Biodiesel Technology and Applications 1119724643, 9781119724643

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Biodiesel Technology and Applications

Scrivener Publishing 100 Cummings Center, Suite 541J Beverly, MA 01915-6106 Publishers at Scrivener Martin Scrivener ([email protected]) Phillip Carmical ([email protected])

Biodiesel Technology and Applications

Edited by

Inamuddin, Mohd Imran Ahamed, Rajender Boddula and Mashallah Rezakazemi

This edition first published 2021 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA © 2021 Scrivener Publishing LLC For more information about Scrivener publications please visit www.scrivenerpublishing.com. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions. Wiley Global Headquarters 111 River Street, Hoboken, NJ 07030, USA For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com. Limit of Liability/Disclaimer of Warranty While the publisher and authors have used their best efforts in preparing this work, they make no rep­ resentations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchant-­ ability or fitness for a particular purpose. No warranty may be created or extended by sales representa­ tives, written sales materials, or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further informa­ tion does not mean that the publisher and authors endorse the information or services the organiza­ tion, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Library of Congress Cataloging-in-Publication Data ISBN 9781119724643 Cover image: Pixabay.com Cover design by Russell Richardson Set in size of 11pt and Minion Pro by Manila Typesetting Company, Makati, Philippines Printed in the USA 10 9 8 7 6 5 4 3 2 1

Contents Preface xvii 1 Biocatalytic Processes for Biodiesel Production 1 Ubaid Mehmood, Faizan Muneer, Muhammad Riaz, Saba Sarfraz and Habibullah Nadeem 1.1 Introduction and Background 2 1.2 Importance of Biodiesel Over Conventional Diesel Fuel 3 1.3 Substrates for Biodiesel Production 4 1.4 Methods in Biodiesel Production 6 1.5 Types of Catalysts Involved in Biodiesel Production 7 1.5.1 Chemical Homogenous Catalysts 7 1.5.2 Solid Heterogeneous Catalysts 8 1.5.3 Biocatalysts 8 1.6 Factors Affecting Enzymatic Transesterification Reaction 8 1.6.1 Effect of Water in Enzyme Catalyzed Transesterification 9 1.6.2 Effect of Bioreactor 10 1.6.3 Effect of Acyl Acceptor on Enzymatic Production of Biodiesel 10 1.6.4 Effect of Temperature on Enzymatic Biodiesel Production 14 1.6.5 Effect of Glycerol on Enzymatic Biodiesel Production 14 1.6.6 Effect of Solvent on Biodiesel Production 16 1.7 Lipases as Biocatalysts for Biodiesel Production 17 1.7.1 Mechanisms of Lipase Action 19 1.7.2 Efficient Lipase Sources for Biodiesel Producing Biocatalyst 19 1.8 Comparative Analysis of Intracellular and Extracellular Lipases for Biodiesel Production 21 1.9 Recombinant Lipases for Cost-Effective Biodiesel Production 26 1.10 Immobilization of Lipases for Better Biodiesel Production 28 v

vi  Contents 1.11 Recent Strategies to Improve Biodiesel Production 1.11.1 Combination of Lipases 1.11.2 Microwave and Ultrasonic-Assisted Reaction 1.12 Lipase Catalyzed Reaction Modeling and Statistical Approaches for Reaction Optimization 1.13 Conclusion and Summary References

31 31 33 35 38 38

2 Application of Low-Frequency Ultrasound for Intensified

Biodiesel Production Process 59 Mohd Razealy Anuar, Mohamed Hussein Abdurahman, Nor Irwin Basir and Ahmad Zuhairi Abdullah 2.1 Current Fossil Fuel Scenario 60 2.2 Biodiesel 60 2.3 Transesterification 61 2.4 Challenges for Improved Biodiesel Production 62 2.5 Homogeneous Catalyst for Biodiesel Production 63 2.6 Heterogeneous Catalyst for Biodiesel Production 64 2.7 Immiscibility of the Reactants 65 2.8 Ultrasound-Assisted Biodiesel Production Process 66 2.8.1 Fundamental Aspects of the Process 66 2.8.2 Homogeneously Catalyzed Ultrasound-Assisted System 69 2.8.3 Heterogeneously Catalyzed Ultrasound-Assisted System 72 2.8.3.1 Heterogeneously Acid Catalyzed System 72 2.8.3.2 Heterogeneous Based Catalyzed Ultrasound-Assisted System 74 2.8.3.3 Influence of Reaction Parameters 78 2.9 Conclusions 79 Acknowledgement 80 References 80

3 Application of Catalysts in Biodiesel Production Anilkumar R. Gupta and Virendra K. Rathod 3.1 Introduction 3.2 Homogeneous Catalysis for the Biodiesel Production 3.2.1 Homogeneous Acid Catalyst 3.2.2 Homogeneous-Base Catalyst 3.3 Heterogeneous Catalyst 3.3.1 Heterogeneous Acid Catalyst 3.3.2 Heterogeneous-Base Catalyst

85 85 89 89 93 96 97 106

Contents  vii 3.4 Biocatalysts 3.5 Conclusion References

115 119 124

4 Hydrogenolysis as a Means of Valorization of Biodiesel-Derived Glycerol: A Review 137 Manjoro T.T., Adeniyi A. and Mbaya R.K.K. 4.1 Introduction 138 4.2 Ways of Valorization of Biodiesel-Derived Glycerol 139 4.2.1 Catalytic Conversion of Glycerol Into Value-Added Commodities 140 4.2.1.1 Catalytic Oxidation of Glycerol 140 4.2.1.2 Catalytic Dehydration of Glycerol 143 4.2.1.3 Pyrolysis of Bioglycerol 144 4.2.1.4 Glycerol Transesterification 145 4.2.1.5 Glycerol Direct Carboxylation 146 4.3 Hydrogenolysis of Glycerol 147 4.3.1 Definition of Hydrogenolysis 147 4.3.2 Catalytic Hydrogenolysis of Glycerol 148 4.3.3 Product Spectrum from Hydrogenolysis of Glycerol 148 4.3.4 Hydrogenolysis of Glycerol to 1,2-PDO (Propylene Glycol): Reaction Systems Overview 149 4.3.5 Catalyst Selection 151 4.3.6 Reaction Conditions That Influence the Hydrogenolysis of Glycerol to 1,2-PDO 153 4.3.6.1 Effect of Reaction Temperature 153 154 4.3.6.2 Effect of H2 Pressure 4.3.6.3 Effect of Initial Water Concentration 155 4.3.6.4 Effect of Reaction Time 156 4.3.6.5 Effect of Catalyst Weight 156 4.3.6.6 Proposed Reaction Mechanisms for Glycerol Hydrogenolysis to Produce 1,2-PDO 157 4.4 Conclusion 159 References 159 5 Current Status, Synthesis, and Characterization of Biodiesel Akshay Garg, Gaurav Dwivedi, Prashant Baredar and Siddharth Jain 5.1 Introduction 5.2 Status of Biodiesel in India 5.3 Biodiesel Production in India

167 167 169 169

viii  Contents 5.3.1 Feedstocks Popular in India 5.3.1.1 Jatropha (Jatropha curcas) Oil 5.3.1.2 Pongamia Oil 5.3.1.3 Mahua Oil 5.3.1.4 Neem Oil 5.3.1.5 Linseed Oil 5.3.1.6 Rubber Seed Oil 5.3.1.7 Tobacco Oil 5.3.1.8 Castor 5.3.1.9 Waste Cooking Oil 5.3.1.10 Algae Oil 5.3.2 Advantages of Non-Edible Oils 5.3.3 Modification Techniques 5.3.3.1 Blending 5.3.3.2 Micro-Emulsification 5.3.3.3 Cracking 5.3.3.4 Transesterification 5.3.4 Biodiesel Production Methodology 5.3.4.1 Catalytic Transesterification 5.3.4.2 Non-Catalytic Transesterification 5.3.5 Optimization Methodology for Biodiesel 5.3.5.1 Central Composite Design Technique 5.3.5.2 Box Behnken Technique 5.4 Properties of Biodiesel 5.5 Analytical Methods 5.5.1 Titration 5.5.2 Chromatic Methods 5.5.2.1 Gas Chromatography 5.5.2.2 High-Performance Liquid Chromatography 5.5.3 Spectroscopic Methods 5.5.3.1 Nuclear Magnetic Resonance Spectroscopy 5.5.3.2 Infrared Spectroscopy 5.5.4 Rancimat Method 5.5.5 Viscometry 5.6 Conclusion References 6 Commercial Technologies for Biodiesel Production Chikati Roick, Leonard Okonye, Nkazi Diankanua and Gorimbo Joshua Abbreviation

169 171 171 171 171 171 172 172 172 172 172 173 173 173 173 174 174 174 174 178 179 179 179 180 181 181 181 183 184 184 184 185 185 186 186 187 195 196

Contents  ix 6.1 Introduction 6.2 Biodiesel Production 6.3 Technologies Used for Biodiesel Production 6.3.1 Chemical Reaction (Transesterification) 6.3.2 Thermochemical Conversion 6.3.3 Biomechanical Conversion 6.3.4 Direct Combustion 6.4 Other Technologies in Use for Biodiesel Production 6.5 Feedstock Requirement 6.6 Some Problems Facing Commercialization of Biodiesel in Africa 6.7 Case Studies/Current Status and Future Potential 6.8 Conclusions Acknowledgments References

196 197 198 199 199 201 201 201 203 203 204 207 208 208

7 A Global Scenario of Sustainable Technologies and Progress in a Biodiesel Production 215 , M. B. Kumbhar, P. E. Lokhande , U. S. Chavan and V.G. Salunkhe 7.1 Introduction 216 7.2 Current Status of Feedstock for Biodiesel Production Technology 218 7.3 Scenario of Biodiesel in Combustion Engine 222 7.4 Biodiesel Production Technologies 223 7.4.1 Direct Blending 223 7.4.2 Pyrolysis 224 7.4.3 Microemulsification 225 7.4.4 Transesterification 226 7.5 Microwave-Mediated Transesterification 227 7.6 Ultrasound-Mediated Transesterification 229 7.7 Catalysis in Biodiesel Production 230 7.7.1 Homogeneous Catalysts 230 7.7.2 Heterogeneous Catalysts 231 7.7.3 Heterogeneous Nanocatalysts 232 7.7.4 Supercritical Fluids 232 7.7.5 Biocatalysts 232 7.8 The Concept of Biorefinery 234 7.9 Summary and Outlook 236 7.10 Conclusion 237 References 237

x  Contents 8 Biodiesel Production Technologies 241 Moina Athar and Sadaf Zaidi 8.1 Introduction 242 8.2 Biodiesel Feedstocks 242 8.2.1 Selection of Feedstocks 243 8.3 Biodiesel Production Technologies 248 8.3.1 Pyrolysis 248 8.3.2 Dilution 249 8.3.3 Micro-Emulsion 249 8.3.4 Transesterification 249 8.3.4.1 Homogeneously Catalyzed Transesterification Processes 250 8.3.4.2 Heterogeneously Catalyzed Transesterification Processes 252 8.3.4.3 Enzymatic Catalyzed Transesterification Processes 252 8.4 Intensification Techniques for Biodiesel Production 253 8.4.1 Supercritical Alcohol Method 253 8.4.2 Microwave Heating 253 8.4.3 Ultrasonic Irradiation 255 8.4.4 Co-Solvent Method 256 8.5 Other Techniques of Biodiesel Production 256 References 257 9 Methods for Biodiesel Production 267 M.Gul, M.A. Mujtaba, H.H. Masjuki, M.A. Kalam and N.W.M. Zulkifli 9.1 Selection of Feedstock for Biodiesel 267 9.1.1 First-Generation Feedstock 268 9.1.2 Second-Generation Feedstock 268 9.1.3 Third-Generation Feedstock 269 9.2 Methods for Biodiesel Production 269 9.2.1 Dilution With Hydrocarbons Blending 269 9.2.2 Micro-Emulsion 269 9.2.3 Pyrolysis (Thermal Cracking) 270 9.2.4 Transesterification (Alcoholysis) 271 9.2.4.1 In Situ Transesterification (Reactive Extraction) 271 9.2.4.2 Conventional Transesterification 272 9.2.4.3 Microwave/Ultrasound-Assisted Transesterification 278

Contents  xi 9.2.4.4 Variables Affecting Transesterification Reaction 278 References 282 10 Non-Edible Feedstock for Biodiesel Production 285 Chikati Roick, Kabir Opeyemi Otun, Nkazi Diankanua and Gorimbo Joshua List of Abbreviations 286 10.1 Introduction 286 10.2 Reports Relevant to Global Warming and Renewable Energy 287 10.3 Biofuels as an Alternative Energy Source 288 10.3.1 First-Generation Biofuels 288 10.3.2 Second-Generation Biofuels 289 10.3.3 Third-Generation Biofuels 290 10.4 Benefits of Using Biodiesel 290 10.5 Technologies of Biodiesel Production From Non-Edible Feedstock 291 10.6 Biodiesel Production by Transesterification 292 10.7 Non-Edible Feedstocks for Biodiesel Production 295 10.7.1 Non-Edible Vegetable Oils 296 10.7.2 Waste Cooking Oil 297 10.7.3 Algal Oil 298 10.7.4 Waste Animal Fat/Oil 299 10.8 Fuel Properties of Biodiesel Obtained From Non-Edible Feedstock 299 10.9 Advantages of Non-Edible Feedstocks 302 10.10 Economic Importance of Biodiesel Production 302 10.11 Conclusions 303 Acknowledgments 303 References 304 11 Oleochemical Resources for Biodiesel Production Gayathri R., Ranjitha J. and Vijayalakshmi Shankar 11.1 Introduction 11.2 Definition of Oleochemicals 11.3 Oleochemical Types 11.4 Production of Biodiesel 11.5 Types of Feedstocks 11.5.1 Non-Edible Feedstocks 11.5.2 Non-Edible Vegetable Oil

311 311 312 313 315 317 317 317

xii  Contents

11.6

11.7

11.8

11.9

11.5.3 Tall Oil 11.5.4 Waste Cooking Oils 11.5.5 Animal Fats 11.5.6 Chicken Fat 11.5.7 Lard 11.5.8 Tallow 11.5.9 Leather Industry Solid Waste Fat 11.5.10 Fish Oil Uses of Oleochemicals 11.6.1 Polymer Applications 11.6.2 Application of Plant Oil as a Substitute for Petro-Diesel 11.6.3 Used as Surfactants 11.6.4 Oleochemicals Used in Pesticide 11.6.5 Oleochemicals Used in Spray Adjuvants and Solvents Methyl Ester or Biodiesel Production 11.7.1 Palm Oil 11.7.2 Sunflower Oil 11.7.3 ME From AFW Parameters Affecting the Yield of Biodiesel 11.8.1 Reaction Conditions 11.8.2 Catalyst 11.8.2.1 Alkali Catalyst 11.8.2.2 Acid Catalyst 11.8.2.3 Biocatalyst 11.8.2.4 Heterogeneous Catalyst 11.8.2.5 ME Conversion by Supercritical Method 11.8.3 Properties of Feedstock 11.8.3.1 Composition of FA 11.8.3.2 FFA 11.8.3.3 Heat 11.8.3.4 Presence of Unwanted Materials 11.8.3.5 Titer 11.8.4 Characteristic of Feedstock Optimization of Reactions Conditions for High Yield and Quality of Biodiesel 11.9.1 Pre-Treatment of Feedstock 11.9.1.1 Elimination of Water 11.9.1.2 Elimination of Insoluble Impurities

318 318 318 319 319 320 321 322 322 322 323 323 324 324 324 326 326 327 327 327 327 327 329 329 329 329 330 330 330 330 330 332 332 332 332 332 332

Contents  xiii 11.9.1.3 Elimination of Unsaponifiables 11.9.2 Characterization and Selection of Feedstocks 11.9.3 Selection of Reaction Conditions 11.10 Oil Recovery 11.10.1 Alkaline Flooding Method 11.10.2 Additives 11.11 Quality Improvement of Biodiesel 11.11.1 Additives for Improving Combustion Ability 11.11.2 Additives for Enhancing the Octane Number 11.11.3 Additives for Improving the Stability 11.11.4 Additives to Enhance Cold Flow Property 11.11.5 Additives to Enhance Lubricity 11.11.6 Additives to Enhance Cetane Number 11.12 Conclusion Abbreviations References

333 333 333 333 333 334 334 334 334 334 334 335 335 335 335 336

12 Overview on Different Reactors for Biodiesel Production V. C. Akubude, K.F. Jaiyeoba, T.F Oyewusi, E.C. Abbah, J.A. Oyedokun and V.C. Okafor 12.1 Introduction 12.2 Biodiesel Production Reactors 12.2.1 Batch Reactor 12.2.2 Continuous Stirred Tank Reactor 12.2.3 Fixed Bed Reactor 12.2.4 Bubble Column Reactor 12.2.5 Reactive Distillation Column 12.2.6 Hybrid Catalytic Plasma Reactor 12.2.7 Microreactors Technology 12.2.8 Oscillatory Flow Reactors 12.2.9 Other Novel Reactors 12.3 Future Prospects 12.4 Conclusion References

341

13 Patents on Biodiesel Azira Abdul Razak, Mohamad Azuwa Mohamed and Darfizzi Derawi 13.1 Introduction 13.2 Generation of Biodiesel 13.3 Development of Catalyst

361

341 342 343 344 346 347 349 350 350 353 353 354 354 354

361 362 363

xiv  Contents 13.3.1 Homogeneous Catalyst 13.3.2 Heterogeneous Catalyst 13.4 Method Producing Biodiesel 13.4.1 Pre-Treatment Process 13.4.2 Direct Use and Blending of Oils 13.4.3 Esterification of FFA 13.4.4 Transesterification of TAG 13.4.5 Pyrolysis 13.5 Reactor’s Technology for Biodiesel Production 13.5.1 Continuous Stirred Tank Reactor 13.5.2 Fixed Bed Reactor 13.5.3 Micro-Mixer Reactor 13.6 Conclusion References

364 364 365 365 366 366 367 368 369 370 370 371 372 372

14 Reactions of Carboxylic Acids With an Alcohol Over Acid Materials 377 J.E. Castanheiro 14.1 Introduction 377 14.2 Zeolites 378 379 14.3 SO3H as Catalyst 14.4 Metal Oxides 380 14.5 Heteropolyacids 382 14.6 Other Materials 384 14.7 Conclusions 384 References 385 15 Biodiesel Production From Non-Edible and Waste Lipid Sources Opeoluwa O. Fasanya, Aishat A. Osigbesan and Onoriode P. Avbenake 15.1 Introduction 15.2 Non-Edible Plant-Based Oils 15.2.1 Jatropha curcas 15.2.2 Calophyllum inophyllum 15.2.3 Mesua ferrea 15.2.4 Jojoba Oil 15.2.5 Azadirachta indica 15.2.6 Rubber Seed Oil 15.2.7 Ricinus communis as Feedstock (Castor Oil) 15.2.8 Other Non-Edible Oils

389 390 394 394 397 397 398 398 399 402 403

Contents  xv 15.3 Waste Animal Fats 15.4 Expired and Waste Cooking Oils 15.5 Algae/Microalgae 15.6 Insects as Biodiesel Feedstock 15.7 Deacidification 15.8 Other Technologies 15.9 Conclusion References

404 405 406 411 414 414 415 415

16 Microalgae for Biodiesel Production 429 Charles Oluwaseun Adetunji, Victoria Olaide Adenigba, Devarajan Thangadura and Mohd Imran Ahamed 16.1 Introduction 430 16.2 Physicochemical Properties of Biodiesel From Microalgae 431 16.3 Genetic Engineering/Techniques Enhancing Biodiesel Production 432 16.4 Nanotechnology in Microalgae Biodiesel Production 434 16.5 Specific Examples of Biodiesel Production From Microalgae 434 16.6 Methodology Involved in the Extraction of Algae 438 16.6.1 Chemical Solvents Extraction 439 16.6.2 Extraction by Supercritical Carbon Dioxide 439 16.6.3 Extraction Using Biochemical Techniques 439 16.6.4 Extraction Involving Direct Transesterification 440 16.6.5 Extraction Using Transesterification Techniques 440 16.7 Conclusion and Future Recommendation to Knowledge 440 References 441 17 Biodiesel Production Methods and Feedstocks Setareh Heidari and David A. Wood 17.1 Introduction 17.2 Biofuel Classification in Terms of Origin and Technological Conversion of Raw Materials 17.3 Techniques Capable of Producing Biodiesel on Commercial Scales 17.3.1 Direct and Blending Methods With the Aim of Biodiesel Generation 17.3.2 Microemulsion Methods 17.3.3 Pyrolysis Methods 17.3.4 Transesterification Methods 17.4 Influential Parameters on Biodiesel Production

447 448 449 451 452 452 453 453 454

xvi  Contents 17.4.1 The Choice of Transesterification Catalysts 17.4.2 Effects of Catalyst Characteristics on Biodiesel Production Efficiency 17.5 Biodiesel Markets and Economic Considerations 17.6 Challenges Confronting Biodiesel Uptake 17.7 Corrosion and Quality Monitoring Issues for Biodiesel 17.8 Conclusions References

454 454 455 456 457 457 458

18 Application of Nanoparticles for the Enhanced Production of Biodiesel 465 Muhammad Hilman Mustapha, Akhsan Kamil Azizi, Wan Nur Aini Wan Mokhtar and Mohamad Azuwa Mohamed 18.1 Introduction 465 18.2 Solid Nanoparticles 466 18.3 Nanobioparticles/Nanobiocatalyst 471 18.4 Magnetic Nanoparticles 473 18.5 How Nanoparticles Enhanced Biodiesel Production? 475 18.6 Conclusion 477 References 477 Index 481

