Green Technologies for Waste Management: A Wealth from Waste Approach 1032230819, 9781032230818

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Green Technologies for Waste Management Proper waste disposal is still a serious concern worldwide. This book addresses various types of wastes such as industrial, agricultural, and municipal solid and liquid wastes, their generation, and the status of waste management in developed and developing countries. It discusses advanced green technologies used in harnessing energy and bioproducts from wastes such as electricity, biofuel, biopolymers, fertilizers, and chemicals without damaging the quality of the environment but rather creating a source that is an added value to the environment. Through many applications and case studies, this comprehensive book helps readers build a state-of-the-art knowledge on waste utilization and energy generation. FEATURES • Provides a comprehensive, state-of-the-art coverage of waste management practices, their challenges, and solutions from a global perspective • Discusses conceptual principles and practices of various green technologies that can be used to generate valuable products from waste and improve environmental quality • Includes case studies from the United States and Japan, providing detailed explanations of advanced bioremediation technologies • Takes a holistic approach to waste management and bioproducts recovery • Offers an easy-to-understand and target-oriented approach that helps both students and professionals advance their knowledge in creating wealth from waste Written for undergraduate and graduate students taking courses in environmental biotechnology, environmental microbiology, non-conventional energy sources, waste treatment technologies, environmental waste utilization, energy, and environment taught in universities and colleges. The book can also be used by professionals and researchers at different levels in related fields.

Green Technologies for Waste Management A Wealth from Waste Approach

J.P.N. Rai Shweta Saraswat

Designed cover image: © the authors and CorelDRAW Graphics Suite 2019 Software; Cover images provided by the authors and © Shutterstock First edition published 2024 by CRC Press 2385 NW Executive Center Drive, Suite 320, Boca Raton FL 33431 and by CRC Press 4 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN CRC Press is an imprint of Taylor & Francis Group, LLC © 2024 J.P.N Rai and Shweta Saraswat Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, access www.copyright.com or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-7508400. For works that are not available on CCC please contact [email protected] Trademark notice: Product or corporate names may be trademarks or registered trademarks and are used only for identification and explanation without intent to infringe. ISBN: 978-1-032-23081-8 (hbk) ISBN: 978-1-032-24530-0 (pbk) ISBN: 978-1-003-27913-6 (ebk) DOI: 10.1201/9781003279136 Typeset in Times by MPS Limited, Dehradun

Contents Preface............................................................................................................................................xvii Authors............................................................................................................................................xix

PART I Environmental Wastes: Status, Prospects, and Management Chapter 1

Waste: Classification, Generation, and Status............................................................3 1.1 1.2

Introduction .......................................................................................................3 Definition and Classification of Waste ............................................................3 1.2.1 Waste: The Concept ............................................................................ 3 1.2.2 Classification of Waste........................................................................ 4 1.2.2.1 Classification Based on the Physical State .........................4 1.2.2.2 Origin/Source-Based Classification .....................................5 1.2.2.3 Classification of Wastes Based on Degradability...............8 1.2.2.4 Classification of Wastes Based on Toxicity .......................8 1.3 Techniques to Estimate Waste Generation ......................................................9 1.3.1 Load Count Analysis........................................................................... 9 1.3.2 Weight Volume Analysis .................................................................... 9 1.3.3 Material Mass Balance Analysis ...................................................... 10 1.4 Waste Generation, Composition, and Status (Global and National Scenario) ..........................................................................................10 1.4.1 Global Generation of Waste ............................................................. 11 1.4.1.1 Waste Generation in Different Regions ............................11 1.4.1.2 Global Waste Generation in Different Income Groups....11 1.4.2 Global Waste Composition ............................................................... 11 1.4.3 Global Projections of Waste Generation .......................................... 14 1.4.4 Status of Environmental Waste in India .......................................... 16 1.4.4.1 Composition and Status of Municipal Solid Waste in India.................................................................................... 16 1.5 Conclusion ......................................................................................................17 References.................................................................................................................. 17 Chapter 2

Waste as a Resource .................................................................................................19 2.1 2.2

2.3

Introduction .....................................................................................................19 Classification of Wastes .................................................................................19 2.2.1 Municipal Solid Waste (MSW) ........................................................ 20 2.2.2 Industrial Wastes ............................................................................... 20 2.2.3 Institutional/Commercial Wastes ...................................................... 20 2.2.4 Agricultural Wastes........................................................................... 20 Resource Generation from Waste ..................................................................21 2.3.1 Resource Generation from Agricultural Wastes .............................. 22 2.3.2 Resource from Woody Plants Waste................................................ 22 2.3.3 Resources from Urban Biowastes and Animal Husbandry ............. 23 v

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2.3.3.1 2.3.3.2 2.3.3.3

Direct Land Application ....................................................23 Direct Animal Feed (DAF) ...............................................24 Biological/Biochemical Conversion of Biowaste to Resource .............................................................................25 2.3.3.4 Resource Generation through Physico-Chemical Treatment of Biowastes ..................................................... 27 2.3.3.5 Resource Generation through Thermochemical Treatment ........................................................................... 28 2.3.4 Resources from Municipal Sewage Sludge...................................... 29 2.3.4.1 Amino Acids and Proteins.................................................29 2.3.4.2 Short-Chain Fatty Acids ....................................................30 2.3.4.3 Enzymes .............................................................................30 2.3.4.4 Bio-Fertilizers and -Pesticides........................................... 30 2.3.4.5 Bio-Plastics......................................................................... 31 2.3.4.6 Bio-Flocculants ..................................................................31 2.3.4.7 Biosurfactants.....................................................................31 2.3.5 Valorization of Crop Byproducts/Processed Agrowastes ................ 32 2.3.5.1 Agricultural Wastes as Low-Cost Adsorbents ..................32 2.3.5.2 Biochar ...............................................................................32 2.3.5.3 Cellulose and Pectin ..........................................................32 2.3.5.4 Microbial Protein ............................................................... 32 2.3.5.5 Natural Rubber...................................................................33 2.3.5.6 Plant Fibers and Paper.......................................................33 2.3.5.7 Nanocellulose .....................................................................33 2.3.5.8 Lignin .................................................................................34 2.3.5.9 Oils and Fats (O and F)..................................................... 34 2.3.5.10 Terpenes.............................................................................34 2.3.5.11 Natural Polyelectrolytes ....................................................34 2.3.5.12 Nanoparticles (NP) ............................................................35 2.3.5.13 Graphene ............................................................................36 2.3.6 Resource Generation from Industrial Wastes................................... 36 2.3.6.1 Bakery Products ................................................................. 37 2.3.6.2 Biocompost......................................................................... 37 2.3.6.3 Mushroom Production Oil Palm Industry Waste ............. 37 2.3.6.4 Nutritional Supplements and Medical Aids from Aquaculture Waste.............................................................37 2.3.6.5 Biofuel from Pulp and Paper Industry Waste...................37 2.3.6.6 Lac Dye and Gummy Mass from Lac Industry Waste ....37 2.3.7 Algae as Biofuel Resource................................................................ 38 References.................................................................................................................. 38 Chapter 3

Life Cycle Assessment of Waste Management Systems .........................................45 3.1 3.2 3.3

Introduction .....................................................................................................45 Product Life Cycle..........................................................................................46 Methodology of LCA in Context of Waste Management ............................48 3.3.1 Goal.................................................................................................... 49 3.3.2 Scope.................................................................................................. 50 3.3.2.1 Product System ..................................................................50

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3.3.2.2 Functional Unit ..................................................................50 3.3.2.3 Reference Flow ..................................................................51 3.3.2.4 System Boundaries.............................................................51 3.3.2.5 Assumptions and Limitations ............................................ 53 3.3.2.6 Data Quality Requirements ...............................................53 3.3.2.7 Multifunctionality and Allocation .....................................53 3.3.2.8 Documentation of Data...................................................... 54 3.3.3 Life Cycle Inventory (LCI)............................................................... 54 3.3.4 Life Cycle Impact Assessment (LCIA) ............................................ 55 3.3.5 Interpretation...................................................................................... 56 3.4 Conclusion ......................................................................................................58 References.................................................................................................................. 58

PART II Green Technologies for Wealth Generation Chapter 4

Bioremediation .......................................................................................................... 63 4.1 4.2

4.3

4.4

4.5

Introduction .....................................................................................................63 Classification of Bioremediation ....................................................................64 4.2.1 Ex-Situ Bioremediation..................................................................... 65 4.2.1.1 Landfarming .......................................................................65 4.2.1.2 Compositing .......................................................................65 4.2.1.3 Biopiling.............................................................................66 4.2.2 In-Situ Bioremediation ...................................................................... 66 4.2.2.1 Bioventing .......................................................................... 66 4.2.2.2 Bioslurping ......................................................................... 67 4.2.2.3 Biosparging ........................................................................68 4.2.2.4 Bioaugmentation ................................................................ 68 4.2.2.5 Biostimulation ....................................................................69 4.2.2.6 Phytoremediation ............................................................... 69 4.2.2.7 Phytoextraction...................................................................71 4.2.2.8 Phytotransformation ...........................................................72 4.2.2.9 Phytostabilisation ............................................................... 73 4.2.2.10 Phytodegradation ............................................................... 73 4.2.2.11 Phytohydraulics..................................................................74 4.2.2.12 Phytofiltration.....................................................................74 4.2.2.13 Phytovolatilization .............................................................75 Factors Affecting Phytoremediation ..............................................................75 4.3.1 Types of Contaminants ..................................................................... 75 4.3.2 Concentration of Contaminants ........................................................ 75 4.3.3 Plant Growth Rate............................................................................. 75 4.3.4 Characteristics of Plants.................................................................... 76 4.3.5 Roots’ Nature .................................................................................... 76 Bioremediation of Various Pollutants............................................................76 4.4.1 Organic Pollutants ............................................................................. 76 4.4.2 Inorganic Pollutants........................................................................... 78 4.4.3 Heavy Metals..................................................................................... 78 Limitation of Bioremediation .........................................................................79

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4.6 Root-Zone Technology ...................................................................................79 4.7 Conclusion and Future Outlook .....................................................................80 References.................................................................................................................. 81 Chapter 5

Biodegradation...........................................................................................................89 5.1 5.2 5.3

Introduction .....................................................................................................89 Nature of Pollutants........................................................................................90 Biodegradation Methods.................................................................................92 5.3.1 Composting........................................................................................ 92 5.3.1.1 Composting Methods .........................................................92 5.3.1.2 Microbiological Aspects of Composting...........................94 5.3.1.3 Biochemical Aspects of Composting ................................95 5.3.1.4 Factors Affecting Composting Process .............................95 5.3.2 Vermicomposting .............................................................................. 96 5.3.2.1 Role of Earthworm in Vermicomposting..........................96 5.3.2.2 Vermicomposting Methods................................................97 5.3.2.3 Factors Affecting Vermicomposting ................................. 99 5.3.2.4 Soil Fertility Maintenance through Vermicomposting ............................................................... 99 5.3.3 Solid State Fermentation (SSF) ...................................................... 100 5.3.3.1 Organisms Used for SSF .................................................101 5.3.3.2 Diversity of SSF Applications to Valorize Waste and Biomass..........................................................101 5.3.4 Bio-Fertilizer Production................................................................. 104 5.3.4.1 PGPR as Biofertilizer ...................................................... 105 5.3.4.2 Types of Biofertilizers ..................................................... 107 5.3.5 Biofilm Technology......................................................................... 109 5.3.5.1 Benefits of Bacterial Biofilms ......................................... 110 5.3.6 Aerobic Granular Sludge Technology ............................................ 112 5.3.6.1 Formation of Aerobic Granules.......................................114 5.3.6.2 Applications of Aerobic Granular Sludge Reactors .......115 5.3.7 Biopolymer Technology.................................................................. 115 5.3.7.1 Classification of Biopolymers ......................................... 116 5.3.7.2 Applications of Biopolymers........................................... 117 5.3.8 Electronic Waste (E-Waste) Management...................................... 119 5.3.8.1 Metallurgical Technologies to Treat E-Waste ................119 References................................................................................................................ 122

Chapter 6

Biosorption Technology ..........................................................................................137 6.1 6.2

6.3 6.4

Introduction ...................................................................................................137 Biosorption: A Green Option for Pollution Abatement ..............................137 6.2.1 Biosorption Mechanisms................................................................. 139 6.2.2 Factors Affecting Biosorption......................................................... 141 Affinity Ligand-Based Technologies ...........................................................142 Bioflocculation Technology.......................................................................... 143 6.4.1 Mechanism of Bioflocculation ........................................................ 144 6.4.2 Measures of Bioflocculation ........................................................... 147

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6.4.2.1 Flocculation Mediated by Plant-Based Product..............147 6.4.2.2 Animal-Based Bioflocculants .......................................... 147 6.4.2.3 Microbial Bioflocculation ................................................148 6.4.2.4 Autoflocculation ............................................................... 151 6.4.3 Bioflocculants’ Applications ........................................................... 152 6.4.3.1 Biopharmaceuticals ..........................................................152 6.4.3.2 Pulp and Paper Industry ..................................................152 6.4.3.3 Precious Metal Extraction ...............................................152 6.4.3.4 Production of Upstream Oil and Gas..............................152 6.5 Biocoagulation .............................................................................................. 152 6.6 Biosurfactants................................................................................................154 6.6.1 Sources of Biosurfactants................................................................ 154 6.6.1.1 Glycolipids ....................................................................... 155 6.6.1.2 Lipopeptides and Lipoproteins ........................................156 6.6.1.3 Surfactin ........................................................................... 156 6.6.1.4 Lichenysin ........................................................................ 156 6.6.1.5 Neutral Lipids, Phospholipids, and Fatty Acids ............. 156 6.6.1.6 Polymeric Biosurfactants .................................................156 6.6.2 Applications of Biosurfactants........................................................ 156 6.6.2.1 Food Industries................................................................. 156 6.6.2.2 Removal of Oil and Petroleum Contamination ..............157 6.6.2.3 Bioremediation of Toxic Pollutants ................................ 157 6.7 Biochar Technology......................................................................................158 6.7.1 Role of Biochar in Soil Health Management................................. 159 6.7.2 Effect of Biochar on Plant Growth and Soil Biota........................ 159 6.7.3 Biochar: A Solution to Mitigate Climate Change.......................... 160 References................................................................................................................ 161 Chapter 7

Single-Cell Protein Technology..............................................................................171 7.1 7.2

7.3

7.4

Introduction .................................................................................................171 Microorganisms for Single-Cell Protein .................................................... 172 7.2.1 SCP from Algae ............................................................................ 173 7.2.2 SCP from Fungi ............................................................................ 175 7.2.3 SCP from Bacteria ........................................................................ 176 Industrial Production of SCPs ....................................................................177 7.3.1 Fermentation Strategies................................................................. 178 7.3.1.1 Submerged Fermentation ...............................................178 7.3.1.2 Semisolid Fermentation .................................................178 7.3.1.3 Solid-State Fermentation ...............................................179 Potential Feedstocks/Substrates for SCP Production................................. 179 7.4.1 Industrial Wastes ........................................................................... 179 7.4.1.1 Molasses ......................................................................... 180 7.4.1.2 Dairy Waste ...................................................................180 7.4.1.3 Fruit Waste (Simple Sugar Rich) .................................. 180 7.4.1.4 Starch Rich Sources and Bran.......................................180 7.4.1.5 Soybean Meal................................................................. 181 7.4.1.6 Methanol......................................................................... 181 7.4.2 Agricultural Wastes....................................................................... 181

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7.5

SCP Production Process .............................................................................181 7.5.1 Media Preparation ......................................................................... 182 7.5.1.1 Media Preparation Using Fruit and Vegetable Wastes ............................................................................182 7.5.1.2 Media Preparation Using Lignocellulose Wastes .........182 7.5.1.3 Media Preparation Using Liquid Waste........................ 183 7.5.2 Enrichment of the Media .............................................................. 183 7.5.3 Sterilization of Growth Media ...................................................... 183 7.5.4 Inoculum Isolation and Growing .................................................. 183 7.5.5 Inoculation and Incubation............................................................ 184 7.5.6 Harvesting and Protein Content Determination ........................... 184 7.5.7 Processing of SCP......................................................................... 184 7.6 Patented Technologies for Single-Cell Protein Production....................... 185 7.6.1 The Bel Process............................................................................. 185 7.6.2 The Symba Process ....................................................................... 185 7.6.3 Pekilo Process................................................................................ 186 7.6.4 Bioprotein Process......................................................................... 186 7.6.5 Pruteen Process.............................................................................. 187 7.6.6 Quorn Production .......................................................................... 187 7.6.7 The Waterloo Process ................................................................... 188 7.7 Safety of SCPs ............................................................................................ 188 7.8 Recovery of Other Value-Added Products during SCP Production .........189 7.8.1 Production of Ethanol ................................................................... 189 7.8.2 Production of Hydrogen................................................................ 190 7.8.3 Production of Methane.................................................................. 190 7.8.4 Production of Biodiesel................................................................. 190 7.8.5 Production of Bioactive Compounds by Fermentation of Food Waste ............................................................................... 190 7.9 Arena of SCP Applications .......................................................................... 191 7.10 Benefits and Drawbacks of Single-Cell Protein .......................................... 191 7.11 Challenges Ahead .........................................................................................192 References................................................................................................................ 193 Chapter 8

Bioenergy Production Technologies .......................................................................199 8.1 8.2

8.3

Introduction ...................................................................................................199 Fuel Cell Technology ................................................................................... 199 8.2.1 Introduction...................................................................................... 199 8.2.2 Principle........................................................................................... 200 8.2.3 Microbial Resources........................................................................ 200 8.2.4 Electron Transfer Mechanism......................................................... 201 8.2.5 Microbial Fuel Cell Designs........................................................... 201 8.2.5.1 Single-Chamber MFCs (SCMFCs) ................................. 201 8.2.5.2 Double-Chamber MFC .................................................... 202 8.2.5.3 Up-Flow Microbial Fuel Cell.......................................... 202 8.2.5.4 Stacked Microbial Fuel Cell............................................ 203 8.2.5.5 Forced-Flow MFCs ..........................................................204 8.2.6 Applications of Microbial Fuel Cells ............................................. 204 8.2.7 Future Challenge ............................................................................. 205 Biohydrogen Production ...............................................................................205 8.3.1 Biohydrogen Production Technologies........................................... 206

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8.3.1.1 Dark/Anaerobic Fermentation ......................................... 206 8.3.1.2 Bio-Photolysis ..................................................................207 8.3.1.3 Photofermentation ............................................................207 8.3.1.4 Hybrid System ................................................................. 208 8.3.2 Limiting Factors in Biohydrogen Production Systems .................. 208 8.3.3 Future Prospects .............................................................................. 208 8.4 Microalgal Valorization Technology ...........................................................208 8.4.1 Algal Strains, Cultivation, and Harvesting, and Dewatering......... 209 8.4.2 Pretreatment of Microalgal Biomass .............................................. 210 8.4.2.1 Physical Pretreatment....................................................... 210 8.4.2.2 Chemical Pretreatment..................................................... 210 8.4.2.3 Biological Pretreatment ................................................... 211 8.4.2.4 Combined Pretreatment ................................................... 211 8.4.3 Biological Hydrogen Production .................................................... 211 8.4.3.1 Biohydrogen Production from Microalgal Biomass by Dark Fermentation ...................................................... 211 8.4.3.2 Biohydrogen Production from Microalgal Biomass by Photofermentation.......................................................212 8.4.3.3 Biohydrogen Production by Co-Digestion of Microalgal Biomass .........................................................212 8.4.4 Challenges and Future Prospects .................................................... 212 8.5 Pelletization...................................................................................................213 8.5.1 Biomass Sources.............................................................................. 213 8.5.2 Pelletization Process........................................................................ 213 8.5.3 Post-Pelletization Process (Thermal Conversion Modes) .............. 214 8.6 Coal-Bed Methane Technology....................................................................215 8.6.1 CBM Reservoir Exploration and Geology ..................................... 215 8.6.2 CBM Production Process ................................................................ 216 8.6.2.1 Adsorption Isotherms.......................................................216 8.6.2.2 Evaluation......................................................................... 216 8.6.2.3 Drilling .............................................................................216 8.6.2.4 Coring...............................................................................216 8.6.2.5 Hydraulic Fracturing ........................................................217 8.6.3 Enhancement Techniques................................................................ 217 8.6.3.1 CO2 Injection ...................................................................217 8.6.3.2 N2 Injection ......................................................................217 8.6.3.3 N2 and CO2 Mixture........................................................217 8.6.4 Microbially Enhanced Coalbed Methane (MECBM) .................... 218 8.6.5 Limitations....................................................................................... 218 8.7 Conclusion ....................................................................................................218 References................................................................................................................ 218 Chapter 9

Nanobiotechnology: Concept and Scope for Wealth Generation..........................225 9.1 9.2

Introduction ...................................................................................................225 Nanoparticles Synthesis................................................................................225 9.2.1 Bioresources for NP Synthesis ....................................................... 226 9.2.1.1 Food and Agro-Industrial Waste: A Source of Polyphenols ......................................................................227 9.2.1.2 Forest and Garden Waste ................................................228 9.2.1.3 Plants-Mediated NBPs ..................................................... 228

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9.2.1.4 Bacteria-Assisted NPs...................................................... 229 9.2.1.5 Fungi-Mediated NPs ........................................................229 9.2.1.6 Algae-Mediated NPs ........................................................231 9.3 Applications of Biogenic Nanoparticles ...................................................... 231 9.3.1 Medical Applications ...................................................................... 232 9.3.2 Industrial Applications .................................................................... 234 9.3.3 Environmental Applications............................................................ 235 9.3.4 Energy Production........................................................................... 237 9.3.5 Agricultural Applications ................................................................ 238 9.3.6 Food Processing and Safety............................................................ 238 9.3.7 Electronics Field.............................................................................. 239 References................................................................................................................ 240 Chapter 10 Hydrometallurgy and Biomining ............................................................................247 10.1 10.2

Hydrometallurgy: Introduction ...................................................................247 Hydrometallurgical Process........................................................................ 249 10.2.1 Types of Metal Leaching ............................................................ 249 10.2.1.1 Bioleaching................................................................. 249 10.2.1.2 Chemical Leaching .................................................... 250 10.2.2 Concentration and Purification of Metals................................... 254 10.2.2.1 Solvent Extraction...................................................... 255 10.2.2.2 Ion-Exchange ............................................................. 255 10.2.2.3 Adsorption ..................................................................255 10.2.3 Metal Recovery ........................................................................... 256 10.2.3.1 Electrodeposition........................................................256 10.2.3.2 Precipitation ............................................................... 256 10.3 Recent Advances ........................................................................................258 10.4 Future Perspectives ..................................................................................... 258 10.5 Biomining: Introduction .............................................................................259 10.6 Why Biomining?.........................................................................................259 10.7 Biomining Processes................................................................................... 259 10.7.1 Mechanisms of Biomining .......................................................... 260 10.7.1.1 Pyrite and Other Non-Acid-Soluble Metal Sulfides: Thiosulfate Pathway ...................................262 10.7.1.2 Acid-Soluble Metal Sulfides: Polysulfide Pathway ......................................................................263 10.7.2 Factors Affecting Biomining ...................................................... 263 10.8 Metals Recovered in Biomining Processes................................................263 10.8.1 Copper.......................................................................................... 264 10.8.2 Gold ............................................................................................. 264 10.8.3 Uranium ....................................................................................... 266 10.8.4 Biomining of Other Metals......................................................... 266 10.9 Recent Developments in Biomining Technologies ...................................267 10.9.1 Bioleaching at Low Redox Potentials ........................................ 267 10.9.2 Bioreductive Dissolution of Minerals......................................... 267 References................................................................................................................ 268 Chapter 11 Constructed Wetlands and Microcosm Technology............................................... 275 Constructed Wetlands .................................................................................275

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11.1 11.2

Introduction .................................................................................................275 Types of Constructed Wetlands ................................................................. 276 11.2.1 Constructed Wetlands with Free Water Surface ........................ 276 11.2.2 Constructed Wetlands with Horizontal Sub-Surface Flow ............................................................................................. 277 11.2.3 Constructed Wetlands with Vertical Sub-Surface Flow ............................................................................................. 278 11.2.4 Hybrid Constructed Wetlands..................................................... 278 11.3 Sustainable Design and Operation of Constructed Wetlands ...................279 11.3.1 Constructed Wetland Vegetation ................................................ 279 11.3.2 Constructed Wetland Substrate................................................... 281 11.3.3 Constructed Wetland Microorganisms........................................ 282 11.3.4 Constructed Wetland Design Criteria......................................... 283 11.3.4.1 Design Criteria for Free Water Surface Constructed Wetlands ................................................283 11.3.4.2 Design Criteria for Sub-Surface Flow Constructed Wetlands ................................................285 11.4 Treated Wastewater Reuse Opportunities..................................................286 11.4.1 Case Studies on Constructed Wetlands for Treated Wastewater Reuse ....................................................................... 287 11.5 Guidelines for Decision Making in Constructing Wetlands .....................288 11.6 Challenges in Constructed Wetlands (CWS).............................................289 11.6.1 Environmental Impacts................................................................ 289 11.6.1.1 Climate Change..........................................................289 11.6.1.2 Global Warming.........................................................289 11.6.2 The CWS Mosquito Outbreaks................................................... 290 11.6.3 Cyanobacterial Threat to CWS................................................... 291 11.6.4 CWS Operational Reassessment................................................. 292 11.7 The Current Scenario.................................................................................. 292 Microcosm Technology ..............................................................................294 11.8 Microcosms .................................................................................. 294 11.9 Historical and Current Applications............................................ 295 11.10 Design Factors ............................................................................. 295 11.10.1 Sourcing, Seeding, and Energy Matching...................295 11.10.2 Spatial Scaling, Wall, and Isolation Effects ...............296 11.10.3 Temporal Scaling .........................................................297 11.10.4 Replication, Variability, and Divergence ....................298 11.11 Similarity to Natural Ecosystem.................................................. 298 References................................................................................................................ 298

PART III Holistic Approach for Waste Management and Bioproducts Recovery Chapter 12 Principles and Practices for Zero Waste Concept..................................................307 12.1 12.2 12.3

Introduction .................................................................................................307 Zero Waste Concept ................................................................................... 309 Key Factors for Zero Waste Development................................................309 12.3.1 Zero Waste Extraction and Process............................................ 309

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12.3.2 12.3.3 12.3.4 12.3.5 12.3.6

Zero Waste Design and Production............................................ 309 Sustainable Consumption and Waste Generation ...................... 310 Zero Waste Management and Treatment ................................... 310 Zero Waste Regulatory Policies and Assessment ...................... 310 Overarching Guidelines for Strategic ZW Development........... 311 12.3.6.1 Zero Waste Certification............................................ 312 12.4 The Notion of the “Zero Waste City” .......................................................313 12.5 Decoupling and Improvement of Environmental Burdens........................ 313 12.6 The Holistic Model of Zero Waste City.................................................... 313 12.6.1 Extended Producer and Consumer Responsibilities................... 315 12.6.2 100% Recycling of Waste .......................................................... 315 12.6.3 100% Recovery of Resources from Waste ................................ 316 References................................................................................................................ 316 Chapter 13 Technology Integration for Zero Waste Production ..............................................319 13.1 13.2

Introduction .................................................................................................319 Integrated Approaches for Zero Waste...................................................... 321 13.2.1 Agri- and Food Waste Valorization through the Production of Biochemicals and Packaging Materials .............. 321 13.2.1.1 Food Waste-Based Biorefinery.................................. 321 13.2.1.2 Production of Bioenergy from Waste ....................... 322 13.2.1.3 Production of Biodegradable Plastics ....................... 324 13.2.1.4 Production of Biopolymers from Waste ...................325 13.2.1.5 Bioprocesses for Bio-Lipids Synthesis ..................... 326 13.3 Enzyme Immobilization Technology .........................................................327 13.3.1 Carbohydrates .............................................................................. 328 13.3.2 Polysaccharide ............................................................................. 329 13.3.3 Lipids ........................................................................................... 330 13.3.4 Proteins ........................................................................................ 331 13.3.5 Bio-Based Chemicals .................................................................. 331 13.3.6 Sugars .......................................................................................... 331 13.3.7 Lignin........................................................................................... 332 13.3.8 Acids ............................................................................................ 333 13.3.9 Polymer Substrates ...................................................................... 334 13.4 Technology Integration for Zero Waste Generation from Pulp and Paper Industry .............................................................................335 References................................................................................................................ 338 Chapter 14 Recovery of Byproducts and Other Value-Added Products from Waste ............. 347 14.1 14.2

Introduction .................................................................................................347 Bio-Based Products for Sustainable Bioeconomy .....................................348 14.2.1 Chemicals .................................................................................. 348 14.2.2 Minerals and Nutrients.............................................................. 350 14.2.3 Proteins and Enzymes ............................................................... 351 14.2.4 Vermiwash and Biofertilizers ................................................... 353 14.2.5 Food and Microbial Protein ...................................................... 354 14.2.6 Biopesticides.............................................................................. 355 14.2.7 Biosurfactants ............................................................................ 357 14.2.8 Bioplastic and Biopolymers ...................................................... 358

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14.2.8.1 14.2.8.2 14.2.8.3

Starch-Based Plastics ...............................................359 Cellulose-Based Plastics .......................................... 359 Biodegradable Plastic from Petrochemical Sources .....................................................................359 14.2.8.4 PHA Production from Waste Streams of Different Industries ..................................................360 14.2.9 Bioenergy ..................................................................................... 361 14.2.10 Biochar ......................................................................................... 366 References................................................................................................................ 367 Index..............................................................................................................................................373

Preface Worldwide, the generation of waste is increasing and is projected to double in the next 15–20 years. While there has been significant progress in waste collection and disposal in the developed nations, a large fraction of the population in developing countries do not have access to solid waste collection, and so, its accumulation is a major public health concern. Waste management is considered a basic human necessity and often can interfere with the provision of other essential services including potable water, healthcare, energy, and other basic needs and has to be seriously looked upon. There have been several case studies where unmanaged waste has created problems concerning public health, choking of water bodies and streams, environmental and atmospheric pollution, and even navigation issues. There are even instances of hazardous wastes impacting public utilities, like water supply and agricultural produce, creating serious implications. Recently, the target has now shifted to integrated waste management, which incorporates a radical rethinking of wastes as resources against waste disposal and treatment, which necessitates concerted efforts to identify the resource potential of wastes, be it municipal solid waste, agricultural, industrial, or even domestic waste and find avenues for their value addition as part of a “circular economy.” In this context, the present book embodies various types of environmental wastes such as industrial, agricultural, and municipal solid and liquid wastes, their generation, and present status at a national and global scale. It also addresses various green techniques and technologies being used for the utilization of waste to generate wealth, such as electricity, biofuel, biopolymers, fertilizers, and chemicals, without impairing the quality of environment. These technologies have been broadly classified into two categories; one that degrades particular compounds that are very toxic and recalcitrant in nature to prevent/reduce their environmental impact and another that generates value-added usable products concurrently achieving volume reduction or eliminating the need for subsequent disposal. A range of issues pertaining to bioproducts and bioenergy production, and the degradation of pollutants resulting in usable and/or less harmful products, and their latest developments, can be used as a reference point on which new research can be constructed. While the merits of green technologies and their applicability have been elaborated, efforts have also been made to highlight the prospective technologies and their integration employing a multidisciplinary approach to resolve their inherent limitations in a way to create avenues for new resources and thus ease out handling of environmental waste judiciously. The green technologies, such as bioremediation, phycoremediation, root-zone technology, biochar technology, microcosm technology, single cell technology, cell/enzyme immobilization, nanobiotechnology, biomethanation, and fuel cell technology, have been comprehensively explained in this book by quoting possible case studies to generate wealth from waste. We owe our sincere thanks and acknowledgments to the revered authors for their valuable research materials constituting this book. Since there is acute shortage of skill and technology-oriented books and monographs in a singlewindow manner, this book will serve as a hot cake in the academic market especially for environmentalists, microbiologists, chemists, biotechnologists, waste treatment engineers and managers, green energy seekers, and administrators involved in policy making in the field. It will also fill the knowledge gaps in refinement of the technologies. We hope that the readers will not only find the updated information to be useful but will also find the future direction for research in the field of environmental management. As merciless criticism and vigorous use of a book certainly improve it, we shall very much appreciate a flow of comments and suggestions from the readers. J.P.N. Rai Shweta Saraswat

xvii

Authors J.P.N. Rai, PhD, is presently working as a full-time professor in the Department of Environmental Sciences, at G.B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India, and has been the Head of the Department for eight years. Dr. Rai has supervised more than 25 PhD theses and teaches postgraduate and PhD courses titled Biodegradation and Recycling of Wastes, Waste Treatment Design, and Environmental Waste Utilization. He has published two books along with more than 200 publications to his credit, including research papers, review articles, and chapters in scientific journals of national and international repute, apart from being a versatile reviewer of several journals. He has over 37 years of teaching and research experience in the field of environmental science, particularly in environmental biotechnology. He has successfully completed a dozen research projects in various fields of ecotechnology, bioenergy production, bioremediation of wastewater and terrestrial sites, as well as nanobiomaterial synthesis and their applications in addressing environmental issues. Currently, he is actively engaged in the research of environmental waste degradation and its utilization, wastewater treatment, and purification, employing a diverse nature of bioresources. Shweta Saraswat, PhD, is an assistant professor in the Department of Environmental Sciences at G.B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India. She is also a former postdoctoral fellow in various projects funded by the Department of Science and Technology, Indian Council of Medical Research and Ministry of Environment, Forest and Climate Change, and the Government of India. She has 13 years of research and teaching experience to her credit. Her previously published works include a book, more than 15 research papers, including review articles and book chapters in reputed scientific peer-reviewed journals in the field of bioremediation of terrestrial and aquatic systems, bioenergy production, green technology development for environmental waste reduction and their effective utilization. She is now working on integrating nanotechnology with bio-based systems for sensing, analyzing, and treating the contaminated wastewater in an efficient and sustainable manner.

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Part I Environmental Wastes Status, Prospects and Management

1

Waste Classification, Generation, and Status

1.1 INTRODUCTION Increasing waste volume and complexity threaten ecosystems and human health. Every year, an estimated 11.2 billion tonnes of solid trash are collected annually. Population expansion, urbanization, a flourishing economy, and changing lifestyles in developing countries have boosted solid waste generation (Minghua et al 2009). The fastest-growing waste stream in both developed and developing countries is from electrical and electronic equipment containing new and complicated hazardous compounds. The wastes can range from being harmless to extremely toxic based on sources of their generation. The organic fraction of such wastes and their proper disposal is becoming a serious challenge around the world as Organic waste decomposition contributes 5% of worldwide greenhouse gas emissions. Large populations in towns and communities lead to littering and open dumps that, over time, produce rats, vermin, and microbes, endangering public health. Rapid industrialization has increased output and consumption, resulting in garbage piles from agricultural, commercial, home, industrial, institutional, social, and community activities. Solid waste disposal is a priority for all human settlements – educational, industrial, commercial, and residential. Quantifying and characterizing municipal solid waste (MSW) are the foundations of solid waste management. Quantity and composition of solid wastes vary by country and community due to differences in income, socioeconomic distribution, consumption habits, and disposal practices. The chapter highlights the generation of the growing volume of waste, its classification, and status concerning both developing and developed countries globally.

1.2 DEFINITION AND CLASSIFICATION OF WASTE 1.2.1 WASTE: THE CONCEPT Waste is any useless, unwanted, worthless, unwanted, or wasted product or material. Waste originates from the Latin vastus, which means vacant or desolate (Lynch 1990). Waste originally signified something humans should overlook and reject. Various agencies have defined wastes as per their perspective. Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal (2019) (2019) defines wastes as – “substances or objects, which are disposed of or are intended to be disposed of or are required to be disposed of by the provisions of national law.” Under the Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain Directives Text with EEA relevance (2008), the European Union defines waste as “an object the holder discards, intends to discard or is required to discard.” Additionally, solid waste has diverse definitions in other nations. Typically, it refers to MSW. The term “solid waste,” according to the United States Environmental Protection Agency (EPA), refers to any garbage, refuse, sludge from a waste treatment plant, water supply treatment plant, or air pollution control facility, as well as other discarded materials, including solid, liquid, semi-solid, or DOI: 10.1201/9781003279136-2

3

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Green Technologies for Waste Management

contained gaseous material resulting from industrial, commercial, mining, and agricultural operations, in addition to community activities. However, solid or dissolved materials in domestic sewers are not considered to be “solid waste.” Municipal wastes, hazardous wastes, medical wastes, and radioactive wastes are the several types of solid waste that are classified in India. The Ministry of Environment, Forest and Climate Change, Government of India, defines MSW as commercial and residential wastes produced in a municipal or notified area in either solid or semi-solid form, excluding treated biomedical wastes but containing industrial hazardous wastes.

1.2.2 CLASSIFICATION

OF

WASTE

Waste can be classified based on its physical state, source/origin, degradability, hazard properties, management, or a mix of these concepts. 1.2.2.1 Classification Based on the Physical State According to their physical state, wastes are commonly categorized as solid, liquid, and gaseous wastes. 1.2.2.1.1 Solid Wastes Solid waste generation is a constant in modern human societies. Solid wastes including agricultural, industrial, domestic, biomedical, and radioactive wastes generated by humans in residential, industrial, or commercial environments. The Resource Conservation and Recovery Act (RCRA) defines “solid waste” as industrial, commercial, mining, agricultural, and community garbage, refuse, sludge from a wastewater treatment plant, water supply treatment plant, air pollution control facility, and other abandoned material. Solid waste includes solid or semi-solid domestic waste, sanitary waste, commercial waste, institutional waste, catering, and market waste, street sweepings, silt removed or collected from the surface drain, agriculture, aquaculture, dairy waste, treated biomedical waste excluding industrial waste, e-waste, battery waste, radioactive waste generated in the area under local authorities, and other waste. Examples of solid wastes composition and their source of generation are presented in Table 1.1. 1.2.2.1.2 Liquid Wastes Liquid wastes can be defined as liquids/fluids that are generated from washing, flushing, manufacturing processes of the industries, household liquids for cleaning and washing, agrochemicals

TABLE 1.1 Composition of Solid Waste and Its Source of Generation Composition of Solid Wastes

Sources of Their Generation

Organic

Yard (leaves, grass, brush) waste, wood, process residues, food wastes

Paper Plastic

Paper scraps, cardboard, newspapers, magazines, bags, boxes, wrapping paper, telephone books, shredded paper, beverage cups. Bottles, containers, packaging waste, bags, toys, disposable syringes,

Glass

broken bottles, glassware, light bulbs, colored glass, impaired screens

Metal

Cans, tins, sheets, foil, scrap metal, non-hazardous aerosol cans, appliances, railings, bicycles, discarded vehicle items Textiles, leather, waste tires, rubber, multi-laminates, e-waste, appliances, ash, inert materials, i.e., construction and demolition debris

Others

Source: Urban Development Series, World Bank (2014).

Waste

5

Institutional

Industrial

Commercial

Residential

Waste

Biomedical

Agricultural

Municipal Services

Construction and Demolition

FIGURE 1.1 Classification of wastes based on their origin.

laden wastewater from ponds, farms, etc. EPA defines liquid waste as waste that passes through a 0.45 micron filter at 75 psi (Friedman 1981). Liquid wastes are challenging to handle since they can’t be simply picked up and discarded, making them a waste management concern. Liquid wastes easily spread and harm nearby soil, groundwater, plants, animals, and humans. 1.2.2.1.3 Gaseous Wastes It’s a waste product emitted into the atmosphere by automobiles, factories, nuclear power plants, fossil fuel burning, etc. Gaseous wastes include carbon oxides, sulfur dioxide, nitrogen oxides, hydrocarbons, aerosols, carbon monoxide, methane, etc. A lot of gaseous wastes are entering the environment as a result of the quick expansion of companies, industrial areas, and vehicles. 1.2.2.2 Origin/Source-Based Classification The generation of solid wastes, in essence, is an inherent characteristic of modern lifestyles and is categorized based on their origin or generation (Figure 1.1). Table 1.2 lists significant solid waste sources and types. 1.2.2.2.1 Municipal Solid Waste (MSW) MSWs are wastes collected from urban homes, marketplaces, streets, and other places by municipal agencies. MSW includes paper, plastic, clothing, metals, glass, street wastes, dead animals, market wastes, abandoned vehicles, domestic garbage, rubbish, building and demolition debris, sanitation residue, packaging materials, trade refuges, etc. MSW includes treated and raw sewage, settled solid components, and residual or semi-solid debris from sewage treatment plants and septic tanks. The quantities of different waste ingredients vary by season and location based on lifestyle, food habits, standard of living, and commercial and industrial operations. Locally collected solid wastes rely on population size and consumption. The composition of Indian MSW is illustrated in Table 1.3.

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Green Technologies for Waste Management

TABLE 1.2 Major Sources and Types of Solid Wastes Produced in the Environment Major Source Residences (Households, family establishments) Institutions (Universities, colleges, schools, government centers, military barracks, etc.)

Solid Wastes Produces Garbage of food wastes, papers, plastics, wood articles, leather, glass, cardboard, electronic items, old mattresses, leaf litter, yard trimmings, etc. Food wastes, plastics, wood, rubber, paper, metals, cardboard, plastics, wood, etc.

Municipal services (Cities and towns)

Street cleaning wastes, landscaping wastes, sludge, wastes from recreational areas

Industries (Heavy and light manufacturing industries, factories, mills, fabrication plants, recycling plants, canning plants, etc.) Commercial establishments (Markets, hotels, restaurants, go-downs, stores and office buildings) Construction and demolition sites (Building construction, renovation, demolition, road repairment)

Food wastes, housekeeping wastes, packaging wastes, plastics, hazardous wastes, woody material, heavy metals, construction and demolition material, ashes, etc. Glass, woods, wools, cloth pieces, plastics, metals, food wastes, papers, packaging material, plastics, bottles, medicines, hazardous wastes, etc. Concrete, bricks, steel materials, rubber, wood, glass, plastics, copper wires, dirt, etc.

Treatment plants (Chemical plants, processing plants, power plants, refineries, mineral extraction plants, etc.)

Metals, plastics, ashes, coal powder, plastics, oils, husk, peels, hazardous wastes, etc.

Medical establishments (Hospitals, dispensaries, medical research institutes/ universities, pharmaceutical companies, health centers, clinics, dispensaries, medical stores/shops, etc.) Agriculture (Crop fields, gardens, vineyards, poultry farms, feedlots, dairies, etc.)

Medicines, syringes, cottons, gloves, bandages, plastics, chemicals, anatomical and pathological wastes, etc.

Electronic wastes

Computer parts such as monitors, motherboards, cathode ray tubes, printed circuit board, mobile phones and chargers, compact discs, headphones, electronic scrap components

Fertilizer bags, pesticide containers, plastics, dung, manure, feathers, spoilt eggs, food wastes, husk, crop residues, etc.

1.2.2.2.2 Industrial Wastes Industrialization has provided a huge number of products of human use. At the same time, it has also created havoc of solid waste pollution. Industrial wastes include those from chemical plants, paint factories, metallurgical plants, thermal power plants, petroleum, coal, gas, sanitary, textile, food processing, and paper industries. Industrial wastes include chemical solvents, paints, sandpaper, paper products, industrial by-products, metals, and radioactive wastes. Food processing plants, cotton mills, paper mills, sugar mills, and textile industries produce organic, non-hazardous waste, while metals, chemicals, medicines, leather, pulp, electroplating, dye, and rubber sectors produce hazardous waste. 1.2.2.2.3 Institutional/Commercial Wastes Solid wastes originate from numerous public and government organization, administrative, educational and public buildings such as offices, government centers, schools, colleges, warehouses, hospitals, restaurants, hotels, markets, prisons and other commercial establishments like wholesale and retail stores. Various examples of institutional and commercial wastes consisting of combustible as well as non-combustible waste as listed in Table 1.2.

Waste

7

1.2.2.2.4 Residential Waste Residential wastes include household and garden waste, generated from single-family and multifamily housing establishments. It consists of organic and inorganic waste, for example, garbage of food wastes, papers, plastics, wood articles, leather, glass, cardboard, electronic items, old mattresses, leaf litter, yard trimmings, etc. (Table 1.2). 1.2.2.2.5 Agricultural Wastes Agriculture wastes comprise natural (organic) and non-natural wastes generated by crop harvesting, dairy farming, horticulture, seed producing, animal breeding, grazing land, gardens, orchards and vineyards, nursery plots, and woods. Spoilt food grains, vegetables, animal and plant wastes, litter, insecticides, fertilizers, etc. are agricultural wastes. In addition, sugarcane factories, tobacco processing plants, slaughterhouses, cattle, poultry, etc. produce other agricultural wastes. Agricultural refuge is mostly biodegradable but pesticide containers, and fertilizers bags are toxic in nature (Table 1.2). 1.2.2.2.6 Construction and Demolition Waste Construction wastes are inert materials which come from construction of new buildings, refurbishment, repair, re-modeling and orientation, demolition of houses, commercial buildings, roads, and other structures. Construction and demolition debris include shattered plastics, glass, steel, concrete, electrical tools and wires, roofing materials, plumbing supplies, heating systems, etc. 1.2.2.2.7 Biomedical Wastes Biomedical wastes come from human/animal diagnosis, treatment, immunization, research, and biological production/testing. Biomedical wastes include discarded blood, needles, syringes, cytotoxic pharmaceuticals, abandoned medicines, chemical wastes, etc. The pharmaceutical industries release plentiful amounts of natural, inorganic, bio- and non-biodegradable waste into the environment, which toxify water streams, aquatic, and plant lives therein. These wastes are highly infectious and may pose severe threat if not managed properly. 1.2.2.2.8 Mining Wastes Mining wastes include waste generated during the extraction, beneficiation, and processing of minerals. Most extraction and beneficiation wastes from hardrock mining (the mining of metallic ores and phosphate rock) and 20 specific mineral processing wastes are categorized by EPA as “special wastes” and have been exempted by the Mining Waste Exclusion from federal hazardous waste regulations under Subtitle C of RCRA. Beneficiation operations include crushing, grinding, washing, dissolution, crystallization, filtration, sorting, sizing, drying, sintering, pelletizing, calcining, roasting, etc. The extraction and beneficiation of minerals generate large quantities of waste. Besides, other waste materials like slags, mine water, mine tailings, water treatment sludge and gaseous wastes, etc. are released during or after processing of mineral ores. Some of these wastes are inert and do not pose an environmental danger. However, other fractions formed by the mining industry for non-ferrous metals contain substantial quantities of hazardous compounds, such as heavy metals. After extraction and further mineral processing, these metals and metal complexes tend to become chemically more accessible and reactive, resulting in the production of acid or alkaline outflow. 1.2.2.2.9 E-Waste E-waste or electronic waste refers to abandoned electrical or electronic equipment which includes used electronics destined for refurbishment, reuse, resale, salvage recycling through material recovery, or disposal. A high rate of obsolescence in the electronics industry has resulted in one of the world’s fastest-growing waste streams, which is comprised of end-of-life electrical and electronic equipment. Due to the presence of potentially hazardous compounds such as lead, cadmium, beryllium, and brominated flame retardants, informal processing of e-waste in poor nations can

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Green Technologies for Waste Management

have negative consequences on human health and the environment. Recycling and disposal of electronic trash may pose major health risks to employees and communities. It includes a wide variety of electrical and electronic products, including refrigerators, washing machines, computers and printers, compact discs, televisions, cathode ray tubes, mobiles, i-pods, chargers, headphones, printed circuit board, and electronic garbage components. 1.2.2.3 Classification of Wastes Based on Degradability The wastes are classified based on their nature of degradability using biological, chemical, and thermal means. 1.2.2.3.1 Biodegradable/Organic Wastes Biodegradable waste can be broken down into carbon dioxide, water, methane, or simple organic compounds. Biodegradable wastes from plant or animal sources are decomposed via composting, aerobic/anaerobic digestion, and bioremediation to carbon dioxide, methane, water, and other organic molecules. Biodegradable wastes can be degraded by natural/biotic factors, e.g., bacteria, fungi, detrivores, and abiotic elements, i.e., temperature, ultraviolet rays, oxygen, etc. Some of the biodegradable wastes include MSW, leaf litter, food wastes, paper waste, vegetable and fruit peels, crop and animal residues, tea leaves, egg shells, slaughterhouse wastes, etc. 1.2.2.3.2 Non-Biodegradable/Inorganic Wastes Non-biodegradable wastes are tenacious and can’t be eliminated by biological organisms. These are categorized into recyclable and non-recyclable waste. Recyclable wastes can be reused after converting waste materials into new materials and objects along with their energy value, e.g., plastic, glass, metals, ceramics, asbestos, etc. However, non-recyclable wastes do not have economic worth of recovery, e.g., carbon paper, thermocol, tetra packs, pesticide/herbicide bags, styrofoam, hazardous chemicals and containers, egg cartons, light bulbs, nuclear wastes, etc. 1.2.2.4 Classification of Wastes Based on Toxicity Waste management is crucial due to environmental hazards posed by waste materials, hence are classified based on their toxicity in detail as below. 1.2.2.4.1 Hazardous Wastes According to the Hazardous Waste (Management and Handling) Rules, 1989 as amended, “hazardous waste” is any waste that, due to its physical, chemical, reactive, toxic, flammable, explosive, or corrosive properties, poses a danger to health or the environment, alone or in combination with other wastes or substances. Hazardous waste is waste that can affect human health or the environment. Chemical production, manufacturing, and other industrial activities generate hazardous solids, liquids, sludges, and gases. Some hazardous wastes include lead, mercury, cadmium, chromium-laden items, pharmaceuticals, leather, pesticides, dye, rubber, solvents, paints, etc. The characteristics which make the wastes toxic or hazardous are discussed hereunder. Characteristics of hazardous wastes: Explosive: substances and preparations that are more susceptible to shocks or friction than dinitrobenzene and may explode when exposed to flame. Oxidizing: substances and preparations that undergo extremely exothermic reactions in the presence of other compounds, especially combustible ones. Flammable: substances and preparations with a flash point between 21 and 55°C. Irritant: non-corrosive substances and preparations that can cause inflammation by direct, prolonged, or recurrent contact with the skin or mucous membranes.

Waste

9

Harmful: substances and preparations that, if inhaled, swallowed, or absorbed through the skin, may provide minimal health hazards. Corrosive: substances and formulations that are capable of causing corrosion. Toxic: substances and preparations (including extremely toxic compounds and preparations) that, if inhaled, swallowed, or absorbed through the skin, pose substantial, acute, or chronic health risks and even death. Carcinogenic: substances and preparations that, if inhaled, swallowed, or absorbed via skin, may cause or increase the risk of cancer. Infectious: compounds containing viable microorganisms or their toxins that are known or strongly suspected to cause disease in humans or other creatures. Teratogenic: substances and preparations that, if inhaled, swallowed, or absorbed via skin, may cause or increase the incidence of non-hereditary congenital abnormalities. Mutagenic: substances and preparations that, if inhaled, swallowed, or absorbed via skin, can cause or increase the incidence of inherited genetic abnormalities. Ecotoxic: substances and formulations that may provide immediate or delayed threats to one or more environmental sectors. 1.2.2.4.2 Non-Hazardous Wastes The US EPA defines non-hazardous industrial waste as – waste generated from processes associated with the production of goods and products, such as electric power generation and manufacturing of materials such as pulp and paper, iron and steel, and glass and concrete. Non-hazardous wastes cause no harm to human or environmental health and thus safe to utilize industrially, commercially, agriculturally, or economically, e.g., plastics, metal, paper, glass, beverage cans, paint, oil, antifreeze, buffers, salts, organic waste, etc. But, still non-hazardous waste also requires certain management requirements for their safe disposal.

