogen sulfite in biogas and oxidizes propionate. In addition, Se also promotes the syntrophic hydrogenotrophic methanogenesis process (Banks et al., 2012; Zhang et al., 2012). Studies also show that the addition of these trace elements improves biogas production potential and reduces the accumulation of VFA (Xu et al., 2018).

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Food Waste to Valuable Resources

2.3.6 Foaming Substrate surfactants, liquids, and biogas produced in the digester produce foaming in AD, which traps biogas and disperses it into the liquid. Thus, biogas keeps accumulating within the system, reducing the volume of the digester and energy production, and also blocking gas pipes. Thus, it affects the overall process flow and leads to overflow of effluent (Xu et al., 2018). Fatty acids, proteins, and detergents are commonly found compounds responsible for foaming Lindorfer and Demmig (2016) reported that the presence of compounds such as antibiotics, ammonia, heavy metals, mycotoxins, and limonene also form foam in AD. Rasi et al. (2007) reported that foaming can also be caused by CO2, which is a part of biogas. Carbon dioxide dissolves in the liquid medium to form carbonic acid and HCO3, which alter the system conditions, such as temperature rise and a reduction in pH, and favors foaming (Rasi et al., 2007; Subramanian et al., 2015; Lindorfer and Demmig, 2016). In order to control foaming, antifoam chemical agents are generally used. Chemicals such as natural oil, salts, silicone, esters, and long-chain fatty acids are used as antifoam chemical compounds (Kougias et al., 2014; Lindorfer and Demmig, 2016). Among these, vegetable oils and biodiesel are economically viable options to be used as antifoaming agents. Kougias et al. (2014) showed that rapeseed oil and octanoic acid are more effective than tributylphosphate at both batch and continuous modes of digestion. The study also proposed that, if the foaming occurs over the long term, then the dosage of these antifoaming agents must be increased from time to time during operation of the digester. As a result, microorganisms in the digester will adapt to this agent. When these agents are added in excess, it may upset the digester performance both economically and operationally. This can be nullified by systematic application of different antifoams, such as vegetable oil and commercially available antifoams (Lindorfer and Demmig, 2016). In general, the literature suggests that foaming can be controlled by following practices other than applying antifoam agents. These include avoiding foam-causing substrates, effective process control, altering the physical and chemical conditions of the process, optimization of mixing pattern, and installing additional equipment for foam control. Similarly, overfeeding also causes foaming where the OLR of these substrates needs to be reduced. In addition, the hydrolysis technique can be adopted before or after AD to avoid foaming. This technique includes acid hydrolysis, alkaline hydrolysis, and enzymatic hydrolysis, of which, enzymatic hydrolysis is considered to be the better option for lipid0based foaming problems by degrading lipid.

2.4

Process configuration

Process configuration plays a vital role in defining the methane production efficiency of the digestion system. The various process configurations such as single-, two-, and multistage digestion are discussed next.

2.4.1 Single-stage digestion Single-stage AD is a commonly adopted technique where anaerobic processes such as hydrolysis, acidogenesis, acetogenesis, and methanogenesis occur in a single reactor (Uc¸kun Kiran et al., 2014). Around 95% of full-scale plants functioning in Europe are single-stage anaerobic processes for treating organic waste (Nagao et al., 2012). It is a simple reactor setup which requires lower investment and minimum maintenance cost, and also faces a lower number of failures compared to other systems (Forster-Carneiro et al., 2008). A single-stage anaerobic system has a number of other advantages such as low retention time and OLR (Xu et al., 2018). In general, a single-stage system can be classified into two types, dry AD and wet AD, based on the substrate composition. In dry-type digestion, the water content of the substrate must be less than 12% of its total solid content. Studies state that wet AD has better methane production and better VS reduction than dry-type AD due to the accumulation of VFA in dry-type digestion (Nagao et al., 2012). Due to the presence of acidogenic microorganisms the pH level decreases suddenly, which affects the methanogenic process (Pramanik et al., 2019). El-Mashad et al. (2008) noted that the accumulation of VFA in the digester lowers the pH and reduces methane production. By optimizing these factors methane production efficiencies can be improved (Lee et al., 1999; Deepanraj et al., 2014). Xiao et al. (2018a) compared the performances of single- and two-stage thermophilic AD. The result shows that single-stage thermophilic AD performed better than two-stage thermophilic AD in the aspect of energy recovery. As different kinds of microorganism are produced in a single chamber, the growth rate difference between acid and methane formers may change the reactor volume and lead to system failure, which may be overcome by operating the reactor at lower HRT and OLR (Cohen et al., 1979; Horan, 2018).

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2.4.2 Two-stage digestion In two-stage AD, two separate reactors are used for the production of hydrogen and methane. The first reactor mainly contains acidogens and hydrogen-producing microorganisms, employed to use hydrolysis, acidogenesis, and acetogenesis to produce hydrogen and VFAs. The second reactor is mainly employed for the methanogenic process where slowly growing acetogens and methanogens are enriched, converting VFAs into methane and carbon dioxide (Chu et al., 2008; Uc¸kun Kiran et al., 2014). Two-stage digestion has several advantages, including higher methane production, better stability, higher volatile solid removal efficiency, and higher OLR. At the same time, it requires higher capital investment, and high operational and maintenance costs are disadvantages of the system. Xu et al. (2018) showed that at lower HRT (2
3 days), acidification pH (5.5
6.5) need to be maintained, whereas during the application of higher HRT (20
30 days) pH need to be maintained at 6
8 to enrich methanogenic bacteria (Xu et al., 2018). In contrast to the findings of Xiao et al. (2018a) as discussed in Section 2.4.1, Micolucci et al. (2014) reported that two-stage thermophilic AD resulted in higher biogas production, organic matter reduction, and volatile solid reduction using FW as a substrate than single-stage thermophilic AD. Park et al. (2008) conducted experiments on both singleand two-stage thermophilic systems with synthetic kitchen waste as substrate, where the single-stage thermophilic system was highly fluctuated at propionate concentrations due to an unstable digestion process whereas the two-stage thermophilic system showed stable performance (Park et al., 2008). Massanet-Nicolau et al. (2013) compared the biogas production potential of both single- and two-stage digestion using FW as substrate. The authors reported that two-stage fermentation achieved 37% higher methane yield than single-stage fermentation at shorter HRT and higher loading rates. Similar results were also obtained by Lee and Chung (2010) during the operation of two-stage digestion (Lee and Chung, 2010; Massanet-Nicolau et al., 2013).

2.4.3 Multistage digestion To reduce the acidification rate during FW digestion as it inhibits the methanogen process, multistage digestion was proposed, where hydrolysis, acid production, and methane production occurred in a different reactor (Grimberg et al., 2015). Thermal phased AD systems are one such multistage system, where the thermophilic condition is maintained at stage I and the mesophilic condition is maintained at stage II. Wu et al. (2015) reported a multistage system treating oily FW and reported that the thermophilic temperature enhances hydrolysis as well as pasteurization of the substrate at stage I, similarly mesophilic condition maintained at stage II favors the methanogenic process (Wu et al., 2015). Yun et al. (2017) operated a multistage system and reported sulfidogenesis in an acidogenesis stage reactor where sulfate was reduced into H2S, as sulfate-reducing bacteria have greater tolerance of acidic conditions than methanogenic bacteria (Chen et al., 2008; Yun et al., 2017). Zhang et al. (2017a,b) fabricated a three-stage anaerobic digester. In this reactor, hydrolysis, acidogenic, and methanogenic processes occurred in separate reactors which were connected vertically. Due to vertical connection reactor setup the surface area was greatly reduced and flow occurred due to gravitational forces. This reactor paves the way for better optimization of process parameters. For example, the acidogenic process required a lower pH than the hydrolysis process possible in this reactor setup. In addition, Zhang et al. (2017a) reported that when OLR is increased in excess of 5 g VS/L, the single-stage AD faces process failure similarly to OLR in excess of 8 g VS/L affecting the performance of a two-stage system, whereas the three-stage system can handle OLR greater than 10 g VS/L. A maximum of 85% VS removal was achieved by this three-stage system (Zhang et al., 2017a,b). The literature also shows that around 20% energy improvement can be possible by adopting a multistage system rather than a single-stage system. Among the digesters, a three-stage reactor achieved a 50% improvement in methane production and threefold improvement in VS removal compared with a single-stage reactor. Based on these studies it can be concluded that the multistage system is more stable, and provides better degradation and methane production capacity when compared to a single-stage reactor system (Voelklein et al., 2016; Zhang et al., 2017b). In a multistage reactor, each chamber can be run based on the required optimal condition. The efficiency of the multistage reactor is mainly affected by pH, type of substrate, OLR, and other operational parameters (Voelklein et al., 2016; Yun et al., 2017). Paudel et al. (2017) reported that higher HRT could affect the substrate (carbon and hydrogen) degradation efficiency in multistage digestion. However, for lactate degradation, greater HRT is preferable. Lindner et al. (2016) reported that the pH is an important parameter that affects the substrate degradation rate and biogas production efficiency. Similarly, Voelklein et al. (2016) showed that OLR also affect substrate solubilization during multistage digestion. On the whole, by optimizing operational parameters as well as the choice of substrate, multistage systems perform better than singlestage systems. However, they need to be carefully selected to avoid additional energy wastage. Further studies need to be conducted to fine tune the system to make it suitable for different operating conditions as well as substrate (Grimberg et al., 2015; Lindner et al., 2016; Voelklein et al., 2016; Paudel et al., 2017).

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Food Waste to Valuable Resources

2.4.4 Codigestion Codigestion is a process which involves digestion of two mixed substrates simultaneously, which avoids the occurrence of backlogs due to monodigestion of FW (Shi et al., 2018). In codigestion, the additional capital investment for FW treatment can be eliminated. However, attention on the process control measures is essential to avoid a foaming problem. Codigestion has several advantages such as enhanced process stability, energy production, and useful end products, such as fertilizer (Tyagi et al., 2018). Transporting FW into the treatment facility adds additional cost (Mata-Alvarez et al., 2000). FW is highly biodegradable in nature and has a low buffer capacity and high C/N ratio, thus animal manure needs to be added to enhance the process dynamics as animal manure has a higher buffering capacity (Leung and Wang, 2016; Xu et al., 2018). Similarly, sewage sludge is also considered as a better cosubstrate due to its lower organic load and higher trace compounds. As sewage sludge is enriched with active microorganisms when added to FW for codigestion it accelerates methane production by up to 1.4 times greater than conventional digestion (Xu et al., 2018). Thus, codigestion is considered a viable opportunity for process enhancement without further investment.

2.5

Reactor configuration

Various reactor configurations have been tested for enhanced and economically feasible energy recovery. Parawira et al. (2005) conducted an experiment on two different reactor setups: integrated with an up-flow anaerobic sludge blanket (UASB) as a methanogenic reactor linked with a solid bed for hydrolysis (a hydrolysis reactor) and a solid-bed reactor (hydrolysis) linked with a packed biofilm reactor (a methanogenic reactor). In the packed bed biofilm reactor, wheat straw was used as a biofilm carrier for AD of solid potato waste. The result of this study showed that a packed biofilm reactor digests the substrate more efficiently when compared to the UASB. However, methane production in both reactors was similar (Parawira et al., 2005). A UASB is a widely used reactor setup. A UASB has a sludge blanket which contains microbial granules, where anaerobic microbes are immobilized. This immobilized anaerobic bacterial population degrades organic matter in the UASB. The UASB has the capacity to treat high-strength wastewater (e.g., food processing wastewater) and also works under high OLR. Packed bed reactors are another essential bioreactor for AD. They have advantages such as handling of high loading rate, immobilization of microbes (so that biomass washout can be prevented), and stable methanogenic activity (Kastner et al., 2012). Kastner et al. (2012) investigated AD in both a continuously stirred tank reactor and a fluidized bed reactor. A maximum of 670 normalized liters (NL) biogas/kg VS was achieved in the continuously stirred tank, whereas the fluidized bed reactor achieved 550 NL biogas/kg VS. In both reactors, methane covers 60% of the biogas, however, fluidized bed reactors showed better stability and performance when compared to continuously stirred tank reactors (Kastner et al., 2012). Koike et al. (2009) conducted a study on two-stage digestion treating FW and reported a biogas yield of 850 L/g VS biogas, of which 85% of the energy was valorized (Koike et al., 2009).

2.6

Hydrogen production: dark fermentation

Hydrogen is an eco-friendly, renewable energy which is an ideal choice for a sustainable fuel for future energy demand, thus attracting the researchers’ attention. Biologically hydrogen can be produced by several techniques, such as anaerobic fermentation, biophotolysis, photofermentation, or a combination of these process (Venkata Mohan, 2009; Dahiya et al., 2018). Hydrogen produced during the stages of acidogenesis and acetogenesis in AD was quickly converted into methane due to methanogenic bacteria in single-stage digestion reactors (Singh and Harvey, 2010; Sen et al., 2016). Similarly, in dark and photofermentation processes, hydrogen synthesis is carried out by the bacterial enzymes such as hydrogenase and nitrogenase. FW can be a suitable and feasible substrate for biohydrogen production. Dark fermentation is a biological process which uses anaerobic bacteria to biodegrade organic matter to produce mainly biohydrogen. As the name suggests, it is a light-independent process and requires less energy (Sreela-Or et al., 2011). Thus, it is a feasible process to produce biohydrogen (Wang and Wan, 2009). Studies have been conducted on the feasibility of the dark fermentation process using FW as a substrate to produce bioenergy. As FW is mainly composed of carbohydrate, it would be a suitable substrate to produce hydrogen using this process (Show et al., 2012). The efficiency of the dark fermentation process mainly depends on operational parameters such as pH, F/M ratio, and temperature. Optimization of these parameters would improve bioenergy production due to its effect on bacterial growth and enrichment in the reactor (Wongthanate and Chinnacotpong, 2005; Meher Kotay and Das, 2008). In dark fermentation, mixed cultures are recommended for the production of bioenergy. While adopting dark fermentation as a route to produce hydrogen, it also produces VFAs such as acetate, butyrate, lactate, malate, and

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alcohols such as butanediol, ethanol, and propanediol (Wei et al., 2010). Thus, the theoretical hydrogen yield differs based on the type of metabolic pathway that occurs and organic acid/alcohol retained in the fermentation, which may be a limiting factor for biohydrogen production or may be considered as an energy supply for this process (Falco and Basile, 2015). These by-products can be further utilized as a substrate for biomethane production based on their nature (Luo et al., 2011; Chu et al., 2012). In dark fermentation, microorganisms decompose and convert substrate into different types of fatty acids (Li and Fang, 2007; Abbasi et al., 2012a). The fermented effluent after dark fermentation cannot be disposed of into the environment without proper treatment as it has a high COD value. To eliminate this threat, studies have proposed utilizing acid-rich fermented effluent as substrate in the second-stage methane reactor (Cooney et al., 2007). Thus, two-stage fermentation is a better choice for substrate degradation when compared to single-stage digestion (Zong et al., 2009). In the two-stage fermentation process, the acidogenesis process produces hydrogen in the first stage and methanogenesis produces biomethane in the second stage. The produced carbon dioxide, VFAs, and some of the hydrogen in the acidogenesis process are further converted into methane in the second phase by methanogenesis. Thus, the main issue related to fermentative effluent can be rectified and further improves biogas yield and energy recovery (Nathao et al., 2013; Bolzonella et al., 2018). Two-stage fermentation is more eco-friendly as it emits much less carbon dioxide and carbon monoxide compounds (Luo et al., 2011). Fig. 2.4 illustrates the typical pathway of the dark fermentation process.

2.6.1 Biohydrogen production from food waste Various studies have been conducted on biohydrogen production from different types of FW such as vegetable waste (Venkata Mohan, 2009), FW (Sarkar and Mohan, 2016), and FW water. FW-based biohydrogen production has provided successful results in various studies including pilot-scale studies (Pasupuleti et al., 2014; Sarkar and Mohan, 2016; Chiranjeevi et al., 2018). Various studies on biohydrogen production from FW imply that dark fermentation is a possible route for sustainable biohydrogen production (Kim et al., 2008, 2009; Nazlina et al., 2009; Bundhoo, 2017; FIGURE 2.4 Typical fermentation.

pathway

of

dark

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Food Waste to Valuable Resources

Dinesh et al., 2018). The degradation pathways of cellulose, hemicelluloses, fat, and carbohydrates present in FW during biohydrogen production have been reported in the literature. Most studies reported that the carbohydrate degradation pathway through the acidogenesis and acetogenesis route is highly sensitive to environmental conditions including pH, temperature, inoculum sources, VFAs, and FW concentration (Ren et al., 2006; Vijayaraghavan et al., 2006). Pasupuleti et al. (2014) produced biohydrogen in a semipilot-scale bioreactor with FW as substrate. The authors were concerned that the hydrogen production efficiency was affected by acidification due to the accumulation of soluble metabolites. Yeshanew et al. (2016) studied a two-stage CSTR coupled with AFBR which showed better performance for hydrogen production (Pasupuleti et al., 2014; Yeshanew et al., 2016).

2.6.2 Biohydrogen production from food industry waste Food processing industries produce enormous amounts of wastewater and also fruit leftovers after processing. Generated wastewater contains similar characteristics to FW. It mainly consists of starch and sugar, which can be used as better sources of substrate for biohydrogen production (Van Ginkel et al., 2005). Fruit leftovers include mixed fruit peels, pineapple waste, orange peel, apple pomace, mango peel, and fully ripened fruits such as apples, pears, and grapes. Most of these are rich in sugar and can be utilized as a substrate for biohydrogen production (Vijayaraghavan et al., 2007; Doi et al., 2010; Feng et al., 2010). Hwang et al. (2011) conducted an experiment on a combined two-stage fermentation system to produce biohydrogen from fruit waste. They achieved a maximum hydrogen yield of 2.2 mol H2/mol glucose. Castello´ et al. (2009) investigated the performance of a UASB reactor in producing biohydrogen from cheese whey. Cheese whey, which mainly contains protein, increased the hydrogen yield to 122 mL H2/L media/day (Castello´ et al., 2009). Similarly, Davila-Vazquez et al. (2009) ran a two-stage fermentation with cheese whey as substrate and achieved a maximum hydrogen yield of 2.8 mol H2/mol (Davila-Vazquez et al., 2009). Oh and Logan (2005) investigated the possibility of hydrogen production through a microbial fuel cell from cereal wastewater and achieved a maximum of 0.79 mol H2/mol glucose (Oh and Logan, 2005). Ferchichi et al. (2005) investigated the biohydrogen production potential of cheese whey mediated by a monoculture bacterium, Clostridium saccharoperbutylacetonicum (Ferchichi et al., 2005).

2.7

Factors affecting biohydrogen production

Anaerobic fermentation-based hydrogen production depends on various process parameters such as pH, temperature, pretreatment techniques, reactor configuration, and feed composition. Mohd Yasin et al. (2011) investigated the influence of pH on hydrogen production and revealed that the batch hydrogen fermentation process was enhanced at pH 7, whereas the continuous mode was favored by a pH of 5.5 (Venetsaneas et al., 2009). Various factors affecting the process dynamics are discussed below.

2.7.1 Components/composition of food waste FW is a viable feedstock for biohydrogen production. It contains protein, carbohydrate, fat, cellulose, and hemicellulose in various ranges based on the type of food mixed, as shown in Fig. 2.5. The chemical composition of these components affects the substrate biodegradation rate and energy production. Fang et al. (2006) utilized rice slurry waste as substrate as it is rich in carbohydrate for biohydrogen production. They achieved a maximum biohydrogen production rate of 2.79 mmol H2/L/day. Among the various components of FW, carbohydrate favors biohydrogen production. However, numerous studies have also investigated the possibility of utilizing FW substrate rich in protein, fat, and cellulose (Lay et al., 2003; Fang et al., 2006; Lee et al., 2010a). Lee et al. (2008) utilized vegetable kitchen waste as substrate rich in cellulose for hydrogen production and achieved a maximum yield of 18.4 mmol H2/L/day. Compared to carbohydrate, protein and lipid are difficult to hydrolyze. The rate of hydrolysis determines the production rate of biohydrogen from feedstock. In this context, hydrogen is difficult to harvest from protein and lipids. Lay et al. (2003) proved the biohydrogen production potential of substrate rich in carbohydrate. They found that substrate rich in carbohydrate yielded 20 times greater biohydrogen when compared to substrate rich in lipids. During anaerobic fermentation lipids cause flotation and clogging problems. Vidal et al. (2000) found that biohydrogen production from lipid-rich substrate was slower as compared to carbohydrate-rich substrate. In addition, VFA accumulated along with biohydrogen greatly decreased the medium pH, thus optimization played a major role in hydrogen synthesis from lipid-rich feedstock. FW such as cheese, fish, meat, chicken, and eggs contains protein as a main ingredient.

Valorization of food waste for biogas, biohydrogen, and biohythane generation Chapter | 2

25

FIGURE 2.5 Main components and properties of food waste.

FIGURE 2.6 Valorization pathway of food waste for the circular economy.

During the anaerobic fermentation process, proteins converted into polypeptides and amino acids, where amino acids were further biodegraded into VFA, CO, hydrogen, ammonia, and sulfur. The biodegradation rate of protein is also very low and incomplete compared to carbohydrate and lipid (Vidal et al., 2000; Lay et al., 2003). Thus, protein-rich substrate can be added along with other compounds for biohydrogen production rather than a single substrate. Cellulose and lignocelluloses are commonly found compounds in fruits and vegetables. Fruits such as jackfruit peels, apple waste, and pineapple waste contain cellulosic compounds, which can be successfully used as a feedstock for biohydrogen production (Vijayaraghavan et al., 2006; Wang et al., 2006; Hwang et al., 2011). Cellulose- and lignocellulose-rich compounds give varying results in biohydrogen production. Lee et al. (2008) proposed that cellulose is difficult to use in the production of hydrogen biologically due to its rigid structure which can be overcome by applying physical or chemical pretreatment (Levin et al., 2009) (Fig. 2.6).

2.7.2 Pretreatments Pretreatment of substrate is an essential parameter that influences the biohydrogen production potential. Lee and Chung (2010) proposed that hydrolysis of substrate through pretreatment resulted in enhanced biohydrogen production. Kim et al. (2005) confirmed that thermal, enzymatic, and a combination of these pretreatments improve COD solubilization of substrate and in turn enhance biohydrogen production. Among these, combined thermal enzymatic treatment showed

26

Food Waste to Valuable Resources

a better performance. Elbeshbishy et al. (2011) showed that ultrasound pretreatment of FW produced a better hydrogen production rate than acid and alkali pretreatment. In contrast, Bundhoo (2017) reported ultrasonic pretreatment as less favorable as it resulted in less solubilization and reduced biohydrogen yield. An analogous result was reported by Wongthanate et al. (2014). However, when sonication was combined with other pretreatments, such as acid, it showed positive results as it enhanced biohydrogen production efficiently. Other pretreatments, such as thermal or alkali, can be adopted for enhancement of the process as several studies confirm that hydrogen production is effectively enhanced after these pretreatments. Kim et al. (2009) proposed that pretreatment favors the microbial population rather than an improvement in process enhancement. Hydrothermal pretreatment is another technique where complex compounds are converted into simple sugars. Ding et al. (2017) reported that thermal pretreatment of FW at 140 C for 20 min improved the solubilization of carbohydrates and proteins, which in turn enhanced the two-stage fermentation of hydrogen and methane production. Acid and alkali pretreatment techniques are mainly adopted due to their easy operation and nonrequirement for additional equipment. In acid pretreatment, acids such as hydrochloric acid (HCl), sulfuric acid (H2SO4), and acetic acid (CH3COOH) are mainly employed, whereas in alkali pretreatment, aqueous ammonia (NH3  H2O), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide [Ca(OH)2], and magnesium hydroxide [Mg(OH)2] are employed to increase the efficiency of hydrogen production (Zhao et al., 2011). Among these, NaOH possesses the maximum efficiency, followed by KOH. However, increasing the concentration of Na and K ions may suppress anaerobic fermentation (Vavouraki et al., 2014). Zhao et al. (2011) investigated alkali pretreatment potential on FW. In their study, they performed alkali pretreatment at pH 13 on kitchen FW, which increases the solubilization of carbohydrate, SCOD, protein, and lipid and achieved 283%, 108%, 203%, and 259% increments, respectively, over controls. Similarly, the hydrogen production rate increases dramatically after the pretreatment at 105.38 mL/g VS, which is 2.66 times greater than controls. This study also investigated acetic acid pretreatment and reported that 87%, 79%, 41%, and 135% increments in solubilization of carbohydrate, SCOD, protein, and lipid were achieved over controls. Jang et al. (2015) showed a maximum hydrogen yield after alkali pretreatment under a pH range of 11
12. Vavouraki et al. (2014) found that the concentration of soluble sugars increased to 120% compared with a nonpretreated sample while using 1.12% HCl for a treatment time of 94 min. Kim et al. (2005) showed that the VFA fraction increased from 6.3% to 7.9% in the combined pretreatment. Enzymatic pretreatment improves VFA production during fermentation, which improved the process by more than 320% compared with the control. Studies agree that hydrolysis of FW with acidic pretreatment at pH 2 would improve hydrogen production threefold compared with a control (Kim et al., 2014a). Both acidic and alkali pretreatments possess greater advantages, however sometimes these pretreatments are considered uneconomical due to the higher chemical requirement during the pretreatment and for neutralizing (Vavouraki et al., 2014; Jang et al., 2015; Jarunglumlert et al., 2018).

2.7.3 Volatile fatty acids An anaerobic process produces a number of intermediate compounds. These intermediate compounds include propionic acid, acetic acid, lactic acid, and butyric acid (Ren et al., 2006; Kim et al., 2008). VFAs are short-chain fatty acids such as acetic acid, propionic acid, butyric acid, and valeric acid, which are the primary compounds produced during AD of FW (Zhang et al., 2014). Studies have highlighted that alkalinity, VFA, CO2, and bicarbonate (HCO3) production during AD affect hydrogen production. By controlling the VFA and HCO3 concentrations, the system pH can be adjusted to the optimum value for effective biohydrogen production (Krishna and Kalamdhad, 2014). For effective hydrogen production, VFA and HCO3 ratios can be maintained as 1:1 (Appels et al., 2008). Xu et al. (2014) investigated the anaerobic fermentation of kitchen waste as a substrate and achieved VFA production of 5800
6900 mg/L. Shi et al. (2018) conducted a similar experiment with FW and wheat straw as the substrate and achieved comparable results (Xu et al., 2014; Shi et al., 2018). When FW degradation is conducted at room temperature, lactic acid bacteria are formed which reduce the hydrogen yield (Jo et al., 2007; Kim et al., 2009). Heat with chemical pretreatment has been applied to eliminate hydrogen-consuming bacteria (Valdez-Vazquez et al., 2005; Kim et al., 2009). The controlled environmental conditions further enhance the process and suppress lactic and propionic acid production in FW and food processing waste fermentation.

2.8

Biohythane production from food waste

Hydrogen and methane are commonly harvested as energy from waste. Each has its advantages. Hydrogen is an ecofriendly and clean fuel which produces water while combusting, making it a carbon-free fuel. The downside is that currently employed processes are costly. Methane, on the other hand, is widely used as natural gas and is also a clean

Valorization of food waste for biogas, biohydrogen, and biohythane generation Chapter | 2

27

energy compared with gasoline or diesel (Liu et al., 2013). During combustion, methane undergoes complex reactions resulting in carbon dioxide, and methane itself is the main contributor to global warming. It also has several shortcomings such as constricted flaming range, slow burning speed, and poor combustion efficiency (Sen et al., 2016; David et al., 2019). As a whole methane and hydrogen have limitations such as the reactive and flammable nature of hydrogen causing storage issues, whereas methane has low flammability (Dahiya et al., 2018). These shortcomings have turned research focus to the combined possibility of hydrogen and methane, biohythane. In the AD process, hydrogen evolves at the fermentation and acetogenesis stage, and is further converted into methane during the methanogenesis process (Chinellato et al., 2013). To obtain both methane and hydrogen through an anaerobic process a two-phase AD proposed (Chinellato et al., 2013). By blending a small amount of hydrogen into methane the combustion rate is improved and the efficiency of vehicles increased. Combining methane and hydrogen in the ratio of 1:4 produces a new fuel called hythane. Hythane normally consists of 5%
10% hydrogen, 50%
65%, methane and 30%
40% carbon dioxide (Dahiya et al., 2018). Biohythane is a newly emerging eco-friendly fuel which has good calorific value (Pasupuleti and Venkata Mohan, 2015; Sen et al., 2016; Kumari and Das, 2019). Due to the advantages of biohythane, commercial firms such as Volvo, Fiat, and others have shown a great deal of interest in utilizing hythane as a fuel in vehicles (Liu et al., 2013; Yeshanew et al., 2016). Some of the highlighted characteristics of biohythane are higher fuel efficiency, lower energy to ignite the engine, and better heat efficiency, making this fuel industry friendly (Mamimin et al., 2015; Roy and Das, 2016; Yeshanew et al., 2016). Industrial-based biohythane production relies on hydrogen and methane production. Industrial-grade hydrogen and methane production depend upon physical or chemical approaches which restrict the original positivity toward this energy. To achieve the truly green value of these energies, biological-based approaches are possible options which help to build a green economy around biohythane. The biological-based production process of biohythane is an energyefficient one, as it is mainly produced through the AD process, especially the two-stage anaerobic process. FW as a source for this production makes this fuel more affordable, further eliminating environmental issues (Cavinato et al., 2009, 2012; Banks et al., 2010). By controlling the processing parameters, biohythane can be generated efficiently. The ratio between hydrogen and methane can be modified by changing the microbial fermentation conditions.

2.8.1 Process description Integrating both biohydrogen and biomethane production provides an opportunity to generate biohythane. An economy based on biohythane shows a positive business model, however further studies are needed to optimize the process effectively. Here we summarize the optimal working process to effectively generate biohythane. The anaerobic methane fermentation process includes hydrolysis, acidogenesis, acidogenesis, and methanogenesis steps. In the methanogenesis process, some of the bacteria convert acetic acid to methane, whereas others convert carbon dioxide and hydrogen into methane. To obtain hydrogen from this process, conversion of methane from hydrogen alone needs to be restricted, whereas conversion of acetic acid to methane is allowed (Liu et al., 2013). In anaerobic digestors, the buffering capacity is very important. Shock loadings may result in acidogenesis which produces a high quantity of acid intermediates which in turn reduce the pH level of the reactor beyond the tolerant limit of methanogenic bacteria (Sen et al., 2016). However, this may favor a higher hydrogen yield (Lee et al., 2008). The traditional single-stage reactor setup is not favorable for biohythane production. The two-stage process is a modern option for the production of both biomethane and biohydrogen by changing the native pathway rather than the conventional single-stage process. As both of these fuels can be produced in this process, improved energy recovery can be possible compared with the conventional process (Siddiqui et al., 2011). The advantages of two-stage fermentation are: (1) the two-stage process improves complex biomass fermentation and produces better VFAs, which positively affect methane production (Ueno et al., 2007); (2) improved net energy for both hydrogen and methane than a single-stage system (Ruggeri et al., 2010; Perera et al., 2012); (3) as the methanogenesis process occurs in a separate stage the required microbes can be enriched (Cooney et al., 2007); (4) the overall fermentation time is greatly reduced as the hydrogenogenesis retention time is shorter than with methanogenesis which enables a stable operation and higher OLR (Ueno et al., 2007); and (5) a two-stage process also gives the possibility to optimize both processes (methane fermentation and hydrogen fermentation) independently. For example, better methane yield is reported at mesophilic conditions, whereas thermophilic conditions favor hydrogen production. In a single-stage system the temperature cannot be adopted separately, whereas it is possible in this two-stage process (Koutrouli et al., 2009; Micolucci et al., 2014). Micolucci et al. (2014) reported on a two-stage pilot-scale thermophilic anaerobic digester using FW as a substrate which aimed to run for 310 days to harvest biohythane. In this study the obtained biohythane had a

28

Food Waste to Valuable Resources

gas mix of 58% methane and 7% hydrogen. The reactor produced 0.69 m3 biogas/kg TVS as an average specific gas production and the achieved gas production rate was 2.78 m3/m3 day.

2.9

Enhancement strategies of biohythane production

Based on the above understanding, a two-stage fermentation process was recommended over traditional single-stage digestion. By controlling the H2/CH4 ratio, biohythane can be produced effectively. Biohythane production can be significantly improved by providing optimized conditions for hydrogen and methane such as pH, HRT, temperature, type of reactor, and pretreatment technique (Cavinato et al., 2016; Roy and Das, 2016). Bong et al. (2018) highlighted that thermal pretreatments which involve heating of substrates to more than 120 C for the treatment period of 30 min, improved process efficiency, particularly for FW containing lignocelluloses as substrate. Youn and Shin (2005) investigated a two-stage thermophilic process and obtained a hydrogen yield of 2.4 mol H2/mol hexose and biogas yield of 0.24 L/g VS, which contains 68% methane. A total net energy of 826 MJ/ton of FW was achieved with 70.5% as methane and 9.3% as hydrogen (Youn and Shin, 2005). Some studies recommend pH optimization by the addition of reagents which would improve the production effectively. However, the main drawback of maintaining optimal pH is the chemical cost associated with pH adjustment. Therefore recirculation of methanogenic effluent is carried out to maintain the optimal pH and to reduce the operational cost. Bacterial inoculum is another important parameter needing optimization. Among pure and mixed cultures, a mixed culture is normally recommended as diverse microbial communities can adopt different operational conditions than a pure one (Ghimire et al., 2015).

2.10

Applications of biohythane

Biohythane is a promising future fuel with a number of environmental benefits such as lower CO2 equivalent and NOx emissions and carbon-free nature. Biohythane, a combined fuel originating from methane and hydrogen, has better performance in internal combustion engines, eco-friendly nature, heat efficiency, and easy ignition and better burning. Biohythane burn expand time on stable combustion, which make this fuel a more attractive alternative for the automotive sector (De Simio et al., 2016). Hythane can be utilized for electrical energy as well as vehicle fuel, and has several field-scale productions, such as concept hythane vehicles developed by Toyota, Volvo, and Fiat. Another main advantage is that hythane can be easily used in currently available engines with only minor modification in combustion control (Falco and Basile, 2015; Bolzonella et al., 2018). Emission studies also show that when comparing hythane and diesel combustion processes, hythane-powered engines produce a very minimal amount of particulate matter compared with diesel engines, and does not produce harmful compounds like sulfur and benzene. As hythane contains less carbon than fossil fuels, it has lower CO2 emissions. Genovese and Ortenzi (2016) highlighted that average CO2 emissions from combustion decreased from 3.2 kg CO2/kg diesel fuel combustion to 2.8 kg CO2/kg fuel. The Montreal Hythane Bus Project used hythane with 10% hydrogen and showed a greater decrement (45%) in NOx emissions than methanepowered vehicles. A similar project was conducted by SunLine Transit Agency, California, on hythane with 20% hydrogen which emitted 50% less NOx than a methane-powered vehicle. ENEA, Italy, tested a hythane-powered bus with varying concentrations of up to 25%. The results of this experiment showed that an increase in the percentage of hydrogen resulted in a decrease in NOx and CO emissions. Fiat introduced a model vehicle named the Fiat Panda Aria that has a twin-cylinder engine which can use hythane for combustion. It uses a hythane mix consisting of 30% hydrogen, and emits 69 g/km of CO2. Based on various studies, it has been highlighted that some limitations need to be answered for a better hythane-based economy (Bolzonella et al., 2018). In the automobile sector, over the last two decades, hydrogen-based commercial vehicles have failed to be commercialized due to number of limitations. One of the major problems associated with hydrogen is the distribution system. A normal gas pipeline cannot be adopted, requiring some modifications such as using steel for the distribution system which is less prone to hydrogen. However, modifications to existing systems require higher capital investment and a period of time for construction (Xiao et al., 2018b), in which time hythane should become a more suitable alternative. Biohythane can be used as a liquid fuel or a value-added product. Patel et al. (2017) examined the production of methanol from biohythane through adsorption and covalent immobilization methods on solid support. The results showed that methanol production was increased by almost 200% compared with production from methane as a feedstock, due to the presence of hydrogen in hythane (Patel et al., 2017). This study also showed the possible production of polyhydroxyalkanoates from biohythane (Basset et al., 2016; Revelles et al., 2016). Thus, biohythane can be directly used as a fuel in the automobile industry and also as a feedstock to produce value-added products.

Valorization of food waste for biogas, biohydrogen, and biohythane generation Chapter | 2

2.11

29

Challenges in the commercialization of biofuel from food waste

Studies clearly show that bioenergy can be harvested from FW using the available techniques. Table 2.1 shows bioenergy produced using various treatment techniques. However, some challenges need to be addressed to make them available to the commercial market. Based on currently available techniques, fuel produced from waste is not as costeffective as fossil fuels (Lee et al., 2019). While waste to energy techniques reduce overall environmental pollution by switching over from landfill disposal to energy recovery, the processing of waste to energy may lead to the emission of some toxic gases into the atmosphere. Toxic compounds such as lead, mercury, polychlorinated dioxins, and cadmium are emitted into the environment due to improper operation of systems for the generation of electricity (Ruth, 1998). However, other conversion techniques, such as controlling equipment, may provide a solution to this problem. The mission of these toxic gases needs to be considered when selecting waste-to-bioenergy technology along with the efficiency of the system. AD could be a better option for this problem. Current studies do not provide much knowledge about enzymes and microbes in this process, and this also applies to micronutrients and how their quantity affects microbes in the system. This creates a problem when scaling up these processes to an industrial level. There is a significant difference between lab-scale and large-scale studies, which needs to be rectified (Waqas et al., 2018). Similarly, in a lab-scale environment, an operational parameter such as pH can be accurately controlled whereas, in large-scale field applications, it can vary during the daily process, leading to a lethal environment for the microbes present in the system (Amanullah et al., 2001). When scaling up, technological gaps might lead to less process control and poor output (Moon et al., 2009). Several pilot-scale studies have been conducted to harvest bioenergy from FW. These studies have indicated that the combined production of hydrogen and methane is a more suitable option than the production of methane alone from an economical point of view (Wang and Cai Zhao, 2009; Ratanatamskul et al., 2015). Thus, this needs to be rectified to enable successful commercialization. Several full-scale industries set up in Indian have also proved the feasibility of this system. A waste to energy project initiated in Tamil Nadu, India, produces 15 MW power at an estimated cost of $37.5 million (Singh et al., 2011). Similarly, a biogas plant erected in Madhya Pradesh, India, produces 34,000 m3 biogas/day from waste materials at an estimated cost of $325,000. The important merit of this system is that is requires has lower investment ($500 per kW) and operational costs ($0.1 per kWh) compared with traditional waste disposal units. Further studies would reduce the overall process cost and also improve the efficiency of the system while reducing the environmental pollution load (Dinesh et al., 2018). Developing Asian countries like India and China have adopted anaerobic techniques in various mode including pilot-scale and full-scale plants for household and commercial FW. Reports have also shown that most of these plants lack appropriate functioning due to technical failures, improper operations, or management constraints (Mu¨ller, 2007).

2.12

Future perspectives

This chapter highlights possible methods of valorizing FW into bioenergy. Studies clearly show that FW is a viable substrate to produce bioenergy with several techniques such as AD and dark fermentation. However, further studies are needed to make this process more commercially viable (Ma et al., 2018). As FW is an organic matter with varying composition due to the source, geological location, and season, the degradation rate may differ for different FW. Thus, a common pretreatment would be impractical due to the heterogeneous composition of FW pretreatment optimization (Parthiba Karthikeyan et al., 2018). Many reports have suggested that recommended operational conditions and pretreatment could enhance the process. To make this process more practical, investigations need to be conducted into both batch and continuous flow reactors. Second, impurities such as nondegradable organic content which are commonly found in FW have been scarcely reported in the literature to date (Ma et al., 2018). The influence of these crabs inprocess dynamic need to be studied before moving toward full-scale commercial setup which would avoid the instability of reactors and favor an optimal bioprocess. Studies have shown that carbon storage is an important issue in AD and dark fermentation of FW. Moisture removal or freezing would rectify this problem as reported in lab studies. However, pilot-scale tests need to be conducted to evaluate its efficiency (Parthiba Karthikeyan et al., 2018). The construction costs of reactors used for valorization of FW to recover bioenergy are one of the most important problems that need to be addressed. Sen et al. (2016) suggest that small-scale AD systems could be installed in buildings rather than a largescale centralized system, as this would reduce transportation costs and the initial investment needed to start up the process. Based on the reported studies it is noted that the quantity and quality of the end product may differ due to process conditions (Curry and Pillay, 2012; Sen et al., 2016). Therefore many pilots and full-scale studies need to be conducted to better understand the system (Xu et al., 2018).

TABLE 2.1 Biohydrogen and biomethane recovery potential of various reactor setup potential food wastes as substrate. Type of waste

Technique used

Hydrogen yield

Setup type for hydrogen production

Methane yield

Setup type for methane production

Main observation

References

Food waste

Anaerobic digestion (BMP test)

NA

NA

114 mL/g TCODsub

Batch reactor

Preincubated inoculum reduces methane production

Elbeshbishy et al. (2012)

Food waste from canteen

Anaerobic fermentation

69.95 mmol

Bench-scale anaerobic sequencing batch reactor

NA

NA

Substrate load and operational condition affect the production rate

Reddy et al. (2011)

Food waste

Anaerobic process

310 mL/g VS

Leaching bed reactor

210 mL/g VS

UASB

Sequential batch mode would be a better option for environmental factor optimization for hydrogen fermentation

Han and Shin (2004)

Cheese whey

Two-stage anaerobic process

106 mL/g COD

CSTR

310 mL/g COD

Periodic anaerobic baffled reactor

Indigenous microorganisms present in whey wastewater are able to ferment hydrogen, eliminating the requirement for additional inoculum

Antonopoulou et al. (2008)

Vegetable waste

Dark fermentation

85.65 mL/g VS

Batch reactor

NA

NA

Rahnella sp. 10 shows a better hydrogen production rate on both xylose and cellobiose

Marone et al. (2012)

Food waste

Anaerobic digestion

NA

NA

494 mL/g VS

CSTR

Hydrogenotrophic methanogens are mainly found in the system

Jo et al. (2018)

Municipal food waste with kitchen wastewater

Dark fermentation

245 mL/g COD

Anaerobic baffled reactor

NA

NA

Increasing the OLR reduce hydrogen production rate

Tawfik and ElQelish (2012)

Municipal food waste

Anaerobic process

370 mL/g VS

Lab-scale anaerobic baffled reactor

NA

NA

G

G

First stage, hydrogen produced from particulate COD conversion Second stage, hydrogen forms soluble COD

Tawfik et al. (2011)

Kitchen waste

Anaerobic fermentation

1.7 mmol/g COD

CSTR

NA

NA

Carbohydrate degradation closely linked with butyrate production

Lee et al. (2010b)

Kitchen waste

Anaerobic fermentation

1.27 mmol/g COD

CSTR

NA

NA

Hydrogen fermented from soluble carbohydrate hydrolyzed from rice starch

Wang et al. (2009)

Kitchen waste

Anaerobic process

118 mmol/L/ day

CSTR

NA

NA

G

Maximum removal efficiency of VSS and the total carbohydrate were 35% and 66%, respectively G Less organic nitrogen transforms into ammonia Oil and grease were not degraded

Li et al. (2008)

Kitchen waste

Anaerobic digestion

72 mL/g VS

Plug flow reactor

NA

NA

Hydrogen production occurs through butyric acid pathway

Jayalakshmi et al. (2009)

Kitchen waste

Dark fermentation

2.1 mmol g/ COD

CSTR

NA

NA

Microorganisms such as Thermoanaerobacterium sp. and Clostridium sp. were responsible for secreting amylase

Wang et al. (2010)

Vegetable waste from kitchen

Dark fermentation

0.57 mmol g/ COD

Batch reactor

NA

NA

Butyrate is the main intermediate component produced

Lee et al. (2008)

Food waste

Two-stage fermentation

205 mL/g VS

CSTR

464 mL/g VS

Fluidized bed reactor

Low pH condition with short HRT separate hydrogen production from methanogenesis process

Chu et al. (2008)

Food waste

Two-stage thermophilic fermentation

2.5 mol/mol hexose

CSTR

287 mL gCOD21

Biogas sparging reactor

Long-term process stability can be achieved by returning high alkalinity sludge

Lee et al. (2010a)

Food waste mainly containing potato waste

Two-stage thermophilic fermentation

85 mL/g

CSTR

338 mL/g

CSTR

The H2 yield was dependent on the proportion of carbohydrate and pH during hydrolysis of the organic waste

Chu et al. (2012)

Food waste

Two-phase hydrogen and methane fermentation

1.82 mol/ mol hexose

CSTR

15000 L/ day

UASB

G

Food waste

Anaerobic digestion

332 mL/g VS

CSTR

3.2 L/L. D

CSTR

Sonication at first reactor improved the treatment process and increased the production rate

Food waste

Two-stage fermentation process

0.065 mL/g VS

Semicontinuous rotating drum

0.546 mL/ g VS

CSTR

G

G

G

Degreasing HRT increased hydrogen production Organic acids converted into acetic acid after methane production

In hydrogen fermentation stage 5.78% of COD converted into H2 In methane fermentation stage 82.18% of COD converted into CH4

Lee and Chung (2010)

Elbeshbishy and Nakhla (2011) Wang and Cai Zhao (2009)

32

Food Waste to Valuable Resources

A high concentration of VFA may affect the start-up period of the reactor. Therefore many investigations need to be conducted on the effects of VFA on rector stability. Studies also show that there is a significant difference between theoretical hydrogen production and the actual hydrogen yield of the system. To obtain a clear picture more pilot-scale studies need to be conducted. A circular industrial model needs to be designed for enhanced product recovery. Also, many studies need to be conducted to make this process sustainable. Figures illustrate the various possibilities for valorization of FW for a circular economy (Fig 2.6).

2.13

Conclusion

FW is a major concern due to its incredible increment in recent years because of a shift in the standard of living and with urbanization and industrialization increasing globally. Studies have shown that both developed and developing countries have contributed toward an FW increase at a rate of 107 and 56 tons/year, respectively (Thi et al., 2015). FW rich in organic matter has been confirmed as suitable to produce bioenergy. Biological processes like AD and dark fermentation do not only play major roles in FW treatment but also in producing bioenergy. This chapter elaborately discusses biological routes, such as AD and dark fermentation, and their feasibility in bioenergy production. Valorization of FW will boost the bio-based economy and also reduce the requirement for raw first-generation feedstock for bioenergy production. This bio-economy can also be further strengthened by optimizing the production route and upscaling the available integrated techniques. Approximately 833,555 kWh/year of methane energy was produced from FW by 21 countries, reducing their reliance on fossil-based fuels. The effective implementation of the 5Rs concept would boost these production goals (Dung et al., 2014). In addition to energy production, value-added products like ethanol and chemicals are also proposed by adopting the biorefinery concept. Thus, waste utilization has become an economical process for renewable energy production by adopting cutting-edge techniques and requires additional full-scale and detailed studies on the process as suggested in this chapter.

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244. Algapani, D.E., Qiao, W., di Pumpo, F., Bianchi, D., Wandera, S.M., Adani, F., et al., 2018. Long-term bio-H2 and bio-CH4 production from food waste in a continuous two-stage system: energy efficiency and conversion pathways. Bioresour. Technol. 248, 204
213. Amanullah, A., McFarlane, C.M., Emery, A.N., Nienow, A.W., 2001. Scale-down model to simulate spatial pH variations in large-scale bioreactors. Biotechnol. Bioeng. 73, 390
399. Antonopoulou, G., Stamatelatou, K., Venetsaneas, N., Kornaros, M., Lyberatos, G., 2008. Biohydrogen and methane production from cheese whey in a two-stage anaerobic process. Ind. Eng. Chem. Res. 47, 5227
5233. Appels, L., Baeyens, J., Degre`ve, J., Dewil, R., 2008. Principles and potential of the anaerobic digestion of waste-activated sludge, Prog. Energy. Combust. Sci. 34, 755
781. Ariunbaatar, J., Panico, A., Frunzo, L., Esposito, G., Lens, P.N.L., Pirozzi, F., 2014. Enhanced anaerobic digestion of food waste by thermal and ozonation pretreatment methods. J. Environ. Manage. 146, 142
149. Elsevier Ltd. Banks, C.J., Zotova, E.A., Heaven, S., 2010. Biphasic production of hydrogen and methane from waste lactose in cyclic-batch reactors. J. Clean. Prod. 18. Banks, C.J., Zhang, Y., Jiang, Y., Heaven, S., 2012. Trace element requirements for stable food waste digestion at elevated ammonia concentrations. Bioresour. Technol. 104, 127
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1463. Elsevier Ltd.

Chapter 3

Valorization of food waste for bioethanol and biobutanol production R. Yukesh Kannah1, P. Sivashanmugham2, S. Kavitha1 and J. Rajesh Banu3 1

Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India, 2Department of Chemical Engineering, National Institute of

Technology, Tiruchirappalli, India, 3Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, Tamil Nadu, India

3.1

Introduction

Food waste (FW) is the most frequently generated biowaste among the other biodegradable wastes. Countries like the United States are the major contributors to the generation of FW. According to a global FW report, in the United States the average person wastes approximately 188 kg of food per annum. The generation of FW is not a simple issue associated with social, economic, and environmental aspect of individuals, it is a serious issue, where every citizen should think before wasting of food. This issue can have a drastic negative impact on the availability of food for others. According to an FAO report from 2015, global FW statistics indicate that one third of the food produced for human consumption is wasted each year, which is estimated as 1.3 billion tonnes of food with a cost of around 0.65 trillion USD (Gustavsson et al., 2011). Paritosh et al. (2017) reviewed the statistics of FW generated in Asian countries, which was found to be almost 278 million tonnes in the 2020 and this was forecast to increase to 416 million tonnes by 2025. FW is not only food wasted by human activity, but also food wasted during its processing (Gustavsson et al., 2011). Food processing industries (FPIs) generate substantial amounts of wastewater with a high concentration of organic solids (FW), which are highly biodegradable with less toxic substances. The management of FW and FPI waste is an extremely challenging task for developed and densely populated countries. FW can be classified into two categories: (1) edible FW, which can be easily reduced, and (2) nonedible FW, which requires a proper management system and can be utilized for the recovery of numerous value-added products. FW is generated from the domestic and industrial sectors, and is composed of protein, lipid, organic acids, and carbohydrate polymers such as starch, cellulose, and hemicelluloses. A small fraction of lignin and inorganic mineral components may also occur (Banu et al., 2019a; Kavitha et al., 2017a; Shanthi et al., 2018). It has a high moisture content, which causes a negative impact on FW management. Various methods have been followed for FW management including composting, landfill, incineration, gasification, waste to energy, and recovery of value-added products. Among these, waste to energy and recovery of value-added product from FW are the most profitable methods of FW management. FW contains approximately 60% carbohydrate in its total solids. This indicates that FW has a high carbon content, which can be easily converted into bioalcohols via acetone
butanol
ethanol (ABE) fermentation. During the fermentation process, Saccharomyces cerevisiae and Clostridium acetobutylicum strains play a major role in the conversion of carbohydrates into bioalcohols. Due to the complexity of the structure of carbohydrate, microbes face difficulties in this conversion process. To overcome these scientists and researchers have employed pretreatment and hydrolysis prior to fermentation. Pretreatment of complex organic waste is primarily classified into five groups: physical (Banu et al., 2019b; Kavitha et al., 2018), chemical (Banu et al., 2018a; Kannah et al., 2019a), mechanical (Kavitha et al., 2019a), biological (Banu et al., 2018b; Kavitha et al., 2019b), and combinative pretreatment (Kannah et al., 2019b; Kavitha et al., 2014a). Pretreatment aims to break the complex structure of carbohydrates into simple monomers and extend the surface area of the biomass for further hydrolysis (Banu et al., 2017a; Kavitha et al., 2014b; Shanthi et al., 2018). Usually thermal-, acid-, or enzyme-mediated hydrolysis follows, prior to fermentation. For example, acid hydrolysis is preferred for the elimination of inhibitory substances (lignin compounds) from the biomass

Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00003-1 Copyright © 2020 Elsevier Inc. All rights reserved.

39

40

Food Waste to Valuable Resources

structure. However, FW holds a smaller fraction of lignin compounds and can be easily hydrolyzed using enzymes. Thermal hydrolysis of FW leads to denaturing of biopolymer compounds (proteins, carbohydrates, and lipids), which significantly affects alcohol fermentation. It also demands a high amount of energy compared with other hydrolysis processes. from an economic point of view, enzyme hydrolysis is cheaper than other methods. The final products of fermentation are acetone, butanol, and ethanol in the ratio of 3:6:1. In order to increase the yield of ethanol, a separate pathway has been introduced. In this process, the fermentable sugar is directly converted into ethanol using yeast (S. cerevisiae) (Liu and Chen, 2016), bacteria (Zymomonas mobilis) (Ma et al., 2016), and fungi (Mucoralean) (Satari and Karimi, 2018). Many researchers have suggested bioalcohol fermentation using FW and FPI waste to be cheaper than other biomasses.

3.2

Bioalcohol production from food waste

Recently, the research toward bioalcohol production from FW and FPI has gained increasing attention. The combustion of petroleum fuel has resulted in several environmental issues including greenhouse gas emissions, global warming, and climate change. Bioalcohols such as bioethanol and biobutanol can replace petroleum fuel (Balat and Balat, 2009). Different types of organic waste biomass are used in the production of bioalcohols. These include food crops and plants (first generation), lignocellulose biomass (second generation), and algae biomass (third generation). Among these, FW and FPI are considered as an excellent feedstock for the production of bioalcohols. FW and FPI are enriched with micro- and macronutrients, which are essential in the production of bioalcohols. FW consists of protein (5%
10%), carbohydrates (40%
65%), and lipids (10%
25%) (Kannah et al., 2018; Kavitha et al., 2017a). Micronutrients such as Ca21, K1, Na1, Mg21, Fe31, Mn21, Zn21, P, and S are also present in FW (Hegde et al., 2018).

3.2.1 Bioethanol Bioethanol is also referred to as ethyl alcohol, its chemical structure comprises two carbon atoms linked with six hydrogen atoms and one atom of oxygen. The chemical formula of biobutanol is C2H5OH. Ethanol is as essential organic solvent, which is used for dye removal, to prevent microbial contamination, and as a dehydrating agent. Generally, ethanol is classified into two types based on the production route: bioethanol via microbial fermentation and synthetic ethanol via chemical reactions. Bioethanol and synthetic ethanol have similar chemical structures and physical properties. Bioethanol can be processed using different organic wastes such as food crops, food grain, FW, food processing industrial waste, plant materials, lignocellulose, and algae biomass. Bioethanol has a high heating value of 26.7 MJ/kg (Khuong et al., 2016). During petroleum refining, the catalytic hydration of ethylene leads to the generation of a byproduct called synthetic ethanol. Bioethanol has more advantages than synthetic ethanol. The production cost of bioethanol is cheaper than the processing costs of petroleum products to yield synthetic ethanol. Bioethanol is a chief alternative to petroleum products in Brazil.

3.2.2 Biobutanol Biobutanol is referred to as butyl alcohol, its chemical structure comprises four carbon atoms linked with 10 hydrogen atoms and one atom of oxygen. The chemical formula of biobutanol is C4H10O. There are four types of butanol, namely primary butanol, secondary butanol, tertiary butanol, and isobutanol. It occurs with different isomers with respect to the position of the 2OH radical and C atoms. They have different chemical structures and physical properties but similar chemical properties and applications. Biobutanol has a high heating value of around 29.2 MJ/dm3 (Stoeberl et al., 2011). It is considered to be the best alternative to petroleum fuel. Its benefits include less corrosive, nonhazardous, highly biodegradable, and high energy content.

3.2.3 Comparison of bioalcohol properties and their applications Bioalcohols act as good oxygenating blending components of gasoline. Therefore they are considered as a possible future liquid transportation fuel (Hegde et al., 2018). The use of bioalcohol as a transportation fuel mainly depends on its properties such as oxygen content, octane number, density, Reid vapor pressure, boiling point, and viscosity. The oxygen content in bioethanol is around 34.7% and in biobutanol it is about 21.5%, which stimulates complete combustion and results in lower particulate pollutant emissions (Patakova et al., 2011). Similarly, fuel with a high octane number prevents damage to engines from impulsive ignition. Bioethanol (120
135) has a higher octane number than

Valorization of food waste for bioethanol and biobutanol production Chapter | 3

41

biobutanol (97
103), which improves its thermal efficiency (Yusoff et al., 2015). The density of biobutanol (809 kg/m3) is higher than that of bioethanol (794 kg/m3). Both bioethanol and biobutanol have lower Reid vapor pressures compared to gasoline. However, the vaporization capability of bioethanol is higher than that of biobutanol, which emits a greater amount of instable volatile organic compound (VOC) into the atmosphere as pollutant. The emitted VOC compounds coupled with NOx are converted into toxic ozone gas with the help of ultraviolet radiation (Szulczyk, 2010). The boiling point of biobutanol (117 C) is higher than that of bioethanol (78 C). This is due to an increase in the length of the carbon atom in its structure. The boiling point of bioalcohol act as an indicator of its evaporative behavior. The viscosity, which is used to represent the property of fuel flow, of bioalcohols is higher than gasoline.

3.3

Bioalcohol production processes

The bioalcohol yield relies on the nature of substrate used for fermentation. At first, the substrate is subjected to pretreatment, for sugar release and size reduction. During the ABE process, yeast or bacteria play a vital role in conversion of released sugar into bioalcohols. After adopting separation and purification technologies, bioalcohols can be directly used as a liquid transportation fuel. This section provides detailed information regarding the process involved in bioalcohol production from FW. Fig. 3.1 shows the overall concept of bioalcohol production from FW.

3.3.1 Upstream process In the upstream process, three major steps are involved. These are pretreatment, hydrolysis, and detoxification to enhance the bioalcohol yield. The upstream process aims to improve the substrate surface area for effective utilization by microbes involved in the fermentation process. Pretreatment reduces the biomass particle size, hydrolysis increases the concentration of fermentable sugar, and detoxification removes recalcitrant compounds.

3.3.1.1 Pretreatment Pretreatment is the first step in the upstream process. FW pretreatment has a great impact on the bioalcohol yield and overall production cost (Hafid et al., 2017). It also favors microbes involved in the hydrolysis and fermentation process (Kannah et al., 2019c; Kavitha et al., 2019c). Hence pretreatment is essential to improve the digestibility of the complex

FIGURE 3.1 Overall concept of bioalcohols production from food waste.

42

Food Waste to Valuable Resources

sugar content during hydrolysis (Banu et al., 2019c; Banu and Kavitha, 2017). There are several pretreatment methods used to solubilize organic matter, such as thermal (Raj et al., 2013), thermochemical (Banu et al., 2018c; Tamilarasan et al., 2018), microwave (Kavitha et al., 2016a), ultrasonication (Kavitha et al., 2016b), disperser (Kavitha et al., 2016c), acid (Eswari et al., 2016), alkaline (Banu et al., 2012), ozone (Kannah et al., 2017a), fungal (Pleissner et al., 2014), bacterial (Banu et al., 2018b; Kavitha et al., 2013), and combinative pretreatment (Banu et al., 2018a; Kannah et al., 2017b). Several articles have reported that harsh pretreatment is not required for the conversion of organic FW into fermentable sugar compounds. The selection of a suitable method for pretreating FW is essential. This should especially be focused on attaining a higher liquefaction potential, greater substrate biodegradability, less toxic compound formation, and lower energy demand (Alvira et al., 2010). Table 3.1 shows various types of FW pretreatments and their yields. 3.3.1.1.1

Physical pretreatment

Physical pretreatment includes thermal (Banu et al., 2011; Kavitha et al., 2017b; Raj et al., 2013), microwave (Ebenezer et al., 2015a,b; Eswari et al., 2017), autoclave (Tampio et al., 2014), and ionizing irradiation (Fei et al., 2020). Temperature-based pretreatment is frequently used to enhance the solubilization of organic matter and its subsequent fermentation in FW. If excess heat or irradiation is applied to FW, depolymerization of reduced sugar occurs. This causes a negative effect on the subsequent hydrolysis and fermentation process. Fei et al. (2020) employed ionizing irradiation pretreatment on four different FWs (mixed FW, rice, tofu, and pork) to improve the organic release. During ionizing irradiation hydroxyl radicals (OH2) are generated. The OH2 radicals interact with organic matter and improve digestibility. Simultaneously they decompose or mineralize the inhibitory substances generated. These authors have documented ionizing irradiation pretreatment as a novel technique for FW pretreatment and subsequent anaerobic fermentation. In their study, they varied the irradiation dose from 0 to 12.42 kGy. As a result, a higher COD solubilization of 70.6% was achieved at 8.28 kGy irradiation. Similarly, at this irradiation dosage three FWs (rice, tofu, and pork) exhibited COD solubilization of 41.7%, 16.8%, and 11.3%, respectively. Microwave pretreatment of FW was suggested by Marin et al. (2010a) to increase organic matter release. They operated microwaves under fixed, microwave power, heating rate, and irradiation frequency of 1200 W, 7.9 C/min, and 2450 MHz, respectively. During microwave pretreatment, formation of a dipolar molecule arrangement was induced. Polar molecules then started to rotate and created friction between polar molecules and substrate. This action increased the biomass liquefaction and organic matter release. A maximum organic release of 154 mg/g was achieved. In another study, Marin et al. (2010b) achieved a maximum organic release of 246 mg/g at optimized microwave pretreatment conditions (175 C, 7.9 C/min). Autoclave pretreatment is the combined application of steam and pressure. Generally, autoclaves maintain temperature in the range of 120 C
160 C and pressure in the range of 5
20 bar. This may vary depending on the type and configuration of autoclave and biomass loading. Tampio et al. (2014) fixed the conditions for autoclave pretreatment such as temperature and pressure treatment as 160 C and 6.2 bar, respectively. As a result, a maximum organic release of 117.5 g/L was achieved. The same researchers, Tampio et al. (2015), documented a maximum organic release of 112.8 g/kgFM at the fixed autoclave pretreatment condition (160 C, 6.2 bar). Thermal pretreatment is classified into two types based on the operating temperature: (1) low-temperature (,100 C) and (2) high-temperature pretreatment ( . 100 C, above the boiling point of water). During thermal pretreatment, a multiphase reaction occurs between amino acid and sugar monomers. This reaction is referred to as the Maillard reaction, and is mainly dependent on the reaction temperature and composition of the substrate. If a temperature above 140 C is used to induce Maillard reactions, it causes the formation of an inhibitory substance called melanoidin. This suppresses the metabolic activity of enzymes involved in subsequent steps. The presence of a brown color in the pretreated substrate indicates occurrence of the Maillard reaction. Elbeshbishy et al. (2011) employed low-temperature thermal pretreatment of FW at 70 C for 30 min. This resulted in 20%, 10%, and 8% increases in soluble COD, carbohydrate, and protein, respectively. In another study, Yeshanew et al. (2016) documented high-temperature thermal pretreatment for FW solubilization. They carried out a pretreatment experiment at 120 C for 2 h. This resulted in a maximum soluble COD of 103.8 g/kg, soluble protein of 4.45 g/kg, and soluble carbohydrate of 32.8 g/kg. 3.3.1.1.2 Chemical pretreatment Chemical pretreatment is carried out using acid such as sulfuric, hydrochloric, or nitric (Eswari et al., 2016; SolarteToro et al., 2019), ionic salt such as sodium chloride (Kavitha et al., 2015a), magnesium chloride (Kavitha et al., 2015b), or calcium chloride (Kavitha et al., 2015c), a strong alkaline such as sodium hydroxide (Kavitha et al., 2016b), potassium hydroxide (Kavitha et al., 2015d), or calcium hydroxide (Kavitha et al., 2015d), cation-binding agents such

TABLE 3.1 Various types of food waste pretreatment and their yields. S. no.

Substrate

Characteristics before pretreatment

Pretreatment type

Pretreatment condition

Characteristics after pretreatment

Reference

Kitchen waste

TCOD

303

mg/g

Microwave

TCOD

320

mg/g

Soluble COD

78

mg/g

Time:1 min HR: 7.9 C/min Temperature: 175 C

Soluble COD

154

mg/g

Marin et al. (2010a)

TCOD

367

mg/g

TCOD

443

mg/g

Soluble COD

159

mg/g

Soluble COD

246

mg/g

TCOD

91,900

mg/L

Soluble COD

20

%

Total carbohydrate

46,500

mg/L

Soluble Carbohydrate

8

%

Total protein

14,960

mg/L

Soluble protein

10

%

Physical 1.

2.

3.

Kitchen waste

Food waste

Microwave

Thermal (low temperature)

Time: 1 min HR: 7.8 C/min Temperature: 175 C Time: 30 min Temperature: 70 C

Marin et al. (2010b) Elbeshbishy et al. (2011)

4.

Food waste

Soluble COD

98.2

g/L

Autoclave

Temperature: 160 C Bar pressure: 6.2 bar

Soluble COD

117.5

g/L

Tampio et al. (2014)

5.

Food waste

Soluble COD

101.7

g/kgFM

Autoclave

Temperature: 160 C Bar pressure: 6.2 bar

Soluble COD

112.8

g/ kgFM

Tampio et al. (2015)

6.

Food waste

Soluble COD

68.4

g/L

92

g/L

12

g COD/ L

Time: 20 min Temperature: 134 C

Soluble COD

Soluble protein

Thermal (high temperature)

Soluble protein

19

g COD/ L

Pagliaccia et al. (2016)

Soluble carbohydrate

8

g COD/ L

Soluble Carbohydrate

14

g COD/ L

TCOD

400

g/kg

Total carbohydrate

134

g/kg

Total protein

30.4

Total phenol

2.8

7.

Food waste

Soluble COD

96.7

g/kg

Soluble carbohydrate

39.2

g/kg

g/kg

Soluble protein

4.0

g/kg

g/kg

Soluble phenol

0.348

g/kg

Thermal (low temperature)

Time: 2 h Temperature: 80 C

Yeshanew et al. (2016)

(Continued )

TABLE 3.1 (Continued) S. no.

Substrate

Characteristics before pretreatment

Pretreatment type

Pretreatment condition

Characteristics after pretreatment

Reference

8.

Food waste

TCOD

400

g/kg

99.2

g/kg

134

g/kg

Time: 2 h Temperature: 100 C

Soluble COD

Total carbohydrate

Thermal (low temperature)

Soluble carbohydrate

33.6

g/kg

Yeshanew et al. (2016)

Total protein

30.4

g/kg

Soluble protein

4.1

g/kg

Total phenol

2.8

g/kg

Soluble phenol

0.384

g/kg

TCOD

400

g/kg

Soluble COD

103.8

g/kg

Total carbohydrate

134

g/kg

Soluble carbohydrate

32.8

g/kg

Total protein

30.4

g/kg

Soluble protein

4.45

g/kg

Total phenol

2.8

g/kg

Soluble phenol

0.441

g/kg

TCOD

400

g/kg

Soluble COD

105.3

g/kg

Total carbohydrate

134

g/kg

Soluble carbohydrate

30.1

g/kg

Total protein

30.4

g/kg

Soluble protein

4.67

g/kg

Total phenol

2.8

g/kg

Soluble phenol

0.527

g/kg

Food waste

SCOD

140.1

g/L

COD solubilization

70.6

%

Rice

SCOD

52.5

g/L

COD solubilization

41.7

%

Tofu

SCOD

38.1

g/L

COD solubilization

16.8

%

Pork

SCOD

15

g/L

COD solubilization

11.3

%

9.

10.

11.

Food waste

Food waste

Thermal (high temperature)

Thermal (high temperature)

Ionizing radiation

Time: 2 h Temperature: 120 C

Time: 1 h Temperature: 140 C

Radiation dose: 8.28 kGy

Yeshanew et al. (2016)

Yeshanew et al. (2016)

Fei et al. (2020)

Chemical 12.

13.

14.

Food waste

Food waste

Kitchen waste

TCOD

91,900

mg/L

Total carbohydrate

46,500

mg/L

Total protein

14,960

mg/L

TCOD

91,900

mg/L

Total carbohydrate

46,500

mg/L

Total protein

14,960

mg/L

TCOD

259,500

mg/L

Acid (HCl)

Alkaline (NaOH)

Acid (HCl)

pH: 3.0 (1 N HCl) Time: 24 h

pH: 11.0 (1 N NaOH) Time: 24 h

Time: 3 h Dosage: 1.5% (v/v) Temperature: 90 C

Soluble COD

25

%

Soluble carbohydrate

18

%

Soluble protein

23

%

Soluble COD

25

%

Soluble Carbohydrate

21

%

Soluble protein

26

%

COD solubilization

36.2

%

SCOD

94,050

mg/L

COD solubilization

58.1

%

SCOD

99,650

mg/L

COD solubilization

11.6

%

15.

Kitchen waste

TCOD

259,500

mg/L

Acid (H2SO4)

Time: 3 h Dosage: 1.0% (v/v) Temperature: 90 C

16.

Fruit and vegetable waste

TCOD

29,200

mg/L

Surfactant (sodium dodecyl sulfate)

Time: 60 min Dosage: 0.035 g/g SS

SCOD

930

mg/L

SCOD

3400

mg/L

Lignin

16.7

% of TS

Lignin removal

18.5

%

TCOD

91,900

mg/L

Soluble COD

25

%

Total carbohydrate

46,500

mg/L

Soluble carbohydrate

16

%

Total protein

14,960

mg/L

Soluble protein

17

%

TCOD

244

g/kg

COD solubilization

35

%

Soluble COD

85

g/kg

Soluble COD

22.1

%

Soluble carbohydrate

30.3

%

Soluble protein

13.6

%

Elbeshbishy et al. (2011)

Elbeshbishy et al. (2011)

Hafid et al. (2015)

Hafid et al. (2015)

Shanthi et al. (2018)

Mechanical 17.

18.

19.

Food waste

Kitchen waste

Food waste

Soluble COD

49,900

mg/L

Soluble carbohydrate

20,000

mg/L

Soluble protein

8710

mg/L

Ultrasonic

High-pressure homogenizer

Ultrasonic

Power: 500 W SE: 79 kJ/g TS

Pressure: 10 bar

Time: 30 min SE: 23,000 kJ/g TS

Elbeshbishy et al. (2011)

Ma et al. (2011)

Elbeshbishy et al. (2012)

(Continued )

TABLE 3.1 (Continued) S. no.

Substrate

Characteristics before pretreatment

Pretreatment type

Pretreatment condition

Characteristics after pretreatment

Reference

20.

Food waste

Soluble COD

22,080

mg/L

Ultrasonic

Time: 15 min SE: 16,875 kJ/g TS

Soluble COD

66,847

mg/L

Gadhe et al. (2014)

21.

Fruit and vegetable waste

TCOD

29,200

mg/L

Ultrasonic

SE: 5400 kJ/kg TS

COD solubilization

11.6

%

Shanthi et al. (2018)

SCOD

930

mg/L

SCOD

3400

mg/L

TS

35,000

mg/L

SS reduction

10.6

%

SS

23,000

mg/L

SS concentration

20,670

mg/L

TCOD

259,500

mg/L

COD solubilization

57.57

%

SCOD

104,500

mg/L

pH: 4.0
4.5 Time: 24 h Dosage: 10% (v/v) Temperature: 55 C

Free amino nitrogen

0.361

g/L

Glucose yield

36.9

g/L

pH: 4.0
4.5 Time: 24 h Dosage: 10 U/g dry FW Temperature: 60 C

Free amino nitrogen

2.4

g/L

Glucose yield

89.1

g/L

SCOD

165

g/L

Biological 22.

23.

24.

25.

Kitchen waste

Food waste

Food waste

Carbohydrate

42.7

mg/ 100 g

Protein

10.5

mg/ 100 g

Starch

461

mg/g

Protein

111

mg/g

Carbohydrate

153

Enzymes

Fungal mash

Fungal mash

pH: 5 Time: 6 h Dosage: 85 U/mL Temperature: 60 C

mg/g a

Hafid et al. (2015)

Han et al. (2015)

Uc¸kun Kiran et al. (2015)

Food waste

SCOD

1400

mg/L

Fungal mash

pH: 7.9 Time: 24 h Dosage: 2 g/L Temperature: 60 C

SCOD

6853.8

mg/L

Yin et al. (2016)

Food waste

TCOD

91,900

mg/L

UA

Soluble COD

27a

%

Total carbohydrate

46,500

mg/L

Power: 500 W SE: 79 kJ/g TS 1 pH: 3.0 (1 N HCl)

Soluble carbohydrate

31

%

Elbeshbishy et al. (2011)

Total protein

14,960

mg/L

Soluble protein

36a

%

Combined 26.

27.

28.

29.

30.

31.

Food waste

Food waste

Food waste

Food waste

Fruit and vegetable waste

TCOD

91,900

mg/L

Total carbohydrate

46,500

mg/L

Total protein

14,960

mg/L

TCOD

91,900

mg/L

Total carbohydrate

46,500

mg/L

Total protein

14,960

mg/L

TCOD

22,000

mg/L

SCOD

2800

mg/L

TCOD

22,000

mg/L

SCOD

2800

mg/L

TCOD

29,200

mg/L

SCOD

930

mg/L

UB

UH

TC

TCD

UCS

Power: 500 W SE: 79 kJ/g TS 1 pH: 11.0 (1 N NaOH)

Power: 500 W SE: 79 kJ/g TS 1 Temperature: 70 C

pH: 10 (using 1 N NaOH) Temperature: 80 C Energy input: 114.95 kJ Time: 5 min Temperature: 80 C Disperser: 10,000 rpm pH: 10 (using 1 N NaOH) SE:5400 kJ/kg TS Dosage: 0.035 g/g SS

Soluble COD

33

%

Soluble carbohydrate

27

%

Soluble protein

40

%

Soluble COD

27

%

Soluble carbohydrate

18

%

Soluble protein

25a

%

COD solubilization

44

%

SCOD

9680

mg/L

COD solubilization

61.3

%

SCOD

13,500

mg/L

COD solubilization

26

%

SCOD

7592

mg/Lb

TS

35,000

mg/L

SS reduction

16

%

SS

23,000

mg/L

SS concentration

19,250

mg/L

Elbeshbishy et al. (2011)

Elbeshbishy et al. (2011)

Kavitha et al., (2017a)

Kavitha et al., (2017a)

Shanthi et al. (2018)

HR, Heating rate; SCOD, soluble chemical oxygen demand; SE, specific energy; SS, suspended solids; TC, thermochemical; TCD, thermochemodisperser; TCOD, total chemical oxygen demand; TS, total solids; UA, ultrasonic coupled acid; UB, ultrasonic coupled base; UCS, ultrasonic coupled surfactant; UH, ultrasonic coupled heat. a Calculated from graph. b Calculated value.

48

Food Waste to Valuable Resources

as citric acid (Gayathri et al., 2015) or EDTA (Kavitha et al., 2013), chemical surfactants such as sodium tripolyphosphate (Banu et al., 2019d), Tween 80 (Kumar et al., 2018), dioctyl sodium sulfosuccinate (Ushani et al., 2017a), or sodium dodecyl sulfate (Kavitha et al., 2014b), and a power-oxidizing agent such as ozone (Kannah et al., 2017b; Packyam et al., 2015) or hydrogen peroxide (Eswari et al., 2017; Kavitha et al., 2016d). Generally, dilute acid pretreatment of FW is preferred for bioalcohol fermentation. During acid pretreatment, the substrate pH falls below 3, which indicates the presence of a high concentration of hydrogen ion (H1) and stimulates the transformation of protons from amino acid with H1 ions resulting in an ionization process. Hydrolysis of carbohydrate polymers using acid has the following benefits; short duration, lower energy demand, and high solubilization. However, this pretreatment induces the formation of inhibitory substances such as furans, carboxylic acids, and phenolic compounds. Hafid et al. (2017) used two different pretreatments for FW, namely hydrothermal and dilute acid pretreatment. Dilute acid pretreatment is conducted at varied temperatures (80 C
100 C) and varied acid concentrations of (0.5
2.0% v/v of HCl and H2SO4). Pretreatment of both acids (HCl and H2SO4) yields a higher sugar content. In another study, Nimbalkar et al. (2018) pretreated vegetable waste (pea pod waste) using H2SO4 (1.3% v/v) for biobutanol production. A total sugar yield of 48.07 g/L was achieved. Many researchers have documented sodium hydroxide (NaOH) as a strong and best alkali for pretreatment. It is also cheaper than other chemicals. During alkaline pretreatment, the presence of OH2 ions increases the pH value of the substrate, which turns the peripheral surface of the FW to be more negatively charged. In addition to these, saponification occurs and is responsible for biomass liquefaction. Elbeshbishy et al. (2011) carried out FW pretreatment for 24 h at pH 11 (NaOH). They recorded a maximum increase in COD solubilization of 28%, carbohydrate of 21%, and protein 26% with these conditions. Shanthi et al. (2018) suggested surfactant [sodium dodecyl sulfate (SDS)] pretreatment for organic matter solubilization. They varied the SDS dosage from 0.005 to 0.1 g/g SS and fixed the treatment time at 60 min. As a result, a maximum organic release of 3400 mg/L and 11.6% of COD solubilization was achieved at an optimized surfactant dosage of 0.035 g/g SS. 3.3.1.1.3 Mechanical pretreatment Ultrasonic (Ushani et al., 2017b) and disperser pretreatments (Kavitha et al., 2016c; Kumar et al., 2018; Tamilarasan et al., 2017) are the most commonly employed mechanical pretreatment methods. During ultrasonic pretreatment, vapor bubbles are generated, and collapse inducing biomass disintegration. The ultrasonic horn causes a violent hydromechanical shear force during pretreatment, which results in the formation of a vapor bubble. Gadhe et al. (2014) studied the effect of ultrasonic pretreatment on FW to improve the performance efficiency of anaerobic fermentation. They spent an input energy of 16,875 kJ/kg TS to attain 42.3% COD solubilization. Increasing the input energy beyond 16,875 kJ/ kg TS results in a decrease in COD solubilization. Similarly, Shanthi et al. (2018) used an input energy of 5400 kJ/kg TS to enhance biomass liquefaction. At this energy, nearly 16% of organic matter is solubilized and 10% of suspended solids are reduced. In another study, Elbeshbishy et al. (2011) reported a lower amount of input energy (79 kJ/kg TS) to attain 25% of COD solubilization. Ma et al. (2011) recommended high-pressure pretreatment of FW for liquefaction. Approximately 12% 6 7% of COD solubilization and 85 6 14 g/kg soluble COD were recorded. 3.3.1.1.4

Biological pretreatment

Biological pretreatment demands low cost and low energy (Banu et al., 2017b; Kavitha et al., 2019d). Biological pretreatment is employed using bacteria (Gopikumar et al., 2016; Kavitha et al., 2013; Lakshmi et al., 2014; Merrylin et al., 2013), enzymes (Lam et al., 2015; Uc¸kun Kiran and Liu, 2015), and fungi (Pleissner et al., 2014) for solubilizing biomass. The biological agents used for pretreatment of FW have the ability to secrete hydrolytic enzymes such as amylases (Banu et al., 2018b; Kavitha et al., 2014c), cellulases (Kavitha et al., 2017c), proteases (Kavitha et al., 2017d), lipases (Meng et al., 2017), and xylase (Pleissner et al., 2014). Meng et al. (2017) compared enzymatic pretreatment efficiency for three different substrates. They selected animal fat, vegetable oil, and floatable grease as substrates for selected microorganisms (Aspergillus, Candida, and porcine pancreatic). Among these, Aspergillus and Candida showed higher hydrolysis rates of 74.4% and 79.8% for animal fat at 4 h retention time. However, porcine pancreatic demands a higher retention time of 24 h for utilizing animal fat to achieve a 25.6% hydrolysis rate. In contrast to these three microorganism (Aspergillus, Candida, and porcine pancreatic), enzyme lipase showed greater hydrolysis rates of 77.3%, 86.0%, and 22.9% for substrates of animal fat, vegetable oil, and floatable grease. In another study, Uc¸kun Kiran and Liu (2015) used Aspergillus awamori to pretreat FW. As a result, yields of 127 and 1.8 g/L of glucose and free amino nitrogen, respectively, were achieved. The increment in the concentrations of glucose indicates the effectiveness of pretreatment. Similarly, Pleissner et al. (2014) carried out FW pretreatment using fungal species A. awamori and Aspergillus oryzae. Pretreatment resulted in the production of 143 g/L of glucose, 1.8 g/L of free amino nitrogen,

Valorization of food waste for bioethanol and biobutanol production Chapter | 3

49

and 1.6 g/L phosphate. Biological pretreatment is more effective in the conversion of freely and readily available complex sugar monomers into fermentable sugar. A higher fermentable sugar yield can be easily achieved in multistrains (biological pretreatment agents) rather than a single or pure strain. In addition to these, the crude enzyme can be directly used for pretreatment instead of using expensive pure or single strains. It also reduces the risk of biological contamination and processing charge. The advantages of biological pretreatment include lower generation of inhibitory substance and eco-friendliness. 3.3.1.1.5 Combined pretreatment Combined pretreatment achieves desired solubilization at relatively less energy than other methods (Kannah et al., 2019d; Kavitha et al., 2016b). In combined treatment, more than two pretreatments are coupled to improve the digestibility of substrate and to attain a higher sugar yield (Kannah et al., 2019e). Hafid et al. (2017) evaluated the efficiency of hydrothermal pretreatment of FW. The hydrothermal pretreatment was carried out by varying the temperature from 80 C to 100 C. The authors optimized the pretreatment efficiency based on the fermentable sugar yield. For hydrothermal pretreatment a higher sugar yield of 27.59 g/L was recorded at 90 C. Further increasing the temperature shows an insignificant yield. At high temperature the ionization constant of water is accelerated and the water molecules divide into H1 ions and OH2 radicals in the medium. This could be the reason for the insignificant yield achieved beyond 90 C. In another study, Elbeshbishy et al. (2011) evaluated combined pretreatment to achieve higher solubilization in FW. They coupled ultrasonic (specific energy 79 kJ/kg TS) with heat (70 C for 30 min), acid (maintain pH 3 using 1 N of HCl for 24 h), and alkali (maintain pH 11 using 1 N of NaOH for 24 h) at fixed conditions. Of these, ultrasonic coupled with alkali pretreatment shows the maximum increase in the percentage of soluble COD (33%) and protein (40%). However, the highest increment in the soluble carbohydrate of 31% was found in the ultrasonic coupled with acid pretreatment. Shanthi et al. (2018) reported that ultrasonic combined surfactant (SDS) pretreatment improves COD solubilization of FW. They optimized the ultrasonic energy as 5400 kJ/kg TS and surfactant dosage as 0.035 g/g TS and achieved 26% and 16% COD solubilization and SS reduction, respectively. Similarly, Shanthi et al. (2019) combined another surfactant (dimethyl sulfoxide) with ultrasonic and achieved greater COD solubilization. They varied the surfactant dosage from 0.002 to 0.01 g/g SS at fixed ultrasonic energy of 5400 kJ/kg TS and achieved 23% and 17% of COD solubilization and SS reduction, respectively. Kavitha et al. (2017a) documented the energy-efficient thermochemodisperser pretreatment of FW. They spent less input energy (174 kJ/kg TS) and achieved a COD solubilization of 61.3%.

3.3.1.2 Hydrolysis or saccharification Hydrolysis or saccharification is the second step in the upstream process for effective bioalcohol yield. This often takes place after the pretreatment process, to hydrolyze the complex polysaccharides (cellulose and hemicellulose) into simple monomers prior to bioalcohol fermentation. Usually hydrolysis of complex polysaccharides can be done using thermal, acid, or enzyme treatments. As a result, the cellulose and hemicellulose are hydrolyzed into hexoses and pentose. A small amount of hexoses may also be derived from hemicellulose during acid hydrolysis. In addition, some inhibitory compounds are also generated, including phenol (lignin deviates), furfural, and 5-hydroxyl-methyl-furfural (5-HMF) compounds. Similarly, thermal hydrolysis also generates the above-listed inhibitory compounds and denatures the sugar monomers. However, it requires a large amount of energy for hydrolysis. In the case of enzyme hydrolysis (EH) the amount of phenolic compounds generated is insignificant (Juturu and Wu, 2013). From the above it can be concluded that EH is more efficient than the other methods. There are several factors which can influence EH, these include biomass composition, crystalline structure complexity, and particle size. In addition, lignin composition in the biomass plays a major role in the performance of EH (Kennes et al., 2016). In order to overcome these issues, pretreatment is mandatory before EH. During pretreatment the hemicellulose fraction is broken down and undigested. In that case, the undigested hemicellulose can be hydrolyzed using different hemicellulase. The structure of hemicellulose (a nonlinear chain of glucose) is more complicated than cellulose (a linear chain of glucose). Table 3.2 shows the various types of FW hydrolysis and their yields. Many researchers have suggested that EH is the best option for FW hydrolysis. Optimization of EH is based on obtaining the maximum amount of fermentable sugar from cellulose. During EH, the cellulose content in the FW is converted with the help of the following cellulolytic enzymes: endocellulases, exocellulases, and β-glucosidases, which break down the internal structure of cellulose. Exocellulases convert the product of endocellulases into fine sugar molecules referred to as cellobiose. Similarly, β-glucosidase cleaves fine cellobiose into glucose monomers. Hence, a mixture of all three cellulases is required for effective conversion. However, is composition and concentration may differ from substrate to substrate. Usually cellulase employed for EH is from Clostridium sp. (anaerobic bacteria) or

50

Food Waste to Valuable Resources

TABLE 3.2 Various types of food waste hydrolysis and their yields. S. no

Substrate

Hydrolysis type

Hydrolyzing agents

Hydrolysis condition

Hydrolysis yield

References

1.

Food waste

Mixed enzyme

Carbohydrase 1 protease

pH: 4.5 Time: 12 h Temperature: 35 C Mixing: 150 rpm

Fermentable sugar: 0.63 g /g

Kim et al. (2011)

2.

Kitchen waste

Sequence mixed enzyme

α-Amylase

pH: 5.5 Time: 1 h Temperature: 95 C Mixing: 150 rpm

Fermentable sugar: 64.7 g /L

Uncu and Cekmecelioglu (2011)

Glucoamylase

pH: 5.5 Time: 6 h Temperature: 60 C Mixing: 150 rpm

3.

Food waste

Fungal mash

Aspergillus awamori and Aspergillus oryzae

pH: 4.0
4.5 Time: 24 h Dosage: 8.5 g/ 100 g FW Temperature: 60 C

Glucose yield: 143 g/L

Pleissner et al. (2014)

4.

Kitchen waste

Enzyme

Glucoamylase

pH: 5 Time: 6 h Dosage: 85 U/mL Temperature: 60 C

Conversion efficiency: 79% Fermentable sugar: 0.79 g/g

Hafid et al. (2015)

5.

Food waste

Fungal mash

A. awamori and A. oryzae

pH: 4.0
4.5 Time: 24 h Dosage: 7.7 g/L Temperature: 60 C

Glucose yield: 127 g/L

Uc¸kun Kiran and Liu (2015)

6.

Kitchen waste

Enzyme

Glucoamylase

pH: 5 Time: 10 h Dosage: 70 U/mL Temperature: 60 C

Conversion efficiency: 59.37% Fermentable sugar: 62.62 g/L

Hafid et al. (2016)

7.

Food waste

Acid

Hydrochloric acid

Time: 1 h Dosage: 1.5% (v/v) Temperature: 90 C

Conversion efficiency: 42.4% Fermentable sugar: 50.5 g/L

Hafid et al. (2017)

8.

Food waste

Enzyme

Glucoamylase

pH: 5.0 Time: 6 h Dosage: 85 U/mL Temperature: 55 C
60 C

Conversion efficiency: 50.6% Fermentable sugar: 60.32 g/L

Hafid et al. (2017)

(Continued )

Valorization of food waste for bioethanol and biobutanol production Chapter | 3

51

TABLE 3.2 (Continued) S. no

Substrate

Hydrolysis type

Hydrolyzing agents

Hydrolysis condition

Hydrolysis yield

References

9.

Food waste

Sequential acidenzyme hydrolysis

Hydrochloric acid 1 glucoamylase

Time: 1 h Dosage: 1.5% (v/v) Temperature: 90 C pH: 5.0 Time: 6 h Dosage: 85 U/mL Temperature: 55 C
60 C

Conversion efficiency: 86.8% Fermentable sugar: 103.4 g/L

Hafid et al. (2017)

10.

Soaking assisted and thermal pretreated cassava peel waste

Sequence mixed enzyme

α-Amylase

pH: 7 Time: 60 min Temperature: 90 C

Conversion efficiency: 78.66% Fermentable sugar: 0.58 g /g

Aruwajoye et al. (2019)

Amyloglucosidase

pH: 4.5 Time: 24 h Temperature: 60 C

Cellulase

pH: 5.5 Time: 120 min Temperature: 55 C

Aspergillus sp. (aerobic fungi). Among these, aerobic fungi are more commonly available than anaerobes, because anaerobes grow very slowly and demand a strict anaerobic environment. FW has a high starch content, in order to reduce its structure complexity α-amylase and glucoamylase enzymes are suggested. α-Amylase targets 1,4-α-glucosidic linear connections in the starch and breaks it down into small compounds like maltose, glucose, and maltotriose. Similarly glucoamylase breaks 1,6-α-glucosidic connections at the branching point of amylopectin along with 1,4-α-glucosidic. When both enzymes are combined a single final product such as glucose is the result. The optimization of EH of pretreated cassava peel waste for the production of bioethanol was carried out by Aruwajoye et al. (2019). For EH, enzymes such as α-amylase (90 C, pH 7 for 60 min), amyloglucosidase (60 C, pH 4.5 for 24 h), and cellulase (55 C, pH 5.5 for 120 min) are used at different concentrations and working conditions. At optimized conditions, 0.58 g/g of sugar yield is achieved with 78.66% hydrolysis efficiency. Uncu and Cekmecelioglu (2011) carried out two-step EH of kitchen waste to obtain glucose. In the first step, α-amylase enzymes were used to liquefy the starch content in the kitchen waste into cellulose and polysaccharides under optimized conditions (pH 5.5, enzyme dosage 120 U/g, temperature 95 C, preliminary hydrolysis time 1 h, with an agitation speed of 100 rpm). After successful completion of α-amylase EH, the temperature of the hydrolysate was cooled to 55 C. Then, in the second step, three different glucoamylase enzymes such as amyloglucosidase, cellulase, and β-glucosidase were added to the α-amylase hydrolysate to produce glucose. As a result, 64.7 g/L of glucose was obtained. Kim et al. (2011) studied the efficiency of EH on FW using four different enzymes, namely glucoamylase, protease, cellulase, and carbohydrase. During treatment, carbohydrase produces the maximum amount of glucose (0.63 g glucose/ g TS) when compared with other enzymes. Likewise, when glucoamylase and carbohydrase are mixed with protease, a greater glucose yield results. Hafid et al. (2016) employed glucoamylase to hydrolyze kitchen waste with a high concentration of carbohydrates. They reported that glucoamylase was effective in the production of glucose (62.62 g/L) at its optimized conditions (pH 5, time 10 h, and temperature 60 C). Hafid et al. (2017) studied the individual and sequential effects of acid and EH on pretreated FW. FW used for this study was composed of rice, meat, and vegetables, containing a high amount of carbohydrate (60.87%), protein

52

Food Waste to Valuable Resources

(20.53%), fat (13.65%), and fiber (1.67%). Initially, the authors compared the individual effect of acid (1.5% of HCl at 90 C) and enzyme (glucoamylase dosage 85 U/mL at 55 C
60 C). From the results it is evident that a higher amount of sugar production and substrate conversion efficiency is detected in EH (60.32 g/L and 50.6%, respectively) than acid hydrolysis (50.5 g/L and 42.4%, respectively). In order to increase the substrate conversion efficiency and sugar yield, sequential acid-EH followed. The working conditions for the sequential process were the same as the individual process (1.5% of HCl at 90 C, cooled to 55 C
60 C to inoculate 85 U/mL of glucoamylase). The sequential process showed a significant increase in the sugar yield to 103.4 g/L and substrate conversion efficiency to 86.8%. The addition of nonionic surfactant (Polysorbate 20 or Polysorbate 80) increases the cellulose conversion rate and reduces enzyme denaturation (Kennes et al., 2016). The sugar yield during EH is obviously higher, almost equal to 100%. The hydrolysis product is quantified based on the concentration of glucose and cellobiose produced. However, EH has certain drawbacks, such as the cost of enzymes and their slow reaction time. In some cases, the accumulation of hydrolysis product in the medium resisted enzyme metabolic activity. from an environmental point of view EH is the best choice t, as it does not generate any toxic or inhibitory substances.

3.3.1.3 Detoxification Detoxification is the third step involved in bioalcohol production. The process of removing toxic or recalcitrant substances such as weak acids, furfural, 5-hydroxymethylfurfural (5-HMF), and phenolic (lignin) compounds from the fermentable medium is known as detoxification. Harsh pretreatment or hydrolysis of FW leads to partial digestion of sugar monomers and the formation of toxic inhibitory compounds (Pham et al., 2015). This can have a negative impact on the subsequent fermentation process. To solve this issue, upstream various detoxification methods are employed to eliminate all above-mentioned toxic inhibitory compounds before fermentation. Many researchers have suggested different detoxification methods for the removal of inhibitory compounds. These methods include physical (adsorption, membrane, electrodialysis), chemical (neutralization, overliming, sulfide supplementation, anionic and cation exchange resin), biological (enzymes and fungi), and integrated (Niemisto¨ et al., 2013; Nimbalkar et al., 2018; Okuda et al., 2008; Shukor et al., 2014). Nimbalkar et al. (2018) pretreated vegetable waste (pea pod waste) using H2SO4 (1.3% v/v) for biobutanol production. As stated earlier, harsh pretreatment leads to the formation of certain inhibitory compounds (phenol, weak acids, 5-HMF, and furfural compounds). In order to overcome this issue the authors suggested using activated charcoal for the removal of these fermentation-inhibitory substances. This is achieved by adjusting the pretreated medium pH to 10 and the addition of 5% (w/v) activated charcoal. After 2 h of continuous agitation at 200 rpm the pretreated medium is filtered to recover the added activated charcoal along with inhibitory compounds (absorption). Almost 95% of phenolic compounds and 30% of organic acid (acetic) are successfully removed by this method. Shukor et al. (2014) improved the biobutanol production from palm kernel cake using a combination two different detoxification agents. Prior to ABE fermentation, the palm kernel cake was subjected to acid pretreatment. The hydrolysate contains 310 6 5 and 20 6 6 mg/L of 5-HFM and furfural compounds, respectively. The authors used two different detoxification agents, activated charcoal (25 g for every 1 L of pretreated hydrolysate) and Amberlite XAD-4 resin (nonionic polymeric column with adsorbent resin contains 75 g for every 0.5 L of pretreated hydrolysate), to remove inhibitory compounds. About 50% and 77.42% of furfural and 5-HMF compounds, respectively, are removed by this method. In another study, Telli-Okur and Eken-Sarac¸o˘glu (2008) compared the individual and combined effects of physical and chemical methods to remove inhibitory compounds. Initially, they compared the individual effect on inhibitory removal by neutralization and overliming. About 42% and 41% of furfural and HMF compounds, respectively, are removed by this method. For the combined effect, the overliming is coupled with sulfide supplement and adsorption, which results in 48% and 68% removal of furfural and 5-HMF compounds, respectively. Similarly, Okuda et al. (2008) coupled chemical (overliming) and biological (thermophilic enzyme Ureibacillus thermosphaericus) detoxification methods to remove furfural and 5-HMF from pretreated FW. Initially, the pretreated hydrolysate was detoxified using thermophilic enzyme at 50 C for 24 h. However, the concentrations of inhibitory compounds are not decreased to the desired level (resisting the growth yeast cell). In order to achieve greater removal of toxic compounds, the biological method is coupled with a chemical method. Table 3.3 shows various types of detoxification methods and their efficiency rates.

3.3.2 Midstream process In this stage, enzyme hydrolysate is directly converted into bioethanol and biobutanol via ethanol and ABE fermentation processes. During ethanol fermentation FW is converted into bioethanol with the help of the metabolic activity of

Valorization of food waste for bioethanol and biobutanol production Chapter | 3

53

TABLE 3.3 Various types of detoxification methods and their efficiencies. S. no.

Detoxification agent

Detoxification mechanism

Detoxification condition

Detoxification inhibitory removal rate

References

Physical method 1.

Activated charcoal

Adsorption

Time: 1 h Dosage: 1:10 (w/v) Temperature: 30 C Continuous stirring: 100 rpm

Furfural: 38.7% Acetic acid: 46.8% Total phenolic: 57%

Chandel et al. (2007)

2.

NEOSEPTA CMX and NEOSEPTA AMX

Electrodialysis

NA

Furfural: 7% Acetic acid: 100% Total phenolic: 70% Hydroxymethylfurfural: 7%

Lee et al. (2013)

3.

Activated charcoal

Adsorption

pH: 2 Time: 30 min Dosage: 2 g per 100 mL of hydrolysate Temperature: 90 C Continuous stirring: 150 rpm

Furfural: 80.0% Formic acid: 29.6% Acetic acid: 26.4% Levulinic acid: 99.9% Phenolic compounds: 99.9% Hydroxymethylfurfural: 87.9%

Lu et al. (2013)

4.

Activated charcoal

Adsorption

pH: 10 (using NaOH) Time: 2 h Dosage: 5% (w/v) Temperature: 60 C Continuous stirring: 200 rpm

Phenol removal: 95% Acetic acid removal: 30%

Nimbalkar et al. (2018)

5.

Activated charcoal

Adsorption

pH: 6 Time: 2 h Dosage: 5% (w/v) Temperature: 60 C Continuous stirring: 200 rpm

Furan derivatives: 77.9% Aromatic monomers: 98.6%

Zhang et al. (2018)

Hydrophobic

Time: 1 h Dosage: 1:10 (w/v) Temperature: 30 C Continuous stirring: 100 rpm

Furfural: 63.4% Acetic acid: 85.2% Total phenolic: 75.8%

Chandel et al. (2007)

Chemical method 6.

DIAION Resin

(Continued )

54

Food Waste to Valuable Resources

TABLE 3.3 (Continued) S. no.

Detoxification agent

Detoxification mechanism

Detoxification condition

Detoxification inhibitory removal rate

References

7.

Calcium hydroxide

Overliming

pH: 10 Time: 1 h Temperature: 30 C Continuous stirring: 100 rpm

Furfural: 45.8% Acetic acid: unaffected Total phenolic:35.87%

Chandel et al. (2007)

8.

Calcium oxide

Overliming

pH: 10 Time: 30 min Dosage: 66.67 g/L Temperature: 30 C Continuous stirring: 100 rpm

Furfural 1 hydroxymethylfurfural: 41%

Telli-Okur and EkenSarac¸o˘glu (2008)

9.

Calcium oxide

Neutralization

pH: 6 Time: 30 min Dosage: 66.67 g/L Temperature: 60 C Mixed vigorously during rapid addition of CaO

Furfural 1 hydroxymethylfurfural: 42%

Telli-Okur and EkenSarac¸o˘glu (2008)

10.

Calcium hydroxide

Overliming

pH: 10 Time: 30 min Temperature: 90 C Continuous stirring: 100 rpm

Furfural: 14.7% Formic acid: 25.9% Acetic acid: 100% Levulinic acid: 24.6% Phenolic compounds: 57.9% Hydroxymethylfurfural: 99.9%

Lu et al. (2013)

11.

Amberlite XAD-4 resin

Hydrophobic

Time: 8 h Dosage: 1% (w/v) Temperature: 30 C Continuous stirring: 200 rpm

Furfural: 75% Hydroxymethylfurfural: 100%

Sandhya et al. (2013)

12.

Amberlite XAD-7 resin

Hydrophobic

Time: 8 h Dosage: 1% (w/v) Temperature: 30 C Continuous stirring: 200 rpm

Furfural: 55% Hydroxymethylfurfural: 100%

Sandhya et al. (2013)

13.

Amberlite XAD16 resin

Hydrophobic

Time: 8 h Dosage: 1% (w/v) Temperature: 30 C Continuous stirring: 200 rpm

Furfural: 55% Hydroxymethylfurfural: 100%

Sandhya et al. (2013)

(Continued )

Valorization of food waste for bioethanol and biobutanol production Chapter | 3

55

TABLE 3.3 (Continued) S. no.

Detoxification agent

Detoxification mechanism

Detoxification condition

Detoxification inhibitory removal rate

References

14.

Amberlite XAD-4 resin

Hydrophobic

Flow rate: 8 mL/ min Dosage: 75 g per 0.5 L of hydrolysate

Furfural: 50% Hydroxymethylfurfural: 77.42%

Shukor et al. (2014)

15.

Calcium hydroxide

Overliming

pH: 10 Time: 2 h Temperature: 60 C Dosage: 15.32 g per 1 L of hydrolysate

Furan derivatives: 75.6% Aromatic monomers: 68.1%

Zhang et al. (2018)

Biological method 16.

Cyathus stercoreus

Bioremediation or bioleaching

Time: 4 h Temperature: 30 C Dosage: 100 U/ 100 mL Continuous stirring: 100 rpm

Furfural: unaffected Acetic acid: unaffected Total phenolic: 77.5%

Chandel et al. (2007)

17.

Ureibacillus thermosphaericus

Bioremediation or bioleaching

Time: 12 h Temperature: 50 C Dosage: 2.4 g dry cell/L

Furfural: 50% Hydroxymethylfurfural: 20%

Okuda et al. (2008)

18.

Coriolopsis rigida

Bioremediation or bioleaching

Time: 12 h Dosage: 0.5 U/ mL Temperature: 50 C

Phenolic compounds: 75%

Jurado et al. (2009)

Integrated method 19.

Calcium oxide 1 sodium sulfite

Overliming 1 sulfide supplementation

pH: 10 Time: 30 min CaO dosage: 66.67 g/L Na2SO3 dosage: 3 g/ L Temperature: 30 C Continuous stirring: 100 rpm

Furfural 1 hydroxymethylfurfural: 48%

Telli-Okur and EkenSarac¸o˘glu (2008)

20.

Calcium oxide 1 activated charcoal

Overliming 1 adsorption

pH: 10 Time: 24 h CaO dosage: 66.67 g/L AC dosage: 1 g/ 200 mL Temperature: 30 C Continuous stirring: 100 rpm

Furfural 1 hydroxymethylfurfural: 68%

Telli-Okur and EkenSarac¸o˘glu (2008)

56

Food Waste to Valuable Resources

yeast (S. cerevisiae; Hafid et al., 2017), bacteria (Z. mobilis; Ma et al., 2016), and fungi (Mucoralean; Satari and Karimi, 2018). Similarly, anaerobic bacteria (Clostridium species) are also responsible for biobutanol production during ABE fermentation of FW (Abo et al., 2019). These strains effectively consume glucose-rich hydrolysate as their food and produce diluted bioalcohols as a final product.

3.3.2.1 Biobutanol fermentation In biobutanol fermentation, sugars are fermented into butyl alcohol by anaerobic bacteria (Clostridium species). Biobutanol fermentation is also referred to as ABE fermentation. Fig. 3.2 shows the metabolic pathway of glucose using the anaerobic bacterium Clostridium. At the end of the ABE fermentation process, acetone, butanol, and ethanol are produced. In addition, certain organic acids such as acetic acid (CH3COOH), lactic acid (C3H6O3), propionic acid (CH3CH2COOH), acetone [(CH3)2CO], isopropanol (CH3CHOHCH3), and ethanol (CH3CH2OH) are also produced. FW is comprised of different sugar monomers such as glucose, galactose, cellobiose, mannose, and xylose. During the ABE fermentation process, butanol producers target these sugar monomers to produce biobutanol. The product obtained from fermentation needs purification to improve the quality and quantity of biobutanol. In ABE fermentation, most commonly the following Clostridium (C. acetobutylicum, C. beijerinckii, C. saccharobutylicum, and C. saccharoperbutylacetonicum) are used as butanol producers (Buakhiaw and Sanguanchaipaiwong, 2017). Clostridium plays a major role in both the acidogenesis and solventogenesis phases of ABE fermentation. In the acidogenic phase, it is responsible for the production of acetic (CH3COOH) and butyric (C4H8O2) acid. Similarly, in the solventogenic phase, it is responsible for the production of (CH3)2CO, C4H10O and CH3CH2OH. During the fermentation process, bio-alteration of acetyl-CoA into biobutanol uses the following list of enzymes acetoacetyl-CoA thiolase, aldehyde/alcohol dehydrogenase, butyryl-CoA dehydrogenase, 3-hydroxybutyryl-CoA dehydrogenase, and crotonase.

FIGURE 3.2 Metabolic pathway of glucose by anaerobic bacterium clostridium.

Valorization of food waste for bioethanol and biobutanol production Chapter | 3

57

The bio-transformation of acetyl-CoA (C23H38N7O17P3S) to butyryl-CoA (C25H42N7O17P3S) improves the process thermal stability. However, the condensation of C23H38N7O17P3S to acetoacetyl-CoA (C25H40N7O18P3S) is a rate-limiting step (Zheng et al., 2009). At the final fermentation, Clostridium yields two different products, namely liquid [CH3COOH, C4H8O2, (CH3)2CO, C4H10O, and CH3CH2OH] and gaseous products (carbon dioxide and hydrogen). Among these, hydrogen is considered to be an electron donor and can be employed to prime the solventogenic phase for the production of (CH3)2CO, C4H10O and CH3CH2OH. Purging carbon monoxide into the fermentation medium suppresses the activity of hydrogenase and reduces the formation of hydrogen gas. ABE fermentation is a biphasic (acidogenesis and solventogenesis) process, in which pH level maintenance is crucial. During the acidogenic phase, the pH of the fermentation medium is lowered to pH 5.5 due to the production of organic acid. When the produced acids are reassimilated, the solventogenic phase starts and solvents are produced (Lee et al., 2008). The solvent production is possible when the pH of fermentable medium is 4.5. Enhancing the buffering capacity of fermentable medium is a possible solution for improving the digestibility of carbohydrate by Clostridium to produce biobutanol. Butanol is a predominant final product of ABE fermentation. Finally, the ABE fermentation process produces solvents in the following proportions 3:6:1 of (CH3)2CO, C4H10Os and CH3CH2OH (Jones and Woods, 1986).

3.3.2.2 Bioethanol fermentation In the bioethanol fermentation process, glucose produced during enzyme hydrolysate is converted into ethanol by the metabolic activity of S. cerevisiae (yeast), Z. mobilis (bacteria), or Mucoralean (fungi). Fig. 3.3 shows the metabolic pathway of ethanol producers converting glucose into bioethanol. S. cerevisiae utilizes different forms of

FIGURE 3.3 Metabolic pathway of ethanol producers converting glucose into bioethanol.

58

Food Waste to Valuable Resources

fermentable sugar as the carbon source under a strict anaerobic environment. A series of enzymatic reactions takes place to convert glucose into pyruvic acid (C3H4O3) through the glycolysis pathway. During the ethanol fermentative pathway, initially glucose is phosphorylated using the complex chemical molecule [adenosine triphosphate (ATP)] as the energy source to biosynthesize glucose 6-phosphate which is isomerized to form fructose 6-phosphate. This reaction is mediated by the enzyme, phosphogluco isomerase. Fructose 6-phosphate again undergoes phosphorylation and is converted into fructose 1,6-biphosphate. This reaction is mediated by the enzyme, phosphofructo kinase. Fructose 1,6biphosphate is in turn cleaved into two different isomers, namely glyceraldehyde-3-P and dihydroxyacetone-P. This reaction is mediated by the enzyme, aldolase. The produced isomers, glyceraldehyde-3-P and dihydroxyacetone-P undergo reversible reactions through the enzyme, triose phosphate isomerase. Glyceraldehyde-3-P undergoes a dehydrogenation reaction and is converted into 1,3-bisphophoglycerate. This reaction is mediated by the enzyme glyceraldehyde 3-phosphate dehydrogenase. During this reaction NAD1 is reduced to NADH and H1. Then 1,3-bisphophoglycerate is phosphorylated to 3-phosphoglycerate. This reaction utilizes a high energy bond and ADP as an acceptor of phosphate and 3-phosphoglycerate and ATP. 3-Phosphoglycerate is reduced to 2-phosphoglycerate through phosphoglycerate mutase. 2-Phosphoglycerate is converted into phosphoenolpyruvate. This reaction is mediated by the enzyme enolase. Usually enolase generates phosphoenolpyruvate with help of magnesium ions. Phosphoenolpyruvate is converted into pyruvate through substrate-level phosphorylation. The enzyme pyruvate decarboxylase involved in glycolysis reacts with pyruvate and removes the carboxyl group with the liberation of CO2. During this reaction, an intermediate compound, acetaldehyde, is generated and acts as an electron acceptor. The produced acetaldehyde is converted into bioethanol through the enzyme alcohol dehydrogenase. The following equation shows the conversion of glucose to ethanol. C6 H12 O6 1 2ADP 1 2Pi 1 2NAD1 2C H O 1 2ATP 1 2H1 1 2NADH1 - 3 4 3 Glucose Pyruvate CH CHO 1 CO 2C H OH 1 2CO2 1 NAD1 3 2 2 5
!
!## Acetaldehyde Ethanol  pyruvate decarboxylase; # alcohol dehydrogenase It is calculated stoichiometrically that 1 mole of 100% fermentable sugar (C6H12O6) can be fermented into 51% bioethanol (C2H5OH) and 49% carbon dioxide (CO2) (Balat and Balat, 2009).

3.3.3 Downstream process In this process, biosynthesized alcohol is recovered and purified using different techniques, to improve the quality and quantity of the final product. Distillation is the most familiar and widely used technique for the recovery of alcohol from fermented liquid. Other techniques used for bioalcohol extraction and purification include: gas stripping, adsorption, and pervaporation. Table 3.4 shows various types of bioalcohol recovery methods and their efficiency rates.

3.3.3.1 Distillation Distillation is the most promising and well-known purification technique employed in industries and pilot-scale plants for harvesting of bioalcohols (Jin et al., 2019). In this process, the fermented liquid is heated below the boiling point of water, to separate the water and bioalcohol. Bioalcohol has a low boiling point, therefore, it can more easily turn to vapor under mild heating and this can easily be reversed to the liquid phase by the condensation process. In this process, product recovery is very high and it is recognized as the most efficient technique in liquid
liquid separation (Li et al., 2019). A high processing charge is the major drawback to this process (Han and Chen, 2018). On an industrial or pilot scale, purification of bioalcohol requires proper design of the distillation tower, to separate alcohol and water molecules. The alcohol compounds are vaporized and pass through the top of the distillation tower for condensation. Then the remaining water molecules are drawn from the bottom of the tower. Improper design hampers the process efficiency.

3.3.3.2 Gas stripping Gas stripping is the most simple and easiest process for separating bioalcohols from fermented liquid. In this process, hot oxygen free nitrogen or fermentative gases such as hydrogen and carbon dioxide are introduced into fermented liquid (Abdehagh et al., 2014). Bioalcohols then accumulate in the fermented liquid and are vaporized due to their equilibrium partial pressure. The vapor-containing fractions of acetone, butanol, and ethanol are passed through a condenser to

TABLE 3.4 Various types of bioalcohol recovery methods and their efficiencies. S. no.

Microorganism

Fermentation

Recovery methods

Recovery conditions

Product recovered

References

1.

Clostridium acetobutylicum ATCC 824

ABE fermentation

Pervaporation

Hydrophobic polydimethylsiloxane (PDMS) membrane Flux: 374 g/m2/h Condensation temperature: 2 C

Acetone: 44.7 g/L Butanol: 64 g/L Ethanol: 8.4 g/L Total ABE yield: 117.1 g/L

Van Hecke et al. (2012)

2.

C. acetobutylicum ATCC 824

ABE fermentation

Pervaporation

Hydrophobic PDMS membrane Flux: 374 g/m2/h Temperature: 37 C

Acetone: 47.25 g/L Butanol: 131.6 g/L Ethanol: 8.1 g/L Total ABE yield: 202 g/L

Van Hecke et al. (2013)

3.

Clostridium beijerinckii CC101

ABE fermentation

Gas stripping

Flow rate: 1.25 L/min Condensation temperature: 1 C

Acetone: 3.23 g/L Butanol: 9.38 g/L Total ABE yield: 12.89 g/L

Lu et al. (2013)

4.

C. acetobutylicum B3

ABE fermentation

Permeating
heating
gas stripping

Preheat temperature: 70 C Flow rate: 1 L N2/(1 L liquid vol. min) Condensation temperature: 20 C

Acetone: 30.15 g/L Butanol: 66.09 g/L Ethanol: 10.3 g/L Total ABE yield: 106.27 g/L

Chen et al. (2014)

5.

C. acetobutylicum DP217

ABE fermentation

Pervaporation

Silicalite-1 filled PDMS/polyacrylonitrile (PAN) composite membranes Temperature: 37 C

Acetone: 72.2 g/L Butanol: 122.4 g/L Ethanol: 7.21 g/L Total ABE yield: 117.1 g/L Total ABE yield: 201.8 g/L

Li et al. (2014a)

6.

C. acetobutylicum DP217

ABE fermentation

Pervaporation

Silicalite-1 filled PDMS/PAN composite membranes Membrane area: 0.0072 m2 Permeate side pressure: 280 Pa

Acetone: 47.3 g/L Butanol: 104.6 g/L Ethanol: 8.12 g/L Total ABE yield: 160 g/L

Li et al. (2014b)

7.

C. acetobutylicum JB200

ABE fermentation

Gas stripping

Flow rate: 1.6 L/min Condensation temperature: 10 C
15 C

Acetone: 139.2 g/L Butanol: 515.3 g/L Ethanol: 16.6 g/L Total ABE yield: 671.1 g/L

Xue et al. (2014)

(Continued )

TABLE 3.4 (Continued) S. no.

Microorganism

Fermentation

Recovery methods

Recovery conditions

Product recovered

References

8.

C. acetobutylicum ABE 1401

ABE fermentation

Gas stripping

Flow rate: 2 L/min Condensation Temperature: 5 C

Acetone: 66.5 g/L Butanol: 166.8 g/L Total ABE yield: 255.6 g/L

Cai et al. (2015)

9.

C. acetobutylicum ABE 1401

ABE fermentation

Gas stripping
pervaporation

Hydrophobic PDMS membrane Flow rate: 1 L/min Condensation temperature: 25 C

Acetone: 169.93 g/ L Butanol: 482.55 g/ L Ethanol: 54.2 g/L Total ABE yield:706.68 g/L

Cai et al. (2016)

10.

C. acetobutylicum JB200

ABE fermentation

Gas stripping
pervaporation

Flow rate: 1.5 L/min Condensation temperature: 2 C

Acetone: 91.5 g/L Butanol: 521.3 g/L Ethanol: 10.1 g/L Total ABE yield: 622.9 g/L

Xue et al. (2016)

Valorization of food waste for bioethanol and biobutanol production Chapter | 3

61

yield bioalcohol. Then the gas with bioalcohol removed is again recirculated into the fermentor for another cycle of bioalcohol recovery. During alcohol fermentation, the use of gas stripping reduces the concentration of inhibitory compounds and increases the yield (Pyrgakis et al., 2016). Recycling of the gas stream does not affect bioalcohol producers, but causes foaming. The performance efficiency of this process mainly depends on factors such as gas flow rate, degree of foam forming, and the composition of the fermented substrate (Ezeji et al., 2005).

3.3.3.3 Adsorption The adsorption process is energy-efficient technique used to recover and purify the final product from the fermented liquid (Abdehagh et al., 2014). Adsorption is more suitable for the recovery of bioalcohols (acetone, biobutanol, and bioethanol) from fermented liquid. The adsorbed bioalcohols over the surface of the adsorbent can be easily removed by applying heat. For effective recovery of bioalcohols, the adsorbent should possess high adsorption and desorption capability. Activated charcoal is the most commonly used adsorbent due to its easy availability, high desorption property, and low cost (Pyrgakis et al., 2016). Chemical adsorption agents such as zeolite, polymeric resin, and polyvinyl pyridine are also employed for the recovery of bioalcohols (Abdehagh et al., 2014).

3.3.3.4 Pervaporation In pervaporation bioalcohols are separated from fermented liquid by partial vaporization via hydrophobic membranes (Abdehagh et al., 2014). In this process, under vacuum conditions the fermented liquid is exposed to one side of the membrane and bioalcohol recovery (vapor) happens on the other side of the membrane (the permeate side). The obtained permeate vapor is passed through the condensor to yield liquid bioalcohol. This process is strongly recommended for the recovery of bioalcohols from fermented liquid as it demands less energy, there is no harm to bioalcohol producers, and nutrient loss is reduced (Cai et al., 2016). This process holds the following benefits: operatable under low temperature, lower energy demand, and high recovery efficiency. Bioalcohol recovery efficiency of pervaporation mainly depends on the membrane flux rate. To attain greater flux in membranes is challenging as it depends on the surface area of the membrane. Fabricating membrane with a larger surface area is the major limitation to the pervaporation process (Lipnizki et al., 2000).

3.3.3.5 Integrated downstream process In the integrated downstream process, two or more methods are combined to recover and purify bioalcohols. Cai et al. (2016) employed an integrated approach (gas stripping
pervaporation) to reduce the process cost and increase the concentration of biobutanol. Almost, 98.8% 99.5%, and 82.8% (w/v) of biobutanol, acetone, and bioethanol, respectively, are recovered through the integrated approach. Similarly, Pyrgakis et al. (2016) established a novel integrated approach for recovery of bioalcohols. These authors employed gas stripping for the removal of inhibitory compounds during glucose fermentation. At the final stage, to recover bioalcohols they used an adsorption technique. Finally, they employed distillation to removal water molecules and achieved .99% product recovery (isopropanol, biobutanol, and bioethanol).

3.4

Various bioalcohol fermentation methods

There are generally four types of fermentation process involved in bioalcohol production: (1) separate hydrolysis and fermentation (SHF), (2) simultaneous saccharification and fermentation (SSF), (3) simultaneous saccharification and cofermentation (SSCF), and (4) consolidated bioprocessing (CBP). Fig. 3.4 shows the steps in involved in SHF, SSF, SSCF, and CBP. In this section there is a detailed discussion of these four types of fermentation. Table 3.5 shows various types of bioalcohol fermentation and their yields.

3.4.1 Separate hydrolysis and fermentation SHF is a two-step process, in which EH and fermentation are performed separately. EH and fermentation have different optimal conditions. Therefore, SHF has the drawbacks of a long processing time, high energy demand, and high processing charge. Kim et al. (2011) studied the effect of SHF in batch and continuous modes. In batch mode, carbohydrase (30 C and pH 5.0) and S. cerevisiae (35 C and pH 4.5) are employed for EH and fermentation, respectively. During EH, carbohydrase increases the glucose concentration to 135 g/L (0.83 g glucose/g TS) after 18 h of hydrolysis. Then S. cerevisiae converts glucose (135 g/L) into ethanol (0.43 g ethanol/g TS) within 20 h of fermentation. In a continuous

62

Food Waste to Valuable Resources

FIGURE 3.4 Steps in involved in SHF, SSF, SSCF and CBP.

SHF process, ethanol yield and volumetric ethanol production rate are found to be 0.3 g ethanol/g TS and 1.18 g/L h, respectively. SHF operated at continuous mode produced 70% of the theoretical ethanol. Jin et al. (2012) proposed an SHF method for enhancing bioethanol yield using pretreated substrate containing glucose and xylose. Commercially available mixed enzymes were used in their study [Spezyme CP, Novozyme 188 (Multifect xylanase and Multifect pectinase)] for EH and S. cerevisiae for bioethanol synthesis. The mixed enzymes increased the glucose and xylose concentrations to 52.3 and 25.5 g/L respectively, after 96 h hydrolysis. On the other hand, yeast consumes the produced glucose and xylose and synthesizes bioethanol (35 g/L). Hafid et al. (2016) compared the substrate conversion efficiency in SHF using three different strains S. cerevisiae, Candida parasilosis, and Lachancea fermentati. These authors used commercially available glucose and enzyme-hydrolyzed kitchen waste as a substrate for bioethanol production. Of these, C. parasilosis utilized enzyme-hydrolyzed kitchen waste as a substrate and attained a higher substrate conversion efficiency of 98% than the other strains. Its ethanol yield was noted to be 0.5 Yp/s. Likewise, L. fermentati utilizes commercial glucose as a substrate and yields a higher substrate conversion efficiency of 91% than the other strains. Its ethanol yield is noted to be 0.47 Yp/s. Similarly, Liu and Chen (2016) reported that the SHF process effectively converts a high concentration of glucose and xylose into bioethanol. As a result, 68.4% and 0.47 g/L h of ethanol yield and productivity were achieved.

3.4.2 Simultaneous saccharification and fermentation SSF is a single-step process, in which enzymatic hydrolysis is combined with fermentation to attain a higher bioalcohol yield. In this process, hydrolysis of FW produces glucose, and accumulation of glucose in the medium affects the enzyme activity and decreases the hydrolysis efficiency. In order to overcome this issue, simultaneous production of glucose and its utilization is encouraged in SSF. Rapid utilization of the produced glucose improves the EH efficiency and leads to higher bioalcohol synthesis. In addition, the processing cost of SSF is cheaper than conventional bioalcohol synthesis. It requires a single reactor for hydrolysis and fermentation. It also reduces the processing time, energy demand, and cost of alcohol synthesis. Chohan et al. (2020) employed glucoamylase and S. cerevisiae BY4743 for EH and ethanol fermentation, respectively. Soaking assisted thermal pretreated potato peel waste was used as a substrate for ethanol production. Glucoamylase takes 2 h to produce a sufficient amount of glucose for the growth of yeast cells. After 2 h, the fermentation is initiated and leads to the production of 22.54 g/L ethanol in 16 h. For this 97% of glucose

Valorization of food waste for bioethanol and biobutanol production Chapter | 3

TABLE 3.5 Various types of bioalcohol fermentations and their outcomes. S. no.

Substrate

Fermentor operation mode

Fermentation agents

Fermentation conditions

Fermentation outcome

References

Separate hydrolysis and fermentation 1.

Food waste

Batch volume: 3 L

Saccharomyces cerevisiae

pH: 4.5 Time: 20 h Temperature: 35 C

Ethanol yield: 0.43 g ethanol/g TS

Kim et al. (2011)

2.

Food waste

Continuous volume: 3 L

S. cerevisiae

pH: 4.5 HRT: 24 h Temperature: 35 C

Ethanol concentration: 44 g/L Ethanol yield: 0.47 g ethanol/g TS Ethanol productivity: 1.83 g/L/h

Kim et al. (2011)

3.

Kitchen waste

Batch volume: 100 mL

S. cerevisiae

pH: 6.5
7.0 Time: 24 h Temperature: 30 C Mixing: 120 rpm

Ethanol yield: 0.45 Yp/s Ethanol productivity: 0.46 g/L/h Conversion efficiency: 88.59%

Hafid et al. (2016)

4.

Kitchen waste

Batch volume: 100 mL

Candida parasilopsis

pH: 6.5
7.0 Time: 24 h Temperature: 30 C Mixing: 120 rpm

Ethanol yield: 0.50 Yp/s Ethanol productivity: 0.44 g/L/h Conversion efficiency: 98.19%

Hafid et al. (2016)

5.

Kitchen waste

Batch volume: 100 mL

Lachancea fermentati

pH: 6.5
7.0 Time: 24 h Temperature: 30 C Mixing: 120 rpm

Ethanol yield: 0.42 Yp/s Ethanol productivity: 0.47 g/L/h Conversion efficiency: 82.06%

Hafid et al. (2016)

6.

Commercial glucose

Batch volume: 100 mL

S. cerevisiae

pH: 6.5
7.0 Time: 24 h Temperature: 30 C Mixing: 120 rpm

Ethanol yield: 0.37 Yp/s Ethanol productivity: 0.44 g/L/h Conversion efficiency: 72.62%

Hafid et al. (2016)

7.

Commercial glucose

Batch volume: 100 mL

Candida parasilopsis

pH: 6.5
7.0 Time: 24 h Temperature: 30 C Mixing: 120 rpm

Ethanol yield: 0.46 Yp/s Ethanol productivity: 0.47 g/L/h Conversion efficiency: 90.62%

Hafid et al. (2016)

(Continued )

63

64

Food Waste to Valuable Resources

TABLE 3.5 (Continued) S. no.

Substrate

Fermentor operation mode

Fermentation agents

Fermentation conditions

Fermentation outcome

References

8.

Commercial glucose

Batch volume: 100 mL

L. fermentati

pH: 6.5
7.0 Time: 24 h Temperature: 30 C Mixing: 120 rpm

Ethanol yield: 0.47 Yp/s Ethanol productivity: 0.45 g/L/h Conversion efficiency: 91.32%

Hafid et al. (2016)

9.

Food waste

Batch volume: 100 mL

S. cerevisiae

pH: 6.5
7.0 Time: 24 h Temperature: 30 C Mixing:120 rpm

Ethanol yield: 10.92 g/L Ethanol productivity: 0.46 g/L/h Conversion efficiency: 85.38%

Hafid et al. (2017)

Simultaneous saccharification and fermentation 10.

Food waste

Batch volume: 450 mL

S. cerevisiae KF-7

pH: 4.5 Time: 14 h Temperature: 30 C Mixing: 100 rpm

Ethanol concentration: 22 g/L Ethanol yield percentage: 84.3% Ethanol productivity: 1.57 g/L/h

Koike et al. (2009)

11.

Food waste

Batch volume: 3 L

S. cerevisiae

pH: 4.5 Time: 20 h Temperature: 35 C

Ethanol yield: 0.31 g ethanol/g TS

Kim et al. (2011)

12.

Food waste

Continuous volume: 3 L

S. cerevisiae

pH: 4.5 HRT: 24 h Temperature: 35 C

Ethanol concentration: 27 g/L Ethanol yield: 0.2 g ethanol/g TS Ethanol productivity: 0.8 g/L/h

Kim et al. (2011)

13.

Food waste

Batch

Saccharomyces coreanus

pH: 5.5 Time: 24 h Temperature: 37 C

Ethanol concentration: 40.5 g/L Ethanol productivity: 1.69 g/L/h

Jeong et al. (2012)

14.

Potato waste

Batch volume: 100 mL

S. cerevisiae BY4743

pH: 3.72 Time: 15
24 h Temperature: 30 C

Ethanol yield: 0.26 g/g Ethanol productivity: 0.22 g/L/h

Sanusi et al. (2019)

(Continued )

Valorization of food waste for bioethanol and biobutanol production Chapter | 3

65

TABLE 3.5 (Continued) S. no.

Substrate

Fermentor operation mode

Fermentation agents

Fermentation conditions

Fermentation outcome

References

15.

Potato peel waste

Batch volume: 50 mL

S. cerevisiae BY4743

pH: 5.78 Time: 16 h Temperature: 40 C

Ethanol concentration: 22.5 g/L Ethanol yield: 0.32 g /g

Chohan et al. (2020)

Simultaneous saccharification and cofermentation 16.

Food waste

Batch

S. coreanus 1 Pichia stipitis

pH: 5.5 Time: 24 h SC dosage: 0.2% (v/v) PS dosage: 0.3% (v/v) Temperature: 30 C

Ethanol concentration: 48.63 g/L Ethanol productivity: 2.03 g/L/h

Jeong et al. (2012)

17.

Pineapple peel Banana peel Plantain peel

Batch volume: 100 mL

Aspergillus niger 1 S. cerevisiae

pH: 5.5 Time: 7 days Mixed dosage: 5% (v/v) Temperature: 30 C

Ethanol yield: 8.34% (v/v) Ethanol yield: 7.45% (v/v) Ethanol yield: 3.98% (v/v)

Itelima et al. (2013)

18.

Banana waste

Batch volume: 100 mL

Aspergillus terreus 1 Kluyveromyces marxianus

pH: 5.5 Time: 3 days Mixed dosage: 10% (v/v) Temperature: 38 C

Ethanol concentration: 0.35 g/L Ethanol productivity: 0.07 g/L/d

Teoh and Syed Zuber (2016)

Consolidated bioprocessing 19.

Food waste

Feed batch volume: 3 L

Clostridium sp. strain HN4

pH: 6.2 Time: 20 h Temperature: 35 C

Butanol concentration: 17.64 g/L Butanol yield: 0.15 g/g

Qin et al. (2018)

20.

Potato peel waste

Bench-scale bioreactor volume: 5 L

Wickerhamia sp.

pH: 7.0 Time: 4 days Temperature: 30 C

Ethanol concentration: 30.4 g/L Ethanol yield: 0.3 g ethanol/g starch

Hossain et al. (2018)

is utilized. The rapid utilization of produced glucose improves the hydrolysis and ethanol yield. As a result, a higher bioethanol yield of 0.32 g/g (concentration 22.54 g/L) is achieved at the optimized condition (pH 5.78 at 40 C with solid loading of 12.25% w/v). Beyond 16 h the ethanol concentration is reduced due to insufficient supply of glucose to the yeast cell and the formation of organic acid suppresses the activity of ethanol producers. Similarly, Sanusi et al. (2019) investigated the influence of metal oxide nanoparticles (NPs) in SSF for cost-effective bioethanol production. NPs act as a catalyst in the fermentation process. NPs with higher surface area to volume ratio are considered as good catalysts. NPs boost the contact and interaction between microbes and substrate and improve the metabolic activity of microbes to achieve higher substrate utilization. They used two different metal oxide nanoparticles, nickel oxide (NiO) and iron (III) oxide (Fe3O4). Of these, the use of 0.01 wt.% of Fe3O4 in SSF shows complete substrate utilization (99.9%) and achieved 50% fermentation efficiency. The ethanol yield and productivity were observed to be 0.26 g/g

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Food Waste to Valuable Resources

and 0.22 g/L/h, respectively. The authors concluded that addition of NPs rapidly increased the degree of substrate utilization, fermentation efficiency, and product yield. Kim et al. (2011) compared the batch and continuous operation of SSF. During batch operation, a higher ethanol yield of 0.31 g ethanol/g TS was obtained. Similarly, under the continuous operation, a maximum ethanol yield of 0.2 g ethanol/g TS and productivity of 0.8 g/L h were achieved. Liu and Chen (2016) reported that the SSF process effectively converts a high concentration of glucose and xylose into bioethanol. As a result, 73.3% and 0.5 g/L h of ethanol yield and productivity were achieved. Aruwajoye et al. (2019) obtained a maximum bioethanol yield of 0.53 g/g in a batch mode under optimized conditions (pH 7, 30 C, and 10.16% w/v organic loading).

3.4.3 Simultaneous saccharification and cofermentation SSCF is an improved SSF of and has benefits such as a shorter fermentation time, continuous conversion of glucose into bioalcohol, and less generation of recalcitrant compounds. In this process, the bioalcohol yield is based on cofermentation of both hexose and pentose in a single-step process (Liu and Chen, 2016). Jeong et al. (2012) improved the ethanol yield by employing the cofermentation of hexose and pentose from FW using Saccharomyces coreanus and Pichia stipites. The authors evaluated the performance of individual yeasts. Both yeasts have their own growth conditions: S. coreanus (pH 5.5 at 37 C) and P. stipites (pH 4
7 at 25 C
35 C). S. coreanus shows better performance under anaerobic conditions. After 24 h, under anaerobic conditions S. coreanus reduced sugar and glucose concentrations from 107 to 9 g/L and from 79 to 1.8 g/L, respectively. The decrease in the concentration of sugar and glucose leads to the production of bioethanol (40.59 g/L) and its productivity is found to be 1.69 g/L h. The microorganism P. stipites shows less bioethanol productivity (0.71 g/L h at 24 h) than S. coreanus. However, when they are mixed a maximum bioethanol yield and productivity of 48.63 g/L and 2.03 g/L h are obtained. The use of mixed yeast resulted in a 16% higher ethanol yield than by S. coreanus alone. Teoh and Syed Zuber (2016) studied the effect of SSCF using banana and pineapple waste as substrate for bioethanol production. The cofermentation was carried out using fungi (Aspergillus terreus) and thermo-tolerant yeast (Kluyveromyces marxianus). The enzyme secreted by A. terreus converts xylose and sucrose into glucose and fructose within 12 h of fermentation. Beyond 12 h the concentration of substrate (glucose and fructose) was decreased. This is due to the metabolic activity of thermo-tolerant yeast, which utilizes substrate and produces bioethanol. As a result, 0.35 and 0.27 g/L of bioethanol production are achieved in banana and pineapple waste, respectively. Jin et al. (2012) introduced a two-step SSCF process for improving the bioethanol yield in pretreated substrate containing glucose and xylose. In the first step, substrate is hydrolyzed to improve bioethanol production. After successful completion of prehydrolysis, the second step is carried out. The authors have carried out 6 and 24 h prehydrolysis. Of these 6 h prehydrolysis coupled with SSCF shows greater ethanol yield (39.9 g/L) than 24 h prehydrolysis (37.9 g/L yield). Similarly, Liu and Chen (2016) reported that the SSCF process effectively converts a high concentration of glucose and xylose into bioethanol. As a result, 75.3% and 0.63 g/L h ethanol yield and productivity are achieved.

3.4.4 Consolidated bioprocessing CBP is a combination of three biological methods which aim to achieve cellulase production, enzymatic hydrolysis, and microbial fermentation in a single operation (Fan, 2014). CBP is recognized as a potential process for the conversion of complex carbohydrates into bioalcohol. Recently, CBP has been widely explored using different waste biomasses as a substrate. Okamoto et al. (2011) first reported a single microbe sufficient for bioethanol production using the CBP method. The white rot fungus Trametes hirsuta is efficient in hydrolyzing biomass to produce fermentable sugar and simultaneously it converts the fermentable sugar into bioethanol. This shows that the suggested strain is capable of carrying out hydrolysis and saccharification simultaneously. This strain has the capability of utilizing a variety of substrates such as glucose, mannose, cellobiose, and maltose for ethanol production. In addition to these it also favors the fermentation process by consuming xylose and producing ethanol. A maximum bioethanol concentration of 9.1 g/L is achieved, which is about 89.2% of the theoretical yield under optimized conditions. The direct conversion of ethanol from carbohydrate-rich biomass by a single strain of fungus would be a profitable approach for bioethanol synthesis. CBP will reduce the overall process charge, reduce contamination, and avoid the use of hazardous chemicals. The same researchers in another study synthesized 9.8 g/L bioethanol using 20 g/L commercial corn starch (Okamoto et al., 2014). Similarly, Hossain et al. (2018) utilized potato peel waste as a substrate for bioethanol synthesis using the CBP method. The maximum bioethanol yield of 30.4 g/L was achieved utilizing 100 g/L of starch in 4 days. Qin et al. (2018) utilized FW for biobutanol production using the CBP method. Amylatic and solventogenic (Clostridium sp.

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67

strain HN4) enzymes were used for biobutanol production. The authors stimulated the activity of amylase by supplying 3 g/L of calcium carbonate (lime) and 0.5% of Tween 80 (nonionic surfactant). As a result, nearly 17.64 g/L of biobutanol was synthesized from FW.

3.5

Other strategies to increase the bioalcohol yield

Increasing the bioalcohol yield above the theoretical yield could pave the way for process commercialization. This can be achieved through the use of high-tolerance bioalcohol producers (Horinouchi et al., 2018), gene-modified strains (Di Donato et al., 2019), addition of nanoparticles (Sanusi et al., 2019), cell recycling using membrane (Grisales Dı´az and Willis, 2018), inoculum and strain immobilization (Hans et al., 2019), coculture (Li et al., 2013; Tran et al., 2010) and combination of alcohol producers with other enzymes (Kim et al., 2011). To improve the substrate utilization efficiency in ABE fermentation Tran et al. (2010) suggested a coculture: amylase-secreting aerobic bacteria (Bacillus subtilis) cocultured with an anaerobic alcohol producer (Clostridium butylicum). This coculture not only improves the bioalcohol yield and substrate conversion efficiency but also maintains strict anaerobic conditions inside the fermentor. This will minimize nitrogen purging and reduce associated costs. Therefore this approach makes for more attractive industrialized bioalcohol production. Similarly, Li et al. (2013) improved the coculture process by an immobilization technique. These authors compared the effect of coculture in free and immobilized cells. In addition, the effects of pure culture were also analyzed. C. beijerinckii and Clostridium tyrobutyricum strains were used for fermenting substrates such as glucose, cassava starch, and cane molasses. The coculture effectively utilized cassava starch as substrate and achieved higher biobutanol yield and volumetric productivity of 0.18 g/g and 0.96 g/L/h, respectively. Similarly, the pure culture (C. beijerinckii) exhibited a higher biobutanol yield and volumetric productivity of 0.14 g/g and 0.13 g/L/h using glucose as a substrate. Watanabe et al. (2012) reported that inoculum processing (enriching) and enzyme production for hydrolysis are relatively expensive. This can be overcome by use of immobilized inoculum, which can be used repeatedly (recycling). This approach significantly improves the bioalcohol production rate and reduces the cost of inoculum processing and enzyme production. Immobilized strains are more effective than free strains. However, they have drawbacks such as space requirement, difficulties in free floatation, and viscosity (Hans et al., 2019). According to Kim et al. (2011), the combination of an alcohol producer (carbohydrase) with protease is considered a promising technique to increase the bioalcohol yield. The addition of protease to the alcohol producer helps in breaking down the complex structure of carbohydrates into a simple reducing sugar. The maximum bioethanol yield achieved during this study was 0.43 g ethanol/g TS and 0.3 g ethanol/g TS for batch and continuous operations, respectively. This relates to 70% higher bioethanol production than the theoretical yield. The addition of nanoparticles in fermentation significantly improves the bioalcohol concentration and yield. For example, Sanusi et al. (2019) introduced two different nanoparticles, nickel oxide (NiO) and iron (III) oxide (Fe3O4), to increase the bioethanol yield from potato waste. As a result, the bioethanol production was increased and found to be 1.60 and 1.13 times higher than conventional methods.