Preface

Energy technologies have attracted great attention due to the fast development of sustainable energy. Biodiesel technologies have been identified as the sustainable route through which overdependence on fossil fuels can be reduced. Biodiesel has played a key role in handling the growing challenge of a global climate change policy. Biodiesel is defined as the monoalkyl esters of vegetable oils or animal fats. Biodiesel is a cost-effective, renewable, and sustainable fuel that can be made from vegetable oils and animal fats. Compared to petroleum-based diesel, biodiesel would offer a non-toxicity, biodegradability, improved air quality and positive impact on the environment, energy security, safe-to-handle, store and transport, and so on. Biodiesels have been used as a replacement of petroleum diesel in transport vehicles, heavy-duty trucks, locomotives, heat oils, hydrogen production, electricity generators, agriculture, mining, construction, and forestry equipment. This book describes a comprehensive overview, covering a broad range of topics on biodiesel technologies and allied applications. Chapters cover history, properties, resources, fabrication methods, parameters, formulations, reactors, catalysis, transformations, analysis, in situ spectroscopies, key issues and applications of biodiesel technology. It also includes biodiesel methods, extraction strategies, biowaste utilization, oleochemical resources, non-edible feedstocks, heterogeneous catalysts, patents, and case-studies. Progress, challenges, future directions, and state-of-the-art biodiesel commercial technologies are discussed in detail. This book is an invaluable resource guide for professionals, faculty, students, chemical engineers, biotechnologists, and environmentalists in these research and development areas. This book includes the eighteen chapters and the summaries are given as follows. Chapter 1 details the biocatalytic production of biodiesel. Microbial enzymes such as lipases act as biocatalysts in the transesterification process of biodiesel production. Suitable and cost-effective feedstocks or xvii

xviii  Preface substrates for biodiesel production including their percentage yields are discussed. Factors that affect the enzymatic transesterification reaction are also explained. Chapter 2 addresses ultrasonic energy which can increase the interface area while creating a thermal effect in heterogeneous biodiesel production process to result in higher biodiesel yield. Fundamental understanding of the improved reactant-catalyst interaction, the nature of the thermal effect, favorable process behaviors, reaction kinetic, as well as the effect on biodiesel quality is particularly addressed. Chapter 3 is about the study of different types of catalysts used for biodiesel production. The classification of catalysts, advantages, and limitations, along with their mechanism, is explained. The heterogeneous catalysts’ synthetic methods and immobilization of biocatalyst are also discussed in detail. Chapter 4 discusses various methods used to produce value-added chemicals from biodiesel-derived glycerol. The main focus being is given to hydrogenolysis as a transformative process to selectively produce 1,2propanediol and the advancements in biodiesel technologies. Furthermore, knowledge gaps are highlighted based on extensive literature research on the subject. Chapter 5 discusses various techniques of synthesizing biodiesel and review of various existing analytical technologies for characterization of biodiesel. The chapter focuses on the current status of biodiesel in India, i.e., using non-edible sources and future feasibility of developing new methods of characterization to reduce the cost of biodiesel production. Chapter 6 examines various established technologies available for the production of biodiesel, viz., chemical reaction, direct combustion, thermochemical conversion, and biomechanical conversion. Each technology is apportioned to a certain type of feedstock. Case studies, current status, and future potential of commercialization of biodiesel production in Africa are also discussed. There is a huge demand for sustainable biofuel production in coming decades. The key challenges for biodiesel production are high FFA with the desired level of yield, stability, optimized and flexible production, commercialization of feedstock and environmentally friendly cycle. The collective effort and commitment of research survey regard feedstocks and commercialization of technology around the globe towards sustainable energy are expressed in terms of accelerating the biofuel economy in Chapter 7. Chapter 8 provides an overview of the available feedstocks, production methods, and the benefits and constraints of using homogeneous, heterogeneous, and enzymatic catalysts for biodiesel. Some latest

Preface  xix intensification techniques to manage mass transfer restrictions of oil and alcohol phases along with some production cost reduction measures are also highlighted. Chapter 9 discusses different types of feedstocks used for synthesizing biodiesel and feedstock selection criteria. Moreover, all biodiesel production methods (i.e., dilution with hydrocarbons blending, micro-emulsion, pyrolysis, and transesterification) are also described in detail with their advantages and disadvantages. The major focus is given to the various transesterification methods. Production methods also include experimental setup layouts, all process parameters, reaction conditions, the latest advancement in reaction processes, and their effects on biodiesel yield. Chapter 10 reviews the potential use of non-edible feedstocks in the production of biodiesel. Special attention is given to the types of feedstocks available and their production pathways to biodiesel. The state-of-the-art technology, the properties of the fuel produced, and the environmental concerns of biofuels are also discussed. Chapter 11 discusses the various types of oleochemicals and their usage. Optimization and production of biodiesel derived from oleochemicals and their properties are also discussed. The primary focus is given for the advantage of oleochemicals to be used as a potential feedstock for biodiesel production from the available literature. Chapter 12 provides details about the different configurations of reactors used in biodiesel production. There are two types, namely, batch and continuous reactors. Recently, other improved configurations like microreactors have emerged. This chapter also discusses the merits and demerits of these reactors. Chapter 13 highlights and discusses the international patents on biodiesel applications. This chapter reviews the recent patents on the generation of biodiesel which depends on the feedstock used, catalysts development, the latest method for biodiesel production, and reactor technology for the biodiesel production. Chapter 14 overviews different reactions between a carboxylic acid (fatty acids) and alcohol (methanol and ethanol) over heterogeneous catalysts, an important step in biodiesel production. The nature of solid materials, like zeolites, heteropolyacids, materials with sulfonic groups, inorganic mixed oxides, and clays towards biodiesel production is discussed. Chapter 15 sheds light on inedible feedstock that could be utilized for biodiesel production. Plant-based and non-plant feedstock are discussed. The waste lipid sources which are unfit for consumption are also highlighted. The chemical composition, economic viability, and sustainability of some of these feedstocks are equally explored.

xx  Preface Chapter 16 provides detailed information on the fabrication of biodiesel from microalgae. Specific information on the physical properties, amount of biodiesel production, and level of transesterification of biodiesel are discussed. The application of photobioreactors for the production of biodiesel with the special consideration of several factors such as flow rate, temperature, light intensity, CO2 concentration, and time is highlighted. Several techniques for the extraction of biodiesel such as supercritical CO2, physicochemical, direct transesterification, chemical solvents, and biochemical respectively are highlighted. Chapter 17 discusses the biofuel classification in terms of origin and technological conversion of raw materials. Techniques capable of producing biodiesel on commercial scales are also presented. Furthermore, influential parameters and their roles in biodiesel production are elaborately covered. Finally, challenges and limitations confronting biodiesel uptake are presented. Chapter 18 mainly explicates the application of nanoparticle catalysis for the high production of biodiesel. In particular, various types of catalyst nanoparticles with different synthesis strategy and their roles in enhancing the biodiesel production are discussed. Inamuddin, Mohd Imran Ahamed, Rajender Boddula and Mashallah Rezakazemi

1 Biocatalytic Processes for Biodiesel Production Ubaid Mehmood1, Faizan Muneer2, Muhammad Riaz3, Saba Sarfraz4 and Habibullah Nadeem2* College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, China 2 Department of Bioinformatics and Biotechnology, Government College University Faisalabad, Pakistan 3 Department of Food Sciences, University College of Agriculture, Bahauddin Zakariya University, Multan, Pakistan 4 Department of Chemistry, Government College Women University Faisalabad, Faisalabad, Pakistan 1

Abstract

Enzymes such as microbial lipases can be effectively used as biocatalysts for biodiesel production in a sustainable manner. Biocatalytic processes to produce biodiesel or biofuel is the need of time to reduce the emission of greenhouse gases produced from conventional diesel or fossil fuels. Lipases with excellent biochemical and physiological properties are most commonly used to catalyze the transesterification process for biodiesel production. Lipases obtained from microbes such as bacteria and fungi produce 70%–95% ethanol and methanol. Biodiesel is usually composed of fatty acid alkyl esters which are mono-alkyl esters of either fatty acid methyl esters or fatty acid ethyl esters depending upon the alcohol (acyl acceptor) being used in the reaction. Factors such as bioreactor type, acyl acceptor, temperature, and glycerol can affect the enzymatic transesterification reaction. Recombinant enzymes such as recombinant lipases can be employed to obtain higher percentage of biodiesel due to their high specificity and biocatalytic activity for different substrates used for biodiesel production. Keywords:  Lipases, biodiesel, biocatalysis, biofuels, Novozyme, free fatty acids, ethyl acceptors *Corresponding author: [email protected] Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (1–58) © 2021 Scrivener Publishing LLC

1

2  Biodiesel Technology and Applications

1.1 Introduction and Background Biofuels are crucial for the conservation of our natural environment and the climate. Biofuel such as bioethanol can be used for energy generation purposes which are currently being produced by fossil fuels such as petrol, diesel, and kerosene oil [1]. Being non-renewable energy sources, fossil fuels will not only deplete from the planet earth but will also leave a long-term impact on the globe both in terms of economy and climate change. Apart from being limited natural fuel reserves, there are countless reasons available that justify the need of natural and eco-friendly energy sources such as biofuels. Transportation, power generation, and house hold appliances use fuels directly or indirectly and for that purpose we are almost dependent on fossil fuels [2]. If efficient and robust methods and technologies are not worked out, we might come to a permanent stand still condition in the future when all our natural fossil fuel reserves will be vanished. The use of fossil fuel produces gases such as carbon dioxide (CO2), carbon monoxide (CO), sulfur oxides (SOx), and nitrogen oxides (NOx) which are unhealthy for human beings causing health issues such as asthma, skin diseases, and even cancers [3]. These by-products of fuel consumption affect not only human but also animals and plants on a broader view. Plant production and growth rates are highly effected by the changing environmental and climatic conditions due to heavy use of fossil fuels and their derivatives such as plastics [4]. Vehicular CO2 emission in the past decade was 20%, and it is estimated that by 2030, it will reach up to 80%. Liquide biofuels got prominence with the automobile industry. Peanut oil was used to make biofuel, i.e., biodiesel by Rudolph Diesel in 1898. Henri Ford who was the founder of Ford Company an automobile industry was also convinced by the idea of using biofuels in his automobile. During World War-II, Germany used biomass-based fuels for their machines which is the evidence of its use back in 1940s. The utilization of biofuels was presented, but after two major oil crises, first was in 1973 and second in 1978, and brought back its importance to public again. Biofuels that are produced using a large number of biomass sources are a sustainable solution for the environment and biosphere conservation. Being renewable energy resources and eco-friendly to the environment and life on earth, these are highly desirable products produced from renewable biomass substrates [5]. Currently, biofuels from various agricultural sources such as soybean oil, rapeseed oil, recycled waste oils, and waste plant residues are being studied. Depending on the feedstock type, processing technology and their developmental level, biofuels can be classified into first-, second-, and third-­ generation biofuels. Biofuels produced directly from edible feedstock such

Biocatalytic Processes  3 as crops, sugars, and edible oil using conventional techniques are considered as first-generation biofuels [6]. Non-edible feedstock such as waste crop residues like lignocelluloses and waste vegetable oils are required to produce second-generation biofuels which are comparatively economical and more sustainable as there is no food versus fuel competition. Highly advanced methods are used to produce second-generation biofuels which has certainly less flaws and ultimately improved to get greater yield [7]. We are currently in the phase of second-generation biofuels. Most of the processing techniques for second-generation biofuel production are not available at commercial level. One must think that the land dedicated for edible feedstock/crops will be compromised if we start cultivating non-edible crops in that land. Marginal lands can be used for the cultivation of grasses and other plants that are not a food for human or nor a fodder for animals on a larger scale. These plants or marginal grasses can be used for the production of second-generation biofuels. There have been a lot of research investigations to produce biodiesel using non-edible plant oils such as keranja oil, Jatropha curcas oil, tobacco oil, Calophyllum inophyllum oil, and castor oil [8]. Jatropha is an effective source of biodiesel production because of 30%–50% oil contents in its seeds [9]. The actual precursors of most of the second-generation biodiesel production are waste oils either in the form of waste cooking or industrial oils or animal fats. The utilization of these waste materials as feed stock helps in managing and disposing of waste material, which is one of the biggest problem for earth, for the benefit of environment [10]. In order to comprehend different biofuels, we can categorize them into four types which include biodiesel, bioalcohol (biomethanol, bioethanol, biobutanol), biogas, and biohydrogen. The most widely used biofuels are liquid biofuels such as biodiesel and bioethanol. Biofuels can be blended with other petro-based fuels in order to manage and enhance quality and quantity of fuel. Biofuel production includes chemical, thermal, and enzymatic methods. Among all methods, the most effective way to produce biofuels is through enzymes or biocatalysts [11]. Enzymes are becoming the focus of research to produce biofuels because of their advantages over other biofuel production techniques [12]. In this chapter, we discuss biodiesel production using biocatalytic processes and methods where different microbial enzymes (obtained from microorganisms) are used.

1.2 Importance of Biodiesel Over Conventional Diesel Fuel Chemically, biodiesel is composed of fatty acid alkyl esters (FAAEs) which are mono-alkyl esters of either fatty acid methyl esters (FAME) or fatty

4  Biodiesel Technology and Applications acid ethyl esters (FAEE) depending upon the alcohol (acyl acceptor) being used in the reaction [10]. Rudolf Diesel, the inventor of diesel engine, first used biodiesel in 1900 but that was highly viscous so that engine could not run effectively for a longer time [13]. Biodiesel is very suitable alternative to diesel fuel because of its remarkable properties and advantages, i.e., biodiesel carries 4.5 times greater energy than fossil fuel [14] and similar in chemical structure and energy content to conventional diesel [15]. It reduces approximately 85% carcinogenic compounds emission that is why it is very less toxic than conventional diesel fuel, free of sulfur, free of polycyclic aromatic hydrocarbons and metals, biodegradable, high cetane number (CN), and flash point [16]. It has the potential to reduce pollutants and emission of greenhouse gases [17] and is 66% more efficient lubricating agent than petro-diesel, which enhances life and performance of engine [18]. Blending of biodiesel with petro-diesel fuel that can affect important properties of fuel such as flash point, CN, kinematic viscosity, and lubricity is enhanced. It also decreases exhaust emissions and heat of combustion [19]. The largest biodiesel producer is EU (European Union) and biodiesel accounts 80% of the overall transport fuel in EU [20–22]. Biodiesel produced from different resources will have different composition and properties, but it must fulfill the standards and requirements of international standards of American society for testing materials and EU standards for biodiesel. Biodiesel has lots of applications such as it can be used as a fuel for aviation purposes [20], for electricity production using generators [21, 22] and in diesel fueled marine engines, because of its nontoxic and biodegradable properties environmental impacts on engines can be reduced. Alcohol type, quality of substrate that is to be converted, catalyst used, temperature of the reaction, and alcohol-to-oil molar ratio determine the performance of biodiesel production [23–25].

1.3 Substrates for Biodiesel Production Biodiesel feedstock accounts for 60%–80% of the total cost; therefore, appropriate feedstock is required for economically valuable production of biodiesel [26]. In order to obtain economically beneficial and sustainable biodiesel, feedstock must be easily available, cheap, and sustainable. Feedstock is selected on the basis of biodiesel production that must be compatible to chemical composition and properties of feedstock to be used, percentage per dry biomass, agricultural potential, yield per hectare, and geographical region of that feedstock [27]. For example, soybean oil, palm oil, coconut oil, and rapeseed oil are mainly used as feedstock in

Biocatalytic Processes  5 US, tropical countries like Indonesia, coastal areas, and European countries, respectively. Cultivation and climate conditions of the feedstock production area are also considered for its selection [28]. Depending on the nature, there are two types of feedstock for biodiesel production. First is the lipid raw material and second includes alcohol feedstock. Lipid sources can be divided into three categories, i.e., oils derived from plant sources (edible and non-edible oils), waste oils (waste cooking oils, industrial wastewater, lard, yellow grease, and animal fats), and oils from oleaginous microorganisms such as bacteria, fungi, and microalgae [29]. Properties of biodiesel like cold filter plugging point and oxidation stability are determined from the feedstock used for production. Feedstock properties like moisture content, impurities, content, and composition of free fatty acids (FFAs) affect the performance of engine [27, 28]. Composition of fats and oils including monoglycerides, diglycerides, and triglycerides are used for biodiesel production. Utilization of edible plant oils as feedstock is an expensive way for biodiesel production that leads to imbalance in food market and industry. It is also associated with some environmental problems like disruption of vital soil resources and deforestation due to mass propagation [29]. In order to solve problems linked with edible plant oils, the best alternate is the production of second-generation biodiesel which is produced by using non-edible (inedible) feedstock which are more favorable than edible oils due to reduction in cost and waste pollution, lower aromatic, sulfur contents, and high calorific value [8]. Inedible oils involve inedible plant oils, industrial waste, cooking oils, animal fats, and microalgal oils. Inedible oil producing plants have certain remarkable features that make them favorable to use, for example, they can be managed to grow in arid and semi-arid conditions and they do not require fertilizers and moisture for growth [24]. Repeated use of fried vegetable oils at high temperature leads to the production of waste cooking oils. Moreover, chemical composition of waste cooking oil is totally dependent on the oil from which it is derived. Hydrogenation, oxidation, and polymerization are the main chemical reactions that lead to production of very toxic and detrimental compounds for consumption. Fatty acid content of these oils lies in the range of 0.5% to 15% which is very much higher than refined oil having fatty acid content less than 0.5%. The waste cooking oil is known as yellow grease if the fatty acid content is less than 15% and it is called low value brown grease if the fatty acid content is higher than 15% [28]. Animal waste products like lard, tallow, animal fat, poultry fat, fish oil, and pork fat are also very effective feedstock for biodiesel production [30, 31]. Animal-based biodiesel is a good lubricating agent and has high percentage of saturated fats which decreases sedimentation risk and low temperature fluidity.

6  Biodiesel Technology and Applications Moreover, it increases oxidative stability and cold filter plugging point of biodiesel which are the characteristics of good quality biodiesel. Utilizing these waste materials is an effective solution to encounter waste disposal. Apart from all these mentioned advantages of non-edible or waste oils, there are also some shortcomings or disadvantages, for example, low oil yield, higher carbon residue, unsaturated fatty acid content, and low volatility [29]. In some cases, large plantation land for inedible oils is required compared to edible ones, e.g., Pongamia pinnata and Jatropha has 2–50 folds less oil yield per hectare than palm oil so that is why they require much area to meet the demand [31]. Because of the drawbacks associated with second-generation biodiesel, scientists are looking for more efficient methods for biodiesel production. Biodiesel production using oleaginous microorganisms like bacteria, algae, microalgae, and fungi are considered as the future of biodiesel production that can meet global biodiesel demand for transportation fuels and other energy consuming applications [32]. Microbial oils are better than other plant oils because of their short life cycle and rapid growth, less requirement of space, labor, and easier scaling [33–35]. Microalgae as a feedstock is very effective because of its enormous advantages like they have high oil yield, can grow in salty and waste waters, use of non-arable land, and growth in 24 hours so multiple harvesting in a year is possible. If we give land area for microalgal growth then according to an estimate, only 2% of the US cropping land is enough for meeting 1/3 demand of US transportation fuels and less than 5% land is required to completely replace all transportation fuels [36–38]. Moreover, dry algal biomass can accumulate more than 80% oil without water and they have a capacity to produce oil yield 250 times greater than soybean water free oil [35]. Some examples of microalgae used for biodiesel production are Botryococcus sp., Cylindrotheca sp., Schizochytrium sp., Chlorella sp., and Nitzschia sp.

1.4 Methods in Biodiesel Production There can be many ways for biodiesel production but esterification and transesterification are the two most widely used methods. Esterification is the reaction of FFAs and alcohol to make FAAEs and water is released, while transesterification is the reaction of triglycerides or triacylglycerols (TAGs) with alcohol to make FAAE and glycerol is produced as by-product [9]. Transesterification is slower than esterification process because of its multiple steps or reactions. It is a three-step process to convert TAGs into FAAE. In the first step, TAG reacts with one molecule of alcohol to produce one

Biocatalytic Processes  7 molecule of FAAE and diacylglycerol (DAG). In second step, DAG further reacts again with one molecule of alcohol to produce one molecule of FAAE and monoacylglycerol and in the last step monoacylglycerol is converted into one molecule of glycerol and FAAE after reacting with an alcohol molecule. In each of these three steps, FAAEs are produced and in total one molecule of TAG and three molecules of alcohol are consumed to produce three molecules of FAAE and one molecule of glycerol [6–10]. Transesterification is a reversible reaction, and in order to make the reaction go forward to produce more biodiesel, we have to supply alcohol in large excess so that the reaction equilibrium shifts toward the product [36, 37].

1.5 Types of Catalysts Involved in Biodiesel Production Biodiesel production process is carried by either catalytic or non-catalytic methods. Non-catalytic methods include use of alcohols or supercritical fluids or ionic liquids in the reaction system to produce biodiesel but mostly catalytic methods have been used for last 2 or 3 decades because of their advantages over non-catalytic methods [38]. Catalytic methods can be categorized into chemical homogenous catalysts, solid heterogenous catalysts, and biocatalysts.

1.5.1 Chemical Homogenous Catalysts Chemical homogenous catalysts include combination of base and acid catalysts. NaOH, KOH, and methoxides are the base catalysts while HCl and H2SO4 are the acid catalysts [39]. Acid catalysts are mostly used to overcome the problem of FFAs in the reaction system but the rate of trans esterification by acid catalyst is slower than alkaline or base catalysts [8]. Chemical catalytic processes either alkaline or acid catalysis both have several disadvantages. Alkaline catalysis provides high conversion of triacyl glycerol into the alkyl esters in a very short time but it has many drawbacks. Alkaline catalysis is very prone to FFA concentration (>2.5%) in the reaction system because high FFA concentration results in saponification reaction producing soaps and leads to loss in enzymatic activity and makes difficult to separate transesterification by-product, i.e., glycerol from biodiesel. Hence, biodiesel yield decreases. Moreover, it needs high energy requirement [40]. To counter FFA problem, acid catalysts are used, e.g., sulfuric acid but it also causes some technical problems regarding separation and purification of glycerol. Moreover, acid catalysis is a slow process

8  Biodiesel Technology and Applications compared to alkaline process. Reactors, pipelines, and other equipment are badly affected by acid catalysts because of their corrosive nature that can increase the cost of biodiesel production [41].

1.5.2 Solid Heterogeneous Catalysts Solid heterogeneous catalysts include acid heterogenous catalysts and base heterogenous catalysts. Solid acid heterogenous catalysts include heteropolyacid catalysts (HPAs), mineral salts, acids, and cationic exchange resins. Among these, titanium oxide, sulfonic ion exchange resin, tin oxide, sulfonated carbon-based catalysts, zirconium oxide, zeolites, and sulfonic modified mesostructured silica are the main acid heterogeneous catalysts. Solid base heterogeneous catalysts have been categorized as mixed metal oxides, supported alkaline earth metals, single metal oxides, and nano-­ oxides. Among these, the most studied are magnesium oxide, calcium oxide, and strontium oxide [44, 45].

1.5.3 Biocatalysts Biocatalysts include enzymes especially lipases which are very popular in biodiesel production [43]. Enzymatic biodiesel production method diminishes problems associated with alkali and acid catalyzed methods. Use of enzyme catalysts has several economic and environmental advantages over chemical biodiesel production processes. Advantages of enzyme catalysis include production of pure and high market value glycerol, minor, or no waste water generation that is why treatment of waste water is not required, mild reaction conditions are required, no soap formation because enzymes can esterify low quality feedstock having high concentration of FFA that is why this method is insensitive to feedstock concentration. Enzymatic biodiesel production is simple so energy consumption is very low, enzymes can be reused because of their easy separation from the reaction mixture, and overall chance of contamination is lower than other transesterification methods [13].

1.6 Factors Affecting Enzymatic Transesterification Reaction There are a lot of factors effecting enzymatic transesterification reaction such as source of enzyme, its type, preparation method, applying technique, its dosage, activity, and life time. Apart from these enzymes related factors, there are also some other factors which affect transesterification

Biocatalytic Processes  9 reaction, e.g., feedstock type and its quality, type of alcohol as acyl acceptor, reaction pH, presence or absence of solvent, type of solvent, reaction temperature, alcohol-to-oil molar ratio [46].