1.3 TECHNIQUES TO ESTIMATE WASTE GENERATION Amount of solid waste generation is assessed either on the basis of solid waste characterization survey or using earlier statistical report of solid waste or several amalgamations of any two analyzing methods, which are explained here under:

1.3.1 LOAD COUNT ANALYSIS This method records the number of loads and their waste characteristics (types, estimated volume) throughout a given time period. Recording the expected volume and general composition of each batch of waste delivered to a landfill or transfer station over a specific time period determines solid waste quantity and composition. Total mass and compositional mass distribution are determined using average waste density.

1.3.2 WEIGHT VOLUME ANALYSIS Similar to the load-count method, this method also records mass of each load. Unless each waste category’s density is established separately, composition-based mass distribution must use average density values. Sample data is obtained by measuring the truck’s solid waste volume and load weight. Number of loads and time period aren’t limited.

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Green Technologies for Waste Management Outflow Combustion gases & ashes

Inflow (Raw material)

Stored material (Raw material, products, solid waste)

Outflow (Material) Outflow (Product)

System Boundary

Outflow (Solid waste)

FIGURE 1.2 Material mass balance analysis.

1.3.3 MATERIAL MASS BALANCE ANALYSIS In this method, mass of solid waste is analyzed in a regulated volume. There is an analysis of rate of generation and movement of waste with any grade of consistency. There is an execution of a complete material mass balance analysis for individual kind of solid waste generated at different source. In the system, mass of solid waste enters should be equal to mass of solid waste left as shown in Figure 1.2. From Figure 1.2, the equation for material mass balance analysis can be formulated as: Accumulation = Inflow – Outflow ± Generation

Symbolic representation of above equation: dM / dt = Minflow

M outflow ± w

where dM/dt is the rate of change of mass of material within the controlled volume or system boundary (kg/d); ƩMinflow is the sum of inflow of every material into the controlled volume or system boundary (kg/d); ƩMoutflow is the sum of outflow of every material into the controlled volume or system boundary (kg/d); and Ɣw is the rate of change of mass of waste generation within the controlled volume or system boundary (kg/d). The rate of generation will be positive if rate of generation within the system boundary is higher than rate of decay. Similarly, if rate of decay within the system boundary is higher than rate of generation, then rate of generation will be negative.

1.4 WASTE GENERATION, COMPOSITION, AND STATUS (GLOBAL AND NATIONAL SCENARIO) The geographical locations, climate, living conditions, economic standard, and customs affect waste generation rate. Waste generation rate reflects a region’s socioeconomic progress. Developed cultures produce huge volumes of municipal solid trash (e.g., food wastes, packaged goods, disposable items, and used gadgets) (e.g., demolition waste, incineration residues, refinery sludge). The United States generates the maximum MSW per capita per day among industrialized

Waste

11

nations. In 2016, the world’s cities produced 2.01 billion tonnes of municipal solid refuse, or 0.74 kg per capita per day, but national rates range from 0.11 to 4.54 kg per capita per day. Rapid population expansion and urbanization will raise annual waste production by 70% by 2050. Solid waste varies in quantity and properties. Income and urbanization correlate with waste volumes. Increasing waste volume increases waste variety. Population growth, average income, consumption, social behavior, geographical location, climate, energy sources, industrial production, and the market for waste products all affect waste quantity and composition (Kaza et al 2018). Every citizen, organization, and human action generates waste. Low-income countries’ garbage will likely be triple by 2050. East Asia and the Pacific produce 23% of the world’s trash, while the Middle East and North Africa produce 6%. By 2050, waste generation is anticipated to triple in Sub-Saharan Africa, double in South Asia, and double in the Middle East and North Africa. More than half of low- and middle-income countries’ waste is food and green waste. In high-income countries, the volume of organic waste is similar in absolute terms, but the fraction of organics is roughly 32%. Recyclables make up 16% of waste streams in low-income countries and 50% in high-income countries. As countries’ incomes improve, the amount of recyclables in the waste stream rises, with paper rising the most (Kaza et al 2018).

1.4.1 GLOBAL GENERATION

OF

WASTE

As a country urbanizes and its population becomes wealthier, inorganic resources (such as plastics, paper, and metals) are consumed more, whereas organic materials are used less. In low- and middle-income countries, 40–80% of urban garbage is organic. Likewise, material used for construction (e.g., wood versus steel), fuel for heating (e.g., coal versus gas) also differs according to the geography and climate of the place, thereby influencing type of MSW generated. The global solid waste generation scenario is discussed further at various levels. 1.4.1.1 Waste Generation in Different Regions East Asia and Pacific and Europe and Central Asia produce 43% of the world’s waste (Figure 1.3a). Middle East, North Africa, and Sub-Saharan Africa contribute 15% of the world’s waste. East Asia and Pacific produced 468 million tons of waste in 2016, while the Middle East and North Africa generated the least 129 million tonnes (Figure 1.3b) (Kaza et al 2018). 1.4.1.2 Global Waste Generation in Different Income Groups Waste generation boosts economic growth and urbanization. North America, with the highest urbanization rate (82%), produces 2.21 kg per capita per day, while Sub-Saharan Africa produces 0.46 kg per capita per day. In 2016, the global average daily waste generation was 0.74 kilos, ranging from 0.11 to 4.54 kg. High-income countries, which account for 16% of the world’s population, contribute 34%, or 683 million tonnes, of the world’s waste, whereas low-income countries generate 5%, or 93 million tonnes (Figure 1.4a,b). Waste generation increases quicker at lower-income levels than higher-income levels for incremental income changes. At low-income levels, waste per capita declines with income. Slower trash growth at higher-income levels may be related to lower marginal demand for consumption and waste (Kaza et al 2018).

1.4.2 GLOBAL WASTE COMPOSITION Waste composition categorizes type of materials present in waste. It is estimated that food and green waste generate 44% of world waste (Figure 1.5), but dry recyclables (plastic, glass, metal, paper, cardboard, etc.) contribute 38%. Waste composition varies by wealth, reflecting consumption habits (Figure 1.6). In general, amount of organic waste decreases with increasing income. Higher-income countries consume

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Green Technologies for Waste Management

(a)

Waste Generation by Region 6% 20%

Middle East and North Africa North America

14%

East Asia and Pacific Sub Sahara Africa

11%

South Asia 23% Latin America and the Caribbean 17% Europe and Central Asia

9%

(b)

Amout of waste generated

500

468

Millions of tonnes per year

450 392

400 350

334 289

300 250

231

200 150

174 129

100 50 0 Middle East and North Africa

Sub Sahara Africa

Latin America and the Caribean

North America

South Asia

Europe and Central Asia

East Asia and Pacific

FIGURE 1.3 Percent (a) and amount (b) of waste generation in different regions globally. Source: Adapted from Kaza et al (2018).

more paper, plastic, rubber, and wood waste. High-income countries generate less food and green waste (32% of total waste) and more recyclable dry garbage (51% of waste). Middle- and low-income countries generate 53% and 57% of food and green waste, with organic waste growing with economic development. In low-income countries, organic wastes are more prevalent than recyclables (20%). All regions produce 50% or more organic garbage, except Europe, Central Asia, and North America, which produce more dry trash. In general, the amount of industrial waste increases with income. Industrial waste generation is 18 times more than MSW in nations with available statistics. The amount of industrial waste increases with income. The generation of global agricultural waste is 4.5 times higher than MSW. Large-scale agriculture activities in countries produce the most agricultural waste.

Waste

13

(a) 5% 34%

Low income

29% Lower-middle income Upper-middle income High-income

32%

Millions of tonnes per year

(b)

800 655

700

683

586

600 500 400 300 200 100

93

0 Low income

Lower-middle income

Upper-middle income

High-income

FIGURE 1.4 Percent (a) and amount (b) of waste generation at different income levels globally. Source: Adapted from Kaza et al (2018).

FIGURE 1.5 Composition of waste at global level ( Kaza et al 2018).

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Green Technologies for Waste Management

FIGURE 1.6 Variation in waste composition by income levels globally in 2016. Source: Adapted from Kaza et al (2018).

1.4.3 GLOBAL PROJECTIONS

OF

WASTE GENERATION

By 2030, the world is predicted to generate 2.59 billion tonnes of waste yearly, which will increase to 3.40 billion tonnes by 2050 (Figure 1.7). Waste generation and income level are correlated.

Waste

15

FIGURE 1.7 Projections of waste generation globally. Source: Adapted from Kaza et al (2018).

High-income countries are estimated to generate 19% more waste per capita by 2050 than low- and middle-income countries. At low-income levels, waste generation initially reduces and subsequently grows faster than at high-income levels. Low-income countries’ waste will triple by 2050. East Asia and the Pacific produce 23% of the world’s trash, and the Middle East and North Africa produce 6%. Sub-Saharan Africa, South Asia, and the Middle East and North Africa are predicted to have the most waste by 2050. In some locations, more than half of waste is openly discarded, and waste increase will have huge ramifications for the environment, health, and prosperity. Since waste output increases with economic development and population growth, regions with many expanding low-income and lower-middle-income countries are projected to produce the most waste. Sub-Saharan Africa and South Asia are predicted to triple and double trash levels in the next three decades due to economic expansion and urbanization (Figure 1.8). North America, Europe, and Central Asia are predicted to gradually increase trash levels.

FIGURE 1.8 Regional projections of waste generation. Source: Adapted from Kaza et al (2018).

16

1.4.4 STATUS

Green Technologies for Waste Management OF

ENVIRONMENTAL WASTE

IN INDIA

Developing countries like India have environmental issues related to waste generation, collection, transit, treatment, and disposal. Rapid industrialization and population growth in India have led to rural–urban migration, generating hundreds of tons of MSW per day (Kumar et al 2008). Over 377 million urban people generate 62 million tonnes of municipal solid garbage annually, of which 5.6 million tonnes are plastic waste, 0.17 million tonnes are biomedical waste, 7.90 million tonnes are hazardous waste, and 15 lakh tonne is e-waste (CPCB 2016; MNRE 2016; Sharma and Jain 2019). Indian cities generate approximately 200–600 grams per capita per day. Only 75–80% of MSW is collected, 11.9 million is treated, and 31 million is thrown in landfills, therefore only 22–28% is processed and treated. Waste output is expected to rise from 62 million tonnes to 165 million tonnes by 2030. 1.4.4.1 Composition and Status of Municipal Solid Waste in India India is in a rapid phase of urbanization with nearly 32% population residing in urbanized areas according to 2011 census. This rapid urbanization is putting immense demand on its resources, infrastructure and energy requirements. Adding to this is the rapidly growing volume of MSW, which is posing another serious challenge. The average waste production in India is 370 g/capita/day, compared to 2000 g/capita/day in the United States and 700 g/capita/day in China (Annepu 2012). Every capita waste generation is rising 1.3% per year. North India, South India, West India, and East India produce the most urban garbage (about 40%) (Table 1.4). The main components of urban MSW are organic material (51%), recyclables (17.5%), and inert garbage (31%). This composition was recorded at MSW dumping locations; hence the real proportion of recycled waste in India is unknown because informal waste collection is not considered. Informally collected waste will modify the composition of MSW and help estimate real waste generated (Annepu 2012). In small towns/cities with populations 0.2 million, solid waste generation is 200–300 g/capita/day. On average, cities having population 200,000–500,000, 500,000–1 million, and >1 million generate approximately 300–350 g/capita/day, 350–400 g/capita/day, and 400–600 g/capita/day, respectively (CPCB 2016; CPHEEO 2016; MNRE 2016). In 2001, 366 Indian cities generated 31.6 Mt of garbage and 47.3 Mt in 2011. It’s anticipated that these 366 cities will produce 161 Mt of MSW in 2041, or about 5 times more in 4 decades. If this rate of waste production continues, total urban MSW will be 165 Mt by 2030, 230 Mt by 2041, and 436 Mt by 2050 (Annepu 2012; WtR 2014). Table 1.5 shows population growth’s impact on solid waste till 2041.

TABLE 1.3 Municipal Solid Waste Composition of India ( CPCB 2016) Waste Description

% by Weight

Paper

0.81

Plastic Metals

0.62 0.64

Glass/ceramics

0.44

Grass

3.80

Compostable matter Stones/ashes

40.15 41.81

Miscellaneous

11.73

Waste

17

TABLE 1.4 Municipal Solid Waste Composition in Varied Regions of India Region/City

MSW (TPD*)

Compositions of MSW Compostable Matter (%)

Recyclable Materials (%)

Inert Waste (%)

Moisture Content (%)

Metro cities

51402

50.89

16.28

32.82

46

Other cities East India

2723 380

51.91 50.41

19.23 21.44

28.86 28.15

49 46

North India

6835

52.38

16.78

30.85

49

South India West India

2343 380

53.41 50.41

17.02 21.44

29.57 28.15

51 46

51.3

17.48

31.21

47

Overall Urban India

130000

Sources: Annepu (2012), *TPD, tonnes per day.

TABLE 1.5 Projections of Population Growth and Associated Waste Generation Rate Year

Urban Population Growth (million)

Waste Generation Rate (kg/capita/day)

National Waste Generation Rate (million tons/year)

2001 2011

197.3 260.1

0.439 0.498

31.63 47.3

2021

342.8

0.569

71.15

2031 2036

451.8 518.6

0.649 0.693

107.01 131.24

2041

595.4

0.741

160.96

Sources: Annepu (2012); WtR (2014).

1.5 CONCLUSION Waste has always been a perennial and serious concern worldwide owing to its devastating effects and threat to environment and public health. Rapid urbanization, industrialization, population growth, and economic development have boosted global waste generation. Asian and Pacific countries’ solid waste generation is predicted to double in coming decades. Developed countries generate more waste per capita than developing nations. Most developing countries lack updated data on waste quantities, characteristics, seasonal fluctuations, and projected developments. Hence, waste management remains a big predicament and challenge till date due to continuous and unforeseen increase in amount of solid waste. As such, developing ecologically sound, socially acceptable, and techno-economically viable solid waste management methods requires a good understanding of trash volumes and characteristics.

REFERENCES Annepu, R.K., 2012. Sustainable solid waste management in India. Columbia University, New York, 2(01). Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal (187 signatory countries as of February 2019). Available at: http://www.basel.int/TheConvention/ Overview/TextoftheConvention/tabid/1275/Default.aspx

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Green Technologies for Waste Management

CPCB (Central Pollution Control Board), 2016. Central pollution control board (CPCB) bulletin, Government of India. http://cpcb.nic.in/openpdffile.php?id=TGF0ZXN0RmlsZS9 CPHEEO (Central Public Health and Environmental Engineering Organization), 2016. Municipal solid waste management manual. Part I: An overview. Ministry of Urban Development. http://cpheeo.gov.in/ upload/uploadfiles/files/Part1(1).pdf Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain Directives (Text with EEA relevance)”. europa.eu. 22 November 2008. Available at https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32008L0098 Friedman, D., 1981. Definition of―Liquid Waste. In National Service Center for Environmental Publications. Retrieved March 19, 2017, from https://nepis.epa.gov/ Kumar, R., Singh, S., andSingh, O.V. (2008). Bioconversion of lignocellulosic biomass: biochemical and molecular perspectives. Journal of industrial microbiology and biotechnology, 35, 377–39110.1007/ s10295-008-0327-8 Kaza, S, Yao, L.C., Bhada-Tata, P., Van Woerden, F., 2018. What a waste 2.0: A Global Snapshot of Solid Waste Management to 2050. Urban Development, Washington, DC: World Bank. https:// openknowledge.worldbank.org/handle/10986/30317 Lynch, K., 1990. Wasting away. San Francisco: Sierra Club Books. Minghua, Z., Xiumin, F., Rovetta, A., Qichang, H., Vicentini, F., Bingkai, L., Giusti, A. and Yi, L., 2009. Municipal solid waste management in Pudong New Area, China. Journal of Waste Management, 29, pp. 1227–1233. MNRE (Ministry of New and Renewable Energy), 2016. Power generation from municipal solid waste. http:// 164.100.47.193/lsscommittee/Energy/16_Energy_20.pdf Sharma, K.D. and Jain, S., 2019. Overview of municipal solid waste generation, composition, and management in India. Journal of Environmental Engineering, 145(3), pp. 04018143. World Bank, 2014. Waste composition, Urban Development Series- Knowledge paper 3. Status of Solid waste in India, CPCB, http://www.cpcb.nic.in/divisionsofheadoffice/pams/Status_Municipal.pdf WtR (Waste to Resources), 2014. Waste to resources: A waste management handbook. The Energy and Resource Institute, New Delhi, India.

2

Waste as a Resource

2.1 INTRODUCTION Humans have produced solid garbage throughout the course of history and have disposed of it in a number of methods, including incineration and landfills. After the industrial revolution, people used and discarded more products. Population growth, urbanization, and industrialization have increased solid and liquid wastes. Human activity and lifestyle changes have increased solid waste rates. Manufacturing, agriculture, industries, and municipal solid wastes (MSWs) generate waste (Kan 2009). According to the UN Environment Program, 11.2 billion tonnes of solid waste are generated annually, causing environmental degradation and serious health implications, especially in lowincome countries where >90% of waste is openly dumped or burned (UNEP 2020). Directly or indirectly, trash impacts our health and well-being in many ways: methane emissions contribute to climate change, air pollutants are released into the environment, freshwater sources are contaminated, crops are grown in contaminated soil, and fish consume harmful compounds, ending up on our dinner plates. Waste management is a global concern as it represents an economic loss and burden to our society. Also, waste management requires money, labor, and other inputs (land, energy, etc.). Poor waste management harms many ecosystems and species by contributing to climate change and air pollution. Most advanced countries found ways to cope with solid waste. These include creating more efficient products and packaging, recycling useful materials, composting green wastes, burning with energy recovery, and sanitary landfilling that prevents aqueous and gaseous emissions. Recycling is a significant component of modern waste reduction and the third component of the ―Reduce, Reuse, Recycle‖ waste hierarchy, according to Directive 2008/98/EC. Turning waste into a wealth is one of the European Union’s goals for a resource-efficient Europe. Waste management also recovers valuable resources. The pressure to extract more natural resources for the production of new products will increase if the resources embedded in solid waste are not recovered. Solid, liquid, gaseous, and radioactive wastes require various approaches and skills. Industrial ecology, life cycle analysis, material flow analysis, ecological footprint, and other ideas have long shown the need and possibility of reintegrating recyclable materials into production flows, decreasing resource waste, and preserving the environment. Academic research is also required to determine the best available technology for treating diverse waste materials and goods derived from them. Traditionally, landfills were effective solid waste disposal systems for biodegradable waste, such as food, paper, and garden waste, but they generate methane, a potent greenhouse gas (GHG), and may contaminate soil and water, leading to environmental damage. Waste collection, transport, and disposal release carbon dioxide and other atmospheric pollutants. Non-separated, recycled, and reused wastes can be utilized to produce energy, and thus minimizing landfilling. Waste can be used to produce heat or electricity, replacing fossil fuels. Energy recovery from waste can cut GHG emissions. Recycling reduces the need to extract natural resources and generate new materials along with reduction in GHG and other emissions.

2.2 CLASSIFICATION OF WASTES According to their physical state, wastes are typically divided into three categories: solid, liquid, and gaseous wastes. Any trashed items or garbage that is solid or semi-solid are considered solid wastes. Plastics, Styrofoam containers, bottles, tyres, septage, scrap metal, latex paints, furniture, toys, rubbish, appliances, cars, empty aerosol cans, paint cans, compressed gas cylinders, asbestos, DOI: 10.1201/9781003279136-3

19

20

Green Technologies for Waste Management

FIGURE 2.1 Multiple sources of biomass. Source: IEA, ETP 2017.

etc. are a few examples of solid wastes. In Figure 2.1, various sources of solid waste are shown and are covered in more detail.

2.2.1 MUNICIPAL SOLID WASTE (MSW) Street waste, dead animals, market waste, abandoned vehicles, domestic garbage, junk, building and demolition debris, sanitation residue, packing materials, trade refuge, etc. are all examples of MSW, often known as trash, garbage, or refuse. Municipal entities collect them from homes, markets, streets, and other locations—mostly in urban areas—and dispose of them. The ratio of the various components of municipal trash varies from location to location and season to season based on the locals’ dietary preferences, way of life, standard of living, and level of commercial and industrial activity. In many nations, kitchen and garden waste dominate MSW. Sewage waste includes settled solids, residuals, and semi-solids from sewage treatment facilities and septic tanks. Sewage waste is biological and inorganic and hence a resource.

2.2.2 INDUSTRIAL WASTES Industrial wastes include wastes from chemical industries, paint, textile, food, cement, metallurgical, petroleum, coal, paper industry, thermal power plants, etc. Chemical solvents, paints, sandpaper, paper products, byproducts, metals, steel, radioactive wastes, etc. are industrial wastes. Industrial bulky wastes include cardboard, wood boxes, crates, cartons, fiber, plastic, steel barrels, loose and bundled paper, textiles, plastics, cables, furniture, and equipment.

2.2.3 INSTITUTIONAL/COMMERCIAL WASTES Institutional and commercial wastes come from offices, schools, colleges, hospitals, government centers, and other business facilities like wholesale and retail stores, restaurants, hotels, markets, warehouses, etc. Industrial and commercial wastes include paper, cardboard, plastics, wood, food wastes, glass, and metals.

2.2.4 AGRICULTURAL WASTES Agriculture wastes include organic and inorganic wastes. Dairy farming, horticulture, seed growing, livestock breeding, grazing land, ruined food grains, vegetables, animal wastes, litter,

Waste as a Resource

21

nursery plots, and woods produce these wastes. Sugarcane factories, tobacco processing plants, slaughterhouses, cattle, poultry, etc. produce other agricultural wastes. Few agricultural wastes, including pesticides and fertilizers, are poisonous.

2.3 RESOURCE GENERATION FROM WASTE Biomass and waste are two readily available materials that can be turned into biofuels and chemicals. Novel technologies and biotechnologies applied to biomass feedstocks and waste streams, such as urban wastes, agricultural residues, or food and feed wastes, can turn renewable resources into high-value sustainable bio-based products, boosting resource sustainability. Woody and herbaceous species, agricultural and industrial residues, MSW, biosolids, waste paper, food processing waste, animal wastes, aquatic plants, algae, etc. are biomass resources (Balat 2010; Demirbas 2009a, 2009b). Biomass contains lignocellulosic chemicals, inorganics, and proteins. The major categories of biomass feedstock are listed in Table 2.1. Wood and forestry businesses produce biomass and residues (branches, leaves, bark, sawdust, etc.). Herbaceous biomass includes wheat, corn, switchgrass, sugarcane, and others. Agricultural wastes have huge potential for renewable energy (FAO and UNEP 2010). Firstgeneration biofuels are made from these crops, although there is fear that doing so may compete with food production and overuse land (Hayes 2016; Tripathi and Sahu 2016). Second-generation biofuels are made from herbaceous agricultural wastes like straw, husk, and stover (Hayes 2016). Third-generation biofuels are made from micro and macroalgal biomass (Alam et al 2015). Bioethanol from wasted crops and crop residues, activated carbon from agricultural wastes such as bagasse for cadmium and zinc adsorption, nanofibers from agricultural residues such as wheat straw and soy hulls, biochar from crop residues, biofuels from crop residues, chitosan as an adsorbent from agro-waste, etc. are examples of value-added products obtained from agricultural wastes. However, plastics, textiles, paper, wood, and glass are non-biological wastes. Inorganic matter, such as carbonates, sulfates, oxalates, oxides, etc., is a major component of biomass and wastes (Hon and Shiraishi 2000). Many inorganic elements can be present, including Ca, K, Mg, Na, P, Cl, Si, S, Fe, Mn, Al, and others (Van Loo and Koppejan 2008). Recycling means recovering or reusing materials from garbage. Waste can be recycled by extracting and reprocessing raw materials or converting heat to electricity. Direct combustion, gasification, pyrolysis, and anaerobic digestion are ways to use biomass energy. In poor countries, dried agricultural waste is burned for heating and cooking. Dry biomass can be burned for energy, gasified to produce methane, hydrogen, and CO, or transformed to a liquid fuel. Wet biomass like sewage sludge, animal dung, and food waste can be fermented into fuel and fertilizer. Biomass can be transformed directly into a liquid fuel, therefore it could meet future auto fuel needs. Biomass conversion can utilize solar and wind energy.

TABLE 2.1 Various Biomass Feedstocks for Resource Generation No.

Major Category

Biomass Feedstock

1.

Forest products

Wood, logging residues, trees, shrubs and wood residues, sawdust, bark, etc.

2.

Food crops

Residue from grains and oil crops

3. 4.

Sugar crops Energy crops

Sugar cane, sugar beets, molasses, sorghum Short-rotation woody crops, herbaceous woody crops, grasses, forage crops

5.

Industrial organic wastes

Plastics, oils, leather, rubber, organic acids, etc.

6. 7.

Aquatic plants Algae, kelps, lichens, and mosses

Algae, water weed, water hyacinth, reed, and rushes Water hyacinth, mushrooms, etc.

22

Green Technologies for Waste Management

2.3.1 RESOURCE GENERATION

FROM

AGRICULTURAL WASTES

Future projections predict increasing agricultural production for human, animal, and industrial demands (FAO 2017). The rapid increase of bioenergy from biofuel (Hazell and Pachauri 2006) is an example of crop diversification in recent years, notably starch and cellulose-rich crops. Cereal starch from maize and wheat is used to make ethanol. Developing and growing economies rely on these fuels. Biomass can be utilized to produce hydrogen gas. Biological hydrogen generation uses waste materials to provide a renewable energy source that could replace fossil fuels. Microorganisms that use carbohydrate-rich, non-toxic source materials can produce biohydrogen. Hydrogen is created as a byproduct of converting organic wastes into organic acids under anaerobic circumstances. Manipulating anaerobic garbage digestion’s acidogenic phase can boost hydrogen production. Algae use CO2 and H2O to produce hydrogen gas. Some photo-heterotrophic bacteria use organic acids to generate H2 and CO2. Crop residue, straws, husks, olive pits, nut shells, etc. are agricultural residues. The residue can be classified into two categories: (1) field residue, which is left in the fields or orchards after harvesting, and (2) process residue, which is left after processing the product into an useable resource. Staves, stems, leaves, and pods are field wastes. Husks, seeds, bagasse, and roots are residues. Agricultural wastes are utilized for animal feed, soil management, and manufacturing. Cereal straw is the dried plant stalk left behind after combining. After harvesting, some straw is utilized as feed, animal bedding, mushroom compost, or garden mulch. The rest is burned or integrated into the soil. Many countries have banned field burning as a method of straw disposal due to pollution concern. Corn stover consists of stalk, tassel, leaves, cob, husk, and silk. Corn stover offers possibilities for direct burning, biofuels, fiber for pulp and paper, particle board, etc. (Savoie and Descôteaux 2004). The most prevalent residue is rice husk. Four tons of rice yield one ton of husk. Rice husk is homogeneous and flows better than other biomass. Gasification can employ husk because it produces uniform fuel quality. Husk’s high silica concentration might create ash and slag in the boiler during combustion. Sugarcane has a high photosynthetic efficiency, converting 2% of incident solar energy into biomass. Each ton of burned and cropped sugarcane yields 135 kg of sugar and 130 kg of dry bagasse with 19.2 MJ/kg-dry wt. Most sugar mills burn bagasse to provide heat for cooking cane and evaporating water from syrup. Agricultural wastes can also be used in engineering. Ashes from agriculture are used to make glass and glass ceramics. Silica is a key agricultural waste ash element. In addition to silica, CaO, MgO, K2O, and trace metals are found (Bondioli et al 2010). Burning rice husk creates nanosized silica particles (Yalçin and Sevinç 2001). Sugarcane leaf ash contains silica, alkali, and alkaline earth metal oxides (Singh et al 2009). Silica from waste can be used to make glasses, refractories, capacitors, glass sealants, bioceramics, fibers, and optical cavities (Chandrasekhar et al 2003; Nayak and Bera 2010; Zhao et al 2010). Activated charcoal can be used to convert silica to silicon. Refined silicon can be utilized for solar energy and computer circuits (Amick 1982). Agriculture waste glass and glass ceramics have various benefits. It’s an eco-friendly, affordable, renewable supply of silica. It could be a better approach to manage agricultural waste for engineering materials. During melt-quench, waste organics transform to gases which can be used in various applications. Agricultural waste ashes supply network forms (SiO2), network modifiers (K2O, CaO, MgO, etc.), and trace elements for glass formation. Various other value-added products generated from agrowastes are discussed further.

2.3.2 RESOURCE

FROM

WOODY PLANTS WASTE

Herbaceous woody crops, short-rotation woody crops, forage crops (alfalfa, clover, switchgrass, and miscanthus grasses), sugar crops (sugarcane, sugar beet, fiber sorghum, and sweet sorghum), starch crops (corn, barley, and wheat), and oil crops can convert solar energy into biomass

Waste as a Resource

23

efficiently (soybean, canola, palm, sunflower, safflower, rapeseed, and cotton). Energy crop firms are focusing on woody crops (willow and poplar) and tropical grasses (napier grass and elephant grass). Herbaceous plants grow quicker with loosely connected fibers due to lower lignin concentration than woody plants. The relative percentage of cellulose and lignin determines the usefulness of plant species as energy crops. Woody and herbaceous plants require certain growing conditions, including soil type, soil moisture, nutrient balances, and sunlight. These elements impact their appropriateness and production rate. The oil palm is a West African native, which was cultivated by Malaysia later. Oil palms produce 4–5 tons of oil/ha/year; ten times more than soybeans. Jatropha curcas is another nonedible oil plant gaining popularity. Apart from this, forest harvesting is done to thin young stands, cut old stands for timber/pulping, or to remove insect, disease, or fire-damaged stands. Tops and branches with limited timber or pulp value are used for energy. Forest residues are low-density and have high fuel values, so reducing biomass density in the forest reduces transport costs. Avoiding forest fires is another source of biomass.

2.3.3 RESOURCES

FROM

URBAN BIOWASTES

AND

ANIMAL HUSBANDRY

Animal husbandry and cities produce biowaste. Compost, digestate, etc. can be used as soil supplements to improve crops and agricultural soils. Biowaste can be used directly or after physicochemical, biological, and thermochemical treatment. Direct uses of biowastes include direct land application (DLA), animal feeds (DAF), and open combustion. 2.3.3.1 Direct Land Application DLA is the practice of spreading raw trash on fields. Except for segregation, DLA evaluates the practice when no treatment phase is involved. Land application of waste describes spreading manure and/or crop residue on fields. DLA helps crops that need lots of organic fertilizers (Dulac 2001). Raw organic garbage spread on DLA fields biodegrades aerobically. Degradation increases soil organic matter and nutrients. DLA of garbage produces high-organic-matter soil amendments. Organic matter acts as a nutrition and energy source for bacteria, buffers pH variations, and influences soil structure and characteristics. DLA dangers depend on the biowaste’s content. As waste contains pathogens or trace elements, they can bio-accumulate in plants and soil (Olowolafe 2008), posing health risks from food contamination or water pollution from runoff (Smith et al 2015). Dulac (2001) says that landspreading raw organic matter helps damaged desert soils. When applying non-stable organic material, studies show a risk of decreased micronutrient availability for plant growth. Landspreading and crop planting should be separated by enough time to minimize soil and plant danger. 2.3.3.1.1 Dairy Waste-Derived Lacto-gypsum as Soil Amendments In agriculture, especially the dairy industry, there is tremendous room to valorize milk processing leftovers and utilize them as farm inputs. The global milk industry creates a huge amount of dairy leftovers, which contributes to their rise (Finnegan et al 2017). New technologies, such integrated dairy processing residue bio-refineries, turn dairy residues into valuable byproducts. Fats, oils, greases, organic compounds, suspended particles, and nutrients like phosphorus are removed from dairy residues (Ryan and Walsh 2016; Ashekuzzaman et al 2019). In Ireland, researchers are developing an industrial-scale biorefinery to valorize over 25,000 tons (100% dry matter) of dairy processing side streams per year. This comprises the extraction and reuse of excess whey permeate and de-lactosed whey permeate, as well as the production of Lactic acid (LA), polylactic acid (PLA), minerals for human nutrition, and bio-based fertilizers. Calcium sulfate, or lacto-gypsum, is a dairy byproduct. Bondi et al (2021) showed that lacto-gypsum can be used as a soil amendment or acidification agent for animal slurry to reduce ammonia gas emissions during landspreading.

24

Green Technologies for Waste Management

2.3.3.2 Direct Animal Feed (DAF) Feeding biowaste to animals is a straightforward technique to recover value. Since domestication began, humans have fed animals biowaste. Biowaste is turned into swine, poultry, and fish feeds in South Korea, Taiwan, and Japan to replace conventional components (Cheng and Lo 2016). Animal feed should provide enough carbohydrates, amino acids, minerals, vitamins, critical nutrients, fibers, and lipids (Lardinois and van De Klundert 1993) and reduce contaminants that harm animals or meat quality. Alternative protein sources like insects or worms are being studied. Animals can eat biowaste from produce markets. Pulp, peels, culls, chips, fragments, etc. can be used as animal feed. Decentralized home DAF can produce animal protein from waste. Biowaste can also be processed centrally, such as by grinding or drying, and fed to animals pure or combined with other feeds. Animals metabolize biowaste, which contributes to their physiological demands, body mass, and targeted value goods (e.g., meat, eggs, and milk). Pineapple fruit residual (PFR) silage is healthy feed for cattle. Annually, India wastes more than 1.3 million tons of non-edible pineapple fruit leftovers. PFR includes significant moisture (65–70%) and sugar (>50%), making it sensitive to fungal growth and deterioration within two days. Through silage technology, fruit residue has been transformed into animal meals. PFR silagebased total mixed ration had no negative effects on sheep growth. A PFR silage-based diet improved daily milk output by 20% and fat content by 0.6 units. Green fodder made from pineapple silage. Pineapple silage is more nutritious than maize green fodder which enhances milk production and fat content. Animal husbandry yields high-value items like meat, eggs, milk, and leather. As mentioned above, the biggest risk is ensuring good waste quality for animal feed. In previous research, biowaste-based diets enhanced meat and milk quality (Cheng et al 2015; Mo et al 2014). DAF diverts biowaste from the main waste stream, saving waste management money, and infrastructure (Lohri et al 2017). Biowaste containing fish was reported to create mild taste changes in hog meat (Márquez et al 2011). Fish and shellfish processing creates a large amount of trash containing protein, fat, minerals, and other beneficial substances. Such wastes are used to feed cattle, poultry, pigs, pets, and fish. Fish waste feed is high in nutrients and accepted by farmed species. By adding acid, waste can be turned into silage or dried for use in feed. ICAR-CIFT (Indian Council of Agricultural Research–Central Institute of Fisheries Technology) has optimized pig, poultry, and fish technology. The food waste hierarchy favors animal feeding over composting and anaerobic digestion (Papargyropoulou et al 2014). Apart from this, biowaste composting and vermicomposting, e.g., Yard trash (branches, leaves, and grass), food waste, agricultural waste, manure, and even septage and human excrement can be used to make humus by biological treatment. A complex community of microbes and invertebrates drives organic matter composting, and population dynamics vary temporally and geographically (Insam and de Bertoldi 2007). Microorganisms decompose organic matter and create CO2, water, and heat. Controlling the process means managing organic material composition (carbon–nitrogen ratio), particle size, free air space, aeration, temperature, moisture, or pH to achieve quick decomposition and good compost quality. Compost is rich in humus and microorganisms that promote plant growth (Brinton and Evans 2001). Composting of acidic heavy metal contaminated sites reduced soil contamination with minimal danger (Farrell and Jones 2009). Vermicomposting is less energy-intensive, cost-effective, and economically feasible than conventional treatment methods. Under controlled conditions, microbes and earthworms degrade and stabilize organic waste aerobically. Microbial population break down organic matter, whilst earthworms feed on the waste to generate vermicompost. Earthworms can digest domestic garbage, organic municipal waste, sewage sludge, and organic waste residues from diverse industries (paper, wood, and food) but not dairy products, meat and fish waste, grease and oils, and salty and vinegary meals. Smaller feedstock particles improve surface area, speeding degradation, and vermicomposting. Vermicompost has 1–2% more nitrogen than compost and is more easily

Waste as a Resource

25

available to plants. Earthworms can be employed as pro-biotic fish or poultry feed additives. Enzymes and microbes from the gut control illnesses in soil and plants. Small-scale systems use leachate from worm bins as liquid fertilizer. Earthworms, which are high in protein (65%) and necessary amino acids, can be utilized as animal feed (Lalander et al 2015). Black soldier fly (BSF) treatment transforms organic waste into insect protein and oil (St‐Hilaire et al 2007). BSF larvae can be fed food waste, animal dung, human excreta, and fish waste (Diener et al 2011; Nguyen et al 2015). Grown larvae can (partially) replace fish meal in animal feed and have demonstrated good results with fish, chicken, and pigs (Makkar et al 2014; Stamer 2015). Residue provides nutrients and can be utilized as a soil amendment. 2.3.3.3 Biological/Biochemical Conversion of Biowaste to Resource Biochemical conversion uses microorganisms to convert biomass into liquid or gaseous biofuel and other value-added products like hydrogen, biogas, ethanol, acetone, butanol, organic acids (pyruvate, lactate, oxalic acid, levulinic acid, citric acid, and acetic acid), 2,3- butanediol, 1,4butanediol, isobutanol, and xylitol (Chen and Wang 2016) (Figure 2.2). Biochemical conversion uses microbial enzymes to break down biomass in anaerobic digestion, fermentation, or composting. Two important biochemical conversion mechanisms are anaerobic digestion and fermentation, which are green technologies for biomass conversion in terms of the carbon cycle (Fiorentino et al 2017; Gouveia and Passarinho 2017). Figure 2.3 shows bioenergy generation pathways from various biomass sources. 2.3.3.3.1 Anaerobic Digestion Anaerobic digestion (AD), also called biomethanation, is a well-established procedure to produce bioenergy by biochemically converting liquid and solid organic materials in an anoxic environment. Biogas is a mixture of methane (40–75% v/v) and carbon dioxide. The anaerobic biodegradation of complex organic matter to CH4 and CO2 consists of a series of microbial processes: hydrolysis, acidogenesis, acetogenesis, and methanogenesis. AD feedstock comprises sewage sludge, animal manure, food industry waste (including slaughterhouse waste), energy crops, and harvesting residues (including algae) (Romero-Güiza et al 2016).

FIGURE 2.2 Overview of bioenergy pathways. Source: IEA Bioenergy Roadmap, 2017.

26

Green Technologies for Waste Management

Biomass conversion

Biochemical conversion

Anaerobic digestion

Fermentation

Chemical conversion

Microbial Fuel Cell

Trans-esterification

Bio-diesel Biogas

Electricity

Hydrogen

Bio-ethanol

FIGURE 2.3 Biochemical conversion of waste.

This bioconversion takes place in “digesters,” or sealed, airless containers, where microorganisms ferment organic feedstock to biogas. Simple stoichiometry for plant carbohydrate digestion is: C6 H10 O5 + H2 O

3 CH 4 + 3 CO2

The biogas is formed through the conversion of the organic carbon of the feedstock into its most reduced form, i.e., CH4 and its most oxidized state, i.e., CO2. Apart from CH4 (55– 60%) and CO2 (35–40%), biogas also contains several other gaseous impurities such as hydrogen sulfide, nitrogen, oxygen, and hydrogen (Cecchi et al 2003). Raw biogas coming from anaerobic digesters may contain some trace components viz. hydrogen sulfide, particles, droplets, siloxanes, thiols and terpenes, longer alkanes, cycloalkanes and aromatic compounds, and alcohols depending on the feed material used. In particular, α-pinene, camphene, β-myrcene, β-pinene, α-terpinene, D-limonen, γ-terpinene p-cymene, and D-limonene have been reported to represent the add volatile organic compounds in place of VOCs in the biogas (Arrhenius et al 2016). Generally, 30–60% of wastes are transformed to biogas during anaerobic digestion. Raw or enriched biogas can generate heat and electricity with gas, diesel, or “dual fuel” engines up to 10 MW (e). On average, 0.2–0.3 m3 biogas per kg dry solids is produced. Biogas yield of the individual substrates varies considerably, dependent on the feedstock origin, organic matter content, and substrate composition. Fats provide the highest biogas yield, but require a long retention time due to their poor availability for the microorganisms. The average methane yield of solid organic waste is between 0.36 and 0.53 m3/kg VS (Bouallagui et al 2005). The produced slurry (digestate) is rich in nitrogen and, depending on the nature of the feedstock, and adequate cropspecific dilution, can be utilized in agriculture as a nutrient fertilizer and/or organic amendment (Groot and Bogdanski 2013; Möller and Müller 2012). This waste management technology uses low-cost feedstock and has environmental benefits.

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27

2.3.3.3.2 Fermentation (Ethanol Formation) Ethanol, a leading global biofuel, is produced from biowaste by acid and enzyme hydrolysis, fermentation, and distillation. USA (corn) and Brazil (sugarcane) produce 56.7 and 26.7% of the world’s ethanol, respectively (Gupta and Verma 2015). Fermentation is crucial to making bioethanol (EtOH). Bioethanol/gasoline blends are advertised as a clean-burning, environmentally friendly fuel that minimizes car emissions (Balat and Balat 2009). In total, 820 million automobiles and trucks use bioethanol (Sarris and Papanikolaou 2016). Different conversion processes can produce bioethanol from sugar, starch, and lignocellulose. Currently, it’s produced from maizederived (starch-based) feedstocks like corn, wheat, barley, and rice; root crops like potato and cassava; and sugarcane-derived (saccharose-based) feedstocks like sugarcane, sugar beet, sweet sorghum, molasses, and fruits. However, bioethanol production from edible (first generation) feedstocks raises concerns about food and feed competitiveness. Woody materials, straw, agricultural waste, and crop residues are suggested as a sustainable alternative substrate. Approximately 40% of global bioethanol output comes from sugar crops and 60% from starch (Vohra et al 2014). Source-separated urban solid biowaste, including kitchen waste, food trash, garden waste, and fruit waste, is being investigated for ethanol generation (Gupta and Verma 2015; Liguori et al 2013). 2.3.3.3.3 Biohydrogen Production Bio-hydrogen gas production from renewable sources, generally known as “green technology,” has gained much attention in recent years. Hydrogen is a clean and high-energy source compared to hydrocarbon fuels. Biomass and water can produce hydrogen gas. Kim (2003) examined using gaseous, liquid, and solid carbonaceous wastes to generate hydrogen gas via steam reforming. Despite the inexpensive cost of waste materials, high temperature (1200°C) is a key restriction. Anaerobic and photosynthetic bacteria can produce biohydrogen from carbohydrate-rich solid wastes and food industry wastewaters. Organic wastes converted anaerobically into organic acids yield hydrogen. Some photo-heterotrophic bacteria use organic acids to generate H2 and CO2. 2.3.3.4 Resource Generation through Physico-Chemical Treatment of Biowastes Physico-chemical treatment involves chemical or mechanical conversions. Transesterification and densification are chemical processes for producing biodiesel and fuel pellets and/or briquettes, respectively. 2.3.3.4.1 Transesterification For biodiesel production, vegetable oils or animal fats undergo transesterification or alcoholysis (Knothe et al 2010). Biodiesel’s energy density is 38–45 MJ/kg (HHV), which is 90% of petroleum-based diesel (Guo et al 2015). It involves catalyzing oil or fat in alcohol to generate biodiesel and glycerol (Bhuiya et al 2016). Transesterification reduces oil or fat viscosity to make it suitable for diesel engines. Waste cooking oil, animal fats from slaughterhouses, and grease from restaurant grease traps are biodiesel feedstocks (Canakci 2007; Park et al 2010). Several ways for valorizing glycerol have been researched for using it as animal feed ingredient (Yang et al 2012), after converting it into useful compounds using bacteria, yeast, fungi, and microalgae (Li et al 2013). Glycerol can be used in anaerobic digestion, ethanol generation, or microbial fuel cells to create power. 2.3.3.4.2 Densification Densification involves compacting biomass with mechanical force or binding chemicals to establish inter-particle cohesion, resulting in homogenous briquettes or pellets with consistent shapes and sizes and bulk densities of 450–700 kg/m3 (Kaliyan and Morey 2010). Briquettes and pellets can replace wood-based and fossil fuels as residential heating, cooking, and industrial fuel.

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Increasing bulk density makes biomass easier to handle, saves storage and transportation costs, and improves fuel quality and application options (Tumuluru et al 2011). Biowaste used for densification includes crop wastes (e.g., paddy, bean, soya, maize, and wheat) and agro-industrial leftovers (e.g., logwood, rice, coffee and soybean husk, bagasse, peanut shells, cotton stalks, coconut fibers, palm fruit fibers, sawdust, and other wood processing products). Roy and Corscadden (2012) evaluated the possibilities of burning hay and switchgrass briquettes in residential stoves. They found that hay and grass briquettes can be utilized in domestic wood stoves with similar or superior performance and gas emissions (CO, NOx, and SO2). 2.3.3.5 Resource Generation through Thermochemical Treatment Heat is used in thermochemical conversion of biowaste to extract and create energy carriers. The thermochemical processes involve combustion, pyrolysis, liquefaction, and gasification. Figure 2.4 depicts the final products of these processes. 2.3.3.5.1 Pyrolysis Pyrolysis is the thermal degradation of materials at high temperatures to make biofuels, fuel additives, and petrochemical substitutes. The end products of pyrolysis include char, bio-oil, and syngas (the non-condensable vapor). Slow pyrolysis produces char and quick pyrolysis bio-oil. Dry, unmixed, homogenous, and uncontaminated substrate with high carbon and low ash content is required for both slow and quick pyrolysis. Char is used as a soil supplement (biochar) (Nanda et al 2016), solid fuel (Lohri et al 2016), and precursor for catalysts and pollutant adsorbents (Inyang and Dickenson 2015; Mohan et al 2014). The pyrolysis liquid is called bio-oil or pyrolysis oil. Pyrolysis gas contains carbon dioxide, carbon monoxide, methane, hydrogen, ethane, ethylene, and water vapor. The pyrolysis gas can be used directly to produce heat or power, cofired with coal, to produce CH4, H2, or other volatiles, or to synthesize liquid biofuels (Kan et al 2016). 2.3.3.5.2 Liquefaction Hydrothermal liquefaction (HTL), also called direct liquefaction, involves processing of biomass in hot, highly pressurized water to break down the solid biopolymeric structure into predominantly liquid

Thermochemical conversion

Combustion

Gasification

Char

Elecricity

Pyrolysis

Syngas

Liquifection

Bio-oil

Petrol

Methanol

Hydrogen

FIGURE 2.4 Thermochemical conversion of wastes.

DME

Biodiesel

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bio-oil or bio-crude (Elliott et al 2015). HTL products are a two-phase mixture of bio-oil, process water, and synthesis gas (Arturi et al 2016). These gaseous, aqueous, and solid-phase byproducts can be used in improved carbon materials, chemicals, or as transportation fuel (Xue et al 2016). 2.3.3.5.3 Gasification Gasification is a thermal process that turns carbonaceous material into fuel or value-added compounds (producer gas, synthesis gas, or syngas). The feedstock is gasified by adding hydrogen (H2) and removing carbon (C). Gasification requires dry (10–20%) biomass. Wood, peat, black liquor (a paper industry byproduct), rice husk, trimmings, pruning, urban park and garden waste, and mixed MSW are common biomass gasification feedstocks. The syngas combination includes carbon monoxide (CO), hydrogen (H2), methane (CH4), carbon dioxide (CO2), ethane, propane, and tars. Syngas can also contain hydrogen sulfide (H2S), hydrogen chloride (HCl), or inert gases like nitrogen (N2) (Molino et al 2016). Gasification produces 1–3 Nm3/kg of syngas, with a modest heating value of 4–15 MJ/Nm3. Syngas is a significant chemical industry intermediate used to make Fischer–Tropsch liquids, methanol, ammonia, pure hydrogen, and carbon monoxide (Ahmad et al 2016).

2.3.4 RESOURCES

FROM

MUNICIPAL SEWAGE SLUDGE

In addition to urban biowaste, biologically treated urban wastewater sludge can be a source of organic fermentiscible matter (to be bioconverted into carboxylic acids or biomethane) and nutrients. Urban biorefinery designs may consider these wastewaters. Biomass, biosolids, char/ash, and nutritional chemical compounds are obtained from wastewater. Phosphorus and nitrogen minerals are the most abundant in sewage sludge. The lack of policies and regulations on wastewater resource recovery must be addressed. Sustainable waste-activated sludge (WAS) management entails recovering and reusing valuable products and minimizing environmental and human health risks. Due to its high organic matter and nutrient content, sustainable WAS management has traditionally been used in agriculture or as a feedstock for anaerobic digestion, especially when coupled with primary sludge. WAS contains six groups of components: (1) non-toxic organic carbon compounds (approximately 60% on dry weight basis), including extracellular proteins and polysaccharides (carbohydrates), either in pure form or in conjugation with other compounds, such as glycoproteins, rhamnolipids, lipoproteins Kjeldahl-N, and phosphorus-containing components; (2) heavy metals, such as Zn, Pb, Cu, Cr, Ni, Cd, Hg, and As (concentrations vary from 1000 ppm). Zhang et al (2018) extensively studied WAS as a reservoir of amino acids, proteins, enzymes, SCFAs, biopesticides, bioplastics, bioflocculants, and biosurfactants. The potential of WAS for generating value-added products has also been emphasized further. 2.3.4.1 Amino Acids and Proteins WAS can be harvested as a protein or amino acid source because its organic matter consists of lipids, polysaccharides, and proteins (70–80% combined). The protein fraction accounts for roughly 50% of bacterial dry weight (Raunkjær et al 1994). WAS-derived protein has substantial potential to be used as the main constituent for animal feeds compared with traditional protein sources, while effective detoxifications of sludge (i.e., sterilization, removal of heavy metals and other toxicants) should be performed (Adebayo et al 2004). Intracellular solubilization is essential to recover protein from WAS. Breaking sludge flocs and lysing microbial cell walls increases WAS dewaterability. Low treatment costs, effective heat exchange, no extra chemicals, and no waste stream are the main benefits. Chishti et al (1992) explored alkali solubilization and precipitation for protein extraction from WAS. Ammonium sulfate (40%) was the most effective precipitant, recovering 91% of the protein. Hydrochloric acid, sodium lignosulfate, sulfuric acid, acetic acid, and ammonium sulfate were all examined. Protein

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recovered from WAS has also been utilized to generate amino acid-chelated trace element (AACTE) fertilizers, an environmentally benign fertilizer for cotton, fruits, and other cash crops in China (Zhang et al 2012). Due to their amphiphilic molecular structure combining amino and carboxyl groups, WASderived amino acids are an unique corrosion inhibitor for industrial pickling. Application of amino acids as effective inhibitors to control corrosive reactions in several different metals in acidic media has been verified by a series of investigations (Eddy 2011; Gece and Bilgiç 2010; Khaled 2010; Zhang et al 2008). Using an ultrasonic-assisted hydrochloric acid hydrothermal method, Su et al (2014) reported 50 different amino acids in the hydrolysate, which may be readily adsorbed onto steel surfaces through hydrophilic (–COOH) groups. Secondary WAS protein can be utilized as an eco-friendly wood adhesive. Pervaiz and Sain employed an alkaline cell-disruptive approach to extract protein, and the resulting product had 41% of the shear strength of standard protein-based wood adhesives such as soy protein isolate and phenol formaldehyde resin (Pervaiz and Sain 2011). 2.3.4.2 Short-Chain Fatty Acids Short-chain fatty acids (SCFAs) including acetic acid, formic acid, and propionic acid can be recovered from WAS utilizing anaerobic digestion or thermal techniques such as wet air oxidation and hydrothermal treatment (Rulkens 2004). SCFAs can be used as a chemical feedstock and transformed to ketones, carboxylic acids, esters, and ethers (e.g., primary alcohols, secondary alcohols, and hydrocarbons). WAS lipids are also utilized to make biodiesel. Dufreche et al (2007) highlighted sludge’s high lipid content as a cheap biodiesel source. Kwon et al (2012) proved the high lipid yields and feasibility of WAS-based biodiesel production, with outputs of 980,000 L ha−1 year−1, 100–1000fold more than microalgal and soybean oil. Based on the high oil yield and cheap cost of WASderived oil (US$ 0.03 L−1), the author underlined the possibility for sustainable WAS-based biodiesel production (Kargbo 2010). 2.3.4.3 Enzymes Domestic WAS contains a variety of microbial enzymes (e.g., protease, lipases, glycosidase, galactosidases, aminopeptidases, dehydrogenase, catalase, peroxidase, phosphatases, amylase, and glucosidase) that break down complex organic matter (i.e., lipids, proteins, and carbohydrates) into smaller compounds that (Tyagi et al 2009). If WAS-derived enzymes could cost-effectively replace commercial medium ingredients in industries like detergents, food, pulp and paper, dairy, agrochemistry, cosmetics, pharmaceutical, diagnostics, and fine chemicals, the economic benefits could be significant as 30–40% of the production costs in these industries relate to industrial enzymes (Juwon and Emmanuel 2012). 2.3.4.4 Bio-Fertilizers and -Pesticides WAS is rich in carbon, nitrogen, phosphorus, and other nutrients, making it a potential growth medium for industrial microbes. Bacillus thuringiensis (Bt) has long been recognized to produce endotoxin, the most prominent bio-pesticide utilized in agronomy, forestry, and public health (Bravo et al 2011). Reusing WAS sludge as a low-cost “eco-alternative” medium for Bt production and pest control in agricultural crops and forests is cheap and compatible with existing sludge disposal procedures (Tyagi et al 2009). WAS has also been used to produce endotoxins, spores, and insecticidal chemicals (hemolysins, enterotoxins, chitinases, proteases, phospholypases, and others). Verma et al (2005) used WAS to make Trichoderma sp.-based bioherbicides/biopesticides, which are more effective than Bt. Apart from this, magnesium ammonium phosphate (MAP), calcium phosphate, and iron phosphate are other phosphate compounds that can be recovered from urban wastewater. MAP is a slow-releasing granular P-fertilizer. Presently, struvite from urban wastewaters not an EU-approved fertilizer.