3.6

Conclusion

A large amount of FW and food processing industrial waste are generated globally due to the rapid increase in population and industrialization. Its management is a challenging task for developed and developing countries. Recovering value-added product instead of waste management is the best solution to reducing several issues associated with FW management. FW contains a high fraction of carbohydrate polymers, which are suitable substrate for driving bioalcohol. Recently the price of petroleum products has increased due to scarcity in supply. In addition, the negative effects of oil products on the environment cause several concerns, which increases the urgency of the search for alternative sources of fuel. Bioalcohol (bioethanol and biobutanol) synthesized from FW meets and replaces the use of petroleum fuel. It has little impact on the environment compared with conventional fuels.

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Chapter 4

Valorization of food waste for biodiesel production M. Dinesh Kumar1, S. Kavitha1 and J. Rajesh Banu2 1

Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India, 2Department of Life Sciences, Central University of

Tamil Nadu, Neelakudi, Thiruvarur, Tamil Nadu, India

4.1

Introduction

Increasing demand for energy has stimulated researchers to develop renewable energy raw materials to meet the energy demand. In addition, the burning of fossil fuels raises environmental issues which increase the need to investigate the possibilities of using alternative fuel energy to replace conventional oil derivatives. Biodiesel has gained increasing attention due to its highly biodegradable nature, lower toxicity, and its advantages of high combustion efficiency, low aromatic, low sulfur content, zero hydrocarbon and particulate matter, and smokeless nature compared to petrochemical fuels (Atabani et al., 2012). Biorefinery is an interesting concept which is used to convert the biological components of organic-rich waste biomass such as proteins, carbohydrates, and lipids to valuable products such as biodiesel. Additionally, biodiesel has an advantage compared with other biofuels as it can be mixed with petroleum-derived diesel. This could be used in existing diesel engines without any alterations needed (Christopher et al., 2014). Some researchers have been working on blending the crop waste or agricultural waste such as rice husks (Panithasan et al., 2019) with diesel fuel to enhance the diesel engine performance. Food waste is recognized as an organic-rich resource consisting of protein (5%
10%), lipid (10%
40%), and carbohydrate (20%
45%), and also it contain nutrients such as proteins, phosphate, and fatty acid (Kannah et al., 2018) so that it can be used by means of valorization for conversion into biodiesel. Nizami et al. (2017) reported that food waste consists primarily of fat and waste cooking oil or used cooking oil, so that it can be considered as organic-rich waste biomass for biodiesel production. Many researchers have investigated the viable production of biofuel using food waste as substrates. For example, Kavitha et al. (2017a) studied converting food waste into useful biofuel, and kitchen food waste was a potential feedstock for biodiesel production (Barik and Paul, 2017). Food waste contains minor quantities of lignin, therefore mild pretreatment is required for the conversion of biodiesel compared to other wastes or residues. Biodiesel is defined as long-chain fatty acid alkyl esters obtained from vegetable oils or animal fats by the transesterification process. In the transesterification process, vegetable oils and fats (or triglycerides) from animals are converted into esters, and alcohol then reacts with fatty acids to form mono alkyl esters. The transesterification process can be mediated through enzymes, bases, and acids. There are two major conversion techniques involved in the transesterification reaction, namely chemical (acidic and basic catalytic conversion) and biological techniques [enzymatic (lipase) or bacterial or fungal conversion]. Recent advances in enzymatic (lipase)-mediated transesterification processes involve the immobilization of enzymes which increases the enzyme stability and shows great potential in industrial-scale biodiesel production. Fig. 4.1 displays the overall biorefinery concept of food waste to biodiesel production. This chapter focuses on recent advances in biodiesel production by valorization of food waste. It also summarizes various pretreatments involved in biodiesel production, the transesterification process, lipase immobilization, biodiesel production using bioreactors, and scalability of biodiesel production.

4.2

Various food waste pretreatments for biodiesel production

In biodiesel production, pretreatment is used to eliminate contamination and other particles or reduce the water content and acidity value. It also enhances the transesterification process. The transesterification reaction is a process in which Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00004-3 Copyright © 2020 Elsevier Inc. All rights reserved.

75

76

Food Waste to Valuable Resources

FIGURE 4.1 Overall biorefinery concept for food waste to biodiesel production.

glycerides are converted into esters in the presence of a catalyst and an alcohol. Several researchers have studied various pretreatments, such as disperser (Kumar et al., 2018), microwave (Eswari et al., 2017), ultrasonication (Tamilarasan et al., 2018), thermal (Kavitha et al., 2016), chemical (Sharmila et al., 2017), bacterial (Kavitha et al., 2017b), and combinative (Kannah et al., 2017) pretreatments for effective disintegration of biomass and enhanced biofuel production. The pretreatments are categorized as physical, mechanical, chemical, and biological, which also are used in the production of biodiesel from food waste either directly or indirectly. Table 4.1 displays the various pretreatments involved in biodiesel production.

4.2.1 Physical pretreatment In physical pretreatment, extraction of biodiesel from the substrate can take place by applying pressure or heat. Wang et al. (2017a,b) investigated enhanced biodiesel production from kitchen waste through physical (hydrothermal) pretreatment in the presence of an alkaline catalyst, sodium methoxide (CH3ONa). In this experiment, with 0.9% CH3ONa, a maximum transesterification productivity of 80.9% was obtained under hydrothermal conditions at 160 C for 80 min. In microwave treatment or microwave-aided transesterification, heat energy is generated by electromagnetic microwave and the produced heat energy converts the substance into fatty acid methyl ester (FAME) or biodiesel (Ruhul et al., 2015). During this process, the thermal energy can be quickly transmitted into the substance. This method has gained more attention due to its advantages such as uniform quick thermal distribution, higher yield with less energy consumption, and reduction of the amount of catalyst required. Microwave pretreatment at a cell pressure 2.2 MPa at 170 C for 4 min were the optimum conditions for the highest biodiesel yield of 96.89% from kitchen waste. Moreover, the authors reported that the microwave method consumed 2.7% less energy as compared with other conventional heating processes. Panadare and Rathod (2016) achieved a 94% biodiesel yield from waste cooking oil through combinative enzyme (Lipase 435 and molar ration 6:1) and microwave-mediated transesterification.

4.2.2 Chemical pretreatment Chemical pretreatment is a process of extracting biodiesel from waste using chemicals (acid or base). Jain et al. (2011) studied biodiesel production using hostel mess waste cooking oil through acid
base treatment. They used 1% (w/w) of

TABLE. 4.1 Various pretreatments used in biodiesel production. Feedstock

Pretreatment

Conditions

Enzyme/catalyst used

Alcohol

Biodiesel yield (%)

References

Kitchen waste

Thermal

Temperature: 160 C

Sodium methoxide (alkaline)

Methanol

80.9

Wang et al. (2017b)

KOH

Methanol

72

Jung et al. (2019)

Lipase 435




94

Panadare and Rathod (2016)

KOH

Methanol

97.65

Milano et al. (2018)

KOH

Methanol

98

Kumar et al. (2010)

Time: 80 min Fish waste

Thermal

Temperature: 380 C Time: 80 min

Waste cooking oil

Microwave

Microwave power: 70 W

Waste cooking oil

Microwave

Time: 7.15 min

Coconut oil

Ultrasonication

Time: 7 min

Time: 4 h



Waste frying oil

Ultrasonication

Temperature: 40 C

Candida antarctica, Thermomyces lanuginosus, Rhizomucor miehei

Ethanol

70

Poppe et al. (2018)

Waste frying oil

Chemical (base)

Temperature: 65 C

Calcium base catalysts

Methanol

96

Catarino et al. (2017)

Sulfonated carbon microspheres

Methanol

89.6

Tran et al. (2016)

KOH

Methanol

94

Sahar et al. (2018)

Waste cooking oil

Waste cooking oil

Chemical (acid) Chemical (base)

Time: 2.5 h Temperature: 110 C Time: 4 h Temperature: 50 C Time: 6 h

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Food Waste to Valuable Resources

H2SO4 and sodium hydroxide (NaOH) and achieved 90.6% conversion at an optimum temperature of 50 C. Rashid et al. (2013) extracted oil from Citrus reticulata (mandarin orange) seed, a potential feedstock for biodiesel. In this treatment, sodium methoxide is used to obtain biodiesel. Nizami et al. (2017) reported producing biodiesel from animal fat using potassium hydroxide (KOH) as catalyst.

4.2.3 Mechanical pretreatment Mechanical pretreatment is an effective method for releasing the organics from biomass through mechanical means. Ultrasonic treatment is an efficient technique to improve the mass transfer rate between immiscible liquid phases. During biodiesel production, ultrasonication emulsified the immiscible liquid reactant through cavitation bubbles. Due to the high-frequency sound waves, molecules in the medium vibrate and create cavities by compression. By sudden extension and intense collapse, microfine bubbles are formed and generate mechanical and chemical effects (Ruhul et al., 2015). Maneechakr et al. (2015) reported that ultrasonic-aided transesterification reduces the reaction period and alcohol-to-oil molar ratio. This method minimizes the consumption of energy when compared with other conventional mechanical methods. The authors performed the experiment with ultrasonication and achieved a biodiesel yield of 90.8% at a time of 8.8 min and temperature of 117 C. Gupta et al. (2015) studied biodiesel production from waste cooking oil with ultrasonication treatment using calcium diglyceroxide as an alkaline catalyst. They achieved a maximum biodiesel yield of 93.5% at a sonication power of 120 W. Moreover, ultrasonic treatment produces high biodiesel yield by reducing the reaction time by at least 30 min as compared to conventional treatment methods. Poppe et al. (2018) reported that ultrasonic treatment with immobilized lipases (combi-lipases) of waste frying oil attained a 70% biodiesel yield in 18 h treatment. Mohod et al. (2017) used a high-speed homogenizer to obtain a 97% biodiesel yield from waste cooing oil using 3% KOH at 2 h and 50 C.

4.2.4 Biological pretreatment Biological pretreatment is a process of treating a substance by biological means to achieve biodiesel. It is a more attractive pretreatment because it is an effective and environment-friendly method. Wastes from vegetables and meat, bakery waste, noodles waste, and used cooking oil are some of the food wastes that can be subjected to enzymatic hydrolysis biologically to obtain lipids for subsequent biodiesel production (Karmee and Lin, 2014). Kannah et al. (2018) described valorization of food waste into biodiesel through microalgae species like Chlorella vulgaris, Microcystis aeruginosa, Botryococcus braunii, Dunaliella tertiolecta, and Chlorella prothothecoides which consist of FAME, for biodiesel production. Biodiesel production using enzymes is elaborately discussed in Section 4. Using oleaginous yeast Yarrowia lipolytica, a biodiesel yield of 0.88 g was achieved from waste cooking oil at a temperature and treatment time of 50 C and 8 h (Katre et al., 2018).

4.2.5 Combined pretreatment A combination of two or more pretreatment methods would improve the oil or lipid release for enhanced biodiesel yield. Khatun et al. (2014) achieved a maximum conversion of 99.5% from waste cooking oil into biodiesel through microwave base-catalyzed treatment. In this treatment, the authors used NaOH and KOH as the base catalyst and a maximum conversion was achieved at 0.5% concentration of KOH. Hsiao et al. (2018) obtained a biodiesel conversion rate of 90.2% from used cooking oil using a homogenizer and calcium methoxide as a homogeneous catalyst. The optimum conditions for this experiment were reported to be 65 C with a rotation speed of 7000 rpm for 90 min. Various pretreatments are involved in the extraction of lipids from food waste and these pretreatments increase the yield of biodiesel production. Pretreatment techniques such as ultrasound and microwave are often used to reduce the reaction time in transesterification and to achieve a high yield, but these techniques have their own advantages and disadvantages.

4.3

Lipids to biodiesel conversion

Lipids are combined with other constituents such as sugar, protein, nutrients, and other carbon-containing matters present in food waste. Food waste contains lipid, a probable substrate which can be utilized in biodiesel production. Normally 5%
30% of lipids exist in waste produced from food. Lipids can be extracted from food waste by many techniques such as extraction, centrifugation, thermal, and fungal hydrolysis. There are also methods involved in lipid

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79

ˇ stariˇc et al., 2012). The identification of a extraction such as supercritical extraction and solvent extraction (Soˇ suitable extraction method of lipids from food waste could provide a better option for biodiesel production. Centrifugation could be used to separate lipids directly or after extraction from feedstocks. In fungal hydrolysis, enzymes produced by the fungus itself are used in the process and there is no need to add commercial enzymes, which is an advantage in hydrolysis. Pleissner et al. (2014) reported that fungi such as Aspergillus awamori and Aspergillus oryzae were used to isolate the lipid content present in waste through fungal hydrolysis. After fungal hydrolysis at 100 C, the lipid mixture is heated to eliminate the water content and the water-free lipid could then be a source for biodiesel production (Karmee and Lin, 2014). Novozyme-435, an enzyme, and KOH are usually used as a catalyst in biodiesel production to obtain high yield from lipid, which is isolated from food waste. Karmee et al. (2015) reported lipid conversion into biodiesel by KOH and Novozyme-435, achieving a conversion of about 100% in 2 h using KOH and 90% in 24 h using Novozyme-435. Karmee (2017) discussed lipid extraction by a rotary evaporator from mixed food waste. Yang et al. (2014) used isolated oil or lipids from noodle waste in biodiesel production. They obtained 5 mL of lipid from 100 g of noodle waste using n-hexane which can be used in the biodiesel production. Barik and Paul (2017) extracted lipids from food waste through Soxhlet extraction and the Bligh
Dyer method using methanol and chloroform. Using the transesterification process, Trzcinski (2017) attained 0.95 FAME/g lipid of biodiesel from 0.74 g/g lipids which was obtained from waste cooking oil. using this method, 647 kilotonnes of biodiesel could be produced annually around the world. Karmee et al. (2014) used supercritical carbon dioxide for extracting lipids from food waste. Unlike the conventional method, supercritical carbon dioxide has no contamination of organic solvents in lipids. Lipid extracted using this method is clean, and can be directly used for biodiesel production. Wang et al. (2017a,b) used a hydrothermal pretreatment method to extract lipids from kitchen waste. They achieved 43.28 g lipids/kg of waste, which shows that lipid yield by hydrothermal pretreatment showed an increment of 27.4 g/kg as compared to a control. Zhang et al. (2018) demonstrated microalgae cultivation from anaerobically digested food waste as a nutrient source for biodiesel production. They obtained a lipid content of 41.69% 6 4.38% and 47.39% 6 2.96% from cultivated microalgae Chlorella sorokiniana SDEC-18 and Scenedesmus SDEC-8, respectively. Schneider et al. (2013) produced 1.5 g/L of FAME or biodiesel from starch-containing wastewater from the food industry. Barik et al. (2018) demonstrated that 37.3% of lipid was extracted from kitchen food waste. The obtained lipids were converted into 33.2% biodiesel yield using methanol as solvent and H2SO4 as catalyst by transesterification.

4.4

Transesterification process

Transesterification is the process of converting mono-, di-, and triglycerides into FAME, known as biodiesel (Karmee and Lin, 2014). Transesterification indicates vegetable oil or fat reactions with an alcoholic group in the presence of a catalyst (Yaakob et al., 2013). The catalyst can be either a base, acid, or an enzyme. Methanol is the most widely used alcohol in the transesterification process due to its low cost, and it has advantages such as producing clean fuel with a lower molecular weight and viscosity. These authors also reported that biodiesel produced through this process has low viscosity which prevents damage to engines. The transesterification process consists an order of three sequential and reversible reactions, where intermediates are produced in the form of diacylglycerols and monoacylglycerols (Veljkovi´c et al., 2012). Generally, the transesterification process is carried out by two methods in biodiesel production: (1) chemical-catalyzed method and (2) enzyme-catalyzed method. Moreover, chemical-catalyzed methods are divided into heterogeneous and homogeneous reactions, depending upon the chemicals used being in solid or liquid form, respectively. Based on the catalytic substances used, the catalyzed transesterification process is mainly classified into two types: (1) acid-catalyzed (heterogeneous and homogeneous) and (2) base-catalyzed transesterification (heterogeneous and homogeneous). Biodiesel production through various transesterification processes is shown in Table 4.2.

4.4.1 Acid-catalyzed transesterification The transesterification process carried out through acids is known as acid-catalyzed transesterification. These types of acid-catalyzed transesterification are best suited for biodiesel production from organic substrates. Tajuddin et al. (2016) detailed the general mechanism of biodiesel production using acid catalyst as follows: a carbonyl group is stimulated to nucleophilic attacks by H1 protonation. Primarily, carbonyl is protonated before OH2. As a result, the carbonyl group is more nucleophilic than OH2. Protonation destabilizes the carbon
oxygen bond, thus causing carbonyl carbon, a stronger electrophile. When alcohol is introduced, proton transfer occurs more rapidly and generates intermediates. Acid enables the removal of water and as a result ester is generated. Fig. 4.2 shows the acid-catalyzed transesterification mechanism.

TABLE 4.2 Biodiesel production through various transesterification processes. Substrate

Catalyst/enzymes

Amount of catalyst used (wt.%)

Alcohol used

Alcohol:oil molar ratio

Reaction time (h)

Temperature ( C)

Yield (%)

References

Acid catalytic transesterification Waste vegetable oil

Carbon-based acid

0.2

Methanol

16.8

4.5

220

80.5

Shu et al. (2010)

Waste olive pomace

H2SO4

20

Methanol

35:1

1

40

97.8

Ouachab and Tsoutsos (2013)

Waste bitter apple

2-(4-Sulfobutyl) pyrazolium hydrogen sulfate

5.2

Methanol

15:1

6

170

89.5

Elsheikh (2014)

Fish waste

SO422/SnO2-ZrO2

5

Ethanol

6.5:1

6

78

82.58

Emanuela et al. (2018)

Waste cooking oil

Sulfamic acid

1

n-Butanol

10:1

2

110

95.6

Gao et al. (2019)

Alkaline or base catalytic transesterification Palm oil

CaO

3

Methanol

8:1

6

60

93

Suryaputra et al. (2013)

Melon seeds

KOH

0.75

Methanol

6:1

1

60

93.16

Fadhil (2013)

Waste vegetable oil

CH3ONa

1.4

Ethanol

8:1

2

45

99.08

Sanli et al. (2018)

Waste cooking oil

Activated carbon—CaO catalyst

11

Methanol

40:1

7

120

96

Konwar et al. (2018)

Waste cooking oil

KOH

1

Methanol

1:3

50

60

94

Sahar et al. (2018)

Enzymatic or lipase transesterification Waste cooking oil

Novozyme-435

1

Methanol

6.2:1

10

50

90

Haigh et al. (2012)

Waste cooking oil

Pseudomonas aeruginosa

0.782 g

Methanol

3.05:1

24

44.2

86

Ali et al. (2017)

Waste cooking oil

Rhizomucor miehei and Candida antarctica




Methanol

3:1

10




91.5

Babaki et al. (2017)

Fish waste

Novozyme-435

50

Ethanol

4.66:1

8

35

82.91

Marı´n-Sua´rez et al. (2019)

Valorization of food waste for biodiesel production Chapter | 4

81

FIGURE 4.2 Acid-catalyzed transesterification mechanism.

Sulfuric acid (H2SO4), sulfonic acid (H2O3S), boron trifluoride (BF3), hydrochloric acid (HCl), and phosphoric acid (H3PO4) are used as homogeneous acid catalysts as H2SO4 and H2O3S are preferable acids in transesterification (Bharathiraja et al., 2014). These homogeneous catalysts are used in liquid form. Yang et al. (2014) reported that 97.8% of biodiesel was produced from noodle waste using 5% v/v H2SO4 as a catalyst. Biodiesel production from low-grade feedstocks and free from fatty acid and water content are benefits of homogeneous catalysts. Homogeneous acidcatalyzed transesterification has some disadvantages such as corrosion problems, contamination, difficult to recycle, secondary products formation, reaction temperature, slow reaction, and weak activity (Abbaszaadeh et al., 2012). To avoid corrosion and contamination problems, better separation and purification methods are essential in biodiesel production. Su and Guo (2014) reported that compared to base-catalyzed methods, acid-catalyzed biodiesel is a better alternate to conventional methods due to its simplicity in promoting a transesterification process without saponification. Biodiesel can be produced directly from high-acidic and low-grade waste oil through this method. Heterogeneous or solid acid catalysts are considered as replacements for homogeneous acid catalysts to avoid toxic waste production (Su and Guo, 2014). Various solid catalysts, such as zirconium oxide (ZrO2), titanium oxide (TiO2), tin oxide (SnO2), sulfonic ion-exchange resin, zeolites, modified sulfonic meso-structured silica, carbon-based sulfonated catalyst, heteropolyacids, sulfated zirconia, tungstated zirconia, and Nafion-NR50, are some of the heterogeneous acid catalysts used in biodiesel production. Fig. 4.3 displays the acid-catalyzed transesterification process. Gao et al. (2019) produced biodiesel at a yield of 95.6% from waste cooking oil using heterogeneous acid catalyst, sulfamic acid with n-butanol. Using carbon microsphere sulfonated (CM-SO3H), a low-cost acid catalyst, Tran et al. (2016) achieved 89.6% biodiesel yield from food waste cooking oil at 110 C and 4 h. Some benefits of solid acid catalysts are insensible to free fatty acid, easy separation, less contamination, recycling and regeneration of catalyst are easy, and less corrosion (Lam et al., 2010). Fadhil et al. (2016) reported that acid catalyst was employed to remove free fatty acids and to increase the biodiesel yield to 97%. In addition, the acid-catalyzed transesterification process is an effective process in biodiesel production, especially from waste cooking oils with high water and fatty acids contents (Li et al., 2018). Refaat (2010) stated that acid catalysts have the advantage of producing biodiesel directly from lowcost lipid feedstocks which is related to their high FFA concentrations.

4.4.2 Alkaline-catalyzed transesterification A transesterification process that involves the application of alkali or base as catalyst is known as alkaline- or basecatalyzed transesterification. Tajuddin et al. (2016) briefly explained the mechanism involved in transesterification using alkaline catalysts, as shown in Fig. 4.4. In alkaline condition, RO2 ions attack the carbonyl group of triglyceride ions to form tetrahedral intermediary products. Then the process is followed through the readjustment of the intermediate which produces molecules of methyl ester and diglyceride ion. Finally, there is a further nucleophilic attack on the electrophile-producing glycerol and biodiesel (FAME).

82

Food Waste to Valuable Resources

FIGURE process.

4.3 Acid-catalyzed

transesterification

FIGURE 4.4 Alkaline-catalyzed transesterification mechanism.

MgO, Al2O3, mixed oxides of CaO
MgO, Li4SiO4, and Na2SiO3 are some of the alkaline-based catalysts used in the transesterification process. NaOH, KOH, sodium methoxide, potassium methoxide, sodium butoxide, and sodium propoxide are the most commonly used homogeneous alkali catalysts in biodiesel production (Norjannah, 2016). Lam

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83

et al. (2010) stated that this type of catalyst is usually used in industrial biodiesel production because it has the capability to catalyze at low temperature and pressure, it takes little time for conversion, it has wide availability, and is cost effective. Additionally, the authors reported that the reactions mediated by these catalysts could be 4000 times faster than acidic catalyst. However, use of this type of catalyst is inadequate when substances have a low free fatty acid content. No water molecule formation takes place, which is an advantage of using alkaline catalysts in transesterification. With a reduced period of 30
60 min, a high grade of biodiesel can be produced with a better yield using these chemical catalysts when the feedstock has less than 0.5 wt.% of free fatty acid (Atadashi et al., 2013). The alkaline-catalyzed transesterification process is shown in Fig. 4.5. NaOH, methoxide, or KOH are some homogeneous alkaline catalysts which may have the tendency to produce saponification when the feedstock has more than 3 wt.% of free fatty acids (Wilson and Lee, 2012). However, Yan et al. (2010) reported that this may make the process difficult during separation. Yang et al. (2014) experimented with KOH (2% w/v) base catalyst under optimized conditions such as 60 C in 2 h and achieved 98.5% of biodiesel from noodle waste. Easier biodiesel production, a simple purifying process, economical production, and less impact on the environment are considerations for heterogeneous catalysis gaining attention in transesterification biodiesel production (Aransiola et al., 2013).

4.4.3 Enzyme-catalyzed transesterification Enzymatic transesterification has gained increasing attention because it gives a high-quality product, and is easily separable, reusable, and has less of an impact on environment. Moreover it effectively employs high free fatty acid feedstocks with low energy input (Kuan et al., 2013). Lipase, an enzyme, is a significant biocatalyst which can be used in reactions such as hydrolysis, acidolysis, alcoholysis, or transesterification and aminolysis. They have excellent physiological and biochemical properties which enhance biodiesel production (Yu¨cel et al., 2013). In transesterification, lipase initiates the reaction and enhances the process in low temperatures and also stimulates the selectivity for fatty acid composition preferred in biodiesel synthesis (Sanaz et al., 2010). In the first step, enzymes react with triacylglyceride substrates, then form into a complex enzyme substrate. Triacylglyceride ester bonds are hydrolyzed, then form as

FIGURE 4.5 Alkaline-catalyzed transesterification process.

84

Food Waste to Valuable Resources

FIGURE 4.6 Enzyme-catalyzed transesterification mechanism.

diacylglycerides and fatty acid. In the second step, diacylglycerides are free from complex enzyme diacylglyceride fatty acid substance and leave the enzyme in a complex fatty acid. When alcohol reacts with complex fatty acids, it forms alkyl ester (biodiesel) (Chen et al., 2018). Fig. 4.6 illustrates the enzymatic catalyzed transesterification mechanism. Enzyme source, solvent used, temperature, and water content are some of the factors that influence enzymatic transesterification. Normally, enzymatic or lipase biocatalysts are categorized into either intracellular or extracellular lipase. Lipase separated from microbial broth and purified is described as extracellular lipase. Mucor miehei, Rhizopus oryzae, Candida antarctica, and Pseudomonas cepacia are microbes which produce extracellular lipases. Through submerged or solid-state fermentation, extracellular lipase is produced and purified subsequently. Depending on the lipase structure, the purification process is determined. Most immobilized lipases are extracellular, such as Novozyme-435, Lipozyme RM IM, and Lipozyme TL IM (Ghaly et al., 2010). The high cost associated with separation and purification is the major disadvantage of biodiesel production through extracellular lipase. Intracellular lipases are present in cells or cell membranes, and are produced as whole-cell biocatalyst (Gog et al., 2012). The ester yields can be attained at a lower cost by employing intracellular lipase as catalyst. However, the process mediated by intracellular lipases is slower than using extracellular lipases. R. oryzae and Aspergillus are widely used intracellular lipases in biodiesel production. Though soluble lipases are easy to produce at low cost, they can be used only once and then become inactive. Hence, lipases must be improved to increase biodiesel production economically also. This can be solved by immobilization techniques. Immobilization technologies improve lipases with better operative solidity and reusability, which results in greater conversion rates and reduced reaction time (Luna et al., 2016). The advantages of enzymatic catalyzed transesterification over chemical transesterification are mild reactions, easy recovery, catalyst being recyclable, no inhibitory products, high product quality, no saponification, a lower alcohol-to-oil ratio, and complete free fatty acids (Norjannah et al., 2016; Kayode and Hart, 2017). Fig. 4.7 illustrates biodiesel production through the enzyme-catalyzed transesterification process.

4.4.3.1 Immobilized enzyme-catalyzed transesterification Immobilization is an advanced technique in which enzymes are attached to an insoluble supporting carrier or entrapped in a substance. To acquire more stable, active, and economic lipases, the enzymes must be subjected to physical and chemical modifications and gene expression methods. Lipase reuse may be a solution to reducing the cost of enzymes and making them available on an industrial level.

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85

FIGURE 4.7 Enzyme-catalyzed transesterification process.

4.4.3.2 Various enzyme immobilization techniques and their applications To improve the enzyme stability in biodiesel production, various immobilization techniques have been developed (Tan et al., 2010). Ushani et al. (2017) studied the immobilized bacterial pretreatment to enhance biogas generation. Physical adsorption, cross-linking, entrapment, encapsulation, and covalent bonding are techniques involved in the immobilization enzymatic process. Additionally, immobilization techniques can be further categorized as reversible or irreversible, depending on the connection between carriers and enzymes (Zhao et al., 2015). In mild conditions, the enzymes can be separated from the supporting carrier, known as reversible immobilization, whereas in irreversible immobilization, the enzymes cannot be separated without abolishing or terminating their supporting carrier as well as biological action of the enzyme. Adsorption and several noncovalent bonding, such as affinity bonding and chelation bonding, are familiar reversible immobilization techniques. Cross-linking, covalent bonding, and entrapment are commonly used irreversible immobilization techniques. However, each technique has its own benefits and drawbacks in enzymatic transesterification. Fig. 4.8 shows the various immobilization techniques involved in biodiesel production. 4.4.3.2.1 Adsorption In the adsorption process, enzymes are affixed to the outer layer of the supporting material physically through van der Waals forces, dispersion forces, or hydrophobic bonds. In this method, a solid supporting carrier is soaked in enzymes or the enzymes may be coated on the surface of the carriers. By increasing hydrophobic or electrostatic forces, the contact between the enzymes and carriers can be strengthened. Using a charged carrier or enzyme, a strong electrostatic interaction can be obtained. Polystyrene, polyacrylate, and polypropylene are commonly used polymer-supporting materials as they are available commercially. Properties such as particle size, surface area, porosity, pore size, polarity, molar ratio, and chemical composition can define the quantity of enzyme attached and enzyme activity. Enzymes from C. antarctica immobilized on acrylic resin (Novozyme-435) and enzymes from Candida sp. 99
125 immobilized on cheap textile membrane are the most commonly used enzymes in industrial applications (Tan et al., 2010). Candida sp. 99
125 was immobilized on Fe3O4 hollow submicrospheres through physical adsorption and achieved 93.4% FAME yield from waste cooking oil (Liu et al., 2016). At low temperature, a biodiesel yield of 89.6% was achieved for the same immobilized enzymes after eight reuse cycles. Immobilization conditions and supporting carrier properties have major impacts on the enzyme activity and recovery (Stoytcheva et al., 2011). Increased contact between enzymes and

86

Food Waste to Valuable Resources

FIGURE 4.8 Various enzyme immobilization techniques.

supporting carriers without affecting enzymatic activity is essential for further enhancement of the immobilization technique. Adsorption has several merits such as easy preparation, recyclability and reuse, economical availability, no need for chemicals, and high enzyme activity, which make this the most widely used immobilization technique commercially. 4.4.3.2.2

Cross-linkage

Cross-linkage is the process of immobilizing the enzymes through the intermolecular cross-linking. This immobilization is accomplished through adding multifunctional reagents such as glutaraldehyde (Zhao et al., 2015). Luna et al. (2016) described this type of immobilization as a formation of a three-dimensional structure within the enzyme, supporting carrier, and reagent used. Reagents used in cross-linkage can alter the conformation of enzymes that possibly lead to considerable enzyme activity loss. Yan et al. (2011) discussed biodiesel production from waste cooking oil using enzymes from Geotrichum sp. by cross-linked immobilization. This immobilized enzyme enhanced thermostability and improves pH as compared to free enzyme. Using methanol, they achieved an 85% biodiesel yield. Enzymes from Aspergillus niger immobilized by cross-linkage in a macroporous anion resin obtained 48.3% biodiesel from conversion of agroindustrial food waste (Aliyah et al., 2016). In cross-linkage, low immobilization yield and absence of required mechanical properties are some of the demerits which can be rectified through combined immobilization techniques. 4.4.3.2.3 Entrapment The entrapment technique is a type of immobilization technique that involves seizing enzymes within a network that allows substrate and product to pass through while holding the enzymes. Alternately, it can be stated that the enzyme polymer blends capture the enzyme through cross-linkage. This immobilization can be classified into three types: gel entrapment, fiber entrapment, and microencapsulation. The following are the most commonly used supporting carriers in entrapment: resins, acrylic polymer, alginate, celite, and carrageenan. Entrapment enzymes are more stable and show enhanced activity as compared to adsorption enzymes. Biocatalysts were entrapped in alginate beads and used in the conversion of agroindustrial raw waste products (Regner et al., 2019). By comparing with free enzymes, immobilized enzymes achieved 95.89% biodiesel conversion, whereas free enzymes achieved only 57.32%. The mass transfer problem is the main disadvantage of entrapping immobilization. Furthermore, glycerol produced during this process increases the viscosity and sticks to the outer layer of the supporting material, which may control the diffusion of product and reactant.

Valorization of food waste for biodiesel production Chapter | 4

4.4.3.2.4

87

Encapsulation

Encapsulation is a technique for trapping the enzymes in an insoluble gel polymer (Poppe et al., 2015). Encapsulation endows a cage-like protection which stops leaking of enzymes and advances mass transfer. Sol
gel encapsulation has proven to be an easy and effective way to immobilize enzymes. Razack and Duraiarasan (2016) immobilized enzymes from Burkholderia cepacia and Bacillus subtilis by encapsulation and used these for biodiesel production. They achieved 93.6% maximum biodiesel yield from restaurant waste cooking oil. Jegannathan et al. (2010) reported that encapsulation of enzymes from B. cepacia into κ-carrageenan could increase biodiesel conversion to 100%. Enzymes from Rhizomucor miehei were encapsulated in pure inorganic silica shell to obtain an 86% biodiesel yield (Macario et al., 2013) and moreover the encapsulated enzymes were 60% active even after five reuse cycles. 4.4.3.2.5 Covalent binding Covalent binding is a technique for forming a covalent bond connection between the aldehyde group of a supporting carrier and active amino acid residue on the enzyme surface. Chitosan, chitin, nylon fibers, hydrophobic polypeptides, and methacrylamide are materials used as supporting carriers in covalent binding immobilization. As a natural polymer, chitosan is widely used as a supporting carrier because of its membrane developing and adhesion capacity, high strength, and ability to develop an insoluble film in water. Using lipase from an enzymatic mixture of R. oryzae and Candida rugosa which were covalently immobilized on silica, Jang et al. (2012) obtained 88.9% biodiesel conversion from canola oil. Zhang et al. (2012) stated that combined use of two immobilized enzymes with balancing position specificity instead of a single enzyme may produce biodiesel economically by reducing the cost. Thermomyces lanuginosus enzymes immobilized on Fe3O4 by covalent binding were used to produce biodiesel from vegetable oil and as a result 97.2% biodiesel production was achieved in 50 C for 24 h (Raita et al., 2015). Tan et al. (2010) reported the probable advantage of covalent binding immobilization as irreversible binding of the lipase to the support matrix. Table 4.3 displays the biodiesel yield achieved in various immobilization techniques. Compared with chemical catalysis, the enzymatic method of biodiesel production has advantages in economic perspective, operation, and eco-friendly methods. Industrial biodiesel production through enzymatic processes has been significantly developed recently. Immobilized enzymes offer great potential for industrial biodiesel production. Enzymes are the greatest single cost in biodiesel production. This can be reduced by using the correct amount of enzymes or by increasing the reuse of enzymes. To enhance the economic competiveness of immobilized enzymes in biodiesel production, the following aspects should be considered: increasing the stability of immobilized enzymes, developing unique reactors, comprehensive study of the kinetics of immobilized enzymes in conversion of substrate into biodiesel, and optimization of the process.

4.5

Reactors involved in biodiesel production

Various reactors have been developed for the transesterification process. Reactors used in biodiesel production are operated either in batch, semibatch, or continuous mode, depending on the scale of biodiesel production. The following reactors are commonly used bioreactors in biodiesel productions: stirred tanks, packed beds, fluidized beds, expanding beds, and membrane reactors. Various reactors involved in biodiesel production are illustrated in Fig. 4.9. The stirred tank reactor (STR) is the most commonly used reactor due to its simple setup and suitability for highly viscous solutions. It consists of a reactor and a propeller. Helwani et al. (2009) discussed using batch-mode STR in industry as having the disadvantage of shear stress enacted through mechanical agitation which affects the enzymes during the process. To avoid this, a porous basket is fitted with the STR. This basket holds enzymes and allow substrate to react with enzymes through the pores (Baltaru et al., 2009). The agitation speed and type of stirrer used in batch mode are also important factors. In batch-mode STR, productivity is low but this can be increased by means of a continuousmode STR in which a filter is employed at the reactor outlet to hold the enzymes (Christopher et al., 2014). Usually the batch mode takes a long period time for the reaction, hence in large-scale operations it requires a large volume of tanks and the process is not continuous. This leads to steady enzymatic activity loss which affects the reaction period that needs to be increased to obtain a high conversion rate. This may cause low production along with being more time consuming but this time can be reduced by replacing the enzymes (Nielsen et al., 2008). The benefits of batch-mode operations include high substrate dispersion, simple setup, ease reaction control, and simple reaction kinetics. Packed-bed reactors (PBRs) can function either in batch or continuous mode by recycling the reaction mixture. Recycling the substrate can be carried out by allowing the substrate to move a desired velocity through the column. In an industrial scale, up flow is usually preferred over down flow as it does not compact the enzyme bed, which can result in blockages with poor oxygen transfer and pressure drops (Fjerbaek et al., 2009). Enzymes can be effectually reused without separation.

TABLE. 4.3 Biodiesel yield achieved using various immobilization techniques. Substrate

Immobilization technique

Immobilized enzyme

Supporting carrier

Acyl acceptors

Acyl acceptor: oil ratio

Temperature ( C)

Reaction time (h)

Biodiesel yield (%)

References

Waste cooking oil

Adsorption

Candida sp. 99
125

Fe3O4 hollow submicrospheres

Methanol

1.1:1

10




93.4

Liu et al. (2016)

Waste cooking oil

Adsorption

MAS1 enzyme

XAD1180 macroporous resin

Methanol

3:1

30

24

95.45

Wang et al. (2017)

Waste sardine oil

Adsorption

Aspergillus niger

Activated carbon

Methanol

9:1

30

10

94.55

Arumugam and Ponnusami (2017)

Waste cooking oil

Cross-linkage

Geotrichum sp.

K2SO4

Methanol

4:1

50

4

85

Yan et al. (2011)

Waste vegetable oil

Cross-linkage

Candida antarctica lipaseB

Magnetic nanoparticles of magnetite (Fe3O4)

2-Propanol

6:1

30

72

92

Cruz-Izquierdo et al. (2014)

Manilkara zapota seed

Cross-linkage

C. antarctica lipase-B




Methanol

3:1

40

4

84

Karmee (2017)

Waste cooking oil

Entrapment

Pseudomonas cepacia

Polyallylaminemediated biomimetic silica

Methanol

3:1
5:1

43.3

36

68

Kuan et al. (2013)

Waste frying oil

Entrapment

Thermomyces lanuginosus

Poly vinyl alcohol
alginate beads

Methanol

6:1

45

90

92

Cruz-Ortiz and Rı´os-Gonza´lez (2017)

Waste vegetable oil

Covalent

P. cepacia

Epoxy
acrylic resin

Ethanol

1:1

250

2

47

Lopresto et al. (2015)

Waste cooking oil

Covalent

Rhizomucor miehei and C. antarctica

Silica gel

Methanol

3:1

-

10

91.5

Babaki et al. (2017)

Waste cooking oil

Covalent

C. antarctica

Magnetic nanoparticles

Methanol

3:1

50

96

100

Mehrasbi et al. (2017)

Palm oil

Encapsulation

Burkholderia cepacia

k-Carrageenan

Methanol

7:1

30

72

100

Jegannathan et al. (2010)

Waste cooking oil

Encapsulation

B. cepacia

Sodium alginate

Methyl acetate

12:1

35

60

93.61

Razack and Duraiarasan (2016)

B. subtilis

Valorization of food waste for biodiesel production Chapter | 4

89

FIGURE 4.9 Reactors involved in biodiesel production.

Continuous-mode PBR has advantages such as being economical, and having better efficiency, easy mode of operation, and less construction and maintenance. Veny et al. (2014) reported a PBR with circulation mode which allows the enzyme to be active due to the circulation, providing adequate mixing conditions with solid retention times. Moreover, the downward circulation of the reaction mixture can reduce the mass transfer limitation. Generally, the operation period is long under steady-state conditions to avoid productivity losses in enzymatic reactors (Amini et al., 2017) and the continuous-mode reactor is a better choice for industrial applications than batch reactors. Buasri et al. (2012) achieved an 86.7% biodiesel conversion rate using a potassium hydroxide catalyst supported PBR at a temperature and reaction time period of 60 C and 2 h from waste frying oil. Moreover, in this study Jatropha curcas fruit shell activated carbon was also used with potassium hydroxide to enhance the process. Using soybean oil, Zhou et al. (2014) prepared biodiesel in a magnetically stabilized, fluidized bed reactor using immobilized R. oryzae lipase in magnetic chitosan microspheres and achieved 91.3% (w/v) of biodiesel at a fluid flow rate of 25 mL/min and a magnetic field intensity of 150 Oe. Hingu et al. (2010) investigated biodiesel production using a sono-chemical reactor at 45 C with time and power of 40 min and 200 W, respectively. They achieved 94.5% purity of biodiesel. Reaction and separation take place as a single process in membrane reactors. In membrane reactors, enzymes are immobilized on the membrane either as a flat sheet or hollow fiber. He et al. (2012) reported that a membrane reactor enhances the transesterification yield and rate in biodiesel production at the lab level and needs to be improved for large-scale use. They also reported that membrane reactors are employed for filtration of biodiesel. In the biodiesel process, three types of filtration—microfiltration, nanofiltration, and ultrafiltration—and three configuration types—flat or frame sheet, tubular, and hollow fiber—are used. The membrane separation method is employed to eliminate glycerol during biodiesel filtration. Gomes et al. (2010) reported 99.6% as the highest retention rate of glycerol during biodiesel separation using ceramic membranes. Membrane reactors have several advantages in transesterification, such as short reaction time, a process requiring a small number of steps, high yield, with better quality. Baroutian et al. (2010) reported biodiesel produced through membrane reactors as being of good quality with standard specifications. However, using membrane in a reactor and in the separation process were inadequate because of the intense reaction and conditions. Choedkiatsakul et al. (2015) worked on a new method of biodiesel production using a microwave-assisted reactor. This experiment was carried out at the optimum conditions of 70 C with a microwave power of 400 W; using 1 wt.% of NaOH as catalyst and a methanol to oil ratio of 12:1, 99.4% biodiesel production was obtained. Additionally, the energy consumed (0.1167 kWh/L) using microwaves was 50% less than in a conventional process. Elkady et al. (2015) investigated biodiesel produced from waste vegetable oil using KM micromixer by the transesterification method. In this experiment, the authors used 1% of NaOH as catalyst with a methanol to oil molar ratio of 12:1 and obtained 97% biodiesel conversion. Various reactors involved in biodiesel production are discussed in Table 4.4.

TABLE 4.4 Various reactors involved in biodiesel production. Reactor

Configuration

Feedstock

Enzyme/catalyst

Alcohol

Yield (%)

References

Continuous stirred tank reactor




Waste oil

Carbon-based solid acid catalyst

Methanol

68.61

Keong et al. (2016)

Continuous stirred tank reactor




Waste cooking oil




Methanol

91

Aboelazayem et al. (2017)

Membrane reactor

Diameter: 47 mm

Vegetable oil

Immobilized Candida rugosa

Methanol

97.2

Kuo et al. (2013)

Soybean oil




Methanol

90

Luo et al. (2017)

Vegetable oil

Immobilized Rhizopus oryzae

Methanol

82

Zhou et al. (2014)

Vegetable oil

Immobilized Novozyme-435

Ethanol

98.1

Fidalgo et al. (2016)

Waste cooking oil

Immobilized Pseudomonas mendocina

Methanol

91.8

Chen et al. (2017)

Vegetable oil

Immobilized Pseudomonas cepacia

Methanol

88

Wang et al. (2011)

Waste food oil

Immobilized enzymes of Candida antarctica, Thermomyces lanuginosus, Rhizomucor miehei

tertButanol

50

Poppe et al. (2018)

Pore size: 0.45 μm Thickness: 140 μm Membrane reactor

Thickness: 3.5 mm

Fluidized bed reactor

Internal diameter: 300 mm

Diameter: 65 mm

Height: 400 mm Fluidized bed reactor

Inner diameter: 12 mm Height: 375 mm Volume: 42.4 m3

Fluidized bed reactor

Inner diameter: 100 mm Length: 950 mm

Packed-bed reactor

Inner radius: 1.6 cm Axial height: 20 cm

Packed-bed reactor

Inner diameter: 10 mm Height: 65 mm Volume: 5.1 L

Valorization of food waste for biodiesel production Chapter | 4

91

In recent years, biodiesel production has been carried out using various microreactors (Dennis et al., 2013) with homogeneous base catalyst. Using microreactors gives a higher chemical reaction than conventional batch reactors and also reduces the time taken for the reaction and conversion (Billo et al., 2015). Microreactors have numerous merits over batch conventional reactors, such as minimum size of the reactor for the process, mild temperature, less pressure, less energy used, and capability to produce a greater amount of biodiesel in a shorter time without compromising the standards and minimum capital cost. Machsun et al. (2010) developed a membrane microreactor with a diameter of 63.5 mm which attained a biodiesel conversion rate of 80% at 19 min and 35 C. Another membrane reactor made from ceramic consists of a pore size of 0.05 m, length of 40 cm, and inner and outer diameters of 1.60 and 2.54 cm, respectively, which obtained 94% biodiesel conversion (Baroutian et al., 2010).

4.6

Scalability of biodiesel production

Commercial production of biodiesel mainly depends on the feedstock used, reactor configurations, conditions such as temperature, acyl acceptor or alcohol used, type of catalysts used, and treatment process. Price et al. (2016) demonstrated a pilot-scale plant for the transesterification process with a capacity of 80 L fed-batch scale process reactor combined with 4 m3 CSTR process through NS-40116 enzyme catalyst isolated from T. lanuginosus. They evaluated the performance of both fed batch and CSTR by operational parameters such as reaction time, enzyme efficiency, and reactor productivity. By comparing both reactors, they found that fed-batch operation showed better results than CSTR in commercial aspects. Tan et al. (2010) discussed a biodiesel production factory in Shanghai, China, with a capacity of 10,000 tonnes enzymatic production. From waste cooking oil, the factory obtained a biodiesel yield of 90% under suitable conditions with immobilized enzymes from Candida sp. 99
125 as the catalyst. Nizami et al. (2017) stated that all the fat content in food waste that is produced in Makkah might produce 62,500 tonnes of biodiesel through the transesterification method. In the Kingdom of Saudi Arabia, a net saving of 76.5 million Saudi Arabian Riyal could be added to their economy by developing transesterification. There are two processes widely used in these industries: one is the liquid enzymatic process and the other is the immobilized enzyme process. Chen et al. (2018) stated that Viesel Fuel LLC and TransBiodiesel are two industries using liquid enzymes and immobilized enzymes, respectively, for large-scale biodiesel production. In addition, Viesel fuel was the first biodiesel plant to implement enzyme biodiesel production using liquid enzymes in CSTR. Although CSTR has poorer reactor productivity, Viesel Fuel still adapted the CSTR in their production, because they consider that continuous and steady operation is vital in industrial biodiesel production. TransZymeA, an immobilized enzyme produced by TransBiodiesel Ltd. can be reused for 300 cycles, in continuous and discontinuous reactor systems (Budˇzaki et al., 2018). Both in batch and continuous reactors, TransZymeA provided maximum conversion rates of 86% and 95%, respectively (Ilmi et al., 2017). The European Union is the largest biodiesel producer in the world. Annually, 22,117,000 tonnes of biodiesel production takes place in the European Union. In the European Union, currently there are 150 biodiesel-producing facilities including 120 active biodiesel plants. Lin et al. (2013) reported on a UK-based company which produces biodiesel from food waste which includes animal byproducts. This company currently has an operational potential of processing 2000 metric tonnes/year of food waste sources. Biodiesel can be used in diesel engines with some alterations in many sectors, such as transportation, vehicles like locomotives, agricultural equipment, and construction machinery, and in stationary equipment such as furnaces and generators.

4.7

Future prospects and conclusion

In biodiesel generation, any economic possibilities are mainly influenced by the catalyst, reactors used, and raw materials. The use of low-cost feedstocks can introduce many impurities and high fatty acid and water contents. Therefore such feedstock requires further pretreatment and purification or a filtration process to produce better product. This demands higher expenditure in production and, to avoid this, there should be a concession concerning the cost reduction while using cheaper feedstock. The conversion of food waste into biodiesel is a time-consuming and cost-ineffective process due to the chemicals or treatment processes involved and correcting this is challenging. It could be addressed by escalating the research and optimization studies and focusing on integrating value-added products with the production methods. For example, fats or lipids present in food waste can be extracted by several methods which may be useful in the production of biodiesel. This approach could permit us to reach the preferred food waste management approach of decreasing the waste economy and enabling a more sustainable bio-based society. Additionally, the seriousness of food waste should be highlighted to the public and they should be made aware of the need to reduce waste at source. By growing lab-scale

92

Food Waste to Valuable Resources

treatment into a full-scale operation proves that biodiesel production from food waste is technically and economically viable. In future, biofuel will play a substantial role in meeting global energy demands.

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60055. Ouachab, N., Tsoutsos, T., 2013. Study of the acid pretreatment and biodiesel production from olive pomace oil. J. Chem. Technol. Biotechnol. 88, 1175
1181. Panadare, D.C., Rathod, V.K., 2016. Microwave assisted enzymatic synthesis of biodiesel with waste cooking oil and dimethyl carbonate. J. Mol. Catal. B: Enzym. 133, S518
S524. Panithasan, M.S., Gopalakichenin, D., Venkadesan, G., Veeraraagavan, S., 2019. Impact of rice husk nanoparticle on the performance and emission aspects of a diesel engine running on blends of pine oil-diesel. Environ. Sci. Pollut. Res. 26 (1), 282
291. Pleissner, D., Kwan, T.H., Lin, C.S.K., 2014. Fungal hydrolysis in submerged fermentation for food waste treatment and fermentation feedstock preparation. Bioresour. Technol. 158, 48
54. Poppe, J.K., Fernandez-Lafuente, R., Rodrigues, R.C., Ayub, M.A.Z., 2015. Enzymatic reactors for biodiesel synthesis: present status and future prospects. Biotechnol. Adv. 33, 511
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359. Razack, S.A., Duraiarasan, S., 2016. Response surface methodology assisted biodiesel production from waste cooking oil using encapsulated mixed enzyme. Waste Manag. 47, 98
104. Refaat, A.A., 2010. Different techniques for the production of biodiesel from waste vegetable oil. Int. J. Environ. Sci. Technol. 7, 183
213. Regner, E.L., Salvatierra, H.N., Baigorı´, M.D., Pera, L.M., 2019. Biomass-bound biocatalysts for biodiesel production: tuning a lipolytic activity from Aspergillus niger MYA 135 by submerged fermentation using agro-industrial raw materials and waste products. Biomass Bioenergy 120, 59
67. Ruhul, A.M., Kalam, M.A., Masjuki, H.H., Fattah, I.M.R., Reham, S.S., Rashed, M.M., 2015. State of the art of biodiesel production processes: a review of the heterogeneous catalyst. RSC Adv. 5, 101023
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226. Sanli, H., Alptekin, E., Canakci, M., 2018. Production of fuel quality ethyl ester biodiesel: 1. Laboratory-scale optimization of waste frying oil ethanolysis, 2. Pilot-scale production with the optimal reaction conditions. Waste Biomass Valoriz. 10, 1
10. Sanaz, S., Cheng, N.G., Yusoff, R., 2010. An overview on transesterification of natural oils and fats. Biotechnol. Bioprocess. Eng. 15, 891
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63. Sharmila, V.G., Dhanalakshmi, P., Banu, J.R., Kavitha, S., Gunasekaran, M., 2017. Effect of deflocculation on photo induced thin layer titanium dioxide disintegration of dairy waste activated sludge for cost and energy efficient methane production. Bioresour. Technol. 244, 776
784. Shu, Q., Gao, J., Nawaz, Z., Liao, Y., Wang, D., Wang, J., 2010. Synthesis of biodiesel from waste vegetable oil with large amounts of free fatty acids using a carbon-based solid acid catalyst. Appl. Energy 87, 2589
2596. ˇ stariˇc, M., Klinar, D., Bricelj, M., Golob, J., Beroviˇc, M., Likozar, B., 2012. Growth, lipid extraction and thermal degradation of the microalga Soˇ Chlorella vulgaris. N. Biotechnol. 29 (3), 325
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374. Trzcinski, A.P., 2017. Biofuels from Food Waste: Applications of Saccharification Using Fungal Solid State Fermentation. CRC Press. Ushani, U., Kavitha, S., Johnson, M., Yeom, I.T., Banu, J.R., 2017. Upgrading the hydrolytic potential of immobilized bacterial pretreatment to boost biogas production. Environ. Sci. Pollut. Res. 24, 813
826. Veljkovi´c, V.B., Avramovi´c, J.M., Stamenkovi´c, O.S., 2012. Biodiesel production by ultrasound-assisted transesterification: state of the art and the perspectives. Renew. Sust. Energ. Rev. 16, 1193
1209. Veny, H., Aroua, M.K., Sulaiman, N.M.N., 2014. Kinetic study of lipase catalyzed transesterification of jatropha oil in circulated batch packed bed reactor. Chem. Eng. J. 237, 123
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nanoparticle biocomposite. Bioresour. Technol. 102, 6352
6355. Wang, C., Xie, S., Zhong, M., 2017a. Effect of hydrothermal pretreatment on kitchen waste for biodiesel production using alkaline catalyst. Waste Biomass Valori. 8, 369
377. Wang, X., Qin, X., Li, D., Yang, B., Wang, Y., 2017b. One-step synthesis of high-yield biodiesel from waste cooking oils by a novel and highly methanol-tolerant immobilized lipase. Bioresour. Technol. 235, 18
24. Wilson, K., Lee, A.F., 2012. Rational design of heterogeneous catalysts for biodiesel synthesis. Catal. Sci. Technol. 2 (5), 884
897. Yaakob, Z., Mohammad, M., Alherbawi, M., Alam, Z., 2013. Overview of the production of biodiesel from waste cooking oil. Renew. Sustain. Energy Rev. 18, 184
193. Yan, S., Dimaggio, C., Mohan, S., Kim, M., Salley, S.O., Ng, K.Y.S., 2010. Advancements in heterogeneous catalysis for biodiesel synthesis. Top. Catal. 53, 721
736. Yan, J., Yan, Y., Liu, S., Hu, J., Wang, G., 2011. Preparation of cross-linked lipase-coated micro-crystals for biodiesel production from waste cooking oil. Bioresour. Technol. 102, 4755
4758.

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Yang, X., Jun, S., Young, H., Suk, H., Park, C., Wook, S., 2014. Biorefinery of instant noodle waste to biofuels. Bioresour. Technol. 159, 17
23. ¨ zc¸imen, D., 2013. Lipase applications in biodiesel production. Biodiesel - Feed. Prod. Appl. 209
250. Yu¨cel, S., Terzio˘glu, P., O Zhang, B., Weng, Y., Xu, H., Mao, Z., 2012. Enzyme immobilization for biodiesel production. Appl. Microbiol. Biotechnol. 93, 61
70. Zhang, L., Cheng, J., Pei, H., Pan, J., Jiang, L., Hou, Q., et al., 2018. Cultivation of microalgae using anaerobically digested effluent from kitchen waste as a nutrient source for biodiesel production. Renew. Energ. 115, 276
287. Zhao, X., Qi, F., Yuan, C., Du, W., Liu, D., 2015. Lipase-catalyzed process for biodiesel production: enzyme immobilization, process simulation and optimization. Renew. Sustain. Energy Rev. 44, 182
197. Zhou, G.X., Chen, G.Y., Yan, B.B., 2014. Biodiesel production in a magnetically-stabilized, fluidized bed reactor with an immobilized lipase in magnetic chitosan microspheres. Biotechnol. Lett. 36, 63
68.

Further reading Feng, Y., Zhang, A., Li, J., He, B., 2011. A continuous process for biodiesel production in a fixed bed reactor packed with cation-exchange resin as heterogeneous catalyst. Bioresour. Technol. 102 (3), 3607
3609. Ren, Y., He, B., Yan, F., Wang, H., Cheng, Y., Lin, L., et al., 2012. Continuous biodiesel production in a fixed bed reactor packed with anionexchange resin as heterogeneous catalyst. Bioresour. Technol. 113, 19
22.

Chapter 5

Thermochemical conversion of food waste for bioenergy generation R. Uma Rani1, J. Rajesh Banu2, Daniel C.W. Tsang3 and Chyi-How Lay4 1

Department of Civil Engineering, Ponjesly College of Engineering, Nagercoil, India, 2Department of Life Sciences, Central University of

Tamil Nadu, Neelakudi, Thiruvarur, India, 3Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, P.R. China, 4Master’s Program of Green Energy Science and Technology, Feng Chia University, Taichung, Taiwan ROC

5.1

Introduction

The growing significance of environmental issues involving global concerns, together with the energy crisis and the gradual but inexorable depletion of fossil fuels, have become increasingly unavoidable. The utilization of fossil fuels has undoubtedly led to scientific and technological progress, and this has focused the attention of researchers on food waste as a truly sustainable, untapped resource that offers a renewable source of carbon for energy generation. Food and energy are the two interconnected crucial elements of all developing and developed countries. The average food waste production rate per capita in developing countries is 56 kg/capita/year and demand is anticipated to increase as global energy consumption is forecast to rise by 53% by 2035 (EIA, 2011). The conversion of food waste to bioenergy is a process with immense potential, and is environmentally friendly and economically feasible, given the rapidly increasing costs related to energy supply and waste disposal and growing public concerns over environmental issues. The transformation of food waste into bioenergy can take three main routes: thermochemical, biochemical, and physiochemical. The main challenge of these technologies is the diversity of food waste, which generates a highly fluctuating chemical constituency of the energy products they produce. Each technology is unique in the production of a substantial calorific end product and a mixture of byproducts. The option of a processing technology often relies on its sources, their physiochemical condition, and their applications. This chapter provides insights into thermochemical technologies, their advantages, and the major hurdles in converting food waste into bioenergy. Also, from the perspective of resource restoration, we postulate future pathways for more efficient methods of handling food waste for energy generation.

5.2

Thermochemical routes for bioenergy generation

Thermochemical conversion is a mechanism of chemical transformation at higher temperatures that cleaves the bonds of organic compounds (Uma Rani et al., 2012; Khac-Uan et al., 2009; Jayashree et al., 2014) and converts them into solid (char), liquid (highly oxygenated bio-oil), and gas (syngas). The thermochemical process encompasses several stages, in the primary stage solid biomass is transformed into gases. The second stage entails the condensation of gases into oils. These oils are conditioned and synthesized to produce syngas in the third and final stage. These technologies are often sorted by their oxygen and heating rates, ranging from endothermic to full exothermic oxidation of biomass. The motivating force for this transformation pathway is the generation of heat energy, which includes incineration, combustion, cocombustion, pyrolysis, gasification, and hydrothermal carbonization (HTC), as depicted in Fig. 5.1. The main advantages of the thermochemical conversion of biomass over other technologies are improved energy efficiency, no gas emissions, efficient recovery of value-added nutrients, smaller footprint, short reaction time, and the ability to handle and combine a variety of waste biomasses.

Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00005-5 Copyright © 2020 Elsevier Inc. All rights reserved.

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FIGURE 5.1 General path of food waste to bioenergy conversion technologies.

5.2.1 Incineration Incineration is a thermochemical waste conversion technology which uses surplus oxygen to assure complete combustion at temperatures over 900 C and these are designed primarily to enhance waste burning and heat output while minimizing emissions by equalizing the oxygen and the three “Ts”—time, temperature, and turbulence. Food wastes typically have low oxygen content, and high nitrogen, ash, and energy contents (Caton et al., 2010). Incineration transforms the biomass into heat energy for industrial processes, and this heat can be used to generate steam to produce electrical power via a steam turbine or as process heat used in food processing facilities. Flue gases comprise small amounts of nitrogen, carbon dioxide, and sulfur dioxide, each of which is better used, when used efficiently. The major advantages of incineration are instantaneous waste reduction, short residence time, inert and nonputrescible ash residues, the solid mass of organic waste is reduced by 80%
85% and the volume by 95%
96%, which is commendable.

5.2.1.1 Technologies Thermochemical technologies have been used to reduce the impact of biomass processing on the environment and to recover energy from waste. Nevertheless, if the biomass is not dried prior to thermochemical conversion, it is feasible and sustainable to thermochemically transform wet feedstock with a low moisture content (Wang et al., 2010). The main types of incinerators include the following rotary kiln, moving grate, and fluidized bed. 5.2.1.1.1 Moving grate Mass incineration with a moving grate incinerator is a commonly and widely adopted technology. It fulfills the technical performance requirements and can satisfy wide variations in the composition of waste and calorific value. Food waste is pulled by a crane onto the grate that descends into the combustion chamber and finally moves down to drop the burnt residues on the other end of the grate into an ash pit where ash is removed by a water lock. The moving grate is a metallic permeable bed that allows primary combustion air to move from the bottom and secondary combustion air is provided through nozzles from the top of the grate, promoting complete combustion by incorporating turbulence for proper blending and by assuring a surplus of oxygen. Various grate designs are available including forward, backward, double, rocking, and roller movement. The main advantages are no need for presorting, it allows a total thermal efficiency of up to 85%, and a single moving grate boiler handles 15
35 metric tonnes/h; and the disadvantages of this process are comparably high capital and maintenance costs, and each furnace is confined to a capacity of up to 1200 tonnes/day.

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5.2.1.1.2

99

Rotary kilns

This is a common technology often used for industrial and hazardous wastes, but also in certain municipal solid waste incinerators. The main design is comprised of two thermal treatment chambers: (1) a primary inclined chamber in which feedstock is fed, revolved, and thermally disintegrated from the secondary chamber by means of heat radiation; and (2) the recombustion chamber located at the rear end of the kiln in which the decomposing air and the remaining waste are fully burned with a secondary air supply. The major advantages of rotary kilns are no need for presorting, they have a total thermal efficiency of up to 85%, low NOx emissions, and thermal destruction of hazardous chemicals. The disadvantages are high capital and maintenance costs, it is a less common technology for waste incineration, and each furnace is confined to 480 tonnes/day.

5.2.1.1.3

Fluidized bed

This is a common technology often used for municipal solid waste incinerators, but is also used in certain hazardous waste incinerators. Different types of fluidized bed incineration include bubbling, rotating, and circulating fluidized beds, but the design principles remain the same. The upward flow of combustion air injected from below expels waste particles and assumes a fluid-like character through which the turbulence produced increases uniform mixing and heat transfer, which in turn increases the efficiency of combustion. The major advantages are enhanced combustion efficiency, quite low capital and maintenance costs, allowing up to 90% overall thermal efficiency, and being able to handle liquid or solid waste either in combination or separately. The disadvantages are relatively strict demand on the size and composition of waste, that generally need thorough disintegration, and this is not a common or extensively tested incineration technology.

5.2.2 Combustion Combustion is a thermochemical conversion technology in which chemical energy stored in feedstock is transformed into heat, mechanical power, or electricity. When heating food waste biomass, its constituents start to hydrolyze, oxidize, dehydrate, and pyrolyze with increasing temperature, forming combustible volatiles, tarry substances, and highly reactive carbonaceous char. The combustion of biomass is primarily used for heat production in small- and mediumscale units, and the selection of the furnace type is principally swayed by the operating scale, fuel type, and fuel residence time. The direct combustion of biomass remains the dominant bioenergy path throughout the world (Gaul, 2012). Complete combustion entails the generation of heat due to oxidation to CO2 and H2O from carbon- and hydrogen-rich biomass and with partial combustion, methane, carbon monoxide, and particulates are released. Fuel contaminants, including sulfur and nitrogen, are also linked to emissions of SOx and NOx (Robbins et al., 2012). Nevertheless, the extensive chemical kinetics reactions in the course of biomass combustion are complicated (Babu, 2008).

5.2.2.1 Principles Drying—The biomass comprises moisture that must be removed before combustion takes place. Radiation from flames and from the stored heat in the combustion body unit provides the heat for this process. Pyrolysis—The volatile gases are freed when the dry biomass temperature ranges from 200 C to 350 C. The products of pyrolysis comprise CO, CO2, CH4, and tar, liquefied when cooled and blended with airborne oxygen and burned to create a yellow flame. This mechanism is independent of utilizing gas heat generation to dry the fresh fuel and release extra volatile gases. Char is the leftover material after the cauterization of all the volatiles. Oxidation—The char decomposes at around 800 C. Oxygen is needed again, for carbon oxidation both in the fire bed and above the fire bed where it blends with CO to form CO2 released into the air. A longer reaction time enables total fuel consumption in a combustor. Complete combustion—This happens for the correct amount of time in a proper fuel to air ratio under suitable temperature and turbulence circumstances.

5.2.2.2 Technologies Fixed bed, fluidized bed, and suspension burners are the most common types of combustion technology.

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5.2.2.2.1

Fixed bed combustion

In this technology, primary/underfire air is provided from below the grate and the combustion process occurs on the grate. When secondary/overfire air is supplied, the combustible gases produced are burnt, generally in a combustion zone isolated from the fuel bed. Temperatures typically rise to 900 C
1400 C and fixed bed systems are of two types, grate furnaces and underfeed stokers. The purpose of a grate system is to dispense fuel and bed analogously across the grate areas, which is ideal for combusting fuels with varying particle sizes and higher moisture and ash contents. The capacity generally reaches approximately 20 MWth. Grate furnaces are of various kinds: fixed, moving, traveling, rotating, and vibrating grates. The fuel is delivered by screw conveyors from underneath in underfeed stokers through the combustion chamber and is conveyed over a grate, making it ideal for lower ash content and lower particle size fuels. The capacity generally goes up to approximately 6 MWth. The time of reaction for combustion is about 45
60 min, hence the rate of heating of the particles are about 1 C/s, which is the key limit of the technology and is therefore restricted to industrial and small-scale power plants. 5.2.2.2.2

Fluidized bed combustion

In a fluidized bed, fuel is burned in a self-blending suspension of gas and solid bed material where air for combustion comes in from below. It can manage fuels with a higher moisture content of up to 65% and a higher ash content of up to 50%. Extreme heat and blending transfer provide ideal combustion conditions, with relatively low excess air requirements that in turn lessen the flow of flue gas volume and enhance the efficiency of combustion. The capacity goes up to approximately 30 MWth and is particularly interesting for large-scale implementation. A major drawback is the increased dust loads in the exhaust gas, requiring effective precipitators of dust and cleaning systems for boilers. Bubbling and circulating fluidized bed combustion can be characterized contingent on the fluidization velocity. The combustor is separated into two regions in a Bubbling Fluidized Beds system, namely, a region with free-moving sand bed particles aided by upward flowing air, and a freeboard region over the fluidized bed. The flow in a Circulating Fluidized Beds reactor carries the lighter bed particles and fuel particles in a circular motion, creating a cyclone and reverting back to the reactor afterward. 5.2.2.2.3 Suspension burner Suspension burners in the form of fine particulates are used for dry biomass. Suspension burners, however, are not very efficacious as they require more air to inhibit the formation of slags and also result in generating huge amounts of fly ash. Table 5.1 sums up the advantages and disadvantages of different types of combustors.

5.2.3 Cofiring Cofiring is an attractive technology for a fossil-fuel like coal/natural gas with a feedstock biomass. Cofiring facilitates biomass-based power generation with greater efficacy attained in contemporary and mass-scale coal-fired plants, that is far greater than the efficacy of 100% biomass-devoted power plants. Overall the energy efficiency can be significantly enhanced, where cofiring occurs in combined heat and power (CHP) plants, and it is presently the most highly competitive option for both electricity and heat generation to utilize the potential of biomass energy. Currently, 230 CHP plants are using cofiring, with a potential of 50
700 MW, mainly in northern Europe and the United States (Baxter and Koppejan, 2013). Cofiring has now been accomplished in a number of ways. It is usually done before combustion by blending coal and biomass, and while biomass could also be volatilized and combusted in separate burners, here the gaseous fuel is blended with the boiler streams of the coal-fired power plant. Cofiring offers several advantages over power plants that burn 100% biomass, including lower investment costs, higher efficacies, lower CO2 emissions as biomass can replace around 50% of the coal, better economies of scale, and low electricity cost.

5.2.3.1 Technologies 5.2.3.1.1 Direct cofiring This is the most popular cofiring method involving direct cofiring of biomass fuel and coal in the combustion chamber of the boiler. The options in direct cofiring are: (1) untreated biomass is blended with coal upstream of the coal feeders and subsequently comilled in pulverizers, (2) biomass is crushed in separate mills by means of subsisting coal burners and introduced into the furnace, and (3) biomass utilizes distinct burner, mills, and other preparations for feed. The first option is the easiest method and requires low capital costs, however it entails the greatest risk in interfering with the

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TABLE 5.1 Advantages and disadvantages of different types of combustors. Combustor type Fixed bed

Advantages Grate furnaces

G

G

Underfeed stokers

G

G

Fluidized bed

Bubbling furnaces

G

G

G

Circulating bed furnaces

G

G

G

Suspension burners

G

Disadvantages

Lower capital costs for plants under 20 MWth Cost of operation and the dust load in flue gas are lower

G

Lower capital costs for plants under 6 MWth Easy and efficient load control owing to constant fuel feeding

G

Appropriate for biomass fuels with lower ash and higher ash melting point

No mobile components in the hot combustion chamber Greater flexibility in terms of moisture content and biomass type Low oxygen level increases efficiency

G

Higher capital costs for plants over 20 MWth Higher cost of operation

Higher specific heat transfer owing to high turbulence Greater flexibility in terms of moisture content and biomass type Very low oxygen level increases efficiency

G

Considerably higher specific capacity

G

G

G

G

G

Special designs are required for mixed fuel Surplus oxygen reduces efficiency

Higher capital costs for plants over 30 MWth Higher level of dust in flue gas

To lessen emissions, drying of fuel and size reduction are necessary Biomass needed with moisture less than 15%

FIGURE 5.2 Direct cofiring.

coal-firing capacity of the boiler unit. It therefore applies to circumscribed biomass types and to very low biomass to coal cofiring ratios, that are normally below 5% by weight (Tillman, 2000). The second option increases the pipe work that is already being jammed around the boiler and the burner-operating characteristics can also be difficult to control and manage. The third option has the highest capital costs and the lowest risk for normal operation of the boiler as well as an added advantage that biomass can be used as a reburn fuel for NOx control. Fig. 5.2 shows an outline of the direct cofiring of biomass. Direct cofiring may lead to many problems owing to the higher chlorine and alkaline contents of biomass and the major issues stated include corrosion, fouling in the boiler, heat exchanger, and piping, slagging, catalyst poisoning, and electrostatic precipitator performance problems (Heidenreich and Foscolo, 2015). Indirect and parallel cofiring was initiated to overcome these issues (Sami et al., 2001; Agbor et al., 2014). 5.2.3.1.2 Indirect cofiring Biomass is initially gasified followed by cofiring of fuel gas in the main boiler. Often the gas must be cooled and cleaned, which is more difficult, however this technique enables a high degree of flexibility in the fuel. Biomass ash and primary fuel are completely separated, as thermal conversion takes place in separate processing facilities, resulting in comparatively high operational costs compared to direct cofiring. Fig. 5.3 shows an outline of the indirect cofiring of biomass.

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FIGURE 5.3 Indirect cofiring.

FIGURE 5.4 Parallel cofiring.

Steam turbine

Coalgas

Mills

Biomass

Mills

5.2.3.1.3

Burners

Boiler

Fuel gas treatment

Storage

Burners

Parallel cofiring

Parallel firing is carried out using distinct boilers and combustion plants for the biomass source and coal-fired power plants, as shown in Fig. 5.4. The steam generated is supplied to the main power plant where it is converted to high pressures and temperatures to deliver greater energy transformation efficiencies. This enables the use of problematical fuels with high alkaline and chlorine contents and ash separation. The other advantages include excellent reliability and no fouling or corrosion. However, it is expensive, although some costs can be compensated for by enabling the boiler to discharge its flue gas upstream of the main boiler’s existing particulate separator and fan system.

5.2.4 Cocombustion Cocombustion of biomass is an accepted and feasible method to generate power by burning more than one fuel. Biomass cocombustion guarantees the production of renewable energy with limited capital costs, increased electrical efficiency of existing coal and gas power plants, lower CO2 emissions, improved economies of scale, lower electricity costs, and SO2 emissions are further avoided due to special interactions between the biomass and coal during combustion.

5.2.4.1 Principles Premixing—This is the easiest method in theory, with the lowest capital investment. If the biofuel ratio is quite low, it could be fed together with coal and then burned in the burners. This technology also holds the greatest risk of fuel feeding systems malfunctioning. Premixing is related with direct cofiring. Joint direct injection—This method entails completely separate handling, measuring, pumping, and injection of biofuel straight into the burner. This technique needs a number of biomass pipes to be safely positioned at the front of the boiler. It can also be more difficult to handle and retain the operating traits of the burner. Direct injection is also related with direct cofiring. Separate burning of coal and biomass—This third method entails the distinct handling and pulverization of biofuel in several combustion burners. This technique requires higher investment and has lower risk for boiler operation. This process is related with indirect/parallel cofiring. Reburn of biomass in upper furnace—The final option is to use biofuel as a reburn fuel NOx emission control. While there have been small-scale tests conducted, this method is still being developed. This process is related with direct/indirect cofiring.

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5.2.4.2 Technologies 5.2.4.2.1 Atmospheric fluidized bed combustor This is an accepted coal cocombustion plant technology that has a bed, generally made of sand, which provides a medium to ensure high combustion temperatures and low/high moisture content of the injected fuel. Low SO2 and NOx emissions and low capital costs are its major advantages. The most common types of this technology are circulated, bubbling, and stationary fluidized bed boilers. 5.2.4.2.2

Pressurized fluidized bed combustor

Except that the combustion occurs at significantly greater than atmospheric pressure, the basic principles are identical to those of the atmospheric fluidized bed combustor. Thus, there is an issue of crossing the biomass fuel into the reactor all over the pressure boundary.

5.2.5 Pyrolysis Pyrolysis transforms the biomass into highly heterogeneous solid, liquid, and gaseous intermediates with a 95.5% fuel to feed efficiency (Demirbas, 2004), at relatively low temperatures (400 C
600 C) in an oxygen-free environment. The precise temperature depends on the type of reactor and the characteristics of waste, notably ash softening and melting temperatures (Demirbas, 2002, 2007; Higman and van der Burgt, 2008; Yaman, 2004). The yield products of pyrolysis can be summed up as: (1) solid (biochar) at low temperature, low heating rate, long gas residence time process, (2) liquid (bio-oil with heating value about 17 MJ/kg) at moderate temperature, high heating rate, short gas residence time process (Digman and Kim, 2008), and (3) syngas (CO 1 H2) at high temperature, low heating rate, long gas residence time. Engineering research predominantly focuses on the system variables including temperature, heating rate, oxidation environment, product upgrade processes, and the nature of the biomass (Liu and Balasubramanian, 2012). The use of renewable resources by carbon-neutral routes, self-sustaining energy, transforming low-energy biomass into highenergy-density liquid fuels and the ability to produce chemicals from bio-based resources has attracted a great deal of attention, both economically and environmentally.

5.2.5.1 Technologies The main types of operating-based pyrolysis processes are slow/conventional, fast, and ultrafast/flash pyrolysis. 5.2.5.1.1 Slow/conventional pyrolysis Slow pyrolysis is defined by slower heating rates (less than 10 C/s), comparatively long solid and gas residence times (5
30 min) typically at 400 C
500 C. Usually the primary yield is the solid product (biochar), but it is always accompanied by liquid and gas products, contingent on heating rate, temperature of the reactor bed, and apparent residence time of the gas. The pyrolizers used in slow pyrolysis are fixed beds and rotary kilns. Fixed bed Fixed bed technology is simple, efficient, and suitable for biomass of relatively uniform size and has traditionally been used for biochar and gas production. These are further subdivided into downdraft and updraft fixed bed reactors. Solids pass gradually in a downdraft reactor, revealing a vertical shaft and air and reacting to gasification waste supported by the throat. In a cocurrent mode, solid and product gas move downward and comparatively clean gas is generated with lower tar content and higher carbon conversion. In contrast, a solid heading down a vertical shaft countercurrently defines the updraft reactor. With high tar levels, the product syngas is filthy, despite tar crackers being developed to mitigate this problem. Rotary kiln These reactors are best suited for producing superior-quality biochar and high-calorific gas for electricity production. Two kinds of rotary kilns are available: drum and screw. Drum pyrolizers move waste through the action of paddles via an externally heated, horizontal cylindrical shell prior to entering the drum to assure good-quality biochar and gas. In a firebox just underneath the drum, a portion of the gas generated is burned to heat the biomass to the pyrolysis temperature, often referred to as “slow pyrolysis,” as traveling through the drum takes a few minutes. Screw pyrolizers use a rotating screw to shift the waste through a tubular reactor. Some pyrolizers are heated outside, while a heat carrier like sand is used by many to heat biomass through the tube. Due to its ability to work on comparatively small scales, the screw pyrolizer is an affordable solution used in recent years to transform biomass into bio-oil and biochar.

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5.2.5.1.2

Fast pyrolysis/thermolysis

Fast pyrolysis is a rapid degradation of carbonaceous materials at average to high heating rates without oxygen (100 C/s), typically between 400 C and 650 C (Titirici et al., 2007). The main target product is bio-oil and the yields are 30%
60% liquid condensates, 15%
35% gases (methane, carbon monoxide, carbon dioxide, hydrogen, and light hydrocarbons), and 10%
15% biochar. It is the most reliable method in both research and practical implementations. Thermolysis includes fluidized bed, rotating cone, ablative pyrolysis, and pyrolysis reactor vacuum. Fluidized bed Due to their reliability and easiness of scaling to commercial plant sizes, fluidized beds are the most common configurations. They offer stable temperature control and highly effective heat transfer to waste particulates. The reaction time can be governed by the fluidizing gas flow, while special consideration must be given to the system isolating the coke from the reaction products. Rotating cone reactor In this reactor, rather than using inert gas, the pyrolysis reaction occurs on the impulsive blending of waste and hot sand. The sand and waste materials are placed at the base of the cone although rotating induces centrifugal force to ultimately shift the solids to the cone’s lip. Pyrolysis vapors are sent to a condenser as the solids flow through the cone lip. The biochar and sand are directed toward a combustor where the sand is reheated before being reintroduced with the fresh waste materials in the cone base (Lehmann et al., 2009). Liquid yields of 60%
70% have been reported, however commercial application on a large scale is not available. Ablative pyrolysis reactor This technique entails developing high pressure between a waste material and a reactor wall, enabling the liquid product to be melted through unrestrained transfer of heat from the wall to the waste material. At the back of a liquid film, the waste particles gliding over the wall dissipate and leave the pyrolysis zone. A liquid yield of up to 80% has been reported, due to the shorter gas residence time and higher heat transfer (Schmidt et al., 2002), and the other benefits include no biomass milling needed, compact design, high energy efficiency, and low cost. Pyrolysis reactor vacuum This method entails the thermal breakdown of waste under lower pressure and a longer residence time. The produced vapors are promptly detached from the vacuum and recovered as bio-oil. Other important characteristics are lower gas velocities, less char in the liquid product, and no carrier gas is needed. A liquid yield of up to 35%
50% has been reported (Lehmann et al., 2009). Table 5.2 described the advantages and disadvantages of different types of pyrolizers. 5.2.5.1.3

Ultrafast/flash pyrolysis

Flash pyrolysis is the incredibly quick pyrolysis of thermal decomposition, typically between 700 C and 1000 C, with a higher heating rate and relatively low residence times (,0.5 s). The main target products are gases and bio-oil, and the yield consists of 10%
20% liquid condensates, 60%
80% gases, and 10%
15% biochar.

5.2.6 Gasification Thermochemical gasification occurs at higher temperatures in the presence of an oxidizing agent, usually air, oxygen, carbon dioxide, nitrogen, or a combination thereof, as shown in Fig. 5.5 (Ruiz et al., 2013). The gasifier receives heat directly or vicariously, helping to raise the temperature of gasification by 600 C
1500 C. In the vicinity of an oxidizing agent at higher temperatures, gasification transforms the biomass into permanent gases rich in 18%
22% carbon monoxide (CO), 8%
12% carbon dioxide (CO2), 8%
12% hydrogen (H2), 2%
4% methane (CH4), and 45%
50% nitrogen (N2), with the remainder including other contaminants such as char, tar, and ash (McKendry, 2002). Char and tar result from partial biomass conversion. The precise characteristics of the gas depend on the type and properties of biomass, type and quantity of catalysts, flow rates of biomass, equivalence ratio, moisture, gasifying agent, gasification temperature, and reactor configuration (Mohammed et al., 2011; Parthasarathy and Narayanan, 2014). A simple method of calculating the general reaction in a gasifier is given in Eq. (5.1). CHx Oy ðbiomassÞ 1 O2 ð21%of airÞ 1 H2 OðsteamÞ 5 CH4 1 CO 1 CO2 1 H2 1 H2 Oðunreacted steamÞ 1 CðcharÞ 1 tar (5.1) The end products are separated to generate clean syngas with a net calorific value of 4
10 MJ/Nm3, that can be used as an engine fuel or upgraded to liquid fuels or chemical feedstocks via biological fermentation (Datar et al., 2004)

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TABLE 5.2 Advantages and disadvantages of different types of pyrolizers. Type of pyrolyzer Slow pyrolysis

Advantages Fixed bed

G G G

Rotary kiln

G

G

Fast pyrolysis

Fluidized bed

G G G G

Rotating cone

G G G G

Vacuum reactor

G G G

G

Ablative reactor

G G G G

Disadvantages

Easy to operate and build Excellent control of temperature The fluid to solid phase speed is comparatively higher

G

A broad range of waste types and sizes are allowed No need for carrier gas

G

Lower efficacy in heat transfer and scale-up constraints

Excellent control of temperature Good blending of solids Ease of scaling Higher rates of heat transfer

G

The transfer of heat to bed should be demonstrated on a massive scale Maximum allowable particle size of 6 mm

Good blending of solids No need for carrier gas Ease of scaling Low capital costs and wear

G

No need for carrier gas Clean oil production Larger particles of 3
5 cm can be handled Faster condensation of liquids

G

Does not enquire inert gas Low temperature needed Larger particles can be handled Compact design

G

G G

G

G G

G G G G

G

Higher solid residence time and conservation of carbon Lower ash carryover Hard to take off char

The transfer of heat to bed should be demonstrated on a massive scale Need for small-size waste particles Complex process Lower rate of heat transfer Solid residence time Quite low yield of liquids Produces more water Slow process Abrasion of char Expensive scaling

or catalytic upgrades through the Fischer
Tropsch process (Wang et al., 2007). Gasification is widely favored due to its many advantages including carbon-neutral nature, climate change mitigation, energy recovery, efficient waste consumption, earning carbon credits, mature technology, small and modular, flexible operation, economically feasible, and socioeconomic benefits.

5.2.6.1 Principles The temperature ranges and kinetic parameters of the degradations depend primarily on the heating rate of transfer, the food waste composition, and the degree of the oxidizing environment (Kumar et al., 2008; Varhegyi et al., 1997; Biagini et al., 2006). Generating gas from food waste is enabled by various major reactions that occur within the gasifier as listed here. Drying—This is an endothermic process at 100 C
150 C, with a moisture content reduction of less than 5% which is then transformed to steam. Devolatilization/pyrolysis—Following drying, the food waste biomass undergoes pyrolysis as heating persists. It is the thermal degradation (200 C
500 C) of biomass in an oxygen-free environment which reduces the volatile content of solid waste. Consequently, biomass disintegrates into solid, liquid, and gas combinations. The solid part which remains is the charcoal, with tar making up the liquid part, and the gaseous part being made up of flue gases. Oxidation—Oxidation between oxygen and solid carbonized occurs at approximately 800 C
1200 C , resulting in carbon dioxide and heat formation as shown in Eq. (5.2). If substoichiometric amounts of oxygen are available, limited oxidation of carbon may lead to carbon monoxide formation. C 1 O2 -CO2 1 Heat

(5.2)

Reduction—Gasifier reduction is attained at high temperatures (650 C
900 C) and under reduced conditions by passing carbon dioxide or water vapor over a charcoal bed to generate combustible gases like hydrogen, methane, and carbon dioxide. Most of these reactions are endothermic.

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FIGURE 5.5 Gasification technology.

Coal

Bunker Feeder Aqueous liquor Coal lock hopper

Coal Water

Gas to clean up

Air

Rotating grate Crude gas

Steam and oxygen

Ash lock

Slag

5.2.6.2 Technologies The major types of gasifiers are fixed/moving bed, fluidized bed, and entrained bed, pursuant to the flow configurations. Table 5.3 depicts the typical process conditions of various gasifiers. 5.2.6.2.1 Fixed/moving bed gasifier Fixed bed gasifiers are easy to build, and operate with higher carbon conversion, longer period of residence, lower gas velocity, and ash carryover. A longer residence time implies that the rate of production of syngas per unit volume of gasifier is at a minimum under the same feeding rate, and therefore this gasifier is less feasible for hydrogen and chemical production as the carbon dioxide content is high (Mondal et al., 2010). Only solid feedstocks can be handled with a fixed bed gasifier, but this applies to highly active feedstocks that include high ash such as wood and low-grade coal (Nuno et al., 2013). Fixed beds are most significant in terms of cold gas efficiency, which is a gauge of the effective transformation of fuel energy into syngas energy. There are two kinds of fixed bed gasifiers: updraft/countercurrent and downdraft/ cocurrent. In the updraft gasifier, the carbonaceous biomass to be treated is fed from above, while the gasifying agent such as oxygen and steam is injected near the bottom of the gasifier. The air flows to the fuel countercurrently and the fuel passes through the various temperature levels, and the product gas flows from the reactor without really interacting with the rest of the biomass regions. The gas that leaves the gasifier has a high tar content (Ciferno and Marano, 2002).

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TABLE 5.3 Typical process conditions and traits of gasifying technologies (Bridgwater, 2003; Basu, 2010; Arena, 2012; Luque and Speight, 2015; Jin et al., 2013; Mohammad, 2014; Geo et al., 2010).

Feed size (mm) Residence time 

Reaction temperature ( C) 

Exit gas temperature ( C) 

Ash melting point ( C)

Fixed/moving bed

Fluidized bed

Entrained flow

5
50

0.5
5

,0.15

15
30 min

10
100 s

1
10 s

1300
1800

900
1200

1500

425
650

600
1050

1250
1600

.1000 (U)

. 1000

. 1250

55

15

10
200

2
100

.1250 (D) Maximum fuel moisture

60 (U) 25 (D)

Capacity (MWth)

1
10 (U) ,1 (D)

Cold gas efficiency

Moderate (84%)

High (89%)

Moderate (81%)

Hot gas efficiency (%)

90
95 (U)

89

80

Limited

Limited

1
100 MWe

5
100 MWe

85
90 (D) Turndown capability

Good (U) Limited (D)

Admissible power

Up to 10 MWe (U) Up to 1 MWe (D)

3

Oxygen/feed (Nm /kg)

0.64

0.37

0.37

Scale-up potential

4 dry kg/h feed rate (U)

10
15 dry tonnes/h feed rate

. 20 dry tonnes/h feed rate

Medium scale

Large scale

500 kg/h feed rate (D) Application

Small scale

D, Downdraft; U, updraft.

In a downdraft/cocurrent gasifier, biomass to be treated and the oxidizing agents enter from the top of the gasifier. The product gas passes via the combustion zone that can break the tars formed during the pyrolysis reaction. The product gas leaves the gasifier with minimum tar content. Gasification options are based on several factors such as application, size limitations, turndown capability, gas heating value, end-use of gasifier locations, type of biomass, cost, and availability (Collot, 2006). 5.2.6.2.2 Fluidized bed gasifier A fluidized gasifier functions as a hot bed of inert sand particles constantly agitated by the air. Air is supplied via nozzles at the bottom and the bed media are kept at a temperature of 800 C
1000 C during normal operation. Researchers often use operating temperatures below 1000 C and feedstock sizes not exceeding 50 mm because of the lower operating costs and simple construction (Pengmei et al., 2007; Xianbin et al., 2013; Scott et al., 2012; Siyi et al., 2009; Andrea et al., 2010). When the fuel is introduced under high-temperature conditions, the drying and pyrolyzing reactions occur rapidly and at comparatively low temperatures, and all gaseous portions of the fuel are removed. The ash is taken from the bottom and the gas flows through the gasifier top. Based on the bulk velocity of gas moving in the bed, three different types of fluidized bed gasifiers exist: bubbling bed, circulating fluid bed, and transport reactor. The bubbling bed gasifier is defined by discrete gas bubbles that move at a comparatively low gas velocity of less than 5 m/s (Panwara et al., 2012; Mi-Kyung et al., 2009). A circulating fluid bed has a higher fluidization gas velocity of 5
8 m/s and also includes smaller particles transformed into syngas above the bed or segregated in a cyclone to return to the bed.

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Food Waste to Valuable Resources

The transport reactor needs a higher gas velocity of about 15 m/s and includes segregating particulate matter from gas (Geo et al., 2010; Mi-Kyung et al., 2009). 5.2.6.2.3

Entrained bed gasifier

In this, the gasifying agent is blended with the fuel when it enters the gasifier. The reaction occurs at higher temperature (1200 C
1600 C), higher pressure (20
80 bar) with a shorter residence time (0.5
4 s), and thus prevents the formation of tar and methane. Two sorts of gasifiers exist: slagging and nonslagging. The ash generated in nonslagging gasifiers flows via the reactor with the gas created, allowing the ash to exit the gasifier in order to separate it downstream during the process. In slagging gasifiers, the ash glides down the gasifier’s walls during the reaction. This is the preferable technique for biomass transformation, but the content of ash and volatile matter must be taken into account. Table 5.4 describes the advantages and disadvantages of the different gasifying technologies.

5.2.7 Hydrothermal carbonization HTC, a wet thermochemical conversion technology, is incredibly feasible owing to its excellent capability to convert food waste into carbonaceous hydrochar and energy at significantly higher yields without energy-intensive drying prior to or during the course of its use. The heating value of the hydrochar is greater than the raw feedstock, with low hydrogen/carbon and oxygen/carbon ratios and an energy density equivalent to natural coal (Ramke et al., 2009; Hwang TABLE 5.4 Advantages and disadvantages of different gasifying technologies.

Advantages

Fixed/moving bed

Fluidized bed

Updraft gasifier Simple design and reliable technology G Feedstocks and products are flexible G Higher conversion of carbon and lower temperatures of exit gas G Tolerant to waste particle size, shape, and moisture content G Average calorific value syngas with higher ash and tar content G Adapted to capacity up to 250 kW and higher solid residence time Downdraft gasifier G Low tar content and best possible use in gas engines G Simple, low cost, and proven technology G Higher carbon conversion and solid residence time

G

Updraft gasifier G Low amount of gas produced G Exhaustive system of gas cleaning is needed Downdraft gasifier G Huge loss of fine particles in the preparation of feed G High ash and dust levels in the gas and the demands for steam are high

G

G

Disadvantages

G G G G

G

G

Compact design and ease of use Higher flexibility of fuel in size and type Good temperature profile within the gasifier High heat transfer rates Persistent to biomass size and variations in feed amount and moisture conditions Moderate calorific value syngas with low tar and high particulate matter Load flexibility under design load

Entrained flow G

G

G

G

G

G

G

G

G

G

G

Quite complex system in the fuel bed owing to low stickup of biomass Possible to use different kinds of biomass, but fuel flexibility applies to biomass of size 0.1 cm to 1 cm Produced high quantity of tar and highly corrosive ash The gas may entrain particles

G

G

G

G

G

Appropriate for large systems Good temperature profile throughout the gasifier Higher carbon conversion efficiency Good gas
solid contact and mixing Nearly tar-free syngas and good potential for scale-up Molten slag highly impervious to leaching Short solid residence time Fuel flexibility

Intake of primary air is very high and heavy investment Necessitates the mashing of feedstock fractions Waste spraying/ atomization is required Not well proven technology Raw gas cooling

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et al., 2012). Typically, the process occurs under alkaline conditions and the residence time extends from 0.2 to 120 h (Pham et al., 2013), relying primarily on the traits of the product to be obtained. The greater the temperature, the greater the pressure and, consequently, the hydrochar’s carbon content. Funke and Ziegler (2010) outlined several operating parameters related to HTC. First, the water present in food waste biomass is an excellent solvent and reaction medium and must exist in order to preclude hydrothermal gasification resulting in gaseous carbon products like methane and hydrogen. Second, for reactions to begin, temperatures must exceed 100 C, however the practical implementation of HTC has been noticed at a low temperature of 180 C
250 C. Third, there should be liquid water, and minimum saturated pressure is required (Siskin and Katritzky, 2001; Akiya and Savage, 2002; Watanabe et al., 2004; Berge et al., 2011; Hoekman et al., 2011; Libra et al., 2011; Titirici and Antonietti, 2010). Fourth, feedstock must be fully immersed throughout the process. Fifth, a neutral or weakly acidic environment will enhance the rate of reactions. Sixth, residence times typically vary from 1 to 72 h and together with the temperature regime, residence times join to create a “reaction severity.” A simple way of depicting the overall reaction in HTC is shown in Eq. (5.3). C6 H12 O6 ðCarbohydratesÞ-C6 H2 OðCharÞ 1 5H2 OðWaterÞ 1 B950kJ=molðHeatÞ

(5.3)

HTC has several upsides, including lower treatment footprints, higher waste volume reduction, and no odors allied to the process (Hoekman et al., 2011). The high process temperature also helps to negate microorganisms and deactivates possible organic contaminants (Libra et al., 2011). Another advantage related to HTC is the recovery of nutrients from nitrogen-containing liquids that can be used as a fertilizer. Fig. 5.6 illustrates the HTC path of conversion of food waste (Tradler et al., 2018).

5.2.7.1 Transformation process Simultaneous reactions occur at subcritical temperatures during HTC including hydrolysis, dehydration, decarboxylation, condensation polymerization, and aromatization (Libra et al., 2011; Sevilla and Fuertes, 2009). Hydrolysis—Under ambient conditions, the presence of water at higher temperatures improves the solvent properties of water, promotes the organic compound hydrolysis, and also leads to the cleavage of biomacromolecules chemical bonds. In contrast to dry pyrolysis reactions, hydrolysis has lower activation energy, resulting in lower temperatures for decomposition (Libra et al., 2011). Cellulose is hydrolyzed substantially above 200 C under hydrothermal conditions (Funke and Ziegler, 2010), hemicellulose between 180 C and 200 C, and decomposition of lignin between 180 C and 220 C (Libra et al., 2011). Dehydration—Food waste biomass is considerably carbonized in the course of chemical dehydration by reducing the hydrogen/carbon and oxygen/carbon ratios. The dehydrated organic compounds join together to form a system of various carbon compounds (Titirici et al., 2007). Decarboxylation—In the course of decarboxylation, carboxyl (
COOH) and carbonyl (
CQO) groups degrade, leading to carbon dioxide and carbon monoxide, respectively, with this process occurring quickly above 150 C. The eradication of hydroxyl and carboxyl groups results in the production of unsaturated biomacromolecular fragments. Condensation polymerization—Certain fragments are extremely reactive and combine primarily through condensation polymerization, leading to the loss of a small molecule, often water.

FIGURE 5.6 HTC pathway for conversion of food waste.

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Food Waste to Valuable Resources

Aromatization—Under hydrothermal conditions, the aromatic structures arising out of polymer aromatization are relatively persistent and are therefore considered to be building blocks of HTC coal (Funke and Ziegler, 2010).

5.2.7.2 Influence of reaction parameters Parameters like temperature, pressure, residence time, pH, feedstock composition, and solid load govern the HTC process (Funke and Ziegler, 2009). Temperature—Temperature is the most notable criterion of an HTC process. Enhancing the temperature promotes dehydration and decarboxylation reactions, which corresponds to a reduction in the hydrogen/carbon and oxygen/carbon ratios of the treated feedstock and subsequently enhances the carbon content of the hydrochar. Higher temperatures also lead to the reaction having higher liquid and gaseous yields, resulting in a reduction in the solid phase (typically 15%
60% dry weight food waste biomass). In addition, higher temperatures can allow part of the hydrochar generated to degrade, assisting in the reduction of the mass yield (Xiu et al., 2010). Most polysaccharides fail to degrade at low temperatures, culminating in a hydrochar much like the original raw feedstock. Pressure—Pressure is deemed to be an indirect process parameter, as it is highly temperature dependent. The pressure to maintain water in the liquid phase is kept high (10
40 bar), and under these circumstances, hot pressurized water evinces higher production of ions under ambient conditions, acting as a precursor to the acid/base catalyst and as a solvent, reactant, catalyst, or product. Also, higher pressures seem to weaken the typical reactions that occur during dehydration and decarboxylation. Residence time—The HTC process typically takes time ranging from a few minutes to many hours. Enhancing the residence time of food waste within the HTC reactor usually leads to higher hydrochar carbon content (Xiu et al., 2010; Muller and Vogel, 2012; Erlach et al., 2012; Kruse, 2010; Heilmann et al., 2011; Erlach and Tsatsaronis, 2010) and higher heating value. The residence time is usually thought to lessen the total solid mass, enabling higher quantities of water-soluble compounds to be formed. Recirculating the process water would be an economically viable way to enhance the residence time. pH—As many works have suggested (Orem et al., 1996), the pH generally falls during an HTC reaction owing to the creation of a number of acidic compounds including acetic, formic, and lactic acids. Typically, acidic conditions accelerate the biomass carbonization (Titirici et al., 2007), aiding the hydrolysis of cellulose. Funke and Ziegler (Funke and Ziegler, 2010) stated that weak acidic conditions enhance the overall HTC reaction rate and, nevertheless, the HTC reactions may be inhibited by pH values that are too low (Kruse, 2010). Solid load—Higher solid load can lead to a lower residence time, by enhancing the rate at which the monomer concentration increases, enabling for earlier polymerization (Funke and Ziegler, 2010). To boost the coal production in a reactor, the solid load must be as high as possible (Kruse, 2010).

5.3

Scalability of thermochemical conversion of food waste

5.3.1 Incineration Incineration has been extensively used to produce energy from waste materials and can reduce the waste volume by almost 80% (Digman and Kim, 2008). The heat produced by incinerating food waste could be used effectively to operate steam turbines for generating power or as process heat for use in food processing plants (Khoo et al., 2010). Traditionally, in the general flow of municipal solid waste, food waste is disposed of and transformed into heat and energy by incineration. Nevertheless, there are limited studies in the literature that focus on the direct restoration of energy from food waste through incineration. This is because, owing to noncombustible components and higher moisture, nitrogen and ash content, and lower oxygen content, food waste alone appears to be inappropriate for incineration (Mardikar and Niranjan, 1995). Caton et al. (2010) assessed and compared the emissions and temperatures from incineration of wood pellets, dried pelletized food waste, and dried nonpelletized food waste and revealed higher temperatures for incineration of food waste owing to its higher energy content. Kim et al. (2013) investigated global warming and energy recovery options for food waste disposal in Korea. Following drying, food wastes were released with Municipal Solid Waste (MSW) and incinerated at 850 C
1100 C, and an average energy consumption of 649 kWh/tonnes of food waste was calculated. Findings showed that 37.7 kJ of heat was generated from dryer incineration of 1 g total solid of food waste. This draws the conclusion that dryer incineration may have been the best option for recycling food waste, but these positive outcomes came from both MSW and dried food waste incineration. Recuperation of energy by incineration of food waste alone is not always economically viable, owing to the loss of energy to evaporate the higher water content in the organic waste. Caton et al. (2010) examined the restoration of energy through direct combustion

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from postconsumer food waste and the outcomes revealed that recuperation of energy can promote cost savings more easily by reducing fuel consumption and lowering the cost of disposal. Food waste emissions for nitrogen oxide, hydrocarbons, and soot were also found to be substantially higher. Another key reason to limit the use of incineration in the food industry is growing concern about the various environmental impacts of dioxin emissions (Digman and Kim, 2008).

5.3.2 Combustion/cofiring Combustion/cofiring is the most commonly available biomass conversion method for power generation and the scale can range from very small to large (1
100 MW). Accurate blending control between biomass fuel and air is a key component of advanced combustion technologies to deliver higher fuel efficiency and reduce emissions of pollutants such as hydrocarbons, nitrogen oxide, carbon monoxide, and particulate matter. Cofiring biomass has been suggested for very large-scale direct combustion ( . 300 MW), and it is an efficient method for reducing greenhouse gas emissions. However there are still issues with biomass cofiring, such as changes in ash properties and heat exchanger fouling, that need to be addressed.

5.3.3 Gasification Gasification transforms the feedstock’s entire carbon content, making it more affordable than conventional anaerobic digestion processes, which transform only some portions into fuel. Mansaray et al. (1999) utilized a fluidized bed gasifier for rice husks at a velocity between 0.22 and 0.33 m/s, an air equivalence ratio between 0.25 and 0.35, and temperature between 665 C and 830 C. The results revealed that the yield ranged from 1.30 to 1.98 Nm2/kg, 55% to 81%, and 3.09 to 5.03 MJ/Nm3, respectively, for syngas, carbon conversion, and higher heating value. A cyclone gasifier was employed for gasification of bagasse powder at 39
53 kg/h at 820 C
850 C and the findings showed that the higher heating value of syngas was found to be between 3.5 and 4.5 MJ/Nm3 at an air equivalence ratio of 0.18
0.25 (Gabra et al., 2001). The key benefit of gasification is syngas, which can be transformed into a wide range of biofuels (hydrogen, bio-SNG, and synthetic diesel) and synthesize biochemicals which can be alternatives to petroleum-based products. Overcoming the high capital and operating costs is a major obstacle to biomass gasification. This is due to the smaller plant sizes (,500 tonnes/day), and this size is defined by the intrinsic availability of biomass and transportation costs in the distributed resource. Several other issues include the presence of alkaline materials like sodium and potassium which cause slag and fouling problems. Lower temperatures also lead to unwanted tar formation, resulting in serious operational problems. Several catalysts and process configurations have been developed to tackle these problems, but tar issues remain. The gasifier outlet was also supplemented with a catalytic tar cracker to disintegrate the tar into smaller molecules. Gasification is an expedient method of providing heat and power from residues of grain processing. However, food waste gasification remains difficult to achieve energy efficiency and operational reliability (Digman and Kim, 2008).

5.3.4 Pyrolysis Pyrolysis can transform dry food wastes into bio-oils (Gercel et al., 2002; Ozcimen and Karaosmanoglu, 2004; Yorgun et al., 2001; Ozbay et al., 2001). Bio-oils are highly complex mixtures of acetic acid, methanol, aldehydes, ketones, alkylphenols, phenols, and lignin-derived and other nonvolatile compounds. Since bio-oil can be readily stored and transported, compared with heavy biomass and gaseous fuels, pyrolysis provides substantial logistical and economic benefits over combustion and gasification methods (Bridgwater et al., 2001). Gercel et al. (2002) pyrolyzed sunflower oil cake using a fixed bed tubular reactor. At a temperature of 550 C and a heating value of 5 C/s, the best yield of bio-oil was 49% by weight and the calorific content was 32.15 MJ/kg, which is fairly close to that of petroleum fractions. Duman et al. (2011) conducted a slow and rapid pyrolysis comparison study. The highest yield of bio-oil of cherry seeds by slow pyrolysis was 21% by weight, while fast pyrolysis yielded 44%. Flash pyrolysis is a novel technology that needs to be discussed for a number of key issues. Bio-oil should be replaceable with petroleum crude oil, in such a way that the transportation and refining infrastructure can be utilized either in the existing form or with insignificant changes. Bio-oil, however, has noticeable physical and chemical issues that are difficult to use in existing petroleum refineries. Bio-oils also need to be refined and upgraded to transportation fuels by lowering viscosity, oxygen content, removal of water and acidity, and enhancing heating value (Zhang et al., 2007).

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Food Waste to Valuable Resources

5.3.5 Hydrothermal carbonization Several studies have recently focused exclusively on HTC covering a typology of biomass, including algae (Gai et al., 2015; Yu et al., 2004), cellulose, lignin, hemicelluloses, starch (Fiori et al., 2012; Lu and Berge, 2014; Pala et al., 2014; Xiao et al., 2012; Yedro et al., 2014; Subagyono et al., 2014), animal manure (Cao et al., 2011), and municipal sludge (Peng et al., 2016; Liu et al., 2013; Parshetti et al., 2013; Gao et al., 2012; Kobayashi et al., 2008; Kang et al., 2012; Yan et al., 2009). HTC yields have interesting hallmarks, such as permeability, water retention capacity, availability of nutrients, and diverse applications including soil amelioration, soil carbon sequestration, as a solid fuel source (Paraknowitsch et al., 2009), a new carbon material (Cui et al., 2006; Demir-Cakan et al., 2009), and an adsorbent (Liu et al., 2010), making HTC an important technique for treating problematic biomass. HTC experiments were performed over a period of 0.2
120 h within the temperature range of 200 C
350 C. Studies have shown that HTC of food waste is advantageous, resulting in hydrochar generation with high carbon (45%
93% of initial carbon) and energy contents (15
30 kJ/g dry solids). Table 5.5 illustrates the yield of hydrochar from various food waste using HTC. Erdogan et al. (2015) found that HTC hydrochar yields on orange pomace followed a declining trend with temperature enhancement, whilst the reaction time had an insignificant impact on yield. Li et al. (2013) collected food waste as raw materials from local restaurants for HTC processing and revealed that a substantial portion of carbon ( . 70%) in the initial substratum remained solid during the 96-h reaction period. This observation is persistent in literature studies of food waste (dog and rabbit food) and many other raw materials including cellulose, xylose, and glucose (Hwang et al., 2012; Sevilla and Fuertes, 2009; Kang et al., 2012; Goto et al., 2004; Lu et al., 2012). Pala et al. (2014) analogized HTC and grape pomace torrefaction and revealed that HTC results in products with higher energy density, energy output, frailty, and combustion reactivity than torrefaction. Lu et al. (2012) stated that hydrochar-derived energy from HTC of model food waste is significantly higher than incineration. Berge et al. (2015) analogized HTC, composting, and anaerobic digestion treatment of food waste, stating that HTC is economically and practically much more promising due to its lower residence time, disintegration, and significantly better market for hydrochar sales. Fernandez et al. (2015) studied the HTC of orange peels. HTC of food waste was reported with various substrates including rabbit food (Berge et al., 2011; Goto et al., 2004), food waste and wood (Wang et al., 2018; Berge et al., 2015), dog food (Hwang et al., 2012), orange peels (Fernandez et al., 2015), corncob (Arellano et al., 2016), fish meat (Kang et al., 2012), rice bran (Sugano et al., 2012), tomato peels (Sabio et al., 2016), food waste (Berge et al., 2015; Idowu et al., 2017; Zhai et al., 2018), wheat bran

TABLE 5.5 Hydrochar from various HTC food wastes. Substrate

Temperature ( C)

Reaction time

Hydrochar (%)

References

Food waste

230
260

8h

NR

Zhai et al. (2018)

Food waste

225
275

96 h

45
95

Tradler et al. (2018)

Food waste

150
350

20 min

36
68

Kaushik et al. (2014)

Walnut shells

200
300

60 min

0
98

Lui et al. (2006)

Orange waste

200
250

24 h

NR

Ren et al. (2006)

Sugarcane

220

1h

47

Pruksakit and Patumsawad (2016)

Watermelon peel

190

12 h

5

Chen et al. (2012)

Orange waste

300

30 min

37.5

Pellera et al. (2012)

Food waste

250

3h

NR

Kantakanit et al. (2018)

Sweet corn

250

96 h

96

Lu and Berge (2014)

Rabbit food

200
350

20 h

33
48

Goto et al. (2004)

Rabbit food

250

20 h

44

Berge et al. (2011)

Kitchen waste

190

4h

63

Malata´k and Dlabaja (2016)

Peanut shell

300

30 min

50.1

Huff et al. (2014)

Thermochemical conversion of food waste for bioenergy generation Chapter | 5

113

(Reisinger et al., 2013), sweet corn (Lu and Berge, 2014), peanut shell (Huff et al., 2014), orange waste, olive pomace (Pellera et al., 2012), grape, eggshell, sweet potato, and pomelo peels (Wu et al., 2013), sugar beet pulp (Cao et al., 2013), grape pomace (Pala et al., 2014), leftover food (Busch et al., 2013; Wiedner et al., 2013), orange pomace (Erdogan et al., 2015), and restaurant food waste (Kaushik et al., 2014; Ren et al., 2006). HTC is of enormous benefit to food waste as exhaustive energy is not required for drying. HTC is seen as an effective carbon sequestration process to alleviate climate change in comparison to other processes. Some of the original carbon in the substratum is transformed into carbon dioxide and released into the atmosphere while food waste is fermented or anaerobically digested. However, HTC incorporates most of the original food waste carbon in the final hydrochar product (Digman and Kim, 2008).

5.4

Concluding remarks, challenges, and future prospects

Appropriate treatment of food waste has been a serious environmental and pecuniary concern. Conversion of food waste to bioenergy is a process with immense potential and recent trends show that the integration of highly advanced waste to energy technologies based on the priorities of the waste treatment method is moving away from single solutions such as landfill. The composition of food waste differs greatly depending on its source. The notable traits of food waste reported include 74%
90% moisture content, 15
36:1 carbon to nitrogen ratio and 0.8
0.97:1 volatile solids to total solids ratio (Zhang et al., 2007). However, no cost of food waste can compensate for the initial high capital costs of the biorefineries together with the environmental benefits in taking waste disposal into account. In addition, the efficiency could be improved by improving research and scalability studies on the integration of various value-added product technologies. Investigations indicate that it is progressively feasible to transform food waste into bioenergy through thermochemical conversion. Efficient transformation of food waste into bioenergy needs proper combination of advanced thermochemical conversion techniques with feedstocks that can be extended to replace fossil energy (Botha and von Blottnitz, 2006; Campbell et al., 2009; Cherubini et al., 2009; Giuntoli et al., 2013; Searcy and Flynn, 2010). Some concerns need to be addressed to facilitate the long-term use of food waste conversion to bioenergy. Incineration technology is comparatively better because it requires minimal land area, but it has high investment, operation, and maintenance costs with low public approval. Gasification technology affords more optimistic solutions with regard to public consent, flexibility of feedstock, flexibility of product, near zero emissions, safety, and reliability. In contrast, pyrolysis has relatively lower air emissions and medium public approval. Both pyrolysis and gasification methods are Odor problem

VG, very good; G, good; M, moderate; P, poor Hydrothermal carbonization Pyrolysis/gasification Incineration/combusion

VG Speed of process Air/water pollution

Energy yield

Greenhouse effect VG

VG VG

VG

VG VG

P

M

G M

VG M

Capital cost

M P

Environmental issues

M P P Health issues

G

M

P Energy-economical issues

FIGURE 5.7 Complete thermochemical conversion technologies for the environment, health and energy-economic aspects.

114

Food Waste to Valuable Resources

beneficial, especially when it comes to lowering CO2 emissions and cost of maintenance in comparison to incineration. Nevertheless, the core issues are the substantially higher moisture content, low heating values, and strongly disparate food waste, leading to technological and financial issues in pyrolysis and gasification. Combustion decreases the quantity of waste by 85%
95%, but the emission criteria for food waste have declined rapidly in recent years. Fig. 5.7 illustrates the complete thermochemical conversion technologies for the environment, health, and energy-economic aspects. HTC is an affordable technique for transforming food waste into beneficial products, amongst the various thermochemical technologies. However, to review the technical practicality of using HTC for large-scale operations, a thorough techno-economic analysis is required. Ultimately, with input from expert professionals in the field, an interdisciplinary methodological solution is required to identify the advantages of food waste processing for short- and long-term energy and material restoration. The high temperature of the HTC process negates pathogens and inactivates potential organic contaminants (Libra et al., 2011). Also, the HTC reaction time (,1 h) is significantly shorter than the traditional anaerobic digestion method ( . 20 days), which greatly enhances the continuous food waste transformation and improves product yields. While there are many advantages to the HTC process for food waste compared with other energy conversion techniques, there are some disputes and issues in this research that may attract technical attention for future directions (Thi et al., 2015). The main scientific questions are listed here (Thi et al., 2015). (1) Is it practicable to identify the right catalyst, particularly for the HTC process at higher temperatures, to lessen the reaction pressure and temperature? (2) Can HTC metabolize food waste biomass to generate carbonaceous hydrochar materials for potential energy uses? (3) Can we find clear and elaborate mechanisms for HTCs relevant to food waste at lower and higher temperatures? (4) Can the HTC process be used to regulate exhaustive hydrochar and liquid product materials? Future resolution of these barriers and problems could further assist and enhance the ability to design a range of hydrochar materials and extend their potential applications for soil amendment, as an activated carbon adsorbent for environmental remediation, as catalyst supports/catalysts, as a feedstock for carbon fuel cells, as a carbon sequester or a soil fertilizer, as a renewable energy carrier, and for electrochemical energy storage with lithium-ion batteries or supercapacitors.

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214. Schmidt, M.W.I., Skjemstad, J.O., Jager, C., 2002. Carbon isotope geochemistry and nanomorphology of soil black carbon: black chernozemic soils in central Europe originate from ancient biomass burning. Glob. Biogeochem. Cycles 16, 1123. Scott, H., Chunbao, X., Fernando, P., Yuanyuan, S., Hanning, L., Jinsheng, W., et al., 2012. Catalytic gasification of woody biomass in an air-blown fluidized-bed reactor using Canadian limonite iron ore as the bed material. Fuel 91, 170
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Further reading Benavente, V., Calabuig, E., Fullana, A., 2015. Upgrading of moist agro-industrial wastes by hydrothermal carbonization. J. Anal. Appl. Pyrolysis 113, 89
98.

Chapter 6

Production of organic acids and enzymes/biocatalysts from food waste J. Merrylin1, R. Yukesh Kannah2, J. Rajesh Banu3 and Ick Tae Yeom4 1

Department of Food Science and Nutrition, Sarah Tucker College, Tirunelveli, India, 2Department of Civil Engineering, Anna University

Regional Campus, Tirunelveli, India, 3Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, Tamil Nadu India, 4

Graduate School of Water Resources, Sungkyunkwan University, Suwon, South Korea

6.1

Introduction

The factors responsible for the elevated demand for alternative fuels and chemicals are overpopulation, the risk of global warming, and the shortage of fossil reserves, which put strains on our resource system and hence requires the advancement of sustainable and novel approaches for many industries. The general public has been encountering increasing constraints created by our resource structure, which drives industry to enhance its effectiveness in general by improving existing procedures for finding innovative uses for waste. Because of the variety of the functionalized chemical composition contained within the food supply chain, waste has surfaced as a resource with significant potential to be employed as a raw material for the production of value-added products including different organic acids (He et al., 2012; Pan et al., 2008; Zhang et al., 2013). The composition of food waste varies from source to source but mainly consists of organic matter such as proteins, carbohydrates, and fats, with a fraction of inorganic components such as sugars, amino acids, and fatty acids (Dahiya and Joseph, 2015; Lin et al., 2013). Food waste can be converted into a spectrum of bio-commodity chemicals and bioenergy by employing bioprocesses (Dahiya and Joseph, 2015; Lin et al., 2013; Uc¸kun Kiran et al., 2014). The bioprocesses usually employed are fermentation, methanogenesis, solventogenesis, acidogenesis, photosynthesis, bio-electrogenesis, etc., which yield various value-added products. Hydrolysis of the polysaccharide components in food waste may lead to the breakage of glycoside bonds, thus resulting in the formation of oligosaccharides and monosaccharides, which are more prone to fermentation, leading to valuable products. The total protein and sugar components in food waste range between 3.9%
21.9% and 35.5%
69%, respectively (Uc¸kun Kiran et al., 2014). Due to the presence of such organic matters, food waste acts as a better inoculum for fermentation without the addition of any nutrient supplements. Thus food waste has been used as the only microbial feedstock for the production of various kinds of value-added bioproducts. This chapter deals with the exploitation of food waste for the production of various biopolymers and feed proteins such as polysaccharides, polyhydroxyalkanoates, baker’s yeast, single-cell protein, and single-cell oil production.

6.2

Production of organic acid from food waste

6.2.1 Citric acid Citric acid is a tribasic hydroxyl acid (C6H8O7, 2-hydroxy-1,2,3-propane tricarboxylic acid) and a natural constituent of a number of citrus fruits (Makut and Ekeleme, 2018). It is a naturally occurring weak acid with a pH of less than 2. It is the most widely used organic acid in the food, pharmaceuticals, and cosmetics industries, and thus is produced in tonnage through fermentation. It confers a pleasing, tart flavor to various food and beverages. In the food industry, citric acid is utilized as an acidulant, emulsifier, stabilizer, flavor enhancer, preservative, chelative, buffer, and antioxidant. It also finds application as an additive in detergents, pharmaceuticals, toiletries, and cosmetics. Due to its wide application, the food industry is the major consumer of citric acid, using 70% of the global production, while pharmaceuticals Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00006-7 Copyright © 2020 Elsevier Inc. All rights reserved.

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and other industries use 12% and 18% of the total production of citric acid, respectively (Vandenberghe et al., 2004). Citric acids can be synthesized both chemically and biologically. However, better results were obtained only through microbial fermentation. Biological production of citric acid has become the ultimate choice due to its economic advantages over chemical synthesis. Recently, much attention has been paid to improving the production of citric acid biologically by improving the microbial strains and maintaining their production capacity. A variety of microbes have the capacity to accumulate a significant amount of citric acid in culture media. Among these, fungal species such as Aspergillus niger, Mucor pyriformis, Penicillium lactum, and Tricoderma viride have the ability to produce citric acid (Kirimura et al., 1990). Yeasts are also considered to be active producers of citric acid. These belong to the species of Saccharomyces, Candida, and Yarrowia (Crolla and Kennedy, 2001; Good et al., 1985; Rane and Sims, 1993). A. niger is considered as the organism of preference for the production of citric acid due to its various advantages. The main advantages of A. niger are that it can generate more citric acid per unit time, it is easy to handle, and it can ferment a wide range of cheap raw materials. Its only disadvantage being the simultaneous production of isocitric acid. Recent researchers have developed an interest in using food wastes as substrate for the production of citric acid, including pineapple (Kareem et al., 2010; Sarkar and Das, 2017), waste grape pomace (Papadaki and Mantzouridou, 2019), apple pomace (Vendruscolo et al., 2008), corn cobs (Hang and Woodams, 2001), date pulp (Assadi and Nikkhah, 2002), kiwifruit peel (Kumar et al., 2003), cassava bagasse (Prado et al., 2005; Vandenberghe et al., 2004), banana peel (Max et al., 2010), and wheat bran and soya bean meal (Sauer et al., 2008). Citric acid-producing strains can be improved by biotechnological applications such as mutation and selection. Mutations can be carried out by mutating the parental strains with the help of mutating agents such as gamma radiation, UV radiation, and chemicals. For hyperproduction of citric acid, a combination of mutagens can be applied. The inoculum for citric acid production is usually introduced in the fermentation medium in the form of spores (Ikram-ul et al., 2004). Spores can be inoculated while sparging air through the medium or they can be inoculated in the form of spore suspension, which is then introduced at an optimum temperature into glass bottles containing solid substrates (Show et al., 2015). The viability of the spore is based on the time of incubation and the medium of sporulation. Viability increases with time and for a higher citric acid yield, Aspergillus requires an incubation time of 7 days. However, after 7 days, the germination of spores decreases with time (Ferna´ndez Vergano et al., 1996). The majority of citric acid produced around the world today is obtained by fermentation. It is more advantageous than other methods as it has an uncomplicated and steady operation, requires easier control systems, consumes less energy, and is unaffected by power cuts (Soccol et al., 2006). Citric acid can be produced by different means of fermentation such as solid-state fermentation (SSF; Vandenberghe et al., 2004), liquid surface fermentation, and submerged fermentation (Narayanamurthy et al., 2008). The same strain can differ in the citric acid yield using different fermentation methods. Citric acid production by fermentation usually involves three phases, namely selection, preparation, and inoculation of the substrate, followed by fermentation, and finally downstreaming of the end product. A variety of fermenters are used in the production of citric acid, including glass incubators, Erlenmeyer conical flasks, single-layer and multilayer packed bed bioreactors, and horizontal and rotating drum bioreactors. Surface fermentation is usually performed in fermentation chambers which use trays made of high-grade steel, aluminum, or polyethylene (Bauweleers et al., 2014). Surface fermentation involves two phases. In the first phase, there is formation of fungal mats on the surface and in the second phase, there is production of citric acid. Recovery is carried out by washing the mycelial mats impregnated with the product (Max et al., 2010). The trapped citric acid is further extracted. Submerged fermentation is the most commonly used technique for the production of citric acid. It is mostly used in batch reactors (Kishore et al., 2008). The fermenters used are usually Erlenmeyer flasks which are placed on an orbital shaker and stirred continuously. Darouneh et al. (2009) found that surface fermentation was superior compared to submerged fermentation in terms of citric acid production. Koji fermentation or SSF is the simplest process of citric acid production and utilizes various food wastes as a raw material. In SSF, an insoluble material acts as a source of nutrient as well as physical support and the microorganisms are developed in this low-water activity environment (Falony et al., 2006). A. niger is commonly used in SSF. Strains which require more nitrogen and phosphorus are not ideal for koji fermentation as they have a low diffusion rate. Production of by-products during the process does not affect the production of citric acid and this is the primary advantage of SSF (Berovic and Legisa, 2007). The factors which affect citric acid fermentation are carbon, nitrogen, and phosphorus sources, trace elements, lower alcohols, oils, fats, and other compounds such as sodium fluoride and iron cyanide (Soccol et al., 2006).

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6.2.2 2,3-Butanediol 2,3-Butanediol (2,3-BD) is a chemical of high value which is usually generated petrochemically and can also be synthesized by some bacteria. It is an organic molecule with two hydroxyl substituents which finds its application in the pharmaceuticals, food, and cosmetics industries. Butanediol is also used in the synthesis of inks used for printing, cologne, artificial gums, flavorings, fumigants, antibiotics, plasticizers, moisteners, and softening agents (Koutinas et al., 2014; Rebecchi et al., 2016). It can also be used commercially as an antifreezing agent due to its low freezing point, which is about 260 C (Priya et al., 2016; Rahman et al., 2015). 2,3-BD is traditionally produced by fermentation of hexose and pentose sugars such as glucose through the enzymatic activity of a complex of enzymes. However, due to the high cost of pure sugars as substrates, cheaper raw materials such as wastes from the food industry or corn have been used recently for the production of 2,3-butanediol (Yang et al., 2015). Food industry residues are also considered as a promising alternative to noncellulosic substrate due to their higher sugar content and their compatibility with all the biological processes. The wastes which have been utilized for the production of 2,3-BD include the raw molasses generated after extraction of sugar from beets, discolored molasses generated after extraction of sugar from beets, whey from the cheese industry, molasses generated after crystallization of sucrose from sugarcane juice, and starch hydrolysates generated during the processing of corn. Among these substrates, starch hydrolysates are considered as the ideal raw material due to their high production yield. Microbes such as Klebsiella oxytoca, Klebsiella pneumoniae, Serratia marcescens, and Paenibacillus polymyxa are known to produce 2,3-BD by fermentation. Among these, microbes belonging to the Klebsiella species are considered to be the most important producers because they are able to yield high amounts of 2,3-BD and they can convert any type of sugar such as glucose, galactose, mannose, xylose, cellobiose, arabinose, and lactose present in the hemicellulose and cellulose hydrolysates into 2,3-BD (Cheng et al., 2010). However, their use is restricted in large-scale production due to the pathogenicity of the microbes. Hence Bacillus licheniformis or P. polymyxa are used primarily in the industrial production of 2,3-BD due to their nonpathogenicity, though their yield potential is a little lower than the primary producers (Jurchescu et al., 2013; Perego et al., 2003). 2,3-BD exists as three different stereoisomers, dextrorotatory and levorotatory optically active forms, and an optically inactive meso-isomer. The isomer accumulated during the process is usually based on the microbe employed for the production of 2,3-BD. Often a mixture of two different stereoisomers is generated (Celi´nska and Grajek, 2009). Three important enzymes are involved in the biosynthesis of pyruvic acid, namely α-acetolactate synthase, α-acetolactate decarboxylase, and 2,3-BD dehydrogenase (acetoin reductase). These enzymes are secreted by microbes during the late log phase and the stationary phase when there is minimal oxygen availability. There are many intermediates formed during fermentation such as α-acetolactate, acetyl-methyl carbinol (acetoin), and diacetyl. Other than 2,3-BD, additional end products are also synthesized such as ethanol, lactic acid, acetic acid, formic acid, and succinic acid. Based on the growth rate of the microbes, their age, and the composition of the medium, the chemical constituents of the microbes can be varied. Despite these variations, product generation can be enhanced in a number of methods (Kent, 2003). Metabolic engineering of the producing strains has been developed as a promising approach for optimizing the fermentation process using DNA recombinant technology. Microbial metabolism is also affected by oxygen content, culture temperature, pH, and supplementation of acetic acid. Thus genetic engineering has been introduced to increase the production of 2,3-BD since 1983 (Yu and Saddler, 1983). For commercial production of 2,3-BD through microbes, it is advantageous to use cheaper substrates such as food waste (Chen et al., 2013a; Zheng et al., 2008a). To utilize waste from the food industry and to produce the desired products, the metabolic performance of the producing strains should be increased genetically (Jin et al., 2014). Mutants with new improved characteristics can be acquired by introducing a mutation (Zheng et al., 2008a) or altering a few genes which are essential in the 2,3-BD pathway, leading to overexpression of the enzymes involved in the 2,3-BD fermentation process (Park et al., 2015; Shin et al., 2012). The separation of 2,3-BD from the media is a major economic challenge because 2,3-BD has great affinity for water and it also has an elevated boiling point. The solid and the dissolved components in the fermentation broth also hinder the efficient downstreaming of 2,3-BD. Thus it is necessary to develop a cheap and efficient downstream process. Separation techniques such as reverse osmosis, pervaporation, steam stripping, solvent extraction, and distillation have been used (Afschar et al., 1993; Garg and Jain, 1995; Qureshi et al., 1994). Due to greater energy consumption by these processes, more advanced technologies such as aqueous two-phase extraction (Fulgence et al., 2018), combined solvent extraction and pervaporation (Shao and Kumar, 2009), and in situ recovery (Anvari and Khayati, 2009) are used. These advanced processes consume less energy and lead to efficient product recovery.

6.2.3 Succinic acid Succinic acid is a naturally occurring four-carbon dicarboxylic acid with the molecular formula C4H6O4 that is produced by liquefied petroleum gas (Cok et al., 2014). However, petroleum gas is expensive and thus succinic acid (SA)

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is generated by different microbes (Raja and Dhanasekar, 2011). SA is naturally formed by most living cells as an outcome of anaerobic digestion (Song and Lee, 2006). It is a common organic acid, which can be used in many food, chemical, and pharmaceutical industries as a precursor to generate many chemicals such as solvents, perfumes, lacquers, plasticizer, dyes, and photographic chemicals. Succinic acid is also used as an antibiotic and curative agent. It also finds application as a surfactant, ion chelator, and as an additive in various industries (Zeikus et al., 1999). By biorefinery, SA can be generated through microbial fermentation of carbohydrate (Zeikus et al., 1999). The common microorganisms used in fermentative SA bioproduction are Actinobacillus succinogenes (Lin et al., 2008), Anaerobiospirillum succiniciproducens (Samuelov et al., 1999), Mannheimia succiniciproducens (Kim et al., 2004), and recombinant Escherichia coli (Vemuri et al., 2002). These strains can fix carbon dioxide during fermentation and thus reduce greenhouse gas emissions. Food waste is composed of nearly 60% carbohydrate and can be used as a substrate for production of SA (Lin et al., 2014). Moreover, food wastes are also rich in organic nutrients (Uc¸kun Kiran et al., 2014). Thus, food waste can be used as a substrate for production of various value-added chemicals without any addition of supplementary nutrients. However, some food waste may not contain sufficient nutrients and supplementary nutrients should be added (Lin et al., 2013). The production of SA through fermentation has been widely used recently compared to conventional production using petrochemicals because it does not involve harsh operating conditions and thus requires less energy (Leung et al., 2012). There are several literatures assessing the possibility of producing succinic acid from various kinds of food waste (Uc¸kun Kiran et al., 2014). Usually succinic acid is produced from just one type of pure food waste, and there is little literature focusing on SA fermentation from mixed food waste, such as that by Sun et al. (2014). These authors produced succinic acid through lab-scale fermentation using genetically engineered microorganisms (E. coli) and A. succinogenes. The mixed food waste consisted of vegetables, fruits, meat, rice, and noodles obtained from various canteens in Hong Kong. They concluded that production of SA fermentatively with the help of the fast-growing microbes was beneficial without any production of by-products, thus resulting in an easier downstreaming process. Zhang et al. (2013) investigated the possibility of using pastry waste from Starbucks Hong Kong for the production of succinic acid. Leung et al. (2012) described a biorefinery concept which used bread waste as a raw material for production of SA fermentatively. Lam et al. (2015) estimated the commercial feasibility of SA production from bakery waste through fermentation in a pilot plant, based on the results displayed by Leung et al. (2012). Yu et al. (2010) researched fermentative SA production from corncob by A. succinogenes. Li et al. (2010) examined the production of SA from orange peelings by Fibrobacter succinogenes. Nutrients in some of food wastes are larger molecules, such as starch and proteins, which slow down the activity of microbes. Thus, these wastes have to be pretreated before fermentation to facilitate the enhanced growth of microorganisms (Banu and Kavitha, 2017; Ebenezer et al., 2015a; Eswari et al., 2016; Kannah et al., 2017a; Kavitha et al., 2013; Merrylin et al., 2013a; Ushani et al., 2017). These macromolecules have to be broken down into simpler micromolecules such as sugars and amino acids.

6.2.4 3-Hydroxypropionic acid The use of fossil resources for generation of fuels causes serious environmental issues. Thus, biorefineries are helpful in generating these fuels. Of all the molecules produced by biorefineries, 3-HPA occupies an important position. 3-HPA is one among the 12 feedstock chemicals which serve as a platform for the development of various 3-carbon petrochemical intermediates. 3-HPA is an isomer of lactic acid (2-hydroxypropionic acid) structurally. It has two functional groups, hydroxyland carboxyl groups, and thus it is can be adapted to both functions and activities. This property makes the compound suitable for use in organic synthesis (Della Pina et al., 2011; Zhang et al., 2004). It is customarily dehydrated to form acrylic acid, which is generally used in consumer products such as personal care products, metal lubricants, and adhesives, and it can also be integrated as a cross-linking agent in various surface polymer coatings, and as an antistatic agent in fibers (Gokarn et al., 2007). One of the most important applications of 3-HPA is in the production of superabsorbent polymers. These polymers constitute the major part of baby and adult diapers. They are also a significant part of many incontinence products (Jensen et al., 2014). 3-HPA can be produced by various chemical routes but they are not commercially feasible due to their high cost and environmental incompatibility. There are studies on biological production of 3-HPA as far back as the early 2000s. Recombinant strains of E. coli and K. pneumoniae have been used. The potential substrates generally used are glycerol and glucose. Sugars such as glucose and xylulose act as substrate for the growth of microorganisms. Sucrose obtained

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from sugarcane and sugar beet, and glucose obtained through the hydrolysis of corn starch can be used as raw materials for the production of 3-HPA. Such sugars constitute most of the biomass in the planet (Kildegaard et al., 2015), and they can be used as substrate for production of 3-HPA. There are various pathways which convert sugars to 3-HPA, some of which are the malonyl-Co-A pathway (Choi et al., 2015), beta-alanine pathway (Song et al., 2016), propionylCo-A pathway (Luo et al., 2012), glycerate pathway, and lactate pathway. In one study, recombinant E. coli and Saccharomyces strains were developed to convert glucose into lactic acid and then to 3-HPA (McGall, 1996). There are four different type of enzymes involved in this pathway and these enzymes are used to transform lactic acid into 3-HPA, as these heterologous strains overexpress the enzymes. The enzymes, CoA-transferase and lactyl-CoA dehydratase, were extracted from Megasphaera elsdenii which is used to convert lactate to acryloyl-CoA. The other two enzymes, 3-HP-CoA dehydratase and 3-HP-CoA hydrolase, are derived from Candida aurantiacus which converts the earlier formed acryloyl-CoA to 3-HP. These two recombinant strains were able to produce 3-HPA, but the separation of 3-HP and lactic acid during downstream processing is difficult (Jiang et al., 2009). Recombinant strains such as Meyerozyma guilliermondii, Lactobacillus sp., M. elsdenii, Candida rugora, C. aurantiacus, and Corynebacterium glutamicum are used for heterologous expression of various enzymes. There has been significant progress in the bioproduction of 3-HPA in the past decade. Various pathways are being developed and tested for environmental compatibility and economic feasibility. An efficient and cheaper downstreaming process for separation and purification of 3-HPA is being optimized for a better product.

6.2.5 1,3-Propanediol Traditionally, glycerol obtained from the food and biodiesel industries is used to generate 1,3-propanediol (1,3-PDO), which is a valuable block chemical used in the synthesis of various organic compounds. It is a monomer for the manufacture of biodegradable polymers such as polyurethanes, polyesters, and polytrimethylene terephthalate (used in textile industries) (Lee et al., 2015). It is also used in the production of cosmetics, adhesives, lubricants, solvents, and medicines (Katrlı´k et al., 2007; Ma et al., 2009; Nakamura and Whited, 2003; Zhang et al., 2007). In addition, plastics containing 1,3-PDO are highly biodegradable compared to other synthetic polymers. A recent analysis compared the production of 1,3-PDO from glucose (obtained from corn) and from fossil (using ethylene oxide) (Urban and Bakshi, 2009). The study concluded that 1,3-PDO from glucose consumed less energy (38%) and emitted fewer greenhouse gases (42%) compared to the latter. Moreover, compared to chemical synthesis of 1,3-PDO, the microbial fermentation method is advantageous as it has mass production at low cost, and the opportunity to be carried out at normal temperature (37 C) and standard atmospheric pressure. Perfect fermentation requires microbes that can produce the required product from cheaper renewable resources (Rao et al., 2008). Fermentation is carried out either in batch mode, fed-batch, or continuous mode. In general a few microbes such as Klebsiella, Clostridium, and Citrobacter can produce 1,3-PDO but they use glycerol as their resource which is expensive. Unfortunately, no natural microbes have been discovered so far which can convert glucose to 1,3-PDO directly (Hartlep et al., 2002). Hence, in various studies microbes are genetically engineered to convert glucose into 1,3-PDO. However, this approach has not been accepted as the production of 1,3-PDO by genetically engineered S. cerevisiae or K. pneumoniae was only 0.4 or 1.2 and 0.58 g/L, respectively (Ma et al., 2009; Rao et al., 2008; Zheng et al., 2008b). Research by Mendes reports that two steps were developed for the production of 1,3-PDO from glucose (obtained from the food industry). The first step is the conversion of sugar into glycerol using genetically modified strains of S. cerevisiae and the next step is the production of 1,3-PDO from glycerol by C. acetobutylicum. This resulted in a flexible process which remains to be optimized. The role of these bacteria in diol production can be improved by using efficient genetic engineering tools.

6.2.6 Lactic acid Food waste contains more biodegradable carbohydrates which could be perfect for organic acid production. Lactic acid is highly valued when compared to other acids, and is the dominant product produced under normal digestion conditions. It is widely used commercially and thus there is a need to increase the production of lactic acid. It is the only monomer used to synthesize biodegradable polymers such as poly lactic acid (Ghaffar et al., 2014), and it can be synthesized either chemically or through fermentation. However, lactic acid produced by fermentation is preferred as chemically obtained lactic acid is more expensive and also not as ecofriendly. Fig. 6.1. shows the production of lactic acid from food waste.

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FIGURE 6.1 Production of lactic acid from food waste.