1.6.1 Effect of Water in Enzyme Catalyzed Transesterification Presence of water is not only required for chemically catalyzed biodiesel production but also very much required for enzymatic biodiesel production. It helps in maintaining enzyme structural confirmation and stability so it directly affects activity of enzyme. Oil-water interface is required for enzyme-substrate complex to proceed and water helps to increase this interfacial area [44]. So, without water, transesterification is not possible and absence of water can lead to permanent or temporal changes in protein (enzyme) structure. If water content is minimal, then increase in water concentration moves the reaction equilibrium toward more hydrolysis. Thus, it enhances reaction rate by providing greater stability to enzyme [45]. Excess of water content also has some negative effects on the reaction as well as on enzyme. Excess water content can be accumulated in the reaction medium and within enzyme active site, that leads to decrease the reaction rate as well as its alkyl ester yield [46]. So, concentration of water should be optimally perfect in order to gain maximum benefit from it. Every enzyme has its specific water content requirement, i.e., optimal water requirement, at which that particular enzyme performs its best [47, 48]. Optimal water content not only provides great support, flexibility, and stability to the enzyme but also maximizes transesterification yield by diluting methanol that has an inhibitory effect on enzyme. Factors that determine optimal water content include feedstock and type of solvent used, enzyme, and its immobilization technique used [48]. Chaudhary et al. [49] studied the effect of water content in lipase catalyzed transesterification. At low water activity (aw = 0.33), synthetic activity of enzyme was increased and at high water activity (aw = 0.96) enzyme became more hydrolytically active. They tested various enzymes/lipases at different water activity to check transesterification rates. The lipase from Aspergillus niger was found more prominent to give maximum transesterification rate of 0.341 mmolmin−1 mg−1 at aw = 0.75. Measuring water content as weight percentage is a better choice and more convenient to use than water activity (aw), measured by Karl-Fischer method [50]. Maximum methyl ester yield was at water concentration of 10-15% while increasing water content from 0% to 40% to study the effect of water in conversion of salad oil into methyl ester. But after much increased water concentration, methyl ester yield became very low. So, for maximum transesterification yield, optimum water concentration is required.

10  Biodiesel Technology and Applications

1.6.2 Effect of Bioreactor In order to maximize production and benefit of product we need to perform optimized laboratory experimental procedure at a large industrial scale, so, bioreactors are used in this regard. But results should be equivalent to laboratory procedure [45]. There are some complications like production should be cost effective and in good quality. Carefully planned methodologies and objectives should be designed for effectively large-scale production. This also includes bioreactor parameters like fluid flow performance and unexpected environmental variation. In case of industrial transesterification process, the main hurdle is multiphasic nature of lipase catalyzed synthesis and hydrolysis because this does not allow the bioreactor equivalent to laboratory experiment. Many types of bioreactors such as fluid beds, recirculation membrane reactors, expanding beds, static mixers, batch stirred tank reactors (STRs), and packed bed reactors (PBRs) have been used for enzymatic biodiesel production [51, 52]. One of the leading differences between STRs and PBRs is presence of enzyme at specific location in reactor, e.g., in STRs it is dispersed in the reaction mixture but in PBRS it is fixed in a column. STRs are the simplest type of bioreactors containing just reactor and propeller that stirs reaction mixture mechanically. Batch operated STR need to be empty, clean, and again add reactants for the reaction in order to start new batch process and this is main reason of batch process to produce less yield of the product. Solution of this problem is to use STRs with continuous mode. This does not require to remove enzyme and ingredients to start another cycle. There is a filter attached at the reactor outlet that preserves enzyme in the reactor [52]. PBRs can also be used in both batch and continuous mode but later is more advantageous because of its low labor cost, stable and automated controlled operating conditions, high efficiency, protects enzyme from shearing stress, continuous glycerol removal, and ease of maintenance [53–55]. Currently, most of the bioreactors are used in batch mode with STRs but a lot of research has been done on PBRs usage and its optimization for enzymatic biodiesel production to find this PBR method is better than batch mode STR [56–59].

1.6.3 Effect of Acyl Acceptor on Enzymatic Production of Biodiesel Alcohols are mostly used as an acyl acceptor for biodiesel production. To get maximum economical profit at industrial scale, acyl acceptor (alcohol) should be cheap and readily available and that is why ethanol and especially methanol are widely used for this purpose. Usually, three moles of alcohol

Biocatalytic Processes  11 are required for each mole of oil and in order to keep the reaction moving forward [56]. By increasing alcohol concentration, yield also increases but up to a certain limit [57]. Methanol as an acyl acceptor is frequently used for biodiesel production [58] because it is less expensive, has low chain length, more volatile, and more reactive, and gives high yield than other alcohols [55]. A lot of research has been done utilizing methanol as acyl acceptor to convert various types of oils such as soybean oil, jatropha oil, and canola oil, in the presence of free or immobilized lipase 96.4% yield of FAME was obtained from microalgal oil using methanol as acyl acceptor in the presence of Candida rugosa lipase immobilized on bio-silica polymer [59, 60]. Different alcohols with different substrates may result in different yield so alcohol-substrate combination should be kept in mind for maximum output. Excess of methanol causes inhibitory effect in the reaction because it changes the stability and configuration of biocatalyst/lipase that can leads to partial or complete inactivation of lipase [60–62]. Moreover, it also causes hindrance in separation of glycerol [61, 62]. Methanol inhibition was observed with Novozym® 435 lipase in transesterification of waste oils [63], microalgae oils, and various vegetable oils [64–67]. Inhibitory effect was also observed with some other lipases such as lipases obtained from Rhizopus oryzae and Burkholderia glumae [65]. Addition of alcohol in each step should be done after considering type of substrate and enzyme to determine alcohol substrate molar ratio [66]. This method of sequential addition of alcohol in reaction system was first performed by [67]. 98% biodiesel yield was obtained utilizing T. lanuginosus lipase to convert soybean oil using stepwise addition of methanol [68]. Inhibition of lipases such as C. rugosa lipase, P. cepacia lipase, R. oryzae lipase, and P. fluorescens lipase was prevented using stepwise addition of methanol and 90% yield was also obtained by converting waste cooking oil into biodiesel [69]. Methanolysis of olive oil increases by 34% using stepwise addition of methanol compared to batch methanolysis [70]. Transesterification of waste cooking oil using Novozym 435 was also reported to yield 93% and 96% conversion for continuous and batch process and lipase did not lose its activity even after 20 cycles [50]. Three-step addition of methanol resulted in 97% conversion of plant oil with 0.25- to 0.4-h intervals. But this method of stepwise addition requires low level maintenance of methanol concentration so it cannot be effectively used for industrial scale. Alcohols as an acyl acceptor other than methanol include high chain primary alcohols, secondary, branched, and linear chain alcohols such as ethanol, isopropanol, t-butanol, and octanol [71]. Choice and selection of appropriate alcohol is important as it can influence some biodiesel properties like lubricity and cold flow properties [75, 76]. Moreover, high chain alcohols cause less lipase inhibition

12  Biodiesel Technology and Applications and produce high yield than methanol because lipase show more affinity toward higher chain alcohols than lower chain [12]. The most widely used alcohol as an acyl acceptor after methanol is ethanol as it is less inhibitory, less toxic, and derived from renewable resources [73] unlike methanol which is derived from coal and natural gas. There is minor difference between characteristics of fuels obtained after methanol and ethanol, i.e., FAME and FAEE, respectively. As FAEE has large viscosity and lower pour and cloud points [74, 75]. Hernandez-Martin and Otero [76] showed that, Novozym 435 catalyzed transesterification of sunflower oil, that was performed using methanol and ethanol separately to check which acyl acceptor would perform better. Methanol-mediated transesterification showed more lipase inhibition than ethanol containing reaction. Moreover, ethanol transesterification reaction was faster than methanol reaction. Acyl acceptors other than alcohols can also be used as an alternative such as methyl acetate, ethyl acetate, and dimethyl carbonate (DMC). Methyl acetate was utilized as an acyl acceptor for transesterification of soybean oil catalyzed by Novozym 435. In addition, 92% methyl ester yield was obtained [77]. Similarly, >90% ethyl ester yield was obtained when utilizing ethyl acetate as an acyl acceptor for transesterification catalyzed by Novozym 435 [78]. Use of DMC resulted in over 90% yield even after 10 times reuse of Novozym 435 lipase to convert Chorella sp. KR-1–derived triglyceride [79]. But use of methyl acetate and ethyl acetate is cost expensive and also make the product difficult to separate. Another strategy can be used to reduce methanol inhibition problem, i.e., use of solvents in the reaction mixture [80]. Use of solvents is beneficial for various reasons such as it increases solubility of alcohol and glycerol that results in prevention of lipase denaturation [81]. It increases the rate of reaction because it improves mass transfer rate. Use of solvents do not allow to form new separate phase that hinders enzyme activity because it dissolves most part of alcohol that makes a separate phase if remained undissolved. Moreover, it reduces viscosity and stabilizes lipase [45, 55]. Enzyme stabilization is associated with the presence of water molecules and their activity surrounding the lipase structure. So, use of polar, less hydrophobic solvents is not a good idea because that can lead to distortion of enzyme confirmation [82]. A higher yield of FAME was obtained from microalgae lipids catalyzed by intracellular lipase when non-polar n-hexane solvent was used as compared to polar tert-butanol solvent [83]. Organic solvents such as hexane, petroleum ether, tert-butanol, n-heptane, and ionic liquids are widely used for lipase catalyzed transesterification purpose [88]. Sometimes, it also happens that use of solvents becomes necessary in

Biocatalytic Processes  13 transesterification reaction if short chain alcohols are being used as an acyl acceptor in order to completely dissolve alcohol and produce maximum output but for the same reaction conditions solvent-free reaction system can be used if higher chain alcohols are used as an acyl acceptor. Iso et al. [85], immobilized P. fluorescence lipase catalyzed transesterification was performed using methanol and ethanol as an acyl acceptor. They also provided 1,4-dioxane solvent to the reaction to carry out effective transesterification reaction. But when they used propanol and butanol as an acyl acceptor, they did not provide any solvent to the reaction because addition of solvents was not necessary required for transesterification. Without solvent reaction worked and appropriate result was obtained. Similar type of findings was also observed in another experiment that in which hexane as solvent was used for methanolysis of various oils or substrates like rapeseed oil, soybean oil, recycled restaurant grease, and tallow. That reaction was catalyzed by C. antartica lipase (SP 435) and M. miehei lipase (lipozyme IM 60) [53]. Solvents stabilized the lipase activity shown by Li et al. [86], where lipase AK did not loss its activity. 1,4-dioxane was used as solvent and gave higher yields. Presence of t-butanol as solvent also resulted in the improvement of methyl ester yield [84]. Effects of various solvents like benzene, tetrahydrofuran, chloroform, and 1-4 dioxane were investigated using different enzymes such as P. cepacia (Lipase PS), C. rugosa (Lipase AY), M. javanicus (Lipase M), P. fluorescens (Lipase AK), and R. niveus (Newlase F) by [85]. Use of solvents definitely increases the reaction rate and solubility of alcohol which is beneficial but it is not economical and environment friendly because to separate organic solvent from reaction mixture a solvent recovery unit is also required that increases the cost of recovery. Its flammability and toxicity is another concerning factor [87]. Choice of lipase according to alcohol is also important as some lipases show more resistance toward different alcohols. Yang et al. [88] found that Photobaterium lipolyticum lipase was more tolerant to methanol inhibition than C. antartica lipase B (Novozym 435) when transesterification was performed using one step methanol addition. Similarly, Pseudomonas lipases were found to be more alcohol tolerant compared to lipases from R. miehei and T. lanuginosus. That is why pseudomonas lipases have higher methanol-to-oil molar ratio. Out of nine lipases, only Pseudomonas cepacia lipase showed high ester yield from soybean oil with 8.2:1 methanol-to-oil molar ratio [93, 94]. A recent and novel approach of countering methanol inhibition is addition of silica gel in the reaction system. Silica gel absorbs methanol and keeps its concentration level below to prevent lipase inhibition. But presence of silica gel makes separation of products difficult.

14  Biodiesel Technology and Applications

1.6.4 Effect of Temperature on Enzymatic Biodiesel Production Use of enzyme in any chemical reaction makes the reaction less energy intensive, but, like every other chemical reaction, increase in temperature enhances reaction speed and rate. Similarly, in case of enzymatic biodiesel production, increase in temperature increases enzyme activity, reaction speed, its rate, and production yield [45]. When Lipozyme TL IM lipase was used to transesterify crude palm oil using methanol then the resulting FAME yield was 96.15% and 85.86% at 40°C and 30°C, respectively [95, 96]. But this effect is limited to certain extent because beyond enzyme optimum temperature, enzyme structure becomes unstable and that leads to enzyme denaturation and reaction becomes slower and yield also decreases. Novozym 435 catalyzed biodiesel production from microalgal lipids, there was 19% decrease in product yield when temperature went from 45°C to 55°C, i.e., higher than optimum temperature [97, 98]. Enzyme temperature should remain below the boiling point of alcohols being used in the reaction system to avoid evaporation of alcohol. In case of methanol and ethanol-mediated transesterification, reaction temperature is 65°C and 78°C, respectively [8]. Free bacterial lipases are considered thermally stable but if they get immobilized thermal stability increases [45]. Optimum enzyme temperature is influenced by lipase thermal stability, type of solvent, ­alcohol-to-oil molar ratio, and lipase immobilization. Every enzyme has different optimum temperature depending on the source and type of enzyme. Normally, lipases have optimum temperature range that is 20°C–70°C. Optimum temperature for C.antartica lipase is 40°C [99, 100].

1.6.5 Effect of Glycerol on Enzymatic Biodiesel Production Glycerol is another product obtained along with TAG in transesterification reaction for biodiesel production when alcohols are used as an acyl acceptor. Like methanol inhibition effect, glycerol also hinders enzymatic transesterification. Production of glycerol cause reversal of reaction equilibrium and thus opposes biodiesel production. Glycerol insolubility in the reaction system makes it to accumulate in the system and increases the viscosity of the reaction mixture. Not only it just increases viscosity but because of its hydrophilic nature, it surrounds the lipase and hence prevents substrate to interact with enzyme and binding at enzyme catalytic site. This effect is more prominent when enzyme is in immobilized state. These things all together impacts negatively on the transesterification reaction [93]. According to a research study, rapeseed oil was transesterified using ethanol as an acyl acceptor with different immobilized enzymes such as Novozym 435, Lipozyme TL HC

Biocatalytic Processes  15 (immobilized on polymeric resin) and Lipozyme TL IM (immobilized on silica). Among all reactions, glycerol became more accumulated and hindered reaction when silica was used for immobilization purpose because it had large number of micropores that helped in accumulation [94]. A lot of methods have been devised to overcome and tolerate glycerol inhibition problem such as continuous removal of glycerol, use of solvents, and use of acyl acceptors other than alcohols. Biodiesel production in PBR is effective for continuous production and also to tolerate glycerol inhibition because it allows continuous removal of glycerol from it [95]. BélafiBakó [96] showed that 97% conversion yield was obtained by methanolysis due to continuous removal of glycerol. Use of solvents is another strategy to resolve glycerol inhibition problem. Solvents, for example, tert-butanol and ionic liquids dissolve glycerol and thus reduce the glycerol inhibition problem. Moreover, lipases also perform better in the presence of solvents [97]. Azócar et al. [4] inferred that inhibition effect was eliminated when tert-butanol was used as solvent to convert soybean oil into biodiesel production in a continuous way because it is an excellent solvent for methanol and glycerol to dissolve in it and, thus, reduces inhibitory effects of both methanol and glycerol. These methods have shown promising work but these are not as good for industrial scale production. There is another novel method in which instead of alcohols other compounds like methyl acetate, ethyl acetate, and DMC are in use. Use of methyl acetate or ethyl acetate does not produce glycerol as a product along with the main product instead it leads to produce triacetylglycerol that does not inhibit any enzymatic or reaction activity and further downstream processes are not halted [98]. According to Zhang et al. [99], transesterification of palm oil was done using Novozyme 435 as catalyst and DMC as acyl acceptor with reaction conditions were 10:1 DMC to oil ratio, 55°C reaction temperature and 20% lipase in a solvent-free system. In addition, 90.5% conversion yield, i.e., FAME was obtained, and after eight reaction cycles, no reduction in enzyme activity and loss of yield was observed. It was just because glycerol was not produced instead glycerol dicarbonate was formed because of DMC as acyl acceptor for the reaction. After discussing all negativity about glycerol, it seems glycerol does not have any positive effect but it’s not true. Glycerol if purified absolutely from the transesterification, as mostly huge biodiesel producing companies do, has vast number of uses in diverse industrial fields. Moreover, 99.7% purified glycerol can be used as a raw material for various types of fields such as paints, toiletries, animal feed, emulsifiers, pharmaceuticals, textiles, drugs, tobacco, cosmetics, toothpaste, leather, plasticizers, paper, food, and for different chemicals production [100, 101].

16  Biodiesel Technology and Applications

1.6.6 Effect of Solvent on Biodiesel Production One of the major problems in enzymatic biodiesel production is enzyme inhibition by short chain alcohols such as methanol and ethanol that are used in the reaction. These alcohols’ insolubility in the reaction system denatures the enzyme and hence reduces yield of biodiesel. So, solvent application plays its role in this regard. Organic solvents are used to solubilize these excessive alcohols so that enzyme denaturation can be prevented. Hence, it stabilizes the enzyme. Solubility of oils and alcohols become increased due to presence of organic solvents, this provides the required environment for substrate to interact with enzyme at its active site. Organic solvents also reduce viscosity of the reaction mixture and enhances mass transfer toward the enzyme that leads to improved reaction rate [101]. Organic solvents also eliminate the need of stepwise addition of alcohol. All these things in combination increase production of biodiesel. Organic solvents that are commonly used include tert-butanol, petroleum ether, hexane, and n-heptane [102]. Some other organic solvents that are used are 2-butanol, cyclohexane, isooctane, acetone, 1,4-dioxane, and chloroform. While considering nature of organic solvents, hydrophobic organic solvents are majorly used. Hydrophobicity of the organic solvents helps in accumulating water molecules around enzyme which is important for enzyme structural stability [103]. Polar or hydrophilic solvents work opposite to hydrophobic organic solvents by playing role in distortion of enzymatic structure. But solvent with little polarity can be beneficial to dissolve oil and alcohol. For example, hydrophilic 1,4-dioxane and tert-butanol have produced some good results by producing high enzymatic transesterification yield [104]. Tert-butanol, having moderate polarity, eliminates glycerol and methanol inhibition problem for enzyme because it can dissolve both in itself. This makes the enzyme more stable and active and then ultimately produce better reaction yield [105]. Tertbutanol is the most common solvent that proved its effectiveness in various cases. According to Royon et al. [84], cottonseed oil was transesterified in the presence of Candida antartica lipase. Methanol was found to be the cause of enzyme inhibition in the reaction but when tert-butanol was used as solvent, reaction yield goes up to 97% with minimal enzyme inhibition. Similarly, in another research experiment, tert-butanol was tested for its effectiveness when rapeseed oil was used as substrate for biodiesel production. In solvent-free system, methyl ester yield was 10% but after utilizing tert-butanol yield was 75%. But under optimum conditions having Lipozyme TL IM and Novozyme 435 both in the reaction system, biodiesel yield reached 95% and the reaction was so stable that enzymes did not lose their activity even after 200 cycles. Reaction was favored and well supported by tert-butanol [86].

Biocatalytic Processes  17 Use of solvents provide many benefits but they also come with some disadvantages such as organic solvents do not completely dissolve glycerol, by-product of the reaction, that causes the enzyme to lose its activity and become unstable. Use of solvents also make the process very costly because there is a need of extra purification step to separate out solvent and product from the reaction mixture. Organic solvents are mostly toxic and highly flammable so there are also environmental and health concerns while using them [11]. In order to tackle problems of conventional organic solvents, researchers have suggested some alternatives. Diesel oil was found to be an interesting alternative but the most recent, beneficial, and popular alternatives are super critical carbon dioxide (SC-CO2) and ionic liquids (ILs). Researchers have also confirmed the positive effect of using SC-CO2 and ILs in the enzymatic transesterification [106, 107].

1.7 Lipases as Biocatalysts for Biodiesel Production Transesterification of oils for biodiesel production is done using either chemical or enzymatic catalyst [108]. An enzymatic catalyst is used at first place due to their normal reaction conditions, reusability, easy products separation, and production of high-quality product. There is less energy consumption in enzyme catalysis as it occurs at a low temperature as compared to chemical catalysis requiring high energy consumption [109, 110]. Further, enzymatic catalysis is environment-friendly as there is no wastewater production and produces pure biodiesel as compared to chemical catalysis [107]. Among enzymatic catalysts, lipase with excellent biochemical and physiological properties is most commonly used to catalyze the transesterification process. Lipases play their role in several industrial processes like alcoholysis, acidolysis, amynolysis, and hydrolysis reactions but their leading role in biodiesel production is considered very important [108–111]. The use of lipase in biodiesel production is proved to be beneficial due to its characteristics like high efficiency, convert FFAs completely into methyl/ethyl esters, reaction specificity, require low temperature, minimum energy consumption, and fewer side products [109]. Lipases belong to class “hydrolases” as they carry out hydrolyses of triglycerides producing glycerol and fatty acids from it in an oil-water interface [110]. A general reaction for biodiesel production using lipase is as follows: Triglycerides + 3 Alcohol



lipase

3 Fatty acid methyl ester + Glycerol (biodiesel) (by-product)

18  Biodiesel Technology and Applications Lipases work on specific substrates and carry out catalysis of heterogeneous reactions in water-soluble as well as insoluble systems. Further, lipases have the properties like chemo-specificity, region-specificity, and stereo-specificity [111]. When classification is made based on region-­ specificity, there come three classes of lipases: 1) non-specific lipases, 2) 1,3specific lipases, and 3) fatty acid-specific lipases. Non-specific lipases have ability to attach with all the possible positions of triglycerides to give FFAs and glycerol. The intermediates of the reaction, diglycerides, and monoglycerides do not accumulate in the reaction as they are instantly hydrolysed into fatty acids and glycerol [112]. 1,3-specific lipases are specific for the 1 and 3 positions of triglycerides and remove fatty acids from these positions. 1,3-specific lipases carry out the conversion of triglyceride to diglycerides much faster than diglyceride to monoglyceride [113]. Fatty acid-specific lipases carry out hydrolysis of a specific type of esters which have double bonded long chains of fatty acids in cis position between C-9 and C-1. Hydrolysis of esters with unsaturated fatty acids occur slowly and such class of lipases is not much common [114]. All the hydrolytic enzymes including lipases have common folding pattern involve in a hydrolytic activity called α/β hydrolase fold which is made up of a β sheet of eight strands (one of which is antiparallel while remaining seven strands are parallel) connected by α helices. Histidine residue, catalytic acid residue and Nucleophilic residue are present in α/β hydrolase fold. Pentapeptide sequence (Gly-X-Ser-X-Gly) which is a highly conserved in most of the lipases involved in the construction of ‘nucleophilic elbow’ which is a typical β-turn-α motif having active nucleophilic serine residue between a β strand and an α-helix. Catalytic triad made up of amino acids like histidine, serine, and aspartic acid or glutamic acid build the active site of lipases. The same catalytic triad is seen in serine proteases predicting common catalytic mechanism in them. Amphiphilic α helix peptide sequence forms a lid or flap which covers the active site of lipase and has a structural variability depending upon the lipase source organism. Changes in the structure of the lid are responsible for the activation/inactivation of lipases [114]. Changes in the conformation of lipase structure as well as the quality and quantity of interface being used in the reaction are responsible for the activation of lipase. When the lipase enzyme meets the oil/water interface there occur some changes in lipase structure that results in its activation. For the activation of lipase first, the lid opens to uncover the active site of lipase upon its contact with the ordered interface [115]. Due to this restructuring of lipase, electrophilic region is created around serine residue present in active site, lid hydrophilic side which was exposed in native form now partly buried inside the polar cavity and hydrophobic side

Biocatalytic Processes  19 of lid completely exposed, thus creating a non-polar surface around the active site for efficient attachment of lipid interface with it [115].