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2.3.4.5 Bio-Plastics Volatile fatty acids (VFAs) are one of the urban waste-derived products with the most promise for future valorization in the carboxylate platform and for the manufacture of polyhydroxyalkanoates (PHAs). Open bioreactors fed with VFA-rich effluents can produce Polyhydroxyalkanoates (PHA) from urban biowaste. This approach, combined with NaOH digestion for the downstream (if needed), could be an economically sustainable process for obtaining fully bio-based and biodegradable polymers, most likely poly(hydroxybutyrate-co-hydroxyvalerate) (PHB/HV), suitable for industrial use as bio-based substitutes for commodity plastics like polypropylene. PHAs and PHB are biodegradable polyesters that have received a lot of attention as an environmentally friendly alternative to petroleum-based plastics in applications such as packaging films, disposable utensils, diapers, cosmetic containers, bottles, cups, etc. (Wu et al 2009). Polyhydroxyvalerate (PHV) is softer and more flexible than PHB. Over 75 bacterial genera synthesize PHAs as an internal carbon and energy reserve and/or as a sink for lowering redundant power consumption or electrons under unfavorable environmental and nutritional conditions (Lee 1996). Bacterial fermentation of sugar or fats produces microbial PHAs. WAS has PHAaccumulating bacteria that may accumulate 0.3–22.7 mg polymer/g sludge (Baetens et al 2002). Polyphosphate- and glycogen-accumulating microbes accumulate PHAs by consuming SCFAs in anaerobic environments from agricultural, industrial, and residential WAS (Satoh et al 1999). The plastics industry is interested in plant-based monomers and polymer building blocks. Several oilsbased biopolyamides have established a commercial foothold, and novel biopolymers like PHAs are evolving quickly. 2.3.4.6 Bio-Flocculants Bio-surfactants and bioflocculants are biodegradable and non-toxic byproducts of microbial metabolism of organic substrates. Bioflocculants are microorganism-produced macromolecular polymers that may flocculate cells and colloidal particles. Bioflocculants (extracellular biopolymers such as functional proteins), polysaccharides, cellulose derivatives, lipids, etc. released by microorganisms in synthetic growth medium are employed in wastewater treatment, dredging, downstream processing, fermentation, and food industries. The cost of organic substrates limits the greater usage of these byproducts (i.e., glucose and sucrose). WAS is a cheap supply of carbon, nitrogen, and phosphate for microorganism growth and bioflocculants. WAS is one of the ideal reservoirs for bio-flocculant-producing bacteria since bio-flocculation happens spontaneously during aerobic activities. Bacteria, algae, fungus, and actinomycetes create bioflocculants (Prasad et al 2013). Achromobacter sp., Agrobacterium sp., Acinetobacter sp., Bacillus cereus, Exiguobacterium acetylicum, Enterobacter sp., Galactomyces sp., Haemophilus sp., Citrobacter sp., Klebsiella sp., Ochrobactium cicero, Pichia membranifaciens (Batta et al 2013; Guo et al 2013; Wan et al 2013; Wang et al 2013, 2014). It is also reported that biomass can also remove arsenate from wastewater (Zhang et al 2015). 2.3.4.7 Biosurfactants Biosurfactants lower surface and interfacial tension and are generated or excreted by microbes. During development, microorganisms emit surface-active biosurfactants to emulsify hydrophobic organic carbon substrates. Sophorolipids and rhamnolipids are extracellular or cell membrane surface-active chemicals generated by microbes. Compared to chemically produced surfactants, biosurfactants are more effective and efficient, and their critical micelle concentration is 10–40 times lower (Desai and Banat 1997). They are biodegradable, less poisonous, antibacterial, and resistant of physicochemical changes (pH, temperature, and ionic strength) (Cameotra and Makkar 1998). In food, personal-care products, and household/laundry detergents, biosurfactants are used as emulsifiers, humectants, dispersants, and detergents. After microbial cultivation in WAS-derived media, biosurfactants and bioflocculants can be collected via physical (centrifugation, heating, and

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Green Technologies for Waste Management

sonication) and chemical procedures (alkaline-NaOH, acid-H2SO4, trichloroacetic acid, boiling benzene, crown ether, EDTA, ethanol precipitation, enzymes, glutaraldehyde, sulfide, and NaCl treatments).

2.3.5 VALORIZATION

OF

CROP BYPRODUCTS/PROCESSED AGROWASTES

2.3.5.1 Agricultural Wastes as Low-Cost Adsorbents Agricultural wastes and byproducts could be low-cost adsorbents for heavy metals and synthetic dyes. Agricultural waste is an efficient, low cost, and renewable source of biomass for heavy metal adsorption. Agricultural materials, especially cellulose, can biosorb metals. Agricultural waste biomass contains hemicellulose, lignin, extractives, lipids, proteins, simple sugars, hydrocarbons, and starch with functional groups that promote metal complexation and sequestration (Bailey et al 1999, Hashem et al 2007). In their natural state or after physical or chemical alteration, these agricultural waste materials remove metal ions. 2.3.5.2 Biochar Agricultural waste and weeds are pyrolyzed to make biochar. Biochar is a carbon-rich substance generated by incomplete combustion of organic sources. Biochar retains carbon in the soil for hundreds to thousands of years, reducing CO2 and CH4 emissions. Biochar improves soil pH, fertility, fertilizer use efficiency, water retention, aeration, tilth, and crop production. Cocopeat, a valuable soil conditioner, can be made by solid-state fermenting Coirpith (a coir industry byproduct) with Aspergillus heteromorphus. 2.3.5.3 Cellulose and Pectin Banana sheath fibers yield cellulose and microcrystalline cellulose. Banana fiber is mostly cellulose, with some hemicelluloses, lignin, wax, and pectin. Fermented banana fibers produce ferulic acid. Acid-hydrolyzed fibers also generate nano cellulose. Cellulose fibers are used as adsorbents, chemical filters, and reinforcement biocomposites, comparable to designed fibers. Cellulase can be produced as a value-added product by microbial fermentation using groundnut shell as a substrate employing Trichoderma sp. and Phanerochaete sp. The groundnut shell produced in bulk in countries such as India can be used to produce cellulase at industrial scale by microbial fermentation. Cellulase is utilized in bio-polishing fabrics/garments, bio-stone washing, animal feed, textile, food sector, enzymatic saccharification of agro-waste, etc. Bacillus-group bacteria can also create amylase and protease from potato peel waste. Besides, Pectin can be extracted from premature discarded fruits and citrus trash. Pectin is used as a thickening, emulsifier, texturizer, and stabilizer in food. It gels jams and jellies. It’s also used as a fat alternative in spreads, ice cream, and salad dressings. 2.3.5.4 Microbial Protein Dried microbe cells are used as a protein supplement. This non-conventional protein source is made from bacteria, fungi, yeast, and algae. High protein content and short development times contribute to quick, environmental-independent biomass production. Using lignocellulosic waste from agriculture and industry as a cheap carbon source for microbial protein production could make the process viable. This handles agro-residues effectively and converts them into microbial protein. This protein is safe for human consumption and can be used to fortify food. Pre-treated corn cob is a cheaper supply of carbon and nutrients for fermentation. Protein was produced in corn cob medium with Saccharomyces cerevisiae yeast. The obtained microbial protein is 45.5% crude protein. Cysteine (5.22 mg/100 mg) and Methionine (5.65 mg/100 mg) are sulfur-containing amino acids that are found in this protein.

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2.3.5.5 Natural Rubber Natural rubber is derived from the rubber tree Hevea brasiliensis, which is largely cultivated in South East Asia (Malaysia, Indonesia, Vietnam, and Thailand accounting for 70–75% of global production). Guayule, Russian dandelion, rubber rabbitbrush, figtree, goldenrod, and sunflower yield natural rubber. Guayule and Russian dandelion have been studied as large-scale NR alternatives. In the Mediterranean, guayule is the most promising crop, while dandelion should be grown in northern and Eastern Europe. Both forms of rubber may be used for tyres and automobile parts, but guayule rubber may have medical applications due to its lack of allergenic proteins. Diversifying natural rubber sources from the current feedstock, H. Brasiliensis (cultivated in tropical regions), by including guayule rubber (arid climates) and Russian dandelion rubber (temperate climates), mitigates overconcentration of natural rubber production in a certain region and from a certain crop. This reduces deforestation and reliance. Guayule processing generates high-quality rubber, although costs are greater than H. Brasiliensis. Guayule processing yields attractive byproducts that could sell well. Low-molecular-weight rubber could feed liquid natural rubber, which is used in adhesives and molded items. After rubber and resin extraction, bagasse can be utilized as a fuel and soil amendment. Polymerization of bio-based, sustainable isoprene monomers can also produce high molecular weight polyisoprene chains. This is the case of polyisoprene derived from plant oils or natural turpentine (Mathers 2012) or algae (Zuber 2017), which is under investigation mainly in the United States (Texas-based GlycosBio announced in May 2010 a collaboration with Malaysia’s Bio-XCell Sdn Bhd to build a biorefinery with a planned 20,000 tonne/year capacity to produce isoprene using oil palm glycerine) (Ajinomoto Co. has successfully manufactured bio-based isoprene at the laboratory scale using a fermentation process from biomass raw material). Biologically produced synthetic isoprene monomer technique produces high yields of isoprene from low-cost feedstocks, such as crude glycerol. 2.3.5.6 Plant Fibers and Paper Developing a process to make handmade paper from jute fiber, specifically jute residue will open up a new field where jute waste may be utilized to make commercially valuable handmade paper. Farmers previously burned or discarded jute waste, creating a disposal concern. The use of plant fibers in creative fields of materials science garnered interest due to their biorenewable nature, widespread availability, and inexpensive cost. Industrial interest in plant fibers is focused on using them as renewable reinforcing fillers for plastic-based composites, mainly for automotive and packaging applications, or for the production of sustainable textiles and fabrics exploiting waste residues. Plant fibers are renewable alternatives for artificial fibers such as carbon fibers, currently made from fossil-based poly(acrylonitrile) fibers, or glass fibers. 2.3.5.7 Nanocellulose Nanocellulose derived from wood pulp has a greater surface area, bonding potential, and waterbinding capacity than regular pulp fibers. Nanocellulose is a pseudo-plastic that may form thick fluids or gels. Nanocellulose’s lateral dimensions range from 5 to 20 nm, and its longitudinal dimensions are several microns. This product has considerable potential as a biodegradable reinforcement for bioplastics, suggesting it could replace carbon fibers in technical composites. Microfibrils of cellulose dispersed in a polar liquid create creamy materials used as nonwoven binders, in foods, paints, cosmetics, and medicine. They offer remarkable spraying qualities and a high viscosity at rest. They’re also used as stabilizers for water-in-oil or oil-in-water emulsions and as water-absorbing, retaining, and releasing materials for medical and hygiene products. Inorganic matrices reinforced with plant fibers are another construction innovation. Nanocellulose is created from wood waste, hemp, and flax.

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Green Technologies for Waste Management

2.3.5.8 Lignin Lignin is the only chemical having aromatic characteristics that can be extracted from biomass. Waste-derived lignin has great value-added product potential. Lignin’s unique structure and chemical capabilities allow the creation of aromatic substances. Due to the difficulties of producing pure aromatic compounds from lignin, the entire potential of lignin for commodity polymers is untapped. New technologies are needed to convert lignin into benzene, toluene, xylene, phenols, hydroxybenzoic acids, coniferyl, sinapyl, and p-coumaryl compounds, including vanillin. Lignin is decomposed into aromatic chemicals, monomers, and polymers (Kumar et al 2008). The combination of new and present technologies could convert lignin to polyethylene terephthalate, polystyrene, unsaturated polyesters, polyaniline, and aromatic polymers such as phenolic resins. Carbon fibers from lignin can replace peroxy acetyl nitrate-derived carbon fibers with less environmental impact. 2.3.5.9 Oils and Fats (O and F) Fats and oils are the most important renewable biomass feedstocks after carbohydrates and lignin. Their versatile chemical nature allows them to be used in a variety of synthetic ways, giving rise to an almost endless range of bio-based compounds beyond biodiesel. Biosurfactants, biolubricants, and bio-based monomers for innovative polymers are high-value compounds generated from renewable oils and fats. Plant oils, animal fats, and marine oils are renewable O and F. Chemically and technically, most O and F are interchangeable, but processing costs and end-use requirements vary. This also leads to notable pricing discrepancies depending on the source, which may be a real renewable source, such as a specialized crop, or a byproduct, as with animal fats. Many industrial sectors are developing bio-based lubricants. Biolubricants are renewable, non-toxic, economical, and environmentally friendly. They offer better stability and performance than mineral-based lubricants (e.g., suitable for heavy truck engines). Cosmetics, medicine, and nutraceutics use green compounds from renewable oils. Plant oils used as cosmetic bases protect the epidermis from water loss. Emollients are oils, softeners, smoothers, and protectors. Medicine recognizes the benefits of dietary plant oils, such as in cell membrane biosynthesis. Omega-3 fatty acids are important for preventing and treating atherosclerosis, thrombosis, arthritis, and malignancies. 2.3.5.10 Terpenes Terpenes are a vast class of bioactive natural compounds used as flavors, perfumes, vitamins, and medicines. Terpenes are promising bio-based building blocks for polymer synthesis. Terpenes are a category of compounds whose structure is based on isoprene units. Secondary metabolites are generated by plants, insects, marine microorganisms, and fungi. Strong odors may deter herbivores. Citrus peels and fruit juice residue are rich in antibacterial d-limonene, which could hinder energy valorization bioprocess. Citrus byproducts processing appears to be a good feedstock for high-value product recovery or energy bio-processes. Terpenes are used in bioplastics and biopolymers. Abundant terpenes are the precursors to bulk polyterpenes. Pinenes, easily separated from turpentine, are prospects. Most researched is pinene. Recently, limonene has gained interest as a monomer for bioplastics, especially polycarbonates, because it could replace bisphenol-A (BPA), a fossil fuel-derived chemical that is a probable endocrine-disruptor, neurotoxin, and carcinogen. Green propellants, insecticides, and antioxidants based on terpene are gaining popularity. Chemical qualities paired with breakthrough technologies like microencapsulation are releasing new commercial options. 2.3.5.11 Natural Polyelectrolytes Polyelectrolytes are polymers with ionic chains. Alginates (carboxylic polyelectrolytes), carrageenan, and agars (sulfated polyelectrolytes, except agarose, and a neutral polysaccharide) are found in seaweed cell walls, whereas pectins are found in fruits. Chitin and chitosan are animal-derived

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polyelectrolytes. Chitin is a linear polysaccharide and the second most prevalent polysaccharide in nature after cellulose. Fungi produce chitosan by deacetylating chitin. Algae create natural polyelectrolytes, with anionic alginates and carrageenans as significant representatives. Shrimp shells can be turned into chitin and chitosan. Demineralization and deproteinization of crustacean shell yield chitin. Chitin deacetylation produces chitosan. Chitosan can be used to make biodegradable and antimicrobial packaging films for food, freshness, and time-temperature indicators, beads for removing lead and fluoride from water, membranes for periodontal applications and plastic surgery, an edible fish coat, etc. Adding strong hydrochloric acid to shrimp, lobster, and crab shell chitin produces glucosamine hydrochloride. Glucosamine is a nutraceutical used to treat osteoarthritis that fights joint inflammation and inhibits cartilage-destroying enzymes. Chitooligosaccharides (COSs) are derived from shrimp shell waste chitosan. Chitosan depolymerized. COS is a low-molecular-weight nitrogenous carbohydrate. Enzyme hydrolyzes chitosan to generate COS. COS is antioxidant, antibacterial, anti-fungal, anti-tumor, and anti-inflammatory. COS is utilized in medicine, health supplements, food packaging, agriculture, cosmetics, etc. Owing to have antioxidant and antibacterial properties, COS-based bio-composite film uses shrimp shell waste, fish skin waste, and chitosan to form gelatin. Gelatin is utilized in the food and pharmaceutical industries as a gelling agent. Gelatin is a soluble polypeptide generated from collagen, a structural protein in skin and bones. About 30% of fish processing waste includes highcollagen skin and bone that can be used to produce gelatin. Hydrolysis of collagen obtained from fish scale, bone, skin, etc. yields collagen peptide. Middle-aged and geriatric populations, osteoporosis patients, and athletes should eat meals fortified with collagen peptide. These peptides have antioxidant, antihypertensive, antiproliferative, anticoagulant, calcium-binding, anti-obesity, and anti-diabetic properties. It strengthens bones and supports healthy joints. It has good potential in the cosmetic industry to prevent skin aging by improving hydration, elasticity, and deep wrinkle formation. The most significant characteristics of polyelectrolytes are thickening, stabilizing, and gelforming ability. Many companies produce and supply the basic ingredient as a food additive. They are employed in medicinal and biomedical applications, cosmetic and personal care formulations, and wastewater treatment chemicals due to their flocculation and precipitation capabilities. Due to their charge, they can react with opposite ionically charged polymers to form polyelectrolyte complexes. These supramolecular structures have different physical properties than their constituent macromolecules, making them promising materials for gene therapy to deliver modified nucleic acids and other biomolecules into a patient’s cell as a drug to treat diseases. 2.3.5.12 Nanoparticles (NPs) Due to their eco-friendliness and low toxicity, scientists prefer biosynthesized nanoparticles (NPs) for their unique electrical, magnetic, optical, catalytic, large surface-to-volume ratio, and surface energy features. NPs have potential in medical research, IT, food, energy, environment, transportation, biotechnology, agriculture, robotics, aerospace, and other industries. Industrial wastes like batteries, tires, wastewater, and sludges have been examined as low-cost and abundant NP preparatory materials (Samaddar et al 2018). Carbon, lead, zinc, copper, and palladium are found in industrial batteries, tires, wastewater, and biosolids. End-of-life consumer products produce tons of e-waste and trash. E-waste contains valuable and semi-valuable metals. Plastic waste can be recycled or reused as packaging material, or it can be utilized as raw material for construction materials, paper, fiber composites, novel polymers, and carbon NPs. Pb, Hg, Cu, Fe, Au, Ag, Pd, Pt, and Rh NPs and polymers can be recovered from computer circuit boards, cell phones, laptops, cars, and supercapacitors (Singh and Lee 2016; Vermisoglou et al 2016; Xiu and Zhang 2012). Most attempts focus on recovering metal NPs from discarded batteries. Microemulsion methods were used to make Cu NPs from CuCl2 waste etchants from printed circuit board (PCB) production (Mdlovu et al 2018). Chemically reducing CuSO4 from PCBs creates organically stabilized Cu nanoparticles (Tatariants et al 2018). Waste PCBs are

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recycled to yield Cu, Pb, Fe, Au, and Hg (Calgaro et al 2015; Chen et al 2015a, 2015b; Chu et al 2015; Fogarasi et al 2015; Hadi et al 2015; Cui and Anderson 2016). Waste PCB metals can form NPs. Copper–tin (Cu–Sn) NPs were also made from used waste PCBs using selective thermal transformation while isolating harmful lead (Pb) and antimony (Sb) (Shokri et al 2017). Lead (Pb) NPs were produced from waste PCB solders using vacuum evaporation and inert gas condensation (Zhan et al 2016). Purified carbon nanotubes, Cu2O NPs, and Cu2O/TiO2 catalysts can be made from e-waste. In another work, zinc oxide (ZnO) NPs were produced from a spent Zn–C battery at 900°C in an argon environment (Farzana et al 2018). NPs can be biosynthesized from biowaste. Food waste contains cellulose, hemicelluloses, pectins, lignins, proteins, and biodegradable polysaccharides. Waste contains polyphenols, carotenoids, flavonoids, dietary fibers, and essential oils. These serve as templates for NP synthesis, determining shape and size. Biomolecules reduce the metal salts into metal or metal oxide NPs (Heim et al 2002). Biodegradable food waste has been used to make NPs. Food waste contains polyphenols, flavonoids, carotenoids, and vitamins that act as templates (Kim et al 2012). Metal precursors are reduced by the numerous functional groups included in these compounds. The waste thus serves as a “biofactory.” Mango peel extract has been utilized successfully in the synthesis of Au NPs (Yang et al 2014). The wine business generates a lot of grape waste, which is a source of plenty of organic chemicals that cause metals to be converted to NPs. Silver ions were reduced into NPs in the presence of grape seed extract, resulting in spherical and polygonal-shaped Ag NPs with an average diameter of 25–35 nm (Xu et al 2015). Chicken eggshell membrane (ESM) is used to make fluorescent Au NPs (Devi et al 2012). Metal oxide NPs synthesized from agro and food wastes haven’t been thoroughly studied. However, magnetic iron oxide (Fe3O4) NPs with cuboid/pyramid shape were made from tea residue (Lunge et al 2014). Eggshells from the food processing and baking industries are also considered waste. No food value, but used to make hydroxyapatite NPs. Eggshells comprise 94% calcium carbonate, 1% magnesium carbonate, 1% calcium phosphate, and 4% organic content. Calcium helps produce hydroxyapatite NPs (Rivera et al 1999; Wu et al 2013). Banana peel extract has been utilized to make super-capacitive Mn3O4 NPs (Yan et al 2014). 2.3.5.13 Graphene Graphene is a honeycomb-shaped layer of sp2 hybridized carbon atoms with outstanding characteristics such as high surface area, electrical conductivity, optical characteristics, superior chemical stability, and mechanical strength (Nair et al 2008; Rao et al 2009). Graphite and organic molecules are the two main raw materials used in the manufacture of graphene. Graphite and organic compounds are needed to make graphene (Strudwick et al 2015). Graphene can be prepared using various bio-precursors including chitosan, glucose, rice husk, hemp, disposable paper cups, and alginate, among others. Even coal and discarded plastics can be used to synthesize graphene quantum dots. Manukyan et al (2013) discovered an energy-saving combustion process to make graphene sheets from Polytetrafluoroethylene (PTFE) and silicon carbide (SiC). Ruan et al (2011) devised a green synthesis process to turn waste polystyrene, grass blades, food waste, and grass into high-quality single-layered graphene.

2.3.6 RESOURCE GENERATION

FROM INDUSTRIAL

WASTES

Industrial solid waste includes several hazardous compounds. Industrial waste includes paper, packaging, food processing waste, oils, solvents, resins, paints and sludges, glass, ceramics, stones, metals, plastics, rubber, leather, wood, fabric, straw, etc. Many bioenergy routes can transform raw biomass into a final energy product. Heat and power from biomass are well-developed. Diverse conversion technologies are being developed to increase efficiency, prices, and environmental performance.

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2.3.6.1 Bakery Products Okara is a tofu-and-soy-milk byproduct. Okara is 3–4% protein, 76–80% moisture, and 20–24% solids. Okara has 12.5% crude fiber and 24% protein when dry. Okara’s high moisture and nutrient content make it putrefactive, limiting its commercial application. Okara is used to make proteinrich bread and fermented soy products. Using okara in food preparation helps dispose of soy processing unit waste by generating soy-based foods like biscuits, cakes, muffins, Gulabjamun, idli, dosa, etc. high in protein. Okara is used as animal feed near soy milk or tofu manufacturers. Okara is a natural nitrogen fertilizer. It adds nutrients and nitrogen to compost. Using okara can improve the economic situation of rural populations/farmers/women involved in soy milk and tofu production. Besides, cotton stalk, a lignocellulosic biomass, contains 50–60% hemicellulose, 25–28% lignin, 6–8% ash, and potassium. This makes them a possible substrate for mushroom development, which could benefit farmers. 2.3.6.2 Biocompost Press mud, a sugar industry residue, can be used to make soil-less planting media, which feeds plants with nutrients without soil. BioCompost is a formulation of Phanerochaete chrysosporium, Trichoderma viride, Aspergillus awamori, and Pleurotus florida. The consortium can convert wheat, rice, mustard, maize, and soybean residues into compost in 65–70 days using pit or windrow methods. 2.3.6.3 Mushroom Production Oil Palm Industry Waste Oil palm bunch debris and mesocarp waste are sterilized during oil extraction from fresh fruit bunch. These waste materials are good for growing edible mushrooms including Paddy straw mushroom, Oyster mushroom, Summer white milky mushroom, and Summer white button mushroom (on mesocarp waste) directly or after generating compost. 2.3.6.4 Nutritional Supplements and Medical Aids from Aquaculture Waste Fish bone is a high-bioavailability source of calcium as dicalcium phosphate. Compared to conventional calcium capsules, which are calcium carbonate, fish-source calcium contains phosphorus. Bones from fish fillets and mince can be used. Protein is removed with enzymes, and fat is eliminated with alcohol. The treated bone is washed to remove alcohol, dried, powdered, and capsuled. This method uses fish bone, a major fish processing byproduct. ICAR-CIFT has helped certain entrepreneurs. A low-cost method for making absorbable surgical sutures using live fish gut has also been developed. Fish scale and bone are used to make bio-ceramic hydroxyapatite. Hydroxyapatite aids bone grafting and osseointegration as a bioactive natural substance. ICAR-CIFT has spread this technology. 2.3.6.5 Biofuel from Pulp and Paper Industry Waste The pulp and paper industry generates a lot of bark, leaves, needles, branches, and sludge. Nonsludge biomass can be used to make biofuel. Most pulp mill sludge is deposited in landfills, where it degrades to methane gas, a more destructive GHG than carbon dioxide. Landfill contamination can be avoided by using it to make biofuel. Black liquor, which contains dissolved lignin, is another result. Black liquor is currently burned to produce paper mill energy, and the extra energy is used to export power. Black liquor contains dissolved lignin degradation products and cellulosic and hemicellulosic hexose and pentose sugar degradation products. 2.3.6.6 Lac Dye and Gummy Mass from Lac Industry Waste Lac dye, a byproduct of the lac industry, is lost in the effluent during washing of sticklac in primary processing, in which sticklac is turned into seedlac. Sticklac contains lac coloring and lac resin

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(laccaic acid). Effluent from lac washing can recover up to 50% of sticklac’s color. India produces 17,000 tons of lac yearly. During washing, 100 tons of lac color are lost annually. The dye has huge potential as a dairy industry byproduct. Lac dye is used to mordant wool and silk. Natural, non-toxic lac dye is used as food coloring. Lac mud is a waste product of lac processing enterprises, accounting for 2.5–4.5% of the raw material (sticklac) in primary processing. Organic Lac Mud improves soil fertility. Gummy mass is a byproduct of Aleuritic acid production. Effluent from Aleuritic acid production is sticky and doesn’t dry at room temperature, causing problems for producers. Lac industry has long demanded proper use. Gummy mass is utilized in varnish, paint, gasket cement, and bio-composite board. GM from Aleuritic acid effluent is used to make coatings (varnish and paint), adhesive/binder, and bio-composite boards. It’s also utilized to seal oil-leaking joints in auto-cementing compositions.

2.3.7 ALGAE

AS

BIOFUEL RESOURCE

Green microalgae are third-generation feedstock that processes sunlight more efficiently. Algae can produce biodiesel and biohydrogen. Algae are the fastest-growing photosynthesizing creatures, completing a cycle in days. Some algae contain 50% oil. Due to their high oil and lipid content and quick biomass production, algal oil for biodiesel is receiving attention. High-oil microalgae grown in photobioreactors can yield 19,000–57,000L per acre per year. Algae oil output is 200 times that of plant/vegetable oils (Chisti 2007). Culture conditions affect microalgae lipid and fatty acid concentration. Algal biomass can be used as food additives, protein-rich animal and aquaculture feed, biofertilizer, nutraceuticals, and medicines, after biodiesel extraction. Wastewater treatment also uses immobilized algal beads. Moreover, hydrogen is a possible future fuel and renewable energy source; however, existing technologies are energy consuming, expensive, and ecologically unfriendly. Due to the urgency of the energy problem, many diverse works are being done in the field of algal-mediated biohydrogen production, such as increasing growth rate, improving harvesting methods, genetically engineering crops, and optimizing chemical and thermal methods for producing biofuels.

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Mdlovu, N.V., Chiang, C.L., Lin, K.S. and Jeng, R.C., 2018. Recycling copper nanoparticles from printed circuit board waste etchants via a microemulsion process. Journal of Cleaner Production, 185, pp. 781–796. Mo, W.Y., Cheng, Z., Choi, W.M., Man, Y.B., Liu, Y. and Wong, M.H., 2014. Application of food waste based diets in polyculture of low trophic level fish: effects on fish growth, water quality and plankton density. Marine Pollution Bulletin, 85(2), pp. 803–809. Mohan, D., Sarswat, A., Ok, Y.S. and Pittman Jr, C.U., 2014. Organic and inorganic contaminants removal from water with biochar, a renewable, low cost and sustainable adsorbent–A critical review. Bioresource Technology, 160, pp. 191–202. Molino, A., Chianese, S. and Musmarra, D., 2016. Biomass gasification technology: The state of the art overview. Journal of Energy Chemistry, 25(1), pp. 10–25. Möller, K. and Müller, T., 2012. Effects of anaerobic digestion on digestate nutrient availability and crop growth: A review. Engineering in Life Sciences, 12(3), pp. 242–257. Nair, R.R., Blake, P., Grigorenko, A.N., Novoselov, K.S., Booth, T.J., Stauber, T., Peres, N.M. and Geim, A.K., 2008. Fine structure constant defines visual transparency of graphene. Science, 320(5881), pp. 1308–1308. Nanda, S., Dalai, A.K., Berruti, F. and Kozinski, J.A., 2016. Biochar as an exceptional bioresource for energy, agronomy, carbon sequestration, activated carbon and specialty materials. Waste and Biomass Valorization, 7(2), pp. 201–235. Nayak, J.P. and Bera, J., 2010. Effect of sintering temperature on mechanical behaviour and bioactivity of sol–gel synthesized bioglass-ceramics using rice husk ash as a silica source. Applied Surface Science, 257(2), pp. 458–462. Nguyen, T.T., Tomberlin, J.K. and Vanlaerhoven, S., 2015. Ability of black soldier fly (Diptera: Stratiomyidae) larvae to recycle food waste. Environmental Entomology, 44(2), pp. 406–410. Olowolafe, E.A., 2008. Effects of using municipal waste as fertilizer on soil properties in Jos area, Nigeria. Resources, Conservation and Recycling, 52(11), pp. 1266–1270. Papargyropoulou, E., Lozano, R., Steinberger, J.K., Wright, N. and bin Ujang, Z., 2014. The food waste hierarchy as a framework for the management of food surplus and food waste. Journal of Cleaner Production, 76, pp. 106–115. Park, J.Y., Lee, J.S., Wang, Z.M. and Kim, D.K., 2010. Production and characterization of biodiesel from trap grease. Korean Journal of Chemical Engineering, 27(6), pp. 1791–1795. Pervaiz, M. and Sain, M., 2011. Protein extraction from secondary sludge of paper mill wastewater and its utilization as a wood adhesive. BioResources, 6(2), pp. 961–970. Prasad, K.S., Ramanathan, A.L., Paul, J., Subramanian, V. and Prasad, R., 2013. Biosorption of arsenite (As+ 3) and arsenate (As+ 5) from aqueous solution by Arthrobacter sp. biomass. Environmental Technology, 34(19), pp. 2701–2708. Rao, C.E.E., Sood, A.E., Subrahmanyam, K.E. and Govindaraj, A., 2009. Graphene: the new two‐dimensional nanomaterial. Angewandte Chemie International Edition, 48(42), pp. 7752–7777. Raunkjær, K., Hvitved-Jacobsen, T. and Nielsen, P.H., 1994. Measurement of pools of protein, carbohydrate and lipid in domestic wastewater. Water Research, 28(2), pp. 251–262. Rivera, E.M., Araiza, M., Brostow, W., Castano, V.M., Dıaz-Estrada, J.R., Hernández, R. and Rodrıguez, J.R., 1999. Synthesis of hydroxyapatite from eggshells. Materials Letters, 41(3), pp. 128–134. Romero-Güiza, M.S., Vila, J., Mata-Alvarez, J., Chimenos, J.M. and Astals, S., 2016. The role of additives on anaerobic digestion: a review. Renewable and Sustainable Energy Reviews, 58, pp. 1486–1499. Roy, M.M. and Corscadden, K.W., 2012. An experimental study of combustion and emissions of biomass briquettes in a domestic wood stove. Applied Energy, 99, pp. 206–212. Ruan, G., Sun, Z., Peng, Z. and Tour, J.M., 2011. Growth of graphene from food, insects, and waste. ACS Nano, 5(9), pp. 7601–7607. Rulkens, W.H., 2004. Sustainable sludge management-what are the challenges for the future?. Water Science and Technology, 49(10), pp. 11–19. Ryan, M.P. and Walsh, G., 2016. The characterisation of dairy waste and the potential of whey for industrial fermentation. Limerick (Ireland): University of Limerick. Report, (173). Samaddar, P., Ok, Y.S., Kim, K.H., Kwon, E.E. and Tsang, D.C., 2018. Synthesis of nanomaterials from various wastes and their new age applications. Journal of Cleaner Production, 197, pp. 1190–1209. Sarris, D. and Papanikolaou, S., 2016. Biotechnological production of ethanol: Biochemistry, processes and technologies. Engineering in Life Sciences, 16(4), pp. 307–329. Satoh, H., Mino, T. and Matsuo, T., 1999. PHA production by activated sludge. International Journal of Biological Macromolecules, 25(1–3), pp. 105–109.

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Wu, Q., Wang, Y. and Chen, G.Q., 2009. Medical application of microbial biopolyesters polyhydroxyalkanoates. Artificial Cells, Blood Substitutes, and Biotechnology, 37(1), pp. 1–12. Wu, S.C., Tsou, H.K., Hsu, H.C., Hsu, S.K., Liou, S.P. and Ho, W.F., 2013. A hydrothermal synthesis of eggshell and fruit waste extract to produce nanosized hydroxyapatite. Ceramics International, 39(7), pp. 8183–8188. Xiu, F.R. and Zhang, F.S., 2012. Size-controlled preparation of Cu2O nanoparticles from waste printed circuit boards by supercritical water combined with electrokinetic process. Journal of Hazardous Materials, 233, pp. 200–206. Xu, H., Wang, L., Su, H., Gu, L., Han, T., Meng, F. and Liu, C., 2015. Making good use of food wastes: green synthesis of highly stabilized silver nanoparticles from grape seed extract and their antimicrobial activity. Food Biophysics, 10(1), pp. 12–18. Xue, Y., Chen, H., Zhao, W., Yang, C., Ma, P. and Han, S., 2016. A review on the operating conditions of producing bio‐oil from hydrothermal liquefaction of biomass. International Journal of Energy Research, 40(7), pp. 865–877. Yan, D., Zhang, H., Chen, L., Zhu, G., Wang, Z., Xu, H. and Yu, A., 2014. Supercapacitive properties of Mn 3 O 4 nanoparticles bio-synthesized from banana peel extract. RSC Advances, 4(45), pp. 23649–23652. Yang, F., Hanna, M.A. and Sun, R., 2012. Value-added uses for crude glycerol – A byproduct of biodiesel production. Biotechnology for Biofuels, 5(1), pp. 1–10. Yang, N., WeiHong, L. and Hao, L., 2014. Biosynthesis of Au nanoparticles using agricultural waste mango peel extract and its in vitro cytotoxic effect on two normal cells. Materials Letters, 134, pp. 67–70. Yalçin, N., and Sevinç, V. 2001. Studies on silica obtained from rice husk. Ceramics International, 27, pp. 219–224. Zhan, L., Xiang, X., Xie, B. and Sun, J., 2016. A novel method of preparing highly dispersed spherical lead nanoparticles from solders of waste printed circuit boards. Chemical Engineering Journal, 303, pp. 261–267. Zhang, J., Ding, T., Zhang, Z., Xu, L. and Zhang, C., 2015. Enhanced adsorption of trivalent arsenic from water by functionalized diatom silica shells. PLoS One, 10(4), p.e0123395. Zhang, W., Alvarez-Gaitan, J.P., Dastyar, W., Saint, C.P., Zhao, M. and Short, M.D., 2018. Value-added products derived from waste activated sludge: A biorefinery perspective. Water, 10(5), p. 545. Zhang, D.Q., Cai, Q.R., He, X.M., Gao, L.X. and Zhou, G.D., 2008. Inhibition effect of some amino acids on copper corrosion in HCl solution. Materials Chemistry and Physics, 112(2), pp. 353–358. Zhang, W.F., Su, R.J., Guo, G.L. and Li, D.X., 2012. Experimental research on protein extraction from excess activated sludge by papain hydrolysis. In Advanced Materials Research (Vol. 518, pp. 3367–3370). Trans Tech Publications Ltd. Zhao, P., Guo, X. and Zheng, C., 2010. Removal of elemental mercury by iodine-modified rice husk ash sorbents. Journal of Environmental Sciences, 22(10), pp. 1629–1636. Zuber, M., Zia, K.M., Noreen, A., Bukhari, S.A., Aslam, N., Sultan, N., Jabeen, M. and Shi, B., 2017. AlgaeBased Polyolefins. In Algae Based Polymers, Blends, and Composites (pp. 499–529). Elsevier.

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Life Cycle Assessment of Waste Management Systems

3.1 INTRODUCTION The exponential growth of the global population contributes to an increase in waste generation. If not adequately managed, municipal, agricultural, and industrial waste can create an unhealthy and unpleasant environment and potentially spread illness. To be able to establish comprehensive waste management strategies, it is vital to recognize waste sources and types precisely and to have a solid understanding of waste types and their composition. With growing worries about waste and the demand for “greener” products, it is vital to conduct life cycle assessments (LCAs) of products, which will assist manufacturers in taking the initial steps toward greener solutions by analyzing the carbon output of their products. One of the primary aims of the environmental policy of the European Union is to blend environmental sustainability with economic growth and prosperity. In recent years, a number of techniques have been proposed to move toward sustainable production and consumption and develop an energy- and resource-efficient economy. Within the framework of Integrated Product Policy (Commission of the European Communities, COM (2001) 68 final), recommendations on waste management and sustainable use of natural resources (Commission of the European Communities, COM (2005) 666 final), (Commission of the European Communities, COM (2005) 670 final), ecodesign of energy-intensive products (Directive 2005/32/EC of the European Parliament and of the Council 2005), and the use of essential components as Green Public Procurement (Commission of the European Communities, COM (2008) 400/2) and Ecolabels (Commission of the European Communities, COM (2008) 401/3). Life cycle analysis is a decision-supporting methodology to analyze multiple scenarios and highlight the environmental pinch points in the life cycle of a product or a system (UNI EN ISO 14040, 2006; UNI EN ISO 14044, 2006; USEPA 2006; Guinée, 2002). According to the US EPA, LCA evaluates a product, material, process, or activity’s environmental consequences. An LCA assesses all direct and indirect environmental impacts throughout a product’s life cycle, from materials acquisition to manufacturing, usage, and disposal (disposal or reuse). LCA studies examine environment impacts by identifying energy, materials, and emissions produced to the environment; they also highlight potential for environmental improvements (Consoli et al 1993; Christiansen et al 1995; Jensen et al 1997). It is a science-based method for assessing a product’s environmental impact (Winkler and Bilitewski 2007). Several reviews have examined LCA’s application to solid waste management. Their focus is on specific methodological features of waste types or management techniques. Numerous studies are available concerning LCA of different products and their management (Figure 3.1). Villanueva and Wenzel (2007) analyzed nine LCA studies on paper and cardboard waste management. Cleary (2009) analyzed the methodological conduct and findings of 20 studies assessing municipal waste management; Lazarevic et al (2010) analyzed 10 LCA studies assessing the management of post-consumer plastic waste in Europe; Michaud et al (2010) reviewed the findings of 55 LCA studies focusing on the benefits of recycling; Gentil et al (2010) and Björklund et al (2010) provided overviews of existing solid waste LCA models. Bernstad and la Cour Jansen (2012) evaluated 25 LCA studies of biowaste treatments, while Morris et al (2013) meta-analyzed 82 papers on organic waste management. Woon et al (2016) also evaluated the environmental implications of anaerobic digestion of food waste. Karka et al (2017) conducted a large-scale LCA of 23 products made from five categories of biomass waste (wood chips, municipal solid waste

DOI: 10.1201/9781003279136-4

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FIGURE 3.1 Technologies for waste management analyzed through 222 studies, expressed as a percentage of studies. Arrows are for illustrative reasons only. Since some studies are restricted to evaluating particular aspects of solid waste management systems, the number of studies stated in a given upstream process may not add up to the total number of studies indicated in the downstream processes (and vice versa). Source: Laurent et al (2014).

(MSW), rapeseed oil, wheat straw, and waste cooking oil). Most LCA research focused on biogas or energy production, with a handful on high-value chemical synthesis.

3.2 PRODUCT LIFE CYCLE Environmental performance of products and processes has become a vital issue as environmental awareness rises. A product’s life begins with its design or development, undergoes various stages, and ends with end-of-life operations, e.g., collection or sorting, reuse, recycling, disposal, etc. various stages of life cycle of a product are exemplified here: • Raw material acquisition: All actions required to extract raw materials and energy from the environment, including transport. • Processing and manufacturing: Generating a product from raw materials and energy. This stage is sometimes divided into sub-stages, with intermediate products generated along the way. • Distribution and transportation: Shipment to the final consumer. • Use, reuse, and maintenance: Using a product over its lifetime. • Recycle: After the product has served its primary purpose, it is recycled inside the same product system (closed-loop recycle) or enters a new product system (open-loop recycle). • Waste management: This starts when a product has completed its purpose and is discarded. All activities or processes during a product’s lifecycle have environmental implications owing to resource consumption, emissions, and other exchanges. LCA considers climate change (greenhouse

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RESOURCES

MATERIAL PROCESSING

END OF LIFE

COMPONENTS OF LCA

PRODUCT MANUFACTURING

USE

DISTRIBUTION

FIGURE 3.2 An overview of life cycle of a product.

gases like carbon dioxide, methane, nitrous oxide and chlorofluorocarbons, smog, tropospheric ozone, etc.), human health (pollutants causing cancer, respiratory ailments and toxicity like particulate matter, nitrogen oxide, sulfur oxide, mercury, lead, benzene, etc.), and ecosystem toxicity (e.g., eutrophication, acidification, pollutants harmful to wildlife and their habitats viz. DDT, lead, mercury, zinc, and polyvinyl chloride, etc.). Figure 3.2 shows a typical product life cycle. LCA identifies and describes all stages of a product’s life cycle, from extraction and pretreatment of raw materials to production, transport, distribution, and use, to reuse, recycle, or disposal of waste. In every stage of the product life, the LCA method is extremely effective at bringing these additional undesired outputs to light. By evaluating the resources consumed, the emissions generated during a product’s manufacturing, usage, and end of life, as well as the ensuing effects on ecosystems and human health, LCAs quantify the environmental impacts. LCAs are frequently used by policy makers and corporations to compare particular technologies in a specific context and location when it comes to waste management. In order to help decision-making processes, the information from an LCA is combined with other information, such as economic and social elements. As geographic regions, waste characteristics, energy sources, the availability of disposal methods, and the size of markets for products obtained from waste management vary greatly, LCA offers an appropriate tool for solid waste management (Mendes et al 2004). Since 1995, LCA has been used for sustainable MSW management (Güereca et al 2006).

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FIGURE 3.3 ISO 14040 series on life cycle assessment.

In 1998, the LCA process was standardized, and it was updated in 2006 (International Organization for Standardization, ISO 14040 2006). Solid waste management systems employ a life cycle analysis technique to evaluate the environmental effects of the creation, use, and disposal of goods and materials in our society from birth to death (Figure 3.1). In addition to these efforts, the International Organization for Standardization also established a number of frameworks and core principles to systematically characterize LCA and its key components (Figure 3.3), which serve as the prerequisites for carrying out an LCA study. The development of the ISO 14040 series was accompanied by the creation of numerous impact assessment techniques. The ISO 14040 series, which offers an essential foundation for LCA, frequently suggests a variety of options to practitioners with a big impact on the outcomes. In order to provide advice on planning, creating, and reporting the life cycle emission and resource consumption inventory (LCI) data sets and LCA studies, the European Commission set up the International Reference Life Cycle Data (ILCD) System. According to every description, LCA is a method created to evaluate the environmental effects connected to every step of a product’s life, from raw material extraction to manufacturing, distribution, usage, repair and maintenance, and ultimate disposal or recycling.

3.3 METHODOLOGY OF LCA IN CONTEXT OF WASTE MANAGEMENT LCA is a “cradle to grave” approach for monitoring and assessing a product’s environmental effect and resource usage across its full lifecycle, from raw materials procurement to waste management (Scientific Applications International Corporation, SAIC 2006) (Figure 3.4). A LCA study comprises four phases: goal and scope definition, life cycle inventory analysis (LCIA), life cycle impact assessment, and interpretation. LCA compares the whole range of environmental effects of products and services by quantifying inputs and outputs of material flows and analyzing their environmental impact. In Scope Definition and Inventory Analysis, inputs should be natural raw materials and outputs should be emissions to nature (Finnveden et al 2009). That is Inputs collected from the environment without human transformation and outputs released to the

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FIGURE 3.4 An overview of stages for life cycle assessment of a product.

environment without human change (ISO 14040 2006). Each phase of LCA study is discussed in detail further.

3.3.1 GOAL An LCA study typically starts with an explicit goal statement that establishes the study’s context and specifies how and to whom the results will be shared. The purpose must clearly explain the following things in accordance with ISO guidelines: 1. 2. 3. 4.

The intended use Justifications for doing the study The target audience, to whom the findings are to be communicated Whether the findings will be included in a comparative statement made public (Matthews et al 2014)

The study’s intended use and justifications might include, for example, the first-ever LCA of a particular product to ascertain when the most important environmental effects occur during its life cycle. The objective, which outlines the investigation’s purpose, is the first stage of an LCA. For example, a LCA for waste management may examine the effects on the environment of recycling plastic bottles, incineration of those bottles, and energy recovery. The effectiveness of the waste sorting program, the accessibility of the required infrastructure, and the nature of the nation’s energy supply would all have a big influence on the outcomes in this case. What kinds of environmental effects do the products typically have? This is just one type of inquiry that might be posed. Which phases of a product’s life cycle affect its overall impact the most? What actions can be performed to improve the environmental performance of the product?

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The intended audience could be that the outcome is only intended for internal use as input for product development, or it could be intended for use in external communication to inform customers or consumers, and so on. A comparative assertion is a statement that a product’s environmental performance is equivalent to or better than that of rival items that serve the same purpose. Due to the critical nature of this declaration, special requirements must be adhered to for this sort of LCA to be considered legitimate. There are specific reporting requirements and an evaluation by a panel of interested parties or stakeholders. By taking into account the entire waste management system and the full spectrum of environmental impacts, LCA helps to solve the issue of the burden being transferred from one area of the waste management system to another (such as global warming potential, ozone depletion potential, photochemical ozone production potential, terrestrial toxicity potential, aquatic toxicity potential, eutrophication potential, acidification potential, human health potential, resource depletion potential, etc.). For instance, the increased transportation distances may balance the perceived benefits of a certain waste treatment.

3.3.2 SCOPE The scope of the study must be determined after the goal by describing the qualitative and quantitative data that will be used in it. The goal may only require a few phrases, but the scope usually necessitates numerous pages (Matthews et al 2014). It is intended to provide an overview of the study’s detail and depth and to illustrate how the goal can be attained within the given constraints. The scope of a study establishes the methodology to be used, the underlying hypotheses, the functional unit, the criteria for the quality of the data, and the method for assessing the impact. The following should be included in the study of scope according to the ISO LCA Standard. 3.3.2.1 Product System It is a group of processes (activities that convert inputs to outputs) that fall within the study’s system boundary and are required to carry out a certain function. It serves as an example of each step in the life cycle of a process or product (Matthews et al 2014). 3.3.2.2 Functional Unit The functional unit expresses the function that the product system provides. This is a crucial component of the LCA, and the study needs to outline it in detail. Functional unit provides a framework for comparing/analyzing various commodities or services; which precisely specifies what is being examined, quantifies the service provided by the system, and acts as a reference to which the inputs and outputs can be compared (Rebitzer et al 2004). A crucial element of LCA is the functional unit, which must be precisely specified. Based on it, one or more product systems that can carry out the function are chosen. The functional unit makes it possible to treat various systems as functionally equivalent. The functional unit should not incorporate product system inputs or outputs (e.g., kg CO2 emissions), be quantifiable, take temporal coverage into account, or include units (Matthews et al 2014). Additionally, Hauschild et al (2018) proposed the following inquiries to consider it: 1. 2. 3. 4. 5.

What? What amount? How often and for how long? Where? How is it?