However, the cost of the raw material for microbial production of lactic acid amounts to 35% of the total manufacturing cost. Several attempts have been made to generate lactic acid from cheap resources. The biomass selected as a raw material to produce lactic acid should be rich in carbon, nitrogen, and oxygen sources. Biomass from food waste, agricultural waste, feedstock, mucilage from coffee, and agro-industrial residues are being considered for the production of lactic acid in an environmentally friendly process that will be cheap and reasonably priced. Lactic acids are either produced through SSF or solid submerged fermentation. Both fermentation processes are employed in commercial-scale production of lactic acid. Lactic acids are produced in two isomeric forms through fermentation, L 1 lactic acid and D
lactic acid. However, only the former isomeric form is consumable by humans and thus it plays an important role both commercially and economically (Castillo Martinez et al., 2013). Lactic acid bacteria, Lactobacilli in particular, remain the most commonly used microorganisms for the synthesis of lactic acid on a commercial scale (Mazzoli et al., 2014) as they are able to ferment both monosaccharides (hexose as well as pentose) and disaccharides (Kandler, 1983). They can also tolerate a wide range of temperatures (from 20 C to 55 C) and pH (they can survive at low pH), and they are highly flexible. A number of studies have been carried out to optimize the best operating conditions including pH, temperature, aeration, agitation, and inoculum size, to realize the highest productivity and yield of lactic acid. By-products from the food industry, such as molasses and whey, can be used for the production of lactic acid. They are carbohydrate sources consisting of hexose and pentose sugars. Molasses are rich in sucrose, cheap, and abundant (Kotzamanidis et al., 2002). Whey has a high lactose content which when disposed of leads to serious environmental issues (Bu¨yu¨kkileci and Harsa, 2004). Date juice is also used to produce lactic acid (Nancib et al., 2009). Raw materials containing polysaccharides are not directly fermented by microbes as they need to be undergo hydrolysis pretreatment (Gopikumar et al., 2016; Kannah et al., 2017b; Kavitha et al., 2014; Merrylin et al., 2014a; Sharmila et al., 2017; Tamilarasan et al., 2017). These substrates contain starch, which is a biopolymer of many glucose units joined through α-1,4-bonds forming chains of different lengths. Some may be linear and a few branched through α-1,6-linkage bonds. Two different fractions are available in starch, namely the linear polymer and the branched amylopectin. Starch can be converted into glucose monomers by primarily subjecting the substrate to liquefaction through thermostable α-amylase. This is subsequently saccharified by α-amylase and amyloglucosidase prevents gelatinization of starch (Massoud and Abd El-Razek, 2011). The resulting glucose monomers can be used immediately as a carbon source to generate lactic acid. Amylase-secreting microorganisms can directly assimilate these raw materials without any pretreatment (Banu et al., 2018a; Kavitha et al., 2015a,b, 2016a; Lakshmi et al., 2014;

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Merrylin et al., 2013b; Ushani et al., 2018). Recently lignocellulosic food waste raw materials have characterized the most remarkable substrate as feedstock for the production of lactic acid due to their abundance and cheapness (Jiang et al., 2016). However, the only factor which restricts their utilization on a pilot scale is that these raw materials are not directly accessible for fermentation. Expensive pretreatments are required to remove and separate lignin, cellulose, and hemicellulose (which constitutes 90% of the dry matter) in order to increase the surface area for the efficient action of the hydrolytic enzymes prior to microbial fermentation (Banu et al., 2018b, 2019a; Hassan and Idris, 2016; Kannah et al., 2019a; Ponnusamy et al., 2019). Recently lactic acid has been obtained from lignocellulosic materials by concurrent saccharification and fermentation (Nakano et al., 2012), thereby preventing enzyme inhibition by the product (Romanı´ et al., 2008). Fungi belonging to the genus Rhizopus are also able to ferment starchy materials without any preliminary hydrolysis as they secrete extracellular amylase. They produce L 1 isomer. Raw materials such as corn, rice, potato, wheat, and pineapple have been subjected to fermentation by fungi to generate lactic acid (Bai et al., 2004; Fukushima et al., 2004; Jin et al., 2005). The fermentation media should be rich in carbon and nitrogen, which promote the growth of microbes (AbdelRahman et al., 2011). The fermentation media must include biomass from raw material, a nitrogen source, yeast extract, magnesium sulfate, calcium chloride, sodium chloride or any other salt, sodium hydroxide to balance the pH, a phosphate source, and potassium sulfate. The optimal conditions for fermentation are usually in the range of 45 C
60 C with a pH to 5.0
7.0 for the action of Lactobacillus strains. The medium is always maintained in an acidic condition to stabilize the lactic acid produced and to prevent its degradation (Ghaffar et al., 2014). Purification of lactic acid is the most expensive step in the production process (Abdel-Rahman et al., 2011). Lactic acid is purified or separated from the media by different approaches or techniques such as distillation (Mujtaba et al., 2012), nanofiltration, ultrafiltration, microfiltration, electrophoresis, and ion exchange resins (Neu et al., 2016).

6.2.7 Volatile fatty acids Volatile fatty acids (VFAs) are linear short-chain aliphatic mono-carboxylate compounds, such as acetic acid, propionic acid, and butyric acid, which are the building blocks of different organic compounds; VFAs have two (acetic acid) to six (caproic acid) carbon atoms. They are extremely useful in the chemical industry due to their functional groups. They also can be exploited as a raw material in various biological practices for the production of biopolymers, such as polyhydroxyalkanoates and biofuels like methane and hydrogen which are of high value (Raganatia et al., 2014). The composition of food wastes, with easily degradable constituents and the requirement for only mild pretreatments, makes them suitable to be utilized for VFA production (Kannah et al., 2018; Kavitha et al., 2017a; Sarkar et al., 2016). Although there is variation in food wastes, these differences are negligible as they are generally very similar. Food wastes contain a high level of organic matter (15%
20% of total volatile solids) and high levels of nitrogen and phosphorus (about 3
15 and 0.5
1.0 g/kg, respectively), which are essential nutrients for the metabolic pathway of microbes. VFAs are generally produced through anaerobic digestion, which consists of three steps, namely (1) hydrolysis, (2) acidogenesis, and (3) methanogenesis. Hydrolysis is the rate-limiting step during anaerobic digestion. During hydrolysis the complex organic materials are converted into simple molecules such as simple sugars, amino acids, and glycerol. Usually the hydrolyzed products and the degree of hydrolysis affect fermentation in which there is availability of only biodegradable substance (He et al., 2012). During acidogenesis the hydrolyzed products are fermented by mixed microbial cultures into VFAs, carbon dioxide, and hydrogen (Parawira et al., 2004). To enhance VFA production, pretreatment of food wastes has been reported (Chen et al., 2013b; Yin et al., 2014). Physical, chemical, and biological methods are widely employed for pretreatment of food waste. Physical pretreatment involves reduction of the size of the particles, thereby providing greater surface area for the action of enzymes and microbes (Banu et al., 2019b; Ebenezer et al., 2015b; Eswari et al., 2017; Gayathri et al., 2015; Kavitha et al., 2015c, 2018, 2019a; Tamilarasan et al., 2018). Various types of millers, such as ball milling, hammer milling, and roll milling, are used for physical pretreatment (Paudel et al., 2017). Chemical pretreatment solubilizes the wastes with the help of acids, alkalies, and organic solvents at various concentrations (Banu et al., 2012, 2018c; Kannah et al., 2019b; Kavitha et al., 2016b; Kumar et al., 2018; Sowmya Packyam et al., 2015), increasing the surface area (Passos et al., 2017). Biological pretreatment involves the addition of enzymes or enzyme-producing microbes which intensifies the hydrolysis and so improves sugar production (Banu et al., 2016; Braguglia et al., 2018; Kavitha et al., 2017b,c, 2019b,c; Merrylin et al., 2014b).

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FIGURE 6.2 Schematic flow of the steps involved in conversion of food waste into different enzymes.

The other parameters which influence the production of VFA are (1) the composition of FW and (2) operational parameters such as pH, temperature, hydraulic retention time, and organic loading rate. In a study by Reddy et al. (2018) bioaugmented cultures produced more butyric acid and caproic acid compared to nonaugmented cultures. Various methods have been used for the effective recovery of VFA from waste streams. Methods such as gas stripping with adsorption, adsorption, solvent extraction, electrodialysis, reverse osmosis, membrane contractor, and nanofiltration are employed for the recovery of VFAs. VFAs recovered from waste streams are further used in the production of bioplastics, biogas, biohydrogen, biodiesel, and bioelectricity. They have also been used to remove biological nutrients from wastewater (Lee et al., 2014).

6.3

Production of enzymes

Alpha amylases are extracellular enzymes capable of catalyzing and hydrolyzing α-1,4-glycosidic linkages of starch to release the subunits of glucose. They are major starch-degrading enzymes. The standardized pH of α-amylases ranges between 2 and 12, which is thermostable. These enzymes have established significant applications in the starch liquefaction, paper, food, sugar, and pharmaceutical industries. Especially in the food industry, amylolytic enzymes have been involved in the large-scale production of glucose syrups, high-fructose corn syrups, and maltose syrup, lessening of viscosity of sugar syrups, decrease of turbidity to produce clarified fruit juice for longer shelf-life, solubilization, saccharification of starch, and delaying the staling of baked products (Li et al., 2013). Commercially available glucoamylase is usually produced from species of Aspergillus and Rhizopus. The conversion of food and beverage wastes to valuable chemicals and biodiesel using different enzymes can facilitate the waste management process. Most fungal glucoamylases from the A. niger strain are active at a range of acidic pH (Lam et al., 2015). Food-processing waste streams rich in carbohydrates are readily amenable to enzymatic valorization by hydrolases and isomerases into value-added products (Andler and Goddard, 2018). Fig. 6.2 illustrates the schematic flow of steps involved in conversion of food waste into different enzymes.

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Lactases are produced by the hydrolysis of the saccharide lactose and impart a vital role in biotechnological applications of the food industry. The main enzyme β-galactosidase catalyzes the hydrolysis of complex lactose. It belongs to the family of hydrolases. Mutant strains of Polyporus versicolor are used in the production of laccase enzymes. Strain improvements of laccase-producing bacteria improve food sensory parameters such as the odor and taste of numerous food products (Osma et al., 2010). In addition, such modification of laccase may lead to new quality improvement, cost reduction, and even possess new functional properties for commercial purposes with industrial applications. The fermented ragi with submerged fermentation mode using source lactose and ragi with Lactobacillus sp. produce lactase enzyme after 12 h of fermentation time. The recovered lactases are used for dairy products in the preparation of lactose-free foods (Akolkar et al., 2005). Laccases are enzymes that belongs to a multicopper oxidase family. They help to catalyze the oxidation of phenolic compounds with the assistance of molecular oxygen. The bacterial laccases and fungal laccases are periplasmic and extracellular in origin. The fungal laccases are more abundant in nature and found most often in wood-rotting fungi. There are three kinds of fungi which produce laccase enzyme, white rot fungi, brown rot fungi, and soft rot fungi. Of these, white rot fungi have been found to be the most efficient lignin-degrading microbes. Laccases are commercially important enzymes due to their ability to degrade phenolic and nonphenolic lignin along with recalcitrant pollutants. They are used for the decolorization and synthesis of dyes, bio-bleaching, baking, bio-pulping, degradation of xenobiotics, and effluent treatment. Tannin acyl hydrolase, referred to as tannase, is a smart biocatalyst for tannin biodegradation (Tahmourespour et al., 2016). It is mainly utilized in food, beverage, feed, and food additives, as well as in environment pollution treatments. Its present in numerous tannin-rich plant materials and can also be produced on a large industrial scale through microbial production using food waste as a source material to meet societal demands (Cha´vez-Gonza´lez et al., 2012). Tannase production methods include SSF and submerged liquid fermentation (SLF) (Cha´vez-Gonza´lez et al., 2014), of which the former is preferred because of its lower cost, minimal water usage, easier operation, and higher enzyme activity than SLF. In SSF, tannase activity is extracellular in nature, whereas in SLF, tannase activity is intracellular in nature (Bhoite and Murthy, 2015). Lipases are primarily ester hydrolases. They catalyze the hydrolysis of triacylglycerol to glycerol and fatty acids. Lipases are ubiquitous enzymes due to their substrate specificity and diversity of different properties such as widespread sources, short cycle, wide pH, and wide range of temperature. They can be produced from the organism Aspergillus sp. using various sources such as banana peel, potato peel, and cassava peel through SSF with an initial 55% moisture content at an incubation temperature and time of 30.5 C and 30 h, respectively. They are used in meat processing and for leather products (Gerber et al., 2013). The lipases obtained from Thermomyces lanuginosus and Candida antarctica B have environmental and commercial prospects for waste lipid valorization. Pectinase enzymes provide an efficiently viable substitute, but are also ecological companion. Microbial pectinase covers approximately 25% of total worldwide enzyme sales. The production of pectinase by thermophilic fungi had been reported earlier. Pectinase production from A. niger was performed by both SMF and SSF. Increasing energy demand has focused worldwide attention on the utilization of renewable agricultural and industrial wastes as their disposal poses environmental problems (Voragen et al., 2004). Fig. 6.3 shows the production of enzyme from A. niger utilizing food waste as a substrate. Xylanases are the enzymes most commonly used for hydrolysis of xylan. These enzymes are produced from coffee waste by-products with an initial moisture content of 50% via submerged fermentation mode using Penicillin sp. at a temperature of 30 C and 5 days of fermentation. Recovered xylanases are used for bleaching, deinking of paper, baking, and animal nutrition (Sundarram and Murthy, 2014). Cellulase is an enzyme belonging to a family of three groups of enzymes: (1) endo-(1,4)-β-D-glucanase (EC 3.2.1.4), (2) exo-(1,4)-β-D-glucanase (EC 3.2.1.91), and (3) β-glucosidases (EC 3.2.1.21). Exoglucanase acts on the ends of the cellulose chain and releases β-cellobiose as the end product; endoglucanase (EG) arbitrarily attacks the internal O-glycosidic bonds, resulting in glucan chains of different lengths, and the β-glycosidases perform specifically on β-cellobiose disaccharides and produce glucose (Singh et al., 2013). Cellulases act as inducible enzymes produced by a large variety of microbes including both fungi and bacteria during their growth under aerobic, anaerobic, mesophilic, or thermophilic conditions on cellulosic substrates. These microbes synthesize a considerable amount of cellulase enzymes. The extensively studied cellulase producers include the genera of Clostridium, Cellulomonas, Thermomonospora, Trichoderma, and Aspergillus. Although the mechanism of cellulose degradation by aerobic bacteria is similar to that of aerobic fungi, it is clear that anaerobic bacteria operate on a different system. Cellulosomes located on the cell surface mediate the adherence of anaerobic cellulolytic bacteria to the substrate, which thereafter undergoes a supramolecular reorganization, so that the cellulosomal subunits redistribute to interact with the different target

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FIGURE 6.3 Production of enzyme from Aspergillus niger utilizing food waste as a substrate.

substrates. Cellulases have been commercially available for more than 30 years. Various enzymes produced from a number of sources are tabulated in Table 6.1.

6.4

Extraction and purification

The different types of extraction and purification processes are dialysis, diethylaminoethyl (DEAE) cellulose, ultrasound-assisted enzymatic extraction, ion exchange chromatography, size-exclusion chromatography, and hydroxyapatite adsorption (Singh and Mandal, 2016), which differs with specific enzymes. Table 6.2 shows the types of chromatography and their details. The alteration or destruction of the natural morphology of an enzyme may cause a decrease in enzyme activity, and also disturbs its stability. This is due to undesirable extraction conditions. It is vital to optimize the extraction process to yield enzymes. The extracted enzymes should possess high activity and stability. Specific characteristics such as thermostability, high temperature, high activity at acidic pH, and high stability of the enzyme vary in the presence of ionic and nonionic surfactant agents. Optimization of the extraction process should result in achieving the maximum enzyme activity, specific activity, temperature stability, pH stability, surfactant agent stability, and storage stability. These are the factors that affect the enzyme activity. The extraction conditions include the buffer-to-sample (B/S) ratio (2:1 to 6:1 w/w), mixing time (60
180 s), extraction temperature (specific to the enzyme), and the pH of the buffer (2.0
8.0).

6.4.1 Dialysis Dialysis is the method of sorting out molecules in solution by the dissimilarity in their rates of diffusion through a semipermeable membrane, such as dialysis tubing. Diffusion involves the thermal movement of molecules in solution that leads to the net association of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached. Due to the pore size of the membrane, larger molecules in the sample cannot pass through the membrane, thereby restricting their dispersal from the sample chamber. In contrast, small molecules will freely diffuse across the membrane and obtain equilibrium diagonally in the entire solution volume, thereby changing the overall concentration of these molecules in the sample and dialysate (buffer solution). Once equilibrium is reached, the final concentration of molecules is dependent on the volumes of the solutions involved. If the equilibrated dialysate is replaced

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TABLE 6.1 The different food waste sources for enzyme production. Enzyme

Strains used

Fermentation process

Food source

References

α-Amylase

Bacillus licheniformis AZ2

Batch fermentation

Rice husk

Deljou et al. (2018)

Cellulose and protease

Strains of lactic acid-producing bacteria

Solid-state fermentation

Fermented foods such as “tapaipulut,” “tempeh,” “tempoyak,” and “fuyu”

Ho and Yin Sze (2018)

α-Amylase

Bacillus subtilis

Solid-state fermentation

Apple peel, banana peel, rice bran, wheat bran, green gram husk, and pineapple peel

Mohammed (2018)

Protease

Theobroma cacao L. (PH-16 and HRT-1188)

Solid-state fermentation

Cocoa seeds

Sousa et al. (2016)

Amylase

B. subtilis ATCC6633

Solid-state fermentation

Dry wheat bran

Maity et al. (2015)

α-Amylase

Lactobacillus fermentum 04BBA19

Submerged fermentation

Corn, wheat bran

Fossi and Tavea (2013)

α-Amylase

B. subtilis RSKK96

Solid-state fermentation

Rice husk, lentil husk, cotton stalk, coarse meal of corn, coarse meal of millet and wheat bran

Akcan et al. (2012)

α-Amylase

Bacillus KR-8104

Solid-state fermentation

Wheat bran

Derakhti et al. (2012)

Amylase

B. subtilis

Solid-state fermentation

Banana waste

Unakal et al. (2012)

Amylase

Bacillus species

Solid-state fermentation

Wheat bran, gram husk, rice bran, and mustard oilseed cake

Saxena and Singh (2011)

α-Amylase

B. licheniformis M27

Solid-state fermentation

Wheat bran

Ramesh and Lonsane (1989)

(or exchanged) with fresh dialysate, diffusion will further reduce the concentration of the small molecules in the sample. Dialysis can be used to either introduce or remove small molecules from a sample, because small molecules move freely across the membrane in both directions. This makes dialysis a functional procedure for a variety of applications (Shanti et al., 2014). Various enzymes can be easily purified by dialysis via ammonium sulfate pretreatment method. The standardized concentration of ammonium sulfate of 40% is added. Precipitation is obtained by the centrifugation process. Then the precipitate is dissolved in 0.1 M phosphate buffer (pH 7) and is further dialyzed overnight against 0.01 M phosphate buffer. The dialysis removes unwanted salts and detergents. The membrane is selected according to the enzyme size. The membranes have a cut-off of 13 kDa. The sample is loaded in the dialysis tubing, and can be processed for 2
4 h. The processing is carried out under a low temperature of 40 C to prevent denaturation. The sample thus obtained is subjected to polyacrylamide gel electrophoresis using specific markers such as albumin and oval albumin (Garg, 2013).

6.4.2 Microwave-assisted extraction The electromagnetic energy of microwaves is converted to heat energy upon absorption by a material. The frequency for commercial microwave instruments of 2450 MHz (2.45 GHz) is commonly used and has an energy output of 600
700 W. It is an environment-friendly and economical technique for the direct mining of biologically active compounds from different plant materials. Microwave energy is absorbed by components in the sample in accordance with their dielectric constants. When plant material is immersed inside a microwave-transparent solvent, the temperature of microwave irradiation directly reaches the solid without being absorbed by the solvent, resulting in instant heating of

TABLE 6.2 Types of chromatography and their details. Types

Principle

Stationary phase

Mobile phase

Advantages

Disadvantages

Example

Ion exchange chromatography

Separate proteins by fixed positive charges on the stationary phase, anion exchanger, or fixed negative charges, cation exchanger

Ion exchangers are usually classified as weak or strong when used as stationary phase

Ammonium acetate buffers have increased the resolution of the mobile phase

Powerful protein purification techniques available and probably the most frequently used chromatographic technique for the separation of proteins, polypeptides, nucleic acids, polynucleotides, and other charged biomolecules

The main disadvantage of IEXC is its limitations in selectivity

CaptoS SP Sepharose SP Sephadex

Size-exclusion chromatography

In SEC, the matrix consists of porous particles and separation is instead achieved according to the size and shape of the molecules. The technique is sometimes also referred to as gel filtration, molecular sieve chromatography, or gel-permeation chromatography

The matrices used in SEC are often composed of natural polymers such as agarose or dextran but may also be composed of synthetic polymers such as polyacrylamide when used as stationary phase

There is no adsorption involved, and the mobile phase should be considered as a carrier phase and not one which has a large effect on the chromatography

Size exclusion has a wide range of applicability both in preparative and analytical protein purification

SEC separation method gives the least resolution with the lowest capacity and largest dilution of the sample with respect to all other forms of chromatography

First commercial SEC media, Sephadex, composed of dextran that was cross-linked with epichlorohydrin

Reversed-phase chromatography

Interactions between hydrophobic ligands covalently attached to the adsorbent and the hydrophobic patches of molecules that are applied in the aqueous mobile phase

Synthetic organic polymers, for example, beaded polystyrene, are also available in values up to 12

The two most widely used are acetonitrile and methanol, although acetonitrile is the more popular choice

Shorter polypeptides usually have no real secondary structure to preserve, and cannot be denatured in the conventional sense and RPC is often the purification of choice in these cases

The strong adsorption and the organic modifiers needed for desorption in RPC usually lead to protein denaturation




Affinity chromatography

Various biological affinities for laboratory purification of proteins. A specific ligand is then

Agarose has been the most popular base for affinity matrices. It is a biospecific ligand that can be covalently

The ideal binding buffer conditions are optimized to ensure that the target molecules interact

Affinity chromatography has a broad range of applications for protein purification.

The enzymes which have low affinity to ligands are not used in this process

Purification tags are glutathione Stransferase (GST), the maltose-binding protein (MBP), the

Immobilized metal affinity chromatography

covalently attached to an inert chromatographic matrix

attached to the chromatographic matrix. Ligands can be extremely selective and bind to only a single or a very small number of proteins. Examples are antibodies, protein receptors, steroid hormones, vitamins, and certain enzyme inhibitors

effectively with the ligand and are retained by the affinity medium while nonspecific interactions are minimized

Some frequently used biological interactions

Formation of weak coordinate bonds between immobilized metal ions and some amino acids on proteins, mainly histidine residues. Since it does not operate through a biospecific interaction in the general sense it is usually called a pseudo-affinity technique

Beaded agarose is the support predominantly used. A suitable spacer arm plus a simple chelator are then attached to the matrix. Some commonly used chelators are imino diacetate (IDA), nitrotriacetic acid (NTA), and tris (carboxymethyl) ethylene diamine (TED). Electron-donor atoms (N, S, O) present in the chelators are capable of coordinating metal ions and forming metal chelates

Buffers of relatively high ionic strength (containing 0.1
1.0 M NaCl) are preferably used to reduce nonspecific ionic adsorption

IMAC over biospecific affinity techniques is its structureindependent interaction that makes it applicable under denaturing conditions

FLAG tag, the S-tag, the Z-domain, the calmodulin binding peptide, the BioTag, the Strep tag, and the His-tag

IMAC cannot be classified as highly specific, but only moderately so

Numerous histidine tags, from very short ones, for example, HisTrp, to rather long extensions, containing up to 10 histidine residues, have been employed

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the residual humidity in the solid. Heating causes the moisture to evaporate and creates a high vapor pressure that breaks the cell wall of the substrate and releases the content into the solvent. Solvents used for most microwave-assisted extraction (MAE) operations have a high dielectric constant and excellent capacity to absorb microwave energy. A change in parameters such as modulation using mixtures of solvents, extraction selectivity, and the ability of the medium to interact with microwaves can be done accordingly. It is not uncommon to use a binary mixture of solvents, with only one solvent capable of absorbing microwaves. Nonetheless polar solvents are usually more improved than nonpolar ones. The addition of water to the solvent may lead to increased yields. In the case of a methanol:chloroform mixture, the former generally provides better heating efficiency because of its high dissipation factor. Because of its low polarity, chloroform remains transparent (Kothari et al., 2009). Microwave-transparent solvents (e.g., hexane) are particularly suitable for extraction of thermolabile components. Rathnakumar et al. (2017a) extracted enzymes from pineapple waste through an MAE process. These authors used an MAE technique with water as the solvent to extract the proteolytic enzyme, bromelain, from pineapple waste (core and peel). The extracted enzymes are utilized in the food and pharmaceutical industries.

6.4.3 Ultrasonication-assisted extraction Ultrasonication-assisted extraction (UAE) encompasses the application of high-intensity, high-frequency sound waves and their interactions with materials. UAE is a potentially useful technology as it does not require complex instruments and is relatively low cost. UAE involves the ultrasonic effects of acoustic cavitation. Under ultrasonic action solid and liquid particles are vibrated and accelerated. This causes the solute to quickly diffuse from a solid phase to a solvent. Several probable mechanisms for ultrasonic development of extraction such as cell disruption, improved penetration, enhanced swelling, capillary effect, and hydration process have been proposed. If the intensity of ultrasound is improved in a liquid, then it reaches a point at which the intramolecular forces are not able to hold the molecular structure intact, and therefore it breaks down and bubbles are created—this process is called cavitation. Collapse of bubbles can produce physical, chemical, and mechanical effects which result in interference of the biological membranes to facilitate the release of extractable compounds and enhance penetration of solvent into cellular materials and improve mass transfer (Metherel et al., 2009). The advantageous effects of sound waves on extraction are attributed to the formation and asymmetrical collapse of microcavities in the vicinity of cell walls, leading to the generation of microjets rupturing the cells. UAE has a retaining effect on the extraction of enzymes. Studies into the effects of different solvents and their mixtures, effects of solvent volume, sonication power, and sonication time have indicated that UAE has the potential to improve extraction efficiency and reduce processing time, and during processing the enzyme nature was also unaffected by the use of ultrasound. Rathnakumar et al. (2017b) reported on the ultrasound-assisted extraction of enzymes from pineapple waste. These authors extracted the protein-digesting enzyme bromelain. The bromelain enzyme can be used in the tenderization of meat, bread and cake making, and also in pharmaceutical industries.

6.4.4 Supercritical fluid extraction Supercritical fluid extraction (SFE) can be used to extract enzyme from plants at a temperature close to ambient, thus preventing the enzyme from thermal denaturation. SFE is an old technique but its commercial application grew slowly due to the sophisticated and expensive high-pressure equipment and technology employed. SFE is currently a wellestablished method for extraction and separation because its design and operating criteria are now fully developed (Ty´skiewicz et al., 2018). The favorable transport properties of fluids near their critical points allow deeper penetration into solid plant matrix and more efficient and faster extraction than with conventional organic solvents. The extraction is carried out in high-pressure equipment in a batch or continuous way. In both cases, the supercritical solvent is put in contact with the material from which a desirable product is to be separated. Generally, cylindrical extraction vessels are used for sample preparation (Handa et al., 2008). In batch processing a solid is placed into the extraction vessel and the supercritical solvent is fed in until the target extraction conditions are reached. In semibatch processing, the supercritical solvent is fed continuously through a high-pressure pump at a fixed flow rate, to precipitate solute from supercritical solution one or more separation stages are used. Supercritical fluid technology is now recognized as an effective analytical technique with efficiency comparable to existing chemical analysis methods. Many factors such as temperature, pressure, sample volume, cosolvent addition, flow, and pressure control are considered important during extraction by SFE. The fluid possesses properties bounded by the extremes of the gaseous and liquid states, and these properties may be adjusted with alteration of the applied pressure and temperature (Kroon and Raynie, 2010).

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Under suitable conditions, any fluid can reach its supercritical state. The possibility of using supercritical fluids as extraction solvents is directly linked to their density. A supercritical fluid is referred to as a dense gas, a fluid above its critical temperature (Tc) and critical pressure (Pc) to a certain extent. To be supercritical, the reduced temperature Tr (i.e., T/Tc) must not exceed 1.2 or 1.3, whereas the reduced pressure Pr (i.e., P/Pc) may be as high as allowed by technological limits (Handa et al., 2008). For water, the critical conditions for temperature (Tc) and pressure (Pc) are 374 C and 220 atm, respectively, and for carbon dioxide Tc is 30.9 C and Pc is 73.8 atm. Several solvents can be used for SFE, such as hexane, pentane, butane, nitrous oxide, sulfur hexafluoride, and fluorinated hydrocarbons. Carbon dioxide (CO2) is the most commonly used extraction solvent in SFE (Handa et al., 2008). Park et al. (2008) employed SFE for extracting digestive enzymes such as protease, lipase, and amylase from fish waste such as Mackerel viscera. The authors obtained nearly 67.3%, 83.3%, and 84.1% of protease, lipase, and amylase enzymes, respectively.

6.4.5 Enzyme purification by chromatography It is essential to isolate a specific enzyme from a crude blend without disturbing the physical and/or chemical properties of the individual enzyme. There is no single or easy way to purify all kinds of enzymes. Procedures and conditions used in the purification process of one enzyme may effect the inactivation of another. If an enzyme is employed in washing powder preparation, in some circumstances, a relatively impure sample is sufficient if it does not contain impure substances. However, if the enzyme is meant for therapeutic use it must be extremely pure and purification must then be ended in several subsequent steps. The aim of a purification process is not only removal of unwanted impurities, but also to ensure the correct concentration of the desired enzyme and the relocation to an environment where it is stable and in a form ready for the intended application. In the early days, the only practical way to separate different types of enzymes was by taking advantage of their relative solubility. During purification, part of a enzyme mixture can be precipitated through various means, for example, addition of salts, organic solvents, or polymers, or varying the pH or temperature. Fractional precipitation is still regularly used for the separation of gross impurities, membrane proteins, and nucleic acids. Under certain conditions, enzymes adsorb to a variety of solid phases, preferably in a selective manner. Calcium phosphate gels have regularly been used to specifically adsorb enzyme proteins from heterogeneous mixtures. Due to their high resolving power, different chromatography techniques have become central to enzyme purification.

6.5

Downstream processing

The downstream processing is the final step and the universal process for the recovery and purification of enzymes produced by microbial fermentation of food waste. The cells are separated in the initial steps, referred to as primary recovery. This requires different strategies depending on the enzyme secreted into the culture medium or inside the cell, moreover as inclusion bodies, as in the soluble form in the cytosol or periplasm, or it can be anchored to the membrane. Centrifugation, sedimentation, deep bed filtration, and microfiltration or combinations thereof are normally used as the next steps. Usually, chromatography plays a trivial role in these initial steps, which are discussed in Table 6.2. It is mainly concentrated on the removal of suspended solids such as cells or cell debris. However, chromatography, implemented through the use of fluidized or expanded beds, can also be used for the direct capture of secreted enzymes from supernatants. In these systems, the liquid flows upwards through an initially settled bed of dense adsorbent particles. The particles become fluidized above a definite flow velocity and the bed expands allowing free passage of cells and other suspended matter while the enzymes are directly captured by the adsorbent. This approach is currently used for diluted suspensions, nevertheless bed expansion is meanwhile directly influenced by the food waste feed density and its viscosity, and the operation tends to be critically affected by variations in the composition of the broth. In the runthrough, the high viscosity and cell density encountered in modern fermentation technology make it challenging to implement this approach reliably on an industrial scale. An unusual possibility for capture without purification is to use adsorption beds packed with large particles, sometimes referred to as “big beads.” If the particles are larger than about 400 μm in diameter, the interparticle spaces are sufficiently large to allow passage of cells and cell debris. The efficiency of capture is condensed by the diffusional limitations that accompany the larger particle diameter, thus ensuring a reduction in the number of processing steps. This, in turn, can provide overall economic and operative advantages. Unlike expanded beds, packed bed processes are not very sensitive to food waste or feed viscosity, so that constant operation with large diameter beads can be achieved even with viscous feedstocks. Generally the downstream

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processing scheme consists of successive capturing of enzymes as products, purification, and polishing steps, each comprising one or more operations.

6.6

Recovery

The final step for enzyme recovery depends on the production system, the microorganism used, and the time of extraction. In SSF, enzymes are produced extracellularly and recovery is easily achieved, simply add two or three volumes of extractant (distilled water or buffer) mixing and compression, to obtain an enzyme extract. In the case of SMF, the location of the enzyme depends on the microorganism and the incubation time. In the fermentation process, either the microbes or fungi produce intracellular enzymes during the initial period of incubation. At this stage, enzyme recovery implies cell disruption and extraction with an appropriate agent. Enzymes in the intracellular phase are lately excreted, making their recovery easy. However, at the moment of maximal production, 75% of the enzymes remain bound to the mycelium in the fungal strains. On the other hand, most of the bacterial strains produce extracellular enzymes in SMF. Cell disruption can be achieved by chemical, enzymatic, or mechanical processes. It was frequently reported by many researchers that the classical physical and chemical methods were unable to release the enzymes attached to the fungi. Not more than 5% of the enzyme was recovered by grinding mycelium with sand or glass beads or pulverizing with homogenizer, neither were osmotic shocks or ultrasonic waves in various buffers productive. For the efficient recovery of these mycelium-bound enzymes, they proposed an enzymatic hydrolysis of cell walls using a chitinase from Streptomyces griseus followed by reverse micellar extraction. This protocol resulted in the recovery of 43% active enzymes. On the other hand, Bhardwaj et al. (2017) found that enzyme extraction from the mycelium strongly depends on the pH of the extractant agent and that maximum enzyme recovery was reached at pH 5.5.

6.7

Conclusion

This chapter was focused on the various platform chemicals produced from food wastes, which is one of the most abundantly generated organic feedstocks around the world. The fermentation efficiency of these wastes can be increased by employing suitable pretreatment methods. The various strains used in the production of these chemicals can be improved for better substrate utilization efficiency. Many more metabolically engineered strains are being experimented with for the effective production of these value-added products. An increase in demand for platform chemicals has paved the way for developing conventional and sustainable methods for their production. A necessity still exists to culture high-performance microbial strains or to augment their activity by genetic modifications to generate these chemicals on a large scale.

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Chapter 7

Production of biopolymers and feed protein from food wastes J. Merrylin1, Preethi2, Ganesh Dattatraya Saratale3 and J. Rajesh Banu4 1

Department of Food Science and Nutrition, Sarah Tucker College, Tirunelveli, India, 2Department of Civil Engineering, Anna University Regional

Campus Tirunelveli, Tirunelveli, India, 3Department of Food Science and Biotechnology, Dongguk University, Seoul, Republic of Korea, 4

Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India

7.1

Introduction

It is estimated that one-third of the food produced globally for human consumption is wasted, with the total amount of food wasted annually estimated to be around 1.3 billion tonnes (Gustavsson et al., 2011, 2013). These estimations conclude that lignocellulosic biomasses are the most plentiful carbon, renewable source, which could be used to decrease the emission of carbon dioxide and environmental pollution. Consequently lignocellulosic biomasses are a promising substitute for the production of crude oil, whose availability is limited, and it is also an excellent resource for the production of biomolecules and biofuels. Cellulose is the major constituent of lignocellulosic biomasses and can be used as an alternative source for the production of petroleum-based biopolymers due to its environmental-friendly properties, such as its compatibility with living tissues, its ability to be broken down into simpler substances by enzymes produced by microorganisms, and its renewability (Isikgor and Becer, 2015). Thus, a process needs to be developed to convert these lignocellulosic-rich food wastes into microbial organic matter and single-cell oils (SCOs).

7.2

Food waste as a valuable resource

It has been calculated that roughly 75% of food products are expended carelessly somewhere between the field and the fork. Food wastes are classified as preconsumption food waste and postconsumption food waste. As per the data produced by United Nations Food and Agricultural Organization, approximately 1.3 billion tonnes of food waste were disposed of in 2011, and this is forecast to reach 2.2 billion tonnes by 2025, which is sufficient to feed many in parts of the world with food shortages (Dogliotti et al., 2014). Asia contributes mainly to postconsumption food waste rather than preconsumption food waste due to the lack of proper legislation and policies regarding disposal of food waste, with food waste being separated from mainstream wastes without any proper planning, and a lack of plans to collect and manage food wastes (Thi et al., 2015). Thus, these food wastes are generally mixed with municipal solid wastes and discarded in landfills or open dumps, leading to volatile methane gas emissions. However, in other developed continents, preconsumption waste is lower than postconsumption waste, and this food waste also goes to landfills. Thus there is a very urgent need to reduce the future socioeconomical environmental impacts of food waste and also reduce the financial losses due to investment in wasted resources. Due to the reduced resources available as fossil fuels and the growing global energy demands, cheap raw materials such as food wastes are treated either by conventional methods or using modern technologies. These wastes are advantageous as they (1) decrease those food products which are assigned for fuel and animal feed, (2) provide energy and fuel, thereby reducing the global fossil fuel demand worldwide, and (3) enable the use of more productive lands and resources for production of food for human consumption. Hence, selection of the best method to maximize gains from food waste is very important. While selecting the technology best suitable for the treatment, the advantages and disadvantages of the process should be kept in mind, both in the longer and shorter term. In addition, it should also be taken into account that the composition and quality of the food waste generated is based on the time of collection, location, Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00007-9 Copyright © 2020 Elsevier Inc. All rights reserved.

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season, culture, income, legislation and policies, education and awareness, etc. This chapter deals with the extraction of various biopolymers, polysaccharides, baker’s yeast, single-cell protein, and SCOs.

7.2.1 Biopolymers Microbes can produce biopolymers intracellularly under certain growth parameters, such as surplus carbon and ratelimiting nitrogen. The biopolymers thus produced are biodegradable within a few months after disposal in the soil and resemble normal plastics. Extensive research is being carried out to explore alternative substrates other than petroleum. However, the problems arising due to the disposal of food waste are also reduced by the production of biopolymers with the help of microbes. Financial and environmental requirements are pushing the development of sustainable and renewable biopolymers (Amulya et al., 2015). Hence a biopolymer that does not contaminate the global environment is an extremely important value-added product (Doi, 1990). The biopolymers produced must retain the preferred properties of the usual synthetic plastic, and when discarded should decompose completely without depositing any unwanted residues. However, such biopolymers are not currently widely used due to their high cost. Biopolymers are expensive due to the carbon source usually employed during fermentation and the use of large amounts of organic solvents to extract the polymers within the microbial cell during the recovery process (Hassan et al., 1997). To avoid an increase in price, food wastes, which are widely available, can be used as the carbon source. There are various bioplastics, such as polyhydroxyalkanoates (PHA) and polyhydroxybutyrates (PHB), which can be produced using food waste as a potential substrate (Xu et al., 2019). The polyhydroxyalkanoates and polyhydroxybutyrates are biopolyesters of hydroxyalkanoates and hydroxybutyrates which are biodegradable and produced under circumstances with excess carbon and limited nutrient supplies. PHAs are obtained by the acidogenic fermentation of volatile fatty acids (VFAs). PHAs are thermosoftening polymers made of 3-, 4-, 5-, and 6hydroxyalkanoic acids. These plastics have similar properties to conventional petroleum-derived plastics and are biodegradable. Thus they could replace conventional plastics. PHAs are produced by a group of naturally occurring bacteria. Under suitable environmental conditions biopolymers are stored up as a reserve material within the cells of the microbes as granular inclusions (Arcos-Hernandez et al., 2015). PHA and PHB are produced within the microbial cells as granular intracellular inclusions from fatty acids and sugars with the help of the enzyme polymer synthase. These granules are stored under unfavorable conditions such as a limited supply of nutrients, etc. The size of these cytoplasmic inclusions ranges from 0.2 to 0.5 μm. with a center made of polyester, surrounded by proteins and phospholipids (De Grazia et al., 2017). Producers of PHA include more than 90 strains of both Gram-positive and Gram-negative bacteria, either in anaerobic or aerobic conditions. These microbial strains can utilize a wide variety of carbon sources for PHA production. Being the direct precursors, VFAs are more preferred (Anjum et al., 2016; Girotto et al., 2015). Thus, to reduce the production cost, a great deal of research is being carried out worldwide, focusing on using different wastes as the sole carbon source (Raza et al., 2018). Efficient acclimatization of PHA-producing bacteria can be achieved with the use of organic waste as a carbon source, thereby reducing the production cost. Thus, food wastes are considered as the cheapest raw material for production of PHA due to their high biodegradability and continuous accessibility (Nielsen et al., 2017). Food wastes such as used cooking oil, blood, fats, residues from intestines of animals, and organic crop residues are used in the production of PHA (Mozejko and Ciesielski, 2013; Lin et al., 2013; Bussemaker and Zhang, 2013; Cesario et al., 2014) Production of PHA by pure cultures is very expensive as there is a greater requirement for control devices and equipment, and also strict aseptic conditions should be provided. Thus, to further reduce cost, mixed microbial cultures can be used (Koller et al., 2017; Morgan Sagastume et al., 2017). PHB are produced by certain bacteria such as Escherichia coli, Clostridia sp., and Alcaligenes eutrophus by the condensation of D3-hydroxybutryl Co-A (formed from acetyl Co-A through acetoacetyl Co-A) and butyryl Co-A. This is a biodegradable and biocompatible thermosoftened plastic, however due to its high price compared to conventional thermoplastics, it has not been commercialized (Lee and Yu, 1997). Though food waste is considered to be a good and cheap raw material for the production of PHA or PHB, it should be pretreated to increase and alter the physicochemical and biological properties of the waste. The pretreatment methodologies are classified as physical, chemical, biological, and enzymatic hydrolysis, which ensure better yield of PHA or PHB. The schematic representation of PHA production from food waste is shown in Fig. 7.1. An effective pretreatment method leads to total or partial release of monomers from food waste, thereby increasing the accessibility of proteins, carbohydrates (starch and cellulose), and fats for the following enzymatic hydrolysis and fermentation.

Production of biopolymers and feed protein from food wastes Chapter | 7

FIGURE 7.1 Schematic representation of PHA production from food waste.

Nutrients Isolation of bacterial cultures

Nutrients

Screening of PHA producers

Food waste fermentation

Carbon source

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Cultivation of PHA producers

PHA acclimatization and accumulation

Pretreatment of food waste

PHA production

Food waste

Separation of collected biomass

PHA

PHA extraction

Drying

7.2.1.1 Fermentation process PHA or biodegradable thermoplastic polyhydroxyalkanoates can be produced from food waste in two phases. During the initial phase, the complex organic compounds are digested under anaerobic conditions by microbes into VFAs, such as lactic acid, acetic acid, propionic acid, and butyric acid. In the second step, the microbial cultures producing PHAs are acclimatized and enriched. In the third step there is accumulation of PHA in the microbes. Then, in the final stage, the PHA-producing microbes, such as Ralstonia eutropha, can make use of the VFAs and polymerize the acids into biopolyesters of hydroxyalkanoates as carbon and energy reserves under nutrient-limited circumstances. Fermentation of food waste is usually carried out using a bioengineering fermenter seeded with either pure culture or mixed cultures, with the growth conditions set at dissolved oxygen 5 20, T 5 35 C and pH 5 7. Antifoam is also used occasionally to avoid foaming; and the pH can be adjusted using NaOH. Although high-density cells are acquired during fermentation, the nitrogen-limited medium is fed to the fermenter continuously to increase the carbon:nitrogen ratio, which in turn increases the production of biopolymers within the microbial cells. The composition of PHA thus obtained after fermentation depends on the composition of the VFA used as a precursor. Studies show that differences in the composition of fermented cheese whey with respect to lactic acid, acetic acid, propionic acid, valeric acid, and butyric acid produced PHAs of different compositions. Whey containing all the VFAs mentioned produced PHAs comprising of 3-hydroxyvalerate and 3-hydroxybutyrate, while whey without propionic acid and valeric acid produced PHAs comprised of 3-hydroxybutyrate only (Colombo et al., 2016).

7.2.1.2 Extraction and purification The fermentation broth is concentrated by centrifugation and the pellets are treated with chloroform and sodium hypochlorite. After treatment, they are centrifuged again to separate out the ballistic in the middle phase among the three phases. Finally, the biopolymer is precipitated by mixing methanol with chloroform. The precipitate obtained is filtered and dried.

7.2.1.3 Application Bioplastics have wide application in packaging, as adhesive bonds, as paints, and in the field of medicine as gloves, surgical sutures, and chiral substrate for drug synthesis and drug delivery. Exploiting valueless food wastes as a carbon source in fermentation would enormously decrease the price of the production of biopolymers and reduce the amount of waste, while simultaneously producing environmentally friendly bioplastics.

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7.2.2 Single-cell oil Oils obtained from microbial sources are called microbial, unicellular, or SCOs. In general, such oils are called SCOs to denote oils obtained from microorganisms. An interesting fact is that the composition of SCOs is very similar to the composition of oils obtained from plants and animals (Boswell et al., 1996). SCOs are mostly produced by lipid-producing microbes (oleaginous yeasts). The lipids in these organisms are generally triacylglycerols, which contain long-chained fatty acids that are comparable with plant oils. The efficiency of the SCOs synthesized by oleaginous yeast and the composition of the oil are purely based on the genetic characteristics of the strain being used, its growth conditions, and the culture medium used during the process. The demand for SCOs is more attractive due to it having two functions, both as a provider of functional oils and as a raw material for the production of biodiesel. However, for the industrialization of SCOs, the high price incurred during the fermentation and the hydrolysis process needs to be reduced. To overcome this barrier, various hydrophilic and hydrophobic substrates of low cost are used for SCO production. Lignocellulosic substrates are abundantly available and are a renewable source that could be a perfect raw material for the production of SCOs. Recent researches have focused on SCO production from such substrates and have evaluated their feasibility. Lignocellulosic biomass can be generated with fast and at a lower cost. It is also cheaper than crude oil (Huber, 2008). Conversion of lignocellulosic biomass into SCO still faces challenges due to the recalcitrance of the biomass. In the process of evolution plant cells have become stronger and thus act as an efficient barrier to pathogens. Thus research is being carried out worldwide to address this problem (Slavin et al., 2011). Lignocellulosic biomasses are portrayed with micro- and macrofibrils arranged in crystalline structures. Those closely packed structures need to be pretreated to increase the surface area for the action of microbes by degrading hemicellulose, cellulose, protein, lignin, and a smaller quantity of pectin and ash, thus making them available for the consequent enzymatic hydrolysis step (Galbe and Zacchi, 2002). The composition of the linocellulosic biomasses are not similar as they depend on the age, species, and optimal growth conditions of the biomass (Carpita et al., 2001). The selection of the pretreatment method must also avoid the degradation of carbohydrates because they represent the most vital substrate for the metabolic action of the microbes. Pretreatment of the lignocellulosic biomass is also essential to prevent the formation of inhibitors, which in turn are directly proportional to the lignin fractions. Therefore pretreatments are considered as the most vital step because they have a greater influence on all the other steps during the conversion process. However, pretreatment methods utilize more energy and thus increase the overall production cost (Agbor et al., 2011). The pretreatment processes usually employed to treat lignocellulosic biomasses for the production of SCOs can be classified as physical, chemical, physiochemical, and biological. Some of the physical pretreatments include irradiation by microwaves, mechanical shredding, milling, grinding, and incineration (Komolwanich et al., 2014; Barakat et al., 2014). The chemical pretreatments which are employed include delignification by organic solvents, hydrolysis by ozonation, and acidic and basic hydrolysis (Berlin et al., 2006; Morikawa et al., 2014). Physiochemical pretreatments include carbon dioxide and sulfur dioxide explosion, ammonia fiber explosion, and steam explosion (Sassner et al., 2005). Biological pretreatments include the activity of fungi, bacterial enzymes, and actinomycetes.

7.2.2.1 Application Being a sole source of docosahexaenoic acid and arachidonic acid, it has wide applications in various fields. Recently it has been tested in experimental animals and humans to study its effects. Makrides et al. (1996) studied the composition of breast milk after the mother was supplemented with docohexaenoic acid SCO. The metabolism of these fatty acids and their biological composition have been studied through this research. Further research on the metabolism of SCO was carried out by growing microbial strains in a medium containing D-[1
13C] glucose, which generates SCOs labeled with stable isotope 13C (Szitanyi et al., 1999). Further studies are to be carried out for use as a nutritional supplement in infant formulas.

7.2.3 Baker’s yeast Fresh baker’s yeast is composed of about 30%
33% dry matter, 6.5%
9% nitrogen, 41%
58% proteins, 35%
45% carbohydrates, 4%
6% lipids, 5%
8% minerals, and vitamins dependent on its growth parameters and type. Marketable fresh baker’s yeast is comprised of active dry yeasts as well as products in runny, creamy, or condensed forms. Condensed baker’s yeast is the most commonly used product and consists of only one species of yeast, such as Saccharomyces cerevisiae. Exceptional strains of S. cerevisiae are generally used for the manufacture of dry yeast

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products, such as instant dry yeast or active dry yeast. Active dry yeast includes grains or granules of live and dried yeast cells with the power of leavening, whereas instant dry yeast is generally available in the form of fine powder that does not require to be rehydrated before use. Inactive dry yeast is a product devoid of the leavening power, in contrast to the active dry yeast, and is used for the conditioning of dough in baking or for the development of a distinctive flavor. The feedstocks used as substrate for commercial yeast biomass production are generally food wastes and agricultural and forestry by-products. There are usually two different types of raw materials depending on the microorganism grown: traditional materials like straw, whey, starch, wood, fruit and vegetable waste, molasses, distiller’s wash, etc., and the modern ones including ethanol, methanol, natural gas, and petroleum by-products (Jay, 1996). The most commonly used substrate for the production of baker’s yeast is cane molasses or beet molasses, the major by-product of the sugar industry. Molasses contains 46%
54% fermentable sugars, including sucrose, galactose, raffinose, glucose, fructose, and melibiose. The fermentation medium for optimum production of baker’s yeast biomass is usually limited to a pH range of 4.5
5.0 and is supplemented based on the composition of the molasses with the addition of macronutrients such as nitrogen, phosphorus, magnesium, and calcium, and micronutrients such as iron, zinc, copper, manganese, and vitamins like biotin. Molasses also constitutes about 40% of its dry matter with nonfermentable sugars. These sugar are generally not utilized and thus disposed of, leading to an increase in pollution. There is also an increased production cost due to the necessity for wastewater treatment. To reduce the cost and pollution, these sugars are generally collected, dried, and used as animal feed or fertilizers. Commercial yeast production usually involves many stages, including (1) propagation, which involves a number of fermentation stops, (2) harvesting, (3) drying or compression, (4) packaging, and (5) transportation (Fig. 7.2). Food waste is generally used for commercial production of yeast due to its easy availability and low cost. Baker’s yeast is produced using successive submerged fermentations. After the fermentation process, the yeast biomass produced is harvested and then further subjected to downstream processing such as washing, disruption of cells, extraction of proteins, and purification. During the initial propagation of the yeast cells, they are grown in aerobic fermenters. The cells from a pure culture of yeast are grown in an acclimatized mixture of molasses in the lab and the biomass generated is transferred to one or more fermenters aseptically. These fermenters operate in batch mode with no air supply. The next fermenter also operates in a fed-batch mode, but with an air supply. The biomass thus produced is used to pitch the stock fermenter. The biomass generated is harvested by centrifugal force and used in pitch fermentation. These two steps operate in fed batch with forceful aeration with the addition of nutrients. The biomass, which is harvested in the pitch fermenter is used to pitch the final trade fermenter. The maturation stage is the final step which involves vigorous aeration for an additional period of time. The amount of baker’s yeast produced increases from one fermenter to the next fermenter. The sequence of fermentation and the number of fermenters used differ dependent on the manufacturer. A schematic representation of the production process of Baker’s yeast from food waste is shown in Fig. 7.2. Thus the yeast generated in the trade fermenter is concentrated by centrifugal force and finally it is harvested with the help of a rotary vacuum filter or a filter. The process is repeated until the biomass constitutes 27%
33% dry matter. The yeast cake remaining after concentration and compression of the biomass is mixed with a suitable amount of water, emulsifiers, and cutting oils to acquire its extrudable form. The yeast is then packed and transported as baker’s yeast. These baker’s yeasts are often used as a raw material for the production of single-cell proteins.

7.2.4 Single-cell protein The universal shortage of protein can be solved by the promiscuous technology of single-cell protein production. This technology can convert cheap by-products, such as wastes, into value-added products with more nutritional and market capitalization. The uniqueness of this bioconversion process in using unwanted waste to produce single-cell protein has increased its financial value, as the production cost was reduced by the use of no-cost substrates and the generation of value-added products. The benefits of this production process include manufacturing food products as well as conservation of the environment. It is well-known that the greater part of our population exists below the poverty line and is underfed. These, in turn, have caught the attention of scientists and authorities in general, with the aim of providing them with nutritious, balanced food, which includes all the essential ingredients including proteins which are necessary for growth and development. Furthermore, disposal of organic waste, including fruit and vegetables, remains a huge problem. Hence it is important to make use of these cheaper raw materials for culturing fungal species such as Aspergillus oryzae, Rhizopus oligosporus, and several species of Agaricus and Morchella. Various other microorganisms are used worldwide for human consumption as SCP or as constituents of conventional food starters, including bacteria (Lactobacillus,

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FIGURE 7.2 Schematic representation of the production process of baker’s yeast from food waste.

Food waste Pure yeast culture Food waste grinding Yeast culture growth in fed batch reactor Pretreatment of food waste Seed fermenter

Aeration

Centrifugation

Yeast powder

Nutrients

Pitch fermenter

Drying

Centrifugation

Filtration

Biomass maturation in trade fermenter

Centrifugation

Alcaligenes, etc.), algae (Spirulina, Chlorella, etc.) and yeasts (Saccharomyces, Kluyveromyces, Candida, etc.) (Jay, 1996; Ravindra, 2000). S. cerevisiae and Candida utilis, among the different species of yeast, are completely accepted for human consumption, but only a very few species of yeast are available commercially. These species can in turn be harvested as a source of single-cell protein to be consumed by animals and humans. They can also be supplemented with food and fodder. Single-cell proteins can be used as food and will also reduce environmental pollution. If single-cell proteins are harvested regularly from cheap substrates, they can serve to bridge the gap between the demand and supply of proteins. Substrates such as food wastes are used for SCP production (Bekatorou et al., 2006) as they are rich in carbohydrates. This is due to the fact that carbohydrates are easily utilized by microbes as substrates and they also constitute a renewable raw material. Molasses also contains essential minerals such as phosphorus, potassium, iron, magnesium, copper, and zinc, amino nitrogen, and asparagine, aspartic acid, alanine, glutamic acid, and glycine, and also have vitamins such as biotin, pyridoxine, thiamine, pantothenic acid, and inositol. These nutrients vary in concentration according to the specific type of molasses, its geographical origin, agricultural crop practices, and sugar mill operations. Molasses can be used for the production of SCP due to its wide availability, presence of carbohydrate, and low cost. Also, it does not produce any toxic substances or fermentation inhibitors (Bekatorou et al., 2006). Molasses is the liquid residue generated after crystallization of concentrated sugar solution, which is obtained after milling of sugar beet or sugar cane. Molasses contains 45%
55% sugars, such as galactose, sucrose, melibiose, glucose, raffinose, and fructose. Though molasses is considered to be a suitable raw material for SCP production, it needs to be supplemented with phosphorus and ammonia salts (Ugalde and Castrillo, 2002a,b). Banana peels (Musa paradisiaca) are considered as an organic waste which is highly rich in carbohydrate and some other essential nutrients. and thus could enhance microbial growth. The part of the fruit consisting of sugars is utilized by microorganisms in the production of single-cell proteins either as a food or feed. Use of such low-priced and easily available substrate is advantageous in lowering the cost of production. It also helps reduce waste disposal and waste management problems, preserves natural resources, and supplies feed for livestock. Kamel (1979) reported the use of dates as a potential substrate for the production of SCP. Sweet potato residue has been used to produce SCP by Yang et al (1993). Mahnaaz et al. (2009) studied the production of SCP from fruit wastes by R. oligosporus. It was revealed in this study that papaya waste generated more protein compared to cucumber peelings, pineapple peel, pomegranate rind, and watermelon peel. The amount of protein produced was about 57.3, 51.6, 48.0, and 43.2 mg, respectively, due to the mycelial growth. Maragatham and Panneerselvam (2011) used papaya waste as substrate for production of SCP using S. cerevisiae.

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Other wastes include citric waste (Lanuzza et al., 2014; Zhou et al., 2017), pineapple cannery effluent (Nigam, 1998), yam peel (Aruna et al., 2017), whey concentrates (Paraskevopoulou et al., 2003; Schultz et al., 2006), corn stover (Ahmed et al., 2010), rice effluent and polishings (Rajoka et al., 2004; Zepka et al., 2010), soy molasses (Cheung, 1997; Gao et al., 2012), guava peel (Moharib Sorial, 2003), and hydrolyzed sugar cane bagasse (Pandey et al., 2000). Single-cell proteins can be produced by various fermentation processes such as submerged fermentation, semisolid fermentation, and solid-state fermentation. In submerged fermentation, the substrate used for SCP production is in a liquid state which supplies the nutrients needed for microbial growth. The fermenter is operated continuously and the product is also harvested continuously using different methods. The product is then filtered/centrifuged and dried (Varavinit et al.,1996). In semisolid fermentation, the substrate is close to a solid state (e.g., cassava waste) (Adedayo et al., 2011). The operation of fermenters involves various steps, such as stirring and mixing, sparging of oxygen to the microorganisms through the liquid phase, and the process of transferring heat from the liquid phase to the surroundings (Andersen and Jorgensen, 2005). Solid-state fermentation has been widely used in the production of SCP. In this fermenter, rice bran or wheat bran is deposited on the flatbeds after seeding with microbes. The fermenter inoculated with the substrate is left in a temperature-controlled room for many days (Singhania et al., 2009). A schematic representation of the production process of single-cell proteins from food waste is shown in Fig. 7.3.

7.2.4.1 Applications of single-cell protein Single-cell protein is a good source of dietary fibers, minerals, amino acids, vitamins, etc., and thus provides energy instantly and is a suitable supplement for malnourished children. It also nourishes the skin and eyes and prevents the accumulation of high-density lipids, thereby reducing obesity. It is also helpful in controlling obesity by lowering the level of blood sugar. Single-cell proteins also serve as a good feedstock for cattle, fish, and birds, as it is an excellent and suitable source of proteins.

7.2.5 Polysaccharides Polysaccharides are usually produced by plants, microbes, and animals, but plants are the most important source of these carbohydrates. The majority of natural polysaccharides are found in vegetables. They are classified into three groups based on their functional role: (1) structural sugars, which help in maintaining the shape and structure, such as cellulose, hemicelluloses, and pectin present in plant cell walls and chitin present in the exoskeleton of arthropods,

Microorganisms culture (yeast, fungi, bacteria, algae)

FIGURE 7.3 Schematic representation of the production process of single-cell protein from food waste.

Food waste Carbon source

Sterilized medium Semisolid fermentation

Submerged fermentation

Solid-state fermentation

U loop fermenter

Airlift fermenter

Airlift fermenter

Biomass harvesting

Biomass harvesting

Biomass harvesting

Processing

Centrifugation

Processing

Purification

Processing

Drying

Drying

Single-cell protein

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(2) water-binding sugars such as agar, pectin, and alginates extracted from plants and mucopolysaccharides present in animals, and (3) energy-storage sugars such as starch and inulin in plants and glycogen in animals. Polysaccharides are an important component of vegetable biomass. These biomasses are presently exploited for the production of chemicals and energy. Polysaccharides are massively processed for the production of building molecules such as succinic acid, fumaric acid, malic acids, 3HPA (3-hydroxypropionic acid), 2,5-furandicarboxylic acid, glutamic acid, aspartic acid, glycerol, and sorbitol. These chemicals find application in various areas, such as food nutrients, drug delivery, biotechnological application, food additives, health care, and sustainable energy production (Persin et al., 2010). The major source of chitin is the shells of crustaceans such as crabs, shell fish, lobsters, shrimps, and krill. Chitin is present in α, β and γ forms based on its crystallinity (Aam et al., 2010). α-Chitin is mostly found in shrimp shells, lobster tendons and shells, and crab shell and has an 80% crystallinity index (Joao et al., 2015). β-Chitin is found in squid pens with a 70% crystallinity index and γ-chitin is a combination of α- and β-chitins (Joao et al., 2015). Chitosan is the polysaccharide obtained by the deacetylation of chitin. A schematic representation of the production process of chitin and chitosan from crustacean waste is shown in Fig. 7.4. Since the shell of crustaceans is rich in chitin, this cheap substrate provides a higher production source for chitin. The chitin or chitosan is extracted by two main methods: chemical and biological. The chemical method mainly includes deproteinization, demineralization, and decoloration of the crushed shells. In the biological method deproteinization is done either by an enzymatic method or by fermentation with lactic and nonlactic microbes (Arbia et al., 2013). The conversion of chitin to chitosan is done by deacetylation with alkali or acid in the case of the chemical method (Hajji et al., 2014) or by enzyme chitin deacetylase in the case of the biological method (Zhao et al., 2010). Food wastes such as vegetable residues including seeds, husks, peels, worn out pulps, damaged and unripe fruits, and skins can be used to produce polysaccharides. Such vegetable residues are rich in structural sugars, glycans, and dietary fibers. Different polysaccharides are extracted from various vegetable residues in order to obtain biopolymers. These extraction processes are influenced by both economical and environmental costs. These expenditures are not only based on the thermal and chemical treatments, but also the feedstocks. Polysaccharides such as inulin, pectin, hemicellulose, and cellulose, are usually exploited for the above applications due to their physiochemical properties such as viscoelasticity, stabilizing ability, emulsifying capability, adhering capacity, and biocompatibility. Sweeteners, syrups, dietary fibers, and sugars are generated from polysaccharides obtained from plant sources. Sweeteners such as maltose, fructose, and glucose, various prebiotics, ethanol, mannose, sorbitol, etc., are obtained from corn starch, potato, and other starchy plants. Pectin obtained from apple and other citrus fruits is used widely as a functional food ingredient (Kaur and Gupta, 2002). Nonstarch polysaccharides obtained from fruits and vegetables are widely employed to produce additives, gelling agents, emulsifying agents, thickeners, etc. (Sanjay and Gross, 2001). Inulin from artichokes and chicory is used as a functional ingredient. FIGURE 7.4 Schematic representation of the production process of chitin and chitosan from crustacean waste.

Crustacean shell waste

Washing and crushing

Chemical method of chitin/chitosan production

Biological method of chitin/chitosan production

Demineralization 1 M Hcl, H2SO4

Organic acid release from microbes

Deproteinization Enzymatic deproteinization by protease

0.125–5 M KoH or NaOH

40%–50% NaOH Deacetylation

Deproteinization by fermentation

Chitin Chitin deacetylase enzyme Chitosan

Lactic acid fermentation

Nonlactic acid fermentation

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Pomace is a solid waste obtained by pressing fruits or vegetable waste and can contain skin, seeds, pulp, and stones. Apple pomace is widely used to obtain polysaccharides, which are obtained by pressing. Apple pomace is a good source of dietary fibers and phenolic compounds, including flavanols and flavonols (Schieber et al., 2003). Depending on the extraction method employed apple pomace can be an important source of both pectins and arabinans, which account for 5%
12% of hemicelluloses and cellulose. Pectins are produced from pressed and dried cakes obtained after extraction of juice from the fruit. Pectins are also obtained from dried peels and the remains of citrus fruits after the extraction of citrus juice. The total amount of pectin that can be recovered from citrus fruits depends on the extraction process employed and is also dependent on the species of fruits. The yield of pectin can vary from 18% to 25% of the total weight of an orange fruit (Kratchanova et al., 2004; Pourbafrani et al., 2010), 23% of the total weight of mandarin peel (Sanchez-Vazquez et al., 2013), and 14.3% of the total weight of lemon residues (Poli et al., 2011). In addition to pectin, some structural glycan, such as hemicelluloses and cellulose, can also be obtained from citrus residues. Exhausted pulps of vegetables such as carrots also contain 54% dietary fibers of their total weight. The important polysaccharides present in the fibers are pectin, hemicelluloses, and cellulose. Ten percent of the total dry weight of coffee wastes also contain pectin as the main polysaccharide. Pectin is also produced from sunflower heads, sugar beets, and waste from various fruit-processing industries. Pectin is usually extracted by heating the food waste at a pH of 2 maintained by the addition of hot mineral acid. The boiling pectin extract is separated from the enlarged and partially disintegrated food waste with the help of centrifugation and filtration. The extract obtained is thus clarified and brought to a pH of 4, and the extract is then concentrated under vacuum preceding the precipitation by alcohol, pressing, and drying (Waldron, 2009). Pectins can be found in most fruit pomaces and, after the process of extraction and purification, it can be added as a gelling agent in various food products such as jellies, sweets, jams, fillings, and confectioneries. Pomace can also supply other food additives including natural sweeteners, cellulose, pigments, lactic acid, dietary fibers, and vinegar (Nawirska and Kwasniewska, 2005). Banana waste, that is, the peel, accounts for more than 40% of the total weight of the fresh fruit and the peel consists of 50% of the dietary fiber, of which 1% is cellulose, 4% are hemicelluloses, and 22% are pectin polysaccharide. After processing of grains, the main residues formed are corn bran and fibers. Bran is the residue obtained after dry milling of grains for corn meal and production of flour, while fibers are residues obtained after wet milling of grains for oil and starch recovery. Of the total corn grain, 6.5% is bran and 9.5% is fiber. Corn bran consists of starch, cellulose, and hemicelluloses. Corn fibers also contain a considerable quantity of starch. Potato residues do not only contain starch, but also an appreciable quantity of polymers such as cellulose and hemicelluloses. Tomato residues obtained from canning industries contain structural polysaccharides in their cell wall, as well as a new polysaccharide known as xyloglucan which is isolated from the peel of tomatoes with the help of alkaline extraction. The husks of peanuts are a good source of polysaccharides such as galactans, mannans, and arabinans which account for 1% of the total weight of the residues. Some tropical fruits have protein-lysing enzymes, such as papain present in papaya and bromelain present in pineapple which are used as meat tenderizers, in detergent powders, or for brewing beer. Beta-glucans traditionally are extracted from barley bran, which involves a few steps such as inactivation of the enzyme present endogenously in the barley, extraction of the glucan using either water or alkali solutions, use of hydrolytic enzymes to remove impurities in the form of proteins and starch, precipitation of the purified glucans, and freeze drying (Izydorczyk and Dexter, 2008). Polysaccharides such as cellulose and starch obtained from food wastes are important building blocks for the preparation of materials like composites or biopolymers. Cellulose is the main polysaccharide found in lignocellulosic waste which in turn is used as a probable renewable source of fibers for the textile, material, and paper industries. Cellulose can be recovered by fractionation of the waste biomass using different pretreatment methods, such as ionic liquid-based separation, steam explosion, and acidic treatment, which is usually followed by mechanical pretreatment such as shearing. Cellulose polymers can be recovered using the above method from wastes such as wheat husk (Dufresne et al., 1997), rice straw (Ping and Hsieh, 2012), and sugarcane bagasse (Mandal and Chakrabarty, 2011). The cellulose extracted from these wastes is nanocrystalline in nature. Cellulose nanofibers, extracted from wheat straw by these methods, have been used for strengthening of polypropylene composites, which are then used for the preparation of biocomposites and also for the preparation of thermoplastic starch-based nanocomposites, and for the manufacture of composition panels which are resistant to earthquakes (Kalia et al., 2011). Polysaccharides of tomato waste are used in the preparation of bioplastics. Glucans extracted from tomato residues after addition of glycerol become a good plasticizer agent with similar properties to plastics. These bioplastics have mulching and solarization applications (Tommonaro et al., 2008). Hemicellulose polysaccharides from food wastes can find applications in packaging. Arabinoxylans extracted by alkali treatment from barley wastes are used to produce edible films which have mechanical properties after casting

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with water (Mikkonen and Tenkanen, 2012). Pectins from food waste are also used to produce bioactive coatings and films which increase the shelf-life of foods (Raybaudi-Massilia and Mosqueda-Melgar, 2012). Thus such food wastes are available as renewable sources of polysaccharides, which in turn can be exploited as the raw material for the production of renewable energy and value-added building block chemicals.

7.3

Reactors used for the production of biopolymers and feed proteins

The most widely used reactors for the production of PHA are batch, fed-batch reactors, bubble column loop bioreactors, airlift loop bioreactors, continuous stirred tank reactors, and two-phase partitioning bioreactors. In a bubble column reactor the transport and operations lead to the clear understanding of heat and mass transfer and hydrodynamic properties. The Taguchi design shows the impact of the various parameters on PHB production using a column bubble reactor. The nitrogen and inoculum size are the major parameters for the production of PHB from methane (Yazdian et al., 2009). The major characteristics of airlift loop bioreactors are simplicity in design, low shear stress, and low energy requirement. The efficiency of the reactor is decreased when the bacterial culture consumes a higher amount of oxygen and the configuration of the sparger is changed to achieve efficiency. The continuous growth of culture and PHB accumulation are achieved well in a continuous stirred tank bioreactor. The two-stage CSTR was used to select and enrich the PHA-producing microorganism by a feast
famine cycle or aerobic dynamic feeding in the case of mixed microbial culture using waste as the sole carbon source. The two-phase partitioning bioreactor is very effective for the removal of compounds with low solubility. It eliminates about 33%
45% of the methane produced during the growth phase of microorganisms and allows the accumulation of PHB in high concentrations (Martin, 2016). Table 7.1 shows the biopolymer production from different food wastes using different microbial strains. The two-stage cultivation methods have been widely adopted for the production of copolymers like P(3HB-co-3HV). Hafuka et al. (2011) carried out a two-stage cultivation of Cuprividus necator to produce PHB from food waste. The food waste fermentation were carried out in a fed-batch reactor of 2 L capacity and the PHB production took place in air bubbling cylindrical reactors with 1.5 L capacity. The continuous feeding regime produced a PHB content of 87% at 259 h with a decrease in the content with time. Bacterial cellulase synthesis can be increased by designing appropriate reactors. Some of the commonly used reactors for cellulase productions are rotating disk reactors, rotating biofilm contactors, bioreactors with a spin filter, and silicon membrane reactors. In a rotating disk reactor the bacterial biomass is attached to the surface of the disk and the nutrients are supplemented by the medium and air from the atmosphere. In a study by Krystynowicz et al. (2002) the maximum cellulose production was achieved at 4 rpm with 0.71 cm21 surface area to medium ratio. In a rotating biofilm contactor, a number of disks mounted on the shaft are placed horizontally. Gluconacetobacter sp. can produce about 5.67 g/L of bacterial cellulose using eight disks and a 1.25 gas volume flow per unit of liquid volume per minute vvm aeration rate (Kim et al., 2007). The performance of spin filters was investigated in a study by Jung et al. (2005) who found that bacterial cellulose production of about 4.57 g/L was achieved in 140 h using Gluconacetobacter hansenii PJK. In a reactor with silicone membrane cellulose was formed on the surface of the oxygen-permeable synthetic membrane. This reactor was developed by Yoshino et al.(1996) to analyze the bacterial cellulose yield by Acetobacter pasteuri-anus AP-1SK and was found to be about twice the yield of a conventional culture. Hyo-Jeong et al. (2009) used a spherical-type bubble column reactor to produce bacterial cellulase from saccharified food waste. A batch reactor with 10 L capacity was used to saccharify the food waste using Trichoderma inhamatum KSJ1. The cellulase was produced by inoculating Acetobacter xylinum KJ1 in saccharified food waste under two culture methods: a spherical-type bubble column reactor of 10 L capacity and a modified airlift-type bubble column bioreactor of 50 L capacity. The common bioreactors used in the production of baker’s yeast are the fed-batch reactor, batch reactor, stock fermenter, trade fermenter, and pitch fermenter. Fed-batch reactors are the proven model for the production of baker’s yeast, whereas the single-celled protein does not favor this model in large-scale industries. Table 7.2 shows feed protein production from different food wastes under different operating conditions. It is inadequate for the microbes to produce a single-celled protein using a batch fermenter. The deep jet fermenter and airlift fermenter have effective configurations for the continuous production of single-celled protein. Yeast cells usually need a series of fermenters for their production. After cultivation in a fed-batch reactor, the biomass is pitched to the stock fermenter and the centrifuged biomass from this fermenter is sent to the pitch fermenter. These reactors works in a fed-batch mode with greater agitation. The biomass from pitch bioreactors is then sent to the trade bioreactor for maturation. The yeast biomass increases at each stage of the bioreactor operations (Modl, 2004). SCO can be efficiently produced by cultivating the microbes in batch, fed-batch, and continuous stirred bioreactors. In batch cultivation, the lipid accumulation is shown to be higher and thus the oleaginuous organisms have the

TABLE 7.1 Biopolymer production from food waste using different microbial strains. S. no.

Type of food waste

Bioreactor involved

Operating conditions

Inoculum or microbes used

Obtained biopolymer

Production/ yield

References

1

Saccharified food waste

Spherical-type bubble column bioreactor

pH: 5.25

Acetobacter xylinum KJ1

Bacterial cellulose

5.8 g/L

Hyo-Jeong et al. (2009)

A. xylinum

Bacterial cellulose

0.43 gcellulose/g-R.S

Moon et al. (2006)

Gluconacetobacter swingsii sp.

Bacterial cellulose

2.8 g/L

Castro et al. (2011)

Gluconacetobacter xylinus

Bacterial cellulose

4.35 g/100 mL

Moosavi-Nasab and Yousefi (2011)

Komagataeibacter medellinensis

Bacterial cellulose

4.81 g/L

Molina-Ramı´rez et al. (2017)

Bacillus subtilis

PHA

4.2 g/L

Umesh et al. (2017)

Haloferax mediterranei

P(3HB-co3HV)

9.86 g/L

Pais et al. (2016)

H. mediterranei

P(3HB-co3HV)

7.92 g/L

Pais et al. (2016)

H. mediterranei

P(3HB-co3HV)

16.42 6 0.02 g/L

Bhattacharyya et al. (2014)



Temperature: 30 C Time: 3 days

2

Saccharified food waste

Spherical air circulation bioreactor

pH: 5.25 

Temperature: 30 C Time: 5 days Agitation rate:150 rpm

3

Pineapple peel juice

Batch

pH: 3.5 

Temperature: 28 C Time: 8 days

4

Low-quality date syrup

Batch shake flask

Rotten banana juice

Batch

Temperature: 28 C Time: 30 days Agitation rate: 240 rpm

5

pH: 3.5 Temperature: room temperature Time: 3 days

6

Carica papaya waste

Batch reactor

pH: 7 

Temperature: 37 C Time: 72 h

7

Cheese whey

Batch shake flask

pH: 7.2 Temperature: 37 C Time: 120 h

8

Cheese whey

Batch bioreactor

pH: 7.2 

Temperature: 37 C Time: 47 h 9

Waste rice stillage

Batch shake flask

pH: 7.2 

Temperature: 37 C Time: 96 h

(Continued )

TABLE 7.1 (Continued) S. no.

Type of food waste

Bioreactor involved

Operating conditions

Inoculum or microbes used

Obtained biopolymer

Production/ yield

References

10

Waste frying oil

Batch fermentation

Temperature 30 C

Cupriavidus necator

PHB

1.2 g/L

Verlinden et al. (2011)

Mixed culture

PHA

61%

Albuquerque et al. (2010)

Agitation rate: 150 rpm Time: 72 h 11

Sugar molasses

Two-stage CSTR

pH: 6 

Temperature: 30 C HRT: 10 h 12

Shrimp waste

Batch

Fermentation time: 6 days

Pseudomonas aeruginosa

Chitin

47%

Sedaghat et al. (2017)

13

Crab waste

Batch shake flask

Temperature 30 C

Lactobacillus sp. B2

Chitin

34%

Flores-Albino et al. (2012)

Cocultivation of Lactococcus lactis and Teredinobacter turnirae

Chitin

64.5%

Aytekin and Elibol (2009)

Kurthia gibsonii and Aspergillus sp.

Chitin

16.062%

Bahasan et al. (2016)

Agitation rate: 180 rpm Time: 6 days 14

Prawn shell

Batch shake flask

Temperature 30 C Time: 7 days pH: 8.8 6 0.5

15

Green tiger shrimp shell waste

Batch

Temperature 40 C for demineralization and 37 C for deproteinization Agitation rate: 110 rpm Time: 3 days for demineralization and 72 h for deproteinization

Production of biopolymers and feed protein from food wastes Chapter | 7

155

TABLE 7.2 Feed protein production from different food wastes under different operating conditions. S. no.

Type of food waste

Bioreactor involved

Operating conditions

Inoculum or microbes used

Type of feed protein

Production/ yield

References

1

Cheese whey

Sequencing batch reactor

pH: 4.5

Dioszegia sp.

Singlecell protein

13.14 g/L

Monkoondee et al. (2015)

Saccharomyces cerevisiae

Singlecell protein

4.67 g/L

Umesh et al. (2017)

S. cerevisiae

Protein

35% 6 0.45%

Choi et al. (2002)

Kluyveromyces marxianus

Protein

44% 6 0.38%

Choi et al. (2002)

Pichia stipitis

Protein

36% 6 0.65%

Choi et al. (2002)

Candida utilis

Protein

43% 6 0.36%

Choi et al. (2002)

S. cerevisiae

Singlecell protein

60.31%

Mondal et al. (2012)

Kluyveromyces marxianus

Singlecell protein

59.2%

Aggelopoulos et al. (2014)

Aspergillus niger

Singlecell protein

1.49 6 0.02

Oshoma and EguakunOwie (2018)

S. cerevisiae

Baker’s yeast

7.4 6 0.06 g/L

Choi et al. (2002)

HRT: 4 days SRT: 8.22 days

2

Carica papaya waste

Batch reactor

pH: 5 Temperature: 25 C Time 120 h

3

Chinese cabbage waste

Batch shake flask

pH: 5 Temperature: 25 C Time: 120 h

4

Chinese cabbage waste

Batch shake flask

pH: 5.7 Temperature: 30 C Time: 24 h

5

Chinese cabbage waste

Batch shake flask

pH: 5.7 Temperature: 30 C Time: 24 h

6

Chinese cabbage waste

Batch shake flask

pH: 5 Temperature: 30 C Time: 24 h

7

8

Fruit waste

Food waste mixture

Batch shake flask

pH: 5.5

Batch reactor

pH: 5.5

Temperature: 28 C

Temperature: 30 C Time: 4 days

9

Banana waste

Batch reactor

pH: 5 Temperature: 28 6 2  C Time: 8 days Agitation rate: 120 rpm

10

Chinese cabbage waste

Batch shake flask

pH: 5 Temperature: 30 C Time 24 h

(Continued )

156

Food Waste to Valuable Resources

TABLE 7.2 (Continued) S. no.

Type of food waste

Bioreactor involved

Operating conditions

Inoculum or microbes used

Type of feed protein

Production/ yield

References

11

Food waste from Shinchuan University

Batch reactor

pH: 6

Rhodosporidium toruloides

Singlecell oil

7.3 g/L

Zeng et al. (2016)

Cheese whey

Batch reactor

Mortierella isabellina

Singlecell oil

4 g/L

Vamvakaki et al. (2010)

R. toruloides

Singlecell oil

6.37 g/L

Ma et al. (2018)

Trichosporon fermentans

Singlecell oil

24.6 g/L

Zhan et al. (2013)

Yarrowia lipolytica

Singlecell oil

49.0% 6 2%

Johnravindar et al. (2017)

Temperature: 28 C Time: 5 days

12

pH: 6 6 0.1 Temperature: 28 C Time: 5 days Agitation rate: 180 rpm

13

Food waste saccharified liquid

Batch reactor

pH: 4 Temperature: 30 C Time: 6 days Agitation rate: 200 rpm

14

Waste sweet potato wine hydrolysate

Batch reactor

pH: 5.5 Temperature: 30 C Time: 12 days Agitation rate: 200 rpm

15

Food waste leachate

Batch reactor

pH: 6 Temperature: 30 C Time: 8 days Agitation rate: 150 rpm

HRT, Hydraulic retention rate; SRT, sludge retention time.

capability of high lipid accumulation and use up the carbon for biomass growth. In nitrogen-exhausted conditions lipid accumulates (Muniraj et al., 2015). The fed-batch reactors are used to control the inhibition of substrates and improve the production of oil, and thus they are a proven model for oil production (Amaretti et al., 2010). The oils and cells are simultaneously withdrawn with the addition of fresh biomass in a continuous stirred tank reactor (Muniraj et al., 2015).

7.4 Economic aspects and commercialization of biopolymer and protein feed production In biopolymer production, industrialization and commercialization are not yet well established due to the cost of production, resulting in a higher commodity price. The cost of PHA polymer ranges between US$2.25 and 2.75/lb which is three to four times higher than conventional polymers. The price of polypropylene and polyethylene ranges between US

Production of biopolymers and feed protein from food wastes Chapter | 7

157

$0.60 and 0.87/lb (Eno and Hill, 2011). Many companies, including Biomatera, Biomer, Bio-On Srl, BluePHA, and PHB Industrial S.A have been established for the production of biopolymer and still face issues in the overall production cost, the major reasons being the substrate cost and its mode of cultivation. It has been published in a report that the PHA market globally will increase to US$93.5 million by 2021. Bacterial cellulose production at an industrial level is facing many obstacles mainly due to high production cost. A great deal of research has been carried out to reduce the production cost and increase the properties of the cellulose produced. Efforts have been made to reduce the bacterial cellulose production cost by adopting newer production methods, new designs of bioreactors, waste carbon sources, and new effective and genetically modified strains. These efforts have enabled enormous changes to the production technology which are now utilized at a global level (Islam et al., 2017). Single-cell protein production increases the economic viability of the biorefinery process and decreases the processing cost for disposal of waste. The feasibility from an economic point of view is assessed by the total production cost, capital investment, and profits earned. The consumption of waste biomass drastically reduces the substrate cost when the cost of natural substrates is high (Ritala et al., 2017). Single-cell proteins have major problems in upscaling of their production as they requires a sterile environment for culture and also other limitations such as allergic reactions in cell walls and indigestion problems (Nasseri et al., 2011). The major obstacles to the commercialization of products are the bioreactor designs for the cultures. However, some of products, such as Mycoprotein of Rank Hovis McDougall’s, Pruteen of Imperial Chemical Industry’s (ICI), and Quorn mycoprotein of Marlow Foods have adopted single-cell protein on an industrial level. Other companies to produce single-cell protein include BlueBioTech Int. GmbH, Cangzhou Tianyu Feed Additive Co., Ltd., CBH Qingdao Co., Ltd., Lallemand Inc., LeSaffre, TerraViaHoldings, Inc. and UniBio A/S, Denmark (Ritala et al., 2017). These establishments have shown that the production of single-cell proteins has commercial and economical viability (Gaur et al., 2015). The continuous design is considered to be the more profitable for the production of single-cell proteins on an industrial scale (Ugalde and Castrillo, 2002a,b).

7.5

Conclusion

Food wastes are the most promising sustainable resource for chemicals, fuels, and energy. The exploitation of food wastes for the synthesis of biofuels and platform chemicals has been a focus of research for many years. The gradual shift to a biobased economy in the past decade (an economy system based on the utilization of renewable resources such as food wastes) has established an increased global demand for goods produced primarily from components of fruits and vegetable biomass made from polysaccharides. This trend, however, causes many ecological, social, and economic issues, such as intense land degradation (e.g., for energy crops), competition with the food chain, and the consequent increase in food prices, which is particularly dramatic for developing countries. To ensure more sustainable productivity and global food security, waste from the cultivation, harvesting, and processing of fruits and vegetables from biomass is currently considered as the best alternative source of polysaccharides and proteins which are used in the production of energy and commodity chemicals. Nonetheless, various types of wastes, such as food wastes generated from industrial processing of fruits, vegetables, and cereals, or agricultural wastes resulting from sugar or cereal crop cultivation and postharvesting operations are massively produced annually. As a result, several millions of tonnes of such residual biomass are available as valuable sources of polysaccharides and proteins which could be used as feedstock for the production of a broad range of valueadded chemicals and for the generation of renewable energy. The future development of a biobased economy will be constrained only by the availability of biomass; thus, in such a scenario, polysaccharides from food waste can represent not only a more environmentally friendly and sustainable source of products, but also a cost-effective solution to substitute feedstock for a broad range of industrial activities.

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438. Monkoondee, S., Kuntiya, A., Chaiyaso, T., Leksawasdi, N., Techapun, C., Kawee-ai, A., et al., 2015. Treatability of Cheese Whey for Single-Cell Protein Production in Non-Sterile Systems: Part II. The Application of Aerobic Sequencing Batch Reactor (Aerobic SBR) to Produce High Biomass of Dioszegia sp. TISTR 5792. Preparative Biochemistry and Biotechnology. Available from: https://doi.org/10.1080/10826068.2015.1045612. Moon, S.H., Park, J.M., Chun, H.Y., Kim, S.J., 2006. Comparisons of physical properties of bacterial celluloses produced in different culture conditions using saccharified food wastes. Biotechnol. Bioprocess. Eng. 11 (1), 26
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46. Zhou, Y.M., Chen, Y.P., Shen, Y., 2017. Single cell protein-feed: taking orange waste as raw material for fermentation. In: Advanced Materials and Energy Sustainability: Proceedings of the 2016 International Conference on Advanced Materials and Energy Sustainability (AMES2016). World Scientific, Singapore, pp. 323
335.

Further reading Bhattacharyya, A., Saha, J., Haldar, S., Bhowmic, A., Mukhopadhyay, U.K., Mukherjee, J., 2014. Production of poly-3-(hydroxybutyrate-co-hydroxyvalerate) by Haloferax mediterranei using rice-based ethanol stillage with simultaneous recovery and re-use of medium salts. Extremophiles 18, 463. Available from: https://doi.org/10.1007/s00792-013-0622-9.

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Koller, M., 2016. Recent Advances in Biotechnology Volume, 2: Microbial Biopolyester Production, Performance and Processing Bioengineering, Characterization, and Sustainability. Bentham Science Publishers. Mondal, A.K., Sengupta, S., Bhowal, J., Bhattacharya, D.K., 2012. Utilization of fruit wastes in producing single cell protein. Int. J. Sc. Environ. Technol. 1 (5), 430
438. Monkoondee, S., Kuntiya, A., Chaiyaso, T., Leksawasdi, N., Techapun, C., Kawee-ai, A., et al., 2015. Treatability of Cheese Whey for Single-Cell Protein Production in Non-Sterile Systems: Part II. The Application of Aerobic Sequencing Batch Reactor (Aerobic SBR) to Produce High Biomass of Dioszegia sp. TISTR 5792, Preparative Biochemistry and Biotechnology. DOI:10.1080/10826068.2015.1045612. Umesh, M., Priyanka, K., Thazeem, B., Preethi, K., 2017. Production of single cell protein and polyhydroxyalkanoate from Carica papaya waste. Arab. J. Sci. Eng. Available from: https://doi.org/10.1007/s13369-017-2519-x.

Chapter 8

Production of fine chemicals from food wastes V. Godvin Sharmila1, S. Kavitha1, Parthiba Karthikeyan Obulisamy2 and J. Rajesh Banu3 1

Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India, 2Department of Civil and Environmental Engineering,

University of Michigan, Ann Arbor, MI, United States, 3Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India

8.1

Introduction

Bioactive chemicals are extra nutritious elements available in some plants and food materials. These chemicals have an excellent role in yielding functional foods and food additives (Gil-ch et al., 2013). In addition, these bioactive chemicals have valuable benefits in promoting human health as they have been identified as possessing antiinfectious potential. This helps in the prevention of cancer, heart disease, and other diseases due to antioxidant and antibiotic properties. Hence, a quest for technology development for generating bioactive chemicals from food waste (FW) has become a unique challenge and also provides opportunities for FW management (Baiano, 2014). In the present scenario, the increased demand for green energy (Dinesh et al., 2018), bioactive materials, and biochemicals has inspired researchers to innovate eco-friendly technologies to process FW (Lin et al., 2013). Therefore, organic-rich FW can be used as a potential feedstock for producing more value-added products. Owing to its intrinsic chemical resources, FW can be used for generating chemicals through various techniques such as extraction, hydrolysis, digestion, and fermentation (Matharu et al., 2016; Sharmila et al., 2018). One report advised that the fine chemical production from biomass waste is 3.5 times more beneficial than transforming to biofuels (Venkata Mohan et al., 2016). The unconsumed components of food such as seeds, peels, and decayed residues, contain a rich source of phytochemicals and essential nutrients (Sagar et al., 2018). For example, orange, lemon peels, grapes residues, rice waste, and fruit seeds have a 15% higher phenolic content than fruit and vegetable consumables. The outline of the chapter is given in Fig. 8.1. This chapter highlights biochemical generation from various FWs and also demonstrates the various bioreactors used for biochemical generation. It also discusses the bioactive chemical extraction methods. The conventional and nonconventional extraction techniques are illustrated in depth, along with the purification process. Also, novel techniques for reusing waste materials to generate bioactive chemicals are also discussed. The applicability, limitations, scale up, and challenges, along with the future perceptions, of processing FWs to fine chemicals are also discussed briefly.

8.2

Food waste as a valuable source of bioactive chemicals

FW is a reservoir of value-added chemicals which are rich in protein, fibers, minerals, starch, and phytochemicals. FW includes plant-derived waste such as fruit and vegetable waste and animal-derived waste. Bioconversion of FW offers a better platform for resource recovery. The biorefinery concept minimizes the hurdles of FW management by providing a logistic strategy for generating valuable fine chemicals (Serna-Loaiza et al., 2018). Various FW derived biochemicals are listed in Table 8.1 and discussed below.

8.2.1 Aromatic compounds Aromatic compounds are fine chemicals with more powerful volatility characteristics present in most consumable products, which assist in the sensory evaluation of products and their quality (Chambers and Koppel, 2013). The increased Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00008-0 Copyright © 2020 Elsevier Inc. All rights reserved.

163

164

Food Waste to Valuable Resources

FIGURE 8.1 Overview of fine chemicals extraction from food waste.

demand for a natural and safe source of materials augments the market for these aromas, flavors, and fragrances. Food waste could be used as a potential source for generating flavors and aromas. Aromatic compounds can be generated from food waste by physiological, enzymatic, and fermentation processes in the form of hydrocarbons, ketones, acids, alcohols, aldehydes, esters, or lactones (Langos et al., 2013). Usually, submerged fermentation technology is adopted for generating natural flavors. The implementation of submerged fermentation for flavor production on a large scale is uneconomical. This increased the demand for developing alternative technology, such as solid-state fermentation and various extraction processes. Some fruit species waste can be processed to obtain volatile and nonvolatile substances for aromatic and cosmetic purposes. Microbial transformation of vegetable waste and cereal waste generates aroma substances used in the food, cosmetics, pharmaceuticals, and detergent industries (Sagar et al., 2018).

8.2.1.1 Ester Ester is a class of organic aromatic compound which usually has a sweet smell (Akacha and Gargouri, 2015). The ester compound was used in perfumery products and as a plasticizer for cellulose. Recently, some esters such as isoamyl acetate (banana, pear, and fruity aroma), ethyl esters (apple, fruity, sweetish, floral, and aniseed aroma), and phenyl ethyl acetate (roses and honey aroma) have been produced from orange peel waste by liquid fermentation using Saccharomyces cerevisiae (Mantzouridou et al., 2015). Also, fermenting orange peel using a yeast strain generates a fruity-like volatile aroma (ethyl hexanoate) within 48 h. In Japan, the popular citrus fruit Citrus natsudaidai has been cultivated extensively. The peel waste from this citrus species has the ability to generate 23 different aromatic compounds (Lv et al., 2015). Fresh banana peel waste can generate 10 ester aroma compounds, whereas dried banana peel gives three more ester compounds (Comim et al., 2010). Solid-state fermentation of apple pomace using the microorganism Ceratocystis fimbriata generates ethyl butyrate, which is a pineapple flavor (Bicas, 2010).

8.2.1.2 Terpenes Terpenes are a significant category of aromatic compounds comprised of various fragrances such as flowers, fruits, seeds, leaves, woods, and roots. Terpenes have gained high significance due to the herb-flavored wines such as vermouth and fruit-flavored wines. Terpenes are classified based on isoprene units, including limonene, camphor, menthol, carvone, terpineol, alpha-lonone, linalool, nerol, lemonal, myrcene, and geraniol. Limonene terpene is the predominant aroma present in citrus fruits and can be extracted from citrus waste. The distillation of orange peel generates limonene terpenes (Negro et al., 2016). Other compounds such as myrcene, linalool, alpha-lonone, nerol, generiol, and terpineol

Production of fine chemicals from food wastes Chapter | 8

165

TABLE 8.1 Fine chemical generation from food waste. S. no.

Food waste

Fine chemicals

Extraction method

Treatment condition

Yields

References

1. Aroma compound 1.

Olive mill waste

Limonene

Microbial fermentation

Microbes used: Rhizopus oryzae and Candida tropicalis (cultured at 0.325 vvm aeration rate under 120 rpm at 30 C temperature) Reactor used: stirred tank reactor with 4 L capacity

185.56 μg/kg and 294. 54 μg/kg of olive mill waste, respectively

Guneser et al. (2017)

2.

Orange peel waste

Five type of esters

Solid-state fermentation

Used yeast strain: VitilevureMT- S. cerevisiae (cultured at 35 C
37 C)

250 mg/kg of orange peel

Mantzouridou et al. (2015)

Approximately 9050 μg/kg, 2034 μg/kg and 8925 μg/kg of apple pomace, respectively, for each yeast strain

Madrera et al. (2015)

50 mL Erlenmeyer conical flask Treatment duration: 5 days 3.

Apple pomace

50 types of esters

Solid-state fermentation

Three strains of indigenous cider yeasts: Saccharomyces cerevisiae, Hanseniaspora valbyensis, and Hanseniaspora uvarum Bioreactor: Biostat B Bonus, Sartorius with a working volume of 2 L in batch Treatment time: 1 month

4.

Caraway seeds

Carvone and limonene

Ultrasoundassisted extraction

US bath at 25 kHz frequencyIntensity: 1 W/ cm2 water: solventTime: 30 min

Carvone 5.93 mg/g and limonene 5.47 mg/g of seed

Assami et al. (2012)

5.

Citrate (lemon and orange) and grape peels

Monoterpene, limonene, menthol, γ-terpinene, linalool, and citral

Ultrasoundassisted and supercritical fluid extraction process

Ultrasonic extraction: US bath Time: 5 min Cycle: 5 s21 Amplitude: 53% Supercritical fluid extraction: Temperature: 35 C; CO2 flowrate: 1 mL/min Time: 5 min

Extraction of aroma compound in ultrasonic and supercritical process was 2%
20% and 4%
19%, respectively

Omar et al. (2013)

6.

Garlic bulb waste

Thiols

Water-based ultrasoundassisted method

Sonicator: 30 kHz frequency Amplitude: 4%
12% distilled water: solvent Time: 60 min

About 0.10 mM thiols was extracted from 10% (w/v)

Ismail et al. (2014)

7.

Grape pomace

Thiols

Solvent extraction process

Solvent: acetone/water/ ethanol (40:50:10 ratio)

1.19 and 3.16 mg/kg of pomace, respectively

Jelley et al. (2016)

Time:1 h Temperature: 22 C

(Continued )

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Food Waste to Valuable Resources

TABLE 8.1 (Continued) S. no.

Food waste

Fine chemicals

Extraction method

Treatment condition

Yields

References

8.

Vanilla pods

Aldehydes

Ultrasoundassisted extraction process

US horn: 22.4 kHz

140 ppm vanillin concentration

Jadhav et al. (2009)

4.5 mg carotene pigment/g dry peel (0.45%)

Kodal et al. (2017)

1.63 mg carotenoids/g of dry peel

Ordonez et al. (2015)

Time: 1 h pulsed mode Substrate used: 1 g/ 100 mL solvent

2. Pigments 9.

Orange peel

Carotene pigment

Soxhlet extraction process

Solvent used: ethanol 

Temperature: 79 C Size of waste: 1.41
3.36 mm Liquid:solid ratio: 40:1

10.

Peach palm fruit peel

Carotenoids

Ultrasoundassisted extraction process

Solvent used: sunflower oil Power: 1.528 kW Temperature: 35 C Time: 30 min

11.

Grape skin waste

Anthocyanin

Microwaveassisted extraction

Liazid et al. (2011)

Power: 100
500 WTemperature: 50 C
100 C Solvent: 80% methanol in water

12.

Egg peel waste

Anthocyanins

Solvent extraction method

Solvent used: ethanol acidified, tartaric acid and malic acid Concentration: 1.25% v/vTemperature: 40 C

65.8
76.4 mg/ 100 g of peel

Todaro et al. (2009)

Duration: 60
80 min 13.

Cucumber waste

Chlorophyll a and b

Solvent extraction

Temperature: 20
55 CSolvent: methanolTime: 60 min

Chlorophyll a,b: 480.144 mg and 342.46 mg/100 g waste

Manuela et al. (2012)

14.

Spinach byproducts

Chlorophyll a and b

Solvent extraction

Solvent: ethanol (conc. 0%
95%, v/v)

96% of chlorophyll

Derrien et al. (2017)

Astaxanthin was 29.814 μg/g of dried waste

Kazumi et al. (2018)

39% Astaxanthin (20.7 μg/g waste)

Sanchez et al. (2011)

Solvent to raw material ratio: 1/33
1/100 v/w Time: 1
7 h Temperature: 20 C
60 C 15.

16.

Waste from processing pink shrimp Brazilian red spotted shrimp waste

Astaxanthin

Astaxanthin

Water-based ultrasoundassisted method

Solvent: palm olein

Supercritical CO2 extraction

Temperature: 40 C

Time: 15 min Temperature: 50 C
70 C

CO2 flowrate: 1.5 L/min Time: 200 min Extractor capacity: 50 mL

(Continued )

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167

TABLE 8.1 (Continued) S. no.

Food waste

Fine chemicals

Extraction method

Treatment condition

Yields

References

Cephalosporin

Fermentation process

Fungal strain used: A. chrysogenum NCIM 1069

900 μg of cephalosporin C/mL waste

Shruti et al. (2017)

Soya oil: 40 g/L, beet molasses: 180 g/L, and corn steep liquor: 330 g/L

Lotfy (2007)

22.1 g/L of penicillin V

Parameswari and Sivasankari (2017)

1.20 g/L penicillin

Rahman et al. (2012)

600.65 6 47.1 μg/ g of erythromycin

Noor et al. (2015)

140.86 g of oxytetracycline

Ezejiofor et al. (2012)

3. Antibiotics 17.

Butter milk processing waste

Temperature: 30 C pH: 6
6.5 Time: 168 h

18.

Beet molasses

Cephalosporin

Fermentation

Culture strain: Acremonium chrysogenum EMCC 904 Inoculum: 105.5 spores/mL; initial pH maintained: 4.3

Soy oil and corn steep liquor

Aeration rate: 9364 mL/min 19.

Rice burn medium

Penicillin

Solid-state fermentation

Microbes used: P. chrysogenum Treatment time: 6 days pH: 5.8 Temperature: 25 C

20.

Spoiled fruits, vegetables, breads, and grains

Penicillin

Fermentation

Microbes used: P. chrysogenum Treatment time: 300 h pH: 5.4 Inoculum: 1.3 3 105 spores/100 mL Temperature: 25 C

21.

Sugarcane bagasse

Macrolides

Fermentation

Microbes used: Saccharopolyspora erythraea Treatment time: 10 days pH: 7.2 Temperature: 30 C

22.

Kitchen waste (cocoyam peel)

Oxytetracycline

Fermentation

Microbes used: Streptomyces speibonae OXS1 Treatment time: 7 days pH: 7 Temperature: 28 C

(Continued )

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TABLE 8.1 (Continued) S. no.

Food waste

Fine chemicals

Extraction method

Treatment condition

Yields

References

Essential oil

Ultrasoundassisted extraction process

Solvent: hexane

8.2%

Abbasi et al. (2008)

6.9%

Comim et al. (2010)

0.23%

Xhaxhiu and Wenclawiak (2015)

3.3%

Gok et al. (2015)

28.9%

Cravotto et al. (2011)

23.3%

Samaram et al. (2015)

353%

Ekinci and Guru (2014)

59.1%

Goula (2013)

4. Essential oil 23.

Pomegranate by-products

Energy: 3000 W Frequency: 0.05
0.06 kHz Time: 45 min

24.

Banana peels

Essential oil

Supercritical CO2 extraction

Temperature: 40 C; Pressure: 30 MPa CO2 flowrate: 5 mL/min Time: 240 min

25.

Citrus byproducts

Essential oil

Supercritical CO2 extraction

Temperature: 40 C Pressure: 20 MPa CO2 flowrate: 1.6 mL/min Time: 15 min

26.

Citrus waste

Lemon oil

Supercritical CO2 extraction

Temperature: 40 C; Pressure: 10 MPa CO2 flowrate: 1000 mL/ min Time: 180 min

27.

Kiwi seed

Essential oil

Ultrasoundassisted extraction process

Solvent: n-hexane Power: 80 W Temperature: 50 C Time: 30 min

28.

Papaya seed

Essential oil

Ultrasoundassisted extraction process

Power: 700 W Frequency: 40 kHz Temperature: 62.5 C Time: 38.5 min

29.

Peach pomace

Essential oil

Supercritical CO2 extraction

Temperature: 40 C Pressure: 20 MPa CO2 flowrate: 7 mL/min Time: 180 min

30.

Pomegranate by-product

Essential oil

Ultrasoundassisted extraction

Solvent: hexane Power: 130 W Frequency: 20 kHz Temperature: 20 C Time: 20 min

(Continued )

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TABLE 8.1 (Continued) S. no.

Food waste

Fine chemicals

Extraction method

Treatment condition

Yields

References

Methane

Anaerobic fermentation

Reactor used: completely mixed reactors

480 mL/g VS methane

Zamanzadeh et al. (2017)

2.3 mol H2 mol21 hexose

Doi et al. (2010)

4.9 mol H2 mol21 hexose

Tawfik and ElQelish, (2012)

0.107 g/g FW

Matsakas et al. (2014)

0.3 g/g FW

Kim et al. (2012)

5. Fermentative products 31.

Food waste

Reactor working volume: 6 L (two reactors) HRT: 20 days Cosubstrate used: cow manure added with food waste; cosubstrate ratio: 60:40 OLR: 3 g VS/L/d Microbes: Methanothermobacter and Coprothermobacter 32.

Apple pomace waste

Hydrogen

Hydrogen fermentation

Reactor used: Batch reactor Temperature: 35 C pH: 6 Microbes: Rice rizhosphere microflora

33.

Municipal food waste

Hydrogen

Hydrogen fermentation

Reactor used: anaerobic baffled bed reactor Temperature: 26 C pH: 5
6 Inoculum pretreatment condition: Heat: 80 C Time: 20 min Microbes: anaerobic sludge

34.

Household food waste

Bioethanol

Alcohol fermentation

Reactor used: batch reactor Working volume: 100 mL conical flask Time: 16 d (substrate was pretreated) Microbes: baker’s yeast

35.

FW

Bioethanol

Alcohol fermentation

Reactor used: continuous reactor Working volume: 5 L fermenter Time: 13 d (substrate was pretreated) Microbes: Saccharomyces cerevisiae

(Continued )

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Food Waste to Valuable Resources

TABLE 8.1 (Continued) S. no.

Food waste

Fine chemicals

Extraction method

Treatment condition

Yields

References

36.

Mixed food waste

Methane

Anaerobic fermentation

Reactor used: continuous stirred tank reactor

468.2 mL/g VS methane

Kiran et al. (2014)

0.321 g lipid/g cell

Pleissner et al. (2013)

0.49 g lipid/g cell

Papanikolaou et al. (2011)

0.27 g/g FW

Kawa et al. (2012)

75% methane

Moon and Song (2011)

Working volume: 1.6 L (continuous mode) Time: 30 d (substrate pretreated with fungus) Microbes used: anaerobic sludge 37.

FW

Biodiesel

Fungal fermentation

Reactor used: batch reactor Pretreatment: fungal Hydrolysis by A. oryzae and A. awamori, sterilization Working volume: 2 L Time: 6 d Microbes: Schizochytrium mangrovei

38.

Waste olive oil

Biodiesel

Fungal fermentation

Reactor used: batch reactor Pretreatment: filtration Working volume: 250 mL flask Time: 5 d Microbes: Aspergillus niger NRRL

39.

Waste bread

Bioethanol

Alcohol fermentation

Reactor used: batch reactor Pretreatment: heating Working volume: 250 mL flask Time: 72 h Microbes: S. cerevisiae (Ethanol Red yeast)

40.

FW

Methane

Anaerobic fermentation

Reactor used: upflow anaerobic sludge blanket reactor (UASB) Pretreatment: enzymatic Working volume: 2.7 L Time: 72 d Microbes: anaerobic sludge

(Continued )

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TABLE 8.1 (Continued) S. no.

Food waste

Fine chemicals

Extraction method

Treatment condition

Yields

References

41.

Kitchen waste

Lactic acid

Lactic acid fermentation

Reactor used: batch reactor

0.44 g/g waste

Wang et al. (2011)

Working volume: 200 mL (500 mL conical flask) Temperature: 45 C pH: 5.5
6 Time: 2 days Microbes: Lactobacillus TY50

are also extracted from C. natsudaidai peel in Japan (Matsuo et al., 2019). The microbial fermentation of olive mill waste by Rhizopus oryzae and Candida tropicalis generates a higher concentration of limonene and menthol terpenes (Guneser et al., 2017). Terpene can be extracted from the waste of all carrot species. Camphor terpenes can also be extracted from sage leaves, which have medicinal properties. Solvent extraction of waste citrus peels, for example, clementines, yields carvone aroma. The application of terpenes in any essential oil can be used for aromatherapy treatment which has a powerful antiinflammatory property.

8.2.1.3 Ketones In general, lipid oxidation, citrate, and glucose metabolism derive the ketone compounds which give off a fruity or musty aroma. Some ketones such as acetoin and diacetyl possess a buttery aroma (Bicas, 2010). Fish waste on enzymatic hydrolysis generates ketones, namely heptanone, 2-octanone, 2-nonanone, and undecanone, which are used as a seafood flavor (Peinado et al., 2016). Microbial processing of cassava bagasse along with soybean or apple pomace using Ceratocystis fimbriate generates some ketones (Panda et al., 2017). Methyl ketones are highly extracted from milk by high-temperature heat treatment. Fruit waste such as pineapple residues and banana peel have also been used for extracting ketone compounds.

8.2.1.4 Lactones The condensation of acid and alcohol yields lactones, which are cyclic aroma compounds (Elhadi et al., 2013). Processes such as microbial treatment, lipid oxidation, or thermal method are generally utilized for extracting lactones from food waste. Lactones exhibit a fruity, coconut-like, buttery, creamy, sweet, or nutty aroma. The biofermentation of food waste using fungus and yeast strains for yielding lactones is greatly preferred (Berger, 2015). Fermentation of castor oil using fed-batch cultivation of yeast (Yarrowia lipolytica) enhanced the decalactone production. Sugarcane bagasse on fermentation produces unsaturated lactone 6-phenyl pyrole (6-PP) with a coconut-like aroma, whereas cassava bagasse gives off a fruity aroma. Nearly 1.6 mg/L of 4-decalactone with peach odor is produced by Sporobolomyces odors yeast through a de novo process (Smid and Kleerebezem, 2014).

8.2.1.5 Aldehydes Usually, a fresh floral or fruity aroma represents most aldehydes. In rare cases, the large alkyl group of aldehydes generates an oily or fatty aroma (Bicas, 2010). Some essential oils have residues of several aldehydes and many promote auspicious fragrances such as cinnamaldehyde, cilantro, and vanillin. One of most highly utilized flavor compounds vanilla, which has vanillin as its major component. Certain industries, for example the food, cosmetics, pharmaceuticals, and detergent industries, make use of vanilla flavor in many their product (Sagar et al., 2018). The aldehyde flavor can also be produced by food waste such as carrot pomace, sugar beet pulp, wheat bran, corn cob, and apple pomace by microbial biotransformation (Belrhlid et al., 2018).

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8.2.1.6 Thiols The low odor threshold with roasted, coffee, or meat-like aroma is thiols. Cysteine and glutathione are the primary thiols which have significant roles in the pharmaceuticals, cosmetics, and food industries (Smid and Kleerebezem, 2014). Waste derived from bakery products, boy choy, beans, cabbage, coffee, chocolate, dairy products, onion, spices, garlic, some fruits, etc., can be the source of thiols. There are about 23 thiol compounds in waste cheese. Grape skin gives off 30 μg/kg thiols (Jelley et al., 2016). Garlic waste bulbs, a thiol-rich waste product, yield 0.170 mM thiols for 10% (w/v) garlic concentration by the ultrasound-assisted process at 100% amplitude (Ismail et al., 2014).

8.2.2 Pigments Pigment usage in industries such as the food, cloth, cosmetics, painting, and pharmaceuticals industries is increasing, leading to bio-pigment development (Pankaj and Kumar, 2016). The main advantage of producing bio-pigments is the avoidance of environmental toxicity and a reduction in reactive chemical by-product generation. In recent years, the application of bio-pigments in foodstuffs, dyestuffs, cosmetics, and pharmaceuticals manufacturing processes is increasing almost daily. The bio-pigments derived from food waste are trusted to be safe as they do not have any hazardous or carcinogenic substances and are easily biodegradable (Malik et al., 2012).

8.2.2.1 Prodigiosin A class of tripyrrole antibiotic pigments with red color produced by strains of Serratia marcescens is known as the prodigiosins. This pigment was highly utilized in carbonated drinks, textiles, cosmetics, and dairy products due to its immunosuppressant and anticancer properties (Pradeep et al., 2013). About 560.04 mg/mL of prodigiosins was produced from waste peanut powder using S. marcescens MBB05. The solid-state fermentation of bagasse yielded 40.86 g/kg of dry solids using S. marcescens (Xia et al., 2016). Another ideal substrate used for producing prodigiosin is kitchen waste, which yielded 41.55 mg/kg of waste (Fang et al., 2011). Corn cob powder produces 25.42 OD units/g of dry substrate during solid-state fermentation using Monascus purpureus KACC 42430 microbes (Velmurugan et al., 2011).

8.2.2.2 Monascus A secondary metabolite which consists of yellow (monascin and ankaflavin), orange (rubro-punctatin and monascorubin), and red (rubropunctamine and monascorubramine) constituents is the monascus pigments which are substantially produced by a fermentation process (Patakova, 2012). Numerous food and agro-based wastes are utilized for production of this pigment. Subhasree et al. (2011) utilized jackfruit seed for producing monascus pigment by fermentation using M. purpureus. In addition, the corn cob was used to produce monascus pigments of quantity 0.95 AU/mL using the M. purpureus strain ATCC 16436 (Amira et al., 2018). Durian fruit is a tropical fruit with high nutritional benefits, however its seed are discarded as waste. Seed waste from the durian fruit is considered to be a valuable substrate for monascus pigment generation in the form of ankaflavin by Monascus sp., and yielded 50 mg/kg of waste (Srianta et al., 2012). Other wastes such as orange processing waste and bakery waste are also used to produce this pigment using the M. purpureus fungal strain (Haque et al., 2016; Kantifedaki et al., 2018). This pigment can be used as a flavor, coloring agent, and preservative in food.

8.2.2.3 Chlorophyll The natural lipid-soluble green-colored pigment which is found in plants species and in cyanobacteria is chlorophyll. Green leafy spinach is a healthy vegetables which is consumed at a high rate throughout the world, generating 25% waste material. This waste material can produce 96% chlorophyll by the solvent extraction process. Utczas et al. (2018) collected 20 varieties of overripe fruits and vegetables from a local market in Italy and extracted various pigments, with chlorophyll pigment accounting for about 5.51 mg/kg of samples used. The use of ultrasound-assisted solvent extraction process techniques in yellowish-green and reddish-green bell peppers generates chlorophyll pigment at 380.00 μg/g and 807.89 μg/g, respectively (Manolopoulou et al., 2016). This harmless chlorophyll pigment is used in consumable products, cosmetic products, sanitary products, inks, candles, resins, and also in some leather products (Hosikian et al., 2010).

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8.2.2.4 Astaxanthin Astaxanthin is a 3,30 -dihydroxy-β, β-caroten-4,40 -dione which is an oxygenated pigment with colors ranging from yellow to red. This type of pigment is utilized in aquaculture products, mainly the fish foods, cosmetics, antibiotics, nutrition, and medicine manufacturing industries. This pigment has high commercial demand and was produced from various organic waste substrates using different microorganisms such as Haematococcus pluvialis, combined Brevibacterium spp. and Mycobacterium lacticola bacteria, Rhodotorula sp., Sporidiobolus sp., Xanthophyllomyces dendrorhous, and Y. lipolytica yeasts (Rodrı´guez et al., 2010). Of these microorganisms, Xanthophyllomyces dendrorhous and Haematococcus pluvialis are most utilized in commercial-scale production. Although this pigment can be manufactured synthetically, microbial generation using Xanthophyllomyces dendrorhous has achieved high market value (Malik et al., 2012). In addition, pressurized hot ethanol also assists in the extraction of astaxanthin from shrimp waste (Sanchez et al., 2011). Tinoi et al. (2006) have successfully extracted this astaxanthin pigment from mustard waste using X. dendrorhous.

8.2.3 Antibiotics The name antibiotic originated from the Greek words anti (against) and bios (life), which was derived by Paul Vuillemin, a pupil of Louis Pasteur in 1889. Later, Selman Waksman coined the term antibiotic in 1945 (Dezfully and Heidari, 2016). Antibiotics are natural, synthetic, or semisynthetic substances which affect microbial growth and induce death, especially in bacteria, providing greater immunity against infective diseases. Overconsumption of antibiotics without proper prescription is now causing antibiotic resistance on a global scale. Hence, numerous researches are in progress in the field of antibiotic generation (Livermore et al., 2011). Some antibiotics such penicillin, cephalosporin, tetracycline, and macrolides are discussed below. The extraction of antibiotics from food waste is an eco-friendly technique.

8.2.3.1 Penicillin The antibiotic penicillin was first introduced in the 1940s to treat infectious diseases. The various forms of penicillin include penicillin G, penicillin V, procaine penicillin, benzathine penicillin, etc. (Lobanovska and Pilla, 2017). Mostly the fungi Penicillium chrysogenum performs a vital role in the generation of these antibiotics by solid-state and submerged fermentation processes. Rice bran is one major residue of rice-processing units. This waste can be used to produce 22.1 g/L of penicillin V. From rotten orange waste, the Penicillium species chrysogenum and notatum can be isolated (Parameswari and Sivasankari, 2017).

8.2.3.2 Cephalosporins Like penicillin, cephalosporin is a secondary antibiotic compound. Highly potent derivatives of this antibiotic are cephalothin, cephaloridine, and cephaloglycin (Watkins and Bonomo, 2017). The large-scale generation of cephalosporin is done with the help of the fungus Acremonium chrysogenum (Pathak and Bose, 2017). Some types of food waste are used in the production of this antibiotic. Fermenting buttermilk processing waste by A. chrysogenum produces 900 μg/ mL of cephalosporin on the seventh day. Also, dairy farm waste milk contains cefquinome (a fourth-generation cephalosporin) at about 1400 μg/kg of waste (Shruti et al., 2017; Horton et al., 2015). In addition, sugarcane bagasse also yields 428
3200 μg/g of cephalosporin C by A. chrysogenum C10 (Cuadra et al., 2008). Other food wastes with cephalosporin content include beet molasses (180 mg/L), corn steep liquor (330 mg/L), and soy oil (40 g/L) (Lotfy, 2007).

8.2.3.3 Tetracycline The Streptomyces genus of actinobacteria produces antibiotics which are grouped under the family of polyketide including tetracycline (Raja and Prabakarana, 2011). The solid-state fermentation of groundnut shell, sweet potato residues, cassava peel, and cocoyam peel yields tetracycline by using the microbes Streptomyces rimosus, S. vendagensis, and S. speibonae (Sadh et al., 2018). Different types of tetracycline compound include chlorotetracycline, demeclocycline, oxytetracycline, and other active types (Petkovic et al., 2017). The microbial processing of pineapple waste by three different bacteria, namely S. aureofaciens, S. rimosus, and S. viridifaciens, gives tetracycline at 12.9, 12.94, and 12.45 of substrate used, respectively (Granados and Rodriguez, 2017).

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Food Waste to Valuable Resources

8.2.3.4 Macrolides Macrolides include erythromycin, clarithromycin, and azithromycin (Dezfully and Heidari, 2016). Erythromycin is a 14-carbon macrolide antibiotic produced by Saccharopolyspora erythraea species (Vardanyan and Hruby, 2016). Sugarcane bagasse produces erythromycin at 197.97 μg/g of substrate by solid-state fermentation using Saccharopolyspora erythraea NCIMB 12462 (Noor et al., 2015). Beet sugar root yields 735.65 μg/g of erythromycin (Farid et al., 2015). Clarithromycin has advantages over erythromycin such as improved antibiotic activity and a high volume of distribution (Sadh et al., 2018).

8.2.4 Essential oils Essential oils are the natural form of hydrophobic liquid that is extracted from plant varieties and organic substances which contain typical aroma substances. They are highly utilized in nutritional, therapeutic, and aesthetic products (Soquetta et al., 2018). Specific types of essential oils are identified for their antibacterial, antioxidant, and antifungal activities (Thongnuanchan and Benjakul, 2014). This method of extraction was used for extracting oil from medicinal plants in China. Distillation, such as water distillation, water and steam distillation, steam distillation, cohobation, maceration, and enfleurage are ancient methods of extracting oils (Hesham et al., 2016). Nowadays, various extraction techniques have been formulated. There are about 100 compounds present in essential oils which are grouped into three major elements: terpene hydrocarbons, oxygenated compounds, and nonvolatile compounds (Dhifi et al., 2016). Nearly 50% to more than 95% of essential oils have terpene mixtures. The most highly utilized forms of these oil in most industries are seed oil, fish oil, and peel oil.

8.2.4.1 Seed oil Seed oil is a form of vegetable oil mainly extracted from seeds of various fruits and vegetables. Since most of the seeds are disposed of as waste, it can be used as an excellent source of essential oils. Waste seed used for oil production includes grape, cucumber, mango, cherry, corn, etc. Pressurized hot water extraction (PHWE) is a widespread green extraction process for extracting fine bioactive compounds. Mustafa and Turner (2011) performed a comparative analysis of PHWE, Soxhlet, and hydro-distillation techniques to extract essential oils from coriander seeds. The outcome depicts that better quality essential oil invaluable oxygenated components were obtained by PHWE, whereas hydrodistillation and Soxhlet extraction showed more efficacies. Ultrasound-assisted extraction was preferred to extract oil from pomegranate seed and yielded 59.8%. In addition, the spray-drying method and supercritical CO2 extraction process can also be employed for oil extraction in pomegranate seed (Gornas and Rudzinska, 2016). About 4%
11% of the oil was extricated from grape seed by the supercritical CO2 extraction process. From mango seed, kernel oil was obtained (Nowshehri et al., 2015).

8.2.4.2 Fish oil The two major fatty acids, eicosapentaenoic acid and docosahexaenoic acid, are present in fish oil, which is a natural source of long-chain omega-3 fatty acid. Both these acids have been confirmed to promote health and can be used as food additives. This oil is widely utilized in pharmaceutical industries, food industries, agriculture, and aquaculture as a feed additive (Ivanovs and Blumberga, 2017). Oil is extracted from fish waste from processing industries and unsold whole fish by traditional (pressing, thermal, and solvent extraction) methods, using eco-friendly extraction units (supercritical fluid, enzyme-assisted process, microwave-assisted unit, and ultrasound-assisted unit) (Rubio et al., 2012; Lucia et al., 2015). Dried fatty fish yields 40
50 g of oil/100 g dry fish. Nearly 10 g oil/100 g dry fish was extracted from several portions of sardines (Rubio et al., 2012). Liver oil was extracted from catfish using a microwave process (Ghosh et al., 2016). Also, an enzymatic extraction method was adopted in different fatty fish, such as salmon, mackerel, and catla species.

8.2.4.3 Peel oil Orange peel can be exploited for extricating essential oils through various extraction processes such as a solvent extraction process, steam, and water distillation. Distillation by steam gives a high yield of 4.40%, whereas water distillation and solvent extraction generated 3.47% and 2.53%, respectively (Golmohammadi et al., 2018). Also, there are some alternative technologies for extracting oil from orange peel, namely microwave, ultrasonication, enzyme, and supercritical fluid extraction processes. Theses alternative technologies save time and energy (Gavahian et al., 2018). In addition,

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tomato waste from processing industries and tomato peel can also be used to generate edible essential oil (Lisichkov and Kuvendziev, 2011). Raw and ripened banana peel can yield essential oil approximately in the range of 39.53%
64.24% (Hamid et al., 2016).

8.2.4.4 Biolubricants Lubricants are the oil-based chemicals produced from mineral oil to minimize damages from friction, wear, and heat in machinery. The use of mineral-based lubricants contaminates soil and water, thereby increasing pollution in the ecosystem (Heikal et al., 2017). The growth of strict legislative policies to minimize pollution by petroleum-based components has encouraged the development of bio-based fuels (Anand et al., 2019). Organic food waste materials such as waste oil and waste edible animal fats are used for producing biolubricant oil (McNutt and He, 2016). One such waste material is waste cooking oil that may damage and block sewage systems and soil porosity on disposal. Hence, recycling of this waste oil to biolubricants improves its reusability (Alotaibi and Yousif, 2016). An oscillator flow reactor using a catalyzed isomerization process transforms nearly 94% of palm oil to biolubricant oil (Masudi and Muraza, 2018). Also, the epoxied form of soybean oil is converted to biolubricants by solid acid catalysts in the presence of alcohol. Confectionery industrial waste and wheat mill waste are fermented by fungal strains Rhodosporidium toruloides and Cryptococcus curvatus to produce microbial oil which can undergo transesterification to produce biolubricants and yielded 88% and 82.7% for each strain, respectively (Papadaki et al., 2018). Chicken fat was also transesterified to form biolubricants (Hernandez-Cruz et al., 2017).

8.3

Bioreactors used for fine chemical production

Biochemical processing of FW to derive valuable chemicals using green methods is a highly challenging task. Solidstate fermentation (SSF) has been highly preferred for effective bioprocessing of food waste to derive fine chemical over past centuries and remains an area of intensive research. Microbial products obtained using food waste as a substrate in SSF include enzymes, organic acids, antibiotics, aroma compounds, carbohydrates, bioalcohol, etc. (Lin et al., 2013). Highly utilized bioreactors for fine chemical generation from food waste on a laboratory scale are Erlenmeyer flask, Petri dishes, jars, and roller bottles. Lab-scale process optimization was achieved using a flask sealed by cotton plugs with diffused aeration. The advantages of a laboratory-scale study are handling, economical costs, and several confirmatory analyses (Nayak and Bhushan, 2019). Other bioreactors used for bioprocessing of FW include packed bed reactors, perforated tray reactors, continuously stirred tank reactors, fluidized bed reactors, horizontal drum reactors, and up-flow anaerobic sludge blanket reactor, as shown in Fig. 8.2. A packed bed reactor is also known as a fixed bed reactor with filled solid substrate or supports. This bioreactor is included in the category of bioreactors without forced aeration. The fixed matrix within the reactor is made of materials such as glass fibers, porous ceramic beads, a polyester disc, etc. which provide surface area for cell attachment. This closed system of bioreactor limits microbial contamination. It is used in fermentation and extraction processes and reduces the temperature gradient. Introduction of air through the sieve prevents clogging of the bed. Pilot-scale use of this fermentation process helps in better implementation of this bioreactor in large scale by parameter optimization (Pitol et al., 2016). Humid air is passed through the substrate bed continuously. The temperature rise in the fermentation process is regulated by cool water circulation. It has the capacity to treat a few kg of waste in dried form. In a koji bioreactor, a similar type of configuration is followed (Kumar et al., 2014). The major disadvantage is nonuniform microbial growth for fermentation, which affects the product yield and causes difficulty in temperature maintenance, which in turn affects the implementation of this bioreactor on a large scale. A perforated tray bioreactor consists of trays arranged parallel to each other in a chamber under regulated temperature and pressure. This tray is made from a wooden or stainless-steel material with perforations for air convection. The substrate to be treated is spread over this tray as thin layers over a few centimeters (5
15 cm) with space for air circulation. It consists of flat trays. It can be scaled up easily but has a few disadvantages such as large area and the need for a greater number of trays, skilled labor for maintenance, and difficulty in cleaning (Figueroa et al., 2011). The working concept of the bioreactor is based on a static bed with a forced aeration system. A horizontal drum bioreactor works under continuous agitation and air circulation. Mixing of substrate and inoculum is achieved by rotating the whole container or by several agitation tools such as paddles and baffles (Wang et al., 2010a,b). This reactor is drum-shaped with agitation tools. According to Ali and Zulkali (2011), a 200-L stainless steel rotating drum is considered to be the largest reactor as per a literature report which has the capacity to use 10 kg of steamed wheat bran as substrate and investigated the kinetics growth of Rhizopus.

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Food Waste to Valuable Resources

FIGURE 8.2 Bioreactors used for fine chemical generation.

A fluidized bed reactor is a bioreactor in which particles are in a continuous mode of aeration and mixing. Liquid or gas act as a carrier for energy input. It has the advantage of greater mixing with minimal pressure drop. The fluid stream of this reactor consists of bed material in suspension. This type of reactor was successfully used by Jakovetic et al. (2013) to produce an ester compound using immobilized lipase within 6 h. The effectiveness of this reactor depends on the amount of enzyme embedded within the matrix. It is highly suitable for small scale generation of high-cost products. A continuous stirred tank reactor is a highly utilized reactor as it is simple and cost effective. The substrate in this reactor is kept under continuous and complete mixing (Smith et al., 2012). It is highly utilized for treating organic wastes such as kitchen waste, food waste, sewage, and manure. In this reactor, the waste is fed in a continuous or intermittent mode. It is often used to generate lactic acid from cheese whey. The configuration of this reactor is more suitable for kinetic study of the substrate inhibition reaction (Wang et al., 2010a,b).

8.4

Various methods of extraction and purification of chemicals

The methods of extracting bioactive fine chemicals from solid and liquid FW are numerous, and have been grouped into two categories: traditional and modern methods. The traditional methods of extraction include solid
liquid extraction, Soxhlet extraction, and liquid
liquid extraction. These methods have the disadvantages of excess energy depletion, increased solvent usage, thermal deterioration of heat-labile components, and prolonged time for extraction. The modern processes of extraction, supercritical fluid extraction (Lisichkov and Kuvendziev, 2011), microwave-assisted extraction (Khaw et al., 2017), ultrasound-assisted extraction (Kumar et al., 2017), high-voltage electric discharge extraction, pulse electric field extraction (Vorobiev and Lebovka, 2016), and ionic liquid extraction (Chemat et al., 2017) are discussed below.

8.4.1 Microwave-assisted extraction The perpendicular oscillation of electromagnetic waves with electric and magnetic fields is in the frequency range of 0.3
300 GHz. This microwave energy with ionic diffusion and dipole spin has a direct impact on substances. Polar

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materials can be warmed as per the dielectric constant. The microwave heat source offers effective heating, acceleration of the transferring energy, and a reduction of the thermal gradient (Banu et al., 2018; Eswari et al., 2016, 2017; Ebenezer et al., 2015). Thus, microwave-assisted extraction is documented as a potential method for fine biochemical extraction from solid food waste (Fig. 8.3A). Consequently, this method efficiently extricates fine chemical substances, specifically essential oils, pigments, aromas, and other organic compounds. The use of microwave equipment could be a flourishing technology as a result of its higher attainable temperatures in a safe manner with good yield in a shorter time duration, therefore improving the purity of biochemicals. This method can be carried out either with or without the addition of a solvent. Aromatic compounds have been extracted from chokeberries waste using this technique with ethane as a solvent under various microwave powers from 300 to 600 W (Simic et al., 2016). The maximum yield was 420.1 equivalents mg gallic acid/100 g of substrate with a power of 300 W within 5 min. Also, Krishnan and Rajan (2016) extracted phenolic compounds from grape seed. Citrus seed waste was used to extract 14.1% peel oil by the microwave method with a temperature of 110 C and using hexane as the solvent (Attard et al., 2014). Kernel of mango yields 8.7% tannic acid equivalent phenolic compound at pH 8 (Dorta et al., 2013), and pumpkin kernel waste gives 64.1% oil using a microwave-assisted enzyme extraction process.

8.4.2 Ionic liquid extraction techniques As per the intensive research, alternative solvents, that is, ionic liquid, are preferred to replace the lower requirement of organic media. This has gained importance recently and is currently under investigation (Fig. 8.3B). Huge application of ionic liquid for the extraction process was due to variations in the physiochemical characteristics of ionic liquids based on cation and anion selection. In addition, the ionic liquid was the major component for extracting solvent and separating gas. Ionic liquids are the organic salt component made up of organic cations and inorganic anions with melting points below or at ambient temperatures. These liquids have a tunable property and are used as a reaction media with negligible vapor pressure and regeneration taking place when minor solvent losses occur. This liquid has great chemothermal constancies and an extensive liquidus array. The use of ionic liquid in a negative-pressure cavitation process

FIGURE 8.3 Various extraction units: (A) microwave-assisted extraction; (B) ionic liquid-assisted extraction; (C) ultrasound-assisted extraction; (D) high-voltage electric discharge (HVED).

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Food Waste to Valuable Resources

yields three different flavonoids in the range of 0.291
0.491 mg/g from pigeon pea roots (Chemat et al., 2017). Ultrasound-assisted ionic extraction and ionic liquid heat-refluxing extraction also promote better flavonoid yields (Li et al., 2017).

8.4.3 Ultrasound-assisted extraction This type of extraction is used to extract bioactive compounds including polysaccharides, essential oils, proteins, peptides, dyes, pigments, and other compounds. Fig. 8.3C shows the ultrasound-assisted extraction setup. Ultrasonic sound wave frequencies higher than 20 kHz promote expansion and compression cycles (Sowmya et al., 2015). Expansion deflects the particles away from each other, whereas compression impulses them together. In a fluid, the expansion can produce lathers, that is, cavitation which grows and collapses. This cavity collapse is unequal due to high-speed liquid motion which promotes a high impact on the solid surface (Shanthi et al., 2019; Kavitha et al., 2016). Ultrasound accelerates the heat and mass transfer by disrupting the particle structure and enhancing the liberation of bioactive substances from waste biomass (Rosello et al., 2015). The temperature, pressure, frequency, and sonication time are some of the aspects that regulate the ultrasound-assisted extraction process. The ultrasound-assisted extraction process has been used to extract essential oils from tomato waste (frequency, 40 kHz; power, 300 W; time, 29 min), raspberry waste (frequency, 22 kHz; power, 650 W; temperature, 40 C), wheat bran waste (frequency, 40 kHz; power, 250 W; time, 25 min), and flax seed (frequency, 20 kHz; power, 50 W; time, 30 min) (Kumar et al., 2017; Chemat and Khan, 2011).

8.4.4 High-voltage electric discharge Several researchers have selected this technology for recovering bioactive chemical composites from numerous FWs by rupturing the cell structure of FW using electrical energy (Boussetta and Vorobiev, 2014). This was attributable to the streamer propagation of an intense electrical field (up to 40 kV and 10 kA) from a high-voltage needle electrode to the grounded one as a result of an electron avalanche (Fig. 8.3D). This electrical collapse is combined with numerous events, such as shock wave development due to pressure changes with a higher amplitude, hydrodynamic cavitation, liquid turbulence formation, and active species generation. Overall these effects promoted fragmentation of FW components and damaged its microbial structure, which in turn facilitates the release of intracellular components. The formation of air bubbles within the substrate due to heating enhances the extraction process. High-voltage electric discharge (HVED) promotes oil extraction from palm kernel. On investigation, it was observed that a temperature of 20 C with energy 80 kJ/kg using water as a solvent yielded 11% oil, whereas palm pomace yields 36% oil in HVED treatment under similar conditions except an energy requirement that seems to be higher at about 240 kJ/kg (Boussetta and Vorobiev, 2014). Boussetta et al. (2012) demonstrated that the implementation of HVED in a pilot-scale study promotes bioactive compound extraction in a similar amount to that extracted in a lab-scale investigation. HVED also was applied to extract oil from linseed press-cake.

8.4.5 Pulsed electric field extraction The pulsed electric field (PEF) works under the basic principle of creating electroporation of the substrate cell membrane for increasing the generation of product (Fig. 8.4). An electric potential permits the particles through the cell membrane and segregates them. This repulsive pore improves permeability (Azmir et al., 2013; Rajha et al., 2015). PEF has been applied for food preservation and to recover valuable compounds from food wastes. PEF was highly selective in recovering valuable compounds from different fruit and vegetable wastes in a sustainable way owing to its capacity to relax and interrupt the cell membranes, hence serving as the platform for releasing the intracellular compounds. In waste biomass, the cell content is protected by the cell wall and the cell membrane which acts as a natural barrier and also stops chemical release. The applied pulsed electric field has a direct impact on cells, which may increase the permeability of cell membrane to release the biomolecules within the medium at the levels of 0.4
0.8 kV/cm. On applying PEF between electrodes, electric pulses with high voltage were discharged. PEF treatment of maize corn produces 88.4% oil for an electric field strength E 5 0.6
7.3 kV/cm and 120 exponential decay pulses with a specific energy input of 0.62 kJ/kg (ΔT 5 0.1 K) at a field strength of 0.6 kV/cm (Vorobiev and Lebovka, 2016). The extraction of oil from sesame seeds in a pulsed electric field treatment was detailed by Sarkis et al. (2015). Tomato juice yielded bioactive substances during PEF extraction with a 0.4
2 kV/cm electric field with 5
30 pulses.

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FIGURE 8.4 Pulse electric field-assisted extraction unit.

8.4.6 Supercritical fluid extraction In this method of extraction, supercritical fluids were used as an extracting agent that segregates the extractant from FW, as shown in Fig. 8.5. The much preferred supercritical fluid is CO2 (carbon dioxide), which imparts changes in polarity of the co-solvents such as ethanol because of its safe utility, cheap availability, recyclability, and better extractable product yield than other conventional techniques (Soares et al., 2015). With the help of supercritical CO2 extraction with dense liquefied petroleum gas (LPG), rice bran oil was extracted, which has the advantage of high solute diffusivities, less viscous with lower surface tension, and probable adjustment of solvating power with respect to pressure and temperature. Likewise, the solute separation from the fluid is readily enabled. This type of extraction is widely applied in extracting food additives and aromas. The major obstacle to the commercialization of this method is unaffordable investment outlay. Because of this limitation, its usage was limited for isolation techniques in achieving the final product. This hurdle was conquered by adopting an integrated processing operation, that is, incorporating a material preprocessor by solvent extraction or inducing physical segregation for promoting fractional concentration, adopting an in situ treatment process, imparting microbial preprocessing of substrate for production of a wide variety of biochemicals, and pretreating FW by chemical or enzymatic reactions to eliminate the bonding of compounds to be extracted from the FW. These integrated processing procedures are under investigation and are currently in the developmental stage. From kiwi fruit seed, 26.2% essential oil was extracted by this extraction process using n-hexane as a solvent medium with 1 h of extraction. Seeds of citrus species give off 0.6% limonene at 50 C (Cravotto et al., 2011). Lisichkov and Kuvendziev (2011) extracted seed oil from tomato waste using this extraction process. Seed oils were also produced from pumpkin seed. Banana peel waste gives essential oils at 40 C
50 C, and Brazilian cherry seeds were processed to yield aroma compounds at 45 C under a pressure of 17.16 MPa. The overall analysis of the extraction process indicates that implementation of innovative zero waste (green) extraction instead of conventional organic solvent-based processes may promote the development of an eco-friendly method. Based on the economic considerations and bioactive compound yield, the extraction process has been selected under optimized process conditions. Hence, extraction process selection was slightly challenging and the quantum of material needs to be analyzed. The highly putrescible nature of FW avoids the conventional process for scale up at a larger scale. Among the various eco-friendly techniques, the microwave, supercritical, ultrasonication-assisted extraction process was more widely recognized than others due to its simplicity in field applicability. The moisture content of the FW helps in biocomponent disruption with microwaves (Attard et al., 2014). Due to the impact on the extracted product, in terms of cost, manufacturing method, safety issues, and disposal method, water could not be used as a solvent. However, alcohol has quick recovery at a lower boiling point. Ionic liquid is one such novel medium which is in high use currently because of its high viscosity, good ion conductors, good solubility, and high boiling point, and was a designer solvent with the capability to dissolve hydrophilic and hydrophobic components. Studies confirmed that adopting substitutional/innovative modern extraction techniques can be a conservational and environment-friendly approach in the field of fine chemical yield.