1.7.1 Mechanisms of Lipase Action Lipases interact with ester bonds of their substrate like acylglycerols to catalyze the reactions of hydrolysis, synthesis, and transesterification. Triglycerides, which are insoluble and long chained fatty acids, are precisely catalyzed by lipases [113]. Lipase carries out triglyceride oil transesterification with methanol in three reversible steps with the first step for conversion of triglycerides to diglycerides followed by the second step of diglycerides to monoglycerides conversion, and finally, monoglycerides convert into glycerol molecules. Here, each conversion step produces one FAME molecule; hence, a total of three FAME molecule are produced from one triglyceride [116]. Two models are mainly under discussion to describe the kinetics mechanism for esterification reactions, Michaelis-Menten kinetics and Ping Pong Bi Bi model. Lipase catalyzed esterification mainly elaborated by Ping Pong Bi Bi mechanism which is a bi-substrate reaction that releases two products. It involves following steps: 1) acyl-donor donate their acyl group to the enzyme resulting in the formation of acyl-enzyme complex, 2) release of the water molecule as a product, 3) binding of acyl acceptor with the enzyme complex, and 4) release of ester [117, 118]. Many researchers made some modifications in this model depending upon inhibiting factors [118]. The catalytic activity begins with the transient tetrahedral intermediate formation with a negatively charged carbonyl oxygen atom. The reaction between the hydroxyl group oxygen present in nucleophilic serine residue of lipase enzyme and activated carbonyl carbon of the substrate involved building this transient tetrahedral intermediate. The intermediate thus formed is stabilized by its interaction with two peptide NH groups. After that nucleophilic hydroxyl group of water react with the carbonyl carbon of acyl-enzyme complex resulting in the formation of acyl product and enzyme is released for further catalysis [119].

1.7.2 Efficient Lipase Sources for Biodiesel Producing Biocatalyst Lipases can be obtained from plants, animals, and microorganisms and based on that lipases can be classified on it as plant, animal, and microbial lipases depending on their origin respectively. Lipases from different sources with different structure has different properties and catalytic activities. We can use this to counter lipase problems in biodiesel production

20  Biodiesel Technology and Applications like lipase cost and methanol inhibition. We need to optimize reaction conditions according to chosen substrate and lipase from specific source [107]. Microbial lipases are widely used at industrial and commercial level as biocatalysts for biodiesel production because microbial lipases are more stable and can be produced in bulk amount from microorganism [23]. Microbial lipases can be manipulated genetically with ease, seasonal changes have nothing to do with lipase production, and rapid growth of microbes makes them the ideal candidates as lipase source [120, 121]. Use of microbial lipase is increasing day after day and currently 5% of the world enzyme market is being shared with microbial lipases [121]. Microbial lipase weighs around 30–50 kDa and their optimum pH to work at is 7.5. Based on temperature tolerance, microbial lipases can be categorized as mesophilic and thermophilic lipases. Mesophilic lipases normally work at 35°C–50°C and they become denature above 70°C while thermophilic or thermostable lipases normally work at 60°C–80°C, but some also work at 100°C under specific conditions [122, 123]. According to Hotta et al. [123], lipases from Pyrobaculum calidifonti (hyperthermophilic archae) showed its activity at 90°C. Similarly, thermostable lipases from Caldanaerobacter subterraneus and Thermoanaerobacter thermohydrosulfuricus (highly thermophilic bacteria) performed well in the range of 40°C–90°C. They not only performed well at high temperatures but also were resistant toward organics solvents [124]. Lipase producing microorganisms can be isolated from soil, waste water, marine water, and industrial wastes. Isolates of Mucor, Sclerotina, Candida, and Aspergillus strains have been reported, which were isolated from soil. Similarly, various strains of microbes such as P. alcaligenes, Bacillus acidophilus, Enterobacter intermedium, P. fluorescens, and Geotrichum asteroids are also reported as lipase producing strains when isolated from vegetable oil processing plants [141]. Screening of microbes is done by checking their lipolytic. Generally, lipases are screened using batch cultures having agar as substrate but this is time consuming. So, the two mostly used methods for lipase production are solid state fermentation and using submerged culture [142]. Purified form of lipases is used in biochemical reaction to get maximum benefit from it, so purification is required. Purification of lipase requires several techniques including ammonium sulfate precipitation or ultrafiltration and after that more sensitive and advanced techniques are utilized like gel filtration, ion exchange chromatography, and affinity chromatography [143]. Moreover, some other novel techniques can also be applied to purify lipases such as immunopurification, column chromatography, hydrophobic interaction chromatography, and membrane process. Generally, the strategy used for purification lipases starts with the removal of lipase producing cells from

Biocatalytic Processes  21 their growth culture to get extracellular lipases after fermentation. Then, the extract without cells is concentrated by organic solvents, ultrafiltration, and precipitation using ammonium sulfate. Ammonium sulfate precipitation is used in the first stages of purification and it crudely separate out things from mixture. After that advanced techniques of chromatography are used to finely purify lipases [144]. According to Javed et al. [112], diverse data from various research work suggested that purification had been done from 2.4 to 500 folds with an increase in yield from 10.3% to 36%. Effective production and purification strategies of lipases are being designed to get maximum yield at a very small expense. Among microbial lipases, the most commonly used lipase sources are bacteria, fungi, yeast, and algae; see Table 1.1 for some bacterial lipases and Table 1.2. for fungal lipases that are used for biodiesel production [46]. Some of the commercially available enzymes for biodiesel production are enlisted in Table 1.3.

1.8 Comparative Analysis of Intracellular and Extracellular Lipases for Biodiesel Production Transesterification reaction for biodiesel production is done with both extracellular and intracellular lipases. Preference for their use is dependent upon either we want simple upstream processes as in case of intracellular lipase or high enzymatic conversion as in case of extracellular lipase. But either we use intracellular lipase or extracellular lipase there is no need for some downstream processes including separation and recycling. Further, both immobilized lipase (extracellular) and immobilized whole-cell lipase (intracellular) are proved to have highly efficient when compared with free lipase used for transesterification [165]. Some experimental studies for both intracellular and extracellular lipases are given in Table 1.5. Intracellular lipases are the enzymes present inside the cells or linked to the walls of cells producing it known as whole-cell biocatalysts. They are not purified or separated from their cells and used as a whole-cell for transesterification (whole-cell biocatalyst) or immobilized (whole-cell immobilization) [55]. Rhizopus and Aspergillus which are filamentous fungi are most widely used as whole-cell biocatalyst for transesterification process [166]. As the main issue related to biodiesel production at large scale is cost and the use of intracellular lipase for transesterification resolves this problem like the use of intracellular lipase is considered cost-effective because of the elimination of costly processes of lipase isolation and purification before immobilization which are required in case of extracellular lipase [167]. Intracellular lipase producing cells or whole-cell

22  Biodiesel Technology and Applications Table 1.1  Some of the commonly used bacterial lipases for biodiesel production. Enzyme

Immobilized on

Substrate

Acyl acceptor

Yield

Reference

Burkholderia cepacia Lipase

Hydrophobic silica monolith

Jatropha oil

Methanol

95%

[125]

Hybrid matrix of alginate and κ-carrageenan

Jatropha curcas L. oil

Ethanol

100%

[126]

κ-carrageenan

Palm oil

Methanol

100%

[127]

Modified attapulgite

Jatropha oil

Methanol

94%

[128]

SiO2-PVA

Babassu oil

Ethanol

100 %

[129, 130]

SiO2-PVA

Babassu oil

Ethanol

100%

[131]

Nb2O5

Babassu oil

Ethanol

74.1%

[132]

Epoxy-acrylic resin

Waste vegetable oil

Ethanol

46–47%

[133]

Phyllosilicate solgel matrix

restaurant grease

Methanol and Ethanol

98%

[134]

Fe3O4 nanoparticle biocomposite

Soybean oil

Methanol

>88%

[135]

Accurel

Madhuca indica

Ethanol

96%

[136]

Protein-coated microcrystals

Soybean oil

Ethanol

98.93%

[137]

Celite

Jatropha oil

Ethanol

98%

[89]

Octyl-silica resin

Babassu oil

Ethanol

97.5%

[85]

Hydrophobic sol-gel

Soybean oil

Methanol

65%

[138]

Porous kaolinite particles

Triolein

Methanol and Ethanol

90%

[139]

Asymmetric membrane

Triolein

Methanol

80%

[140]

Pseudomonas cepacia Lipase

Pseudomonas fluorescence

Biocatalytic Processes  23 Table 1.2  Some of the commonly used fungal lipases for biodiesel production. Acyl acceptor

Yield

Reference

Waste cooking oil

Methanol

91.08%

[157]

Polyurethane foam

Soybean oil

Ethanol

81%

[158]

Acrylic resin

Sunflower oil

Ethyl acetate

92.7%

[78]

Soybean oil

Methanol

83.31%

[95]

Microporous bio silica-polymer

Scenedesmus quadricauda microalgal oil

Methanol

96.4%

[59]

Poly(styrenemethacrylic acid) microsphere

Soybean oil

Methanol

86%

[159]

within an activated carbon as support

Palm oil

Methanol

70%

[160]

Olive pomace

Pomace oil

Methanol

93%

[161]

Phyllosilicate sol-gel matrix

Grease

Ethanol

80-90%

[162]

Mesoporous polyhydroxybutyrate particles (PHB)

Oleic acid

Methanol and Ethanol

90%

[163]

Toyopearl AF-amino-650M resin

Babassu oil

Ethanol

86.6%

[164]

Enzyme

Immobilized on

Substrate

Candida antartica Lipase

Activated textile cloth

Candida rugosa Lipase

Thermomyces lanuginosus Lipase

biocatalysts are directly employed for immobilization without separation and purification steps for lipase enzymes [55]. Porous biomass support particles (BSPs) are mostly used for whole-cell immobilization. BSPs was developed by Atkinson et al. [168] and used by many scientists and each scientist provide an efficient way of immobilization on it giving out a high yield of biodiesel. A study to check the lipolytic activities of Bacillus species using intracellular as well as extracellular lipase showed higher intracellular lipase activity than extracellular lipase activity [169]. Reported wholecell biocatalysts are Aspergillus oryzae, Burkholderia cepacia, filamentous fungus Rhizopus chinensis, R. oryzae, and Enterococcus faecium [170–174]. Aspergillus oryzae used as whole-cell biocatalyst exhibited 98.1% relative

24  Biodiesel Technology and Applications Table 1.3  Some examples commercial lipases commonly used for biodiesel production. Reaction yield

Reference

Dimethyl carbonate and methanol mixture

90%

[145]

Sunflower oil

Methanol, Absolute ethanol, 1-propanol

>90%

[146]

Oleic acid

Ethanol, n-propanol, and n-butanol

>90%

[147]

Crude soybean oil

Methanol

94%

[148]

Soybean oil

Ethyl acetate

63.3 %

[149]

Soybean oil

Ethanol

Soybean oil

Methanol

>90%

[151]

Crude palm oil

Methanol

96.15%

[90]

Waste cooking oil

Methanol

92.8%

[152]

Palm oil

Oleyl alcohol

79.54%

[153]

Corn oil

Methanol

92%

[154]

Crude rapeseed oil

Monoacylglycerol

90%

[155]

Sunflower oil

Methanol

>80%

[82]

Castor oil

Ethanol

98%

[3]

Soybean oil deodorizer distillate

Ethanol

>88%

[156]

Enzyme

Substrate

Acyl acceptor

Novozyme 435

Chlorella sp. KR-1

Lipozyme TL IM

Lipozyme RM IM

[150]

Biocatalytic Processes  25 stability after the fourth batch and produced more than 97% FAME in 32 hours. Extracellular lipases are the purified form mainly fungal and bacterial cells for their use in transesterification process. Extracellular lipases are separated from broth containing lipase producing cells and after purification used as a catalyst in biodiesel production processes [55]. The way to purify extracellular lipases depends upon its structure and source organism [80]. Mostly extracellular lipases are used in the immobilized form for transesterification than as free lipases because of the low conversion rate and costly process [11]. Literature is full of different methods as well as materials used for immobilization of extracellular lipases. Main methods for immobilization involve cross linking, carrier binding and entrapment while the most commonly used materials for immobilization include silica, magnetic particles, and nanofibers or nanoparticles for carrier binding, alginate beads, gels, and silicon polymers for entrapment and glutaraldehyde for cross-linking [47]. The use of a suitable solvent in case of extracellular lipase is a key factor for high yield in transesterification as the use of unrelated solvent or absence of solvent results in very low yield [102, 165]. The use of extracellular lipase is also adapted because the use of intracellular lipase results in difficulties of extraction and purification of the final product [171]. Extracellular lipases are obtained from Candida guilliermondii, Burkholderia glumae, Pseudomonas aeruginosa, and Yarrowia lipolytica [176–179]. Table 1.4 indicated a comparison between intracellular and extracellular lipases. Table 1.4  Comparison between intracellular and extracellular lipase. Intracellular lipase

Extracellular lipase

Present inside the cell or linked to its walls (cell bound lipase)

Separated from cells producing it

No need of isolation and purification steps

Complex isolation and purification are required before using it for biodiesel production

Low conversion rate

High conversion rate

Not analyzed by direct sampling

Analyzed by direct sampling

Direct immobilization of lipase producing cells (whole-cell immobilization

Purification is required before immobilization

Biodiesel production is cost-effective

Biodiesel production is costly

26  Biodiesel Technology and Applications

1.9 Recombinant Lipases for Cost-Effective Biodiesel Production In order to produce economically feasible and cost-effective enzymatic biodiesel production, various methods have been used. For example, improvement in purification procedures, use of better bioreactors, various immobilization techniques, use of easy to handle solvents and solution, finding novel organisms that can produce more stable and effective lipases. These genetic manipulations enable recombinant organism to overexpress active lipases. A lot of work has been done to produce recombinant lipases from recombinant organisms by deriving desired gene from another specie or organism to meet our demands. According to Huang et al. [173], a good conversion of microalgal oil into FAME and FAEE was obtained (95%

[184]

Fusarium heterosporum

Soybean oil

Methanol

95%

[185]

Rhizomucor miehei (RML)

Soybean oil

Methanol

83.14%

[186]

Microalgal oil

Methanol

>90%

[187]

Thermomyces lanuginosus (Tll)

Waste cooking oil

Methanol

82%

[176]

Rhizopus oryzae IFO4697

Soybean oil

Methanol

71%

[188]

Biocatalytic Processes  29 main process involves in biodiesel production using lipase enzyme, the use of immobilized enzyme (extracellular) and immobilized whole-cell (intracellular enzyme) both reported highly efficient as compared to the use of free enzymes. Bayramoglu et al. [59] set two reaction setups, one with free enzyme and other using immobilized enzyme, and then reaction comparison was measured using gas chromatography-mass spectrophotometry (GC-MS) by noticing FAME components. They Candida rugosa lipase was immobilized on microporous bio-silica polymer. Both enzymes then further used for transesterification of Scenedesmus quadricauda microalgal oil using methanol in the presence of n-hexane solvent. Reaction setup having immobilized lipase produced 96.4% yield as compared to free lipase that produced 85.7% yield. Moreover, immobilized lipase was very much stable as it just lost 17% of its activity after six cycles. Kalantari et al. [193] used Pseudomonas cepacia lipase, immobilized on mixture of mesoporous and nanoporous silica coated composite particles, for transesterification of soybean oil into FAME using methanol. Immobilization effect retains 55% enzymatic stability after five consecutive cycles compared to free lipase reaction. Shah et al. [194] showed that three enzymes were selected initially and then Chromobacterium viscosum was further chosen because of its better results. Celite 545 was used as immobilization material applied to enzyme. Transesterification of Jatropha oil using ethanol was conducted with and without immobilized lipase. After immobilization, reaction yield increased from 62% to 71% and then after further addition of water and immobilization, it reached to 92%. Moreover, in another study [85], triolein transesterification was conducted using methanol, ethanol, and immobilized Pseudomonas fluorescens in the presence of 1,4-dioxane solvent. Reaction yield for both free and immobilized lipase reaction setups was same, i.e., 90%. But the stability provided by immobilization, loss of lipase activity was minimal in immobilized reaction setup than other. Reaction time was 10h for immobilized as compared to 25h reaction time in free lipase system. Further, when we use water free media, free enzyme molecules tend to clump together and decreasing the surface area. Enzyme immobilization inhibit clump formation and increase the surface area of the biocatalyst [195]. Kumari et al. [97] carried out transesterification of jatropha oil with Enterobacter aerogenes lipase immobilized on surface and reported high yield (94%) of biodiesel production and noticed that lipase activity reduced in little extent even after repeated use. Enzyme properties like resistance to proteolytic digestion and denaturants, temperature profile, pH-dependence, thermostability, and kinetics are mainly affected by enzyme immobilization. The chief issues for enzyme immobilization

30  Biodiesel Technology and Applications are preference for the selection of immobilization techniques and support matrices that permit both rapid enzyme activity and enzyme stability under the constraints imposed by the substrate medium [89, 196]. Some examples of different investigations regarding biodiesel production methods using whole-cell immobilized biocatalysts are given in Table 1.7. Table 1.7  Investigation of immobilized whole-cell biocatalysts to produce biodiesel. Lipase cell factory

Immobilized on

Substrate

Acyl acceptor

Rhizopus oryzae cells

Biomass support particles

Soybean oil

Mucor circinelloides

Poly-Urethane Foam

Mucor circinelloides URM 4182

Yield

Reference

Methanol

70%– 83%

[197]

Sardine (Sardinella lemuru) oil

Methanol

NA

[198]

polyurethane support

Babassu oil

Ethanol

98.1%

[199]

Rhizopus oryzae IFO4697

biomass support particles

Oleic acid

Methanol

90%

[200]

Soybean oil

Methanol

72%

Rhizopus oryzae (ROL)

biomass support particles

Jatropha curcas oil

Methanol

90%

[201]

Soybean oil

Methanol

90%

[202]

Rhizopus oryzae 262

Calcium alginate beads

waste cooking oil (sunflower oil)

Methanol

84%

[203]

Rhizopus oryzae ATCC 34612

biomass support particles

Cottonseed oil

Methanol

27.9%

[204]

Pseudomonas fluorescens MTCC 103

Sodium alginate

Jatropha oil

Methanol

72%

[205]

Aspergillus niger

Biomass support particles

Palm oil

Methanol

>90%

[104]

Biocatalytic Processes  31

1.11 Recent Strategies to Improve Biodiesel Production 1.11.1 Combination of Lipases Lipases from different sources or organisms possess different properties. Just like no ideal gas really exists, similarly, there is no ideal lipase that will be considered as absolutely perfect. Just one lipase cannot have all properties that are ideally required for optimal biodiesel production. But researchers are trying to find the best among the lot. Novel sources provide different features of lipase that can be good for biodiesel production. Some lipases are good at tolerating high temperatures, some may work at low temperature, some provide a good temperature range, some may have good catalytic activity, and some may have good hydrolytic activity. Raw material or substrate that is used for biodiesel production is very diverse in nature. Feedstock is mainly comprised of FFA, triglycerides, diglycerides, or monoglycerides, so it is difficult for one lipase to tackle all these things with best possibility. Likewise, every lipase has different alcohol inhibition capacity to tolerate it. So, all in all, these things make it very difficult for one lipase to be perfectly suitable to give best results. So, researchers have come with an idea to use combination of enzymes/lipases. One may be best at providing specific feature and other may be good at giving another specific feature and so on. This way combination of enzymes will provide many features that will be good for biodiesel production. A lot of combination of enzymes have been studied recently for biodiesel production. According to Li et al. [206], combined use of Lipozyme TL IM and Novozym 435 lipase resulted in 96.38% conversion of stilingia oil into FAME. Reaction conditions were methanol-to-oil molar ratio (6.1:4), temperature 20°C along with the use of co-solvent consisting of acetonitrile and t-butanol. At these conditions even after 30 cycles, there was no loss in lipase activity. Similarly, many investigations have been done and some of them are given in Table 1.8. Another way of using compound lipases is cloning and expression of two or more different lipase coding genes from different organism in a host organism. But cloning and effective expression of lipases from host organism is a difficult and cumbersome process, but it has also provided better results. For example, according to Guan et al. [184], Pichia pestoris was selected as a host organism to express two lipase coding genes cloned from two different organisms, one of them was R. miehei (source of 1,3-­specific lipase) and the other was Penicillium cyclopium (source of non-specific  lipase).

32  Biodiesel Technology and Applications Table 1.8  Some examples to produce biodiesel using combination of lipases. Combination of lipases

Immobilized on

Substrate

Acyl acceptor

Yield

Reference

Thermomyces lanuginosus lipase and Rhizomucor miehei lipase.