The analysis and development of the data that have been gathered should be utilized to define the functional unit that will be used for a project. In the context of waste management, the

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management of a specific quantity of garbage with a particular composition in a given area is frequently the functional unit. For instance, if the objective of a study is to assess various waste management options in a particular area, the functional unit could be the volume of MSW that is processed there over the course of a year. The functional unit also makes it possible to compare two crucially distinct systems. The functional unit provides a reference to which the inputs and outputs to the product system are associated and is a quantitative measure of the function of the researched system. This makes it possible to compare two various product systems. For instance, paint’s purpose is to keep a surface safe. In this situation, a 5 m2 unit surface that has been preserved for 10 years may be considered the functional unit for a paint system. It is then possible to compare the environmental effects of two distinct paint systems using the same functional unit, even though the two systems may have different technical characteristics in terms of durability, upkeep, etc. (Hauschild et al 2018). 3.3.2.3 Reference Flow The functional unit requires a physical flow of materials or energy, which is the reference flow (Hauschild et al 2018). However, there are some situations when they can be the same. Typically, the reference flow is different subjectively and quantitatively for various products or systems over the same reference flow (Hauschild et al 2018). The amount of paint required to protect a 5 m2 unit surface for 10 years would serve as the reference flow in the case of a paint system. Additionally, when comparing several paint systems, the quantity of paint required to perform the same job can vary based on the various technical characteristics of the paints. 3.3.2.4 System Boundaries The system boundaries specify which unit processes, as well as inputs and outputs, should be included in the product system. According to the purpose of the study and the anticipated use of the findings, the system’s processes are chosen. In actuality, creating a preliminary flowchart of the product system that illustrates the operations that will be integrated into the system as well as their connections facilitates the process of defining system boundaries. This makes it easier to comprehend the system. The first flowchart serves as the starting point for the LCA’s inventory analysis phase, which gathers data for each of the processes in the flowchart. Since the majority of technical activities are interconnected, it is important to specify which activities, inputs, and outputs should be included and which can be removed. This is crucial in order to concentrate efforts and narrow the work’s scope. “Cut-offs” are the exclusion of some system components, inputs, or outputs. However, the study’s objective must always be the basis for the exclusion of any life cycle components. It is necessary to identify precisely which inputs and outputs, or elementary flows, should be included from and to the environmental system. The first step in a product’s life cycle is typically the extraction of energy and material resources from the environment. Then, during the many production and transportation phases of the life cycle, emissions are produced that end up in the earth, water, or air. Additionally, garbage is produced and needs to be controlled. A product’s life cycle typically concludes with some type of end-of-life processing that could ultimately wind up in the environment, such as leakage from landfills or emissions from garbage incineration. In fact, how the environmental impact assessment should be carried out and what environmental consequences should be examined in the LCA dictate the choice of inputs and outputs that begin or end up in the environmental system. The susceptibility of ecosystems to environmental influences can vary spatially, and contaminants may have a varying lifespan in the atmosphere. This may also involve geographical or temporal factors. For the LCA results to be accurate, the scientific scope and boundary definition are equally crucial. The actions from the collection, treatment, and ultimate disposal of the residue are all included within the waste management system boundaries. Which unit processes are included in the LCA analysis is determined by the system boundaries? The infrastructure that is required, such as collection vehicles,

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biogas plants, waste-to-energy plants, and material recovery facilities, as well as the energy utilized in the facilities’ operations, is all included within the system limits. The most significant and vital step in the LCA study for the planning and data collecting for the inventory analysis is the definition of the system boundaries. The following boundaries can be taken into account during LCA study: • Boundaries between technological systems and the natural world – A life cycle typically starts at the point where raw materials and energy carriers are extracted from the environment. Typically, the last processes include the production of heat or waste. • Geographical area – The majority of LCA analyses take geography into consideration because different regions have different infrastructures for producing electricity, managing waste, and transportation. The city, region, or nation where the waste is produced and processed is frequently tied to the geographic borders of waste management LCAs. Additionally, the vulnerability of ecosystems to environmental effects varies regionally. The geographic limits dictate a number of crucial elements in the LCA, including the makeup of the waste to be processed, the technological sophistication of facilities, and the kind of power used. • Time horizon – In addition to space, time also needs to have boundaries established. LCAs basically try to assess current affects and forecast potential futures. Time limits are determined by the technology used, the longevity of pollutants, etc. • Boundaries between the current life cycle and related life cycles of other technical systems – Since most activities are interconnected; they must be studied separately in order to be fully understood. One can compare the economic viability of new, environmentally friendly processes with the technology now in use while evaluating, for instance, the manufacturing of capital goods. Product system interrelations frequently involve very intricate relationships. In a perfect world, life cycles of the materials and products that were the subject of the inquiry would also be necessary. Otherwise, there would be a long and complicated record of inflows and outflows. As a result, boundaries and limits must be established for the exclusion of specific components, which may change the study’s overall conclusion. Figure 3.5 illustrates a system boundary for LCA of MSW treatment systems.

FIGURE 3.5 System boundary for life cycle assessment of municipal solid waste treatment processes. (Adapted from Mali and Patil 2016).

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3.3.2.5 Assumptions and Limitations These cover any decisions or assumptions made over the course of the study that might have an impact on the outcomes. It is crucial that these are communicated because failure to do so could lead to incorrect interpretation of the results. Throughout the course of the project, further assumptions and constraints are frequently be established, and they should be noted as appropriate (USEPA 2006). 3.3.2.6 Data Quality Requirements This outlines what categories of data will be used and any limitations (ISO 14044:2006). According to ISO 14044, the scope should include the following data quality considerations: 1. Temporal Coverage, i.e., what time period should the data represent in terms of temporal coverage? 2. Geographical Coverage, e.g., what region or geographic area should the data represent? Materials are frequently produced in many locations around the world over the typical life cycle of a product. 3. Technological Coverage, e.g., what level of technology is used to manufacture materials and goods for the listed processes? It must be decided which technology should be used in the study, such as the best available technology, standard industrial practice, etc., because different types of technologies may be employed to generate a material that is included in the study. 4. The data’s accuracy, completeness, and representativeness 5. Reproducibility and consistency of the techniques utilized throughout the study 6. Data Sources, e.g., from what sources should data be gathered? Data can be collected, for instance, from internal information systems, vendors, trade groups, commercial LCA databases, etc. 7. Information uncertainty and any identified data gaps; in other words, how should information uncertainty and data gaps be handled? 3.3.2.7 Multifunctionality and Allocation For processes that generate several products, or co-products, allocation procedure is used to divide the inputs and outputs of a product. This is often referred to as a product system’s multifunctionality (Hauschild et al 2018). Given that the choice of co-product allocation method can have a major impact on the outcomes of an LCA, ISO 14044 offers a hierarchy of solutions to address multifunctionality challenges. These are the hierarchy methods: 1. Avoid Allocation by Sub-Division – This technique aims to break down the unit process into more manageable sub-processes so as to distinguish between the production of the product and the creation of the co-product (Hauschild et al 2018; Matthews et al 2014). 2. Avoid Allocation by System Expansion (or Substitution) – This approach aims to enlarge the co-production product’s process using the most likely means of supplying the determining product’s secondary purpose (or reference product). To put it another way, by enhancing the co-product system in the most likely other method of independently generating the co-product (System 2). In order to isolate the impacts in System 1, the impacts arising from the alternate method of manufacturing the co-product (System 2) are then deducted from the deciding product (Hauschild et al 2018). 3. Allocation (or partitioning) based on Physical Relationship – this approach aims to separate inputs and outputs and distribute them based on the physical connections between the products (such as mass, energy use, etc.) (Hauschild et al 2018; Matthews et al 2014).

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4. Allocation (or split) based on Other Relationship (non-Physical) – this approach aims to separate inputs and outputs and assign them in accordance with non-physical relationships (such as economic worth) (Hauschild et al 2018; Matthews et al 2014). Modeling waste treatment systems presents a number of issues because most processes are multifunctional, i.e., they manage waste while also generating products like heat, energy, biogas, and fertilizer. As a result, each of these services must share in the facility’s resource use and emissions. The responsibilities for a multifunctional process must be distributed among the many services offered by the waste treatment facility. For instance, an incineration plant’s environmental effects must be shared with the production of heat and electricity, but a recycling plant’s environmental costs must be shared with the production of secondary materials like paper, plastic, glass, and metals. The distribution of flows, including discharges to the air, water, and land, is a particularly delicate stage in this computation process. The majority of the technical systems in use today produce many products. As a result, it’s frequently necessary to divide out the various products’ material and energy flows, environmental discharges, and process-related flows. In a multifunctional system, allocation is an alternative of dividing environmental burdens. The environmental burdens of a system’s inputs and outputs are divided among its co-products through allocation. The two most popular criteria for allocation are physical (mass, volume, energy, etc.) and economic. Allocation can be based on other factors as well. The burdens of the transportation should be distributed in relation to the bulk or volume of each product in the truck, for instance, when considering the transportation of a specific waste flow, such as plastic collected along with other waste products. Similar to this, a combined heat and power incineration plant may divide the costs of electricity and heat by utilizing energy or product energy as the criterion. The system under study is frequently multi-functional, which means that the processes result in more than one useful output (product or service). 3.3.2.8 Documentation of Data This is the explicit recording of the individual flows (inputs and outputs) employed in the study. This is required because most assessments do not take into account all of a product system’s inputs and outputs, and it gives the audience a clear depiction of the chosen data. Additionally, it makes clear the rationale for the selection of the system boundary, product system, functional unit, etc. (Matthews et al 2014).

3.3.3 LIFE CYCLE INVENTORY (LCI) An inventory of flows from and to nature (ecosphere) for a product system is created as part of a LCI analysis. Quantifying the raw material and energy needs, air emissions, land emissions, water emissions, resource usage, and other releases during the course of a product or process is what this method entails (USEPA 2006). It entails gathering information about the operations taking place within the system’s boundaries and calculating inputs and outputs in reference to functional units. It is frequently advised to begin developing the inventory with a flow model of the technical system utilizing information on the inputs and outputs of the product system. In general, the more intricate and thorough the flow diagram, the more precise the research and outcomes (USEPA 2006). For all actions taking place within the system boundaries, including those from the supply chain, the input and output data required for the model’s building is gathered (Hauschild et al 2018). The methods listed below should be employed to document an LCI in accordance with ISO 14044: 1. Setting up data collection based on the goal and scope 2. Data collection

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3. 4. 5. 6. 7.

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Data validation (even if utilizing data from another work) Data allocation (if needed) Relating data to Unit Process Correlating data with the functional unit Aggregation of data (Matthews et al 2014)

The data must be related to the functional unit, goal, and scope, as stated in the ISO 14044 standard. On-site data collection typically involves the use of questionnaires, which may even be given to the relevant manufacturer or business to complete. The following items may be listed on the questionnaire: “Product for Data Collection,” “Data Collector and Date,” “Period of Data Collection,” “Detailed Explanation of the Process,” “Inputs,” “Outputs,” “Emissions to Air, Water, and Land,” and “Quantity and Quality of Each Input and Output” (Lee and Inaba 2004). The amount of each product, pollutant, resource, etc. must be measured consistently throughout the LCA for all unit operations. Energy, raw materials, auxiliary inputs, co-products, waste, and emissions into the air, water, and land should all be included in the inventory. For instance, the containers used to temporarily store the disposed waste, the fuel used by the collection vehicles, the manufacture of the collection vehicles, and the emissions related to the process, such as the exhaust gases from the vehicles, should all be included in the inventory of an MSW collection scheme. The foreground data, or data that corresponds to a certain process in the modeling, is typically the focus during data gathering. The waste composition in the research area, sorting effectiveness, energy usage, collection vehicle types, or emissions from a particular plant could all be in the foreground in a waste management LCA. Background data, on the other hand, refers to details for general materials, energy, transportation, and waste management systems, and these are often available in books and databases.

3.3.4 LIFE CYCLE IMPACT ASSESSMENT (LCIA) Life cycle impact assessment (LCIA) follows life cycle inventory analysis. The purpose of this LCA phase is to assess the potential effects of the LCI‘s identified elementary flows on the environment and human health. LCIA offers a summary of the impact categories that were chosen as areas of interest for the study, along with the technique that was chosen to determine each impact category’s influence. According to Hauschild et al (2018) and Matthews et al (2014), environmental effect scores are created by converting LCI data into categories like human toxicity, smog, global warming, and eutrophication (ISO 14044:2006). Since the primary examination of the effect categories is covered in the study’s LCIA phase, just an overview of each category needs to be supplied as part of the scope. The inputs and outputs acquired during the inventory analysis are used in this step of the scope study to determine the environmental impacts. The inventory analysis offers a detailed description of the various resources consumed and the emissions into the air, water, and land compartments, which must be converted into units that reflect the environmental impacts, such as global warming, acidification, eutrophication, and effects on human health. Numerous approaches exist for conducting impact assessments, and most of them compute the environmental effects at the middle or end of the impact chain. These methodologies take affects into account in varying degrees of depth. A midpoint indicator assesses the affects earlier in the cause-effect chain, whereas an end-point indicator shows the environmental impact at the end of the chain. For instance, the release of nitrogen compounds and their accumulation in lakes raises the concentration of nutrients, accelerates algal development, and consequently raises the demand for oxygen (midpoint), harming freshwater species and raising the chance of their extinction (end point). In the ILCD Recommendations for Life Cycle Effect Assessment methodologies handbook, the Joint Research Centre of the European Union suggests midpoint characterization approaches for a

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TABLE 3.1 Overview of the Impact Categories as Recommended by ILCD (International Reference Life Cycle Data System) ILCD Midpoint Categories Climate change Ozone depletion Human toxicity, cancer effects Human toxicity, noncancer effects Particulate matter Ionizing radiation (human health) Ionizing radiation (ecosystems) Photochemical ozone formation Acidification Terrestrial eutrophication Freshwater eutrophication Marine eutrophication Freshwater ecotoxicity Water resource depletion Landuse Mineral, fossil fuels, and renewable resource depletion

number of impact categories (Chomkhamsri et al 2011). The ILCD Life Cycle Impact Assessment methods’ recommended impact categories are listed in Table 3.1. As a result, life cycle impacts can also be divided into the many stages of a product’s conception, production, usage, and disposal. These effects generally fall under three categories: beginning, use, and end of life. Raw material extraction, manufacture (converting raw materials into a product), transportation of the product to a market or site, construction and installation, and the start of usage or occupancy are some of the first impacts. Demolition and the processing of waste or recyclable materials are examples of end-of-life consequences (USEPA 2006: Sustainable Management of Construction and Demolition Materials).

3.3.5 INTERPRETATION A systematic method for identifying, quantifying, verifying, and evaluating data from the outcomes of the life cycle impact assessment and/or LCI is known as “life cycle interpretation.” During the interpretation phase, the outcomes of the inventory analysis and impact assessment are condensed. The results and suggestions for the study are the result of the interpretation phase. ISO 14043 (ISO 2006; Lee and Inaba 2004) states that the following should be included in the interpretation: • Identifying important issues based on LCI and LCIA results • Evaluating the study for completeness, sensitivity, and consistency • Conclusions, constraints, and recommendations Life cycle interpretation determines the confidence level in final outcomes and communicates them in a fair, full, and accurate manner. Interpretation begins with establishing the correctness and relevance of the results. This involves identifying the data elements that contribute significantly to each impact category, evaluating their sensitivity, assessing the study’s completeness and

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FIGURE 3.6 System boundary of food waste valorization LCA. Source: Lam et al (2018).

consistency, and drawing conclusions and recommendations based on a clear understanding of how the LCA was conducted and the results were developed (Lee and Inaba, 2004; Hauschild et al 2018). The interpretation process comprises identifying significant results based on the inventory and impact assessment analysis, evaluating data quality, limitations, conclusions, and suggestions. Several studies have investigated the environmental feasibility of biomass waste conversions using LCA. One case study on food waste valorization to value-added goods is also discussed: Renewable biomass is a great carbon source with high carbohydrate, lignocellulose, and fatty acid content (van Putten et al 2013). Food waste can replace fossil-derived feedstocks to produce value-added compounds such hydroxyl methyl furfural (HMF), but their environmental performance has not been studied, hampering informed decision making. Lam et al (2018) used LCA to examine the environmental performance of eight food waste valorization scenarios with varied solvents, catalysts, and experimental circumstances to determine the most environmentally beneficial food waste valorization alternative to create HMF (Figure 3.6). Environmental consequences of water solvent, organic co-solvents, metal catalysts, reaction temperature, and time were calculated. The LCI was prepared using experimental data. The conversion of bread waste utilizing water-acetone medium with the catalyst aluminum chloride (AlCl3), at 140°C for 30 min, was proven to be the most ecologically friendly food waste valorization method, due to the use of less polluting co-solvent (acetone) and catalyst (aluminum chloride) as well as the comparatively high yield of HMF (27.9 C mol%). When large-scale valorization systems mature and more information is available, the decision-supporting tool could be expanded to (1) evaluate pilot-scale and industrial-scale food waste valorization for HMF synthesis and (2) include the economic performance of the scenarios to provide more comprehensive results to aid decision making. Composting is another well-known illustration of managing renewable solid waste. Organic substrates undergo a biological, aerobic process called composting during which they break down and settle, producing a material with land-use potential. Composting can be done in a variety of settings, including residences, fields, and centralized facilities. The environmental performance of a particular composting technique will primarily be influenced by the technology itself, the waste’s makeup, and how the process is carried out. The waste composition and decomposition, as well as the stabilization rates of the material that enters the system, are some crucial inventory components of the LCA. Additionally, the LCA must take waste distribution, collection, and composting into account. The facility’s air emissions of methane, carbon dioxide, and ammonia are the focus of the LCAs for composting (Figure 3.5).

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Methane emission is minimal when a composting process is effectively run, that is, when aerobic conditions are preserved. However, if anaerobic conditions develop during the composting process, methane and hydrogen sulfide emissions may be generated. Nitrous oxide (N2O) and ammonia are two additional usual air pollutants from the composting process. If it is of sufficient quality, the composting process’ output provides useful qualities that can be applied to soil. In addition to improving soil structure and microbial activity, it can offer nutrients. Composting has the advantage of requiring less mineral fertilizer, and in this instance, the substitution rate should be determined by the amount of nutrients present in the compost, which are frequently nitrogen, phosphorus, and potassium. Compost can serve as a substitute for peat in soil conditioning, according to some study. The analysis by Laurent et al (2014) of LCA data from high-quality studies examining the treatment of plastic, paper, organic, and mixed household waste fractions with various waste treatment technologies revealed no obvious agreement, save for the poor environmental performance of landfilling. Inconsistent generalization of LCA conclusions, as attempted in past research and symbolized by the waste hierarchy, is impeded by the strong dependence of each solid waste management system on its context or local particulars. Such generalizations can be deceptive and obscure the real contribution of LCA to solid waste management, which is a comprehensive understanding of the solid waste management system that identifies significant environmental issues and suggests options for improvement to decision makers. Stakeholders in solid waste management should apply LCA to construct “context-specific waste hierarchy” commensurate with the local conditions of each solid waste management system.

3.4 CONCLUSION Waste composition, sorting efficiencies, and system technology influence LCA modeling of waste management systems. Extrapolating data to different regions is risky. Recycling and thermal treatment are less detrimental to the environment than landfilling for paper and plastic waste, according to most research. The data also demonstrate that there is no consensus regarding which technologies have the lowest environmental implications for any waste fraction, except for landfilling, which has the worst performance for all materials in most studies. This illustrates that regional variables have an essential impact and extrapolations must be done with caution, proving that LCA is a useful tool for guiding authorities to make better environmental decisions. LCA information is often combined with economic feasibility or social elements to enhance policy or commercial decision making. Methodological decisions affect LCA outcomes. The LCA report must explicitly define assumptions, constraints, and uncertainties and test uncertain data. For each unit process, the materials, energy, emissions, products, and wastes are mapped. A comprehensive method and systematic approach identifies environmental hotspots which further helps compare the environmental implications of different choices and uncover areas for improvement.

REFERENCES Bernstad, A. and la Cour Jansen, J., 2012. Review of comparative LCAs of food waste management systems–current status and potential improvements. Waste Management, 32(12), pp. 2439–2455. Björklund, A., Finnveden, G. and Roth, L., 2010. Application of LCA to waste management. In: Christensen, T.H. (Ed.), Solid waste technology and management. Blackwell Publishing Ltd., Chichester, UK. pp. 137–160. Chomkhamsri, K., Wolf, M.A. and Pant, R., 2011. International reference life cycle data system (ILCD) handbook: Review schemes for life cycle assessment. Towards life cycle sustainability management, pp. 107–117. Christiansen, K., Hoffman, L., Virtanen, Y., Juntilla, V., Rønning, A., Ekvall, T. and Finnveden, G., 1995. Nordic guidelines on life-cycle assessment. Nordic Council of Ministers.

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Cleary, J., 2009. Life cycle assessments of municipal solid waste management systems: A comparative analysis of selected peer-reviewed literature. Environment International, 35(8), pp. 1256–1266. Commission of the European Communities. Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions. Taking sustainable use of resources forward: a thematic strategy on the prevention and recycling of waste. COM (2005) 666 final. Brussel, BE: Commission of the European Communities; 2005. Commission of the European Communities. Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions. Thematic strategy on the sustainable use of natural resources. COM(2005) 670 final. Brussel, BE: Commission of the European Communities; 2005 < http://eur-lex.europa.eu/LexUriServ/ LexUriServ.do?uri = COM:2005:0670:FIN:EN:PDF>. Commission of the European Communities. Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions. Public procurement for a better environment. COM(2008) 400/2. Brussel, BE: Commission of the European Communities; 2008. http://ec.europa.eu/environment/gpp/pdf/com_2008_400.pdf. Commission of the European Communities. Green paper on Integrated Product Policy. COM(2001) 68 final. Commission of the European Communities, Brussel, BE (2001). < http://eur-lex.europa.eu/LexUriServ/ site/en/com/2001/com2001_0068en01.pdf>. Commission of the European Communities. Proposal for a Regulation of the European Parliament and of the Council on a Community Ecolabel scheme (presented by the Commission). COM (2008) 401/3. 2008/ xxx (COD). Brussel, BE: Commission of the European Communities; 2008. http://ec.europa.eu/ environment/ecolabel/pdf/com_2008_401.pdf. Consoli, F., 1993. Guidelines for life-cycle assessment. A code of practice. Directive 2005/32/EC of the European Parliament and of the Council of 6 July 2005 establishing a framework for the setting of ecodesign requirements for energy-using products and amending Council Directive 92/ 42/EEC and Directives 96/57/EC and 2000/55/EC of the European Parliament and of the Council, 2005. < http://ec.europa.eu/enterprise/eco_design/directive_2005_32.pdf>. Finnveden, G., Hauschild, M.Z., Ekvall, T., Guinée, J., Heijungs, R., Hellweg, S., Koehler, A., Pennington, D. and Suh, S., 2009. Recent developments in life cycle assessment. Journal of Environmental Management, 91(1), pp. 1–21. Gentil, E.C., Damgaard, A., Hauschild, M., Finnveden, G., Eriksson, O., Thorneloe, S., Kaplan, P.O., Barlaz, M., Muller, O., Matsui, Y. and Ii, R., 2010. Models for waste life cycle assessment: Review of technical assumptions. Waste Management, 30(12), pp. 2636–2648. Güereca, L.P., Gassó, S., Baldasano, J.M. and Jiménez-Guerrero, P., 2006. Life cycle assessment of two biowaste management systems for Barcelona, Spain. Resources, Conservation and Recycling, 49(1), pp. 32–48. Guinée, J.B. and Lindeijer, E. eds., 2002. Handbook on life cycle assessment: operational guide to the ISO standards (Vol. 7). Springer Science and Business Media. Hauschild, M.Z., 2018. Introduction to LCA methodology. In Life cycle assessment (pp. 59–66). Springer, Cham. International Organization for Standardization, ISO, I., 2006. ISO 14040 international standard. Environmental Management-Life Cycle Assessment-Principles and Framework. International Organisation for Standardization. International Standard Organization (ISO) (2006). ISO 14040: Environmental management— Life cycle assessment, Principles and framework (Report). Geneve, CH: UNI EN ISO 14040. Environmental management—life cycle assessment—principles and framework, 2006. < www.iso.org>. ISO 14040, 2006. ISO 14040: 2006/AMD 1: 2020: Environmental management–Life cycle assessment–Principles and framework–Amendment 1. Jensen, A.A., Elkington, J., Christiansen, K., Hoffmann, L., Moller, B.T. and Schmidt, A., 1997. Life Cycle Assessment (LCA): A Guide to Approaches. Experiences and Information Sources, (6). Karka, P., Papadokonstantakis, S. and Kokossis, A., 2017. Cradle-to-gate assessment of environmental impacts for a broad set of biomass-to-product process chains. The International Journal of Life Cycle Assessment, 22(9), pp. 1418–1440. Lam, C.M., Iris, K.M., Hsu, S.C. and Tsang, D.C., 2018. Life-cycle assessment on food waste valorisation to value-added products. Journal of Cleaner Production, 199, pp. 840–848. Laurent, A., Bakas, I., Clavreul, J., Bernstad, A., Niero, M., Gentil, E., Hauschild, M.Z. and Christensen, T.H., 2014. Review of LCA studies of solid waste management systems–Part I: Lessons learned and perspectives. Waste Management, 34(3), pp. 573–588.

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Lazarevic, D., Aoustin, E., Buclet, N. and Brandt, N., 2010. Plastic waste management in the context of a European recycling society: Comparing results and uncertainties in a life cycle perspective. Resources, Conservation and Recycling, 55(2), pp. 246–259. Lee, K.M. and Inaba, A., 2004. Life cycle assessment: best practices of ISO 14040 series. Center for Ecodesign and LCA (CEL), Ajou University. Mali, S.T. and Patil, S.S., 2016, November. Life-cycle assessment of municipal solid waste management. In Proceedings of the Institution of Civil Engineers-Waste and Resource Management (Vol. 169, No. 4, pp. 181–190). Thomas Telford Ltd. Matthews, H.S., Hendrickson, C.T. and Matthews, D., 2014. Life cycle assessment: quantitative approaches for decisions that matter. Open access textbook. pp. 174–186. Mendes, M.R., Aramaki, T. and Hanaki, K., 2004. Comparison of the environmental impact of incineration and landfilling in São Paulo City as determined by LCA. Resources, Conservation and Recycling, 41(1), pp. 47–63. Michaud, J.C., Farrant, L., Jan, O., Kjær, B. and Bakas, I., 2010. Environmental benefits of recycling. Waste and Resources Action Programme-WRAP, Oxon. Morris, J., Matthews, H.S. and Morawski, C., 2013. Review and meta-analysis of 82 studies on end-of-life management methods for source separated organics. Waste Management, 33(3), pp. 545–551. Rebitzer, G., Ekvall, T., Frischknecht, R., Hunkeler, D., Norris, G., Rydberg, T., Schmidt, W.P., Suh, S., Weidema, B.P. and Pennington, D.W., 2004. Life cycle assessment: Part 1: Framework, goal and scope definition, inventory analysis, and applications. Environment International, 30(5), pp. 701–720. Scientific Applications International Corporation (SAIC), Curran, M.A., National Risk Management Research Laboratory (US) and Office of Research and Development, Environmental Protection Agency, United States, 2006. Life-cycle assessment: principles and practice. UNI EN ISO 14044, ISO, 2006. 14040. Environmental management—life cycle assessment—principles and framework, pp. 235–248. USEPA, 2006. Life Cycle Assessment: Principles and Practice. U.S. Environmental Protection Agency, Cincinnati, Ohio. 2006. pp. 3–9. van Putten, R.J., Van Der Waal, J.C., De Jong, E.D., Rasrendra, C.B., Heeres, H.J. and de Vries, J.G., 2013. Hydroxymethylfurfural, a versatile platform chemical made from renewable resources. Chemical Reviews, 113(3), pp. 1499–1597. Villanueva, A. and Wenzel, H., 2007. Paper waste–recycling, incineration or landfilling? A review of existing life cycle assessments. Waste Management, 27(8), pp. S29–S46. Winkler, J. and Bilitewski, B., 2007. Comparative evaluation of life cycle assessment models for solid waste management. Waste Management, 27(8), pp. 1021–1031. Woon, K.S., Lo, I.M., Chiu, S.L. and Yan, D.Y., 2016. Environmental assessment of food waste valorization in producing biogas for various types of energy use based on LCA approach. Waste Management, 50, pp. 290–299.

Part II Green Technologies for Wealth Generation

4

Bioremediation

4.1 INTRODUCTION The ecological equilibrium is now seriously threatened by the rapid industrialization, technological development, and unchecked urbanization. Every element of the environment, including the land, water, and air, is being contaminated by vast quantities of harmful chemicals. A wide range of pollutants, such as industrial and pharmaceutical waste, chemical industry acids and bases, fertilizers, pesticides used in agriculture, textile industry dyes, electroplating wastes, heavy metals (As, Hg, etc.), are regularly released in water bodies without being treated beforehand (Chandra and Kumar 2017a; Chandra et al 2017a; Tomei and Daugulis 2013). Finally, these toxicants infiltrate the food chain and damage every aspect of the environment. Both organic and inorganic contaminants that are found in soil (solid substrate), water (liquid substrate), or the air can be treated using a variety of physicochemical techniques (Raskin et al 1994; Salt et al 1998). These conventional soil remediation methods destroy biological activity, including beneficial microbes that fix nitrogen, mycorrhiza, fungus, and animals during the decontamination process, rendering the area unusable for plant growth. Bioremediation decontaminates contaminated environments using microbes/plants to break down complicated contaminants into harmless or nontoxic chemical intermediates that can be used as nutrition for other plants and microorganisms (Chandra and Kumar 2015a; Kumar and Chandra 2020). Bioremediation uses microorganisms like fungi, bacteria, algae, etc. (Azubuike et al 2016; Frische 2003; Tomei and Daugulis 2013). Microorganisms are ubiquitous and have remarkable metabolic systems that enable them to break down and use different toxins as a source of energy for their growth through aerobic and anaerobic respiration, fermentation, and cometabolism. Plant growth-promoting rhizobacteria (PGPR) have evolved multiple ways by which they can immobilize, mobilize, or convert metals, rendering them inactive to endure the intake of heavy metal ions. This allows them to survive in metal-stressed environments. (1) One of these mechanisms is exclusion, which prevents the metal ions from reaching the target locations, (2) extrusion – through chromosomal/plasmid-mediated processes, the metals are forced out of the cell, (3) compliant metals combine with other cell components or metal-binding proteins, such as metallothioneins, a low-molecular-weight protein (Kao et al 2006; Umrania 2006), (4) biotransformation, which involves reducing harmful metal to less hazardous ones, and (5) methylation and demethylation. Bioremediation is the process of removing contaminants directly using living creatures like plants, bacteria, fungi, algae, and other microorganisms. Since bioremediation doesn’t employ any poisonous, volatile, or dangerous chemicals, it has the advantage of being ecologically viable and sustainable (Irankhah et al 2019). Utilizing bioactive molecules like catalytic enzymes, bioremediation breaks down complex organic contaminants into harmless byproducts. By exploiting their metabolic pathways, bacteria and fungi that have been isolated from contaminated locations remediated the contaminants (Shishir and Mahbub 2019). Applying the bioremediation technique can successfully remove almost all types of pollutants, including simple inorganic pollutants, heavy metals, complex aromatic hydrocarbons, synthetic colors, surfactants, pesticides, medicines, and nitroaromatic pollutants (Rampazzo et al 2018). Due to the use of natural resources, costeffectiveness is another important advantage of this procedure. Compared to other systems, this process uses less energy and requires less manual control. The ability of a microbial population to break down contaminants, the bioavailability of contaminants to microbes, and environmental factors like temperature, pH, nutrients (organic and DOI: 10.1201/9781003279136-6

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Ex-situ bioremediation

Landfarming

In-situ bioremediation

Biopiling Composting

Natural attenuation

Enhanced

Bioventing

Bioaugmentation

Phytoremediation

Biostimulation

Mycoremediation

FIGURE 4.1 Different approaches for bioremediation of contaminants.

inorganic and their availability), electron acceptor(s), redox potential, water activity, osmotic pressure, and contaminant concentration all play a role in bioremediation (Thakur 2004). Numerous enzymatic processes that bacteria use to alter specific metal species include oxidation, reduction, methylation, and alkylation. Other biological reactions that produce less toxic metal species can be used in bioremediation in addition to the enzymatic transformations that result in metal precipitation and immobilization. The elements for which these reactions have been most thoroughly researched are mercury and arsenic. By producing siderophores, some bacteria, such as Ralstonia metallidurans CH34, can solubilize metals in soil and adsorb them into their biomass (Diels et al 1999). The surface-active chemical species known as biosurfactants are produced by bacteria or fungus and can help with the solubilization and desorption of metals from contaminated sediments or soils. These compounds are less toxic than synthetic surfactants, biodegradable, and have good surface characteristics (Desai and Banat 1997). Pseudomonas aeruginosa produces rhamnolipids, which have undergone substantial research and are now commercially available (Reis et al 2011). The numerous bioremediation techniques covered in this chapter include phytoremediation, mycoremediation, biosparging, bioventing, biostimulation, bioaugmentation, and natural attenuation. On either aerobic or anaerobic biotransformation processes, various strategies are involved. Figure 4.1 depicts a brief description of various bioremediation techniques for common hazardous pollutants.

4.2 CLASSIFICATION OF BIOREMEDIATION Depending on the type of contaminants and the availability of bioremediate, various techniques are used. Bioremediation is broadly categorized into two types: in-situ and ex-situ bioremediation, depending on the place to be cleaned up. Ex-situ bioremediation is performed at sites other than native sites, whereas in-situ bioremediation is performed at the native (niche) site of pollution (Azubuike et al 2016).

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4.2.1 EX-SITU BIOREMEDIATION The contaminated soil on the site must be removed or excavated in order to be treated, and the treated soil must be brought back to the original location. The traditional ex-situ remediation techniques involve excavating the polluted soils, detoxifying and/or destroying the contaminants chemically or physically. As a result, the contaminants go through stabilization, solidification, immobilization, combustion, or destruction. However, in the case of ex-situ bioremediation, living entities are given the optimal environmental circumstances in order to increase their activity of completely oxidizing contaminants. The water is removed from the mixture when the degradation of the contaminants is finished, and the decontaminated soil is then separated. Solid-phase bioremediation is the second method of ex-situ bioremediation. This type of remediation includes additional techniques like composting, biopiling, and landfarming (Gomes et al 2013). For the full mineralization and degradation of pollutants, all of the aforementioned procedures guarantee the continuous and accurate monitoring of oxygen (aeration) and a sufficient supply of nutrients. This can be further classified into the following categories. 4.2.1.1 Landfarming For soils with petroleum compounds, landfarming, often referred to as land treatment or land application, is an aboveground bioremediation method. When using this approach, excavated contaminated soils are often placed in a thin layer on the ground surface, and aerobic microbial activity is then stimulated inside the soils by aeration and/or the addition of minerals, nutrients, and moisture. Through microbial respiration, the increased microbial activity causes the components of adsorbed petroleum products to degrade. In order to safeguard both public health and the environment, this technology relies on the use of agricultural practices and soil microorganisms in an aerobic environment to reduce soil contamination and the risk of public exposure through processes of transformation, immobilization, and detoxication. By achieving the recycling of organic carbon and nutrients within the biosphere and maintaining the fundamental soil properties required to promote plant growth (forestation, vegetation, etc.), landfarming technology helps to ensure the sustainability of natural resources. The effective treatment of soil contamination by microorganisms in a soil farm environment is essential for the success of landfarming technologies. 4.2.1.2 Compositing In a controlled biological process called composting, microbes convert organic pollutants into safe, stabilized byproducts under aerobic and anaerobic circumstances. Which requires the excavation of contaminated soil and the use of bulking agents and organic amendments like wood chips, hay, manure, and vegetal wastes (like potato). The right choice of amendments ensures proper porosity (for the supply of oxygen, moisture, and nutrients) and provides a balance of nitrogen and carbon (appropriate nutrients) to support the best possible microbial activity. For soil polluted with dangerous organic pollutants to compost correctly, temperatures between 55 ‒ 65°C must be maintained. When waste is degraded, bacteria release heat and raise the temperature, which increases waste solubility and metabolic activity in composts. Maximum degrading efficiency is obtained by maintaining oxygenation (e.g., daily windrow turning), irrigation as required, and meticulous temperature and moisture content monitoring. The two most popular methods of composting are windrow composting and aerated static pile composting, which involves forming compost into long piles (windrows) and aerating them using blowers or vacuum pumps on a regular basis. The most economical method of composting, windrow composting, may also produce the highest levels of fugitive emissions. The procedure is frequently used on sediments from lagoons and soils that have been contaminated with biodegradable organic substances. Explosives (TNT, RDX, and HMX) and PAH-contaminants can be safely reduced in concentration and toxicity through aerobic composting (at temperatures 93% contaminant elimination after 7 months. The removal of diesel from clayey soil was not significantly affected by airflow intensities or airflow intervals, suggesting that longer air injection intervals and low air injection rates may be more cost-effective for bioventing in diesel-polluted clayey soil (Thomé et al 2014). Rayner et al (2007) found that in a sub-Antarctic hydrocarbon-polluted site, singlewell bioventing was ineffective due to a shallow water table and thin soil cover, which led to channel development. However, microbioventing using nine small injection rods (0.5 m apart) removed a considerable amount of hydrocarbons due to more uniform distribution of oxygen. It becomes clear that even while airflow rates and air intervals are among the fundamental components of bioventing, the effectiveness of bioventing-based bioremediation depends on the quantity of air injection points, which aids in achieving uniform air distribution. Although the purpose of bioventing is to promote aeration in unsaturated zones, it can also be utilized for anaerobic bioremediation, particularly for the treatment of vadose zones contaminated with chlorinated chemicals that are resistant to aerobic treatment. In this latter method, hydrogen serves as an electron donor and a mixture of nitrogen, low amounts of carbon dioxide, and hydrogen can also be added in place of air or pure oxygen to reduce chlorinated vapor (Shah et al 2001; Mihopoulos et al 2000, 2002). Pure oxygen injection may result in a higher oxygen concentration in a low-permeability soil than air injection. Additionally, ozonation may help hasten biodegradation by partially oxidizing refractory substances (Philp and Atlas 2005). Contrary to bioventing, which increases microbial degradation at the vadose zone with modest air injection (Magalhães et al 2009), soil vapor extraction (SVE) maximizes volatile organic compound volatilization through vapor extraction. SVE has a higher airflow rate than bioventing does (Baker and Moore 2000). Due to its mechanism for removing pollutants, SVE may be considered a physical approach of remediation; nevertheless, the mechanisms used by both strategies for removing pollutants are not mutually exclusive. Due to additional environmental conditions and unique properties of the unsaturated zone to which air is pumped, getting equivalent findings acquired during laboratory studies is not always possible during on-site field testing; as a result, with bioventing, treatment duration may be extended. It appears that high airflow rates cause volatile organic chemicals to move from the soil to the vapor phase, necessitating off-gas treatment of the resultant gases before discharge into the atmosphere (Burgess et al 2001). Combining bioventing and biotrickling filter techniques can tackle this particular problem by lowering the levels of outlet gas emissions and contaminants, which will shorten the lengthy treatment time required by bioventing alone (Magalhães et al 2009). 4.2.2.2 Bioslurping This method combines SVE, bioventing, and vacuum-enhanced pumping to remediate soil and groundwater by indirectly supplying oxygen and encouraging pollutant biodegradation (Gidarakos and Aivalioti 2007). The method is made to recover free products such as light non-aqueous phase liquids (LNAPLs), which can be used to remediate saturated, unsaturated, and capillary zones. Additionally, it can be used to clean up soils that have been contaminated with organic volatile and semi-volatile substances. The device employs a “slurp” that extends into the free product layer and takes up liquids (free products and soil gas) from this layer similarly to how a straw draws liquid from any vessel. LNAPLs are propelled upward to the surface by the pumping mechanism, where they are separated from water and air. Once all free products have been removed, the system

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can easily be configured to function as a standard bioventing system to finish the remediation process (Kim et al 2014). In this method, too much soil moisture restricts air permeability and slows the pace at which oxygen is transferred, which in turn lowers microbial activity. The technique saves money because it produces less groundwater as a result of the operation, which reduces the expenses associated with storage, treatment, and disposal even though it is not ideal for remediating soil with low permeability (Philp and Atlas 2005). One of the main issues with this particular in-situ technique is creating a vacuum on a deep, highly permeable site and variable water table, which could lead to saturated soil lenses that are challenging to aerate. 4.2.2.3 Biosparging To raise groundwater oxygen concentrations and speed up the biological breakdown of pollutants by naturally occurring microorganisms, air under pressure is injected below the water table. Through biosparging, the saturated zone’s mixing is increased, resulting in more groundwater and soil interaction. Underground storage tank locations can reduce petroleum products by using biosparging. Mid-weight petroleum liquids, like diesel and jet fuel, are the ones that biosparging is most commonly used for; lighter petroleum compounds, like gasoline, tend to volatilize more easily and be removed more quickly via air sparging. In this method, which is very similar to bioventing, air is injected beneath the soil’s surface to encourage microbial activity and aid in the removal of pollutants from polluted regions. Contrary to bioventing, air is pumped at the saturated zone, which might transfer volatile organic molecules upward to the unsaturated zone to encourage biodegradation. The soil permeability, which affects the pollutant’s bioavailability to microorganisms, and the pollutant’s biodegradability are the two main parameters that influence how effective biosparging is (Philp and Atlas 2005). Similar to SVE and bioventing, in-situ air sparging (IAS) is a closely related approach that uses high airflow rates to produce pollutant volatilization while biosparging encourages biodegradation. Diesel and kerosene contamination of aquifers has been successfully treated by biosparging in many cases. According to Kao et al (2008), biosparging of a benzene, toluene, ethylbenzene, and xylene (BTEX)-contaminated aquifer plume led to a change from anaerobic to aerobic conditions, which was shown by an increase in dissolved oxygen, redox potentials, nitrate, sulfate, and total culturable heterotrophs and a decrease in dissolved. A further indication that biosparging can be utilized to clean up BTEX-contaminated groundwater is the overall decline in BTEX reduction (>70%). The main drawback, though, is determining the airflow’s direction. 4.2.2.4 Bioaugmentation In order to clean contaminated soil or water, bioaugmentation entails the introduction of a collection of naturally occurring microbial strains with exceptional efficacy or a genetically modified strain. By adding microorganisms that break down pollutants, this strategy aims to increase the degree or rate of degradation of complex contaminants (Adams et al 2015). In addition to improving the removal of pollutants from the specific location, improving the microbiota of a contaminated site also boosts the genetic potential of the intended site. Bioaugmentation employs a variety of microorganisms, including bacteria, lignolytic fungus, etc. For bioaugmentation, pure cultures, mixed cultures, and genetic components such as plasmids and genetically modified organisms are the most often utilized inocula. As a substitute for bioremediation, bioaugmentation is typically carried out in settings that are oil contaminated. Bioaugmentation is utilized to totally decompose chlorinated ethane pollutants, such as tetrachloroethylene and trichloroethylene (TCE), to harmless ethylene and chloride at locations where soil and groundwater are affected. In the augmentation of the contaminated locations, bio-augmenting microorganisms played a variety of roles, according to scientific literature. Examples are Dehalococcoides ethenogenes for the dichlorination of tetrachloroethene and Pseudomonas stutzeri for the degradation of carbon tetrachloride. Furthermore, the biodegradation process can be accelerated by using genetically modified organisms. 2,4-D, toluene, indole, mercury, and phenol are all degraded in it (Dejonghe et al 2000; Watanabe et al 2002).

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The studies carried out by Wang et al (2004) and Xu et al (2015) reported the biodegradation efficiency of Burkholderia pickettii against Quinoline. It was observed that though the indigenous organisms of the contaminated site were incapable of degrading Quinoline but these organisms in cooperation with the newly introduced Quinoline degrader Burkholderia pickettii can degrade Quinoline (concentration of 1 mg/g of soil), within 6 and 8 hours. The experiments carried out by Tchelet et al (1999) showed the efficiency and capability of β-Proteobacterium Pseudomonas sp. strain P51 to degrade chlorinated benzenes. Their results demonstrated the possibility of successful bioaugmentation by applying preselected strains to degrade poorly degradable substance like TCB in the contaminated site. 4.2.2.5 Biostimulation The most sophisticated approach of bioremediation for hydrocarbons is believed to be biostimulation, a designed remediation process. It entails adding rate-limiting nutrients to highly polluted areas, such as phosphorus, nitrogen, oxygen, and electron donors, in order to encourage the local microorganisms to break down the harmful and toxic chemicals (Tyagi et al 2011). Although there are many species in nature that can do bioremediation and be used to remove a wide variety of pollutants. But the constant availability of nutrients, electron donors, and acceptors is what allows microorganisms to degrade pollutants into benign or less hazardous forms. As a result, the pace of decontamination is greatly accelerated by the addition of rate-limiting nutrients, which also enhances the degradation capacity of the resident microbes (Adams et al 2015). The nutrients that are most frequently needed for microbial development are phosphorus and nitrogen, which are typically given as orthophosphate and ammonia, respectively. The most popular electron acceptor in bioremediation is oxygen. Petroleum hydrocarbons, sulfates, and polyester polyurethanes are the main pollutants that can be successfully remedied by biostimulation. The addition of chemical nutrients and microorganisms, either separately or in combination, kicks off the process of biostimulation. Each bacterium has a unique capacity for adsorbing substances. Physically, the bacteria cannot enter the clayey soil because of its limited permeability. As a result of the creation of cationic bridges connecting divalent metals, there is net negative surface charge on bacteria as well as on the surface of the clay. 4.2.2.6 Phytoremediation The generic name “phytoremediation” combines the Latin root remedium (to repair or eliminate an evil) with the Greek prefix phyto (plant) (Cunningham et al 1996). The term “phytoremediation” refers to the process of removing, containing, or neutralizing pollutants from soils and sludges using living plants. Based on the idea of using nature to clean up nature (UNEP), phytoremediation is an in-situ ecofriendly, solar-energy-driven remediation technology that can be used in place of mechanical conventional clean-up technologies, which frequently require high capital inputs and are labor and energy intensive. The distinguishing characteristics of plants include helping to keep toxins in their vegetative areas and remove them from the environment (Cunningham et al 1995). The primary benefit of phytoremediation is its lower costs compared to both in-situ and ex-situ traditional procedures. The plants may be easily observed, and important products may be recovered and used again. In addition, the method preserves the environment’s natural state by using naturally occurring species. Numerous studies revealed that different plant species respond differently to pollutants by accumulating, metabolizing, and extruding them to the surface (Baker et al 2000; Chandra et al 2017b). For their growth and development, plants have a built-in ability to accumulate the necessary heavy metals (Fe, Mn, Zn, Cu, Mg, Mo, and Ni) from soil or water. A few plants can also accumulate heavy metals such as Cd, Cr, Pb, Ag, As, and Hg, which have uncertain biological activities. Various strategies adopted by plants to decontaminate aquatic and terrestrial systems are presented in Table 4.1. In order to lessen the hazardous effects of pollutants, phytoremediation techniques exploit plant interactions (physical, biochemical, biological, chemical, and microbiological) in polluted areas.

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TABLE 4.1 Strategies of Phytoremediation Adopted for Removal of Varied Contaminants by Various Plants Species Application

Media

Contaminants

Typical Plants

Phytoextraction

Soil, sediments, brownfields

Metals (Pb, Cd, Zn, Ni, Cu)

Brassica juncea; Helianthus spp.; Thlaspi carulescens

Phytotransformation

Soil, groundwater, landfill leachate, land application of wastewater

Herbicides; chlorinated aliphatics (e.g., TCE); aromatics

Phreatophytic trees (Salix family, including poplar, willow, cottonwood); grasses

(e.g., BTEX); ammunition wastes (TNT, RDX, HMX, perchlorate); nutrients (nitrate, ammonium, phosphate) Metals (Pb, Cd, Zn, As, Cu, Cr, Se, U); hydrophobic organics

(rye, fescue, Bermuda grass, sorghum, switchgrass, Reed canary grass); legumes (clover, alfalfa, cowpeas) Phreatophytic trees for hydraulic control; grasses with fibrous roots for erosion control

Phytostabilization

Soils

Rhizosphere bioremediation

Soil, sediments, land application, confined disposal facilities

Biodegradable organics (BTEX, TPH, PAHs, PCBs, pesticides)

Grasses with fibrous roots (Bermuda, fescue, rye); phenolics releasers (mulberry, apple, osage orange); phreatophytic trees

Rhizofiltration

Groundwater, wastewater through constructed wetlands

Metals (Pb, Cd, Cu, Ni, Zn); radionuclides, hydrophobic organics

Aquatic plants: emergent (bullrush, cattail, coontail, pondweed, arrowroot); submergents (algae, stonewort, parrot feather, Hydrilla spp.)

Phytovolatilization

Soils and sediments

Metals (Se, As, Hg) volatile organic compounds (e.g., MTBE)

Brassica juncea; wetlands plants; phreatophytic trees for groundwater capture

Abbreviations: BTEX, benzene, toluene, ethylbenzene, and total xylene; HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7tetrazocine; MTBE, methyl-tert-butyl ether; PAHs, polycyclic aromatic hydrocarbons; PCBs, polychlorinated biphenyls; RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine; TCE, trichloroethylene; TNT, 2,4,6-trinitrotoluene; TPH, total petroleum hydrocarbons.