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FIGURE 8.5 Supercritical fluid extraction unit.

8.5

Economic consideration

Cost analysis for extracting biochemicals from food waste including fruit and vegetable waste has only been described in a few reports. The economic analysis aids in the feasibility investigation of the extracting method (Attard et al., 2014; Pfaltzgraff et al., 2013). Based on the present market value of the bioactive compound in European countries, the cost of bioproducts could rise to h515 billion in 2020 from h228 in 2015 (EFIB, 2016). Hence, in future, there is scope for improvement in bioproduct recovery and its usage. About 360,000 metric tonnes (MT) of mango processing waste were processed to generate 12,983 MT of essential oil, with a net profit of $9.6 million, in which the cost consumption in the recovery process and cost incurred for reactor setup was taken into consideration. Using microwave extraction techniques, d-limonene was extracted from wet orange peel, consuming $7.2 million applied energy cost for processing 50,000 MT of wet orange peel. The above process yielded 1.5% d-limonene with $11.3 million as a net profitable cost when considering raw orange peel cost as zero. The microwave energy consumption cost varies based on the source of food availability. When considering raw orange peel cost as $0.02/kg, the net profit cost will be $10.5 million, as reported in the literature (Pfaltzgraff et al., 2013). Do et al. (2014) extracted 70% bio-oil from empty bunch fruit waste (residue from the palm oil industry) by fast pyrolysis in a fluidized bed reactor with a profit of $0.47/kg waste, consuming 20 kilo tonnes of waste per year. Although the bioproduct recovery increases at a commercial scale, the market value may reduce due to consumer demand without any improvement in bioprocessing. Paggiola et al. (2016) introduced a novel method for replacing toluene with limonene, hence reducing the capital investment using an emerging biorefinery process for citrus species. Aruldassa et al. (2015) extracted violet pigment from liquid pineapple waste. Oil extraction from grape seed using a supercritical fluid extraction process has a manufacturing cost of about $11.93/kg of seed with a capacity of 500 L and operation duration of 300 minutes. From spent coffee bean waste, nearly 400 tonnes/year of oil was extracted by a supercritical fluid extraction process with 2 h duration under 300 bar pressure at 50 C and using 30 kg CO2/kg raw material/h. This process needs h2.4 M for manufacturing purposes and yielded a net profit of h56.6 M (Melo et al., 2014). This extraction process reduces the production cost by $235.70. In general, the raw material cost accounts for 75% of the total biolubricant production costs. To avoid this issue, waste cooking oil was used as the raw material to minimize the cost of generating biolubricants and improve the commercial affordability of bio-oil. Use of lower cost and readily available food waste in preference to more expensive complex food waste encourages cost-effective bioproduct generation in large-scale production (Kavitha et al., 2017).

8.6

Scale up and commercialization

Challenges in the process, infrastructure cost, and design of the reactor create difficulties in scaling up of technologies for chemical production from food waste. This was due to the lack of consistency in laboratory-scale extraction units and large-scale industries. At a commercial scale, the advancement of a technique to augment the process requirements

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accompanied by employing suitable approaches to incorporate various food waste treatments toward the production of good and profitable biochemical products has been considered. Commercialization of beneficial constituents originating from food waste is typically a four-step process: 1. Laboratory research procedure to recover bioproduct and function analysis of the final product by characterization; 2. Authorized patent rights attainment; 3. Pilot-scale and large-scale industrial expansion of the process; 4. Utilization in the food zone and product confirmation in the market. The investigation of extracted products was confirmed by the patented process in each case using a patent applicant name. The production method is high secretive and was not found in literature. As per the legal agreements, the main international/regional patent systems, such as Patent Cooperation Treaty (PCT), European Patent Convention (EPC), African Intellectual Property Organization, and Eurasian Patent Organization have been used. Table. 8.2 provides the commercial applications of some food wastes. Essential oils from mango peel extract were implemented in a large scale, with a market price of $7.5/kg of extract. The peel oil extracted from citrus peel has a high market price of $60
70/kg of extract. In addition, olive pomace and food waste also yield edible oils which have a similar market price. Dalian Marine Fisheries Group Co., Ltd. in Dalian applied an enzymatic process followed by centrifugal extraction to extract astaxanthin pigment from Antarctic krill fish waste. In Lorrainergies Universite of Lorraine, waste cooking oil was processed to generate biolubricants which could minimize excess oil disposal. The market value of the extract varies and depends on the quantity of product obtained and its demand.

8.7

Applications, limitations, and challenges during chemical recovery

Implementation of the extraction process to recover biochemicals from food waste at an industrial scale is troublesome due to the following: laboratorial research, preserving the optimized parameters of the extraction process, precise enlargement of pilot-scale to large-scale operations, and the obvious development of the accurate final product (Nayak and Bhushan, 2019). These conditions seem to be essential for confirming sustainable process development, profitable costs for food industries, and the constant launch of derived products in the market. The above extraction techniques appear to be more difficult in real applications than in theoretical reports (Khaw et al., 2017). Certain difficulties to be considered during biochemical recovery from FW include variations in food waste characteristics at each instance of waste generation which could impart changes to the extracted output and transportation of the collected FW from the source may lead to microbial degradation of FW biomass which also increases cost. Scale up of a biochemical generation method is mainly associated with handling of FW and shifting from a batch to a continuous process. Also, the material obtained as the outcome needs proper examination which could partially affect the product’s functionality. Hence, necessary step needs to be taken to overcome this issue in the future. Subsequently, the characteristics of the final product during examination are altered and also increase the cost. Mixing and thermal effects could also affect the value of the final product (Galanakis, 2012). These limitations can jointly cause the failure of the product. Subsequently, increment extraction costs at an industrial scale are mainly due to the high quantity of food processing required to achieve the recovered bioproduct which was obtained in the lab-scale investigation. This necessitates proper management during FW collection by preserving it in a cooler/freezer, and through the addition of chemical preservatives. Additional problematic issues include the extensive availability of diverse FW compounds at the source, which may contain unwanted compounds. This may be observed by a modified pretreatment stage. The latter usually includes a perceptive blending of by-product streams at the process origination with elementary parameter consideration and by considering the macroscopic features such as water and solids content.

8.8

Future perspectives and conclusions

This chapter has focused on the various fine chemicals and their extraction techniques adopted in FW. Thus, ideas have been provided for utilizing FW for generating biomolecules using green and safer methods with zero waste generation and enabling complete usage of FW and providing extra compensation for industries through the sale of residues from food-processing industries. This, in turn, reduces the environmental pollution due to FW dumping on land. Numerous reports about the diverse collection of bioactive chemicals from particular FW residues provided suggestions for the utilization of advanced techniques. The advanced highly sensitive measurement tools predict the metabolic activity of microbes involved in the production process. This tool may provide a better strategy for exact final

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Food Waste to Valuable Resources

TABLE 8.2 List of commercialized fine chemical products with patents. S. no.

Waste source

Name of the product obtained

Commercialized application/usage

Applicant/ company

Patent application number

References

1

Coffee spent waste

Aroma

Used in distilled beverages

University of Minho CEB (Centre of Biological Engineering) (Braga, Portugal)

PT 105346

Mussato et al. (2010)

2

Extract powder of pomegranate and cranberry

Antibiotic agent

POM cran capsules (25
5000 mg)

Mackler, Ari (POM Wonderful LLC) (2014)

US2014/0010871 A1

Mackler (2014)

3

Peels of citrus species

Aroma and essential oil

Food additive

Movaghar et al. (2013)

US20130064947 A1

Movaghar et al. (2013)

4

Pomegranate peel

Polyphenols

Treatment of prostate cancer by increasing doubling time of a prostatespecific antigen

Liker; Harley (2014)

US2014/0056930 A1

Liker (2014)

5

Mango peels

Polyphenols

Gelling agent, stabilizing agent in fruit juices, preservatives

Taboada, Evelyn., Francis Dave Siacor (2013)

WO2013141723 A1

Taboada and Siacor (2013)

6

Tomato processing waste

Lycopene

Therapeutic value

BIOLYCO Srl.

US20100055261A1

Lavecchia and Zuorro (2010)

7

Olive pomace

Polyphenols and oil

Cosmetic purposes and food additives

University of Porto

WO/2017/212450

Oliveira et al. (2017)

8

Plant food waste

Phytochemicals

Functional food ingredients

Minister of Agriculture and Agri-Food, Canada

US07943190

Mazza and Cacace (2011)

9

Food waste

Methane

Food storage and treatment system

Emerson Electric Co.

US201462017883P

Whitener (2014)

10

Food waste

Lactic acid

Biofield generator to ferment food waste

TSNT GLOBAL CO., Ltd, Daegu.

US20180016196A1

Choi (2018)

generation of bioactive chemicals in the future. Upgrading of extraction technology with less or no use of solvents will help in creating a sustainable bioprocess. The feasibility of commercializing biochemicals can be improved by predicting alternative technologies with a certain degree of flexibility. Simplification of the extraction process with a few steps makes scale-up easier and also saves cost. Without this investigation, the extracted product is doomed to failure in the market as it could not yield the benefits mentioned in research. The encapsulation techniques used in the packing of the obtained products for sale in the market require further investigation to assist in improving product functionality and shelf life. Finally, various new aspects of the emerging technology for extraction of biochemicals need to be considered. Nanotechnology implementation in the field of biochemical recovery can improve the quality and safety of products recovered from FW which could be formulated in future. The beneficiary of recovered product in market level can also be investigated in further research.

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14.

Further reading Jaime, L.C., Dalia I.S.M., Karl R.F.R., 2012. Hplc method and mixture for quantifying astaxanthin in fermented shrimp waste. Patent no: WO 2012/ 057596 Al. Jiang, Q., Song, S., Wang, H., Xia, W., Liu, J., Xu, Y., et al., 2015 Method for separating and purifying astaxanthin from antarctic krill shells. Patent no: CN103274979B. Michel, L., Abaga, A.E., Mohamed, G., 2013. Method of treatment of a used frying oil. Patent no: FR3009311A1. Naik, C., Srisevita, J.M., Shushma, K.N., Farah, N., Shilpa, A.C., Muttanna, C.D., et al., 2012. Peanut oil cake: a novel substrate for enhanced cell growth and prodigiosin production from Serratia marcescens cf-53. J. Res. Biol. 2012 (2), 549
557. Pratt, L.M., 2017. Method and apparatus for extracting oil from food waste. Patent no: US 2017/0368474 A1. Thornhill, R., Pennock, P., 2010. Extraction of oil from food wastes. Patent no. US 2010/0029965 A1.

Chapter 9

Specialty chemicals and nutraceuticals production from food industry wastes T. Poornima Devi1, S. Kavitha1, R. Yukesh Kannah1, M. Rajkumar2 and J. Rajesh Banu3 1

Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India, 2Department of Environmental Science, Bharathiyar

University, Coimbatore, India, 3Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India

9.1

Introduction

Enormous amounts of food waste by-products are generated at industrial levels which accommodate high-value bioactive compounds (Kavitha et al., 2017; Kannah et al., 2018). Multifarious studies have shown the evolution of high-value specialty products as the ultimate substrates for the recapture of functional compounds such as proteins, polysaccharides, fibers, and flavor compounds, which can be reused as nutraceuticals and functional ingredients aiming to mitigate environmental problems (Baiano, 2014). These new classes of food products have gained huge attention in the food market, and the pharmaceutical and food domains have shown significant interest in obtaining bioactive components which can be used as drugs, functional food ingredients, or nutraceuticals. Products segregated or purified from food and customarily sold in medicinal forms usually not conjoined with food, such as capsules, are referred to as nutraceuticals (Joana Gil-Cha´vez et al., 2013). Bioactives from food waste can be extracted and utilized for the development of nutraceuticals and functional foods and also possess therapeutic properties that extend from antihypertensive to antiinflammatory and encourages their use as functional foods for health purposes. Solvent extraction (SE) and extraction with supercritical fluids are the traditionally used techniques for the isolation of phenolic compounds. Choosing the appropriate extraction solvent is of paramount importance as it greatly affects the yield and extract composition. Optimizing the sample-to-solvent ratio, extraction temperature and time, agitation degree, and particle size also engenders augmentation of the extraction procedure (Banerjee et al., 2017). On the other hand, certain aspects such as a high amount of solvent, time-consuming, and difficulty in scale-up constrain conventional techniques from being used in a large-scale manner. To overcome the above limitations and with the aim of “zero waste,” present research focuses on promoting greener, sustainable, and viable extraction processes. The modern extraction techniques comprise microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), pressurized liquid extraction (e.g., pressurized hot water extraction), enzyme-assisted extraction (EAE), and other emerging techniques (Heng et al., 2017), applied alone or together with solvent use to reduce the energy and solvent requirements. This chapter chronicles the use of various techniques for the recovery of high-value specialty chemicals and nutraceuticals from food waste and also examines the opportunities and challenges in the field that hamper the broad commercial implementation of these emerging technologies. Fig. 9.1 shows a simplified view of the nutraceutical compounds recovered by applying different extraction techniques and their relative applications.

9.2

Bioactive compounds

The growth of the term nutraceuticals has led to the pursuit for natural compounds isolated from fruit and vegetable waste and as a single component with propitious health benefits that has been researched worldwide. Thereupon, the term bioactive compound is coined in current literatures to describe the nonnutritive compounds existing in foods with strong human health enhancing qualities (Biesalski et al., 2009). Indeed, these compounds serve as an alternative source of natural antioxidants. They are fundamentally present as primary and secondary metabolites of vegetable waste. Some high-value products such as phenolic compounds, carotenoids, dietary fiber (DF), vitamins, and Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00009-2 Copyright © 2020 Elsevier Inc. All rights reserved.

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FIGURE 9.1 Simplified view of the nutraceutical compounds recovered by applying different extraction techniques and their relative applications.

minerals are periodically added as natural food additives (Martins and Ferreira, 2017). Consequently, bioactive compounds exist as an exemplary source for the production of nutraceuticals, functional foods, and food additives (Joana Gil-Cha´vez et al., 2013). Fruit and vegetable waste (FVWs) embody the elementary form of functional foods as they are enriched by several bioactive compounds. The bioactive compounds recovered from FVW are rich in prophylactic and therapeutic properties and thereby are seen as health-enhancers with significant emphasis in the food, pharmaceuticals, and cosmetics industries as they increase the functional value of food waste and limit its liberation into the environment (Nasri et al., 2014; Sharma et al., 2017). Many studies based on food waste question the ubiquity of numerous bioactive compounds present in a large-scale manner with variance in residual fractions. This chapter outlines the assorted bioactive components which are seen as functional ingredients in food waste.

9.2.1 Phenolic compounds from food waste Phenolics are high-value compounds that strengthen the vitality of food waste. They are customarily portrayed as a band of secondary metabolites that render defense against UV radiation, pathogens, and other environmental factors (Koubaa et al., 2015). Phenolic compounds contain an array of molecules that possess a polyphenol structure with several hydroxyl groups on aromatic rings or else with one phenol ring, such as phenolic acids and phenolic alcohols (Ignat et al., 2011). Polyphenols have acquired growing attention due to their potential to scavenge free radicals and hamper oxidation reactions to displace synthetic preservatives (Deng et al., 2012). Polyphenols are primarily apportioned as flavonoids, phenolic acids, tannins, stilbenes, and lignans. Studies conclude that peels, seeds, and other components of FVW are relevant sources of phenolic compounds, including both phenolic acids and flavonoids (Wijngaard et al., 2012). Hence, food waste that contains phenolic compound in condensed form to a great extent typifies suitable sources of bioactive compounds which serve as an add-on in functional foods. Polyphenolic extracts for instance, resveratrol from grape pomace and olive waste, have become commercialized (Akhtar et al., 2015). Likewise, ferric reducing antioxidant power analysis has revealed that prickly pear seed extract (50 ppm) inhibited the oxidation of margarine in comparison to a control sample (Chougui et al., 2015) containing vitamin E (100 ppm). Additionally, it encompassed a composite of 16 polyphenols inclusive of hydroxyl-cinnamic acid and displayed antioxidant potency proportionate to marketed antioxidants. Numerous in vitro studies have shown that devouring polyphenols drastically reduce the risks of cardiovascular diseases by cutting in vitro oxidation of low-density lipoproteins. The therapeutic

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properties of polyphenols include antiulcer, antiinflammatory, and anticarcinogenic activities. Moreover, many polyphenols like anthocyanins are perceived as increasing the pigmentation of plant cells (Moreno-Montoro et al., 2015).

9.2.1.1 Flavonoids Flavonoids are low-molecular-weight compounds that contain 15 carbon atoms presented in a C6
C3
C6 form. Flavonoid belongs to the imperative class of bioactive compounds due to its antioxidant, anticarcinogenic, and antiinflammatory properties and also its potentiality for lipid antioxidation effects (Chen et al., 2012). The vital classification of flavonoids based on their quantities in food waste is flavonols and flavones, isoflavones, flavanones, anthocyanins and proanthocyanidins, and catechins. Flavonoids are often found as phytochemicals that help to shield plants from UV light, fungal parasites, herbivores, pathogens, and oxidative cell injury (Ignat et al., 2011). Glycosylated flavones (luteolin, apigenin, and diosmin glucosides) and polymethoxylated flavones are the main classes of flavonoids in citrus fruits. Some glycosylated flavones can be transposed as dihydrochalcones, which act as influential natural sweeteners and serve as indicators of adulteration in commercial juices (Okino Delgado and Fleuri, 2016). Also, flavonoids like hesperidin, narirutin, naringin, and eriocitrin are found in citrus waste. The prime phenolic compounds markedly present in ´ orange peel are naringin and (neo)hesperidin which are valuable components (Sharma et al., 2017). Cetkovi´ c et al. (2012) tested tomato extracts to assess the competency of phenolic antioxidants and anticancer agents inclusive of phenolic acids and flavonoids and found them to display good antioxidant properties.

9.2.1.2 Phenolic acids Phenolic acids make up about one-third of the dietary phenols that exist in free or bound forms in vegetables and are associated through ester, ether, or acetal bonds. They are divided into hydroxyl-benzoic and hydroxyl-cinnamic acids (Sova, 2012). Hydroxybenzoic acids are further subdivided into gallic, p-hydroxybenzoic, protocatechuic, vanillic, and syringic acids, whereas hydroxycinnamic acids are subdivided into caffeic, ferulic, p-coumaric, and sinapic acids. Hydroxyl-cinnamic acids (especially caffeic acid) prevail as ester derivatives (chlorogenic acid, other cinnamoyl quinic acids, phenylethanoic glycosides) in fruits and vegetables which exhibits strong antioxidant properties. Ferulic and sinapinic acids are plentiful in sour orange peel (Sharma et al., 2017). An analogous study of phenolic acids (ferulic acid, gallic acid, ellagic acid, and myricetin) from freeze-dried peels of purple star apple, yellow cashew, and red cashew has been investigated (Moo-Huchin et al., 2015). This study showed that purple star apple has the highest gallic acid content, with a concentration of 229.49 mg/100 g DW and was proved to be an exemplary source of antioxidant compounds. Also, they could be used as a functional food ingredient in the pharmaceutical and food industries. These phenolic compounds found in freeze-dried fruit peel were also detected in gac fruit peel and pomegranate fruit peel (Kubola and Siriamornpun, 2011; Middha et al., 2013). Therefore phenolic acids are potent antioxidants with proclaimed antibacterial, antiviral, anticarcinogenic, antiinflammatory, and vasodilatory qualities.

9.2.1.3 Tannins Tannins, with a molecular mass of up to 30,000 Da, are identified as secondary metabolites in fruit waste. In consonance with their structure, tannins are catalogued widely as hydrolyzable tannins and condensed tannins. Hydrolyzable tannins possess molecular mass between 500 and 5000 Da, while condensed tannins or proanthocyanidins have a molecular mass of up to 30,000 Da. Along with good astringent quality they also possess excellent antioxidant characteristics (Oroian and Escriche, 2015). They are enunciated to be endowed with antithrombotic, antiatherogenic, antimutagenic, antidiabetic, and antiproliferative effects, and also anticarcinogenic, antiinflammatory, antiviral, and antibacterial properties. The chemical configuration of exhausted coffee waste was examined by Pujol et al. (2013), and their study disclosed total polyphenols and tannins to be ,6% and ,4% of the exhausted coffee waste, respectively. Gallotannin-rich extracts of mango kernel and peel stand as a rich source of anticancer agents (Saad et al., 2012). Sung et al. (2012) analyzed the antibacterial and antioxidant activities of tannins extricated from agricultural by-products including green tea waste and acorn, chestnut, and persimmon hulls. The results illustrated that green tea waste displayed strong antibacterial and antioxidant activities compared with other agricultural by-products.

9.2.1.4 Stilbenes and lignans Stilbenes are phenolic compounds that enclose two aromatic rings linked by an ethylene bridge, and occur in monomeric and oligomeric forms. Resveratrol is an important stilbene which originates in the vinification process and is obtained in cis and trans isomeric forms, particularly in glycosylated forms. It has been identified in about 70 plant

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species, including grapes, berries, and peanuts (Ignat et al., 2011). Small amounts of stilbenes are usually found in the human diet as an efficient antioxidant and antimicrobial agent. Casas et al. (2010) discovered that resveratrol, an eminent bioactive compound observed in grape by-products (such as seed, stem, skin, and pomace)n was skillfully recovered using supercritical CO2. Lignans are a class of phenolic compound that are organized as C6
C3 units (a propyl benzene framework) coming from a cinnamyl unit (Oroian and Escriche, 2015). They are widely present in FVW. Lignans and their synthetic derivatives have received huge attention by virtue of their prominent applicability in cancer chemotherapy and heterogeneous pharmacological effects (Landete, 2012).

9.2.2 Carotenoids Carotenoids are natural and fat-soluble pigments extensively exploited in the food industry as a colorant. Taking into consideration their proficiency in oxygen fixation, they are branched as carotenes (b-carotene and lycopene) and xanthophylls (astaxanthin, b-cryptoxanthin, canthaxanthin, capsanthincapsorubin, fucoxanthin, lutein, and zeaxanthin) (Martins and Ferreira, 2017). Carotenoids are available in distinctive colors, such as red to orange and even yellow, and are broadly infused in many foodstuffs as food additives. In addition, they are also comprised of a nutritional fraction which appears to be the precursors of fundamental vitamins, including vitamin A (Maria et al., 2015). A preponderant level of carotenoid is disseminated along the exterior of the fruit tissues (peel) and seeds. The carotenoid content of mango peel was remarkably superior to that observed in fresh and powder samples (3337 and 3092 mg/g, respectively) (Ajila et al., 2010). Papaioannou and Karabelas. (2012) investigated carotene production using Blakeslea trispora, a heterothallic fungus, on solid agro-food wastes such as cabbage, watermelon husk, and peach peel. The study results illustrated a carotenoid yield of 76% in all the wastes tested. Lycopene which is found in the carotenoid assemblage is present in huge quantities in tomatoes and has shown value as a cancer-fighting compound (O’Shea et al., 2012). Benakmoum et al. (2008) explored the carotenoid effect (inclusive of lycopene) on industrial tomato wastes (namely, tomato puree and tomato peel) for the enrichment of edible oils (refined olive oil, extra virgin oil, refined sunflower oil, etc.). The study showed that the addition of tomato peel improved the b-carotene and lycopene levels more than tomato puree. Nonetheless, integration of both tomato peel and puree improved the thermal stability of edible oils used in the study. In recent times, numerous carotenoids, like astaxanthin and lycopene, have been universally utilized as nutraceutical by-products. As a matter of fact, carotenoids are used extensively owing to their therapeutic effects, notably as immune-modulatory agents, and also in reducing cancer and cardiovascular disease risk and working as antioxidants (Kumar et al., 2012; Strati et al., 2015). Furthermore, numerous authors have assessed the expediency of carotenoids elicited from wastes and by-products utilized as food additives in foodstuffs in boosting their nutritional qualities without losing their cooking, textural, and sensory characteristics (Ajila et al., 2010). Along these lines, carotenoid recovery from food industrial wastes has paramount biological and health-promoting benefits. Additionally, carotenoid embodiment in various foodstuffs increases the nutritional content and with their chemical immobility create an alternate opportunity in the evolution of contemporary functional foods (Martins and Ferreira, 2017).

9.2.3 Bioactive peptides Protein-enriched food waste materials act as forerunners for bioactive peptide production, heightening their value in the food and pharmaceuticals industries. Bioactive peptides gamut 3
20 amino acid entity and their bioactivity hinges on their amino acid configuration and position amongst amino acids chain that stems out the peptide. Disparate in vitro and in vivo studies describe a spectrum of pharmacological properties that bioactive peptides possess, from antihypertensive to antiinflammatory. In a study by Lemes et al. (2016) bioactive peptides were proclaimed as rejuvenated biologically active regulators that counteract oxidation and microbial deterioration in food waste, and were thereby integrated into value-added products which was found to be advantageous in therapeutic treatments. Also, the antioxidant effect of bioactive peptides in food waste reduces lipid oxidation and its cognate by-products aid in upholding the organoleptic properties during food storage, while also reducing the oxidative stress effect in humans (Power et al., 2013). The existence of amino acids such as histidine, proline, tyrosine, methionine, and cysteine in bioactive peptides facilitated the destruction of metal ions and reactive oxygen species and, thus, acts as an antioxidant (Sarmadi and Ismail, 2010). A look at bioactive compounds such as segregation of vicilin-like protein from watermelon seeds (Wani et al., 2008), leptin from jackfruit seeds (Devalaraja et al., 2011), or proteolytic enzyme actinidin from kiwi fruit seeds (Boland, 2013) illustrates the bioavailability in food waste. Recovery of bioactive peptides from cherry waste illustrated antioxidant and antihypertensive properties, and also protein content in these seeds was around 39% of the dried and

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defatted seed (Garcı´a et al., 2015). Correspondingly, fish and shellfish waste by-products are creditable sources of bioactive peptides due to their immense protein level, at around 10%
23% (w/w) (Harnedy and FitzGerald, 2012). In a study by Robert et al. (2014) hydrolysates of white shrimp (Litopenaeus vannamei) by-products transacted by Protamex enzymes at 50 C led to the recovery of bioactive peptides with antibacterial activity. Hence, the evolution of performable techniques for the substantial recovery and purification of peptides elevates their appropriateness for use in the pharmaceutical and food industries.

9.2.4 Dietary fiber DF is a part of bioactive compounds which is resistant to hydrolysis by human digestive enzymes. It is subdivided into soluble dietary fiber (SDF) and insoluble dietary fiber (IDF). The SDF/IDF ratio is a crucial aspect as it illustrates both dietary and functional properties. IDF is constituted from cellulose, hemicellulose, or chitin, while SDF is composed of pectins, b-glucans, gums, mucilage, oligosaccharides, or inulin. Among other things, a finest nutritional property is espied when SDF/IDF ratio is around 1. Furthermore several literatures ascertain that citrus fruits comprise an SDF/IDF ratio of about 1:5, which has different ramifications for the liability for the evolution of chronic diseases (Sharoba et al., 2013). In addition to their nutritional benefits, DFs are positive owing to their functional and technological qualities, such as water-holding capacity, oil-holding capacity, glucose retardation index, swelling capacity, viscosity, gelforming capacity, texture, and chelating capacity. These qualities earmark DF as an integral component in the food industry (Martı´nez et al., 2012). Garcı´a Herrera et al. (2010) analyzed tomato peel with about 80% of total dietary fiber content being IDF. Likewise, the addition of DF to reformed food products enhances the textural, rheological, nutritional, and sensory qualities (Sharma et al., 2016). A study by de Moraes Crizel et al. (2013) used orange fibers as an eminent equivalent as a fat replacer component in ice cream, reducing the fat content by about 70%, without changes to color, odor, and texture. Similarly to this study, Sharoba et al. (2013) used orange waste, carrot pomace, potato peel, and green pea peel as grist to produce dietary fiber powders for cakes. In addition to the above, acting as an antioxidant is another important quality of DF that undoubtedly dispenses health effects associated with DF and dietary antioxidants. Fractional swapping of wheat flour with 5% watermelon rind or Sharlyn melon peel powders to create a cake batter proved to be an excellent antioxidant and strengthened the shelf-life of the cake (Al-Sayed and Ahmed, 2013).

9.3

Biosurfactants

Biosurfactants (BSs) are amphiphilic molecules composed of hydrophobic and hydrophilic remnants. They can be extracted from food waste such as FVW by biological means using microbes (Kavitha et al., 2015). These BSs pare down the surface and interfacial tension, thereby increasing solubility. They are commercially available as emulsifiers, demulsifiers, and food additives, and are employed in the cosmetics, pharmaceuticals, and food industries (Chen et al., 2018). In line with their molecular weights, they are categorized as low-molecular-mass BS inclusive of phospholipids, glycolipids, and lipopeptides, and high-molecular-mass BS comprising amphipathic polysaccharides, proteins, and lipoproteins (Banu et al., 2018). BSs in reference to chemosynthetic surfactants (Devi et al., 2014) have garnered wide attention by virtue of their limited toxicity, efficient biodegradability, and biocompatibility, in addition to their use at extreme conditions of temperature, pH, and salinity. Also they are widely found due to their efficient production from renewable resources (used frying oil, vegetable and fruit processing wastes, etc.) via microbial fermentation (Kaur et al., 2015). Rhamnolipid BS, a division of glycolipid BS, with exemplary surface activity has been widely used recently (Kavitha et al., 2019). Among the various substrates (orange peel, carrot peel, lime peel, coconut oil cake, and banana waste) employed for fermentative production of rhamnolipid BS from Pseudomonas aeruginosa MTCC 2297, orange peel was found to be the best substrate with 9.18 g/L of rhamnolipid BS production (George and Jayachandran, 2009). Rhamnolipid BS production from waste cooking oil fomented using a bacterium, Pseudomonas SWP-4, displayed exquisite physicochemical properties in terms of surface activity and stability measurements (Lan et al., 2015). In a study by Patowary et al. (2016) paneer whey waste was used as a substrate medium for rhamnolipid BS production, and proved to be effective, with prodigious pharmaceuticals applications. Chooklin et al. (2014) utilized banana peel as substrate for lipopeptide BS production by Halobacteriaceae archaeon AS65, which resulted in high abatement in surface tension and a low critical micelle concentration value, along with thermal and pH stability. Also, the recovered BS was found to be a potent antimicrobial and therapeutic agent. Aside from its implicit surface active property, BS has also been delineated as antimicrobial and antibiofilm agent, finding use as an adaptable functional food additive in the food industry.

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9.4

Fermentation methods

Fermentation is a primeval technology which uses the recovery and transfiguration of food waste by-products for nutraceutical and functional food compound production with the assistance of microorganisms. Various nutrient-encumbered food wastes are created from dairy, fruit, brewery, bakery, and fishery industries, and are exemplified as substrates for the diverse microorganisms being used in the fermentation process. Fermentation is generally differentiated into solidstate and submerged/liquid fermentation. Recently solid-state fermentation (SSF) has been illustrated as a better process than submerged fermentation (SMF) for bioactive compounds acquisition from food waste as it results in greater yield and superior quality of recovered compounds. In SSF, microbial growth on solid substrates is deprived of the liquid content, whereas in SMF microbial growth occurs in a liquid medium (Lasrado and Rai, 2018). The choice of suitable substrates and microorganisms plays a crucial role in the efficacious recovery of high-value compounds (Martins et al., 2011). SSF of apple pomace using Phanerocheate chrysosporium enhanced the polyphenolic compound yield, thereby elevating the nutraceutical value (Ajila et al., 2011). Aguilar et al. (2008) used pomegranate husk as a substrate and extracted ellagic acid by SSF with Aspergillus niger GH1. In another study, lycopene recovery by SSF using tomato waste as substrate was successfully done by Parveen et al. (2016). Lately, lactic acid fermentation (LAF) has also received wide attention for nutraceuticals recovery from various food wastes. Augmented recovery of bioactive protein hydrolysate, such as lipid and protein, by LAF using freshwater fish head waste was carried out by Ruthu Murthy et al. (2014). Along these lines, nutrient tapping of food waste by fermentation is a profound medium to extract several bioactive compounds for use in the food industries.

9.5

Various extraction techniques for nutraceuticals recovery

Recently, various technologies have helped diverse food industries to recover nutraceuticals efficaciously in a sustainable manner with minimal energy consumption, thus replacing conventional heat-based processing methods. As described in various literatures, extraction is a vital step in the isolation and recovery of high-value compounds, in particular phenolic compounds in which many technologies have been gauged toward the recovery of targeted compounds. Nonetheless, the extraction conditions play a highly vital role due to their effect on the release of by-products from the matrix into the medium (Casazza et al., 2010). SE is an extensively applied technique to extract bioactive compounds and is primarily based on a heating process that expedites the mass transfer amidst different phases of the system, thereby consuming abundant energy and resulting in deterioration of the thermolabile compounds (Barba et al., 2016). Innovative technologies such as pulsed electric fields (PEFs), ultrasounds, and high-pressure processing, are being investigated to reduce this problem to meet the requirements of a green extraction concept (Galanakis, 2013). This chapter scrutinizes the different innovative technologies that are in existence to recover nutraceutical compounds from food waste, as presented in Table 9.1.

9.5.1 Solvent extraction technique SE works on the principle of mass transfer where the extraction of substances enclosed in a matrix occurs when they are brought into contact with a solvent or mixed together. SE, depending upon the biomass characteristics, may be liquid
liquid extraction or solid
liquid extraction. Generally samples are centrifuged and exuded to eliminate the solid residue and are used as additives, food supplements, or for the preparation of functional foods (Zulkifli et al., 2012). The choice of extraction solvent is a decisive factor in the extraction process. The typical solvents used for extraction are acidified methanol or ethanol. Many studies have confirmed the potency of various solvents for the extraction and recovery of antioxidant compounds, and ethanol transcends other compounds such as water, acetone, hexane, ethyl acetate, and methanol (Hidalgo and Almajano, 2017). In a study on anthocyanin extractions from grape pulp (Castan˜edaOvando et al., 2009), methanol (20% and 73%) was found to be competent for ethanol and water extraction. Thus, on the grounds of toxicity, ethanol is favored in comparison to methanol in the food industry. This was further substantiated by Bandar et al. (2013), where among the various organic solvents used in their study, ethanol was found to be effective while extracting bioactive compounds such as hexane and generated the highest extraction yield. An increase in SE yield was also discovered, with a rise in extraction time. In a corelative study by Strati and Oreopoulou (2011) ethyl lactate gave the highest carotenoid yield which was increased with the extraction time. the extraction efficiency is known to be a function of the process conditions. A few factors that cloud the concentration of the extract components are temperature, liquid
solid ratio, flow rate, and particle size (Ignat et al., 2011).

TABLE 9.1 Extraction techniques used in the recovery of nutraceuticals and functional food ingredients and their beneficial applications. Food waste source

Compounds extracted

Bioactivity/applications

Blueberry wine pomace

Anthocyanins; phenolics

Grape pomace

Pectin

Penggan peel

Hesperidin

Has antioxidant, antiinflammatory, and antiallergic properties

Satsuma peels

Flavonoids

Antioxidant and anticancer agent

Mango seeds

Tannins; proanthocyanidins

Grape skins

Anthocyanins

Grape pomace

Polyphenols

Natural preservatives, anticancer agents

Extraction technique used UAE

Advantages

G G G

Used as gelling agents in food industry; food additive

G G

MAE

G G

Has antithrombotic, antiatherogenic antimutagenic, antidiabetic, and antiproliferative properties

G G G

Limitations

High extraction yield Low solvent usage Minimal extraction time Simple, inexpensive Prevent thermal damage to extracts

G

Low solvent use Low energy Higher yield efficiency Reduced extraction time Better quality of extracts

G

Low extraction time and energy cost Improved extraction yield

G

Optimization of parameters such as ultrasound frequency and power input is required for higher yield

References

Chemat et al. (2011) He et al. (2016) Ma et al. (2008)

G

Poor extraction yield for nonpolar compounds High temperature causes degradation of heat-sensitive bioactive compounds

Dorta et al. (2013)

Process parameters, energy inputs, treatment temperature, field strength are required to be maintained

Barba et al. (2016)

Liazid et al. (2011)

Has antioxidant and anticarcinogenic effects Has anticarcinogenicity, antimutagenicity, antiallergenicity, and antiaging properties

Grape pomace

Anthocyanins

Orange peel

Hesperidin

Has antioxidant, antiinflammatory, and antiallergic properties

Onion skin (by-product)

Quercetin

Possesses anticancer, antivirus, and antiinflammatory properties

Grape skins

Anthocyanins

Used as an antioxidant and natural food colorant

Mango peel

Phenolic compound

PEF

G

G

Used as an anticancer agent

Used as an antioxidant

El Kantar et al. (2018) Parniakov et al. (2014)

SCW

G

Less expensive operation, environmentally friendly, lower working temperatures

G

More laborious and time-consuming method

Bleve et al. (2008) He et al. (2012) Ko et al. (2011) Tunchaiyaphum et al. (2013)

Found to be advantageous against cancer and diabetes (Continued )

TABLE 9.1 (Continued) Food waste source

Compounds extracted

Bioactivity/applications

Extraction technique used

Possesses antioxidant and antimicrobial properties

SFE

Grape seeds, stems, skin, and pomace

Resveratrol

Tomato waste

Lycopene

Has defensive effect against cardiovascular, coronary, heart diseases, and cancer

Apple pomace

Total phenolics

Possesses antioxidant property

Banana peels

Total phenols; anthocyanins

Used as antioxidant compounds in food industry

Eggplant peel

Anthocyanins

Has antioxidant property; food colorant

Flax seeds

Lignans

Used as a fat substituent; has an antiobesity effect

Grape skins

Polyphenols

Possesses antibacterial, anticarcinogenic, antiviral, and antiinflammatory properties

Advantages

G

G

SE

G G

Orange peel

Carotene

Grape skins

Flavonoids

Tomato waste

Lycopene

Has antioxidant, antiatherogenic, antiinflammatory, immunomodulatory effects

Apple pomace

Pectin

Has anticancer property; used as fillers in confectionery and dietary fiber supplement

Nontoxic, environmentally friendly, nonflammable Supercritical fluids have a superior selectivity

G

Inexpensive Performed using feasible and simple equipment

G

References

Limited ability to dissolve polar compounds; more parameters to optimize

Casas et al. (2010)

Low selectivity, low extraction efficiency

Gonza´lezMontelongo et al. (2010)

Machmudah et al. (2012)

Sainvitu et al. (2012) Todaro et al. (2009)

HHPE

G G G

Used in treating cancer and cardiovascular diseases and has an immune-modulatory effect Used as an antioxidant and anticancer agent

Limitations

EAE

G G G

Shorter extraction time Energy-saving process Extraction of nonpolar compounds is possible

G

High extraction yield Eco-friendly Moderate extraction conditions

G

G

High investment cost Complex material handling

Casazza et al. (2012) Parniakov et al. (2014)

G

High enzyme cost Longer extraction time

Cheng et al. (2015) Oroian and Escriche (2015) Tomaz et al. (2016)

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FIGURE 9.2 Schematic representation of (A) solvent extraction and (B) microwave-assisted extraction.

Elevated temperatures aided in the extraction in view of the higher diffusion coefficient. Galanakis et al. (2010) scrutinized the influence of temperature on total phenol and anthocyanin extraction from olive waste using ethanolic extraction at diverse temperatures, such as 25 C, 50 C, 60 C, and 85 C. Fig. 9.2 shows a schematic representation of SE. Also, hydroxycinnamic acids and flavonol concentrations of the extracts abated with increasing temperature despite minimal differences. In view of its low processing cost and ease of operation, SE was found to be advantageous in comparison with other methods. Despite the above facts, use of large amounts of toxic solvents, requirement for evaporation/concentration steps for recovery and extended time are detrimental in the extraction process. Likewise, high temperatures of solvents with long extraction times probably lead to the thermal degradation of natural bioactive components which cannot be averted (Kumar et al., 2017).

9.5.2 Microwave-assisted extraction MAE is an extraction technique that uses simplified manipulation, abridged extraction time, and reduces solvent volume and has a lower energy input without reducing the extraction yield of the intended compound (Kavitha et al., 2018; Banu et al., 2018). Fig. 9.2 shows a schematic representation of MAE. Along these lines, electromagnetic energy, in the frequency range of 300 MHz
300 GHz, disseminates heat following ionic conduction and dipole rotation. Symbiotic synthesis of mass and heat transfer acting in the same direction illustrates the stimulation of extraction rates (Mason et al., 2011). The elements that affect MAE are choice of solvent, ratio of solvent to material, irradiation temperature, irradiation time, microwave power, and nature of the matrix. Correspondingly, amplified power and contraction in microwave irradiation time increases the degradation of thermolabile components. Liazid et al. (2011) examined MAE of anthocyanins from grape skins and achieved an evident reduction in the extraction time from 5 h to 5 min compared to a traditional solid
liquid extraction method. Prakash Maran et al. (2014) validated the maximal pectin yield from waste Citrullus lanatus fruit rind (25.79%) under optimum MAE conditions with a microwave power of 477 W, irradiation time of 128 s, pH of 1.52, and solid
liquid ratio of 1:20.3 g/mL. The results of the study by Pedroza et al. (2015) revealed that phenolics extraction from dehydrated waste grape skins pretreated by MAE was a feasible choice for SLE because of the contingency of reaching the extraction time precisely. Also, MAE can be branched out as solvent-free microwave extraction

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(SFME) and microwave hydrodiffusion and gravity (MHG), and is performed at atmospheric pressure. SFME hinges on the amalgamation of microwave heating and dry distillation, which forbids solvent addition (Michel et al., 2011). In MHG, mass transfer escalates in the course of microwave extraction since higher penetration capacity subsequently causes cell disruption and is habitually used for polyphenol extraction. Also, MHG is a cost-effective, efficacious, and ecofriendly extraction method which uses limited energy and has no solvent requirement (Chemat et al., 2008).

9.5.3 Enzyme-assisted extraction EAE has garnered wide attention because hydrolytic enzymes rupture the structural integrity of cell walls, revealing the intracellular materials and thus intensifying the yield extraction of bioactive compounds (Kavitha et al., 2013). Enzyme pretreatment by SE is described as EAE (Kavitha et al., 2014). The designated enzymes can either scale down the solvent volume essential for extraction, or maximize the yield of extractable compounds (Oroian and Escriche, 2015). Hydrolytic enzymes such as cellulase, pectinase, hemicellulase, and glucosidase are broadly used in EAE and have been used to increase the extraction efficacy for antioxidants including phenolics, flavonoids, anthocyanins, and carotenoids (Tomaz et al., 2016). The crucial factors that leverage the extraction efficacy are the category of enzymes, concentration, pH, incubation temperature, incubation time, liquid to solid ratio, and particle size (Liu et al., 2016). Mushtaq et al. (2015) illustrated phenolic compound extraction using EAE from watermelon rind using a mixture of pectinase, protease, amylase, and glycosidase. Under optimum conditions (2.24% enzyme concentration, 6.58 pH, 51.8 C, 30 min) the study concluded that optimized EAE increased the ejection of antioxidant phenolic up to threefold in comparison with the usual SE. Likewise, phenolic compound extraction from grape waste was explored by Go´mezGarcı´a et al. (2012) by adopting enzymes such as celluclast, pectinex, and novoferm by EAE and it was found that novoferm had a robust effect on phenolic release. Additionally, these authors showed EAE to be an expedient option to recover bioactive compounds from agro-industrial by-products. Aside from the above facts, high enzyme cost and divergence in enzyme actions owing to environmental factors such as temperature and nutrient feasibility create possibilities for use of EAE on an industrial scale. Lately, integration of EAE with ultrasound, microwave, and high hydrostatic pressure extraction (HHPE) has evolved in improving the extraction yield. EAE combined with a high hydrostatic pressure (HPP) technique was investigated by Park et al. (2016) for siphoning tricin (flavonoid) from rice hull. The results showed that 0.5% cellulase-assisted hydrolysis applied as a preliminary step increased the tricin yield by twice that obtained by SE. Zhang et al. (2013) used microwave-assisted enzyme extraction as a cogent and eco-friendly technique, and polyphenols recovered from peanut shells have vital antioxidant and antibacterial activities when used as an imperative source of antioxidants and preservatives.

9.5.4 Supercritical fluid extraction Recovery of high-added value compounds using supercritical fluid extraction (SFE) has been probed extensively in the interest of the purity of extracts. Fig. 9.3 shows a schematic representation of SFE. SFE can be employed as an environmentally conducive alternative in comparison to the conventional organic SE technique. SFE utilizes fluids in their supercritical states in contrast to the normal SE technique. Above a critical point, surging of temperature/pressure creates supercritical fluids (Rosello´-Soto et al., 2015). Excellent transit properties which augment the solvent’s competency for the recovery of valuable compounds are claimed (Oroian and Escriche, 2015). SFE is thus recapitulated as close to the critical point, the transition of solvent properties occurs expeditiously with little disparity in pressure. Carbon dioxide (CO2) is the predominantly used supercritical fluid by virtue of its availability, low toxicity, nonflammability, lower cost compared with liquid organic solvents, compatible solvent properties, and conformable critical temperature and pressure which enable amelioration in mass transfer (He et al., 2012). Furthermore, the extraction processes using supercritical CO2 transpire in the absence of light and air, curtailing the degradation reactions that eventuate during conventional extraction techniques (Bleve et al., 2008). In a study by Machmudah et al. (2012), extraction using supercritical CO2 from tomato peel by-product incorporating tomato seed bolstered the yield of lycopene extraction. Jung et al. (2012) analyzed the extraction of oil from wheat bran (a rich source of antioxidants) using supercritical CO2 and Soxhlet extraction. It was ascertained that oil procured by supercritical CO2 extraction had greater resistance against oxidation and improved radical scavenging activity. Considering the nonpolar nature of CO2, it is typically blended with organic cosolvents such as ethanol, methanol, acetone, chloroform, and water, which are also called modifiers. These solvents accruals the solvating power of CO2 and hence inflating the derivability of polyphenols (Barba et al., 2016). Extraction of phenolic compounds from black walnut (Juglans nigra) husks was demonstrated by Wenzel et al. (2017) using supercritical CO2 (68 C)with an ethanol modifier (20%), which was accomplished under optimal extraction conditions.

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FIGURE 9.3 Schematic representation of supercritical fluid extraction.

9.5.5 Subcritical water extraction Subcritical water (SCW) extraction is a burgeoning environment-friendly technology for the recovery of value-added product from food waste. Fig. 9.4 shows a schematic representation of subcritical fluid extraction. SCW is found to be advantageous compared to conventional techniques due to assorted factors such as superior extract quality, reduced extraction time, cost-effective extracting agent, and an eco-friendly technique. SCW is delineated as the water that sustains its liquid state at temperature surpasses the boiling point (100 C) under sufficient pressure enforced in the process. Water is considered to be subcritical in the range from 100 C at 0.10 MPa to 374 C at 22 MPa and is also called superheated water or pressurized hot water (Tunchaiyaphum et al., 2013). Under these conditions, variations in the physicochemical properties of the water result in a downturn of dielectric constant making it act as a solvent with hydrophobic characteristics and also the ionic product of water upsurges at increasing temperatures (Yoswathana and Eshtiaghi, 2013). On the other hand, when the temperature and pressure are circumscribed within the subcritical range, nonpolar compounds can also be siphoned out. SCW has remarkable mass transfer properties resulting in a high diffusivity that consequently enhances the extraction efficiency. There is no environmental impact associated with SCW, in contrast to organic solvents (Guo et al., 2014). Tunchaiyaphum et al. (2013) extracted a larger amount of phenolic compounds from mango peel using SCW which outperformed the Soxhlet extraction technique used in the same study. Likewise, Mayanga-Torres et al. (2017) employed two abundant coffee waste residues (powder and defatted cake) for recovery of total phenolic compounds adopting SCW under semicontinuous flow conditions. The highest amount of total phenolic compounds (26.64 mg GAE/g coffee powder) was recovered at 200 C and 22.5 MPa. The results of the study by Aliakbarian et al. (2012) demonstrated that SCW extraction was found to be efficient for the recovery of phenolic compounds from grape pomace. SCW is found adept for phenolic compound extraction from pomegranate seed residues (He et al., 2012) and other phenolic compounds from potato peel (Singh and Saldan˜a, 2011) and flavanones from citrus peel (Cheigh et al., 2012). The SCW extraction process was constituted to be productive as an organic solvent and aqueousbased system at atmospheric pressure for antioxidant recovery. In this technique, avoidance of an organic solvent engenders a product free of residual solvent which makes it favorable for the production of functional foods and nutraceuticals.

9.5.6 Ultrasound-assisted extraction UAE is a growing extraction technique as a plausible option to conventional methods to enhance the extraction of polyphenols, flavonoids, flavonols, sugars, minerals, and carotenoids (Casazza et al., 2010). Fig. 9.5 shows a schematic

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FIGURE 9.4 Schematic representation of subcritical fluid extraction.

representation of UAE. UAE is based on the cavitational phenomenon that stimulates mass transfer by cell wall disruption (Gayathri et al., 2015; Packyam et al., 2015; Kavitha et al., 2018). UAE is used as a stand-alone process or embodied with other techniques for the recovery of high-value compounds. In conjunction with the above facts, the oxidative energy of radicals generated during sonolysis of the solvent culminated in a high extractive power (Chemat et al., 2011). UAE is beneficial in terms of economical and practical areas which incorporate shortened extraction times, reduced solvent volume, a comprehensive increase in the extraction rate, improved extract quality, and enrichment of the aqueous extraction processes, which implies no solvents and increased extraction of heat-sensitive compounds which would usually have little yield (Deng et al., 2015). UAE was examined by Garcia-Castello et al. (2015) for flavonoid extraction from grapefruit waste and ascertained to be as effective as conventional SE and harbored greater extraction yields at lower temperatures and extraction times. In addition, an increment in the polyphenol yield from pomegranate peel was confirmed by applying continuous and pulsed-UAE (20 kHz/2.4
59.2 W/25 C/2
90 min) (Pan et al., 2011) and eventualized energy savings of up to 50% in a continuous ultrasound treatment. Furthermore, SFC extraction and the UAE effect on total carotenoid and lutein recovery from tropical agro-industrial wastes (auyama, cabbage, and lettuce) have been examined (Alzate et al., 2013). This study disclosed an increase in total carotenoid content after applying UAE at optimized conditions (25 kHz/300 W/40 C/60 min), which illustrates a synergistic effect of the two processes. A study into optimizing crude polysaccharide extraction utilizing UAE from Nephelium lappaceum L. fruit peel using factors such as LS ratio, ultrasonic power, extraction temperature, and extraction time authenticated it as being profitable at an industrial level (Maran and Priya, 2014).

9.5.7 Pulsed electric field Exploring different techniques is of paramount importance to phase out the toxic solvent requirement which results in a reduced operational time and energy, additionally boosting extraction yields. Fig. 9.5 shows a schematic representation of PEF-assisted extraction. PEF treatment is a propitious nonthermal technique on the grounds of immense adaptability, shortened treatment times, and minimal heating effects for the recovery of highly valuable compounds from food waste (Galanakis, 2012; Koubaa et al., 2015). This technique entails high-tension electric pulse (up to 70 kV/cm) release for a few microseconds on a material placed between two electrodes (Deng et al., 2015), which instigates breakage of the cell wall, engendering the formation of temporary (reversible) or permanent (irreversible) pores, called

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FIGURE 9.5 Schematic representation of (A) ultrasound-assisted extraction, (B) pulsed electric field extraction, and (C) high hydrostatic pressure extraction.

“electroporation.” PEF reinforces mass transfer rates by fostering tissue softness, inducing textural properties, and electroporation of vegetable waste (Donsı` et al., 2010). PEF competence depends on the process parameters, which are epitomized by the electric field intensity, specific energy inlet, and number of pulses, temperature, and material property to be dealt with (Oroian and Escriche, 2015). Therefore PEF is seen as a measurable technique in food and pharmaceutical industries to recover compounds vulnerable to heat, for instance, anthocyanins, chlorophyll, and carotenoids. The electric field vitality is an influential parameter that impacts the extraction of recoverable compounds. Parniakov et al. (2016) analyzed the expediency of PEF and high-voltage electrical discharge treatment integrated with hot water extraction at mild temperatures for the reclamation of antioxidant compounds, notably total phenolic compounds (1400%), and proteins from mango peel. The outcome of this study confirmed PEF 1 supplementary aqueous extraction (SAE) and UAE 1 SAE as more beneficial than traditional methods for colorant recovery from peels and pulps of opuntia stricta fruit. PEFs were more lucrative than UAE due to low energy consumption. In addition, SEM images illustrated PEF ability to actuate cell wall permeability, which eases the recovery of the proposed intracellular valuable compounds (Koubaa et al., 2016).

9.5.8 High hydrostatic pressure extraction HHPE is an innovative nonthermal technique that increases the mass transfer rate while shortening the extraction time and elevating the process efficiency (Ignat et al., 2011). Fig. 9.5 shows a schematic representation of HHPE. HHPE strengthens the mass transfer rates by mending the concentration gradient and diffusivity, which enhances the cell permeability causing an increase in the infiltration of the extraction solvent into the cells. This leads to a reduction in the processing time, and is cost-effective and has a higher extraction yield. Certain factors that have an impact on HHPE are pressure, time, temperature, solvent types, and liquid/solid ratio (Huang et al., 2013). In recent times, HHPE has been used to retrieve bioactive compounds such as anthocyanins from grape by-products (pomace, skin, seeds) (Corrales et al., 2009), pectin from orange peel (Guo et al., 2012), and cartenoids and lycopene from tomato waste (Strati and Oreopoulou, 2014). EAE and HHPE of carotenoids, especially lycopene, from tomato waste were tested using various organic solvents (Strati and Oreopoulou, 2014). The results show that HHPE gave greater extraction yields (from 2% to 64%) in comparison to conventional SE operated at ambient pressure for 30 min. HHPE was used to recover anthocyanins from grape skin at 600 MPa and

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70 C and the results were reviewed with hot water, UAE, and PEF extraction efficiency (Corrales et al., 2009). A higher anthocyanin content of 11.21 mg/g DW was obtained in HHPE as to hot water. Antioxidant activity also saw an evident surge by 1.7 times that for UAE, and 3 times that of hot water extraction. Guo et al. (2012) proclaimed HHPE as a dynamic, cost-effective, and eco-friendly technique for pectin extraction from navel orange peel, similar to divergent extraction techniques, and showed that viscous properties and pectin stability at steady-state conditions by HHPE were superior to those obtained by heating extraction and MAE. In contrast, the competency of high pressure/high temperature (HPHT) to recover phenolic compounds from grape by-products was calculated by Casazza et al. (2010). HPHT’s capacity to recover phenolic compounds from grape skins was also tested by Casazza et al. (2012). The results illustrated that apical total phenolic compound (60.7 mg GAE) and total flavonoid (15.1 mg CE) yields were observed at 150 C during 270 and 15 min, respectively, and it also validated that polyphenol extracts were enriched with high antiradical content.

9.6 Potential applications of food waste-derived nutraceuticals in the food, pharmaceuticals, and cosmeceuticals industries Nutraceuticals and functional food additives are consumed for their health benefits, reducing the disease liability and so reducing healthcare costs (Joana Gil-Cha´vez et al., 2013). FVWs comprising peels, stems, seeds, kernels, shells, and bran are potential sources of functional food and nutraceutical components owing to their beneficial nutritional and rheological properties (Socaci et al., 2017). These wastes are enriched with bioactive compounds such as fibers, phenolic compounds, carotenoids, and other antioxidants which have salubrious effects on human health and also at reduced industrial cost, making them an influential source for use as food additives in the food industry, thereby increasing the nutritional value and extending the shelf-life, including the sensory characteristics, of foods (Martins and Ferreira, 2017). In light of the above facts, an insight into the possible applications of food waste by-products in food, pharmaceuticals, and cosmeceuticals industries is described in the following sections.

9.6.1 Use as food additives Food additives which are obtained from assorted food wastes, such as citric/exotic FVW, peels, and seeds, contain an enormous amount of bioactive components like bioactive peptides, polysaccharides, carotenoids, and phenolic compounds that are employed as antioxidants, antimicrobials, colorants, flavorings, and thickener agents in the food industry. Onion by-products, particularly onion peel and stems, are considered as an appropriate food additives considering their antioxidant and antibrowning properties (Rolda´n et al., 2008). Also, different studies have speculated on the lucrative addition of food waste extracts to bakery, dairy, and meat products to increase the performance of foodstuffs. Plus, integration of dietary fiber-rich food by-products by partially replacing flour, fat, or sugar in food stuff aids as noncaloric bulking agents, which boosts the emulsion stability (Elleuch et al., 2011). Incorporation of mango peel powder in macaroni and bakery products (like biscuits) was found to maximize the utility and antioxidant value (Caleja et al., 2017). Guava peel flour exploited as a fractional fat replacer component for wheat flour during cookies preparation was found to increase its nutrition quality without altering its sensory characteristics like color, aroma, and taste, and also function as antioxidant and antimicrobial components (Bertagnolli et al., 2014). On the other hand, FVWs serve as an excellent source of natural colorants, and include yellow-orange-red carotenoids, red-blue-purple anthocyanins, and red betanins. Lycopene, a carotenoid pigment from tomato peel, has been ratified as a natural colorant and employed as a coloring agent for dairy products such as butter and ice cream, and retains its stable reddish color up to 4 months (Rizk et al., 2014). By-products of citrus fruits (like peel and seed powders) are envisioned to be feasible sources of texturizing agents in view of their high pectin content and dietary fiber (Sundar Raj et al., 2012). Red grape pomace efficaciously thwarted lipid oxidation in minced rainbow trout, which further ameliorated the shelf-life of this seafood product (Gai et al., 2015).

9.6.2 Use as nutraceuticals Nutraceuticals have garnered wide attention due to the rising demand for health-endorsing products. In this regard, carotenoids like astaxanthin and lycopene have been extensively used as immunomodulatory agents, strong antioxidants and also to reduce the risks of cancer and various cardiovascular diseases (Kumar et al., 2012; Maria et al., 2015; Martins and Ferreira, 2017; Strati and Oreopoulou, 2014). Pomegranate peel has sufficient quantity of polyphenol compounds, such as ellagic acid and gallic acid, which are responsible for the antimutagenicity of peel extracts (Ismail et al., 2012).

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A study by Bertagnolli et al. (2014) discusses the existence of resveratrol and coumarin in passion fruit, guava, and surinam cherry by-products (peel and skin), which manifests as bioactive compounds with antiinflammatory and antioxidant properties. Anthocyanins in mango kernel extract exhibited substantial therapeutic properties against human diseases related to oxidative stress, such as coronary heart disease and cancer (Asif et al., 2016). A parallel study by Tewtrakul et al. (2008) gauged the antiallergic and antimicrobial properties of waste parts of peel and seed of different crops including mango, banana, germinated rice, okra, durian, jackfruit, rambutan, jampadah, huasa potato, tamarind, coconut, fan palm fruit, and dioscorea tuber. The study results corroborated that the highest antiallergic and antimicrobial activity was endowed by mango seed and banana peel. Furthermore, potato peel was epitomized as an excellent source of aglycone glycoalkaloid, and solanidine is employed to manufacture novel anticancer and apoptotic drugs, while potato peel peptides exhibited antiinflammatory, antihypertensive, and antioxidant traits (Kenny et al., 2013). Cocoa pod gum recovered from cocoa pod husks was used as a binder for binding pills in the pharmaceutical industry (Baiano, 2017). Additionally, astaxanthin recovered from shrimp shells regulates HDL-cholesterol levels and is also utilized as a dietary supplement for blood pressure control (Ambigaipalan and Shahidi, 2017).

9.6.3 Use as cosmeceuticals Cosmeceuticals are contemporary products used to improve human skin appearance by antioxidant flavonoids and other polyphenolic compounds present in food waste by-products (Samaranayaka and Li-Chan, 2011). Antioxidant peptides from discrete food sources including phenolic acids and cartenoid from citrus FVWs are currently introduced in cosmeceutical products to reduce aging and skin bruising due to UV radiation and erythema due to inflammation (Allemann and Baumann, 2008). Taking into account, their preservative and organoleptic capabilities, carotenoids bestow aroma, flavors, and color qualities to cosmetic products (Nisar et al., 2015). In vitro studies by Rodrigues et al. (2016) using coffee waste on divergent cosmetic compositions, such as a body cream and a hand cream, revealed no toxicity either to keratinocytes or fibroblasts. Coffee silverskin embodies an immense volume of antioxidants as a result of chlorogenic acid, phenolic compounds, diterpenes, xanthines, and vitamin precursors and imparts in vivo safeguards against free radical impairment (Sato et al., 2011).

9.7

Challenges and future prospects

The pursuit of nutraceuticals and functional food components has been enhanced using variegated food waste byproducts in the food and pharmaceuticals industries. The recovery of nutraceuticals from food waste poses a challenge for investigators worldwide, with commercialization an even more difficult process. Hence, evaluating the bioactive compound content is crucial prior to use of food waste as a functional food ingredient. Antioxidant bioactive peptides and dietary fibers have immense potential in the fortification of healthier and functional foods. Extensive attempts are vital to identify the negative effects of bioactive peptides and dietary fibers during clinical trials to foresee and remove these side effects. Bioactive peptide recovery using a fermentation method with enzymes has been assessed as a great tool, although isolated enzymes have high caliber in retrieving the intended bioactive peptides. Correspondingly, biosurfactants can have a number of properties such as emulsifying, antiadhesive, and antimicrobial behaviors. Application of SSF, fortified food waste, and comingling biosurfactants with commercially available products aims to reduce the production costs of biosurfactants and also needs to be critically analyzed before implementation on a large scale. The chemical stability of several food colorants is controlled by elements such as pH, temperature, light, oxygen, solvents, enzymes, proteins, and metallic ions. The above limitations can be overcome by improving the extraction efficiency and stability. Numerous green and viable emerging extraction techniques have been employed recently to recover nutraceuticals from food waste. Among the available techniques, the SFE technique has proven to be eco-friendly. In addition to the above strategies, an insightful knowledge between the nutraceutical component and the food matrix is vital as they have an impact on the bioavailability and bioefficency of the nutraceutical added to it.

9.8

Conclusion

Food waste by-products contain bioactive compounds such as phenolic compounds, carotenoids, dietary fiber, and proteins which serve as functional food ingredients and nutraceuticals. Diverse nutraceuticals are siphoned from various fruits, vegetables, and seafood wastes and their utility in the food, pharmaceuticals, and cosmeceuticals industries is summarized in this chapter. Various extraction techniques are applied to recover nutraceutical components from food waste, among which SFC extraction, EAE, and MAE when joined with other techniques result in substantial

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augmentation of the extraction yield and also possess remarkable product quality. Furthermore, SSF is a growing fermentation technology to recover bioactive compounds from food waste and testifies to be a promising one as a result of the up surge in demand from consumers for healthy food.

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Chapter 10

Enzymes/biocatalysts and bioreactors for valorization of food wastes U. Ushani1, A.R. Sumayya1, G. Archana1, J. Rajesh Banu2 and Jinjin Dai3 1

Department of Biotechnology, Karpagam Academy of Higher Education, Coimbatore, India, 2Department of Life Sciences, Central University of

Tamil Nadu, Neelakudi, Thiruvarur, India, 3School of Ecological and Environmental Sciences, East China Normal University, Shanghai, P.R. China

10.1

Introduction

Enzymes are molecular catalysts that exist in every species and can trigger chemical reactions, by lessening the activation energy they can persist unaltered until the end of the reaction. As they endure unaltered they can be reprocessed for several reactions in lower quantities. Most of the enzymes are thermolabile and are suitable for the handling of food waste and boost product recovery. They are employed for the effective recovery of bioproducts such as biodiesel and biogas from food waste in eco-friendly green technologies. They can also act as prospective catalysts for food waste valorization and beverage exploration based on the pureness and specificity of the product. There are various types of enzymes resources, including plants, animals, and microbes that are utilized for food waste valorization. However, the use of plants and animal-based enzymes for food waste valorization has certain drawbacks such as poor accessibility, alterations to the action of enzymes, and their extremely perishable nature. These plant enzymes are outperformed by microbial enzymes, which are cost effective and can be produced in a large scale in a compact space. Microbial enzymes such as amylases, cellulases, and xylanases play an active role in transforming food waste streams into valueadded products including sweeteners, bioplastics, biofuels, and prebiotics. For example, starch-containing potato processing wastewater has been found to contain a biological oxygen demand of 5000 mg/L, which makes it unsuitable for release into the environment without treatment. However, enzymatic bioconversion of these starch-rich waste streams gives rise to value-added products. Therefore the action of the above-described microbial enzyme helps these food waste streams to be converted into value-added bioproducts. This chapter reviews the conversion and production of sustainable energy resources from food waste using enzymes, bioreactors, etc. (Table 10.1).

10.2 Enzymatic valorization of food waste for fermentative polyhydroxybutyrate production Polyhydroxyalkanoates (PHA) are a class of synthetic or natural polymer, which usually consists of an ester group in their main chain structure. They are classified as natural polyesters produced by microbial fermentation of sugars or lipids (Banu et al., 2019). The most commonly used strains include recombinant Bacillus subtilis str. pBE2C1 and B. subtilis str. pBE2C1AB that are isolated from malt (germinated cereal grain waste). This polyester has a characterization equal to plastics synthesized through petroleum by-products and it is biodegradable and has been categorized as a “green plastic.” PHA consists of around 150 monomeric units of hydroxyacids in which polyhydroxybutyrate (PHB) plays a major role compared to other monomers. One of the important limitations for large-scale production of PHA is the price of the carbon source used for PHA-synthesizing microorganisms (Kosseva and Rusbandi, 2018; Kourmentza et al., 2018). The manufacturing cost could be possibly reduced by up to 50% with the utilization of a carbon source from waste such as lignocellulosic biowaste (Kumar et al., 2018), marine algae (Kumar, 2016), and food waste (Nielsen et al., 2017).

Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00010-9 Copyright © 2020 Elsevier Inc. All rights reserved.

211

TABLE 10.1 Different food waste sources for production of different by-products. S. no.

Food waste

Type of fermentation

Enzyme involved

Nature of enzyme (free or immobilized)

Role and application of enzymes

Recovered product

Product yield or recovery (%)

References

1

Bakery waste 1 seawater

Batch and fedbatch fermentation

Glucoamylase and protease

Halomonas boliviensis

Hydrolysis of carbohydrate and proteins present in bakery waste

PHB

30

Pleissner et al. (2014)

2

Whey

Fed-batch fermentation

Lactase

Escherichia coli CML3-1

Breakdown of lactose present in whey into the simple sugars

PHB

28.65

Pais et al. (2014)

3

Kitchen waste

Batch fermentation

Decarboxylase

Cupriavidus necator CCGUG 52238

Hydrolysis of organic acid

PHB

52.79

Omar et al. (2011)

4

Restaurant waste

Batch fermentation

Decarboxylase, hydrogenylase, oxidase

E. coli pnDTM2

Hydrolysis of organic acid

PHB

45

Eshtaya et al. (2013)

5

Pea shells

Batch fermentation

Protease

Bacillus cereus strain EGU3

Breakdown of proteins in the shells

PHB

71

Patel et al. (2011)

6

Household

Liquefaction

Hydrolysis of sugar molecules and enhanced saccharification process

40.81

reactor

Saccharomyces cerevisiae

Bioethanol

food waste

Amylolytic, glycolytic enzymes

Matsakas and Christakopoulos (2015)

7

Bread crust, potato chips, rice grains

Consolidated continuous solid-state fermenter

Invertase

Dry yeast

Hydrolysis of sugar and enhanced saccharification process

Bioethanol

80.7

Moukamnerd et al. (2013)

8

Kitchen waste

Batch fermenter

Glucose oxidase, pectinase, α-amylase

Aspergillus niger

Hydrolysis of sugar molecules

Bioethanol

30

Moon et al. (2009)

Hydrolysis of sugar and proteins

Bioethanol

82.06
98.19

Halimatun and Kalsom (2014)

Efficiently degrades cellulose

Bioethanol

38.6

Matsakas and Christakopoulos (2015)

Aspergillus aculeatus S. cerevisiae

9

Restaurant

Batch fermenter

Amylase, protease

kitchen waste

S. cerevisiae Candida parasilapsis Lachancea fermentati

10

Household waste

Batch fermenter

Thermophilic cellulolytic and hemicellulolytic enzymes

Myceliophthora thermophila

11

Mixed food waste

Solid-state fermenter

Cellulases, xylanases, and pectinases

A. niger Aspergillus awamori

Efficiently degrades cellulose, xylene, and pectin

Bioethanol

58

Kiran and Liu (2015)

S. cerevisiae 12

Food waste

Solid-state fermenter

Amylase

S. cerevisiae H058

Efficiently degrades carbohydrates

Biodiesel

93.86

Yan et al. (2013)

13

Instant noodle waste

Solid-state fermenter

Amylase

S. cerevisiae K35

Efficiently degrades amylose

Biodiesel

98.5

Yanga et al. (2014)

14

Spent coffee ground food waste

Solid-state fermenter

Microcrystals of lipases

Mucor miehei, Candida antarctica lipase-B (Novozyme-435)

Efficiently degrades

Biodiesel

96

Banerjee et al. (2013)

Spent coffee grounds

Batch fermenter

Lipases

Pseudomonas fluorescence and C. antarctica lipase-B (Novozyme-435)

Biodiesel

96

Karmee et al. (2018)

15

lipid Efficiently hydrolyzes lipid

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Food Waste to Valuable Resources

10.2.1 Mechanism of polyhydroxybutyrate synthesis PHB biosynthesis by microbes occurs by the concentration of dual molecules of acetyl-CoA that would result in acetoacetyl-CoA which would be consequently condensed to hydroxybutyryl-CoA. This final complex would be utilized as a single unit for the synthesis of PHB. PHAs particles are then retrieved by disturbing the cell structure. PHB is a typical eco-friendly plastic, which was first seen in the bacterium Bacillus megaterium. PHAs are accumulated by a range of bacterial types during unstable growth circumstances. PHAs ensure thermomechanical characteristics similar to manmade polymers such as polypropylene, however, they are strictly decomposable in the environment. The molecular structures of PHBs act as an energy reserve ability and are established while the bacteria are in environments comprised of surplus carbon, and there is a lack of any nutrients (Shah, 2014). PHB is produced from acetylCoA-yielding bacteria mediated by the action of triple enzymes. First, 3-etothiolase (phbA gene) catalyzes the building of a carbon
carbon bond by condensation of two acetyl-CoA molecules. Second, acetoacetyl-CoA reductase (NADPH dependent) catalyzes the reduction of acetoacetyl-CoA to R-3-hydroxybutyryl CoA. Third, enzyme PHB synthase catalyzes the polymerization of R-3-hydroxybutyryl-CoA to form PHB. The mechanism of PHB production is shown in Fig. 10.1. Through biosynthetic reaction of acetyl-CoA a partly crystal-like PHB polymer similar to polypropylene and polyethylene is produced. Thus, PHB has been claimed to be one of the most auspicious bio-decomposable plastics and a substitute for petrochemical and manmade plastics. The chief properties of PHB such as biocompatibility, biodegradability, and multipurpose uses mark it as a biological auxiliary for manmade polymers. PHB has many merits because of its lower permeability and less leaky nature than polyethylene and polypropylene, and it is known to be a superior substance for packing food as it is unnecessary to practice antioxidation. However, the industrial use of PHB has been hindered due to its lower thermal steadiness and proneness to breaking upon storing (Matsusaki et al., 2000).

10.2.2 Production of polyhydroxybutyrate Polyhydroxybutyrate is a short-chain polymer that can accumulate in great quantities in cells cultivated on a multiple range of carbon resources (Reddy et al., 2003). Cupriavidus necator has been documented to ensure as high as 74% of its total cell weight as PHB, and recombinant Escherichia coli has been recognized to reserve up to 85% of PHB as its dry cell weight (Wang, 2009). FIGURE 10.1 The pathways.

mechanism

of

PHB

production

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The valorization of food waste using environmentally sound bio/chemo-technological procedures is more promising from the practical, economic, and sustainability standpoints in which the diversified generation of multiple products from a single feedstock could be achieved. Rapeseed meal was converted into a suspension full of free amino nitrogen and was recycled as a nitrogen resource, whereas crude glycerol was used as a carbon resource for the synthesis of PHB. The strain C. necator was used in the fed-batch fermentation, where PHB concentration at 24.75 g/L with an output of 0.21 g/L was obtained. About 86% (w/w) PHB was produced by C. necator from the feedstock of rapeseed (Salakkam and Webb, 2018). Spent coffee grounds (SCGs) waste from coffee brewing industries were also used for the production of PHB. The strains of Halomonas halophile played a major role in the production of PHB from fermentable sugars obtained from SCG. These strains used SCG hydrolysates as a carbon source for their growth. They were able to hydrolyze SCG of about 440
825 kDa and achieved more than 27% (w/w) of PHB (Kovalcik et al., 2018). Bakery waste feedstock was fermented with the help of Aspergillus awamori. This feedstock was fermented with seawater in batch and fed-batch fermenters for the production of PHB using the strain Halomonas boliviensis. This process established that H. boliviensis using bakery waste hydrolysate and seawater achieved PHB production above 30% (Pleissner et al., 2014). Kitchen waste containing organic acids is fermented by batch fermentation using strains of C. necator CCGUG 52238 for the production of PHB. A yield of PHB greater than 52.79% was obtained from the kitchen waste-derived organic acids by the above method. There was an increase in the PHB yield of up to fourfold by the fed-batch culture (Omar et al., 2011). Hafuka et al. (2011) examined the effects of different feeding natures in fermenters, namely, one-pulse, stepwise, and continuous fermented food-waste liquid for the production of PHB. In that study it was observed that one-pulse feeding generated the maximum cell count of C. necator. However, there was a remarkable increase in PHB concentration in the stepwise- and continuous-feeding procedures. The results showed that the continuous-feeding procedure could be followed for constant PHB yield for 259 h (above 10 days), which showed a highest yield of 87% of PHB. Many recombinant strains have also been reported for the production of PHB. Burkholderia xenovorans LB400 is one of the most desired bacteria for the degradation of polychlorobiphenyls and a wide range of aromatic compounds present in food wastes. This specific bacterium has the ability to accumulate polymers such as PHA and PHB as a carbon and energy reserve in the cytoplasm (Urtuvia et al., 2014). The halophile Halomonas TD01 and its by-products have been effectively proposed as an economic area for the endless manufacture of chemicals. The halophile Halomonas TD08 is a recombinant strain that has the unique property to extend its shape to become 1.4-fold lengthier than its unusual size, which would aid in the superior production of PHB from 69 to 82 wt.% (Tan et al., 2014).

10.3

Enzymatic valorization of food waste for biodiesel production

Biodiesel is a yellowish fluid acquired from leftover waste oil, lipids, and grease by the process called “transesterification” in using a catalyst (alcohol and alkaline). Currently, enzymes/microbial enzymes have replaced the alcohol and alkaline catalysts during biodiesel production. Enzymatic conversion of waste oil into biodiesel is a sustainable and eco-friendly approach. Lipase is the chief enzyme catalyst in biodiesel production. Lipases are capable of transforming triglycerides into glycerol and fatty acid. The prospective environmental and commercial impact of these types of valorization of waste lipid is a noteworthy approach. For instance, in the United States above 2 billion pounds of waste grease were created during 2015 (ScienceDaily, 2015).

10.3.1 Mechanism of biodiesel synthesis During transesterification, glyceride (waste cooking oils) reacts with alcohol (usually methanol or ethanol) in the presence of a catalyst (enzyme or microbial enzyme) forming fatty acid alkyl esters (biodiesel) and an alcohol. The transesterification process is a reversible reaction and is carried out by mixing the reactants—fatty acids (waste oil), alcohol, and catalyst (enzymes). Biodiesel and glycerol are the end products of the transesterification process.

10.3.2 Production of biodiesel The enzymatic synthesis of biodiesel from waste cooking oil through lipases is often researched as an alternative energy resources. Lipases from Thermomyces lanuginosus, Mucor meihei (Lipozyme), Geotrichum candidum, Pseudomonas

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cepacia (PS-30), Burkhoderia cepacia (IM-BS-30), and Candida antarctica B were successively utilized for hydrolysis and esterification, for the synthesis of biodiesel from leftover catering fat. Lipase-producing strains such as M. meihei (Lipozyme IM 60), C. antarctica (SP 435), G. candidum, and P. cepacia (PS 30) were isolated and utilized as catalysts for the production of biodiesel from olive oil, soybean oil, and tallow with short-chain alcohols (Nelson et al., 1996). A yield of 95% ethanol was obtained with the strain M. meihei. The addition of methanol to enhance transesterification of waste cooking oil was studied by Watanabe et al. (2001). Methanol prevents the inactivation of lipase produced by C. antarctica and increased the yield of ethanol by up to 90%. Other raw materials such as waste animal fat (WAF) could also be utilized for biodiesel production. The physical and chemical properties of biodiesel obtained from WAF were similar to those of diesel produced from vegetable oil. In fact, another important point that would differentiate biodiesel production from vegetable oil is that methanol could be used instead of ethanol which would result in a higher biodiesel yield as well as ensuring viscosity of the biodiesel. The main parameters to be considered during this production of biodiesel are temperature, molar ratio of alcohol/oil, and the type of alcohol to be used. Lipid extracted from food waste is converted to biodiesel giving a yield of up to 95%
97%. Various cheap carbon substrates such as molasses, grape must (Buzzini and Martini, 2000), radish brine (Malisorn and Suntornsuk, 2008), and hydrolysates of Arundo donax agricultural leftovers (Pirozzi et al., 2012) have been utilized in the last few decades for biodiesel production. Recently, food waste derived from cheese whey (Prazeres et al., 2012) and corncob liquor (Venkata and Venkata, 2011) has been exploited by oleaginous fungi Aspergillus sp. that resulted in a 22.1% lipid yield. Food waste leachate is frequently produced through food waste recycling processes in food processing industries. The nutrient content of food waste leachate was so high that is resulted in phycoremediation where microalgae species were used for biodiesel production. Usually microalgae species, such as Dunaliella tertiolecta and Cyanobacterium aponinum, are employed for phycoremediation as they possess a high concentration of saturated fatty acids such as C16 and C18 that give them an extraordinary potential basis for biodiesel production (Wu et al., 2018).

10.4

Enzymatic valorization of food waste for bioethanol production

Bioethanol is an alcohol synthesized during microbial fermentation, frequently from a substrate rich in carbohydrates, chiefly sugarcane, corn, sweet sorghum, or lignocellulosic biomass. Ethanol was considered as a potential substitute for gasoline. The fermentation process encompasses minimal consumption of energy and the manufacturing arrangement is considerably simpler than that for biodiesel. In addition, the fermentation process by-product CO2 can be reused as a carbon source for microalgae cultivation, thus also reducing greenhouse gas emissions.

10.4.1 Mechanism of bioethanol synthesis Enzymes such as cellulase, hemicellulase (xylanase), and invertase catalyze the hydrolysis of cellulose and sucrose molecules through the breakdown of 1,4-β-glycosidic bonds between the biomass. The breakdown of sucrose involves invertase enzymes produced by microbes during fermentation. Xylanase plays a major role in the saccharification of carbohydrate compounds for the production of ethanol. The fermentation process that produces ethanol mainly involves yeast or other microorganisms which have the ability to break sucrose into glucose and fructose in the absence of oxygen (anaerobic conditions).

10.4.2 Production of bioethanol The production of bioethanol using hydrolytic enzymes such as cellulase synthesized from the thermophilic fungus Myceliophthora thermophila will reduce the cost of bioethanol production (Matsakas and Christakopoulos, 2015). Liquefaction/saccharification steps were employed not only to reduce the thickness of solid compounds but also to ensure the proper collaboration of the microorganisms involved in fermentation. This phase increased ethanol production, with a noteworthy rise in values ranging from about 40.81% (Hashem and Darwish, 2010). The residual solids left after later fermentation at 45% w/v dry material consist of the unhydrolyzed portion of cellulose and were exposed to a hydrothermal pretreatment and used as raw resources for bioethanol fermentation (Fig. 10.2). This practice raised ethanol production by 13.16% reaching an ethanol production rate of 107.58 g/kg (Matsakas and Christakopoulos, 2015). In order to lessen the energy and cost of bioethanol production a combined continuous solid-state fermentation (CCSSF) method was designed with a reactor comprising a rotating drum, a humidifier, and a condenser

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FIGURE 10.2 Illustration of ethanol generation from fungal mash.

(Moukamnerd et al., 2013). In CCSSF, solid substrates such as rice grains (uncooked rice, Japanese rice), potato chips, and bread crust were utilized for the production of bioethanol. The bioethanol yield reached up to 100.9% 6 5.1% and 108.0% 6 7.9% for cereal-based food waste. However, the high salt content of solid substrate such as potato chips directly increased yeast action and resulted in low bioethanol production (80.7% 6 4.7%). A study was conducted in Korea in which food wastes were collected and divided into four groups comprising of vegetables (5%), grains (22%), fish and meat (10%), and fruits (17%). A mixture of amyloglucosidase and carbohydrate enzymes were used with Saccharomyces cerevisiae and fermented for 15 h resulting in a high ethanol yield. The results illustrated that amyloglucosidase was more effective than carbohydrates for bioethanol production (29.1 g/L) (Moon et al., 2009). The approach of transforming kitchen waste into bioethanol through yeast species resulted in ethanol production of 0.45
0.5 g/g with the productivity ranging from 0.44 to 0.47g/L h. The total yield corresponded to total conversion productivity was 82.06%
98.19% (Halimatun and Kalsom, 2014). A comprehensive balanced nutrient stream consisting of 1.8 g/L free amino nitrogen was prepared after enzymatic treatment of waste from food by a fungal mash at 24 h. This method resulted in bioethanol production and yield of 58 g/L with 0.5 g/g glucose. During solid-state fermentation A. awamori, Aspergillus niger, and S. cerevisiae were commonly utilized for the production of bioethanol (Kiran and Liu, 2015). Recently, bioconversion of the predried and tattered organic portion of kitchen waste into useful energy such as bioethanol was also explored through yeasts S. cerevisiae and Pichia stipitis (Scheffersomyces stipitis). Consequently, the efficiency of ethanol synthesis from kitchen waste was evaluated by synchronized saccharification and fermentation trials. Various amounts of cellulolytic enzymes and combinations of cellulolytic with amylolytic enzymatic fusions were tried with the aim of improving the effectiveness of kitchen waste transformation and an ethanol yield up to 45 g/L was obtained (Ntaikou et al., 2018).

10.5

Enzymes involved, their roles, and applications

Microbial enzymes perform a leading role in food industries, rather than plant- and animal-produced enzymes, due to their stable characteristics. For the production of microbial enzymes, time and space requirements along with factors such as reliability, process distinction, and optimization, can be assessed easily (Gurung et al., 2013). Various standardized fermentation techniques are utilized for the mass production of these enzymes. Various types of these enzymes play a foremost role in food industries such as amylolytic enzymes that are involved in preparing products such as crystalline and syrup of glucose, corn syrups rich in fructose, and maltose rich syrups as raw materials (Pandey et al., 2000). In food

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Food Waste to Valuable Resources

industries, hydrolytic enzymes (lipases, proteases, xylanases) have wider significance as additives to remove starch-based stains, hydrolysis of fruit peels, meat processing industries, and so on (de Souza and Magalha˜es, 2013).

10.5.1 Fermentation of food waste Fermentation denotes the metabolic system in which organic compounds (usually glucose) are transformed into acids/ alcohol/gases in the presence/lack of oxygen. In 1856, the French chemist Louis Pasteur initiated the study of zymology, which is about fermentation and its practical uses. Types of fermentation and their details are listed in Table 10.2. Waste from food material has been recycled as a solitary feedstock for microbes to harvest numerous by-products such as bioethanol, biogas, biodiesel, biohydrogen, and biopolymers (Kiran and Liu, 2015; Kavitha et al., 2017). Rigorous experimental research has been on-going into the biological conversion of food waste to biofuels, biopolymers, and intermediate chemicals (Ren et al., 2017). Fermentation of food waste leads to the production of organic acids (lactic acid, succinic acid), alcohol (ethanol, butanol), and biopolymers (3-hydroxybutyrate) (Maina et al., 2017). Currently, the valorization of food waste for the production of various marketable products has drawn attention from both the public and scientific communities. Thus, this module is particularly planned to evaluate the transformation of food waste to numerous fermentation by-products. Microorganisms are frequently chosen as resources for the production of enzymes due to their characteristics such as growing fast, easy control, and genomic modification for obtaining a preferred product (Sooch et al., 2014). The microorganisms secrete the enzymes to digest the food substrate and thereby its aroma, texture, and flavor are increased, which makes the food be preserved naturally and convertible to a new form. Fermented food waste can be used for enzyme production using various techniques, raw materials, etc. However, they fall into four categories namely alcoholic, lactic acid, acetic acid, and alkaline fermentation.

10.5.2 Types of fermenter 10.5.2.1 Continuous stirred tank fermenter A continuous stirred tank (CST) fermenter is a batch reactor furnished with an impeller or other mixing device to provide efficient mixing. A steady-state environment can be attained with the time period, strength of microorganisms, and constituents of the medium. It includes the tuning of the flow rate of the bioreactor to a suitable and continual value and permitting the microbes, substrates, and organic product concentration to achieve their normal intensities. Autocatalytic activity of microorganisms is the most significant aspect of continuous processing. Fig. 10.3 is a schematic design of different types of bioreactors. Using CST, biohydrogen was produced with food waste as a substrate in an anaerobic mixed culture. The optimum hydrogen yield of 261 mL H2/g-VSadded was obtained at HRT of 60 h (Reungsang et al., 2013; Rajesh Banu et al., 2008).

10.5.2.2 Packed-bed bioreactor Packed-bed reactors are multipurpose reactors widely utilized in numerous chemical handling applications such as absorption, catalytic reactions, distillation, and separation methods. Through the various uses for which they are exploited, the physical sizes of the beds vary significantly. Distinctive reactors comprise of a compartment that consists of a tube that grasps catalyst elements and a fluid that streams through the catalyst. The fluid intermixes along the catalyst substance transversely through the length of the tube, leading to shifting of the chemical composition of the substance. While configuring a packed-bed bioreactor, factors such as transfer of mass and heat should be taken into account. In order to reduce the cost of the packed-bed bioreactor, optimization of heat transfer through packed beds should be considered. The catalyst packed also plays an analytical role for the successful modeling of the device (Rajesh Banu et al., 2007). Herna´ndez-Montelongo et al. (2018) designed a packed-bed reactor for biodiesel production with canola oil as fatty acid, methanol as reactant, and viable cation exchange resin (Purolite CT725) was utilized as a solid-acid catalyst. Buasri et al. (2012) designed a packed-bed reactor for waste frying oil using alkaline (KOH) as supporter on Jatropha curcas fruit shell as solid catalyst.

10.5.2.3 Airlift bioreactors This type of bioreactor works on the source of an air lift pump. It introduces a fluid (air/liquid) in an upward motion and leads to circulatory flow through the entire bioreactor. Airlift bioreactors are distinguished as internal

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TABLE 10.2 Types of fermentation and their details. Type

Description

Advantages

Disadvantages

Batch fermentation

Closed-culture system

Less contamination and mutation

G

Biofuel production

Possibility of contamination and mutation because of prolonged incubation Possibility of wastage of nutrient medium Process becomes more complex and difficult to accomplish when the desired products are antibiotics

Production of singlecell protein, antibiotics, organic solvents, starter cultures

G

Not possible to measure the concentration of the feeding substrate

Production of baker’s yeast, penicillin production, thiostrepton by Streptomyces laurentii

G

Costs more money Requires special media like viscous media

Biogas and biohydrogen

G

G

Continuous fermentation

Closed system of fermentation, run for indefinite period

Continuously used

G

Only small quantity of initial inoculum is needed G

G

Fed-batch fermentation

Modification to the batch fermentation

Production of high cell densities

Examples

Increased, frequency of sterilization Yield of the desired product may also vary More personnel are required

Alternative mode of operation for fermentations dealing with toxic substances or lowsolubility compounds No additional special piece of equipment is required Anaerobic fermentation

Carried out in the absence of oxygen

Production of economically valuables by-products

Aerobic fermentation

Carried out in the presence of oxygen

Can produce primary metabolites

Wine, beer, citric acid, and acetic acid vinegar

Solid substrate/ state fermentation

The growth of the microorganism on moist solid materials in the absence or almost absence of free water

Product formation has been found superior in solid culture process

Aroma compounds, biosurfactants, biopesticides, carotenoids, pigments

Production of secondary metabolites

G

Low capital cost Overcomes catabolite repression Simplicity High reproducibility

loop type and external loop type dependent on the flow of air. The reactor rate of airflow rests on the volumetric mass transfer coefficient. This affords necessary dissolved O2 concentration for definite microbial population. Additionally, it lessens the operational price for propelling air over the bioreactor. A by-product of the dairy industry, cheese whey is continuously fermented in an airlift bioreactor with S. cerevisiae as the biocatalyst (Klein et al., 2003).

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Food Waste to Valuable Resources

Reactant 1

(A)

Electronic valve control

(B)

Level gauge

Reactant 2

Diffusion-convection To vent system Floor level

c

Products overflow from reactor

Coolant

Diffusion-reaction r Stirrer Gas (C)

Solid

Gas bubble

Solid particle

Solid

Gas Distributor FIGURE 10.3 Schematic designs of different types of bioreactor: (A) continuous stirred tank bioreactor; (B) packed-bed bioreactor; (C) fluidizedbed bioreactor.

10.5.2.4 Fluidized-bed bioreactors The unique characteristic of a fluidized-bed reactor consist of the frame of hard elements or solid catalyst is sustained by a gas flow on upward direction. The main significant of this reactor is stress-free filling and devoid of catalyst. This is beneficial when the solids bed must be detached and substituted regularly. The main advantage of this type of rector leads to high conversion with a large throughput with excellent heat transfer and mixing features. In India, a group of researchers has produced bioethanol through magnetically assisted fluidized-bed bioreactor with agriculture residues such as wheat and corn waste and obtained a yield of 17 g/L h (Velichkova et al., 2017).

10.5.2.5 Membrane bioreactors Membrane bioreactors are very practical in abundant microbial biotransformation such as production of alcohol through fermentation, organic acid, solvents, and wastewater treatment. The separation of product from the substrate and soluble enzyme is carried out through a membrane bioreactor in an effective way. On one side of the membrane the soluble enzyme and substrate are introduced and product is forced out through the other side of the membrane (Rajesh Banu et al., 2009). Thus, membrane holds back the enzyme and it can be utilized further. The most widely used membrane

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materials include polysulfonate, polyamide, and cellulose acetate. Membrane bioreactors can improve anaerobic lactic acid fermentation using Bacillus coagulans with decreased product inhibition. Hence, the yield of lactic acid can be increased (Fan et al., 2017; Rajesh Banu et al., 2006).

10.5.3 Scaling up of the fermentation process Microbes are noteworthy due to their capacity to synthesize enzymes and various other organic substances in diverse industries. Applying these microbes in a large-scale bioreactor would be advantageous in producing more recombinant or natural enzymes. The scale-up practice is the development of a lab procedure (0.5
10 L fermenters) to large-scale industry (20,000
2,000,000 L fermenters) for the production of fermented products. It is not a matter of aggregate culture and the volume of vessel. Consequently, it can be unexpected when the large-scale production does not achieve as good results as the small-scale research laboratory practice. It is often mentioned that the yields of biomass and several growth-related products are regularly reduced on the scaling up of an aerobic method. George et al. (2000) reported that they achieved a 7% improvement in biomass yield of S. cerevisiae while scaling down the fermentation using molasses as substrates from 101 to 120 m3. Similarly, Bylund et al. (2000) achieved a cell density concentration of 20% less in fed-batch cultivation of recombinant protein while scaling up from 3 to 9 m3. In the course of another study throughout fed-batch cultivation with a recombinant strain of E. coli it was found to differ on scale-up from the lab scale to large scale with 10
30 m3 bioreactors. This comprised lower biomass yields, recombinant protein amassing is found when scaling up with fermentation. To overcome this scaling up of lab protocol to large industrial practices is preferably concluded in two parts: the first phase is a pilot plant study with 100
10,000 L fermenters that match the downstream protocol and equipment. The main ideas behind the pilot-scale study are to decode the lab-scale protocol into an accurate scaled-down version for the industrial process. The second phase of scaling up is a demo scale with 10,000
100,000 L fermenters that is in line with the downstream process. This helps to minimize the risk of a huge capital investment in the full-scale industrial process (Crater and Lievense, 2018). Acknowledging the basics of scale-dependent fermentation factors such as accurate biological, chemistry, and engineering aspects of fermentation, protocol flow diagrams, substrate and energy equilibriums, unit operation designs, and technocommercial replicas could reduce the scale-up risk. Indeed, years of constant in-plant knowledge and operational experience on an elegant plan, with a systematic approach toward scalable fermentation, will finally perform in a superior fashion in the industrial unit than in the lab-scale study.

10.5.4 Application of enzymes Proteases are used for an extensive range of applications in food manufacturing industries. Protease enzymes have the capability of altering the characteristics of proteins present in food to increase their nutritious value, solubility, digestibility, flavor, and to reduce the allergenic compound content (Rosana et al., 2002). Moreover, as their elementary purpose, they are utilized to adapt functional characteristics such as clotting, emulsification, lathering, gel forte, and binding of digestibility of proteins in food (Sabir et al., 2007). The catalytic characteristics of proteases are utilized in the manufacturing of protein hydrolysate of great dietary value, baby foods, therapeutic nutritional foods, and strengthening of fruit juice. Proteases are utilized predominantly in dairy production units, such as in cheese production for obtaining casein peptide bonds that are hydrolyzed. Protease plays a major role in the tenderization of meat by hydrolyzing proteins in connective tissues and muscle fiber. In baking units, protease enzymes have a major role in improving the dough constancy, flavor, and texture of baked products, especially bread. In juice and liquor-based industries hydrolytic enzymes are useful for turbidity removal and hydrolysis of gelatin (Christopher and Kumbalwar, 2015). The proteases are used for foodstuffs, drugs, animal fodder, leather, diagnostics, and waste management (Nascimento et al., 2011). The production of amylases was carried out with feedstock of a brewers’ spent grain hydrolyte with submerged fermentation mode using Bacillus sp. for 30 h. The recovered amylases are used for baking, brewing, aquaculture, and biofuel (Rajagopalan and Krishnan, 2008). The gelatinization process mainly involves the development of a viscous solution by suspension of starch particles, followed by a liquefaction process. The end process reduces the viscosity and leads to restricted hydrolysis. Glucose and maltose are additionally formed by saccharification, which requires an extremely thermostable enzyme. The maximum starch saccharification is by α-amylases from various Bacillus sp. (Van der Maarel et al., 2002).

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β-Galactosidases are extracted from copious biological systems of various floras, faunas, and microbes. β-Galactosidases using microorganisms have a significant role in milk and dairy foodstuffs production. To degrade lactose in dairy and dairy-based products lactase enzymes are widely used. The breakdown of lactose into monomers increases the sweetness of foodstuffs (Zhou and Chen 2001). Many humans are susceptible to lactose intolerance and incapable of consuming dairy products. To overcome this lactose intolerance, lactase enzymes are produced on a large scale and ingested in the form of therapeutic foodstuffs (Ianiro et al., 2016). β-Galactosidases derived from fungal species, generally Aspergillus, are stable at low pH and mediate the proper functioning of the stomach (Panesar et al., 2007). Almost 15,936 U/gds of β-galactosidase was produced by the action of Aspergillus tubingensis GR1 on food wastes such as cabbage leaves, orange peel, and deoiled groundnut seed cake (Raol et al., 2015). The hydrolysis of long-chain fatty acid is important for humans and other animals in order to hydrolyze fats and lipids. Enzyme lipases are involved in catalyzing long-chain fatty acids into smaller elements. Many bacteria, fungi, and yeasts are involved in the production of lipase (Guerrand, 2017). Microbial lipases from Candida sp. have countless applications other than chemical synthesis. Lipases are produced from different waste streams of food industries (Aravindan et al., 2007), dairy industries (Jaganmai and Rajeswari, 2017), castor bean and rapeseed lipases (Mounguengui et al., 2013), and papaya pulp waste (de Marı´a et al., 2006). Phospholipase enzyme hydrolyzes phospholipids into fatty acids, which are widely utilized in the dairy food industry in the production of cheese without altering its quality and enhancing the flavor (de Maria et al., 2007; Karahan and Akin, 2017); it also plays a major role in the manufacture of oils and numerous bakery foodstuffs (Borrelli and Trono, 2015). Cellulase and xylanases are lignocellulolytic enzymes that are mainly used for breaking down celluloses and hemicelluloses. Tiana et al. (2019) utilized various fungal strains such as Aspergillus, Penicillium, and Trichoderma for the production of cellulase and xylanases from food waste. Maximum syntheses of cellulase and xylanase of 28.81 6 0.67 and 213.47 6 10.66 U/g ds were obtained with A. niger species. Xylanases are extensively utilized in bread production in addition to other enzymes. The prospective efficacy of xylanolytic enzymes is their enabling bread to rise and improving its quality. Xylanase is capable of breaking down hemicellulose, which raises the water-binding ability of dough. Hence, it improves the texture, flavor, and deliciousness of biscuits (Butt et al., 2008). In beer production, xylanases play a major role in hydrolyzing the cellular wall of barley. Thus it reduces the presence of oligosaccharides, which lessens the turbidity and viscosity of the beer (Polizeli et al., 2005). Catalase helps in the breakdown of hydrogen peroxide to water and oxygen along with the formation of bubbles. In industries it acts on fruit or vegetable sources. Catalase is used with glucose oxidases for food preservation and this cocktail of enzymes acts as a catalyst for removal of O2 from wine before bottling and is assessed in the production of acetaldehydes (Ro¨cker et al., 2016). In dairy industries, catalase is utilized for the removal of peroxide from milk, in baking industries for the elimination of glucose from egg white, and it prevents the oxidation of foodstuffs that are utilized in food wrapping to reduce the perishability of food (Kaushal et al., 2018).

10.6

Immobilized biocatalysts and their applications in food waste valorization

The biological materials/substrates that are used to speed up chemical reactions are known as biocatalysts. These biocatalysts are sensitive to various factors such as pH and temperature. To overcome these limitations, these biocatalysts which are cells or enzymes, are subjected to immobilization. For the last few centuries the most used and effective technique employed in industries has been the immobilization technique. Numerous immobilization methods have been utilized in small-scale and large-scale industrial processes such as biomedical manufacture, detergent industry, food processing, textile industry, wastewater treatment, and now in the biofuel industry such as biodiesel, bioethanol, and biohydrogen production (Kavitha et al.,2014; Jayashree et al., 2016; Ushani et al., 2017). These techniques are specific for particular productions, typically dependent on the budget and susceptibility of the method. This immobilized biocatalyst holds potential strength for valorization of food waste as illustrated in many studies (Breguet et al., 2010). Food waste generated through the use of chemicals as well as artificial approaches produces harmful by-products which grow as pollutants as well as being the root causes of health hazards. As an alternative, these bioorganic wastes could be utilized for generating biomolecules such as cells/enzymes which act as biocatalysts. Although immobilized enzymes have an advantage over conventional chemical catalysts during valorization of food waste, a main task arises in holding their stability and functionality in the distinctive processing conditions of food waste (e.g., increased temperature, varied pH). Additionally, immobilization techniques increase their recovery, stability, and economic feasibility (Rajesh Banu et al., 2017; Ushani et al., 2018).

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10.6.1 Carbohydrates The water stream from food processing industries is composed of mainly polysaccharides, which can be converted into value-added products such as sweeteners through the action of enzymes such as amylase and xylanase. Predominantly in the food industry α-amylase is an essential enzyme for the liquefaction of starch from food waste. In food industries, the enzymes undergoing long-time operation can lose their stability and therefore reusability can be very challenging. Hence, α-amylase beads were produce by immobilizing them on ion-exchange resin which improved the stability and consequent liquefaction of starch (Gupta et al., 2013). Another example of the significance of immobilization of a thermostable α-amylase from Bacillus licheniformis was on six different cross-linked enzymes which expressed favorable affinity (Torabizadeha et al., 2014). α-Amylase from B. licheniformis and amyloglucosidase from A. niger were immobilized on ion-exchange resin beads for the production of 96 dextrose syrup from a starch water stream from the processing industry (Gupta et al.,2013). A chitooligosaccharide was obtained from a chitosan wastewater stream through α-amylase obtained by Bacillus amyloliquefaciens which was immobilized on glyoxyl-agarose beads (SantosMoriano et al., 2016). β-Glucosidase plays a major role in cellulose hydrolysis from lignocellulosic waste. β-Glucosidase produced by Trichoderma reesei was immobilized on glyoxyl-agarose and on polyacrylic resin. This immobilized β-glucosidase was applied on bagasse of sugarcane and thus recycling of lignocellulosic waste was obtained (Borges et al., 2014). Pectinase enzymes are derived from fruit and vegetable waste streams and are used for thickeners, texturizers, fillers, and glazes. Immobilization enhanced the significance of pectinase production from unprocessed waste such as onion skins which are rich in pectin (Baldassarre et al., 2018). Pectinase produced by B. licheniformis was immobilized in agar
agar retained its activity and stability after 10 cycles (Rehman et al., 2014). In juice industries, pectinase plays a vital role in degrading fruit peels. In juice industries, enzymes have to withstand various pH alterations to give different products. A change in pH will alter the stability of enzymes; hence, immobilization techniques play a vital role. Pectinase enzymes are immobilized in calcium alginate (Rehman et al., 2014), polyvinyl alcohol (PVA) sponge (Esawy et al., 2016), magnetite nanoparticles coated with silica (Ucoski et al., 2013), and magnetic microspheres of cornstarch (Wang et al., 2013) exposed noteworthy stability, and tolerance for pH and temperature were enhanced. Sugar beet pulp is used to produce arabinose and galacturonic acid in the presence of pectinases. Hence pectinases were immobilized on cross-linkers such as glutaraldehyde and polyethylenimine to obtain arabinose and galacturonic acid (Leijdekkers et al., 2013). These immobilized pectinases played a wide role in the synthesis of biofuels and bioplastics from wastewater streams (Abdel et al., 2018).

10.6.2 Proteins Food industries, such as dairy, egg, and oil processing streams, release wastewater rich in proteins. These proteins can be converted into peptides and polymers through enzymes such as protease and trypsin. An immobilization technique improves the reusability of enzymes by up to 5- to 10-fold without losing its stability and originality (Prasertkittikul et al., 2013; Singh et al., 2011). Food processing waste has been reutilized as value-added products by concentration and separation of whey protein from the by-products of casein, cheese, and yogurt manufacture. As whey protein is rich in lactose, it is an outstanding example of food waste valorization (Erickson, 2017). Enzyme trypsin was immobilized on polymethacrylate monoliths to hydrolyze whey protein from dairy wastewater. Above 9.6% hydrolysis was obtained when compared with free trypsin enzyme (Yuhong et al., 2017). Antioxidant peptides were produced from waste whey protein through immobilized aspartic protease obtained from Salpichroa origanifolia fruit on a glutaraldehyde-agarose carrier (Rocha et al., 2017). Nanoparticles now play a major role in immobilization. An alkaline protease obtained from B. licheniformis was immobilized on magnetic chitosan-coated nanoparticles for the hydrolysis of soy proteins in water streams. Above 18.38% hydrolysis was obtained with immobilized protease (Wang et al., 2014). Oat polypeptide produced through alkaline protease (B. licheniformis) was also immobilized on magnetic nanoparticles (Hu et al., 2015). Above 36% protein hydrolysis was obtained from immobilized trypsin on glyoxyl-agarose.

10.6.3 Lipids As previously discussed in Section 10.3, biodiesel is obtained from waste oil. In this section, the role of immobilized enzymes in the extraction of valuable products from waste oil is discussed. Lipase plays a vital role in extracting valuable products from waste oil. Lipase obtained from Rhizomucor miehei lipase and C. antarctica was immobilized on

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epoxy-functionalized silica and above 91% biodiesel conversion was attained from waste cooking oil in 10 h (Babaki et al., 2017). Some commercialized immobilized lipase enzymes include Novozym 435 (immobilized on acrylic resin) and Lipozym TL IM (immobilized on silica gel) (Hama et al., 2013). Above 91% and 89% of biodiesel was obtained from sunflower and soybean oil utilizing immobilized lipases from Pseudomonas fluorescens (Ferrero et al., 2016). Above 95% of biodiesel was obtained within 24 h from waste cooking oil through lipases produced from marine Streptomyces sp. which was immobilized on styrene divinylbenzene resin (Wang et al., 2017). Lipases from Malassezia globosa were immobilized on epoxy-functionalized resin which converted above 98% of high-acid content waste cooking oil into biodiesel (Li et al., 2017).

10.6.4 Organic acids Above 70% of lactic acid from waste whey was obtained from Lactobacillus brevis cells immobilized on cellulosic material (Elezi et al., 2003). Bifidobacterium longum immobilized on sodium alginate beads produced high lactic acid content from cheese whey (Li et al., 2005). A recent study investigated the manufacture of various organic acids (OAs) (lactic, fumaric, or succinic) through numerous microorganisms, such as Rhizopus oryzae (F-814, F-1127) and Actinobacillus succinogenes B-10111. These microbes were immobilized on cryogel made from poly(vinyl alcohol) derived from natural resources such as wheat and rice straw, pine sawdust, and macro- and microalgae biomass. The study exposed that the productivity, output, and concentrations of OAs were higher in immobilized cells when compared with free cells. The immobilized cells were utilized in long-term exchange of numerous natural resources into OAs (Maslova and Tekleva, 2012).

10.6.5 Biofuel In brewing industries, S. cerevisiae is mainly utilized in the fermentation process. The main problem faced by the brewing industry is instability due to different cell physiologies and cell aging, which lead to a poor taste in beer. Immobilization techniques were utilized to overcome these limitations in order to improve the beer quality. This method manufactured beer with better physiognomy such as color, taste, and aroma (Almonacid et al., 2012). Yeast S. cerevisiae immobilized on β-D-galactosidase cross-linked with glutaraldehyde showed a higher fermentation rate compared with free yeast (Lewandowska and Kujawski, 2007). A good ethanol yield was obtained when yeast was immobilized in organic substrates such as corncobs, wine industry residues, and chitosan-magnetic microparticles (Ganatsios et al., 2014; Sojitra et al., 2017; E¸s et al., 2015). Some species such as E. coli, Clostridium butyricum, and Streptococcus henryi undergo dark fermentation of fruit, vegetable waste, and cottage cheese whey for the generation of biohydrogen. Hence, numerous species are under assessment to obtain high hydrogen yields from food waste (Basaka et al., 2018).

10.6.6 Bioreactors with immobilized cells/enzymes Bioreactors operated with cells that are immobilized have higher productivity and functioning, with easier downstream processing. An additional benefit for the cells that are immobilized in bioreactors is related to the accessible fermenters that are have free cells have a quicker fermentation process in a shorter time. In regard to this benefit, the cell bioreactors are immobilized and have been functional in many industrialized processes, as well as in brewery production. An appropriate immobilized cell bioreactor should focus on the parameters such as immobilization types and the support that is utilized, transfer of mass in cells, and the environs of the process. For example, it has gained huge significant toward the endurance of the immobilized cell method (Genisheva et al., 2014a). Citric acid is synthesized from a food waste that consists of starch by the action of α-amylase enzymes. Bacillus mycoides was utilized for the transformation of starch into glucose, and citric acid was produced from glucose using A. niger. Immobilized cells can be exposed to various bioreactors such as an air lift-fermenter, batch reactor, or column reactor as shown in Fig. 10.4. Above 75.5% enzyme activity was seen in immobilized cells when compared with free cells. Maximum production of above 73% and 80% of glucose and citric acid was obtained in an air lift-bioreactor with immobilized cells (Bholay et al., 2018; Gayathri et al., 2015). Numerous organic supports such as grape pomace (Genisheva et al., 2012), grape skins (Genisheva et al., 2014b), and agro-industrial wastes (Moreno-Garcı´a et al., 2018) have been utilized for immobilizing yeast cells. Genisheva et al. (2014a) immobilized Oenococcus oeni cells on natural residues such as corn cobs, grape skins, and grape stems

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FIGURE 10.4 Immobilized cell fermenter with (A) packed-bed fermenter; (B) fluidized-bed fermenter; (C) air lift fermenter; (D) bubble column fermenter.

for the fermentation of white wine. The fermentation analysis reported a 100%, 83%, and 75% conversion of malic acid using immobilized O. oeni on organic carrier such as corn cobs, grape stem, and grape skins, respectively. Yan et al. (2011) produced bioethanol from concentrated food waste through continuous fermentation. With the utilization of calcium-alginate as a supportive material, S. cerevisiae H058 was immobilized at the optimum conditions of 30 C and pH 5.0. Fig. 10.5 shows a schematic diagram of an immobilized cell fermenter. Above 90% of lactose was hydrolyzed through an immobilized β-galactosidase (Kluyveromyces fragilis) which was filled in a packed-bed reactor (Szczodrak, 2000). About a 23% hydrolysis rate was obtained using immobilized trypsin on glyoxyl in a packed-bed reactor. Biological hydrogen production and ethanol production are two of the core components that can be obtained from food waste. Biohydrogen production was done through hydrogen-producing microbes such as Clostridium

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FIGURE 10.5 Schematic diagram of an immobilized cell fermenter.

tyrobutyricum JM1. For the growth of C. tyrobutyricum a supportive matrix of polyurethane foam was utilized in a fixed-bed bioreactor. An effective, stable, and continuous yield of hydrogen was obtained with 97.4% substrate conversion. Hence hydrogen production is comparatively increased using an immobilized technique compared with traditional methods (Jo et al., 2008). Multienzyme methods expressed potential improvements in product conversion rates, which probably speed up the reaction and increase the product yield through various catalytic reactions. Some of the food waste, such as lignocellulose waste, is complex in nature as it is comprised of cellulose, hemicellulose, and lignin. To hydrolyze this kind of food waste multienzyme coordination is required. Periyasamy et al. (2016) immobilized multienzymes composed of cellulase, β-1,3-glucanase, and xylanase for hydrolyzing sugarcane bagasse and obtained 150% greater conversion than free enzyme. Recently, a three-dimensional (3D) printing technology has been implemented for manipulating supportive material for immobilizing microbial cells. Propionic acid is produced by Propionibacterium sp. as a cell immobilized from glucose which was deliberately used as a mock-up system. Throughout three rounds of cell cultivation, the nylon beads with 3D printing were supplementary for cell adsorption to the culture medium. Nevertheless, the size of the bead and matrix structure, adsorption, and fermentation kinetics were analogous. Beads of size 15 mm are bounded by cells that exhibit a condensed fermentation duration as compared to fermentations of free cell, and this gives a maximum yield of propionic acid of 0.46 g/L h and 25.8 g/L. A bead treated with polyethyleneimine binding with cell
matrix shows a more progressive outcome than the other polycation carrier. The cells located in scanning electron micrographs reveals gaps in the beads, but they were further consistently dispersed on carrier coated with PEI, which indicates the charge
charge collaboration (Belgrano et al., 2018; Saratale et al., 2018).

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FIGURE 10.6 Diagram of the use of multipoint interactions for the stabilization of enzymes.

10.6.7 Kinetic aspects of immobilized cells or enzymes Even though numerous advantages of immobilized cells are accepted and established, immobilization causes alterations to the kinetics and properties of entire cells, which in turn reduces the specific activity of free cells. The decline in catalytic activity might be due to a number of factors, such as the chemical nature of the carrier material, carrier toxicity utilized in a specific immobilization method, and mass transfer diffusional effects. The pore size of the immobilized beads plays a vital role in the substrate and product concentration gradient. Mass transfer is another key factor that influences the kinetics of free and immobilized cells. Mass transfer is resist to internal and external cell aggregates within the immobilized beads. The lower surface area of cells and the existence of the carrier set up lead to additional obstacles to mass transfer in comparison to free cells. This tends to reduce the overall reaction rate. The stability of an enzyme is also disturbed by the immobilization technique. The inhibition of the activity of enzymes might feasibly cause denaturation, by the process of immobilization, when the enzymes are introduced to extreme temperatures or pH. Conversely, substantial stabilization may occur in an unstrained multipoint adhesion between the enzyme and the stability (Fig. 10.6). This inactivation mainly leads to enormous conformational variation within the protein structure. The enzyme particles interrelate with each other and maintain that immobilization provides further stabilization by avoiding proteolytic and microbial attack. The structural modifications have their end result due to an array of diffusional tribulations and the cover-up to enzyme attack. The development of various unstrained covalent or noncovalent linkages attains extreme stabilization; the exteriors of the enzyme should be paired. Frequently, this feature needs to be stable, in addition to others, such as the expenditure of the procedure and the necessity for a precise carrier substance. Furthermore, it should be ensure that there is no hindrance to the substrates diffusing to the active site of the immobilized enzyme in order to respond at an adequate rate. During the research progression, the kinetic nature of the immobilized enzyme, mass transfer, diffusion mechanism of substrate, and product should be taken into consideration to improve the application of immobilized enzymes. Immobilizations in large scale are more difficult while using synthetically prepared substrates because it impacts on the enzyme constancy. This is predominantly correct for multienzyme systems, in which inhibitor sensitivity, activity of water, solvents, and necessities for cofactors need to be carefully considered for every single enzyme. Due to the intricacy of the method it is difficult to compare and utilize the technology for a specific enzyme/process to another. For instance, lipases are stable at a hydrophobic interface, but other enzymes will lose their activity. For that reason, balanced, sensible design such as selecting an equilibrium technique for an enzyme stability, immobilization methods, profitable application conditions, and better understanding of biocatalytic systems is essential for the effective and productive employment of immobilized enzymes. Exploitation of immobilized enzymes/cells kinetics, factors influencing substrate and product concentration gradient/ and their significance to catalyze the fermentation methods will lead to the promotion of benefits and progress in the process economics.

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Food Waste to Valuable Resources

Conclusion

The valorization of waste from food to fermentative by-products such as biogas or diesel substitute for petrol fuel using microbial enzymes would have the highest positive impact on environmental as well as economic development. However, the selection of such methods depends on the type and composition of food waste and its by-products. This chapter has explored various recovered products from food waste valorization through enzymatic action by microbes. PHB developed from food waste valorization would offer the most auspicious eco-friendly plastics and act as a substitute to plastics derived from petrochemicals. The chapter presented a descriptive review on numerous distinct groups of enzymes involved in the production of biofuels such as PHB, biodiesel, and bioethanol. Enzyme-catalyzed transesterification is an identical choice to a whole chemical-catalyzed reaction which has high impact on environment; however, it needs to be further developed to enable commercialization. The manufacturing cost could also be reduced with the utilization of a carbon source from waste such as lignocellulosic food wastes. It has been assessed that the carrier material involves 47% of the total price of the immobilized process. Moreover, the utilization of a pure form of enzymes as an alternative to whole-cell or crude extract raises the cost of biocatalysis considerably. Rigorous experimental research remains ongoing in the case of immobilization of enzymes directly from crude extract. Overall, the valorization of food waste using the correct techniques would enhance the bio-economy and provide a useful outcome for management of the waste food, particularly in developing countries where food waste appears as a major problem. Thus, the prompt management of these wastes would be a successful tool for policy makers in promoting sustainability transitions.

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Further reading Abdullah, S., Mudalip, S.K., Shaarani, S.M., Pi, N.A., 2010. Ultrasonication extraction of oil from Monopterus albus: effect of different ultrasonic power solvent volume and sonication time. J. Appl. Sci. 10, 2713
2716. Bhardwaj, N., Chanda, K., Kumar, B., Prasad, H., Sharma, G.D., Verma, P., 2017. Statistical optimization of nutritional and physical parameters for xylanase production from newly isolated Aspergillus oryzae LC1 and its application in the hydrolysis of lignocellulosic agro-residues. BioResources 12, 8519
8538. Dai, J., Mumper, R.J., 2010. Plant phenolics: extraction, analysis and their antioxidant and anticancer properties. Molecules 15 (10), 7313
7352. FAO, 2012. Towards the Future We Want: End Hunger and Make the Transition to Sustainable Agricultural and Food Systems. Food Agriculture Organization of the United Nations, Rome. Ganzler, K., Andra´s, S., Klara, V., 1987. Microwave extraction: a novel sample preparation method for chromatography. J. Chromatogr. A 371, 299
306. International Journal for Research in Applied Science & Engineering Technology (IJRASET). ISSN: 2321 -9653; IC Value: 45.98; Vol. 6 Issue I, January 2018. Available at: ,www.ijraset.com.. Rodrı´guez Couto, S., Toca Herrera, J.L., 2006. Industrial and biotechnological applications of laccases: a review. Biotechnol. Adv. 24, 500
513.

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Rodrı´guez-Dura´n, L.V., Valdivia-Urdiales, B., Contreras-Esquivel, J.C., Rodrı´guez-Herrera, R., Aguilar, C.N., 2011. Novel Strategies for upstream and downstream processing oftannin acyl hydrolase. Enzyme Res. 1, 823619. Singh, R.K., Tiwari, M.K., Singh, R., Lee, J.K., 2013. From protein engineering to immobilization: promising strategies for the upgrade of industrial enzymes. Int. J. Mol. Sci. 14 (1), 1232
1277. Thi, N.B.D., Kumar, G., Lin, C.Y., 2015. An overview of food waste management in developing countries: current status and future perspective. J. Environ. Manage. 157, 220
229. Waqas, M., Nizami, A.S., Aburiazaiza, A.S., Barakat, M.A., Ismail, I.M.I., Rashid, M.I., 2018. Optimization of food waste compost with the use of biochar. J. Environ. Manage. 216, 70
81.

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Chapter 11

Aerobic biodegradation of food wastes S. Gopikumar1, R. Tharanyalakshmi2, R. Yukesh Kannah2, Ammaiyappan Selvam3 and J. Rajesh Banu4 1

Department of Civil Engineering, SCAD College of Engineering and Technology, Tirunelveli, India, 2Department of Civil Engineering,

Anna University Regional Campus Tirunelveli, India, 3Department of Plant Science, Manonmaniam Sundaranar University, Tirunelveli, India, 4

Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India

11.1

Introduction

In developing countries like India, 55% of generated food waste directly reaches landfill, whereas in South Korea this has been prohibited since 2005. Alternatively, German and Belgium planned to reduce their dumping of food waste in landfills by 70% by 2020 (Sidaine and Gass, 2013). The emissions of greenhouse gases during food waste landfill causes threats to the environment, which can be tackled by adopting open aerobic composting (Mu et al., 2017; Zhang and Sun, 2014). Composting is an out-fashioned technology but remains in frequent use. The above-mentioned treatment technology mainly depends on three parameters—agitation, forced aeration, and turning. These parameters are coupled with each other for better treatment, such as agitation accompanied by tumbling and stirring, followed by forced aeration, where the air is allowed to penetrate through the composting mass in all directions. This leads to a balance in microbial growth, which improves the various phases of food waste composting, such as the lag, log, stationary, and mature phases. In the lag phase, microbes acclimatize to their new environment, followed by multiplication in the log phase. Furthermore, these microbes are allowed to decompose the organic matter without any ill effect in the stationary phase. Finally, in the final phase the mature compost is extracted as a valuable end product. If these conversion processes are progressed in a well-planned manner then it leads to successful conversion of organic waste into a hygienic valueadded product, which is cost effective (Qian et al., 2014). The beneficiaries in the treatment processes are heterogeneous and biochemical, which involves the mineralization of organic compounds into carbon dioxide (CO2), ammonia (NH3), and water (H2O), and results in a stable end product (Kavitha et al., 2017; Kannah et al., 2018), reducing the presence of toxic pathogens (Das et al., 2011). Mature compost may be used as a source of organic fertilizer because of its sanitized condition and reduced negative effects, which will enhance ecological agriculture. Rather than dumping this high water content and organic-rich food waste near an agricultural field, it may be recovered conventionally (Zhang et al., 2013). The degradation potential of macro- and microorganisms must be studied and contaminant matrix studies carried out (Wang et al., 2015). Application of these studies will make compost a challenger in the global fertilizer market (Proietti et al., 2016). Artificial fertilizers cannot be compared with natural compost because of its humus formation (Hermann et al., 2011). This humic-like fraction naturally encourages the health and growth of plants. If agricultural soil is contaminated with heavy metals, natural compost can be introduced, to bioremediate the soil by immobilizing the metal (Kulikowska et al., 2015). Apart from the successful bioremediation potential, it is possible to enhance the process efficiency by adopting a suitable mixing ratio (Zang et al., 2016). The success rate of the application depends on the rate of aeration, the use of bulking agents, the moisture content, and the introduction of an acceptable mathematical model for running the process effectively (Vasiliadou et al., 2015). One of the major challenges hindering the success of composting is assessing its maturity and stability, as no measuring parameters have been identified to date. The key parameters that disrupt the success rate of composting are porosity, availability of inert materials, respirometric techniques, and stability limits. Although composting is recognized as an environment-friendly treatment, it emits volatile compounds such as organic sulfur, hydrocarbons, alcohols, esters, ketones, and aldehydes. These components are responsible for the formation of secondary aerosols. The volatile Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00011-0 Copyright © 2020 Elsevier Inc. All rights reserved.

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emission of food waste is higher compared with paper and municipal solid waste (Zhang et al., 2013). Recently many researchers have reported that aerobically treated food waste manure has superior quality than commercially available inorganic manure (Chowdhury et al., 2015). A model reactor treating food waste was created by Zhang et al. (2012), influent to effluent emission was monitored by Gallego et al. (2012), and aerobic composting was tested by Kumar et al. (2011). Fig. 11.1 illustrates the overall process concept of food waste to compost.

11.2

Aerobic digestion of food waste and their types

Based on the climatic conditions it takes a variable amount of time to break down the complex organic matter in the initial stage of composting. However, a suitable temperature increases the microbe density leading to more effective decomposition (Hou et al., 2017). Aerobic digestion is carried out in a plug flow reactor, rotating drum reactor, rectangular coupled reactor, cylindrical reactor, or batch reactor. In a plug flow reactor forced aeration is introduced at the bottom of the closed system, where air is allowed to move over the top layer, creating over condensation in the upper layer. In a rotating drum reactor, a tumbling mode of reactor is introduced, which was one of the earliest modern methods and the partially composted material needs to be windrowed. The coupled reactor is a combination open, horizontal, and rectangular tank, where air is passed through the perforated plates followed by windrowing with adequate retention times. This system is one of the most successful vessel systems. The cylindrical reactor is a system with a combination of forced aeration and stiffening. Air is forced through perforations without a steady retention time, finally the compost is windrowed to give it stability. In a semibatch reactor the aeration tank is filled with organic food waste, which is further allowed to decant after stabilizing, before the cycle is repeated. In a continuous batch reactor activated sludge process principles are followed by fixed aeration. The stabilized organic composition is periodically removed; this is a highly reliable process and is less sensitive to environmental factors (Chatterjee et al., 2013). Table 11.1 shows the effects of food waste composting.

11.3

Roles of microbes in composting

The rate of biodegradation of organic matter mainly depends on the potential of different microorganisms, such as bacteria, actinomycetes, yeast, and fungi and their acceptable climatic conditions (Jurado et al., 2014; Kinet et al., 2015). In food waste decomposition, adenosine triphosphate (ATP) and phospholipid fatty acid (PLFA) plays predominant

FIGURE 11.1 Overall process concept diagram for food waste composting.

TABLE 11.1 Effect of food waste composting. S. no. 1.

Substrate G

G

2.

G G G

Inoculum

Nature of composting

Simulated food waste alone— 50% (1.2 kg rice, 250 g meat and fish, 450 g vegetables and fruits, 70 mL oil, 15 mL sauce, 40 mL distilled water) Dried leaves (25%) and rice bran (25%) used as bulking agent

Effective microorganism (EM)—1.2 L

Thermophilic ( . 45 C)

Food waste alone Rice bran used as a bulking agent Weight ratio—17:5:2

Commercial inoculum (firmicutes, proteobacteria, Bacteroidetes, actinobacteria)

Composting type and period G G

Home composting Decomposition period—8 weeks

Initial parameter Compost with EM G

G

Thermophilic

G

G

Fed batch aerobic composting Decomposition period—30 days

G G G G G

C/N— 23.78 pH— 4.51

Compost without EM G

G

C/N— 25.10 pH— 5.06

MC—83.7% pH—5.2 OM—94.4% Oil and fats—35.0% C/N—19.8

G

G

G

G

G

G

3.

G G

G

4.

G

G

G G

Food waste—200 kg Codigestion: G Green waste (grass trimmings, small plants, leaves)—100 kg FW:GW—2:1 (by weight)

Food waste—vegetable and bakery waste Codigestion: G Horse manure, grass clippings, branches of palm trees FW:HM:GC:PT—6:2:1:1 Total quantity—30 kg

Microbial inoculum (EM1)—500 mL EM1:water— 1:20

Salmonella enterica serovar Typhimurium— 300 mL

Thermophilic (due to addition of microbial inoculum EM1)

G

Thermophilic

G

G

Drum composting (modified composting drum) Decomposition period—60 days

G G G G G

C/N—23.3 MC—55% pH—4.9 EC—2.2 ds/M TOM—95.8%

G G

G

G

G

Aerated, static and plowed composting (new closed loop heating system or in door composting system) Decomposition period—70 days

G G

G G G

MC—54% Injection of air to aerated system—80 L/ min C/N—49.5 pH—3.5
3.6 Temperature G Aerated—36 C

G G G

G

Composting outcome

References

No significant difference in properties in both compost with and without EM Nitrogen content, odor control, humification in EM compost

Van Fan et al. (2018)

Feeding ratios for composting achievement—5% and 10% but not 15% Firmicutes et al. are dominant phyla Oil and fat removal—76.1% and 65.1% Weight loss achieved—65%

Wang et al. (2017)

C/N—9
15 Finer fraction— , 15 mm Waste volume reduced up to 50 L Decomposition period reduced to 36 days due to inoculum and natural air ventilation

Manu et al. (2017)

C/N—less than 20 pH—7.0
8.0 Escherichia coli persisted beyond 70 days Salmonella inactivated 6
7.0

Pandey et al. (2016)

(Continued )

TABLE 11.1 (Continued) Plowed—37 C Static—45 C Salmonella—7.0 log10 CFU/g

log10 CFU/g in 5
34 days

G G G

5.

G G

6.

G

G

Food waste alone Mushroom residue used as a bulking agent

Synthetic food waste—bread:rice: cabbage:fully boiled pork— 13:10:10:5 Saw dust as bulking agent

AOB (Nitrosomonas europaea/ eutropha)

Nil

Thermophilic

G

G

Thermophilic

G

G

7.

G G

G

G

Vegetable waste Dry leaves 10 kg used as bulking agent Codigestion: G Cow dung and saw dust Total quantity—100 kg

Culture tube media with Lauryl tryptose broth and EC medium

Thermophilic

G

G

8.

G

G

Food waste—vegetable and fruit waste Codigestion: G Yard trimmings (90% grass clipping and 10% tree leaves)

Nil

Thermophilic ( . 45oC) %

G

Lab-scale composting reactor Decomposition period—15 days (under aerobic conditions)

G

20 L Bench-scale reactor composting (struvite-based food composting) G Lime—0.75%, 1.5%, 2.25%, 3% G Struvite (Mg 1 P salts)—0.05 M/kg Decomposition period—35 days

G

550 L Batch-scale rotary drum composting G Trial 1—5:4:1 G Trial 2—6:3:1 G Trial 3—7:2:1 G Trial 4—8:1:1 Decomposition period—20 days

G

Home composting system (batch fed) G Wood and plastic bin (WB and PB)

G

G G G G

MC—74.06% pH—6.08 EC—8.90 ms/cm OM—91.43% C/N—17.26

G

G

G G G

MC—55.5% C/N—33.7% TOC—47.0% TN—1.41%

G

G

G

G G G G

MC—91.20% pH—5.23 C/N—19 TN—2.59% TP—6.6%

Higher diversity indices of AOB appeared during the mesophilic and cooling phases N. europaea/ eutropha dominated the thermophilic stage

Shi et al. (2016)

2.25% lime is recommended for struvite-based composting Nitrogen loss reduced from 44.3% to 27.4% Salinity reduced to less than 4 ms/cm which improves compost maturity

Wang et al. (2016)

Trial 1 G

G

G

C/N— 15 TN— 2.31% TP— 4.30%

Trial 2 G

G

G

C/N— 12 TN— 3.01% TP— 3.27%

Varma and Kalamdhad (2015)

ü CO2 evolution and oxygen uptake rate reduced completely Inactivation of pathogens with higher degradation G

G

C/N—17.1 (for all) Bulk density—235 ( 6 6) kg/m3 Water content—76 ( 6 1.0)%

G

G

C/N—10.8 (WB), 11.9 (PB), 10.2 (GPM), 11.2 (GP) Organic matter— 50.4% (WB and

Adhikari et al. (2013)

G

FW:YT—1:1

G

9.

G

G

G

10.

G

G

G G

Mixed and unmixed ground pile(GPM and GP) Decomposition period—150 days

G

Full-scale rotary drum composting Decomposition period—100days (under aerobic condition)

G

G

Food waste—mixed uncooked vegetables (70 kg) Codigestion: G Cattle manure—15 kg G Tree leaves—10 kg G Saw dust—5 kg Total quantity—100 kg

Culture dependent and culture independent

Food waste—rice, noodles, vegetables, meats, seafood Codigestion: G Green waste—raked leaves and grass clippings Seeding material—2 kg Rice husk used as bulking agent

Nil

Thermophilic

G

G

G

G G G

Organic matter— 75.3% (WB), 75.2% (GPM and PB), 77.0%(GP) pH—6.1 for all HC MC—75% pH—7.61 TC—30% TN—1.43%

G

G

G

Thermophilic

G

G

In-vessel lab-scale composting Decomposting period—12 days

G G G

MC—60% C/N—19.6 pH—8.97

G

G

GP), 45.8% (PB), 49.05 (GPM) pH—7.5 (WB and GP), 7.7 (PB and GPM) Culture dependent: Heterotrophic bacteria, Salmonella et al. showed reduction during composting period Culture independent: 16S rRNA identifies presence of actinobacteria, Bacillus species et al., clustered in phylogenetic tree

Bhatia et al. (2013)

33% of TVS reduced at C/N (19.6) and MC (60%) Seed undergoes germination index suitable for soil application

Kumar et al. (2010)

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roles and the growth parameter should be monitored and measured analytically for assessment of large-scale applications (Amir et al., 2010; Jurado et al., 2014). The composition of the bacterial and fungal communities should be monitored using terminal restriction fragment length polymorphism analysis (T-RFLP), so that the decomposition status of the food waste can be evaluated during processing (Antunes et al., 2016; Tiquia, 2010). The pH and nitrate play basic roles in maintaining the nitrogen cycle and this is enhanced by the presence of NH3-oxidizing bacteria (AOB) populations (Shi et al., 2016). Turning of the pile during the degradation process is an important event to maintain the microbial count, and should take place from initiation to the final maturity phase (Antunes et al., 2016). During the process of composting the microbial factor, biotic or abiotic, plays an active role in microbial count fluctuations, and this determines the pH value and the generation of odorous gases (Lo´pez-Gonza´lez et al., 2015). It is mandatory to maintain the initial pH value by introducing a higher rate of aeration, periodical cooling, and adding recycled compost (Sundberg et al., 2013). The roles of microbiome richness, diversity, and adaptable environmental conditions are essential for successful startup of the food waste degradation process and this can be assessed by adding psychrotrophic bacteria to enable correct composting (Hou et al., 2017; Kinet et al., 2015; Xie et al., 2017). As the microbial community depends on inoculation in food waste decomposition, the inocula for microbial activity enhancement are identified from mature compost rather than by adding commercial inoculants (Karnchanawong and Nissaikla, 2014). Normally substrate characteristics play an essential role in introducing the quantity of inoculums, which determines the composting time and compost quality (Ke et al., 2010). In the food waste composting process the use of inocula such as Pichia kudriavzevii RB1 removes the lag phase and plays an active role in stimulating the microbiome because of its acid-consuming capability (Nakasaki and Hirai, 2017). Ding et al. (2016) outlined the initial stage of food waste composting with the addition of Bacillus, Pseudomonas, and Lactobacillus as inoculating microorganisms, which act as antiacidification agents that enhance the humic character of the compost resulting in a higher yield. To decompose the cellulose in food waste composition, lignocellulosic microorganisms plays an important role in stabilizing the compost at the stable phase (Jurado et al., 2014; Nair and Okamitsu, 2010). The lignocellulosic microorganisms are effective in decomposition when inocula are added and are reported as being cost effective in treating food waste (Nair and Okamitsu, 2010). The quality of the inocula naturally determines the degradation effectiveness, including specific the phototrophic bacteria, yeast, lactic acid-generating bacteria along with commercially available artificial inocula that benefit the compost. In food waste degradation the inoculants play an active role as they reduce the process time in which the complex nature of the mature compost is neutralized (Manu et al., 2017). Irrespective of the quantity of organic materials, the addition of inocula has an immediate effect in breaking down the structure, which is enhanced with the help of enzymatic activity. Normally the organic matters such as starch, sugar, and protein are easily broken down with the help of enzymes secreted by the fungi and bacteria, leading to oxidation with the catalytic reaction of enzymes (Wang et al., 2016). The specific enzyme responsible for catalytic activity causes breakdown of cellulose, protein, and starch into cellulase, protease, and amylase (Pandey et al., 2016).

11.4

Four phases of the compost process

The practice of composting needs to be a systematically organized process, which is carried out in mesophilic, thermophilic, cooling, and maturation stages. Considering the nature of food waste, it is heterogeneous with a habitat having a higher moisture content and higher organic to ash ratio. For a successful food waste composting strategy the physicochemical parameters of the raw material should be maintained within the standards, and the parameters governing successful composting include pH, carbon to nitrogen ratio, humidity content, exposure to air rate, particle size, and porosity. It is observed that an inadequate initial feeding stage, and subsequent altering of the mixing composition will lead to the development of bulking agent and because of this the process will be under stress, causing odor emissions and yielding a low-quality compost. To improve the quality of compost it is mandatory to monitor the progress of the microorganisms, which have direct and indirect influences on the maturity of the compost (Chandna et al., 2013; Lo´pez-Gonza´lez et al., 2015).

11.4.1 Mesophilic phase As it composting is an environment-friendly process, the influence of climate naturally varies the processing time and degradation potential. The role of bacteria in composting plays a predominant part as they react with carbon and oxygen to produce CO2 and energy, and this energy is utilized for multiplication and the remainder produces heat. Even the bacteria found in the intestinal tract such as Escherichia coli can be responsible for the initial startup of degradation,

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241

and they normally emerge with the increase in temperature under favorable conditions available in the cluster. The addition of inocula along with raw material shows a drastic improvement in the organic degradation rate in the mesophilic stage (Karnchanawong and Nissaikla, 2014; Onwosi et al., 2017). The inoculants may be a pure culture (Hou et al., 2017; Zhao et al., 2016a), or mixed culture (Manu et al., 2017; Van Fan et al., 2018), used for compositing (Kinet et al., 2015).

11.4.2 Thermophilic phase The process of composting takes place at a temperature of 55 C, which normally destroys any microorganisms which cannot survive at this temperature. This creates a sanitized compost, which after 3 days becomes a sterilized compost which is ready for further degradation (Ravindran and Sekaran, 2010; Zhang and Sun, 2014). The removal of E. coli and the associated pathogens in the process of initial composting is essential for the compost to enter the sterilized phase, in which time and temperature are the most important parameters for assessing the thermophilic phase (Chan et al., 2016). As the operating temperature is monitored in the range of 45 C
60 C, organic food waste enters the thermophilic composting phase. This is the indicator for the start of the decomposition stage and the continuous maintenance of this stage produces stable compost (Rich and Bharti, 2015). The optimum and stabilized state of decomposition in this phase is identified as 45 C
55 C, which shows a gradual improvement in the composting process. During this thermophilic progression it is identified and observed that the value of pH illustrates a gradual decrease with an increase in pressure, which may be due to the constant heat that enhances the growth of nitrifying bacteria and improves the ammonia content in the compost. As preventive measures are implemented in monitoring the heating process where excessive heat energy is supplied irrespective of the optimized temperature, this may remove the microorganisms which favor the thermophilic activity and as a result the process will be under serious threat. The spore-forming bacteria alone can sustain in the thermophilic temperature range, which is a root cause of thermophilic activity (Varma and Kalamdhad, 2015). A further increase in temperature above the optimized 65 C may inactivate the fungi, actinomycetes, and some of the predominant microorganisms responsible for the successful degradation of food waste (Chen et al., 2011). The maintenance of appropriate temperature favors the rate of degradation with microbial support (Awasthi et al., 2014). The transition of food waste to compost at the thermophilic phase is observed to be a hygienic process, where there is no role for pathogenic organisms in the digestate (Pandey et al., 2016). Auto thermal heat treatment has emerged as one of the best technologies, and in this method heat generation is enhanced with the help of an exothermic reaction due to breakdown of organic compounds, thus reducing the retention time. The source of heat generation is enhanced further due to the degradation process, which kills all pathogens. At optimized thermophilic conditions composting will be faster, but the oxygen content is decreased as nitrification emerges. This process of digestion is easy, and may be practiced globally. The composting equipment is kept closed during the heating process to reduce heat loss and the equipment is maintained with digester covers along with the oxygen generator. In this treatment phase it is observed that the reduced volume of the reactor may enhance the digestion potential.