Lewatit VP OC 1600

Soybean oil

Ethanol

90%

[207]

TLL immobilized on acrylic resin, RML immobilized on anion-exchange resin

Palm oil

Ethanol

80%

[208]

Pseudomonas fluorescens and Candida rugosa

Accurel PE-100 microporous polypropylene powder

Used palm oil

Ethanol

>67%

[209]

Immobilized Pseudomonas fluorescens lipase followed by immobilized Pseudomonas cepacia lipase

macroporous polypropylene

Soybean oil

Methanol

98%

[210]

Combined use of Lipozyme TL IM and Novozym 435

Lipozyme TL IM immobilized on acrylic resin and Novozym 435 immobilized on microporous resin

waste cooking sunflower oil

Methanol

99%

[211]

Novozym 435 (CALB) and Lipozyme RM-IM (RML)

RML immobilized on an anion-exchange resin, and CALB immobilized on a macroporous resin

Soybean oil

Ethanol

80%

[212]

Canola oil

Methanol

>95%

[213]

Combination of Rhizopus arrhizus lipase and Candida antarctica lipase B

microporous polypropylene Accurel MP1000

Triolein

Ethanol

96%

[214]

Candida rugosa lipase followed by Novozym 435

Macroporous acrylic resin

Acid oil, product of vegetable oil

Methanol

91%

[215]

Biocatalytic Processes  33 Extract  containing these two lipases when applied for biodiesel production to transesterify soybean oil at 30°C with 4:1 alcohol-to-oil molar ratio resulted in 99.7% yield after 24 h. In another research, a special recombinant Aspergillus oryzae whole-cell biocatalyst was created that used to co-express two different lipases genes, one of these two lipases was derived from Fusarium heterosporum (FHL) and the other one was mono and diacyl glycerol lipase B. Use of that whole-cell recombinant Aspergillus oryzae biocatalyst resulted in 98% methyl ester yield [179]. According to Yan et al. [216], recombinant Pichia pestoris was developed that displayed two lipases, i.e., T. lanuginosus lipase (TLL) and C. antarctica lipase B (CALB) from different sources on its surface. This whole-cell biocatalyst co-expressing both lipases produced 95.4% biodiesel yield under optimum conditions. Apart from ILs advantages, there is a problem with the biodiesel recovery because during continuous biodiesel removal reaction moves backward and affects the resultant yield. So, to avoid this problem SC-CO2 has been suggested along with ILs. SC-CO2 is very effective in recovering biodiesel because ester molecules have good solubility in it. IL-SC-CO2 combination not only provides easy recovery but also prevent glycerol inhibition effect. SC-CO2 saturated with (substrate) oil is introduced into the reaction system and this creates two phases because of immiscibility in each other. SC-CO2 can diffuse through IL (ionic liquid) phase bringing substrate with it, reaches the enzyme active site and makes the reaction easily possible. After enzyme activity when biodiesel is formed, biodiesel esters become soluble in SC-CO2 phase, So, in this way, biodiesel becomes separate from ILs. Glycerol (by-product of the reaction) does not dissolve into SC-CO2 so it makes another separate layer and then glycerol can be easily taken out in pure form. SC-CO2 containing biodiesel is then processed to recover biodiesel from it by depressurization [217, 218]. In this way, two phase system due to IL-SC-CO2 combination enable to recover biodiesel in good quality. IL-SC-CO2 combination system was first used to extract naphthalene using [bmim] [PF6] as IL [219]. Enzymatic biodiesel was produced with IL-SC-CO2 system by transesterification of triolein using Novozyme 435 as biocatalyst and methanol as acyl acceptor. In IL-SC-CO2 system, 12 different ILs were used and there were two different temperature conditions, i.e., 60°C and 85°C. After 6 h, the resultant biodiesel yield obtained was more than 98% that made this reaction a successful one [220].

1.11.2 Microwave and Ultrasonic-Assisted Reaction Microwave employment in the chemical or biochemical reaction is very clean, economic, fast and energy efficient method. Use of microwave is

34  Biodiesel Technology and Applications very helpful in substrate preparation, extraction, and biodiesel production. Microwave irradiation assists the reaction by providing direct energy to the reactants, and hence, the loss of energy becomes minimal. This feature makes it economic than using other conventional methods of heating to make the reaction possible [221]. Easy energy transfers and use makes the enzyme to perform better and its easy separation leads to cost reduction. So, this environment friendly method provides energy efficient, faster and cost-effective reaction. There have some research investigations been done to analyze how effective it would be to use microwave. Macauba oil transesterification was performed using Novozyme 435 and Lipozyme IM in the presence of ethanol as acyl acceptor. Activities of these enzymes were checked and compared in the presence and absence of microwave. Before microwave assistance enzymatic activity values of Novozyme 435 and Lipozyme IM were 0.09 and 0.08, respectively. But after microwave presence activity value were 0.6 and 0.4, respectively. Results were clear that microwave assistance enhanced enzymatic activity about one order of magnitude [222, 223]. In another experiment, soybean oil and sunflower oil was transesterified using Novozyme 435 and ethanol to oil molar ratio was 3:1. Resultant ester yield was more than 99% within just 3 h when reaction system was accompanied with microwave while conventional heating produced yield about 57% with the same reactions conditions as provided in case of microwave reaction system for biodiesel production. So, microwave-assisted reaction produced better and faster biodiesel yield compared to conventional heating reaction system [224, 225]. According to Zhang et al. [224], microwave and deep eutectic solvents assisted transesterification of yellow horn seed oil using Novozyme 435 resulted in 95% conversion yield. Ultrasonication is another advancement in effective biodiesel production. Just like microwave, ultrasonic assistance increases the reaction rate and ultimately makes the transesterification cost effective [225]. Increase in reaction rate is linked with enhancement in mass transfer and good energy input. Ultrasonication also increases the surface area for the reactant to work efficiently. Moreover, it also boosts the enzymatic catalytic activity and efficiency which provides optimum results even when catalyst is in low quantity [226, 227]. Sometimes, ultrasonication when combined with other method it produces better results and effective rapid transesterification. According to Yu et al. [227], transesterification of soybean oil in the presence of methanol and Novozyme 435 as biocatalyst produced good results when ultrasonic irradiation applied on the reactants. When ultrasonic irradiation with vibration (UIV) applied then conversion of soybean oil into FAME produced 96% yield in just 4 h and Novozyme 435 did not lose any activity after five cycles. But in

Biocatalytic Processes  35 the absence of UIV, comparable results were obtained after 12 h. Results proved that presence of UIV in the enzymatic transesterification reaction gave faster and better yields with no loss in enzyme activity. In another research, Novozyme 435 was utilized to catalyze transesterification of waste cooking oil in an ultrasound-assisted environment. The resultant biodiesel yield was 75.19% in just 2 h. It was also found that ultrasound along with little agitation/vibration made the reaction more efficient [228]. Just like microwave, ultrasonication is also taking attention of researchers to produce better and cost-efficient biodiesel. Researchers have produced some good results in the past couple of years using ultrasonication method. Ultrasound-assisted transesterification of soybean oil using ethanol and Novozyme 435 resulted in ~78 % yield in just 1 h. this method of assistance has the potential to become alternative to the alkali catalyzed or conventional enzymatic biodiesel production [229]. In another experiment, sunflower oil and methanol were used for biodiesel production in the presence of Lipozyme TL-IM under ultrasound-assisted system. Results indicated that ultrasound assistance suppresses the much needed requirement of using methanol, making the reaction fast and clean [230]. Conventional transesterification using bath process technique requires a lot of time because phase separation and recovery of glycerol and biodiesel is a time-consuming process. Use of ultrasound and microwave is very helpful in this regard and it has been proved that ultrasound and microwave assistance make the reaction rapid and cost efficient.

1.12 Lipase Catalyzed Reaction Modeling and Statistical Approaches for Reaction Optimization A lot of methods have been tried for the modelling of lipase catalyzed reactions to fully understand reaction mechanism. Need of better catalyst with great substrate specificity, immobilization, whole-cell catalyst, and manipulation of lipase, all these methods have been applied with various techniques to get better results [231]. But all these methods have been used by hit and trial method to check feasibility. Apart from dealing with lipases, there are many more parameters to set optimally to achieve maximum output. These parameters include temperature, pH, water content, alcohol-to-oil molar ratio, and bioreactor choice. All reaction conditions using various combination of parameters with diverse conditions have been used but it is not actually we need because hit and trial method leads to expensive experimentation. In this era of science and technology,

36  Biodiesel Technology and Applications in silico experimentation is in great demand and it can apply to each and every field. Optimization of biochemical processes is one of key things to produce cost effective results. In order to optimize a reaction, there are various parameters that are dealt with but normally optimization accounts for changing just one parameter at a time by keeping others constant and similarly one by one all parameters are optimized. This technique is called one variable at a time technique. The major limitation of this technique is that it does not show interactive results of parameters. So, it does not produce results based on all parameters effects at the same time on the process. Process modeling, simulation, and statistical approaches are the best way to tackle this problem. Modeling and simulation of the processes are the base of in silico experimentation that provides similar environmental conditions of the processes just like real system without so much investment. This not only provides process mechanism information but also gives support for process development. Reaction optimization is difficult to achieve and it requires a lot of efforts and financial support. While optimization, high efficiency of one of many parameters sometimes reduces the demand of some other parameter and reaction product may not alter so much. For example, according to Tufvesson et al. [232], if enzyme has excellent catalytic activity then this minimizes the need of enzyme specific activity and similarly, if enzyme catalytic activity is fair enough to product healthy amount of product then ultimately need of efficient downstream processes will be reduced. So, all in all optimization of chemical processes is difficult and tedious to achieve. That is why in silico experimentation is helpful in process of optimization and handling. Modeling and simulation of any process gives idea to the researchers what they actually need regarding system conditions, type of catalyst with respect to their mechanism kinetics and energetics from ping pong bi bi mechanism, type of substrate, and various parameters setup. This greatly prevents hit and trial approach and makes the process cost effective. There are two basic approaches in process modeling: (a) empirical approach deal with design of experiments and (b) statistical approach that gives relation between process outcome and parameters [232]. Parameter estimation is a key thing to avoid false outcome in process modeling and more chances of error in estimation leads to wrong direction. Yu et al. [231] observed that, optimal experimental design was developed for the improvement of process estimation in biodiesel production process catalyzed by Novozym. Simulation demonstrated the reduction in producing errors while estimating parameters through optimal experimental design. Response surface methodology (RSM) is a collection of various mathematical and statistical

Biocatalytic Processes  37 techniques that is used when there are multiple variables influencing the reaction response at the same time. RSM is used for improvement, development, and especially optimization of chemical and biochemical reactions. RSM creates a mathematical model that can be used to predict what can be the response of the process under certain variable conditions. That is why it is called RSM. A lot of research has been done using RSM to optimized chemical reactions. For example, protease production in a bioreactor taken from Bacillus mojavensis and statistically optimization of media [233] and lipase catalyzed esterification reactions [234]. RSM is widely used for optimization but it can also be used to determine kinetic constants and enzyme stability. Kinetic constants for protease derived from Bacillus mojavensis was determined using RSM [235]. According to Rana et al., kinetic and stability of b-1,3-glucanase from Trichoderma harzianum and alcohol dehydrogenase was investigated using RSM [236]. RSM for optimization is carried out in 3 stages, (a) independent variable and their level is determined, (b) experimental design is selected then model equation is predicted and verified, and (c) different response plots are obtained and optimum points are determined [237]. The most common and successfully implemented design used in RSM is central composite rotatable design (CCRD) for the optimization of reactions [238, 239]. Like every other thing, RSM surely has advantages as well as disadvantages (Table 1.8). Like other chemical processes, optimization of enzymatic catalyzed biodiesel production process has been widely investigated using RSM statistical approach [241]. According to Sheih et al. [241], conversion of soybean oil into biodiesel was catalyzed using lipase from Rhizomucor miehei (Lipozyme IM-77) in the presence of methanol which was being investigated in this experiment. RSM was implemented with having 5-level-5-factor CCRD. Through this design and RSM, effect of time, methanol-to-oil molar ratio, temperature, water content, etc., were measured and evaluated. Under optimal conditions that were temperature of 36.5°C, reaction time of 6 h, water content of 5.8%, and substrate molar ratio of 3.4:1, resulted in 92.2% conversion yield when analysis was done using ridge max analysis. In another experiment, optimization was done in pretreatment step to lower the concentration of FFA of Mahua oil that would halt the downstream processes and ultimately biodiesel production. CCRD was again used to check the effects of acid and methanol concentration and reaction time in reducing the production of FFA. After pretreatment, Mahua oil was catalyzed through alkaline catalyst, and then, the resultant biodiesel produced was according to American and European standards [242].

38  Biodiesel Technology and Applications

1.13 Conclusion and Summary Currently, the use of fossil fuels is on its verge because of the dependency of our transportation and main industries on it. If its usage goes with even at the same pace, there are great chances of its shortage due to depletion in reservoirs in very near future. So, there is a strict need to divert toward alternate sources like biofuels which not only overcome the shortage of fuel but also environment-friendly. Biodiesel is the most widely used biofuel due to its vast use from direct fuel to a lubricating agent. The production and use of biodiesel are restricted to limited countries but there is a need to broaden its use worldwide. The barriers which constrain its worldwide use are mainly related to biodiesel production cost which can be reduced with optimization of the production process by selection of preferable feedstock, reaction conditions, type of catalyst used, enzymes for catalysis, and many other factors. Researchers are making their full effort to construct a cost-effective biodiesel production process. Oils extracted from various sources are used as a substrate or feedstock for biodiesel production, but microbial oil extracted from microalgae is used at first place due to low cost, easy, and quick production when compared with plant and animal oils. However, biodiesel produced using animal oil act as a good lubricating agent along with good oxidative stability. Biocatalysis involving enzymatic biodiesel production via lipase enzyme is considered a low-price process as compared to other ways. Lipase enzyme is preferably used as biocatalysis because of its easy separation and reusability. There are many factors like acyl receptors, water, and temperature that have a serious impact on enzymatic transesterification and great research have been done for to optimization of these factors to make the process easy and affordable. Lipases from a broad range of sources immobilized by different techniques on a variety of supports have their own resulting impact in biodiesel production process. However, the use of whole-cell immobilization or combination of lipase with optimized reaction conditions like temperature, time of reaction, and pH makes the process industrially favorable. Still, there exists a space for improvement to make the biodiesel production process affordable and easy to conduct.

References 1. M. Naik, L.C. Meher, S.N. Naik, L.M. Das, Production of biodiesel from high free fatty acid Karanja (Pongamia pinnata) oil, Biomass and Bioenergy. 32, 354–357, 2008. https://doi.org/10.1016/j.biombioe.2007.10.006.

Biocatalytic Processes  39 2. W. Parawira, Biodiesel production from Jatropha curcas: A review, Sci. Res. Essays. 5, 1796–1808, 2010. https://doi.org/10.3109/07388551.2010.487185. 3. Oliveira, M. Di Luccio, C. Faccio, C.D. Rosa, J.P. Bender, N. Lipke, S. Menoncin, C. Amroginski, J.V. de Oliveira, Optimization of enzymatic production of biodiesel from castor oil in organic solvent medium., Appl. Biochem. Biotechnol. 113–116, 771–780, 2004. https://doi.org/10.1385/ABAB:115:1-3:0771. 4. L. Azócar, R. Navia, L. Beroiz, D. Jeison, G. Ciudad, Enzymatic biodiesel production kinetics using co-solvent and an anhydrous medium: A strategy to improve lipase performance in a semi-continuous reactor, N. Biotechnol. 31, 422–429, 2014. https://doi.org/10.1016/j.nbt.2014.04.006. 5. L. Azócar, G. Ciudad, H.J. Heipieper, R. Muñoz, R. Navia, Improving fatty acid methyl ester production yield in a lipase-catalyzed process using waste frying oils as feedstock, J. Biosci. Bioeng. 109, 609–614, 2010. https://doi. org/10.1016/j.jbiosc.2009.12.001. 6. K.R. Jegannathan, L. Jun-Yee, E.S. Chan, P. Ravindra, Production of biodiesel from palm oil using liquid core lipase encapsulated in κ-carrageenan, Fuel. 89, 2272–2277, 2010. https://doi.org/10.1016/j.fuel.2010.03.016. 7. X. Meng, G. Chen, Y. Wang, Biodiesel production from waste cooking oil via alkali catalyst and its engine test, Fuel Process. Technol. 89, 851–857, 2008. https://doi.org/10.1016/j.fuproc.2008.02.006. 8. L.P. Christopher, Hemanathan Kumar, V.P. Zambare, Enzymatic biodiesel: Challenges and opportunities, Appl. Energy. 119, 497–520 2014. https://doi. org/10.1016/j.apenergy.2014.01.017. 9. B.R. Moser, Biodiesel production, properties, and feedstocks, Vitr. Cell. Dev. Biol. - Plant. 45, 229–266 2009. 10. Z. Amini, Z. Ilham, H.C. Ong, H. Mazaheri, W.H. Chen, State of the art and prospective of lipase-catalyzed transesterification reaction for biodiesel production, Energy Convers. Manag. 141, 339–353, 2016. https://doi. org/10.1016/j.enconman.2016.09.049. 11. A. Guldhe, B. Singh, T. Mutanda, K. Permaul, F. Bux, Advances in synthesis of biodiesel via enzyme catalysis: Novel and sustainable approaches, Renew. Sustain. Energy Rev. 2015. https://doi.org/10.1016/j.rser.2014.09.035. 12. H. Fukuda, A. Kondo, H. Noda, Biodiesel fuel production by transesterification of oils, J. Biosci. Bioeng. 92, 405–416, 2001. https://doi.org/10.1016/ S1389-1723(01)80288-7. 13. C.C. Akoh, S. Chang, G. Lee, J. Shaw, Enzymatic approach to biodiesel production, J. Agric. Food Chem. 55, 8995–9005, 2007. https://doi.org/10.1021/ jf071724y. 14. A.P.D.S.S.A.M.W.Y.M. Haas, J.A.D.H. Shapouri, Energy Life-Cycle Assessment of Soybean Biodiesel, 2009. 15. A. Demirbas, Progress and recent trends in biodiesel fuels, Energy Convers. Manag. 50, 14–34, 2009. 16. S. Al-Zuhair, Production of biodiesel: possibilities and challenges, Biofuels, Bioprod. Biorefining. 1, 57–66, 2007. https://doi.org/10.1002/bbb.2.

40  Biodiesel Technology and Applications 17. L.J. Konwar, J. Boro, D. Deka, Review on latest developments in biodiesel production using carbon-based catalysts, Renew. Sustain. Energy Rev. 29, 546–564, 2014. https://doi.org/10.1016/j.rser.2013.09.003. 18. A. Demirbas, Biodegradable plastics from renewable resources, Energy Sources, Part A Recover. Util. Environ. Eff. 29, 419–424, 2007. https://doi. org/10.1080/009083190965820. 19. M. Lapuerta, J.M. Herreros, L.L. Lyons, R. García-Contreras, Y. Briceño, Effect of the alcohol type used in the production of waste cooking oil biodiesel on diesel performance and emissions, Fuel. 87, 3161–3169, 2008. https://doi.org/10.1016/j.fuel.2008.05.013. 20. R.O. Dunn, Alternative jet fuels from vegetable oils, Trans. ASAE. 44, 1751– 1757, 2001. https://doi.org/10.13031/2013.6988. 21. N. Hashimoto, Y. Ozawa, N. Mori, I. Yuri, T. Hisamatsu, Fundamental combustion characteristics of palm methyl ester (PME) as alternative fuel for gas turbines, Fuel. 87, 3373–3378, 2008. https://doi.org/10.1016/j. fuel.2008.06.005. 22. Y.C. Lin, C.H. Tsai, C.R. Yang, C.H.J. Wu, T.Y. Wu, G.P. Chang-Chien, Effects on aerosol size distribution of polycyclic aromatic hydrocarbons from the heavy-duty diesel generator fueled with feedstock palm-biodiesel blends, Atmos. Environ. 42, 6679–6688, 2008. https://doi.org/10.1016/j. atmosenv.2008.04.018. 23. M. Aarthy, P. Saravanan, M.K. Gowthaman, C. Rose, N.R. Kamini, Enzymatic transesterification for production of biodiesel using yeast lipases: An overview, Chem. Eng. Res. Des. 92, 1591–1601, 2014. https://doi.org/10.1016/j. cherd.2014.04.008. 24. J.C. Juan, D.A. Kartika, T.Y. Wu, T.Y.Y. Hin, Biodiesel production from jatropha oil by catalytic and non-catalytic approaches: An overview, Bioresour. Technol. 102, 452–460, 2011. https://doi.org/10.1016/j.biortech.2010.09.093. 25. Z. Yaakob, M. Mohammad, M. Alherbawi, Z. Alam, K. Sopian, Overview of the production of biodiesel from waste cooking oil, Renew. Sustain. Energy Rev. 18, 184–193, 2013. https://doi.org/10.1016/j.rser.2012.10.016. 26. P. Nautiyal, K.A. Subramanian, M.G. Dastidar, Production and characterization of biodiesel from algae, Fuel Process. Technol. 120, 79–88, 2014. https:// doi.org/10.1016/j.fuproc.2013.12.003. 27. A. Karmakar, S. Karmakar, S. Mukherjee, Properties of various plants and animals feedstocks for biodiesel production, Bioresour. Technol. 101, 7201– 7210, 2010. https://doi.org/10.1016/j.biortech.2010.04.079. 28. G. Knothe, Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters, Fuel Process. Technol. 86, 1059–1070, 2005. https://doi. org/10.1016/j.fuproc.2004.11.002. 29. D.Y.C. Leung, X. Wu, M.K.H. Leung, A review on biodiesel production using catalyzed transesterification, Appl. Energy. 87, 1083–1095, 2010. https://doi. org/10.1016/j.apenergy.2009.10.006.

Biocatalytic Processes  41 30. M. Canakci, H. Sanli, Biodiesel production from various feedstocks and their effects on the fuel properties, J. Ind. Microbiol. Biotechnol. 35, 431–441, 2008. https://doi.org/10.1007/s10295-008-0337-6. 31. M.M. Gui, K.T. Lee, S. Bhatia, Feasibility of edible oil vs. non-edible oil vs. waste edible oil as biodiesel feedstock, Energy. 33, 1646–1653, 2008. https:// doi.org/10.1016/j.energy.2008.06.002. 32. K. Jawaharraj, R. Karpagam, B. Ashokkumar, S. Kathiresan, P. Varalakshmi, Green renewable energy production from Myxosarcina sp.: Media optimization and assessment of biodiesel fuel properties, RSC Adv. 5, 51149–51157, 2015. https://doi.org/10.1039/C5RA09372D. 33. Q. Li, W. Du, D. Liu, Perspectives of microbial oils for biodiesel production, Appl. Microbiol. Biotechnol. 80, 749–756, 2008. https://doi.org/10.1007/ s00253-008-1625-9. 34. C. Yusuf, Biodiesel from microalgae, Biotechnol. Adv. 25, 294–306, 2007. 35. J. Janaun, N. Ellis, Perspectives on biodiesel as a sustainable fuel, Renew. Sustain. Energy Rev. 14, 1312–1320, 2010. https://doi.org/10.1016/j.rser. 2009.12.011. 36. P. Suarez, S. Meneghetti, Transformation of triglycerides into fulels, polymers and chemicals: some applications of catalysis in oleochemistry, Quim. Nova. 30, 667–676, 2007. https://doi.org/10.1590/S0100-40422007000300028. 37. M. Leca, L. Tcacenco, M. Micutz, T. Staicu, Optimization of biodiesel production by transesterification of vegetable oils using lipases, 2010. 38. G. Kafuku, K.T. Lee, M. Mbarawa, Non-Catalytic and catalytic transesterification: A reaction kinetics comparison study, Int. J. Green Energy. 12, 551– 558, 2015. https://doi.org/10.1080/15435075.2013.834820. 39. A.F. Lee, J.A. Bennett, J.C. Manayil, K. Wilson, Heterogeneous catalysis for sustainable biodiesel production via esterification and transesterification, Chem. Soc. Rev. 43, 7887–7916, 2014. https://doi.org/10.1039/C4CS00189C. 40. M. Mouaimine, J.D. Andriano, P.T. Fidele, V. Pierre, M.S. Mohamed, Plant latex lipase as biocatalysts for biodiesel production, African J. Biotechnol. 15, 1487–1502, 2016. https://doi.org/10.5897/AJB2015.14966. 41. S.A.-Z. Hanifa Taher, The use of alternative solvents in enzymatic biodiesel production: a review, Biofuels, Bioprod. Bioref. 11, 168–194, 2016. https://doi. org/10.1002/bbb.1727. 42. F.G. and Z. Fang, Biodiesel production with solid catalyst, Biodiesel– Feedstocks and Processing Technologies, 2011. 43. G. Jin, T.J. Bierma, C.G. Hamaker, R. Rhykerd, L.A. Loftus, Producing biodiesel using whole-cell biocatalysts in separate hydrolysis and methanolysis reactions., J. Environ. Sci. Health. A. Tox. Hazard. Subst. Environ. Eng. 43, 589–95, 2008. https://doi.org/10.1080/10934520801893576. 44. T. Tan, K. Nie, F. Wang, Production of biodiesel by immobilized Candida sp. lipase at high water content, Appl. Biochem. Biotechnol. 128, 109–116, 2006. https://doi.org/10.1385/ABAB:128:2:109.