There are a number of mechanisms (accumulation or extraction, degradation, filtration, stabilization, and volatilization) involved in phytoremediation, depending on the pollutant type (elemental or organic). Extraction, transformation, and sequestration are the main methods used to eliminate elemental contaminants (toxic heavy metals and radionuclides). In contrast, organic pollutants (such as hydrocarbons and chlorinated chemicals) are primarily eliminated through degradation, rhizoremediation, stability, and volatilization, with the possibility of mineralization when certain plants, such as willow and alfalfa, are utilized (Meagher 2000; Kuiper et al 2004). A plant’s root system, which may be fibrous or tap-like depending on the depth of the pollutant, aboveground biomass, which shouldn’t be suitable for animal consumption, the toxicity of the pollutant to plants, the plant’s ability to survive and adapt to the environment, the plant’s growth rate, site monitoring, and most importantly the amount of time needed to reach the desired level of cleanliness are some of the key considerations. The plant should also be immune to pests and illnesses (Lee 2013). According to San Miguel et al (2013), the process of contaminant removal by plants in some contaminated environments includes uptake, which is primarily a passive process, translocation

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from roots to shoots, which is accomplished by xylem flow, and accumulation in shoot. Additionally, transpiration and the division of xylem sap between adjacent tissues are required for translocation and accumulation, respectively. Nevertheless, the procedure may vary depending on other elements including the type of contamination and the plant. The majority of plants living on any polluted site are likely effective phytoremediators. In order to maximize the remediation capacity of native plants growing in contaminated areas, either through bioaugmentation with endogenous or exogenous plant rhizobacteria or through biostimulation is essential for the success of any phytoremediation strategy. In light of the fact that PGPR tend to increase biomass output and plant tolerance to heavy metals and other unfavorable soil (edaphic) conditions, it has been suggested that PGPR utilization could be crucial in phytoremediation (de-Bashan et al 2012; Yancheshmeh et al 2011). Additionally, Brassica napus L. and Festuca ovinia L. were inoculated with exogenous PGPR during seed germination and 2 weeks after plant growth, protecting the seeds and plants from growth inhibition on heavy metal-polluted soil, according to Grobelak et al (2015). This resulted in increased plant length and root and stem growth. Similar to this, bioaugmentation with endogenous rhizobacteria led to increased plant subsurface biomass, metal buildup, and improved metal removal when Spartina maritima was used to treat metal-contaminated estuaries (Mesa et al 2015). There was a 93.5% total petroleum hydrocarbon (TPH) removal after Serratia marcescens-produced biosurfactant was added to gasoline-contaminated soil where Ludwigia octovalvis were planted. This was due to the biosurfactant’s effects on desorption and solubilization, which in turn increased the bioavailability of gasoline to microbial consortia in the L. octovalvis rhizosphere (Almansoory et al 2015). On the other hand, compared to soil that had been inoculated, Maqbool et al (2012) found that Sesbania cannabina uninoculated soil removed TPHs more quickly. This was attributed to the plant’s long, fibrous roots, which encouraged the growth of rhizobacteria and enhanced contact with the contaminant, leading to unfavorable competition in the infected plant’s rhizosphere. The natural ability of several plant species to remove organic and elemental contaminants from contaminated environments has been described (Table 4.1). Additionally reported as potential phytoremediators of heavy metal-contaminated locations are Brachiaria mutica and Zea mays (Ijaz et al 2015; Tiecher et al 2016). Several transgenic plants for increased phytoremediation with genes transferred have also been published (Ali et al 2013; Kuiper et al 2004; Wang et al 2012a, 2012b; Yavari et al 2015). Additional species with phytoremediation potential have also been comprehensively described (Lee 2013). The following paragraphs outline various phytoremediation techniques used to remove organic and inorganic contaminants from aquatic and terrestrial systems. 4.2.2.7 Phytoextraction The process of extracting chemicals from the environment and concentrating them in plant biomass is known as phytoextraction. Phytomining is the process of mining harmful substances using plants. Metal hyperaccumulator plant species are used in phytoextraction to move large amounts of metals from soils into the harvestable sections of roots and aboveground shoots (Chaney et al 1997). Until it is harvested, a living plant may continue to absorb toxins. The use of higher plants for in-situ decontamination of metal-contaminated soils, sludges, and sediments is an innovation known as phytoextraction (Wenzel and Jockwer 1999). To achieve appropriate metal extraction rates, a significant amount of biomass must be produced along with high rates of metal uptake and translocation into the shoot system. The establishment of the best agronomic management approaches and plant genetic ability are both necessary for effective phytoextraction (Gupta and Sinha 2007). After harvest, less pollutant remains in the soil, therefore the growth/harvest cycle must be performed numerous times to obtain a sufficient clean up. Phytoextraction also employs algae to remove pollutants from soils, sediments, or water. The preferred technique for isolating and removing contaminants largely from soil without compromising the structure and fertility of the soil is phytoextraction. The plant is best adapted for the clean up of diffusely polluted areas because it absorbs, concentrates, and precipitates hazardous metals and radionuclides from contaminated soils into the biomass, where toxins only occur at relatively low concentration and

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superficially (Rulkens et al 1998). Around the past 20 years or so, the use of plants for remediation has been increasingly common all over the world. In general, this method has been tried more frequently for heavy metal extraction than for organics extraction. Utilizing plants, the phytoextraction method converts pollutants from soils, sediments, or water into biomass that can be harvested from plants. Saraswat and Rai (2011) also suggested the possible application of Leucaena leucocephala for the phytoextraction of metal-contaminated sites and their fertility restoration by improving microbial functionalities, enzymatic activities, and N-pool. Assisted and natural phytoextraction are the two main types of phytoextraction. Hyperaccumulators are raised in induced or assisted phytoextraction with the goal of remediation. Hyper accumulators plants are those that have more than 1,000 mg kg−1 dry weight of Ni, Co, Cu, Cr, Pb, or more than 10,000 mg kg−1 dry weight of Zn or Mn in their tissue (Steele and Pichtel 1998). It is connected to the application of chelators to soils to promote metal solubility or mobilization for easier plant uptake. In addition to metal tolerance, hyperaccumulation is hypothesized to benefit the plant through allelopathy, defense against herbivores, or overall disease resistance (Davis et al 2001). Hyperaccumulators are those organisms that take up more pollutants from the soil than is typical. Arabidopsis thaliana, Avena strigosa, Crotalaria juncea, Eichhornia crassipes, Pistia stratiotes, Helianthus annuus, Salix viminalis, Lemna minor, Eragrostis bahiensis, Cynodon dactylon, Festuca arundinacea, Lolium perenne, Phaseolus acutifolius, Cocos nucifera, Panicum virgatum, Spirodela polyrhiza, and others are examples of hyperaccumulators. In a process known as natural phytoextraction, soil pollutants are naturally absorbed by plants. Many naturally occurring hyperaccumulators are metallophyte plants, which can withstand and incorporate significant hazardous metal concentrations (Salt et al 1995, 1998). The plants must extract significant amounts of heavy metals into their roots, translocate the heavy metals to surface biomass, and produce significant amounts of plant biomass in order for this technique to be practical. The contaminated plant biomass can be used to recycle the removed heavy metal (Brooks et al 1998). Additionally, significant factors include growth rate, element selectivity, disease resistance, and harvesting technique (Baker et al 1994; Cunningham and Ow 1996). However, the utilization of hyperaccumulator species is constrained by their slow growth, shallow root systems, low biomass production, and final disposal (Brooks 1994). A local population of Alyssum murale has been observed extracting Ni in-situ from an ultramafic location in Albania (Bani et al 2007). Extensive phytoextraction, an alternative to carefully cultivated crops in the case of phytomining, makes advantage of local populations of hyperaccumulators as well as native flora. 4.2.2.8 Phytotransformation As a direct outcome of plant catabolic and anabolic processes, environmental chemicals undergo a process known as phytotransformation. These actions result in immobilization, deterioration, or inactivation. Certain plants, like canas, metabolize organic pollutants, such as pesticides, explosives, solvents, industrial chemicals, and other xenobiotic compounds, to make them nontoxic. In other instances, these chemicals may be metabolized in soil or water by microbes that coexist with plant roots. Because plant molecules are unable to completely decompose these difficult-to-breakdown chemicals into simpler ones (such as water, carbon dioxide, etc.), the word “phytotransformation” refers to a change in chemical structure rather than a full breakdown of the substance. Given that plants behave similarly to the human liver when interacting with these xenobiotic chemicals (foreign compound/pollutant), the phrase “Green Liver Model” is used to describe phytotransformation. Plant enzymes add functional groups, like hydroxyl groups, to the xenobiotics after they have been absorbed, increasing their polarity. Phase I metabolism describes this process, which is comparable to how the human liver intensifies the polarity of medicines and foreign substances. Enzymes like Cytochrome P450s are in charge of the early responses in the human liver. Enzymes like nitroreductases perform the similar function in plants. In order to further strengthen the polarity of the polarized xenobiotic, plant biomolecules such as glucose and amino acids are added in the second stage of phytotransformation, known as Phase II metabolism (known

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as conjugation). This is akin to the activities that take place in the human liver, where reactive centers of the xenobiotic are subjected to glutathione addition reactions and glucuronidation (the addition of glucose molecules by the UGT (e.g., UGT1A1) class of enzymes). Despite numerous exceptions, phase I and phase II reactions aim to boost the polarity and lessen the toxicity of the molecules. Aqueous channels can easily carry the xenobiotic because to the enhanced polarity. Phase III metabolism, the last stage of phytotransformation, involves the sequestration of the xenobiotic inside the plant. The xenobiotics form a complex structure inside the plant after polymerizing in a lignin-like manner. This guarantees that the xenobiotic is kept safely and does not interfere with the plant’s ability to function. Preliminary research has indicated that these plants can be poisonous to small animals (like snails), thus it’s possible that plants used in phytotransformation will need to be kept in a contained enclosure. In order to sequester the xenobiotics, the plants minimize toxicity (with few exceptions) and engage in phytotransformation (Subramanian et al 2006). 4.2.2.9 Phytostabilisation Utilizing specific plants to immobilize pollutants in soil and water is known as phytostabilization. Contaminants are precipitated in the rhizosphere, adsorbed onto the roots, or absorbed and stored by roots. This lessens or even stops pollutant mobility, preventing migration into the groundwater or air, and contaminant bioavailability, preventing transmission through the food chain. On locations that have been denuded by heavy metal contamination, this approach can also be utilized to re-establish a plant community. The leaching of soil contaminants is decreased if a community of tolerant plants has been created. 4.2.2.10 Phytodegradation The breakdown of organic pollutants by internal and external metabolic processes powered by the plant is known as phytodegradation. Organic substances can undergo phytodegradation either inside the plant or in the rhizosphere. Solvents in groundwater, petroleum and aromatic compounds in soils, and volatile chemicals in the air are just a few of the many distinct substances and types of compounds that can be eliminated from the environment with this technique (Newman and Reynolds 2004). Organic molecules are hydrolyzed by ex-planta metabolic activities into smaller pieces that the plant may absorb. Plant enzymes including oxidoreductase, nitroreductase, phosphatase, and nitrilase from species like bald cypress, cherry black, live oak, yellow poplar, and river birch can absorb some toxins and subsequently break them down (Farmaki and Thomaidis 2008). The enzymes are more efficient in transforming organic pollutants because they work as strong catalysts that can significantly alter the composition and toxicity of contaminants or completely mineralize the organic molecule into less hazardous byproducts (Zawierucha and Malina 2011). The enzymes in plants degrade a variety of pollutants, including trinitrotoluene, chlorinated solvents, and the herbicide atrazine (Thompson et al 1998). TCE, a groundwater contaminant, is taken up by suspension cell cultures of hybrid poplar, as demonstrated by Shang and Gordon (2002), and then becomes a component of the non-volatile, un-extractable section of the cells. Ethylene dibromide (EDB) and TCE were shown to be very well absorbed by the tropical tree Leuceana leucocephala (Doty et al 2003). Organic acids boosted the absorption of 2,2-bis(pchlorophenyl)-1,1-dichlorethylene, according to research by White and Kottler (2002) and White et al (2003) (DDE). Methylobacterium sp. (isolated from hybrid poplar) is capable of decomposing TNT, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5tetrazocine (HMX), as demonstrated by van Aken et al (2004). This bacterium may have a significant role in the breakdown of explosive chemicals in plants. Phytodegradation is frequently used as a phytoremediation technique. Phytodegradation (also known as rhizodegradation) is the decomposition of pollutants through rhizosphere activity. Rhizobacterial nickel extraction is successful (Abou‐Shanab et al 2003). It is assisted by the presence of plant- or soil-produced proteins and enzymes. Rhizodegradation is a symbiotic

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connection in which plants feed bacteria with the nutrients they need to survive, while microbes create a healthier soil environment. Phytodegradation or rhizodegradation is the destruction of pollutants by proteins and enzymes produced by plants or by soil organisms such as bacteria, yeast, and fungi. Rhizodegradation is a symbiotic connection in which plants feed bacteria with the nutrients they need to survive, while microbes create a healthier soil environment. Longcontaminated soils may require extensive treatment (Olson et al 2007) and are less receptive to rhizodegradation than their newly polluted equivalents (Gunderson et al 2007). In order for biodegradation to be effective, it is necessary to improve bioavailability. Occasionally, the selection and creation of plant and microbial strains that affect the solubility and transport of organic contaminants by exudation of biosurfactants becomes necessary and promising (Wang et al 2007). Gene cloning of plants expressing bacterial enzymes for the degradation of organic contaminants such as PCBs would aid in boosting rhizodegradation. In addition, root-colonizing bacteria such as Pseudomonas fluorescens expressing degradative enzymes such as ortho-monooxygenase are utilized for toluene degradation (Yee et al 1998). On numerous contaminated sites in Nigeria, soils and sediments contaminated with crude oil hydrocarbons pose a significant environmental risk. Hydrocarbon-degrading microorganisms are ubiquitously distributed in soils and make up less than 1% of total microbial populations; but, in the presence of crude oil, their proportion can increase to 10% (Atlas and Bartha 1992). In hydrocarbon-contaminated soils, however, the usage of fertilizers acts as biostimulants. In the absence of an easily accessible carbon source, such as labile natural organic materials, some microorganisms are able to utilize hydrocarbon as a carbon and energy source preferentially (van Hamme et al 2003). 4.2.2.11 Phytohydraulics The method of phytohydraulics involves plants absorbing, transporting, and transpiring water from the environment to control pollutants by hydrology, but it excludes the degradation of toxins (Awasthi et al 2020). Plants are used in the hydraulic control approach to limit the buildup and transfer of dissolved metals from both underground and surface waterways. Due to the growth of the roots, phytohydraulic technology might control a broad region without any artificial system (EPA 2000). Eucalyptus, salix, and hybrid populous trees can all be grown profitably for the phytohydraulic system of metal remediation. A single salix tree may transpire up to 5000 gallons of water per day, compared to a five-year-old populus tree’s 100–200 liters per day (Adiloğlu 2018; Pivetz 2001). 4.2.2.12 Phytofiltration Metals present in the solution around plant roots undergo phytofiltration, also known as rhyzofiltration, through adsorption or precipitation onto the roots as a result of exudates (Javed et al 2019); this reduces the amount of metals that leach into groundwater (Ashraf et al 2019). It is similar to phytoextraction, but at low metal-contaminated site, plants reclaim groundwater instead of soil (Mukhopadhyay and Maiti 2010). Metal-tolerant plant species are grown in hydroponics with heavy metals-loaded water to adapt them, and subsequently on contaminated locations where the metals dissolved in water are absorbed by roots, which are then collected once saturated with toxins (Mthembu et al 2020). Rhizofiltration (using plant roots), blastofiltration (using seedlings), or caulofiltration (using shoots) are three types of phytofiltration (da Conceição Gomes et al 2016). The bioremediation method of rhizofiltration is generally utilized to remove toxins from wastewater using either aquatic or terrestrial plants. The majority of people favor plants with fibrous roots that develop quickly. The floating rafts on the ponds or tanks are part of the Rhizofiltration system’s architecture. Tobacco, rye, spinach, Indian mustard, and sunflower are among the plants commonly implemented for rhizofiltration. As heavy metals translocate to their shoots, plants with the potential for hyperaccumulation cannot be employed for this approach. Rhizofiltration has a significant maintenance demand, which includes maintaining the ideal pH of the contaminants and cultivating plants in greenhouses before moving them to remediation locations. Instead of cleaning

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up contaminated soils, rhizofiltration focuses on cleaning up polluted groundwater. Either the pollutants are absorbed by the plant roots or they are adsorbed onto the root surface. Rhizofiltration plants are first acclimated to the pollutant before being placed in place. In place of dirt, plants are hydroponically cultivated in clear water until they have acquired a substantial root system. To acclimatize the plant, the water supply is moved to a polluted water supply once a substantial root system has developed. After acclimatization, the plants are planted in the polluted area, where the roots absorb the contaminated water and its toxins. The roots are harvested and carefully disposed of as soon as they become moist. Aquatic and terrestrial fast-growing plants could be cultivated for rhizofiltration in order to extract the metals Cd, Cr, Cu, Ni, Pb, and Zn (Akpor and Muchie 2010; Ali et al 2019). Terrestrial plants are recommended for phytofiltration because they often have longer, fibrous roots (Dhanwal et al 2017). Rhizofiltration can occur in conjunction with phytoextraction, phytostabilization, or phytovolatilization processes. It is a result of physical and biochemical processes such as adsorption, precipitation, rhizodegradation, and bioaccumulation. The root’s ability to synthesize specific biochemicals, which precipitate heavy metals on plant root surfaces and cause their accumulation in the plant body, is necessary for the rhizofiltration process to function well (Chandra and Kumar 2017a, 2017b). Sunflower (Helianthus annus L.) is effective in removing Pb, U, Cs137, and Sr90, and Indian mustard (Brassica juncea Czern.) is very successful at removing Cd, Cr, Cu, Ni, Pb, and Zn (Vara Prasad and de Oliveira Freitas 2003). Saraswat and Rai (2018) also analyzed great metal rhizofilteration potential in aquatic macrophytes viz. Hydrilla verticillata and Coloasia esculenta for Zn, Cr, Cd, and Pb removal from high voluminous industrial wastewater having moderate concentration of metals. Owing to good capacity of metal accumulation and high biomass potential, these macrophytes can be employed as potential metal miners for decontamination of metal-laden wastewater. 4.2.2.13 Phytovolatilization Phytovolatilization is the process through which contaminants enter a plant and pass through its leaves to the atmosphere. Plants absorb pollutants that are water soluble and release volatile pollutants into the atmosphere, such as compounds containing mercury or arsenic. This process is known as phytovolatilization (Limmer and Burken 2016). The pollutant may change along the route as water moves through the plant’s vascular system from the roots to the leaves, evaporating, or volatilizing contaminants into the air around the plant.

4.3 FACTORS AFFECTING PHYTOREMEDIATION 4.3.1 TYPES

OF

CONTAMINANTS

Various pollutants are detected in the soil and water for degradation. It might be inorganic like heavy metals or organic like volatile as well as heavy organic molecules. Hydrophobic organic pollutants dominate. Plants quickly absorb hydrophobic organic substances (Cunningham et al 1995). While phytoremediation of inorganic pollutants is problematic as it is difficult to remove a combination of metals.

4.3.2 CONCENTRATION

OF

CONTAMINANTS

Estimating the concentration of pollutants is important since a larger concentration could endanger healthy plants’ life and harm their growth.

4.3.3 PLANT GROWTH RATE Growth rate directly correlates with phytoremediation effectiveness. Depending on the need for pollutants to be degraded, different root or plant growth rates above soil may be required. When

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considering plants with rapid growth, the amount of time needed to decompose significant amounts of heavy metals is lowered.

4.3.4 CHARACTERISTICS

OF

PLANTS

Metallophytes are plants that essentially eliminate metal pollutants. Some of the metallophytes that have undergone genetic modification are well-established and are proven to make excellent phytoremediation specimens (Chandra et al 2017b). Helianthus annuus and Nicotiana glaucum are a couple of the metallophytes that have undergone genetic manipulation (Kotrba et al 2009). Easy cultivation, quick growth, simple harvesting, widespread geographic distribution, a highly branched and developed root system, high tolerance and the potential for hyperaccumulation of heavy metals, and vulnerability to genetic modification are all qualities that heavy metal removal plants must possess.

4.3.5 ROOTS’ NATURE Plants have two different kinds of root systems: taproots and fibrous roots. While fibrous roots have subsequent branching that allows them to spread to a broader region in the soil, taproot system is a central root type that extends linearly at the bottom of the soil. Fibrous roots can therefore remove more pollutants.

4.4 BIOREMEDIATION OF VARIOUS POLLUTANTS Bioremediation technologies are effective and long-term solutions for removing contaminants from ecosystems. The plant-assisted bioremediation (PABR) technique, in particular, which relies on the synergistic effects of the plant root system and natural microorganisms (bacteria and fungi), can be successful for stabilizing, storing, and decomposing pollutants in polluted soils. Plant species can enhance biodegradation activities of native soil microorganisms in the rhizosphere by releasing root exudates. Organic additions (e.g., biochar, compost) can also be used in PABR applications to improve plant growth, soil quality, and the biodegradation of some pollutants. Furthermore, PABR technology generates biomass, a byproduct that can be effectively valorized for energy production in accordance with a circular economy. Deeper investigations into the whole processes are desirable in order to increase PABR performance and ensure its zero environmental impact. Table 4.2 enlists some of the plants having good potential to remove various inorganic toxicants via adopting varied approaches of phytoremediation.

4.4.1 ORGANIC POLLUTANTS Bioremediation can either breakdown or transform organic pollutants into less harmful forms, including pesticides, organochlorines, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), synthetic dyes, wood preservatives, munitions waste, and synthetic polymers. Bacteria, fungus, a combination of microorganisms, plants, or perhaps a combination of all of them could mediate this bioremediation. Due to their unique and significant characteristics, such as their persistence in the environment, capacity to magnify and accumulate in ecosystems, remote transportation, as well as their significant negative effects on the environment and subsequently human health, persistent organic pollutants are a group of chemicals that are of global concern (Chandra and Kumar 2015b). Common organic pollutants include xenobiotic substances such as synthetic colors, insecticides, personal care items, medications, and PAHs. There is a huge literature on the effective use of bioremediation methods for the sequestration of different organic contaminants from contaminated soil and aquatic ecosystems. Chen et al (2019) investigated how aged trash affected the biodegradation of TPHs from polluted soil in a paper. As per study,

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TABLE 4.2 Phytoremediation Potentials of Various Plants with Mechanism of Pollutant Removal Plants used

Pollutants

Pollutant Removal Mechanism

Removal

References

1700–2300 mg kg−1 Dinh et al (2018)

Noccaea caerulescens Cannabis sativa

Pb

Rhizofilteration

Cd

Phytoextraction

Ludwigia octovalvis

Gasoline

Biosurfactant enhanced rhizodegradation

93.5%

Almansoory et al (2015)

Aegiceras corniculatum Spartina maritima

Brominated diphenyl ethers (BDE-47) As, Cu, Pb, Zn

Biostimulated degradation

58.2%

Chen et al (2015)

19–65%

Mesa et al (2015)

Bioaugmented rhizoaccumulation

151 mg kg−1

Ahmad et al (2016)

Arundo donax

Cd and Zn

Rhizofiltration

100%

D reńová et al (2014)

Eichhorina crassipes Phragmites australis

Heavy metals (Fe, Zn, Cd, Cu, B, and Cr) PAHs

Rhizofiltration

99.3%

Elias et al (2014)

Rhizodegradation

58.47%

Di Gregorio et al (2014)

Plectranthus amboinicus

Pb

Rhizofiltration

Luffa acutangula

Anthracene and fluoranthene

Phytostimulation

85.9–99.5%

Somtrakoon et al (2014)

Dracaena reflexa

Diesel

Rhizodegradation

90–98%

Silene vulgaris

Hg

Phytostabilization

72–80%

Dadrasnia and Agamuthu (2013) Pérez-Sanz et al (2012)

50–100%

Ignatius et al (2014)

after 30 weeks of treatment, PAH-contaminated soil treated with aged trash had considerably lower TPH level than the control. A significant number of degradation metabolites were found in the GC-MS analysis. The PAH-contaminated soils have also been treated with bioremediation by a number of professionals (Lin et al 2016). A marine bacterium called Rhodococcus sp. P14 was employed in a novel study to biodegrade testosterone and estriol (Ye et al 2019). A short-chain dehydrogenase gene called 17-HSDx was discovered through genomic analysis to be capable of dehydrogenating both contaminants. The significance of a bioremediation technology for the elimination of harmful azo dyes has also been demonstrated. Pandey et al (2018) used Lenzites elegans WDP2 wood rot fungal culture to perform mycoremediation of textile dyes. Amazingly, clearance rates of roughly 92.77%, 21.27%, and 98.8% for brilliant green, malachite green, and Congo red were attained using the culturing broth of the chosen fungus strain. Study proved that the breakdown of synthetic colors was caused by extracellular laccase activity. On soil that had been RBBR-spiked and supplemented with rice husk as the enhancer for healthy fungal development, biodegradation studies were conducted. Within 15 days of therapy, 91% of the dye had been completely destroyed. The investigated fungal strain’s ligninolytic enzyme activity was discovered to be a key factor in the high degradation efficiency. Similarly, Brevibacterium frigoritolerans, Bacillus aerophilus, and P. fulva were used in a mixed microbial consortium by Jariyal et al (2018) to demonstrate effective remediation of an organophosphorus pesticide phorate in soil.

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4.4.2 INORGANIC POLLUTANTS Because of their high degree of water solubility and persistence in the environment, inorganic pollutants like nitrate (NO3−) and phosphate (PO4−3) are known to cause severe environmental damage. Through agricultural runoff and the effluents released by the fertilizer and pesticide industries, they enter the surface and groundwater. These common contaminants from soil and water have been treated quite successfully with bioremediation. According to a report, Ulva lactuca, a microalga, was used to eliminate nitrogenous and phosphorous contaminants from oilfield wastewater (de Oliveira et al 2016). An important study used microbial fuel cells (MFCs) containing an autotrophic denitrifying bacterial consortium to bioremediate nitrate from groundwater (Pous et al 2013). The contents of both nitrate and nitrite in the effluent were dramatically lowered by denitrifying MFC. Additionally, phosphorous compounds encourage the growth of algae in natural aquatic bodies, which results in eutrophication and anoxic conditions. Many attempts have been made to use the bioremediation strategy to address the issue of phosphate contamination. Dey et al (2020) provided evidence of the effective use of bacterial biofilm for the removal of phosphate and nitrate from rubber latex effluent. According to microscopic inspection, the biofilm that allowed the absorption of PO43− and NO3− from the wastewater was primarily composed of EPS matrix. The consortium of biofilm functioned admirably, with total nitrate and phosphate removal rates of 95% and 75%, respectively. At pH 7.0 and 37°C, the best removals of both chemicals were accomplished. In other study, Dunaliella salina, a microalgae, removed nitrates and phosphates from aqueous solutions using a number of batch adsorption techniques (Amini et al 2019). At pH 7.0, 0.05 gL−1 of microalgae biomass dose, and 350 mgL−1 of starting concentration of both pollutants, the greatest elimination (54% for nitrate and 82% for phosphate) was attained.

4.4.3 HEAVY METALS Heavy metals fall under the category of environmental contaminants because they can negatively affect humans, plants, and other ecologically important species. Agriculture, electroplating, distilleries, smelting operations, and mining are examples of anthropogenic activities that have increased the concentration of certain metals, such as Pd, Cd, Co, Cr, As, and Ni, in soil and water to dangerous levels (Chandra and Kumar, 2017a, 2017b; Pratush et al 2018). The removal of these harmful contaminants using bioremediation has proven to be an environmentally and economically sound solution. For the bioremediation of Ni(II), Zn(II), Cd(II), and Cu(II), Piccini et al (2019) tried a novel synergistic approach by using two microalgae, Chlorella vulgaris and Arthrospira platensis (Spirulina), and two macroalgae, Ulva lactuca and Sargassum muticum, as passive bioremediation agents. About 99% of all the metals under examination were eliminated by the algal consortium. San Keskin et al (2018) made an attempt to bioremediate heavy metals from wastewater by creating ultrathin electrospun fiber from cyclodextrins and encapsulating it with a living bacterial strain of Lysinibacillus sp. Additionally, plants have been successfully used to remove metal contamination from places. Using Typha latifolia and Chrysopogon zizanioides, Anning and Akoto (2018) reported chemically assisted phytoremediation of heavy metals. They investigated at how ethylene diaminetetraacetic acid (EDTA), 3 g of aluminum sulfate, and the removal effectiveness and absorption of Hg, As, Pb, Cu, and Zn affected bioaccumulation, removal efficiency, and uptake. The findings demonstrated that for all of the heavy metals, the EDTA and aluminum sulfate adjusted remediation technique demonstrated better removal efficiency than control studies. In a field experiment, Li et al (2019) investigated the effects of heavy metal contamination on the halophyte plant Halogetonglomeratus growing in saline soil. Zn had the greatest removal efficiency. According to a study, seedlings of Triarrhena sacchariflora were also used for the phytoremediation of heavy metal-contaminated wetland habitats (Xin et al 2019). In order to boost apical oxygen secretion and widen the aerenchyma, the seedlings were pre-aerated.

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It was found that this pre-aeration treatment improved Cu2+ and Cd2+ tolerance and absorption compared to the control. An extraordinary attempt was made to remove Cr, Cu, Mn, Sr, and Zn from salty soils using cotton plant (Gossypium hirsutum) (Kaur et al 2018). According to the findings, cotton plants have a lot of potential for heavy metal bioaccumulation and translocation. The wastewater that has been contaminated with heavy metals can also benefit from bioremediation. A paper looked into how well Lemna minor removed several heavy metals (HMs) from two different effluents, including Cd, Cu, Pb, and Ni (Bokhari et al 2016). The implemented plant operated admirably, and it was discovered that the removal efficiency was better than 80% for all metals, with nickel exhibiting the highest removal (99%). Furthermore, a number of macroscopic organisms, including epigeic earthworms (Eisenia foetida, Perionyx excavatus, Perionyx sansibaricus, and Eudrilus eugeniae), contribute significantly to the breakdown of biodegradable agricultural waste, animal manure, and household trash. Animal dung and crop residue are examples of agricultural waste products that are good sources of nutrients for plants. The greater concentrations of plant nutrients in the final products suggest a potential for employing agricultural wastes in sustainable crop production. Various combinations of crop residues and cattle manure were employed in vermicomposting trials to create a value-added product, i.e., vermicompost (Suthar 2007, 2009).

4.5 LIMITATION OF BIOREMEDIATION Common environmental barriers to biodegradation include the toxicity and high waste concentrations of hazardous chemical wastes. Microorganisms need the right pH balance, an adequate supply of mineral nutrients, and a temperature range between 20 and 30°C in order to grow properly. When environmental constraints are removed, the widespread distribution of microorganisms typically enables a spontaneous enrichment of the necessary bacteria. An inoculation with certain bacteria is typically neither necessary nor helpful. In addition to all of these, there are some more elements that affect bioremediation, including the solubility of waste, its origin and chemical composition, its propensity for oxidation and reduction, and interactions with microorganisms. Therefore, scientists should look for genetically distinct types of bacteria that can also thrive in slightly unfavorable conditions. Therefore, bioremediation is still seen as a developing technology to address the ongoing environmental issues that people living in a region confront on a daily basis. There is no doubt about bioremediation’s ability to preconcentrate contaminants. However, there are several drawbacks to this technique that need to be addressed. For biodegradable contaminants, bioremediation is a better use. Heavy metals are nonbiodegradable contaminants that are more difficult to remove or decompose. This method’s poor appropriateness for in-situ treatment of toxicants from soils with low permeability is a significant drawback. There are times when the partial breakdown of macromolecular contaminants results in the production of harmful byproducts that require further treatment methods. Getting the desired effects from bioremediation might often require extended periods of time (from a few weeks to months).

4.6 ROOT-ZONE TECHNOLOGY Using the root zone/rhizosphere of wetland plants or reed beds, the Root Zone Treatment System (RZTS) successfully treats domestic and industrial effluents. The phrase “Root Zone” refers to the interactions between different bacterial species, reed plant roots (helophytes), soil, sunlight, and water. Other names for this technique include “bio-filter,” “reed bed system,” and “built wetland system” (where “constructed” refers to artificial, man-made, or man-made wetlands) (Vymazal 2007). Beginning in 1952, Seidel and Kickuth’s study in Europe at the Max Planck Institute in Plan, Germany, gave rise to the Root Zone technology (Bastion and Hammer 1992). The procedure involves passing the raw effluent horizontally or vertically over a bed of soil with an impermeable

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bottom after grit or floating particles have been removed. The effluent percolates through the bed of wetland plant roots, which are all quite densely spaced out. The great majority of bacteria and fungi that live around roots use their porous membranes to absorb oxygen, which they then use to aerobically oxidize the organic stuff in the effluent. The selection of various plant species is influenced by elements like rooting depth, plant productivity, and tolerance to high wastewater loads. Canna sp., Iris spp., Cyperus sp., Juncus sp., Typha sp., Phragmites sp., Paspalum sp., and Poaceae sp., are the primary emergent macrophyte species employed in constructed wetlands in the Mediterranean countries (Vymazal 2005, 2011). Three interconnected components, reed beds, and microorganisms are crucial to the RZT system. The filter bed material, wetland plants, microorganisms, and wastewater work together to create complex physical, chemical, and biological processes that characterize the functional mechanisms in the soil matrix that are in charge of mineralizing biodegradable materials. The majority of the therapeutic procedures are based on the activity of soil-based microorganisms. The amount of microorganisms would be higher if the filter material’s grain size was smaller and, as a result, the filter bed’s internal surface was larger. Therefore, a finer bed material should have a higher efficiency. However, this process is constrained by the hydraulic characteristics of the filter bed; the finer the bed material, the lower the hydraulic load, and the greater the propensity for clogging. Therefore, the most crucial element in developing RZTS is to optimize the filter material in terms of hydraulic load and biodegradation intensity. Aerobic, anoxic, and anaerobic zones are present in RZTS. This results in the presence of numerous distinct strains of microbes, which in turn leads to the formation of a wide range of metabolic pathways. This is combined with the impacts of the rhizosphere. This explains why compounds that are challenging to handle biodegrade with high efficiency. The roots of plants, atmospheric diffusion, and, in the event of intermittent wastewater feeding, suction into the soil by the outflowing wastewater, provide the oxygen necessary for the microbial mineralization of organic materials. By establishing conditions in the rhizosphere that improve the effectiveness of microorganisms and lessen the potential of an increase in biomass to clog the pores of the bed material, the roots of plants also speed up the biodegradation process. According to the bed material’s grain size and filter thickness, the filtration process by percolation through the bed material is what reduces pathogens so effectively and makes the treated effluent appropriate for reuse. The intentional movement of wastewater through anaerobic and aerobic zones causes the conversion of nitrogen compounds (Nitrification/Denitrification). The soil’s redox potential and the availability of acceptors like iron compounds determine how much phosphorus can be reduced.

4.7 CONCLUSION AND FUTURE OUTLOOK The use of bioremediation-based strategies to reduce ubiquitous environmental pollutants has become widely accepted on a global scale. In conclusion, we discovered that the various bioremediation techniques can contribute significantly to environmental clean up. Water and soil can be cleaned of almost all toxins. It was clear from the cited literature that microbial-assisted bioremediation techniques may convert hazardous organic contaminants into less complex and harmless intermediaries. The treatment of industrial effluent was found to benefit from the technology just as much. In our opinion, if bioremediation is to be more efficient, it is necessary to minimize the significant gaps that currently exist between our knowledge of microbial ecology, physiology, genetic features, site expression, and site engineering. Recently, nanotechnology has become a powerful technology that can be used in conjunction with other technologies to enhance the effectiveness of bioremediation. The regular use of physicochemical methods of decontamination, which are typically not economical, is replaced with bioremediation as a feasible option. The presence of a particular microbial community, the bioavailability of pollutants, and environmental parameters are some of

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the variables that affect the bioremediation process (soil type, temperature, pH, nutrients, and presence of oxygen or other electron acceptors). Although inorganic pollutants (metals and radionuclides) may not be totally detoxified by bioremediation, it can change the oxidation state, which facilitates the adsorption, absorption, accumulation, and concentration of pollutants in micro- or macro-organisms. A successful bioremediation strategy will make strategic use of all local bacteria in a planned manner to obtain the highest levels of detoxification. In conclusion, bioremediation technologies have been effectively used in the field and are becoming increasingly important as the demand for environmentally acceptable remediation methods rises.

REFERENCES Abou‐Shanab, R.A., Angle, J.S., Delorme, T.A., Chaney, R.L., Van Berkum, P., Moawad, H., Ghanem, K. and Ghozlan, H.A., 2003. Rhizobacterial effects on nickel extraction from soil and uptake by Alyssum murale. New Phytologist, 158(1), pp. 219–224. Adams, G.O., Fufeyin, P.T., Okoro, S.E. and Ehinomen, I., 2015. Bioremediation, biostimulation and bioaugmention: a review. International Journal of Environmental Bioremediation and Biodegradation, 3(1), pp. 28–39. Adiloğlu, S., 2018. Heavy metal removal with phytoremediation. Advances in Bioremediation and Phytoremediation, pp. 115–126. Ahmad, R., Tehsin, Z., Malik, S.T., Asad, S.A., Shahzad, M., Bilal, M., Shah, M.M. and Khan, S.A., 2016. Phytoremediation potential of hemp (Cannabis sativa L.): Identification and characterization of heavy metals responsive genes. CLEAN–Soil, Air, Water, 44(2), pp. 195–201. Akpor, O.B. and Muchie, M. (2010). Bioremediation of polluted wastewater influent: Phosphorus and nitrogen removal. Scientific Research and Essays, 5, 3222–3230. Ali, F., Jilani, G., Fahim, R., Bai, L., Wang, C., Tian, L. and Jiang, H. (2019). Functional and structural roles of wiry and sturdy rooted emerged macrophytes root functional traits in the abatement of nutrients and metals. Journal of Environmental Management, 249, 109330. Ali, H., Khan, E. and Sajad, M.A., 2013. Phytoremediation of heavy metals—concepts and applications. Chemosphere, 91(7), pp. 869–881. Almansoory, A.F., Hasan, H.A., Idris, M., Abdullah, S.R.S. and Anuar, N., 2015. Potential application of a biosurfactant in phytoremediation technology for treatment of gasoline- contaminated soil. Ecological Engineering, 84, pp. 113–120. Amini, M., Khoei, Z.A. and Erfanifar, E., 2019. Nitrate (NO3−) and phosphate (PO43−) removal from aqueous solutions by microalgae Dunaliella salina. Biocatalysis and Agricultural Biotechnology, 19, p. 101097. Anning, A.K. and Akoto, R., 2018. Assisted phytoremediation of heavy metal contaminated soil from a mined site with Typha latifolia and Chrysopogon zizanioides. Ecotoxicology and Environmental Safety, 148, pp. 97–104. Ashraf, S., Ali, Q., Zahir, Z.A., Ashraf, S. and Asghar, H.N., 2019. Phytoremediation: Environmentally sustainable way for reclamation of heavy metal polluted soils. Ecotoxicology and Environmental Safety, 174, pp. 714–727. Atlas, R.M. and Bartha, R., 1992. Hydrocarbon biodegradation and oil spill bioremediation. In Advances in microbial ecology (pp. 287–338). Springer, Boston, MA. Awasthi, M.K., Guo, D., Awasthi, S.K., Wang, Q., Chen, H., Liu, T., Duan, Y., Soundari, P.G. and Zhang, Z., 2020. Recent advances in phytoremediation of toxic metals from contaminated sites: A road map to a safer environment. Bioremediation of Industrial Waste for Environmental Safety, pp. 77–112. Azubuike, C.C., Chikere, C.B. and Okpokwasili, G.C., 2016. Bioremediation techniques– classification based on site of application: Principles, advantages, limitations and prospects. World Journal of Microbiology and Biotechnology, 32(11), pp. 1–18. Baker, A.J.M., McGrath, S.P., Reeves, R.D. and Smith, J.A.C., 2000. Chapter 5. Metal hyper accumulator plants: A review of the ecology and physiology of a biological resource for phytoremediation of metalpolluted soils. Phytoremediation of Contaminated Soil and Water, pp. 85–107. Baker, A.J.M., McGrath, S.P., Sidoli, C.M.D. and Reeves, R.D., 1994. The possibility of in situ heavy metal decontamination of polluted soils using crops of metal-accumulating plants. Resources, Conservation and Recycling, 11(1-4), pp. 41–49. Baker, R.S. and Moore, A.T., 2000. Optimizing the effectiveness of in situ bioventing. Pollution Engineering, 32(7), pp. 44–44.

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5.1 INTRODUCTION Solid organic waste is rapidly expanding along with the global population growth, particularly in urban areas. As a result, solid waste management has drawn a lot of attention globally. In India’s urban Municipal solid waste (MSW), organic matter makes up 75–85% of the waste (Sarkar and Chourasia 2017). According to Gupta and Arora (2016), urban India generates 68.8 million tonnes of MSW annually. By 2041, that number is expected to rise to 200 million metric tons annually (https://www.statista.com/statistics/1009110/india-msw-generation-amount/). In most cases, garbage is burned or disposed of in landfills. In landfills, microbes break down organic waste to create various gases that may hasten global warming. Additionally, farmers typically employ organic wastes as manures. However, because of the potential for soil pollution and the establishment of diseases in plants and animals, their land spreading or reuse in agriculture is either prohibited or restricted (Forastiere et al 2011; Gunjal 2019). Currently, attempts are being made to collect, recycle, and recondition organic waste by the bioconversion of it into beneficial value-added products such as bioactive chemicals, enzymes, livestock feed, biofertilizers, biofuel, etc. Vegetable waste is a perfect substrate for solid-state fermentation, which can bioconvert organic waste into products with value added. Microorganisms are crucial to this procedure (Laufenberg et al 2003). Cellulase, xylanase, ligninases, and proteases are industrially significant enzymes that different bacteria and fungi create that can speed up the biodegradation of garbage (Martins et al 2011). Several researchers reported the microbial consortium made up of fungi, bacteria, or both to compost organic waste (Duan et al 2019; Lin et al 2011; Raut et al 2008; Sarkar et al 2011; Sarkar and Chourasia 2017). The biodegradation of organic waste is accelerated by the injection of a bacterial and fungal mixture. Along with the biodegradation of trash, a concept for removing the product’s high water content so that it can be used as animal feed and improve its stability has also been developed. As a nutritional medium for the microorganisms, this liquid that was recovered from the organic waste can be employed. Recently, Dantroliya et al (2022) demonstrated the bioconversion of vegetable waste into crude enzymes (i.e., amylase, cellulase, xylanase, and pectinase), animal feed, compost, and liquid biofertilizer in the presence of different microbial consortia. In general, biodegradation is the process by which living microbial organisms break down organic materials into smaller molecules (Marinescu et al 2009). The material is transformed into useful products by microorganisms through metabolic or enzymatic reactions. There are three steps to the biodegradation process: biodeterioration, biofragmentation, and assimilation (Lucas et al 2008). A surface-level degradation that alters the material’s mechanical, physical, and chemical properties is sometimes used to characterize biodeterioration. This stage happens when the material is exposed to abiotic elements in the outdoor environment and it weakens the material’s structure, allowing for further degradation. Compression (mechanical), light, temperature, and environmental chemicals are some examples of abiotic variables that have an impact on these first modifications (Lucas et al 2008). Though it frequently happens as the initial stage of biodegradation, biodeterioration can occasionally be seen as simultaneous to biofragmentation (Müller 2005). A polymer’s bonds are broken during the lytic process of biofragmentation, producing oligomers and monomers in their stead (Lucas et al 2008). Depending on whether oxygen is present in the solution, different procedures are followed to fracture these components. Anaerobic digestion is the breakdown of materials by bacteria when there is no DOI: 10.1201/9781003279136-7

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oxygen present, and aerobic digestion is the breakdown of materials when there is oxygen present. Anaerobic reactions produce methane, whereas aerobic reactions do not, which is the primary distinction between these two processes. However, both processes result in the production of carbon dioxide, water, a small amount of residue, and new biomass. Anaerobic digestion reduces the volume and mass of the substance more effectively than aerobic digestion, which also happens more quickly in general. Anaerobic digestion technology is commonly utilized for waste management systems and as a source of local, renewable energy since it can reduce the volume and bulk of waste materials and produce a natural gas (Klinkner 2014). The products of biofragmentation are then incorporated into microbial cells during the assimilation stage. Membrane carriers can quickly move some fragmentation-related byproducts inside the cell. Others must still go through biotransformation processes in order to produce goods that can be delivered into the cell. Once within the cell, the products enter catabolic pathways, which either produce adenosine triphosphate (ATP) or contribute to the construction of the cell (Lucas et al 2008). Growth and cometabolism are the two mechanisms that underlie biodegradation. Cometabolism is the metabolism of an organic substance when a growth substrate, which serves as the main source of carbon and energy, is present (Fritsche and Hofrichter 2001). An organic contaminant serves as the only source of carbon and energy for growth. The organic contaminants are completely degraded (mineralized) as a result of this process. Although there are many different biodegradation pathways, carbon dioxide is typically the end result of the decomposition (Pramila et al 2012). Anaerobic (without oxygen) or aerobic (with oxygen) degradation of organic material are both possible (Mrozik et al 2003; Fritsche and Hofrichter 2001). In reality, time is the most important factor in the biodegradation of practically all chemical compounds and materials. While some plastics and glass take thousands of years to decay, some vegetables may do so in only a few days. The European Union has a requirement for biodegradability: within six months, biological processes must convert more than 90% of the original material into CO2, water, and minerals. It is distinct from composting because it is a natural process. Biodegradation takes place during the human-driven process of composting under a certain set of conditions.

5.2 NATURE OF POLLUTANTS Highly poisonous chemical compounds have been created recently and discharged into the environment for long-term use either directly or indirectly. Among these substances include fuels, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), pesticides, and dyes (Diez 2010). In contrast to naturally occurring organic molecules, which quickly dissolve when introduced to the environment, some other manufactured chemicals, such as radionuclides and metals, are very resistant to biodegradation by local flora. • Hydrocarbons: These are organic molecules which have carbon and hydrogen atoms in their cores. Hydrocarbons can be thought of as cyclic, branching, or molecules with linear links. These hydrocarbons are seen to be either aromatic or aliphatic. The aliphatic one comes in three forms: alkanes, alkenes, and alkynes, whereas the first one has benzene (C6H6) in its structure. • Polycyclic aromatic hydrocarbons (PAHs): These compounds represent a class of hydrophobic organic contaminants (HOCs) that are significant pollutants that are frequently detected in air, soil, and sediments. Industrial output is the principal cause of PAH pollution (Mrozik et al 2003). Since more information concerning their toxicity, persistence in the environment, and prevalence has come to light in the past twenty years, there has been an increase in interest in these studies (Okere and Semple 2012). Fish and other aquatic creatures can accumulate PAHs, which can then be consumed by people.

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PAHs can also adsorb to organic-rich soils and sediments (Mrozik et al 2003). One way to think of the biodegradation of PAHs is as a removal of man-made pollutants from the environment, and the other is as a regular part of the carbon cycle. An appealing approach for restoring polluted places appears to be the use of microorganisms for bioremediation of PAH-contaminated environments. Polychlorinated biphenyls (PCBs): PCBs are concoctions of artificial organic compounds. PCBs were used in countless industrial and commercial applications due to their non-flammability, chemical stability, high boiling point, and electrical insulating qualities. These applications included electrical, heat transfer, and hydraulic equipment, as well as plasticizers in paints, plastics, and rubber products, pigments, dyes, and carbonless copy paper. As a result, PCBs are poisonous substances that have the potential to disrupt the endocrine system and lead to cancer. Consequently, worry over environmental degradation caused by PCBs is growing (Seeger et al 2010). Pesticides: Pesticides are compounds or mixtures of substances used to prevent, eliminate, repel, or reduce the impact of pests. Non-persistent pesticides are ones that breakdown quickly, whereas persistent pesticides are those that resist degradation. In current metropolitan environments, pesticides are a frequent source of contamination in the soil, air, and water as well as on non-target creatures. Once there, they may cause damage to non-target plants, fish, birds, and other creatures, as well as valuable soil bacteria and insects. Insecticides, fungicides, herbicides, rodenticides, molluscicides, nematicides, plant growth regulators, and other substances are all included under the umbrella word “pesticide.” Dyes: The textile, rubber, paper, color photography, printing, pharmaceutical, cosmetic, and many more industries utilize dyes extensively. The most significant and prevalent class of synthetic dyes used in commercial applications are azo dyes, which are aromatic compounds having one or more (–N=N–) groups (Vandevivere et al 1998). Due to the structures of these dyes, biodegradation of dye-containing wastewater is typically accomplished using physical and/or chemical processes, such as adsorption, coagulationflocculation, oxidation, filtering, and electrochemical approaches (Verma and Madamwar 2003). Utilizing microorganisms that can successfully decolorize synthetic dyes with various chemical structures is a necessary component for a biological process to remove color from a given effluent. Radionuclides: A radionuclide is an unstable atom with extra energy that can be transferred to a newly formed radiation particle inside the nucleus or by internal conversion. The radionuclide is said to experience radioactive decay during this process, which causes the emission of gamma ray(s) and/or subatomic particles like alpha or beta particles (Petrucci et al 2002). Heavy metals (HMs): A collection of metals and metalloids with an atomic number larger than 20 and an atomic density exceeding 5 gcm−3 are considered heavy metals, and they must also possess metal-like characteristics. Even at ppb levels, HMs are poisonous and difficult to break down. Pb, As, Hg, Cd, Zn, Ag, Cu, Fe, Cr, Ni, Pd, and Pt are a few examples. Bioleaching, which involves mobilizing heavy metals through the excretion of organic acids or methylation reactions, biomineralization, which involves immobilizing heavy metals through the formation of insoluble sulfides or polymeric complexes, biosorption (metal sorption to cell surface by physicochemical mechanisms), intracellular accumulation, and enzyme-catalyzed transformation (redox reactions), are some biological methods by which living organisms remove the heavy metals (Lloyd and Lovley 2001). The major microbial processes that influence the biodegradation of organic materials are summarized in the following sections.