11.4.3 Cooling phase The cooling practice of the compost after prolonged heating results in efficient conversion in decomposition, this is due to the stabilized microbial activities that create energy and start functioning effectively.

11.4.4 Remedial phase Optimization of stabilized compost is a crucial process as there are no corrective measures available to check the maturity, which determines the yield. Normally when on the verge of composting, the curing time is allowed for and then it is packed as a natural fertilizer. A prolonged curing period may have a positive impact on the safety of the compost as microbial activity may naturally be blocked, producing a sterilization stage.

11.5

Types of composting

The process by which organic waste is transformed into nutrient-rich manure by the action of actinomycetes, fungi, and bacteria in the presence of oxygen is called composting (Bhatia et al., 2013; Logakanthi et al., 2006, 2000). This process is described in the Bible and Talmud, and quoted as taking place in Mesopotamian valley of the Akkadian Empire,

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Food Waste to Valuable Resources

and was also used by the Israelites, Greeks, and Romans. Howard, in 1933, introduced the Indore process with a heap and pit method which was the first confirmed Indian technique for composting, and was later followed by the Bangalore process in 1939. The traditional open method comprises of windrow and static types. Among all the organic waste treatment methods available, microorganisms plays an active part in each process with supporting environmental and favorable economic conditions (Hou et al., 2017). The carbon and nitrogen in food waste are converted into energy with the help of oxidation during the biodegradation process. The process of composting in aerobic conditions is carried out using the following methods: windrows, aerated static piles, gore cover systems, tunnels, and in-vessel.

11.5.1 Windrow The process of windrow composting takes place for a period of 22 weeks in open narrow heaps in which the organic waste is recirculated and disturbed on a regular basis for an effective outcome. The periodically agitated feedstock, food waste, is carried forward to the windrow and kept in an array of 1.5 m height and 2 m width. At the time of processing it is mandatory to expose the compost to favorable conditions such as air, light, and temperature through frequent turning, so that the compost bacterial population is active throughout the stabilization period. The turning frequency of the compost plays a predominant role in microbial count enhancement and degradation potential, and it is advisable to turn the compost on a weekly basis or once every 3 days rather than turning daily (Awasthi et al., 2014). In general, composting through the natural aeration mode is observed to be highly successful; meanwhile the introduction of an air blower in a forced aeration system is observed to be successful in supplying oxygen to the microorganism for successful metabolic activity. This leads to the generation of heat energy with oxidation of carbon to carbon dioxide (Białobrzewski et al., 2015).

11.5.2 Static pile Static pile composting is a short-term method over a 5-week period, that may be prolonged for 12 weeks with a supporting aeration system through the attachment of a blower in a stack that is can be either open or covered. The application of an aeration system is both from the downward and upward segments of the biofilter, once the pile is shaped no agitation or turning is enforced. Compared with a forced aeration static pile, one with natural aeration is far better in cost effectiveness and lower energy requirements (Oudart et al., 2015).

11.5.3 In-vessel The process of composting that takes place in a closed circuit channel with high-pressure aeration is the in-vessel system; the change in rate of aeration determines the quality of the compost and it is observed to be a highly controlled process (Pandey et al., 2016). The closed system usually enhances the progress of the microbial community in multiplication and decomposition, meanwhile constant agitation in this module will create complete aeration of the entire system. The introduction of a mechanical turning practice incorporated into this system provides optimum composting quality within a reasonably short time (Makan et al., 2014).

11.5.4 Vermicomposting In vermicomposting, earthworms are used as the composter, as they disintegrate the readily available organic matter into simple molecules. This method of composting is very effective as the organic matter is converted into worm castings. It is enriched with high nutrient content that increases the benefits the compost in all aspects (Cao et al., 2016). With vermicomposting techniques both plant matter and pathogenic microorganisms are destroyed by the change in temperature (Wadkar et al., 2013).

11.5.5 Gore cover system In this system, polytetrafluoroethylene fabric is used to cover the piles. It is easy to expand and breathable. It also allows escape of carbon dioxide generated during composting, but restricts the infiltration of water and odors. Beneath the surface of the fabric cover, the emissions of volatile organic compounds (VOCs) and ammonia are absorbed, which is similar to the windrow composting process (Schmidt et al., 2009).

Aerobic biodegradation of food wastes Chapter | 11

11.6

243

Factors affecting composting of food waste

The conversion of organic food waste into mature natural compost depends on various significant and predominant factors that favor the successful decomposition and are listed below. To define the potential of a composting process, it is essential to monitor the progress that is favored by predominant parameters such as change in the rate of aeration, the carbon to nitrogen ratio, temperature, and pH (Jua´rez et al., 2015).

11.6.1 Temperature Temperature is recognized as one of the most important deciding features which carries forward the composting process in two different stages: active and mature (Zhang et al., 2012; Zhao et al., 2016b). An increase in temperature during the initial phase normally accelerates the process of degradation with dominating microbes and makes the compost suitable even with favorable microorganisms during a drop in temperature (Kulikowska, 2016). With a change in temperature the physicochemical characteristics of the organic compost are disturbed which favors some of the microbes and builds the substrate and compost strength, which directly influences the treatment efficiency (Chen et al., 2015).

11.6.2 pH The pH level indicator is one of the predominant physical parameters that monitors the microbial activity and generally follows a pattern, with a decline near the early stages followed by an elevation in later stages of composting (Chan et al., 2016). As the optimum pH is 7
8, the release of potassium and organic acids leads to higher saturation (Kalemelawa et al., 2012), and the volatilization of ammonium ions by the nitrifying bacteria and mineralization of phosphorous decreases the pH (Wang et al., 2016). During the changeover period from a mesophilic to a thermophilic phase at an industrial level, exceptionally low pH has been shown experimentally. However, due to organic composition degradation, the proteins increase the pH and this alkalinization may hinder the continued existence of microorganisms responsive to varying pH (Paradelo et al., 2013). Various pH ranges in food waste decomposition studies have been found to be 7.5
8.5 (Zhang and Sun, 2016), 6.7
9 (Rich and Bharti, 2015), 5.5
8 (Chen et al., 2015), and 8.0
8.5 (Jua´rez et al., 2015). At critical stages, to balance the pH level the following substances were used: wood ash (Jua´rez et al., 2015), zeolite (Chan et al., 2016), and calcium carbonate (Paradelo et al., 2013). The addition of these substances balances the pH level and accelerates the rate of composting.

11.6.3 Aeration During the composting process, aeration is provided by the frequent turning of the organic matter. This action is helpful for the easy consumption of organic matter by readily available microbes. Adequate aeration has a direct impact on waste stabilization as if it is in the initial stage, the composting time may be reduced, meanwhile excess aeration or turning could lead to a loss of important components (Awasthi et al., 2014). The turning ratio normally benefits with a high rate of hygienization and there is a relationship between the turning frequency and the physicochemical parameters that acts as an indicator of composting efficiency. Meanwhile it has a major influence on other factors determining the compost maturity (Getahun et al., 2012). Composting carried out with multiple organic compounds has proved that aeration is an effective method in degradation and homogenization (Petric et al., 2012). Turning of feed composition maintains the air distribution, oxygen supply, and may range from once a day to weekly turning (Li et al., 2015; Mohee et al., 2015), with mixing for 30 min a day proved to improved the compost quality (Petric et al., 2015).

11.6.4 Porosity To maintain proper porosity it is mandatory to circulate air through the compost matrix that provides adequate propagation of water content, microorganisms, and full aerobic conditions. The optimum porosity level measurement is carried out by identifying a free air space through an empirical formula, which depends on the bulk density and particle size. Cereal residue pellets and wood chips acts as the best bulking agents, meanwhile the free air space is maintained from 30%
33% (Ku¨lcu¨, 2015) or 30%
50% throughout the process (Schwalb et al., 2011). It is always mandatory to adjust the porosity ratio dependent on the food waste treatment (Ku¨lcu¨, 2015; Mu et al., 2017).

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Food Waste to Valuable Resources

11.6.5 C:N ratio The metabolic activity of microorganisms generates energy and releases nutrients such as C, N, P, and K (Chen et al., 2011; Iqbal et al., 2015). The predominant nutrient ratio, C/N, ranges between 25 and 30 (Yang et al., 2015) or 25 and 40 (Petric et al., 2015). Generally this ratio should be lower in the starting stage, though it may be higher resulting in a slower decomposition rate (Awasthi et al., 2014; Chen et al., 2011). The organic composition is mixed with bulking agents such as rice husk and peanut shells to improve the C/N ratio and porosity (Wang et al., 2015; Zhang and Sun, 2016).

11.6.6 Moisture During composting the change in temperature, oxygen uptake rate, and free air space enhance the microbial growth, however these parameters also directly influence the moisture content (Petric et al., 2012). The optimum moisture content required for biological conversion is 40
70 and if it increases there may be a decline in the gas diffusion and oxygen uptake rates (Luangwilai et al., 2011). The water content of compost depends on the temperature and slowdowns the microbial activity if the moisture range reduces as it distributes soluble nutrients (Guo et al., 2012; Varma and Kalamdhad, 2015). A reduction in the moisture content indicates strong decomposition, as very low moisture content may cause early dehydration, but increased moisture will form water logs and slow down the composting process (Makan et al., 2014).

11.6.7 Particle size Large particle sizes normally slow down the process of decomposition and smaller sizes may condense the mass, as these parameters plays an active role in maintaining aeration. The water-holding capacity and gas to water exchange potentials are directly dependent on particle size variation (Zhang and Sun, 2014). By adopting a sieving method the particle size may be identified in the composting process (Ge et al., 2015).

11.6.8 Feedstock The natural process of composting is enhanced through the addition of inoculating agents, which develop the organic matter degradation rapidly (Karnchanawong and Nissaikla, 2014; Onwosi et al., 2017). These inoculants can be a specific strain (Hou et al., 2017; Zhao et al., 2016a), a commercialized mixture of several species (Manu et al., 2017; Nair and Okamitsu, 2010; Van Fan et al., 2018), or even mature compost (Karnchanawong and Nissaikla, 2014; Kinet et al., 2015).

11.6.9 Nutrient balance (micro and macro) In general, the compositions of food waste normally have higher salt concentrations—appropriate grinding and sieving may remove any adverse impurities present. The heavy metal content in compost may include Pb, Cu, Cd, Cr, and Ni (Huerta-Pujol et al., 2011).

11.6.10 Oxygen uptake The main parameters focusing on composting mass stability are the rate of airflow, temperature, time, and circumstances and location of the compost (Bari and Koenig, 2012). The process of aeration provides oxygen for oxidation while allowing excess moisture to evaporate, which directly influences the steadiness of compost (Guo et al., 2012). The optimal decomposition rate of organic matter is evaluated based on physicochemical parameters before and after composting (Rich and Bharti, 2015). Similarly, the generation of excessive heat depends on forced aeration (Tata`no et al., 2015). A mechanical air compressor is adopted for air circulation, and airflow measurement is calibrated using an airflow meter (Petric et al., 2015), with a vacuum pump used for aeration (Sun et al., 2011).

11.6.11 Microbial growth The respiration index of microbes plays an active role in the degradation of organic matter and the systematic microbial development normally regulates the stability of compost, which is the main focus in managing the composting system

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245

(Rich and Bharti, 2015). With adequate succession of microbial growth a porous space and large surface area are created providing favorable conditions for composting (Luo et al., 2014).

11.6.12 Odor and color During the process of maintaining stable compost gas emissions are created, which have a major impact on environmental sustainability (Nasini et al., 2016). In general, the by-product emissions such as CO2, methane (CH4), nitrous oxide (N2O), carbon monoxide (CO), ammonia (NH3), hydrogen sulfide (H2S), and VOCs are the root causes of secondary environmental pollution which has a major impact on air quality (Adhikari et al., 2013; Jiang et al., 2015).

11.7

Advantages and disadvantages of composting

11.7.1 Advantages G

G

G

G G

G

G

G

G

G

The stability of mature compost is identified as a regulatory measure that monitors the performance of the process (Rich and Bharti, 2015). The availability of a large surface area due to turning frequency and the presence of permeable pore space enhances CH4 oxidation (Luo et al., 2014). In evaluating the compost maturity, the nitrogen cycle plays an important role as the nitrification index, ammonium
nitrogen (NH4
N)/nitrate nitrogen (NO3
N) ratio determines the status of the compost (Zhang and Sun, 2014). The C/N ratio present in the final compost indicates the level of compost maturity (Chen et al., 2015). The availability of soluble organic matter and electron transfer capacity in mature compost predicts the degradation potential and acts as an indicator of stability (Yuan et al., 2012). The quantity of VOC emissions during the process of degradation has a significant impact in the compost reaction (Delgado-Rodrı´guez et al., 2011). benefits of aeration during the composting process are removal of H2O, CO2, and VOCs, and the replenishing of O2 plays a predominant role along with temperature control and moisture variations (Gao et al., 2010). At the time of processing compost the reaction is stimulated naturally with ample nutrient and organic carbon contents (Chatterjee et al., 2013). Introduction of inoculating substrate, such as superphosphate addition in compost, successfully minimizes N losses and reduces NH3 gradually (Predotova et al., 2010). At the time of composting gas emissions are naturally reduced with the addition of mineral additives (Wu et al., 2010).

11.7.2 Disadvantages G

G G

G

G

Although various steps are implemented in reducing the emission of odorous gases, it still occurs as a milestone for evaluating compost maturity and reduction of leachate production (Chatterjee et al., 2013; Nasini et al., 2016). To operate a compost yard it is essential to have adequate space for successful operation. It is mandatory to maintain a satisfactory C/N ratio and NH4/NH3, which is even more complicated for successful operation. The presence of organic compounds such as total organic carbon and volatile organic carbon is essential to maintain successful compost, which may be lacking due to changes environmental conditions and composition (Qian et al., 2014; Tian et al., 2012). The dumping of immature compost to soil causes harmful effects to plants and aquatic ecosystems (Jua´rez et al., 2015). The role of leachate in food waste dumping plays an enormous role in creating pollution, and it is a serious concern to focus on the availability of heavy metals, and chlorinated organic and inorganic salts (Chatterjee et al., 2013).

11.8

Current scenario of food waste composting

11.8.1 Developed countries In the United States, the food waste composting process is carried out in numerous facilities to yield a profitable output. This process is employed due to its environmental sustainability and efficiency, meanwhile preference

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Food Waste to Valuable Resources

TABLE 11.2 Revenues through food waste composting. S. no

Nature of work

Value

Source

References

1

Landfill disposal cost

US$50 per tonne

Transportation

Nizami et al. (2017)

2

Food waste to compost onsite

US$40 million per year

Savings in disposal costs

Nizami et al. (2017)

3

Stable mature compost

US$75
200 per tonne

Market value

Alzaydi et al. (2013)

4

Operating cost of process

US$220.48 million

Revenue generation

Alzaydi et al. (2013)

5

Net saving

US$70.72 million per year




Waqas et al. (2018)

is given to compost rich in nutrients. The conversion of food waste to manure project has been recognized as a commercial revenue stream in the United States. For landfilling of food waste individual households pay a nominal fee, therefore composting is cheaper. In the same way, dumping of food waste is entirely banned in Canada; instead each household is encouraged to practice composting of food waste within their home. In various parts of New York, New Jersey, and Connecticut composting facilities have been adapted as a basic module and landfilling as an alternative technology for disposal of food waste is not used (Levis et al., 2010).

11.8.2 Developing countries Economically developing countries like India have an enormous opportunity to implement a food waste composting technique. Because of its urbanized culture and growing population increases in the food waste stream have emerged and the environmentally acceptable composting method could be easily adopted (Sukholthaman and Sharp, 2016).

11.9

Sustainable compost and its application in the global market

Organic food waste can be transformed into a valuable compost. It has a predominant role in economic development, where compost is universally recognized as a natural fertilizer (Awasthi et al., 2016). The disposal of food waste through incineration is not possible due to its high moisture content and the high energy requirement that leads to it not being economically feasible compared with natural composting (Mu et al., 2017). The ancient landfill techniques are not recommended due to the high transportation costs. The composting process is eco-friendly and creates an emerging revenue source for individual households. In Gulf countries, food waste management by composting process is accepted as a revenue-yielding technique for the government and it is approved as an environmentally safe process to achieve a sustainable green revolution. A comparative study has been carried out in Gulf countries and their economic benefits are listed in Table 11.2.

11.10 Conclusion Food waste management remains problematic to engineers and scientists, due to its high organic and nutrient content. It can be transformed into different valuable resources, such as natural fertilizer via composting, biofuel via anaerobic digestion, and bioplastic via fermentation. Among these, composting is recognized as one of the best approaches for achieving a sustainable green revolution. From an economic point of view, it is by far the cheapest process and it yields revenue from its final product, with natural fertilizers replacing the use of commercial fertilizers. This chapter provides information regarding the advantages and disadvantages of food waste composting.

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Chapter 12

Bioenergy recovery from food processing wastewater—Microbial fuel cell C. Subha1, M. Dinesh Kumar1, R. Yukesh Kannah1, S. Kavitha1, M. Gunasekaran2 and J. Rajesh Banu3 1

Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India, 2Department of Physics, Anna University Regional Campus,

Tirunelveli, India, 3Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India

12.1

Introduction

Food handled in all places and forms for storing, processing, packing, handling, etc. results in the generation of wastewater. At every stage of cleaning in a food processing unit a huge quantity of wastewater will be generated. The wastewater so produced will have both environmental and economic effects in terms of treatment and disposal. Treatment efficiency depends on the nature of the pollutants, their composition, and strength. Treatment methods vary based on the quantity and quality of wastewater generated. Though various parameters influence the choice of treatment methods, volume of discharge, relative strength of wastewater, energy requirement, and end products of treatment are considered especially important. The customary methods of food waste treatment are landfilling, incineration, composting, anaerobic digestion (AD), etc. Food processing is generally categorized into six groups, namely dairy processing, seafood processing, meat processing, edible oil processing, confectionery processing, and brewery processing. Food waste being utilized for recovering energy is an upgrading concept as it reduces the unwanted environmental effects and also recovers some useful energy. In this way, food waste can be converted into electric energy through a bioelectrochemical system (BES). In BES, microbes are able to execute a double role by degrading the organic matter and producing electric power simultaneously (Berchmans, 2018). Moreover in BES, production of electric power with biogas (methane and hydrogen) from food waste may lead to feasible energy recovery without any carbon emission. High energy content entrapped within this food processing waste can be recovered using suitable energy conversion processes. Moreover, the organic content and biodegradable nature of food wastewater makes it a suitable substrate for microbial fuel cells (MFCs). MFCs degrade pollutants and generate electricity using exoelectrogens. Up to now a wide range of food industry wastewaters have been studied for electricity generation including from brewery, dairy, winery, slaughterhouse, seafood processing, meat processing, starch, cheese whey processing, etc. High energy density from these wastewaters and their abundant supply has resulted in their treatment with fuel cells on a pilot scale. Other advantages of MFCs are lower biofilm yield, operation at low temperatures, reduced aeration needs, lack of sludge production, and potential for odor control. The essential components include the anode, cathode, proton exchange membrane, and external electrical circuit. The fundamental processes involved are formation of biofilm, bio-oxidation of substrates, exocellular electron transfer to the anode and external circuit, proton diffusion via specific proton exchange membrane, and reduction reactions at the cathode chamber using electron acceptors. Biofilm formed at the anode is heterogeneous in nature, degrading multiple pollutants at the same time. MFCs differ from conventional anaerobic treatment not in the degradation of pollutants but in their metabolic pathways and reduction reactions. The field is gaining rapid development as knowledge of microbiology and microbial interactions with the electrodes is increasing. This chapter discusses the characteristics of various food industry wastewaters, components of MFCs, configurations and factors influencing MFC performance, anodic microbiology, and details of pilot-scale plants. The chapter also discusses the configurations, factors influencing microbial electrolysis cell (MEC) performance, and the effect of MECs in treating various food industry wastewaters.

Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00012-2 Copyright © 2020 Elsevier Inc. All rights reserved.

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12.2

Food Waste to Valuable Resources

Food processing industries and their effluent characteristics

12.2.1 Dairy industry Increasing demand for milk and milk products has led to the tremendous growth of dairy industries, with an expected growth of 2% per year. Every step of the dairy industry consumes water, proportionately discharging wastewater. Diverse products such as pasteurized and sterilized milk, yogurt, cheese, cream, butter, and milk powder are produced. Effluent is generated from both production and packing units. The characteristics of dairy effluent show great variability. The pollutants present in dairy industry wastewater are suspended and dissolved solids, soluble and trace organics, nutrients, fats, chlorides, sulfate, lactose, and they have high chemical oxygen and biological oxygen demands (Deshannavar et al., 2012; Kushwaha et al., 2011). The wastewater may also contain germicides, detergents, and other types of chemicals (Shete and Shinkar, 2013). Dairy wastes are alkaline in nature when they are released, however they rapidly become acidic because of fermentation of milk into lactic acids. The waste stream has casein, solids, and detergents used for washing with a high sodium content. Effluent characteristics of dairy wastewater are as follows: chemical oxygen demand (COD) (1900
2700 mg/L), biochemical oxygen demand (BOD) (1200
1800 mg/L), pH (7.2
8.8), total suspended solids (TSSs) (500
740 mg/L), and total solids (TSs) (900
1350 mg/L) (Deshannavar et al., 2012). Faria et al. (2017) reported on a dual chamber treating synthetic dairy effluent in continuous mode of operation. The authors achieved maximum COD removal of 63% 6 5% after 20 days of continuous mode operation. They also obtained 92.2 mW/m2 and 24.2% 6 1.5% of maximum power density (PD) and coulombic efficiency (CE), respectively. A single-chamber air cathode MFC (SCMFC) with an anode made up of graphite-coated stainless steel mesh (spiral shape) and a cathode made up of polytetrafluoroethylene (PTFE)-coated carbon was fabricated by Mardanpour et al. (2012) to generate electricity from dairy industry wastewater. They operated the MFC for 450 h and obtained maximum COD removal of 91% with 26.87% and 20.2 W/m3 of maximum CE and PD, respectively.

12.2.2 Beverage industry A huge quantity of wastewater effluent is generated from the beverage industry. Compared to the water contained in beverages the bulk of the consumption is for cleaning and washing purposes. In most cases, the effluent disposal costs dominate the production cost (Brewers Association, 2016). Wastewater generated per cubic meter of beer produced is around 3.3 m3, with a COD of 13.2 kg/m3. Malting, milling, mashing, filtration, boiling, fermentation, maturation, stabilization, clarification, and packing are processes involved in the beverage industry. The waste stream has an organic nature due to sugars, starch, volatile compounds acids, etc. The waste stream is highly biodegradable in nature, with a BOD/COD of around 0.7. Effluent characteristics are: COD (800
3500 mg/L), BOD (520
2300 mg/L), TSS (200
1000 mg/L), TS (2901
3000 mg/L), pH (6.5
7.9), nitrogen (12
31 mg/L), and phosphorous (9
15 mg/L) (Brito et al., 2007).

12.2.3 Cassava mill processing Cassava, also called tapioca, is a major commercial crop and is grown in more than 80 countries around the world. Tapioca starch is used both in food and nonfood industries and so is in high demand. One tonne of cassava root produces 0.2 tonne of starch. The starch production process includes rinsing, peeling of roots, grinding, extracting, settling at various stages, and mixing (Mai, 2006). The average wastewater generation is 20 m3 per tonne of starch production. The wastewater is rich in carbohydrates with COD, BOD, and solids. The effluent characteristics are as follows: pH (5.5 6 0.2), suspended solids (3000 6 562 mg/L), ammonia (37 6 2 mg/L), COD (16,000 6 968 mg/L), total Kjeldahl nitrogen (TKN) (350 6 12 mg/L), total carbohydrate (16 6 1 mg/L), cyanide (86 6 2 mg/L), and conductivity (2300 6 123 μS/cm). Cassava mill processed effluent can be a good substrate for MFC because of the higher amount of carbohydrates and lower ammonical nitrogen concentration. The toxic cyanide content in the effluent is released during the production of starch. This may cause adverse impacts during normal biological treatments. Hence MFC, have been tried for cassava mill processing wastewaters (Kaewkannetra et al., 2011). Prasertsung and Ratanatamskul (2014) reported single-chamber MFC treatment of cassava wastewater. Using carbon cloth as an anode and PTFE layers coated with carbon cloth with platinum (Pt) catalysts as the cathode, the authors created MFCs in a batch mode flow operation. A maximum PD of 28.68 W/m3 and COD removal of 91.44% 6 0.72% was achieved in this experiment. Even cassava

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peel was used to produce electricity using SCMFC (Adekunle et al., 2016). In this study, the authors used a graphite brush as the anode and a carbon cloth as the cathode. A maximum PD of 29 mW/m3 was obtained.

12.2.4 Potato processing wastewater Potato chips, frozen French fries, dehydrated diced potato, potato granules, potato flakes, and potato starch are some of the processed forms of potato. The processes used include the following steps: storage, peeling, slicing, sorting, washing, cooking, conveying, etc. Constituents of potato are water with dissolved organic compounds, starch, and cellulose. Hence the wastewater is highly biodegradable in nature. COD, TSS, and TKN are also present in excess quantities, which may pose a serious wastewater problem. For every kg of potato processing, around 17 L of wastewater is generated. The wastewater stream also contains dirt, fat, and chemicals used as preservatives. Caustic soda is used in the potato processing unit for softening. This gives an alkaline nature to the effluent. Potato processing wastewater has the following characteristics: COD (6769 6 970 mg/L), TS (6725 6 1865 mg/L), TSS (2187 6 1046 mg/L), phosphates (36 6 28 mg/L), nitrogen (0.04% 6 0.01%), pH (4.9 6 0.8), and temperature (35 6 15.5). Potato chips processing wastewater is treated using dual-chamber MFCs with graphite as electrodes (Radeef and Ismail, 2019). The results of this experiment showed up to 90% COD removal with 95.7 mW/m2 PD in a continuous operation mode. Another study with a dual-chamber MFC (Du and Li, 2016), using a mixture of uncooked and cooked potato as substrate, produced a maximum PD of 253.9 mA/m2 and CE of 92.7% with COD removal of 84.1%.

12.2.5 Meat processing wastewater Wastewater is generated in meat processing due to the slaughtering of animals, cleaning of the premises, and processing. Bouwman et al. (2013) reported that meat processing would be doubled by 2050. The global production of pork and poultry is also growing rapidly. As the Indian diet is changing to become more like a Western diet, beef production is increasing (Pingali, 2007). Hence the number of slaughterhouses will increase, leading to the generation of a huge quantity of meat processing wastewater. Slaughterhouse wastewaters can deoxygenate surface waters and pollute groundwater. Meat processing wastewaters are detrimental because of their composition of fats, proteins, and fibers. The main contaminants are from blood and mucus from the stomach and intestine, but the wastewater characteristics depend on the type of animal slaughtered. The main effluent characteristics include pH, COD, BOD, total nitrogen, total organic carbon, and TSSs, along with odor (Bustillo-Lecompte and Mehrvar, 2016). They also contain pathogens, nonpathogens from the gut, and chemicals from detergents and disinfectants (Tritt and Schuchardt, 1992). Heavy metals such as iron, manganese, copper, and zinc are added from manure and blood. The range of slaughterhouse wastewater contents is as follows: TOC (70
1200 mg/L), BOD5 (150
4635 mg/L), COD (500
15,900 mg/L), TN (50
841 mg/L), TSS (270
6400 mg/L), pH (4.90
8.10), TP (25
200 mg/L), Orto-PO4 (20
100 mg/L), K (0.01
100 mg/L), color (175
400 mg/L Pt scale), and turbidity (200
300 FAU). The range of slaughterhouse wastewater contents has also been found to be: TSS (0.39
9938 mg/L), COD (527
1,256 mg/L), BOD5 (200
8231 mg/L), TOC (72.5
1718 mg/L), TN (60
339 mg/L), TP (2.7
75.9 mg/L), Orto PO4 (30.1
77.3 mg/L), K (0.01
0.06 mg/L), color (178
391 mg/L Pt scale), turbidity (271
279 FAU), and pH (6.0
6.9) (Bustillo-Lecompte and Mehrvar, 2015). An ACMFC was fabricated to treat slaughterhouse wastewater (Mateo-Ramı´rez et al., 2017) with graphite granules as the anode and carbon cloth as the cathode. With 72% COD conversion, the authors achieved a PD of 32 mW/m3 and reported that slaughterhouse wastewater could be a good feedstock for MFCs. Dual chambers with graphite and copper as the anode and cathode, respectively, were used to treat slaughterhouse wastewater (Prabowo et al., 2016). The results showed that 700 Wm/m2 of PD with 67.9% COD removal were obtained.

12.2.6 Seafood processing wastewater Sea fishing is one of the major sources of income for people around the world, and seafood is an important commodity exported all over the world. Filleting, salting, and canning are some of the seafood processing methods. The negative environmental impact of seafood processing include the huge consumption of water and the discharge of processed wastewater which is highly organic in nature. The nature and quantity of pollutants vary depending on the type of fish used and the method of processing. Commonly observed pollutants are volatile compounds, nitrogen, phosphorus, fats, oil, and grease. Trace amounts of heavy metals are also present because the majority of terrestrial wastes end up in the sea. Processing equipment can be disinfected with chemicals like hypochlorite, causing the wastewater stream to contain chemicals, such as

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caustic soda. The waste stream also has common salt and acids which are used as seafood preservatives. The effluent also has a high amount of fecal coliform and E. coli concentration as untreated sewage mixes with water bodies. The following are the characteristics of seafood processing wastewater: TS (12.4 6 0.12 kg/m3), TDS (5512 6 67 g/m3), TSS (6962 6 139 g/m3), total COD (4000 6 120 g/m3), soluble COD (2700 6 60 g/m3), chloride (432 6 50 g/m3), alkalinity (205 6 23 g/m3), and pH (9) (Jayashree et al., 2016). The authors achieved a maximum PD of 105 mW m22 with COD removal of 83% through tubular up-flow MFC. Fish market wastewater was used as substrate in single-chambered MFC (Noori et al., 2016) and obtained 80% COD removal and 6.06 W m23 PD using stainless steel as the anode and vanadium pentoxide microflower-catalyzed carbon cloth as the cathode.

12.2.7 Cereal processing Whole grains consumed directly are more nutritious and healthy, however most grains are processed to make them more appealing to consumers. Processing of cereals mainly removes the bran, germs, and poorly digested compounds, and increases the concentration of desirable compounds. Highly utilized cereals include corn, wheat, oats, grain, pulses, rice, millet, ragi, maize, and sorghum. Cereal processing units normally have the following equipment: conveyors, shredders, extruders, storage tanks, and pipe networks, with most equipment being sterilized using pressurized steam which requires a huge quantity of water to be heated and cooled. In addition, wastewater is also generated from the dust scrubbers used to control air pollution and from discharge sites. The characteristics of cereal processing effluent are TSS (300
500 mg/L) and COD (2000
3000 mg/L). These values may increase if the processing includes the addition of sweeteners and frequent change of products.

12.2.8 Cheese whey processing Cheese whey is a by-product of the cheese industry. It is a yellowish liquid with a green tint and is free from fats. The origin of the milk used for cheese manufacturing affects the characteristics of the whey produced. Of all dairy products, cheese whey contributes the largest quantity to wastewater generation. Cheese whey wastewater is generally acidic in nature, but the pH may show different values when more alkaline chemicals are used for washing. The effluent contains a huge amount of ammonium nitrogen, total phosphorus, COD, BOD, and suspended solids. The effluent has biodegradability with a BOD/COD ratio of 0.4
0.8 (Prazeres et al., 2012). Proteins, lipids, lactose, and all mineral acids of milk are also present in the wastewater. The following are the characteristics of cheese whey processing wastewater: TS (126.8 6 8.6 g/L), volatile solids (VS) (116.8 6 7.8 g/L), COD (122.1 6 5.6 g/L), lactose (103.4 6 2.1 g/L), acetate (246 6 57 mg/L), lactate (3016 6 123 mg/L), alkalinity (1.8 6 0.2 mg CaCO3/L), pH (4.68 6 0.04), N-NH4 (108 6 3 mg/L), TKN (1200 6 26 mg/L), Cl (981 6 9ppm), sulfate (430 6 15 ppm), phosphate (1455 6 89 ppm), sodium (181 6 19 ppm), calcium (1260 6 139 ppm), magnesium (783 6 68 ppm), and potassium (525 6 18 ppm) (Moreno et al., 2015).

12.3

General components of microbial fuel cells

The elemental peripherals of an MFC are the anode and cathode chambers which hold the electrodes, membrane separator, and electrode catalyst (optional). The cathodic chamber and membrane separator are requisite in the case of a single-chambered air cathode MFC. The chambers are made of glass, polycarbonate, or plexiglass. Membrane separators are constructed from nafion, ultrex, polyethylene, salt bridge, porcelain material, etc., while platinum, platinum black, manganese dioxide, polyaniline, and ferric compounds are used extensively for the electrode catalyst. Each of the above components is further discussed in detail below, and Fig. 12.1 displays the schematics of an MFC.

12.3.1 Anode Electrodes selected for MFCs should satisfy the following properties; high conductivity, large surface area, high permeability, corrosion free, and being less prone to microbial fouling. Electrodes must be cytocompatible and nontoxic, which ensures bacterial viability and colonization. Electrodes should not be expensive and widely available for largescale MFC setup. The choice of anode materials for a study is complex because of (1) the large diversity of available materials, (2) performance is not solely related to materials as they undergo different surface treatments, and (3) performance is also related to the biological process, MFC assembly, and architecture. Hence, the choice of anodic material is dependent on the objective of the study, cost, and availability.

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FIGURE 12.1 Schematic of an MFC.

Metals used need to be highly compatible to meet the basic requirements of the anode, and copper is not utilized because of its lethal nature. Platinum (Pt), gold (Ag), titanium (Ti), and stainless steel (SS) are usually adopted for the anode. However, SS shows lower performance compared to graphite materials because of its low surface roughness and low electrode
biofilm interface. Modified stainless steel grids show higher performance than carbon cloth. Graphitecoated SS in a spiral shape as the anode is cheap and shows good stability, with higher power production due to its porous surface (Mardanpour et al., 2012). Due to the spiral geometry, the anode area is increased per unit volume and electrode spacing is reduced. Mardanpour et al. (2012) reported that a spiral-shaped anode showed more than a 2.5-fold maximum open circuit voltage compared with other MFCs. The authors treated dairy wastewater in SCMFC and achieved 20.2 W/m3, 26.8%, and 91% of PD, CE, and COD removal, respectively. They also reported that good biofilm attachment with high specific area per unit volume, the spiral stainless steel mesh with a graphite coating looked to be a promising alternative to conventional electrodes for power generation in MFCs. Cha et al. (2010) reported that increasing the anode surface area could enhance bacterial adhesion, electron transfer, and PD.

12.3.1.1 Carbon-based anodes Carbon-based substances are frequently used as anode materials (Santoro et al., 2017). They satisfy properties like high conductivity, nontoxicity, biocompatibility, chemical stability, and very low sensitivity to corrosion, accessibility, and ease of use. Their surface can be gently abraded to improve bacterial adhesion. However, low porosity and low specific surface are limiting factors of carbon rods and sheets as anodes. Carbon papers are porous, stable, inelastic, and more costly (Zhou et al., 2011). It can be prepared by coating carbon powder mixed with PTFE. Carbon cloth, tissue, and mesh are flexible with high specific area and porosity, but are expensive. Carbon fiber veils are hard and contain randomly distributed carbon fibers over their surface area. Graphite powder id composed of micrometric pieces of (activated or not) carbon. These used in MFCs are well compacted to provide electrical conductivity between the granules. Graphite plates or rods used as electrodes are useful and have a large surface area (Jayashree et al., 2014a,b). Graphite fiber brush is made up of carbon fibers, which protrude from a central titanium stem. The fibers are produced from fabricated polymers and plant materials containing cellulose (Kalathil et al., 2017). They provide high surface area but have the tendency to clog. Carbon foam (reticulated vitreous carbon) is made of rigid interconnected carbon walls that have porosity similar to carbon felt, but are less resistant and more expensive. Carbon plates or rods are widely used by the researchers because of their widespread availability and active surface area. Carbon papers without surface treatment produce good power densities of 20
250 mW.m22. Carbon fibers offer huge surface area and hence produce power densities greater than 250 mW.m22. Carbon brush or felt with surface treatment produces power densities of 50
1000 mW.m22. Cashew apple juice is used as a substrate for MFCs by Priya and

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Setty (2019), who constructed MFCs with carbon cloth as the anode and achieved 31.58 mW/m2 PD. Penteado et al. (2017) discussed a study in which three types of carbon material were used as anode material treating winery wastewater. They identified that anodes made up of carbon felt showed a high PD of 420 mWm22, due to the greater adhesion of microbes in the anode.

12.3.1.2 Surface treatment of anodes To augment bacterial adhesion for biofilm formation and transfer of electrons, certain surface treatments are adopted to the anode materials. Compared with raw fiber brush, carbon fiber brush heated and treated with acid produces 34% higher power. Ammonia treatment to carbon cloth (1 hour heat treatment at 700 C under gas feeding of 5% NH3 in a helium gas vector) increases power by 48%, CE by 30%, and decreases acclimatization time by 60% (Cheng et al., 2006). Surface modification can also be done by immobilization of nanotubes made of carbon, graphene suspensions, manganese/iron oxide, neutral red, etc. Carbon nanotubes help in producing 20% higher power. Transfer of electrons from bacteria is reduced with an increase in distance from the electrode. Nanoparticles, because of their size and electrical properties, can be used to communicate with the biological systems. The charge transfer capacity of carbon nanotubes (CNTs) increases with the help of π
π stacking of carbon atoms and the pili (Erbay et al., 2015). CNTs are highly stable and biocompatible. Polypyrole
carbon nanotubes enhance the electrochemically active area as they have some molecular units similar to mediators of the oxidation reduction reaction. Attachment to the bacterial surface is favored by treating activated carbon (AC) with nitric acid and ethylene diamine. Using multiwalled carbon nanotubes, the current density is improved by a factor of 82 in comparison with bare glass nanotubes (Peng et al., 2010).

12.3.2 Cathodes In a cathode, electron (e2), proton (H1), and oxygen (O2) combine to form water. The reduction reaction in a cathode is a limiting factor in MFC performance. Cathode performance is improved by using catalysts like noble metals (platinum), liquid chemicals (ferricyanide), and microorganisms (biocathodes). Anode materials are mostly selected as cathodes (Tharali et al., 2016). The cathode usually is a carbon material, with platinum-coated carbon or plain carbon immersed in a catholyte solution (Logan et al., 2006) like iron-chelates, permanganate, hexacyanoferrate, manganese, hydrogen peroxide, and nitrobenzene. Oxygen is a sustainable material and is frequently utilized as an electron acceptor. However, in a neutral solution at low temperature, oxygen shows poor kinetics. The choice of cathode material is critical as it affects the performance of the MFC. Platinum is an oxygen-reducing catalyst. Though platinum-based oxygen electrodes are very useful, they have limitations such as being expensive, formation of a poisonous platinum oxide layer over the electrode, sensitivity to biological environment, and chemical fouling. This has resulted in the search for alternative electrodes. Minimizing and eliminating platinum usage in MFCs reduces the capital cost. Less expensive materials such as carbon, nitrogen functionalized, and co-tetramethylphenylporphyrine, have been tried as replacements for platinum. Lead oxide is a good substitute for platinum cathode catalysts, as it displays four times higher power recovery than platinum. However, its use is limited due to its toxicity. Low-cost materials such as porphyrines and phthalocyanines have also been tried as alternatives for platinum. In MFCs, an air cathode means one side of the cathode is exposed to the atmosphere and that it is hydrophobic in nature. It is leak resistant and oxygen can diffuse through it (Logan et al., 2006). A Pt-free cathode with hydrophobic carbon cloth (acting as an air transport layer) is placed as a leakage barrier (outer layer) and a microporous layer is placed close to the solution (inner layer). A mixture of AC and PTFE, when coated as thin layer over the surface of nickel or stainless steel mesh, reduces the cost of Pt. The formation of a biofilm in air cathodes reduces the performance stability, and noncatalytic activity depreciates power generation (Rabaey and Keller, 2008). Fig. 12.2 shows the steps involved in the preparation of an air cathode. Ferric cyanide is considered to be an excellent electron donor and is frequently used in MFCs. The properties which favor the use of ferric cyanides are faster reduction kinetics than oxygen, high redox potential, high solubility, and no requirement for expensive metals like platinum catalyst. Ferric cyanide shows greater mass transfer capability and power generation than oxygen. Theoretical cathode potentials when calculated showed oxygen to have higher value than ferric cyanide. However greater performance is seen in ferric cyanide because oxygen has high over potentials. Adekunle et al. (2016) discussed a single chamber air cathode MFC using cassava peel. They used carbon cloth as the cathode with a gas diffusion layer coated 60% Pt C and achieved 29 mWUm23 of PD.

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FIGURE 12.2 Steps involved in the preparation of an air cathode: (A) coating of the carbon base layer; (B) air drying; (C) heating at 370 (D) curing; (E) coating of the PTFE layer; (F) coating of the platinum catalyst.

12.3.2.1 Biocathodes Biological catalysts are a better alternative to chemical catalysts to reduce the oxygen over potential. Biocatalysts can be enzymes or microbes. Microorganisms like algae produce oxygen by photosynthetic reactions, reducing the external cost for oxygen supply. Microbial metabolism produces useful compounds and removes unwanted wastes. Power generation can also be coupled with a denitrification process. The power production of the biocathode increases with time (Luo et al., 2011). The surface area of cathode influences its performance, if the cathode size is increased twofold its power production increases by 65% (Rahimnejad et al., 2015). Further knowledge about the bacterial density and surface area gives an idea of the optimum design, but biocathodes require a longer start-up time. This can be minimized by modifying the cell surface properties, promoting the enzyme activities, and reducing the doubling time of bacteria. Various biocatalysts are available which make use of other electron acceptors (chromium, nitrate, perchlorate, acetate, fumarate, hydrogen, carbon dioxide, et.,) than oxygen. Based on the electron acceptors, biocathodes are subdivided into aerobic and anaerobic. Aerobic biocathodes use oxygen as electron acceptors and reduce iron and manganese, whereas anaerobic biocathodes directly reduce nitrates and sulfates.

12.3.3 Membrane separator Dual-chamber MFCs have a cathode and anode chamber separated by a membrane. Microbial metabolism produces electrons and protons from the substrates at the anode. The movement of protons and electrons produces a potential difference (Chae et al., 2007). It is important for the membranes to be impermeable to oxygen and substrate. The desirable

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properties of a membrane separator are elevated proton conductivity, electron conductivity, impermeability to electrolytes and oxygen, chemical, thermal, and mechanical stability, sufficient diffusion and electro-osmotic properties to transport water, high durability, and lower cost. The dividers can be salt bridge or ion exchange membranes (IEMs). IEMs are of two types: (1) cation exchange membranes (CEM)/proton exchange membranes (PEM) and (2) anion exchange membranes (AEM). Cation exchange membranes have negative charges and permit cations to diffuse and refuse anions. Examples of CEM are Nafion, ultrex CMI-7000, Zirfon, Hyflon, and polystyrene. Among these, Nafion is extensively used as a CEM. Nafion perfluorosulfonic acid membrane consists of hydrophobic fluorocarbon (-CF2-CF2-) to which a hydrophilic sulfate group (SO32) is attached. These negative charges enable them to conduct protons. Advantages of Nafion are specific conductance of cations, durability, and hydration. The drawbacks of Nafion include (1) expensiveness (40% of total cost), (2) instability at high temperatures (100 C), (3) amenable to chemical and bio-fouling (increase internal resistance and lowering MFC performance), and (4) greater transmission of other cations (Na1, K1, NH41) than protons. It also partially permits oxygen and ferric cyanide from the cathode side to the anode. Ultrex CMI 7000 is another cation exchange membrane that has comparatively higher mechanical stability than Nafion. Low-cost CEMs include Zirfon and Hyflon. The main limitation of Zirfon in comparison to Nafion is its high permeability to oxygen, which causes adverse anodic reactions. Hyflon exhibits better conductivity and chemical stability then Nafion. However, its greater internal resistance limits its applications. Conductivity, ion transfer, and diffusion coefficient are reduced because of membrane fouling. This leads to a drop in electricity production and requires membrane replacement, which increases the cost of the process. Along with high cost, oxygen permeability and pH splitting are potential barriers to the use of membrane separators. To overcome these drawbacks anion exchange membranes (AEMs) have been tried with carbonate and phosphate buffers which show higher substrate permeability. AEMs have a positive charge on the surface and attract a negative charge (Jayashree et al., 2014a,b). The anode chamber needs to be maintained in strict anaerobic conditions. Oxygen transfer via a membrane separator may damage anaerobic bacteria or lead to a loss of substrate by aerobic bacterial respiration. Air diffusion through the membrane can be halted by applying sparging nitrogen at the anode compartment. The PD of nitrogen-sparged MFCs is three times higher than nonsparged MFCs. MFCs with the same membrane but different configurations also result in different performance. Membrane resistance has a low impact on internal resistance, is not constant, and relies on the characteristics of the electrolytes. Jayashree et al. (2016) experimented with tubular upflow MFCs to treat seafood processing wastewater with proton exchange membrane. They obtained 105 mW m22 with 83% COD removal. pH splitting of cation exchange membrane led to the development of anion exchange membranes. Hydroxide and carbonate ions transfer from the cathode to anode side carrying protons. AFN, ACS, and AM-1 are widely utilized anion exchange membranes. The highest current production is in the order of AFN, AM-1, and ACS (Ji et al., 2011). In addition to its advantage, the main drawback of AEM is crossover of the substrate resulting in membrane fouling. To overcome issues caused by CEM and AEM, membraneless approaches have been tried also. Because of the cross-over of substrate and oxygen, membraneless MFCs are not preferred. Recently, to overcome the cost of Nafion membranes, sulfonated polymer membranes [SPEEK—sulfonated poly(ether ether ketone)] have been used. These materials are stable chemically, thermally, and mechanically. SPEEK membranes generate a higher PD of around 670 mW/m2 and 75% columbic efficiency (Ayyaru and Dharmalingam, 2011). Nylon nanoporous membranes and polycarbonates with their open structures facilitate proton transfer and produce maximum power densities. Cheap and low-conducting polymers combined with SPEEK produced a PD of 170 mW/m2 with a columbic efficiency of 68% (Lim et al., 2012). Adding polymers/nanoparticles may increase the surface roughness, which may cause membrane fouling, reducing MFC performance (Lim et al., 2012). However many recent studies have been carried out using nanocomposites because of the material cost (Ghasemi et al., 2013). Porous membranes such as glass wool (Mohan et al., 2008) and microfiltration (Sun et al., 2009), which are less expensive, can also be used. They have similar disadvantages to membraneless technologies. Radeef and Ismail (2019) used cation exchange membrane as a separator in a dual-chamber MFC treating potato chips processing wastewater. The results showed that 90% of COD with 95.7 mW/m2 PD was obtained in continuous mode operation.

12.4

Various configurations of microbial fuel cells

MFCs have a varied range of applications including electricity generation, wastewater treatment, bioremediation, degradation or removal of pollutants, production of by-products, etc. To meet all these applications a single type of reactor configuration is not sufficient; the following are a few selected types of reactor configurations.

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FIGURE 12.3 Schematic of a dual-chamber MFC.

12.4.1 Dual chamber This is the earliest model and is similar to a chemical fuel cell. It has separate cathode and anode chambers which are connected by a salt bridge or proton exchange membrane. This membrane transfers positive electric charges from the anode to the cathode and inhibits the movement of oxygen to the anode, ensuring maintenance of the anaerobic condition. Generally they work in a batch mode. These dual configurations are highly energy consuming as they need a continuous oxygen supply to the cathode. Dual-chambered MFCs showed reduced performance in PD when converted into a larger scale. Increasing the volume of reactors resulted in a decreasing ratio of surface area to volume, resulting in decreased surface reactions of electrodes. An increase in reactor size also leads to over potentials and surface loses, reducing power densities. Dual configurations are of the following types: simple H-shaped, cuboid shaped, dual chambered upflow, concentric tubular type, etc. A dual chamber was performed to treat dairy effluent, as reported by Elakkiya and Matheswaran (2013). They operated the MFC in a fed-batch mode and achieved maximum values of 2.7 W/m3 (PD), 91% (COD removal), and 17% (CE). A schematic of a dual-chamber MFC is shown in Fig. 12.3.

12.4.1.1 Double-chambered H-shaped chamber This is a simple setup with two chambers and the chambers are connected by a bridge. A cation exchange salt bridge made of agar and salts (NaCl, KCl, and KNO3) is solidified and placed in the glass tube. The PD will be meager because of high internal resistance and reduced surface area. Goat rumen fluid from slaughterhouse wastewater using an H-shaped dual-chambered MFC generated electricity of 8.49 W/m2 (Meignanalakshmi and Kumar, 2016).

12.4.1.2 Cuboid-shaped double chamber This is also called a flat plate MFC or cassette. It has rectangular cathode and anode chambers with a separator membrane between them. The chambers are usually plexiglass. The electrodes are carbon felt, paper, titanium plate, or mesh. Reactions are catalyzed either biologically or chemically. The importance of this configuration is minimization of the spacing between the chambers, reducing internal resistance, and increasing ionic transfer rates. Generally, flat plates operate in continuous mode and individual modules can be stacked either in series or parallel. In series connection fluid flows sequentially in the modules, whereas in parallel connection all modules receive the fluid. This configuration was preferred for research because of its compactness and easiness in handling.

12.4.1.3 Double-chamber upflow microbial fuel cell An upflow MFC is designed to work in continuous mode. It is cylindrical in shape with an anode chamber placed at the bottom and a cathode chamber at the top. The anode and cathode chambers are separated from each other by PEM. Graphite felt is used as electrode (anode and cathode) material (Kaewkannetra et al., 2011; Goud et al., 2011). They are placed at the edges of the chamber. In order to prevent gas build up in the anode chamber and to enhance PEM surface contact, the joints of the anode and cathode intersection are inclined to an angle of 15
20 . To enable a continuous

260

Food Waste to Valuable Resources

FIGURE 12.4 Schematic of an upflow MFC.

mode, provision for entry and exit of wastewater are arranged at the bottom and top of the anode chambers. Using this MFC, sustainable power production over a period of time is possible. Fig. 12.4 shows a schematic of an upflow MFC.

12.4.1.4 Dual-chamber upflow U-shaped microbial fuel cell In this type of MFC, the cathode chamber is modified into a U shape. Javed et al. (2017) constructed an MFC using two polypropylene random tubes of around 30 cm in length in a U shape by means of a union connecting the elbows. A CMI 7000 cation exchange membrane was placed in the joint of the union. Graphite rods were used as electrodes and connected by aluminum wires. The U-shaped configuration was found to be more advantageous than the H shape. This modified U shape also gave the advantage of growing microbes at the bottom. A maximum PD of 88,990 mW/m2 was obtained.

12.4.1.5 Dual-chambered concentric tubular Cathode and anode chambers were made of two concentric PVC pipes of inner diameters 4.5 cm and 6.5 cm, respectively. Their capacities were 300 mL and 500 mL, respectively. The electrodes are made of carbon felt and CMI 7000 is the cation exchange membrane.

12.4.2 Single chambered Dual chambers are expensive and it is difficult to make their dimensions proportionate. All these complexities are avoided in a single-chambered air cathode MFC. No aeration is required in a single-chamber MFC, the anodic chamber alone is present and the cathode is exposed to air directly. The cathode material may be strong enough to withstand the hydraulic pressure and produce minimal or no leakage of electrolyte. The cathode was made of platinum catalyst, carbon cloth base layers, and diffusion layers like PTFE. The cathode side was exposed to air, maintaining the anaerobic condition inside the chamber. To increase the performance of single-chambered reactors multiwalled carbon nanotubes were used. This configuration is preferred for its simplicity in construction and design. A schematic of a singlechamber MFC is shown in Fig. 12.5.

12.4.2.1 Single-chambered upflow Upflow reactors have the advantage of operating in continuous mode. They also facilitate a packed-bed anode, providing more aerial surface for biofilm development. Mohanakrishna et al. (2010) used a single-chambered upflow

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261

configuration operating in batch mode for treating distillery wastewater. The material used for chamber construction was Perspex with 0.5 L capacity. Graphite plates were used as electrodes and Nafion 117 as PEM. The cathode was fixed over PEM and the other side was exposed to air. Copper wires were used for connections, and ports were provided for the inlet and outlet. They observed 72.84% COD removal and color reduction of about 31.67% with PD of 124.35 mW/m2.

12.4.2.2 Single-chambered concentric tubular Concentric tubular structures can operate in continuous mode, which favors their integration with a single-flow wastewater treatment process. The hydraulic retention time can be adjusted to obtain the required efficiency.

12.4.3 Stacked microbial fuel cell Stacked arrangement of MFCs in series has the advantage of producing increased current. In this design several MFCs are interconnected in parallel or series and this facilitates increased power production. The flow rates of electrons from substrate to electrodes vary in series during operation of stacked MFCs. Keeping the flow rate as constant, parallel connections showed six times greater power production with enhanced organics removal. Stacked MFCs are scalable, which is one of the important advantages over other configurations. Fig. 12.6 displays a schematic of stacked MFCs. Stacking was able to produce stable and high electricity with minimal electron loses compared to individual cells. A FIGURE 12.5 Schematic of a single-chamber MFC.

FIGURE 12.6 Schematic of a stacked MFC.

262

Food Waste to Valuable Resources

tubular stacked air cathode MFC was developed to treat swine wastewater in which graphite felt and carbon fiber cloth coated with MnO2 were used as the anode and cathode, respectively, with cation exchange membrane (Zhuang et al., 2012). Removal values of 77.1% and 80.7% for COD and NH14
N, respectively, were obtained with a maximum PD of 175.7 W/m2.

12.4.4 Membraneless Treating wastewater containing more suspended solids using MFC on a large scale has practical limitations such as cost and membrane fouling, giving way to membraneless MFC. Khan et al. (2012) used membraneless reactors for treating food industry wastewater. The anode (16 cm depth) and cathode (12 cm depth) chambers were made of polyacrylic material. Glass beads and glass wool were placed at 2 cm depth on top of the anode surface which separated the anode and cathode. Graphite rods were used as electrodes and copper wires for connecting the circuit. An inlet is provided at the bottom and an outlet at the top. The cathode compartment has a port for aeration and is continuously aerated, maintaining a temperature of 28 6 2 C. The maximum PD obtained was 15.12 mW/m2. Tanikkul and Pisutpaisal (2015) studied the performance of a membraneless single-chambered air cathode reactor for treating distillery wastewater and electricity generation. They made a cylindrical chamber of acrylic material without membrane. The anode and cathode were made of carbon cloth without wet proofing and with 30% wet proofing, respectively. Like a normal air cathode the air side was coated with a gas diffusion layer and the solution side was coated with a catalyst layer. The maximum current density recorded was 77.7 mA/m2. Mohanakrishna et al. (2018) experimented with a cylindrical graphite MFC by eliminating the separate casing and membrane to treat whey wastewater and achieved a high substrate degradation efficiency of 72.76%.

12.5

Reactor design and performance

MFCs involve both biological and electrochemical principles. Therefore, the design of an MFC is more complex than conventional reactors. There is a need to try more MFC models to obtain optimization of the full scale reactor design. MFC reactor design needs to focus on energy recovery, high electron transfer rate, efficient energy conversion, economic reactor design, better treatment efficiency, operational easiness, etc. The long-term performance of a 20-liter continuous-flow MFC treating brewery wastewater was tested by Lu et al. (2017). They used carbon cloth as the electrode and obtained 94.5% organic removal with a PD of 1.61 mW m22. In another study, Zhuang et al. (2012) discussed stacked MFCs made up of graphite felt (anode) and carbon cloth (cathode) for treating swine wastewater. A maximum PD of 226.3 mW m22 with 83.8% COD removal was achieved. Dong et al. (2015) tested 90 liters of stacked MFCs for treating brewery wastewater and achieved 87.6% COD removal with a PD of about 159 6 7.4 mW m22. The authors used carbon brush as the anode and stainless mesh as the cathode material. Therefore the performance of the MFC depends upon the reactor design, electrode material, substrate used, and the microbes present in the MFC. Table 12.1 discusses different MFC performances treating various food wastewaters.

12.6

Anodic biofilm

Microorganisms break down the organic substrate to generate electrons and thus release electrons that are transferred to the electrode. The electrons then flow through the circuit and cause the generation of power in the MFC. Microbes present in the anode play a vital role in converting the organics and producing energy. Shewanella, Geobacter, Proteobactor, Enterococcus, and Planctomyces are commonly found species in MFCs which convert the simple content into electrons that are transferred to the electrode. Thus the microbes form biofilm that is attached to the electrode for energy conversion. The biofilm is a group of microorganisms which adheres to biotic or abiotic surfaces and is capsuled in self-developed polysaccharide material. Biofilm matrix is made of water, microorganisms, ions, and extracellular polymeric substances. This matrix is essential for biofilm formation. The extracellular polymeric substrate has 40%
90% polysaccharides, 1%
60% proteins, 1%
10% nucleic acids, and 1%
40% lipids (Flemming and Wingender, 2001). Biofilm formation occurs in a sequence of steps such as conditioning of the surface, bacterial transport, adhesion, growth, and biofilm expansion. Bacterial attachment is facilitated by fimbriae, pilli, flagellae, and extracellular polymeric substances. Biofilms may have a single community or mixed community of species. Biofilm initially forms as a single layer on the surface and develops into a three-dimensional structure. The pathway of organic matter degradation that leads to power production in MFCs is displayed in Fig. 12.7.

TABLE 12.1 MFC performance in treating various food wastewaters. S. no.

Wastewater

Reactor configuration

Cathode

Anode

Separator

Treatment efficiency (COD removal, %)

Power production

References

1.

Brewery wastewater

Singlechamber air cathode

Carbon cloth containing platinum

Carbon cloth

PTFE diffusion layer

87

528 mW/m2

Feng et al. (2008)

2.

Brewery wastewater

Singlechambered air cathode

Pt-coated air cathode

Carbon cloth




87

483 mW/m2

Wang et al. (2008)

3.

Starch processing wastewater

Air cathode

Pt-coated carbon paper

Carbon paper

Nafion 117

98.0

239.4 mW/m2

Lu et al. (2009)

4.

Yogurt waste

Dual chamber

Platinum mesh

Graphite felt

Ultrex, CMI7000 (proton exchange membrane)

91

1450 mA/m2

CercadoQuezada et al. (2010b)

5.

Brewery wastewater

Singlechamber air cathode

Stainless steel net

Carbon fibers

Nafion 117

20.7
48

669 mW/m2

Wen et al. (2010)

6.

Rice mill wastewater

Dual chamber

Graphite plates

Stainless steel

Earthen pot

96.5

2.3 W/m3

Behera et al. (2010)

7.

Seafood wastewater

Dualchamber, U shaped

Packed granular graphite

Packed granular graphite

Arc shape of tube acted as separator

80

16.2 W/m3

You et al. (2010)

8.

Cyanide-laden cassava starch processing wastewater

Dual chamber

Graphite plates

Graphite plates

Glass wool supported by acrylic sheet

28

1.8 W/m2

Kaewkannetra et al. (2011)

9.

Canteen-based composite food waste

Single chamber

Noncatalyzed graphite plates

Noncatalyzed graphite plates

Nafion 117 membrane

64.83

390 mA/m2

Goud et al. (2011)

10.

Food waste leachate

Dual chamber

Pure carbon

Pure carbon

Ultrex

90

15.14 W/m3

Rikame et al. (2012)

11.

Seafood wastewater

Single chamber

Wet-proofed carbon cloth pretreated with carbon powder and 20 wt.% PTFE emulsion

Carbon cloth without wet roof attached with stainless steel mesh

Membraneless

85.1

358.8 mW/m2

Sun (2012)

(Continued )

TABLE 12.1 (Continued) S. no.

Wastewater

Reactor configuration

Cathode

Anode

Separator

Treatment efficiency (COD removal, %)

Power production

References

12.

Seafood wastewater

Dual chamber

Wet-proofed carbon cloth pretreated with carbon powder and 20 wt.% PTFE emulsion

Carbon cloth without wet roof attached with stainless steel mesh

Proton exchange membrane

64.7

291.6 mW/m2

Sun (2012)

13.

Canteen food waste

Singlechamber air cathode

Carbon cloth containing platinum

Graphite fiber brush with titanium core




86.4

556 mW/m2

Jia et al. (2013)

14.

Food waste leachate

Dual rectangular chamber

Carbon felt

Carbon felt

Cation exchange membrane

87

432 mW/m3

Li et al. (2013)

15.

Food waste leachate

Singlechamber air cathode

Wet-proof carbon cloth with Pt catalyst

Graphite brush with pretreated ammonia

Membraneless

96

769.2 mW/m2

Choi and Ahn (2015)

16.

Canteen food waste

Singlechamber air cathode

Carbon cloth with Pt diffusion layers

Carbon cloth




90.3

5.6 W/m3

Li et al. (2016)

17.

Food waste leachate

Air cathode

Air-diffusion cathode with Pt catalyst

Carbon felt

Nafion 115 membrane

95.4 6 0.3

1.86 W/m3

Wang and Lim (2016)

18.

Seafood processing wastewater

Upflow microbial fuel cell

Activated carbon fiber felts

Activated carbon fiber felts

Per fluorinated Nafion membrane

95

105 mW/m2

Jayashree et al. (2016)

19.

Solid potato waste

Dual chamber

Carbon felts

Carbon felts

Cation exchange membrane

86.3

243.3 mA/m2

Du and Li (2016)

20.

Food waste leachate

Dual chamber

Carbon rod

Carbon rod

Ultrex (proton exchange membrane)

72.7

29.23 mW/m2

Moharir and Tembhurkar (2018)

21.

Dairy wastewater

Dual chamber

Nanoparticles on uncoated carbon paper

Cu-doped FeO nanoparticle-coated carbon paper

Proton exchange membrane (Nafion membrane)

75

161.5 mW/m2

Sekar et al. (2019)

22.

Dairy wastewater

Tubular air cathode

Carbon cloth

Graphite rod attached with carbon cloth

Proton exchange membrane (Nafion membrane)

62

1.32 W/m3

Marassi et al. (2019)

23.

Dairy wastewater

Single chamber

Plain carbon cloth coated with platinum black

Carbon fiber graphite brush

Nafion membrane

42
58

5.04 6 0.39 mW/ m2

Boas et al. (2019)

24.

Cashew apple juice

Dual chamber

Platinum-coated carbon cloth

Carbon-coated carbon cloth

Nafion 117




31.58 mW/m2

Priya and Setty (2019)

25.

Synthetic dairy wastewater

Dual chamber

Graphite plates

Stainless steel

Earthenware

89

47.77 mW/m2

Behera and Behera (2019)

266

Food Waste to Valuable Resources

FIGURE 12.7 Pathway of organic matter degradation that leads to power production in MFC.

Velasquez-Orta et al. (2011) reported that multiple species are responsible for the organic degradation and energy conversion in food wastewater treatment. The startup process of the MFC is important in biofilm formation. Improving the long-term stability of the reactor is mainly dependent upon the startup process. Indigenous species are commonly used to inoculate the reactor. Cercado-Quezada et al. (2010a,b) discussed various inocula that were used to treat yogurt wastewater. They achieved a maximum PD of 92 mW/m2 when compost leachate inoculum was used compared with anaerobic sludge inoculum (54 mW/m2). Li et al. (2013) reported that three types of inocula (domestic wastewater, anaerobic sludge, and activated sludge) were used to treat acidic food leachate, and they obtained a high PD of 432 mW/m3 when anaerobic sludge was used as the inoculum.

12.6.1 Factors influencing biofilm formation and performance 12.6.1.1 Wastewater characteristics Wastewater characteristics are a major factor that directly affects the microbiology and conversion performance of an MFC. For MFC feedstock, most industrial wastewater with high toxic content is not considered suitable. However, food wastewater or food processing wastewater may be used as substrate for an MFC, but the PD and CE vary considerably depending on the type of wastewater and its characteristics, such as composition, conductivity, and pH.

12.6.1.2 Anodic microbes MFCs produce electricity when the microbes start to degrade organic substrate to produce the electrons and consequently transfer the produced electrons to an electrode, either through direct contact or using soluble electron shuttles. In most MFCs, the anode chamber acts as anaerobic conditions and microbes present in play a crucial role in bioconversion and bioenergy. Many electrochemically active microbes (ECAMs) such as Shewanella, Geobacter, and Proteobactor along with other growing species like Enterococcus and Planctomyces have been widely found in MFC systems. They show

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267

great ability to break simple carbohydrates into electrons and then the released electrons are transferred to the electrode. However, most ECAMs cannot degrade the complex substance directly.

12.6.1.3 Reactor design Reactor design is significant and directly related to substrate, microbes, and electrode interactions which manages the efficiency and scalability of an MFC. Reactor configuration, anode and cathode materials, and membrane are three major parameters of MFC design that significantly affect the energy losses and electron satiating reactions at the anode. Cheng et al. (2010) used an upflow membraneless MFC to treat high-strength palm oil mill effluent, with enhanced mass transfer and a maximum PD of 44.6 mW/m2 was achieved. Katuri and Scott (2010) discussed an improved upflow MFC that consisted of an upper clarifier zone, a middle single-chamber MFC zone, and a bottom AD zone. In this study, brewery wastewater was treated and obtained a peak PD of about 330 mW/m2. You et al. (2010) designed a U-shaped MFC with anoxic/oxic architecture for seafood wastewater treatment. An arc-shaped tube acted as a separator connecting the anoxic zone (anode chamber) and oxic zone (cathode chamber). This reactor setup enabled smooth flow of the anolyte to the cathode while efficiently preventing the intrusion of oxygen to the anode. With this type of reactor setup, a PD of 16.2 W/m3 with 15% CE and COD removal up to 80% was obtained.

12.6.1.4 Operational parameters In MFCs, the process performance is affected by the wastewater properties and operation conditions, such as organic loading rate (OLR), temperature, and dissolved oxygen (DO) concentration. Moreover, in MFCs, the anodic microbial activity and electron transfer are closely linked to electrochemical parameters such as electrode potential. Wastewater strength is a serious operating parameter that governs the efficiency and substrate metabolism in an MFC. Thus, OLR or hydraulic retention time (HRT) can considerably affect the production of electric power. One major advantage of food wastewater as a fuel for MFC is the high energy content per unit volume. Thus, food waste-fed MFCs generally show higher PD than those fed with domestic wastewater (Nam et al., 2010). Goud et al. (2011) stated that high OLR would badly suppress the microbial activity, which decreases the power production.

12.7

Energy recovery from food waste using microbial electrolysis cell

MFCs have been advanced by conversion into MEC after several treatment cycles to recover energy as biogas (CH4 or H2). MFCs or MECs use bacteria as the catalyst, and have been developed for effective bioenergy generation from a wide range of organic wastes and wastewater, such as domestic wastewater, palm oil mill effluent, food waste, wasteactivated sludge, and corn stoves (Jia et al., 2013; Sun et al., 2014; Nor et al., 2015; Cao et al., 2009). Therefore both MFCs and MECs are combined in what is known as a microbial electrochemical system (MES). MESs convert organic waste into H2, CH4, and other valuable compounds through bioelectrochemical reactions. Yu et al. (2017) experimented with single-chamber MFCs made from a graphite brush anode and stainless steel cathode to treat soya bean edible oil refinery wastewater. These authors introduced the wastewater in four concentrations (low, medium, medium high, and high) and obtained 90.6% COD removal with a maximum CE of 33.6% with low-concentration wastewater. MFC was then converted into MEC by providing 1.2 V constant voltage to maintain the cathode potential for CH4 production. A high CH4 yield of 45.4 6 1.1 L/kg-COD was obtained in MECs. Winery wastewater was treated using pilot-scale continuous flow MEC, made up of a graphite fiber brush anode and a stainless steel mesh cathode (Cusick et al., 2011). A maximum of 7.4 A/m3 current production and maximum gas production of 0.19 6 0.04 L/L/day were achieved, with 86% 6 6% gas was converted as CH4. A novel MEC-assisted upflow anaerobic (upflow MEC) reactor was constructed for beer wastewater treatment for CH4 production (Sangeetha et al., 2016). In this study, the authors used three different cathodes (stainless steel, nickel. and copper) and granular graphite as anode materials. The maximum COD removal of 85% and CH4 yield of 142.8 mL/gCOD was achieved using nickel as the cathode, possibly because this cathode may have electrochemically induced high CH4 production. MES is a promising technology for treating food wastewater and a new method for renewable energy production. Different configured MEC performances in treating various food wastewaters are shown in Table 12.2.

12.8

Microbial fuel cell coupled with anaerobic digestion of food waste

Customarily food wastes are incinerated or landfilled. These processes have their limitations. For example, the incineration process in addition to consuming more energy also releases hazardous gases and ashes which pollute the

TABLE 12.2 MEC performance treating various food wastewaters. S. no.

Type of food industry wastewater

Type of MEC

Mode of operation

Cathode

Anode

Membrane

COD removal efficiency (%)

Power production

Biogas production

References

1.

Beer wastewater

Upflow

Continuous

Nickel

Granular graphite

Membrane less

85

8.6 mA (current)

367 mL CH4/L reactor/d

Sangeetha et al. (2016)

2.

Beer wastewater (artificial)

Single chamber

Semicontinuous

Stainless steel mesh

Graphite fiber brush

Membrane less

65
80

1082.1 6 25.4 mA/ m2 (Cathodic current density)

0.14 m3CH4/m3/d

Guo et al. (2016)

3.

Cheese whey




Continuous

Gas diffusion electrode— Ni

Carbon felt




82

0.13
0.15 mA/ cm2

0.5 LH2L-1 d21

Moreno et al. (2015)

4.

Molasses wastewater (artificial)

Single chamber

Fed-batch mode

Carbon cloth

Graphite fiber brush

Membraneless




131.1 6 0.06 A/m3

2.27 6 0.015 m3 H2/m3 d

Wang et al. (2014)

5.

Refinery wastewater

Single chamber

Fed-batch mode

Stainless steel mesh

Graphite plate




79

2.1 6 0.2 A/m2




Ren et al. (2013)

6.

Brewery wastewater

Single chamber

Batch

Pt/nickel foam

Carbon brush




87
94

232 6 1 A/m3

2.12 6 0.09 m3 H2/m3 d

Lu et al. (2016)

7.

Potato processing wastewater

Single chamber

Fed batch

carbon cloth

graphite fiber brushes




79

0.64 mA/cm2

0.74 m3 H2/m3 d

Kiely et al. (2011)

8.

Winery wastewater (pilot scale)

Single chamber

Continuous flow

Stainless steel mesh

Graphite fiber brushes




62 6 20

7.4 A/m3

0.074 LH2/L/d

Cusick et al. (2011)

9.

Winery wastewater

Single chamber

Fed batch

Carbon cloth

Graphite fiber brushes




47 6 3




0.17 6 0.09 m3 H2/m3 d

Cusick et al. (2010)

10.

Soybean oil refinery wastewater

Single chamber

Batch

Stainless steel mesh

Graphite fiber brushes




95.8%

200 A/m3

0.133 6 0.005 m3 /(m3 d)

Yu et al. (2017)

11.

Ethanol-type fermentation CSTR effluent (molasses)

Single chamber

Fed batch

carbon cloth

Carbon fiber brushes

Membraneless




158 A/m3

1.52 m3 H2/m3 d

Lu et al. (2009)

12.

Olive brine processing wastewater

13.

Piggery wastewater

14.

15.

29

7.1 6 0.4 A/m2

109 6 21NmLCH4/ gCOD

Marone et al. (2016)

Cation exchange membrane (Nafion 424 membrane)

45
52

1.75 A/m2

0.061 m3 H2/m3 reactor liquid volume/d

Jia et al. (2010)

Graphite fiber brushes




19 6 15 to 72 6 4

112 6 25 A/m2

1 6 0.1 m3 H2/m3/ d

Wagner et al. (2009)

Graphite fiber brushes




67

2.4 A/m2

0.41 6 0.02 m3/ m3/d

Tenca et al. (2013)

Fed batch

Pt-radium

Graphite plates

Two chamber

Batch

Titanium plate electrode

Graphite felt

Swine wastewater

Single chamber

Fed batch

Air cathode with a platinum catalyst

Food processing wastewater

Single chamber

Fed batch

Platinum

270

Food Waste to Valuable Resources

atmosphere. Landfills require increasing land surface and the leachate contaminates surface and ground waters, leading to complicated problems. Later this is followed by composting and biofuel production from food. Composts so produced have low commercial value and the process may also release greenhouse gases along with nitrate-containing leachate. Huge costs are associated with biofuel production and purification (Nicholson et al., 2017). AD of food waste has gained increasing attention because of the tremendous volume reduction of food waste and its conversion into biogas. The AD process cannot be adapted for nitrogen-rich wastewater treatment, therefore it requires a backup process for organic and nutrient removal, which increases the operational and maintenance cost. MFC can be used for recovering nutrients (Kuntke et al., 2012; Zamora et al., 2017), and when integrated with AD, a new wastewater treatment system recently gained attention due to its power production as well as biogas production. Kim et al. (2015) reported on an MFC integrated with AD treating swine wastewater. These authors used carbon felt and carbon cloth as the anode and cathode, respectively, and used cation exchange membrane as the separator. In this study, removal of total ammonia nitrogen (TAN) was 77.5% in MFC and 5.8% in AD. Antonopoulou et al. (2019) studied the energetic valorization of household food waste (HFW) into electricity using MFC and methane through AD. With the help of an extraction process, liquid residue is separated and used to produce power by the MFC while the solid residues were used in the CH4 production through biochemical methane potential experiments (AD process). In this experiment, the authors operated continuous-mode air cathode MFCs using GORE-TEX s cloth wrapped on plexiglass tubes and coated with MnO as the cathode and graphite rod as the anode. The maximum PD of 7.7 W/m3 and CE 12.3% were obtained with COD removal of 74% and with an energy yield of 0.78 MJ/kg CODin. Park et al. (2017) reported on a study that improved biogas production in an AD reactor through MEC technology. This study discussed the effects of the MEC on the rate of methane production from food waste which were observed by comparing an AD reactor and an AD reactor combined with an MEC. In this study, the MEC supplied some voltage (0.2
0.8 V) to the AD reactor. In the AD reactor, exoelectrogenic microbes decompose organic matter and release electrons at the anode. The electrons then moved to the cathode through a closed circuit and were consumed, thereby producing methane and hydrogen.

12.9

Current status of pilot microbial fuel cell

In the wake of numerous researches into utilizing MFCs for bioelectricity generation, many pilot-scale MFCs have been developed. Dong et al. (2015) developed a stackable baffled MFC for treating brewery wastewater on a pilot scale. They used a rectangular vessel of volume 100 L with a working capacity of 90 L. The system had five modules and operated for 6 s with its own energy. Cathodes were made of activated carbon and PTFE, whereas anodes were made of carbon brush over a titanium wire. The U portion served as an air chamber. To avoid short circuiting inside the reactors two layers of textile separators were used between the anode and cathode. The system was allowed to operate under ambient temperature. COD and SS removals were 87.6% and 86.3%. The electricity produced was sufficient to operate two pumps with an excess of 0.034 kWh/m3. The economic analysis revealed that a reduction in cost can be achieved by using low-cost materials instead of PVC and CEM. Feng et al. (2014) fabricated a horizontal stackable MFC with a capacity of 250 L. Carbon mesh with Pt coating was used as the anode, and a carbon brush on titanium wire was the cathode. The carbon brush was pretreated by dipping it in acetone for 2 h. Polypropylene plates were used as separators. The maximum power achieved by the system was 116 mW with a COD removal efficiency of 79%. The overall cost was US$250 with an operational cost of 0.2%. The total cost of the project was subdivided as follows: 27% for the reactor, 7% for other parts, 4% for carbon mesh, 11% for carbon brush, 3% for PTFE, 3% for acetone, 13% for nafion, and 32% for catalyst.

12.10 Conclusions and future directions Extensive research in the field of MFC technology has led to a cost reduction for electrode materials without compromising their performance. Mediator-less air cathode MFCs are greatly preferred as they require no oxygen, thus reducing the operational cost (Logan et al., 2015). Up-scaling of the units and making them ready to use for handling large quantities of wastewater commercially are required. Energy losses and initial costs can be minimized by using application-oriented reactors. Along with electricity production, researchers should focus on nutrient recovery using MFCs which may intensify the popularity of this technique. Studies related to the integration of MFC with other techniques for improved performance (Zhang and Angelidaki, 2014) should be a focus of attention. Simulation and modeling studies can be used for optimizing MFC parameters. This technology is still in the lab scale because of the electrode

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material type, their spacing, configurations, substrate utilized, operating parameters, etc. while exceeding the pilot-scale level has been hampered due to performance dropping abruptly due to increased losses.

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Further Reading Bustillo-Lecompte, C., Mehrvar, M., Quin˜ones-Bolan˜os, E., 2016. Slaughterhouse wastewater characterization and treatment: an economic and public health necessity of the meat processing industry in Ontario, Canada. J. Geosci. Environ. Prot. 4 (04), 175. Guo, K., Chen, X., Freguia, S., Donose, B.C., 2013. Spontaneous modification of carbon surface with neutral red from its diazonium salts for bioelectrochemical systems. Biosens. Bioelectron. 47, 184
189. Nakhate, P.H., Patil, H.G., Shah, V., Salvi, T., Marathe, K.V., 2019. Process validation of integrated bioelectrochemical and membrane reactor for synchronous bioenergy extraction and sustainable wastewater treatment at a semi-pilot scale. Biochem. Eng. J. 151, 107309.

Chapter 13

Integrated biorefineries of food waste G. Ginni1, S. Adish Kumar2, T.M. Mohamed Usman3, Peter Pakonyi4 and J. Rajesh Banu5 1

Department of Civil Engineering, Amrita College of Engineering and Technology, Amritagiri, Nagercoil, India, 2Department of Civil Engineering,

University V.O.C College of Engineering, Anna University, Thoothukudi Campus, Thoothukudi, India, 3Department of Civil Engineering, Anna University Regional Campus, Tirunelveli, India, 4Research Institute on Bioengineering, Membrane Technology and Energetics, University of Pannonia, Veszpre´m, Hungary, 5Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India

13.1

Introduction

Food waste (FW) is one of the mostly commonly generated biowastes in developing and developed countries. The disposal of FW pollutes the environment and results in a loss of valuable nutrients. In order to conserve natural resources and to meet the environmental discharge standards, the management of FW for the production of high valueadded products has grown rapidly (Jin et al., 2018). FW biomass has been mostly used for the production of biofuels with the aim of partially or completely replacing highly polluting fossil-oriented fuels (Gutierrez et al., 2017). Various treatment technologies have been explored, such as fermentation, electrofermentation, anaerobic digestion (AD), thermal processes, and nonthermal processes for recycling of FW into valuable products (Galanakis, 2018; Hao et al., 2015). The major disadvantages by these traditional treatment technologies are excessive time, poor feasibility, high cost, the emission of greenhouse gases, and sludge production (Hao et al., 2015). Therefore the selection of technologies is based on the benefits and drawbacks in exploiting the valuable byproducts obtained from FW. The integration of a biorefinery is the most promising technology used to convert FW into value-added products. Therefore various novel technologies have been integrated in order to recover and produce numerous products on a commercial scale and make the process cost effective (Karthikeyan et al., 2017; Jin et al., 2018). This chapter provides a framework for evaluating various systems to be integrated for enhancing the overall efficiency. It also systematically discusses the key bioprocesses to describe various advanced technologies and the application of an integrated biorefinery concept using FW as a possible resource to produce biofuel, biopower, and bioenergy for developing a bioeconomy. This chapter also discusses the production of volatile fatty acids (VFAs) through fermentation of FWs for maximizing VFA production. An economic analysis with relevant policies for the commercialization of the biorefinery process is also considered in this chapter.

13.2

Food waste integrated biorefineries: an overview

The concept of biorefineries is the bioconversion of FW into biofuels, power, heat, and bioproducts with the effective utilization of FW (Aslanzadeh et al., 2014). The complexity of integrated biorefineries is based on factors such as feedstock, by-products, and the applied technologies (Aslanzadeh et al., 2014). An overview of an FW biorefinery concept is illustrated in Fig. 13.1. Conventional biorefineries are designed around separate unit operations such as processing of feedstock, fermentation, and postfermentation recovery of the biofuels. For instance, the processing of feedstocks such as corn or corn starch needs hydrolysis, followed by batch fermentation, and then recovery of product. These individual processes necessitate improved principal and operational costs, and production costs. However, the progress made with these new technologies can permit these unit operations to be integrated as hard as possible, increasing the viability of existing biorefineries. In this system, FW and waste cooking oil are converted into biogas and biodiesel via AD and transesterification processes, respectively. Digestate residue from the AD process can be used as a stand-alone fertilizer or as a coenzyme in the composting process. Karthikeyan et al. (2018) integrated FW recycling by means of cultivation of Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00013-4 Copyright © 2020 Elsevier Inc. All rights reserved.

275

276

Food Waste to Valuable Resources

FIGURE 13.1 Integrated biorefinery concept diagram.

Rhodotorula glutinis and AD for the fuel precursors. It was reported that dominant fatty acid methyl esters such as palmitic (C16: 0%
26%), stearic (C18: 0%
17%), and oleic acids (C18: 1%
38%) were found to be perfect for biodiesel production. The maximum yield of methane was achieved from AD of derived residual solids. Table 13.1 shows the integrated biorefinery routes of various food wastes. The integrated biorefinery approach is foreseen as a potential approach to contribute to the accomplishment of the needed targets and, at the same time to decrease the use of both fossil and biobased resources.

13.3

Integrated two-stage processes

13.3.1 Methane
lactic acid production Lactic acid is the simplest hydroxyl acid that can be generated by fermentation of carbohydrates such as glucose, sucrose, and lactose, or through chemical synthesis. Batch fermentation is the most extensively used method for the production of lactic acid (Ghaffar et al., 2014). Microorganisms such as lactic acid bacteria and filamentous fungi use glucose in aerobic conditions for the production of lactic acid. Lactic acid can further be synthesized chemically and is mainly due to the hydrolysis of lactonitrile using strong acids. Currently, lactic acid is also produced by the bacterium Phragmites australis using FW as feedstock. For the commercial production of lactic acid, Lactobacillus rhamnosus and Lactococcus lactis are generally used (Zhang et al., 2018). In AD of FW, lactate is the intermediate formed through acidic fermentation with effective utilization of substrate by methane-yielding microbial communities. Detman et al. (2018) studied the metabolic transformation of lactate in AD of biomass and it was reported that lactate oxidation through the acetogenic step creates the pathway for methanogenesis. AD is a biological process and the biodegradation process mainly includes four steps, namely hydrolysis, acidogenesis, acetogenesis, and methanogenesis. During the first stage, fermentative bacteria convert proteins and carbohydrates into fatty acids and amino acids. During the second stage, the organic acids are converted to VFAs with the generation of by-products. In the third stage, the organic substrates are converted to H2 and carbon dioxide that are utilized by

TABLE 13.1 Integrated biorefinery routes of various food waste. S. no.

Type of food waste

Integrated biorefinery route

Conditions employed

Main product

Side stream valorized product

Products yield

References

1.

Poultry waste

Anaerobic digestion

Mesophilic conditions

Biogas




55.1 mL g VS/substrate

(Achinas and Euverink, 2019)

2.

Potato Peels

Anaerobic digestion

G

Varying inoculum to substrate ratios Acid hydrolysis

Methane




283.4 mL CH4/g VSadded

(Achinas et al., 2019)

Two-stage anaerobic digestion

Thermophilic at 55  C and mesophilic at 35  C

Methane

Hydrogen

G

G

3.

Canteen food waste

G

529.5/kg VS CH4 135 L kg VS H2

(Algapani et al., 2019)

4.

Potato peel waste

Hydrolysis

Acidic hydrolysis Enzymatic hydrolysis

Ethanol




7.58 g/L

(Arapoglou et al., 2010)

5.

Potato waste

Simultaneous saccharification combined fermentation

G

Aspergillus niger and Saccharomyces cerevisiae coculture Incubation time between 24 and 120 h

Bioethanol

Biomanure

G Optimum ethanol yields 9.3% Biomanure enriched with NPK ratio 2:1:1

(Chintagunta, Jacob, and Banerjee, 2016)

6.

Pineapple leaf waste

Simultaneous saccharification combined fermentation

G

Optimal process incubation time 24 h with 37  C

Bioethanol

Biomanure

G

7.

Food waste

Two-stage anaerobic digestion

Combined thermophilic acidogenic hydrogenesis Mesophilic/thermophilic methanogenesis

8.

Cheese whey powder

Two-stage anaerobic digestion

G

Two-stage anaerobic digestion

Mesophilic at 35  C

Two-stage anaerobic digestion

Thermophilic at 55  C

9. 10.

Canteen raw food waste Cassava wastewater

G

Mesophilic at 37  C

(Chintagunta, Ray, and Banerjee, 2017)

G

Optimum ethanol yields 7.12% v/v Biomanure enriched with F. muscicola contains NPK ratio of 3.5:1:2

Methane

Hydrogen

G

0.464 L CH4/g VS

(Chu et al., 2010)

Methane

Hydrogen

G

28 L H2/L/d 3.0 L CH4/L/d

(Cota-Navarro et al., 2011)

511.6 mL g VS 43 mL g VS

(Ding et al., 2017)

164.87 mL CH4/g COD applied 54.22 mL H2/g COD

(Intanoo et al., 2014)

0.248 L CH4/g VS 0.061 L H2/g VS

(Kanchanasuta and Sillaparassamee, 2017)

G

Methane

Hydrogen

G G

Methane

Hydrogen

G

G

11.

Palm oil mill effluent

Two-stage anaerobic digestion

Thermophilic at 55  C and mesophilic at 37  C

Methane

Hydrogen

G G

(Continued )

TABLE 13.1 (Continued) S. no.

Type of food waste

Integrated biorefinery route

Conditions employed

Main product

Side stream valorized product

Products yield

12.

Beverage wastewater

Two-stage anaerobic digestion

Mesophilic at 35  C

Methane

Hydrogen

G

References

0.172 L/g COD H2 0.7 mL/g COD Ch4

(Lay et al., 2019)

G

13.

Orange peel waste

MFC




Bioelectricity




G

0.59 6 0.02 V

(Miran et al., 2016)

14.

Palm oil mill effluent

Two-stage anaerobic digestion

Thermophilic

Methane

Hydrogen

G

0.414 L CH4/g VS 0.135 L H2/g VS

(O-Thong et al., 2016)

Two-stage anaerobic digestion

Mesophilic at 37  C

0.728 L g VS CH4 0.0998 L g VS H2

(Paudel et al., 2017)

Chemical activation

Activation temperature 2 600 C Activation time 1 h

Activated carbon




81.76% Carbon content 44.13% Production

(Sayʇili, Gu¨zel, and ¨ nal, 2015) O

Methane

Hydrogen

0.458 L CH4/g VS d 0.028 L H2/g VS d

(Shen et al., 2013)

0.0163 L H2 /g VS 0.240 L CH4/g

(Suksong, Kongjan, and O-Thong, 2015)

15. 16. 17.

18.

Food waste Grape processing waste

G

Methane

Hydrogen

G G

Food waste coupled with fruit and vegetable waste

Two-stage anaerobic digestion

Mesophilic condition

Palm oil mill effluent

Two-stage anaerobic digestion

Thermophilic at 60  C

G G G G

Methane

Hydrogen

G G

19.

Mandarin orange peel

Microbial flora fermentation




Methane




G

CH4 production rate at 0.014 mL/h

(Tomita and Tamaru, 2019)

20.

Dairy processing waste

Two-stage anaerobic digestion

Thermophilic at 60  C

Methane

Hydrogen

G

0.483 L CH4/l-d 2.36 L H2/L d

(Zhong, Stevens, and Hansen, 2015)

G

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methanogens to produce CH4 (Wang et al., 2011). The acetogenesis and methanogenesis include syntrophic relations between acetogenic bacteria and hydrogenotrophic methanogens. Thus, lactate oxidation is a thermodynamic process that allows acetogenesis, thereby lowering the partial pressure of hydrogen (Detman et al., 2018). In addition, lactate can act as a substrate for the nonmethanogen Archaeoglobus oxidizing lactate to carbon dioxide (Detman et al., 2018). Avinas Thakur (2018) investigated the enhancement in lactic acid production in a continuous fermentation process by integrating it to a cell-recycling system. It was reported that 1.8 times higher lactic acid productivity (8.0 g/L-h) was obtained by Lactobacillus plantarum from cassava starch during continuous cell recycling as compared to conventional continuous and batch fermentation. Moreover, the two-stage fermentation process facilitates greater process stability and better acidification control as compared to a single-stage process (Thakur, 2018).

13.3.2 Hydrogen
methane production As mentioned in the previous section, AD is a complex sequential process and shows a balanced equilibrium that involves accumulation of VFAs within the digester system. The over accumulation of fatty acids inhibits the methanogenic process. Therefore integrating hydrogen and methane production through two-stage fermentation is the possible route. The blend of hydrogen and methane gas with a composition of 10%
15% H2, 50%
55% CH4, and 30%
40% CO2 is called biohythane, which is produced using two-stage anaerobic fermentation (AF) processes. The raw materials used for the production of hydrogen are sugars, starch, and carbohydrates. Biohythane is considered as an energy carrier with a higher conversion efficiency, with the replacement of fossil fuels by the biological process. The addition of a lower amount of H2 extends the flammability range of CH4 due to its higher mass specific heating value than CH4. The burning speed of H2 is about sevenfold higher than CH4, thereby reducing the burning time of the engine (Hans and Kumar, 2018). Furthermore, the presence of hydrogen reduces the emission of greenhouse gases into the atmosphere with decreases CO2 gas production (Hans and Kumar, 2018). Biohythane is considered to be an environment-friendly gas (Bolzonella et al., 2018). Hydrogen is produced from FW rich in starch and cellulose (Lukajtis et al., 2018). Dark fermentation produces hydrogen during the acidogenic stage of AD of organic matter, which is considered to be a promising technique relative to the conventional chemical process because the need for chemical energy is less and it is therefore more eco-friendly. Based on energy recovery, the output of energy is seven to nine times greater by the combined production of H2 and CH4 than conventional H2 production alone, and 10%
12% higher than the production of CH4. Therefore, two-stage fermentation plays a significant role in maximum recovery of energy from FW substrate (Jarunglumlert et al., 2017a,b). Effective biomethane production from nongaseous fermentation products could make biological production of biohydrogen economically attractive (Detman et al., 2017). Navarro et al. (2011) studied the viability of producing biological hydrogen and methane in a two-stage cheese whey fermentation system process. It was reported that over 70% of the energy is recovered by the two-stage process with the continuous production of hydrogen and methane. Numerous investigations have been carried out employing FW (Cavinato et al., 2012; Sarkar and Venkata Mohan, 2017; Thong et al., 2018) as substrate for biohythane production. The generation of biohythane has been investigated both in labscale and semipilot-scale extents. In the first stage, a higher hydrogen production of 66.7 L/kg VS was obtained, whereas in the second stage a higher biogas production of 0.72 m3/kg VS was obtained as distinctive biohythane composition (Cavinato et al., 2012). The maximum theoretical yield of hydrogen through Clostridium-type fermentation is 4 moles of hydrogen per mole of glucose, when all of the substrate is converted to acetic acid (Detman et al., 2017). Wongthanate and Mongkarothai (2018) executed a two-stage fermentation process for enhancement of bioenergy from FW. The results revealed the maximum yield of methane was observed by utilizing effluent from the first stage. In addition, COD removal of 70%
90% was obtained under optimum conditions. The overall reaction rate and yield of biogas were improved by the production of combined hydrogen and methane in a two-stage process related to the conventional two-phase process (Luo et al., 2012). Another strategy is the combination of AF with photo-fermentation, which improves the production of hydrogen by utilizing the metabolites produced during AF (Dahiya et al., 2017). Table 13.2 shows the two-stage fermentation of various food waste.

13.3.3 Ethanol
methane production Ethanol has been known as a cleaner biofuel as there is no release of CO2 through combustion (Vohra et al., 2014). The cost of ethanol production for conventional cooking processes is greater due to the consumption of energy and large cooling water requirement. The successful utilization of this process by using FW for ethanol fermentation will benefit the environment and reduce the ethanol fermentation cost. Ethanol can be produced by both simultaneous

280

Food Waste to Valuable Resources

TABLE 13.2 Two-stage fermentation of various food wastes. S. no.

Type of food waste

Integrated biorefinery route

Conditions employed

Main product

Side stream valorized product

Products yield

1.

Canteen food waste

Two-stage anaerobic digestion

Thermophilic at 55  C and mesophilic at 35  C

Methane

Hydrogen

G

Two-stage anaerobic digestion

G

2.

Food waste

G

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

Combined thermophilic acidogenic hydrogenesis Mesophilic/ thermophilic methanogenesis

G

G

0.464 L CH4/g VS

(Chu et al., 2010)

Hydrogen

G

28 L H2/L/d 3.0 L CH4/L/d

(Cota-Navarro et al., 2011)

511.6 mL g VS 43 mL g VS

(Ding et al., 2017)

164.87 mL CH4/ g COD applied 54.22 mL H2/g COD

(Intanoo et al., 2014)

0.248 L CH4/g VS 0.061 L H2/ g VS

(Kanchanasuta and Sillaparassamee, 2017)

0.172 L/g COD H2 0.7 mL/g COD Ch4

(Lay et al., 2019)

0.414 L CH4/g VS 0.135 L H2/g VS

(O-Thong et al., 2016)

0.728 L g VS CH4 0.0998 L g VS H2

(Paudel et al., 2017)

0.458 L CH4/g VS d 0.028 L H2 / g VS d

(Shen et al., 2013)

0.0163 L H2/g VS 0.240 L CH4/g

(Suksong, Kongjan, and OThong, 2015)

0.483 L CH4/l-d 2.36 L H2/L d

(Zhong, Stevens, and Hansen, 2015)

Mesophilic at 37  C

Methane

Canteen raw food waste

Two-stage anaerobic digestion

Mesophilic at 35  C

Methane

Cassava wastewater

Two-stage anaerobic digestion

Thermophilic at 55  C

Methane

Two-stage anaerobic digestion

Thermophilic at 55  C and mesophilic at 37  C

Methane

Two-stage anaerobic digestion

Mesophilic at 35  C

Methane

Two-stage anaerobic digestion

Thermophilic

Two-stage anaerobic digestion

Mesophilic at 37  C

Food waste coupled with fruit and vegetable waste

Two-stage anaerobic digestion

Mesophilic condition

Palm oil mill effluent

Two-stage anaerobic digestion

Thermophilic at 60  C

Two-stage anaerobic digestion

Thermophilic at 60  C

Palm oil mill effluent Food waste

Dairy processing Waste

(Algapani et al., 2019)

Hydrogen

Two-stage anaerobic digestion

Beverage waste water

529.5/kg VS CH4 135 L kg VS H2

Methane

Cheese whey powder

Palm oil mill effluent

References

G

Hydrogen

G G

Hydrogen

G

G

Hydrogen

G

G

Hydrogen

G

G

Methane

Hydrogen

G

G

Methane

Hydrogen

G

G

Methane

Hydrogen

G

G

Methane

Hydrogen

G

G

Methane

Hydrogen

G G

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saccharification and fermentation or individual hydrolysis and fermentation processes (Vohra et al., 2014). In general ethanol fermentation may be accomplished either by yeast such as Saccharomyces cerevisiae or bacteria such as Zymomonas mobilis. The yeast is able to utilize sugars, for instance, S. cerevisiae is capable of converting glucose to ethanol and it can also remove 50% proteins and lipids (Saeed et al., 2018). FW is considered as a potential feedstock for the production of ethanol. Among the types of FW, fruit waste is the predominant feedstock because it has a high carbohydrate content (Polo et al., 2018). Walker et al. (2013) focused on the study of ethanol production from restaurant waste. A two-step process was adopted for converting FWs to ethanol in which alpha-amylase and glucoamylase were used for the digestion of starch followed by fermentation, resulting in the conversion of sugars into ethanol using yeast. It was reported that the ethanol concentration increased with increasing enzyme dosage levels. Ma et al. (2014) carried out an experiment by adopting lactate oxidase for converting the formed lactic acid into pyruvate subsequent to fermentation of ethanol. The results illustrated that about 70% lactic acid was converted to pyruvate by the immobilization of enzyme with calcium alginate, resulting in a 20% increased ethanol yield compared with the control. The economic viability of bioethanol generation is closely associated with the marketability of its chief end-products—dried grain distillate which can be utilized as animal feed. A major difficulty for the scalability of bioethanol production occurs when the marketability of dried grain distillate is dropped. In addition, nitrogen is an essential nutrient in the production of ethanol that regulates the production potential and impacts the capital costs. In this regard, chemical supplements can be utilized as a source of nitrogen for the production of ethanol. This could increase the production cost of ethanol. In addition, AD has been valued as an effective and viable technique for bioenergy generation. Notably, the digestate obtained after AD has organic residues in the form of nitrogen. This can be used as a source of nitrogen for ethanol production. As a result, employing digestate as a raw material for ethanol production can enhance the potential of the process and decrease the cost of nutrient sources (nitrogen) for ethanol generation. The integration of biogas and bioethanol production processes is thus considered as an appropriate approach to increase the affordability of fermentation industries via integrated biogas and bioethanol production in a biorefinery concept. This approach entails the integration of material flows of diverse biobased industries, to facilitate the application of residues from an industry as an input for another process.

13.3.4 Biolipid
methane production The reaction of triglycerides with mono-alcohol, such as ethanol or methanol, through a transesterification process produces biodiesel, which is a mixture of fatty acid alkyl esters. The various raw materials used for biodiesel production include vegetable and animal oils, cooking oil waste, etc. Microalgae are considered as an alternative source to traditional crops as they can produce biodiesel without sulfur content and with reduced emissions of CO, hydrocarbons, and SOx (Zhu et al., 2014). Among the raw materials oleaginous yeasts producing biolipids, including tricylglycerol, are considered to be more effective for the production of biodiesel. Along with yeasts, there are numerous types of microorganisms that can accumulate lipids, such as microalgae, bacteria, and fungi. Although accumulation of lipids is greater by microalgae using sunlight energy, carbon dioxide, and nitrogen, they are not capable of converting starch or other feedstocks to lipids. In the case of bacteria, accumulation of lipids takes place in their external membrane thereby making extraction difficult. The filamentous fungus Mortierella alpina can digest starch-based FW and produce lipid, but the accumulation and quantity of lipid is lower. Consequently, oleaginous yeast is a possible substitute oil resource for production of biodiesel from starch-based FW (Tanimura et al., 2014). Oleaginous microorganisms are technologically significant organisms that use glucose as a carbon source and biologically convert into microbial lipids under culture-limited conditions (Gao et al., 2017). Yeast is considered to be the most important microorganism due to its faster biomass growth rates, with lipid accumulation of up to 72% of their biomass. More than a 70% increase in lipid content per gram dry biomass has been achieved in R. glutinis under nutrientlimited culture conditions. Hao et al. (2015) studied an integrated biorefinery process for the production of lipid and biogas from pretreated carbohydrate-rich FW. In their study, the carbohydrate-rich hydrolysate obtained after pretreatment of FW was subjected to fermentation by the yeast R. glutinis for lipid accumulation. The solid residue obtained after pretreatment was subjected to AD for biomethane recovery. The yeasts, Saccharomyces sp., Cryptococcus sp., Lipomyces sp., Rhodotorula sp., and Yarrowia lipolytica are often used for valorization of FW leachate into biolipids. Johnravindar et al. (2017) studied the effectiveness of three oleaginous yeasts, Y. lipolytica, R. glutinis, and Cryptococcus curvatus, and evaluated their biolipid accumulation ability using FW leachates as a substrate. The results revealed that cultivation of Y. lipolytica using FW leachate accumulated lipid contents of 49.0% 6 2% on a dry weight basis with a high biomass growth rate.

282

Food Waste to Valuable Resources

13.3.5 Methane
biofertilizer Biofertilizers are natural fertilizers that consist of live biomass or dormant cells of effective microbial strains. They are activated through seed or soil interactions with the rhizosphere, thereby increasing the availability of nutrients to the plants (Alfa et al., 2014). The AD process, also described as biomethanation, converts biological wastes into two reasonably valuable by-products: biogas and plausible fertilizer, the anaerobic digestate (Nkoa, 2014). The anaerobic digestates can be disposed of by direct application to soil for the reuse of their mineral and organic constituents for plant cultivation (Alburquerque et al., 2012). FW can be used as feedstock to produce biofertilizers through a composting process or by employing AF effluent. The composting of FW can be done in either aerobic or anaerobic conditions, classified as aerobic and anaerobic composting, respectively. Using effluents as biofertilizer is a viable strategy in integrated FW biorefineries as they are cheaper than plant cultivation. The effluents generated after acidogenesis normally consist of microbes such as Pseudomonas sp., Klebsiella sp., and Bacillus sp., that take part in biofertilizer production. The free-living nitrogen-fixing biofertilizers are Klebsiella and Clostridium. Bacillus and Pseudomonas are phosphate-solubilizing biofertilizers (Alfa et al., 2014; Maurer et al., 2019; Barzee et al., 2019). These microbes can speed up the process mediated by the microbes in soil and enhance the accessibility of nutrient sources to plants. Effluents of digester contain a considerable quantity of decomposable organics and microbes. This can be applied to enhance the fertility of soil. It consists of enormous quantities of existing source of nutrients which enhance its feasibility in crop cultivation when compared to chemical fertilizers.

13.3.6 Volatile fatty acids
PHA PHA production can be achieved by bacterial fermentation of FW containing an adequate quantity of carbon sources and nutrients. Numerous biopolymers like PHAs, polysaccharides, and polyamides are produced by heterotrophic microorganisms. Over the past decade, FW has been converted into PHA as a constructive alternative for the valorization of FW. In addition, petroleum-derived plastics are replaced by biodegradable PHA possessing plastic-like properties. Many kinds of bacteria have been employed for the production of PHA using different low-priced substrates. PHA production takes place when the cultivation of cells happens in the presence of an excess carbon source and under definite conditions of limited nitrogen, phosphorus, or oxygen, and a few microorganisms accumulate maximum concentrations of PHAs in the presence of surplus sources of carbon (Pagliano et al., 2017; Nielsen et al., 2017). As PHAs are biodegradable, they have been broadly used for different applications such as packaging materials, biomedical, pharmaceutical industries, energy, and fine chemicals. The raw materials that are mostly commonly used for PHA production are food crops, sugarcane, and vegetable oil (Tsang et al., 2019). Aljuraifani et al. (2018) studied biopolymer production by isolating 26 different bacterial strains for the production of polyhydroxyalkanoate. It was reported that Pseudomonas strain-P(16) is a powerful PHA-accumulating microbe that may be helpful for the production of biopolymer economically. Polyhydroxyalkanoates (PHA) production is a promising technique with the extensive use of VFAs recovered via acidogenic fermentation. Therefore much interest has been focused on decreasing the cost of PHA production using renewable feedstocks as a source of carbon (Strazzera et al., 2018). The utilization of residual organics as sources of carbon for PHA accumulation is a feasible approach to minimize the cost associated with production. Based on this, FW has been used as a suitable feedstock (cheap source of carbon), because of its extensive incessant supply and greater biodegradable nature. An alternative route to minimize the cost of production is using mixed microbial cultures (containing selective PHA producers and PHA accumulators). The mixed microbial culture obtained from VFA-rich effluent generated after acidogenic fermentation of FW is used as substrate. For instance, PHAs can be generated via a three-stage integrated approach. In this approach, acidogenic fermentation occurs as the first stage. Next, a selection process occurs through a feast and famine series. Finally, the development of PHA accumulating bacteria modified occurs and the production of PHA takes place in batch operations (Strazzera et al., 2018). The composition of VFA generated during acidogenic fermentation of FW intensely impacts the type of generated PHA. An investigation into PHA production using FW as the raw material was carried out by Reddy and Mohan (2012). They used fresh FW and fermented FW residuals from a hydrogen-producing fermenter in separate experiments. The fermentation was performed for 3 days achieving about 0.3 g PHA/gVFAs on completion of 1 day. An overall production of PHA ranging from 30% to 40% dry mass was obtained. Thus, an integrated system is emerging as a feasible process for the production of bioenergy and biopolymers at a reasonable cost using derived products and waste as organic carbon sources.

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13.3.7 Volatile fatty acids
bioenergy The accumulation of VFAs in a reactor environment leads to inhibition of methanogens. To circumvent this issue, application of two-stage digestion is recommended. During this process, VFAs are subjected to partial neutralization via recirculation of reaction medium from second-stage digester which are rich in ammonia and other buffer agents (Ueno et al., 2007). In the first stage, fermentative and sacidogenic bacteria are developed in optimum conditions for the production of VFAs. In the second, methanogenic, stage, acetogens and methanogenic microbes are inoculated by employing the VFAs produced in the first stage. Microbes taking part in digestion can potentially transform VFAs into acetic acid, permitting their use as a source of carbon for the production of methane. Some of the generated organic acids are found to be low in concentration for further valorization. For instance, it has been noted that accumulation of butyric acid in a first-stage digester treating FW was found to be an issue for microbes to transform into biomethane. The advantages of this process are increased energy recovery, removal effectiveness, stability of the reactor, methane production rates, and pureness of gas products in contrast to a one-stage fermentation.

13.4

Liquefied food waste for biomass cultivation and multiproduct recovery

13.4.1 Cultivation of microalgae: biodiesel Microalgae are a rich source of carbon compounds and capable of producing biofuels mainly due to the presence of oil which has similar characteristics to vegetable oil. The four techniques used for cultivation of microalgae are phototrophic, heterotrophic, mixotrophic, and photoheterotrophic. For the production of biodiesel, microalgae species with lipid contents of about 50%
70% are favorable. For a viable culture of algae, the biomass yield must be . 30 g/m2/day (Khan et al., 2018). In phototrophic cultures, microalgae make use of sunlight for harvesting energy, and assimilate CO2 as inorganic carbon for the production of chemical energy by the process of photosynthesis. Heterotrophic algae utilize organic carbon without being subjected to sunlight for cultivation, which is known as heterotrophic culture. In other literature, it has been reported that about 27.3% lipid productivity was achieved in microalgae cultivation under mixotrophic conditions (Devi and Mohan, 2012; Patel et al., 2018). The main advantage of heterotrophic over phototrophic cultivation is that it avoids problems connected with inadequate light and also there is a considerable microalgal biomass production yield (Cruz et al., 2018). The main issue associated with this is the elevated cost of the raw material. Thus, the effluent generated after acidogenic fermentation and FW can be considered a suitable substrates for heterotrophic and mixotrophic cultivation of microalgae. This approach yields greater biomass productivity and lipids when grown in the heterotrophic and mixotrophic modes of operations using food processing wastewater as the raw material (Devi and Mohan, 2012). Almost 22.9% intracellular lipids can be accumulated in Chlorella sorokiniana under heterotrophic conditions using food wastewater as the substrate (Chi et al., 2011). The microalgal species, such as Schizochytrium mangrovei and Chlorella pyrenoidosa, can accumulate lipids up to 300 mg/g dry mass using canteen FW (rice, noodles, meat, and vegetables) as the substrate (Pleissner et al., 2013). In addition, effluents generated from acidogenic fermentation were employed for culturing microalgae and lipid accumulation of 26% was obtained in heterotrophic conditions (Devi and Venkata Mohan, 2012). The microalgal species Chlorella ellipsoidea and Scenedesmus quadricauda can be grown on digested kitchen waste effluent. A higher lipid accumulation can be obtained through this approach (Pei et al., 2017). Thus, effluent from acidogenic fermentation can be considered to be a potent substrate for production of lipid through integration of heterotrophic microalgal cultivation. Consequently, algae-based technologies are emerging rapidly and the rising demand for sustainable technologies is clear from the increasing demand for energy and the threat of global warming (Gopalakrishnan, 2014).

13.4.2 Cultivation of microalgae: value-added products recovery The integration of microalgae cultivation with value-added products recovery has been considered as a promising approach. By integrating FW-based acidogenic effluent to microalgae cultivation, the nutrient-accumulated microalgal biomass can be used as a substrate for value-added product recovery. Integrating microalgal cultivation with bioplastics production resulted in higher process efficiency than using FW as the sole substrate. In view of its wide availability, utilization of FW hydrolysate or acidogenic FW as substrate for microalgal cultivation and subsequent value-added products recovery is a promising strategy and the process has economic feasibility. The amount of biomass and oil content produced by microalgae may serve as a feedstock for the generation of value-added chemicals, and as a rich source of bioactive compounds such as proteins, lipids, carbohydrates, and

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pigments. Microalgae are capable of accumulating high amounts of polysaccharides and are also used as a feedstock for value-added products. Microalgae possess certain medical properties and function as nutraceuticals and antioxidants. They are widely used as preventives against diseases such as cancer, diabetes, and cholesterol (Bhalamurugan et al., 2018). Lutein, carotenoids, omega-3, docosahexaneoic acid (DHA), eicosapentaneoic acid (EPA), lycopene, and phycobilins are the most commonly produced value-added products from microalgae (Tang et al., 2016). Chlorella sp., Coelastrella sp., Parachlorella kessleri, and Scenedesmus bijugatus are some of the strains of microalgae which can clearly accumulate significant amounts of lutein, varying from 0.28 to 6.49 mg/g. The microalgae Haematococcus pluvialis-based valuable product astaxanthin has received a great deal of interest for its natural extracts. Carotenoids are the most commonly produced value-added product and β-carotene is part of the pigment in carotene, which imparts a red, yellow, or orange color to plants, algae, and animals, and it was reported that the highest production of ß-carotenoids achieved by high stress light techniques resulted in an enhanced productivity of 30 pg/cell/day in Dunaliella salina (Sun et al. 2018). The most frequently applied microalgae for the production of bioactive compounds include Arthrospira, Chlorella, Dunaliella, Haematococcus, and Nostoc (Bhalamurugan et al., 2018; Kothari et al., 2017). Another value-added product, astaxanthin, acts as an effective antioxidant by reducing and stabilizing free radicals and facilitates the fight against ulcer disease from Helicobacter pylori.

13.4.3 Cultivation of yeast: biodiesel, biogas recovery, and biofertilizer production Biodiesel is renewable, harmless, biodegradable, viable, fire-resistant, eco-friendly, and free from sulfur and aromatic contents. Oleaginous microorganisms belonging to the genera of algae, bacteria, yeast, and fungi can accumulate lipids, producing biodiesel under the correct cultivation conditions with a similar chemical composition and energy value as that obtained from oilseed crops and animals (Javaid et al., 2017). Some strains of microalgae produce biofuels deriving energy from sunlight, accumulating lipid contents of up to 50% of dry weight. The species of oleaginous yeasts such as Rhodosporidium, Rhodotorula, Cryptococcus albidus, Yarrowia, Lipomyces, and Trichosporon contain a high lipid content and a faster growth rate (Patel et al., 2016). The lipids extracted from yeast can be utilized for biofuel production (Javaid et al., 2017). Cheirsilp et al. (2011) suggested that the mixed culture of microalgae and yeast improves biomass production and lipid content using R. glutinis and Chlorella vulgaris in seafood-processing effluent (Ling et al., 2016). A diverse range of cheap carbon sources such as food industry waste, grape must, radish brine, cheese whey permeate, food industrial wastewater, and derivatives of flour have been widely used as raw materials for oleaginous yeast cultivation. Some of the yeast species including Rhodotorula sp., Lipomyces sp., and Rhodosporidium sp., were considered for lipid accumulation of up to 70% of dry mass. Ekpeni et al. (2014) reported that the maximum biogas production was achieved from S. cerevisiae, also known as baker’s yeast, under optimum conditions of temperature 0 C
40 C with fermentation for 0
24 h at a pH 5.3. Yeast can also be used as a biofertilizer because it has beneficial microbes which can increase nutrient accessibility by their biological activity, thereby improving the soil health. Nitrogen and phosphorus are activated by microbes involved in the formulation of biofertilizers producing crops and foods naturally. S. cerevisiae can promote the growth of different crops. Agamy et al. (2013) investigated the effects of three yeasts, Kluyveromyces walti, Pachytrichospora transvaalensis, and Saccharomycopsis cataegensis, as biofertilizers on the growth and yield of sugar beet. Among these three yeasts, K. walti gave the best results with an increase in sucrose content in sugar beet of about 43%.

13.5

Electrofermentation process: multiple value-added products recovery

Electrofermentation is an effective electron-capturing process which improves microbial metabolism, leading to the production of value-added products. In this process, the generation of electrons and protons takes place with the utilization of organic matter by electrochemical bacteria (electrofermentation). Microorganisms extract energy from redox reactions through electron donors/acceptors conditions. These microorganisms are called lithotrophic, lithoheterotrophic, or lithoautotrophic, based on the utilization of inorganic or organic compounds, or CO2, respectively, as a carbon source (Schievano et al., 2016).

13.5.1 Bioethanol fermentation: microbial electrolysis cell system A microbial electrolysis cell (MEC) is a technology that resembles microbial fuel cells (MFCs). In MFCs, an electric current is produced by the microbial decomposition of organic compounds, whereas in MECs, electrochemically active bacteria oxidize the organic matter by the application of an electric current to generate hydrogen or methane, CO2,

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electrons, and protons. The use of petroleum-based fossil fuels has been replaced by the utilization of different energy resources, thereby reducing the environmental problems caused by the increasing consumption of oil and its derivatives. The efficiency of MECs is based on the microorganism and membranes used, electrode materials, range of applied potential, substrate concentration, and design of the MEC. Bioethanol is used as the only electron donor in MECs to establish a mass and electron balance for the process and to confirm methanogenesis as an important electron sink (Herna´ndez et al., 2016). S. cerevisiae is mostly employed yeast for ethanol production and is extensively used in the production of beverages (Aslanzadeh et al., 2014; Tesfaw and Assefa, 2014). Nuanpeng et al. (2018) studied the effect of ethanol-producing yeast S. cerevisiae, a thermotolerant strain DBKKUY-53 from sweet sorghum juice immobilized in an alginate-loofah matrix. The concentration of ethanol was found to be 0.54 g/L under the optimum conditions. It was reported in the literature that the maximum ethanol production rate was obtained at an organic loading rate of 24 kg/m3 (Han et al., 2011). The generation of electro-fuels such as hydrogen, bioethanol, and bioelectricity with more metabolic products from FW in a solid-state bioelectrofermentation system such as formic acid, lactic acid, and propionic acid are emerging in the valorization of FW. The synergic strategy, which involves integration of microbial surroundings with electrochemistry, is an emerging and promising technique.

13.5.2 Hydrogen fermentation: microbial electrolysis cell system MEC is a developing technology for the production of hydrogen by the degradation of organic matter. In these systems, anode-respiring bacteria transfer electrons to a simple product such as acetate or hydrogen. At the cathode, hydrogen generation takes place by the combined effect of the electrons that are produced which pass through the external circuit and protons passing through the solution (Liu et al., 2010; Herna´ndez et al., 2016). Wang et al. (2011) integrated the process of dark fermentation and MFCs for the production of hydrogen gas. The results revealed that the integrated system increased the overall hydrogen production to about 41%, with a production rate of 0.24 m3 H2/m3/d and an overall energy recovery efficiency of 23% without any external electrical energy requirement (Wang et al., 2011). Lu et al. (2009) studied the production of hydrogen combining MEC with the fermentation system and achieved an overall hydrogen recovery of 96%, with a production rate of 2.11 m3 H2/m3/d, corresponding to an electrical energy efficiency of 287%.

13.6

Integrated biorefineries of different food wastes

13.6.1 Plant-derived food waste (fruit and vegetable waste) FW obtained from various sources can be classified into two major groups: plant- and animal-derived FWs. Plant-derived FW can be further subdivided into fruits and vegetables, cereals, oil crops, roots, and tubers, and animalderived FW includes meat products, fish, and dairy products (Galanakis, 2018). Of these two major groups, plantderived FWs comprise the major portion. Plant-derived waste is the most important source of carbohydrates, lipids, proteins, minerals, and other phytochemicals. Approximately, it is estimated that the generation of fruit and vegetable wastes are about 10%
20% through cultivation and 15%
20% of wastes are produced due to processing (Jin et al., 2018). Currently, low-value animal feed is derived largely from fruit and vegetable waste, and a small portion of this waste is utilized as a staple to obtain phytochemicals, and soluble and insoluble nutritive fibers. Fig. 13.2 shows an integrated biorefinery of plant-derived FW.

13.6.1.1 Apple pomace Apples are eminent and prevalent fruits of the genus Malus belonging to the family Rosaceae. Apple and apple products are major sources of phytochemicals and antioxidants in daily food intake. Apple pomace is a residue that is generated in huge volumes during the processing of apple products such as juice, sweet cider, jelly, and vinegar. Apple pomace consists of 95% apple peel and whitish flesh, 2%
4% seeds, and 1% stems (Perussello et al., 2017). Apple pomace and apple pomace solids are rich sources of carbohydrates, pectin, polyphenols, and other essential nutrients. They can be utilized for the production of organic acids, bioethanol, and other value-added products. Vegetable oils produced with apple seeds have antioxidant contents such as catechins, procyanidins, and caffeic acid, and antiinflammatory, antiatherosclerotic, and anticancerous compounds associated with the presence of tocochromanols, carotenoids, flavonoids, phytosterols, and phenolic acids. Apple is an important resource with a polyphenolic content obtained by the various methods of processing in which the phenolic compounds are released by the utilization of pectinolytic enzymes followed by pasteurization, or fermentation in cider production (Dhillon et al., 2013). Apple polyphenols possess

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FIGURE 13.2 Integrated biorefinery of plant-derived food waste.

beneficial properties exhibiting antitumor qualities and inhibition of carcinogenesis in the skin, mammary glands, lung, and colon, etc. (Ploscutanu et al., 2019). Yates et al. (2016) studied the extraction of apple pomace in deionized water to form carbohydrates and sugars. The liquid was then treated with 94% ethanol to precipitate the pectin and was subsequently separated by centrifugation, purified, and filtered with 9% ethanol to remove traces of monosaccharides and disaccharides. Catana et al. (2018) studied the characterization of functional ingredients produced from apple waste in powder form from the apple juice industry. Apple waste was subjected to a convective drying process turning it into powder form. The functional ingredient powder is characterized by total nutritional fiber, iron, potassium, calcium, magnesium, and total polyphenol content.

13.6.1.2 Grape waste (wine lees) Grapes are one of the most valued and the second highest fruit crop in the world. The presence of high concentrations of lignin, cellulose, and hemicellulose in grape stalks acts as an excellent renewable carbon source when divided into fractions (Amendola et al., 2012). About 75% of total grape production is utilized for wine-making. In the winery industry, the major solid organic wastes that are generated during the process of pressing and fermentation are called grape pomace (Beres et al., 2017). The compounds that are recovered from grape pomace include tartrates, citric acid, grape seed oil, hydrocolloids, and dietary fibers. The composition of grape seeds generated from wine industries consists of fiber, lipid, protein, unsaturated fatty acids, phenolic compounds, sugars, and minerals. The oil extracted from grape seeds is rich in unsaturated fatty acids and phenolic compounds. Amendola et al. (2012) investigated the recovery of hemicellulose and lignin pretreated by autohydrolysis from red grape stalks followed by an organosolv process. Ethanol was added to autohydrolysis liquor to precipitate hemicellulose, while acidification precipitates lignin from both processes. Dimou et al. (2015) developed a novel wine lees-based integrated biorefinery for the production of value-added products. Initially, the wine lees were centrifuged and the supernatant was used for hydrolysis. The residual liquid was transformed into a fermentative nutrient for production of poly(3-hydroxybutyrate) using the strain Cupriavidus necator DSM 7237.

13.6.1.3 Citrus waste A part of the citrus fruit yield, predominantly oranges, is industrially processed for juice production. The by-product of citrus pulp is used as a low-cost dietary supplement in various forms for animals and has been recommended to inhibit the growth of both Escherichia coli and Salmonella (Alnaimy et al., 2017; Zoiopoulous et al., 2008). Dried citrus pulp is utilized as a valuable feed for cattle growth by partly replacing energy sources safely in the diets of cattle without affecting animal health. The production of juice from these citrus fruits commercially results in the huge generation of waste. About 40%
60% of citrus fruits are used for juice extraction, of which 50%
60% remains as residue. The byproduct of fruit-juice production, namely orange peel, has been widely used as a raw material for pectin production and citrus pectins are extracted by hot diluted mineral acid extraction and recovered from the acid with an antisolvent, for example, ethanol (Satari et al., 2017). Citrus peel waste consists of D-limonene, possessing the antimicrobial properties and applicability in food, cosmetics, and pharmaceutical industries and requires the removal of essential oils for production of ethanol and methane (Patsalou et al., 2019). Fig. 13.3 shows an integrated citrus waste biorefinery.

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FIGURE 13.3 Integrated biorefinery of citrus waste.

Satari et al. (2017) extracted pectin and obtained a maximum yield of 45.5% at pH 1.8, 80 C, and 2 h, which was 50% higher than the pectin yield at pH .1.8. Citrus fruits contain N, lipids, sugars, acids, insoluble carbohydrates, enzymes, flavonoids, peel oil, volatile constituents, pigments, vitamins, and minerals (Bampidis and Robinson, 2006). Wikandari et al. (2014) investigated the enhancement of biogas production from citrus waste by the application of a membrane bioreactor. The citrus fruit was pretreated using a cell protection technique. In the membrane bioreactor, the biogas is generated by the digestion of citrus wastes by the bacteria producing dissolved compounds, which can pass through the membrane.

13.6.1.4 Tomato waste The tomato is an edible fruit and it is considered as a vegetable crop that ranks third subsequent to the potato and sweet potato. Globally, tomato production is around 130 million tonnes, of which 30% is used to acquire by-products. The tomato-processing industry produces huge quantity of biowastes, such as the seeds and skin of the fruit. Tomato byproducts are generally used as feedstock for animals. Moreover, the utilization of tomato waste includes the production of enzymes, bioactive compounds, or biomass to produce biofuels or to generate electricity. Tomato pomace is comprised of mashed skin and seeds enriched with protein, fat, and crude fiber and it is also tremendously rich in antioxidant compounds, especially lycopene (Gonzalez et al., 2011). Lycopene is a pigment found in low amounts in several fruits and vegetables, with tomatoes being the main source; the concentration of tomato lycopene is very intense on the skin and also on the water-insoluble portion directly underneath the skin. In some genus of tomato, namely S. pimpinellifolium, the concentration of lycopene was found to be 40 mg/100 g (Lovdal et al., 2019). Nour et al. (2018) investigated the composition of tomato processing waste containing dietary fibers and antioxidant properties and reported that the dried tomato waste was found to contain protein, fat, crude fiber, ash, with substantial amounts of lycopene and β-carotene, and had good antioxidant properties. Encinar et al. (2008) conducted a study on tomato plant waste to determine the characteristics of charcoal by conventional pyrolysis. It was reported that according to their characteristics and energy contents, the three phases could be used as fuel. Cifarelli et al. (2016) extracted the cutin from tomato peel using a green chemistry protocol devoid of organic solvents.

13.6.1.5 Potato peel waste The potato belongs to the solanaceae family of flowering plants. Potatoes are considered as a chief source of food with a variety of species worldwide. The wastes that are generated during the processing of potatoes include pieces of raw potato, raw and cooked pulp, starch, potato peel, potato juice, and dissolved solids. The starch present in potatoes is one of the best and variously applicable polysaccharides. To reduce the pollution effects on the environment, existing plastics can be replaced by starch-based bioplastic (Priedniece et al., 2017). The processing of starch is a technology employing enzymatic liquefaction and saccharification for the production of glucose, which undergoes further

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FIGURE 13.4 Integrated biorefinery of potato peel waste.

hydrolysis by fermentation to produce ethanol by Saccharomyces yeasts. Fig. 13.4 shows an integrated biorefinery for potato peel waste. Arapoglou et al. (2010) conducted a study by hydrolyzing starch-containing potato peel waste with a variety of enzymes and acid, and fermented by S. cerevisiae var. bayanus for the production of ethanol. Chintagunta et al. (2015) described a study on the production of ethanol from potato peel and mash wastes with the use of Aspergillus niger and S. cerevisiae cultures without enzymes. After that, the residue obtained from the ethanol production was inoculated with seven different microorganisms in the same ratios for the enrichment of nitrogen, phosphorus, and potassium. The by-products of potato waste are used as low-cost animal feed or for the production of biofuels, pharmacy, food production, and medicine applications, thus wasting the nutrition-rich materials (Wu, 2016). Moreover, its high content of carbon and nutrients renders it as a good feedstock for biogas production via the AD process. Achinas et al. (2019) conducted a performance study on AD of potato peel for the production of biogas and reported that the maximum production of methane obtained was 217.8 mL CH4/g VSadded.

13.6.1.6 Rice waste Rice is a leading crop, principally consumed in the extremely heavily populated region of South and Southeast Asia. The rice industry produces a large amount of waste and the major solid wastes generated during the milling process consist of straw, husk, ash, bran, and broken rice grains. Rice straw contains ash, lignin, silica, and lignocellulosic substances which are renewable. Rice straw which is acid-pretreated produces pentose-sugar-rich hydrolysates that act as a source of carbon during production (Tsang et al., 2019). The outermost layer of the paddy grain is the rice husk which is removed from the rice grains during the milling process. Rice husk accounts for about 20% w/w of rice, and is one of the most important agro-industrial side-products produced worldwide. The rice husk is used an as animal feed, as a fertilizer preservative, stock breeding rugs, cooking fuel, and other valuable uses of rice husk include as composites and partition boards, and production of biochar for the enhancement of soil quality. The rice husk also has the potential to generate bioenergy, a another renewable source of power (Pode, 2016). During the rice polishing process, the major byproduct obtained is rice bran, which consists of phytosterols, a mixture of ferulic acid esters of triterpene alcohols such as cycloartenol and 24-methylene cycloartenol. Ferulic acid is extensively used in foods and beverages and lactic acid bacteria help in the biotransformation of ferulic acid to other derivatives of phenolic compounds where ferulic acid esterase and ferulic acid decarboxylase perform important roles (Varzakas et al., 2016). Rice husk consists of a huge quantity of residue and lignin, which causes an adverse effect to the environment (Barana et al., 2016). Barana et al. (2016) applied an integrated biorefinery process depending on acidic leaching, alkaline treatment, and hydrolysis of concentrated sulfuric acid to recover lignin, hemicelluloses, silica, and cellulose nanocrystals. Furthermore, pure amorphous silica was obtained from rice husk with maximum output and purity, preventing incineration.

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13.6.2 Food processing industrial waste 13.6.2.1 Palm oil effluent Palm oil is the most commonly consumed vegetable oil, contributing about 33% of total global vegetable oil production. Palm oil milling generally involves processing of oil palm fresh fruit bunches into crude palm oil and palm kernel (Rahim et al., 2011). The overall biomass generated is composed of only 10% of the extracted oil, while the remainder is considered as waste by the oil palm plantations. On average, 50
70 tonnes of biomass residues are produced from each hectare of oil palm plantation (Shuit et al., 2009). In addition to palm oil production, the by-products generated are oil palm trunk, oil palm frond, empty fruit bunch, mesocarp fruit fiber, palm kernel shells, and palm oil mill effluent (POME) (Kurnia et al., 2016). By-products such as mesocarp fiber and shell materials are utilized as solid-fuel feedstock for the generation of steam and electricity (Rahim et al., 2011). Iwuagwu and Ugwuanyi (2014) used POME as the sole source of carbon and nitrogen. They carried out a fermentation process at 150 rpm, 28 C 6 2 C using an inoculum size of 1 mL of 106 cells. It was stated that using Saccharomyces sp. L31 resulted in the maximum accumulation of biomass, along with the COD removal of 83% with the greatest accumulation of biomass in 96 h. Biogas can be produced by the decomposition of organic matter by anaerobic bacteria without oxygen. It consists of 65% methane, 35% carbon dioxide, and 2000 ppm of hydrogen sulfide (Keong, 2006). In an anaerobic process, the POME is degenerated into methane, carbon dioxide, and water by a series of reactions including hydrolysis, acidogenesis, and methanogenesis. Lipids are one of the most important organic contaminants in POME. During anaerobic treatment, lipids are hydrolyzed into glycerol by hydrolytic extracellular lipases (Ahmad et al., 2011). Moreover, the palm oil can be converted into biofuel, which is an extra possible resource of power generation. It is considered as eco-friendly, with low of sulfur dioxide and nitrogen dioxide emissions (Keong, 2006). Cellulose and hemicellulose are polysaccharides that can be transformed into sugar monomers. They can be used as fermentation substrates for a variety of products. Rizal et al. (2018) conducted a study into the pretreatment of oil palm biomass to modify the lignocellulosic constituents by altering the structural arrangement and eliminating the lignin component, thereby exposing the internal structure of cellulose and hemicellulose for cellulases to assimilate it into sugars.

13.6.2.2 Olive mill waste The wastes discarded from the olive oil industry are huge in quantity, and they contain potentially interesting compounds. For instance, pure olive oil, due to its notable composition of orthodiphenolic compounds, is of remarkable quality with high resistance to auto-oxidation. The ideal production of olive oil is in three phases with two wastes: olive oil, solid waste, and aqueous liquor. The solid waste is a composition of olive pulp and stones (Bolanos et al., 2006). Olive oil is obtained only from the fruit of the olive tree and the abstraction of olive oil results in the formation of a huge amount of by-products, with 100 kg of treated olives producing 35 kg of solid waste and 100 L of liquid waste. Such an extensive amount of by-products may have detrimental effects on the surrounding environment. Fig. 13.5 shows an integrated biorefinery for olive mill FW. Numerous experiments have confirmed the effects of these by-products on soil microbial populations, on aquatic ecosystems, and even in the air. Nevertheless, these wastes also contain beneficial resources, such as organic matters, sugars, oils, fibers, polyphenols, and a varied range of nutrients that can be reprocessed. Olive oil cake has been found to be an excellent substrate for the production of lactones by solid-state fermentation. This is due to the high concentration of oleic acid in the substrate, which acts as a precursor substance for the synthesis of lactones. High oleic acid-containing oils are preferred for biodiesel production. This is because of the increased strength of their alkyl esters, improved fuel properties, and also because they are suitable for biodiesel production in winter (Kamini et al., 2009). Olive oil has an oleic acid content of 74.2% and is a good candidate for biodiesel production (Kamini et al., 2009). Pomace can be directly plowed into soil as a soil conditioner, which is evidently a very easy and direct utilization method, and therefore, it is a recurrent method. Pomace not only improves the physical texture of soil but also adds nutrients such as carbon, potassium, nitrogen, and phosphorus in substantial amounts (Peri and Proietti, 2014). In addition, olive by-products, such as plant sterol, which is a source of functional components, has been shown to reduce blood cholesterol levels. Many “functional” foods have been prepared with these natural phytonutrients. Olive oil and olive by-products are ample sources of these functional components. A great deal of effort has been taken to obtain phytosterols from olive oil by-products (Berbel and Posadillo, 2018).

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FIGURE 13.5 Integrated biorefinery olive mill food waste.

13.6.2.3 Oil-extracted residues In the process of extracting oil from oil seeds, residues are retained. These residues contain phenolic compounds, which are bioactive substances. These could be used as natural antioxidants for the protection of fats and oils against oxidative degeneration. Natural compounds with antioxidant activity property are obtained from the extracts of spices, cereal crops, barks, roots, rosemary or sage, and other herbs. Such compounds include tocopherols, phospholipids, amino acids, peptides, and phenolic compounds. Oil seeds also contain phenolic compounds such as hydroxylated derivatives of benzoic and cinnamic acid, coumarins, flavonoid compounds, or lignins. The by-products obtained from the process of oil extraction are usually used as nutritious foods to feed animals. They are also used as fuel in thermal power stations (Matthaus, 2002). Flourat et al. (2019) focused on the development of phenolic compounds. One such major compound was sinapine which was extracted from the residues of industrial mustard production. Under ideal conditions more than 10 mg/g of defatted and dried matter of phenolics were extracted and 13 mg/g of phenolics were extracted from nonpretreated matter. The seeds of evening primrose (Oenothera biennis) are rich in unsaturated fatty acids, especially γ-linolenic acid. This acid is present only as fragments in most foods. In the past few years these seeds have served as raw materials for the extraction of oil, which is widely used for therapeutic purposes as a natural remedy for skin diseases. Hanczakowski et al. (1993) calculated the composition and nutritious value of the residues obtained from the extraction of oil from the seeds of evening primrose. It was stated that the seeds contained 17% fat and 22.2% protein. This protein was enriched with sulfur amino acids but was meager in lysine (4.9 and 1.8 g per 16 g of N). In 2001, Meessen et al. (2001), through the three- and two-phase centrifugation systems, tested olive oil residues for their composition in simple phenolic compounds. It was found that the phenolic compound extraction with ethyl acetate was effective, with the recovery of 28.8% and 42.2% of total phenols. This is present in dry olive oil residues emanating from three-phase and two-phase systems. The phenolic extract from the two-phase system had the highest concentration of hydroxytyrosol [1.16% (w/w) dry residue] and the greatest antioxidant activity.

13.6.2.4 Rapeseed oil waste Rapeseed plant has conventionally been used for the production of edible vegetable oil and as feedstock for animals. In recent years, an increasing portion of rapeseed oil has been used as raw material for the production of biodiesel (Luo et al., 2011a,b). The oil is extracted from rapeseed, resulting in the production of solid by-products such as rapeseed meal or cake. Rapeseed oil is also used mainly as a substrate for biodiesel production. Rapeseed cake, with 75% extraction of oil, can create 0.51
0.55 m3 of methane per kg of volatile solids. During processing of rapeseed meal, the exact theoretical production of methane is 0.45 m3/kg (Kolesarova et al., 2013). Luo et al. (2011a,b) conducted a study on a biorefinery concept for multibiofuel production utilizing the entire rapeseed plant. The results demonstrated that by

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combined alkaline peroxide and stream pretreatment from straw 0.15 g ethanol yield/g dry straw was produced. The byproducts obtained were assessed for hydrogen and methane production. In contrast to several species of crop, B. napus has been bred to produce a collection of products from rapeseed oil to animal silage with the considerable phenotypic and genotypic variations. Wood et al. (2015) explored saccharified and fermented straw obtained from 17 B. napus cultivars of different types of crops to ascertain differences in biomass composition relevant to cellulosic production of ethanol.

13.6.2.5 Cassava waste Cassava is an annual crop broadly cultivated for use in producing starch and alcohol, and amongst other products yielding a considerable quantity of cassava waste. Cassava residue is mainly used for producing animal feed, fermentative production of biogas, in culture media for mushrooms, and as a fuel. Huang et al. (2018) extracted cassava dietary fiber from cassava residue using enzymes by employing a physicochemical method. The enzymes were added to the physically pulverized cassava residue in order to remove starch, fat, and protein. It was reported that a soluble dietary fiber yields of 75.63% and 37.55% were obtained. Cassava peel and sieviate, which are by-products of cassava yield used for the bioethanol or biogas production when it is subjected to the combined alkaline and enzymatic pretreatment. Aderemi and Nworgu (2007) conducted a study to enhance the nutritional importance of cassava root sieviate and peel through biodegradation by A. niger. The cassava root sieviate has a protein content of 2.09%, 5.21%, and 7.34% for the corresponding 0, 5, and 10 days, whereas for cassava peel these values were found to be 5.35%, 10.70%, and12.64%. From the results, it was clear that the biodegradation performed by A. niger was capable of supplementing the protein content of both sieviate and peel. Jamal et al. (2012) investigated the production of an enriched animal feedstock from cassava peel studying the consequences of the course of action using a locally isolated white rot fungus, Panas tigrinus.