42  Biodiesel Technology and Applications 45. L. Fjerbaek, K. V. Christensen, B. Norddahl, A review of the current state of biodiesel production using enzymatic transesterification, Biotechnol. Bioeng. 2009. https://doi.org/10.1002/bit.22256. 46. P.Y. Stergiou, A. Foukis, M. Filippou, M. Koukouritaki, M. Parapouli, L.G. Theodorou, E. Hatziloukas, A. Afendra, A. Pandey, E.M. Papamichael, Advances in lipase-catalyzed esterification reactions, Biotechnol. Adv. 31, 1846–1859, 2013. https://doi.org/10.1016/j.biotechadv.2013.08.006. 47. K.R. Jegannathan, S. Abang, D. Poncelet, E.S. Chan, P. Ravindra, Production of biodiesel using immobilized lipase--a critical review., Crit. Rev. Biotechnol. 28, 253–264, 2008. https://doi.org/10.1080/07388550802428392. 48. J. Lu, Y. Chen, F. Wang, T. Tan, Effect of water on methanolysis of glycerol trioleate catalyzed by immobilized lipase Candida sp. 99-125 in organic solvent system, J. Mol. Catal. B Enzym. 56, 122–125, 2009. https://doi.org/10.1016/j. molcatb.2008.05.004. 49. G.. Chowdary, S.. Prapulla, The influence of water activity on the lipase catalyzed synthesis of butyl butyrate by transesterification, Process Biochem. 38, 393–397, 2002. https://doi.org/10.1016/S0032-9592(02)00096-1. 50. K. Nie, F. Xie, F. Wang, T. Tan, Lipase catalyzed methanolysis to produce biodiesel: Optimization of the biodiesel production, J. Mol. Catal. B Enzym. 43, 142–147, 2006. https://doi.org/10.1016/j.molcatb.2006.07.016. 51. A. Canet, Kí. Bonet-Ragel, M.D. Benaiges, F. Valero, Biodiesel synthesis in a solvent-free system by recombinant Rhizopus oryzae: comparative study between a stirred tank and a packed-bed batch reactor, Biocatal. Biotransformation. 35, 35–40, 2017. https://doi.org/10.1080/10242422.2016. 1278211. 52. S. Nigam, S. Mehrotra, B. Vani, R. Mehrotra, Lipase immobilization techniques for biodiesel production: An Overview, Int. J. Renew. Energy Biofuels. 1–16, 2014. https://doi.org/10.5171/2014.664708. 53. P.M. Nielsen, J. Brask, L. Fjerbaek, Enzymatic biodiesel production: Technical and economical considerations, Eur. J. Lipid Sci. Technol. 110, 692–700, 2008. https://doi.org/10.1002/ejlt.200800064. 54. G.-Q. Chen, Biofunctionalization of polymers and their applications Guo-Qiang, Adv. Biochem. Eng. Biotechnol. 125, 29–45, 2011. https://doi. org/10.1007/10_2010_89. 55. A. Gog, M. Roman, M. Toşa, C. Paizs, F.D. Irimie, Biodiesel production using enzymatic transesterification-Current state and perspectives, Renew. Energy. 2012. https://doi.org/10.1016/j.renene.2011.08.007. 56. A.P. Vyas, J.L. Verma, N. Subrahmanyam, Effects of molar ratio, alkali catalyst concentration and temperature on transesterification of Jatropha oil with methanol under ultrasonic irradiation, Adv. Chem. Eng. Sci. 01, 45–50, 2011. https://doi.org/10.4236/aces.2011.12008. 57. M. Mathiyazhagan, a Ganapathi, Factors affecting biodiesel production, Res. Plant Biol. 1, 1–5, 2011.

Biocatalytic Processes  43 58. T. Zhao, D.S. No, Y. Kim, Y.S. Kim, I.H. Kim, Novel strategy for lipase-catalyzed synthesis of biodiesel using blended alcohol as an acyl acceptor, J. Mol. Catal. B Enzym. 107, 17–22, 2014. https://doi.org/10.1016/j.molcatb.2014.05.002. 59. G. Bayramoglu, A. Akbulut, V.C. Ozalp, M.Y. Arica, Immobilized lipase on micro-porous biosilica for enzymatic transesterification of algal oil, Chem. Eng. Res. Des. 95, 12–21, 2015. https://doi.org/10.1016/j.cherd.2014.12.011. 60. Y. Wang, J. Liu, H. Gerken, C. Zhang, Q. Hu, Y. Li, Highly-efficient enzymatic conversion of crude algal oils into biodiesel, Bioresour. Technol. 172, 143–149, 2014. https://doi.org/10.1016/j.biortech.2014.09.003. 61. E. Bardone, A. Brucato, T. Keshavarz, T.M. Mata, I.R.B.G. Sousa, N.S. Caetano, Transgenic corn oil for biodiesel production via enzymatic catalysis with ethanol, Chem. Eng. Trans. 27, 19–24, 2012. 62. J.M. Encinar, J.F. González, J.J. Rodríguez, A. Tejedor, Biodiesel fuels from vegetable oils: Transesterification of Cynara cardunculus L. Oils with ethanol, Energy and Fuels. 16, 443–450, 2002. https://doi.org/10.1021/ef010174h. 63. J. Yan, Y. Yan, S. Liu, J. Hu, G. Wang, Preparation of cross-linked lipasecoated micro-crystals for biodiesel production from waste cooking oil, Bioresour. Technol. 102, 4755–4758, 2011. https://doi.org/10.1016/j. biortech.2011.01.006. 64. K.P. Zhang, J.Q. Lai, Z.L. Huang, Z. Yang, Penicillium expansum lipase-­ catalyzed production of biodiesel in ionic liquids, Bioresour. Technol. 102 2767–2772, 2011. https://doi.org/10.1016/j.biortech.2010.11.057. 65. C. Santambrogio, F. Sasso, A. Natalello, S. Brocca, R. Grandori, S.M. Doglia, M. Lotti, Effects of methanol on a methanol-tolerant bacterial lipase, Appl. Microbiol. Biotechnol. 97, 8609–8618, 2013. https://doi.org/10.1007/ s00253-013-4712-5. 66. J.B. Rédéo Wilfried Moussavou Mounguenguia, Christel Brunschwiga, Bruno Baréab, Pierre Villeneuveb, Are plant lipases a promising alternative to catalyze transesterification for biodiesel production?, Prog. Energy Combust. Sci. 39, 441–456, 2013. 67. Y. Shimada, Y. Watanabe, T. Samukawa, A. Sugihara, H. Noda, H. Fukuda, Y. Tominaga, Conversion of vegetable oil to biodiesel using immobilized Candida antarctica lipase, J. Am. Oil Chem. Soc. 76, 789–793, 1999. https:// doi.org/10.1007/s11746-999-0067-6. 68. Y. Xu, Wei Du, Jing Zeng and Dehua Liu, Conversion of soybean oil to biodiesel fuel using lipozyme TL IM in a solvent-free medium, Biocatal. Biotransformation. 22, 45–48, 2004. https://doi.org/10.1080/1024242041000 1661222. 69. T.Y. Shimada Y, Watanabe Y, Sugihara A, Enzymatic alcoholysis for biodiesel fuel production and application of the reaction to oil processing, J. Mol. Catal. B Enzym. 17, 133–142, 2002. 70. S.H. Lee, D.R. Park, H. Kim, J. Lee, J.C. Jung, S.Y. Woo, W.S. Song, M.S. Kwon, I.K. Song, Direct preparation of dichloropropanol (DCP) from glycerol using

44  Biodiesel Technology and Applications heteropolyacid (HPA) catalysts: A catalyst screen study, Catal. Commun. 9 1920–1923, 2008. https://doi.org/10.1016/J.CATCOM.2008.03.020. 71. J.M. Marchetti, V.U. Miguel, A.F. Errazu, Techno-economic study of different alternatives for biodiesel production, Fuel Process. Technol. 89, 740–748, 2008. https://doi.org/10.1016/j.fuproc.2008.01.007. 72. P.S. Wang, M.E. Tat, J. Van Gerpen, The production of fatty acid isopropyl esters and their use as a diesel engine fuel, J. Am. Oil Chem. Soc. 82, 845–849, 2005. https://doi.org/10.1007/s11746-005-1153-7. 73. Q. Li, J. Xu, W. Du, Y. Li, D. Liu, Ethanol as the acyl acceptor for biodiesel production, Renew. Sustain. Energy Rev. 25, 742–748, 2013. https://doi. org/10.1016/J.RSER.2013.05.043. 74. K. Bozbas, Biodiesel as an alternative motor fuel: Production and policies in the European Union, Renew. Sustain. Energy Rev. 12, 542–552, 2008. https:// doi.org/10.1016/J.RSER.2005.06.001. 75. P. Verma, V.M. Singh, Assessment of diesel engine performance using cotton seed Biodiesel, Integr. Res. Adv. 1, 1–4, 2014. 76. E. Hernández-Martín, C. Otero, Different enzyme requirements for the synthesis of biodiesel: Novozym® 435 and Lipozyme® TL IM, Bioresour. Technol. 99, 277–286, 2008. https://doi.org/10.1016/j.biortech.2006.12.024. 77. W. Du, Y. Xu, D. Liu, J. Zeng, Comparative study on lipase-catalyzed transformation of soybean oil for biodiesel production with different acyl acceptors, J. Mol. Catal. B Enzym. 30, 125–129, 2004. https://doi.org/10.1016/j. molcatb.2004.04.004. 78. M.K. Modi, J.R.C. Reddy, B.V.S.K. Rao, R.B.N. Prasad, Lipase-mediated conversion of vegetable oils into biodiesel using ethyl acetate as acyl acceptor, Bioresour. Technol. 98, 1260–1264, 2007. https://doi.org/10.1016/j. biortech.2006.05.006. 79. O.K. Lee, Y.H. Kim, J.G. Na, Y.K. Oh, E.Y. Lee, Highly efficient extraction and lipase-catalyzed transesterification of triglycerides from Chlorella sp. KR-1 for production of biodiesel, Bioresour. Technol. 147, 240–245, 2013. https:// doi.org/10.1016/j.biortech.2013.08.037. 80. A.E. Ghaly, D. Dave, M.S. Brooks, S. Budge, Production of biodiesel by enzymatic transesterification: Review, Am. J. Biochem. Biotechnol. 2010. https:// doi.org/10.3844/ajbbsp.2010.54.76. 81. Y. Liu, H. Xin, Y. Yan, Physicochemical properties of stillingia oil: Feasibility for biodiesel production by enzyme transesterification, Ind. Crops Prod. 30, 431–436, 2009. https://doi.org/10.1016/J.INDCROP.2009.08.004. 82. M.M. Soumanou, U.T. Bornscheuer, Improvement in lipase-catalyzed synthesis of fatty acid methyl esters from sunflower oil, Enzyme Microb. Technol. 33, 97–103, 2003. https://doi.org/10.1016/S0141-0229(03)00090-5. 83. M. Xiao, R. Intan, J.P. Obbard, Biodiesel production from microalgae oillipid feedstock via immobilized whole-cell biocatalysis, in: Third Int. Symp. Energy from Biomass Waste Venice, Italy; 8-11 Novemb. 2010, 2010.

Biocatalytic Processes  45 84. D. Royon, M. Daz, G. Ellenrieder, S. Locatelli, Enzymatic production of biodiesel from cotton seed oil using t-butanol as a solvent, Bioresour. Technol. 98, 648–653, 2007. https://doi.org/10.1016/j.biortech.2006.02.021. 85. M. Iso, B. Chen, M. Eguchi, T. Kudo, S. Shrestha, Production of biodiesel fuel from triglycerides and alcohol using immobilized lipase, J. Mol. Catal. - B Enzym. 16, 53–58, 2001. https://doi.org/10.1016/S1381-1177(01)00045-5. 86. L. Li, W. Du, D. Liu, L. Wang, Z. Li, Lipase-catalyzed transesterification of rapeseed oils for biodiesel production with a novel organic solvent as the reaction medium, J. Mol. Catal. B Enzym. 43, 58–62, 2006. https://doi. org/10.1016/j.molcatb.2006.06.012. 87. A. Robles-Medina, P.A. González-Moreno, L. Esteban-Cerdán, E. MolinaGrima, Biocatalysis: Towards ever greener biodiesel production, Biotechnol. Adv. 27, 398–408, 2009. https://doi.org/10.1016/j.biotechadv.2008.10.008. 88. K.S. Yang, J.H. Sohn, H.K. Kim, Catalytic properties of a lipase from Photobacterium lipolyticum for biodiesel production containing a high methanol concentration, J. Biosci. Bioeng. 107, 599–604, 2009. https://doi. org/10.1016/j.jbiosc.2009.01.009. 89. H. Noureddini, X. Gao, R.S. Philkana, Immobilized Pseudomonas cepacia lipase for biodiesel fuel production from soybean oil, Bioresour. Technol. 96, 769–777, 2005. https://doi.org/10.1016/j.biortech.2004.05.029. 90. J.H. Sim, A.H. Kamaruddin, S. Bhatia, Biodiesel (FAME) productivity, catalytic efficiency and thermal stability of lipozyme TL im for crude palm oil transesterification with methanol, JAOCS, J. Am. Oil Chem. Soc. 87, 1027– 1034, 2010. https://doi.org/10.1007/s11746-010-1593-y. 91. H. Taher, S. Al-Zuhair, A.H. Al-Marzouqi, Y. Haik, M. Farid, Enzymatic biodiesel production of microalgae lipids under supercritical carbon dioxide: Process optimization and integration, Biochem. Eng. J. 90, 103–113, 2014. https://doi.org/10.1016/j.bej.2014.05.019. 92. G.T. Jeong, D.H. Park, Lipase-catalyzed transesterification of rapeseed oil for biodiesel production with ter-butanol, Appl. Biochem. Biotechnol. 148, 131–139, 2008. https://doi.org/10.1007/s12010-007-8050-x. 93. M. Szczesna Antczak, A. Kubiak, T. Antczak, S. Bielecki, Enzymatic biodiesel synthesis - Key factors affecting efficiency of the process, Renew. Energy. 34, 1185–1194, 2009. https://doi.org/10.1016/j.renene.2008.11.013. 94. Y. Xu, M. Nordblad, P.M. Nielsen, J. Brask, J.M. Woodley, In situ visualization and effect of glycerol in lipase-catalyzed ethanolysis of rapeseed oil, J. Mol. Catal. B Enzym. 72, 213–219, 2011. https://doi.org/10.1016/J.MOLCATB.2011.06.008. 95. H.C. Chen, H.Y. Ju, T.T. Wu, Y.C. Liu, C.C. Lee, C. Chang, Y.L. Chung, C.J. Shieh, Continuous production of lipase-catalyzed biodiesel in a packed-bed reactor: Optimization and enzyme reuse study, J. Biomed. Biotechnol. 2011, 5–10, 2011. https://doi.org/10.1155/2011/950725. 96. K. Bélafi-Bakó, F. Kovács, L. Gubicza, J. Hancsók, Enzymatic biodiesel production from sunflower oil by Candida antarctica lipase in a solvent-free

46  Biodiesel Technology and Applications system, Biocatal. Biotransformation. 20, 437–439, 2002. https://doi.org/10.10 80/1024242021000040855. 97. A. Kumari, P. Mahapatra, V.K. Garlapati, R. Banerjee, Enzymatic transesterification of Jatropha oil, Biotechnol Biofuels. 2, 1, 2009. https://doi.org/17546834-2-1 [pii]\r10.1186/1754-6834-2-1. 98. Y. Xu, W. Du, D. Liu, J. Zeng, A novel enzymatic route for biodiesel production from renewable oils in a solvent-free medium, Biotechnol. Lett. 25, 1239–1241, 2003. https://doi.org/10.1023/A:1025065209983. 99. L. Zhang, S. Sun, Z. Xin, B. Sheng, Q. Liu, Synthesis and component confirmation of biodiesel from palm oil and dimethyl carbonate catalyzed by immobilized-lipase in solvent-free system, Fuel. 89, 3960–3965, 2010. https:// doi.org/10.1016/j.fuel.2010.06.030. 100. Z. Wang, J. Zhuge, H. Fang, B.A. Prior, Glycerol production by microbial fermentation: A review, Biotechnol. Adv. 19, 201–223, 2001. https://doi. org/10.1016/S0734-9750(01)00060-X. 101. Y. Zheng, J. Quan, X. Ning, L.M. Zhu, B. Jiang, Z.Y. He, Lipase-catalyzed transesterification of soybean oil for biodiesel production in tert-amyl alcohol, World J. Microbiol. Biotechnol. 25, 41–46, 2009. https://doi.org/10.1007/ s11274-008-9858-4. 102. P.S. Bisen, B.S. Sanodiya, G.S. Thakur, R.K. Baghel, G.B.K.S. Prasad, Biodiesel production with special emphasis on lipase-catalyzed transesterification, Biotechnol. Lett. 2010. https://doi.org/10.1007/s10529-0100275-z. 103. H. Ghamgui, M. Karra-Chaâbouni, Y. Gargouri, 1-Butyl oleate synthesis by immobilized lipase from Rhizopus oryzae: a comparative study between n-hexane and solvent-free system, Enzyme Microb. Technol. 35, 355–363, 2004. https://doi.org/10.1016/J.ENZMICTEC.2004.06.002. 104. M. Xiao, C. Qi, J.P. Obbard, Biodiesel production using Aspergillus niger as a whole-cell biocatalyst in a packed-bed reactor, GCB Bioenergy. 3, 293–298, 2011. https://doi.org/10.1111/j.1757-1707.2010.01087.x. 105. Ö. Aybastıer, C. Demir, Immobilization of Candida antarctica lipase A on chitosan beads for the production of fatty acid methyl ester from waste frying oil, energy sources, Part A Recover. Util. Environ. Eff. 36, 2313–2319, 2014. https://doi.org/10.1080/15567036.2011.567233. 106. S. Kojima, D. Du, M. Sato, E.Y. Park, Efficient production of fatty acid methyl ester from waste activated bleaching earth using diesel oil as organic solvent, J. Biosci. Bioeng. 98, 420–424, 2004. https://doi.org/http://dx.doi.org/10.1016/ S1389-1723(05)00306-3. 107. A. Bajaj, P. Lohan, P.N. Jha, R. Mehrotra, Biodiesel production through lipase catalyzed transesterification: An overview, J. Mol. Catal. B Enzym. 62, 9–14, 2010. https://doi.org/10.1016/j.molcatb.2009.09.018. 108. S. Ycel, P. Terziolu, D. zime, Lipase Applications in Biodiesel Production, in: Biodiesel - Feed. Prod. Appl., InTech, 2012. https://doi.org/10.5772/ 52662.

Biocatalytic Processes  47 109. M.Y. Noraini, H.C. Ong, M.J. Badrul, W.T. Chong, A review on potential enzymatic reaction for biofuel production from algae, Renew. Sustain. Energy Rev., 2014. https://doi.org/10.1016/j.rser.2014.07.089. 110. P. Priji, K.N. Unni, S. Sajith, P. Binod, S. Benjamin, Production, optimization, and partial purification of lipase from Pseudomonas sp. strain BUP6, a novel rumen bacterium characterized from Malabari goat, Biotechnol. Appl. Biochem., 2015. https://doi.org/10.1002/bab.1237. 111. A. Kumar, S.S. Parihar, N. Batra, Enrichment, isolation and optimization of lipase-producing Staphylococcus sp. from oil mill waste (Oil cake), J. Exp. Sci., 2012. 112. S. Javed, F. Azeem, S. Hussain, I. Rasul, M.H. Siddique, M. Riaz, M. Afzal, A. Kouser, H. Nadeem, Bacterial lipases: A review on purification and characterization, Prog. Biophys. Mol. Biol. 132, 23–34, 2018. https://doi.org/10.1016/j. pbiomolbio.2017.07.014. 113. B.D. Ribeiro, A.M. de Castro, M.A.Z. Coelho, D.M.G. Freire, Production and use of lipases in bioenergy: A review from the feedstocks to biodiesel production, Enzyme Res. 2011, 1–16, 2011. https://doi.org/10.4061/2011/615803. 114. M. Kapoor, M.N. Gupta, Lipase promiscuity and its biochemical applications, Process Biochem., 2012. https://doi.org/10.1016/j.procbio.2012.01.011. 115. A.L. Paiva, V.M. Balcão, F.X. Malcata, Kinetics and mechanisms of reactions catalyzed by immobilized lipases, Enzyme Microb. Technol., 2000. https://doi. org/10.1016/S0141-0229(00)00206-4. 116. A. Türkan, Ş. Kalay, Monitoring lipase-catalyzed methanolysis of sunflower oil by reversed-phase high-performance liquid chromatography: Elucidation of the mechanisms of lipases, J. Chromatogr. A. 1127, 34–44, 2006. https:// doi.org/10.1016/j.chroma.2006.05.065. 117. D. Bezbradica, M. Stojanović, D. Veličković, A. Dimitrijević, M. Carević, M. Mihailović, N. Milosavić, Kinetic model of lipase-catalyzed conversion of ascorbic acid and oleic acid to liposoluble vitamin C ester, Biochem. Eng. J., 2013. https://doi.org/10.1016/j.bej.2012.12.001. 118. A.E.M. Janssen, B.J. Sjursnes, A. V. Vakurov, P.J. Halling, Kinetics of lipase-­ catalyzed esterification in organic media: Correct model and solvent effects on parameters, Enzyme Microb. Technol., 1999. https://doi.org/10.1016/ S0141-0229(98)00134-3. 119. K.-E. Jaeger, B.W. Dijkstra, M.T. Reetz, Bacterial biocatalysts: Molecular biology, three-dimensional structures, and biotechnological applications of lipases, Annu. Rev. Microbiol. 53, 315–351, 1999. https://doi.org/10.1146/ annurev.micro.53.1.315. 120. F. Hasan, A.A. Shah, A. Hameed, Industrial applications of microbial lipases, Enzyme Microb. Technol. 39, 235–251, 2006. https://doi.org/10.1016/j. enzmictec.2005.10.016. 121. H. Treichel, D. de Oliveira, M.A. Mazutti, M. Di Luccio, J.V. Oliveira, A Review on Microbial Lipases Production, Food Bioprocess Technol. 3, 182– 196, 2010. https://doi.org/10.1007/s11947-009-0202-2.