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5.3 BIODEGRADATION METHODS 5.3.1 COMPOSTING The natural process of turning organic waste, such as leaves and food scraps, into an useful fertilizer that can improve soil and plants is known as composting. Composting merely expedites the decomposition process by creating the perfect habitat for bacteria, fungi, and other decomposing creatures (such as worms, sowbugs, and nematodes) to carry out their functions. Everything that develops eventually decomposes. Compost is the term used to describe the final decomposed material, which frequently resembles fertile garden soil. Compost, affectionately known by farmers as “black gold,” is nutrient rich and useful in agriculture, horticulture, and gardening. Anaerobic or aerobic composting is a secure way to manage trash. Compost is created when organic waste transforms under controlled aerobic circumstances (particle size, moisture content, pH, temperature, C:N ratio, etc.) (Lasaridi et al 2018). Biogas and effluents that can be employed as biofertilizers are produced during anaerobic treatment (Khan et al 2018). The byproducts differ from those present in native soil, coals, and peats because they contain “humic-like” substances. Different degradable wastes can be converted into products that can be utilized safely and advantageously as biofertilizers and soil additives through the process of composting (Bai et al 2010; Cai et al 2007; Yu et al 2019). Among other possibilities, organic waste can be handled in anaerobic digesters, community composting systems, and industrial-scale composting facilities. Contrary to the landfilling technique of waste disposal, which could endanger subsurface water, the composting process helps prevent the pollution of groundwater. This is due to the fact that microorganisms and chemical contaminants are reduced during composting. Due to the adequate nutrient content of composted materials and the presence of plant growth-promoting organisms (Pane et al 2014), composting is used to boost agricultural production and the organic matter content of soil (Luo et al 2017). In addition to being used as fertilizer, compost is beneficial for bioremediation (Ventorino et al 2019), controlling plant diseases (Pane et al 2019), weeds (Coelho et al 2019), preventing pollution (Uyizeye et al 2019), erosion, and restoring wetland areas. Additionally, composting boosts soil biodiversity and lowers the environmental concerns connected to synthetic fertilizer (Pose-Juan et al 2017). 5.3.1.1 Composting Methods There are various composting techniques, and each one has pros and downsides. Therefore, the composting technique to be used must be determined by the method that best achieves the researcher’s objectives and the sort of material to be composted. Some of the composting methods are discussed below. • Indian Bangalore Composting The Bangalore composting technique was created in Bangalore, India (Misra et al 2003). The technique is strongly advised for composting waste and night soil. Composting is done by excavating trenches or pits that are about one meter deep and alternatingly layering organic waste and night soil. Finally, a layer of trash that is 15– 20 cm thick has been placed over the pit. For three months, the materials are left in the pit without being turned or watered. In order to minimize moisture loss and the growth of flies, the volume of the materials is reduced during this time, and more night soil and garbage are added on top in alternate layers and covered with mud or dirt. The final output of this form of composting takes between six and eight months to produce. This process is time-consuming and costly to maintain. • Vessel Composting Composting that takes place inside of a container, structure, or other enclosed space is referred to as “in-vessel composting.” To speed up the composting process, in-vessel solutions use a range of

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forced aeration and mechanical rotation techniques (Gonawala and Jardosh 2018). It costs a lot of money and manpower. • Windrow Composting In windrow composting, the raw materials are placed in long, thin stacks or windrows that are regularly turned. Aeration of the setup is made possible by the materials’ mixing. For solid materials like manure, a conventional windrow composting setup should start at a height of 3 feet, and for fluffy materials like leaves, it should start at a height of 12 feet (Gonawala and Jardosh 2018). Although it is expensive and difficult to support, it retains heat quickly. • Vermicomposting The term describes the practice of composting biodegradable organic material with earthworms (Arumugam et al 2017). Almost every type of organic material can be degraded by earthworms by feeding on it. Earthworms are allowed to eat their body weight each day. For instance, 0.1 kg earthworms can consume 0.1 kg of waste every day. The worms’ excretions, known as “castings,” are nitrate rich and contain accessible forms of potassium, calcium, phosphorus, and magnesium, which increase soil fertility (Bhat et al 2018). The growth of bacteria and actinomycetes is facilitated by the presence of earthworms in the soil. Vermicomposting is a popular non-reactor bioconversion technique for managing solid waste. In this bioconversion process, the ecosystem engineers, or epigeic earthworms, consume organic matter and subsequently convert it into vermicompost and vermiwash, which are nutrient-rich humified organic fertilizers. For vermicomposting, a variety of earthworms have been employed, including Megascolex mauritii, Eisenia foetida, Eudrilus eugeniae, Perionnyx excavatus, Lampito mauritii, Eisenia andrei, Lampito rubellus, and Drawida willis (Manyuchi and Phiri 2013). These earthworms have been used for vermicomposting for a variety of wastes including animal, plant, pharmaceutical, food, and sewage waste throughout vermicomposting periods ranging from 28 to 120 days. The feedstock substrate is initially ground in the gizzard to create smaller particles, increasing the surface area during the vermicomposting process. Earthworm gut microorganisms and digestive enzymes continue to work on the material to create a fine granular product that is rich in healthy nutrients and microbiota. In addition to the physical and physiological processes at play, earthworms’ burrowing behavior promotes aeration, which helps the material mix uniformly. According to Hazarika and Khwairakpam (2022), vermicomposting can be utilized to manage solid waste and produce biofertilizers. Vermicompost yields of 30–50% are possible with a range of organic wastes and composting times. Both vermicompost and vermiwash can be used as biofertilizers since they are high in nitrogen, phosphorous, and potassium (NPK). Vermicomposting is one of the greatest ways to recycle organic waste since it provides a practical, cost-effective way to produce a high-quality good that is rich in a variety of bioactive components. • Static Composting Using passive aeration, waste is composted using a classic approach that uses aerobic fermentation (little and infrequent turnings or static aerations like perforated poles or pipes). In comparison to vermicomposting, windrow, vessel, and Indian Bangalore composting, this method is simple yet time-consuming. It also has lower operational and capital expenditures. The only labor- and resource-intensive part of this procedure is the creation of a pile of basic materials. The primary method of aeration is the passive passage of air through the pile, which gradually degrades the organic matter (Gonawala and Jardosh 2018). • Sheet Composting Sheet composting, also known as lasagna composting, provides the benefits of decomposed organic matter without the need for a compost pile. In this technique, organic materials such as

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leaves, garden debris, grass clippings, weeds, and plant food are applied directly as mulch on the soil. The organic components are then worked into the soil with a hoe, spade, or garden fork and allowed to decompose there, rather than in a pile or container. The growing space is covered with one or more layers of organic material, which is then carefully watered and left to degrade until planting time. More layers of organic matter are added to the bottom layers, which degrade completely (Misra et al 2003). The procedure is simple and inexpensive. • Indian Indore Composting The Indian Indore technique utilizes a combination of raw resources, including plant leftovers, animal feces and urine, dirt, wood ash, and water. All organic wastes accessible on a farm, such as weeds, stalks, stems, fallen leaves, pruning, chaff, and leftover fodder, are layered 15 cm deep until the pile reaches 1.5 m in height. The heap is divided into 20–25 kg vertical slices for the night’s slumber. Within one week, the bedding is transported to the composting pits and filled layer by layer. A sufficient amount of water is sprayed over the materials in the pit to adequately soak them. The compost is only moistened three times throughout the duration of the composting process. The moisturizing is performed 15 days after the compost pit is stacked, 15 days after the initial moisturizing, and one month after the initial moisturizing. This procedure is labor and time intensive. It is especially susceptible to insects and pest disturbances and wind can cause nitrogen loss (Misra et al 2003). • Berkley Rapid Composting This is a quick process of composting. Materials decompose more quickly if they are between 0.5 and 1.5 inches in size. Since soft, succulent tissues disintegrate swiftly, they do not need to be sliced into very small pieces. To facilitate decomposition, tissues must be minced finer as their firmness increases. Once a pile has been established, nothing should be added because it takes a certain amount of time for the initial components to decompose, and anything added must begin the breakdown process from the beginning, hence extending the decomposition time for the entire pile (Misra et al 2003). 5.3.1.2 Microbiological Aspects of Composting According to Hafeez et al (2018), the resident microbial community is primarily responsible for the biodegradation and conversion process during composting. The process of composting is driven by the activities of a diverse microbial community. The biggest number of microorganisms reported to be present during composting consists of bacteria and fungus (Galitskaya et al 2017). Composting involves two distinct kinds of aerobic microorganisms: the mesophilic organisms and the thermophilic species. These organisms may be bacteria, actinomycetes, fungi, or yeasts, and they dominate various periods of composting. Important phases of the composting process are the mesophilic stage, the thermophilic stage, and the second mesophilic stage, often known as the cooling stage. The composting process could begin with a mesophilic phase in which the temperature ranges from 20 to 40°C. The thermophilic phase follows the mesophilic phase. Compared to the mesophilic stage, active breakdown occurs at the thermophilic stage (40–70°C) (Hafeez et al 2018). The population and diversity of thermophiles and/or thermotolerant bacteria, actinomycetes, and fungi increase during this phase (Chennaoui et al 2018). The second mesophilic phase, also known as the curing phase, follows the thermophilic phase, and it is during this phase that the compost matures. Actinomycetes have been shown to possess biodegradation capabilities; they release a diverse array of extracellular enzymes (Limaye et al 2017). They are also capable of metabolizing recalcitrant compounds. Composting involves certain bacteria that degrade lignocelluloses. Lignocellulose is made up of carbohydrates (cellulose and hemicellulose), a phenolic polymer, and lignin (Ghanbarzadeh, and Almasi 2013). The ability of organisms to digest organic matter is contingent on their ability to manufacture the enzymes necessary to decompose the substrate’s

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constituents (cellulose, hemicellulose, and lignin). An enzyme needed to biodegrade organic matter depends on how complicated the substrate is (Ogbonna et al 2015). Hundreds of fungi are capable of decomposing lignocellulose (Singh and Nain 2014). According to them, three major forms of fungi are known to inhabit lignocellulose-containing dead woods. They include soft-rot, brown-rot, and white-rot fungus. The wood components are degraded by these microbes. Soft rot fungi (Chaetomium, Ceratocystis, and Kretzschmaria deusta) can decompose cellulose but degrade lignin slowly and insufficiently. Therefore, the regulation and control of these microbes help expedite the composting process. 5.3.1.3 Biochemical Aspects of Composting A variety of aerobic and facultative organisms decompose organic matter into inorganic chemicals, with stabilized humic acid or humus being the primary end result. Fulvic acid, humic acid, and humin are the three primary humus fractions. Humus is composed of amino acids, purines, pyrimidines, aromatic compounds, uronic acid, amino sugars, pentose, hexose, sugars, alcohols, methyl sugars, and aliphatic compounds. In addition, CO2, NO2, SO4, and PO4 are emitted during composting. These are released in the presence of oxygen as gaseous forms (aerobic conditions). 5.3.1.4 Factors Affecting Composting Process Composting is affected by input material texture, temperature, moisture content, pH, oxygen content, and C/N ratio. 5.3.1.4.1 Temperature and Carbon to Nitrogen (C:N) Ratio Temperature is an important aspect of composting since it speeds up the decomposition process and eliminates pathogenic organisms that are detrimental to soil organisms, plants, animals, and humans (Hafeez et al 2018). The temperature at which they reside determines what type of microorganisms is present during the composting process. Mesophilic microorganisms are those that thrive between 20 and 40°C, whereas thermophilic bacteria thrive between 40 and 70°C (Chennaoui et al 2018). Mesophilic organisms initiate the composting process by decomposing the waste’s readily biodegradable components. Their metabolism causes a rapid increase in the temperature of the compost. If the volume of wastes being processed is low, it may not be possible to achieve the desired high temperature. Occasionally, the temperature during the composting process does not reach 45°C, but pathogens can still die if the nutrients in the composting materials are depleted and if competitive organisms secrete enzymes that are capable of eliminating pathogens. A C:N ratio of 30 is optimal for composting processes (Gonawala and Jardosh 2018; Yan et al 2015). When the C:N ratio of composting materials is low, air cannot permeate the pile, resulting in anaerobic conditions and odor creation, as well as nitrogen loss in the form of ammonia gas. In addition, if the C/N ratio is too high, the activities of microorganisms and the pace of decomposition will be lowered (Méndez-Matías et al 2018). 5.3.1.4.2 Oxygen and pH During the composting process, the presence of oxygen is essential. When organisms oxidize carbon to make energy, oxygen is consumed and gases are produced. Without sufficient oxygen, the composting process will become anaerobic and gases (methane, carbon dioxide, and ammonia) will be created, which will result in the formation of unpleasant odors (Gonawala and Jardosh 2018). The pH of the composting materials influences the composting rate. It has been reported that an alkaline pH is optimal for composting. When pH is acidic, composting is extremely sluggish because microorganisms are killed (Ameen et al 2016). 5.3.1.4.3 Moisture Content, Particle Size, and Raw Material Texture Moisture is important to the metabolic processes of microorganisms. The moisture content of composting materials should range between 40 and 60% (Ameen et al 2016). According to reports,

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the moisture in compost originates from either the initial water added or the metabolic water created by the microorganisms. The presence of excess water lowers the diffusion of oxygen, which in turn decreases the metabolic processes of the organisms. For their metabolic processes, microbial cells rely entirely on water. Thus, organic molecules must be dissolved in water for bacteria to be able to metabolize them. Moisture diminishes as the composting process continues (Chennaoui et al 2018). Typically, optimal composting conditions are achieved when the material’s particle size is between 1 and 2 inches in diameter (Misra et al 2003). This size results in a greater surface area, which enhances microbial activity and the composting process. As particle size diminishes, so does the rate of aerobic breakdown. However, extremely small particles may inhibit oxygen passage within the pile, so slowing the pace of decomposition (Zhao et al 2017). In addition, small particle size promotes moisture retention and decreases airspace, hence reducing the composting process. Hard, lignin-rich, or coarse-textured biodegradable organic compounds typically decompose slowly. For instance, leaves with a firm texture tend to decompose more slowly than leaves with a smooth texture. As a result of their physical barrier, thorny leaves may also require more time to decompose. It is possible that leaves with a leathery or rigid texture have a high lignin concentration.

5.3.2 VERMICOMPOSTING Vermicomposting is the nonthermophilic biodegradation of organic waste into humus-like compounds caused by earthworms (Arancon et al 2004). Vermicomposting (from the Latin vermis, “worm”) is a mesophilic process in which earthworms (at temperatures between 10 and 32°C) and mesophilic bacteria convert organic wastes into a valuable end product known as vermicompost. During vermicomposting, organic waste materials travel through earthworms’ gizzards and generate vermicast (Sharma and Garg 2019), which is rich in important plant nutrients and plant development-stimulating chemicals (Hemalatha 2012). Due to its potential significance in organic waste management and sustainable soil fertility management, vermiculture has attracted significant attention during the past few decades. As an organic fertilizer, soil supplement, and growth medium, vermicompost is utilized. By adding vermicompost, soil physical and chemical qualities, such as porosity, aeration, and water-holding capacity, as well as plant nutrient uptake efficiency, are enhanced (Edwards et al, 2004; Pramanik et al 2007; Puga-Freitas and Blouin 2015). Due to its fine texture, the vermicompost has a very high surface area. Increase micro sites for microbial activity and nutrient retention will result. In vermicompost, beneficial bacteria, fungi, and actinomycetes for soil health can be detected (Adhikary 2012). Vermicomposting produces a higher-quality final product than composting due to the combined action of enzymatic and microbiological processes. As the material goes through the earthworm’s digestive tract, the process is accelerated, and the resulting earthworm castings are rich in microbial activity and plant growth regulators, as well as possessing pest-repellent properties. 5.3.2.1 Role of Earthworm in Vermicomposting Earthworms are invertebrate organisms from the family Lumbricidae, class Oligochaeta, and phylum Annelida. There are around 3,320 earthworm species in the world (Bhatnagar and Palta 1996), however, only 8–10 species are acceptable for vermicompost processing. Numerous organic wastes, including MSWs, wheat straw, sewage sludge, forestry waste, vegetable waste, farmyard manure, sorghum stalk, wheat straw, paddy straw, and coir pith, have been recycled using earthworms. Charles Darwin referred to earthworms as the “unheralded soldiers of mankind,” and Aristotle referred to them as the “intestine of the earth” due to their ability to digest a wide variety of organic materials. In vermicomposting, two tropical species, African night crawler, E. eugeniae (Kinberg), and Oriental earthworm, Perionyx excavates (Perrier), as well as two temperate species, red earthworm, E. andrei, and tiger earthworm, E. foetida, are utilized extensively. Due to their high rate of consumption, digestion, and assimilation of organic matter, tolerance to a wide range

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of environmental factors, short life cycles, high reproductive rates, and endurance and resistance during handling, E. andrei and E. fetida are utilized in the majority of vermicomposting facilities and studies. Under some situations, additional species, such as Drawida nepalensis, Lampito mauritrr, Dichogaster sp., Polypheretima elongate, Amynthas sp., Dendrobaena octaedra, and Eisenia hortensis, have also been employed for composting. Earthworms stimulate the growth of “good decomposer aerobic bacteria” in organic waste and also operate as a grinder, crusher, chemical degrader, and biological stimulant for waste (Singleton et al 2003). Earthworms are home to millions of decomposer (biodegrader) microorganisms, hydrolytic enzymes, and hormones that aid in the rapid decomposition of complex organic matter into vermicompost in 1–2 months, as opposed to the standard composting approach which takes approximately 5 months. The method of vermicompost generation by earthworms consists of the following steps: organic material ingested by earthworms is softened by their saliva. Food in the esophagus is further softened and neutralized by calcium, and physical breakdown in the muscular gizzard produces particles of size 99% conversion and >99% selectivity. To produce 1 ton of ethylene, 1.7 tons of ethanol are required. Given the size of ethylene facilities (more than 300,000 tonnes), a single ethylene plant would be a significant consumer of ethanol. Ethanol dehydration yields ethylene, which can be dimerized to yield butenes. Butene and ethylene can be reacted to produce propylene via metathesis. Butanol can be produced through the fermentation of carbohydrates or the generation of syngas through the gasification of biomass. N-butanol is employed as a solvent in paints and chemical stabilizers, as well as in a variety of polymers and plastics. Dehydration of butanol yields butene, which can subsequently undergo a

FIGURE 13.7 Ethylene-derived biochemicals (PE, polyethylene; PET, polyethylene terephthalate; PS, polystyrene; ABS, acrylonitrile butadiene styrene; SBR, styrene butadiene rubber; PVA, polyvinyl alcohol).

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FIGURE 13.8 CO2 utilization routes and their state of deployment on a commercial, demonstration, and lab scale.

metathesis process with ethylene to produce propylene. The biodiesel byproduct propane can be dehydrated to make propylene. Through catalytic cracking, vegetable oil can be transformed into propylene. Methanol Biomass gasification produces syngas that can be converted to methanol. Using methanol-to-olefins technology, propylene can be manufactured. The global demand for propylene is roughly 50 million tonnes. Ethylene is primarily employed in the production of polypropylene (60% of propylene demand), but it is also utilized in the production of propylene oxide, acrylonitrile, acrylic acid, polyethylene terephthalates, polystyrene, polyvinyl alcohol, and butanol. Figure 13.7 depicts various ethylene derived value-added products. Global Bioenergies in France is scaling up a fermentation process that converts glucose to acetone and isopropanol using modified bacterial strains. These two C3 compounds are widely utilized in solvents, cosmetics, and other industries and can be turned into propylene. Mitsui Chemicals, Inc. has reported isopropanol synthesis by fermentation (Matsumoto et al 2015; Takebayashi et al 2015) and its conversion to propylene (de Jong et al 2012). Propylene glycol is used in unsaturated polyester resins, coolants, antifreeze, hydraulic and brake fluid, aircraft de-icing fluid, heat transfer fluids, paints, and coatings. Higher-grade propylene glycol is used in fragrance, cosmetics, personal care, food and flavorings, pet food/animal feed, and pharmaceuticals. Glycerol availability will also affect bio-based propylene glycol’s growth. Moreover, the CO2 produced during the fermentation process may also be used to generate a variety of products. There are additional ways to use CO2 with reactants besides hydrogen. Figure 13.8 depicts CO2 products produced at different scales.

13.4 TECHNOLOGY INTEGRATION FOR ZERO WASTE GENERATION FROM PULP AND PAPER INDUSTRY The global production and demand for paper and associated products is rising dramatically. In order to increase production, the pulp and paper sector is consuming more energy and emitting

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more carbon dioxide as a result. The waste produced by the paper industry is contingent on the unprocessed material used in production and the type of paper produced (Haq and Raj 2020). Lime sludge, boiler ash, fly ash, primary sludge, and secondary sludge are produced by pulp and paper operations (Monte et al 2009). Paper industry waste generation exceeds one million metric tonnes annually (Kinnarinen et al 2016). One tonne of paper produces 650 kg of boiler and fly ash and 600 kg lime sludge (Monte et al 2009). Pulp and paper industry waste is also a potential feedstock for developing paper and pulp biorefinery. Using the biorefinery concept, it is possible to establish an integrated strategy for the valorization of pulp and paper industry waste by integrating multiple processes, beginning with the reduction of chemical load and continuing with pretreatment procedures. Such waste can be used to generate energy with the assistance of other integrated industries. Utilizing these wastes to generate valuable resources is a significant step toward green energy and environmental sustainability. The pulp and paper industry produces lignocellulosic compounds, which are widely employed as a source of raw materials for the manufacture of renewable energy and useful chemicals (Sagues et al 2018). Biohydrogen production from pulp and paper industry wastes and integration with biorefinery emerged as a viable option since it generates energy from waste that can be used in industry (Kumar et al 2018; Mongkhonsiri et al 2018; Pathak et al 2016). Waste from the pulp and paper industry can potentially be used to generate energy in the form of biogas, biofuel, or electricity. Zalas and Cynarzewska (2018) analyzed the utilization of waste from the pulp and paper sector to produce dye-sensitized solar cells (DSSC). Enzymes play a crucial role in biohydrogen generation because they hydrolyze the substrate and make it suitable for hydrogen synthesis (Kumar et al 2019a,b). In an experiment, pulp and paper effluent was hydrolyzed with cellulase enzyme from Trichoderma reesei and treated with Enterobacter aerogenes to yield biohydrogen. With a starting sugar content of 22 g l−1, the highest hydrogen output of 2.03 mol H2 mol−1 sugar was obtained (Lakshmidevi and Muthukumar, 2010). In addition, ultrasonication is a viable pretreatment approach for increasing biohydrogen production. Ultrasonication enhances effluent solubilization, modifies membrane shape, and enhances metabolite transport. Rhodobacter spheroids NCIMB were pretreated with ultrasonication at 60% amplitude and 45 min (A60:T45) for the maximum yield of 5.77 ml H2/mL medium (Hay et al 2015). In another investigation, intermittent ultrasonication of photofermentative broth containing Rhodobacter spheroids NCIMB8253 increases biohydrogen production to a maximum of 14,438 cc H2/ml medium (Budiman et al 2017; Usman et al 2019). In addition to energy generation, preparing clinker and cement is one of the alternative techniques of utilizing pulp and paper industry waste. CaO, Al2O3, SiO2, and Fe2O3 are present in the pulp waste, making it appropriate for clinker manufacture. The primary waste materials used are lime mud, biosludge, and fly ash. Using waste from the pulp and paper industries as unprocessed material, belite and portland clinker were effectively produced. This cement-based mortar was twice as resistant as the limit value of roughly 13 N/m2 (Buruberri et al 2015). Low water content and tiny particle size make lime mud and fly ash acceptable for cement manufacturing. The preparation of nanosilica from boiler ash and its manufacture in clinker form with other pulp and paper waste is also a novel waste utilization technique. Such ecoclinkers can be combined with gypsum to produce ecocement. Using the precipitation process, nanosilica was generated and combined with lime sludge for clinker preparation. Thus, the commercialization of clinker production in conjunction with the pulp and paper industry is a viable method to move forward in the field of zero waste production and contribute in CE (Vashistha et al 2019). Recovery of additional materials, such as adsorbents and valuable chemicals from pulp and paper industry waste, is an expensive procedure (Cao et al 2018; Oliveira et al 2018). Kouhia et al (2015) developed the notion of integrating a biorefinery that uses microalgae with a pulp and paper mill. Using the appropriate algal strain, pulp mill waste can be converted into fertilizers, biogas, and algal extracts. Tao et al (2017) cultured Scenedesmus acuminatus in pulp and paper mill biosludge in order to eliminate hazardous chemicals and produce methane during anaerobic digestion. Manool, a diterpene utilized in the fragrance and taste business, may also be recovered

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FIGURE 13.9 Pulp and paper waste valorization methods. Source: Gupta and Shukla (2020).

from a pulp and paper industry waste condensate using an integrated biorefinery (Sun et al 2016; Zhang et al 2017). To implement a zero-emission strategy in the pulp and paper business, commercialization of all waste utilization strategies is required. Lignin is valorized via technical advancements for sustainable resource management. Thus, the thermochemical manufacture of various chemicals with added value, such as ethylbenzene, guaiacol, vanillin, and carbon materials. All of these are utilized in many scientific domains, such as the organic synthesis of phenolic resin and the production of essential scents (Regmi et al 2018). Other major lignin-derived value-added products include useful sugars, flocculants, adsorbents, dispersants, fuels, battery plates, and dust suppressants (Kai et al 2016). Various methods for valorization of pulp and paper industry wastes are highlighted in Figure 13.9. The leather industry also makes a significant contribution to the world economy, with annual trade reaching up to USD 414 billion in 2018. Rawhide is used to make a variety of leather goods, including footwear, clothing, gloves, handbags, purses, hats, and watch straps, with 95% of the raw materials coming from the meat and dairy industries (Sivaram and Barik 2018; Saran et al 2019). With 48.5% of the global export market, Asian and European countries lead the globe in the export of leather goods due to the abundance of readily available raw materials in those regions (Saranya and Shanthakumar 2019). China produced 25% of the world’s leather in 2020, followed by Brazil (10%), Russia, Italy, and India (7%), who all had significant output levels (Omoloso et al 2021). India has the largest livestock population in the world (536.76 million), making up 11.54% of all cattle and 56.7% of all buffalo (Singh 2020). Adopting integrated cleaner technologies can help tanneries attain zero waste because these procedures aim to replace or reduce the use of dangerous chemicals and stop the production of hazardous waste. Studies revealed that even if zirconium, aluminum oxide, and titanium compounds are not economically viable for the tannery industry, chromium can be replaced with

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alternative tanning agents (Sreeram and Ramasami 2003). Chromium can be replaced with titanium as a promising step toward cleaner production by extracting titanium from the waste collected from the metal sector (Mutlu et al 2014). A blended tanning process is also environmentally friendly because it has no detrimental impact on the quality of the produced leather (China et al 2020). High-quality leather is manufactured by combining chemicals, such as titanyl sulfate with citrate, aluminum sulfate with polyhedral oligomeric silsesquioxane-methacrylic acid, aluminum with titanium, and chromium with zirconium (Al-Jabari et al 2021). The industrial community perceives these studies as theoretical approaches as they are still in the early stages. As a result, tactics now emphasize increasing chrome uptake during the tanning process and minimizing chrome concentration in tannery wastewater (Zhang et al 2016). The innovative tanning procedure has increased chrome uptake from 70% to 90%, hence decreasing chrome levels in effluent (Yao et al 2019). The Council of Scientific and Industrial Research, Government of India, has developed cutting-edge technologies from leather wastes that can produce value nearly as high as that of leather itself. Biofuels from tannery wastes, hair composts for plants, shoe soles made from limed flesh wastes, regenerated leather from leather trims, and fabrics made from leather wastes are a few of these innovations that have attracted notice. One of the CSIR’s key study areas has been collagen, the main protein component of skin. The institution has developed a range of health care products based on collagen and other proteinous materials like gelatin and keratin in addition to altering collagen structure and crosslinking for tanning. Products from the institute include highgrade gelatin, demineralized bone, burn dressing materials, and wound healing supplies. Additionally, the council is conducting research and development in the areas of leather made from ray fish, chicken feet, and products made from leather and natural fiber.

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14.1 INTRODUCTION Depletion of petroleum supplies and rising environmental laws are spurring the development of environmentally friendly, fossil fuel-free materials and goods. The need to create unique goods and other cutting-edge technology that can break society’s broad reliance on fossil fuels is becoming more urgent. As the fourth-largest energy source in the world today, biomass supplies up to 14% of global primary energy consumption. Given its ease of storage and conversion into heat and power, biomass is a flexible source of energy. It could potentially be utilized to make fuel and chemical feedstock. According to the European Commission (2015), agriculture is one of the biological industries that produce the most biomass, which is a crucial input for the bioeconomy (Bracco et al 2018; European Commission 2012). The Biobased Economy uses biomass from crops and sidestreams from agriculture, forestry, marine sources, and the food industry for food, feed, materials, chemicals, transport fuels, and energy. Industrial products for durable goods are produced from renewable agricultural and forestry feedstocks such as wood, agricultural waste, grasses, and natural plant fibers made of carbohydrates such as sugars and starch, lignin and cellulose, vegetable oils, and proteins. This presents a great opportunity, not only because its use and exploitation reduces fossil fuel use and greenhouse gas emissions (McCormick and Kautto 2013), but also because it promotes the conversion of vegetable waste into value-added products (byproducts) such as food, feed, bioproducts, and bioenergy (EC 2013; 2017a; Mohanty et al 2002; Scarlat et al 2015). Biorefineries are facilities that transform biomass into products with added value, including biofuels, biochemicals, bioenergy/biopower, and other biomaterials. Most of them are classified primarily according to the type of feedstock they use, such as biorefineries that use algae, corn, wood, ore, ore from forests, ore from palm trees, ore from forests, ore from forests, etc. On the other hand, some researchers and technicians categorize biorefineries into first-, second-, and thirdor fourth-generation categories based on the creation of the feedstock. These include energy crops, edible oil seeds, food crops, animal fats, etc. (algae and other microbes). However, the idea of an integrated biorefinery, which concentrates on the integration of several biomass conversion methods, is presented in order to further increase the efficiency of such a biorefinery. Multiple feedstocks can be used in an integrated biorefinery to produce a variety of products. Proteins, oils, sugars, vitamins, waxes, colorants, and flavor and fragrance compounds must be extracted from food waste using integrated processes, while the majority of food waste will then be processed to generate case-specific fermentation media or treated chemically or thermochemically to produce bioethanol or biogas as main products. Plant oils could be replaced by oil-rich fractions derived from food waste as the chemical industry’s raw materials for chemical conversions and the manufacture of chemically pure chemicals. The synthesis of biofuels, surfactants, stabilizers, fatty amines, dicarboxylic acids, resins, plasticizers, soaps, lubricants, and polyols could be done using these oil-rich fractions (Carlsson 2009; Wisniewski et al 2010). Enzymatic hydrolysis of food waste polysaccharides and proteins yields useful compounds that can replace commercial nutrient supplements for platform manufacturing, such as succinic, fumaric, malic, 3-hydroxypropionic, glutamic, and itaconic acids and sugars like xylitol and arabinitol. These goods can be used to DOI: 10.1201/9781003279136-17

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synthesize monomers or biodegradable polymers to make unique compounds, biofuel precursors, and bio-based polymers (Farges-Haddani et al 2006; Vazquez and Murado 2008). The production of single-cell oil utilizing distinctive oleaginous bacteria, whose composition varies on the chosen organism, can also be accomplished by the hydrolysis of food waste through fermentation. This cell oil has a similar fatty acid make up to vegetable oils, making it a viable alternative to plant oils in cooking, as well as a potential raw material for biodiesel and oleochemical manufacturing (Carlsson 2009; Koutinas et al 2014). Reforms to the Common Agricultural Policy (CAP) have prioritized and facilitated the implementation of the circular bioeconomy by giving assistance and incentives to farmers to optimize and make effective use of resources along the value chain and promoting the valorization of biomass resources (European Commission, 2017b; European Commission 2017European Commission, 2019). In addition, the policies and restrictions compelled many industries to reevaluate their manufacturing methods and transition to greener technologies. The acceleration of sustainable development goals will result from the conversion of diverse waste products into biofuels, bio-based fertilizers, enzymes, chemicals, proteins, molecules, and other resources.

14.2 BIO-BASED PRODUCTS FOR SUSTAINABLE BIOECONOMY 14.2.1 CHEMICALS Food waste valorization for the synthesis of building block compounds is emerging as a promising solution. The variety of elements found in food wastes shows the potential influence on a wide range of chemical industries, which might replace some of the traditional petroleum-based feedstocks with renewable feedstocks. Using food waste in chemical synthesis will shift public attitude and assist develop renewable supply chains for a closed-loop economy. These compounds containing a variety of functional groups that can be used to produce a wide range of chemicals or materials with additional value derived from biomaterials, such as specialty chemicals, commodity chemicals, consumer chemicals, and niche chemicals. It has been shown that specific food wastes can be used to create sugars (like glucose), organic acids (like lactic acid), pectin, polysaccharides, polyphenols, and fatty acids. Food wastes also produce secondary compounds. For instance, glycerol (10% (w/w)) is a significant byproduct in the manufacturing of biodiesel and is often burned in a kiln. It offers excellent opportunities for the synthesis of secondary compounds such as hydrogen, 1,3-propanediol, acrolein, citric acid, lipids, and others. Oranges are frequently used to prepare orange juice or consumed fresh. In last 20 years, the global orange production has risen by 22%. Orange or citrus peel can be used to produce a number of bioeconomically valuable byproducts, including D-limonene (an essential oil), pectin, dietary fibers, soluble solids, proteins, enzymes, citric acid, flavonoids, and sugars. One of the key highvalue items derived from orange peel waste is undoubtedly the mixture of volatile compounds known as orange essential oil, which is also known by its commercial name, D-limonene, due to the fact that it makes up 90% of the oil. New and more environmentally friendly methods, such as supercritical fluid extraction, ultrasound, subcritical water, and microwave-aided extraction, have been used to extract the essential oil from citrus fruits. Additionally, pectins are intricate polysaccharides that are mostly found in the major cell wall and intercellular sections of non-woody biomass. The homogalacturonan (HG) or “smooth area” of them is made up of a-(1-4)-Dgalacturonic acid polymer chain, while the “hairy” portion is made up of branched neutral sugar chains. A typical technique for extracting pectin is citrus peel acid hydrolysis with heat assistance, followed by ethanol precipitation. Cellulose obtained from agricultural waste can be converted into a variety of chemicals, some of which are recognized as platform chemicals, including furfural, 5-hydroxymethylfurfural (5-HMF), levulinic acid (LA), formic acid, acetic acid, and lactic acid. One of the most promising platform chemicals for the synthesis of fuels and chemicals produced from lignocellulosic biomass is LA (Bozell and Petersen 2010; Werpy and Petersen 2004). It is viewed as a platform chemical

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with numerous uses, including textile dyes, additives, fuel extenders, antimicrobial agents, herbicides, and plasticizers. It is also used as a source of monomers for the synthesis of polymer resins and as a component in the flavoring and fragrance industries (Fang and Hanna 2002; Suganuma et al 2008). Many of the highly selective manufacturing and separation technologies for LA are still in the early stages of development. Therefore, it would be desirable to identify an economically effective method for converting more complex biomass feedstock to fuels and chemical precursors for industrial production in order to lessen atmospheric CO2 emissions without jeopardizing the availability of food. In order to reduce the cost of producing organic acids, food wastes rich in organic compounds are also utilized in the process (Abdel-Rahman et al 2019; Kim et al 2018). Lactic acids, citric acids, succinic acids, 3-hydroxypropionic acids, volatile fatty acids (VFAs), tartaric acids, acetic acids, butyric acids, and other organic acids are formed from FW. Additionally, the content of the food waste has an impact on how organic acids are produced during the acidogenesis stage. During the saccharification process, the complex carbohydrates in the food waste are transformed into simple fermentable sugars including galactose, glucose, and fructose. The acidogenic bacteria present in the food waste convert these simple carbohydrates into organic acids, including Lactobacillus, Bacillus, Propionibacterium, Butyribacterium, etc. (Wang et al 2005). Consequently, food wastes are fermented to form pure acids, whereas organic acid cocktails are produced via mixed acid fermentation. Specialty chemicals, which are frequently referred to as functional compounds, have the unique capacity to be used in the food, pharmaceutical, and cosmetics industries as antioxidants, antimicrobials, flavoring agents, and colorants. Numerous research studies have shown that various functional substances recovered from food waste, such as phenolic compounds, bioactive peptides, carotenoid, and dietary fiber, serve as a useful source of nutraceuticals, enhancing human health. Phenolic compounds belong to a broader class of bioactive substances that have an abundant number of hydroxyl groups in aromatic rings and a polyphenol structure. Flavonoids, phenolic acids, tannins, stilbenes, and lignans are other subclasses of polyphenols that are suitable for usage as antioxidants due to their propensity to scavenge free radicals (Deng et al 2012). The peels, rinds, and seeds of fruits and vegetables typically contain a significant amount of phenolic chemicals, according to earlier studies. Recent developments have led to the commercialization of Resveratrol, an important stilbene molecule isolated from grape leftovers using supercritical CO2 (Casas et al 2010). According to Choi et al (2016), potato peel extracts were found to be higher in phenolic acids than potato cortex, particularly chlorogenic acid and caffeic acid. Valdez- Morales et al (2014) found that tomato peels are three times richer in organic and cinnamic acids and contain four times as much flavonoids as in tomato seeds. Furthermore, employing microwave-assisted extraction (MAE), the total phenolic components recovered from grape skin byproducts were 28% higher than those obtained using traditional extraction techniques and likewise had good antioxidant competency (Medouni-Adrara et al 2015). In comparison to the other byproducts, green tea waste was found to have higher antibacterial and antioxidant tannin content (Sung et al 2012). Carotenoids are widely used in the food industry as natural colorants and are well known for their antioxidant properties due to their strong radical scavenging activity. They are generally divided into the xanthophylls and the hydrocarbon carotenoids (lycopene, alpha-carotene, and beta-carotene) (lutein, astaxanthin, and zeaxanthin). Carotenoids are widely distributed in the peels of fruit and vegetable waste and come in a variety of colors from red to orange and even yellow. They also serve as a nutritional precursor to important vitamins like vitamin A. The use of carotenoids, such as astaxanthin and lycopene, as preservatives and health promoters is widespread in business. Takeungwongtrakul et al (2015) discovered that pink shrimp may be used to extract a surplus of astaxanthin and beta-carotene by combining hexane with isopropanol (50:50, v/v). Further ultrasound-aided extraction (UAE) increased the carotenoids recovery from tomato waste by 43% without deteriorating the carotenoids compared to standard extraction methods (Luengo et al 2014). Similarly, the recovery of carotene and numerous other carotenoids from carrot peels

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was accomplished using MAE (intermittent radiation) without undergoing thermal deterioration (Hiranvarachat and Devahastin 2014). Additionally, Ajila et al (2010) recorded that adding mango peel powder, which is rich in carotenoids and other bioactive compounds, to macaroni increased its nutritional content without altering its cooking, textural, or sensory qualities. Short-chain fatty acids (SCFAs) including acetic acid, formic acid, and propionic acid can be extracted from waste-activated sludge via anaerobic digestion (AD) or thermal methods such as moist air oxidation and hydrothermal treatment (Rulkens 2004). The recovered SCFAs can be used as a chemical feedstock and transformed into a variety of compounds, including fuels and esters, ethers, and carboxylic acids (e.g., primary alcohols, secondary alcohols, and hydrocarbons). Another resource for wood adhesive that is environmentally beneficial is protein recovery from secondary waste-activated sludge from a paper mill. For instance, Pervaiz and Sain (2011) extracted protein using an alkaline cell-disruptive method similar to that used by Hwang et al (2008), and the resulting material achieved up to 41% of the shear strength of conventional protein-based wood adhesives like soy protein isolate and phenol formaldehyde resin (Pervaiz and Sain 2011). VFAs are also regarded as the primary component of biodiesel and biohydrogen synthesis. VFAs are formed as intermediary compounds during AD of food waste (Zhou et al 2018). These develop during the fermentation’s acetogenesis or acidogenesis phases. The food waste can be fermented by either a pure anaerobic bacterium strain or a mixture of anaerobic bacteria for the efficient generation of VFAs (Stams et al 2006). Lactic acid is the significant product accumulated from food waste among the many organic acids created since it is used as a raw material for the creation of polylactic acid, a platform chemical for the creation of biodegradable and disposable environmentally friendly polymers (Narayanan et al 2004). In a study by Kim et al (2003), food wastes were fermented by Lactobacillus delbrueckii and an amylolytic enzyme; thus lactic acid was produced through fermentation and saccharification up to 91%. Liquid fermentation (surface and submerged fermentation) and solid-state fermentation of food waste yield citric acids. Usually, Saccharomyces cerevisiae and Aspergillus Niger are used in the commercial synthesis of citric acid. Lodhi et al (2001) found that waste bread fermented with A. Niger for 48 h at 37°C and pH 4.0 produced 7.25 mg/ml of citric acid. Succinic acid, a precursor of butyrolacetone, tetrahydrofuran, and butanediol, is also used in detergents, medications, and other products (Leung et al 2012). Actinobacillus succinogenes and Escherichia coli are the most prevalent succinogens (Wu et al 2007). These microorganisms naturally create succinic acid and can withstand the osmotic pressure put on them by the acid and simple carbohydrates. In a study by Leung et al (2012), A. succinogenes fermented the hydrolysate of bread trash and produced approximately 47 g l−1 of succinic acid, the greatest output to date. In addition to these benefits that organic acids provide, product recovery is a crucial step in the fermentation process. One of the most underutilized rice byproducts that can be used to make anticancer products is rice bran. Many chronic diseases, including colon and human breast cancer, may be prevented by phenolic components found in rice bran, such as caffeic acid, ferulate, and ferulic acid. In rice bran, phenols, tricin, and ferulic acid, malignant cell proliferation and apoptosis have been shown to be inhibited. Because of their widespread use, potatoes produce a huge amount of garbage. The peel is processed to extract phenolics, which are significant antioxidants. While gallic acid, protocatechuic acid, coumaric acid, syringic acid, vanillic acid, and p-hydroxy benzoic acid have also been identified from potato peel, ferulic, chlorogenic, and caffeic acids are the most prevalent phenolic acids.

14.2.2 MINERALS

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NUTRIENTS

Compared to synthetic inorganic fertilizers, waste streams have low nutrient contents (1–200 mgl−1), and the most dilute waste streams contain the most nutrients. Nitrogen (N), phosphorus (P), and potassium (K) are essential to intensive agriculture, but their long-term availability and cost are

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uncertain, especially for P and K, which are mostly mined. These nutrients contribute significantly to the environmental effect of home, agricultural, and industrial waste streams due to poor recycling and nutrient management. Phosphorus fertilizer is frequently used to boost plant production since phosphorus (P) is a macronutrient that higher plants need for growth and development. The primary raw material used to make P fertilizers is phosphate rock (PR). PR is a limited and scarce resource, and its supply is projected to drop dramatically over the next 50–100 years. Globally, enormous waste streams are generated every year, and they are incredibly P-rich. For instance, the amount of P found in important waste streams created in the United States includes biosolids, pig manure, sheep dung, cattle manure, and poultry manure. The presence of phosphorus in these waste streams poses a threat to the ecosystem as a result of nutrient enrichment, which causes numerous complicated ecological problems, such as eutrophication of fresh and coastal water. The use of these waste streams as a nutrient source is currently not economically viable due to the vast volume needed to reach sufficient nutrient levels in large-scale agricultural production. This is because they have a low nutrient concentration when compared to commercial fertilizer. Currently, environmentally sustainable methods for the utilization of these waste streams are being investigated. In the United States, manure transfer programs allow for the transportation of manure to croplands low in phosphorus. These transfer projects are intended to mitigate pollution concerns in locations with excessively phosphorus-rich soils. However, the transportation of manure becomes less costeffective as its distance from animal-producing farms increases. If P can be recovered and concentrated, it will be easier to transport P from waste streams over vast distances for use in agricultural crops. Phosphorus present in waste streams can be removed and eventually recovered in concentrated form through a variety of processes, such as enhanced biological P removal, precipitation as sparingly soluble phosphate compounds, nucleation of P present in waste streams using nanomaterials, and adsorption of dissolved P using suitable high-affinity adsorbents.

14.2.3 PROTEINS

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ENZYMES

Single-cell proteins (SCPs), which are derived from yeast, algae, moulds, and bacteria, are an essential source of protein for fish, animals, and humans (Myint et al 2020; Nikos and Jelle, 2012; Ravindra 2000). Recently, SCPs have been derived from a variety of FW, including sugarcane bagasse (Pandey et al 2000), rice polishing (Zepka et al 2010), citric wastes (Zhou et al 2017), soy molasses (Gao et al 2012), yam peels (Aruna et al 2017), etc. The amount of SCP produced is contingent upon both the substrate and the medium. Trichoderma reesei and Kluyveromyces marxianus were co-cultivated with beet pulp to generate 51% of the SCP (Ghanem 1992). The resulting protein was determined to contain all essential amino acids in accordance with FAO recommendations. Due to their extremely high protein content and their ability to grow rapidly on low-cost substrates without severe growth requirements, bacteria may constitute a potential protein source in the future (Ravindra 2000). Agricultural waste includes coffee pulp from the coffee industry, cereal husks from the cereal industry, and starch-based industry peels. Agricultural waste is now an unquestionable prerequisite of rural ecological civilization construction in order to limit the negative repercussions that affect long-term human development and health. Recycling and utilization of agricultural waste are essential for promoting the growth of modernized agriculture. One of these initiatives includes the recovery of waste-bound proteins. In the food, chemical, and pharmaceutical industries, these proteins are of essential importance. The primary, secondary, tertiary, and quaternary structures of protein are formed by the peptide bonds between amino acids. Despite the greater quantity of protein in animals compared to plants, plant-derived protein has emerged as a viable solution for addressing the growing environmental problem produced by animal-protein production. Protein extracted from plants is currently gaining interest as a sustainable protein source. Bromelain or plant protease is said to be present in the peel, core, crown, and leaves of pineapples. The

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maximum proteolytic activity is reported in pineapple crown extract. Bromelain has many industrial applications, including tenderization, food, detergents, and the textile sector. The plant, microbial, and animal kingdoms have amylase. Amylase is a sort of plant-derived protein that has activation sites. Amylase is one of the most important industrial enzymes, accounting for more than 30% of the global enzyme industry. It is primarily utilized in the food, fermentation, and pharmaceutical industries. Amylases are enzymes that degrade starch by hydrolyzing -1-4 glycosidic bonds in alpha polysaccharides. Plant-derived amylases have been exploited extensively in the brewing business for millennia, whilst fungiform amylases are routinely employed in the manufacturing of oriental delicacies. Amylases have a wide range of industrial applications. In order to satisfy the need for amylases, several technologies and agricultural wastes have been investigated in order to generate a high output of amylase with fewer stages and less expensive methods. The biotechnology sector is paying more attention to the extraction of amylase from plant sources due to its reduced cost and toxicity. This expands the opportunities for using agricultural waste in amylase production. For the extraction and purification of enzymes, filtration, membrane extraction, precipitation, liquid–liquid extraction, ultrasonication, and chromatography are significant conventional techniques. In addition to field and processing wastes, agricultural residues consist of stems, stalks, leaves, seed pods and husks, seeds, roots, bagasse, and molasses. These protein-rich residues are gaining interest due to their commercially advantageous value and recoverability. The residues are currently utilized mostly for the extraction and application of useable protein in foods and supplements. This agricultural waste should be treated as a potential resource in accordance with a comprehensive life cycle analysis system and the modern food technology process. Along with the present technology for recovering protein-rich wastes, the identification of useable protein from these wastes will be conceivable. As prospective options for protein recovery from waste, membrane separation, adsorption, microbe-assisted protein recovery, and other standard extraction methods have been described. The recovery of enzyme protein is one of the industry’s deliberate efforts to transform these wastes into useful protein. Enzymes are proteins that function as biological catalysts in a number of biochemical reactions. They improve the rate of reaction by decreasing the activation energy, which reduces the cost of production in terms of required resources. Enzymes have been utilized for centuries to manufacture foods such as yogurt, wine, and cheese. Due to its potential industrial applications, enzyme extraction from agricultural waste has been known for a while. Agricultural waste valorization significantly enhances the capacity to lower production costs and improve enzyme performance for industrial purposes. Amylase, cellulase, tannase, xylanase, protease, and laccase are some of the enzymes produced economically from agricultural waste as an alternate means of utilizing the biomass generated as trash. After cellulose, chitin is the second most abundant natural biopolymer. It is a (1,4)-linked homopolymer of N-acetyl-D-glucosamine (GlcNAc). It occurs as structural body parts in fungi, marine diatoms, molluscs, arthropods, crustaceans, nematodes, etc. In the food processing and enzyme manufacturing industries, large quantities of discarded chitin are accumulated. It is believed that 20–50% of the wastes generated by the food processing sector possessing chitin. These are primarily produced during the preparation of shellfish. Shellfish are therefore regarded as a good source of chitin. However, chitin extraction from shellfish wastes is hampered by seasonal harvesting of crustaceans, restricted raw material availability, and the production of environmentally toxic substances during deproteination of waste chitin. These are the reasons why researchers are searching for new and sustainable chitin sources. Since the cell wall of fungi is predominantly made of chitin biopolymer, fungal biomass may emerge as a viable and alternative source for chitin manufacturing. Chitin is mass produced from the byproducts of the crustacean harvesting business. Chitin is also known to be abundant in fungal biomass. For chitin extraction and isolation, filamentous fungi such as Rhizopus, Penicillium, Aspergillus, Fusarium, Choanephora, and Zygorhynchus are commonly utilized. In addition to chitin, chitosan and other polysaccharides are present in the cell wall of fungi. Chitinase is manufactured by a variety of biotechnological processes, including

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submerged fermentation, solid-state fermentation, fed-batch fermentation, continuous fermentation, and biphasic cell system, among others. Chitin from crab or shrimp excrement could be utilized to manufacture chitinase. Demineralization, deproteinization, and deacetylation are the three fundamental processes in the usual manufacture of chitosan from crab shell. In general, shrimp are sold without their heads and are frequently stripped of their shells and tails. About 30–40% by weight of shrimp raw material is wasted as waste when headless, shell-on shrimp products are produced. The rate-limiting stage in the conversion of FW into diverse products with added value is the hydrolysis of complex carbs into simple sugars. FW often has a high concentration of carbs, which must be hydrolyzed into monosaccharides by saccharifying enzymes. Consequently, the synthesis of cellulases and amylases is of enormous importance (Teeri, 1997). Using solid-state fermentation, enzymes such as pectinase, lipase, protease, and amylase are isolated from various types of FW. Bacillus ferments wastes such as potato peel at 35°C and pH 7.5 to produce around 676 U/ml of amylase (Elayaraja et al 2011). Microorganisms such as Penicillium sp., Bacillus sp., and Aspergillus sp. are capable of fermenting and producing pectinase from a variety of FW, including apple pomace, orange peel, and citrus wastes, among others (Martinez Sabajanes et al 2012). Within 24 h, Pseudomonas aeruginosa acted on shrimp wastes to produce about 15,000 U/mL of the protease enzyme. The trash was fermented at 37°C and continually mixed at 200 rpm (Jellouli et al 2008). In a study conducted by Alkan et al (2007) at 37°C and pH 7, several wastes, including banana wastes, melon wastes, and watermelon wastes, were fermented by Bacillus coagulans to produce lipase with a titer value of around 148.9 U/g from melon waste. Depending on the food waste purification procedure and its transportation cost, recovered enzymes may have a variety of industrial applications. Thus created enzymes can be combined into other biorefinery processes to produce a variety of platform chemicals and biofuels. The use of agricultural byproducts has the potential to minimize the cost of enzyme production at an industrial scale that employs submerged fermentation. In addition to Paecilomyces variotii, agricultural byproducts such as coffee husk have been employed to produce caffeinase, pectinase, and tannase. Using fungus organisms such as Aspergillus oryzae, Penicillium sp., A. niger, and Neurosporacrase, coffee byproducts have also been used to create enzymes including protease, amylase, and xylanase. During mushroom cultivation, substantial volumes of waste are produced (up to 20% of total production). Mushroom waste consists primarily of mushrooms with malformed caps and/or stalks that do not fulfill retailers‘ criteria. These mushroom byproducts are extremely nutritious. Mushroom waste could be used to create vitamin D2-rich extracts that could be exploited by the pharmaceutical sector as dietary supplements or by the food business as an additive. Mushrooms are suitable for such a diet, and although they are weak in vitamin D, readily available varieties such as shiitake and button mushrooms are rich in ergosterol, a precursor to vitamin D2. Ergosterol can be transformed into vitamin D2 through exposure to natural or artificial UV light. Utilizing vitamin D extracts derived from mushroom waste in novel foods could be advantageous for the food sector.

14.2.4 VERMIWASH

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BIOFERTILIZERS

Biofertilizer is commonly referred to as the fertilizer that contains living microorganisms and it is expected that their activities will influence the soil ecosystem and produce supplementary substance for the plants. Recently, many studies and research have been focused on developing and commercializing agro-waste-based biofertilizer. Agro-waste is defined as waste which is produced from various agriculture activities. These agro-wastes include manures, bedding, plant stalks, hulls, leaves, and vegetable matter. Agro-waste is usually produced through farming activities. In farming situation, the agro-waste is often useless and will be discarded. The accumulation of agro-waste may cause health, safety, environmental, and esthetic concern.

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Agro-wastes that were used for biofertilizer production are wastes from pineapple, watermelon, banana, papaya, and citrus orange. Composting is the process of enhancing the aerobic biological decomposition of solid organic component, which drastically reduces the amount of waste sent to landfills (Makan et al 2020). Composting is the most common and economical approach for the quick stabilization of solid organic fractions in anaerobic environment (Huang et al 2006). In this process, aerobic microorganisms play a crucial role in the transformation of solid organic material into compost (biofertilizer), heat, and carbon dioxide. Different populations of microorganisms, pH, temperature, aeration, moisture level, and biodegradable fraction all contribute to the efficiency of the composting process. In some instances, some microorganisms aid in accelerating the composting process. When compared to the manufacturing of synthetic fertilizer, compost (biofertilizer) significantly reduces energy and water consumption (Farrell and Jones 2009). According to Chang and Chen (2010), the water-holding capacity of the composting feedstock is the primary physical attribute that has a negative effect on the composting rate. The treated organic waste (digestate) produced during the biogas production process can also be utilized as an organic fertilizer for arable land in place of mineral fertilizer and as an organic substrate for greenhouse development. One of the main organic wastes that will be detrimental to the environment if they are not managed properly is manure waste, which is obtained from the animal industries. A nutritional imbalance and environmental contamination are brought on by the excessive concentrations of nitrogen (N) and phosphorus (P) found in animal manure. Furthermore, hazardous compounds including growth hormones, antibiotics, and heavy metals can be found in livestock faeces. On the other side, bacteria in animal excrement may contaminate the environment, leading to an increase in the spread of diseases that affect humans. In this regard, it has been discovered that the environment is polluted as a result of the disposal of livestock manure, which contaminates air, soil, and water sources. Therefore, the AD process for treating animal manure and slurries has the advantages of providing high-quality fertilizer, reducing smells and microbiological pathogens, and producing biogas sustainably. Vermiwash, on the other hand, is a honey-colored liquid extract of organic composts that is typically the wash of earthworms present in the medium collected after water has been passed through the various layers of a worm culture unit from the increased moisture content due to heat generated during vermicompost. It is an extract of the worm’s coelomic fluid that includes a number of enzymes, plant growth hormones (i.e., Indole acetic acid, Cytokinin), vitamins, macro and micronutrients, excretory materials, and mucus secreted by earthworms. These substances, along with humic acid from the soil and organic waste, are easily absorbed by plant tissues. Vermiwash is a liquid organic fertilizer made from organic waste that can be broken down. The nitrates, ammonia, organic soluble compound, volatile solids, silica, auxin present in vermiwash and other materials released by dead earthworm tissue improve the nutritious quality of vermiwash. Vermiwash contains a variety of nitrogen-containing enzymes, such as protease, amylase, urease, and phosphatase along with nitrogenous worm excretory chemicals, and plant growth hormones. A microbiological investigation of vermiwash also revealed the presence of bacteria that fix nitrogen, including Azotobacter sp., Agrobacterium sp., and Rhizobium sp., as well as certain bacteria that dissolve phosphate.