13.6.2.6 Jatropha waste Jatropha curcas is a plant harvested in tropical and subtropical regions, and its high oil content in the seeds is of emerging interest as a bioenergy resource. The conversion of oil to biodiesel takes place through transesterification easily. Chavan et al. (2013) performed esterification and transesterification reactions for biodiesel production by subjecting esterified Jatropha oil to transesterification with calcined egg shell powder as a heterogeneous catalyst. The results proved that the maximum yield of purified biodiesel was achieved by taking different parameters such as a suitable methanol to oil molar ratio, reaction temperature, and reaction time. A good potential for biogas feedstock is Jatropha seed cake due to it having a 60% higher biogas production (Primandari et al., 2018). Jatropha seed cake does not require densification for the generation of heat and can be pyrolyzed in order to produce biodiesel. Ramı´rez et al. (2019) evaluated the use of biochar produced during the pyrolysis of Jatropha seed cake along with Jatropha shell waste forming a pellet combustion fuel. Mixtures used different proportions of biochar and Jatropha shell waste. Pellets composed of 50% Jatropha shell waste and 50% biochar, with 25% additional water and 4 mm particle size, presented the greatest mechanical durability (96.83%), a and higher heating value (22.14 MJ/kg). Kumar et al. (2015) studied various pretreatment methods of sewage sludge inoculum of de-oiled Jatropha waste and reported that peak hydrogen production rate and hydrogen yield of 0.36 L H2/L/d and 20 mL H2/g volatile solids were obtained when heat shock pretreatment (95 C, 30 min) was employed. Nonedible Jatropha curcas oil was used as a feedstock for the synthesis of biodiesel.

13.7

Integrated biorefineries in various sectors

Ismail (2016) assessed and presented a case study of waste-based biorefineries in the Kingdom of Saudi Arabia (KSA), which is a developing country. It was reported that there was no energy or value-added product recovery facility in KSA, and all untreated municipal wastes were disposed of in landfill or dump sites. As a consequence, there were greenhouse gas emissions, and contamination of groundwater and soil which in turn had detrimental effects on the environment. The results revealed that if the FWs had been utilized properly in an AD system, an estimated potential power generation from such resources would have been 2.99 TWh annually. Based on the waste composition, generation rates, and energy contents of KSA, an integrated waste-based biorefinery system with multiple processes and products was proposed. Due to the implementation of this system, there was a drastic reduction in GHG emissions and the costs of waste landfill. In addition, there was an improvement in public health and protection of land resources, and the generation of renewable electricity.

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In 2010, Santos et al. presented a new method, implemented by companies in Brazil, to produce chemicals and fuels in a biorefinery. A new technology that is emerging in Brazil is extracting the waste generated in the production of ethanol from food processing industries (sugarcane) and then utilizing it as a raw material in developing a wide range of products through integrated and interdependent processes. Braskem is one of the three largest Brazilian industries. The by-product is bioethanol from which the biopolymers, also known as green polymers, are synthesized. These biopolymers can be recycled to produce other products.

13.8

Integrated biorefineries: techno-economic analysis

Techno-economic evaluation is mandatory for a novel process to be upgraded for commercialization. It provides useful data including profitability. These data serve as a directive for emerging and changing capital spending plans, for evaluating operating and maintenance costs, for forecasting profitability, and for guiding future research and development efforts of the process (Cristo´bal et al., 2018). The first step in an economic viability study is the evaluation of overall capital investment, which commonly consists of fixed capital cost and working capital cost. In 2017, Jarunglumlert et al. (2017a,b) evaluated the economic feasibility of the production of H2 from FW by a dark fermentation process. It was concluded that even though the initial investment was high, the operating cost was low and hence large-scale production of H2 was considered both economical and environmentally friendly (Jarunglumlert et al., 2017a,b). Ghosh et al. (2017) evaluated a general techno-economic comparison between a two-stage integration system and a single-stage system. It was reported that the single-stage system was less expensive than the two-stage integration system owing to the lack of the prerequisite processing of the dark fermentation effluent. It was also recommended that the systematic integration of dark and photo-fermentation processes in a consecutive manner was much easier than a single-stage system due to the significant variation in the most favorable operating conditions of both types of microorganisms. Thus, it was concluded that the single-stage system of dark and photo-fermentation is more cost effective than the two-stage integration process. In 2018, Cristobal et al. presented an economical assessment of four FW biorefineries that used tomato, potato, orange, and olive wastes as feedstock. A screening method was employed to assess the capital and operating costs, and two profitability ratios were adopted. The results showed that all the waste feedstocks had different potentials. Dark fermentation due to low energy requirements provided a promising process for clean hydrogen fuel compared to other traditional chemical processes. The production of biohythane in a two-stage AD process was found to be beneficial due to the lower yields instead of individual dark fermentation in order to lessen the expenditure and to acquire valuable fuels with high yields. It was reported that the yield of hydrogen was directly related to the operational costs, whereas the rate was directly related to the cost of the reactor or the equipment cost (Hans and Kumar, 2018). RedCorn et al. (2018) analyzed the possibility of utilizing industrial FW for either specialty products or methane. It was reported that potato peel could be converted to lactic acid through a fermentation process which yielded an income of US$5600 million per year. On the other hand, potato peel may be transformed to methane through an AD process, resulting in a revenue of US$900 million per year. In the near future, the waste-to-biofuel market could be a major energy market ready for financial development. The presence of a wide variety of biomasses, and their compilation and alteration to high-value products would reduce the cost of conventional fuels. This in turn would reduce the dependency on petroleum fuel. In addition, transportation fuels such as gasoline and diesel could be replaced by bioethanol and biodiesel which are produced from FW and other renewable sources (Waqas et al., 2019). There are many economic benefits to the production of biofuels. The emission of greenhouse gases is reduced in biofuels when compared with conventional fuels. In 2017, Nizami et al. developed a waste-based biorefinery system that was composed of an AD system, a transesterification system, a pyrolysis system, and a refuse-derived fuel system. This waste-based biorefinery system was able to treat around 87.8% of the total municipal solid waste. The remaining 12.2% of municipal solid waste was to be recycled. The amazing result of this waste-based biorefinery system, along with the recycling process, was that it generated a saving of about 87.6 million Saudi Arabian Riyal (SAR) from carbon credits. It also reduced the global warming potential by 1.15 million Mt.CO2 eq.

13.9

Integrated biorefineries: policies and regulations

FW is a potential and cost-effective feedstock to produce various by-products which are of high quality and yield. The food products must adhere to the quality and safety requirements of the food regulations of the respective countries (Leon et al., 2018). The recent changes to legislative frameworks have encouraged industries to recover by-products

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from FW without affecting the environment. The legal aspects for evaluating food safety in potential consumers should be considered while evaluating FW as a source of food additives. Guidelines for the effective utilization of collected FW should be designed. These should help to segregate FW from nonbiological wastes and should also include methods to sort and transport FW to the collection facilities (Waqas et al., 2019). Nongovernment organizations, food industries, government, and civil society groups should take necessary initiatives in creating awareness among the population about the value of FW by conducting campaigns. This will aid in converting this no-value resource into useful products. In order to make biofuel cheaper, duty reductions and tax exemptions on its procurement are essential. Such policies and initiatives will help in building a sustainable society (Karmee, 2016).

13.10 Conclusions: remarks and future perspectives The quality of the end-products, control of the process conditions, and high construction costs of digesters are the major factors which have to be considered in the conversion of FW to value-added products (Waqas et al., 2019). The food processing facilities have to be integrated with the biorefinery concept in order to develop cost-effective and valueadded products along with the generation of heat and power to sustain the biorefinery with lower environmental impacts (Waqas et al., 2019). The emergence of novel techniques for the recovery of commercially significant by-products for the safety of public health and the environment necessitate the implementation of strict legislation. Technologies for the recovery of highadded-value compounds are pivotal in the utilization of FW for commercial applications (Ravindran and Jaiswal, 2016). First, most of the present researches focus on cereal or oil crop wastes, whereas there is lack of attention given to fruit and vegetable wastes. The plant-derived wastes such as grape pomace and citrus wastes usually contain value-added compounds such as polyphenols and essential oils together with cellulose, hemicellulose, and lignin. For better utilization of those waste feedstock, first and foremost it is essential to develop a database for plant-derived wastes. The data collected from various types of plant-derived wastes can offer guiding principles for supplementary process design and selection of the final products (Jin et al., 2018). The advancement in microbial electrosynthesis has provided innumerable options to construct and remove useful chemicals from clean substrates as well as biowastes. Additionally, integrating these processes with other biodegradation methods may result in the creation of models for biorefinery waste with an acceptable bioeconomy. In order to decrease the emissions of greenhouse gases and environmental damage caused by municipal solid waste, recycling is a key component of modern wastereduction practices. A more elaborate study of the local social-economic factors, such as local culture, human behavior, and customs are also essential in the selection of appropriate WTE technologies for waste-based biorefineries (Nizami et al., 2017).

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107. Yates, M., Gomez, M.R., Luengo, M.A.M., Iban˜ez, Z.V., Serrano, A.M.M., 2016. Multivalorization of apple pomace towards materials and chemicals. Waste wealth. J. Clean. Prod . Available from: https://doi.org/10.1016/j.jclepro.2016.12.036. Zhang, Y., Li, M., Nie, T., Ni, Z., 2018. A process study of lactic acid production from Phragmites australis straw by a thermophilic Bacillus coagulans strain under non-sterilized conditions. Processes 6 (10), 175. Zhong, J., Stevens, D.K., Hansen, C.L., 2015. Optimization of anaerobic hydrogen and methane production from dairy processing waste using a twostage digestion in induced bed reactors (IBR). Int. J. Hydrogen Energy. Zhu, L.D., Hiltunen, E., Antila, E., Zhong, J.J., Yuan, Z.H., Wang, Z.M., 2014. Microalgal biofuels: flexible bioenergies for sustainable development. Renew. Sustain. Energy Rev 30, 1035
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101.

Further Reading Cantu, R.C.R., Jones, K.D., Mills, P.L., 2013. A citrus waste-based biorefinery as a source of renewable energy: technical advances and analysis of engineering challenges. Waste Manag. Res 31 (4), 413
420. Cesaro, A., Belgiorno, V., 2015. Combined biogas and bioethanol production: opportunities and challenges for industrial application. Energies 2015 (8), 8121
8144. Chandrasekhar, K., Lee, Y.J., Lee, D.W., 2015. Biohydrogen production: strategies to improve process efficiency through microbial routes. Int. J. Mol. Sci 16, 8266
8293. Gacheva, G., Dimitrova, P., 2015. New strain Haematococcus cf. pluvialis rozhen-12
growth, biochemical characteristics and future perspectives. Genet. Plant. Physiol 5 (1), 29
38. Krishna, B.S., Nikhilesh, G.S.S., Tarun, B., Saibaba, K.V.N., Gopinadh, R., 2019. Industrial production of lactic acid and its applications. Int. J. Biotech. Res 1 (1), 42
54. Kumar, P., Chandrasekhar, K., Kumari, A., Sathiyamoorthi, E., Kim, B.S., 2018. Electro-fermentation in aid of bioenergy and biopolymers. Energies 11, 343. Lee, M.J., Song, J.H., Hwang, S.J., 2009. Enhanced bio-energy recovery in a two-stage hydrogen/methane fermentation process. Water Sci. Technol 59 (11), 2137
2143. Sathasivam, R., Ki, J.S., 2018. A review of the biological activities of microalgal carotenoids and their potential use in healthcare and cosmetic industries. Mar. Drugs 16, 26. Shah, M.M.R., Liang, Y., Cheng, J.J., Daroch, M., 2016. Astaxanthin-producing green microalga Haematococcus pluvialis: from single cell to high value commercial products. Front. Plant. Sci 7 (531). Venkata Mohan, S., Devi, M.P., 2012. Fatty acid rich effluent from acidogenic biohydrogen reactor as substrate for lipid accumulation in heterotrophic microalgae with simultaneous treatment. Bioresour. Technol 123, 627
635. Wang, H., Xu, J., Sheng, L., Liu, X., Lu, Y., Li, W., 2018. A review on bio-hydrogen production technology. Int. J. Energy Res 42, 3442
3453. Zgheib, N., Saade, R., Khallouf, R., Takache, H., 2018. Extraction of astaxanthin from microalgae: process design and economic feasibility study. Mat. Sci. Eng 323.

Chapter 14

State of the art of food waste management in various countries A. Vimala Ebenezer1, M. Dinesh Kumar2, S. Kavitha2, Do Khac Uan3 and J. Rajesh Banu4 1

Department of Civil Engineering, V V College of Engineering, Tirunelveli, India, 2Department of Civil Engineering, Anna University Regional

Campus Tirunelveli, Tirunelveli, India, 3Department of Environmental Engineering, Hanoi University of Science and Technology, Hanoi, Vietnam, 4

Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India

14.1

Introduction

The disposal of enormous quantities of food waste (FW) is an emerging issue which has a significant influence on global, economic, and environmental conditions. The Food and Agriculture Organization (FAO, 2013) estimated that, globally, about 1.3 billion tonnes of food in various forms are wasted every year, making up to one-third of the total food produced for human consumption. By 2050, 49% greater food production is anticipated compared with 2012 owing to the increasing population, economic growth, and living standards (Kiran et al., 2014). FW from food processing and kitchens forms a major component of municipal solid waste (MSW) and hence it is of global concern (Ren et al., 2017). FW not only contributes to wastage of energy and resources, but also greenhouse gas (GHG) emissions, which are estimated to be about 3.3 billion tonnes per year of CO2 into the atmosphere (FAO, 2013). FW, when disposed in landfill, results in serious environmental damage to air and soil through its leachate and odor (Kibria, 2017; Waqas et al., 2018b). The global food system contributes about one-third of GHG emissions, and has the largest impact on climate change. Incineration of FW results in the formation of dioxins and also loss of nutrients and valuable chemical compounds, thus affecting the economic value of the substrate (Katami et al., 2004). Proper and efficient handling of FW not only serves as a valuable resource but also reduces the impacts on the environment (Kim and Kim, 2010). In developing countries, FW management issues unintentionally result from inefficient manufacturing, handling, and storage processes, whereas in developed countries, aesthetic preferences and arbitrary sell-by dates might be the deciding factors (FAO, 2013). The global average per capita FW in high-income countries is double that in low-income countries, owing to inefficient food distribution and consumption patterns (FAO, 2013). Limited budgets in developing countries are the cause of the disposal of most FW through landfills (Waqas et al., 2018b). FW in China has increased rapidly and contributes about 70% of total household and commercial waste. Since FW imposes serious threats to economic, environmental, and public health, its appropriate management is essential (Kavitha et al., 2017). FW is considered as a valuable energy resource due to its high biodegradability, moisture content, and greater organic content (Lin et al., 2014). FW management includes conventional treatments such as animal feed, anaerobic digestion (AD), incineration, and composting (Thi et al., 2015). Through AD, a reliable source of heat and electricity can be retrieved and utilized, replacing centralized power distribution systems. If FW is composted properly, it emits less CO2, which is a GHG. FW is rich in proteins, amino acids, carbohydrates, minerals, and oils, which can be used various microbial and enzymatic processes (Pham et al., 2015). France and Italy have enacted legislation that obliges retailers to donate edible food to be distributed to those in need through charities (Azzurro et al., 2017). In the United States, the government and charitable campaigns work together to create awareness to reduce food losses at every stage of the food chain. WRAP (Waste & Resources Action Programme) is a registered charity in the United Kingdom that aims to meet the nation’s target for reducing biodegradable waste and increase the rate of recycling and diversion of waste from landfill.

Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00014-6 Copyright © 2020 Elsevier Inc. All rights reserved.

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Recently, the valorization of FW into different marketable components has been investigated (Du et al., 2018; Bosmans et al., 2013). Current valorization strategies include processing of FW to animal feed, energy production such as biogas and biofuels, organic fertilizers, and compost. There are some drawbacks, such as FW production capacity, seasonal production, and FW compositions, which hinder its industrial implementation. AD can be an option which helping global energy security by converting FW into biogas and nutrient recycling. This chapter discusses the problems of FW and its economic and environmental impacts globally, focusing on the need for effective management, available treatment strategies, legislation regarding FW, and product recovery in developed, developing, and underdeveloped countries.

14.2

Climate change and economic impact

According to a World Bank report, globally around 87% of wastes dumped openly or in landfill produces 300
1000 kg of CO2 per tonne of waste, based on the organic matter present in it. It is estimated that the carbon footprint of food produced and not eaten is 4.4 G tonnes of CO2 equivalent. It is a broadly accepted fact that the greenhouse effect is due to increased CO2 levels in the atmosphere, and that this will result in extensive warming of the Earth’s surface, leading to potential adverse environmental impacts. One of the greatest dangers of climate change is the threat it poses to global food production (United Nation Climate Change, 2017). Climate change is expected to lead to consequences such as extreme weather events, land degradation and desertification, water scarcity, rising sea levels, and shifting climates. This will hamper our efforts to feed the whole planet. Annually, total global food losses cost US$2.6 trillion. The total volume of water used each year to produce food that is lost or wasted sums is 250 km3, and the land resources used for the production of food that is lost or wasted are estimated to be as high as 1.4 billion hectares (Manongdo, 2016). Sheahan and Barrett (2017) summarized the value of postharvest losses in sub-Saharan Africa as being US$4 per year. Venkat (2011) made a life cycle model of 134 US food commodities, from production to disposal, and evaluated the impacts of FW on climate change and the economy in the United States. This analysis was based on food availability data from the US Department of Agriculture with some assumptions. The analysis showed that avoidable FW in the United States exceeds about 29% by weight of annual production and GHG emissions of 113 million metric tonnes (CO2) annually, which is equivalent to 2% of national emissions. Total FW in the manufacturing and retail sectors in the United Kingdom for the year 2014
15 was estimated to be d1.9 billion (Garcia-Garcia et al., 2019; Parfitt et al., 2016). The estimate for FW in the European Union (EU) by FUSION, for the year 2012, showed about 88 million tonnes per year, costing around 143 billion Euros. Every year, nearly $32 billion worth of food is thrown away in China. Globally, the FAO estimates that food worth about $940 billion is lost or wasted (Hanson et al., 2015). In Singapore, this wastage was 785,500 tonnes in 2015 (Manongdo, 2016). In Australia, the rise in the economic cost of FW was from US$5.2 billion in 2009 to US$8 billion in 2014 (Torrisi, 2014).

14.3 Current scenario and development of food waste management in various countries 14.3.1 Developed countries Anaerobic digesters have been successfully installed in several European and Asian countries to stabilize FW, and produce beneficial end-products. Germany, Sweden, Austria, England, and Denmark are forerunners in developing new advanced biogas technologies, for conversion of FW into energy. According to a report by the National Resources Defense Council (NRDC), 40% of food goes uneaten in the United States. AD facilities are implemented in several cities in the United States, such as Massachusetts and Vermont, and more have been proposed. Statistics of FW composting in the United States, gathered by EPA, through US State Environmental Agency websites, revealed that 1.57 million tonnes of postconsumer FW was estimated to be diverted through composting in 2014 (Levis et al., 2010). According to the U.S. Environmental Protection Agency (2016) in the United States about 38 million tonnes of FW are thrown away each year into landfills or incinerators. Spoiler Alert is an online business that tackles FW by selling, donating, or giving away unsold food to food banks, kitchens, and charities. Food cowboy is an app that matches food donors and charities to divert extra catered food to charities. A study was conducted by Mun˜oz et al. (2017) to quantify the economic impact of reducing avoidable FW in three EU Member countries (Germany, Poland, and Spain). They modeled impacts on production, GDP, and employment.

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They described the impact of reducing avoidable FW in terms of monetary value of wasted food and resources such as land and labor needed to produce the food. They concluded that the economic impact of reducing FW was greatest in Germany, followed by Spain and Poland. They also showed that reducing FW from households has the greatest impact and hence results in significant benefits for the national economy. Over 5.3 million tonnes of food per year that is intended for human consumption is wasted from households, commercial, and industrial sectors in Australia. A large-scale biodigester was opened in Western Australia to treat FW, generate electricity, and produce compost for agricultural uses. The investments for these operations are often funded through landfill levies. This makes alternative treatment methods such as biodigestion and composting more cost effective for businesses (Commonwealth of Australia, 2017). Based on a report by Commonwealth of Australia (2017), the Australian Government is investing about US$10 million for aiding research work with the aim of retrieving higher value products from FW. In Germany, source separation is done at source by sorting FW, paper, packaging, and leftover garbage into separate colored bins. The pickup schedule is set up to “reward recycling and penalize garbage.” Each bin has a barcode and is read at the point of pick up. The cost per consumer is calculated on a weight basis, whereas FW and recycling have a much lower fee per unit weight. A few biodigesters have been installed to treat 16.3% of the annually generated FW. In Germany, there are no active landfills (DEFRA, 2011). In some Norwegian cities, surplus food obtained by charities is used to prepare meals and/or given out as bags of groceries. This indirect redistribution is a valid and valuable approach to reducing FW. In Oslo, Norway, 46% of FW is separated and used as feed material for a large biogas plant transforming 50,000 tonnes of FW into biogas annually. The produced energy is utilized as fuel to run city buses and garbage collection trucks. The plant also produces biofertilizers which are used by the local farmers in agriculture. Harvest Power near Vancouver, Canada, handles large volumes of FW at its composting facility. It intends to build a 30,000 tonnes per year dry/high solids AD system with an energy output of 220 kWh per tonne (Moriarty, 2013). The food and agriculture industries in Turkey are capable of producing 18 and 13 MW, respectively, as biogas.

14.3.2 Developing countries In developing nations, composting is considered a suitable treatment method due to the high organic fraction of FW. The proportions of FW in MSW in Brazil, Malaysia, Mexico, and India were 54.9%, 55%, 52%, and 51%, respectively (Thi et al., 2015). More challenges in food waste management (FWM) are faced by developing countries than developed countries. Many countries have attempted to implement FWM, but most countries still face many obstacles due to incomplete legislation and policies, and inadequate management and budgets (Thi et al., 2015). Based on FWM current data, with a 90% use rate dumping or landfilling is the most common option in developing countries (Waqas et al., 2018b), and composting is the second most common method, with a rate ranging from 1% to 6%. The AD method has below 0.6% use rate and other treatments, such as incineration, are rarely used. In India, a huge amount of FW is generated, but recycling methods are inadequate and organic wastes are generally disposed of at dump sites. Municipal corporations are responsible for the management of MSW generated in cities in coordination with the local public health department. Waste management in India is carried out by collecting waste from residential and industrial areas and dumping it at landfill sites or on the city outskirts (Agarwal et al., 2015). In Jaipur, India, people can call a 24-h helpline number at Annakshetra, to donate high-quality surplus food, for example, after parties. Collected food is taken to the Annakshetra office, where it is stored in a deep freezer. After quality checking the food is served to workers and their families. If the food is not fit for human consumption, then it is sent for AD/composting. “Feeding India,” which was founded in 2014, operates as a voluntary organization in over 30 cities across the country, connecting hunger and FW as solutions for each other. “Robin Hood Army,” a similar organization, operates not only in India but also in Pakistan. Providing a midday meal, which is a strategic program of the Government of India, is being implemented through “Annamrita” in selected schools across the country with the aim of liberating children from the vicious problem of malnourishment while also reducing FW being sent to landfills. The Association for India’s Development (AID) works toward zero waste management by taking leftover food from markets and feeding it to animals, the animal dung is then collected and used to produce biogas. The FWM and policy for FW treatment in Malaysia are considered less efficient, due to the limited budget allocation in the country (Thi et al., 2015). There were around 291 landfill sites in Malaysia during 2007, of which 179 are still under operation (Jereme et al., 2015). The Petaling Jaya Municipal Council (MBPJ, 2010) was

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implemented among household community, with an objective of introducing and improving household composting with FW. A pilot-scale digester was set up at Kuala Lumpur to process FW into liquid fertilizer and biogas (The Star, 2015). The Malaysian government is working on a project in collaboration with the Ministry of the Environment Japan for FW disposal (Lim et al., 2016a,b). Waste segregation at source was mandated during 2015 by the Ministry of Housing and Local Government (Lim et al., 2016b). China is the largest producer of FW among the Asian countries, with a production of more than 90 million tonnes of FW, contributing about 37%
62% of the total MSW of that country. Based on the publication indicators for the top seven most productive countries in FW research, China showed significant research influence, followed by the United States, South Korea, the United Kingdom, and Japan. Thailand encouraged a National 3R policy in 2011 for tackling the FW problem. The government aimed to achieve a recovery rate of 30% by 2016, 62% by 2021, and 90% by 2026. “Food Recycling Law” which is a pertinent regulation of FWM in Japan, has improved and minimized FW by 1%
2% every year. The government has encouraged citizens by developing incentives for recycling their FW into compost, animal feedstock, and biogas. Although the primary recycling method is composting, it is difficult for the produced compost to compete with chemical fertilizers. Throughout the Gulf region, a limited quantity of FW is utilized for compost production using traditional methods. Although there are several facilities for converting organic waste into compost, because of the low nutritive values, presence of heavy metals, and micronutrients, the quality does not meet international standards (Waqas et al., 2018b; Alzaydi et al., 2013; Al-Turki et al., 2013). In a school in Abu Dhabi compost is made from food and other household waste within hours using a machine. The manure thus produced is used in a farm in the school premises. This is a simple initiative taken to minimize the use of landfills in the UAE with the aim of achieving zero FW (Maniyath, 2019). A new policy named “Vision 2030” has been enacted by the Saudi Arabian government for reducing issues related to waste disposal and to their improve economic benefits (Waqas et al., 2017).

14.3.3 Underdeveloped countries Improper FW management in underdeveloped countries is primarily due to lack of strict regulations and policies, as well as insufficient budget allocation. Nowadays, many underdeveloped countries attempt to increase waste utilization and reduce the amount of FW sent to landfills. According to the study conducted by Gasu et al. (2017) in Robe Town, Ethiopia, there is a lack of standards for recycling and disposal of organic waste. Hence waste is dumped in open spaces causing environmental pollution. It has been concluded that this is due to a lack of awareness about the advantages of compost, limited budget allocation, and lack of a strict policy framework, with the municipality abstaining from initiating compost production. Based on the report by Adhikari (2019), waste management in Nepal is deficient in modern technologies applicable to waste segregation, increasing the chances of diseases being spread from landfill that are not scientifically designed. A pilot project, Biocomp, in Kathmandu, Nepal, which was started in 2011 and scaled-up in 2013, produced 2271 tonnes of compost from 28,890 tonnes of organic waste collected from vegetable markets. The nutrient content of the high-quality compost produced met international quality standards and was sold to local farmers in various districts of Nepal (Myclimate, 2019). The bioenergy potential from FW in developed and developing countries is shown in Fig. 14.1.

14.4

Treatment strategies and product recovery

A sustainable and environmentally viable option is to have a proper waste management strategy. Practically, food that is not sold for various reasons such as unharvested crops, foods with damaged packaging and unaesthetic appearance, and food that is not sold before its “best before” date is donated to organizations like foodbanks (Lipinski et al., 2013). Food that is not suitable for human consumption can be diverted as animal feed. Timely and effective management is essential so as to conserve energy and minimize the environmental hazards associated with FW (Salihoglu et al., 2018). FW holds the highest potential for conversion into biogas and organic fertilizer as it contains a high amount of carbon. Resource recovery through composting also results in value-added products, through eco-friendly processes (Awasthi et al., 2016; Radziemska et al., 2018). Generating energy or other products from FW is beneficial from economic and environmental points of view. Hence, wasted food not fit to be consumed should be treated through composting or AD, so that energy and nutrients can be recovered. Incineration and landfilling are the least preferred disposal methods for FW. The management of FW includes a number of physical, chemical, thermal, and biological treatment methods. Biological processes have been

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FIGURE 14.1 Bioenergy potential from food waste in developed and developing countries.

widely adopted to treat organic matter to meet discharge standards, and to avoid detrimental public health effects and associated environmental problems. There is difficulty in separating MSW attributes from the greater environmental issues associated with landfills. Separate collection of FW makes treatment much more efficient. Since FW, which is mainly organic in nature, can be efficiently biodegraded under controlled conditions and converted into biogas and organic fertilizer (Du et al., 2018), it can either be processed in an anaerobic digester as a single substrate, or can be codigested with other organic wastes such as cow manure, poultry waste, sewage sludge, swine waste, and crop residues. The volume of FW can be reduced in garbage dryers and then incinerated along with MSW for energy recovery (Bosmans et al., 2013). The advantages of biological treatment include cost-effectiveness, stabilization of waste, destruction of pathogens in the waste material, and production of biogas for energy use. The end-products of biological treatment can find application as fertilizers or soil amending agents, or they can be disposed of safely (Pipatti et al., 2006). To achieve policy change on FW, it is necessary to have knowledge about the monetary value of FW and its social and environmental impacts. Recently, intensive research work has been carried out on the biochemical conversion of FW to biofuels, chemicals, biodegradable polymers, and chemical intermediates (Ren et al., 2017; Kiran et al., 2014). Food loss in the food supply chain and bioenergy conversion worldwide are shown in Fig. 14.2.

14.4.1 Animal feed The high nutrient content present in FW poses great potential for use as an animal feed. Some food scraps can be harmful to animals, and regulations pertaining to the types of FW that can be used as animal feed vary between regions. Utilization of FW as animal feed has been common practice for centuries but it has some challenges: suitability of specific substrates to different animal classes (omnivores, ruminants, mammals, etc.), regularity of supply, safety, costs to separate FW from packaging, variability in nature and nutritional levels, rapid spoilage, and economic viability on processing (Lin et al., 2014). Inadequate biological stability and existence of pathogens can cause an increase in microbial activity. In particular, the food industry generates a high amount of biodegradable waste and discards large quantities of residues, with high biochemical oxygen demand and chemical oxygen demand (Girotto et al., 2015). For this reason, worldwide legislative requirements for waste disposal have become increasingly restrictive over the last decade. In some countries with a high demand for animal feed, such as Japan, South Korea, and Taiwan, local laws encourage using FW to feed animals, comprising 33%, 81%, and 72.1% of total FW generation, respectively (Allen, 2012). In contrast, the separation and collection of FW are not practiced in developing countries, and therefore almost all generated FW is mixed with MSW, which cannot be purified and utilized for animal feed.

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FIGURE 14.2 Food loss in the food supply chain and bioenergy conversion worldwide.

14.4.1.1 Japan In order to alleviate the environmental burden from FW, in Japan a food recycling law has been in force since May, 2001. Many projects initiated after enforcing this law were related to the production of compost. However, due to the limited acceptance of this product by farmers, a new proposal was made to process the waste which can be safely used in feed. In 2006, the Minister of Agriculture, Forestry, and Fisheries issued a guideline for the safety assurance of eco feed products. Based on these guidelines, FW containing meat, originally processed for human consumption alone, could be fed to swine.

14.4.1.2 India In India, experiments were done with recycling FW, surplus fruit, vegetables, and their return to the food chain by converting them into animal feed through processing. They concluded that the concentrate mixture is not only rich in protein but also has high nutritive value. Their experiments have shown promising results with the nutraceutical limonin extracted from kinnow juice waste as a growth promoter for poultry.

14.4.2 Composting Composting is an efficient method adopted in developing countries for disposal of FW. It is a slow natural degradation process, which may be accelerated by frequent turnings and shredding or by adding effective inoculating agents to the organic matters (Lim et al., 2016a), natural additives, and minerals. Recently, attention has been focused on continuous thermophilic composting, which is an efficient process in terms of degradation and speed (Lim et al., 2016b). The endproduct, called biocompost, has the potential to replace chemical fertilizers and is rich in nutrients and helps to amend the soil characteristics. Factors influencing optimum biological activity include pH, temperature, oxygen, C/N ratio, and moisture content. Among the types of composting, backyard composting and vermicomposting are generally conducted on a small scale, aerated and in-vessel composting are well suited to full-scale use to be managed by local governments. Vermicompost can act as a fertilizer and contains a good amount of nutrients and has a lower heavy metal content (Lim et al., 2016a). Aerated windrows composting is suited to large volumes of diverse waste, including FW, generated by communities or food processing plants (Waqas et al., 2018a). In-vessel composting can accommodate any type of organic waste and occupies less space compared to aerated windrow composting. Since FW generally has a low C/N ratio, it is not suitable for the production of compost. Codigestion is the best option for composting FW. Since FW can retain moisture, additional bulking agents such as wheat straw, wood chips,

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sawdust, and rice husk were found to reduce the moisture content. Good-quality compost should be devoid of odor, pathogens, pests, and toxins. Most importantly, its organic content and C/N ratio should be 20 g/kg and 10:40, respectively. Radziemska et al. (2018) conducted experiments on leaf yield and macro- and microelemental composition of ice lettuce in a pot, by applying compost produced using fish waste and pine bark. They conducted experiments for nonphytotoxicity, maturity, and stability for suitability for use in agriculture. At 25% compost, they achieved longer root length, negative growth inhibition, a twofold increase in fresh matter, and 50% dry matter yield of the leaves. They proved an increased content of nitrogen, phosphorus, potassium, sodium, calcium, and magnesium in the leaves of the test plant. They suggest that the proposed fish waste compost can be used as an alternate to fertilizer in agriculture. There are 279 composting plants and 138 vermicomposting plants operating successfully in India (CPCB Bulletin, 2016). Ghosh et al. (2018) studied a windrows composting plant with an operating capacity of 150 t/d. About 40
45 d are needed for the composting process, and the plant yields 30
35 t/d compost. FW-based biofertilizer production has already been commercialized in various parts of the world (Du et al., 2018). One-third of the compost produced in the EU is contributed by FW, with the remainder being obtained from other substrates such as manure, sewage sludge, and energy crops.

14.4.2.1 United States In the United States, every year, around 3% of FW is used for the production of composting, which is the most common alternate to landfill. The possibility of using FW as a source for composting was presented, and it was concluded that composting can be used as an alternate for sustainable MSW management and would be more attractive than landfilling.

14.4.2.2 Taiwan Chen (2016) conducted experiments to measure the cost
benefit ratio of compost in Taiwan. For their work, they selected six composting plants, with three federal units and three private firms. Based on the results obtained they confirmed that composting is a cost-effective process with simplicity and ease of operation. They also suggested a local subsidy as being essential in helping compost producers to expand the process. Composting of FW may prove to be a more suitable option for countries like India, Thailand, China, Mexico, and Indonesia, which rely on agriculture for their economy (Thi et al., 2015).

14.4.2.3 Australia Share-Waste is an app launched in 2016, composed of more than 9000 users across the globe with a digital open source map. In this map, we can enter our location and search for nearby collectors of food scraps and contact them and collect all information regarding composting our food scraps. If we already have a compost pile or bin, we can add our compost station to the map, specifying whether we are collecting for an individual household or for a community project. This is a free service, and the whole operation is currently run by volunteers. While the vast majority are based in Australia, compost spots have already sprouted up in Germany, the United Kingdom, the United States, Brazil, Costa Rica, South Africa, and Nepal.

14.4.3 Anaerobic digestion AD is employed to treat waste with high organic and moisture content. Most importantly, AD can generate energy and its digestate is often used as a soil conditioner (Waqas et al., 2018b). FW is one of the most promising substrates used for AD as it contains a high amount of organics (Kavitha et al., 2017). Recently induced hydrolysis by pretreatment methods has been found to reduce the retention time of substrate and to increase the biogas yield. Table 14.1 displays various pretreatments involved in biogas generation from FW. Biogas produced from AD contains methane (65%), carbon dioxide (35%), and trace amounts of H2S. In any typical biogas plant 30%
40% is utilized to generate electricity that can be sold to the grid and the remainder is converted to heat that can be sold to a central heating plant. Methane, derived from AD, burns cleanly and can power steam turbines that generate electricity. Shen et al. (2013) reported the performance of anaerobic codigestion (AcoD) of fruit and vegetable waste (FV) and FW in single- and two-phase AD systems. In this study, single-phase digestion showed better performance, with a 4.1% increase in CH4 production than two-phase digestion at low organic loading rates (OLR) (,2.0 g VS/L/d). However, at

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TABLE 14.1 Various pretreatments involved in biogas generation from food waste. S. no

Substrate

Pretreatment type

Pretreatment condition

Pretreatment outcome

Bioenergy yield

References

1.

Synthetic food waste

Thermal

Temperature: 80 C

COD solubilization:25% Carbohydrate release: 30% Protein release: 15%

442 6 8.6 mL CH4/gVS

Yeshanew et al. (2016)

Kitchen waste

Thermal

Temperature: 120  C

SCOD release: 63.5 6 1.0 g/L

510.4 mL/gVS

Time: 15 min

SCOD degradation: 47 .5%

Li et al. (2016)

0.36 L/g COD removed

Ma et al. (2011)

316 mL CH4/ gVS

Zhang et al. (2016)

SCOD release: 215 6 10 g/L

0.34 6 0.01 L CH4/ gVS

Marin et al. (2010)

2.

3.

4.

5.

Time: 2 h

Kitchen waste

Thermal

Food waste

Microwave



Temperature: 120 C

COD solubilization: 19% 6 3%

Time: 30 min

SCOD release: 93 6 8 g/kg

Temperature: 100 CPower: 1000 W

SCOD release: 19.2 6 1.57 g/L

Frequency: 2450 MHz

Protein: 1.64 6 0.36

Temperature: 175  C

Kitchen waste

Microwave

6.

Kitchen waste

Microwave

Temperature: 145 C, 2.7 C/min

SCOD release: 31.50 g/L

354 mL/L/d

Shahriari et al. (2013)

7.

Synthetic food waste

Alkaline

Dosage: 190 mEq/L (Ca(OH)2)

COD solubilization: 5.99%

864.19 mL/g VS

Junoh et al. (2016)

8.

Kitchen waste

Acid

pH: 2.0 (using 10 N HCl) Time: 24 h

COD solubilization: 13% 6 7%

0.16 L/g COD removed

Ma et al. (2011)

9.

Food waste

Enzyme

pH: 7

Total fatty acid: 8144 mg/L

500.1 mL/g VSadded

Meng et al. (2015)

Long-chain fatty acid: 3301.5 6 115.9 mg/L

67 6 4 mL/d

Meng et al. (2017)

Temperature: 60 C

SCOD release: 6853.8 6 223.7 mg/L

817.0 mL CH4/gVS

Yin et al. (2016)

Time: 24 h

VS reduction: 19.1% 6 3.5%

Time: 20 min

Protein: 5696.59 mg/L

Density: 1 W/mL

Carbohydrate: 19,150.04 mg/L

43.21 mL/g VS

Guo et al. (2014)

0.52 L/g COD removed

Ma et al. (2011)

0.30 L/g COD removed

Ma et al. (2011)



Time: 1 min, 7.8 C/ min

Time: 1 h

SCOD release: 86 6 9 g/kg

Temperature: 40 C Time: 24 h

10.

Food waste

Enzyme

pH: 7 

Temperature: 40 C Time: 24 h

11.

12.

Food waste

Food waste

Fungal

Ultrasonication

VFA: 967.12 mg COD/gVS 13.

14.

Kitchen waste

High-pressure homogenizer

Pressure: 10 bar

COD solubilization: 12% 6 7%,

Time: 30 min

SCOD release: 85 6 14 g/kg

Kitchen waste

Thermochemical

pH: 2.0 (using 10 N HCl) Temperature: 120 C

COD solubilization: 32% 6 8%

Time: 24 h

SCOD release: 111 6 8 g/kg (Continued )

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TABLE 14.1 (Continued) S. no

Substrate

Pretreatment type

Pretreatment condition

Pretreatment outcome

Bioenergy yield

References

15.

Food waste

Thermochemical

pH: 10 (using 1 N NaOH)

COD solubilization: 44%

525 mL/g COD

Kavitha et al. (2017)

Temperature: 80 C

SCOD release: 9680 mg/L

600 mL/g COD

Kavitha et al. (2017)

Energy input: 114.95 kJ 16.

Food waste

Thermochemo disperser

pH: 10 (using 1 N NaOH)

COD solubilization: 61.3%

Temperature: 80  C

SCOD release: 13,500 mg/L

Disperser rpm: 10,000 rpm Time: 5 min

high OLR ( . 2.0 g VS/L/d) two-phase digestion showed CH4 production of 0.455 L/(g VS)/d which was 15.8% higher than single-phase digestion. Grimberg et al. (2015) reported on a comparative study into single- and two-phase AD treatments for kitchen FW. They observed that the CH4 yield of single-phase AD (359 L-CH4/kg CODremoved) was lower than for two-phase AD (481 L-CH4/kg CODremoved). Micolucci et al. (2018) made a comparison of two different stages of AD of FW. In this study, they compared single-stage (230 L) and double-stage (200 and 760 L) thermophilic digesters. Specific biogas production in the doublestage digester (0.88 m3 biogas/kg VS) was higher than in the single-stage digester (0.75 m3 biogas/kg VS). Moreover, the double-stage digester showed 17% higher removal efficiency than the single-stage digester.

14.4.3.1 Malaysia Hoo et al. (2017) made investigations to identify the potential of biogas generation from FW in Malaysia. They calculated the amount of MSW disposed of in landfill from the literature and assumed segregation at source. For the year 2010, they evaluated a production of approximately 60 Mm3 of methane, which is equivalent to 16.3 MW electricity. They estimated that revenue of approximately 42 million MYR is created by selling electricity through the Feed in Tariff scheme.

14.4.3.2 United States East Bay Municipal Utility District (EBMUD) in the United States utilized AD projects owned and operated by municipalities, to accommodate the excess FW capacity. They are able to produce an excess power generation with a range of 7000
15,000 tons per year. Tests conducted by EBMUD to examine the impact of adding FW to AD showed a significant increase in bioenergy production compared with wastewater (ILSR, 2010). FW from residential and commercial sources is collected by Carson City Plant, California waste management, which is then ground into slurry and codigested with sewage.

14.4.3.3 European Union Banks et al. (2011) evaluated methane production from source-segregated domestic food in the United Kingdom. A total of 3936 tonnes of FW were processed, of which 95.5% was source-segregated domestic FW, with the remainder consisting of commercial FW. They achieved a stable specific methane yield of 642 m3/tonne VSadded and also performed mass balance assessment which stated that above 90% of waste material entering into the plant was converted into gas or digestate. Another pilot-scale AD treating FW in London was studied by Walker et al. (2017). This pilotscale plant was monitored for 319 d. During that period, the plant processed 4574 kg FW, producing 1008 m3 of biogas at an average 60.6% methane.

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Sembera et al. (2019) reported on an anaerobic codigestion facility at Moosburg wastewater treatment plant in Germany. At this plant, codigestion was carried out with FW, dairy waste, and sewage sludge at a ratio of 47:18:35 on a volatile solids basis. They stated that high loading of cosubstrate effectively increased the methane potential by 300% 6 50% with a specific methane yield from FW of 383 6 8 L CH4/kg VS.

14.4.3.4 India Mohan and Jagadeesan (2013) demonstrated the biogas yields from FW, produced by a college canteen in India, in a batch UASB reactor conducted for a period of 90 d. They arrived at a decrease in parameters like COD, BOD, pH, acidity, and alkalinity after production of biogas. They made trials to optimize various parameters for maximum biogas production from the digested FW. Abimbola and Olumide (2014) made a comparative study of common FW with a total solid concentration of 8% by employing a batch anaerobic digester for a 70-d digestion period, at mesophilic temperature. Kakodkar et al. (2017) studied a 1-tonne capacity of a biogas plant treating kitchen waste, canteen waste, green grass, and leafy vegetables. The biogas plant was working under a two-stage AD process which generates around 50
100 m3 of biogas (depending on the type of waste material). Thomas et al. (2017) reported on biogas production in the KSRTC biogas plant, Bangalore, using canteen waste. The KSRTC biogas plant can handle canteen waste of 25 kg/ d and produces 1.5 m3 of biogas. Singh and Gu (2010) also reported on a UASB reactor producing 60 m3 biogas/d from 200 t/d poultry waste. The produced biogas was applied to 1.2 MW capacity power production. According to National Institution for Transforming India Aayog (2014), 172 biomethanation plants are successfully operating in India, ranging from 100 kg/d to 10 t/d. Moreover 70
2000 m3 capacity digesters are commercially accessible where biogas from small biogas plants is used for cooking purposes, and larger units are used for electricity generation of up to 2 MW. Ghosh et al. (2018) studied a pilot-scale biomethanation plant with a capacity of 70
75 m3/d/tonne of waste. Mostly the plant treats vegetable waste, and FW from residential and commercial areas. At present the installed capacity can generate 350
375 m3/d of biogas from 5 tonnes of food processing waste.

14.4.4 Fermentation Fermentation is a process in which organic substrates are converted into alcohol or acid through anaerobic microorganisms during the first two steps of AD. Controlling and optimizing the operation parameters of AD can lead to the production of VFAs (Wang et al., 2016; Tang et al., 2016), lactic acid, biohydrogen (Jarunglumlert et al., 2018), and biogas (Kavitha et al., 2017). Lactic acid has found a variety of applications in the preservation, flavor enhancement, and acidulation of food (Waqas et al., 2018a). Dung et al. (2014) have collected data for predicting the potential bioenergy production from FW of 21 countries (developed and developing). According to their data, the average FW production rate per capita of developed countries is 107 kg. Based on their study, the highest biohydrogen potential from FW via photofermentation is calculated to be 833,555 kWh/year, which can significantly reduce future energy demand. Tang et al. (2016) evaluated lactic acid fermentation of FW in batch experiments with indigenous microbiota. At a pH of 6 and temperature of 37 C they achieved a higher lactic acid yield. Using a semicontinuous fermentation bioreactor, at a loading rate of 18 g-TS/L/d, they arrived at a stable production of lactic acid. Wang et al. (2016) investigated the production of lactic acid through open fermentation of FW, without sterilization and inoculum addition. FW is complex in nature, comprising starch, cellulose, and lipids, and hence fermentation by ethanol-producing microorganisms is difficult. Therefore appropriate pretreatment by means of enzymes, heat, alkali, or acid treatment becomes vital to enhance their digestibility (Pham et al., 2015). Effective pretreatment preceding fermentation leads to the production of fermentable sugars, avoids any loss of the sugars produced and limits inhibition. Bioethanol, otherwise called ethyl alcohol, can be produced from various biomasses containing starch (Deng, 2016). Due to its industrial application, the global demand for its production has increased. Bioethanol has the potential to replace gasoline fuel. In most cases, ethanol is used as a supplement for gasoline in a 1:9 ratio. Brazil tops the list of countries for bioethanol use in the automobile industry. Blending ethanol with gasoline oxygenates the fuel mixture, so that it has reduced emissions of particulate matters and NOx. However, the production cost also influences the technology for biofuel conversion of FW. Yan et al. (2013) studied ethanol production from FW using enzymatic fermentation. In this study, a pilot-scale plant with a production capacity of 80,000 L/year was used. They achieved 96.46 6 1.12 g/L ethanol production with ethanol volumetric productivity of 1.79 6 0.03 g/L/h after 60 h fermentation. Loizidou et al. (2017) reported on

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bioethanol production from household FW using a horizontal rotating reactor operated under nonisothermal simultaneous saccharification and fermentation in a fed-batch mode. At high solid concentration, a pilot-scale system can produce bioethanol 188 L from 1 tonne of FW. Another pilot-scale study was carried out by Sotiropoulos et al. (2016) into ethanol production from household biowaste mainly consisting of kitchen waste. In this study, an 80% mass and volume reduction was achieved using dehydration through a decentralized biowaste drying method. Using a saccharification and fermentation process, a maximum ethanol production of 29.12 g/L was achieved. Taghizadeh-Alisaraei et al. (2017) studied ethanol production using citrus waste in Iran. A total of 682,987.97 tonnes of citrus waste was processed for biofuel production, with 27 million liters of ethanol produced. Pilot-scale hydrogen production from school cafeteria FW using anaerobic sequencing reactor was studied by Kim et al. (2010). They stated that the reactor achieved 0.5 mol H2/mol hexoseadded hydrogen yield with a carbon/nitrogen (C/N) ratio of ,20. Tawfik and El-Qelish (2012) studied the performance of a mesophilic pilot-scale anaerobic baffled reactor for hydrogen production from codigestion of municipal FW and kitchen waste. The results showed that a hydrogen yield of 107 6 51.6 mL H2/g COD was achieved at an organic loading rate of 47 g COD total/L/d.

14.4.5 Physicochemical methods 14.4.5.1 Incineration Incineration involves burning FW in an oxygen-rich environment to produce heat that can be efficiently used to run turbines or heat exchangers. The incineration method is costly and requires high energy usage and technology (Thi et al., 2015). Through incineration, high-volume waste reduction at very short reaction times can be achieved, compared to other biological processes. Incombustible ash, which is a by-product of incineration, contains inorganic waste that needs proper disposal. The stack emissions contain dioxins and heavy metals that may cause air pollution and health problems (Zhang et al., 2014). This method is found to be unsustainable for FWM, owing to these impacts on the environment (Thi et al., 2015) and hence its use for FW conversion is limited. Pretreatment processes may be required to reduce the moisture content. FW can be dried with the help of a garbage dryer that reduces the FW volume. The resulting dried FW is then shifted to the incinerator along with municipal solid wastes and burnt for energy recovery (Bosmans et al., 2013). Kim et al. (2013) conducted a study to compare the environmental impacts of FW disposal methods in a metropolitan area in Korea using AD, codigestion with sewage sludge, and incineration after drying. They employed a life cycle assessment (LCA) from the global warming and energy/resource recovery perspectives. The functional unit adopted in their study was 1 tonne of FW from households, for each treatment option. Even though the global warming potential was higher for incineration, the net environmental credit they achieved was 315 kg of CO2-eq for dryer incineration as against 33 kg of CO2-eq for AD by electricity, thermal energy generated, and primary materials avoided. They concluded the dryer incineration to be the best available alternative for producing renewable energy in Korea. Various environmental pollution issues associated with the absence of proper air pollution control measures necessitate the search for an alternative option for FWM (Pham et al., 2015). Caton et al. (2011) attempted to recover energy via direct combustion of a dried FW sample extracted from the US Naval Academy which serves nearly 4400 students. They compared the combustion temperature of three different samples—wood pellets, pelletized FW, and nonpelletized FW. Their study summarized that the nonpelletized FW had the higher energy value (21.7 MJ/kg dry), as against wood pellets (18.7 MJ/kg dry). They also suggested that the exhaust heat could be used to dehydrate the incoming raw fuel. They simulated gasification of FW at high moisture content levels by means of an equilibrium model and determined the possible ranges for successful FW gasification. Based on their study, they claimed cost savings in terms of energy recovery by replacing natural gas and reduced disposal costs. In Singapore, 80% of solid waste was incinerated to produce heat and energy. In 2015, Singapore generated 785,500 tonnes of FW of which only 13% of total FW was recycled, and most of the FW was incinerated at a waste-toenergy plant. Khoo et al. (2010) stated that four incinerators, Ulu Pandan, Tuas, Senoko, and Tuas South, were present in Singapore. The FW input proportion treated by the four incinerators was calculated to be 12.88%, 16.52%, 34.66%, and 35.95%, respectively. Output energy obtained was 89, 128, 136, and 174 kWh/tonne from the incinerators at Ulu Pandan, Tuas, Senoko, and Tuas South, respectively. Dou (2015) stated that through incineration the FW volume is reduced by about 85%
95%, which is a better solution to the problem of site selection and ultimate landfill costs. In 2003, there were 47 incineration plants in China. However, at the end 2012, 138 plants had been built across the country. With the economic development and the

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Food Waste to Valuable Resources

improvement of low calorific value of FW, many cities have ever undertaken to construct incineration and power generation plants for MSW. A total of 24.7% of electricity was generated from treating China’s urban food through incineration. In Malaysia, incinerating of about 600 metric tonnes/d of waste will produce about 400 MWh/d of electrical energy.

14.4.5.2 Pyrolysis Pyrolysis refers to the endothermic process in which the degradation of organic waste is carried out in the absence of oxygen, to produce biochar, oil, and combustible gases. The quantity of each product is dependent on the process conditions, namely temperature, pressure, heating rate, and the residence time. Slow pyrolysis performed at a low heating rate and low temperature (300 C
650 C) and longer residence time, maximizes char production, whereas at very high heating rate and temperature (greater than 1000 C) and a residence of a few seconds, higher gas production is achieved. Pyrolysis typically occurs under pressure and at operating temperatures above 400 C. The off-gases need to undergo further treatment in a separate chamber and can be partially condensed producing an oil/tar residue and contaminated water. Pretreatment of the FW was responsible for the main burden in the pyrolysis process (Opatokun et al., 2017). These authors evaluated the environmental impacts and benefits of three treatment options for FWM-AD, pyrolysis, and integrated AD followed by pyrolysis using LCA. Their results from pyrolysis illustrated higher impact across water, fossil fuel, and mineral depletion due to the burdensome pretreatment of the FW. This also contributed to the increased costs of the overall process. Pyrolysis was performed in a continuous pyrolysis pilot plant treating waste fish oil (Wiggers et al., 2009). The experiment was done under steady-state conditions at a feed rate of 3.2 kg/h. At controlled reaction temperature of 525 C, bio-oil yield of 72.83%, bio-gas yield of 15.85%, and 11.32% of coke were obtained. A pilot-scale pyrolysis plant was studied by Ghosh et al. (2018). This plant was designed to treat organic waste with a capacity of 100 kg/d and the unit was operated at a temperature of 673K
773K. Bio-oil and bio-gas are the end-products, of which the market price of bio-oil is approximately Rs.45 per liter.

14.4.5.3 Gasification Gasification converts FW into synthetic gas (a mixture of carbon monoxide, carbon dioxide, hydrogen, nitrogen, and methane) through partial oxidation at high temperature (greater than 700 C). The characterization of FW to be carried out preceding gasification includes calorific value, ash content, moisture content, quantity of volatile matter, bulk density, particle size, and the presence of other contaminants like nitrogen, sulfur, etc. This characterization step is crucial for favoring preprocessed waste or refuse-derived fuel as feedstock, in the place of raw waste (Arena, 2012). Production of tar along with the syngas prohibits its direct use in internal combustion engines. Synthetic gas (syngas) can be used for producing chemicals such as ammonia and methanol. Using Fischer-Tropsch synthesis, syngas can be converted into synthetic petroleum, which can be as a fuel or lubricant. Recently, syngas production from biomass and waste has gained increasing interest. Syngas is subjected to chemical transformation processes, enabling the generation of bioethanol, biochemical (ethylene glycol, methanol, etc.), Bio-SNG (synthetic natural gas), etc. These products are used for the production of automotive and transportation fuels. The generation of thermal energy is possible by direct combustion of syngas, in heat generation equipment, such as steam boilers, cement kilns, and dryers (Maag et al., 2018). A LCA focused on biochar and bioenergy generation from three thermal process (gasification, fast pyrolysis, and slow pyrolysis) using 10 different biodegradable wastes was carried out by Ibarrola et al. (2012). Of these, 0.9 MW of electricity was generated from FW through gasification. A pilot plant of a 20-kW two-stage biomass gasification system was studied by Ghosh et al. (2018). The plant treats organic waste with a capacity of 2.5
3.0 Nm3 of gas/kg biomass. In this plant, dual-fuel biomass gasification technology was incorporated which produces 40-kW electricity

14.4.5.4 Esterification Biodiesel is a liquid fuel derived from animal fats, vegetable oils, and waste cooking oil, which is a possible replacement for conventional diesel fuel. Biodiesel is produced by a trans-esterification process (Kiran et al., 2014) in which vegetable oils or animal fats are made to react with an alcohol, in the presence of a catalyst such as an acid, base, or enzyme. In this reaction, glycerides of vegetable oils or animal fats are converted into biodiesel with glycerin as a byproduct. Biodiesel can also be obtained from lipids extracted from FW, usually at a rate of 5%
30%. Barik and Paul (2016) have made efforts to produce biodiesel from FW samples collected from a hostel kitchen and oven dried at 105 C to ensure dewatering. Lipids were extracted from the dried samples using solvents and were transesterified for

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biodiesel production. They concluded that conversion of lipids to biodiesel increases with temperature up to the boiling point of methanol, and then decreases. They also analyzed the produced biodiesel and compared it with international standards. A validated system model facilitates and improves system design and optimization, and also reduces the load for tedious experimental work. Torres et al. (2013) studied a pilot-scale biodiesel plant treating waste vegetable oil. The pilot-scale plant was designed to produce 10,000 m3 biodiesel/year from waste oil and animal fats. Using KOH and NaOH as catalysts and a 1:4 oil to alcohol molar ratio, 87.1% of biodiesel was produced. Tan et al. (2010) discussed a biodiesel production factory with 10,000 tonnes capacity enzymatic production facility. From waste cooking oil, the factory obtained a biodiesel yield of 90% under suitable conditions with immobilized enzyme from Candida sp. 99
125 as catalyst. Carlini et al. (2014) demonstrated a pilot-scale biodiesel reactor with a capacity of 100 L treating waste vegetable oils. The results showed a maximum biodiesel yield of 96% with a biodiesel density of 0.873 g/cm3 using NaOH as catalyst with a 6:1 molar ratio. Poojary et al. (2018) reported biodiesel production from waste cooking oil using a 50-L batch reactor. Using a Box-Behnken design method, they obtained a 96% biodiesel yield, which satisfies the fuel properties of American, European, and Indian standards.

14.4.6 Landfilling Landfilling is the most cost-effective but least desirable option for FW disposal, where biological decomposition of waste takes place. Hence landfilling is the most common solid waste disposal method for many communities. It includes four common stages: hydrolysis, fermentation, acetogenesis, and methanogenesis. Biodegradable waste decomposes in landfills, producing landfill gas (LFG) and leachate. The carbon footprint of FW in landfills depends on the energy/nutrient and moisture content of the dumped food (Kibria, 2017). LFG mainly consists of CH4, which has a greater effect than CO2 in causing the greenhouse effect, if left uncaptured. If the leachate produced from landfills is not collected in accordance with the Landfill Directive 1999/31/EC, it can result in contamination of the surrounding land and groundwater. Apart from the gas and leachate problems, landfills may also generate bioaerosols and odors, and are unaesthetic and create health hazards due to the altered habitat. In addition, landfilling requires a large area of land, with transportation and all the necessary facilities, which is a major drawback. In general, most strategies target diverting waste handling from landfill by prevention, reuse, and recycling. The contribution of a balanced policy in the perspective of diverting FW from landfill includes measures such as (1) public awareness, (2) FW landfill bans, (3) collecting taxes for landfilling, (4) development of alternatives such as AD, and (5) implementation of a treatment network. Among the 136 million tonnes of MSW which were sent to landfill in 2014 in the United States, the FW component contributes about 21% (Torrisi, 2014). In the United States FW could power almost 4.5 million households/year based on energy recovery from FW through AD methods, and similarly 28% of the energy could be recovered from LFG. According to a report by CPCB (2016), there exist in India about 59 constructed landfill sites and several more are proposed and under construction. According to the New York Times, in the United States, 32 of the 60 million metric tonnes of FW generated annually, end up in landfills. Landfills must be constructed and engineered in line with the Landfill Directive (impermeable lining, gas-capturing equipment, leachate collection and treatment) to avoid environmental damage. Landfills incorporated with gas collection, leachate treatment, and an electricity generation system can generate revenue. In 2011, Chinese cities began producing waste from fruit (6.0 3 107 tonnes) and vegetables (1.3 3 107 tonnes) annually. Of this less than 20% of waste was properly treated and reused, with most waste used as animal feedstock or dumped into landfills and illegal dump sites (De Clercq et al., 2016). FWM facilities and product recovery are shown in Table 14.2.

14.5

Valorization of food waste around the globe

Valorization of FW is not only environmentally benign, it is also beneficial in terms of nutrients, energy, and goods recovery, and revenue gained (Imbert, 2017). The integration of FW treatment into existing biotechnological processes simultaneously reduces problems with FW along with providing value-added products. Valorization of FW demands the homogeneous nature of the waste (Girotto et al., 2015). Several researches have been carried out with the aim of converting FW into useful products by incineration and AD, or using FW as animal feed, in order to close the nutrient loop. Carbon and nitrogen recovery from FW by biological methods aids in the recycling of valuable nutrients for producing chemicals (Waqas et al., 2018a). In the recent past, conversion of FW into biofertilizer is considered as a

TABLE 14.2 Food waste management facilities and their product recovery. S. no.

Source of food waste

Waste generated/ feed

Location

Name of treatment facility

Operating mode

Techniques employed

Capital cost

Output

References

1.

Industrial food waste

40 t/d

Japan

Kyoto Eco-Energy Project full-scale anaerobic digester

Thermophilic condition

Anaerobic digestion




Methane yield reached 360 m3/tfeed

Ike et al. (2010)

2.

Food waste

50 t

United States

Kean university Composting facility

In-vessel composting

Composting

12,533 USD/Y Investment 15,919 USD/Y operational

13,200 USD/Y by selling compost

Mu et al. (2017)

3.

MSW/ household

36,000 t/Y

Taiwan

Private composting facility

In-vessel composting

Composting

68,734,000 NT$/year

18,000 t/Y compost

Chen (2016)

Government composting facility

Closed and aerated windrow

6,633,333 NT$/year

1300 t/Y compost

3250 t/Y

4.

Urban organic waste

4574 kg

United Kingdom

Methanogen UK Ltd., anaerobic plant

Microscale anaerobic digestion

Anaerobic digestion




1008 m3 of biogas production

Walker et al. (2017)

5.

Waste vegetable oil

350,000 t

Turkey

Vegetable waste oil recycling plant




Recycling




136,889 t of biofuels

Salihoglu et al. (2018)

6.

Rice husk waste

40.8 Mt

Thailand

“A.T. Bio power”, Ministry of Energy




Combustion




20,000 kW of electricity/year

Ong et al. (2018)

7.

Food waste

4.2
5.5 Mt/ Y

South Korea

Dry anaerobic digester plant, “P” city, South Korea

Semicontinuous

Mesophilic dry




4.66 million MW h/year electricity

Nguyen et al. (2017)

Thermophilic dry

4.92 million MW h/year electricity

8.

Food waste

8200 t

European Union, Spain

Urban Ecology Agency of Barcelona

Windrow composters

Composting

4,970,000 euros

2300 t

http://www. bcnecologia. net

9.

Food waste

6 t/d

Guangdong Province, China

Pilot-scale in situ facility

In situ composting

Composting

Investing treatment cost as 61.5 USD/t

118.6 USD/t revenue fertilizer

Guo et al. (2018)

10.

Food waste

8 Mt

Kingdom of Saudi Arabia

Food waste composting facility




Composting

40 million USD

4.16 Mt of compost

Waqas et al. (2017)

t, tons; Mt, million tonnes; t/d, tonnes/d; Mt/Y, million tonnes/year; t/Y, tonnes/year; USD, United States dollars.

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promising approach to complement biogas production (Du et al., 2018). These authors’ review into recent advances in the conversion of FW to biofertilizer using AD, aerobic composting, chemical hydrolysis, in situ degradation, and direct burning methods has shown positive results. Tests conducted on the latest field applications of biofertilizers confirm the viability of this technology, however with a need for an improvement in efficiency. Lin et al. (2014) discussed biodiesel production from waste oil and grease. Moreover, they stated that Hong Kong’s largest biodiesel plant produces 330, 23, 7, and 7 tonnes/d of biodiesel, bio-oil, fertilizer, and glycerol, respectively, from treating around 795 tonnes of waste daily. Using a base-catalyzed transesterification process, potassium hydroxide was used as the catalyst in a biodiesel plant. The produced biodiesel in this plant was sold to international markets. Another interesting study investigated converting bakery waste into valuable products such as succinic acid through a biorefinery process. Succinic acid production from FW via fermentation in a pilot scale was studied by Lam et al. (2013). In this study, succinic acid was produced from bakery FW in a pilot plant design capacity of 1 tonne/d and it was observed that US$374,041/year revenue was generated. MSW organic fraction and FW were used as substrate for lactic acid and bioethanol production. Optimizing the operating conditions such as pH, temperature, and C/N ratio is essential for higher lactic acid yield (Tang et al., 2016). FW utilization for H2 production is another solution to the waste problem and energy recovery. However, conversion of FW to H2 through fermentation has some limitations such as the type of pretreatment, substrate, and inoculum used, reactor configuration, temperature, and micronutrient availability (Tang et al., 2016; Waqas et al., 2018a). Fig. 14.3 displays the fermentative production of various chemicals from FW. Lam et al. (2013) demonstrated the feasibility of producing the enzyme gluco-amylase using pastry waste as feedstock. They obtained a high yield of the crude enzyme extract compared with other waste substrates, and found that the crude enzyme extract produced could hydrolyze 100 g mixed FW in 1 h and generate nearly 53 g glucose. Their work reveals that sustainable enzyme production from FW could be used for potential municipal FW treatment for chemicals production. Pleissner et al. (2013) investigated the fungal hydrolysis of FW to obtain hydrolysate, which is a rich source of nutrients in heterotrophic microalgae cultivation. They achieved a good growth of microalgae rich in carbohydrates, proteins, lipids, and fatty acids. The algal biomass finds application as a feed in aquaculture and the lipids are converted to biodiesel, which is a renewable energy source. Huang et al. (2017) reported on a 100-L pilot-scale AD process treating FW acid hydrolysate. During this process, 81.52% methane content with 0.542 6 0.056 m3/kg COD biogas yield was achieved. Biogas produced in this work can be estimated as 2.5 RMB/m3 at market price. In the United States, 104 of 254 operational AD plants were using FW as

FIGURE 14.3 The fermentative production of various chemicals from food waste.

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the main feedstock in 2016. Based on the analysis of various management practices, evidence suggests that there are several possibilities to valorize FW, thus improving sustainable treatment methods.

14.6

Legislation in various countries

Causes of the generation of FW include poor infrastructure and transportation, lack of refrigeration, poor packaging, and environmental conditions during display. There are policies in different regions which contribute to FW by mandating disposal under stipulated conditions. Legislation aims to promote waste reduction and prevention through penalties for those who do not obey regulatory provisions. In developing and underdeveloped countries, it is necessary that policymakers and environmentalists increase programs that divert waste from landfills through source reduction, recycling, and composting.

14.6.1 United States In the United States, feeding FW to animals is heavily regulated under federal law, with some states going further and banning the feeding of vegetable waste to pigs. The EU also bans reusing FW for animal feed, as enacted in the Animal By-Products Regulations, which first entered into force in 2002. The food disposal bans passed in northeastern states and New York City in the United States specifically target large FW and other organic waste producers in the commercial sector. A study into this food disposal ban could divert up to 848,000 tonnes of FW each year from MSW in Massachusetts (USEPA). The 2017/18 California legislative session has implemented legislation AB 1219 (Eggman) to strengthen and expand the law enacted in 1977. This law encourages food donations by protecting food donors from legal liability. A bill named SB557 (Hernandez) has also been signed by the authority to donate unopened prepackaged food, uncut produce like apples, and milk kept at appropriate temperature to foodbanks through which school students and local communities could benefit (2017, legislative update).

14.6.2 European Union European Directive 2008/98/EC sets the basic concepts and definitions related to waste management, such as definitions of waste, recycling, and recovery. Article 5(2) of Directive 1999/31/EC has set down targets for the diversion of biodegradable MSW from landfills, the last target to be met by the Member States by 2016. The landfilling rate in the EU-27 dropped from 63.8% in 1995 to 25.3% in 2015 (Imbert, 2017). The Parliament and the Council EU Landfill Directive updated in 2015 has proposed a 50% reduction in food waste by 2030. According to the Animal By-Products Regulations, digestate from AD of source-segregated FW is allowed for applying to agricultural land, whereas digestate of mixed waste source cannot be applied to agricultural land.

14.6.3 Japan In Japan, the Food Recycling Law, 2007, encourages the collection, recycling, and purchasing of FW-derived products such as compost/animal feed, forming a “recycling loop” (Takata et al., 2012). Takata et al. (2012) conducted an LCA to evaluate the GHG emissions for FW treatment and a life cycle cost (LCC) to examine its economic efficiency and then compared the looped facilities with that of nonlooped facilities. The data used in the looped facilities and nonlooped facilities were obtained from interview surveys and published reports, respectively. For LCA and LCC, they attempted the following approaches: biogasification, machine integrated and windrows compost, liquid and dry feed. Based on their LCA and LCC, they reported biogasification and dry feed as showing low total GHG emissions and low running cost for composting facilities. They also confirmed that the looped facilities were more economically efficient compared to the nonlooped facilities.

14.6.4 South Korea The Pay-As-You-Throw scheme (PAYT) was introduced by the Ministry of Environment—South Korea, in 2013. Household residents must pay a disposal fee according to the FW quantities they produce. This PAYT scheme has been implemented in different countries, such as the United States, Sweden, Canada, Japan, Taiwan, Korea, Thailand, Vietnam. and China. Korea has an excellent system in recycling FW, with a separate collection rate of more than 90%.

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This practice came into existence in 2005, when the Korean government declared a ban on the direct landfill of FW, to avoid leachate problems (Ju et al., 2016).

14.6.5 France France passed unanimous legislation in 2015, mandating supermarkets above 400 m2 to either give unsold food to charity or send it to farmers for use as feed and fertilizer. France has become the first country in the world to ban supermarkets from throwing away or destroying unsold food, forcing them instead to donate it to charities and foodbanks. Belgium passed a similar law in 2013, and an Italian law has focused on incentives that make it easier for companies to change their behavior.

14.6.6 Italy Italian Law no. 166/16 of 19 August 2016 entered into force on September 14, 2016, with the objective of reducing FW in all stages from production to consumption. The main focus of the law is toward the recovery and donation of surplus food generated in the different stages of the food supply chain to charities (Azzurro et al., 2017).

14.6.7 Malaysia In 2010, the Ministry of Housing and Local Government of Malaysia collaborated with the Ministry of Environment in Japan and proposed a plan known as the National Strategic Plan for FWM in Malaysia. It contains six main strategies, which aim to instruct the public about FWM such as FW segregation for reducing GHG emissions and also about reducing land utilization for FW disposal. In 2015, awareness and responsibility about FW segregation from other wastes for every household resident was created in Malaysia (The Star, 2014). Solid Waste Management Act and Public Cleansing 2007 in Malaysia was enforced to provide for and regulate the management of controlled solid waste and public cleansing mainly for maintaining proper sanitation.

14.6.8 Brazil At present, there is a proposal before the Brazilian Congress to establish a National Policy on FW. According to the National Policy on Solid Waste (Law 12.305/2010), by 2014 all open dumps must be closed and separation and collection of organic and recyclable waste are aimed at 53% and 36%, respectively, by 2031.

14.6.9 India In recent years, all the governments and local (municipal) authorities in India have given greater attention to MSWM. Many public
private, community
public, and private
private partnerships/alliances have shown growing interest in the field of MSWM in Indian cities. The Ministry of Environment and Forests has legislated the Municipal Waste Management and Handling Rules 2000 (Agarwal et al., 2015). The regulatory framework for MSWM was framed and initiated under Jawaharlal Nehru National Urban Renewal Mission. Turkey has a by-law on landfill of waste (No: 27533 2012/03) that aims to reduce landfill use by operating more composting facilities and biogas facilities for electricity production. Table 14.3 shows the FWM strategies followed in various countries.

14.7

Technical challenges, emerging trends, and conclusions

An increasing global population and economic development have resulted in exponential growth of FW (Zhang et al., 2014), posing environmental problems like GHG emissions. If there are no proper protocols about waste management, then the waste producer tends to dump their waste into landfill, drains, or other water courses. Collection of FW is a large challenge for countries, as FW is discarded and commingled with all other wastes in MSW. FW is heterogeneous in nature and its characteristics vary significantly based on their sources. FW should be segregated from other wastes using appropriate separation methods prior to further processing and utilization. Awareness should be created about the significance of segregating the FW at source (Karmee, 2016). FWM techniques and their challenges are shown in Table 14.4.

TABLE 14.3 Food waste management strategies followed in various countries. S. no.

City/country

Policies/regulations/ initiative program

Launch /effective date

Issued department

Target to achieve/action on target technique

Target action implemented

References

1.

Taiwan

Zero waste policy

2003

Taiwan EPA

Zero waste society by 2020

319 townships had food waste recycling systems

Allen (2012)

2.

India




Status of cities and state capitals in implementation of MSW (Management and Handling) Rules, 2000

Central Pollution Control Board (CPCB) and the National Environmental Engineering Research Institute (NEERI)




Government of India sponsored 42 solid waste management projects worth USD 500 million between 2006 and 2009

Annepu (2012)

3.

Thailand

National 3Rs Strategy




Pollution control department

Increase organic waste utilization by 50% before 2026

Thailand invested $27.97 million approximately for in-vessel composting of 1000 tonnes/d in Bangkok Metropolitan Administration

Alice and Janya (2012)

4.

Sweden

Swedish Waste Management Plan

2013

Swedish Environmental Protection Agency

By 2018, the goal was about 50% of food waste to be treated biologically to recover plant nutrients and at least 40% of the waste treated to recover both nutrients and energy

1.3 Mt of certified digestate was produced in 2017 for use as agricultural fertilizer

Sverige (2013)

5.

France

National Pact Against Food Waste

2012

Ministry of Agriculture

Target to reducing food waste by 50% by 2025

Implementation of awareness campaign, and improving regulations

Mourad (2016)

6.

Japan

Food Waste Recycling Law

Enacted in 2001, revised in 2007 and 2015

Ministry of Environment

Target set for reduction and recycling of food waste as 95% for food manufacturers, 70% for wholesaler, 55% for retailers, and 50% for restaurants by March 2020

43% (16.34 million tonnes) of food waste was recycled in 2011

Liu et al. (2016)

7.

Australia

Halving Australia’s food waste by 2030

November 20, 2017

Minister for the Environment and Energy

The strategy launched on November 20, 2017, establishes a framework upon consultation with various sectors

$1 million of funds provided by the Governments to Food Innovation Australia Limited

Tackling Australia’s food waste

8.

Massachusetts, United States

Code of Massachusetts Regulations 310 CMR 19.000

October 1, 2014

US Environmental Protection Agency

Implementing a ban for commercial services not to generate food waste more than 1 tonne/week

4 anaerobic digestion was implemented with 312 tonnes/d capacity

Food Waste Management in the United States (2014)

9.

Europe

Communication (2014) 398

September 25, 2014

European Commission

Toward a circular economy: A zero waste program for Europe

European Commission members need to develop national food-waste prevention strategies and attempt to ensure that food waste is reduced by at least 30% by 2025 in households

Union (2014)

54 anaerobic digestion plants were in existence with 35 MW electricity production

Energy and Climate Change Committee (2016)

10.

United Kingdom

Anaerobic Digestion Strategy and Action Plan




Department for Energy and Climate Change and Department for Environment Food and Rural Affairs

Increase energy produced from waste through anaerobic digestion

TABLE 14.4 Food waste management techniques and their challenges. S. no.

Country

Nature of country

Food waste management techniques

Benefits

Challenges/ issues

Possible solutions

References

1.

Singapore

Developed

Aerobic composting plant

25,534.68 tonnes/ year waste were composed

Aerobic composting has some limitations mainly due to CO2 and NH3 emissions

Anaerobic digestion is preferable to aerobic composting

Khoo et al. (2010)

2.

United Kingdom

Developed

Biogas plant

35 MW electricity production from 54 existing plants

Cost difficult for small developers in initial investment

Action plan must be proposed for the provision of case studies with sample costing

Lord and Gregory (2011)

3.

Australia

Developed

Biogas plant

558,453 dam3 CH4, which can generate approximately 20.3 PJ/year of heating or 1915 GWe/year of electricity generation

Separation of food waste and effluent discharge

Effective source separation and effluent management are needed

Lou et al. (2013)

4.

Japan

Developed

Incineration or landfill disposal

40% is treated by incineration or disposed of in landfills

Households continue to discard amounts of huge food waste

Food waste must be collected separately and the reduction and recycling of food waste generated by households promoted

Liu et al. (2016)

5.

United States

Developed

Anaerobic digestion

239 farm-based anaerobic digestion systems in operation

Generation of digestate

Used as organic fertilizer

Food Waste Management in the United States (2014)

6.

Malaysia

Developing

Biogas plant

Anaerobic digestion has the potential for 1694 MW of electricity generation

Investment cost to build the infrastructure of a biogas plant with electricity generation facilities is high

Malaysian government has introduced various financial schemes such as the Renewable Energy Business Fund (REBF) and the Green Technology Financing Scheme (GTFS) to develop the renewable resources

Kumaran et al. (2016)

India

Developing

Improper segregation

To get rid of tendering system and more public involvement

Ray (2016)

7.

Biogas plant

Replace 20 million kg of liquid petroleum gas per year Avoid 6 million tonnes of GHG emissions per year

Less performance of low-price service through tenders

(Continued )

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TABLE 14.4 (Continued) S. no.

Country

Nature of country

Food waste management techniques

Benefits

Challenges/ issues

Possible solutions

References

8.

Thailand

Developing

Composting

15% of food waste from municipal solid waste was decomposed into biogas and biofertilizer

Improper segregation of food waste from other solid waste. Poor food waste management framework

Proper food waste management framework is needed

Lim et al. (2016a,b)

9.

Hong Kong

Developing

Biogas plant

200 t/d was treated in organic waste treatment facility

Efficiency of electricity produced by combined process of heat and power is low

Converting the biogas into electricity or useful cooking gas for domestic purposes

Woon and lo (2016)

10.

Saudi Arabia

Developing

Composting

Bioremediation saving in disposal cost in landfill USD 40 million per year, market value of compost USD 70.72 million per year

Quality standards are not reached

Application of natural zeolite, biochar from palm tree, and adding specific microbes

Waqas et al. (2018a,b)

The other technical challenge is scaling up of the technology, which requires an in-depth study into the economic and technical feasibility of the process before scaling it up. Since the separation and purification costs of various organic materials from FW are high, innovative methods to integrate food processing facilities for simultaneous production of bioethanol, bio-oil, and biodiesel would reduce the operational cost (Karmee, 2016). Such methods would enhance FW valorization with better economics and lower environmental impacts. High design cost, process control conditions, and low quality products are the main challenges to the valorization of FW to fermentation products (Xu et al., 2018). Biological treatment methods are less capital intensive and are very ease to employ. Long processing time and inhibition possibility due to contaminants in the FW are some of the disadvantages of biological treatment methods. AD systems require high capital investment to implement and their incomes are mainly dependent on waste collection tipping fees and selling the electricity and methane produced. Several technical, economic, and social challenges are present in the AD process of FW management. One important technical challenge is the production of harmful intermediate compounds, which reduces system stability, or causes low methane yield or foaming due to the lack of precise process control and optimization (Pham et al., 2015). Generally, biogas is used for heat and electricity generation without any further purification. A further upgrade to this approach is needed to use biogas as a fuel for vehicles and fuel cells. Due to its high moisture content and complex compositions, FW becomes more challenging in handling and treatment. For an efficient large-scale conversion process, more investigation is needed (Thi et al., 2015; Pham et al., 2015). Pyrolysis, gasification, and incineration are some thermal treatments adopted in FW treatment, but the products are unfavorable because they possess lower calorific values due to the high moisture content. Moreover the thermal process emits toxic pollutants to the atmosphere which cause environmental pollution. Therefore implementation of a proper air pollution control system is necessary. However, the operation cost and CO2 emissions are low in pyrolysis and gasification as compared with incineration (Pham et al., 2015). Therefore alternate and environment-friendly methods are needed for handling and treating FW. Alternatively, a fermentation method is used to convert FW through microbes into ethanol. However, pretreatment is required to hydrolyze the FW and produce fermentable sugars, but this increases

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the process time and cost (Zhang et al., 2014). During pretreatment, some inhibitors may form which tend to inhibit the microbial activity in the fermentation process. FW to energy conversion has gained more attention due to the rapidly rising costs of energy supply and waste disposal, and moreover public concerns about the environment are increasing (Pham et al., 2015). Hence there is a strong impetus for search for various alternatives, which are cost effective and environmentally benign methods of handling FW (Waqas et al., 2018b). A multidisciplinary method is needed for FWM, with inputs from field experts, to derive both short- and long-term benefits, in terms of energy and material recovery from FW. Xu et al. (2018) have suggested FW be added to existing biogas plants, to attain higher electricity and heat production, which will save the additional labor and infrastructure costs. It appears that conversion of FW into energy via anaerobic processes in terms of methane is economically viable. In FWM, cost depends on various processes such as collection, sorting, transportation, and pretreatment. The technoeconomic analysis would provide sufficient data about the methodology, biogas plant cost, and its production facility and biofuel market value (Karmee, 2016). Tran et al. (2018) employed FW composting to treat highly fuel oil-contaminated soil. The removal efficiencies of the fine and coarse grained piles after 45 d of incubation were 82% and 93%, respectively. Residual fuel oil concentration in the coarse pile met the Taiwan EPA standard limit (1000 mg/kg). The results indicated that the efficiency of the composting treatment may be affected by the soil particle size fraction. FW conversion through biochemical methods has gained increasing research attention for valuable products such as biofuels, biopolymers, and chemical intermediates (Ren et al., 2017; Kiran et al., 2014). FW can be converted through fermentation to some valuable chemicals such as butanol, lactic acid, succinic acid, and 3-hydroxybutyrate (Waqas et al., 2018a). However, difficulties accompanying the collection and transportation of FW (Waqas et al., 2018a) should also be considered. There is an urgent need for sustainable and economical waste management practices, which ensure safe disposal, with minimum carbon footprint and maximum energy and material recovery from the conversion of FW. Finally, a systematic multidisciplinary approach using emerging technologies is needed to derive these benefits.

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Further reading Adhikari, P., 2018. Here’s How You Can Manage Your Food Waste in Nepal. ,http://safanepal.com/how-to-reduce-and-manage-food-waste-in-nepal/.. CPCB (Central pollution Control Board), 2000. Management of Municipal Solid Waste in Delhi. Cruz, J., Oslo Takes an Integrated Approach to Treat Waste into Circular Bio-Resources. ,https://circulareconomy.europa.eu/platform/en/good-practices/.. Jhu A., 2014. Srinivasan C on Satyamev Jayate. ,http://www.aidjhu.org/srinivasan_c_on_satyamev_jayate.. Kim, J.H., Lee, J.C., Pak, D., 2011. Feasibility of producing ethanol from food waste. Waste Manage. 31, 2121
2125. Kiran, E.U., Liu, Y., 2015. Bioethanol production from mixed food waste by an effective enzymatic pretreatment. Fuel 159, 463
469. Li, R., Chen, S., Li, X., 2010. Biogas production from anaerobic co-digestion of food waste with dairy manure in a two-phase digestion system. Appl. Biochem. Biotechnol. 160, 643
654. OLIO. The Problem of Food Waste. ,https://olioex.com/food-waste/the-problem-of-food-waste/.. Pleissner, D., Lin, C.S.K., 2013. Valorisation of food waste in biotechnological processes Sustain. Chem. Process., 1, 1-21. Open access. Scarlat, N., Dallemand, J.E., Fahl, F., 2018. Biogas: developments and perspectives in Europe. Renew. Energy 129, 457
472. Swedish National Food Agency, 2016. Report Summaries from the Swedish Food Waste Reduction Project 2013-2015. Tackling Australia’s food waste. 2016. Australian Government, Department of Environment and Energy. Yan, S., Wang, P., Zhai, Z., Yao, J., 2011. Fuel production from concentrated food waste hydrolysates in immobilized cell reactors by Saccharomyces cerevisiae H058. J. Chem. Technol. Biotech. 86, 731
738. Yan, S., Yao, J., Yao, L., Zhi, Z., Xi, C., Wu, J., 2012. Fed batch enzymatic saccharification of food waste improves the sugar concentration in the hydrolysates and eventually the ethanol fermentation by Saccharomyces cerevisiae H058. Braz. Arch. Biol. Technol. 55, 183
192.

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Chapter 15

Techno-economic analysis and environmental aspects of food waste management Mohit Singh Rana1, Shashi Bhushan1, Sanjeev Kumar Prajapati1, Preethi2 and S. Kavitha2 1

Environment and Biofuel Research Lab (EBRL), Hydro and Renewable Energy Department, Indian Institute of Technology Roorkee (IIT-R), Roorkee,

India, 2Department of Civil Engineering, Anna University Regional Campus Tirunelveli, Tirunelveli, India

15.1

Introduction

The ever-increasing global population, urbanization, and industrialization are causing environmental ramifications by generating waste materials in huge amounts. Among the generated waste materials, around 51% is food waste (Gao et al., 2017; Redcorn et al., 2018). Worldwide, each year approximately 1.3 billion tonnes of food are wasted, which is about one-third of total produced food (Elliot et al., 2017; Girotto et al., 2015; Paritosh et al., 2017). This wastage is forecast to rise repeatedly. In Asia alone the annual increase in food waste is estimated to be from 278 to 416 million tonnes from 2005 to 2025 (Uc and Trzcinski, 2014). Food waste is generated due to food spoilage or as a by-product of the food supply chain. Waste generation sites can be categorized as agro-farms, food processing industries, food distribution, and the end-consumer (Lin et al., 2013). However, there is a slight difference in food waste generation patterns. In developed countries, about 40% of food waste generation is reported to be at the distribution and consumer ends. In contrast, in developing countries, about 40% of food waste is generated at agro-industries during various stages of food processing (Girotto et al., 2015; Montoneri, 2017). On a per capita basis, a higher amount of food waste is reported in developed than developing countries. For instance, in Europe and North America, 280
300 kg/year food waste is observed, while 120
170 kg/year food waste is reported for sub-Saharan Africa and South/Southeast Asia. In the industrialized regions of Asia, about 240 kg/year food waste is reported (Arancon et al., 2013). This significant amount of waste has environmental, health, and financial consequences. Food waste is managed by traditional practices, such as landfilling, incineration, composting, and/or use as animal feed (Antonopoulou et al., 2019; Lin et al., 2013). These traditional practices and infrastructures are able to handle only a small proportion of the waste (Ma et al., 2017; Tsang et al., 2019). Nonetheless, the environmental consequences of landfilling are inevitable. Food waste is prone to microbial attack and consequently emits greenhouse gases (GHGs) (Antonopoulou et al., 2019). It has been estimated as the third largest source of GHGs (CH4 and CO2) (Pommeret et al., 2017). Every tonne of food waste creates approximately 4.2 tonnes of CO2 annually (Lin et al., 2013). Methane production at landfill sites may be a fire hazard as methane is a flammable gas and also spreads a repugnant odor. It is also responsible for surface and groundwater contamination by leaching of organic salts and inorganic materials (Arancon et al., 2013). Moreover, incineration of food waste combined with other solid waste may release dioxins and cause air pollution (Kiran et al., 2014b; Ma and Liu, 2019). These technologies are not robust, hence researchers are forced to make effective strategies to mitigate the continuously growing amounts of food waste. Food waste is mostly organic and is comprised of carbohydrate, protein, lipid/fat phenolic compounds, and a very small proportion of inorganic matter (Kiran et al., 2014b). These compounds can be utilized as a renewable resource for the production of biofuel, value-added chemicals, and various materials including biomaterials (Blikra et al., 2018). Food waste contains 74%
90%, 80%
97% and 14.7
36.4 moisture content, volatile solids (VSs) to total solids (TSs) ratio, and carbon to nitrogen ratio, respectively (Arancon et al., 2013). These characteristics enhance its disposition to recycling through a biochemical approach such as anaerobic digestion and fermentation. In this direction, ample Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00015-8 Copyright © 2020 Elsevier Inc. All rights reserved.

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Food Waste to Valuable Resources

research has been done through other technologies also, such as chemical, thermochemical, and solar/thermal-based food waste conversion (Antonopoulou et al., 2019; Arancon et al., 2013; Arora et al., 2018; Pradhan et al., 2019). The food waste supply chain possesses several technical challenges. The key concerns are associated with its collection, transportation to processing sites, storage, and conversion to different products. For instance, the high moisture content of food waste makes it vulnerable to unwanted microbial attack (Antonopoulou et al., 2019). In an LCA study carried out by Gao et al. (2017) anaerobic digestion of food waste was reported as having the least negative impact on climate change. This was followed by composting, heat-moisture reaction, incineration, and landfill. Food waste has a high moisture content and low heating value. Therefore its thermal conversion, such as incineration to recover energy, is also not technologically efficient (Blikra et al., 2018; Girotto et al., 2015). Although anaerobic digestion is favorable for environmental sustenance, its conversion efficiency remains a concern. The recalcitrant nature of the lignin and high degree of polymerization of pectin and other compounds restrict microbes from degrading the biomass efficiently (Paritosh et al., 2017). The biomass availability, composition, and processing within particular technological, geographical, and time frames are crucial factors to be considered (Kwan et al., 2018; Pradhan et al., 2019). In light of the above discussions, a techno-economic analysis (TEA) followed by environmental impact assessment of food waste management system is crucial. The TEA provides a canvas, which makes it easy to select the most suitable particular process and product (Kwan et al., 2015, 2018). Simultaneously, environmental sustainability is assessed by life cycle assessment (LCA), which is an ISO method and gives a broad scenario on the transfer of pollution in each step throughout the processing and supply chain.

15.2

Technical challenges in food waste management

Biomass decomposition technologies have been devised to address food waste. Efforts are being made to mitigate the socioenvironmental and financial consequences of food waste. Policies have been designed to implement and regulate these technologies. However, these food waste management technologies face several challenges and limitations. These are still at the bench and pilot-scale levels. The United States Environmental Protection Agency has developed a food recovery hierarchy for food waste management, as depicted in Fig. 15.1 (EPA, 2014). A reduction in food source is suggested as the most preferable option followed by feeding to hungry people and animals, use in industries, composting, and then incineration/landfill. However, the wasted food is usually disposed of by open burning, incineration, and landfill with other municipal solid waste (Elliot et al., 2017; Ferronato, 2019; Paritosh et al., 2017). In some countries, composting and anaerobic digestion of food waste are also practiced at the household and community levels (Warshawsky, 2019). Nevertheless, in the quest for waste utilization and sustainability, a great deal of research has been carried out into its conversion through biochemical (such as fermentation), chemical, electrochemical, and thermochemical (such as gasification, pyrolysis, hydrothermal carbonization and liquefaction) approaches (Arora et al., 2018; Bhushan et al., 2019; Han et al., 2018; Lin et al., 2013; Pradhan et al., 2019; Tonini et al., 2018). However, these technologies have their own benefits as well as associated limitations. This needs to be considered before establishing a sustainable food waste processing unit. The crucial challenges associated with the available and emerging technologies are now discussed. Landfilling is disposal of solid waste in a landfill. The waste materials are subsequently compacted and decompose. It is one of the conventional solid waste management practices, including for food waste. As microorganisms naturally degrade food waste in these landfills it emits GHGs such as methane into the environment (Arancon et al., 2013; Gao et al., 2017; Girotto et al., 2015). Furthermore, it is a fire risk as methane is a highly flammable gas (Arancon et al., 2013). The requirement of a large area is another drawback. Therefore management of such a large area and mitigation of its consequences is crucial. Incineration is a thermal treatment method, where the biomass is combusted at an elevated temperature of about 400 C
540 C. Generally, food waste is incinerated along with municipal solid waste (Phuong et al., 2014). This approach helps in decomposition of the waste material and energy recovery in the form of heat and electricity (Gao et al., 2017; Phuong et al., 2014). For efficient incineration dry biomass is required as the presence of moisture puts extra cost on the overall process (Kim et al., 2013; Ong et al., 2017). Incineration plants are expensive and have severe environmental consequences, such as emissions of dioxins and other toxic substances, along with GHG (Paritosh et al., 2017). Jereme et al. (2013) described incineration as a waste of energy rather than waste to energy technology. With new legislation, incinerators are being banned around the globe, even in Australia there is no operational incineration plant (Edwards et al., 2018). Composting is a natural process carried out by microbes in aerobic conditions to decompose biomass. Usually at a household level this practice is followed for food waste management. In addition, managing food waste produces

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327

FIGURE 15.1 Food recovery hierarchy (EPA, 2014).

value-added humic substances that can be used as biofertilizer (Majbar et al., 2018). The carbon to nitrogen ratio and moisture content of food waste are two main criteria for complete decomposition of biomass. Due to the low carbon to nitrogen ratio and high moisture content in food waste, it may take longer time for degradation and efficiency may also be reduced (Kumar et al., 2010). Moisture was found to affect microbial activity, temperature, and the overall biomass degradation rate. For instance, Kumar et al. (2010) observed that temperature does not change significantly at a high moisture content (  70%), whereas, at a low moisture content of 45% the temperature increased to 65 C within 3 days and consequently moisture content was reduced to 35%. This led to a sharp fall in temperature below the initial point. Similarly, Liang et al. (2003) documented a reduction in microbial activity at a lower moisture content (30%
40%) even when the temperature was constant at 57 C. Furthermore, Kumar et al. (2010) reported a maximum of a 30% reduction in total VSs of biomass at 60% moisture content and 19.6 carbon to nitrogen ratio. Therefore, a high moisture content and low carbon to nitrogen ratio, or a low moisture content and high carbon to nitrogen ratio are suggested to achieve maximum biomass decomposition. Food waste is a rich source of lipid and it can be utilized for biodiesel production (Girotto et al., 2015). n-Hexane is preferably used for lipid extraction in industries. Furthermore, it requires acidic/alkali catalyst for the conversion of

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Food Waste to Valuable Resources

lipid into biodiesel. n-Hexane and catalyst can pollute water bodies. n-Hexane is classified as a hazardous air pollutant by the US Environmental Protection Agency (Karmee et al., 2014). Moreover, the catalyst used in biodiesel synthesis cannot be recovered easily (Kumar and Singh, 2009). Also, waste cooking oil contains impurities. In order to use it as a biodiesel precursor it needs to undergo pretreatments, such as washing, centrifugation, evaporation, and esterification, negatively impacting on the process economics (Girotto et al., 2015). Alptekin et al. (2014) recommended cotreatment of waste cooking oil with animal fats to reduce the overall cost of biodiesel production. In-depth research is required in the area of waste oil treatment. The polysaccharides present in the food waste can be utilized to produce biofuel and value-added chemicals. For instance, Kiran et al. (2014a) documented a 58 g/L ethanol yield from mixed food waste through enzymatic hydrolysis and subsequent fermentation. However, these polysaccharides are associated with highly polymerized compounds, such as lignin and pectin (Turon et al., 2018). The presence of lignin in biomass implies higher resistance to further chemical and enzymatic decomposition of biomass. Delignification of the biomass is the most important step in the bioconversion process. It is a challenging task to degrade the biomass and expose its effective surface for the reaction. Lignin removal can dramatically increase the biomass pore sizes, and provide more accessible surface area to enzymes for hydrolysis (Zhang et al., 2019). Henceforth, technological interventions are required for lignin decomposition and extraction to enhance biomass conversion efficiency. Anaerobic digestion is one of widely accepted technology for energy generation from organic biomass, as it is more sustainable and eco-friendly than landfilling and incineration (Goswami et al., 2016; Hegde, 2019). It converts the organic biomass into biogas using microorganisms in the absence of oxygen. It includes four key processes in tandem, namely, hydrolysis, acidogenesis, acetogenesis, and methanogenesis (Bhushan et al., 2019; Van, 2020). During hydrolysis, the complex organic biomass is hydrolyzed into monomers. The hydrolytic bacterial consortium secretes extracellular enzymes that mineralize the complex biomass. During acidogenesis, the acidogenic bacteria convert these molecules into volatile fatty acids (VFAs), hydrogen, and carbon dioxide. Following this, these VFAs are converted into acetate, hydrogen, and carbon dioxide under an acetogenesis process. Finally, the acetate, hydrogen, and carbon dioxide are converted into methane and carbon dioxide by acetoclastic and hydrogenotrophic methanogens (Carballa et al., 2015; Stan et al., 2018). Biomass composition, TSs content, VSs content, and susceptibility to hydrolysis are the foremost concerns for maximal biogas production (Tran, 2017). Furthermore, the carbon to nitrogen ratio, hydrogen to carbon ratio, substrate to inoculum ratio, inoculum source, organic loading rate, solid retention time, hydraulic retention time, micronutrient, pH, and temperature are crucial factors for effective anaerobic digestion (Morales-polo et al., 2018; Van, 2020). In practice, only a small fraction of food waste is codigested with manure and other organic waste. Digestion of food waste solely has technical and economical challenges. One of the limitations is process instability due to insufficient trace metals such as Fe, Ni, Mo, Zn, and Co (Xu et al., 2018). Metal ions facilitate binding of enzymes to the substrate and subsequently enhance the reaction rate (Glass and Orphan, 2012). Food waste rich in protein/nitrogen content forms ammonia during the anaerobic digestion and inhibits the process. It is a toxic substance to acetoclastic methanogenic bacteria. Codigestion may improve the process instability by improving the carbon to nitrogen ratio. Some studies have reported the use of trace metals such as Fe and ammonia stripping for improvement of biogas production (Ghyselbrecht et al., 2018; Qiang et al., 2013). In addition, a high salt content in food waste (i.e., kitchen waste), alters the metabolism of microorganisms and inhibits anaerobic digestion. An increase in sodium accumulation from 5 to 10 g/L is observed to reduce methane production from 50% to 10% (Zhao et al., 2017). Codigestion of food waste and activated sludge has been noticed to improve AD performance. Hence, technological advancements are required to decompose food waste, producing methane-enriched biogas.

15.3

Commercial scale-up of food waste valorization technology

Scale-up is a procedure that tunes a system’s size to meet the commercial needs according to the product or service (Lonsane et al., 1992). According to the Cambridge dictionary, to scale-up is to increase something in size, amount, or production. Besides lab-scale studies, investigations on scale-up are also necessary before implementing the appropriate technology at a commercial level. The target product at a commercial scale must have retain the functional properties and meet consumers’ demand continuously (Galanakis, 2012). However, at a commercial scale often a reduction in process performance and slight deviation in product quality is reported (Kowalczyk et al., 2011; Tufvesson et al., 2010). A successful scale-up should be a proper amalgamation of feedstock properties and associated processing conditions in line with lab-scale studies (Lonsane et al., 1992; Tufvesson et al., 2010). Below are listed points of key concern for scale-up:

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1. Biomass composition and availability; 2. Seasonal variation in biomass composition; 3. Biomass collection, transportation, and storage; 4. Process parameters such as flow rate, mixing, and heating time; 5. Limitations in mass and energy balance; 6. Downstream processing; 7. Economic and environmental concerns. For the commercialization aspect, technology should sound technically, economically, and environmentally plausible. Based on the merits of AD over other traditional methods of food waste management, it has been selected for further elaboration of commercial scale-up studies. Morales-polo et al. (2018) observed the potential of food waste in improving anaerobic digestion while codigested with sewage sludge. Food waste was reported to give stability to the anaerobic digestion process (Paritosh et al., 2017). Codigestion of food waste with sewage sludge was found to increase the biomethane production by 20%
40% (Keucken et al., 2018). So far, very few studies have been done on scale-up of solely food waste-based biogas production. Kowalczyk et al. (2011) studied anaerobic digestion of biomass at two different scales, namely, a 22-L laboratory digester and a 390-L continuous digester to assess its commercial potential. They used maize silage, corn cob mix, and cow manure as feedstock. The data showed reproducibility at a large scale in an acceptable range. However, a slight deviation (of  6.33%) was observed and attributed to variation in the organic loading rate. Similarly, Fiore et al. (2016) performed anaerobic digestion of industrial food waste at a semipilot scale and pilot scale. They proposed a semipilot scale procedure for scale-up of the food waste-based biogas production facility. By taking solubilization of biomass as the limiting step, disintegration kinetic constant (kdis) was taken to scale-up the process. As a result, they observed consistency in methane production with a coefficient of 0.81. The authors reported a deviation of 7%
8% at both scales in theoretical and experimental biogas production values. Moving ahead, Kim et al. (2008) explored the commercialization potential of food waste valorization. They adopted a volumetric scale-up strategy for three-stage fermentation of food waste at a pilot scale. The results were consistent, with 90.6% and 72%, and 90.1% and 68%, removal of total chemical oxygen demand, methane production at lab scale and pilot scale, respectively. In addition to technical strength, the technology or service should be reinforced by governmental policies to ensure its smooth adoption. For instance, biogas technology is well subsidized in European countries, such as Germany and Sweden. In Sweden, approximately 4500 vehicles run on biomethane (45%) blended fuel (Cherubini, 2010). In a nutshell, an amalgamation of technical, economical, social, and governmental endorsement is highly desired for successful commercialization. In the last few years, several new reactor designs have been proposed for effective anaerobic digestion at a commercial scale. The history of commercial development of AD technology can be traced back to energy recovery from animal manure and wastewater treatment. The very first design of anaerobic digesters was in China in 1930 and then in 1956 in India (Mukumba et al., 2017; Ramatsa et al., 2014). The development of key anaerobic digester models is depicted in Fig. 15.2. Since then, several designs have enhanced the efficiency of anaerobic digestion. The conventional single-stage system has undergone modifications and met new two-stage and three-stage configurations (Goswami

FIGURE 15.2 Development of key anaerobic digester models.

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Food Waste to Valuable Resources

et al., 2016; Van, 2020). In addition, advanced reactors have been proposed using membrane technology. The membrane has been devised to avoid cell washout, thus providing higher solid retention time for effective digestion and separating inhibitory molecules to stabilize the AD process (Horva´th et al., 2016). Recently, Bhabha Atomic Research Centre (BARC) in India has developed Nisargruna biogas plant. The novel design was highly acclaimed and the plant has been set up in various organizations. Schematic of process flow diagram for nisarguna biogas plant is presented in Fig. 15.3. The plant is capable of handling and processing kitchen waste in large quantities of up to 10 tonnes per day. It is a solar heater-assisted two-stage plant, employing thermophilic microorganisms in a predigester and methanogenic microorganisms in the main digester. It has a processing time of 10
12 days and yields biogas with a methane content of 70%
75%. In contrast, the conventional biogas plant is based on cattle manure and has a long processing time of about 30 days. Additionally, these conventional plants yield biogas with only 50%
55% methane content (Kale and Mehetre, n.d.). These works toward scale-up and progression embrace anaerobic digestion of food waste and offer a sustainable solution for food waste management.

15.4

Cost estimation of different food waste valorization techniques

Cost analysis involves the cost incurred for the valorization of food waste including capital cost, production cost, and the profits gained by undergoing these valorization. The capital cost can be calculated by estimating the land and fixed capital cost of the plant (Han et al., 2016a,b). The production costs include labor cost, raw material cost, wastewater treatment cost, and utility cost. The revenue or the profitability were analyzed by using the market selling price of the obtained product. Table 15.1 depicts the cost estimation of different valorization techniques.

15.4.1 Transesterification Catering or restaurant waste, like waste frying oil or waste vegetable oil, with a production capacity of 8000 tonnes/ year were used as an efficient carbon source for the production of biodiesel. The total investment cost includes both the direct and indirect costs. Lisboa et al. (2014) performed a complete economic analysis of biodiesel production through enzymatic transesterification of waste cooking sunflower oil. An investment cost of h14.8 million was incurred to achieve a higher yield of 86.7%. Biodiesel costs of h1.64/L and h0.75/L were obtained for enzyme prices of h800/kg and h8/kg.

FIGURE 15.3 Schematic flow diagram of nisargruna biogas plant

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331

TABLE 15.1 Cost estimation of different valorization techniques. S. no.

Type of food waste

Valorization technique

Product

Capital cost (US$)

Production cost (US $/year)

Revenue (US $/year)

References

1

Food waste

Solid-state fermentation and dark fermentation

Hydrogen

707,850

366,700

574,800

Han et al. (2016c)

2

Food waste and microalgae

Solid state and algae fermentation

Plasticizer and lactic acid

2,326,170

620,170

1,072,619

Kwan et al. (2015)

3

Food waste and microalgae

Solid-state and algae fermentation

Plasticizer and animal feed

2,053,941

303,468

153,224

Kwan et al. (2015)

4

Bakery waste

Solid-state fermentation

Succinic acid

1,118,243

230,750

143,559

Lam et al. (2014)

5

Residential food waste

Solid-state fermentation

Lactic acid

96,768,814

61,795,925

88,363,792

Kwan et al. (2018)

6

Residential food waste

Solid-state fermentation

Lactide

104,576,164

67,571,270

81,518,450

Kwan et al. (2018)

7

Residential food waste

Solid-state fermentation

Poly lactic acid

116,530,081

72,951,945

96,949,810

Kwan et al. (2018)

8

Waste vegetable oil

Transesterification

Biodiesel

15.6 million

40.2 million

39.6 million

Lee et al. (2011)

9

Waste vegetable oil

Supercritical transesterification

Biodiesel

14.8 million

32.49 million

39.6 million

Lee et al. (2011)

10

Molasses

Dark fermentation

Biohydrogen

478,200

440,000

77,228.6

Han et al. (2016b)

A case study of biodiesel production from waste cooking oil in Hong Kong was performed by Karmee et al. (2015). The authors reported that acid-catalyzed transesterification is cost effective, with an acceptable internal rate of return (IRR) as compared to lipase- and alkali-catalyzed transesterification. Lee et al. (2011) performed an economic analysis for the production of biodiesel from waste vegetable oil with a production capacity of 40,000 tonnes/year and analyzed using the Aspen In-Plant Cost Estimator. The results concluded that the supercritical transesterification process gives an economically viable outcome with very low cost of production and higher net present value. The major factors which affect the cost of production are the oil feed and biodiesel manufacturing cost.

15.4.2 Dark fermentation The valorization of food waste for the production of hydrogen production was carried out by Han et al. (2016a) and an economic valuation was done for 1095 tonnes of food waste per year. The net present value shows an interest rate of 10% with a lifetime exceeding 6.2 years. The net present value was $0.44 M for the lifetime of 15 years giving a return of 24.1%. Han et al. (2016b) investigated hydrogen production from food processing waste such as molasses. The hydrogen production was carried out in an immobilized reactor of various volumes ranging from 10
50 m3. The author found an economic response at 40 and 50 m3 production scale. In turn, they concluded that return on investment increases with an increase in production scale. Bonk et al. (2015) proposed that food waste accounts for 69% of the total municipal waste in Abu Dhabi city. This food waste has been used as substrate for the production of hydrogen, VFAs, and fertilizer. The economic analysis shows that the total investment cost was US$76,200,000 with the annual cost being US$15,500,000/year for

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Food Waste to Valuable Resources

pretreatment. The revenue generated in each product was US$24,000,000/year of VFA, US$4,000,000/year of fertilizers, and US$400,000/year of hydrogen. The maximum cost incurred for the purification of VFA was US$15/m3 effluent.

15.4.3 Anaerobic digestion Anaerobic digestion is an efficient technology to treat waste with higher moisture content and so it can be readily used as an efficient process to convert food waste to energy. Kavitha et al. (2017) studied the economic feasibility of liquefied food waste to achieve higher anaerobic degradability and increased biogas generation. The liquefaction of food waste was carried out by chemo-thermo disperser pretreatment. The economic analysis was carried out for the liquefaction of food waste to about 20%
60%. The positive net profit of US$93/tonne was obtained during liquefaction of 40%, and during 50% and 60% of liquefaction, the obtained net profits were US$104.68 and US$116.13/tonne, which does not show a significant increment. The results concluded that the 40% liquefaction of food waste through the chemo-thermo disperser treatment was economically feasible. Oreggioni et al. (2017) performed a TEA of methane production from food and agriculture industry waste. Pressure vacuum swing adsorption (PVSA) and mono-ethanol amine (MEA) were employed for upgrading biogas to biomethane production. The results concluded that the average lifetime cost of MEA was 10% higher than PVSA and the capital investment cost was about 37% higher than that of PVSA.

15.4.4 Solid-state fermentation Solid-state fermentation has been extensively used for the production of single-cell protein, animal feed, enzymes, ethanol, organic acid, etc. (Barrios-Gonza´lez, 2012; Kosseva, 2013). Aggelopoulos et al. (2014) investigated the production of single-cell protein, aroma, and fat using food waste mixture and showed that the cost incurred toward Kefir was very low and the products have almost the same value as commercial products. The e-pinnene production and livestock feed can reach about h1400/tonne, and this can be increased by increasing the purity of the product to 99%. Koutinas et al. (2016) performed an economic evaluation for the production of 2,3-butanediol from sugarcane molasses with a plant capacity of 10,000 tonnes/year. The minimum cost incurred for the raw materials ranged between US$2.6 and 4.8/kg and included the fixed capital investment and the minimum selling price of the product as greater than US$1/kg. Thus it was concluded that a further increase in plant capacity may decrease the minimum selling price. Lam et al. (2014) used bakery waste for the production of succinic acid on a pilot scale which was set up in Hong Kong for the conversion of 1 tonne of bakery waste per day. The overall revenue obtained in this process was US $374,041/year. The return investment and IRR were 12.8% and 15.3%. Kwan et al. (2015) investigated the valorization of food waste for the production of lactic acid, plasticizer, and animal feed by the cocultivation of food waste and microalgae in a pilot-scale facility with a capacity of 1 tonne/day of food waste. This techno-economic study showed that the lactic acid and plasticizer production were economically feasible with an annual net profit of US$422,699, with a payback period (PBP) of 7.56 years as the lactic acid had higher profit. Dimou et al. (2016) investigated the techno-economic assessment of wine lees for the production of ethanol, antioxidants, and yeast cells, and found that the minimum selling price has a great impact on the wine lees treating plant. An increase in wine lees may cause a decrease in the minimum selling price of antioxidants.

15.5

Cost-competitive food waste biorefinery development

The biorefinery is a platform for valorization of biomass into biofuel and value-added products, and increases the biobased economy (Blikra et al., 2018). The concept of a biorefinery is similar to the established petroleum-based refinery. It is conceived to utilize the optimal biomass as a source of renewable feedstock. Food waste management and valorization in a biorefinery approach is gaining increasing attention, especially in developing a zero-waste system (Lin et al., 2013). Additionally, this is requisite from the climate change, natural resources, and energy security points of view. In a biorefinery approach, more than one process can be integrated. This facilitates utilization of the intermediates and produces in-line by-products (such as value-added chemicals, heat, and power) under a single roof (Cherubini, 2010). A typical biorefinery framework is depicted in Fig. 15.4 (Lindorfer et al., 2019). In general, the subsequent residues can be utilized effectively. Additionally, it can reduce the total cost for the targeted product(s). The International Energy

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333

FIGURE 15.4 General framework for food waste biorefinery

Agency (Ree and Zeeland, 2014) has defined biorefining under the aegis of IEA Bioenergy Task 42 as “Biorefining is the sustainable processing of biomass into a spectrum of marketable products and energy.” The concept of biorefinery was evolved from a sustainability point of view. From this concept, it is expected for a biorefinery to meet the index of environmental, economic, and social sustainability throughout its life cycle. Biofuel production was the major driving force to coin the biorefinery concept (Coma et al., 2017). Gradually, the production of renewable chemicals also entered this segment with environmental concerns (Luque and Clark, 2013). In the formulation of a biorefinery the most indispensable concern is the market competitiveness of the desired product. In the context of biofuel, it must have chemical properties in line to gasoline/diesel/kerosene/natural gas so that it can be used in established infrastructure or engines. Also, the biofuel, renewable chemicals, and other products must be competitive enough in terms of market demand and price (Coma et al., 2017). Hence, a framework was conceptualized to utilize the bioresource(s) optimally with additional environmental and economic benefits in a synergetic way (Carmona-cabello et al., 2018; Cherubini et al., 2009). For example, Demichelis et al. (2017) produced lactic acid from food waste and then subsequently biogas from the fermentation residue. In this sequential approach, they were able to produce 0.33 glactic acid per gram of food waste and, subsequently, 0.90 Nm3 biogas per kg VSs upon anaerobic digestion of fermentation residue was obtained. However, from the fresh food waste, only 0.71 Nm3 biogas per kg VSs was recovered. This biorefinery approach made possible the economic production of lactic acid along with enhancement of biogas production. In another biorefinery approach, Dahiya et al. (2015) executed coproduction of VFAs and biohydrogen from food waste. The findings revealed VFA productivity of 6.3 g/L at pH 10 and this led to the highest biohydrogen production. Similarly, Kitpreechavanich et al. (2016) demonstrated highly optically active L-lactic acid production from kitchen food waste and utilization of residue as functional compost for soil treatment. Bacillus subtilis KBKU21 accumulated 36.9 g/L L-lactic acid with 95.7% optical activity through fermentation at 43 C for 84 h. This biorefinery perspective appears to be a sustainable method for food waste management in a zero-waste approach with value addition.

15.6

Techno-economic analysis of a food waste biorefinery

TEA is an effective tool to evaluate the technical and economic feasibility of any process or technology under defined boundary conditions. There may be different options to synthesize a particular product. For example, from food waste different kinds of biofuels (biomethane, bioethanol, and biodiesel) and value-added products can be synthesized using different processes. However, productivity depends on the employed feedstock and process. An overview of a food waste biorefinery is depicted in Fig. 15.5. For instance, Mladenovic and Radosavljevic (2016) observed that bread

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FIGURE 15.5 An overview of a food waste-based biorefinery.

stillage has the highest lactic acid productivity (1.54 g/L/h) compared to that potato stillage and brewers’ spent grain hydrolysate. Similarly, Oreggioni et al. (2017) reported that in the stage of biogas purification, a pressure swing adsorption cycle has 37% less capital cost compared to solvent-based CO2 adsorption technology. The most indispensable point for commercial viability is that the targeted product should meet the market demand (Shah et al., 2016). Cristo´bal et al. (2018) documented that not all food waste has commercial potential. They found that an orange-based biorefinery has a low PBP (2
3 years) compared to tomato-, potato-, and olive-based biorefineries. Thus to avoid the investment risk, an orange-based biorefinery is reported as being the most suitable of these. Similarly, Arora et al. (2018) carried out a TEA of an integrated mango processing biorefinery. The results were quite surprising. Pectin and seed oil recovery was found to be the most suitable option, with a PBP of 2.4 years. For two other designs, namely only pectin recovery and whole biorefinery with multiple products, 4.2 and 3.4 years PBPs were found, respectively. Therefore, feedstock selection, process/technology selection, and commercial viability assessment are essential before capital investment. This can be done using TEA for the supply chain.

15.6.1 Techno-economic analysis framework The TEA is a project feasibility assessment tool. As the name indicates, it evaluates both the technical and economic feasibility of a given project. The primary objective of a TEA is to estimate the overall cost of production. It is comprised of the design of a process flow diagram, mass and energy balance including process analysis and sizing each process units. Furthermore, it estimates the embodied capital cost, operation/manufacturing/production cost, selling price, and return on investment (ROI; Silla, 2003). Ultimately, the obtained data work as a decisive tool that enables engineers to decide whether they should abandon or proceed with the process. TEA indicates if further research at the bench and/ or pilot scale is required, and mitigates the associated risks and ensures smooth functioning of the facility. It also gives both engineers and financial investors confidence in a particular business plan.

15.6.2 Techno-economic analysis methodology The TEA starts with a process flow diagram for a particular product/service. The process should be described in detail with the most promising studied alternatives. Further, associated process specifications such as flow rates, compositions, temperature, pressure, and energy requirement are established. Based on the obtained data, the sizing of each process unit is carried out. This detailed flow diagram allows conducting mass and energy balance that ensures a precise analysis of the process. After this, an economic evaluation is carried out that includes cash-flows and cost-benefits throughout the supply chain. Economic evaluation is accomplished based on the capital cost and production cost. Capital cost

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is bound with the cost of land, equipment installation, etc. and includes depreciable capital cost and fixed capital cost. Production cost includes all the associated direct costs (proportional to the production rate), indirect costs (i.e., fixed cost, plant overhead cost), and general costs (for management, financing, R&D, and marketing, etc.). The costing framework is depicted in Fig. 15.6 (Cristo´bal et al., 2018). Furthermore, it facilitates calculation of the selling price and revenues. Subsequently, it allows estimating the profitability ratio, ROI, IRR, and PBP. These profitability ratios set a benchmark to assess the feasibility of the targeted product or process (Silla, 2003). However, in some cases, some of the designs or proposed scenarios may show almost equal economic performance. In such cases, the most reliable and easy to operate technical design should be opted for. Moreover, with the sustainability concern, the design must meet environmental performance measures. This must be ensured through the LCA. In addition, there also might be compositional variations in feedstock and uncertainty with the assumed data for employed external resources and energy (Mahmood et al., 2016; Mallah and Bansal, 2011). Therefore, the TEA should be covered up with the sensitivity analysis to appraise the optimized design response with changes in inputs.

FIGURE 15.6 Total cost estimation framework: (a) total capital investment, (b) production cost. Adopted and modified from Cristo´bal, J., Caldeira, C., Corrado, S., Sala, S., 2018. Techno-economic and profitability analysis of food waste biorefineries at European level. Bioresour. Technol. 259, 244
252. https://doi.org/10.1016/j.biortech.2018.03.016.

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15.7

Food Waste to Valuable Resources

Case studies on food waste biorefineries

Within the scope of this chapter, we have selected key TEA studies on food waste biorefineries carried out across the globe. In particular, biofuel production as well as value-added product targeted biorefineries are discussed.

15.7.1 Integrated mango biorefinery in an Indian context India is the world’s largest mango producer and contributes 52.6% of global production (Arora et al., 2018). It is processed in industries profoundly for its succulent taste, and carotenoids and ascorbic acid contents (Gouado et al., 2007). Throughout this extensive processing it generates 25%
40% fruit waste, such as peel and kernel. Among these, mango peel has the largest percentage of wastage. It can be further utilized to obtain other value-added compounds. Arora et al. (2018) performed a TEA of an integrated mango biorefinery. They assumed 250 tonnes waste per day with 24 h processing time for 180 days in a year as baseline. The input data were estimated by direct survey with mango processing industries in western India. Processing data were taken from previous work at a laboratory level. Three scenarios, namely pectin recovery from mango peel (PEP), pectin and seed oil recovery (PSEP), and multiple products extraction from peel and seed (WMB) were formulated. Pectin was considered as the main product of the biorefinery. The devised processing is depicted in Fig. 15.7 (Arora et al., 2018). Biorefinery profitability was analyzed using net productive return (NPV), IRR, and PBP. Further sensitivity analysis was done to assess the effect of uncertainties or fluctuations in inputs. The results showed the pectin and seed oil recovery process (PSEP) to be the most suitable option, with a PBP of 2.4 years. In this case the NPV and IRR were US$41 million and 34%, respectively. The other two designs, namely

FIGURE 15.7 Mango-based integrated biorefinery. Adopted from Arora, A., Banerjee, J., Vijayaraghavan, R., Macfarlane, D., Patti, A.F., 2018. Process design and techno-economic analysis of an integrated mango processing waste biorefinery. Ind. Crop. Prod. 116, 24
34. https://doi.org/ 10.1016/j.indcrop.2018.02.061.

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only pectin recovery (PEP) and whole biorefinery with multiple products (WMB), showed 4.2- and 3.4-year PBPs, respectively. For PEP the lowest NPV of US$14.2 million and IRR of 20% were reported. WMB has US$43.2 million NPV but was limited by a comparatively low IRR of 26% and a high PBP of 3.4 years. Sensitivity analysis showed that for all three cases, a smaller plant of 1 metric tons per hour would not be profitable. Reductions in plant operating days, variations in feedstock composition, and selling price of the main product (pectin) were also found to limiting the plant profitability. In addition, plant operation for 3
6 months was recommended to ascertain the feasibility of the plant.

15.7.2 Food waste biorefinery in a European context Food waste has gained increasing attention from European government officials and has been recommended for the European circular economy action plan (European-Commission, 2015). Cristo´bal et al. (2018) carried out a TEA of food waste, namely tomato, potato, orange, and olive processing conversion to value-added products at a European level. They retrieved the food waste availability data from EUROSTAT and processing data from other research articles. Biorefinery economics was assessed using ROI and PBP based on the considered number of plants (7
70) and market price of the desired products. All the estimated input data and base case are documented in Table 15.2. The results showed a high market price for tomato-, potato-, and olive-based products to make it feasible. However, in the medium case the profitability can be covered by the number of installed plants. For orange-based products a low market price was recommended. In this scenario a PBP of less than 0.6 years with 2%
9% ROI was estimated. On the other hand, tomato-, potato-, and olive-based biorefineries were found to have a high PBP of 3
15 years. Considering the market price, the operation of 28 plants was noticed for profitability with a PBP of 16 years. Similarly, for olive-based biorefineries, up to 42 plants were noted for profitability but there was a very high PBP of 70 years. From an investment point of view the operation of 35 plants was recommended. Overall, orange-based biorefineries were reported as most attractive.

TABLE 15.2 Used data for techno-economic analysis of biorefineries. Input product

Waste amount (t/year)

Tomato peel

1.48 3 10

Potato peel

2.34 3 106

Orange peel

Olive mill waste

6

3.18 3 106

4.1 3 10

6

Valorization pathways SFECO2

Solvent extraction H2O 1 EtOH

MHG 1 MAE 1 UAE

SFECO2 1 EtOH

Output product

Output quantity (kg/year)

Lycopene

Price (EUR/kg) Low

Medium

High

3.6 3 10

4000

4 3 10

4 3 105

β-Carotene

2.9 3 103

400

4000

4 3 104

Neochlorogenic acid

3.1 3 105

30

300

3000

Chlorogenic acid

1.8 3 106

Caffeic acid

1.1 3 105

Alfa-chaconine

4 3 105

Alfa-solanine

1.66 3 105

Solanidine

2.3 3 103

EO

5.5 3 107

1

10

100

TPC

1.86 3 10

10

100

1000

Pectin

7.68 3 10

10

100

1000

TPC

4.68 3 10

200

2000

2 3 104

FAME

3.99 3 10

10

100

1000

Squalene

4.31 3 10

10

100

1000

4

6 8 6 6 6

4

Source: Adopted from Cristo´bal, J., Caldeira, C., Corrado, S., Sala, S., 2018. Techno-economic and profitability analysis of food waste biorefineries at European level. Bioresour. Technol. 259, 244
252. https://doi.org/10.1016/j.biortech.2018.03.016.

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Food Waste to Valuable Resources

15.7.3 Biofuel production from food waste Food waste is seen as a valuable feedstock for biofuel production, and so far, many experimental investigations have been carried out. These interventions have led to the prototype, which shows promising results not only at a laboratory scale but at a pilot scale also (Gumisiriza et al., 2017; Lo and Woon, 2016). However, very few studies are available considering the TEA. In this section the two best available case studies are discussed. Han et al. (2016c) performed TEA of hydrogen production from food waste. They assumed hydrogen-production plant had a capacity of 3 tonnes per day. The food waste was first used to produce glucoamylase and protease enzymes using microorganisms, followed by hydrolysis. The hydrolysate was subsequently taken to dark fermentation for hydrogen production. For economic assessment key parameters were total capital cost (TCC), annual production cost (APC), ROI, IRR, and PBP. The result showed US$583,092 and US$88,298.1 TCC and APC, respectively. The ROI, IRR, and PBP were 26.75%, 24.07%, and 5 years, respectively. Furthermore, the sensitivity analysis showed that a change in price of the input data within a 6 20% range would not make the NPV negative. Variations in hydrogen selling price and operating labor cost were found to affect the plant profitability. It was noted that a hydrogen-production plant of capacity less than 0.3 tonnes food waste per day would not be feasible. Kempegowda et al. (2017) carried out a TEA for heat, power, and biochar production using sewage sludge and food waste. The processing data were assumed based on the simulation study. They carried out TEAs for three cases: (1) hydrothermal/thermal pretreatment of biomass followed by codigestion for combined heat and power (CHP) generation; (2) hydrothermal cotreatment for heat, power, and biochar production; and (3) hybrid cothermal treatment and CHP generation. The process economics was studied based on the NPV, IRR, and benefits to cost ratio. The results showed that hydrothermal cotreatment for heat, power, and biochar production would be feasible with a selling price of US $0.3kWh for electricity. For this case US$123 million NPV, 29.7% IRR, and 1.38 benefits to cost ratio were estimated.

15.8

Conclusion

A sustainable food waste management system is the need of the hour. Concerning the huge amount of waste and environmental consequences, researchers are striving hard to develop alternative technologies. In the urge of economic and sustainable solutions techno-economic analysis (TEA) of the concerned alternatives is indispensable. Studies showed that the traditional methods of food waste management viz. landfilling and incineration are technically inefficient and perilous to the environment as well. On the other hand, food waste utilization as animal feed or feedstock for biogas production was found less harmful. Food waste is being seen as a ladder for bio-based business development. Various technologies and biorefinery system is being developed to extract biofuel precursors and value-added products from food waste. In this venture, selection of feedstock and process/technology, sizing of production unit and market, and commercial viability assessment are key criteria to meet the techno-economic credibility. From the economic sustainability scenario, proposed technology must be secured by techno-economic evaluation.

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631. Redcorn, R., Fatemi, S., Engelberth, A.S., 2018. Comparing end-use potential for industrial food-waste sources. Engineering 4, 371
380. Available from: https://doi.org/10.1016/j.eng.2018.05.010. Ree, Rvan, Zeeland, Avan, 2014. Task 42 biorefining. IEA Bioenrgy . Available from: https://doi.org/10.1016/s0961-9534(07)00064-5. Shah A., Baral N.R. and Manandhar A., Technoeconomic analysis and life cycle assessment of bioenergy systems, Advances in Bioenergy, Elsevier, 1, 2016, pp. 189
247. Available from https://doi.org/10.1016/bs.aibe.2016.09.004. Silla, H., Chemical process engineering: design and economics, CRC Press, 2003. https://doi.org/10.1201/9780203912454. Stan, C., Collaguazo, G., Streche, C., Apostol, T., Cocarta, D.M., 2018. Pilot-scale anaerobic co-digestion of the OFMSW: improving biogas production and startup. Sustain 10. Available from: https://doi.org/10.3390/su10061939. Tonini, D., Federica, P., Fruergaard, T., 2018. Environmental impacts of food waste: learnings and challenges from a case study on UK. Waste Manage. 76, 744
766. Available from: https://doi.org/10.1016/j.wasman.2018.03.032. Tran, K.C., Anaerobic Digestion of Microalgal Biomass: Effects of Solid Concentration and Pre-treatment. Diss. University of Southampton, 2017. Tsang, Y.F., Kumar, V., Samadar, P., Yang, Y., Lee, J., Song, H., et al., 2019. Production of bioplastic through food waste valorization. Environ. Int. 127, 625
644. Available from: https://doi.org/10.1016/j.envint.2019.03.076. Tufvesson, P., Fu, W., Jensen, J.S., Woodley, J.M., 2010. Process considerations for the scale-up and implementation of biocatalysis. Food Bioprod. Process. 88, 3
11. Available from: https://doi.org/10.1016/j.fbp.2010.01.003. Turon, X., Venus, J., Arshadi, M., Koutinas, M., Lin, C.S.K., and Koutinas, A., Food waste and byproduct valorization through bio-processing: opportunities and challenges, BioResour. 9 (4), 2014, 5774
5777. ,https://doi.org/10.15376/biores.9.4.5774-5777 . https://doi.org/10.1007/s12649-014-9311-x. Warshawsky, D.N., The challenge of food waste governance in cities: case study of consumer perspectives in Los Angeles, Sustainability, 11 (3), 2019, 847. https://doi.org/10.3390/su11030847. Xu, F., Li, Y., Ge, X., Yang, L., Li, Y., 2018. Anaerobic digestion of food waste
challenges and opportunities. Bioresour. Technol. 247, 1047
1058. Available from: https://doi.org/10.1016/j.biortech.2017.09.020. Zhang, Y., Huang, M., Su, J., Hu, H., Yang, M., Huang, Z., et al., 2019. Overcoming biomass recalcitrance by synergistic pretreatment of mechanical activation and metal salt for enhancing enzymatic conversion of lignocellulose. Biotechnol. Biofuels 12. Available from: https://doi.org/10.1186/ s13068-019-1354-6. Zhao, J., Liu, Y., Wang, D., Chen, F., Li, X., Zeng, G., 2017. Potential impact of salinity on methane production from food waste anaerobic digestion. Waste Manage. 67, 308
314. Available from: https://doi.org/10.1016/j.wasman.2017.05.016.

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Further reading Garcı´a, A.J., Esteban, M.B., Ma´rquez, M.C., Ramos, P., 2005. Biodegradable municipal solid waste: characterization and potential use as animal feedstuffs. Waste Manage. 25, 780
787. Available from: https://doi.org/10.1016/j.wasman.2005.01.006. Kang, H.Y., Yang, P.Y., Dominy, W.G., Lee, C.S., 2010. Bioprocessing papaya processing waste for potential aquaculture feed supplement
economic and nutrient analysis with shrimp feeding trial. Bioresour. Technol. 101 (20), 7973
7979. Pe´rez-camacho, M.N., Curry, R., and Cromie, T., Life cycle environmental impacts of substituting food wastes for traditional anaerobic digestion feedstocks. 73, 2018, 140
155. https://doi.org/10.1016/j.wasman.2017.12.023. Uso´n, A.A., Ferreira, G., Va´squez, D.Z., Bribia´n, I.Z., Sastresa, E.L., 2013. Environmental-benefit analysis of two urban waste collection systems. Sci. Total. Environ. 463
464, 72
77. Available from: https://doi.org/10.1016/j.scitotenv.2013.05.053.

Chapter 16

Problems and issues of food waste-based biorefineries Jaskiran Kaur, Gini Rani and K.N. Yogalakshmi Department of Environmental Science and Technology, School of Environment and Earth Sciences, Central University of Punjab, Bathinda, Punjab, India

16.1

Introduction

The global human population is growing annually at a rate of 1% and is expected to reach 8 million by 2025 (Ismail and Nizami, 2016). The irresistible expansion of human population has consequently put tremendous pressure on food security and energy reserves. Growing population and changing lifestyles have resulted in a tremendous increase in the generation of food waste worldwide. With some parts of the world still suffering from food shortages and food crises, the rest suffers from problems of obesity, diet-related chronic diseases, and constantly increasing food waste generation. The term “food waste” denotes any uneaten food or food preparation residues that are discarded or excluded from the food supply chain (FAO, 2014; Hunt, 2003). Huge quantities of wholesome unused and discarded food ranging from primary production to the end household consumer level are included in the category of food waste (Fig. 16.1). Food waste is generated in several forms from organic crop residues, food processing residues, and wastewater, animal byproducts, kitchen waste, etc. (Lundqvist et al., 2008; Paritosh et al., 2017; Xu et al., 2018). The quantities of food waste generated vary from country to country. It is estimated that, at a consumer level, Europe and North America produce 95
115 kg/year of food waste, while it is 6
11 kg/year in sub-Saharan Africa and Southeast Asia (FAO, 2011). The United States, alone, generates around 60 million tonnes of waste annually. Of 60 million tonnes of food wasted, around 35 million tonnes is abandoned from convenience stores, restaurants, and supermarkets (Jones, 2005). A food system is vital for the survival of mankind. During the processes of production, distribution, and consumption it creates huge impact on mankind and its surrounding environment. The sustainability of natural resources is vital for a good food system. Likewise a good food system should take care of the natural environment through minimal impact on water, air, and land. Food waste is known to be a medium for spreading contagious diseases, including swine flu, foot and mouth disease, and transmissible spongiform encephalopathies. The incidence of such diseases has been identified in Hong Kong (Woon and Lo, 2016). Thus, management of food waste is one of the great imminent challenges to urban and rural areas of most countries. Numerous environmental problems, such as emissions of greenhouse gases (GHG), leachate production at landfill sites, loss of valuable resources, release of harmful gases, and harm caused to biodiversity are increasingly being raised as a result of food waste disposal (Katami et al., 2004; Lin et al., 2013; Posmanik et al., 2017). According to Khan and Kaneesamkandi (2013), around 76% of the CH4 emissions in the Kingdom of Saudi Arabia are brought about by landfills. The United Nations also declared food waste disposal a global problem, contributing almost 8% of GHG emissions. In the due course of time, the environmental problems of food waste disposal have aggravated and hence stimulated the need for proper management of food waste. Several waste management strategies, including food donation, source reduction, and turning wasted food into animal feed have been adopted by various countries for reduction of food waste. Additionally, industries are under great competitiveness pressure to provide sustainable solutions, customer satisfaction, and improved efficiency under the framework of stricter environmental laws. Hence, considering the environmental aspects, valorization of food waste via an integrated biorefinery approach will be an interesting method for the effective management of food waste (Otles and Kartal, 2018; Sauve´e and Viaggi, 2016). Moreover, food waste, being a reservoir of organic compounds like complex carbohydrates, proteins, and lipids, can act as economical raw materials for the biotechnological production of important chemicals Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00016-X Copyright © 2020 Elsevier Inc. All rights reserved.

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FIGURE 16.1 Classification of food waste.

and energy (Bhatia et al., 2018; Lin et al., 2013). Food waste possesses great potential for valorization in a holistic biorefinery approach. It involves the conversion of food waste into bioenergy and other value-added products with the aim of reducing the stress on fossil fuels and environmental matrices (Cherubini and Ulgiati, 2010; Plazzotta and Manzocco, 2019). Developing countries have adopted various physical, chemical, thermochemical, and biological valorization technologies for converting food waste into innumerable marketable products and renewable energy. The products of biorefinery, such as biofuels, biofertilizers, secondary chemicals, and other products are the results of the biological transformation of waste processes such as composting, anaerobic digestion, biogasification, and fermentation (Ðilas et al., 2009; Nayak and Bhushan, 2019; Schieber et al., 2001). For instance, anaerobic digestion has been proposed as an encouraging option for renewable energy production by utilizing food waste to produce biogas (Xu et al., 2015). In the green method of valorization, biological microorganisms are used to produce carbohydrate-rich food waste and biofuel. All these strategies are thus beneficial in the creation of more sustainable disposal options to produce new materials and energy sources. Additionally, the biorefinery concept also enables overcoming of the problems of landfilling: reductions in the emission of GHG, less resource exploitation, and effective utilization of food waste biomass (Kim et al., 2013; Takata et al., 2012). Thus, biorefineries hold great promise in growing the economy of a country. As per the report published by BCC Research, it is assumed that the biorefinery global market will rise from $466.6 billion in 2016 to $714.6 billion by 2021 (Chaturvedi, 2017). However, the success of a biorefinery approach for management of food waste is more appropriately based on qualitative measurements. This requires that the valorization strategies must be accepted by the community and be quickly implemented. For this, it is essential to assess thoroughly the social, environmental, and economic impacts to the community, which enables further recognition of the proficient strategy for food waste management. By considering these impacts, the policymakers might be able to devise new innovative plans and planning strategies for effective food waste valorization.

16.2

Issues associated with food waste

At every stage of food supply chain, that is, preconsumer (manufacturing, transportation, and storage operation) and postconsumer steps, edible and nonedible fractions of food are discarded. The discarded food substances that do not

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meet the organoleptic standards due to process malfunctioning and contamination by microorganisms are described as food waste. Food waste accounts for the highest amount of generated biowaste throughout the world. Each year around one-third (1.3 billion tonnes) of the total food produced is wasted through all stages of the food supply chain (production, processing, storage, handling, distribution, and consumption), amounting to a total cost of 47 trillion Indian rupees (Paritosh et al., 2017). According to reports, the food waste generation can increase with increasing population growth and lifestyle changes. The current global population is increasing annually at the rate of 1% and the population is estimated to reach 8.2 billion within 10 years, resulting in increased consumption and food waste generation. Although food waste is a huge global issue the fundamental reasons for food loss are different for different countries. For example, in developing countries, most food wastage occurs during the initial stages of the food supply chain (during cultivation, harvesting, storage, and transportation) due to lack of agricultural expertise, effective preservation system, proper transportation facilities, and necessary storage techniques, unlike developed countries where significant food wastage is concentrated once it reaches the end consumer. Sometimes, food is wasted when it does not meet the optimal standards of size, shape, color, etc. Foods that are beyond or close to their best before date are also discarded on a large scale. Lifestyle changes and economic status have also become major reasons for food loss and food waste generation. Economic improvements of families have encouraged people to buy food beyond their requirement. The unused or expired foods is then discarded without considering the loss of resources. Lack of awareness about food wastage, people’s personal preferences for specific foods, wasting food as a social norm, improper and unsystematic planning, and improper knowledge about extending the shelf-life of food products are some of the social reasons for food waste generation. According to Schanes et al. (2018), a lack of social acceptance for sharing the food is also a reason for a huge amount of food waste. Foods that are easily available and those procured at subsidized rates are wasted more than others. In a case study, Shahnoushi et al. (2013) reported that in Iran around 1.83 kg of bread is wasted per week per capita due to its availability at a subsidized rate. Food loss in agriculture may also be attributed to climatic and edaphic factors, pest infestations, and diseases. Annual food waste in the United Kingdom is estimated to be 8.3 million tonnes, with a value of Rs.1.3 trillion. Japan’s domestic and industrial sectors discard around 30% (17 million tonnes) of total edible food annually. In India, due to inadequate storage infrastructure, around 30% of the total vegetables and fruits grown are discarded (Biman and Banikinkar, 2011). According to the FAO, food loss represents a wastage of labor, energy, water, land, seeds, and other resources utilized in the production of food. Cultural and religious practices also result in increased food waste generation. During festivals and religious gatherings, around 30%
50% of food is wasted. The amount of food produced, if not handled properly, affects the economy and social well-being of a country, and the overall ecosystem of the planet. It affects all three pillars of sustainable development. On the social front, wasting food resources might result in hunger among some sections of the global population. Food loss also badly affects the economy of a country, creating a food threat. The third pillar, the environment, is affected throughout the food supply chain, that is, in all stages of food production and consumption. The contribution of the food industry to climate change through GHG emissions is remarkable. Around 15%
28% of GHG emissions are contributed by developed countries. According to Garnett (2011), Europe contributes 31% of the total GHG through the food supply chain. Likewise, the UK contributes around 3% of the GHG emissions only from food waste. Other environmental effects caused by food waste include contamination of natural resources such as the air, water, and land. It also leads to spread of diseases through flies, insects, and other disease carriers that feed on the waste when disposed of in open areas.