48  Biodiesel Technology and Applications 122. C. Song, L. Sheng, X. Zhang, Immobilization and Characterization of a Thermostable Lipase, Mar. Biotechnol. 15, 659–667, 2013. https://doi. org/10.1007/s10126-013-9515-2. 123. Y. Hotta, S. Ezaki, H. Atomi, T. Imanaka, Extremely stable and versatile carboxylesterase from a Hyperthermophilic archaeon., Appl. Environ. Microbiol. 68, 3925–31, 2002. https://doi.org/10.1128/AEM.68.8.3925-3931.2002. 124. M. Royter, M. Schmidt, C. Elend, H. Höbenreich, T. Schäfer, U.T. Bornscheuer, G. Antranikian, Thermostable lipases from the extreme thermophilic anaerobic bacteria Thermoanaerobacter thermohydrosulfuricus SOL1 and Caldanaerobacter subterraneus subsp. tengcongensis, Extremophiles. 13, 769–783, 2009. https://doi.org/10.1007/s00792-009-0265-z. 125. K. Kawakami, Y. Oda, R. Takahashi, Application of a Burkholderia cepacia lipase-immobilized silica monolith to batch and continuous biodiesel production with a stoichiometric mixture of methanol and crude Jatropha oil, Biotechnol. Biofuels. 4, 42, 2011. https://doi.org/10.1186/1754-6834-4-42. 126. R. Abdulla, P. Ravindra, Immobilized Burkholderia cepacia lipase for biodiesel production from crude Jatropha curcas L. oil, Biomass and Bioenergy., 2013. https://doi.org/10.1016/j.biombioe.2013.04.010. 127. K.R. Jegannathan, L. Jun-Yee, E.-S. Chan, P. Ravindra, Design an immobilized lipase enzyme for biodiesel production, J. Renew. Sustain. Energy. 1, 063101, 2009. https://doi.org/10.1063/1.3256191. 128. Q. You, X. Yin, Y. Zhao, Y. Zhang, Biodiesel production from jatropha oil catalyzed by immobilized Burkholderia cepacia lipase on modified attapulgite, Bioresour. Technol. 148, 202–207, 2013. https://doi.org/10.1016/j. biortech.2013.08.143. 129. P.C.M. Da Rós, W.C. e Silva, D. Grabauskas, V.H. Perez, H.F. de Castro, Biodiesel from babassu oil: Characterization of the product obtained by enzymatic route accelerated by microwave irradiation, Ind. Crops Prod. 52, 313–320, 2014. https://doi.org/10.1016/j.indcrop.2013.11.013. 130. P.C.M. Da Rós, G.A.M. Silva, A.A. Mendes, J.C. Santos, H.F. de Castro, Evaluation of the catalytic properties of Burkholderia cepacia lipase immobilized on non-commercial matrices to be used in biodiesel synthesis from different feedstocks, Bioresour. Technol. 101, 5508–5516, 2010. https://doi. org/10.1016/j.biortech.2010.02.061. 131. C.G. Lopresto, S. Naccarato, L. Albo, M.G. De Paola, S. Chakraborty, S. Curcio, V. Calabro, Enzymatic transesterification of waste vegetable oil to produce biodiesel, Ecotoxicol. Environ. Saf. 121, 229–235, 2015. https://doi. org/10.1016/j.ecoenv.2015.03.028. 132. A.-F. Hsu, K. Jones, T.A. Foglia, W.N. Marmer, Immobilized lipase-catalysed production of alkyl esters of restaurant grease as biodiesel, Biotechnol. Appl. Biochem. 36, 181–186, 2002. https://doi.org/10.1042/. 133. X. Wang, X. Liu, C. Zhao, Y. Ding, P. Xu, Biodiesel production in packedbed reactors using lipase-nanoparticle biocomposite, Bioresour. Technol. 102, 6352–6355, 2011. https://doi.org/10.1016/j.biortech.2011.03.003.

Biocatalytic Processes  49 134. V. Kumari, S. Shah, M.N. Gupta, Preparation of biodiesel by lipase-catalyzed transesterification of high free fatty acid containing oil from Madhuca indica, Energy and Fuels. 21, 368–372, 2007. https://doi.org/10.1021/ef0602168. 135. J. Zheng, L. Xu, Y. Liu, X. Zhang, Y. Yan, Lipase-coated K2SO4 micro-crystals: Preparation, characterization, and application in biodiesel production using various oil feedstocks, Bioresour. Technol. 110, 224–231, 2012. https://doi. org/10.1016/J.BIORTECH.2012.01.088. 136. S. Shah, M.N. Gupta, Lipase catalyzed preparation of biodiesel from Jatropha oil in a solvent free system, Process Biochem. 42, 409–414, 2007. https://doi. org/10.1016/j.procbio.2006.09.024. 137. L.N. Lima, G.C. Oliveira, M.J. Rojas, H.F. Castro, P.C.M. Da Rós, A.A. Mendes, R.L.C. Giordano, P.W. Tardioli, Immobilization of Pseudomonas fluorescens lipase on hydrophobic supports and application in biodiesel synthesis by transesterification of vegetable oils in solvent-free systems, J. Ind. Microbiol. Biotechnol. 42, 523–535, 2015. https://doi.org/10.1007/s10295015-1586-9. 138. A.L. Machsun, M. Gozan, M. Nasikin, S. Setyahadi, Y.J. Yoo, Membrane microreactor in biocatalytic transesterification of triolein for biodiesel production, Biotechnol. Bioprocess Eng. 15, 911–916, 2010. https://doi. org/10.1007/s12257-010-0151-7. 139. G. Dors, L. Freitas, A.A. Mendes, A. Furigo, H.F. De Castro, Transesterification of palm oil catalyzed by Pseudomonas fluorescens lipase in a packed-bed reactor, Energy and Fuels. 26, 5977–5982, 2012. https://doi.org/10.1021/ ef300931y. 140. A.B.R. Moreira, V.H. Perez, G.M. Zanin, H.F. de Castro, Biodiesel synthesis by enzymatic transesterification of palm oil with ethanol using lipases from several sources immobilized on silica-PVA composite, Energy and Fuels. 21, 3689–3694, 2007. https://doi.org/10.1021/ef700399b. 141. L. Wang, Z. Chi, X. Wang, Z. Liu, J. Li, Diversity of lipase-producing yeasts from marine environments and oil hydrolysis by their crude enzymes, Ann. Microbiol. 57, 495–501, 2007. https://doi.org/10.1007/BF03175345. 142. N. Li, M.-H. Zong, Lipases from the genus Penicillium: Production, purification, characterization and applications, J. Mol. Catal. B Enzym. 66, 43–54, 2010. https://doi.org/10.1016/j.molcatb.2010.05.004. 143. R. Gupta, N. Gupta, P. Rathi, Bacterial lipases: An overview of production, purification and biochemical properties, Appl. Microbiol. Biotechnol. 64, 763–781, 2004. https://doi.org/10.1007/s00253-004-1568-8. 144. R.. Saxena, A. Sheoran, B. Giri, W.S. Davidson, Purification strategies for microbial lipases, J. Microbiol. Methods. 52, 1–18, 2003. https://doi. org/10.1016/S0167-7012(02)00161-6. 145. J.H. Lee, S.B. Kim, H.Y. Yoo, Y.J. Suh, G.B. Kang, W.I. Jang, J. Kang, C. Park, S.W. Kim, Biodiesel production by enzymatic process using Jatropha oil and waste soybean oil, Biotechnol. Bioprocess Eng. 18, 703–708, 2013. https://doi. org/10.1007/s12257-012-0805-8.

50  Biodiesel Technology and Applications 146. L. Deng, X. Xu, G.G. Haraldsson, T. Tan, F. Wang, Enzymatic production of alkyl esters through alcoholysis: A critical evaluation of lipases and alcohols, JAOCS, J. Am. Oil Chem. Soc. 82, 341–347, 2005. https://doi.org/10.1007/ s11746-005-1076-3. 147. I.G. Rosset, M.C.H.T. Cavalheiro, E.M. Assaf, A.L.M. Porto, Enzymatic esterification of oleic acid with aliphatic alcohols for the biodiesel production by Candida antarctica lipase, Catal. Letters. 143, 863–872, 2013. https://doi. org/10.1007/s10562-013-1044-0. 148. W. Du, Y. Xu, J. Zeng, D. Liu, Novozym 435-catalysed transesterification of crude soya bean oils for biodiesel production in a solvent-free medium., Biotechnol. Appl. Biochem. 40, 187–90, 2004. https://doi.org/10.1042/ BA20030142. 149. S.J. Kim, S.M. Jung, Y.C. Park, K. Park, Lipase catalyzed transesterification of soybean oil using ethyl acetate, an alternative acyl acceptor, Biotechnol. Bioprocess Eng. 12, 441–445, 2007. https://doi.org/10.1007/BF02931068. 150. C. Dalla Rosa, M.B. Morandim, J.L. Ninow, D. Oliveira, H. Treichel, J.V. Oliveira, Continuous lipase-catalyzed production of fatty acid ethyl esters from soybean oil in compressed fluids, Bioresour. Technol. 100, 5818–5826, 2009. https://doi.org/10.1016/j.biortech.2009.06.081. 151. W. Xie, N. Ma, Enzymatic transesterification of soybean oil by using immobilized lipase on magnetic nano-particles, Biomass and Bioenergy. 34, 890– 896, 2010. https://doi.org/10.1016/j.biombioe.2010.01.034. 152. F. Yagiz, D. Kazan, A.N. Akin, Biodiesel production from waste oils by using lipase immobilized on hydrotalcite and zeolites, Chem. Eng. J. 134, 262–267, 2007. https://doi.org/10.1016/j.cej.2007.03.041. 153. M. Basri, M.A. Kassim, R. Mohamad, A.B. Ariff, Optimization and kinetic study on the synthesis of palm oil ester using Lipozyme TL im, J. Mol. Catal. B Enzym. 85–86, 214–219, 2013. https://doi.org/10.1016/j.molcatb. 2012.09.013. 154. Y. Wang, H. Wu, M.H. Zong, Improvement of biodiesel production by lipozyme TL IM-catalyzed methanolysis using response surface methodology and acyl migration enhancer, Bioresour. Technol. 99, 7232–7237, 2008. https://doi.org/10.1016/j.biortech.2007.12.062. 155. D. von der Haar, A. Stabler, R. Wichmann, U. Schweiggert-Weisz, Enzymatic esterification of free fatty acids in vegetable oils utilizing different immobilized lipases, Biotechnol. Lett. 37, 169–174, 2015. https://doi.org/10.1007/ s10529-014-1668-1. 156. N.L. Facioli, D. Barrera-Arellano, Optimisation of enzymatic esterification of soybean oil deodoriser distillate, J. Sci. Food Agric. 81, 1193–1198, 2001. https://doi.org/10.1002/jsfa.928. 157. Y. Chen, B. Xiao, J. Chang, Y. Fu, P. Lv, X. Wang, Synthesis of biodiesel from waste cooking oil using immobilized lipase in fixed bed reactor, Energy Convers. Manag. 50, 668–673, 2009. https://doi.org/10.1016/j. enconman.2008.10.011.

Biocatalytic Processes  51 158. C.M.T. Santin, R.P. Scherer, N.L.D. Nyari, C.D. Rosa, R.M. Dallago, D. de Oliveira, J.V. Oliveira, Batch esterification of fatty acids charges under ultrasound irradiation using Candida antarctica B immobilized in polyurethane foam, Biocatal. Agric. Biotechnol. 3, 90–94, 2014. https://doi.org/10.1016/j. bcab.2014.02.005. 159. W. Xie, J. Wang, Enzymatic production of biodiesel from soybean oil by using immobilized lipase on Fe3O4/Poly(styrene-methacrylic acid) magnetic microsphere as a biocatalyst, Energy and Fuels. 28, 2624–2631, 2014. https:// doi.org/10.1021/ef500131s. 160. J.C. Moreno-Pirajàn, L. Giraldo, Study of immobilized candida rugosa lipase for biodiesel fuel production from palm oil by flow microcalorimetry, Arab. J. Chem. 4, 55–62, 2011. https://doi.org/10.1016/j.arabjc.2010.06.019. 161. Y. Yücel, Biodiesel production from pomace oil by using lipase immobilized onto olive pomace, Bioresour. Technol. 102, 3977–3980, 2011. https://doi. org/10.1016/j.biortech.2010.12.001. 162. A.F. Hsu, K.C. Jones, T.A. Foglia, W.N. Marmer, Transesterification activity of lipases immobilized in a phyllosilicate sol-gel matrix, Biotechnol. Lett. 26, 917–921, 2004. https://doi.org/10.1023/B:bile.0000025903.11697.ae. 163. J.S. Miranda, N.C.A. Silva, J.J. Bassi, M.C.C. Corradini, F.A.P. Lage, D.B. Hirata, A.A. Mendes, Immobilization of Thermomyces lanuginosus lipase on mesoporous poly-hydroxybutyrate particles and application in alkyl esters synthesis: Isotherm, thermodynamic and mass transfer studies, Chem. Eng. J. 251, 392–403, 2014. https://doi.org/10.1016/j.cej.2014.04.087. 164. A.A. Mendes, R.C. Giordano, R.D.L.C. Giordano, H.F. De Castro, Immobilization and stabilization of microbial lipases by multipoint covalent attachment on aldehyde-resin affinity: Application of the biocatalysts in biodiesel synthesis, J. Mol. Catal. B Enzym. 68, 109–115, 2011. https://doi. org/10.1016/j.molcatb.2010.10.002. 165. S.V. Ranganathan, S.L. Narasimhan, K. Muthukumar, An overview of enzymatic production of biodiesel, Bioresour. Technol., 2008. https://doi. org/10.1016/j.biortech.2007.04.060. 166. H. Fukuda, S. Hama, S. Tamalampudi, H. Noda, Whole-cell biocatalysts for biodiesel fuel production, Trends Biotechnol., 2008. https://doi.org/10.1016/j. tibtech.2008.08.001. 167. M.S. Soares, A.L.L. Rico, G.S.S. Andrade, H.F. De Castro, P.C. Oliveira, Synthesis, characterization and application of a polyurethane-based support for immobilizing membrane-bound lipase, Brazilian J. Chem. Eng., 2017. https://doi.org/10.1590/0104-6632.20170341s20140227. 168. B. Atkinson, G.M. Black, P.J.S. Lewis, A. Pinches, Biological particles of given size, shape, and density for use in biological reactors, Biotechnol. Bioeng., 1979. https://doi.org/10.1002/bit.260210206. 169. S. Ertuğrul, G. Dönmez, S. Takaç, Isolation of lipase producing Bacillus sp. from olive mill wastewater and improving its enzyme activity, J. Hazard. Mater., 2007. https://doi.org/10.1016/j.jhazmat.2007.04.034.

52  Biodiesel Technology and Applications 170. V. Ramakrishnan, L.C. Goveas, N. Suralikerimath, C. Jampani, P.M. Halami, B. Narayan, Extraction and purification of lipase from Enterococcus faecium MTCC5695 by PEG/phosphate aqueous-two phase system (ATPS) and its biochemical characterization, Biocatal. Agric. Biotechnol., 2016. https://doi. org/10.1016/j.bcab.2016.02.005. 171. M. Adamczak, W. Bednarski, Enhanced activity of intracellular lipases from Rhizomucor miehei and Yarrowia lipolytica by immobilization on biomass support particles, Process Biochem., 2004. https://doi.org/10.1016/ S0032-9592(03)00266-8. 172. L. Ping, X. Yuan, M. Zhang, Y. Chai, S. Shan, Improvement of extracellular lipase production by a newly isolated Yarrowia lipolytica mutant and its application in the biosynthesis of L-ascorbyl palmitate, Int. J. Biol. Macromol., 2018. https://doi.org/10.1016/j.ijbiomac.2017.08.016. 173. J. Huang, J. Xia, W. Jiang, Y. Li, J. Li, Biodiesel production from microalgae oil catalyzed by a recombinant lipase, Bioresour. Technol. 180, 47–53, 2015. https://doi.org/10.1016/j.biortech.2014.12.072. 174. D. Adachi, F. Koh, S. Hama, C. Ogino, A. Kondo, A robust whole-cell biocatalyst that introduces a thermo- and solvent-tolerant lipase into Aspergillus oryzae cells: Characterization and application to enzymatic biodiesel production, Enzyme Microb. Technol. 52, 331–335, 2013. https://doi.org/10.1016/j. enzmictec.2013.03.005. 175. Y. Luo, Y. Zheng, Z. Jiang, Y. Ma, D. Wei, A novel psychrophilic lipase from Pseudomonas fluorescens with unique property in chiral resolution and biodiesel production via transesterification, Appl. Microbiol. Biotechnol. 73, 349–355, 2006. https://doi.org/10.1007/s00253-006-0478-3. 176. J. Yan, X. Zheng, S. Li, A novel and robust recombinant Pichia pastoris yeast whole cell biocatalyst with intracellular overexpression of a Thermomyces lanuginosus lipase: Preparation, characterization and application in biodiesel production, Bioresour. Technol. 151, 43–48, 2014. https://doi.org/10.1016/j. biortech.2013.10.037. 177. G.-C. Lee, L.-C. Lee, V. Sava, J.-F. Shaw, Multiple mutagenesis of non-­ universal serine codons of the Candida rugosa LIP2 gene and biochemical characterization of purified recombinant LIP2 lipase overexpressed in Pichia pastoris., Biochem. J. 366, 603–611, 2002. https://doi.org/10.1042/ BJ20020404. 178. A. Yoshida, S. Hama, N. Tamadani, H. Noda, H. Fukuda, A. Kondo, Continuous production of biodiesel using whole-cell biocatalysts: Sequential conversion of an aqueous oil emulsion into anhydrous product, Biochem. Eng. J. 68, 7–11, 2012. https://doi.org/10.1016/j.bej.2012.07.002. 179. D. Adachi, S. Hama, T. Numata, K. Nakashima, C. Ogino, H. Fukuda, A. Kondo, Development of an Aspergillus oryzae whole-cell biocatalyst coexpressing triglyceride and partial glyceride lipases for biodiesel production, Bioresour. Technol. 102, 6723–6729, 2011. https://doi.org/10.1016/j. biortech.2011.03.066.

Biocatalytic Processes  53 180. M. Raita, V. Champreda, N. Laosiripojana, Biocatalytic ethanolysis of palm oil for biodiesel production using microcrystalline lipase in tert-butanol system, Process Biochem. 45, 829–834, 2010. https://doi.org/10.1016/j. procbio.2010.02.002. 181. T.P. Korman, B. Sahachartsiri, D.M. Charbonneau, G.L. Huang, M. Beauregard, J.U. Bowie, Dieselzymes: development of a stable and methanol tolerant lipase for biodiesel production by directed evolution, Biotechnol. Biofuels. 6, 70, 2013. https://doi.org/10.1186/1754-6834-6-70. 182. S.H. Kim, S.J. Kim, S. Park, H.K. Kim, Biodiesel production using crosslinked Staphylococcus haemolyticus lipase immobilized on solid polymeric carriers, J. Mol. Catal. B Enzym. 85–86, 10–16, 2013. https://doi.org/10.1016/j. molcatb.2012.08.012. 183. A. Li, T.P.N. Ngo, J. Yan, K. Tian, Z. Li, Whole-cell based solvent-free system for one-pot production of biodiesel from waste grease, Bioresour. Technol. 114, 725–729, 2012. https://doi.org/10.1016/j.biortech.2012.03.034. 184. F. Guan, P. Peng, G. Wang, T. Yin, Q. Peng, J. Huang, G. Guan, Y. Li, Combination of two lipases more efficiently catalyzes methanolysis of soybean oil for biodiesel production in aqueous medium, Process Biochem. 45, 1677–1682, 2010. https://doi.org/10.1016/j.procbio.2010.06.021. 185. T. Takaya, R. Koda, D. Adachi, K. Nakashima, J. Wada, T. Bogaki, C. Ogino, A. Kondo, Highly efficient biodiesel production by a whole-cell biocatalyst employing a system with high lipase expression in Aspergillus oryzae, Appl. Microbiol. Biotechnol. 90, 1171–1177, 2011. https://doi.org/10.1007/s00253-011-3186-6. 186. D. Huang, S. Han, Z. Han, Y. Lin, Biodiesel production catalyzed by Rhizomucor miehei lipase-displaying Pichia pastoris whole cells in an isooctane system, Biochem. Eng. J. 63, 10–14, 2012. https://doi.org/10.1016/j. bej.2010.08.009. 187. Z.L. Huang, T.X. Yang, J.Z. Huang, Z. Yang, Enzymatic production of biodiesel from Millettia pinnata seed oil in ionic liquids, Bioenergy Res. 7, 1519– 1528, 2014. https://doi.org/10.1007/s12155-014-9489-6. 188. T. Matsumoto, S. Takahashi, M. Kaieda, M. Ueda, A. Tanaka, H. Fukuda, A. Kondo, Yeast whole-cell biocatalyst constructed by intracellular overproduction of Rhizopus oryzae lipase is applicable to biodiesel fuel production, Appl. Microbiol. Biotechnol. 57, 515–520, 2001. https://doi.org/10.1007/ s002530100733. 189. B. Zhang, Y. Weng, H. Xu, Z. Mao, Enzyme immobilization for biodiesel production, Appl. Microbiol. Biotechnol. 93, 61–70, 2012. https://doi.org/10.1007/ s00253-011-3672-x. 190. R. Pogaku, A. Bono, C. Chu, Developments in sustainable chemical and bioprocess technology, Springer US, Boston, MA, 2013. https://doi. org/10.1007/978-1-4614-6208-8. 191. S.K. Narwal, R. Gupta, Biodiesel production by transesterification using immobilized lipase, Biotechnol. Lett. 35, 479–490, 2013. https://doi. org/10.1007/s10529-012-1116-z.