14.2.5 FOOD

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MICROBIAL PROTEIN

Each year, the global food sectors produce a significant amount of food wastes and byproducts. Food processing accounts for about 38% of all food waste. The dumping of these food sector wastes in the environment is detrimental to the ecosystem due to their low biological stability, high nutritional value, high concentration of organic chemicals, high water activity, low oxidative stability, and optimal enzymatic activity. However, because of their advantageous nutritional and rheological characteristics, food waste streams offer a promising source of useful chemicals that may be used. Food wastes and byproducts may contain useful ingredients such as polysaccharides,

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proteins, lipids, fibers, flavorings, phytochemicals, and bioactive substances that are good for your health. Byproducts from fruits, vegetables, seafood, meat, and dairy products can be used as raw materials to produce components with value added for the functional food markets, one of the biggest trends in the food industry. Highly nutritive and useful food components, including polysaccharides, vitamins, minerals, dietary fiber, and bioactives like flavonoids and lycopene, can be found in food trash. The functional features of the byproducts include improved water binding, thickening, and gelling. A byproduct of the rice processing industry, rice bran accounts for around 10% of the total weight of white rice. Wheat is a great source of nutritional fiber, important unsaturated fats, vitamins, and minerals. Expanded uses for rice are emerging in the food, pharmaceutical, and nutraceutical industries. Because it contains a lot of dietary fiber and has therapeutic potential, rice bran can enhance the quality of included foods or practical foods. The byproducts of the meat business are known as carcasses, skins, bones, meat trimmings, blood, fatty tissues, horns, feet, hoofs, or internal organs. Lipids, carbohydrates, and proteins are abundant in meat byproducts. Meat proteins can be hydrolyzed, cooked, or fermented to produce bioactive peptides. These bioactive peptides could have beneficial physiological effects as well. The cardiovascular, immunological, neurological, and digestive systems may be impacted by bioactive peptides due to their antibacterial, antioxidant, antithrombotic, antihypertensive, anticancerogenic, satiety regulating, and immunomodulatory effects. Additionally, cancer, diabetes, obesity, and mental health conditions may all be successfully treated using peptides. The main sector of India’s food preparation business is the dairy processing sector. In particular, solvent proteins including lactoglobulin, lactalbumin, immunoglobulin, bovine serum albumin, lactoferrin, and lactoperoxidase are present in the byproduct of the dairy industry known as whey. Whey is an important nutrient. It is now acknowledged as a significant auxiliary dairy crude material that, in deep processing methods, can even surpass skim milk. Whey protein, free amino acids, urea, uric acid, creatine, creatinine, and ammonia are just a few of the nitrogenous compounds found in milk whey, which also has a rich mineral composition. Thus, milk whey can be employed for direct production of the bioactive mixtures for enhancing nutrition. One of the byproducts of the milk industry that functions as a probiotic food is curd. Strong evidence supports the idea that probiotics can treat and prevent diseases such as acute diarrhea. Algae, yeast, bacteria, and fungus all produce SCP, which is essentially a mass of dried cells (biomass). Bioprotein, microbial protein, or biomass are other names for it. These bacteria can be used in the diets of both humans and animals as protein-rich supplements or components. Since they don’t need a lot of land or water to grow, SCP can be an excellent alternative to plant-based protein sources. The selection of inexpensive, appropriate substrates, or biodegradable agricultural industrial leftovers as a source of nutrients for the microorganisms to thrive and create copious amounts of protein is crucial for lowering the cost of SCP production. In the past, many substrates have been employed for this purpose and contrasted. Apple pomace, yam peels, citrus pulp, potato peels, pineapple waste, papaya waste, and other regularly used substrates are a few examples. For this purpose, numerous additional substrates are also employed, including molasses, whey, starch, alkanes, and hydrocarbons. To produce their best work, some microorganisms have additional nutritional and mineral needs for growth and maintenance that must be carefully met.

14.2.6 BIOPESTICIDES Agricultural waste contains pollutants from herbicides, pesticides, insecticides, and other chemicals. Potato peels contain pathogen-fighting chemicals. Potatoes produce 140,000 tonnes of peel, which is only utilized as animal feed due to its toxic content. Steroid alkaloids abound in potatoes. To achieve value-added products that are safe for humans and the environment, agricultural input must be characterized and separated from contaminants. Toxic secondary metabolites such as steroidal alkaloid have antibacterial, antifungal, and insect-repelling effects. In excessive doses,

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these chemicals can produce colic, diarrhea, gastroenteritis, vomiting, fever, low blood pressure, quick pulse, and neurological problems. Potatoes include mostly α-solanine and α-chaconine. Glycosidic chains in these alkaloids block acetyl cholinesterase, cellular membrane, and calcium transport, making them cytotoxic. Waste activated sludge (WAS) has the potential to be an attractive alternative growing medium for industrial microbes to produce valuable metabolic products due to its increased composition of carbon, nitrogen, phosphorus, and other nutrients. Endotoxin, the most widely used bio-pesticide in the world and widely employed in the agronomy, forestry, and public health sectors, is produced during sporulation by organisms such as the aerobic spore-former Bacillus thuringiensis (Bt) (Bravo et al 2011). Conventionally, these entomopathogenic bacteria are produced in synthetic media comprising carbon, nitrogen, yeast extracts, and protein sources (such as soybean meal, fishmeal, glucose, peptone, and trace elements). Reusing WAS sludge as a low-cost “ecoalternative” medium for Bt production and then using it to control pests in agricultural crops and forests is practical and in line with current sludge disposal procedures (Tyagi et al 2009). The three main steps of the WAS Bt production process are (a) sludge fermentation (b) product recovery/harvesting (c) and (d) product formulation. The synthesis of biopesticides can be impacted by a number of parameters during fermentation, including pH, C/N ratio, dissolved oxygen (DO) concentration, foaming, solids concentration, and type of inoculum sludge (Flores et al 1997; Jégou et al 2001). Sachdeva et al (2000) reported on the impact of sludge solids and inoculum concentration on the production of Bt (subsp. kurstaki HD-1) via fermentation. Both the cell and spore counts and the production time met industry norms. Lower solids concentration in sludge samples was shown to significantly increase entomotoxicity while having no discernible impact on cell and spore counts. Based on cell, spore, and insect toxicity counts, Lachhab et al (2001) further optimized two process parameters (i.e., sludge solids and inoculum concentration) of the same process. They came to the conclusion that the oxygen transfer limitation caused an inferior entomotoxicity at higher solids concentrations; the ideal total solids and inoculum concentration was discovered to be 20–26 g/L and 2% (v/v), which improved potency to 12,970 IU/L, cell and spore concentrations to 5.0 × 109 and 4.8 × 109 CFU/mL, respectively, and a sporulation rate of 96%. According to Montiel et al (2001), an acid-hydrolysis pretreatment phase enhanced the sludge’s ability to support Bt growth, sporulation, and endotoxin generation (subsp kurstaki HD-1). In addition to producing Bt, WAS has the potential to produce other useful metabolic products like endotoxins, spores, and some other compounds (vegetative insecticidal proteins, hemolysins, enterotoxins, chitinases, proteases, phospholypases, and others) that are insecticidal in nature and exhibit entomotoxicity. The impact of temperature, pH, and agitation speed during the fermentation on Bt entomotoxicity, cell, and spore counts was also evaluated by Tirado Montiel et al (2003). The oxygen transfer rate was shown to be positively impacted by higher agitation speed in the range of 50–350 rpm, and the ideal pH for Bt production was found to be approximately 7. To promote cell development, sporulation, and endotoxin production by Bt, adequate aeration is required during fermentation. However, depending on the material contents, this process can also result in significant foaming. To maximize Bt productivity, studies of foaming effects on WASbased Bt fermentation production and their subsequent control are needed. The antifoaming effects of synthetic (i.e., polypropylene glycol) and natural (i.e., corn, canola, olive, peanut, sesame, soybean, and sunflower oils) antifoaming agents on Bt productivity were studied by Vidyarthi et al (2000). Despite the fact that all of the agents effectively reduced foaming, synthetic antifoaming compounds had a negative impact on cell respiration and growth by impairing the movement of nutrients through cell walls, including oxygen. However, employing natural oils to minimize foaming had better results, having less of an adverse effect on the yield of entomotoxicity and cell proliferation. Investigations have also been done into how different sludge pretreatment techniques affect the amount of entomotoxicity that Bt produces in secondary and mixed sludge. Verma et al (2005)

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demonstrated the use of WAS as a raw material for the development of Trichoderma sp. based bioherbicides/biopesticides, which possess a larger spectrum of activity than Bt. Similar to Bt fermentation production, it was discovered that thermal alkaline pretreatment was advantageous by improving the solubilization of organic matter; the ideal solid concentration under the study’s conditions was said to be 30 g/L. Barnabe et al (2009) also found that alkaline and thermo-alkaline pretreatment alone, or in combination with partial oxidation using H2O2, significantly reduced the entomotoxicity of mixed and/or secondary sludge by around 50%.

14.2.7 BIOSURFACTANTS The environmental impact of synthetic surfactants has sparked an interest in surfactants derived from natural sources. Biosurfactants are ideally suited for a variety of applications in industries such as the environmental, food and beverage, pharmaceutical, and cosmetic sectors. A compound annual growth rate (CAGR) of 4.3% was recorded for the biosurfactant industry between 2014 and 2020. To address the issue of biosurfactant’s economic production, scientists have shifted their focus to the usage of cheaper/renewable sources, such as agricultural residues or agro-industrial waste. Agro-industrial wastes, made of cellulose, hemicellulose, and lignin, can be used as sugar substrate in fermentation media. The bioconversion of these wastes into valuable products can be of enormous relevance, as it not only reduces the cost of energy, but also the environmental burden associated with their disposal. The sole carbon source for production is orange peel, banana peel, carrot peel waste, lime peel, and coconut oil cake. Utilizing agro-industrial and food waste with a high carbon content is a viable alternative for biosurfactant synthesis. Sophorolipid is produced by Candida bombicola when soy molasses is utilized as a substrate. Biosurfactants have significant uses in the food industry and can be used as an emulsifier, solubilizer, antiadhesive, foaming and wetting agent, and antibacterial substances. Biosurfactants also stimulate formation and stabilization of emulsions, agglomeration of fat globules, improvement of texture, consistency, and shelf life of starch and fat-containing foods. Biosurfactants preserve consistency, prevent staling, and solubilize flavor oils in the baking and ice cream industries. Biosurfactants are utilized efficiently for improving the solubility, biodegradation, and remediation of areas contaminated with organic and inorganic pollutants. Various authors have suggested agro-industrial wastes, i.e., fruit and vegetable peels as a cheap lignocellulosic substrate for biosurfactant synthesis. The effluent from potato processing businesses was a good substrate for the culture of B. subtilis and the recovery of their secondary metabolite, surfactins. Due to high carbon content, bagasse provides a substrate for biosurfactant manufacturing. Bagasse is an agro-industrial byproduct of the sugarcane industry. Under submerged fermentation, the rhamnolipid production of Pseudomonas azotoformans AJ15 was tested using a mixture of bagasse and potato peel. Biosurfactants and bioflocculants are an additional set of valuable metabolic byproducts produced during microbial transformation of organic substrates (i.e., extracellular macromolecules). Bioflocculants (i.e., extracellular bio-polymers such as functional proteins, polysaccharides, lipids, cellulose derivatives, etc.), secreted by microorganisms in synthetic growth media are widely used in chemical and mineral industrial fields including wastewater treatment, dredging, downstream processing, fermentation, and food industries (He et al 2002, 2004). They are anticipated to be rapidly biodegradable and non-toxic to humans and the environment (Kurane et al 1994; Yokoi et al 1996). However, the widespread use of these byproducts is now constrained by the high manufacturing cost, which is mostly connected with the availability of organic substrates (i.e., glucose and sucrose). Sesay et al (2006) demonstrated that enzyme hydrolysis is a gentle yet successful approach for EPS extraction from activated sludge flocs from mixed culture. Using two carbohydrate-specific enzymes (amylase and cellulase), a protein-specific enzyme (proteinase), and a reliable CER extraction method, enzymatic EPS extraction reached equilibrium in a few hours. By increasing the enzyme dosage, the extracted polymer amounts were likewise increased. More et al (2012)

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have suggested using WAS as an inexpensive source of carbon, nitrogen, and phosphorus for microorganism growth and the generation of bioflocculants. WAS has now been considered as one of the best bioresource for the isolation of bioflocculantproducing microorganisms, since bioflocculation naturally occurs in WAS during aerobic processes. Various strains of bioflocculants-producing microorganisms have successfully been isolated from WAS, including Achromobacter sp., Agrobacterium sp., Bacillus cereus, Exiguobacterium acetylicum, Enterobacter sp., Acinetobacter sp., Haemophilus sp., Citrobacter sp., Galactomyces sp., Klebsiella sp., Ochrobactium cicero, Pichia membranifaciens, Rhodococcus erythropolis, Saccharomycete spp., Solibacillus silverstris, etc. (Batta et al 2013; Guo et al 2013; Wan et al 2013; Wang et al 2013; 2014). Some authors have even indicated high flocculation activity using digested WAS liquor (5.5 g/L acetic acid and 0.7 g/L propionic acid) and derived chitosan-like polymers without adding any cations enhancement (e.g., K+, Na+, Ca2+, Mg2+, Fe2+, Al3+, and Fe3+) (Fujita et al 2001). More et al (2012) studied the pretreatment effect (i.e., sterilization, alkaline-thermal, and acid thermal treatment) on bioflocculants production in Serratia sp., with alkaline-thermal pretreatment achieving the highest concentration (3.4 g/L) of bioflocculants through improved sludge solubilization. Sponza (2003) also examined how wastewater components affected EPS (protein, polysaccharide, and DNA) production and physicochemical parameters (surface charge, bound water, and contact angle) in five lab-scale stirred reactors under steady-state settings. Under steady-state conditions, pulp-paper, textile (cotton knit textiles), and petrochemical floc EPS had lower protein (38–42 mg g−1 VSS) and more DNA (11–17 mg g−1). Waste cooking oil accounts approximately 50 kg of oily waste per person in developed countries. Biosurfactants are made from 29 million tonnes of lipid waste. Refineries and food processing plants produce tonnes of oily waste, which can be used as a rich substrate. Waste cooking oil from households and restaurants can replace expensive biosurfactant substrate.

14.2.8 BIOPLASTIC

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Bioplastics are plastics that are either biodegradable or made from renewable resources. According to the European Bioplastics Association, bioplastics are either biobased or biodegradable, or both. Biodegradable bioplastics provide alternate waste disposal methods, hence reducing the amount of plastic trash entering the environment; bioderived bioplastics permit a subspatial reduction in the carbon footprint. According to a report by the European Bioplastics Association, global bioplastic production in 2019 amounted to 2.11 MT, or 0.6% of total plastics production, and is expected to increase to 2.81 MT by 2025. The world desperately requires an effective replacement for plastics derived from petroleum. Food wastes are also used to make biodegradable organic polymers, such as Polyhyroxyalkanoates (PHA) and Polyhydroxybutyrate (PHB), which are biodegradable into carbon dioxide and water within a few months of burial. Microbes such as Ralstonia eutropha, E. coli, Clostridia Sp., Bacillus megaterium, and natural isolates of Actinobacillus, Azotobacter, Agrobacterium, Rhodobacterium, and Sphaerotilius utilize food waste as substrate and produce these polymers either as intracellular metabolite or as carbon reserves when nitrogen is scarce and carbon is abundant (Sanchez-Vazquez et al 2013). The stored polymers are broken down by particular depolymerase enzymes present within the cell and used as a source of carbon and energy when favorable conditions return and there is an adequate supply of nutrients. PHAs can be produced by more than 75 distinct bacterial genera as an intracellular carbon and energy reserve and/or as a sink for lowering redundant power consumption or electrons under unfavorable environmental and nutritional conditions (Lee 1996). Microbial PHAs can be made in nature by bacterial fermentation of sugar or lipids; however, their broad application has been hampered by their comparatively high production costs (i.e., USD 4–6/kg versus USD 0.6–0.9/kg for typical petroleum-derived polymers) (Akaraonye et al 2010). Since the cost of producing microbial PHA is mostly comprised of organic carbon growth substrate (i.e., carbohydrates), which represents around 50% of the total cost (Law et al 2001), changes in

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sugar production and related changes in commodities prices will have a direct impact on the longterm viability and cost-effectiveness of microbial PHA production. Waste-activated sludge bacteria can collect PHAs at 0.3–22.7 mg polymer/g of sludge (Baetens et al 2002). Preethi et al (2012) reported that PHA-producing bacteria could collect 80% of dry cell weight as PHA. PHA is synthesized in two stages: In the early anaerobic phase, the organism utilizes the organic compounds and converts them into VFAs. In the second phase, PHAaccumulating bacteria such as Ralstonia eutropha were grown to exploit SCFAs and polymerize them to polyhydroxyacetones under nutritional limitation. Pleissner et al (2013) also cultured Halomonas boliviensis in seawater and bakery waste hydrolysate and reported intracellular PHB accumulation at a rate of approximately 30% of the dry cell weight under batch and fed-batch cultures. In this view, it is recommended that food waste could maintain bioplastic production. Basically, bioplastic can be divided into three groups: 1. Biodegradable plastics made from biobased resources, such as PLA, PHAs, TPS, and PBS; 2. Biodegradable plastics made from petrochemical resources, such as poly(butylene adipate terephthalate) (PBAT) and poly-caprolactone (PCL); and 3. Non-biodegradable or partially biodegradable plastics from biob (bioPAs). 14.2.8.1 Starch-Based Plastics Plastics based on starch – After cellulose, starch is the most prevalent organic compound on the planet. It is produced by plants as a food reserve and is a member of the family of carbohydrates. Amylopectin (70–90%) and linear amylose (10–30%) are the two main polysaccharides that make up starch. Starch is mostly generated from plants including wheat, rice, corn, potatoes, and barley, where it makes up 60–90% of the dry weight. Since they biodegrade entirely and relatively quickly and are primarily obtainable from renewable sources at a low cost, starch-based products are gaining popularity. Native starch must first be destructurized to make it thermoplastic and meltprocessable before starch-based polymers may be created. To do this, plasticizers like water, glycerin, or other polyols are used, along with thermomechanical procedures. As a result, thermoplastic starch (TPS) is produced, which may be processed using common machinery for making synthetic plastics. TPS can also be combined with other materials and given additives to change its physical-mechanical characteristics, such as stiffness, strength, and water solubility. Packaging items like bags for biowaste disposal and thermoformed trays, agricultural items like mulching films and plant pots, and hygiene and cosmetic products are all made with rapidly biodegradable starch-based polymers. 14.2.8.2 Cellulose-Based Plastics Cellulose, the most prevalent polymer on Earth, is produced by plants as a structural polymer and by acetic acid bacteria. In contrast to bacterial cellulose, which has a very high purity, plant cellulose is typically blended with other polymers such as lignin, hemicelluloses, and pectin. Similar to starch, cellulose is a complex polysaccharide that is made up of monomeric glucose units linked together by b-1,4 links. It is a linear homopolymer. Due to its stronger hydrogen bonds than starch, cellulose is more resistant to hydrolysis. Native cellulose, like starch, is not a thermoplastic polymer since it breaks down before melting; as a result, it must be altered to produce a thermoplastic substance. The cellulose esters and ethers cellulose acetate (CA), CA propionate (CAP), and CA butyrate (CAB), which are often highly stiff but also brittle and exceedingly hygroscopic, are among the most widely distributed cellulose derivatives. 14.2.8.3 Biodegradable Plastic from Petrochemical Sources The most common sources of synthetic polymers are crude oil, natural gas, and coal. Most of these polymers cannot be composted or biodegraded since they do not exist in nature. However,

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degradability can be obtained by integrating unstable bonds (amide, ether, or ester) that hydrolyze under specific conditions. The final product is represented by a small group of biodegradable plastics made from fossil fuels. These plastics are primarily blended with biodegradable polymers to improve their thermomechanical properties, but they also have a few specialized uses as homopolymers. Polybutylene succinate (PBS), poly-caprolactone (PCL), polyvinyl alcohol (PVA), and poly(butylene adipate-co-terephthalate) (PBAT) are among of this group’s most well-known polymers. 14.2.8.4 PHA Production from Waste Streams of Different Industries Poly-hydroxyalkanoate (PHA) is an intriguing category of polyesters that have proven to be an excellent solution to all of these issues due to its biodegradability, thermoplastic and mechanical qualities. Under certain unfavorable conditions, various microbial strains can manufacture PHAs from renewable sources. The spectrum of their qualities can be influenced by the substrate, bacterial strains, and fermentation conditions used. Plant-derived biomass can be utilized as a feedstock in their manufacturing. The selection of appropriate raw materials for biopolymer manufacturing is critical since it might have an additional impact on the environmental pressure created by the process. The essential principle in this regard is to select renewable, inexpensive, and readily available carbon substrates that can sustain both microbial progress and PHA production in an environmentally friendly manner. The microbes can recover PHA from a variety of carbon sources, including low cost, complicated waste outputs, fatty acids, plant oils, alkanes, and simple carbohydrates. Domestic wastewater, food waste, waste cooking oil, olive and palm oil mill effluents, molasses, lingo-cellulosic biomass, coffee waste, cannery waste, biodiesel industry waste, paper-mill wastewater and sludge, and cheese whey are all waste sources that can be used to produce PHAs. In this context, crude glycerol, a byproduct of the biodiesel industry, is a very promising carbon source. Glycerol, fatty acid ethyl (or methyl) esters, residual ethanol or methanol, and residual fatty acids make up the majority of crude glycerol. As glycerol contains more carbon atoms than carbohydrates, cells that utilize glycerol maintain a more concentrated physiological state. These carbon atoms contribute to production by facilitating the synthesis of intracellular polymers. This clearly highlights the fact that glycerol can be employed as one of the most advantageous substrates for producing PHB precursor acetyl-CoA. Whey, a plentiful waste that is produced by the dairy industry, is found all over the world. It has dual benefits for PHA synthesis as a cheap raw material and a disposal problem for the dairy sector due to its excessive chemical oxygen demand (50,000–80,000 ppm) and biochemical oxygen demand (40,000–60,000 ppm). The main source of carbon in whey is lactose, which can be used as a resource for growth and product development. PHA may be produced economically using the whole whey lactose. Utilizing extra whey combines a financial gain with ecological enrichment by turning the polluting whey into useful items. The researchers have employed a cell-recycle system that states that if galactosidase activity of a production strain is not up to the expected higher levels, lactose can be hydrolyzed enzymatically or chemically to glucose and galactose. This system was developed to overcome challenges that arise during the continuous addition of whey feed in fed-batch cultures. Food waste is a rich source of complex proteins, carbohydrates, lipids, and nutraceuticals and can serve as the starting point for metabolites that are crucial for the production of goods. The three primary components of lignocellulosic biomass, which includes agro-food wastes, are hemicellulose, cellulose, and lignin. A large spectrum of metabolites can be obtained by fermenting these sugars with the right bacterium. For the production of PHAs and PHBs, lignocellulosic components, preferably waste from food and agricultural filtrate, have been used as resource. An optimization experiment utilizing mixed aerobic and anaerobic cultures found that microenvironment had the greatest impact on PHA generation. PHA conversion must be scaled up in preparation for imminent industrial consumption of PHA-using materials that help to lower

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financial and operational costs of PHA conversion relative to pure culture. More research into biocomposites made from synthetic PHAs and lignocellulosic fibers is needed so that PHA-based materials can be tailored to the specific needs of the food industry in terms of cost, performance, and sustainability.

14.2.9 BIOENERGY The economics of biofuel production have a significant impact on the future expansion of the biofuels industry. Future sustainable biofuel production also requires a balanced scorecard that considers economic, environmental, and social indicators. From food waste, numerous commercial biofuels have been created utilizing diverse biological methods. Recycling and energy conservation are becoming more and more popular as a result of the economy’s and the environment’s current conditions. Many different technologies have been developed to use rubbish to produce bioenergy. Waste materials are converted into a variety of fuels that can be used to produce power as part of the waste-to-energy conversion process. Recent years have seen the environmentally friendly extraction and conversion of biomass waste into chemical fuels as one of the effective ways to provide renewable energy. Various technologies and processes are available for converting biomass into energy. In addition to the transesterification technique, the two general methods of converting waste biomass into energy are thermochemical conversion and biochemical conversion. Thermochemical conversion decomposes biomass organic components using heat, while biochemical conversion uses microbes or enzymes to transform biomass or waste into energy. Thermochemical conversion includes pyrolysis, gasification, liquefaction, and combustion. On the other hand, biochemical conversion includes AD, alcoholic fermentation, and photobiological response. Recent investigations on waste-to-energy conversion methods are discussed below. Thermochemical technology breaks bonds and reforms organic matter into charcoal (solid), synthesis gas, and highly oxygenated bio-oil (liquid). Thermochemical conversion processes include gasification, pyrolysis, and liquefaction. The kind and quantity of biomass feedstock, the preferred energy, end-use conditions, environmental principles, financial situations, and project specifics can influence conversion type. According to several research studies, thermal conversion technologies have gained attention due to the availability of industrial infrastructure to supply highly developed thermochemical transformation equipment, short processing time, reduced water usage, and the added benefit of producing energy from plastic wastes that cannot be digested by microbial activity. Production-wise, thermochemical conversion is almost environmental independent. Thus, understanding thermochemical process choices is crucial to assessing their future potential. Biogas, also known as biomethane, is a clean energy source mostly made up of methane (60%) and carbon dioxide (35–40%). In addition, the amount of other gases in biogas, such as ammonia (NH3), hydrogen sulfide (H2S), hydrogen (H2), oxygen (O2), nitrogen (N2), and carbon monoxide, is relatively low (CO). AD of biowastes produces biomethane. AD is defined as the break down of organic compounds into simple chemicals by microorganisms that thrive as syntrophy in an oxygen-depleted environment while also producing biogas. AD is a biological process that converts organic waste such as municipal solid waste, food waste, industrial waste, sewage sludge, animal manure, and agricultural residues into energy. The advantages of AD for organic waste include decreased pathogen levels, less odor release, and a reduced need for organic sludge. The conversion of organic food waste into biomethane often depends on anaerobic microorganisms or methanogenic bacteria as well as temperature (Karthikeyan and Visvanathan 2013). The macronutrients (protein, lipids, carbohydrates, and starch) in FW are hydrolyzed by hydrolytic microorganisms into simple monomers (amino acid, fat, and sugar). As a result, methanogenic microorganisms are more active and produce more biogas (Pramanik et al 2019). The recovered biogas consist 50–75% biomethane and the remaining 25–50% carbon dioxide. There are two main categories of AD processes, mesophilic and thermophilic; where former refers to a method in

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which the digester is kept at a relatively low temperature and latter refers to a procedure where the temperature is raised (Obulisamy et al 2016). The conversion of organic waste into methane and carbon dioxide occurs during mesophilic digestion (at 37°C) and thermophilic digestion (at 55°C) to mesophilic and thermophilic bacteria. Maximum biomethane generation was limited by the formation of the byproduct acetate during the AD process. The production rate of biomethane is limited by the hydrolysis process. Conversely, stabilization of organic waste biomass helps mitigate environmental concerns such as groundwater contamination, odor creation, and the breeding of disease-carrying flies. Biomethane is a renewable fuel that can be produced from organic waste that can replace traditional fossil fuels. Yeshanew et al (2016) report that 442 8.6 mL CH4/gVS can be produced via AD, with thermal pretreatment resulting in 25% of COD solubilization. At 175°C for 1 min and 7.8°C per minute, microwave pretreatment FW produced 0.34 L CH4/gVS, as reported by Marin et al (2011). Junoh et al (2016) achieved a biomethane yield of 864.19 ml/gVS during alkaline (Ca(OH)2) pretreatment, and Yin et al (2016) achieved a biomethane yield of 817 mL CH4/gVS following fungal pretreatment at 60°C for 24 h. Due to rising consumer demand for dairy goods, beef, mutton, and poultry meat, farmers have recently become more interested in raising animals and producing chickens. The rising output of farm animal dung in Malaysia as a result of the country’s growing livestock population has made it challenging to dispose of a lot of manure. This may pose a serious threat to the ecosystem from pollution and a significant discharge of nutrients. One of the affordable and regenerative substrates used in the AD process to produce biogas is livestock manure. Thus, by reducing its environmental impact and providing biogas as a useful renewable energy source, the treatment of a large amount of livestock manure in AD aids in the proper management of the waste. Additionally, the increase of crop development on arable land benefits from the conversion of manure to organic fertilizer. Studies have been conducted in the past to gauge the possibility for producing biogas from livestock waste because farm animal waste serves as a significant source of raw materials for energy plants. With a high dry matter fraction, high yield of biogas per unit of fresh weight, low transportation costs, and low generation of liquid digestate, garden, and field waste is another potential raw material for biogas production. Biohydrogen is a non-toxic, environmentally friendly gas with a high level of combustibility. FW increases biohydrogen production by inactivating hydrogen-consuming (methanogenic) anaerobic bacteria. In general, there are five distinct types of biohydrogen generation procedures used, including direct biophotolysis, indirect biophotolysis, photo-fermentation, dark fermentation, and two-stage fermentation (Boodhun et al 2017). Dark fermentation has the greatest favorable impact on the generation of biohydrogen among these categories. The best anaerobic bacteria for consuming the various types of carbon sources present in FW and enhancing hydrogen production during dark fermentation are Clostridium (Gram-positive, rod-shaped, facultative anaerobic, and nonspore-forming bacteria) and Enterobacter (Gram-negative, rod-shaped, facultative anaerobic, and spore-forming bacteria) (Das and Veziroglu 2008). Numerous studies came to the conclusion that dark fermentation contains more hydrogen than other processes. Complex proteins were gradually broken down and transformed into soluble amino acids for the formation of biohydrogen (Liu et al 2013). Acetate, which is the principal byproduct of this process, was created, and the maximum biohydrogen yield was reduced. A maximal biohydrogen output of 162 mlH2/gVS from food waste was reported by Jang et al (2015). Han et al (2015) obtained 219.91 ml H2/g VS in a similar manner. Elbeshbishy et al (2011) obtained a yield of 55 mlH2/gVS and 28% COD solubilization. Anaerobic fermentation of FW produces biohythane, a mixture of biohydrogen and biomethane gas (Dahiya et al 2015). Biohythane is made up of 50–60% biomethane and 10–15% biohydrogen (Mirmohamadsadeghi et al 2019). In order to effectively produce biohythane from FW, two-stage anaerobic fermentation is generally used (Ghimire et al 2017). During the first stage of fermentation, hydrogen-consuming microorganisms play a crucial role in biohydrogen synthesis with a shorter retention period. The synthesis of biomethane at a longer retention period is thus significantly

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influenced by methanogenic microorganisms in the second stage of fermentation. It is a cuttingedge technology that will boost global green economic growth. When compared to conventional fuel, the chemical composition of biohythane will improve its quality and market value. It is commonly known that biohythane is a highly valuable fuel that is utilized in combustion engines and automobiles (Sen et al 2016). According to Jia et al (2017), the first stage of AD produced 13.33 mL H2 per hour, and the second stage produced 15.81 mL CH4 per hour. Similar results were reported by Ding et al (2017), who found that AD produced 43.0 mL H2/gVS during the first stage and 511.6 ml CH4/h during the second. Its advantages over fossil fuel include: (i) less energy is needed to ignite combine and motor vehicle engines (ii) it produces fuel of higher quality than conventional fuel. On the other hand, biohythane also has disadvantages in the production of bioelectricity. For instance, biohythane has a higher market value than conventional gasoline and is currently quite profitable in the United States and India (Cavinato et al 2016). FW also produces biodiesel or fatty acid methyl ester through direct transesterification or indirect transesterification. Alcohols (often methanol) combine with triglycerides present in vegetable oils or animal fats in the presence of a catalyst (acid or base) to generate an alkyl ester of fatty acids and glycerin as a byproduct during the transesterification process. Prior to transesterification, vegetable oil is typically removed from the seeds using mechanical crushing or chemical solvents. The fatty acid alkyl esters are commonly referred to as “biodiesel” and can be mixed with diesel fuel derived from petroleum. The protein-rich waste, also known as cake, is normally sold as animal feed or fertilizer, but it can also be utilized to produce more valuable compounds. In the presence of either alkaline or acidic catalysts, direct transesterification of FW is carried out. In indirect transesterification, oil-producing microorganisms that obtain their carbon supply from FW release microbial oils. These oils undergo transesterification to create biodiesel (Papanikolaou et al 2011). In a study conducted by Barik et al (2018), food waste from kitchens was used to produce biodiesel. In total, 37% of the lipids were extracted from FW using methanol as the solvent. 33% of biodiesel (fatty acid methyl ester) was generated when these lipids were transesterified with methanol as the solvent. In another study, Pleissner et al (2013) discovered that FW hydrolysates serve as a food supply for the growth of microalgae that can be utilized for biodiesel synthesis by indirect transesterification. On the hydrolysates of food waste, the bacteria thrived and produced 20 g of biomass. It was discovered that the fatty acids present in the bacteria’ stored lipids are ideal for biodiesel generation. Very little research has been conducted on the manufacturing of biodiesel from mixed FW, and the stated yield is very low (Karmee and Lin 2014). In order to produce more biodiesel, more transesterification and extraction are required. The presence of residual water in food waste typically inhibits transesterification, which is a key disadvantage of employing mixed food waste for biodiesel production. Hydrogenation of vegetable oil, animal fats, or recycled oils in the presence of a catalyst produces a renewable diesel fuel consisting of hydrocarbons that may be blended in any proportion with diesel derived from petroleum and propane. In the presence of a catalyst, vegetable oil or animal fats are reacted with hydrogen (usually obtained from an oil refinery) in this process. Hydrogenation of vegetable oils and animal fats is a first-generation method that has been commercialized, unlike transesterification. Biofuels that have been hydrogenated have a high cetane number, low sulfur level, and high viscosity. Biodiesel is made from oil seed crops such as rapeseed or soybeans, as well as plants such as oil seed palms. Additionally, it is made from a number of greases, including leftover cooking oil or animal fat waste. This diverse feedstock, ranging from low-cost waste to more expensive vegetable oils, results in biodiesel fuels with more changeable attributes that closely resemble those of the initial oil seed plant. Harmonization of fuel standards and various non-edible oil seed plants are still being developed. In major producing countries such as Brazil, the United States, and the European Union, sugarcane, sugar beet, and cereal grain-derived ethanol production has achieved a high level of energy efficiency. In 2009, the ethanol business in South Brazil significantly enhanced cogeneration efficiency, supplying 5% of the country’s electricity. In India, the Pacific,

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and other Asian nations that produce relatively low-cost ethanol but with limited production levels, ethanol from waste streams from sugar processing is being developed. The cost of producing biodiesel from waste fats and greases is cheaper than that of rapeseed and soybean, but waste fat and grease volumes are limited. Several studies have shown that WAS from municipal wastewater treatment plants can be used as a feedstock for biodiesel synthesis. Many facilities pay considerable costs to transport treated WAS (biosolid) to landfills. The conversion of this waste into a resource for the production of value-added chemicals could reduce the cost of wastewater treatment for municipalities and enterprises. The qualities of the produced biodiesel could be significantly impacted by variations in yields as well as fatty acid profiles caused by variations in wastewater treatment setups and wasteinfluent characteristics. Waste-activated sludge, a mixed microbial consortium and wastewater treatment byproduct, and cellulosic biomass produced on idle lands or for energy production (energy crops) could be an effective resource recovery and biorefinery model to produce biofuels. The gasification process involves chemical reactions taking place in an oxygen-poor atmosphere. This method involves heating biomass at high temperatures (500–1400°C), pressures up to 33 bar, and oxygen levels that are low or absent in order to produce flammable gas combinations. With the help of a gasification agent and catalyst, the gasification process converts carbonaceous elements into syngas that contains hydrogen, carbon monoxide, carbon dioxide, methane, higher hydrocarbons, and nitrogen. This syngas can be used to produce a variety of energy types and energy carriers, such as biofuel, hydrogen gas, biomethane gas, heat, power, and chemicals. According to reports, the gasification process is the best method for producing hydrogen gas from biomass. Gasification is regarded as an independent autothermic approach based on energy balance, in contrast to other thermochemical conversion methods. It is discovered that when compared to combustion and pyrolysis, biomass gasification has a higher heat capacity and the ability to recover more energy. This is due to the most effective use of currently available biomass feedstock for the generation of heat and power. Because pyrolysis and liquefaction are complex processes that depend heavily on operating circumstances and the presence of secondary reactions caused by hot solid particles and volatiles, their ability to convert carbon monoxide and hydrogen is weak. Another advantage of the gasification process is the straightforward conversion of synthetic natural gas from syngas’ carbon monoxide and carbon dioxide by catalytic methanation. Gasification of biowaste is therefore considered to be the best method for converting a variety of biomass feedstocks, including waste products from industry, agriculture, the kitchen, and the food industry. In contrast to thermochemical processes, biochemical operations include a range of microorganisms and often involve more precise reactions that are carried out under milder conditions. These processes may be incorporated into an organism’s metabolic processes or they may be altered through metabolic engineering to produce a particular product. For instance, fermentation is the process by which yeast and other microbes break down carbohydrates with little or no oxygen to create ethanol. E. coli is the bacteria most frequently utilized for industrial biochemical product synthesis, including the production of ethanol, lactic acid, and other chemicals. The most popular yeast for using in industrial ethanol synthesis from carbohydrates is S. cerevisiae. Currently, sugarcane, sweet sorghum, sugar beet, and starch crops (such as corn, wheat, or cassava) are the main raw materials for biochemical conversion. The main commercial result from this process is ethanol, which is mostly utilized as a gasoline alternative in light-duty transportation. The main components of sugar mill byproducts or pressed juices and molasses used to produce sugarcane ethanol. Single-batch, fed-batch, or continuous procedures can be used for fermentation; the latter is more popular and effective since it allows for yeast recycling. Brazil’s fermented liquor has an ethanol concentration of 7–10%; it is then distilled to boost purity to about 93%. Ethanol must be anhydrous in order to be combined with gasoline in the majority of applications, and the combination must be further dehydrated to achieve a grade of 99.8–99.9%. The main dry mill (or dry grind) process for corn-based ethanol fuel starts with hammer milling the entire grain into a coarse flour, which is boiled into a slurry, then hydrolyzed by

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alpha-amylase enzymes to generate dextrins, then hydrolyzed by glucoamylases to form glucose, which yeasts ferment (the last two processes can be combined). Distillers’ grains with solubles, a byproduct, can be sold as animal feed to feedlots close to the biorefinery wet or dried for stabilization before being sold. Natural gas is the most typical source of process heat. For every cumulative doubling of production between the early 1980s and 2005, the energy intensity of typical dry mill operations in North America decreased by 14%. Since then, there have been ten total doubling shavings, and the industry has continued to enhance its energy performance. Wheat-to-ethanol processing, which begins with a malting stage and proceeds through either enzyme or acid hydrolysis to produce sugars for fermentation, is comparable to the dry milling of corn. When desirable raw goods are planted, processed, and eaten, biomass residues and garbage are produced as byproducts. Biomass residues can be divided into primary, secondary, and tertiary groupings, to be more precise. Primary residues, such as maize stalks, stems, leaves, and straw, are often produced following the planting of target food crops and forest products in the field. The secondary residues are generated when food crops are transformed into finished goods. Agricultural and food processing wastes include palm kernel cake, coffee husks, rice hulls, sugarcane bagasse, and woodchips. On the other hand, tertiary residues become accessible after a biomass-derived product has been consumed by humans and/or animals. These residues may initially exist as MSW before being further transformed into sewage sludge and/or wastewater. Wood and agricultural waste (primary and secondary biomass residues), used cooking oil (tertiary biomass residues), and microalgae biomass have all shown promising potentials among the biomass residues and garbage. Waste products from sawmill and timber processing industry, such as sawdust, woodchips, and abandoned logs, can be utilized as feedstock for biofuels. For example, the wood waste and sawdust produced by the paper and saw industries can be used as boiler fuels and as feedstock for the manufacturing of ethanol. It has also been suggested that corn stover, including the stalks, cobs, and leaves, has the potential to be transformed into fermentable sugars for the generation of biobutanol. The bagasse and leaves of sugarcane, in particular, can be a good option for the economically viable usage of residual substrates for the manufacture of bioethanol and other biofuels like biochar in tropical nations. Palm kernel press cake, a byproduct of the extraction of palm oil, has proven useful for producing bioethanol through fermentation. The selected feedstocks provide high-quality food-grade virgin oils, while waste oils like wasted cooking oils can be used to make cheap biodiesel. An effective way to lower the cost of raw materials for biodiesel manufacturing is to use used cooking oil instead of virgin oil as feedstocks. According to a report, using waste oils will likely result in a 60–90% reduction in the cost of producing biodiesel. Reusing used cooking oil also solves the problem of disposing of huge quantities of frying oil that are no longer edible due to their high free fatty acid content. B20 is a blend of 20% biodiesel made from waste oils and 80% diesel that can be used in engines without requiring significant modification. The quality of used edible oils is not much different from that of fresh oils, and water and undesirable solids can be eliminated before transesterification using straightforward pre-treatments such heating and filtration. Algae can broadly be divided into two broad groups: macroalgae (sometimes referred to as seaweeds) and microalgae. Large, multicellular algae that are frequently seen growing in ponds are known as macroalgae. In contrast, microalgae are microscopic, unicellular algae that frequently grow in suspension in water bodies. Although macroalgae have a larger diversity of bioactive chemicals than microalgae, they provide less potential for producing biofuels. Due to their high lipid accumulation and quick development rates, microalgae therefore constitute another prospective source of oil. Furthermore, microalgae don’t compete for extensive freshwater resources or solely agricultural land. After target products like oils or/and other high-value compounds have been extracted and processed from microalgae biomass, the spent microalgae biomass can be converted to biofuels in a manner similar to biomass leftovers and garbage.

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14.2.10 BIOCHAR Agro-industrial byproducts are frequently used, whether they are unprocessed or partially processed. Products including charcoal, oils, gases, and volatile chemicals, among others, can be produced through physical processes. Pine sawdust is one of the most popular materials since it is inexpensive, abundant, and versatile. Biochar provides a high surface area, porosity, nutrients associated with the initial biomass, and the ability to hold water and microbes. It is successfully employed in agriculture as an organic amendment or organic soil conditioner, since it increases soil structural stability, porosity, hydraulic conductivity, soil aeration and CEC, an increase in nutrient availability, soil fertility, and consequently has a positive influence on many crops. Biochar’s high porosity allows soil microorganisms or biological inoculants like plant growth-promoting rhizobacteria (PGPR) to survive and remain metabolically active. Both direct and indirect processes are used by PGPR to stimulate plant growth. Direct mechanism comprises biofertilizer activity, encouragement of root growth, rhizobia-remediation, and plant stress regulation. Biological controls such as antibiosis, competition, and the establishment of systemic resistance in plants are examples of indirect processes. Biochar is a dual-purpose biomaterial that adds stable and slow-release carbon to the soil when used as biocompatible organic substrate for co-inoculation of beneficial microbes. However, biochar serves as a support, shielding bacteria from the effects of environmental factors like temperature, ultraviolet light, desiccation, and predation by soil microbes. Nitrogen-fixing bacteria, bacteria that promote plant development, bacteria that operate as biocontrol agents, and bacteria that break down phosphate are some of the microorganisms that have been combined with biochar and given to soils. Pyrolysis is the process of degrading FW at high temperatures (between 400 and 900°C). Gupta et al (2018) prepared biochar from mixed FW and rice waste that had a carbon concentration of 66% and 71%. A finite amount of the oxygen available in that environment was used throughout this operation (Gupta et al 2018). As a result, incomplete combustion of the feedstock will result in the production of a stable, carbon-rich solid product called biochar, sometimes known as black carbon (Rutherford et al 2012). It is mostly made of a lot of carbon, a substance with low density, and it has a lot of pores (Kumar et al 2016). The physiochemical properties of the resulting biochar are significantly influenced by the substrate composition and decomposition temperature. With each tonne of substrate used for pyrolysis, biochar has a better potential to prevent the production of greenhouse gases, which equals about 870 kg of CO2 (Roberts et al 2010). A very effective absorbent utilized to extract organic and inorganic chemical components from wastewater is biochar. Biochar is sometimes used as a soil conditioner because it has a high water-holding capacity, improves the soil’s fertility, and increases the amount of nutrients available for crop residues and plants to develop. In contrast to other synthetic soil conditioners, biochar persists in the soil for a longer time and requires long time to degrade (Duku et al 2011). Biochar offers a number of benefits, including lowering biological oxygen demand and total nitrogen, preventing greenhouse gas emissions, reducing nutrient leaching, and thus maintaining soil fertility (Kumar et al 2016). Alghashm et al (2018) made biochar from anaerobically digested FW waste. The pyrolysis temperature was controlled by the authors between 400° and 900°C with a fixed pyrolysis time of two hours under a low oxygen environment. At 400°C, the highest biochar output (70.4%) was recorded. At 900°C, increasing the temperature further resulted in a drop in biochar output of roughly 43.7%. Moreover, volatile matter decreased from 40.6% to 4.5%. Wastewater treatment produces semi-solid or residual sewage sludge. Sewage sludge biochar, produced via carbonized thermochemical conversion of biomass in an oxygen-limited environment, is very porous and absorbs heavy metals. The production of sludge during wastewater treatment has piqued the interest of numerous experts concerned with its toxicity and environmental safety in lieu of its disposal. The raw sewage sludge also contains contaminants including heavy metals, potentially hazardous elements, and polycyclic aromatic hydrocarbons in addition to

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beneficial nutrients like N, P, organic matter, and necessary trace elements. Most researchers are fascinated toward sewage sludge biochar for its ability to improve soil quality, reduce heavy metal uptake, and nourish agricultural areas. Using sewage sludge for agriculture is restricted because heavy metals are particularly detrimental to the health of plants, animals, and people. Additionally, sewage sludge contains a variety of nutrients, including potassium phosphorous, a powerful source of fertilizers. In horticulture, sewage sludge biochar can also be used as a component of the growing media. Although, due to the high stability of sewage sludge biochar, they improve organic matter addition, nutrient replenishment (phosphorus and nitrogen), raise cation exchange capacity (CEC), correct soil pH, and reduce nutrient loss by leaching. As a result, the use of biochar made from sewage sludge develops a very positive practice for the advancement of sustainable agricultural practices and systems, but also limits its agricultural use due to the presence of variety of toxic chemicals and pollutants (i.e., heavy metals).