16.3

Valorization of food waste

Food waste is principally comprised of fruit and vegetable remains, spoiled food grains, fruits and vegetables, leftover food particles, bagasse and molasses, blood, flesh, bones, residues from wineries and breweries, cheese whey, and other waste products from dairy processing. They are generated from households, institutions, industries, commercial complexes, markets, agricultural fields, and food production and packaging industries. Unlike other types of solid waste, food waste is easily biodegradable and does not cause any harm to the environment. However, the release of GHGs during the process of degradation cannot be ignored as they are directly linked to climate change. Developed countries release around 15%
28% of GHGs from the food waste generated in the production to consumption chain (Garnett, 2011). Since the concerns about climate change are increasing daily, it has become vital to initiate steps to control GHG emissions. Moreover, the composition of food waste favors it as a source to recover energy. Food waste possesses a net calorific value of around 3344 kJ/kg. The carbohydrates, proteins, fats, and other bioactive compounds can be exploited for the production of energy, and novel by-products like antioxidants and enzymes. Thus food waste has great potential to be valorized in a biorefinery concept.

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Incineration, composting, vermicomposting, biogas production via anaerobic digestion, landfilling, use as animal feed, and fertilizers are some of the common valorization techniques (Banu et al., 2001; Kannah et al., 2018; Kavitha et al., 2017; Logakanthi et al., 2006, 2000). According to Gustavsson et al. (2011), a major portion of food waste is utilized as cattle feedstock and most of the rest (B30% to 40%) is disposed of in landfill, composted, or incinerated. However, the processes of incineration and landfilling result in the generation of GHG (Pham et al., 2015). The high moisture content of food waste limits the use of the incineration process, if energy recovery efficiency is considered (Xu et al., 2016). Moreover, when food waste can be easily converted to valuable products through the biological conversion route, utilization of incineration for food waste valorization becomes limited. Stringent laws and regulations do not favor the use of landfilling or incineration for valorization of food waste. Composting and anaerobic digestion can overcome the deficiencies of landfilling and incineration processes through the production of value-added products such as compost, biogas, and biofertilizers. Although these valorization techniques are popular and accepted worldwide, their effectiveness in food waste management remains questionable. The high generation of food waste and its availability, investment, transportation, and operational cost and stricter environmental regulations, necessitate the requirement for advances in the valorization technologies. Moreover, the food waste valorization techniques result in some residues that could potentially be used as feedstock for the preparation of other products. In the current political, economic, and environmental situation, every industry is forced to drive toward sustainable solutions and alternate sources of energy. Adopting a circular economy approach in every aspect of production would be a solution to many industries. The concept of a circular economy was developed to return the residues as new products into the economy. This would create a solution to achieve sustainable development goals. The concept of a biorefinery would help industries to adopt the circular economy approach. Biorefineries utilize the entire waste stream and other secondary products to convert them into energy or other useful biobased products and chemicals (Hudman, 2016). Hence, the concept of biorefineries in food waste valorization evolves a path to drive the production of other high-value chemicals and biobased products from a potential similar source, that is, food waste. The concept of a food waste-based biorefinery is recognized as an environmentally sound approach. It aims to maximize the production of value-added products (electricity, fuels, heat and power, plastics, etc.) and nutrient recovery. The GHG emissions and energy input cost incurred in biorefineries are much less than traditional energy-synthesizing plants. The products obtained from the valorization of food waste are categorized into bioenergy (biohydrogen, biofuel) production, valuable bioproducts (bioplastics, biosurfactants, lactic acids, etc.), extracted products with applications in food industries and pharmaceuticals, and others such as nanoparticles and foam. The food waste matrix is rich source of nutrients (lipids, sugars, proteins, fibers), phytochemicals and flavouring compounds. These compounds can be recovered and used as cosmetics, flavouring agents/ additives, therapeutics etc. (Galanakis et al., 2018). Waste derived from fruits and vegetables are packed with carotenoids and polyphenols which can be extracted and used as food preservatives. These compounds naturally tend to increase the storage life of the products and boost the antioxidant capacity (Oreopoulou and Tzia, 2007). The description of various recovery techniques for obtaining bioactive components from food waste matrix is mentioned in the forthcoming section.

16.3.1 Techniques used for recovery of bioactive components from food waste The technique of sequential solvent extraction is used to recover sugars, pectin, flavonoids and essential oils from leftover peels of citrus fruits (Bonnell, 1983). The extract from the waste citrus peel, particularly pectin is used as stabilizing and thickening agents in jellies, fruit jams and pharmaceuticals. Hydroxytyrosol, a functional component of bread and food preservative is recovered from olive mill wastewater (Fernandez-Bolanos et al., 2002). Moreover numerous products and chemicals such as citric acid, ethanol, tartrates, dietary fibres, grape seed oil and polyphenols (flavonols, anthocyanins, catachin etc.) are recovered from marc of fruits such as grapes, apple and olives. The grape seed and skin contain polyphenols which prevent low density lipoprotein oxidation in humans. Studies based on extraction and recovery from food waste have been promoted because the newer products formed from the food waste helps in limiting dependence on primary food, increase availability of food/edible, reduces waste load in landfill. The process used for recovery of bioactive components from the food waste stream includes pretreatment, separation, extraction followed by final purification. The technique used for the recovery method depends on the nature of the food waste and ingredient to be recovered.

16.3.1.1 Pretreatment of food waste Pretreatment is the primary step, which is carried out to bring adjustment in the enzymatic activity, moisture content and permeability of food particles to the solvent to be extracted. Wet milling is a type of pretreatment method which

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helps in proper diffusion of extracted solvent into the tissues of waste component. This process ensures better yield of bioactive products (Pellera et al., 2012). However, this method suffers demerit of reduced functionality and productivity of the solvent to be extracted, because of application of heat (Galanakis et al., 2010). Freeze drying is another technique which helps in reducing water content from the food waste but this option is expensive and has low shelf life (Galanakis, 2012). Some of the advanced pre treatment techniques include electro osmotic dewatering, foam mat and micro filtration. Foam based process helps in eliminating issues associated with thermal heating and ensures proper stability against damage caused due to microbial activity, biochemical and chemical reactions (Rajkumar et al., 2007). Waste containing tomato pomace which are highly viscous and other waste containing gelatinous substance require electro osmotic dewatering for drying of waste (Jumah et al., 2005). Micro filtration and centrifugation helps in eliminating oils, fats and other solids from food waste which is essential to prevent its oxidation (Diaz et al., 2004).

16.3.1.2 Extraction The common existing method for the process of extraction is solvent extraction which involves the use of solvents such as acetone, methanol, ethanol and their aqueous forms (Galanakis et al., 2013). This method requires suitable selection of solvent and operating conditions such as pH, particle size, rate of stirring, time of contact and solid to liquid ratio for improving the yield of the bioactive compounds. The disadvantage of this technique is prolonged extraction time and usage of expensive and harmful solvents which requires further elimination. The prolonged extraction timing can be avoided by combining this method with application of pressure. Volatile compounds can be extracted by distillation. Extraction yield can be increased by hydrolyzing structural polysaccharides with the help of enzymes ( amylase, cellulose and pectinase) which break cell wall and increase the availability of solvent. The enzymes, however, are easily affected by temperature change, dissolved oxygen, availability of nutrients etc. which limit the process scale up. The emerging technologies for the process of extraction include application of ultrasound, microwave and pulsed electric field (PEF). In the process of ultra sonication, the sound waves with frequency greater than 20 kHz cause disruption of cell walls and initiate accessibility of solvents into the waste matrix. This helps to release of bioactive substances from the cells and increases the mass transfer. Extraction mediated with the help of microwave utilize electromagnetic radiation within frequency range of 300MHz–300 GHz. In this method, initially the components are separated from the food waste with the help of high temperature and pressure and then solvent is diffused across the waste matrix, thereby the components are released into the solvent. In PEF, high-voltage electric pulse is discharged into the food matrix located between two electrodes for few microseconds (Yan et al., 2015). Polarization of ions takes place across the membrane forming pores in the membrane. It facilitates permeability and release of bioactive substances into the solvent.

16.3.1.3 Isolation and clarification The extract obtained is finally subjected to isolation/ clarification of bioactive compounds. The popular methods for this step include membrane separation and adsorption with the help of resins. The membrane separation includes microfiltration, nanofiltration, ultrafiltration and reverses osmosis. The separation efficiency is remarkable in membrane separation and it requires low-energy input, zero chemical addition, mild operating conditions, simple designing and it is easy to scale up for industrial applications (Li and Chase, 2010). Microfiltration and ultrafiltration have been shown to successfully separate oligosaccharides and other impurities with low molecular weight from compounds with high molecular weight. Fructo oligosaccharide, a functional food ingredient have been purified using nanofiltration method (Li et al., 2004). The major disadvantage with membrane filtration is flux reduction and fouling of membrane. These issues increase operation and maintenance cost therefore requires appropriate pretreatment. The process of adsorption has high efficiency for separating low molecular weight phenolic compounds. Compared to membrane filtration, adsorption technique requires low operation and maintenance cost and is nonsensitive to toxic compounds. However, the efficiency depends on the type of adsorbent utilized. Adsorbents such as activated carbon and resins are hydrophobic and possess high surface area. Therefore they are capable of capturing phenolic compounds using ion exchange, adsorption and size exclusion. However, selective recovery of polyphenolic compounds is not possible using this technique.

16.4

Techniques for the conversion of food waste into valuable products

The various methods applied for the conversion of food waste into valuable products are discussed in the following sections.

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16.4.1 Biological conversion Anaerobic digestion and composting are the main biological conversion routes for food waste valorization. Anaerobic digestion is carried out under controlled conditions and helps in converting organic food waste matter into biofuel and nutrient-packed digestate with soil conditioner properties (Chanakya et al., 2007). Anaerobic digestion processes are packed with benefits including waste reduction by volume, recycling of nutrients, production of renewable energy, and residues with soil-conditioning properties. Food waste is enriched with organic matter, therefore it can serve as a good substrate for anaerobic digestion. However, the major issue with food waste is its high salt (potassium, magnesium, sodium, and calcium) content. These salts play an inhibitory role in anaerobic digestion by limiting the growth and activity of microorganisms (Chen et al., 2008). Likewise, the ammonia released during the degradation of the protein fraction of food waste harms the methanogenic bacteria and restricts the process of biogas or biomethane generation. However, this issue can be overcome by codigesting food waste with waste containing lipid and lower nitrogen contents. It has been reported that codigestion of food waste with sewage sludge increased the amount of CH4 (methane) in biogas by eliminating the buildup of intermediate volatile compounds such as NH3 (Kabouris et al., 2009). The codigestion of food waste with municipal solid waste increases the yield of biogas by 40%
50% under mesophilic anaerobic conditions. The biological process can be made more efficient by carrying out pretreatment of food waste and by suppressing the factors which affect the mass transfer mechanism in every step of anaerobic digestion. Pretreatment can be done either biologically, thermally, chemically, or physically (Banu and Kavitha, 2017; Kavitha et al., 2014; Banu et al., 2017). Physical pretreatment methods utilize high-pressurized machines, unlike thermal pretreatment methods that utilize microwave irradiation, thermochemical liquidation, steam explosion, and enzymatic hydrolysis (Banu et al., 2018; Kannah et al., 2017a,b; Kavitha et al., 2018, 2016, 2015, 2013). Chemical pretreatment methods use bentonite and lime to maintain the pH of low pH-containing wastes. Bioreactors such as anaerobic sequencing batch reactors (ASBRs), continuously stirred tank reactors (CSTRs), upflow anaerobic sludge blankets (UASBs), and fixed-film reactors are currently utilized for anaerobic digestion. Conversion of food waste into energy is also achieved by an ethanol fermentation process. A wide variety of food wastes with different compositions are utilized for the production of bioethanol through ethanol fermentation process. Ethanol production of B30 g/L was achieved by pretreating food waste containing amyloglucosidases and carbohydrates with enzymatic hydrolysis (Moon et al., 2009). However, ethanol production from food waste requires more research to make it cost effective and economically viable. Another remarkable aerobic biological valorization technology is composting. This process enables a 40% reduction of waste volume by the action of microorganisms under favorable conditions such as pH, temperature, moisture, oxygen requirements, and C/N ratio. The resultant product is a nutrient-rich dark-brown, pathogen-free humus-like substance— compost. Compost adds multiple benefits to soil by enriching the nutritive value, increasing the water-holding capacity, encouraging the growth of additional microorganisms, and suppressing plant diseases. Composting as a valorization technique has been used for a long time and its commercialization has been accomplished. However, the collection of food waste from different locations, limited space availability, capacity of treatment facilities, and capital and transportation costs still limit the composting process. Variations in the quality of compost also affect its market value (Otles and Kartal, 2018).

16.4.2 Thermochemical conversion Conversion of waste into heat and energy is achieved using an incineration technique. Incineration is the process of combusting waste at a high temperature of 900 C
1100 C in the presence of an excess oxygen supply. The heat released from the combustion process can either be used in heat exchanger for heating process streams in industrial units or it can be used to run steam turbines to generate electricity. The process of incineration helps to reduce the volume of solid waste by 80%
90%. The traditional method of waste incineration released harmful gases such as carbon monoxide, sulfur dioxide, and oxides of nitrogen and other gases containing dioxins and furans. The noncombustible residual ash obtained after incineration contains concentrated inorganic matter and heavy metals, which require careful disposal. Therefore improved combustion technology and advanced controlled emission systems were developed to comply with stringent environmental regulatory rules and guidelines. The improvement in incineration technology with the added advantage of energy recovery has encouraged its application as an alternative fuel. Incineration of food waste for immediate energy recovery has not been greatly explored. There is limited study in this area owing to the high moisture level and the presence of highly noncombustible substances in food waste (Mardikar and Niranjan, 1995). In one of the studies carried out to estimate energy recovery from the incineration of food waste, the food waste was first dried

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prior to incineration along with municipal solid waste. The cost and benefit analysis showed that drying of food waste consumed energy of around 7.75 MWh per unit tonne of total solid food waste, while the energy generated from the incineration of food waste was around 37 kJ/g of total solid food waste (Kim et al., 2013). Incineration of food waste can therefore be a better option for food waste disposal and alternative fuel generation. Pyrolysis and gasification are other prominent advanced thermal treatment processes which convert food waste into fuel and other value-added products. In the pyrolysis technique, food waste is converted into bio-oil, biochar (devolatized residue), and gas (condensable hydrocarbon) in the absence of oxygen at a temperature of 400 C
600 C. In the gasification process, food waste is partially oxidized in oxygen-limited conditions (800 C
900 C) to yield a mixture of combustible gas hydrogen and carbon monoxide (syngas). The gas mixture can be directly combusted or used as fuel in gas turbines and gas engines, while the syngas can be utilized as feedstock for the production of chemicals such as methanol (Pham et al., 2015). Although the process of gasification is better than incineration, the process is complex and involves several chemical and physical interactions occurring at temperatures .600℃. The temperature can vary according to the characteristics of the food waste and the type of reactor. Syngas (85%) produced during the gasification process is rich in hydrogen and can serve as a precursor for valuable chemicals and an efficient fuel if carried out in the presence of a controlled amount of oxygen. Gasification of food waste is more cost effective than the incineration process and does not cause any emissions. Food wastes are usually rich in carbon compounds, therefore pyrolysis and gasification processes are good options for mitigating the food waste issue. However, some characteristics of food waste such as the content of volatile compounds, elemental composition, moisture level, lower heating value, bulk density, ash content, and size can prove to be limiting factors for the process and gas yield. Preprocessed food waste has been demonstrated to give a higher yield. A high moisture content in food waste is a major issue in most conversion techniques but it can be perfectly utilized in another thermal technique—hydrothermal carbonization (HTC). In the HTC process the wet substrate undergoes hydrolysis followed by condensation, dehydration, and finally carboxylation. HTC has gained much popularity because of several undeniable advantages, such as it works at relatively lower temperature (180℃
350℃) and autogenous pressure, small treatment footprints, wet process, and converts food waste into energy-rich compounds, release of no foul odors, and greater reduction of waste volume. HTC was first experimented with in 1913 for converting cellulose into coal (Libra et al., 2011). The reaction time of HTC is only a few hours, unlike other processes which take days for completion. The liquid portion obtained from the HTC process is rich in nitrogenous compounds and it can be used as a potent fertilizer. The main product obtained from the process of HTC (hydrochar) is quite energy dense and is massively carbonized, making it equivalent to lignite coal. It can be utilized as a substrate for carbon fuel cells. The prototype of its surface functionalization study showed it to be beneficial as an adsorbent for toxic environmental pollutants. It can also be used in soil improvement strategies.

16.5

Impact assessment of food waste valorization technologies

Valorization of food waste has captured the attention of policymakers and researchers over the past few decades. In the present scenario, various environmental associations have developed a keen interest in demonstrating valorization processes and their long-term impacts. The rationale behind the assessment of such impacts is to describe the contemporary position of the valorization process. The food waste valorization strategies are evaluated through societal (feasibility) and economic impacts (costs) as well as through their environmental performance (Fig. 16.2). This involves the complete life cycle analysis (cradle to grave), that is, a technique to assess the potential impacts associated with a product or process during the course of its life cycle. A detailed evaluation of impacts associated with different valorization processes is covered in this section.

16.5.1 Issues in relation to valorization of food waste to compost Composting of food waste is a biodegradation process in which organic matter present in food waste is mineralized and humified. As a result, stabilized organic matter is produced which is comprised of humic-like substances and is generally free of phytotoxins (Lopes et al., 2012). Around 40% of food waste is processed to compost in most Asian countries, for example, Japan, Taiwan, and South Korea (Woon and Lo, 2016). Since synthetic fertilizer has a high market value of over $150 3 109 by 2020, it is high time these synthetic fertilizers were replaced with food waste-derived biofertilizers. Subsequently, this will reduce the dependency on synthetic fertilizers (Research and Markets, 2017). In addition to the replacement of synthetic fertilizers, diverting food waste from landfills to compost is considered as an environment-friendly approach. This is because it reduces landfill emissions of GHGs and increases soil fertility and

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FIGURE 16.2 Valorization of food waste into high-value products and its associated impacts.

plant production (Schott et al., 2016). Irrespective of the benefits, valorization of food waste into compost suffers from certain challenges related to its heterogeneous composition, odors, various parameters (e.g., oxygen supply, moisture content, carbon to nitrogen ratio, particle size, microbiology of process, temperature, etc.) controlling the composting process, as well as gaseous emissions (Cerda et al., 2018). These challenges hinder the expansion of robust large-scale valorization processes (Poeschl et al., 2010). Also, a life cycle assessment study of food waste during the operation stage for composting indicated a large number of environmental impacts, in particular terrestrial eutrophication (80%), terrestrial acidification (60%), fossil fuel depletion (60%), and ozone depletion (90%) (Salemdeeb et al., 2018). The production of a superior quality of compost necessitates proper control and management of the valorization process. As already discussed, food waste is a complex mixture of different components containing a high organic to ash ratio, high moisture content, and an amorphous physical structure (Cerda et al., 2018). Nonetheless, the composition of food waste can be highly variable owing to its generation source. Han and Shin (2004) reported a moisture content of 80%, volatile solids to total solids ratio (VS/TS) of 95%, and carbon to nitrogen ratio (C/N) of 14.7 in dining hall food waste. According to Rao and Singh (2004), food wastes emanating from households, fruits and vegetable markets and juice shops contained 85% , 89% and 36.4% of moisture, VS/TS and C/N ratio, respectively. As a result of the difference in the composition of food wastes, the final products are required to pass multiple maturity tests. Furthermore, some of the food waste contains various impurities such as glass and plastic, which necessitates the need for segregation by preprocessing. Preprocessing adds to the cost of the process and also leads to a reduction in plant capacity. Moreover, the quality of compost also suffers from such impurities. The development of anoxic/anaerobic zones inside the solid matrix leads to the production of GHG, nitrous oxide (N2O), and methane (CH4) (Nasini et al., 2016). CH4 gas is known to be a principal GHG. IPCC declared that for a 100-years horizon, the global warming potential (GWP) of CH4 was found to be 23 times greater than with CO2 (Houghton et al., 2001). During composting, not only can production of N2O and CH4 take place but also release of other gases including CO, NOx, NH3, H2S, volatile organic compounds (VOCs), and aqueous vapor (Adhikari et al., 2013; Cerda et al., 2018; Hao et al., 2004; Peigne´ and Girardin, 2004). The VOCs and NOx accounted for even more global warming potential—as high as 2000 times that of CO2 (Andersen et al., 2010; Berntsen et al., 2005). NOx is emitted as a result of building up of undesired anaerobic conditions, which further cause denitrification (He et al., 2000; Mahimairaja et al., 1995). In the process of denitrification, reduction of nitrate (NO2 3 ) to nitrous oxide (N2O) and molecular nitrogen (N2) occurs under anaerobic conditions at low pH in the presence of organic C. Besides N2 formation, nitric oxide (NO) and nitrous oxide (N2O) are also produced during the composting process (Peigne´ and Girardin, 2004).

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The NO is considered a primary tropospheric pollutant, whereas N2O is known to be an ozone-depleting substance as well as a potent GHG whose global warming potential is recorded to be 320 times greater than CO2. VOCs are the chief source of odorants that are considered as by-products released at the time of composting which are thereby a nuisance to the environment. In severe cases, emission of odors from composting plants can results in their closure or necessitate the enactment of preventive measures. A variety of odorous molecules are emitted, including sulfur compounds (organic sulfides and mercaptans), aromatics, alcohols, volatile fatty acids, aldehydes, amines, ammonia, ketones, terpenes, and ethylbenzene (Ma et al., 2013; Mustafa et al., 2017). These compounds are primarily emitted from plant debris and microorganisms (such as bacteria, fungi) during the aerobic degradation process of composting and are known to exhibit low water solubility. The majority of these compounds are released during the initial stages of the composting process, specifically at the shredders and also at the early active composting period (Eitzer, 1995). The volatile sulfur compounds (VSCs) are basically produced in response to inadequate aeration during composting. VSCs have a low detection threshold with a strong odor. Thus, these compounds can cause odor pollution even if present at very low concentrations (Yu et al., 2007). It has been reported that H2S alone accounts for 39%
43% of the different sulfur compounds produced during composting (Higgins et al., 2006; Zhang et al., 2013). Furthermore, some VOCs such as ketones, alcohols, organic acids, and esters are released from food waste as a result of incomplete aerobic degradation (Font et al., 2011). Numerous factors, namely, C/N ratio, temperature, pH level, particle size, porosity, aeration rate, moisture content, and microbial communities play an indispensable role during the composting process. To produce efficient compost, these factors must be maintained properly (Adhikari et al., 2008; Kumar et al., 2010). These factors are also reported to be responsible for odor generation during food waste composting. Proper aeration, that is, supply of oxygen, is one of the critical requirements for the composting process to occur. The aeration rate affects microbial activity and gas emissions (Guo et al., 2012; Lin, 2008). An aeration supply in the range between 0.2 and 0.6 L/min/kg OM is shown to be vital for improvements in odor and NH3 release, along with the production of mature compost (Zhang et al., 2016; Zhang and Sun, 2016). A low aeration rate of less than 2 L/min/kg OM, however, cause a reduction in degradation rate, moisture loss, and decline in overall NH3 generation (Guo et al., 2012). During food waste composting, insufficient oxygen is always responsible for odor gas production (Scaglia et al., 2011). Apart from the aeration rate, pile temperature also plays an insignificant part in the volatilization of odor gases (Pierucci et al., 2005). According to the study by Pierucci et al. (2005), low O2 concentration together with high composting temperature result in emissions of large quantities of VSCs. Furthermore, NH3 release from food waste is controlled by the composting pile’s pH and temperature. Thermophilic (high temperatures) conditions and high pH are regarded as favorable conditions for the NH3 emissions (Pagans et al., 2006). Ammonia in the natural environment is deposited on land, causing its acidification (Pearson and Stewart, 1993). It can also adversely affect vegetation and, through denitrification, can be converted into a potent GHG, N2O (Krupa, 2003). The moisture content is associated with the aeration rate and microbial activity. Food waste has a high moisture content which results in lengthening of the time required for its treatment or it can lead to low degradation efficiency. Such high moisture contents can limit free air space which results in anaerobic conditions. This leads to the generation of foul odors (Chang and Hsu, 2008).

16.5.2 Issues in relation to valorization of food waste to biogas Anaerobic digestion is a viable approach for simultaneous food waste treatment and renewable energy production in the form of biogas (Weiland, 2010). In Germany, Austria, and Nordic countries, the organic fraction of municipal solid waste, which is generally composed of food waste, is collected in plastic bags (Ba´tori et al., 2018). In doing so, there is a huge risk of contamination of biogas plants with plastic. Though pretreatment of food waste involves pressing of food waste along with the plastic bags through a star press, this method is rather uneconomical. Since food waste is an amalgamation of different components, the development of a robust biogas production plant for treatment of such waste is itself a major challenge. For example, in India, one type of food waste, such as kitchen waste, can contain different types of spices including red chili, turmeric, garlic, coriander, cinnamon, black pepper, and clove which affect the anaerobic digestion process (Sahu et al., 2017). Biochemical compounds (including allicin in garlic, cinnamic aldehyde in cinnamon, eugenol in clove) present in the spices are responsible for their antimicrobial propˇ erties (Skrinjar and Nemet, 2009). Some of these compounds possess high antibacterial activity against Gram-positive and Gram-negative microorganisms responsible for fermentation and methanogenesis in the anaerobic digestion process, which affects the biogas production potential of kitchen waste (Ceylan and Fung, 2004). Sahu and her colleagues

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reported the reduction of more than 85% cumulative biogas yield in the presence of cardamom, cinnamon, and clove. In addition, the presence of metal salts in spices also inhibits the fermentative and methanogenic population in the digester due to their cytotoxicity. Heavy metals either bind to the thiol and other functional groups present on the protein molecules, which in turn disrupt the enzyme structure and function, or they replace the enzymes’ natural prosthetic group metals responsible for methanogenesis (Yang et al., 2011). Likewise, another food waste, citrus waste, is also unfit for anaerobic digestion. Citrus food waste contains acid that is known to affect the digestion process (Kaparaju and Rintala, 2006). It has been found that the microbial activity of microorganisms in the digester is reduced due to the antimicrobial action of limonene present in citric food waste (Espina et al., 2013). During the processing phase, some CH4 is emitted as a result of leakages in the fermentation reactor. Also, in the stationary engine, some of the CH4 is noncombusted. Due to this, as much as 40% of the CH4 is emitted in the processing phase (Negro et al., 2017). Moreover, at the time of biogas combustion in a stationary engine, emission of GHG (NOx) might occur.

16.6

Preventive measures taken during food waste valorization

The production of value-added products from food waste requires the alteration of the original resource. For this, different preventive measures must be taken at every step of valorization of different food wastes. During anaerobic digestion, food waste is collected in plastic bags, which leads to the problem of plastic contamination in the biogas plant. To prevent such contamination, the use of bioplastic bags for collection is considered to be a more feasible approach. Bioplastic is prepared from renewable biomass sources such as agricultural, vegetable fats and oils, cellulose, and corn starch waste. Hence, as it is derived from renewable sources, it is easy to degrade compared to other collection systems such as paper or plastics. Different methods are available in the literature for the degradation of biodegradable plastics including thermo-oxidative degradation, photodegradation, and biodegradation (Amass et al., 1998; Shah et al., 2008). Certain food wastes, namely, citric waste is difficult to valorize because of the presence of acid, which affects the microorganisms in the anaerobic digester. One of the approaches to deal with this problem is the removal of Dlimonene from citrus waste (Zema et al., 2018). To tackle this challenge citrus wastes can be codigested with manure (Negro et al., 2017). In kitchen wastes, the emission of various odorous molecules, like NH3 and H2S, poses serious health problems. To tackle this situation, the addition of bulking agents or additives is essential. The bulking agents can bring the moisture content and the C/N ratio within the range needed for composting. These range from minerals, organic, biological substrates, or a mixture of different substrates (Awasthi et al., 2018; Himanen and Ha¨nninen, 2009; Jurado et al., 2015; Zhang et al., 2017). These bulking agents in addition to acting on the compost’s physical structure (aeration) can also have foreseen or unforeseen effects on composting parameters. They help in improvement of the composting process through a reduction of leaching and gas emissions and also speed up the degradation of organic matter (Barthod et al., 2018; McCrory and Hobbs, 2001; Sa´nchez-Garcı´a et al., 2015). In most parts of China, cornstalks are mostly used as a bulking agent (Guo et al., 2012; Yang et al., 2013). They are known to increase the permeability of air in the piles of composting waste through an improvement in the size and numbers of interparticle voids (Yuan et al., 2015). Cornstalks also reduce the amount of H2S emitted from the food wastes. In order to reduce ammonia in the waste, some pretreatment is required. For this, certain chemicals, for example, ferric chloride, have been extensively used. Adding FeCl3 to kitchen waste is also reported to reduce the H2S content during the anaerobic valorization process. A reduction in the concentration of H2S in the biogas by 20%
30% was documented by Dhar et al. (2011) during chemical pretreatment of activated municipal waste with FeCl3. It has been seen that the FeCl3, by reacting with dissolved sulfide, forms elemental sulfur and sulfates, thereby resulting in a decrease in the concentration of dissolved sulfide (Walton et al., 2003).

16.7

Planning strategies and new innovative plans for food waste valorization

Planning for the management of food waste valorization is an emerging issue in the present scenario. The information emanating from the assessment of various issues from the valorization of food waste sheds light on the importance of planning strategies for effective conversion of food waste into products and energy. This might also enable researchers and policymakers to search for new solutions to food waste valorization technology so as to achieve minimal environmental impacts. Moreover, time to time checking and updating of the regulations implemented by governments for biogas facilities should be done so as to ensure effective meeting of environmental protection goals in inventive and

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flexible ways. Researchers also advocate the need for collaboration between various technical and social scientists (Ingrao et al., 2018a,b). This will help in identifying and addressing the relevant questions related to the bioeconomies of countries. In this context, advanced food waste valorization technologies must be adopted to achieve the dream of sustainable development together with a circular economy.

16.8

Conclusions

The food waste problem is exponentially increasing, especially in developing countries. Food waste, when dumped into landfills or incinerated, can cause environmental problems. After a thorough analysis of different management practices, it can be evidenced that the valorization of food waste is beneficial for the production of value-added products. This energy-focused treatment of food waste has witnessed an improvement in the sustainability performance of management technologies, but the challenges faced during the valorization process cannot be overlooked. Gas emissions, odor generation, eutrophication, and depletion of ozone are some of the aforementioned impacts which are associated with the valorization technologies. These environmental and health impacts provide a continuous hindrance to the successful implementation of valorization technologies.

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Chapter 17

Environmental impacts and sustainability assessment of food loss and waste valorization: value chain analysis of food consumption Preethi1, S. Kavitha2, J. Rajesh Banu3, P. Arulazhagan4 and M. Gunasekaran1 1

Department of Physics, Anna University Regional Campus Tirunelveli, Tirunelveli, India, 2Department of Civil Engineering, Anna University

Regional Campus Tirunelveli, Tirunelveli, India, 3Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India, 4

Centre of Excellence in Environmental Studies, King Abdulaziz University, Jeddah, Saudi Arabia

17.1

Introduction

Food waste management has been introduced by various policies to assure recycling, optimization of resources, and mitigation of the impact on the environment. global resources are limited and requirements need to be fulfilled in a sustainable manner for future generations. The life of the products starts with selecting the resource, its processing, its consumption, and ends with its disposal. The life cycles of products have major impacts on the environment, depending on the consumption pattern, loss of products, and the sustainability of the resource. Many tonnes of foods are wasted daily, having a great negative impact on the environment. A sustainable economy can be maintained by implementing food waste to energy conversion technologies. These technologies have social and environmental benefits as compared to the traditional disposal options such as landfilling and incineration. The impact on the environment due to food loss or waste can be assessed by life cycle analysis (LCA). This consists of major steps such as defining the goal of the study and the functional units, setting out the system boundaries for input and output energy and material flow, assessing the impact associated with each process, followed by the interpretation of results. Apart from LCA, other environmental assessment methods include material flow analysis, energy or exergy analysis, etc., which help to maintain the sustainability of each stage of the food supply chain (FSC). Exergy analysis in food-based industries evaluates the efficiency of processes based on thermodynamic laws to achieve sustainability. An exergetic indicator helps to evaluate high-grade products during production and processing phases in industries. The flow of the process of food production within a constrained system was assessed by material flow analysis. Life cycle costing (LCC) approaches have been widely used to analyze the economic impacts. This chapter introduces the assessment of food waste in a sustainable manner using LCA, exergy analysis, and mass flow analysis. Food waste management has been carried out by different valorization methods in LCA. LCC approaches were included to analyze the cost benefits of food waste management. This chapter also describes the sustainable designs or modeling of structures for FSC and the major challenges and suitable recommendations for the future.

17.2

Life cycle analysis (LCA) of food waste: an overview

According to UNE-EN ISO 14040, LCA is a technique used for assessing environmental and potential impacts associated with processes, products, or services. It is considered to be the best tool to evaluate the environmental impact of products and its main goal is to identify the raw materials (waste) and energy. The consequences on the environment were evaluated using life cycle thinking (LCT) for food waste management systems. Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00017-1 Copyright © 2020 Elsevier Inc. All rights reserved.

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LCA identifies the crucial points by which the improvement of an environmental management system can be done. Sustainable measurements for the food industry and food chain can be done effectively with the help of LCT. The participation of consumers results in food waste prevention and provides better waste management.

17.2.1 LCA methodologies or approaches 17.2.1.1 Scope The purpose of undergoing LCA analysis should be defined, including the purpose of the study, system boundaries, functional units, and presumptions. During this phase the data quality and the critical review process are undertaken in depth. The major goals are to compare the different products, to identify possibilities for improvement, and to identify the life cycle of the product in meeting the eco-labeling criteria.

17.2.1.2 Functional unit The functional unit enables us to combine the output and input system for a reference unit. It enumerates the performance provided by the system and thus shows the evidence for the relationship between the input, output, and major impacts on the environment. The functional unit plays a major role in the food waste to energy conversion system as these systems provide an output as energy generation, as shown in Figs. 17.1 and 17.2. In the case of energy or fuel generation, functional units can be used to compare the alternative methods of energy production. The major obstacle to a food waste functional unit is that it does not have any universal definition and the definition of units for environmental impact assessment include the direct and indirect assumptions on the characteristics of waste streams. The consumption patterns in different regions and seasons have a great impact on the composition of food waste, which in turn affects the LCA output.

17.2.1.3 Biological techniques The combinations of biological and technical processes are distinct challenges during the conversion of food waste to energy. The biological process cannot be completely controlled throughout the system. The excessive emissions due to

FIGURE 17.1 System boundaries of food waste for the generation of energy as a functional unit.

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FIGURE 17.2 System boundaries of food waste for the treatment of waste as a functional unit.

the conversion techniques such as the digestion process, fermentation process, and transestrification process have a larger impact on the environment and the nutrient and energy recovery are drastically reduced. These impacts are controlled in the energy generation process by maintaining the essential parameters responsible for impacts during conversion techniques.

17.2.1.4 System boundaries System boundaries are the fixed boundaries and they illustrate details about the materials and the various processes involved in the system under investigation. In LCA, the waste modeling systems use the “zero-burden approach,” where the food waste in the system has no environmental impact (Ekvall et al., 2007). This approach is compatible with the objectives of the food waste to energy system. Based on the data availability and degree of impact, the collection, segregation, transportation, and storage of food waste may or may not be included. The identification of the system boundary is difficult to define in LCA modeling of food waste conversion technology. It is difficult to include all the gaseous and particulate emissions generated during food waste processing. Based on the objective of the LCA studies, some emissions are excluded and/or simplified. The biofuels and bioenergy system boundaries will vary depending on the objective of the study. The comparison of fossil-based fuels and biobased fuels can be done when the system boundary is extended to the combustion of fuel. This is known as a cradle to grave approach. The widely used approaches have been described by Vertech group SARL (2013): G

G G G

G

Gate to gate: specialized unit process which includes the analysis of reception of the raw materials to the completion of the production process. Cradle to gate: this includes the selection of resource, production, modification, and transportation. Cradle to grave: this includes scope of assessment of life and end of product. It is applied to all commodities. Gate to grave: this gives an idea about the end of life after production. Product market studies uses this type of approach. Cradle to cradle: this is complex and includes all the steps listed above, with the most tedious step being reusing or recycling the residues produced.

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17.2.1.5 Credits of coproducts The food waste to energy conversion technologies includes two main functions as described earlier, that is, treatment of food waste and energy generation. These systems are able to produce coproducts such as fertilizers, animal feed, soil conditioners, and livestock bedding. System expansions are the most preferred methodology, where the system boundaries are expanded to inculcate the processes that are evaded for coproduct generation. The coproduct, such as electricity, is also generated and the major assumption is to create an equal amount of electricity produced by conventional means. The credit is provided to avoid the impacts associated with the amount of electricity produced (Schott et al., 2016). In the case of biofertilizer as a coproduct, the systems are expanded to include the credit and, in animal feed, the expansion of the system shows the impact of results from feeding coproducts rather than feeding traditional products to animals.

17.2.1.6 Life cycle inventory analysis This phase involves the movement of output and input of material, mass, and energy in the process within fixed boundaries. The raw material and energy are to be considered as inputs and emissions to all natural sources are considered as output. Inventory analysis consists of issues such as data collection, refining system boundaries, calculation, verification of data, relating data to the specific system and allocation. In collection phase, the data are used for the preparation of consumed material, waste, and emissions in each phase of the life cycle. These databases are bought together with LCA software. The second step involves system boundary refining and the results are documented for sensitivity analysis. By using the appropriate data, the calculations have to be carried out based on the information available with this being the next step in inventory analysis. The quality of the data are improved by systematic data validation. The last step is the comparison of the obtained data with the reference flow. In some food production processes the inputs are either renewable or nonrenewable resources, raw material, etc., and the outputs are products, emissions to water, air, and land, and solid waste generation (Roy et al., 2009). It consists of the collection and calculation of data on usage of resources and emissions in each process of the life cycle in products, and includes the construction of a flow chart according to its system boundaries, the data collected, the emissions, and the use of resources calculations. Opatokun et al. (2017) underwent a life cycle inventory (LCI) of food waste which included the flow of energy and material for analysis of the end-of-life scenario. The data were collected from an anaerobic digestion (AD) plant for food waste treatment in Sydney, laboratory test for analysis of samples, and using the Ecoinvent 3.1 database for standardization. The database was validated and selected for categorization of the modeling for by-product and disposal actions.

17.2.1.7 Life cycle impact assessment The major goal in environmental impact assessment is to understand and assess the impacts of the environment on LCI data. Life cycle impact assessment (LCIA) is based on abiotic resources, biotic resources, land use (LU), global warming, stratospheric ozone depletion, ecotoxicological impacts, human toxicological impacts, photochemical oxidation, acidification, eutrophication, and the environment. International Life Cycle Data System (ILCD), ReCiPe, Eco-Indicator 99, Cumulative Exergy Demand, etc. are different methods employed for the analysis of impact assessment. Generally, the impact assessment can be done in two types: midpoint and endpoint methods. Midpoint methods are used to calculate specific impacts by weighted exchange with the natural environment quantified in the LCI. These impacts include climate change, freshwater use, natural LU, freshwater eutrophication, ozone layer depletion, etc. Endpoint methods are the combination of several midpoints by means of a weighted sum to examine the overall impact scores. This allows the interpretation and identification of the environmental hot spots and simplifies decision-making (Bare et al., 2000). The average greenhouse gas emissions due to waste generated by food-processing units at each process in the supply chain were studied by Monier et al. (2010). The calculations for greenhouse gases from food waste were also given by WRAP (2013a) and FAO (2013). Global warming is used as an indicator to examine the impact on the environment due to different options of food waste. The evaluation of risk impact is done for the redisposal of by-products (Kim et al., 2011). The food waste generation in Korea during 2006 was about 13,372 tonnes, and there were various disposal options. In order to assess the excluded environmental impact of by-products, the system boundary was simulated (Lee and Park, 2005). The greenhouse gases responsible for global warming were converted to equivalent CO2. One of the harmonized indicator approaches for the assessment of environmental impact is the ReCiPe method (Goedkoop et al., 2009). Three impact categories, that is, climate change, particulate matter formation, and terrestrial acidification, were studied in order to understand their relevancy in waste management sectors (Evangelisti et al., 2014). The overall environmental impact appeared to be negative. The data from inventory steps were used in GaBi software in order to calculate the environmental impacts based on plan, inputs, and outputs in the system. The impact categories like acidification potential (AP),

Environmental impacts and sustainability assessment of food loss and waste valorization Chapter | 17

363

eutrophication potential (EP), global warming potential (GWP), human toxicity potential (HTP), and photochemical ozone creation potential (POCP) were analyzed and calculated with a GaBi tool (Ghinea et al., 2012). In LCA, the AP is given in kg sulfur dioxide equivalents (SO2 equivalents). Emissions of nitric oxide (NOx), ammonia (NH3), phosphorus (P), and nitrogen (N) are responsible for eutrophication and are expressed in kg PO32 4 equivalents in LCA. GWP is responsible for the emissions of carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), dinitrogen monoxide (N2O), chlorofluorocarbon (CFCs), etc., and are expressed as kg CO2 equivalents. HTP is related to volatile organic compounds (VOC), particles, heavy metals, photochemical oxidation potential (POPs), NOx, and sulfur dioxide (SO2) emissions. VOCs and carbon monoxide (CO) are disintegrated into nitrogen oxides (NOx). For midpoint indicators in Europe, the LCIA has been undertaken by international reference life cycle data system (ILCD) impact assessment in order to assure the quality and consistency of the life cycle. The resource extractions, waste, and emissions are expressed in terms of their contribution to impact categories. The LCI data consist of several inputs and outputs that are characterized according to their environmental impacts (Bauman and Tillman, 2004).

17.3

LCA analysis of various biological food waste valorization processes

17.3.1 Anaerobic digestion: biogas recovery AD is one of the most widely accepted techniques for the biodegradation of food waste using bacterial consortia under controlled temperature and pH (Pham et al., 2015). The digestate can be used as fertilizer as it is rich in nutrients. The major food waste sources for AD are food processing waste water (Ebner et al., 2016), restaurant waste (Opatokun et al., 2017), and household food waste (Bernstad and la Cour Jansen, 2011). The food waste characteristics have an impact on methane composition in biogas production as well as nutrient content in digestate. Food waste rich in fats and carbohydrates has a higher biomethane potential and water- and lignin-rich waste has lower biomethane potential (Ebner et al., 2016). The biogas produced can be used for the generation of heat and electricity through cogeneration and this has a positive environmental impact. The complete system boundary of the AD process is shown in Fig. 17.3.

FIGURE 17.3 System boundary diagram for anaerobic digestion of food waste.

364

Food Waste to Valuable Resources

A system using food industry wastes as raw material revealed that GHG emissions can be reduced by 75%
90% using biogas-based fuel with CO2 contributing about 60%
75% and CH4 to 25%
40% (Borjesson and Berglund, 2006). Cogeneration of heat and power also shows a similar trend in the environmental effect. The GWP is normally reduced by 50%
80% when conventional fuels are replaced by biobased fuels (Borjesson and Berglund, 2006). In a study by Woon et al. (2016), the impact categories due to the valorization of food waste to biogas were advantageous in regard to climate change. The fuel generated from 1080, 1800, and 3600 (tonnes per day) tpd food waste contributes 1.9%, 3.1%, and 6.2% of GHG emissions reduction in the transport sector, respectively. Table 17.1 shows different LCA studies for the AD of food waste. Coproducts like organic fertilizers and compost have greater impacts on LCA output. The direct emissions in AD are caused by biogas leaks in tanks or piping (Ebner et al., 2016). It is estimated that the fugitive emission must range between 0% and 10% of the biogas produced. Since the GWP of methane is higher, the uncontrolled release of methane may lead to greater impacts on the environment. The land application of digestate can be used as fertilizer during plantgrowing seasons. The stored digestate can emit CH4, N2O, and NH3 to air depending on climatological conditions. The digestate emission from pond storage has been estimated as 1.5 m3 CH4/tonne (Ebner et al., 2016). The liquid digestate needs additional energy for transportation and also results in the implicit or explicit emissions of contaminants to air, water, and soil.

17.3.2 Fermentation technologies: bioethanol recovery LCA studies for the analysis of bioethanol production from different raw materials have been carried out. Most of these studies have concluded that the production of bioethanol shows good environmental performance, whereas the use of ethanol in practical applications has some adverse effects (Laca et al., 2011). If the objective of the study is to compare the ethanol production technologies then the functional unit will be the unit volume of ethanol (Schmitt et al., 2012). The system boundaries include all the outputs and inputs in the production of unit volume of ethanol. In food waste to energy conversion technologies, the environmental impact from bioethanol production varies due to the varying food waste composition and the system boundary (Borrion et al., 2012). The complete system boundary of a fermentation process is shown in Fig. 17.4. The GWP and cumulative energy demand (CED) were considered till date to assess the environmental impacts of bioethanol production from food waste. The diversion of food waste as an animal feed or as compost may lead to an impact on the system (Ebner et al., 2014). High-sugar industrial food waste, such as banana or pineapple waste (Upadhyay et al., 2013) and fruit syrups (Ebner et al., 2014), does not need additional energy for the pretreatment process. High starch-rich food waste can be easily converted to bioethanol using yeast. Yeasts such as Saccharomyces cerevisiae and Kluyveromyces sp. were used for ethanol production from food waste rich in glucose and lactose. The composition of food waste determines the need for additional pretreatment to obtain the sugars which are easily converted to ethanol. Rigorous treatments are not necessary to convert food waste to ethanol, whereas the yield and purity can be improved greatly by the autoclave method (Kiran et al., 2014). Table 17.2 shows the different LCA studies for the fermentation of food waste. The bioethanol production process, where the complex sugars are converted into simple sugar by the action of enzymes, followed by the bacterial fermentation, is known as separate hydrolysis and fermentation, whereas the hydrolysis and fermentation takes place simultaneously in simultaneous saccharification and fermentation. The major saccharifying enzymes used in bioethanol production are α-amylase, β-amylase, glucoamylase, and cellulase. The industrial enzyme supplier Novozyme used the cradle to gate approach for the environmental assessment of the enzymes used in bioethanol production (Nielsen et al., 2007). Lignocellulosic ethanol production has a cellulase dosage 25
250 times higher than the amylase (Dunn et al., 2012). The purification of ethanol is done by a distillation method which is energy intensive. The environmental impact related to the distillation is dependent on the electricity sources and emissions. The solids that remain after ethanol production are converted into coproducts. These solids have lower lignin content and thus the use of coproduct as energy is less profitable and so they can be used for soil conditioning.

17.3.3 Transesterification: biodiesel production The conversion of vegetable oil or animal fat by the process of transesterification into useful product in the form of diesel is known as biodiesel. The crisis in energy sources has led to the efficient use of food waste as a source of biodiesel production, and this also leads to a decrease in the production cost. The most common transesterification process is the

TABLE 17.1 LCA analysis of the anaerobic digestion process. S. no.

Source/type of food waste

Mode of digestion

Functional unit

System boundaries

Environmental impact

Impact assessment

1

University of Toledo Food waste

Anaerobic digester

Food waste management annually at University of Toledo

Cradle to grave

GWP

G

G

G

2

3

Singapore eatery Food waste

Cattle manure, glycerin, corn stover, rye, and wheat.

Anaerobic digester

Farm scale anaerobic digester

1000 tonnes of Singapore eatery FW and 4400 tonnes of wet sludge

Cradle to grave

1 kWh of electricity

Cradle to gate

Ozone depletion, GW, eutrophication, acidification

G

Results/ interpretation

Four configuration shows higher greenhouse gas emission throughout the process The order of emission is 1 . 2 . 3 . 4, where 1 is the landfill disposal and 2, 3 and 4 are digestion processes with or without pretreatment Manufacturing and operational emissions were similar for 2, 3, and 4

G

Ozone depletion was found to be high with neutral codigestion than mono-digestion

G

G

G

GHG

G

G

In biomass only (BO) scenario the GHG emission was reduced by 88% Biomass and glycerin (BG) scenario the reduction was 12%. The emission in BG is 10 times greater than BO ad the emission factor is glycerin

G

G

Byproducts formed

References

In terms of cost, greenhouse gas emission and energy, the food waste treatment technologies rather than landfill are appropriate Two-stage anaerobic digestion system pretreated ultrasonically provides the better treatment

Methane

Franchetti (2013)

Environmental burden decreases with increase in energy generations The decrease in fossil fuel use and electricity were enhanced

Biogas

Tong et al. (2019)

The generation of power and heat can reduce the total GHG emissions in this system as compared to the coal power plant Sensitivity analysis shows economic feasibility AD system

Electricity

Aui et al. (2019)

(Continued )

TABLE 17.1 (Continued) S. no.

Source/type of food waste

Mode of digestion

Functional unit

System boundaries

Environmental impact

Impact assessment

4

Household food waste

Anaerobic digester

1 tonne of food waste

Cradle to gate

TA, PMF, ME, NLT, ALO

G

G

G

5

Manure

Laser radiation in anaerobic digestion

useful energy

Cradle to gate

GHG (CH4 and N2O)

G

G

6

Melton city council

Anaerobic codigestion

To collect, manage and treat one year’s garbage, food and garden waste sewage sludge

Cradle to grave

FFDP, AP, GWP, ADP, ODP, Htox, EP, POP

G

G

G

Results/ interpretation

Byproducts formed

References

It has lower environmental impacts than incineration and landfill with energy recovery across all categories except ME, PMF, TA and ALO, NLT Recipe model has been used for impact assessment The environmental benefits are significant compared to incineration and landfill

G

Production of electricity and fertilizers has net negative GHG emissions of 239 kg CO2-eq./t and saves 2 GJ/t in primary energy demand (PED)

Electricity

Slorach et al. (2019)

The environmental impact was evaluated by considering the greenhouse gas emissions, global warming potential, energy consumption, biogas production and net energy There is no significant differences among all treatments in terms of environmental impact

G

The photo biostimulation of anaerobic bacteria using 256 laser irradiation has no negative impact on environment Anaerobic digestion is considered as a better emission mitigation strategy

Methane

Abdelsalam et al. (2019)

Sima Pro 8 was used for LCIA The GWP is smaller since the landfills can generate and capture more gases The ODP and EP have large impacts on landfilling and it gets reduces in this system

G

The GWP of this system is smaller and it shows negative GWP when the sorting of households were enacted The greenhouse gas emissions are 5.95 3 106 kg of CO2-eq

Bioelectricity

Edwards et al. (2018)

G

G

7

8

9

Sutherland shire council

Restaurant and hotel food waste from Jiangsu Province

Food wastes from town of Brookhaven

Anaerobic codigestion

Biogas plant

Anaerobic digester

To collect, manage and treat one year’s garbage, food and garden waste sewagesludge

Cradle to grave

Tonne of food waste treated in the system

1 tonne of residential residual MSW collected curbside, with a 100 year emissions time frame

GWP, FFDP, AP, ADP, ODP, Htox, EP, POP

G

Food waste and electricity as material and energy input, and energy and product as outputs

GWP, AP, EP, HTox, e toxicity

G

Cradle to gate

GWP, ODP, TA, TE, FE, ME, ARF

G

Food waste from the Srinakharinwirot University of Thailand

Biogas plant

1 MJ was selected as the functional energy unit of the biomethane produced

G

G

G

Well to wheel

G

The GWP is smaller in this cases too. The greenhouse gas emissions are 1.29 3 107 kg of CO2-eq

Bioelectricity

Edwards et al. (2018)

Midpoint methodology have been used with sigma pro 8 for identifying the impacts of 5 major burdens

G

The integrated food waste system discussed based on LCA and LCIA approaches The operation and management were suggested by the integration of LCA and EC analysis

Bioelectricity

Jin et al. (2015)

AD is better options for the sourceseparated treatment of food waste It provides a greater environmental benefit with lesser burden

Biogas

Thyberg and Tonjes (2016)

Smallest GHG emissions in biomethane productions Pretreatment and fermentation provides higher impact on GWP, RC, AC, EG The digestate provides NPK for fig fertilization

Biomethane

Koido et al. (2018)

G

G

10

Sima Pro 8 was used for LCIA GWP is higher due slower degradation and fugitive emission of gases to the atmosphere

GWP, RC, TA, EG, GHG

G

EASETECH was used for impact assessment GW, TE, and ME are positive and ODP, TA, FE, and ARF are negative AD is best for all categories of impacts except ME The saving in GW in AD provides net benefit in all other impact categories

G

Impact categories assessed through MILCA software and LCIA through Endpoint modeling version 2

G

G

G

G

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Food Waste to Valuable Resources

FIGURE 17.4 System boundary diagram for fermentation of food waste to ethanol.

reaction between triglycerides and alcohol in the presence of catalyst (Mata et al., 2010). During this process, the oils are reacted with methanol in the presence of catalyst at a defined temperature and pressure, producing biodiesel or glycerol. The amount of catalyst required in the transestrification process is largely dependent on the purity of the raw material (De Araujo et al., 2013). The complete system boundaries of the transesterification process are shown in Fig. 17.5. Tuntiwiwattanapun et al. (2017) reported that 73% of the energy is consumed by methanol recovery in the transesterification process. An LCA study gave an idea of the different processes using different raw materials. The amount of GHG emission savings was about 54% in animal fat, and used cooking oil can save GHG emissions of 69% according to an environmental analysis carried out in Ireland (Thamsiriroj and Murphy, 2011). In both cases, a common pattern was identified for biodiesel from waste vegetable oils, beef tallow, and poultry fat. The fact is that waste vegetable oils accounts for much higher biodiesel yields and lower methanol-to-lipid feedstock ratios. Xunmin et al. (2009) revealed that biological-based fuels have a lower impact on climate change than conventional fuels. In his study the biodiesel from Jatropha fruit, ethanol from cassava, and biodiesel from used cooking oil showed better results than the conventional process and corn biodiesel and sorghum ethanol showed higher GHG emissions than conventional fuels.

17.3.4 Composting: compost and fertilizer recovery LCA analysis on composting of food waste was assessed by Giugliano et al. (2011) who pointed out that the indicators for the composting method were not eco-friendly for two main reasons: the impact on collection and separation of food waste and the profit related to the substitution of organic fertilizers. Based on the severity of the impacts of home composting, Lundie and Peters (2005) concluded that it was a better option for food waste treatment. Furthermore, the aerobic conditions of composting without required controls may lead to GHG emissions. Despite the cost, biobased polymers are widely used for packaging in food industries and have replaced oil-based polymers. These polymers are suitable for inclusion in the composting process. The best route for biobased packing material is by municipal composting, as suggested by Davis and Song (2006). The LCA study of biodegradable and plastic cutlery (food waste and noncompostable cutlery) concluded that the valorization of waste by an alternative approach of composting shows good results when the functional unit is taken as serving meals to 1000 peoples (Razza et al., 2009). Table 17.3 shows different LCA studies for the composting of food waste. Kim and Kim (2010) analyzed the GWP of 1 tonne of food waste for all the disposal systems through LCA studies. It was concluded that the composting techniques were eco-friendly; however, a negative effect on environment is possible when their residues are not properly used.

TABLE 17.2 LCA analysis of the fermentation process. S. no.

Source/type of food waste

Type of fermentation

Functional unit

System boundaries

Environmental impact

Impact assessment

1

Food waste

Two-stage anaerobic fermentation

1 MJ of upgraded biohythane

Well to pump

GWP

G

2

3

Lignocellulosic waste from banana

Lignocellulosic Food scrap from supermarket and sugar rich diluent

Bioethanol fermentation

Pilot fermentation plant

1 MJ of energy released by combustion in a passenger car,

1 L of ethanol is used which is then converted to a 1 MJ unit of transport energy

Well to wheel

GWP, AP, EP

G

G

Well to pump

GHG

G

Results/interpretation

The greenhouse emissions for complete system were 173 g CO2-eq/MJ and most dominantly attributed to the emissions from electricity production (41.6%), release of CO2 in pressurized water (27.8%), and energy recovery (19.8%)

G

Downstream wastewater treatment contributed significantly to GHG emissions Increased acidification impact due to the use of chemicals in pretreatment. E65 blend was recommended for Ecuador to obtain net negative emissions

G

Life cycle emissions are obtained from the GREET model and the EcoInvent 2.2 database

G

G

G

G

References

The identification of fundamental process and their improvement are assessed for two stage fermentation of food waste and microalgae under different scenarios The alterations in the growth of microalgae and the biohythane yield have larger impact on conversion of energy and GHG emissions

Sun et al. (2019)

The second generation ethanol from banana lignocellulosic wastes has potential to reduce GHG emissions and fossil depletion and has a positive energy balance. The greatest energy consumption, the wastewater treatment should be improved in order to enhance the performance of the second generation ethanol productive chain

Guerrero et al. (2018)

GHG emissions in life cycle are compared with commercial one Use of readily convertible, sourceseparated commercial or industrial food waste as a feedstock for ethanol offers significant potential for GHG reduction

Ebner et al. (2014)

(Continued )

TABLE 17.2 (Continued) S. no.

Source/type of food waste

Type of fermentation

Functional unit

System boundaries

Environmental impact

Impact assessment

4

Lignocellulosic fiber of MSW in UK

ABE fermentation

1 MJ of liquid biofuels

Well to pump

PED, GWP

G

Impact on product yield, uncertainty of process parameters shows different impacts on GHG emissions.

Results/interpretation G

G

G

5

6

7

Residues from food processing

Food waste from Sweden

Wheat straw

Photo and thermophilic fermentation

Bacterial fermentation

Cofermentation

1 kg H2

1 tonne of processed food waste

1 kg of ethanol produced

Cradle to grave

Cradle to gate

Well to gate

carcinogens, respiratory organics, respiratory inorganics, cc, radiation, ODP, ecotoxicity, A, land use.

G

GWP, AP, EP, H-Tox, Nonrenewable Energy use (NREU) and renewable energy use (REU)

G

CC, ODP,A POP, EP, ARF, E-tox, water depletion

G

G

G

G

G

G

G

References

High biogenic content with relatively low ABE product yield can minimize overall GWP More unconverted biogenic fiber residue generates more coproduct electricity MSW-derived liquid biofuels can contribute to reduce GHG emissions by over 100%

Meng et al. (2019)

Eco-indicator 2 has been used for the impact assessment Three damage categories: damage to human health, damage to ecosystem quality and damage to resources

G

Possible process improvement would lead to an environmental impact that is only twice as high as large-scale SMR

Ochs et al. (2010)

GWP for Succinic acid production was found to be quite low Bacterial fermentation contributes about 39% AP, 68% EP, 58% HTP, 50% NREU and 56% REU

G

In SA production, food waste was found to be an environmentally better option Mixed food waste is ecofriendly raw material for SA production

Brunklaus et al. (2018)

ReCiPe midpoint methodology used for impact assessment The GHG reduced to 73% for E85 and 15% for E15 ODP decreases up to 55% for E85 17% for E15 Slight reduction of POP while using E15 ARF decreases up to 40% for E85 15% for E15

G

E15 and E85 has lower contribution in ARF, ODP GHG emissions, but higher contributions in E-tox, water depletion, A, POP, EP Higher environmental impacts occur at prehydrolysis phase, followed by the saccharification and fermentation process

Borrion et al. (2012)

G

G

Environmental impacts and sustainability assessment of food loss and waste valorization Chapter | 17

371

FIGURE 17.5 System boundary diagram for transesterification of food waste to biodiesel.

17.4

LCA analysis of various nonbiological food waste valorization processes

17.4.1 Combustion and energy recovery Food waste residues produce a combustible biomass which can be used to generate energy by replacing fossil fuels with biomass. The generation of 1 MJ of electric energy consumes about 0.1
0.4 MJ of biomass energy. In heat energy these values are 0.01
0.15 MJ of biomass, and it is calculated as CO2 neutral. In LCA studies, the harvesting of food and fuel for transportation emits a higher amount of greenhouse gases. GHG emissions can be reduced by about 90% when biomass is used as feedstock (Laca et al., 2011). The use of lignocellulose-based food waste for the production of energy saves fossil energy and mitigates GHG emissions. A method has been developed to analyze residual straw based on the energy self-sufficiency of arable farms rich in organics (Kimming et al., 2011). The lignin content produced during ethanol production was used to generate heat and electricity. This study concludes the self-sufficiency of an organic farm to generate energy from its by-products (Kimming et al., 2011). The residue produced from food industries could replace fossil fuels to an extent.

17.4.2 Landfill disposal Landfill is one of the cheapest waste management options, however the policies and legislations against landfills have reduced its use to a degree (Laca et al., 2011). A traditional landfill produces a huge amount of leachate and emits GHGs. The reductions in the impact on the environment due to gas emissions and leachate were assessed by the LCA with mitigation measures (Damgaard et al., 2011). The EASEWASTE model has been applied for most LCA modeling for landfill. In normal dumping, the main impacts are groundwater contamination due to leakage of leachate, which increases ecological and human toxicity via water. The best way to improve the environmental quality is by capping and leachate treatment system. These methods provide a huge benefit with a lower impact. The recycling of food waste provides a better option to avoid the dumping of food waste in landfills. In Korea, the recycling rate was about 94% when the landfilling of food waste was banned in 2006.

17.5

Life cycle costing approaches to food waste and its valorization

The assessment of costs in food waste management is LCC. Its classifications are mainly based on three approaches: conventional LCC (C-LCC), environmental LCC (E-LCC), and societal LCC (S-LCC), which differ in their costs and

TABLE 17.3 LCA analysis of the composting process. S. no.

Source/type of food waste

Type of composting

Functional unit

System boundaries

Environmental impact

Impact assessment

1

Food waste in HongKong

Onsite SFRB system

1 kg of food waste to be treated

Gate-tograve

GHG

G

G

2

3

Household food waste in United Kingdom

In-vessel composting

Food waste from Kean university

In-vessel composting

1 tonne of household food waste

Gate to grave

GWP and particulate emission (CO2, N2O, CO)

G

G

1 tonne fresh matter in food wastes treated

Gate to grave

Fossil fuel use, climate change, acidification, eutrophication, ozone depletion, smog formation, human health impact (carcinogenic, noncarcinogenic, and respiratory effect), and ecotoxicity

G

G

G

G

G

Results/interpretation

Life cycle environmental impacts indicates that the operation of S-FRB at full capacity, reduces the GHG emissions The improvements in resource supply and waste circulation have additional environmental benefits

G

Emissions are combined as 14 environmental and health impacts Highest burdens are evaluated through hotspot analysis

G

TRACI 2 analysis are adopted for impact assessment CO2, CH4 and N2O were used to calculate the GWP AP expressed as SO2 equivalents NOx and NH3 in calculation of AP Eutrophication was characterized with EP

G

G

G

G

G

G

References

S-FRB technology is an emanated eco-friendly technology for decentralized waste treatment and it identifies the pathway to integrate this technology The end product is used as cofired energy generation.

Yeo et al. (2019)

Composting achieve best score for 7 impacts out of 14 Climate change (55%), freshwater eutrophication (95%), depletion of abiotic resources elements (48%) environmental impacts offset by the substitution

Salemdeeb et al. (2018)

In-vessel composting can reduce GHG emissions and eutrophication In-vessel composting is able to lock nutrients in soil and prevent them from leaching Compost manufacturing and electricity use are key factors towards environmental impacts Appropriate composter size and aeration control, the environmental performance and cost can be improved

Mu et al. (2016)

4

Food waste generated in Pennsylvania State University dining facilities

Windrow composting

The collection, processing, transportation and application of one tonne of compost

Gate to grave

CH4, CO2, N2O, NH3,

G

G

G

G

5

Yard waste and food waste

Aerobic invessel composting

91,000 metric tons of collected waste

Gate to grave

CH4, CO2 biomass, CO2 fuel, SOx, NOx, N2O, PMF, CO, NH3, benzene, ethene, toluene, Propene

G

G

6

Food waste from Hwasung city, Gyeonggi province

Composting

1 tonne of food wastes

Gate to grave

GHG

G

G

Followed TRACI 2 impact assessment methodology Combustion and electricity were related to ozone depletion, carcinogenics, noncarcinogenics, and smog formation Eutrophication and acidification, were related to N2O and NH3 values GWP were related to CH4 and the N2O values

G

CH4, CO2, N2O, and CO characterized as GWP NOx, SOx, and NH3, expressed as SO2-equivalents, AP Eco-Indicator 95 method were used for the assessment

G

8.8 kg CO2-eq/f.u., 8.1 kg CO2-eq/f.u., 58.2 kg CO2-eq/f.u., and 45.0 kg CO2-eq/f.u. of GHG emissions during collection, transportation, treatment and disposal Inventories of GWP data were taken through Sigma Pro model

G

G

G

G

G

G

Net positive gain in all the impact categories Use of compost as a soil conditioner The gains of using compost to replace peat

Saer et al. (2013)

No CH4 emission were seen Diversion of recyclable organic materials leads to decrease in GHG emission and energy generation Comparing to bioreactor landfill, invessel composting is lesser efficient as compared to cost and emissions

Cabaraban et al. (2008)

Avoided impact analysis showed animal feeding and composting were potential treatment options Low energy consumption and low greenhouse gases production

Kim and Kim (2010)

GWP, Global warming potential; A, acidification; NE, nutrient enrichment; ODP, stratospheric ozone depletion; POF, photochemical ozone formation; TA, terrestrial acidification; PMF, particulate matters formation; ME, marine eutrophication; NLT, natural land transformation. ALO, agricultural land occupation; FFDP, abiotic fossil fuel depletion; ADP, abiotic depletion. Htox, human toxicity; EP, eutrophication potential; POP, photochemical oxidation potential; TA, terrestrial acidification; FE, freshwater eutrophication; ARF, depletion of fossil fuels; RC, resource consumption; GHG, greenhouse gases; PED, primary energy demand; SA, succinic acid; AD, anaerobic digester.

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potential performances (Hunkeler et al., 2008). These food waste studies always follow the E-LCC approach. Reich (2005) used E-LCC to assess the impact when incorporated with financial LCC.

17.5.1 Functional unit The functional unit has a key role in the analysis of methodologies in the life cycle. When both the LCA and E-LCC are performed together, they should obey ISO 14040-44 (Swarr et al., 2011). The differences in yield were accounted for by the assessment of economic feasibility in cultivation individually or comparing it with a mass-related functional unit (Schmidt Rivera et al., 2014). The mass-related functional units were suitable for food LCC since the food waste was associated with the products obtained rather than land management. In one or more treatment options, the functional unit depends on the mass of food waste treated or disposed of under different scalings. Depending upon the scale of food waste generated, the methodology, database, and perspectives have various system expansion approaches. A FSC using consumed food as a functional unit was studied by Willersinn et al. (2017) who examined various measures to mitigate food loss. The operation of plants and their efficiency over a period of time, such as 1 month or 1 year, were studied by Reich (2005) and were dependent on the quantity of food waste and its characteristics.

17.5.2 System boundaries In almost all cases, the cradle-to-gate approach is followed (Schmidt Rivera et al., 2014). The variation in food waste characteristics needs disposal and treatment in the same system, the system boundaries have both cradle-to-gate and cradle-to-grave approaches. Two types of modeling are used, depending upon the types of waste: consequential modeling and attribution modeling. The attribution type gives an impact assessment of average conditions, whereas consequential modeling provides information on problems due to the external effect or due to any alterations in the system (Weidema and Schmidt, 2010). In LCC, the revenues from coproducts are excluded from the cost, with two limitations: profits are measured with by-product market price (Kim et al., 2011) and the conversion of revenues to the included cost in the external system (Reich, 2005). The first limitation was not possible when a large number of stages were selected. The second limitation was not considered as a proxy for the impact of product substitution economically.

17.5.3 Modeling approaches of cost The four-level characterization for cost modeling includes: stages of life cycle, types of activity, economical cost categories, and other types of cost categories (Hunkeler et al., 2008). The stages of the life cycle are connected with the design of the product to its end of life. The types of activity are a comprehensive identification of the process in all stages. Economical costs are connected to cost types. Other costs include the elaborate cost items in stages. The waste management chain and short supply chain are managed by the economic costing. Allocation of indirect cost is one of the major aspects in cost modeling. In the case of food waste studies, when more than one waste flows, the expenses are overhead costs and during cost breakdowns the costs which are not directly involved in food waste needed to be allocated (Martinez-Sanchez et al., 2015; Schmidt Rivera et al., 2014). The discounting of cost is the most common feature of cost modeling in C-LCC, which deals with the profits at different time periods. The discounting results are carried out in C-LCC and S-LCC (Hunkeler et al., 2008). Some studies apply depreciation for machinery costs instead of discounts in food waste.

17.5.4 Cut-off and externalities Cut-off is a integration between LCC, LCA and system boundaries. These criteria provide the differences between two methods with consistent boundaries. The three cut-off levels are: semifinancial cut-off which provides the assessment in economic dimensions, environmental cut-off which identifies the efficient hotspots for resources, and financial cut-off which is related to business accounting.The organization’s actions have an effect on stakeholders because of the quantified benefits, known as externalities. In LCC, the social and environmental impacts are expressed in monetary terms and vary with the distinct LCC approach (Hunkeler et al., 2008). Martinez-Sanchez et al. (2016) concluded that the impact of economic costs is not included when the E-LCC is combined with LCA to assess the externalities in environmental impacts in order to overcome double counting. In food waste management, the inclusion of externalities has been done by very few researchers (Martinez-Sanchez et al., 2016).

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17.5.5 Environmental impact assessment LCCs are efficient for measuring the sustainability of industries by their products, whereas they have limitations in capturing the impacts of economics at a larger level. In life cycle sustainability assessment, LCCs are incorporated along with other indicators to analyze the profitable aspects of sustainability in system expansion (Hannouf and Assefa, 2016). The most commonly adopted indicators for lifelong expenditure with E-LCC were net present value and internal return rate. The cost distributions between the cost payees are determined in the E-LCC approach (Martinez-Sanchez et al., 2015, 2016). The win
win situation was analyzed between economic and environmental impacts in E-LCC, which was combined with the LCA (Hunkeler et al., 2008).

17.5.6 Analysis of results and interpretation The results are analyzed and reported for both assessments together and are presented in portfolios, plotting results, aggregate indicator scoring, etc. The main assumptions which have large impacts on the results are analysis period, incomplete data, discounts, price variation, and choice value (Hunkeler et al., 2008). The significant variables are assessed by Monte Carlo analysis as suggested by Escobar Lanzuela et al. (2015).

17.6

LCA of the food supply chain

LCA was applied based on the impact categories on the environment: LU; biodiversity; GWP; ozone depletion potential; biotic resource depletion; water use; ecotoxicity potential; AP; HTP; EP; and POCP. GHG emissions in food supply occur at all stages (Monier et al., 2010). The estimation of GHGs has been carried out by the Waste Reduction Award Program (WRAP, 2013a) and the Food and Agriculture Organization (FAO, 2013).

17.6.1 Limited or full food supply chain stages in LCA LCA of the food supply includes mainly the consumption and disposal stages, which cause the major environmental impact. It encapsulates the environmental problems including eutrophication, global warming, and the major environmental emissions to the atmosphere. In the case of multifunctional units the problems in selecting the functional units need to be studied for the analysis of the burden on the environment. In the complete life cycle of food, the environmental impact on water, climate change, ecology of food loss, and food waste are accounted based on a food balancing sheet (FBS). The FBS provides information on the factors like quantity of food waste, stages of the FSC, and the end products which are responsible for the impacts, and identifies the geographical regions associated with food waste. Two approaches were studied in LCA on the EU project: a top-down approach and a bottom-up approach. The top-down approach starts from a large level of GHG emission and ends with the results of emissions due to food waste. The bottom-up approach starts from a particular index of products and ends by hypothesizing the results and follows a polluter pays principle. The functional unit was taken as 1 kg of food consumed in both approaches. The top-down approaches were found to be fast and efficient in assessing the GWP. The waste footprint concepts were developed to incorporate cleaner production in LCA, where the types, sources, and quantity of generated waste are included.

17.6.2 Food waste disposal LCA The process efficiency is analyzed by the disposal methods, which are affected by the source segregation of food waste in the LCA food chain (Bernstad and la Cour Jansen, 2011). The GHG emissions from the treatment processes of household waste were analyzed by LCA. The incineration, source separation, and AD are three methods of treatment design for waste reduction involving edible food loss prevention, moisture content draining, and composting with a reduction of 5%.

17.7

Current efforts on LCA

The international LCA agencies are struggling to obtain the data sets, data collection, and quality goals. European and American countries have made an effort to share their knowledge and experience for the development of LCA. International firms like the International Organization for Standardization (ISO), Society for environmental Toxicology and Chemistry (SETAC), Environmental Protection Agency (EPA), and Global Alliance of LCA Centers (GALAC) were involved in the development and distribution of the tools to assess the risks and trade-off-related problems in the

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whole life cycle. ISO 14040 and ISO 14044 are the two revised standards which are used to integrate the procedures in LCA. This further improvement in the standardization provides the ability to compare different cases. In order to evaluate the impact on the environment with a higher standard of clarity, the LCA center in Tsukuba, Japan, established the life cycle assessment method on end modeling. Eco-efficiency is the nutritional value of food for consumers per day to the life cycle of CO2 from the meals provided per day. The eco-efficiency of the food was determined by the food study group in Japan by collating it with the products having environmental impacts (Ozawa et al., 2007).

17.8

LCA analysis with a case study

Khoo et al. (2010) carried out a study on life cycle analysis of food waste and its environmental impacts in Singapore. Singapore opted for different types of food conversion and the only landfill site in Singapore for waste disposal is Semakau Landfill. Offshore landfill receives inert wastes that are inorganic. The majority of the food waste is sent for incineration. About 10%
15% is sent for recycling through AD followed by composting of the digestate matter. LCA is done to measure and compare the impacts on the environment due to human behaviors. It also acts as a policymaker for all levels of waste management. It identifies and quantifies the environmental impact of different waste management technologies. The major goal of LCA is the selection of proper food waste conversion in Singapore and its impact on the environment. The scope covers the boundary of the total amount of food waste generated per year so as to adopt three processing options: incineration, recycling, and aerobic composting. The stages start with waste generation, pretreatment, conversion, and generation of product and coproduct. The functional units were taken as 570,000 tonnes of food waste generated per year (Khoo et al., 2010). The comparisons of all the food conversion options were done and the impact on the environment explained by means of LCA. Their conclusion was that the AD process is helpful in the reduction of global warming by reducing the energy requirement for the process and saving of carbon dioxide in the composting process from digestate. The second scheme concluded that aerobic composting has eco-friendly results as compared to incineration, but the CO2 and NH3 emissions lead to it being least preferable option. In order to divert the food waste disposal from incinerators, small-scale compost sites are recommended.

17.9

Exergetic indicators in the food industry

Thermodynamic exergy is defined as the work potential of a system in a specified environment. It represents the maximum amount of useful work that can be brought to equilibrium with the environment (Cengel and Boles, 2010). Exergy loss is a proper indicator of the global conversion performance of an energy-conversion chain including complex structures (Sciubba, 2009). Different indicators have been developed in the field of science and some of these indicators are applicable in food industries. Exergetic renewability and environmental capability are the two major indicators developed by Dewulf et al. (2000), where exergetic renewability is the use of renewable exergy to the total exergy input, and environmental capability is the total input exergy needed to decrease waste.

17.9.1 Exergy analysis Exergy analysis is the aggregation of two laws of thermodynamics, that is, the first and second laws, where the maximum work of the system is in relation with the environment, and this analysis was widely done to understand the loses that occur at each unit and in the overall system (Kizilkan et al., 2007). It mainly recognizes the section in the system where exergy is lost or dissipated and analyzes the reason for those shortfalls (Tsatsaronis and Morosuk, 2012). The exergy analysis serves as an indicator for the probability of thermodynamic enhancement of the whole system (Kocoglu, 1993). Depending on the thermo-economic condition of exergy analysis, each unit of the system can be optimized separately which is a great advantage of this type of analysis (Kizilkan et al., 2007). Dincer and Rosen (2013) propose a step-by-step procedure for exergy analysis in the industrial food chain: G G G

G G

Characterize the system boundaries in the food chain; Demonstrate the surrounding source by using it as a reference for the local environment; Plan the mass flow analysis, energy, and exergy analysis using different sources of exergy and construct Grassmann diagrams Characterize and compute the thermodynamic indicators; Illustrate the results;

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G G

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Come up with an improvement to estimate the modifications; Impart the results.

Zeineb et al. (2018) carried out an analysis of exergy for bioethanol production from date waste and considered three forms of exergy: heat transfer exergy, exergy for mechanical work, and exergy for the flow of matter. The expression for heat transfer-associated exergy is:
 To ExQ 5 Q 1 2 T where To is the reference temperature and T is the temperature at the occurrence of heat transfer and Q is the amount of heat transferred. The expressions related to mechanical work and flow of matter are: Exw 5 W ExM 5 Exphy 1 Exchem 1 Exmix The flow of matter depends on the chemical energy (Exchem), physical energy (Exphy), and mixing exergy, that is, potential exergy and kinetic exergy (Exmix). Zeineb et al. (2018) neglected potential and kinetic exergy in their study and balanced the entropy enthalpy and material as
 To Σin Din ExM; in 5 Σout ΣDout ExM; out 1Σk Qk 1 2 1 Σk Wk 2 To Sgen 5 0 Tk Zisopoulos et al. (2015) used cumulative exergy loss (CEL) as an indicator of food waste valorization of bread and arrived with the following expressions: X X CEL 5 Bdestroyed 1 Bi;wasted X X X X Bdestroyed 5 Bi;in 2 Bi;out 2 Bi;wasted P P P where Bi, in, Bi, out, and Bi, wasted are the total useful exergy of all input streams, the total useful exergy of all output streams, and the total exergetic content of all streams that are wasted to the environment and could not be reused respectively. Specific exergy lost (SEL) shows the lost of exergy for the production of 1 kg of product which reaches the consumer and is given as SEL 5

CEL m bread sold

Mahmood et al. (2016) investigated the exergy efficiency of the food waste initially enzymatically pretreated followed by hydrothermal oxidation to produce bio-oil and the exergy balance was given as X X X Exin destroyed 5 Exin 2 Exout where Exin is exergy in, Exout is exergy out, and Exdestroyed is exergy destroyed in the process. The expression for exergy efficiency is given by Exergy efficiency 5

Exergy in products 3 100 Total exergy input

17.9.2 Use of exergetic indicators Exergetic indicators are used to analyze the different characteristics of thermostatic execution in order to gather the information on exergy losses and unreversabilities in the food chain. In the case of a complete food chain, the exergy input is not completely utilized and part of it exits the system and its efficiency can be calculated according to the product output exergy to the exergy input which was utilized (Valero, 1998). The six major exergetic indicators in food chains and processes are: G

One of the important indicators which is widely used is exergetic efficiency which assesses the sustainability of the food chain and gives an idea about the maximum utilization of exergetic inputs in the system.

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G

Absolute exergy loss is the second indicator which provides information about the energy losses occurring while converting the raw material to the final product. These transformations can be expressed by a Grassmann diagram. The expression for exergy loss was given by Aghbashlo et al. (2008). X X X X X Blost 5 Bin 2 Bout 5 Bdestroyed 1 Bwasted

G

The third type of indicator is improvement potential which is used to collate the processes at different scales and different sectors. This expression was given by Icier et al. (2010). X Blost IP 5 ð1 2 ηexergy Þ

G

Entropy is the fourth indicator which relates the exergy destruction by the Gouy-Stodola relation (Gouy, 1889a,b,c). Exergy destruction gives an idea about the irrevocable work. Energy destruction ratio or depletion number is considered to be the fifth indicator. It is the ratio between the destroyed exergy to total input exergy. The sixth indicator is CEL which accounts for the summation of losses during production of products and can be measured by deducting the total useful exergy throughout the process to the cumulative exergy consumed. It is expressed as (Raghu Ram and Banerjee, 2003)

G

G

CEL 5 CEC 2

X

Buseful ;

P where CEC is the cumulative exergy consumption and it is the total input and CEC 5 Binput. In addition to these indicators, many other indicators have been extensively used in the food industry, including renewability fraction (Maes and Van Passel, 2014), eco-exergy (Draganovic et al., 2013) and the indicators that are not widely used are the specific exergy destruction (Tambunan et al., 2010), the exergy loss rate (Pandey and Nema, 2011), the exergy-to-energy ratio (Quijera and Labidi, 2013), the exergy heating effectiveness, the weighted mean overall exergetic efficiency (Xydis et al., 2011), the exergetic factor, productivity lack, relative irreversibility, and peak exergy (Cuce and Cuce, 2013).

17.9.3 Construction of a Grassmann diagram This is also referred to as an exergy diagram and shows the lost work analysis of a material conversion process (Hinderink et al., 1999). The work lost includes the losses due to imperfect processes, whereas the exergy analysis accounts for the heat obtained from the system. It visualizes the physical and chemical exergy flow. The chemical exergy of any streams exceed the physical exergy and thus the chemical exergy was removed from the Grassmann diagram and the physical exergy location was easily identified (Zisopoulos et al., 2015). The chemical exergy of the end product will vary based on the recipes and it gives an illustration of the material yield. It gives an idea about the cumulative exergy process that takes place in a lab scale. The input to the system will be a natural resource and the output illustrates the theoretical work potential of the product and useful heat recovered. The input and output are compared to reveal the loss in work potential which happens due to material inefficiencies (Hinderink et al., 1999).

17.10 Mass and energy flow balance in the process 17.10.1 Mass flow balance in process streams The overall mass flow balance was evaluated by the output streams of the input material. There will be negligible difference in mass when the input waste is recovered in the form of output streams. The solid recovery fuel (SRF) derived from the output of the system was utilized for recovering energy and recycling. In all the processes inside the system, the mass balance principle is applicable to balance the entire process (Allesch and Brunner, 2015). It is a great challenge to analyze the mass balance of food waste due to the complexity of balancing the water and food waste. The mass balance of food waste AD was done in two ways, as demonstrated by Banks et al. (2011): wet weight and volatile solids (VS) bases. The water added to the entire process and facilities was taken as input in wet weight basis. In the VS method, the average of laboratory calculations of each criterion of food waste, fiber, and digestate was considered. In VS determination, metabolites such as VFA and ammonia were sometimes volatilized. The output will be obtained as methane and biogas, and the food waste has a higher yield of methane as compared to other municipal waste (Banks et al., 2011).

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17.10.2 Energy flow balance in process streams The process stream will be facilitated by the law of conservation of energy and based on the input waste energy balance calculated by the summation of energy content in output streams. The total value of heating was calculated by the product of its net calorific value with the corresponding total masses. Part of the energy can be recovered from the reject materials but the amount of energy recovered will be less as compared to SRF. The rejected materials cannot be used for the recovery of energy directly. In the AD process for food waste, the energy input was electricity for the operation of equipment and heat provided for maintaining the temperature of the process. Furthermore, the energy consumed for transportation was also included as input. The output of the energy flow is calculated as gross energy output (Banks et al., 2011).

17.10.3 Energy life cycle analysis and a case study Evangelisti et al. (2014) carried out a study in the United Kingdom with the organic fractions of municipal solid waste (OFMSW) where food waste and kitchen waste from houses, restaurants, and caterers and the waste from foodprocessing plants were used to analyze the energy production in LCA. The LCA quantifies the use of material and energy throughout the life cycle and identifies the waste as emissions and determines the hot spot in the system. The main objective of this system is to dispose of the waste with efficient energy generation and minimal environmental impact due to disposal. Three alternatives were introduced, namely landfill with gas recovery for electricity generation, incineration with energy recovery by combined heat and power (CHP), and AD with CHP and organic fertilizer production. It was estimated that the annual production of food waste as 35,574 tonnes/year. The functional unit in this study is the total amount of OFMSW produced in a town or district equal to 35,574 tonnes/year. The inputs of AD are the pretreatment, CHP production, and spreading of digestate on agricultural land as fertilizers, and the outputs are the production of electricity, heat, and fertilizers. The inventory analysis considers waste composition, renewable carbon, transportation, incineration with energy recovery, landfill with gas recovery, system expansion for electricity and heat production, and AD which includes pretreatment, use of biogas, and digestate. Sensitivity analysis was carried out and four variables were investigated in AD to calculate its impact, namely emissions of methane from the AD plant, efficiency of the internal combustion engine running with biogas (CHP unit), emissions from digestate, and digestate carbon sequestration. Biogas fuel from AD for CHP acts is the best treatment option and the organic fertilizers from digestate served as nonrenewable electricity. The impact is negative in terms of CO and SO equivalents. The suggestion for future AD plants includes the incorporation of two issues: maximizing the electricity produced by the CHP unit fired by biogas, and defining the future energy scenario where the process is embedded.

17.11 Food loss and LCA applications: an overview Food loss is “the amount of food intended for human consumption that, for any reason is not destined to its main purpose” according to FAO (2014). Food loss considers mainly the environmental point of view, and the social and economic dimensions are not considered. The most common framework for food loss in LCA is the accounting of food loss and food loss recovery modeling. In order to use the proper definition of food loss, it is needed to analyze the major problems and to interpret the results.

17.11.1 Types of food loss Food loss is the losses occurring from harvesting till production in FSC. According to the FAO, all types of food that are lost in FSC are food loss. The different types of food loss are avoidable, unavoidable, and qualitative food loss. The foods which are discarded after their expiration are avoidable food losses, whereas the parts of food that cannot be eaten or are nonedible are unavoidable food losses. The major difference between these food losses is dependent on the food use subjectivity and cultural norms. When the analysis is based on the reduction of food loss, there must be a clear distinction between avoidable, unavoidable, and possibly avoidable food losses. The most preferred option for waste management is waste prevention. The impact assessment and waste prevention benefits are included in LCA studies. The food losses at different production levels were compared with the food loss prevention and the LCA studies show the waste prevention to be at a reduced level (Nessi et al., 2012). It is important to measure the qualitative food loss in LCA studies since this inculcates the economic value, nutritional value,

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appreciation of consumers, and food safety (FAO, 2014). According to LCA, the quality of food decides the functional unit and this varies depending on different food products.

17.11.2 Food loss in LCA (different stages) Food loss happens at all stages of the life cycle according to the type of food, social, economic, and cultural aspects, technological development, and availability. In FSC, food loss creates two great impacts on the food products: the increment in food production to deliver the food and environmental impacts due to treatments of food loss (FAO, 2013). The food losses at each and every stage of LCA are given below.

17.11.2.1 Production-stage food loss The environmental burdens faced in agricultural production, meat production, and fish farming are food losses at the production stage. In LCA, the environmental impacts of agricultural products such as wasted fruits and vegetables are considered as a functional unit, which is known as the marketable yield (Romero-Gamez et al., 2014). The productionstage food losses will reach their alternative destination through composting or AD. In the case of animal products or meat, food loss is not considered at this stage. The food losses are considered depending on the quality of the animal products, that is, the diseases affecting the animals and their death rate. Globally, the World Animal Health Organization (2015) estimated about 20% of animal-based products are lost due to the death rates of animals. In the case of sea fisheries, the food losses are considered as wasted fish after the segregation process. The fish which are suitable for human consumption are sold (Davies et al., 2009). The food losses in fisheries are dependent on the season, methods of fishing, and the behavior of the fishermen (Hornborg et al., 2012). Wasted fish and overfishing of some specified fish are major burdens for the environment and cause disturbances to the aquatic ecosystem (Eyjolfsdӧttir et al., 2003). Some indicators have been developed to assess the number of discarded fish (Davies et al., 2009) and the complex nature of discarded fish to the environment.

17.11.2.2 Processing-, transport-, and storage-stage food losses Three kinds of food loss are considered in the processing stage: avoidable, unavoidable, and possibly avoidable food losses. Avoidable food losses are not widely studied, whereas possibly avoidable and unavoidable food losses have undergone major researches where the desired output was not produced for a defined amount of raw material (Rajaeifar et al., 2014). LCA results which were influenced by the process adopted are determined by the modeling procedure. The food losses at the processing stage can be recovered in industrial processes and the wastes are recovered as potential energy. The recovery methods of food loss wastes are animal feeding (Jensen and Arlbjørn, 2014) and fertilizers (Coltro et al., 2006). They are disposed of without any recovery options in certain cases (Gonzalez-Garcı´a et al., 2013). No measurement has been made of the transport and storage of food from the production plant, thereby miscalculating the impact on the environment.

17.11.2.3 Distribution-stage food loss At this stage, food loss occurs at both the retail and wholesale levels. At wholesale, food losses occur during quality control, whereas at retail shops, they occur when there is no demand for product, that is, unsold product (Strid and Eriksson, 2014). According to FAO (2011b), the generation of food loss is dependent on the food type and the regions where it is supplied. Cradle-to-gate approaches are widely used in LCA, therefore the food losses at this stage are not widely assessed (Fantozzi et al., 2015). Some research data are based on specific assumptions (Andersson et al., 1998), primary data (Svanes and Aronsson, 2013), and statistics (Meier and Christen, 2013) for the food losses in the distribution stage and provide an assumption to consider food loss as waste that is sent to a waste treatment plant (De Menna et al., 2014).

17.11.2.4 Consumption-stage food loss This stage is crucial and causes a great burden on the environment. It has a greater effect in developed countries than developing countries. A study by Vanham et al. (2015) showed that food loss is greater in rich countries than poorer countries, since the amount of wasted food is directly proportional to the total amount incurred by households. It also differs with the eating habits of the people and their food preparation methods (Parfitt et al., 2010). One LCA study on

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food loss was based on the diets at the consumption stage (Meier and Christen, 2013). The difference between the agricultural supply per capita and the intake level consumption is estimated as food loss (Hallstrom et al., 2015), whereas it does not involve all the stages of FSC. For single products, the consumption stages are fixed within the system boundaries (Jensen and Arlbjørn, 2014). The food losses are managed as organic waste at this stage and can be allowed to undergo composting (Berlin, 2002).

17.11.3 Modeling approaches to food loss in LCA The food loss in LCA has to be modeled to represent the coproduct with proportion, replacement, and expansion to provide an applicable output (Pelletier et al., 2015). It can be recovered predominantly by industrial ecology (IE) applications and also recovered or rejected by waste treatment techniques. The modeling approaches to food loss are shown in Fig. 17.6.

17.11.3.1 Industrial ecology application recovery This is a mechanism in which wastes are extracted from the environment and used in the industrial system (Lowenthal and Kastenberg, 1998). It is the fabrication of an industrial system with a systematized relation between the industrial and natural systems or within industries themselves. It has an interconnected association with the interchange of material varieties, including waste to energy conversion, to carry out the processes. The food losses are recovered as a product and are made fit for human consumption using this approach (Svanes and Aronsson, 2013). It is necessary to consider the food loss recovery without any environmental impact (Mirabella et al., 2014). LCA was applied with different motives in food loss to overcome this problem by assessing the value of an IE approach (San Martin et al., 2016), by assessing the existing technology for improvement (Contreras et al., 2009), and by comparing the IE approach to conventional industrial processes (Iribarren et al., 2010). The impacts of FSC are excluded in the IE approach which transfers the impacts to other parts of the supply chain (Mattila et al., 2012) and the system boundary enlargement increases the quality risk and uncertainties. LCA studies have been undertaken using a symbiosis relationship of industries for mutual profits (Chertow, 2000). The complex nature of a symbiosis relationship was studied by the application of hybrid LCA (Mattila et al., 2012). The major application of system expansion has been to overcome the multifunctional problem by selecting the reference case for substitution (Mattila et al., 2012). In substitution, for the same study, different approaches to IE have been applied, that is, fuel production, biotransformation, and animal feeding from apple residues (Mirabella et al., 2014). The advantage of system expansion is that it can assess changes in LU indirectly in agricultural production. The impact allocation for coproducts has three different approaches: physical allocation (Rajaeifar et al., 2014), economic allocation (Ayer et al., 2007), and allocation of impact to the functional unit (Milai Canals et al., 2006). When FIGURE 17.6 Modeling approaches for food loss.

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low-value products are generated in higher quantities, the economic allocation of LCA comes into being. The byproducts have large impacts due to physical allocation, whereas the economic allocation has a lower limit due to limited economic value. FAO (2016) proposed economic allocation to distribute the burden on the environment due to meat and animal by-products. Economic allocation results show that the present situation of the market changes with respect to the physical relation (Pelletier et al., 2015).

17.11.3.2 Food loss treatment in waste treatment plants The different waste treatment methods increase the environmental performance as analyzed by different researchers (Bernstad and la Cour Jansen, 2011), whereas the details of food loss recovery or disposal were rarely provided (Gonzalez-Garcı´a et al., 2014; Meier and Christen, 2013). The end of life stage in FSC has a lower burden on the environment as compared to other stages. The assumptions and decisions in waste treatment have a major impact on LCA results. Digestion processes, incineration, landfill, and composting are the major treatment processes in food loss. Some LCA professionals neglect waste (Saarinen et al., 2012) or exclude it from system boundaries (Gonzalez-Garcı´a et al., 2014). Jensen and Arlbjørn (2014) gathered information from different sources and combined them for the modeling of incineration of uneaten food. The modeling problem in waste treatment is multifunctional and can be solved by the system expansion and allocation approach. The modeling approaches were not explicitly reported (Fantozzi et al., 2015), where the present modeling approach did not have any allocation criteria and the burdens on the environment were allocated to the functional unit. The system expansions assess the impact of food waste treatment and are combined with the credits for exchange products, for example, the fertilizers from traditional plants are credited by nutrients obtained from the composting and digestion processes (De Menna et al., 2014). System expansion has a large impact on the results of LCA. The secondary datum of modeling certainly provides a higher burden on the environment for similar products. The limitation of system expansion is that it is difficult to provide a detailed analysis in a substituted system as the waste treatments are unknown.

17.11.4 Food losses and waste, their implications on water and land: a case study China feeds about 21% of world population with its limited natural resources, that is, 6% of total water and 9% of total cultivatable land. The population growth and economic development in China have led to shifts in food habits toward animal-based products and this has had an extreme effect on land and water due to overuse of these resources. The northwestern part of the China river basin is now facing intense water scarcity. Therefore many researchers have analyzed food losses in China through FSC and analyzed the methods to attain food security without degrading the natural resources. Policymakers have sought to improve the sustainability of the use of these limited resources. Liu et al. (2013) discussed different methods to estimate the food loss rate (FLR) at each phase in the food chain and evaluated its impact on water and land compared with other countries, and attempted provided ways reduce food losses. The FLR shows the immensity of food losses and is defined as the ratio of food lost or wasted to the total amount of food produced. The FLR at each phase is calculated as  Xn  i21 L 5 L1 1 L L ð1 2 L Þ i j51 j i52 i21

where Lj51 ð1 2 Lj) represents the percentage of food remaining at the beginning of the i-th phase. The effects of food loss and waste on water and land are determined by calculating the water footprint (WF) and land footprint (LF) during all phases. WF is the volume of water used to produce food items. Quantification is done using the virtual water content (VWC) for production of a food item (p). VWC is the amount of water used to produce a unit quantity of food. LF is the usage of land for the production of food. It is quantified by dividing the total production (P) by yield (Y). WF 5 VWC 3 p LF 5

P Y

The result of this study shows that the FLR varies with each segment of the FSC. The consumption and storage phases show higher FLR. The FLR due to consumption occurs with a mean of 7.3% 6 4.8%. The economic

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development in China has led to an increase in the standard of living. It shows that the consumption pattern for consumers differs in different parts of the country. The FLR of consumption at canteens, homes, and restaurants is 5%, 7%, and 19%, respectively. In restaurants, consumers order too much food and this leads to higher wastage. Storage accounts for about 5.5% 6 3.4% of FLR due to a lack of technology. In addition, harvesting, processing, and transportation also account for food losses. In complete FSC the FLR accounts for 19% 6 5.8%, which is one-fifth of the total grain produced.

17.11.5 Benefits of food donation Food donation is a method of waste recovery which was modeled using different factors of emissions from a waste reduction model of EPA. This type of action conserves the environment and natural resources, and reduces pollution. Food bank, food pantries, and food rescue programs are different organizations which administer food donation to people who have insufficient food. These programs collect food and donate it to people in need. Over 6000 tonnes of food are saved due to food donation each year and this is very helpful in attaining sustainability in developed and developing countries (Margaret, 2012). Products which are not suitable for sale in retail shops but can be suitable for food consumption are donated to foodbanks, pantries, shelters, and soup kitchens. The foodbank donors include farmers, wholesalers, manufacturers, etc. (Schneider, 2013). The major advantage of food donation is saving money that is needed for disposal of waste. The donation of food also helps to improve the climatic conditions as the excess foods are not wasted and the emissions of greenhouse gases and water pollution are reduced compared with using landfill. Donations of food to people benefits both donor and receiver as these donations to nonprofit organizations are tax deductible. The donor can have the opportunity to connect with people in need and enhance social cohesion. Moreover it helps to fight hunger and helps to support the community.

17.12 Current challenges and future trends in designing sustainable food chains In the food chain, sustainability was not maintained due to the standardization issues and the various approaches that have been developed to look after these issues. The three approaches, that is, C-LCC, E-LCC, and S-LCC have been used dependent on the aim of the study. In one stage, the functional unit and the system boundaries are not sufficient to differentiate C-LCC, E-LCC, and S-LCC. In multiple stages the costing approaches differ widely based on the cost payees. Martinez-Sanchez et al. (2016) used a coherence of inventory along with LCA in each stage to differentiate E-LCC and S-LCC. In the future there is a strong recommendation for framing a consequential modeling of E-LCC and S-LCC along with LCA. Attributional modeling is more widely used than consequential modeling. The integration of LCC
LCA structure was recommended with multifunctional aspects. Small economic effects are needed to be considered more than a single large economic effect. The main challenges to a sustainable food chain are emissions and waste water from industries, the nutritional value and safety of the product, extension of methods to include social and environmental impacts, variability in data due to uncertainties, and proper communication and framework. The nutrient availability and safety of food depends on the structure of the food. Some studies show the value of using nutrition while designing a sustainable food chain and the use of exergy analysis throughout the food chain for transformation and nutritional value of food (Shukuya, 2013). The implementation of a systematic framework for exergy analysis in future industries related to food by providing energy preservation programs should be made mandatory for all industries by providing sustainable government projects. A unique opportunity for FSC will be the incorporation of genetically modified crops. These increase yields and provide a larger food supply quantity. Communication in the supply chain will be enhanced by adopting information technology in future for integration and management of supply chain. A strategy for the supply chain helps to identify the FSC and provides the correct direction for completion of the chain (Chopra and Meindl, 2007).

17.13 Conclusion LCA is a well-known method to analyze the impact on the environment of food waste to energy conversion technologies and provides a structure for the comparison of different performances on the environment. It can be achieved accurately by using the appropriate functional unit of food waste to be treated or the energy output and the system boundaries for the input and output of materials. These studies mainly focus on the GWP impact till date and other studies have considered eutrophication, particulate emissions, and CED. The AD process greatly reduces the GWP, along with other impacts. Exergy analysis evaluates the sustainability of the food chain by various exergetic indicators

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in order to design a nutritious food process and to reduce exergy in the food chain. The incorporation of food loss in LCA was necessary for implementing policies to reduce the environmental impacts, thus making the food supply sustainable. The multifunctional modeling of food losses provides an extensive evaluation of the burden on the environment. Sustainability of the FSC can be achieved by the proper consideration of social impacts due to the present policies, costs, and profits.

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1575. Rajaeifar, M.A., Akram, A., Ghobadian, B., Rafiee, S., Heidari, M.D., 2014. Energyeconomic life cycle assessment (LCA) and greenhouse gas emissions analysis of olive oil production in Iran. Energy 66, 139
149. Available from: https://doi.org/10.1016/j.energy.2013.12.059. Razza, F., Fieschi, M., Innocenti, F.D., Bastioli, C., 2009. Compostable cutlery and waste management: an LCA approach. Waste Manage. 29, 1424
1433. Reich, M.C., 2005. Economic assessment of municipal waste management systems
case studies using a combination of life cycle assessment (LCA) and life cycle costing (LCC). J. Clean. Prod. 13, 253
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203. Available from: https://doi.org/10.1016/j.jclepro.2013.10.053. Roy, P., Nei, D., Orikasa, T., Xu, Q., Okadome, H., Nakamura, N., et al., 2009. A review of life cycle assessment (LCA) on some food products. J. Food Eng. 90, 1
10. Saarinen, M., Kurppa, S., Virtanen, Y., Usva, K., Mhakelha, J., Nissinen, A., 2012. Life cycle assessment approach to the impact of home-made, ready-to-eat and school lunches on climate and eutrophication. J. Clean. Prod. 28, 177
186. Available from: https://doi.org/10.1016/j. jclepro.2011.11.038. Saer, A., Lansing, S., Davitt, N.,H., Graves, R.,E., 2013. Life cycle assessment of a food waste composting system: environmental impact hotspots. J. Clean. Prod. 2013. Available from: https://doi.org/10.1016/j.jclepro.2013.03.022. Salemdeeb, R., Daina, M.B., Reynolds, C., Al-Tabbaa, A., 2018. An environmental evaluation of food waste downstream management options: a hybrid LCA approach. Int. J. Recycling Org. Waste Agric. 7, 217
229. Available from: https://doi.org/10.1007/s40093-018-0208-8. San Martin, D., Ramos, S., Zufı´a, J., 2016. Valorisation of food waste to produce new raw materials for animal feed. Food Chem. 198, 68
74. Available from: https://doi.org/10.1016/j.foodchem.2015.11.035. Schmidt Rivera, X.C., Espinoza Orias, N., Azapagic, A., 2014. Life cycle environmental impacts of convenience food: comparison of ready and home-made meals. J. Clean. Prod. 73, 294
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Further reading AnaBele´, G., Mun˜oz, E., 2017. Life cycle assessment of second generation ethanol derived from banana agricultural waste: Environmental impacts and energy balance. J. Clean. Prod. Available from: https://doi.org/10.1016/j.jclepro.2017.10.298. FAO, 2011a. Global Food Losses and Food Waste
Extent, Causes and Prevention. Hall, K.D., Guo, J., Dore, M., Chow, C.C., 2009. The progressive increase of food waste in America and its environmental impact. PLoS One 4 (11), 7940. Hermann, W.A., 2006. Quantifying global exergy resources. Energy 31, 1685
1702. Kaygusuz, K., Bilgen, S., 2009. Thermodynamic aspects of renewable and sustainable development. Energy Sources, Part. A: Recovery, Utilization, Environ. Eff. 31 (4), 287
298. Available from: https://doi.org/10.1080/15567030701715401. Le Pierres, N., Stitou, D., Mazet, N., 2007. New deep-freezing process using renewable low-grade heat: from the conceptual design to experimental results. Energy. 32, 600
608. Leites, I.L., Sama, D.A., Lior, N., 2003. The theory and practice of energy saving in the chemical industry: some methods for reducing thermodynamic irreversibility in chemical technology processes. Energy. 28, 55
97. Pant, D., Singh, A., Van Bogaert, G., Gallego, Y.A., Diels, L., Vanbroekhoven, K., 2011. An introduction to the life cycle assessment (LCA) of bioelectrochemical systems (BES) for sustainable energy and product generation: relevance and key aspects. Renew. Sustain. Energy Rev. 15 (2), 1305
1313. Stichnothe, H., Azapagic, A., 2009. Bioethanol from waste: Life cycle estimation of the greenhouse gas saving potential. Resour. Conserv. Recycl. 53 (11), 624
630.

Chapter 18

Analysis and regulation policies of food waste based on circular bioeconomies S. Logakanthi1, R. Yukesh Kannah2 and J. Rajesh Banu3 1

St. Francis College for Women Autonomous and Affiliated to Osmania University, Hyderabad, India, 2Department of Civil Engineering,

Anna University Regional Campus Tirunelveli, Tirunelveli, India, 3Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India

18.1

Introduction

According to the FAO, the growth of agricultural productivity has stalled, as the yield of grain growth per year at 1% is much lower than the present population growth rate. Exacerbating this is the present level of food wastage, which is nearly a third of production (nearly 1.3 billion tonnes). In China, the most populous country in the world, the food waste generated has been estimated to have the potential to feed 500 million people, while in the EU an estimated 88 million tonnes of food waste is generated. According to FAO (2015) 95% of the food produced in the world consumed by humans is grown in soil. The food produced depends on the fixation of atmospheric carbon by plants. These plants also require nutrients like nitrogen, phosphorus, and potassium for their growth, which are mainly derived from soil. However, decades of unsustainable agriculture have deprived the soil of these essential nutrients and thus affected food production. The global food waste problem further exacerbates the availability of food. With agriculture as the main occupation, humans have lived in rural areas for many centuries. This rural living ensured the recycling of food and agricultural waste and human excreta to soil, thus maintaining its fertility. However, growing urbanization has broken this cycle. According to the report UN (2014) 66% of the human population will live in cities by 2050. This urbanization implies that nutrients extracted from the biosphere as harvested food will become concentrated in cities. The concentrated nutrients are discharged as food waste into solid and liquid waste streams of cities. Rather than returning to the soil, the nutrients in these waste streams go largely unrecovered. For example, in the European Union, 70% of the phosphorus in sewage sludge and biodegradable solid waste is not recovered, while in Bangkok, an estimated 90% of the nitrogen that enters the city each year is lost, primarily through the city’s waterways (Færge et al., 2001). According to a study by Drechsel et al. (2007), the nutrient value of the uncollected solid and liquid waste in Kumasi, a city in Ghana, is sufficient to pay for the city’s entire solid waste management costs of US$180,000 a month. Presently, the management of these waste streams incurs monetary and environmental costs (Ellen MacArthur Foundation, 2017). However, if a value could be attached to the resources in the waste stream, there would be a shift from the present notion of waste treatment as an expensive cost center to a profit-generating center that creates a variety of useful end products. There lies huge potential for food waste to be recovered for many purposes like animal feed, organic fertilizer, energy production through anaerobic digestion, and so on. The global food system is comprised of a long value chain with multiple stakeholders like producers, procurers, distributors, chemical companies, insurers, and consumers, to mention a few. In the developed markets this value chain extends beyond the regional and national boundaries, resulting in more food miles (Kemp et al., 2010). The food value chain can be separated into upstream producers, the “agricultural system,” and downstream consumers, “the urban food system.” Food production and consumption today has adopted a linear approach similar to the present economic production model. Food is mostly produced in rural centers that require water and nutrient-rich soil among other things. The food thus produced gets redistributed to urban centers where maximum consumption happens.

Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00018-3 Copyright © 2020 Elsevier Inc. All rights reserved.

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Realizing the global growing food demand due to population growth and the pressure on existing resources that this creates, along with the large potential for valorization of food waste, researchers and policymakers have acknowledged the importance of a paradigm shift from the current linear model to a circular model of food production. Such a circular economic model will mitigate waste by creating closed-loop systems.

18.2

Circular economic approach

The circular economy (CE) concept owes its origin to industrial ecology and industrial metabolism formulated during the 1970s and 1980s through a rethinking of the industrial processes (Frosch and Gallopoulos, 1989). Pearce and Turner (1990) introduced the phrase circular economy, although the concept has deep roots dating back to Boulding and Jarrett (1966), who suggested implementing a cyclical ecological system instead of the wasteful linear economic model. A cyclic ecological system preserves and enhances natural capital, while optimizing the resource yields. It also minimizes the risks in the system by proper management of limited stock and ensures that economic actors have no net effect on the environment. Although the concept of the circular economy is not entirely new it has recently gained importance among policymakers (Brennan et al., 2015), as evident in the comprehensive European Circular Economy package (European Commission, 2015) and the Chinese Circular Economy Promotion Law (Lieder and Rashid, 2016). CE has been defined by many researchers and organizations. The Ellen MacArthur Foundation, one of the pioneers working in this area, defines CE as “an industrial economy that is restorative or regenerative by intention and design” (Ellen MacArthur Foundation, 2013, 2014). Geng and Doberstein (2008), while presenting the Chinese implementation of the concept, describe CE as the “realization of [a] closed loop material flow in the whole economic system.” According to Webster et al. (2017) “a circular economy is one that is restorative by design, and which aims to keep products, components and materials at their highest utility and value, at all times.” A circular economy by keeping its products, components, and materials at their highest utility and value at all times ensures reuse and renewability of the resource. It works according to the 3R approach of “reduce, reuse, and recycle.” The use of less material where possible helps in reducing material extraction and energy consumption, which ensures environmental protection through minimized material losses and emissions. With an emphasis of eco design and design for environment the products are designed and made in such a way that parts can be reused and products upgraded easily. This not only helps in reusing and recycling but also reduces the quantity of waste generated. Products are thus made durable and reusable. In a circular economy retaining the value creates value. This value retention is achieved by maintaining the purity of materials in the value chain. While in a linear economy reusing usually results in downcycling (melting of plastic bottles to recycle), in a circular economy reusing is intended to be as high grade as possible as the initial function or rather upcycling (reuse of plastic bottles as fillers in a wall) is promoted. This upcycling is achieved by usually transforming the by-product from one industry into a resource for a second industry. This also thus emphasizes strong intersectorial dynamics and cooperation, which is useful and important in attaining sustainable growth. A circular economy thus reduces resource dependency and resource use, including energy, thereby controlling the production costs and narrowing market exposure. This leads to the introduction of economically viable methods of reducing pollution, and separation of reusable waste material from harmful waste. According to the laws of thermodynamics, matter has the tendency to dissipate and so there are always value losses because of a decrease of order in matter when it transforms. However, this dissipation of value of matter in the processes of the natural world is slow as they are circular and the matter is continuously used efficiently. In contrast, in the linear model the dissipation of energy from matter during its transformation is high as it is not efficient. Therefore in order to have efficient use of resources it becomes important to adopt a circular process in such a way that the quality of matter used in the various steps of the process is close to the original matter. This quality retention of the resource used is one of the basic principles of the circular economic model, which it works to achieve even when products are transformed for reuse. It is an acknowledged fact that the present linear economic growth model is putting immense pressure on resources like potable water, clean air, forests, fertile soil, etc., which are being exploited at a very fast rate. Given the global agreement on the need for sustainable development in order to sustain human life on the planet it has become imperative to look at alternate economic growth models. A circular economic model that mimics nature (Benyus Janine, 1997) has been broadly agreed to provide a solution to this global problem.

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Circular economy approach to food waste

Food waste epitomizes an unsustainable system of food production and consumption. Acknowledging this and realizing the importance of utilizing and thus managing this waste in order to restore the balance and achieve sustainable growth as the principle of CE is widely applied in the management of this waste. A circular economy will enhance natural capital by encouraging flows of nutrients within the system and creating the conditions for regeneration of soil and other living systems. In the urban context, this implies that the nutrients will be captured within the organic fraction of municipal solid waste and wastewater streams, and processed to be returned to the soil, in forms such as organic fertilizer. In accordance with the principle of a circular economy which emphasizes upcycling of waste to its downcycling further uses of food waste as animal feed can be explored. And the final option of energy recovery from food waste when all the valorization options are exhausted would ensure maximum optimization of food resources from production through use and disposal. The recovery of postconsumer nutrients, coupled with regenerative agricultural practices, would thus reduce the need to bring in nutrients from nonrenewable sources, like synthetic fertilizers, thus contributing to renewing the nutrient cycle. Thus a circular economy of food would help in regeneration of natural capital by closing nutrient loops, along with providing additional value from organic nutrients as soil conditioner or through its use as animal feed or through energy recovery. According to the Ellen MacArthur Foundation (2017) shifting to a circular economy of food could lead to more economic prosperity, contribute to natural system rebuilding rather than degradation, and lead to better health outcomes. The circular economy emphasizes the optimum utilization of resources, while utilizing the waste generated from one process as a raw material for another. This principle of a circular economy can be well adopted in the management of food waste. This would not only result in creation of new valuable processes but also in the creation of new industries that use these processes, thus helping in economic covalue creation. In the management of food waste the principles of waste management hierarchy are recommended to be followed (Garnett, 2011; Papargyropoulou et al., 2014). The European Union has developed its own approach-waste hierarchy, which is defined by Directive 2008/98/EC8, setting a precise ranking of activities based on the highest level of environmental sustainability. Since defining waste hierarchy, it has been adopted worldwide as the principal waste management framework. Fig. 18.1 shows the food waste management hierarchy. The most preferred step is activities that prevent generation of food waste all along the food supply chain. These include new consumption behaviors like dietary changes, such as reducing the purchase of livestock products while increasing more seasonable vegetables and fruit (Westhoek et al., 2014). The next preferred option is reuse through foodbanks and food redistribution centers. When the first two methods of preventing food waste do not happen the principle of

Avoid excess food waste generation at source

Most preferable option

Food to be reused through donation to serve the needy Valorization of food waste to animal feed, fertilizer, biomaterial etc. Incineration with energy production

Landfill

Least preferable option Disposal

FIGURE 18.1 Food waste management hierarchy.

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cascading is applied to food waste. Cascading maximizes resource effectiveness by using biomass in products that create the most economic value over multiple lifetimes. This approach to production and consumption states that energy recovery should be the last option, and only after all higher-value products and services have been exhausted. Waste valorization of waste provides an alternate good solution (Contreras et al., 2009). Waste valorization is the process of converting waste materials into more useful products including chemicals, materials, and fuels. Waste valorization includes both recycling and recovery measures. Recovery through tapping the energy by anaerobic digestion is recommended only when all high-value options like extraction of nutrients and use as feedstock have been exhausted. The digestate thus obtained from anaerobic digestion is a good fertilizer, like compost, and so it is both a recycling and recovery option. Disposal is the least and last preferred option for food waste. Lin et al. (2014) provide a comprehensive picture of food valorization across different countries with different food waste. The Public Flemish Waste Management Company (from Belgium) has proposed a more detailed food waste management hierarchy: (1) prevention; (2) use for human nutrition; (3) conversion for human nutrition; (4) use for animal feed; (5) use as raw materials in industry (in a biobased economy); (6) process into fertilizer by anaerobic digestion or composting; (7) use as renewable energy; (8) incineration; and (9) landfill. Unlike in a linear economy where recycling usually results in downcycling of a product obtained from waste, valorization of food waste leans toward upcycling and generating products of higher or similar value. Several studies have evaluated the environmental performance of different food waste management options. Some studies have noted a positive value in utilization of organic fraction in food waste in anaerobic digestion along with incineration of its inorganic fraction to landfilling (Cherubini et al., 2009). Lower global warming potential and higher resource recovery compared to landfill disposal were observed in a study that looked at utilization of food waste for feed production and composting. However, it noted higher eutrophication, acidification, and freshwater ecotoxicity potentials (Kim and Kim, 2010; Lee et al., 2007). In a study carried out in Australia, home composting was observed to be the food waste valorization technology to cause the least environmental impact, when operated with proper due care. Various biotechnological processes have also been adopted to valorize food waste. These processes use nutrient-rich food waste as a medium for cultivation of microorganisms that in turn can be utilized as resources for other processes (Lin et al., 2013). These biotechnological processes in combination with various chemical processes enable the recycling of valuable nutrients for the production of chemicals, materials, and energy. From the various studies that have looked at valorization of food waste the conclusion can be drawn that the technologies and methods adopted look at closing the nutrient loop and contributing to the development of a circular economy in terms of food production and utilization. This would not only help in tackling the growing demand for food but also would be able to lessen the pressure on the environment. The utilization of food waste also then points to its opportunity in a bioeconomy.

18.4

Bioeconomic approach

The bioeconomy comprises those parts of the economy that use renewable biological resources from land and sea in a responsible way but with the aim at benefitting businesses, society, and nature alike. The adoption and use of the term bioeconomics has undergone a series of changes. The term bioeconomic, although coined by Russian biologist Barnoff to describe fishery economics, has found significant use after its use by Gordon-Schaeffer in their model in the 1950s (Clark, 1976). With the increase in pressure on natural resources they applied the term bioeconomics as one that would help in achieving maximum yield from resources without damaging the capacity to regenerate. Gordon-Schaeffer’s approach to bioeconomics revolving around the principles of sustainability is considered to be the first phase in the evolution and application of bioeconomics (Vivien et al., 2019). The arrival of the 21st century saw a significant revolution in biotechnology. The application of this knowledge of biotechnology to support the growing demand for resources is regarded as the second phase of the application of bioeconomics (Vivien et al., 2019). The present phase, which is the third phase of bioeconomics, centers around utilization of biomass. This biomass coming from sources ranging from wood to agriculture to waste is transformed in biorefineries. A biorefinery is a facility that integrates biomass conversion processes and equipment to produce fuels, power, and value-added chemicals from biomass. This biomass-based application of bioeconomics is useful in food waste management strategies as food waste constitutes nearly a third of food produced. In terms of the recent bioeconomy policies they have developed along one of the two perspectives, namely innovations in biotechnology or resource substitution. The bioeconomic approach to resource utilization and waste management has gained lot of momentum since 2005 (European Commission, 2005). The European Commission’s (EC) launching of a communication entitled Innovating for Sustainable Growth: A Bioeconomy for Europe in 2012 has provided a framework to stimulate knowledge development, research, and innovation on the conversion of renewable biological resources into products and energy (European Commission, 2012). The EC strategy highlights bioeconomy as

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the production of renewable biological resources and their conversion into food, feed, biobased products, and bioenergy. In doing so the bioeconomy thus contributes in not only solving the challenges of food security but also helps in the sustainable utilization of resources with less dependence on nonrenewable resources apart from creating new employment opportunities through new areas of work. This European bioeconomy strategy has been adopted completely (in all areas like food, energy, waste management, etc.) in many member countries like Finland, Germany, Sweden, France, and Spain (Langeveld, 2015) or restricted to areas of only biotechnology and biofuel policies in some countries (Meyer, 2017). Apart from the EU, many countries across the globe including the United States, South Africa, Malaysia, and Greenland have explicit bioeconomy strategy. Countries like China, India, and Russia, although they do not have an explicit bioeconomy strategy, have strategies related to it (Birner, 2018).

18.5

Bioeconomic application to food waste management

The evolution and application of a bioeconomic approach is mainly to provide a solution for the increasing resource demand to support the growing global population that is resulting in its unsustainable exploitation. Food is one such resource whose demand is ever increasing. Although food is not a finite resource the production of this resource depends on utilization of finite resources like land and shrinking recyclable resources like water. While at one end the demand for food is growing, nearly a third of all food is wasted. Food waste management has two aspects, namely preventable food waste minimization and nonpreventable food waste valorization (Morone et al., 2019). The bioeconomic approach is useful mostly in the tackling nonpreventable food waste that originates mostly from consumers. The food waste can be valorized to different products like animal feed (Salemdeeb et al., 2017), biomaterials (Nesterenko et al., 2013), compost, energy (Vandermeersch et al., 2014), etc., and so requires different technologies, materials, and energy inputs and produces different by-products (Fig. 18.2). Biorefineries play a vital role in the bioeconomic approach as they are especially useful in valorization of food waste. “Biorefinery” is defined as the sustainable processing of biomass into a spectrum of marketable products and energy (IEA, 2007). Biorefineries are comparable to petroleum refineries in that they embrace a wide range of technologies that at first separate the building blocks of biomass and convert them back to value-added products like biofuels and chemicals. There have been ethical concerns with regards to utilization of biomass (that can pose competition for cultivation of food) in biorefineries (Cherubini, 2010), which has been a major cause of criticism of the bioeconomy (Scarlat et al., 2015). However, advanced biorefineries employ innovative and green technologies to produce new types of products from secondary feedstock rich in lignocellulose instead of dedicated crops, and includes a variety of waste streams such as food waste. In doing so, in addition to environmental benefits, they also create new employment opportunities (Bourguignon, 2017). In order to make these biorefineries truly sustainable it is important to not only ensure that the raw materials for their operations are sustainable but also that the products like biofuels and chemicals are environmentally friendly. This FIGURE 18.2 Valorization of food waste into different by-products.

Biochemical processing—extraction of high-value functional substances

Food waste

Biomaterials

Biofuel

Animal feed

Compost

Thermal and electric energy through anaerobic digestion

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can be achieved by integrating the principles of green chemistry. Green chemistry is a set of principles for the manufacture and application of products that aim at eliminating the use, or generation, of environmentally harmful and hazardous chemicals. It offers a toolkit of techniques and underlying principles that any researcher could, and should, apply when developing the next generation of biorefineries. The overall goal of green chemistry combined with a biorefinery is the production of genuinely green and sustainable chemical products (Clark et al., 2009). One example of the application of green chemistry is the application of supercritical carbon dioxide as a green solvent. This carbon dioxide is not only available during biomass fermentation, it is also nonflammable and nontoxic, and leaves no residue (Cherubini, 2010).

18.6

A circular bioeconomy for food waste management

The circular economic approach is based on the biological processes where the entropy of the processes is kept low, thereby enabling the circulation of material for a very long time. This is achieved through technological systems (Murray et al., 2017). The circular economic approach is therefore based on resource efficiency, waste reduction, recycling, and valorization. However, Geissdoerfer et al. (2017) argue that many researchers ignore the biobased sector and focus on circularity of materials like plastic, metals, etc. This is attributed to popular a butterfly graph (Fig. 18.3) on

FIGURE 18.3 Butterfly graph of a circular economy. Reproduced with permission from Ellen MacArthur Foundation, 2013. Towards the Circular Economy Vol. 1: An Economic and Business Rationale for an Accelerated Transition. https://www.ellenmacarthurfoundation.org/assets/downloads/ publications/Ellen-MacArthur-Foundation-Towards-the-Circular-Economy-vol.1.pdf, https://www.ellenmacarthurfoundation.org/circular-economy/ infographic.

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circular economy (introduced by Ellen MacArthur Foundation in 2013), which makes a clear separation of the technosphere and biosphere. These two spheres are often referred to as the bicycle of the circular economy. This distinction implies that the biological resources can be recycled through the biosphere. The first biological cycle focuses on optimizing the use of bioresources by cascading and extraction of biochemicals, while returning their nutrients to the biosphere through composting or anaerobic digestion, recovering biogas where possible. The second technical or abiotic cycle adopts closed-loop production that recycles the abiotic resources that are the key runners in the technosphere. In line with the principle of a circular economy it implies that abiotic materials once mined need to remain in the cycle for as long as possible, not only through recycling, but also by using the inner circles (maintenance, reuse, remanufacturing, refurbishment), keeping the value of materials as high as possible throughout their life cycle. This distinction in the circulation of biotic and abiotic materials is not easy to maintain in practice. With the integration of a bioeconomic approach to a circular economy, new materials (like bioplastics) are created using biomaterials that are nonbiodegradable, thus having characteristics of materials from the technosphere. In such cases the new biomaterial cannot be left for recycling in the biosphere and has to be integrated into the technosphere. Although separation of abiotic and biotic material may be useful, the possibility of overlap cannot be overlooked and should be considered in order for a circular economic approach to attain sustainable development. Bioeconomy rests on the evolution of biotechnology to provide a solution to the ever-increasing demand for resources to run life on our planet. In doing so it focuses more on identification and extraction of resources from renewable biomass sources. On the flip side, the bioeconomy strategy does not pay much attention to product design for repair, reuse, recycling, durability, and preventing wastage as it is focused more on replacement of nonrenewable resources with renewable bioresources (EEA, 2018). Although there is a distinct difference in the two approaches, namely a circular economy and a bioeconomy, the underlining communality that they both function to achieve optimum use of resources to achieve sustainable development cannot be denied. This is explicit while looking at the EU’s 2015 Circular Economy Action Plan and its 2012 Bioeconomy Strategy which both have food waste, biomass, and biobased products as areas of intervention along with common concepts such as the chain approach, sustainability, and the cascading use of biomass (EEA, 2018). This linking of bioeconomy to the principles of a circular economy has also led to the development of the concept of a “biomass-based value web” (Virchow et al., 2016). This concept takes into account that the cascading use of biomass and the use of by-products from the processing of biomass lead to an interlinkage of different value chains which can be analyzed as a “value web.” This value web has been well demonstrated by Scheiterle et al. (2018) through a case study of Brazil’s sugarcane sector. The by-products from the processing of sugarcane, such as filter cake, vinasse, and bagasse, are used for the generation of biogas or bioelectricity, instead of being disposed as waste apart from their potential use in pharmaceuticals as flavoring agent. Thus the integration of a circular bioeconomic approach to food waste management would mean the application of principles of bioeconomics in valorization of food waste. This valorization of food waste depends on the source of food waste and its quality. The valorization of food waste includes extraction of components like proteins, lipids, etc. that can be used as value-added coproducts, bioprocessing of the materials in the waste to polymers like bioplastic, biocomposite, etc., biofertilizers or fuel like bioethanol and biodiesel that can be used as energy sources. The collection of food waste, digesting it and applying the digestate or compost to agricultural land helps in regenerating the soil along with preventing it from getting lost to landfills or water bodies. Thus, the environmental and cost-effective utilization of food waste depends on the type and composition of the food waste, the pretreatment methods, and the extraction/isolation processes. Also, the economic value of the final product has a large impact on the selected process (Morone et al., 2019).

18.7

Challenges in food waste management

The above discussions clearly point to the usefulness of integration of bioeconomy in a circular economy with regards to food waste management. For this integration to occur it is essential to look at the sourcing of raw materials, in this case food waste. In urban settlements there are different sources of generation of food waste, namely individual households, restaurants and takeaways, office and institutional cafeterias, supermarkets, and farmer markets. The collection of wastes from these different institutions across the globe varies depending on the level of awareness of consumers, local or national

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policies, and the execution of these policies through support mechanisms. Indeed, implementation on a larger scale of biorefining from food waste will depend, as stressed by the literature (Kretschmer et al., 2013; Lin et al., 2011), on G

G

G G G

Separate food waste collection mechanism that is however challenging to establish will ensure a high variety of quality and volume of food waste; Increased coordination of the different sources of food waste producers such as distributors, retailers, cafes, restaurants, schools, hospitals, and households; Better infrastructural and storage of these wastes until utilization as it decomposes rapidly; Increased awareness among the public in participation for collection and demand for biobased products; Favorable policy actions that encourage the collection, valorization, and utilization of food waste, like tax cuts and subsidies.

18.8

International approaches to food waste management

Several countries have realized the impact of food waste on the environment and the need to manage it. Countries like Australia, Norway, France, Italy, Denmark, South Korea, and Dubai have committed to its reduction through national policies. These policies look at different aspects of food waste management. The first order in food waste management is prevention. In order to prevent the generation of food waste various measures have been adopted in different countries of the world both at organizational and regulation levels. Some of the measures are: G

G

G

G G

In Denmark, the supermarket chain REMA 1000 has ended quantity-based discounts like “buy one get one free,” which encourage people to buy food in quantities larger than their need, leading to food waste. It has replaced them with offering the same price discount on each unit (EU Fusions, 2016); In Bangkok, the Sofitel Sukhumvit hotel has used a software solution package in its kitchen operations that has reduced the food waste generation and thus has saved money too (Greenhotelier, 2014); The EU Landfill Directive obliges member states to reduce the amount of biodegradable waste going to landfill to 35% of 1995 levels by 2020, thereby banning organic waste from entering landfill. Following this directive some EU member states like Germany, Austria, and Sweden have gone further and banned any food waste to landfill. This is also extended to commercial establishments generating organic waste in excess of a predetermined threshold. They are required to recycle the waste, thereby encouraging businesses to reduce their food waste in the first instance (European Commission, 2016); The city of Vancouver in Canada has also banned the disposal of food waste in garbage (RCBC, 2015); South Korea has gone further to implement “pay as you throw” (PAYT) schemes that charge the producers of food waste for the disposal of waste based on the waste’s weight/volume (Waste Management World, 2017).

The second order in food waste management is reuse or optimization of food. This is again done through organizational interventions or through favorable regulations. Some of the measures taken in countries across the world are: G

G

G

G

G

Food retailer commitment in the UK has a partnership between supermarkets and foodbanks and other community organizations. This partnership works by distributing surplus food arising from supermarkets to charitable organizations. In doing so this partnership not only prevents food waste but also provides nourishment to vulnerable members of society (FareShare, 2017); Software applications like “Too good to go” in the United Kingdom help in the redistribution of cooked food from restaurants, supermarkets, and bakeries at the end of the day, thus reducing food waste generation (World Biogas Association, 2018); Liability to donors in the case of any damage to receivers of donated food discourages the redistribution of surplus food. In order to overcome this the Good Samaritan Law was enacted in the United States in 1996. This has facilitated redistribution of surplus food from donors and foodbanks, exempting them of any liability in the case that redistributed food unexpectedly turns out to be somehow harmful to the consumer, unless there has been gross negligence. This law helps in reducing food waste (Good Samaritan law, 1996); Several European countries including France, Germany, Greece, Italy, and Poland give tax and fiscal incentives for donation of food as a goodwill gesture and to encourage donations (European Economic and Social Committee, 2014); France and Italy have introduced legislation that obliges retailers to donate edible food that has reached its sell-by date to charities that then distribute the food to those in need (World Biogas Association, 2018).

The third order in food waste management is recycling, where the food waste is valorized to produce substances that can be used as animal feed, composite material, fertilizers, or biofuels. It is here that the various bioeconomic

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Donation of edible food through food bank/carving

Food use label

Bioeconomic Intervention

Biofertilizer

Use of ICT for distribution of prepared food Food unfit for human consumption

3

2

Animal feed

Circular economy

Meal plan

Biomaterial Discourage offer based on quantity

Anaerobic digestion Improved storage and transport

1

4

1

Food production

2

Food consumption

3

Food waste

4

Energy

FIGURE 18.4 Bioeconomic strategy application to the circular economy for effective food waste management.

strategies come into play. There is apprehension that extensive use of biomass while adopting a bioeconomic approach to attain sustainable development may pose a threat to food security. The use of food waste as feedstock in these processes helps in overcoming such apprehensions. The different methods of recycling this food waste again rely on the collection of food waste as a separate fraction. In cases where food waste is collected separately it is subjected to anaerobic digestion, composting, liquefaction, or rendering for extracting specific products like tallow or high-protein meal, etc. The collection of specific wastes like spent coffee grounds is useful in the production of biodiesel, solid fuel, and fertilizer rich in nitrogen (Caetano et al., 2014). In cases where the organic fraction is mixed with the inorganic fraction, as in many developing countries that either lack regulation for organic waste management or lack implementation of the regulation, it is subjected to processes like gasification or incineration with energy recovery, landfill with gas collection, and pyrolysis. All these latter processes are least preferred options when it comes to management of food waste. Finally, the disposal of food waste without any productive use is the worst-case scenario of tackling food waste. This option not only adds to global greenhouse gas emissions but also removes a significant amount of nutrients that are vital to maintaining the productivity of the soil from the system. Fig. 18.4 explains the bioeconomic strategy application to the circular economy for effective food waste management.

18.9

Conclusions and future of food waste management

Food is one of the most basic needs of all living beings. According to UN (2015), the world population is projected to increase by more than one billion people within the next 15 years, reaching 8.5 billion in 2030. One of the major impacts of the growing world population is the pressure on production of food that in turn puts tremendous pressure on land resources. According to FAO (2008) approximately one-third of all food produced today goes to landfill. Food wastage not only makes food resources unavailable to a large section of the population but is also highly polluting as it leads to the wasteful use of resources such as fresh water, soil, fertilizers, and energy (FAO, 2013; Lundqvist et al., 2008) that have been used in its production. This wasteful use of resources accounts for nearly a third

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of greenhouse gas emissions (FAO, 2013). Thus with the growing demand for food due to increased population and decreased land productivity, food waste management has gained importance. A linear approach to food production and food waste management has damaged the environment and has taken us far from the goal of sustainability. Food waste management needs to be adopted based on the principles of a circular economy with integration of bioeconomic strategies. A circular approach to food waste management would first ensure that food waste is not generated, and when generated it would look at opportunities for reuse like donation of safe food to economically weaker groups of people. When the food waste generated becomes unfit for human consumption the bioeconomic approaches that rely on the foundations of biotechnology would help in valorizing the food waste as animal feed, fertilizer, biomaterial, or biofuel. When all these options are exhausted food waste enters the last and least preferred option of energy recovery in the circular economic approach. For the effective implementation of a CE-based food waste management approach that is integrated with the strategies of bioeconomics it is important to rope in the various stakeholders involved in the generation and management of food waste, including individuals, business establishments, public and private institutions, industries, and most importantly policymakers. The successful management of food waste requires awareness among stakeholders and operational mechanisms for collection of food waste. Apart from this, the policies and regulations developed in the region should encourage the easy participation of these various stakeholders. With awareness among the various stakeholders on the importance of food waste management and favorable policies that encourage the participation of the various stakeholders, the outputs received from its management would help in closing the nutrient loop that would ultimately restore the balance on our planet.

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Chapter 19

Scaling up of food waste valorization market outlooks: key concerns R.A.A. Meena1, Arpan Ghosh2, Palanivel Sathishkumar3 and R. Jayabalan2 1

Department of Environmental Sciences, Bharathiar University, Coimbatore, India, 2Food Microbiology and Bioprocess Laboratory, Department of

Life Science, National Institute of Technology, Rourkela, India, 3Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education; School of Chemistry and Environment, South China Normal University, Guangzhou, P.R. China

19.1

Introduction

The huge and growing global population has left the natural environment with record high pollution levels and reduced resources, causing chaos for the sustainable environment (Meena et al., 2018). However, the up-scaling processes preceded by refinery approaches are fixing the world’s waste problem. In addition, increased fossil fuel use is associated with serious risk from environmental hazards, including sea level rises and massive air pollution. Therefore nations must strengthen their commitments to combating climate change, and step up their efforts to reduce fossil fuel usage and create a sustainable environment for future generations (Amulya et al., 2015a,b). With a view to creating a sustainable environment, the major obstacle lies in the generation of mountains of waste, especially food wastes. In addition, poor handling of food wastes and their disposal are a serious issue. To overcome this problem, various institutions and enterprises can actively engaged in food waste management practices around the world. To simplify the food waste management practices, certain production guidelines and standards are followed. These include using “Food Use for Social Innovation by Optimising waste preventioN Strategies” (Fusions, 2016) in food waste management and making it a socially innovative one. FUSIONS is a European Union project comprised of recommendations to help build a society with an innovative approach to reducing food waste. The positive impact of these approaches plays a role, particularly in the economic sector in developing countries. Countries including China and Japan have introduced schemes in which the volume of waste generated was linked to the amount charged from the public. A class of functional foods is emerging that can target the food market with its high quality along with improved nutrients. These have the potential to reshape the future of the food industry by managing demand patterns and modern urbanization processes which are directly linked with the rise of supermarkets. As importantly, the food market has the ability to target weight management, diabetes care, and immunity without compromising the fortification of the nutritional value of food. In light of this, we do not require only a waste management strategy; we require a clear-cut approach for the extraction of resources from waste, because currently that is missing from the management practices. According to Paritosh et al. (2017), almost 1.3 billion tonnes of food waste is generated globally per year. Thus, in order to manage food waste, various waste management practices such as aerobic digestion, hydrolysis, and liquefaction are widely applied (Kannah et al., 2018; Kavitha et al., 2017). Although traditional techniques are applied to convert wastes, their success is limited due to practical difficulties. Nowadays, the valorization technique is a booming process of converting waste and wastewater into resources (Meena et al., 2019a). Recent research reports have emphasized that none of the valorization strategies is applicable to all kinds of food waste. What, then, is the most suitable valorization technique for a variety of food wastes? Concerning the new biorefinery concept, there is an integration of various valorization approaches, such as anaerobic digestion and dark fermentation. This concept leads to the production of biochemicals, biomaterials, and biofuels, and aims at the conversion of food wastes into multiple products, such as volatile fatty acids (VFAs), bioethanol, sugar, biopolymers, biohydrogen, biomethane, and biodiesel that are utilized in various sectors. In addition, up-scaling of biorefinery techniques could soon spell the end of traditional valorization procedures. The determinant factors for up-scaling may be embedded in the process itself, namely, the composition of food wastes as Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00019-5 Copyright © 2020 Elsevier Inc. All rights reserved.

401

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well as the phenomenon of disintegration (Fiore et al., 2016). Regulating pH, temperature, and reactor design may enhance the production rate. However, pure cultures, batch mode of operation, and major of food waste contents may be protein and fat, which make it difficult for the refinery process to be up-scaled (Alibardi and Cossu, 2016; Rodriguez-Perez et al., 2018). The pretreatment method and addition of codigestors may have a profound impact on the valorization process, and thus up-scaling (Jarunglumlert et al., 2018). This chapter deals with food waste management practices, institutions and enterprises involved in these processes, production guidelines and standards, market-based products, and food waste valorization techniques, including the biorefinery concept and its future perspectives with a view to transforming it from a linear economy to a circular economy.

19.2

Institutions and enterprises in food waste management

With the increase in the wastage of food currently, there is a need for proper management of this problem. Many nongovernmental organizations (NGOs) and community-based organization (CBOs) are taking initiatives to manage the wastage of food. In this regard, some organizations such as 412 Food Rescue, Food Cowboy, and FoodLoop, use mobile technology (usually mobile apps) to communicate with food wholesalers and restaurants to prevent surplus foods from ending up in landfills. In addition, some other organizations (Caritas, Vatican City, Italy) rely on creating awareness among people regarding food waste management methods. For example, FoodLoop, a Germany-based organization, allows food retailers to sell food products which have a short shelf-life by adjusting the price of the product via its FoodLoop mobile app. In addition, these organizations and some institutions also take part in the food waste management process. Meanwhile, they are creating awareness about food waste management and also highlighting the strategies to control the wastage of food (Organizations fighting food loss and food waste, Food Tank, 2016). Table 19.1 lists some of the organizations and institutions involved in food waste management.

19.3

Production guidelines standards

Regulations concerning food waste reduction, such as restrictions or covenants, compulsory management plants, laws, and standards are being made and adopted in the Netherlands, Belgium, France, and Italy. France has outlined 11 TABLE 19.1 Organizations working on food waste management (Organizations fighting food loss and food waste, Food Tank, 2016). S. no.

Organization name

Location

1

412 Food Rescue

Pennsylvania, United States

2

Caritas

Vatican City, Italy

3

Food Cowboy

Maryland, United States

4

Food Cycle

London, England

5

FoodLoop

Cologne, Germany

6

OzHarvest

Sydney, Australia

7

Satisfeito

Sao Paulo, Brazil

8

Re-Nuble

New York, United States

9

MOGO

Berkeley, California

10

Vermigold

Mumbai, India

11

Harvard Food Law and Policy Clinic

Cambridge, Massachusetts, United States

12

Markets Institute

Washington, DC, United States

13

Natural Resources Defence Council

New York, United States

14

World Resources Institute

Washington, DC, United States

15

World Vegetable Centre

Taiwan City, Taiwan

16

International Institute of Waste Management

Bangalore, India

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403

measures to reduce food waste by 50% by 2025 through the National Pact (Mourad, 2015). FUSIONS, a project funded by the European Union (EU), has framed the guidelines for reducing food waste through socially innovative approaches across the supply chain. Especially, FUSIONS has suggested recommendations under six groups that include policies to be made, practices to be followed, and approaches to be designed for the prevention and reduction of food waste in the European Union and its Member States (Fusions, 2016).

19.4

Financial measures

Food waste has become a primary environmental, social, and economic concern, and food waste reduction policies are being developed at a global level. In general, people reduce their food wastage to save money. Saving money is the primary concern in reducing food waste, rather than social and environmental issues (Stancu et al., 2016). Loss of money through the food waste is considered to be the primary driving factor in reducing food waste (Neff et al., 2015). For example, an economic recession in Greece was the main reason for a reported reduction in food waste (Abeliotis et al., 2014). Similarly, wastage of food is also considered as a waste of time spent on purchasing the provisions and preparation of food (Neff et al., 2015). While comparing the reduction of food waste, other global concerns like global warming and excessive use of resources rank lower in people’s concerns (Pearson et al., 2016). Asian countries including Taiwan and South Korea have started to reduce food waste/municipal solid waste (MSW) generation at the source and have achieved almost a 50% reduction in MSW generation in the past 10 years (Au, 2013). The governments of Taiwan, South Korea, the United States, Japan, Canada, Sweden, China, Vietnam, and Thailand have changed the behavior of people on food waste generation by introducing quantity/volume-based charging schemes [PAYT (pay-as-you-throw)] (UNEP, 2014). This scheme was also supplemented by the introduction of a charging system exclusively for prepaid designated food waste bags to promote the separation of waste at the point of generation (Arancon et al., 2013). If food production exceeds demand, then food will be wasted. This frequently happens in farming due to unpredictable weather and pest attacks. In the case that production exceeds demand, the food crops or foods are sold as animal feed or to processors, which can be economically unprofitable (FAO, 2011).

19.5

Market-based products

In general, foods are broadly categorized into three subsectors. These are (1) crop-based products (wheat, rice, corn, sugar, and other agro-food products); (2) fruit and vegetables; and (3) animal proteins (livestock, fish, seafood, and meat products) (Pullman and Wu, 2011). In the past half century, food systems have undergone a significant revolution with enormous potential impact for the diets of people worldwide (Freire and Rudkin, 2019). Food markets have emerged as a new form of food service establishment in order to provide a wide variety of high-quality food with improved nutrients (Lee et al., 2019). Furthermore, this kind of nutritional transformation is directly connected with managing demand patterns, rising incomes, and modern urbanization processes, which have coincided with the rapid spread of supermarkets (Reardon and Timmer, 2012). In addition, consumers are becoming increasingly aware about their lifestyles and healthy diets, which has greatly increased the demand for functional foods. Thus, food industries are deploying fortification of nutritional additives such as carotenoids, dietary fibers, fatty acids, minerals, vitamins, prebiotics, and probiotics in their food products. The global functional foods market was estimated at US$161.49 billion in 2018. The food market illustrates the distribution of functional food products (such as bakery products and cereals, dairy products, meat, fish, and eggs, soy products, fats and oils, etc.) worldwide. In the market, the dairy-based product area (yogurts, milk drinks, etc.) led the overall market in terms of revenue in 2018, followed by bakery products and cereals. This market serves various roles including (1) sports nutrition, (2) weight management, (3) immunity, (4) digestive health, (5) clinical nutrition, and (6) cardiovascular and diabetes care. Snowdon et al. (2013) reported on the manufacture of market foods sold in Pacific countries. Especially, Pacific countries have powerful economic link with Australia, France, New Zealand and the United States which are the largest market-based food manufacturers. The available market-based foods include juices, soft drinks, cordials, breads, biscuits, noodles, breakfast cereals, confectionary, ready meals, ice-cream, butter/spreads, processed fish, sauces, canned vegetables, frozen vegetables, processed meats, and snack foods. Sauces, biscuits, and snacks had the largest variety at a regional level in these markets. In addition, processed canned fish was a very popular item.

404

19.6

Food Waste to Valuable Resources

Food waste management and valorization

19.6.1 Food waste valorization The raw materials used in the processing of food can deliver more or less equal amounts of waste. Vegetables and fruit, both fresh and processed, fish and meat product waste, grain and grain products, alcoholic beverages, and wastewaters related to the food industry, such as cheese whey, are among the top food wastes described in the literature. The enormous amount of food wastes has shaken the sustainability of food production as well as the environment (GarciaGarcia et al., 2017). The food industry may be a reason for climate change, and processing industries contribute to greenhouse gases due to the way they release heat and moisture into the atmosphere. Hence switching to waste reduction practices could reduce carbon emissions (Capson-Tojo et al., 2016). Waste reduction practices may hold the key to the recovery of valuable materials, chemicals, and fuels from food wastes. Food wastes begin replacing synthetic media by microbial cultivation, paving the way for the production of value-added chemicals (Lin et al., 2014). Moreover, pyrolysis, one among many green processing technologies, may turn food waste into high-value chemicals and fuels, which can play a role in the food and transportation industries, respectively (Arancon et al., 2013). Though the valorization techniques result in better treatment efficiency of food waste, they remain in need of up-scaling. Before implementation, analysis of valorization techniques on food waste and identifying all related factors is needed. Multiple factors, such as faster rate of degradation, high water content, oxidation, and enzymatic activity play roles in the management of food waste, as it has a higher proportion of organic content already. In terms of valorization, strategies such as landfilling, animal feeding, composting, fertilizer supply, incineration, and anaerobic digestion (Kavitha et al., 2014) are more likely to share the first-generation technologies. Of these, landfilling and composting remain the major option for waste disposal and management (McConville et al., 2015). Exposure of wastes to incineration results in energy recovery. In addition, anaerobic digestion has the power to act on food waste, and can contribute to the production of biofuels (Zema et al., 2018). Despite the advantages and attracts of these techniques, they pose environmental hazards, which not only affect the management process but also affect the well-being of those who live near them (Ruiz and Flotats, 2014). Thus, the innovation of advanced valorization strategies plays a role in bridging the gap between the enormous amount of food waste and the need for the production of value-added materials from waste (Sen et al., 2016). These processes offer many potential uses, starting from the use of uneatable waste, with a low environmental impact, and end up with the extraction of precursor compounds for the synthesis of materials to enhance the shelf-life of products. In this context, bioprocesses like acidogenesis, fermentation, methanogenesis, solventogenesis, and bioelectrogenesis hint at the surprising production abilities of biofuels and biofertilizers from food waste. A good way to enhance the economic condition of these processes is switching to biorefinery concept, which allows the integration of the above processes and may result in the recovery of additional products (Dahiya et al., 2018).

19.6.2 Biorefinery approach A good way to exploit the valorization strategy is to switch from the use of a nonrenewable-based narrow approach to a renewable-based, broad and closed-loop approach, which is otherwise known as the biorefinery approach (Venkata Mohan et al., 2016). Here, valorization of food waste is more likely to produce chemicals, materials, and fuels. This approach is accompanied by advanced and sustainable valorization waste strategies and is achieved with the help of various types of food waste, including food processing wastewaters from the kitchen level to the industrial level. As shown in Table 19.2, the biorefinery approach has fueled the rise in the combination of one or more bioprocesses, namely, anaerobic digestion, acidogenic fermentation, solventogenesis, chemical conversion, methanogenesis, and extraction, hinting at the production of biobased products from high organic waste such as food waste (Poggi-Varaldo et al., 2014). Increased exploitation of food waste by these integrated processes using a biorefinery approach not only reverses the limitations of individual processes but also significantly raises the number of products available. For example, the flammable nature of H2 and low-flammable nature of CH4 could be used in the production of biohythane. In this context, various biobased products were discussed on the basis of valorization strategies with a focus on food waste as shown in Fig. 19.1.

19.6.3 Up-scaling In the event of commercialization, up-scaling is a process in which the production system moves ahead, from lab scale to bench scale, which in turn progresses to pilot scale, and finally large-scale industrial levels. In this context, regulating

TABLE 19.2 Profile of processing methods for biorefinery outcomes. S. no.

Source of food waste

Broad range of products

Processing methods

Specific products

References

1

Rice, vegetables, and meat

Biochemicals

Acidogenesis

Volatile fatty acids (VFAs)

Kiran et al. (2014)

Bioethanol

Walker et al. (2013)

Biobutanol

Abd-Alla et al. (2017)

Corn, potatoes, and pasta

Solventogenesis

Potato peel and cheese whey

Stoeberl et al. (2011) Chemical conversion

Sugars

Apple pomace 2

Food processing wastewater

Cheese whey

Arancon et al. (2013) Parmar and Rupasinghe (2013)

Biomaterials

Acidogenic fermentation through VFA production

Biopolymers

Biofuels

Dark fermentation

Biohydrogen

Amulya et al. (2014) Venkateswar Reddy and Venkata Mohan (2012)

Fermented and unfermented food waste 3

Wang et al. (2014)

Azbar et al. (2009)

Wastewater

Gopalakrishnan et al. (2019)

Food processing industry waste

Marone et al. (2014) Anaerobic digestion

Biomethane

Cheese whey With molasses

Aslanzadeh et al. (2014) Fuess et al. (2017)

Algae cultivation and extraction

Biodiesel

Castanha et al. (2014)

Palm oil mill effluent Composite wastewater

Dark fermentation and anaerobic digestion

Biohythane

Mamimin et al. (2017)

From food processing industries

FIGURE 19.1 Biorefinery approach.

Sarkar and Venkata Mohan (2017)

406

Food Waste to Valuable Resources

the system process by using output parameters and operating conditions may help enhance the production efficiency (Liu et al., 2018). Generally, during the course of the process, the initial higher organic loading rate in reactors may increase the accumulation of VFAs later. Instead, a reactor filled with an optimum of 3 gVS/L/d organic loading may also offer potential biogas production (Aslanzadeh et al., 2014). Food waste with a higher amount of soluble carbohydrate, for example, bread and pasta, is the ideal choice in the valorization process. On other hand, food waste teeming with cellulosic biomass threatens the digestion process (Kobayashi et al., 2012). Moreover, the production of ammonium nitrogen and low hydrogen partial pressure may be linked to the digestion of protein and lipid content in food waste, respectively (Ariunbaatar et al., 2015; Dong et al., 2009). To illustrate, the production of amino acids from proteins and long-chain fatty acids from fats have differences in production rate (Chen et al., 2014; Dong et al., 2009). Thus, an optimized organic loading rate and suitable substrates are becoming increasingly good at producing products with higher quality and quantity levels (Pasupuleti et al., 2014). Various pretreatment methods, such as acid, alkali, heat, ultrasonication, and UV light applied during the fermentation process, do not only enhance the disintegration of food waste but also raise the quantity of products (Kim et al., 2009; Elbeshbishy and Nakhla, 2011; Xiao et al., 2013). In addition to the above optimization procedures, the valorization process includes reactor designs like anaerobic sequencing batch reactors (ASBRs), anaerobic baffled reactors (ABRs), continuous stirred tank reactors (CSTRs), anaerobic contact reactors (ACR), anaerobic plug flow reactors (APFRs), anaerobic sludge blanket reactors (UASBs), and anaerobic membrane bioreactors (AnMBRs) to offer better production (Karthikeyan et al., 2016; Tawfik and ElQelish, 2012; Reddy et al., 2011; Sentu ¸ ¨ rk et al., 2012; Chong et al., 2012; Jayalakshmi et al., 2009; Dvorak et al., 2016) and, among these, AnMBR is the perfect candidate for refinery products (Nayak and Bhushan, 2019). Exposure of additives (biochar, lime mud, and sludge) in codigestion appears to have an impact on the production process (Sunyoto et al., 2016; Zhang et al., 2013; Lin et al., 2013). The phenomenon of codigestion was exacerbated by enhancing the buffering capacity, incorporation of mineral salts, and improvisation of the C/N ratio, etc. (Zhang et al., 2017; Lay et al., 2013). Therefore, a perfect pretreatment method, reactor configuration and substrates for codigestion are more likely to develop a format for up-scaling (Shobana et al., 2017; Jarunglumlert et al., 2018). Continuous mode of operation of the digestion of food waste may increase the likelihood of success of the scale-up process and make it possible to reduce the length of the lag phase and shutdown period, and minimize cleaning compared to the batch mode (Nam et al., 2016; Han et al., 2016). Moreover, the level of pH and fermentation period tied to the production level paves the way for up-scaling (Pan et al., 2008). No matter what the type of food waste, using a mixed culture rather than only individual or two microbes as the parent inoculum can most effectively enhance the production rate, which improves up-scaling (Patel et al., 2015; Kumar et al., 2016). In addition, Fiore et al. (2016) applied scale-up technology to evaluate the digestion of food processing wastes from the semipilot to the pilot level and obtained satisfactory results. Jang et al. (2015) analyzed and reported on the up-scaling of the evolution of H2 with pretreated food waste. Ironically, the results concluded that pilot scale production (1.57 mol H2/mol hextose) of H2 was slightly less than lab scale production (1.71 mol H2/mol hextose). Over and above, new baseline engineering data for the scale-up process raise the hope of sustaining the current technology (Venkata Mohan, 2009). Taken together, further research toward the implementation of novel biological techniques and the creation of enzymes for effective disintegration could be turned into efficient scale-up, and may help food waste treatment to be carried out at a commercial level in the near future. Table 19.3 shows the scaling up of food waste valorization strategies leave behind a rich foot print of cost reduction and economic viability.

19.7

Market value of food waste valorization products

Food waste embraces the valorization practice, which uses low-value feedstocks to recover high value-added products. The listed products are not only the precursors for chemicals and energy but also direct usable food, feed, materials, etc. These products are included in the commercial value category and thus are in demand (Cristobal et al., 2018). In short, the market value of these products basically depends on the nature of the feedstock and the overall production cost. First, tomato peels with waste of as much as 1.48 3 106 t/year have undergone valorization with the help of supercritical fluid extraction with CO2 and enabled the production of lycopene and β-carotene with a medium market value of 4 3 104 and 4000 EUR/kg, respectively (Kehili et al., 2016). The same products have low and high values of 4000 and 4 3 105 EUR/kg lycopene and 400 and 4 3 104 EUR/kg β-carotene, respectively. Second, the source for three phenolic acids, neochlorgenic acid, chlorgenic acid, and caffeic acid, and three glycoalkaloids, alfa-chaconine, alfasolanine, and solanidine, is in potato peel and its root valorization pathway is solvent extraction using a mixture of water and acetic acid (Meireles, 2009). The market value of one of these phenolic acids, namely, neochlorgenic acid, with waste of 2.34 3 106 t/year comes under low, medium, and high values of 30, 300, and 3000 EUR/kg, respectively

Scaling up of food waste valorization market outlooks: key concerns Chapter | 19

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TABLE 19.3 Challenges and opportunities for scaling up food waste valorization. S. no

Kinds of food waste

Valorization technique

Challenges

Opportunities

References

1

Coffee husk, rice husk, hazelnut skin, cookie by-products, and pomace

Anaerobic digestion

Disintegration, composition of substrates and H2S productiona

Addition of sodium bicarbonatea

Fiore et al. (2016)

2

Mixture of bread and pasta

Fermentation

Cellulosic carbohydrate

Easily degradable carbohydrate

Alibardi and Cossu (2016) Kobayashi et al. (2012)

Mixture of meat, fish, and cheese; fruit waste and vegetable waste 3

4

5

Protein wastewater

Fermentation

Rich in protein

Cheng et al. (2015)

Rich in lipid

Dong et al. (2009)

Pretreatment done in lab scale only and leads to the formation of VFA production

Pretreatment method

Continuous operation

Food processing industrial waste and bread waste

Anaerobic digestion and fermentation

Batch mode

Kitchen waste

Anaerobic codigestion

Lack of nutrients leads to improper C:N ratio

Xiao et al. (2013) Łukajtis et al. (2018) Fiore et al. (2016) and Han et al. (2016)

Codigestion

Kim et al. (2011a) Zhai et al. (2015)

6

Fruit waste

Anaerobic digestion

Thermophilic

Mesophilic

Zema et al. (2018)

7

School cafeteria food waste

Fermentation

Mesophilic

Thermophilic

Kim et al. (2011b)

8

Composite food waste and cheese whey

Anaerobic fermentation

Pure culture and aseptic conditions

Mixed cultures

Amulya et al. (2015a,b) and Oliveira et al. (2017)

9

Food waste

Fermentation

Acidic and alkaline pH

Neutral pH

Kim et al. (2011c) Nazlina et al. (2009)

10

a

Food waste

Anaerobic digestion

Higher organic loading rate induces inhibition in bacterial community and irreversible instability of reactor

Sodium bicarbonate makes a positive effect which can prevent the risk of H2S overproduction.

Digester with separate acidogenesis and methanogenesis stages

Nayak and Bhushan (2019) Khan et al. (2016)

408

Food Waste to Valuable Resources

TABLE 19.4 Market value of valorized products from food waste. S. no.

Source of food waste

Biorefinery approach

Valorized product

Market value

References

1

Tomato peel

Supercritical

Lycopene

4 3 104 EUR/kg

Kehili et al. (2016)

Fluid extraction with CO2

β-Carotene

4000 EUR/kg

2

Potato peel

Solvent extraction

Neochlorgenic acid

300 EUR/kg

Maldonado et al. (2014)

3

Orange peel

Extraction

Pectin

$10 kg21

Ciriminna et al. (2015)

Limonene

$14 kg21

4

Barley

Malting

Culm

h100 t21
h200 t21

Garcia-Garcia et al. (2019)

5

Organic farm waste with cheese whey

Fermentation and anaerobic digestion

Ethanol

1.89 USD/L

Oleskowicz-Popiel et al. (2012)

Methane

0.72 USD m3

Protein fodder

55 ton21

6

Orange peel

Acid-free extraction

Pectin

h11 kg21

Clark et al. (2013)

7

Olive mill waste

Supercritical fluid extraction with CO2

Polyphenols

2000 EUR/kg

Schievano et al. (2015)

Fatty acid methyl ester (FAME)

100 EUR/kg

Limonene

1.1 USD/kg

8

Citrus peel waste

Solid-state fermentation

Zhou et al. (2007)

(Maldonado et al., 2014). Three types of food waste products valorized from orange peels are identified as essential oils (EO), TPC (polyphenols), and pectin, with market values of 1
70 EUR/kg, around 360 EUR/kg and from 10
350 EUR/kg respectively, which enhances the biorefinery pathway (Davila et al., 2015; MERCK, 2017). In addition, Clark et al. (2013) found the market value of pectin as d11 kg21 from 50,000 tonnes of orange peel. Table 19.4 shows the market value of valorized products from food waste. According to Ciriminna et al. (2015), market values of $10 kg21 for pectin and $14 kg21 for limonene were found for orange peel waste. Notwithstanding, microwave hydrodiffusion and gravity, microwave-assisted extraction, and ultrasound-assisted extraction have positive effects on orange peel valorization, which is linked to the production of EO, TPC, and pectin (Boukroufa et al., 2015). The above-described valorization pathway makes the market value in three categories as low, medium, and high for orange waste biorefinery outputs: low value, 1 EUR/kg for EO; 10 EUR/ kg for both TPC and pectin, medium value, 10 EUR/kg for EO; 100 EUR/kg for both TPC and pectin and high value, 100 EUR/kg for EO; 1000 EUR/kg for both TPC and pectin. In the case of olive mill wastes with 4.1 3 106 t/year as the input amount, supercritical fluid extraction with CO2 with ethanol as solvent can convert olives into valorized products, such as TPC, fatty acid methyl ester, and squalene, with medium market values of 2000, 100, and 100 EUR/kg, respectively (Schievano et al., 2015). Moreover the same study explored the low market value (200, 10, and 10 for TPC, fatty acid methyl ester, and squalene, respectively) and high market value (2 3 104, 1000, and 1000 for TPC, fatty acid methyl ester, and squalene, respectively) for the valorized outcomes. Garcia-Garcia et al. (2019) pointed out the use of culm, a highly nutritious waste from malting of barley, is more likely to be valorized as animal feed with a market value of d100
200 t21. Moreover, spent grain resulting from the mashing process is used as animal fodder with a market value of d25 t21. Oleskowicz-Popiel et al. (2012) coproduced ethanol, methane, and protein fodder in an organic farm using cheese whey as a raw material, with an economic value of US$1.89 L21, US$0.72 m3, and US$55.00 ton21, respectively.

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409

19.7.1 Factors influencing the market value of valorized food waste products The market value of the valorized food waste products may help predict the minimum yield and thus the profitability of the valorization pathway. A significant valorization pathway can increase the volume of the marketable product by decreasing the production cost while increasing the volume of feedstock (Jacquet et al., 2015). Though the production cost plays a major part in determining the market value, several other factors also play a part, including capital cost, manufacturing cost, revenue, and profitability ratios, which play direct and indirect roles in determining the production cost and thus the market value of the products. First, all fixed capital costs, working capital costs, and indirect capital costs make the total capital investment (Jarunglumlert et al., 2018). Second, the cost of manufacturing includes the cost of raw materials, cost of labor, cost of utilities, and cost of waste treatment, which are otherwise related to the daily functioning of the biorefinery process. The market value of the valorized products that affect the revenue rate of the process is another crucial factor found in technoeconomic analyses. In addition, the revenue rate is identified as an indicator, as it has influential effects on the price which is linked with the profitability of the valorized product. Notwithstanding, profitability performance embraces profitability ratios, which uses return on investment, net present value, and payback time to achieve the profitability assessment (Albarelli et al., 2016; Jarunglumlert et al., 2018). To pave the way for achieving profitability in the case of marketing of valorized products, the values of return on investment and net present value should be positive and the payback time should be reduced (Cristobal et al., 2018).

19.7.2 Challenges for attaining the commercial valorization of food waste Though factors such as feedstock volume and suitable valorization pathway have paved for attaining the market value for valorized products, other factors are responsible for disrupting or creating hurdles to achieving the market value. These distrupting factors may be viewed from two sides, that is, economic and technical. From the first point of view, a mixed waste by itself is a risk factor for food waste, but when combined with nonbiological waste from a collection point of view, the sorting process is more difficult. The sorting creates greater risk of having another characterization of waste that could cause severe drawbacks in reaching the commercial value stage for the valorized products. Moreover, geographical area, climate, and people’s food habits can have a negative impact on sorting and characterization of food waste, which is ultimately reflected in the market value of the outputs (Waqas et al., 2019). An uninterrupted supply of food waste is a significant factor, which influences the operation and affects the marketed value of high-yield products with quality assurance. However, the literature suggests that improper supply of food waste is a problem for the large industry food processing sector, as valorization final products with low yield and low quality do not meet the market value standards. Smaller processing units overtake larger ones in the valorization process as they are easily accessed with food waste producers. The chemical composition, such as carbohydrates, amino acids, lipids, proteins, vitamins, phosphate, and nutrients of food waste are identified to reduce its direct use as a raw material in the production of valorized products (Karmee, 2016). The separation and purification of food waste have negative effects on the market value of the final products and is linked with other environmental and public health issues as volatile organic solvents are used for the processes. From a technical point of view, an optimized process condition is the secret to the overall performance of the valorization pathway. Poor control of process conditions has negative effects on final product yield and system stability, and is linked to the formation of noxious compounds. For example, poisonous gases such as hydrogen sulfide (H2S) and long-chain fatty acids made by the lipid and protein contents of food waste put the valorization pathway at risk and adversely impact the final product and thus its market value (Xu et al., 2018). The postvalorization process can impact the market value of the final products and create problems for commercial valorization by recovery and purification (Couto and Sanroman, 2005; Singhania et al., 2009).

19.7.3 Policy framework for commercial valorization of food waste An integrated or single-reaction system is highly sustainable greatly reducing the total cost of the valorization pathway, and paves the way for commercialization of final products (Waqas et al., 2019). This sustainable development needs a policy framework in several areas including renewable feedstock supplies (European Commission, 2012). However, prior to the 1970s, there was no policy framework in practice regarding waste management. Therefore, the European Union (EU) promotes various policies focusing on sustainable development (Fritsch et al., 2017). First, minimization of waste and maximization of reuse, recycling, and environment-friendly alternative materials was encouraged by the EU policy which approved the waste framework directive (75/442/EEC) (Pawelczyk, 2005).

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Food Waste to Valuable Resources

This directive uses a waste policy, with various waste management hierarchies, and the use of waste as an energy resource was one (Pawelczyk and Muraviev, 2003). Second, recently, the valorization of various organic materials including food waste has been motivated by the EU policy which approved the EU directive (Directive (EU) 2018/ 851). This directive aims at reducing the disposal of food waste, such as organic materials, on land, as it poses negative effects both to land and aqueous environments, and is linked to other environmental impacts, such as both noxious and greenhouse gas emissions. In contrast, this directive moved toward a biorefinery concept for better valorized final products, for example, biofuels such as biohydrogen and biomethane (Meena et al., 2019b). The phenomenon is exacerbated by the availability of food waste as feedstock and the ability to use food waste to produce biofuels (Garcia et al., 2019). EU policy, otherwise called integrated product policy (IPP, 2003), is more likely to reduce resource use and environmental impact while enhancing sustainable development. Moreover, this policy is in agreement with the market in such a way that it creates incentives for companies by encouraging the continuous supply and demand for valorized final products. Third, this policy creates a continuous improvement in the sense of decreasing the environmental impact of the product along its life cycle, including its disposal. This policy is more likely to concentrate on decreasing the impacts rather than attaining a threshold level. As a result, companies which follow the policy have been making their decisions by implementing cost-efficient techniques. Hence, this policy is acting as a supplement to current legislation by boosting development in the final products which otherwise do not require legal certification.

19.7.4 Factors contributing to the uncertainties for the market value Various factors, including cost estimation, could act as a catalyst in further impacting the market value of valorized food waste products. These factors are believed to make the market value of valorized products uncertain, which would otherwise be profitable for investment. Low-level technologies involved in valorization of food waste may slow down the biorefinery process and puts the market value of resultant products at risk (Tsagkari et al., 2016). Valorized products of suitable composition and purity state tend to gain greater market value compared to their low-quality counterparts. According to Cristobal et al. (2018), all valorization products fall under two categories, profit or nonprofit, and this phenomenon is exacerbated by the number of plants and the market value. Moreover, utilities such as electricity and natural gas in the production process are linked to uncertainty in the market values of valorized products. EUROSTAT (2017) pinpointed factors such as geographical area, import options, environmental protection costs, political arena, network costs, and levels of excise and taxation, as being responsible for the supply and demand of utilities, which may have an impact on uncertainty of the market value. In addition, laboratory results helped in up-scaling the valorization pathway to an industrial level. However, the quantity and mass balance of valorized output from an industrial scale do not meet the requirements for market value. Hence, process variables also play a crucial role in the market value of valorized products.

19.8

Conclusions

The world’s fossil fuel usage and the resultant shortage is a crisis and this ironical situation could be reversed by the proper waste management strategies in both developed and developing nations, something we would imagine would be an advantage in waste management. It is now time to find solutions to the enormous amount of wasted food. In this context, this chapter discusses the steps taken by institutions and enterprises and also the guidelines and standards followed to achieve waste management. In addition, various revenue generation strategies and market-based products are overviewed. Along with the above guidelines and strategies, food waste valorization, biorefinery approach, and its upscaling are highlighted. Coming to the market outlook, this chapter has discussed the market value of valorized products including animal feed at low, medium, and high prices. In addition, it explored the factors influencing the market value of the final products coming from food waste, including capital cost. Moreover, how improper supply of food waste as feedstock followed by sorting, chemical composition, and further purification of final valorized products, put their market value at risk has been described. Furthermore, this chapter has identified the policies which are helpful for the valorized products in attaining market value. To conclude, this chapter further pointed out the factors believed to play a role in making the market value uncertain.

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Further reading Achmon, Y., Claypool, J.T., Pace, S., Simmons, B.A., Singer, S.W., Simmons, C.W., 2019. Assessment of biogas production and microbial ecology in a high solid anaerobic digestion of major California food processing residues. Bioresour. Technol. Rep. 5, 1
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Agyeman, F.O., Tao, W., 2014. Anaerobic co-digestion of food waste and dairy manure: effects of food waste particle size and organic loading rate. J. Environ. Manage. 133, 268
274. Alexandropoulou, M., Antonopoulou, G., Trably, E., Carrere, H., Lyberatos, G., 2018. Continuous biohydrogen production from a food industry waste: influence of operational parameters and microbial community analysis. J. Clean. Prod. 174, 1054
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157. Banu, J.R., Kavitha, S., Yukesh Kannah, R., Poornima Devi, T., Gunasekaran, M., Kim, Sang-Hyoun, et al., 2019a. A review on biopolymer production via lignin valorization. Bioresour. Technol. Available from: https://doi.org/10.1016/j.biortech.2019.121790. Banu, J.R., Pravathy Eswari, A., Kavitha, S., Yukesh Kannah, R., Kumar, Gopalakrishnan, Jamal, T.M., et al., 2019b. Energetically efficient microwave disintegration of waste activated sludge for biofuel production by zeolite: quantification of energy and biodegradability modelling. Int. J. Hydrog. Energy. 44, 2274
2288. Bhaumik, P., Dhepe, P.L., 2014. Exceptionally high yields of furfural from assorted raw biomass over solid acids. RSC Adv. 4, 26215
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319. Chu, C.Y., Tung, L., Lin, C.Y., 2013. Effect of substrate concentration and pH on biohydrogen production kinetics from food industry wastewater by mixed culture. Int. J. Hydrog. Energy. 38, 15849
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438. Gao, A., Tian, Z., Wang, Z., Wennersten, R., Sun, Q., 2017. Comparison between the technologies for food waste treatment. Energy Proc. 105, 3915
3921. Goud, R.K., Arunasri, K., Yeruva, D.K., Krishna, K.V., Dahiya, S., Venkata Mohan, S., 2017. Impact of selectively enriched microbial communities on long-term fermentative hydrogen production. Bioresour. Technol. 242, 253
264. Gunaseelan, V.N., 1997. Anaerobic digestion of biomass for methane production: a review. Biomass Bioenergy 13, 83
114. Huang, H., Singh, V., Qureshi, N., 2015. Butanol production from food waste: a novel process for producing sustainable energy and reducing environmental pollution. Biotechnol. Biofuels 8, 147. Humbird, D., Davis, R., Tao, L., Kinchin, C., Hsu, D., Aden, A., et al., 2011. Process Design and Economics for Biochemical Conversion of Lignocellulosic Biomass to Ethanol. National Renewable Energy Laboratory (NREL): Golden, CO, 2011; NREL/TP-5100-47764. ,http://www. nrel.gov/docs/fy11osti/47764.pdf.. Indira, D., Das, B., Bhawsar, H., Moumita, S., Johnson, E.M., Balasubramanian, P., et al., 2018. Bioresour. Technol. Rep. 4, 209
213. Jiang, J., Zhang, Y., Li, K., Wang, Q., Changxiu, G., Li, M., 2013. Volatile fatty acids production from food waste: effects of pH, temperature, and organic loading rate. Bioresour. Technol. 143, 525
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78.

Chapter 20

New business and marketing concepts for cross-sector valorization of food waste A. Parvathy Eswari1,*, V. Godvin Sharmila1,*, M. Gunasekaran2 and J. Rajesh Banu3,* 1

Department of Civil Engineering, Anna University Regional Campus Tirunelveli, Tirunelveli, India, 2Department of Physics, Anna University

Regional Campus Tirunelveli, Tirunelveli, India, 3Department of Life Sciences, Central University of Tamil Nadu, Neelakudi, Thiruvarur, India

20.1

Introduction

In this modern time, society contributes more effort toward the impact of manufacturing, marketing, and purchasing products based on communal, moral, and ecological aspects along with the economic perspective. Commercialization of recovered products from waste has more environmental benefits, with unique characteristics and steady costs (Brown et al., 2011). As per the report of the International Energy Agency (IEA), the global trade value of biobased recovered chemicals reached 9% that of synthetic chemicals in 2012 with a market value of US$252 billion. In addition, the implementation of appropriate technology for the biorefinery process is required to withstand the competitive business sector. This competition enables the providence of high-quality recovered products with manufactured assurance to meet consumer requirements (Miandad et al., 2017). Hence, the adoption of cheaper methodology using fewer stages in the recovery process with appropriate performance and better product yield should enable profit during commercialization. The most significant fact in implementing recovered products on a large scale is consumer acceptance, which is an indication of product failure or success. This depends on the storage life, color, healthiness, formulation of the product, and source of the raw materials used. A raw material source has a major responsibility in the biorefinery process. In this framework, food waste (FW) is a better option, as it is an economical, renewable, and excellent feedstock to generate recovered products such as biochemicals, biomaterials, and bioenergy sustainably. The global population increment and urbanization have exacerbated FW generation in the form of liquids and solids (Kavitha et al., 2017). The burden of disposal has instigated a recovery process that is an ultimate strategy in FW management. Consumer’s awareness of environmental issues and strict legislation limits for industries in FW dumping promote the development of eco-safe management options. The valorization of FW alters its composition to beneficial products with better characteristics to gain market value. Nowadays, the beverages and meat-processing industries utilize phenols and dietary fiber extracted from olive mill wastewater (Caporaso et al., 2017). About 27 million tonnes of waste from fish-processing industries are used to recover products in for the cosmetic and pharmaceutical sectors (Ben Rebah and Miled, 2012). Hence, vast scientific knowledge is required to overcome innovation issues and prevent unsuitable products prior to commercialization on a large scale in accordance with the strict regulations for product safety. During the innovation of business and marketing of recovered products, certain barriers such as investment cost, product knowledge, multidisciplinary skills, communication skills for marketing, research efforts, regulation limitations, and policies need to be tackled. An outline to the chapter is given in Fig. 20.1. This chapter describes the commercialization and patented applications in FW biorefineries including policy implications and marketability of products. The necessity for good marketing and formulation of these strategies to attain better value are well elaborated and various business models for implementing product recovery from FW are discussed. The contracts and public interest in the sustainable development of FW biorefineries are also detailed.

*These authors contributed equally. Food Waste to Valuable Resources. DOI: https://doi.org/10.1016/B978-0-12-818353-3.00020-1 Copyright © 2020 Elsevier Inc. All rights reserved.

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FIGURE 20.1 Overview of the business and marketing concept in food waste biorefineries.

20.2

Commercialized and patented applications of food waste biorefineries

Commercialization plays a significant role in achieving good social, environmental, and economic impacts of recovered bioproducts in FW biorefineries. The major objective of FW biorefinery commercialization is to extend the innovative patent idea from laboratory research to a large scale with similar productivity and product quality. Fundamental, methodical, and biological issues must be solved for profitable and successful large-scale operation after detailed study and research. Proper planning for successful implementation of the product with suitable capacities is necessary, with adequate knowledge of commercial and industrial strategic issues (Banu et al., 2018). These tactics assist in the sustainable development of innovative marketing companies.

20.2.1 Intellectual property protection Implementation of unique ideas in developing FW biorefineries is a crucial step to attaining better progress in the business sector with good market value for the recovered product. The term “intellectual property production (IPP)” is the fundamental method of protecting innovative facts to avoid the distortion of scientific and business strategies. Hence, intellectual property (IP) is considered a major feature during the commercialization of FW biorefineries. It is important to understand the fundamental rules and laws to safeguard the IP rights prior to the commencement of operations for industries or companies. Proper documentation of rules, costs, and expected investment, etc. are needed for the IPP application. It is a precautionary step to avoid the interference of third parties which may restrict business operations. Industries must take proper cautionary steps to guard their IP by filing patent applications, proper cataloging of trademarks and copyrights, along with additional suitable steps to protect trade secrets. About 147 members of the World Trade Organization have signed up to protect the IP of the work of individuals within member countries. There are four main types of IPP: G G G G

Copyright protection; Patent protection; Trade protection; Design protection.

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Copyright protection is the protection of creative and factual ideas that promote artistic and literary creation in recovered products. They can be registered once the work is published or voluntary registration can be done which prevents disputes about ownership. This copyright law is valid for 70 years after registration, even after the author’s/creator’s death. After the article publication, copyright is transferred to the author who holds the copyright for 25 years (James and Jennifer, 2014). In the United States, copyrights are valid for 28 years and can be renewed regularly, and it is an offense if the work is revealed to the public without the knowledge of the author. Economic rights and moral rights are protected in copyright by the World Intellectual Property Organization (WIPO). The economic right is the claim for revenue for using the work, and the author can prohibit or authorize the public utilization and translation of their work. Moral rights are the personal rights to protect from offensive worthless profit and the right to obstruct work modification to secure work fame. The WIPO committee on development of IP has an official agenda in implementing the guidelines, and considering queries and recommendations with respect to copyrights. Patent production protects novel methodological facets of the recovered product. It can be achieved by filing the innovative ideas at the patent office, which is the most common protection model. The longevity of a patent filing is 20 years (Williams, 2017). It can be filed at national, international, as well as regional levels. In trade protection, the trade identity is safeguarded to gain the market value by securing the information of business details such as investor details, dealers signs and business ideas. Design protection represents the registration of a product design or shape for marketing that protects the visual appearance of the product. Hence, IPP is an important pivotal phase that should be used to achieve successful marketing of new products recovered from FW biorefineries.

20.2.2 Commercialization and scale-up issues Commercialization of recovered bioproducts at a large scale has several problems including (1) lab-scale research, (2) difficulties faced by biobased recovered product production at the pilot scale and large scale, (3) intellectual property protection (IPP), and (4) proper development of the precise application. Startup and basic optimization of the biorefinery process can also hamper timely product recovery (De Bhowmick et al., 2019). Another major challenge is handling of huge quantities of FW for large-scale production. In addition, it is essential to monitor for microbial contamination prior to processing, as this may drastically affect the biorefinery process and promote failure of the derived final product. This necessitates proper storage facilities, and critical scale-up parameters such as extraction processes and reactor working volume are required. It is not practical for all the physical or chemical parameters to be maintained constantly during scale-up, and it is important to predict crucial parameters which disturb the execution of effective scale-up. On implementing the bioproduct extraction techniques, economic benefits and establishment of recovered product in the market are the major factors to be considered. During the scale-up process, the functional characteristics and quality of the recovered product should not be altered, and they must satisfy the consumer’s need (Pham and El Halwagi, 2011). This is difficult due to the existence of complicated recovery procedures, along with recapturing techniques. Crucial limitations such as time and heavier handling can affect the functional quality of the product. High process cost is attributable to high food formulations of recovered biorefinery products on a large scale compared to lab-scale production. Scale-up and commercialization problems should be resolved to enable the full range of cost-effective biobased product recovery from FW.

20.2.3 Patents and their requirements An IP right granted for an innovative invention which can be used for industrial applications with a creative step is called a patent. The patent provides legal rights to restrict the manufacture, sale, use, and trade-in of recovered products. The patent holder can file a charge when infringement of patent occurs, since patent rights come under civil law. Patents encourage research growth by providing details of innovative, nonobvious biobased recovered products with industrial applicability and enable the right to earn capital during patent implementation (Giugni and Giugni, 2010). Patent offices/servers under process include the United States Patent and Trademark Office (USPTO) (http://www.uspto.gov/), Controller General of Patent Designs and Trademarks (http://www.ipindia.nic.in/), and Google Patents (http:// www.google.com/patents). Based on the USPTO, there are three types of patents: utility patents, design patents, and plant patents. Utility patents include novel methods in the extraction processes, techniques, and manufacturing processes, and are granted for 20 years from the date of filing the patent application. Design patents cover the product’s quality and characteristics with a firm depiction of the product nature. This design patent has 14 years longevity and can be used to stop sale and product manufacture by unauthorized persons (WIPO, 2019). Industrial plant are provided with innovated equipment and innovated design to recover products in the FW biorefinery process. Major requirements

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to obtain patents include for patentable subject matter innovation (new products, processes, business methods, and materials), novelty (no publication before filing for patent), inventive innovation (certainty of new product), and utility innovation (novel industrial applicability). Patents are granted on technical criteria and are not based on commercial or market criteria.

20.2.4 Patented methodologies There are various patented methodologies for biobased recovered products for the existing market, as shown in Table 20.1. Through the patent application, the recovered product is verified and matched with the patented process during each novel innovation. The exact innovation details about the production method are kept secure. Certain commercialized bioproducts from food and vegetable waste are now discussed in detail. A dietary supplement, albumin powder, was extracted from soy protein wastewater. This dietary supplement has analogous properties to whey protein. Lycopene was a highly marketed pigment in the business sector and can be extracted from tomato waste, which is utilized in restaurants to color meat and as a substitute for carmine. The Food and Drug Administration (FDA) confirmed the presence of lycopene in tomato by-products. In addition, the Food and Safety Inspection Service uses this lycopene pigment at a concentration of 50
100 mg/kg as a color agent in various food products. Hence, this biobased recovered pigment has good market value during commercialization. Apple pomace is a by-product of the apple-processing industry and this pomace is used to extract hemicellulose by a solvent extraction process using an alkaline solution. In addition, pectin is also extracted from pomace using acid. Both hemicellulose and pectin are employed in foodstuffs and sweet products as a substitute for flour, fat, or sugar. This recovered product has the ability to preserve liquid, which enhances the suspensions and oxidative immovability. Furthermore, phenolic compounds are extracted from peel and pulp mixture by a sequential extraction process which is disrupted by ultrafiltration. Olive mill waste is exploited to yield sustainable hydroxytyrosol using chromatographic columns filled with two resins: nonactivated ionic and XADtype nonionic. Solvent extraction using acid is performed to treat olive mill wastewater to convert oleuropein to hydroxytyrosol. This recovered product retains antiradical properties associated with vitamins E and C, which inhibits lipid oxidation in fish and is used as a food preservative in bakery products to increase longevity. A polyphenol antioxidant, Hidrox, extracted from olive waste has antiinflammatory and antimicrobial potency. Salmon fish oil is extracted from salmon fish by patented a hydrolysis and mechanical extraction process. Spent grounded coffee is used to extract aroma using patented methodology.

20.3

Policy options and their implications

In order to stimulate the innovation of the biorefinery concept in FW, policies have been formulated which address the challenges in FW, prohibition of excess waste production, diminishing of FW at source, effectual recovered product distribution, and recovered product trading schemes. A short description of the most significant policy options in FW biorefineries is given next.

20.3.1 Social innovation and food waste This policy options focus on fulfilling the social needs in a more efficient manner than the current solution. Research interest and awareness of using biobased products should be boosted through the educational system by proper funding from R&D activities (Issa et al., 2019). Paramount assets include the knowledge provided through the education system (e.g., college and university degrees). Also, educational programs with industrial sectors enhance the education system with long-lasting policies. Proper training has been provided to develop the unemployed employees by providing innovative ideas to provide quality bioproducts for societial concern and also trained to promote the products in the market in order to augment the professional skill and social policies. The core intention of this policy option is to develop scientific knowledge and empirical evidence to encourage innovative technologies.

20.3.2 Policy measures promoting social innovation In order to gain experience for a project to be launched on a large scale, a proper detailed investigation is required at the demo scale/lab scale. This develops the project experience and gains consumer interest, investor interest, and raw material supplier’s interest regarding the final output (bioproduct) of the project and initiates the opportunities for deriving new business. A pilot-scale study may avoid the technical obstacles encountered during implementation. Incentives

TABLE 20.1 Patented methodologies for commercial-scale implementation of various food waste biorefinery products and their market applications. S. no.

Food waste

Recovered bioproducts

Patented methodologies

Applicant/company

Market application

Patent application number

Reference

1

Apple pomace

Dietary fiber

Solvent extraction

Yantai Andre Pectin Co. Ltd (China)

Dietary supplements

CN2008/1139768

Anming et al. (2010)

2

Pomegranate peel and seed

Ellagic acid and punicalagin

Solvent extraction

Xi’an App Chem-Bi(Tech) Co., Ltd (China)

Antioxidant in food industry and cosmetics

WO/1999/030724

Guangyu and Xiaoyan (2011)

3

Chicken feathers

Keratin

Washing, grinding, perforated rotating spiral drum, skimming, compounding

Eastern Bioplastics LLC

Polypropylene packaging, as a sorbent of hydrocarbons

US2012/08182551

Meyerhoeffer and Showalter (2012)

4

Olive mill waste

Medoliva (hydroxytyrosol, tyrosol, caffeic acid, and pcoumaric acid)

Ultrafiltration, ion exchange resin adsorption, solvent elution, spray drying

Polyhealth (Larissa, Greece)

Food supplements and antioxidants, cosmetics, personal care products

GR2010/1006660

Petrotos et al. (2010)

5

Spent coffee grounds

Bioactive silverskin extract

Subcritical Extraction

Consejo Superior de Investigaciones Cientificas/ CIAL (Madrid, Spain)

Cosmetics, nutrition, and health

WO 2013/004873

Del Castillo et al. (2013)

6

Tomato processing waste

Lycopene

Conventional extraction process

BIOLYCO Srl.

Therapeutics value

US20100055261A1

Lavecchia and Zuorro (2010)

7

Grape seed

Polyphenols and pigments

Pulse electric field and highvoltage electric discharge process

Universite Technologie De Compie`gne-UTC (Compie`gne, France)

Food supplements and additives

PCT/EP2011/ 070597

Boussetta et al. (2013)

8

Olive pomace

Polyphenols and oil

Conventional extraction

University of Porto

Cosmetic purpose and food additives

WO/2017/212450

Oliveira et al. (2017)

9

Tamarind seed

Polysaccharide

Solvent extraction

Indena SpA

Active pharmaceutical constituent

EP2575973 A1

Giori et al. (2013)

10

Pomegranate peel

Polyphenols

Conventional extraction

Liker; Harley, 2014

US2014/0056930 A1

Liker (2014)

11

Plant food waste

Phytochemicals

Centrifugation

Minister of Agriculture and Agri-Food, Canada

Functional food ingredients

US07943190

Mazza and Cacace (2011)

12

Food waste

Methane

Anaerobic digestion plant

Emerson Electric Co.

Storage

WO2015199887A1

Michael and David (2015) (Continued )

TABLE 20.1 (Continued) S. no.

Food waste

Recovered bioproducts

Patented methodologies

Applicant/company

Market application

Patent application number

Reference

13

Cranberry and pomegranate extract powders

Antibacterial agents

Thermal extraction

Mackler, Ari (POM Wonderful LLC)., 2014

POMcran capsules (25
5000 mg)

US2014/0010871 A1

Mackler (2014)

14

Spent coffee grounds

Aroma

Solvent extraction

University of Minho. CEB— Center of Biological Engineering (Braga, Portugal)

Distilled beverage

PT 105346

Mussatto et al. (2013)

15

Mango peel

Pectin, polyphenols

Acid hydrolysis

Taboada, Evelyn., Francis Dave Siacor., 2013

Gelling agent, stabilizing agent in fruit juices, preservatives

WO2013141723 A1

Taboada and Siacor (2013)

16

Coffee silverskin

Bioactive silverskin extract

Centrifugation extraction

Ito En, Ltd, (Tokyo, Japan)

Paper industry

US 7,927,460

Sato and Morikawa (2011)

17

Citrus peel

Dietary fiber, flavorant, oil

Solvent and enzymatic extraction

Del Monte Foods Inc

Nutritional supplement, food additive

US20130064947 A1

NafisiMovaghar et al. (2013)

18

Kitchen waste

Lactic acid

Fermentation process

Massachusetts Institute of Technology

Acid regulator, preservatives and flavoring agent

US20160355849A1

Gregory et al. (2016)

19

Plant materials

Phytochemicals

Pulsed electric field




Food additives

US Patent 8147879

Ngadi et al. (2012)

20

Food waste

Lactic acid

Biofield generator to ferment food waste

TSNT GLOBAL CO., Ltd, Daegu

Flavor compound

US20180016196A1

Choi (2016)

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from well-famed biorefinery industries through joint ventures may minimize the investment risk (Rosales Calderon and Arantes, 2019). It supports innovated product development to replace inadequate products in the market. This enables profit, greater distribution of product, more affordable price of product to be decided, good promotion in the market, and also adds trade value. Setting up educational programs at a national/local scale about biobased product usage may assist in the development of innovative technologies. The absence of this may obstruct and hinder the development of innovative technologies due to poor understanding. Hence, proper information about different stakeholder requirements with technical details and their impact is necessary for effective commercialization of biobased products.

20.3.3 Policies and regulations Advancement of opportunities to produce green products is done through firm environmental standards and regulations. The augmentation of goods and service prices result in product loss. It is intended to enhance stakeholders’ expectancies by gathering successful stories about the innovative biorefinery sector. Some negative aspects of this policy include limited data, which may lead to misconception of methodological and commercial information. Japan’s Food Waste Recycling Law was passed to encourage the recycling of FW by industries in order to enhance biobased product businesses. The Amendment of Municipal Solid Wastes (Management and Handling) Rule in 2013 and 2015 categorized FW into biodegradable coded containers by color at the source of generation. The National Environmental Agency (NEA) and Agri-Food and Veterinary Authority (AVA) of Singapore and Malaysia have conducted educational programs to reduce FW generation. China launched the Food Security Law in 2009 to regulate FW treatment.

20.3.4 Resolving challenges into opportunities This policy option exists for areas to meet unnecessary issues that develop during orientation, including a lack of harmonization in national and local governance. This requires public investment and subsidies to establish a structure with proper facilities, such as communication systems, power requirements, and manufacturing unit systems. The decisive option to harmonize service procurement has to be guaranteed to develop a biorefinery. This depends on the FW suppliers, companies involved in collection, mechanical services, stocking and delivering biorefinery products, all aimed at minimizing the operational costs for resourcing innovate logistics systems (Philp, 2015). These are crucial activities in order to guarantee the procurement of services necessary for the development of a biorefinery and to achieve effective coordination. Direct grants for marketing biobased products may distort the market resulting in excess supply. If grants are provided based on quantity, marketability increases. Furthermore, fixing higher price for final products causes issues in transferring wealth to producers from consumers/taxpayers. This addresses the creation of marketability for biobased products along with regulatory challenges. The major limitation of this policy requirement of bioproducts shows no difference, but there is a major difference in cost and benefits of the products. This depends on the feedstock or production methods. Proper recognition needs to be provided by governments for these recovered biobased products with little environmental impact compared to petroleum-based products.

20.4

Applications and marketability of food waste-based biorefinery products

There has been a dynamic development of biobased recovered products from FW biorefineries, with a 20% annual growth rate. Most of these companies are still in their early developmental stage of marketing, as it is a timeconsuming activity due to the multifaceted supply chain and operational process. The bioproducts derived from FW replaces the fossil fuel-based products which could make a huge impression in the present market on a large scale at low price and are considered to be valuable bio-refinery products. Thus, price and environmental impact play vital roles in the application and marketability of these products. This necessitates the prospect of innovating new bioproducts rather than replacing products to satisfy the market need without competing with current products. Though innovation of novel markets has challenges, it could enable a sustainable expansion of these products to new areas. The global marketing for bioplastic polymers is less than 1% as these polymers are used for food packaging only, however they are an innovative green product that was expected to attain 5% of the market by 2020. Biochemical and biomaterial sales in this market could reach 17% and 38%, respectively, of the total market by 2050 (Dusselier et al., 2015). The real marketability of biobased products is governed by industrial growth and policies that shift from a fossil fuelbased economy to a biobased economy. Basic biobased recovered product has a market value in the range of h0.5
2/kg. Perfect innovative products could achieve a good market price. Each year, biomedicines have an 11% increment in the market. Nearly 50%
60%

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medicines are produced by chemical synthesis using natural products as the source material (Straathof and Bampouli, 2017). About 120 medicines currently in the market are prepared from higher plants and 10%
25% of medicines that at least have one active compound from higher plants. A similar marketing approach was achieved for biocosmetics and bionutrients extracted from FW biorefineries.

20.4.1 Fruit and vegetable waste There are some biobased recovered products that are produced on a commercial scale that have high marketability. Europe is a major producer of sugar beet, at 13 million tonnes/year. Sugar beet processing units create beet pulp as a waste product which is processed by a PULP2VALUE approach to extract a valuable compound—microcellulose fiber. This fiber has a high marketing value for manufacturing detergents, oils, paints, personal care substances, and coatings (Yang et al., 2018). One of the leading companies, Royal Cosun, has utilized the PULP2VALUE approach and developed a full-scale plant to produce bioproducts. This product has a market potential of 350 tonnes, with a value of 200 million euros. Another innovative research is Pro-Enrich, which utilizes rapeseed pressed cake, olive pomace, tomato, and citrus waste to generate bioproducts using research designed by the Danish Technological Institute (Denmark). The biobased recovered products generated include protein, polyphenols, pigments, and dietary fibers which are utilized as food additives, animal feed, cosmetics, and adhesives. Global Bioenergies in France has organized an OPTISOCHEM approach to extract isobutene from wheat straw. This extracted product has been used for producing high-value marketable products such as lubricants, flavor agents, fragrances, and sealants. The yield of this isobutene from wheat straw is 20% greater than from fossil fuel-based substances. Food grade protein powder (RuBisCO) is unique in nature as it is extracted from discarded vegetal processing industry waste in an industrial scale. This product has two to five times higher market value than the current artificial protein powder. Phenolic compounds and carotenoid pigment are extracted from paprika, red chili, red pepper, and capsicum species (Yammine et al., 2017). Carotenoid pigment has good market value as a coloring agent.

20.4.2 Coffee waste Worldwide, coffee is a highly utilized food product and the by-products of coffee processing include coffee silverskin and spent coffee grounds as waste during the roasting and brewing processes. This waste has certain biobased compounds such as antioxidants, nutritious fiber, and biostarch which have numerous health benefits (Campos Vega et al., 2015). Coffee silver skin is one of the best functional food additives to improve health, and also can be used to manufacture paper. About 6 million tonnes of spent coffee waste are generated annually, this could be utilized to extract flavors for confectionery, biscuit, cereals, and pastry preparation. Another waste from the coffee bean processing industry is coffee cherry, which has a citrus, floral, or roasted fruit nature. This waste has wide applications in bread, cookies, brownies, pasta, sauces, etc. (Hughes et al., 2014) and wide scope in the food market. Extraction phenolic compounds from winery waste include grape marc and lees (Yammine et al., 2017). These techniques are also used to extricate the carotenoid pigment from paprika, red chili, red pepper, and capsicum species.

20.4.3 Dairy product waste Natural nutrient-rich proteins are a major product recovered from dairy product waste. From the dairy product waste, lactose and aroma compound are extracted by an enzyme-assisted extraction process. The recovered lactose has potential applications in glucose-rich syrup production and sweetener preparation (Dutra et al., 2015). The European dairy industry makes use of this waste to generate whey protein using the AgriChemWhey approach, and also lactic acid, polylactic acid, minerals, etc., which enhance human nutrition and quality biobased fertilizers. This approach attracts an income of up to 325 million euros, with about 80,000 tonnes of lactic acid being exported.

20.4.4 Animal by-products A tremendous quantity of waste is generated by the meat-processing industry with potential nutritive value which can be processed as food additives. The microbial-disintegrated waste of this industry forms a slurry which is processed as fertilizer. The meat industry generates a huge amount of wastes and by-products, which are a good source of nutrients and can be used as food ingredients and additives (Jayathilakan et al., 2011). The meat products processed by the air flotation skimming process form a sludge which has good nutritive value and is purchased for agricultural purposes as a

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fertilizer (Hamawand et al., 2017). Chicken feathers have a high keratin content, which is used for packaging. In addition, omega-6-fatty acid, which can be extracted from chicken waste from the chicken-processing industry, has medicinal uses (Lasekan et al., 2013).

20.4.5 Seafood waste The shells of crab and shrimp are used to extract a polymer-based compound, chitosan, by a solvent extraction process with alkali and chloroacetic acid treatment. This recovered chitosan is used as a thickener in vegetable oil and an antirancidity agent in meat (Muley et al., 2018). The fishery industry produces a huge quantity of waste and by-products that can have high fish oil contents. The omega-3 in this fish waste is used in foodstuffs and therapeutics. Greater attempts have been proposed to valorize fishery wastes and by-products (Lopes et al., 2015). The skin of fresh and burnt salmon fish is used to form gelatin and salmon oil as a result of fish protein hydrolysate. In addition, fish guts, skins, heads, and bones can be used as animal feed (Fan et al., 2017; Jayathilakan et al., 2011).

20.4.6 Emerging innovative marketing technologies High-pressure processing (HPP) units have been utilized for preservation purposes in the past. Currently, HPP has gained significance in the extraction process for valorization techniques to recover valuable compounds. Other innovative technologies such as ultrasonication are used to obtain biopolymers (protein and carbohydrates) from soy waste. Also, pulse electric fields (PEFs) and high voltage electrical discharges act as potential treatment units to recover products from various FWs (Zuntar et al., 2019). The electroporation method extracts food products from meat, fish, and seafood by-products. Certain plant-derived vegetable wastes are utilized to recover biobased products. Phytochemical compounds are extracted by a subcritical water extraction process from plant-based FW; this compound is a rich source of antioxidants (Kumar et al., 2017).

20.5

Need for new marketing approaches

New marketing is one of the major requirements in the business field at present. The growing demand and search for new sustainable biobased products (with zero side effects) by consumers has promoted the development of a new marketing approach. Recently, the marketing trend has focused on eco-friendly products to overcome the various health issues and reduce the purchasing of chemical-based foods in the market. This motivates the innovation of various biorefinery products from FW (Perlatti et al., 2014). These biorefinery products reach the consumer through marketing. This makes the definition of marketing as follows: “marketing is the business action that supplies the exact biorefinery products and amenities from perfect producer to consumer at perfect place, time and price with proper service allocation to fulfill the customer’s satisfaction.” The marketing concept focuses the demands and necessities of consumers in terms of market data for developing strategies in order to fulfill consumer demand and organization goals. This boosts the development of a new market approach by proper collection of FW from source of generation and processing to recover the biobased product. This may easily tackle the problem of FW generation in quantity and quality. The marketing concept includes the following: G

G G

Products in the form of belongings, services or thoughts are distinct based on consumer requirements which has been focused by the organization. Assimilation of entire organizational activities together with production and publicity to meet consumer demands. Attainment of longstanding organizational targets through official and reliable fulfillment of consumer demands.

20.5.1 Cost and safety issues of emerging technologies compared with conventional techniques FW biorefineries process FW to biobased products by conventional techniques including physical processes: boiling and freezing, machine-driven, and electromechanical processes. About 29% of energy was utilized in the boiling process and 16% in freezing techniques. This motivates the development of innovative technologies to reduce the energy cost. This innovative technology also demands reduced operational costs (Sikarwar et al., 2017). Low thermal plasma treatment consumes less energy, at about $0.045/kg, but requires $636
9096/h to feed helium gas as input (operational cost) and $9
72/h for nitrogen as feed gas. Valorization of FW using a PEF extraction process consumes $9
72/h for a flow rate of 10 t/h and requires a lower energy input of 10 kJ/kg, which is sufficient to recover bioproducts from juices, sugar beet, apples, and chicory. The HPP-assisted extraction process consumes $0.107/L as operation costs

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on processing 16,500,000 L/year of FW. However, the labor and capital costs are about 59% ($0.063/L) and 37% ($0.04/L) (Nizami et al., 2017). Innovative techniques also require more operational cost to produce biobased products, but have the advantage of reducing toxic compound generation. Consumers with knowledge of present biorefinery development would purchase biobased products with cost consideration but in knowledge of the environmental benefits. Consumer anxieties toward the regular usage of ideal product and processes enables the food manufacturers to develop innovative technologies in the production field. Hence, this approach has been used to develop new technology for FW biorefinery processes.

20.6

Business models

A business model illustrates the successful implementation of a business by considering the investment and financial details. Business models in FW valorization provide commercial prospects that contribute to sustainable business growth to generate new revenue and shift the attitudes of customers and businesses to protect the economy against product shortage and cost increments. Implementation of business models augments the production of biorefinery products and their marketability.

20.6.1 Triple-layered business model This business model tool was used to explore an innovative and environmentally sustainable business. It explains the method of business development and the value of products created. It includes financial value in addition to the social and environmental values (Joyce and Paquin, 2016). This model enhances the sustainable development of organizations and society to produce good products with better market value. It allows the economic, environmental, and social validation of the model to develop creative user-friendly exploration of products for marketing. It offers a short outline to support visualization, statement, and teamwork throughout sustainable business model development (Lewandowski, 2016). The economic features of this business model to retail FW biorefinery product is illustrated in Fig. 20.2. Expenditures is described through funds such as distribution networks, brand, manufacturing factories, and patents, and activities such as marketing, manufacturing, and logistics. The social impact of the triple-layered business model considers the social value, employees, governance, business partner communities, scale of outreach, etc. The environment aspects of this model are required to assess the environmental benefits of the recovered product. Environmental benefits depend on the raw FW used and the quality of products obtained.

FIGURE 20.2 Triple layer model in social, economical, and environmental aspects.

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FIGURE 20.3 Flowchart representing the purchase incidence model.

20.6.2 Purchase incidence model This model specifies the number of purchases that occur within a specific time. The sale of new product quantities is estimated in terms of customer percentage based on past documentation. This type of model was validated by crosssectional data in accordance with marketing and services. However, it is difficult to deal with individual customers. The model investigates the reward program and events motivating the product purchase, retention, and revenue growth (Tafesse and Korneliussen, 2012). In this model, shareholder value maximization and investments made for marketing recovered products are properly evaluated. This intensifies the attractiveness to certain shareholders and significant analysts to focus alternative business strategies to intensify the growth, revenue, and profit as monitored by the manager (Verhoef et al., 2015). The opted-for techniques must be consistent with the ultimate marketing activities funds, which are calculated with respect to the expected effects on market capitalization. Fig. 20.3 presents a purchase incidence model.

20.6.3 Order size model This model predicts the optimal order quantity at a given time for a given cost and requires sufficient space for storage, which indicates the economic order quantity business model (EOQ model). As per the literature, there are certain limitations in the EOQ model concerning the modern standard management’s role through an effective inventory control system (Zhou et al., 2016). Assumptions made within this model are maintaining constant demand and lead-time and that inventory is instantaneous. This can promote serious financial implications for the organization. Inefficient cost control causes excessive expenses through high storage costs, unwanted product, and a reduction in working capital. The manager should have control of the inventory method, as the private sector acquires its profit when the inventory is controlled. It is obvious to maintain product value that is economically desirable for the customer. The major issues are maintaining inventory value to the lowest cost feasible subsequently saving on working investment and storage costs (Shekarian et al., 2016). The following formula explains the order size model: Q 5 ð2ASÞ1=2 =I

(20.1)

where Q is the economic order quantity (units); A is the yearly demand for specific product for a specific time (units); S is the ordering cost for a single purchase order; and I is the carrying cost to hold 1 yearly unit inventory. The order quantity model with function as the total cost is provided in Fig. 20.4. It was observed that when the Q value increases, orders to be placed decrease for each year. Thus, the supply cost is augmented due to the larger average inventory.

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FIGURE 20.4 Order quantity model plot.

20.7

Marketing strategies and practices

This section illustrates the different strategies that are utilized to supply products to clients and customers of a business. It focuses on the efforts expended by the manufactures to produce the product for the marketing. There are various marketing strategies, namely: food distribution, communication, product and purchase, packing and its types, selling price, and promoting sales. These strategies act as a bridge between companies to collaborate with consumers. Practical implementation of this strategy creates knowledge about the product, awareness of product features, specifications, and benefits (Maniatis, 2016). Hence, these effective marketing strategies support the innovative product production in gaining an advantage over the competition.

20.7.1 Food distribution FW occurs at each stage of food production and distribution. The national food industry and environment organizations are taking drastic steps to prevent these issues. The Feeding Network of America has launched a food biorefinery technique with the distribution of excess FW as food (Paritosh et al., 2017). This is an initial phase of the FW management process in which FW is collected from the source of generation prior to dumping. The collected FW is distributed to those with a shortage of food. Also, the remaining waste including raw vegetables and fruit, like peels, pericarp, decayed food products, etc., are collected and distributed as animal feed and biofertilizers for plant growth.

20.7.2 Communication strategy It is the strategy of biorefinery organizations to reach the market goal by various means of communication and also to share information for political, psychological, or linguistic purpose (Van Dael et al., 2017). During this communication, caution should be taken to avoid incomplete unfinished messages and irrelevant discussions. This strategy can be promoted in seven ways: G G G

G

G

G G

Nomination—This is the method of illustrating relevant clear and truthful information about the product; Restriction—Obligation of responses and reaction raised during communication; Optimal performance—Recognizing the perfect time to perform and communicate by analyzing when and how to speak; Subject control—This is a query section to forward the subject discussion. This also motivates listeners to contribute ideas; Subject shifting—This is a method of incorporating new innovative topics when there is a follow-through, so that new topics continue to be discussed. This can also be used to repair the communicative strategy; Repair—Overcoming communication breakdown to send more comprehensible messages; Termination—Making use of verbal and nonverbal gestures to end the communication.

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20.7.3 Products and processes The strategy for the product is the roadmap of the recovered product with complete manufacturing in the stipulated time to produce authentic products to achieve the market goal (Jayaram et al., 2013). The process strategy focuses on the process performed to fulfill the customer requirements and satisfaction throughout the product cycle.

20.7.4 Packaging and its types Packing is the process, technology, and science of sealing or closing the product for sale, distribution, storage, and use. This significant strategy serves product identification and protection making it clean and convenient for the customer at the point of purchase (Garcı´a Arca et al., 2014). Different types of packing include plastic packing (to pack industrial goods), aluminum packing (to pack animals feeds), cardboard backing (to pack groups of products for distribution), glass packing (to pack medicinal products), and foam packing (to pack animal-based products during shipping).

20.7.5 Selling price Pricing for a new marketing approach must be attractive. It aims to gain the attention of consumers by offering a lower price on recovered product than the competitive, and by delivering the correct message to consumers to capture their attention at critical points of purchase in retail stores with attractive offers for biobased products. About 70% of consumers fall into this marketing strategy. This can be done by emphasizing price benefits and offers. This strategy is efficient for market competition.

20.7.6 Promoting sales One of the top-most strategies in marketing is the creation of awareness and interest toward a product. This strategy mainly focuses on the consumer’s perception of bioproducts rather than cost. Awareness of problem identification and its solution are required in this strategy (Espinoza et al., 2017). Attracting customer attention by digital advertisements such as blogs, content marketing in newspapers, video marketing, and social media marketing and infographics improve product marketability. Also, the direct selling of the biobased product to the doorstep by a virtual marketing technique is helpful. A social media management service promotes the new innovative product directly to consumers in a nonretail environment. Nowadays, this type of marketing strategy has high demand and helps facilitate the rapid growth of innovated biobased products.

20.8

Developing unique selling points

This is the method of maintaining uniqueness in the product among equivalent bioproducts to make the product more valuable during marketing (Ramcilovic and Pu¨lzl, 2018). The unique selling point is created based on consumer need and their satisfaction, current trends and competition, and continuous monitoring of new competitors. Some options that develop unique selling points are given below.

20.8.1 Date labeling Based on the European Food Information to Consumer law, the recovered product requires date marks to indicate the threshold for the product’s safety. This labeling is aimed at sharing information about the duration of food quality without spoilage, along with manufacturing and packing date labeling.

20.8.2 Retailer options This is a method of making product available to the customer using different modes of operation, such as placing products in shopping mall, website, and vending machines. It focuses in selling the product.

20.8.3 Mobile applications This is a method of advertising the product using a mobile app to the customer. The mobile app marketing business is performed throughout the world, with the best-known examples being Amazon, Flipkart, and Snapdeal Through a

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Food Waste to Valuable Resources

mobile app, recovered products are promoted by creating a blog and using social media such as Facebook and WhatsApp to share details of innovated products in the market(Kannan and Hongshuang “Alice” Li, 2017). The Snapdeal app has a separate category called “BIO Daily needs” for selling recovered products. Shopify Inc., a Canadian multinational e-commerce company, has online stores to sell these products.

20.9

Contracts and public procurement of biorefinery products

Public procurement is acquisition by governments and state-owned enterprises of goods, services, and works including for biobased recovered products. The procurement of green biobased recovered products is a complex task due to various environmental aspects (Sherwood et al., 2016). A charitable method to acquire environmental performance certification is ecolabeling. This method of labeling biobased recovered products is in practice throughout the world. This ecolabel assists in product marketability and enables consumers to choose a product with a low environmental impact. This symbol is reliable, enabling producers to demonstrate to the consumer the authenticity of their product. The government has trade constraints to seal foreign products, termed mandatory labels. Voluntary ecolabeling is the labeling of government-sponsored products that are funded and supervised by the private sector. However, there remains a lack of proper recognition for biobased recovered products in the business sector. These green public procurement schemes have secure environmental sustainability requirements. The procurement expert assures ecolabeling with proper selection criteria to identify products and producers and to verify environmental claims. The government passes tenders for contracts to analyze the innovative processes for launching on a large scale. Contracting authorities must consider the total cost incurred on the product recovery project. Recently, 13 innovative contracts have been undertaken in the Netherlands with a total cost of 125 euros to promote the development of a biobased economy (Keegan et al., 2013).

20.10 Food waste and the transition toward sustainable development To have a better transition of FW in the direction of sustainable growth, high-quality experimentation and campaigning are required, as detailed in Fig. 20.5. This helps to achieve more innovative techniques to produce biobased products with lower energy consumption, minimum resource inputs, and using renewable energy sources wherever possible (Jurgilevich et al., 2016). In addition, this ensures that all those involved in the FW biorefinery process work in a nontoxic and sanitized working environment with adequate social welfare and training activities.

20.10.1 Food waste dynamics This is the method of assessing the current FW in the ecosystem and the challenges to manage it. It also explains the regulation, waste to be sorted before treatment, treated FW, and its mass reduction, which play an important role in

FIGURE 20.5 Food waste biorefinery sustainable development.

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determining the FW quality to adopt a proper volarization process (Ingrao et al., 2018). Through dynamic study of FW, policy options are formulated with proper volarization strategies to produce environment-sustainable biobased products.

20.10.2 Multilevel perspective framework Industrial development and population expansion expel a large quantity of FW to the environment. These sustainable tools promote augmentation of food volarization, which contributes efficient processing of the unit. Recently, innovation of biobased industries has shifted the existing producing system to FW loss biorefineries. Reframing of innovative models could enhance the profitable techniques of volarization in the future. A proper business model should be considered to manage the various methods of FW processing and must be considered to have a major impact on the sustainability of FW management.

20.11 Conclusions The major commercialization aspects of FW valorization are to improve and innovate the recovery technologies that promote product flexibility and alternative techniques. Although the methodologies of product innovation are costeffective with easy scale-up technique, crude products may still be found. Proper monitoring of recovered product prior to marketing to achieve better marketability is therefore necessary. The need for beneficial biobased products is increasing daily. Policies and regulations have been tightened to generate high-quality health-promoting biobased products. A broad discussion of the large-scale implementation of biobased biorefineries should motivate research into innovative licensed biobased foods. Tax reductions also assist in the high generation of marketing techniques.

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Further reading Frelinger, A.L., Gerrits, A.J., Garner, A.L., Torres, A.S., Caiafa, A., Morton, C.A., et al., 2016. Modification of pulsed electric field conditions results in distinct activation profiles of platelet-rich plasma. PLoS One 11 (8), e0160933.

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Index Note: Page numbers followed by “f” and “t” refer to figures and tables, respectively.

A Ablative pyrolysis reactor, 104 Acetoacetyl-CoA reductase, 214 Acetobacter pasteuri-anus, 152 Acetobacter xylinum, 152 Acetogenesis, 328 Acetone
butanol
ethanol (ABE) fermentation, 39, 56
57 Acid-catalyzed transesterification, 79
81, 81f, 82f Acidification potential (AP), 362
363 Acidogenesis, 328 Acidogenic process, 21 Acremonium chrysogenum, 173 Actinobacillus succinogenes, 122, 224 Activated carbon (AC), 256 Adenosine triphosphate (ATP), 57
58, 236
240 Adsorption, 61, 85
86 Aeration, 243 Aerobic biodegradation of food wastes, 235 aerobic digestion, 236 composting, 245 advantages, 245 disadvantages, 245 composting, types of, 241
242 gore cover system, 242 in-vessel, 242 static pile, 242 vermicomposting, 242 windrow, 242 composting of food waste, factors affecting, 243
245 aeration, 243 C:N ratio, 244 feedstock, 244 microbial growth, 244
245 moisture, 244 nutrient balance (micro and macro), 244 odor and color, 245 oxygen uptake, 244 particle size, 244 pH level, 243 porosity, 243 temperature, 243 compost process, four phases of, 240
241 cooling phase, 241 mesophilic phase, 240
241 remedial phase, 241 thermophilic phase, 241

current scenario of food waste composting, 245
246 developed countries, 245
246 developing countries, 246 microbes’ roles in composting, 236
240 sustainable compost and its application in the global market, 246 Aerobic biological valorization technology, 348 Aerobic fermentation, 219t Aerobic fermenters, 147 Agaricus, 147
148 AgriChemWhey approach, 424 Agro-industrial wastes, 224
225 Airlift bioreactors, 218
219 Albumin powder, 420 Alcaligenes, 147
148 Alcaligenes eutrophus, 144 Aldehydes, 171 α-amylase, 49
51, 223 Alfa-chaconine, 406
408 1,4-α-glucosidic linear connections, 49
51 1,6-α-glucosidic connections, 49
51 Alfa-solanine, 406
408 Alkaline-catalyzed transesterification, 81
83, 82f, 83f Alpha amylases, 126 Amendment of Municipal Solid Wastes (Management and Handling) Rule in 2013 and 2015, 423 Amylases, 48
49, 211 Amyloglucosidase, 217, 223 Anaerobic bacteria (Clostridium species), 52
56 Anaerobic baffled reactors (ABRs), 404
406 Anaerobic contact reactors (ACR), 404
406 Anaerobic digesters, 300 Anaerobic digestion (AD), 1, 9, 15
18, 276
279, 305
308, 328
329, 332, 344, 346, 348, 363
364 European Union, 307
308 factors affecting, 18
20 foaming, 20 hydraulic retention time (HRT), 19 micronutrients, 19 organic loading rate (OLR), 19 pH, 18 temperature, 18
19 India, 308 Malaysia, 307 microbial fuel cell coupled with, 267
270

pretreatments employed, 17
18 process dynamics, 16f United States, 307 Anaerobic fermentation, 219t -based hydrogen production, 24 Anaerobic membrane bioreactors (AnMBRs), 404
406 Anaerobic plug flow reactors (APFRs), 404
406 Anaerobic sequencing batch reactors (ASBRs), 404
406 Anaerobic sludge blanket reactors (UASBs), 404
406 Anaerobiospirillum succiniciproducens, 122 Analysis and regulation policies, 389 bioeconomic application to food waste management, 393
394 bioeconomic approach, 392
393 challenges in food waste management, 395
396 circular bioeconomy for food waste management, 394
395 circular economy (CE) concept, 390 circular economy approach to food waste, 391
392 future of food waste management, 397
398 international approaches to food waste management, 396
397 Animal by-products, 424
425 Animal feed, 8, 303
304 India, 304 Japan, 304 Anion exchange membranes (AEMs), 257
258 Annamrita, 301 Anode, 254
256 carbon-based anodes, 255
256 surface treatment of anodes, 256 Anodic biofilm, 262
267 factors influencing biofilm formation and performance, 266
267 anodic microbes, 266
267 operational parameters, 267 reactor design, 267 wastewater characteristics, 266 Anthocyanins in mango kernel extract, 202
203 Antibiotics, 173
174 cephalosporins, 173 macrolides, 174 penicillin, 173

435

436

Index

Antibiotics (Continued) tetracycline, 173 Antifoam, 145 Apple pomace, 151, 285
286, 420 Arabinose, 223 Arabinoxylans, 151
152 Archaeoglobus, 276
279 Aromatic compounds, 163
172, 176
177 aldehydes, 171 ester, 164 ketones, 171 lactones, 171 terpenes, 164
171 thiols, 172 Arthrospira, 283
284 Arundo donax Aspen In-Plant Cost Estimator, 331 Aspergillus, 48
49, 84, 127
128, 222 Aspergillus awamori, 48
49, 78
79, 215, 217 Aspergillus niger, 120, 194, 217, 223
224 Aspergillus oryzae, 48
49, 78
79, 147
148 Aspergillus sp., 49
51 Aspergillus terreus, 66 Association for India’s Development (AID), 301 Astaxanthin, 173 Atmospheric fluidized bed combustor, 103 Attributional modelling, 383 Australia composting in, 305 food waste management in, 301 Azithromycin, 174

B Bacillus, 240, 282 Bacillus amyloliquefaciens, 223 Bacillus coagulans, 220
221 Bacillus licheniformis, 121, 223 Bacillus megaterium, 214 Bacillus mycoides, 224 Bacillus sp., 221 Bacillus subtilis, 67, 87 Bacillus subtilis KBKU21, 333 Bacillus subtilis str. pBE2C1, 211 Bacillus subtilis str. pBE2C1AB, 211 Bacterial cellulase synthesis, 152 Bakery waste 1 seawater, 212t Baker’s yeast, 146
147 Banana peels (Musa paradisiaca), 148, 164, 171 Banana waste, 151 Batch fermentation, 219t, 276 Beet molasses, 147 β-1,3-glucanase, 226 β-D-galactosidase, 224 β-galactosidases, 222, 225 Beta-glucans, 151 β-glucosidase, 49
51, 223 Beverage industry, 252 Bhabha Atomic Research Centre (BARC), 329
330 Bicycle of the circular economy, 395 Bifidobacterium longum, 224

Big beads, 133
134 Bioactive chemicals, food waste as a valuable source of, 163
175 antibiotics, 173
174 cephalosporins, 173 macrolides, 174 penicillin, 173 tetracycline, 173 aromatic compounds, 163
172 aldehydes, 171 ester, 164 ketones, 171 lactones, 171 terpenes, 164
171 thiols, 172 essential oils, 174
175 biolubricants, 175 fish oil, 174 peel oil, 174
175 seed oil, 174 pigments, 172
173 astaxanthin, 173 chlorophyll, 172 monascus, 172 prodigiosin, 172 Bioactive components recovery from food waste, 00016#s0070 extraction, 347 isolation and clarification, 347 pretreatment of food waste, 346
347 Bioactive compounds, 189
193 bioactive peptides, 192
193 carotenoids, 192 dietary fiber (DF), 193 phenolic compounds from food waste, 190
192 flavonoids, 191 phenolic acids, 191 stilbenes and lignans, 191
192 tannins, 191 Bioactive peptides, 192
193 Bioalcohol fermentation methods, 61
67 consolidated bioprocessing (CBP), 66
67 separate hydrolysis and fermentation (SHF), 61
62 simultaneous saccharification and cofermentation (SSCF), 66 simultaneous saccharification and fermentation (SSF), 62
66 various types of, 63t Bioalcohol production processes, 40
61, 41f biobutanol, 40 bioethanol, 40 comparison of bioalcohol properties and their applications, 40
41 downstream process, 58
61 adsorption, 61 distillation, 58 gas stripping, 58
61 integrated downstream process, 61 pervaporation, 61 midstream process, 52
58 biobutanol fermentation, 56
57 bioethanol fermentation, 57
58

upstream process, 41
52 biological pretreatment, 48
49 chemical pretreatment, 42
48 combined pretreatment, 49 detoxification, 52 hydrolysis or saccharification, 49
52 mechanical pretreatment, 48 physical pretreatment, 42 Bioalcohol recovery methods, various types of, 59t Bioalcohol yield, strategies to increase, 67 Biobased products, marketability of, 423
424 Biobutanol, 40 fermentation, 56
57 Biocatalysts, 222 Biocathodes, 257 BIO Daily needs, 429
430 Biodegradable thermoplastic polyhydroxyalkanoates, 145 Biodiesel, 9
10, 20, 75
76, 283
284, 310
311 Biodiesel production, 215
216, 364
368 food waste pretreatments for, 75
78 biological pretreatment, 78 chemical pretreatment, 76
78 combined pretreatment, 78 mechanical pretreatment, 78 physical pretreatment, 76 reactors involved in, 89f, 90t reactors involved in, 87
91 scalability of, 91 valorization of food waste for. See Valorization of food waste for biodiesel production from waste cooking oil, 331 Biodiesel synthesis, mechanism of, 215 Bioeconomic approach, 392
393 to food waste management, 393
394 Bioelectrochemical system (BES), 251 Bioenergy, 283 and biofuel conversion approaches, 9
10 valorization of FW into. See Valorization of FW into bioenergy Bioethanol, 40, 308 fermentation, 57
58, 284
285 mechanism of bioethanol synthesis, 216 production of, 216
217 recovery, 364 Biofermentation of food waste, 171 Biofertilizers, 282 production, 284 Biofuel, 224 production, from food waste, 338 Biogas recovery, 284, 363
364 Biohydrogen production factors affecting, 24
26 components/composition of food waste, 24
25 pretreatments, 25
26 volatile fatty acids (VFAs), 26 from food industry waste, 24 from food waste, 23
24 Biohythane, 26
27 applications of, 28

Index

enhancement strategies of production of, 28 production, from food waste, 26
28 process description, 27
28 Biolipid
methane production, 281 Biological conversion, 348 Biolubricants, 175 Biomass-based value web, 395 Biomass decomposition technologies, 326 Biomethane, 17 Bio-oil, 111 Bio-pigments, 172 Bioplastic, 352 Biopolymers, 144
145 application, 145 extraction and purification, 145 fermentation process, 145 Bioreactors used for fine chemical production, 175
176, 176f Biorefinery approach, 404, 405f, 405t case studies on, 336
338 biofuel production from food waste, 338 food waste biorefinery in European context, 337 integrated mango biorefinery in an Indian context, 336
337 commercialized and patented applications of, 418
420 commercialization and scale-up issues, 419 intellectual property protection, 418
419 patented methodologies, 420, 421t patents and their requirements, 419
420 concept of, 333 cost-competitive food waste biorefinery development, 332
333 defined, 392
393 framework, 333f techno-economic analysis (TEA), 333
334 framework, 334, 335f methodology, 334
335 Biorefinery products applications and marketability of, 423
425 contracts and public procurement of, 430 Biosurfactants (BSs), 193 1,3-Bisphophoglycerate, 57
58 Black walnut (Juglans nigra), 198 Blakeslea trispora, 192 Boron trifluoride, 81 Botryococcus braunii, 78 Braskem, 292 Brazil, legislation in, 315 Bread crust, 212t Brevibacterium spp., 173 Bulking agents, 352 Burkholderia cepacia, 87, 215
216 Burkholderia xenovorans, 215 Business models, 426
427 order size model, 427 purchase incidence model, 427 triple-layered business model, 426 2,3-Butanediol (2,3-BD), 121 Butyl alcohol. See Biobutanol Byproduct, 1

C C:N ratio, 244 Caffeic acid, 406
408 Camphor terpenes, 164
171 Candida, 48
49, 120, 147
148 Candida antarctica, 84, 127, 215
216, 223
224 Candida aurantiacus, 123 Candida parasilosis, 61
62 Candida rugora, 123 Candida rugosa, 87 Candida sp., 85
86, 91, 222 Candida tropicalis, 164
171 Candida utilis, 147
148 Cane molasses, 147 Carbohydrase, 61
62 Carbohydrates, 217, 223 Carbon-based anodes, 255
256 Carbon dioxide, 20, 198 Carbon monoxide (CO), 362
363 Carbon nanotubes (CNTs), 256 Carbon to nitrogen ratio, 325
326 Carotenoids, 192, 283
284 Cassava, 252
253 Cassava waste, 291 Castor oil, fermentation of, 171 Catalase, 222 Cathodes, 256
257 biocathodes, 257 Cation exchange membranes (CEM), 257
258 Cellulase, 48
49, 127
128, 211, 222, 226 Cellulomonas, 127
128 Cellulose, 143, 150
151 Cephalosporins, 173 Ceratocystis fimbriata, 164 Ceratocystis fimbriate, 171 Cereal processing, 254 Challenges in food waste management, 395
396 Cheese whey processing, 254 Chemical pretreatment methods, 348 Chemical recovery applications, limitations, and challenges during, 181 Chicken fat, 175 China, food waste management in, 302 Chinese Circular Economy Promotion Law, 390 Chitin, 150 Chitosan, 150 Chlorella ellipsoidea, 283 Chlorella prothothecoides, 78 Chlorella pyrenoidosa, 283 Chlorella sorokiniana, 283 Chlorella sp., 147
148, 283
284 Chlorella vulgaris, 284 Chlorgenic acid, 406
408 Chlorophyll, 172 Chlorotetracycline, 173 Chromatography, types of, 130t Circular economy (CE) approach, 390 abiotic cycle, 395 bioeconomic strategy application to, 397f biological cycle, 395

437

butterfly graph of, 394f to food waste, 391
392 Citrate, 171 Citric acid, 119
120, 224 -producing strains, 120 Citrobacter, 123 Citrullus lanatus, 197
198 Citrus food waste, 351
352 Citrus fruits, by-products of, 202 Citrus natsudaidai, 164
171 Citrus reticulata, 76
78 Citrus seed waste, 176
177 Citrus waste, 286
287 Clarithromycin, 174 Classification of food waste, 344f Clostridia sp., 144 Clostridium, 56
57, 123, 127
128 Clostridium acetobutylicum, 39
40 Clostridium beijerinckii, 67 Clostridium butylicum, 67 Clostridium butyricum, 224 Clostridium saccharoperbutylacetonicum, 24 Clostridium sp., 49
51 Clostridium tyrobutyricum, 67, 225
226 Cocombustion, 102
103 principles, 102 technologies, 103 atmospheric fluidized bed combustor, 103 pressurized fluidized bed combustor, 103 Codigestion, 22, 328 Coelastrella sp., 283
284 Cofermentation, saccharification and, 66 Coffee silverskin, 203 Coffee waste, 424 Cofiring, 100
102 technologies, 100
102 direct cofiring, 100
101, 101f indirect cofiring, 101, 102f parallel cofiring, 102, 102f Combined continuous solid-state fermentation (CCSSF) method, 216
217 Combined heat and power (CHP), 379 Combustion, 99
100, 111 principles, 99 technologies, 99
100 fixed bed combustion, 100 fluidized bed combustion, 100 suspension burner, 100 Commercialization of biofuel from food waste, 29 Commercialization of recovered bioproducts, 417
418 and scale-up issues, 419 Commercial valorization of food waste challenges for attaining, 409 policy framework for, 409
410 Communication strategy, 428 Community-based organization (CBOs), 402 Components/composition of food waste, 24
25, 25f Composting, 8, 10
11, 235, 245, 304
305, 326
327, 346, 348
350 advantages, 245 in Australia, 305

438

Index

Composting (Continued) current scenario of, 245
246 developed countries, 245
246 developing countries, 246 disadvantages, 245 factors affecting composting of food waste, 243
245 aeration, 243 C:N ratio, 244 feedstock, 244 microbial growth, 244
245 moisture, 244 nutrient balance (micro and macro), 244 odor and color, 245 oxygen uptake, 244 particle size, 244 pH level, 243 porosity, 243 temperature, 243 LCA analysis on, 368
370 in Taiwan, 305 types of, 241
242 gore cover system, 242 in-vessel, 242 static pile, 242 vermicomposting, 242 windrow, 242 in United States, 305 Compost process, four phases of, 240
241 cooling phase, 241 mesophilic phase, 240
241 remedial phase, 241 thermophilic phase, 241 Concentrated nutrients, 389 Condensed baker’s yeast, 146
147 Consolidated bioprocessing (CBP), 61, 66
67 Consumption-stage food loss, 380
381 Continuous fermentation, 219t Continuous stirred tank (CST) fermenter, 218, 220f Continuous stirred tank reactors (CSTRs), 404
406 Conventional life cycle costing (C-LCC), 383 Cooling phase, 241 Copyright protection, 419 Corn bran, 151 Cornstalks, 352 Corynebacterium glutamicum, 123 Cosmeceuticals, 203 Cost-competitive food waste biorefinery development, 332
333 Covalent binding, 87 Cradle to grave approach, 361 Cross-linkage, 86 Cross-sector valorization of food waste, 417 business models, 426
427 order size model, 427 purchase incidence model, 427 triple-layered business model, 426 commercialized and patented applications of food waste biorefineries, 418
420 commercialization and scale-up issues, 419 intellectual property protection, 418
419

patented methodologies, 420, 421t patents and their requirements, 419
420 contracts and public procurement of biorefinery products, 430 developing unique selling points, 429
430 date labelling, 429 mobile applications, 429
430 retailer options, 429 food waste-based biorefinery products animal by-products, 424
425 coffee waste, 424 dairy product waste, 424 emerging innovative marketing technologies, 425 fruit and vegetable waste, 424 seafood waste, 425 food waste dynamics, 430
431 marketing strategies and practices, 428
429 communication strategy, 428 food distribution, 428 packaging and its types, 429 products and processes, 429 promoting sales, 429 selling price, 429 multilevel perspective framework, 431 need for new marketing approaches, 425
426 cost and safety issues of emerging technologies, 425
426 policy options and their implications, 420
423 policies and regulations, 423 policy measures promoting social innovation, 420
423 resolving challenges into opportunities, 423 social innovation and food waste, 420 Crustaceans, 150 Cryptococcus albidus, 284 Cryptococcus curvatus, 175, 281 Cryptococcus sp., 281 Cuboid-shaped double chamber, 259 Cumulative Exergy Demand, 362
363 Cumulative exergy loss (CEL), 377 Cupriavidus necator, 214
215, 286 Cuprividus necator, 152 Cyanobacterium aponinum, 216 Cysteine, 172

D Dairy industry, 252 Dairy product waste, 424 Dark fermentation process, 22
24, 23f, 331
332 biohydrogen production from food industry waste, 24 from food waste, 23
24 4-Decalactone, 171 Delignification of the biomass, 328 Demeclocycline, 173 Detergents, 20 Detoxification methods, 52 various types of, 53t

Developed countries current scenario and development of food waste management in, 300
301 Developing countries current scenario and development of food waste management in, 301
302 Diacylglycerides, 83
84 Dialysis, 128
129 Dietary fiber (DF), 150, 193 Dihydroxyacetone-P, 57
58 Dioxin, 15 Direct cofiring, 100
101, 101f Directive 2008/98/EC8, 391 Disposal, 392 Disposed food, 1 Distillation, 58, 364 Distribution-stage food loss, 380 D-limonene, 286 Docosahexaenoic acid, 174 Domestic FWs, 11 Double-chambered H-shaped chamber, 259 Double-chamber upflow microbial fuel cell, 259
260 Downcycling, 390, 392 Downstream process, bioalcohol production, 58
61 adsorption, 61 distillation, 58 gas stripping, 58
61 integrated downstream process, 61 pervaporation, 61 Drum pyrolizers, 103 Dual-chambered MFC, 259
260 cuboid-shaped double chamber, 259 double-chambered H-shaped chamber, 259 double-chamber upflow microbial fuel cell, 259
260 dual-chambered concentric tubular, 260 dual-chamber upflow U-shaped microbial fuel cell, 260 Dunaliella, 283
284 Dunaliella salina, 283
284 Dunaliella tertiolecta, 78, 216 Durian fruit, 172

E EASEWASTE model, 371 East Bay Municipal Utility District (EBMUD), 307 Eco-efficiency, 375
376 Eco-Indicator 99, 362
363 Economic order quantity business model (EOQ model), 427 Edible FW, 39 Eicosapentaenoic acid, 174 Eicosapentaneoic acid (EPA), 283
284 Electrochemically active microbes (ECAMs), 266
267 Electrofermentation process, 284
285 bioethanol fermentation, 284
285 hydrogen fermentation, 285 Electroporation method, 200
201, 425

Index

Emerging innovative marketing technologies, 425 Emerging nations, generation of FW in, 5 Emerging technologies cost and safety issues of, 425
426 Encapsulation, 87 Endoglucanase (EG), 127
128 Endpoint methods, 362
363 Energy flow balance in process streams, 379 Energy life cycle analysis, 379 Energy recovery from food waste using microbial electrolysis cell, 267 Enterococcus, 262, 266
267 Entrained bed gasifier, 108 Entrapment technique, 86 Environmental life cycle costing (E-LCC), 383 Environmental Protection Agency (EPA), 15 Enzymatic valorization of food waste biodiesel, production of, 215
216 biodiesel synthesis, mechanism of, 215 bioethanol, production of, 216
217 bioethanol synthesis, mechanism of, 216 polyhydroxybutyrate (PHB), production of, 214
215, 214f polyhydroxybutyrate (PHB) synthesis, mechanism of, 214 Enzyme-assisted extraction (EAE), 189, 198 Enzyme-catalyzed transesterification, 83
87, 84f, 85f enzyme immobilization techniques and their applications, 85
87 adsorption, 85
86 covalent binding, 87 cross-linkage, 86 encapsulation, 87 entrapment, 86 immobilized, 84 Enzyme hydrolysis (EH), 49 Enzyme immobilization techniques, 86f Enzyme purification by chromatography, 133 Enzymes, 211, 217
222 application of, 221
222 fermentation of food waste, 218 fermentation process, scaling up of, 221 fermenter, types of, 218
221 airlift bioreactors, 218
219 continuous stirred tank (CST) fermenter, 218, 220f fluidized-bed bioreactors, 220, 220f membrane bioreactors, 220
221 packed-bed bioreactor, 218, 220f Enzymes production from food waste, 126
128 downstream processing, 133
134 extraction and purification, 128
133 dialysis, 128
129 enzyme purification by chromatography, 133 microwave-assisted extraction, 129
132 supercritical fluid extraction (SFE), 132
133 ultrasonication-assisted extraction (UAE), 132 recovery, 134

Erythromycin, 174 Escherichia coli, 122, 144, 214, 224, 240
241, 286 Essential oils, 174
175 biolubricants, 175 fish oil, 174 peel oil, 174
175 seed oil, 174 Ester, 164 Esterification, 310
311 Ethanol fermentation, 348 Ethanol
methane production, 279
281 Ethyl alcohol. See Bioethanol Ethyl esters, 164 3-Etothiolase, 214 EU Landfill Directive, 396 Europe, food waste biorefinery in, 337 Europe, generation of FW in, 4
5 European bioeconomy strategy, 392
393 European Circular Economy, 390 European Commission (EC), 1
2 European Union anaerobic digestion (AD) projects in, 307
308 legislation in, 314 Evening primrose, seeds of, 290 Exergetic indicators in the food industry construction of Grassmann diagram, 378 exergy analysis, 376
377 use of, 377
378 Exergy analysis, 359, 376
377 Exergy efficiency, 377 Exocellulases, 49
51 Exoglucanase, 127
128 Extraction and purification, 128
133, 347 dialysis, 128
129 enzyme purification by chromatography, 133 microwave-assisted extraction, 129
132 supercritical fluid extraction (SFE), 132
133 ultrasonication-assisted extraction (UAE), 132

F Fast pyrolysis/thermolysis, 104 ablative pyrolysis reactor, 104 fluidized bed, 104 pyrolysis reactor vacuum, 104 rotating cone reactor, 104 Fatty acid methyl ester (FAME), 76 Fatty acids, 20 Fed-batch fermentation, 219t Feeding India, 301 Feedstock, 244 Fermentation, 145, 194, 218, 219t, 308
309 LCA studies, 364 saccharification and, 62
66 scaling up of, 221 two-stage fermentation of various food wastes, 280t Fermentative polyhydroxybutyrate production, 211
215

439

mechanism of polyhydroxybutyrate synthesis, 214 production of polyhydroxybutyrate, 214
215 Fermenter, types of, 218
221 airlift bioreactors, 218
219 continuous stirred tank (CST) fermenter, 218, 220f fluidized-bed bioreactors, 220, 220f membrane bioreactors, 220
221 packed-bed bioreactor, 218, 220f Ferric cyanide, 256 Fertilizer recovery, 368
370 Ferulic acid, 288 Fiat Panda Aria, 28 Fibers, 151 Fine chemical production, bioreactors used for, 175
176, 176f Fine chemicals, various methods of extraction and purification of, 176
179 high-voltage electric discharge (HVED), 177f, 178 ionic liquid extraction techniques, 177
178, 177f microwave-assisted extraction, 176
177, 177f pulsed electric field (PEF) extraction, 178 supercritical fluid extraction, 179, 180f ultrasound-assisted extraction, 177f, 178 Fine chemicals production from food wastes, 163, 164f, 165t applications, limitations, and challenges during chemical recovery, 181 bioactive chemicals, food waste as a valuable source of, 163
175 antibiotics, 173
174 aromatic compounds, 163
172 essential oils, 174
175 pigments, 172
173 bioreactors used for fine chemical production, 175
176, 176f economic consideration, 180 future perspectives, 181
182 methods of extraction and purification of fine chemicals, 176
179 high-voltage electric discharge (HVED), 177f, 178 ionic liquid extraction techniques, 177
178, 177f microwave-assisted extraction, 176
177, 177f pulsed electric field (PEF) extraction, 178 supercritical fluid extraction, 179, 180f ultrasound-assisted extraction, 177f, 178 scale up and commercialization, 180
181, 182t Fischer
Tropsch process, 104
105 Fish and meat, 217 Fishery wastes and by-products, 425 Fish oil, 174 Fixed bed, 103 combustion, 100 Fixed/moving bed gasifier, 106
107 Flash pyrolysis, 104

440

Index

Flavonoids, 191 Fluidized bed, 99, 104 bioreactors, 220, 220f combustion, 100 gasifier, 107
108 reactor, 176 Foaming, 20 Food additives, 202 Food balancing sheet (FBS), 375 Food cowboy, 300 Food distribution, 428 Food donation, benefits of, 383 Food grade protein powder (RuBisCO), 424 Food industry waste, biohydrogen production from, 24 Food loss, 1
3, 379 in agriculture, 344
345 defined, 1 food losses and waste implications on water and land, 382
383 in life cycle analysis, 380
381 consumption-stage food loss, 380
381 distribution-stage food loss, 380 processing-, transport-, and storage-stage food losses, 380 production-stage food loss, 380 types of, 379
380 Food loss rate (FLR), 382
383 Food processing industrial waste, 289
291 cassava waste, 291 Jatropha waste, 291 oil-extracted residues, 290 olive mill waste, 289 palm oil effluent, 289 rapeseed oil waste, 290
291 Food processing industries (FPIs), 39 and their effluent characteristics, 252
254 beverage industry, 252 cassava mill processing, 252
253 cereal processing, 254 cheese whey processing, 254 dairy industry, 252 meat processing wastewater, 253 potato processing wastewater, 253 seafood processing wastewater, 253
254 Food processing wastes, 6
7 Food recovery hierarchy, 327f Food residuals, 1 Food supply chain (FSC), 1, 4
5, 359 life cycle analysis of, 375 food waste disposal LCA, 375 limited or full food supply chain stages in LCA, 375 Food supply chain waste (FSCW) characterization, 2
3 Food waste (FW), defined, 1
2 France, legislation in, 315 Freeze drying, 346
347 Fresh baker’s yeast, 146
147 Fresh banana peel waste, 164 Fructose 1,6-biphosphate, 57
58 Fructose 6-phosphate, 57
58 Fruit and vegetable waste (FVWs), 189
190, 202, 424

Fruits waste, 9
10, 217 Functional foods, 401, 403 Functional ingredients, 189
190 Future of food waste management, 397
398

G GaBi tool, 362
363 Galacturonic acid, 223 Garlic waste bulbs, 172 Gasification, 104
108, 106f, 111, 310, 349 principles, 105 technologies, 106
108 entrained bed gasifier, 108 fixed/moving bed gasifier, 106
107 fluidized bed gasifier, 107
108 Gas stripping, 58
61 Generation of food waste, 4
5, 4f Geobacter, 262, 266
267 Geotrichum candidum, 215
216 Geotrichum sp., 86 Germany, food waste management in, 300
301 Global Bioenergies in France, 424 Global food system, 389 Global growing food demand, 390 Global warming, 362
363 Global warming potential (GWP), 362
364 Glucoamylase, 62
66 Gluconacetobacter hansenii, 152 Gluconacetobacter sp., 152 Glucose 6-phosphate, 57
58 Glucose metabolism, 171 Glutaraldehyde, 86, 223 Glutathione, 172 Glyceraldehyde-3-P, 57
58 Glycoalkaloids, 406
408 Good Samaritan Law, 396 Gore cover system, 242 Grains, 217 Gram-negative bacteria, 144 Gram-positive bacteria, 144 Grape pomace, 224
225 Grape skins, 224
225 Grape waste (wine lees), 286 Graphite rods, 262 Grassmann diagram, 378 Green chemistry, 393
394 Greenhouse gas (GHG) emissions, 8
9, 299, 345, 364 reduction of, 371 Greenhouse gases, 362
363 Green leafy spinach, 172 Green plastic, 211 Green polymers, 292 Guava peel, 202 Gulf region, food waste management in, 302

H Haematococcus, 283
284 Haematococcus pluvialis, 173, 283
284 Halobacteriaceae archaeon, 193 Halomonas, 215

Halomonas boliviensis, 215 Halomonas halophile, 215 Heavy metals, 351
352 Helicobacter pylori, 283
284 Hemicellulose, 49, 150, 420 Hemicellulose polysaccharides, 151
152 Heterotrophic algae, 283 n-Hexane, 327
328 Hidrox, 420 Hierarchy, food waste, 7, 7f High hydrostatic pressure extraction (HHPE), 198, 201
202 High pressure/high temperature (HPHT), 201
202 High-pressure processing (HPP) units, 425 High-voltage electric discharge (HVED), 177f, 178 Horizontal drum bioreactor, 175 Household/domestic FWs, 11 Household food waste (HFW), 1, 212t, 270 Household waste, 212t Hydraulic retention time (HRT), 17
19, 21, 267 Hydrochloric acid, 81 Hydrogen, 26
27, 279 Hydrogen fermentation, 285 Hydrogen
methane production, 279, 280t Hydrolysis/saccharification, 49
52, 328 Hydrothermal carbonization (HTC), 108
110, 112
113, 349 reaction parameters, influence of, 110 transformation process, 109
110 Hydrothermal pretreatment, 17 Hydroxybenzoic acids, 191 3-Hydroxybutyrate, 145 Hydroxycinnamic acids, 191 3-Hydroxypropionic acid, 122
123 Hydroxytyrosol, 346 3-Hydroxyvalerate, 145 Hythane, 26
28

I Immobilized biocatalysts and their applications in food waste valorization, 222
227 biofuel, 224 carbohydrates, 223 immobilized cells/enzymes, 226f bioreactors with, 224
226 kinetic aspects of, 227 lipids, 223
224 organic acids, 224 proteins, 223 Immobilized cells/enzymes, 226f bioreactors with, 224
226 kinetic aspects of, 227 Immobilized enzyme-catalyzed transesterification, 84 Immobilized lipases, 78, 84 Incineration, 9, 98
99, 110
111, 309
310, 326 technologies, 98
99 fluidized bed, 99 moving grate, 98

Index

rotary kilns, 99 India anaerobic digestion (AD) projects in, 308 animal feed in, 304 food waste management in, 301 integrated mango biorefinery in, 336
337, 336f legislation in, 315 Indirect cofiring, 101, 102f Industrial-based biohythane production, 27 Industrial ecology application recovery, 381
382 Inevitable FW, 2 Innovating for Sustainable Growth: A Bioeconomy for Europe, 392
393 Innovative techniques, 425
426 Insoluble dietary fiber (IDF), 193 Instant noodle waste, 212t Institutions and enterprises in food waste management, 402 Integrated biorefineries of food waste, 275
276, 276f electrofermentation process, 284
285 bioethanol fermentation, 284
285 hydrogen fermentation, 285 food processing industrial waste, 289
291 cassava waste, 291 Jatropha waste, 291 oil-extracted residues, 290 olive mill waste, 289, 290f palm oil effluent, 289 rapeseed oil waste, 290
291 future perspectives, 293 integrated two-stage processes, 276
283 biolipid
methane production, 281 ethanol
methane production, 279
281 hydrogen
methane production, 279 methane, 282 methane
lactic acid production, 276
279 volatile fatty acids, 282
283 liquefied food waste for biomass cultivation and multiproduct recovery, 283
284 microalgae, cultivation of, 283
284 yeast, cultivation of, 284 plant-derived food waste (fruit and vegetable waste), 285
288, 286f apple pomace, 285
286 citrus waste, 286
287, 287f grape waste (wine lees), 286 potato peel waste, 287
288, 288f rice waste, 288 tomato waste, 287 policies and regulations, 292
293 techno-economic analysis, 292 in various sectors, 291
292 Integrated downstream process, 61 Integrated mango biorefinery in an Indian context, 336
337, 336f Integrated product policy (IPP), 410 Intellectual property protection (IPP), 418
419 International approaches to food waste management, 396
397 International Life Cycle Data System (ILCD), 362
363

Intracellular lipases, 84 Inulin, 150 Integrated biorefinery routes of various food waste, 277t In-vessel, 242 Ion exchange membranes (IEMs), 257
258 Ionic liquid extraction techniques, 177
178, 177f ISO 14040, 375
376 ISO 14044, 375
376 Isoamyl acetate, 164 Issues associated with food waste, 344
345 Italy, legislation in, 315

J Japan animal feed in, 304 Food Waste Recycling Law, 423 legislation in, 314 Jatropha curcas, 87
89, 218, 291 Jatropha waste, 291 Juglans nigra, 198

K Ketones, 171 Kingdom of Saudi Arabia (KSA), waste-based biorefineries in, 291 Kitchen wastes, 212t, 351
352 Klebsiella, 123 Klebsiella oxytoca, 121 Klebsiella pneumoniae, 121 Kluyveromyces, 147
148 Kluyveromyces fragilis, 225 Kluyveromyces marxianus, 66 Kluyveromyces walti, 284 Koji fermentation, 120

L Laccases, 127 Lachancea fermentati, 61
62 Lactases, 127 Lactic acid, 123
125, 124f, 276 Lactic acid fermentation (LAF), 194, 308 Lactobacillus, 124
125, 147
148, 240 Lactobacillus brevis, 224 Lactobacillus plantarum, 276
279 Lactobacillus rhamnosus, 276 Lactobacillus sp., 123, 127 Lactococcus lactis, 276 Lactones, 171 Landfill, 8
9 Landfill gas (LFG), 311 Landfilling, 311, 326 Land footprint (LF), 382 Legislation in various countries, 314
315 Brazil, 315 European Union, 314 France, 315 India, 315 Italy, 315 Japan, 314

441

Malaysia, 315 South Korea, 314
315 United States, 314 Life cycle analysis (LCA), 359 of anaerobic digestion process, 365t of biological food waste valorization processes, 363
370 anaerobic digestion, 363
364 composting, 368
370 fermentation technologies, 364 transesterification, 364
368 case study, 376 of composting process, 372t current efforts on, 375
376 energy flow balance in process streams, 379 energy life cycle analysis, 379 of fermentation process, 369t food loss in, 380
381 of food supply chain, 375 food waste disposal LCA, 375 limited or full food supply chain stages in LCA, 375 mass flow balance in process streams, 378 methodologies/approaches biological techniques, 360
361 credits of coproducts, 362 functional unit, 360 life cycle impact assessment (LCIA), 362
363 life cycle inventory (LCI) analysis, 362 scope, 360 system boundaries, 361 zero-burden approach, 361 modeling approaches to food loss in, 381
382 food loss treatment in waste treatment plants, 382 industrial ecology application recovery, 381
382 of nonbiological food waste valorization processes, 371 combustion and energy recovery, 371 landfill disposal, 371 Life cycle assessment (LCA), 326 Life cycle costing (LCC) approaches to food waste and its valorization analysis of results and interpretation, 375 cut-off and externalities, 374 environmental impact assessment, 375 functional unit, 374 modeling approaches of cost, 374 system boundaries, 374 Life cycle thinking (LCT), 359 Lignans, 191
192 Lignin removal, 328 Lignocellulose waste, 226 Lignocellulosic biomasses, 143, 146 Lignocellulosic ethanol production, 364 Lignocellulosic microorganisms, 240 Lignocellulosic substrates, 146 Limonene terpene, 164
171 Linocellulosic biomasses, 146 Lipase, 48
49, 83
84, 127, 215, 222 Lipid oxidation, 171

442

Index

Lipids, 223
224, 289, 310
311 Lipids to biodiesel conversion, 78
79 Lipomyces sp., 281, 284 Lipozyme RM IM, 84 Lipozyme TL IM, 84, 224 Liquefied food waste for biomass cultivation and multiproduct recovery, 283
284 microalgae, cultivation of biodiesel, 283 value-added products recovery, 283
284 yeast, cultivation of biodiesel, biogas recovery, and biofertilizer production, 284 Litopenaeus vannamei, 192
193 Loss of food, 2
3 Loss of quantity, 2
3 Lubricants, 175 Lutein, 283
284 Lycopene, 192, 202, 283
284, 287, 420

M Macrolides, 174 Maillard reaction, 42 Malassezia globosa, 224 Malaysia biogas generation from FW in, 307 food waste management in, 301
302 legislation in, 315 Management, food waste, 404
406 biorefinery approach, 404, 405f, 405t up-scaling processes, 404
406 Management and valorization of food waste, 7
11, 8f animal feed, 8 bioenergy and biofuel conversion approaches, 9
10 composting, 10
11 landfill, 8
9 value-added products recovery, 11 Management hierarchy, food waste, 391f, 392 Mandatory labels, 430 Mango-based integrated biorefinery, 336
337, 336f Mannheimia succiniciproducens, 122 Market-based products, 403 Marketing strategies and practices, 425, 428
429 communication strategy, 428 food distribution, 428 packaging and its types, 429 products and processes, 429 promoting sales, 429 selling price, 429 Market value of food waste valorization products, 406
410, 408t commercial valorization of food waste challenges for attaining, 409 policy framework for, 409
410 factors influencing, 409 uncertainties for market value, factors contributing to, 410 Mass flow balance in process streams, 378 Mass transfer, 227

Meat processing wastewater, 253 Megasphaera elsdenii, 122
123 Membrane bioreactors, 220
221 Membraneless MFC, 262 Membrane separation, 347 Membrane separator, 257
258 Mesophilic phase, 240
241 Metal ions, 328 Methane, 15
17, 26
27, 282, 352 Methane
lactic acid production, 276
279 Methanogenesis, 328 Meyerozyma guilliermondii, 123 Microalgae, 283 cultivation of biodiesel, 283 value-added products recovery, 283
284 Microbes, 121, 144 roles in composting, 236
240 Microbial electrochemical system (MES), 267 Microbial electrolysis cell (MEC), 284
285 Microbial fuel cell (MFC), 251 anode, 254
256 carbon-based anodes, 255
256 surface treatment of anodes, 256 anodic biofilm, 262
267 anodic microbes, 266
267 operational parameters, 267 reactor design, 267 wastewater characteristics, 266 cathodes, 256
257 biocathodes, 257 configurations of, 258
262 cuboid-shaped double chamber, 259 double-chambered H-shaped chamber, 259 double-chamber upflow microbial fuel cell, 259
260 dual-chambered concentric tubular, 260 dual-chamber upflow U-shaped microbial fuel cell, 260 membraneless, 262 single-chambered concentric tubular, 261 single-chambered upflow, 260
261 stacked microbial fuel cell, 261
262 coupled with anaerobic digestion (AD) of food waste, 267
270 current status of pilot microbial fuel cell, 270 energy recovery from food waste using microbial electrolysis cell, 267 food processing industries and their effluent characteristics, 252
254 beverage industry, 252 cassava mill processing, 252
253 cereal processing, 254 cheese whey processing, 254 dairy industry, 252 meat processing wastewater, 253 potato processing wastewater, 253 seafood processing wastewater, 253
254 future directions, 270
271 membrane separator, 257
258 reactor design and performance, 262 Microbial fuel cells (MFCs), 284
285 Microbial growth, 244
245

Microbial organic matter, 143 Microcystis aeruginosa, 78 Micronutrients, 19 Microwave-assisted extraction (MAE), 129
132, 176
177, 177f, 189, 197
198 Microwave hydrodiffusion and gravity (MHG), 197
198 Midpoint methods, 362
363 Midstream process, bioalcohol production, 52
58 biobutanol fermentation, 56
57 bioethanol fermentation, 57
58 Mixed food waste, 212t Mobile app marketing business, 429
430 Modifiers, 198 Moisture, 244 Moisture content of FW, 15 Molasses, 147
148 Monascus, 172 Monascus purpureus, 172 Monascus sp., 172 Mono-ethanol amine (MEA), 332 Moosburg wastewater treatment plant, 308 Morchella, 147
148 Mortierella alpina, 281 Moving grate, 98 Mucoralean, 39
40 Mucor meihei, 215
216 Mucor miehei, 84 Mucor pyriformis, 120 Multifect pectinase, 61
62 Multifect xylanase, 61
62 Multiphased anaerobic baffled pilot-scale reactor (MP-ABR), 17
18 Multistage digestion, 21 Municipal solid waste (MSW), 299 Musa paradisiaca, 148 Myceliophthora thermophila, 216 Mycobacterium lacticola, 173

N Nafion, 258 Neochlorgenic acid, 406
408 Nepal, food waste management in, 302 Nisargruna biogas plant, 329
330, 330f Nitrogen, 281, 284 Nonedible FW, 39 Non-governmental organizations (NGOs), 402 Nonstarch polysaccharides, 150 Norway, food waste management in, 301 Nostoc, 283
284 Novozyme, 364 Novozyme-435, 78
79, 84, 224 Nutraceuticals, 202
203 extraction techniques for recovery of, 194
202 enzyme-assisted extraction (EAE), 198 high hydrostatic pressure extraction (HHPE), 201
202 microwave-assisted extraction (MAE), 197
198 pulsed electric field (PEF), 200
201

Index

solvent extraction (SE) technique, 194
197 subcritical water (SCW) extraction, 199 supercritical fluid extraction (SFE), 198, 199f, 200f ultrasound-assisted extraction (UAE), 199
200 food waste-derived, 202
203 cosmeceuticals, use as, 203 food additives, use as, 202 nutraceuticals, use as, 202
203 Nutrient balance (micro and macro), 244

O Odor and color, 245 Odorous molecules, emission of, 352 Oenococcus oeni, 224
225 Oenothera biennis, 290 Oil-extracted residues, 290 Oleaginous microorganisms, 281 Olive mill waste, 289, 290f, 420 Omega-3, docosahexaneoic acid (DHA), 283
284 OPTISOCHEM approach, 424 Orange peel, 174
175 Order size model, 427, 428f Organic acid production from food waste, 119
126 1,3-propanediol, 123 2,3-butanediol (2,3-BD), 121 3-hydroxypropionic acid, 122
123 citric acid, 119
120 lactic acid, 123
125, 124f succinic acid (SA), 121
122 volatile fatty acids (VFAs), 125
126 Organic acids (OAs), 224 Organic food waste materials, 175 Organic fractions of municipal solid waste (OFMSW), 379 Organic loading rate (OLR), 17
21, 267 Organic matter, 236
240 Organic-rich FW, 15
17, 163 Organizations working on food waste management, 402t Origins of food waste, 3
4 Oxygen, 256 Oxygen uptake, 244 Oxytetracycline, 173

P Pachytrichospora transvaalensis, 284 Packaging, 429 Packed-bed bioreactor, 218, 220f Packed-bed reactors (PBRs), 87
89 Paenibacillus polymyxa, 121 Palm oil effluent, 289 Palm oil mill effluent (POME), 289 Panas tigrinus, 291 Parachlorella kessleri, 283
284 Parallel cofiring, 102, 102f Particle size, 244 Pasteur, Louis, 218

Patented methodologies, 420 for commercial-scale implementation of food waste biorefinery products, 421t Patents, 419
420 Pay-As-You-Throw scheme (PAYT), in South Korea, 314
315 Pay as you throw (PAYT) schemes, 396 Pea shells, 212t Pectin, 7, 150
152, 336
337, 420 Pectin and seed oil recovery process (PSEP), 336
337 Pectinase enzymes, 127, 223 Peel oil, 174
175 Peel waste, 164 Penicillin, 173 Penicillium, 222 Penicillium chrysogenum, 173 Penicillium lactum, 120 Perforated tray bioreactor, 175 Pervaporation bioalcohols, 61 Phanerocheate chrysosporium, 194 Phenolic acids, 191, 406
408 Phenolic compounds, 190
192, 420 flavonoids, 191 phenolic acids, 191 stilbenes and lignans, 191
192 tannins, 191 Phenyl ethyl acetate, 164 6-Phenyl pyrole (6-PP), 171 pH level, 243 Phosphoenolpyruvate, 57
58 2-Phosphoglycerate, 57
58 3-Phosphoglycerate, 57
58 Phospholipase enzyme, 222 Phospholipid fatty acid (PLFA), 236
240 Phosphoric acid, 81 Phosphorus, 284 Phragmites australis, 276 Phycobilins, 283
284 Physical pretreatment methods, 348 Physicochemical methods, 309
311 esterification, 310
311 gasification, 310 incineration, 309
310 pyrolysis, 310 Pichia kudriavzevii, 240 Pichia stipites, 66 Pichia stipitis, 217 Pigments, 172
173 astaxanthin, 173 chlorophyll, 172 monascus, 172 prodigiosin, 172 Pilot microbial fuel cell, current status of, 270 Pineapple residues, 171 Planctomyces, 262, 266
267 Plant-derived food waste (fruit and vegetable waste), 285
288 apple pomace, 285
286 citrus waste, 286
287 grape waste (wine lees), 286 potato peel waste, 287
288 rice waste, 288 tomato waste, 287

443

Poland, food waste management in, 300
301 Policy options and their implications, 420
423 policies and regulations, 423 policy measures promoting social innovation, 420
423 resolving challenges into opportunities, 423 social innovation and food waste, 420 Polyacrylate, 85
86 Polyethylenimine, 223 Polyhydroxyalkanoates (PHA), 144
145, 211 production of, 282 Polyhydroxybutyrates (PHB), 144, 211 mechanism of synthesis of, 214 production of, 214
215, 214f Polyphenols, 190
191 Polypropylene, 85
86 Polysaccharides, 149
152, 328 of tomato waste, 151 Polystyrene, 85
86 Polytetrafluoroethylene (PTFE)-coated carbon, 252 Pomace, 151 Pomegranate peel, 202
203 Porcine pancreatic, 48
49 Porosity, 243 Postconsumption food waste, 143 Postharvest loss, 2
3 Potato chips, 212t Potato peel, 202
203, 406
408 Potato peel waste, 287
288 Potato processing wastewater, 253 Potato residues, 151 Preconsumption food waste, 143 Preharvest losses, 5 Pressure vacuum swing adsorption (PVSA), 332 Pressurized fluidized bed combustor, 103 Pressurized hot water extraction (PHWE), 174 Pressurized liquid extraction, 189 Pretreatments, 9, 25
26 for biodiesel production, 75
78 biological pretreatment, 78 chemical pretreatment, 76
78 combined pretreatment, 78 mechanical pretreatment, 78 physical pretreatment, 76 for recovery of bioactive components, 346
347 Pricing for new marketing approach, 429 Process configuration, 20
22 codigestion, 22 multistage digestion, 21 single-stage digestion, 20 two-stage digestion, 21 Processing-stage food losses, 380 Prodigiosin, 172 Production-stage food loss, 380 Products and processes, 429 Pro-Enrich, 424 1,3-Propanediol, 123 Propionibacterium sp., 226 Propionic acid, 226 Proteases, 48
49, 221

444

Index

Protein-enriched food waste materials, 192
193 Proteins, 20, 223 Proteobactor, 262, 266
267 Proton exchange membranes (PEM), 257
258 Pseudomonas, 240, 282 Pseudomonas aeruginosa, 193 Pseudomonas cepacia, 84, 215
216 Pseudomonas fluorescens, 224 Public procurement, 430 PULP2VALUE approach, 424 Pulsed electric field (PEF), 200
201 -assisted extraction unit, 179f extraction, 178 Purchase incidence model, 427, 427f Pyrolizers advantages and disadvantages of different types of, 105t Pyrolysis, 103
104, 111, 310, 349 fast pyrolysis/thermolysis, 104 ablative pyrolysis reactor, 104 fluidized bed, 104 pyrolysis reactor vacuum, 104 rotating cone reactor, 104 reactor vacuum, 104 slow/conventional pyrolysis, 103 fixed bed, 103 rotary kiln, 103 ultrafast/flash pyrolysis, 104 Pyruvate decarboxylase, 57
58

Q Qualitative loss, 2
3 Quantifying food waste, 6

R Ralstonia eutropha, 145 Rapeseed oil waste, 290
291 Reactor configuration, 22 Reactor design and performance, 262 ReCiPe, 362
363 Red grape pomace, 202 REMA 1000, 396 Remedial phase, 241 Restaurant kitchen waste, 212t Restaurant waste, 212t Rhamnolipid BS, 193 Rhizomucor miehei, 87, 223
224 Rhizopus, 125 Rhizopus oligosporus, 147
148 Rhizopus oryzae, 84, 87
89, 164
171, 224 Rhodosporidium sp., 284 Rhodosporidium toruloides, 175 Rhodotorula, 284 Rhodotorula glutinis, 275
276, 281, 284 Rhodotorula sp., 173, 281, 284 Rice grains, 212t Rice waste, 288 Robin Hood Army, 301 Rotary kilns, 99, 103 Rotating cone reactor, 104 Rural living, 389

S Saccharification, 49
52 and cofermentation, 66 and fermentation, 62
66 Saccharomyces, 120, 147
148 Saccharomyces cerevisiae, 39
40, 57
58, 61
66, 146
148, 164, 217, 221, 224
225, 279
281, 284
285 Saccharomyces coreanus, 66 Saccharomyces sp., 281 Saccharomycopsis cataegensis, 284 Saccharopolyspora erythraea, 174 Salmonella, 286 Salmon fish oil, 420 Salpichroa origanifolia, 223 Scale-up, 328 Scale-up and commercialization, 419 Scenedesmus bijugatus, 283
284 Scenedesmus quadricauda, 283 Scheffersomyces stipitis, 217 Schizochytrium mangrovei, 283 Screw pyrolizers, 103 Sea fishing, 253
254 Seafood processing wastewater, 253
254 Seafood waste, 425 Seed oil, 174 Separate hydrolysis and fermentation (SHF), 61
62 Serratia marcescens, 121, 172 Share-Waste, 305 Shewanella, 262, 266
267 Simultaneous saccharification and cofermentation (SSCF), 61, 66 Simultaneous saccharification and fermentation (SSF), 61
66 Single-cell oil (SCO), 143, 146, 152
156 application, 146 Single-cell protein (SCP), 147
149 applications of, 149 Single-chamber air cathode MFC (SCMFC), 252 Single-chambered concentric tubular, 261 Single-chambered upflow, 260
261 Single-stage digestion, 20 Slaughterhouse wastewaters, 253 Slow/conventional pyrolysis, 103 fixed bed, 103 rotary kiln, 103 Slow pyrolysis, 103 Social innovation and food waste, 420 policy measures promoting, 420
423 Social media management service, 429 Societal life cycle costing (S-LCC), 383 Solanidine, 406
408 Solid recovery fuel (SRF), 378 Solid-state fermentation (SSF), 120, 127, 175, 194, 219t, 332 Soluble dietary fiber (SDF), 193 Solvent extraction (SE) technique, 194
197 Solvent-free microwave extraction (SFME), 197
198 Sources and origins of food waste, 3
4 South Korea, legislation in, 314
315

Soxhlet extraction, 198 Spain, food waste management in, 300
301 Specific exergy lost (SEL), 377 Spent coffee grounds (SCGs) waste, 212t, 215 Spirulina, 147
148 Spoiler Alert, 300 Sporidiobolus sp., 173 Sporobolomyces odors, 171 Stacked microbial fuel cell, 261
262 State of the art of food waste management in various countries, 299 change and economic impact, 300 current scenario and development of food waste management in various countries, 300
302 developed countries, 300
301 developing countries, 301
302 underdeveloped countries, 302 legislation in various countries, 314
315 Brazil, 315 European Union, 314 France, 315 India, 315 Italy, 315 Japan, 314 Malaysia, 315 South Korea, 314
315 United States, 314 technical challenges and emerging trends, 315
319 treatment strategies and product recovery, 302
311 anaerobic digestion (AD), 305
308 animal feed, 303
304 composting, 304
305 fermentation, 308
309 landfilling, 311 physicochemical methods, 309
311 valorization of food waste around the globe, 311
314 Static pile, 242 Stilbenes, 191
192 Stirred tank reactor (STR), 87
89 Storage-stage food losses, 380 Streptococcus henryi, 224 Streptomyces griseus, 134 Streptomyces rimosus, 173 Streptomyces sp., 224 Streptomyces speibonae, 173 Streptomyces vendagensis, 173 Subcritical water (SCW) extraction, 199, 425 Submerged fermentation (SMF), 194 Submerged liquid fermentation (SLF), 127 Succinic acid (SA), 121
122 Sugar beet pulp, 223 Sugars, 150 Sulfonic acid, 81 Sulfuric acid, 81 SunLine Transit Agency, 28 Supercritical fluid extraction (SFE), 132
133, 198, 199f, 200f Supercritical fluid extraction, 179, 180f Surface treatment of anodes, 256 Suspension burner, 100

Index

Sustainable compost and its application in the global market, 246 Sustainable development, transition toward, 430
431, 430f Sustainable food chains, designing current challenges and future trends in, 383 Sweeteners, 150 Sweet potato, 148 Syrups, 150 System boundaries, 361, 374 System expansion, 362, 382

T Taguchi design, 152 Taiwan, composting in, 305 Tannase, 127 Tannin acyl hydrolase, 127 Tannins, 191 Tapioca. See Cassava Technical challenges in food waste management, 326
328 Techniques for the conversion of food waste into valuable products, 347
349 biological conversion, 348 thermochemical conversion, 348
349 Techno-economic analysis (TEA) and environmental aspects of food waste management, 325 case studies on food waste biorefineries, 336
338 biofuel production from food waste, 338 food waste biorefinery in European context, 337 integrated mango biorefinery in an Indian context, 336
337, 336f commercial scale-up of food waste valorization technology, 328
330 cost-competitive food waste biorefinery development, 332
333 cost estimation of different food waste valorization techniques, 330
332 anaerobic digestion, 332 dark fermentation, 331
332 solid-state fermentation, 332 transesterification, 330
331 food waste biorefinery, TEA of, 333
334 techno-economic analysis framework, 334, 335f techno-economic analysis methodology, 334
335 technical challenges in food waste management, 326
328 Temperature, 18
19, 243 -based pretreatment, 42 Terminal restriction fragment length polymorphism analysis (T-RFLP), 236
240 Terpenes, 164
171 Tetracycline, 173 Thailand, food waste management in, 302 Thermal hydrolysis, 49 Thermal pretreatments, 17 Thermochemical conversion, 348
349

scalability, of food waste, 110
113 combustion/cofiring, 111 gasification, 111 hydrothermal carbonization (HTC), 112
113 incineration, 110
111 pyrolysis, 111 Thermochemical gasification, 104 Thermochemical routes for bioenergy generation, 97
110 challenges and future prospects, 113
114 cocombustion, 102
103 principles, 102 technologies, 103 cofiring, 100
102 direct cofiring, 100
101, 101f indirect cofiring, 101, 102f parallel cofiring, 102, 102f combustion, 99
100 principles, 99 technologies, 99
100 gasification, 104
108 principles, 105 technologies, 106
108 hydrothermal carbonization (HTC), 108
110 influence of reaction parameters, 110 transformation process, 109
110 incineration, 98
99 fluidized bed, 99 moving grate, 98 rotary kilns, 99 pyrolysis, 103
104 fast pyrolysis/thermolysis, 104 slow/conventional pyrolysis, 103 ultrafast/flash pyrolysis, 104 Thermodynamic exergy, 376 Thermomonospora, 127
128 Thermomyces lanuginosus, 87, 91, 127, 215
216 Thermophilic AD, 18
19 Thermophilic phase, 241 Thiols, 172 Three-dimensional (3D) printing technology, 226 Tomato peels, 406
408 Tomato residues, 151 Tomato waste, 151, 287 Trametes hirsuta, 66
67 TransBiodiesel Ltd., 91 Transesterification process, 9
10, 79
87, 215, 330
331, 364
368 acid-catalyzed transesterification, 79
81 alkaline-catalyzed transesterification, 81
83 enzyme-catalyzed transesterification, 83
87 adsorption, 85
86 covalent binding, 87 cross-linkage, 86 encapsulation, 87 entrapment, 86 immobilized enzyme-catalyzed transesterification, 84 Transesterification reaction, 75
76 Transport- stage food losses, 380

445

TransZymeA, 91 Triacylglyceride ester bonds, 83
84 Trichoderma, 127
128, 222 Trichoderma reesei, 223 Trichosporon, 284 Tricoderma viride, 120 Triple-layered business model, 426, 426f Tripyrrole antibiotic pigments, 172 Two-stage digestion, 21 Types of food waste, 6
7, 8f

U Ultrafast/flash pyrolysis, 104 Ultrasonication, 425 Ultrasonication-assisted extraction (UAE), 132 Ultrasonic pretreatment, 17 Ultrasound-assisted extraction (UAE), 174, 177f, 178, 189, 199
200 Underdeveloped countries current scenario and development of food waste management in, 302 Unique selling points, developing, 429
430 date labelling, 429 mobile applications, 429
430 retailer options, 429 United Kingdom, generation of FW in, 4 United States anaerobic digestion (AD) projects in, 307 composting in, 305 food waste management in, 300 generation of FW in, 4
5 legislation in, 314 United States Patent and Trademark Office (USPTO), 419
420 Unnecessary FW, 2 Up-flow anaerobic sludge blanket (UASB), 22, 24 Up-scaling processes, 401, 404
406 Upstream process, bioalcohol production, 41
52 detoxification, 52 hydrolysis/saccharification, 49
52 pretreatment, 41
49 biological pretreatment, 48
49 chemical pretreatment, 42
48 combined pretreatment, 49 mechanical pretreatment, 48 physical pretreatment, 42 Urbanization, 389 Ureibacillus thermosphaericus, 52

V Valorization of food waste, 218, 345
347. See also Management and valorization of food waste around the globe, 311
314 extraction, 347 impact assessment of, 350f issues in relation to valorization of food waste to biogas, 351
352 issues in relation to valorization of food waste to compost, 349
351

446

Index

Valorization of food waste (Continued) into different by-products, 393f isolation and clarification, 347 planning strategies and new innovative plans for, 352
353 pretreatment of food waste, 346
347 preventive measures taken during, 352 Valorization of FW for biodiesel production, 75 future prospects, 91
92 lipids to biodiesel conversion, 78
79 pretreatments, 75
78 biological pretreatment, 78 chemical pretreatment, 76
78 combined pretreatment, 78 mechanical pretreatment, 78 physical pretreatment, 76 reactors involved in biodiesel production, 87
91 scalability of biodiesel production, 91 transesterification process, 79
87 acid-catalyzed transesterification, 79
81 alkaline-catalyzed transesterification, 81
83 enzyme-catalyzed transesterification, 83
87 Valorization of FW for bioethanol and biobutanol production, 39 bioalcohol fermentation methods, 61
67 consolidated bioprocessing (CBP), 66
67 separate hydrolysis and fermentation (SHF), 61
62 simultaneous saccharification and cofermentation (SSCF), 66 simultaneous saccharification and fermentation (SSF), 62
66 bioalcohol production from food waste, 40
41 bioalcohol production processes, 41
61, 41f downstream process, 58
61 midstream process, 52
58 upstream process, 41
52 bioalcohol yield, strategies to increase, 67 Valorization of FW into bioenergy, 15 anaerobic digestion of FW, 15
18 pretreatments employed, 17
18 biohydrogen production, 22
24 from food industry waste, 24 from food waste, 23
24 biohydrogen production, factors affecting, 24
26 components/composition of food waste, 24
25 pretreatments, 25
26 volatile fatty acids (VFAs), 26 biohythane, applications of, 28 biohythane production, enhancement strategies of, 28

biohythane production from food waste, 26
28 process description, 27
28 challenges in the commercialization of biofuel from food waste, 29 factors affecting anaerobic digestion of FW, 18
20 foaming, 20 hydraulic retention time (HRT), 19 micronutrients, 19 organic loading rate (OLR), 19 pH, 18 temperature, 18
19 future perspectives, 29
32 process configuration, 20
22 codigestion, 22 multistage digestion, 21 single-stage digestion, 20 two-stage digestion, 21 reactor configuration, 22 Valorization technique, 401, 404, 407t financial measures, 403 food waste management, 404
406 biorefinery approach, 404, 405f, 405t up-scaling processes, 404
406 institutions and enterprises in food waste management, 402 market-based products, 403 market value of food waste valorization products, 406
410, 408t commercial valorization of food waste, challenges for attaining, 409 commercial valorization of food waste, policy framework for, 409
410 factors influencing, 409 uncertainties for market value, factors contributing to, 410 production guidelines standards, 402
403 Valorization techniques, cost estimation of, 330
332, 331t anaerobic digestion, 332 dark fermentation, 331
332 solid-state fermentation, 332 transesterification, 330
331 Valorization technology, food waste commercial scale-up of, 328
330 Valuable resource, food waste as, 143
152 baker’s yeast, 146
147 biopolymer and protein feed production, economic aspects and commercialization of, 156
157 biopolymers, 144
145 application, 145 extraction and purification, 145 fermentation process, 145 biopolymers and feed proteins, reactors used for the production of, 152
156 polysaccharides, 149
152

single-cell oil (SCO), 146 application, 146 single-cell protein (SCP), 147
149 applications of, 149 Value-added products recovery, 11, 283
284 Value web, 395 Vegetable oils, 20 Vegetables, 217 Vermicomposting, 242 Viesel Fuel LLC, 91 Virtual water content (VWC), 382 Volatile fatty acids (VFAs), 15
17, 26
28, 32, 125
126, 144, 275
279, 328, 333 bioenergy, 283 polyhydroxyalkanoates (PHA) production, 282 Volatile organic compound (VOC), 40
41, 351, 362
363 Volatile solids (VSs) to total solids (TSs) ratio, 325
326 Volatile sulfur compounds (VSCs), 351 Voluntary ecolabeling, 430

W Waste animal fat (WAF), 216 Waste generation sites, 325 Waste management hierarchy, 391 Waste treatment plants, food loss treatment in, 382 Waste valorization, 392 Water footprint (WF), 382 Wet milling, 346
347 Whey, 212t Windrow, 242 World Intellectual Property Organization (WIPO), 419

X Xanthophyllomyces dendrorhous, 173 Xylanases, 127, 211, 222, 226 xylase, 48
49 Xyloglucan, 151

Y Yarrowia, 120, 284 Yarrowia lipolytica, 78, 171, 173, 281 Yeast, 147 cultivation of biodiesel, biogas recovery, and biofertilizer production, 284

Z Zymomonas mobilis, 39
40, 279
281