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Index Abatement, 137, 237, 290 Abiotic, 8, 89, 99, 108–110, 172, 294, 298 Absorbent, 98, 248, 366 Absorption, 73, 78–79, 109, 117, 137, 139–140, 157, 206, 277, 279 Abundant, 29, 34–35, 100, 118, 148, 150, 155, 176, 180, 218, 227, 280, 321, 323, 332, 349, 352, 355, 358, 366 Acceleration, 348 Acceptability, 118, 148, 171, 189 Acceptance, 138, 289 Acceptor, 64, 66, 69, 80, 111, 204, 293 Accessory, 320 Acclimatize, 75 Accountability, 314–315 Accumulator, 72, 293 Acidification, 23, 47, 50, 55–56 Acidiplasma, 260–261 Acidogenesis, 25, 321, 349–350 Acidogenic, 22, 326, 349 Acidophile, 260 Acidophilic, 121, 260–261, 267 Acinetobacter, 31, 149, 156, 158, 174, 358 Acquisition, 45–46, 141 Actinobacillus, 350, 358 Actinomycetes, 31, 93–94, 96, 148, 160, 174 Activate, 160, 188, 200 Activation, 352 Acute, 9, 233, 355 Adaptation, 258, 279, 315 Adherence, 140, 151, 234 Adhesion, 112, 140, 150, 260, 276 Adhesive, 30, 33, 235, 327, 333, 350 Administration, 233, 326 Adrenaline, 233 Adsorbate, 140–142, 248 Adsorbent, 21, 28, 32, 115, 117, 140, 142, 235–237, 258, 336–337, 351 Adsorption, 21, 32, 74–75, 78, 91, 113, 117–118, 137, 139–142, 144, 148, 153, 216, 231, 235–236, 238, 248–249, 254–256, 258, 277–278, 281–283, 329, 351–352 Adverse, 108, 291–292, 356 Aeration, 24, 32, 65–67, 79, 93, 96–97, 99–100, 113–115, 175, 178, 180, 185, 209, 275, 282, 290, 292, 354, 356, 366 Aerenchyma, 78, 278 Aerobes, 261 Aerogenes, 336 Aerophilus, 77 Aerosol, 4–5, 19 Aerospace, 35, 225 Agar, 34, 115, 117–118, 184, 329 Aggregation, 55, 113–115, 141, 145–147, 149, 151, 156, 159, 229, 233, 276 Agitation, 142, 144, 147, 204, 356 Agrobacterium, 31, 354, 358

Agricultural, 4–5, 7, 9, 12, 20–24, 30–32, 45, 65, 78–79, 92, 100–102, 105, 108–110, 116–117, 137, 153, 158–161, 176–179, 181, 188, 225–226, 238, 286–287, 320, 327, 347, 351, 353, 365 Agrochemicals, 4, 156, 334 Agronomy, 30, 356 Agrowastes, 22, 32 Ailments, 47 Albumin, 355 Alcaligens, 172 Alcanivorax, 111, 157 Alcoholysis, 27 Alginate, 34–36, 113, 115–118, 148, 153, 232, 239 Alicyclobacillus, 261 Aliphatic, 70, 90, 95, 116–117, 155, 157 Alkaloid, 190, 355–356 Allelopathy, 72 Allergenic, 33 Allergies, 232–233 Alleviate, 160 Alloy, 231, 233 Alteration, 32, 109, 143, 151, 260, 327 Alum, 146, 153 Ambient, 98, 206, 255 Amendment, 23, 25–26, 33, 65–66, 97, 159, 366 Aminopeptidases, 30 Ammonification, 283 Ammonium, 23, 29–30, 57–58, 69–70, 95, 99, 159–160, 181, 183, 187, 252–253, 258, 275–278, 280–281, 285–288, 291, 294, 323, 327, 354–355, 361 Ammunition, 70 Amphipathic, 154–155, 158 Amphiphilic, 30 Amphoteric, 154 Amylase, 30, 32, 89, 97, 103, 142, 182, 211, 329–330, 352–354, 357, 365 Amyloglucosidase, 329 Amylolyquefaciens, 330 Amylolytic, 350 Amylopectin, 359 Amylophilus, 103 Amylose, 359 Anabaena, 104–105, 291 Anabolic, 72 Anaerobe, 205, 211–212, 261 Anatomical, 6 Anhydrous, 364 Anion, 139, 141, 254 Anionic, 35, 138–139, 141, 154, 157, 252–253, 255 Anode, 111, 200–205, 256 Anolyte, 202, 204 Anopheles, 290 Anova, 298 Anoxic, 25, 78, 80, 113–114, 212, 267, 276–279, 290 Antagonistic, 110, 283

373

374 Anthracene, 77 Anthropogenic, 78 Antiadhesive, 357 Antibacterial, 31, 34–35, 156, 231–234, 236, 239, 349, 355, 357 Antibiosis, 366 Antibody, 142–143, 232, 236 Anticancer, 225, 227, 233, 239, 350 Anticancerogenic, 355 Anticoagulant, 35 Anticorrosion, 112 Antifoaming, 356 Antifreeze, 9, 332, 335 Antifungal, 156, 231, 238, 355 Antihypertensive, 35, 104, 355 Antioxidant, 34–35, 103–104, 151–152, 181, 191, 227–228, 233, 238, 322, 330, 349–350, 355 Antioxidative, 239 Antiproliferative, 35 Antithrombotic, 355 Apical, 78 Apoptosis, 350 Apoptotic, 233 Aquaculture, 4, 37, 175, 286, 319 Aquifer, 68, 218, 276, 286, 298 Arabidopsis, 72 Arable, 294, 354, 362 Arbuscular, 105, 107–108 Archaea, 137, 260–261, 267, 291, 294 Architectural, 234 Arid, 33, 118, 287 Aromatic, 26, 34, 63, 70, 73, 76, 90–91, 95, 111, 117, 157–158, 227, 279, 323, 332, 349, 366 Arrangement, 277 Array, 94, 101, 120, 239, 291, 325 Arsenate, 31 Arthritis, 34 Arthropods, 352 Asbestos, 8, 19 Ascorbic, 228, 251 Aseptic, 182, 186 Aspergillus, 32, 37, 102–105, 138, 150–151, 154, 174, 176, 183–184, 230–231, 238, 329, 350, 352–353 Assemblages, 275, 296 Assimilation, 89–90, 96, 326–327 Astaxanthin, 349 Asthma, 233 ATCC, 230, 326 Atherosclerosis, 34 Atmospheric, 19, 80, 104, 107, 259, 276, 349 ATP, 90, 206, 212 Attainable, 316 Attenuation, 64 Augmentation, 68, 234 Autochthonous, 290 Autoflocculation, 147, 151–152 Automobile, 27, 33, 234, 237, 363 Autothermic, 364 Autotroph, 113, 259–261 Auxiliary, 55, 355 Auxin, 100, 106, 354 Axenic, 295

Index Azadirachta, 228, 230 Azolla, 105 Azospirillum, 104, 107 Azotobacter, 104, 354, 358 Backbone, 173 Bactericides, 217 Bacteriocins, 110 Bagasse, 21–22, 28, 33, 102–103, 180, 184, 213, 329, 351–352, 357, 365 Bakery, 37, 359 Barely, 315 Barrier, 79, 96, 98, 111, 145, 202, 292 Baseball, 235 Basel, 3, 17 Basidiomycete, 150 Battery, 4, 35–36, 118–119, 237, 239, 315, 337 Bead, 35, 142–143, 235, 255, 329–330 Bean, 28, 104, 116, 159, 213 Beef, 362 Beer, 320 Beverage, 4, 9, 179, 181, 227, 332, 357 BFBF, 108–109 BFR, 119 BGR, 264–265 Bimetallic, 231 Binder, 33, 142, 214 Bioaccumulation, 75, 78–79, 120 Bioactivity, 148, 206 Bioadsorbents, 322 Bioaugmentation, 64, 68–69, 71, 218 Bioaugmented, 77 Bioavailability, 37, 63, 68, 71, 73–74, 80, 105, 108–109, 111, 157–158, 218, 229 Biobutanol, 101 Biocarriers, 113 Biocatalyst, 111 Bioceramics, 22 Biochar, 21, 28, 32, 76, 158–160, 258, 298, 365–366 Biocoagulation, 152–153 Biocompatibility, 148, 234, 325 Biocompatible, 116, 205, 232, 239, 366 Biocomposite, 32, 226 Biocompost, 37 Biocontrol, 104–106, 110, 112, 290, 366 Bioconversion, 18, 26, 89, 93, 100, 102, 190, 208, 320, 357 Biodegradability, 68, 90, 102, 116, 143, 147, 320, 325, 360 Biodegrade, 23, 66, 77, 80, 95, 359 Biodegrader, 97 Biodeterioration, 89 Biodiversity, 92, 104, 108, 290–291, 293 Bioeconomy, 319, 321–322, 324, 327, 347–348 Bioelectricity, 218, 363 Bioelectrochemical, 111, 203 Bioelectrohydrogenesis, 208 Bioemulsifier, 157 Bioenergy, 22, 25, 36, 199, 201, 203, 205, 207, 209, 211, 213, 215, 217–218, 225, 319–320, 322, 327, 335, 347, 361 Bioethanol, 21, 27, 101–102, 189, 199, 320, 322, 327, 332, 334, 347, 365 Biofactory, 36, 227, 229

Index Biofertilization, 107 Biofertilizer, 89, 92–93, 104–108, 110, 112, 153, 320–322, 353–354, 366 Biofilm, 78, 105, 108–115, 138, 150, 191, 200, 204, 260, 281–282, 296 Biofiltration, 320 Bioflocculant, 29, 31, 143–145, 147–149, 151–152, 357–358 Biofragmentation, 89–90 Biofuel, 21–22, 25, 27–28, 37, 89, 100–101, 189, 199, 205, 209, 213–214, 218, 320–322, 326–327, 329, 334, 336, 347–348, 353, 361, 363–365 Biogas, 25–26, 46, 52, 54, 92, 113, 115, 189–190, 199, 209–211, 215, 320, 336, 347, 354, 361–362 Biogenic, 229–231, 319 Bioherbicides, 30, 357 Biohydrogen, 22, 27, 101, 112, 118, 199, 205–212, 320, 322, 326, 336, 350, 362 Biohydrometallurgy, 249, 259 Biohythane, 362–363 Bioimaging, 233 Bioleaching, 91, 112, 119–121, 156, 249–250, 258–264, 266–267, 320 Bioliquids, 215 Biology, 116, 218 Biolubricants, 34 Biomaterial, 319–321, 347–348, 366 Biomedical, 4–5, 7, 16, 35, 102, 111–112, 116, 148, 233 Biometallurgical, 120 Biomethanation, 25 Biomethane, 29, 115, 322, 361–362, 364 Biomined, 260, 267 Biomineralization, 91, 120, 259, 267 Biomining, 247, 249, 251, 253, 255, 257, 259–267 Biomolecules, 35–36, 72, 141, 143, 154, 226, 228 Biooxidation, 265 Biopesticide, 29–30, 100–102, 355–357 Biopharmaceuticals, 152 Biophotolysis, 362 Biophysical, 142 Biopiling, 64–66 Bioplastic, 29, 33–34, 113, 321, 326, 329, 331, 358–359 Biopolyamides, 31 Biopolymer, 31, 34, 112–113, 115–119, 144, 153, 208, 239, 320–321, 325–327, 330–331, 352, 358, 360 Bioprocess, 34, 149, 187, 319–321, 326 Bioproducts, 305, 319–320, 332, 347 Biopulping, 320 Bioreactor, 31, 111, 113, 178, 207, 209, 265, 267, 320 Bioreductive, 267 Biorefinery, 23, 29, 33, 151, 319–322, 324, 327, 331–332, 336–337, 347, 353, 364–365 Biorefining, 319 Bioremediate, 64, 78, 113, 156 Bioremediation, 8, 63–71, 73–80, 91–92, 101, 110–112, 118, 157–158, 191, 320, 327 Biorenewable, 33, 331 Bioresource, 137, 144, 226, 230, 358 Biosealants, 118 Biosensing, 225, 233, 238 Biosensor, 204, 233, 236, 238 Bioslurping, 67

375 Biosolid, 21, 29, 35, 215, 351, 364 Biosorbed, 137, 141 Biosorbent, 137–139, 141–142, 320 Biosorption, 91, 120, 137, 139–143, 145, 147, 149, 151–153, 155, 157, 159, 320 Biosorptive, 137–138, 141–142 Biosparging, 64, 68 Biosphere, 65, 275 Biostimulants, 74 Biostimulation, 64, 69, 71, 218 Biosurfactant, 29, 31, 34, 64, 71, 74, 77, 101–102, 154–158, 357–358 Biosynthesis, 34, 229, 231 Biosynthesized, 35–36, 171, 231, 233 Biosystems, 320 Biotechnological, 156, 225, 249, 320, 352 Biotechnology, 18, 21, 35, 107, 112–113, 115, 137, 146, 199, 218, 225, 259–260, 320, 333, 352 Bioterrorism, 290 Biotin, 142, 173, 175 Biotransformation, 63–64, 66–67, 90, 120, 292, 321, 330 Biotrickling, 67 Bioventing, 64, 66–68 Biowaste, 23–25, 27–29, 31, 36, 45, 144, 180, 183, 225–226, 229, 319, 359, 361, 364 Biphasic, 353 Blastofiltration, 74 BOD, 144, 204, 281, 283–285, 287 Bovine, 331, 355 BPA, 34 Bran, 101–104, 137, 176, 179–181, 184, 326, 350, 355 Brewery, 111, 113, 174, 176–177, 179 Briquettes, 27–28, 199, 213 Bronchitis, 233 Broth, 77, 147, 149, 151, 155, 182, 184, 186, 231, 336 Brownfields, 70 BTEX, 68, 70 Buffering, 141, 332 Burial, 215–216, 358 Calcareous, 278 Cancer, 9, 47, 56, 91, 119, 189, 232–233, 350, 355 Candida, 102, 154, 158, 171–174, 176, 181, 184, 187, 232, 330, 332, 357 Caprolactam, 332 Caprolactone, 116–117, 332, 359–360 Carbonaceous, 27, 29, 214, 364 Carbonized, 366 Carbonless, 91 Carbs, 153, 180–182, 353 Carcasses, 355 Carcinogenic, 9, 119, 171, 192, 276 Cardiovascular, 355 Carotene, 173, 349 Carrageenan, 34–35, 115–116, 119 Carrier, 28, 52, 90, 105, 107, 140, 205–206, 232, 315, 364 Cartilage, 35 Cascading, 319 Casein, 116 Cassava, 27, 103, 180, 212, 364 Catabolic, 72, 90, 101, 111 Catalase, 30

376 Catalytic, 35, 63, 118, 227, 235, 316, 323, 332, 335, 364 Catalyze, 227, 234, 260–261, 264–265, 267 Catechin, 228 Catechol, 117 Cathode, 6, 8, 111, 200–204, 256 Cation, 115, 138–139, 141, 159, 254, 256, 358 Cattle, 7, 21, 24, 79, 98, 191–192, 337, 351 Caulofiltration, 74 Cecchi, 26 Cellubiose, 206 Celluclast, 211 Cellulase, 32, 89, 97, 101, 103, 182, 184, 208, 211, 329, 336, 352–353, 357 Cellulolytic, 188 Cementation, 247, 264 Centrifugation, 31, 178, 182, 185–187, 209 Ceramic, 8, 16, 22, 36–37, 98, 119, 217, 234–235, 239, 256 Cereal, 22, 101, 227, 331, 351, 363 CFU, 289, 356 Chalcopyrite, 262–263, 267 Charcoal, 22, 159–160, 237, 258, 361, 366 Chelating, 105, 108–109, 115, 251, 255, 332 Chelation, 105, 142, 144 Chemisorption, 139 Chemoautotrophic, 260 Chemoheterotrophs, 207 Chemolithotrophic, 121 Chemotaxis, 111 Chemotherapeutic, 233 Chitin, 34–35, 116, 138, 185, 191, 329, 352–353 Chitinase, 30, 97, 352–353, 356 Chitooligosaccharides, 35, 330 Chlorofluorocarbons, 47 Choline, 173, 175 Chromatography, 142–143, 352 Chromobacterium, 121 Chronic, 9, 350 Chrysosporium, 37, 103 Chymotrypsin, 331 Citrobacter, 31, 211, 358 Cladosporium, 176 Cloned, 156 Clostridium, 102, 104, 206, 211, 358, 362 Coagulant, 117–119, 145, 153–154 Coalification, 215–216 Cocktails, 349 Cocopeat, 32 COD, 144, 152, 203, 210, 236, 281, 287, 362 Coenzyme, 212 Coexisting, 141, 150 Cogeneration, 363 Coliform, 288–289 Collagen, 35, 116 Colloid, 153, 261 Colonization, 101, 110, 297 Colorants, 188, 347, 349 Cometabolism, 63, 90 Commercialization, 212, 336–337, 349 Commodity, 31, 34, 50, 348, 359 Compaction, 159 Complexation, 32, 120, 137, 139, 144, 253–254, 277, 281 Complexolysis, 120 Composite, 33, 35, 111, 119, 140, 231, 234, 316, 332, 361

Index Compost, 22–24, 37, 58, 65–66, 76, 89, 92–100, 160, 281, 354 Condensation, 36, 183 Conditioner, 32, 100, 154, 190, 366 Conductivity, 36, 119, 159, 278–279, 282, 286, 366 Congenital, 9 Conservation, 4, 157, 308, 361 Consortium, 37, 71, 77–78, 89, 107, 137, 260, 263, 364 Coolants, 332, 335 Copolymers, 116–117 Corrosion, 9, 30, 110–112, 234, 248 Corrosive, 8–9, 30, 111, 153, 200, 253, 267 Cosmetic, 30–31, 33–35, 91, 102, 156, 234, 321, 323, 332, 335, 349, 357, 359 Covalent, 139–141, 153 Covid, 199 Cowpeas, 70 CPCB, 16, 18 CPHEEO, 16, 18 Cryoprotection, 145 Crystallization, 7, 180, 248 Cyanobacterium, 137–138, 150, 153, 173–174, 205–206, 291–292, 326 Cyanotoxins, 192 Cysteine, 32, 172–173, 175 Cytochrome, 72 Cytokinin, 100, 354 Cytotoxic, 7, 227, 229, 356 Databank, 264–265 Deacetylation, 35, 353 Decolorization, 145, 327 Decomposition, 3, 24, 57, 73, 90, 92, 94–97, 186, 202, 214, 239, 248, 277, 354, 366 Defective, 232 Defence, 106, 110 Deficiency, 171 Defluoridation, 117 Deforestation, 33, 289 Degradability, 4, 8, 360 Degrader, 69, 97, 157 Dehalococcoides, 68 Dehydration, 114, 152, 182–184, 212, 332, 334 Demineralization, 35, 353 Dendrimers, 235–236 Dendrobaena, 97 Denitrificans, 174 Denitrification, 80, 113, 276–281, 283, 288, 293–294 Denitrifying, 78, 277 Denitrogenation, 237 Densification, 27–28 Depletion, 50, 56, 200, 265, 307, 313, 315–316, 319–320, 347 Depolymerization, 332 Dermatologic, 234 Desalination, 237, 298 Desertification, 116, 118 Desiccant, 236 Desiccation, 275, 366 Desorption, 64, 71, 117, 140–141, 216, 238, 248 Destabilize, 144, 147 Desulphurization, 256, 276 Deterioration, 24, 72, 118–119, 159, 282, 350

Index Detoxification, 29, 119, 233 Detrivores, 8 Dewatering, 147–148, 152, 209–210 Dha, 327 Diabetes, 232–233, 355 Diagnosis, 7, 232, 238 Diatoms, 231, 291, 352 Diazotrophs, 177, 291 Digestate, 23, 26, 190, 354, 362 Digester, 26, 92, 190, 362 Discernible, 66, 114, 356 Discharge, 54, 67, 115, 137, 275, 287, 289, 309, 327, 362 Disinfection, 235, 276, 287 Dispersants, 31, 118, 337 Dispersion, 108, 112, 145, 152, 157, 209, 214, 248 Dissociate, 262 Distillery, 78, 155 Disturbance, 94, 185, 296 Diurnal, 297 Diversion, 310, 316 Domestication, 24 Dominance, 263, 291–292 Dominate, 20, 75, 94, 260, 291 Donor, 67, 69, 139, 207 Doped, 108, 119 Dormant, 104 Dose, 78, 146–147, 355 Ecocement, 336 Ecoclinkers, 336 Ecofriendly, 69 Ecolabels, 45 Ecology, 19, 80, 189–190, 295, 309, 311–312 Economical, 34, 65, 80, 118, 151, 237–238, 265, 308–309, 354 Ecosphere, 54 Ecotoxic, 9 Ectomycorrhizal, 105 Edaphic, 71 Efficacy, 68, 101, 113, 118, 157, 205, 234, 236, 239, 255 Electricigen, 200 Electrochemical, 91, 116–119, 140, 204, 225, 237, 256 Electrode, 119, 201–202, 204, 256 Electroplating, 6, 63, 78, 251, 254, 257 Electrostatic, 144–145, 147, 149, 153, 229, 235 Electrowinning, 249, 252, 255, 264 Elevated, 247–248, 251, 260, 288–289, 291 Elimination, 66–67, 77–78, 97, 100, 137, 143–144, 213, 235, 255, 278, 292, 308 Emergent, 70, 80, 276–278, 280, 285, 287, 290–293 Emulsification, 145, 157, 238 Emulsion, 33, 118, 152, 155–157, 357 Encapsulation, 107, 238–239 Endogenous, 71, 185 Endotoxin, 30, 101–102, 189, 192, 356 Enrichment, 79, 108, 142, 181, 183–184, 256, 351, 360 Enterobacter, 31, 211, 336, 358, 362 Enterotoxins, 30, 356 Entomopathogenic, 356 Entrapment, 150 EPA, 3, 5, 7, 9, 18, 45, 74, 119 Epigenic, 99 Episodic, 291

377 Eradication, 119, 236 Ergosterol, 353 Ermochemical, 28 Erosion, 70, 92, 100, 104, 118–119, 153, 248 Esterification, 26, 327, 330 Estuary, 71, 290 Eutrophic, 279, 291 Eutrophication, 47, 50, 55–56, 78, 238, 280, 351 Evaporation, 36, 66, 294 Evapotranspiration, 289 Exclusion, 7, 51–52, 63, 295 Exoelectrogenic, 201 Exoskeletons, 147 Exothermic, 8 Exotic, 179 Exotoxins, 189 Exposure, 65, 97, 119, 140, 217, 239, 289–290, 295, 353 Extruder, 214 Exudates, 74, 76, 293 Fabrication, 6, 225, 236 Facultative, 95, 211–212, 260–261, 285, 362 Farmyard, 96 Fauna, 290 FDA, 233 Fecal, 288 Feces, 94, 100 Fermenter, 178–179, 185–187 Ferooxidans, 121 Ferredoxin, 206, 212 Fertility, 32, 71–72, 93, 96, 99–100, 107–108, 159, 366 Fertilization, 107 Ferulic, 32, 350 Fibroblasts, 112 Fibrous, 70–71, 74–76 Filamentous, 101, 137, 150, 154, 176, 178, 186–188, 191–192, 352 Filtration, 7, 70, 80, 144, 151–152, 178, 182, 188, 209, 237, 276–278, 281–283, 352, 365 Fishery, 24, 319 Fixation, 107–110, 291, 326 Fixers, 100 Flammability, 91, 181, 235 Flavanones, 227 Flavonoid, 36, 190, 227–228, 327, 348–349, 355 Flavonols, 227 Flavorant, 332 Flax, 33 Floc, 29, 113, 145–147, 149, 151–153, 357–358 Flocculate, 31, 143, 149, 151 Flocculation, 31, 35, 91, 143–153, 209, 278, 358 Flotation, 146, 264 Fodder, 24, 94 Forage, 21–22 Fractionation, 209, 251 Fragrance, 101–102, 333, 335–336, 347, 349 Fructose, 144, 177, 180, 183, 328, 331, 349 Fugitive, 65 Functionality, 72, 108, 232, 290 Fungicides, 91 Fungiform, 352 Furfural, 57, 332, 348

378 Gadgets, 10, 258, 292 Galactomannans, 153 Galactosidase, 30, 328–329, 360 Galena, 262–263 Gaseous, 4–5, 7, 19, 25–27, 29, 95, 179, 217, 249–250, 259, 290 Gasifiers, 213 Gasoline, 27, 68, 71, 77, 323, 363–364 GDP, 313 Gel, 32–33, 35 Gelatin, 35, 116, 153, 232, 239 Geobacter, 201 Geochemical, 215, 262 Geographic, 47, 52, 76 Geological, 215–216, 247 Geologist, 247 Geothermal, 314 Germination, 71, 106, 108, 238 Germs, 209, 235, 260 GHG, 19, 37, 158, 289–290, 292, 319, 327 Globule, 156, 357 Gluten, 116 Glycolipid, 102, 116, 154–155, 157 Glycolysis, 206 Glycolytic, 206, 212 Glycoprotein, 29, 138, 143–144 Glycosaminoglycans, 239 Glycosylation, 143, 327 Graphene, 36, 119 Graphite, 36, 200, 202–203 Greenhouse, 3, 19, 46, 74, 97, 118, 215, 218, 237, 289, 319–320, 322–323, 347, 354, 366 Gypsum, 23, 336 Habitat, 47, 78, 92, 157, 160, 286, 290–292, 295 Halococcus, 230–231 Halogen, 120, 253 Halomonas, 359 Halophyte, 78 Hardrock, 7 Hardwood, 205, 213, 218 Harmless, 3, 63, 66, 68, 80, 111–112, 144, 149 Harnessing, 104 Harvestable, 71 Hazardous, 3–4, 6–9, 16, 63–64, 71–73, 79–80, 110–112, 117–120, 137–139, 147–148, 153, 171, 189, 226, 235, 309, 312, 320 HDPE, 334 Helophytes, 79 Hematite, 235 Hematopoiesis, 233 Hemicellulose, 32, 36–37, 94–95, 138, 173, 208, 329, 331–332, 357, 359–360 Herbicide, 8, 70, 73, 91, 238, 295, 349, 355 Herbivores, 34, 72 Heterobacteria, 187 Heterotrophic, 22, 27, 66, 121, 150, 175, 249, 260–261, 267, 283 Heterotrophs, 68, 113, 260 Histopathological, 233 HMF, 57, 331, 348 Homogenous, 27–28, 233, 296 Homopolymer, 352, 359–360

Index Honeycomb, 36 Hormone, 97, 100, 233, 354 Humic, 92, 95, 201, 354 Humidity, 236, 239, 290 Humification, 100 Humus, 24, 95–97 Husbandry, 23–24 Husk, 6, 21–22, 28–29, 36, 77, 101–103, 180, 199, 227, 236, 282, 351–353, 365 Hydrogel, 111, 116, 118–119, 238 Hydrogenase, 206–207 Hydrogenation, 327, 332, 363 Hydrolases, 328 Hydrology, 74, 276, 281, 292 Hydrolysate, 30, 176, 189, 210–211, 350, 359, 363 Hydrolyze, 35, 185, 205, 328–329, 331, 336, 360 Hydrolyzed, 32, 73, 182, 189, 211, 329, 331, 336, 353, 355, 360–361, 364–365 Hydrometallurgy, 119, 247, 249, 251, 253, 255, 257–259, 261, 263, 265, 267 Hydrophilic, 30, 154, 190, 234 Hydrophobicity, 114, 139 Hydroponics, 74 Hydrothermal, 28, 30, 247–249, 350 Hydroxide, 152, 247–248, 278 Hygroscopic, 359 Hyperaccumulator, 71–72 Hypereutrophic, 279, 291 Hyperpigmented, 234 IAA, 106, 354 Immobilization, 64–65, 72, 137, 143, 151, 327–329, 331 Immobilized, 207, 320, 328–331 Immunization, 7 Immunoassay, 233 Immunogenicity, 189, 232 Immunoglobulin, 143, 355 Immunological, 109, 189, 355 Immunomodulatory, 355 Impermeable, 79 Impervious, 292–293 Implementation, 190, 309–310, 322, 348 Impregnation, 140, 152 Impurity, 26, 137, 214, 235, 252, 255, 257–258 Inactivation, 72, 111, 187, 291 Incineration, 10, 19, 49, 51, 54, 119–120, 291–292, 309, 314–316, 319 Incinerator, 119, 309, 312, 316 Incinerator, 119, 309, 312, 316 Inclusion, 153, 204, 251 INCO, 258 Increasingly, 72, 100, 116, 171, 229, 264, 276, 316 Incubation, 181, 184, 229 Indicator, 35, 55, 215, 288, 292, 361 Indigenous, 66, 69, 107, 109, 260 Indigestible, 182, 192 Industrial, 3–6, 8–9, 11–12, 19–23, 30, 36, 45, 63, 72, 119–120, 137–139, 143–144, 154–158, 177–179, 204, 225, 234–235, 250–254, 263, 265, 267, 275, 278, 286, 307–309, 320–321, 326–333, 338, 347, 352, 355–357, 361, 364 Industrialization, 3, 6, 16–17, 19, 63, 225 Inefficient, 314, 321

Index Inefficiently, 307 Inert, 4, 7, 16–17, 29, 36, 100, 235, 265, 296 Inexhaustible, 199 Infected, 71, 113 Infection, 105, 109, 172, 192, 232–233, 235 Infiltration, 159, 282, 287 Inflammatory, 35, 227, 233, 239 Infrastructural, 234 Infrastructure, 16, 24, 49, 51–52, 311, 313, 361 Ingested, 97, 185 Ingestion, 185, 191 Ingredient, 5, 27, 30, 35, 105, 173, 175–176, 178, 189–190, 214, 233, 239, 332, 334, 354 Inhibition, 71, 101, 110, 112, 205, 291 Inhibitor, 30, 109, 217 Initiatives, 258, 265, 312–314, 320, 351 Innovative, 34, 113, 191, 237, 239, 315–316, 319, 332 Inoculant, 105, 107–108, 366 Inoculating, 179 Inoculum, 181, 183–184, 211, 356 Inositol, 173 Inquiry, 49–50, 52 Insecticidal, 30, 356 Insecticides, 7, 34, 76, 91, 117, 355 Insoluble, 91, 101, 121, 138, 141–142, 144, 157–158, 247, 255, 262, 264–267, 327 Insulation, 234 Insulators, 293 Insulin, 175 Intercellular, 111, 348 Interconnected, 51–52, 80, 216, 314 Interference, 141, 252–253, 257 Intermediary, 80, 262, 332, 350 Intermittently, 278 Interpretation, 48, 52, 56–57, 249 Interrelations, 52 Intracellular, 29, 91, 229, 231, 325, 358–360 Intrusions, 292 Inundated, 290 Invertebrate, 24, 96, 295 Investment, 114, 158, 178, 259 Iodide, 253 Ionic, 31, 34, 114, 119, 141, 154, 179, 235, 238, 251, 256, 289 Ionizing, 56 Irritant, 8 Jatropha, 23, 199, 230 Jute, 33 Kelps, 21 Keratinocytes, 112 Kerosene, 68 Ketones, 30 Kinetic, 141–142, 248, 256, 265, 285 Kingdom, 109, 187, 189, 293, 352 Labile, 74 Laboratory, 33, 67, 143, 205, 247, 287, 295–297 Laccase, 77, 103, 352 Lactobacillus, 103, 172, 181, 230, 349–350 Lactoferrin, 355 Lactoglobulin, 355

379 Lactone, 155–156 Lactoperoxidase, 355 Lactose, 180, 183, 185, 328–329, 360 Lagoon, 65, 283 Landfarming, 64–65 Landfilling, 19, 58, 92, 309, 315 Landspreading, 23 Landuse, 56 Lanthanide, 256 Larvae, 25, 101, 290–291 Larvicide, 290 Larvivorous, 290 Laser, 234, 239 Latex, 19, 78, 177, 180 LCA, 45–53, 55, 57–58 LCI, 48, 54–57 LCIA, 48, 55–56 LDPE, 117, 334 Leachability, 121 Leachate, 25, 66, 70, 111, 113, 260, 267, 275, 287, 326 Leguminous, 107–108 Lentil, 103–104 Leptospirillum, 260–261, 263 Leptothrix, 111 Lettuce, 101 Leukemia, 233 Levulinic, 25, 331–332, 348 Licheniformis, 149, 156, 177, 230, 329, 331 Lichenysin, 155–156 Lifecycle, 46, 48 Lifespan, 51, 310 Lifestyle, 3, 5, 19, 109–110, 308–309 Ligand, 105, 139–140, 142–143, 250–252 Ligninases, 89 Ligninolytic, 77 Lignocellulose, 27, 57, 94–95, 101, 180–182, 329 Lime, 227–228, 336, 357 Limonene, 26, 34, 348 Limonitic, 267 Liner, 275–276, 298 Linolenic, 104, 326 Lipase, 30, 97, 103, 142, 326, 328, 330, 353 Longevity, 52, 214, 292 Lubricants, 34, 330, 347 Lycopersicum, 227 Lyophilization, 107 Lyophilized, 107 Lytic, 89 Macroaggregates, 238 Macroalgae, 78, 137, 365 Macroalgal, 21 Macrocosm, 295, 298 Macroinvertebrate, 297 Macromolecular, 31, 79, 138, 150 Macromolecules, 35, 97, 148, 357 Macronutrient, 351, 361 Macrophyte, 75, 80, 275–283, 287, 289, 291–294, 298 Macroscopic, 79, 157 Maghemite, 233, 235, 257 Magnet, 236–237 Magnetite, 233, 235 Magnetotactic, 229

380 Magnitude, 292–293 Malfunctioning, 288 Malignant, 350 Maltose, 183 Mammalian, 152, 232 Mannose, 147, 183, 331 Maturity, 99, 216 Medicinal, 35, 156, 232, 321, 326 Megaterium, 105, 121, 230, 326, 358 Melanin, 138 MeOH, 323 Mesocosm, 295, 298 Mesophilic, 94–96, 121, 261, 361–362 Meta, 45Metabolism, 31, 66, 72–73, 90, 95, 99, 109, 111, 150, 190, 233, 281, 283, 307 Metabolize, 24, 72, 96 Metagenomic, 329 Metallic, 7, 117, 119, 231, 235, 239, 250, 258, 264, 267 Metalloids, 91, 121, 137, 259–260 Metallophyte, 72, 76 Metallosphaera, 261 Metallothioneins, 63 Metallurgical, 6, 20, 119–120 Meteorological, 289 Methanation, 364 Methanogenesis, 25, 211, 321 Methanogenic, 361–363 Methanogens, 218 Methanol, 28–29, 174, 176, 179, 181, 187, 323–324, 335, 360, 363 Methanotrophic, 184 Methionine, 32, 172–173, 175 Methoxyl, 138 Methylation, 63–64, 91 Methylobacterium, 73 Methylococcus, 173–174, 177, 186–187 Methylocypsa, 184 Methylomonas, 174, 177 Methylophilus, 174, 187 Methylotrophic, 187 Methylotrophus, 174, 187 Methylovibrio, 177 Micelle, 31, 154 Microalgae, 27, 78, 137, 143, 146–152, 173–174, 190, 199, 206, 209–212, 218, 231, 326–327, 336, 363, 365 Microbioventing, 67 Microcolony, 110 Microcosm, 275, 277, 279, 281, 283, 285, 287, 289, 291, 293–298 Microcystin, 192, 291 Microecosystems, 294 Microemulsion, 35 Microencapsulation, 34, 107 Microenvironment, 113, 157, 360 Microfibrils, 33, 188 Microfiltration, 183 Microflocs, 144 Microflora, 260 Micronutrient, 23, 173, 354 Microplastics, 113 Micropollutants, 115 Microporous, 215, 256 Microscopic, 78, 145, 152, 157, 282, 365

Index Microscopy, 115 Mineralization, 65, 70, 80, 90, 100, 158 Mineralogy, 262, 265 Mitigation, 121, 158, 218, 290–291, 327 Mixotrophic, 175, 260, 291 Mnps, 235 Mnre, 16, 18 Modifiers, 22, 188, 333 Modulation, 179 Molar, 154, 208 Molasses, 21, 27, 102–103, 155, 174, 176, 179–180, 186, 351–352, 355, 357, 360, 364 Mold, 148, 172 Molluscicides, 91 Molluscs, 352 Monoliths, 143, 331 Monomer, 31, 33–34, 89, 116, 332, 348–349, 361 Monosaccharide, 180, 182, 186, 329, 353 MRSA, 235 MSW, 3–5, 8, 10–12, 16–17, 19–21, 29, 46–47, 51–52, 55, 89, 96, 319, 365 MTBE, 70 Mulching, 359 Multicellular, 114, 365 Multifunctional, 54, 232, 235 Multimetal, 252 Municipal, 3–6, 10–11, 16–17, 19–20, 24–29, 45, 89, 137, 189, 275, 286–287, 293, 315–316, 319–321, 361, 364 Mutagenesis, 143 Mutagenic, 9 Mutation, 177, 232 Mycelium, 150–151, 184, 188 Mycobacterium, 155, 158, 174 Mycoinsecticide, 104 Myconanotechnology, 229 Mycopesticide, 104 Mycoprotein, 175, 187–189, 191 Mycoremediation, 64, 77 Mycorrhizal, 105, 107–108 Mycorrhizobacteria, 109 Mycotoxins, 188–190, 192 Nadph, 229 Nanoadsorbents, 235 Nanobiocomposite, 231, 236 Nanobioparticles, 225–226, 228–231, 236 Nanobiotechnology, 225, 227, 229, 231, 233, 235, 237, 239 Nanobots, 234 Nanocarbon, 234 Nanocarriers, 233 Nanocatalysts, 236 Nanocellulose, 33 Nanoceramic, 235 Nanoceuticals, 239 Nanoclay, 108, 237 Nanoclusters, 239 Nanocomposite, 116–117, 235, 239 Nanocrystals, 231 Nanodevices, 238 Nanodrops, 239 Nanoencapsulation, 107–108 Nanofabricated, 237

Index Nanofabrics, 237 Nanofibers, 21, 225, 234 Nanogel, 239 Nanoimmunosensors, 239 Nanolubrication, 234 Nanomaterial, 107–108, 208, 232–238, 248, 320, 351 Nanomembranes, 225 Nanometers, 225, 232 Nanoparticle, 35, 107–108, 117–118, 143, 145, 148, 225, 230–231, 326, 331 Nanopores, 237 Nanoscale, 108, 232–233, 237–239 Nanoscience, 225 Nanosensors, 238–239 Nanosilica, 336 Nanosized, 22, 225, 231 Nanosomes, 234 Nanosorbents, 236 Nanostructures, 233–234 Nanotea, 239 Nanotechnology, 80, 107–108, 142, 225, 229, 232, 234–239 Nanotexturing, 237 Nanotubes, 36, 140, 225, 233, 235–236, 238 Nanowires, 201, 225, 233, 261 Nanozeolites, 236, 238 NBT, 225, 231–232, 237 Nematicides, 91 Nematode, 92, 108, 352 Nematodiphila, 230 Neurodegeneration, 117 Neurological, 355–356 Neurospora, 102 Neurosporacrase, 353 Neurotoxin, 34 Neutraceuticals, 332 Neutralization, 144–145, 147, 149, 153 Niacin, 173, 175 Niche, 64, 259, 348 Nitrification, 80, 113, 276–278, 281, 283, 285–286, 288, 293–294 Nitrogenase, 206–207, 212 Nitrogenous, 35, 78, 157, 172–173, 354–355 NMR, 142 Nonbiodegradable, 79, 319 Noncorrosive, 253 Nonrenewable, 309, 311 Nontoxic, 63, 72, 146, 148, 153, 253 Novozymes, 329 Noxious, 292 Nucleotides, 143, 182, 188 Nutraceutical, 35, 151, 349, 355, 360 Nymphoides, 280 Ochrobactium, 31, 358 Ocimum, 230 Odor, 34, 95, 160, 172, 225, 237, 291, 361–362 Oilfield, 78 Oilseed, 101, 227, 331 Oleds, 239 Olefins, 323, 335 Oleophila, 174, 332 Oligomers, 89 Oligonucleotide, 142

381 Oligosaccharides, 328–329 Oligosporus, 184 Oocystis, 174 Optics, 234 Optimization, 155, 292–293, 315, 360 Organophosphorous, 115 Osmosis, 183–184 Osmotic, 64, 101, 183, 350 Osteoporosis, 35, 233 Osteosarcoma, 234 Outbreak, 290–291 Overconsumption, 192, 310, 312 Oxidative, 190, 354 Oxidoreductase, 73 Ozonation, 67 Ozone, 47, 50, 56 Pantothenic, 173, 175 Paraffin, 172, 174 Paratropicalis, 332 Particulate, 47, 56, 155, 278 Passivation, 253, 267 Pasteurization, 182, 185 Pasture, 287 Pathogenic, 95, 109, 112, 154, 232, 234, 238, 294 Pathogenicity, 154, 172 PBA, 117 PBS, 117, 262–263, 334, 359–360 PCB, 35–36, 70, 74, 76, 90–91 Peat, 29, 58, 92, 99 Pectin, 32, 34, 36, 115–117, 119, 138, 147, 329, 348, 359 Pectinase, 89, 101, 211, 329, 353 Pellet, 27, 150–151, 213–214, 217–218, 316 Pelletization, 150, 213–214 Peptide, 35, 104–105, 143, 154, 185, 331, 349, 351, 355 Peptidoglycan, 138 Peptidolipids, 102 Permeability, 67–69, 79, 216–218, 238–239, 275, 282, 291 Peroxidase, 30, 103 Pesticide, 6–8, 21, 30, 63, 70, 72, 76–78, 90–91, 101, 104, 111, 116–119, 236, 238, 295–297, 320, 355–356 Petrochemical, 28, 156–157, 176, 323, 325, 358–359 PGPR, 63, 71, 105–109, 366 Photobioreactors, 175, 326 Photocatalytic, 227, 229, 234, 236–237 Photochemical, 50, 56 Photoelectrochemical, 233 Photofermentation, 205, 207–208, 211–212 Photofermentative, 336 Photoheterotrophic, 207 Photolysis, 206 Photosynthetic, 22, 27, 150–151, 174, 205, 207, 209, 212, 277, 280, 291 Photosystems, 206 Phototrophic, 150–151, 173 Photovoltaics, 239 Phreatophytic, 70 Phycobiliproteins, 207 Phycoremediation, 151 Physiology, 80, 109 Phytochemicals, 190, 227, 229, 239, 355 Phytodegradation, 73–74 Phytoextraction, 70–72, 74–75, 77

382 Phytofermentans, 102 Phytofiltration, 74–75 Phytoflocculants, 148 Phytohormone, 105–106, 108, 110 Phytohydraulic, 74 Phytomass, 281 Phytomining, 71–72 Phytopathogens, 110, 112, 238 Phytoplankton, 291 Phytoremediation, 64, 69–71, 73, 75–78 Phytostabilisation, 73 Phytostimulation, 77 Phytotransformation, 70, 72–73 Phytovolatilization, 70, 75 Piezoelectric, 237 Pigments, 91, 115, 138, 141, 179, 190, 207, 323 Plankton, 200, 277 Plasmid, 63, 68 Plasticizer, 91, 323, 347, 349, 359 Plume, 68 Polarity, 72–73, 154–155 Polyelectrolyte, 34–35, 117 Polyhydroxybutyrate, 116–117, 320, 324, 358 Polyhydroxyvalerate, 31 Polyhyroxyalkanoates, 358 Polymerization, 33, 238 Polymetallic, 259, 267 Polyvinylchloride, 334 Porosity, 65, 96, 98, 140, 159, 216, 255, 282, 366 Prebiotic, 328–330 Preservative, 76, 188, 332, 349 Prevention, 110, 112, 190, 314, 319 Probiotic, 355 Productivity, 80, 108–109, 149, 159, 171, 182, 207–208, 238, 281–282, 356 Prokaryotes, 260 Protease, 30, 32, 89, 97, 103, 182, 211, 331, 351–354, 356 Proteobacterium, 69 Protists, 173 Protozoa, 109, 172, 282–283 Psychrotrophic, 117 PUFAs, 327 Pulping, 23, 183 Pulverized, 217 Purine, 95, 185 Putrefaction, 98 PVA, 239, 334, 360 PVC, 334 Pyridine, 115 Pyridoxine, 173, 175 Pyrimidines, 95 Pyrite, 121, 261–263, 266–267 Pyrolysis, 21, 28, 120, 159–160, 214–215, 361, 364, 366 Pyrometallurgical, 119–121, 250, 259, 264 Pyruvate, 25, 206, 212 Quartz, 247 Quinoline, 69 Quorn, 187, 191 Quorum, 108 Radiation, 56, 91, 140, 210, 234, 275, 289, 291, 350 Radionuclide, 70–71, 90–91, 137–138, 238

Index Raffinose, 180 Ramifications, 15 Rapeseed, 23, 46, 363–364 Rationale, 54 RCRA, 4, 7 RDX, 65, 70, 73 Reactant, 248, 335 Reactor, 93, 111–115, 186, 204, 256, 265, 323, 358 Recalcitrant, 94, 137, 291 Receptor, 114, 143 Recipient, 200, 275 Recirculation, 204 Recrystallize, 247 Recycle, 19, 46–47, 72, 89, 93, 267, 312, 315–316, 360 Redox, 64, 68, 80, 91, 113, 201, 251, 254, 256, 259, 263, 266–267 Reducers, 228 Reductants, 227 Reductase, 229, 231 Reed, 21, 70, 79–80, 276, 279, 281, 283–285 Refinery, 6, 10, 23, 180, 190, 358, 363 Reflectance, 216 Reforms, 214, 348, 361 Refractory, 22, 67, 113, 157, 258, 265–267 Refurbishment, 7 Regeneration, 137, 232 Regime, 283, 289 Regional, 15, 58, 233 Regulator, 91, 96, 105, 141 Reliance, 33, 199, 347 Remedial, 291, 293 Remediate, 67, 118 Remediation, 63, 65, 67–69, 71–72, 74, 77–78, 101, 111, 119–120, 158, 225, 236, 357, 366 Renovation, 6 Repellent, 96, 234, 237, 291 Repercussions, 199, 252, 351 Replicate, 297–298 Replication, 298 Repression, 101 Residential, 3–5, 7, 27–28, 31, 218, 225, 228, 316, 326 Residual, 5, 20, 24, 66, 141, 185, 190, 205, 227, 249, 251, 256, 360, 363, 365–366 Resilient, 109, 111, 213, 314 Resin, 30, 33–34, 36–37, 117, 119, 235, 255–256, 329–330, 332, 335, 337, 347, 349–350 Resistance, 72, 97, 101, 106, 109, 111, 142, 159, 172, 202, 204, 234–235, 238–239, 294, 332, 366 Resistant, 31, 67, 90, 101, 109, 137, 232, 234–235, 263, 265, 267, 336, 359 Resonance, 142 Respiration, 63, 65, 98–99, 111, 261, 356 Response, 72, 109, 151, 189, 204, 281, 292, 294, 330, 361 Restoration, 72, 290 Restriction, 27, 137, 192, 312, 348 Retardants, 7, 119 Retention, 26, 32, 96, 113–115, 159, 235, 276, 278, 283, 328, 330, 362 Retrieved, 18, 99 Retrovirus, 156 Reused, 8, 19, 35, 119, 149, 280, 283, 286–288, 307–309 Reusing, 21, 29–30, 316, 356, 365 Rhamnolipid, 29, 31, 64, 102, 155, 157, 357

Index Rhizoaccumulation, 77 Rhizobacterium, 63, 71, 105–107, 110, 366 Rhizobium, 104–105, 109, 325, 354, 366 Rhizoctonia, 105, 159 Rhizodegradation, 73–75, 77 Rhizofiltration, 70, 74–75, 77 Rhizoglomus, 109 Rhizome, 233, 239, 278–279, 292–293 Rhizomucor, 330 Rhizoplane, 104 Rhizopus, 104, 150, 172, 184, 230–231, 238, 352 Rhizoremediation, 70 Rhizosphere, 70–71, 73, 76, 79–80, 104, 106, 108–109, 279, 293 Rhodamine, 117, 231 Rhodobacter, 207, 212, 336 Rhodococcus, 77, 111, 149, 183, 358 Rhodophyceae, 231 Rhodopseudomonas, 177, 184, 207, 212 Rhodospirillum, 207, 212 Rhyzofiltration, 74 RNA, 182, 185, 188, 192, 233 Robotics, 35, 225 Rotation, 21–22, 93, 213, 218, 278 Runoff, 23, 66, 78, 159, 275, 287, 289, 292 Root Zone Technology, 79–80 Saccharification, 32, 349–350 Saccharomyces, 32, 102, 138, 151, 172–173, 175–176, 181, 327, 350 Safranin, 117 Salinity, 204, 209, 215, 281, 289 Sandy, 118, 275 Sanitary, 4, 6, 19 Sanitation, 5, 20 Sargassum, 78, 230–231 Sawdust, 21, 28, 98, 101, 103, 181, 184, 188, 213, 365–366 Scaffolds, 111, 232, 326 Scavenge, 229, 349 SCFAs, 29–31, 350, 359 Schizochytrium, 173 SCMFCs, 201–202 SCP, 171–189, 191–192, 351, 355 Scrap, 4, 6, 19, 92, 119, 182, 320 Scrubbers, 237 Seafood, 327, 355 Sealants, 22, 118, 333 Seaweed, 34, 137, 231, 365 Secrete, 95 Secretion, 78, 143 Sedimentation, 113–114, 144–146, 152, 257, 276, 278, 282–283 Seedling, 74, 78, 108 Seepage, 218, 266, 282, 292–293 Segregation, 23 Seismic, 215 Semiarid, 118 Semiconductor, 239 Semisolid, 178 Sensitivity, 56, 146, 236, 238, 260, 277, 290, 293 Sensor, 117, 236, 238–239 Septic, 5, 20, 284 Sequential, 203, 207, 321, 330

383 Sequestration, 32, 70, 73, 76, 215, 218, 290, 292 Sheath, 32, 138 Shikimate, 227 Shredding, 98 Siderophore, 64, 105, 107, 109–110 Silage, 24 Siloxanes, 26 Silt, 4, 152 Simulate, 295, 329 Slag, 7, 22, 259, 278 Slaughterhouse, 7–8, 21, 25, 27 Slurry, 23, 26, 98, 111, 354, 364 Smelting, 78, 120, 255, 257, 259, 264 Smog, 47, 55 Socioeconomic, 3, 10, 312, 326 Solidification, 65, 214 Solubilization, 29, 64, 71, 100, 105, 107–109, 120–121, 211, 259, 265, 336, 357–358, 362 Solubilize, 64, 105, 120, 157, 211, 252, 259, 262, 267, 357 Solubilizer, 100, 357 Solute, 255, 259 Sonication, 32, 185 Soot, 237 Sophorolipid, 31, 102, 154–155, 357 Sorbate, 137, 141 Sorbent, 140, 236 Sorbent, 140, 236 Sorption, 91, 137, 140, 216, 236, 278, 293 Sorptive, 158 Speciation, 141, 249 Spinach, 74 Spirodela, 72, 139, 280 Spirulina, 78, 171–175, 191–192, 231 Spore, 30, 101, 150–151, 356, 362 Sporulation, 101–102, 356 SSF, 100–104, 277, 293 Stabilization, 57, 65, 70, 248, 293, 354, 357, 362, 365 Stabilize, 24, 114, 118, 155–156, 187, 252–253, 279–280 Stakeholders, 50, 58 Standardization, 48 Staphylococcus, 101, 143, 229 Sterile, 180, 182, 187, 260 Stimulation, 66, 105 Stoichiometry, 26, 263 Streptococcus, 112, 181, 206 Streptomyces, 110, 174, 230, 328 Stressors, 109, 295 Styrene, 334 Styrofoam, 8, 19 Subcritical, 348 Submergence, 278 Succulent, 94 Superabsorbent, 333 Supercapacitor, 35, 119 Supercritical, 249, 348–349 Supernatant, 152 Superparamagnetic, 235 Suppression, 110, 160 Surfactant, 31, 63–64, 118, 154–158, 231, 323, 327, 329–330, 347, 357 Surfactin, 102, 110, 155–157, 357 Susceptibility, 51, 293 Susceptible, 8, 94, 114, 175, 251

384

Index

Suspension, 73, 146, 152–153, 238, 276, 365 Symbiotic, 73–74, 104–105, 150, 181, 186 Synergistic, 76, 78, 212 Syngas, 28–29, 214–215, 323–325, 334–335, 364 Syntrophy, 361 Systemic, 106, 149, 366

Trophic, 296–297 Trypsin, 331 Tryptophan, 115 Tuberculosis, 233 Tumor, 35, 234 Turbidity, 117, 148, 153–154, 282

Tannery, 236, 337 Tannin, 115, 117, 227–228, 349 Taxa, 297 Taxonomic, 250, 291 TCB, 69 TCE, 68, 70, 73 Technological, 52, 63, 177, 185, 188, 208, 291, 293 Temporal, 50–52, 290, 297 Tensile, 159 Tensioactive, 154 Tension, 31, 114, 154–156 Teratogenic, 9 Terephthalate, 34, 117, 332–335, 359–360 Tergitol, 158 Terpene, 26, 34 Tertiary, 260, 284, 288, 351, 365 Testosterone, 77 Texture, 95–96, 98, 100, 157, 188, 357 TFC, 227–228 Theoretical, 206, 295, 319 Therapeutic, 80, 191, 229, 232–233, 239, 355 Therapy, 35, 66, 77, 225, 232 Thermally, 140, 188, 208, 214 Thermochemical, 23, 28, 321–323, 337, 361, 364, 366 Thermodynamic, 114 Thermophiles, 94 Thermophilic, 94–95, 97–98, 121, 260–261, 267, 361–362 Thermoplasma, 121 Thermoplastic, 333, 359–360 Thermotolerant, 94 Thiamine, 173, 175 Thickeners, 329 Thickening, 32, 35, 210, 212, 355 Thiooxidans, 121, 261–262 Thiourea, 120, 251, 253 Threatening, 171, 289–290 Threshold, 253, 288 Thrombosis, 34 Timber, 23, 365 TNT, 65, 70, 73 TOC, 277, 290 Tolerant, 73–74, 261, 279, 281 Toxin, 9, 63, 69, 71, 73–75, 80, 113, 188–189, 192, 233, 238–239, 291 TPC, 227–228 TPH, 70–71, 76–77 Trade off, 290–291 Transboundary, 3, 17 Transesterification, 27, 190, 322–323, 327–328, 361, 363, 365 Transgenic, 71, 258 Translocation, 70–71, 79 Transmission, 73, 178, 201, 204, 290 Transpiration, 71 Triglyceride, 322–323, 330, 363 Trinitrotoluene, 70, 73

UASB, 204 Ubiquitous, 63, 80, 109 Ultrafiltration, 181, 187 Ultramafic, 72 Ultrasonic, 30, 210 Ultrasound, 210–211, 348–349 Ultraviolet, 8, 289, 366 Underutilized, 101, 329, 350 Undoubtedly, 120, 213, 239, 348 UNEP, 19, 21, 69, 313 Unfavorable, 31, 71, 79, 144, 208, 358, 360 Unicellular, 101, 171, 174, 332, 365 Unstable, 91, 253, 360 Unsustainable, 199, 315 Upcycling, 310–311, 328 Upflow, 204 Upwelling, 289 Urease, 354 USDA, 331 USEPA, 45, 52, 54, 56, 286 Vaccination, 107 Vadose, 66–67 Validation, 55 Vapor, 28, 66–67, 111, 248, 334 Variation, 14, 23, 151, 175, 188, 233, 289–290, 293, 297, 364 Vegetal, 65 Vegetative, 69, 227, 356 Velocity, 276, 292 Venture, 187 Vermicast, 96–97 Vermicompost, 24, 79, 93, 96–100, 354 Vermiculture, 96, 98 Vermin, 3, 97 Vermiwash, 93, 353–354 Versatile, 34, 108, 332, 366 Vesicles, 155–156, 185 VFA, 31, 210, 326, 349–350, 359 Vibration, 210 Vicinity, 174 Virulent, 290 Viruses, 109, 156, 275 Viscosity, 27, 33, 118, 327, 363 Viscozyme, 211 VOCS, 26 Volatilization, 66–68, 70, 277, 282 Volumetric, 113, 203, 205, 213 Warehouses, 6, 20 Washout, 260 Wasteful, 307, 314, 316 Waterway, 74, 275 Watts, 210 Wealth, 11, 19, 61, 225 Weapon, 235, 290

Index Weed, 21, 32, 92, 94, 138, 231, 292 Wetland, 70, 78–80, 92, 275–295, 297–298 Wildlife, 47, 286 Wilt, 106, 231 Windmill, 237 Windrow, 37, 65, 93 Winterization, 102 Worldbank, 18 Wrinkle, 35, 234 WTR, 16–18 Xenobiotic, 72–73, 76, 115 Xylanase, 89, 101, 211, 329, 352–353

385 Xylans, 138 Xylem, 71 Yogurt, 328, 352 Zeaxanthin, 349 Zeolite, 107–108, 247, 282, 298 Zerovalent, 115, 238 Zeta, 146, 153 Zoogloea, 149 ZVI, 115 ZWC, 312 Zymomonas, 102