54  Biodiesel Technology and Applications 192. D. Brady, J. Jordaan, Advances in enzyme immobilisation, Biotechnol. Lett. 31, 1639–1650, 2009. https://doi.org/10.1007/s10529-009-0076-4. 193. M. Kalantari, M. Kazemeini, A. Arpanaei, Evaluation of biodiesel production using lipase immobilized on magnetic silica nanocomposite particles of various structures, Biochem. Eng. J. 79, 267–273, 2013. https://doi.org/10.1016/j. bej.2013.09.001. 194. S. Shah, S. Sharma, M.N. Gupta, Biodiesel preparation by lipase-catalyzed transesterification of Jatropha oil, Energy and Fuels. 18, 154–159, 2004. https://doi.org/10.1021/ef030075z. 195. S. Shah, S. Sharma, M.N. Gupta, Enzymatic transesterification for biodiesel production, Indian J. Biochem. Biophys. 40, 392–399, 2003. https://doi. org/10.1039/C6RA08062F. 196. P. Shao, X. Meng, J. He, P. Sun, Analysis of immobilized Candida rugosa lipase catalyzed preparation of biodiesel from rapeseed soapstock, Food Bioprod. Process. 86, 283–289, 2008. https://doi.org/10.1016/j.fbp.2008.02.004. 197. K. Ban, S. Hama, K. Nishizuka, M. Kaieda, T. Matsumoto, A. Kondo, H. Noda, H. Fukuda, Repeated use of whole-cell biocatalysts immobilized within biomass support particles for biodiesel fuel production, J. Mol. Catal. - B Enzym. 17, 157–165, 2002. https://doi.org/10.1016/S1381-1177 (02)00023-1. 198. M.G.M. Purwanto, M.V. Maretha, M. Wahyudi, M.T. Goeltom, Whole Cell Hydrolysis of Sardine (Sardinella Lemuru) Oil Waste Using Mucor Circinelloides NRRL 1405 Immobilized in Poly-urethane Foam, Procedia Chem. 14, 256–262, 2015. https://doi.org/10.1016/j.proche.2015.03.036. 199. G.S.S. Andrade, A.K.F. Carvalho, C.M. Romero, P.C. Oliveira, H.F. De Castro, Mucor circinelloides whole-cells as a biocatalyst for the production of ethyl esters based on babassu oil, Bioprocess Biosyst. Eng. 37, 2539–2548, 2014. https://doi.org/10.1007/s00449-014-1231-4. 200. W. Li, W. Du, D. Liu, Optimization of whole cell-catalyzed methanolysis of soybean oil for biodiesel production using response surface methodology, J. Mol. Catal. B Enzym. 45, 122–127, 2007. https://doi.org/10.1016/j. molcatb.2007.01.002. 201. S. Tamalampudi, M.R. Talukder, S. Hama, T. Numata, A. Kondo, H. Fukuda, Enzymatic production of biodiesel from Jatropha oil: A comparative study of immobilized-whole cell and commercial lipases as a biocatalyst, Biochem. Eng. J. 39, 185–189, 2008. https://doi.org/10.1016/j.bej.2007.09.002. 202. S. Hama, H. Yamaji, T. Fukumizu, T. Numata, S. Tamalampudi, A. Kondo, H. Noda, H. Fukuda, Biodiesel-fuel production in a packed-bed reactor using lipase-producing Rhizopus oryzae cells immobilized within biomass support particles, Biochem. Eng. J. 34, 273–278, 2007. https://doi.org/10.1016/j. bej.2006.12.013. 203. B. Balasubramaniam, A. Sudalaiyadum Perumal, J. Jayaraman, J. Mani, P. Ramanujam, Comparative analysis for the production of fatty acid alkyl esterase using whole cell biocatalyst and purified enzyme from Rhizopus

Biocatalytic Processes  55 oryzae on waste cooking oil (sunflower oil), Waste Manag. 32, 1539–1547, 2012. https://doi.org/10.1016/j.wasman.2012.03.011. 204. S. Athalye, R. Sharma-Shivappa, S. Peretti, P. Kolar, J.P. Davis, Producing biodiesel from cottonseed oil using Rhizopus oryzae ATCC #34612 whole cell biocatalysts: Culture media and cultivation period optimization, Energy Sustain. Dev. 17, 331–336, 2013. https://doi.org/10.1016/j.esd.2013.03.009. 205. M.G. Devanesan, T. Viruthagiri, N. Sugumar, Transesterification of Jatropha oil using immobilized Pseudomonas fluorescens, African J. Biotechnol. 6, 2497–2501, 2007. https://doi.org/10.4314/ajb.v6i21.58115. 206. Q. Li, J. Zheng, Y. Yan, Biodiesel preparation catalyzed by compoundlipase in co-solvent, Fuel Process. Technol. 91, 1229–1234, 2010. https://doi. org/10.1016/j.fuproc.2010.04.002. 207. R.C. Rodrigues, M.A.Z. Ayub, Effects of the combined use of Thermomyces lanuginosus and Rhizomucor miehei lipases for the transesterification and hydrolysis of soybean oil, Process Biochem. 46, 682–688, 2011. https://doi. org/10.1016/j.procbio.2010.11.013. 208. J.K. Poppe, C.R. Matte, M. Do Carmo Ruaro Peralba, R. Fernandez-Lafuente, R.C. Rodrigues, M.A.Z. Ayub, Optimization of ethyl ester production from olive and palm oils using mixtures of immobilized lipases, Appl. Catal. A Gen. 490, 50–56, 2015. https://doi.org/10.1016/j.apcata.2014.10.050. 209. K. Tongboriboon, B. Cheirsilp, A. H-Kittikun, Mixed lipases for efficient enzymatic synthesis of biodiesel from used palm oil and ethanol in a solvent-­ free system, J. Mol. Catal. B Enzym. 67, 52–59, 2010. https://doi.org/10.1016/j. molcatb.2010.07.005. 210. A. Salis, M. Pinna, M. Monduzzi, V. Solinas, Comparison among immobilised lipases on macroporous polypropylene toward biodiesel synthesis, J. Mol. Catal. B Enzym. 54, 19–26, 2008. https://doi.org/10.1016/j. molcatb.2007.12.006. 211. A.R. Rodrigues, A. Paiva, M.G. Da Silva, P. Simões, S. Barreiros, Continuous enzymatic production of biodiesel from virgin and waste sunflower oil in supercritical carbon dioxide, in: J. Supercrit. Fluids, pp. 259–264, 2011. https://doi.org/10.1016/j.supflu.2010.10.031. 212. J.S. Alves, N.S. Vieira, A.S. Cunha, A.M. Silva, M.A. Záchia Ayub, R. Fernandez-Lafuente, R.C. Rodrigues, Combi-lipase for heterogeneous substrates: a new approach for hydrolysis of soybean oil using mixtures of biocatalysts, RSC Adv. 4, 6863–6868, 2014. https://doi.org/10.1039/c3ra45969a. 213. M. Lee, J. Lee, D. Lee, J. Cho, S. Kim, C. Park, Improvement of enzymatic biodiesel production by controlled substrate feeding using silica gel in solvent free system, Enzyme Microb. Technol. 49, 402–406, 2011. https://doi. org/10.1016/j.enzmictec.2011.06.020. 214. D. Šinkuniene, P. Adlercreutz, Effects of regioselectivity and lipid class specificity of lipases on transesterification, exemplified by biodiesel production, JAOCS, J. Am. Oil Chem. Soc. 91, 1283–1290, 2014. https://doi.org/10.1007/ s11746-014-2465-7.

56  Biodiesel Technology and Applications 215. Y. Watanabe, T. Nagao, Y. Nishida, Y. Takagi, Y. Shimada, Enzymatic production of fatty acid methyl esters by hydrolysis of acid oil followed by esterification, JAOCS, J. Am. Oil Chem. Soc. 84, 1015–1021, 2007. https://doi. org/10.1007/s11746-007-1143-4. 216. Y. Yan, L. Xu, M. Dai, A synergetic whole-cell biocatalyst for biodiesel production, RSC Adv. 2, 6170, 2012. https://doi.org/10.1039/c2ra20974h. 217. A.P. de los Ríos, F.J. Hernández-Fernández, D. Gómez, M. Rubio, F. TomásAlonso, G. Víllora, Understanding the chemical reaction and mass-­transfer phenomena in a recirculating enzymatic membrane reactor for green ester synthesis in ionic liquid/supercritical carbon dioxide biphasic systems, J. Supercrit. Fluids. 43, 303–309, 2007. https://doi.org/10.1016/J. SUPFLU.2007.06.003. 218. P. Lozano, Enzymes in neoteric solvents: From one-phase to multiphase systems, Green Chem. 12, 555, 2010. https://doi.org/10.1039/b919088k. 219. L.A. Blanchard, D. Hancu, E.J. Beckman, J.F. Brennecke, Green processing using ionic liquids and CO2, Nature. 399 (1999) 28–29. https://doi. org/10.1038/19887. 220. P. Lozano, J.M. Bernal, M. Vaultier, Towards continuous sustainable processes for enzymatic synthesis of biodiesel in hydrophobic ionic liquids/ supercritical carbon dioxide biphasic systems, Fuel. 90, 3461–3467, 2011. https://doi.org/10.1016/j.fuel.2011.06.008. 221. D. Yu, C. Wang, Y. Yin, A. Zhang, G. Gao, X. Fang, A synergistic effect of microwave irradiation and ionic liquids on enzyme-catalyzed biodiesel production, Green Chem. 13, 1869, 2011. https://doi.org/10.1039/c1gc15114b. 222. B.M. Nogueira, C. Carretoni, R. Cruz, S. Freitas, P.A. Melo, R. Costa-F??lix, J.C. Pinto, M. Nele, Microwave activation of enzymatic catalysts for biodiesel production, J. Mol. Catal. B Enzym. 67, 117–121, 2010. https://doi. org/10.1016/j.molcatb.2010.07.015. 223. M.L.B. Queiroz, R.F. Boaventura, M.N. Melo, H.M. Alvarez, C.M.F. Soares, Á.S. Lima, M.F. Heredia, C. Dariva, A.T. Fricks, Microwave activation of immobilized lipase for transesterification of vegetable oils, Quim. Nova., 2015. https://doi.org/10.5935/0100-4042.20150031. 224. Y. Zhang, X. Xia, M. Duan, Y. Han, J. Liu, M. Luo, C. Zhao, Y. Zu, Y. Fu, Green deep eutectic solvent assisted enzymatic preparation of biodiesel from yellow horn seed oil with microwave irradiation, J. Mol. Catal. B Enzym. 123, 35–40, 2016. https://doi.org/10.1016/J.MOLCATB.2015.10.013. 225. S. Shah, M. Gupta, The effect of ultrasonic pre-treatment on the catalytic activity of lipases in aqueous and non-aqueous media, Chem. Cent. J. 2, 1, 2008. https://doi.org/10.1186/1752-153X-2-1. 226. G. Kumar, D. Kumar, Poonam, R. Johari, C.P. Singh, Enzymatic transesterification of Jatropha curcas oil assisted by ultrasonication, Ultrason. Sonochem. 18, 923–927, 2011. https://doi.org/10.1016/J.ULTSONCH.2011.03.004. 227. D. Yu, L. Tian, H. Wu, S. Wang, Y. Wang, D. Ma, X. Fang, Ultrasonic irradiation with vibration for biodiesel production from soybean oil by

Biocatalytic Processes  57 Novozym 435, Process Biochem. 45, 519–525, 2010. https://doi.org/10.1016/J. PROCBIO.2009.11.012. 228. G. V. Waghmare, V.K. Rathod, Ultrasound assisted enzyme catalyzed hydrolysis of waste cooking oil under solvent free condition, Ultrason. Sonochem. 32, 60–67, 2016. https://doi.org/10.1016/j.ultsonch.2016.01.033. 229. C.M. Trentin, A.S. Popiolki, L. Batistella, C.D. Rosa, H. Treichel, D. de Oliveira, J.V. Oliveira, Enzyme-catalyzed production of biodiesel by ultrasound-assisted ethanolysis of soybean oil in solvent-free system, ­ Bioprocess Biosyst. Eng. 38, 437–448, 2015. https://doi.org/10.1007/s00449014-1316-0. 230. P.B. Subhedar, C. Botelho, A. Ribeiro, R. Castro, M.A. Pereira, P.R. Gogate, A. Cavaco-Paulo, Ultrasound intensification suppresses the need of methanol excess during the biodiesel production with Lipozyme TL-IM, Ultrason. Sonochem. 27, 530–535, 2015. https://doi.org/10.1016/J. ULTSONCH.2015.04.001. 231. H. Yu, H. Yue, P. Halling, Optimal experimental design for an enzymatic biodiesel production system, IFAC-PapersOnLine. 48, 1258–1263, 2015. https:// doi.org/10.1016/j.ifacol.2015.09.141. 232. P. Tufvesson, J. Lima-Ramos, N. Al Haque, K. V. Gernaey, J.M. Woodley, Advances in the process development of biocatalytic processes, Org. Process Res. Dev. 17, 1233–1238, 2013. https://doi.org/10.1021/op4001675. 233. Q.K. Beg, V. Sahai, R. Gupta, Statistical media optimization and alkaline protease production from Bacillus mojavensis in a bioreactor, Process Biochem. 39, 203–209, 2003. https://doi.org/10.1016/S0032-9592(03)00064-5. 234. B. Manohar, S. Divakar, Applications of surface plots and statistical designs to selected lipase catalysed esterification reactions, Process Biochem. 39, 847– 853, 2004. https://doi.org/10.1016/S0032-9592(03)00192-4. 235. Q.K. Beg, R.K. Saxena, R. Gupta, Kinetic constants determination for an alkaline protease from Bacillus mojavensis using response surface methodology, Biotechnol. Bioeng. 78, 289–295, 2002. https://doi.org/10.1002/bit. 10203. 236. D.S. Rana, K. Thèodore, G.S. Narayana Naidu, T. Panda, Stability and kinetics of β-1,3-glucanse from Trichoderma harzianum, Process Biochem. 39, 149–155, 2003. https://doi.org/10.1016/S0032-9592(02)00323-0. 237. D. Ba, I.H. Boyaci, Modeling and optimization: Usability of response surface methodology, J. Food Eng. 78, 836–845, 2007. https://doi.org/10.1016/j. jfoodeng.2005.11.024. 238. G.-T. Jeong, D.-H. Park, Response surface methodological approach for optimization of enzymatic synthesis of sorbitan methacrylate, Enzyme Microb. Technol. 39, 381–386, 2006. https://doi.org/10.1016/J. ENZMICTEC.2005.11.046. 239. J.-F. Shaw, H.-Z. Wu, C.-J. Shieh, Optimized enzymatic synthesis of propylene glycol monolaurate by direct esterification, Food Chem. 81, 91–96, 2003. https://doi.org/10.1016/S0308-8146(02)00383-7.

58  Biodiesel Technology and Applications 240. H. V. Lee, R. Yunus, J.C. Juan, Y.H. Taufiq-Yap, Process optimization design for jatropha-based biodiesel production using response surface methodology, Fuel Process. Technol. 92, 2420–2428, 2011. https://doi.org/10.1016/j. fuproc.2011.08.018. 241. C.J. Shieh, H.F. Liao, C.C. Lee, Optimization of lipase-catalyzed biodiesel by response surface methodology, Bioresour. Technol. 88, 103–106, 2003. https:// doi.org/10.1016/S0960-8524(02)00292-4. 242. S.V. Ghadge, H. Raheman, Process optimization for biodiesel production from mahua (Madhuca indica) oil using response surface methodology, Bioresour. Technol. 97, 379–384, 2006. https://doi.org/10.1016/J. BIORTECH.2005.03.014.

2 Application of Low-Frequency Ultrasound for Intensified Biodiesel Production Process Mohd Razealy Anuar, Mohamed Hussein Abdurahman, Nor Irwin Basir and Ahmad Zuhairi Abdullah* School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Nibong Tebal, Penang, Malaysia

Abstract

Biodiesel is an energy source that is mostly derived from plant-based oils through a transesterification and esterification reactions with alcohols. Due to the immiscibility of the reactants, the reaction is only limited to the interface and vigorous mechanical stirring is often needed to homogenize the reactants. To achieve high yields (>90%) in about 2 h, temperatures between 50°C and 65°C in the presence of 0.5 to 3.0 wt. % of catalyst are usually required. The use of ultrasonic energy as the source of mixing has become a great interest as it can increase the interface area leading to higher biodiesel yield. During ultrasonication, the cavitation bubbles will be formed and subsequently collapse asymmetrically once the critical sizes are reached. The boundary of the reacting phases will be disrupted by the micro jets that result from these collapses. It will also result in a temperature rise at the locality of the phase boundary. The use of ultrasonic energy in conjunction with a heterogeneous catalyst can lead to shorter reaction times of 10–40 min with two to three times lower amount of catalyst needed as compared to those expected in normal mechanically stirred reactor. Thus, the process will require shorter reaction time, lower catalyst amount and lower energy input to result in high methyl ester yield. Keywords:  Biodiesel, ultrasound, mass transfer, immiscible reactant, transesterification, process intensification, catalyst

*Corresponding author: [email protected] (https://orcid.org/0000-0001-6394-2917) Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (59–84) © 2021 Scrivener Publishing LLC

59

60  Biodiesel Technology and Applications

2.1 Current Fossil Fuel Scenario Recently, the increasing demand on the unsustainable fossil fuels is a challenging topic to be addressed. With the current rate of crude oil consumption, the conventional energy sources could be depleted not even 50 years down the line [1]. The high usage of such fuels to generate energy has also caused associated environmental effects such as global warming [2], greenhouse gas emissions, and acid rain [3] and other environmental pollutions such as particulate matters [4]. It is also reported that carbon monoxide (CO), carbon dioxide (CO2), sulfur oxides (SOx), and nitrogen oxides (NOx) that result from fossil fuels combustion are the key culprits for global warming [1]. It was anticipated that the world’s overall energy consumption and thus the CO2 emissions to the atmosphere could show 60% increase in 2018 as compared to 2008. Furthermore, oil and gas prices had also been increasing in the recent years [5]. Due to the above-mentioned issues, the necessity of finding the environmental-benign alternatives to fossil fuels to address the future energy demand is a worthwhile effort [6, 7]. Alternatives to replace fossil fuels are such as biofuels, wind, and solar energy [2]. The dependence of transportation sector on fossil fuels was about 96% of the current energy consumed in the sector [5]. The current scenario of soaring fossil fuel prices and their finite reserves therefore justify the quest for biofuels as the fifth energy sources.

2.2 Biodiesel Recently, methyl esters of fatty acids in vegetable oils, also known as biodiesel, have been demonstrated to be effectively used to power diesel engines at certain blend ratios [8, 9]. Biodiesel fuel is a result of the alcohol transesterification of triglycerides in vegetable oils or animal fats. Alternatively, free fatty acids in those triglycerides can also be esterified to yield methyl esters. This fuel has been demonstrated to show potentials as a renewable fuel source based on several favorable specifications [6]. It consists of monoalkyl esters and produced through a reaction between the triglycerides and a monohydric alcohol [10]. Biodiesel as a fuel promises the advantages of (1) minimum dependence on fossil, (2) renewability, (3) positive energy balance, (4) better emission quality, (5) non-toxic, (6) agricultural surplus as feedstock, and (7) better safety in handling [11].

Ultrasound-Assisted Biodiesel Production  61 The properties of biodiesel in strongly influenced by the characteristics of feedstock as well as the production system used. There are several methods of biodiesel production reported such as homogeneous acid-mediated process [12], supercritical fluid process [3], enzymatic process [13], and homogenous base catalyzed process [14]. Base catalysts are usually more favorable than acid catalysts or enzymes [15]. Research efforts toward future use of heterogeneous catalysts for this conversion are also actively investigated [16, 17].

2.3 Transesterification Biodiesel is commonly produced by the catalytic reaction between triglycerides (oils or fats) with simple alcohols (i.e., methanol, ethanol, propanol and butanol). Glycerol is co-produced as the side-product. The transesterification process is as schematically shown in Figure 2.1. Stoichiometrically, the reaction involved 3 moles of alcohol and 1 mole of triglyceride to yield 3 moles of methyl esters (biodiesel) and 1 mole of glycerol. However, due to the reversible nature of this reaction, in practice, excess of alcohol is used to push the equilibrium toward favorable side to achieve higher ester yield [9]. In this reaction, diglycerides and monoglycerides are undesired products that should be minimized for the sake of better FAME yield. Esters are the desired products of the transesterification reactions. At the end of the reaction, glycerol is removed by centrifugation or settling O

O CH2 O C R1 O CH2 O C R2 + 3 CH3OH O CH2 O C R3

Triglycerides

Methanol

O

CH2 O C Rx

CH2 O C Rx

CH2 O H O

CH2 O H

CH2 O C Rx

CH2 O H

CH2 O H O

CH2 O H O

CH2 O C Rx O

CH2 O C Rx

CH2 O C Rx

CH2 O H

Diglycerides

Monoglycerides

CH2 O H

R1COOCH3

CH2 O H + R2COOCH3 R3COOCH3

CH2 O H

Note : x=1, 2 or 3

Glycerol

Methyl esters (Biodiesel)

Figure 2.1  Transesterification of triglycerides for the production of biodiesel.

62  Biodiesel Technology and Applications for subsequent purification. Purified glycerol can be used in many conventional applications (pharmaceutical, cosmetic, and food industries). Newly developed applications for glycerol are also found in the fields of animal feed, surfactants, polymers, lubricants, etc. [18, 19]. Glycerol recovery is also crucial because of its several applications in different industrial processes.

2.4 Challenges for Improved Biodiesel Production Conventional biodiesel production processes are still more expensive as compared to those of fossil diesel. The cost of the biodiesel as compared to diesel does not make it favorable alternative to fossil fuels. One of the important issues which can directly reduce the cost is the reduction in the production costs. These expenses are such as the heating, labor work, mixing, and raw material use. On the other hand, generally, biodiesel is produced from various vegetable oils that have undergone extensive purification processes. These oils are relatively costly and at the same time more suitable for edible purposes. There has been heated debate on the fuel versus food dilemma across the globe [20]. Homogeneous catalyst has many environmental impacts due to production of wastewater during the separation process. Alcohol and oil are also immiscible and the reaction only takes place in the interface of the reactants. Thus, the production of biodiesel requires a rather long reaction time and excess of catalyst to assure high yields. These conditions can increase the overall biodiesel production costs. Therefore, as an ultimate objective, alternative method to decrease the process costs and time should be identified. Long reaction time will directly and indirectly affect the production cost of biodiesel while affecting it quality at the same time. Effective transesterification process usually occurs at temperatures higher than 60°C. Lower temperatures often result in poor reaction rates while higher temperatures will require a pressurized reactor considering the methanol boiling point of 64.8°C. Thus, reduction in the reaction time can cause less time of energy consumption for heating the system. This highlights the importance of finding technologies which are less costly and less energy consumption. Time reduction can also reduce the labor work for production of the same amount of biodiesel. Biodiesel also needs to fulfill the strict requirements of ASTM D6751-17 or EN 14212:2008 standards to be used as fuel. The consistent compliance is an uphill task. In order to produce biodiesel that consistently meet the technical standards, strict quality control measures for the feedstock and

Ultrasound-Assisted Biodiesel Production  63 the catalyst should be implemented. However, the severity of the production process should be reduced bearing in mind the low stability of the triglycerides used in the production process [21]. This technology should also have the feasibility to be scaled up. Thus, the reaction rates and optimized operating conditions are also of great concerns in this study.

2.5 Homogeneous Catalyst for Biodiesel Production Biodiesel production process is usually catalyzed by enzymes, acidic or basic catalysts. Sulfuric acid and hydrochloric acids are conventionally used for the acid catalyzed processes. These catalysts are often used for oils feedstock with high water and free fatty acid (FFA) contents. Acidcatalyzed biodiesel production processes normally need longer reaction time and higher alcohol to oil ratio [17]. As such, the production costs are usually higher in this case. As such, biodiesel is more commonly produced now from refined/edible type oils (with lower FFA and water contents) in the presence of an alkaline catalyst. This reaction is relatively higher to make this option more favorable. However, the difficulty of alkalicatalyzed esterification of non-edible oils is excessive soap formation which inhibits the effective separation of ester and glycerin. This phenomenon is attributed to the residual amounts of FFA that present in the oil, particularly in the case of non-edible/not refined oils [16]. For an alkali-catalyzed transesterification process, the glycerides and alcohol must be substantially anhydrous. In the presence of water, the undesired saponification reaction between the catalysts with FFA will produce metal salts of the fatty acids (soaps) [21]. There is also certain environmental impact associated with the catalyst amount used. Excessive amounts will result in large amount of soap which is undesirable as far as product separation and biodiesel quality are concerned. Besides, the remaining catalyst can end up in the product leading to increased biodiesel pH other biodiesel quality parameters such as ash content [2]. The typical catalyst used for the production of biodiesel is homogeneous base catalysts such as KOH and NaOH. This process can produce high methyl ester yield under atmospheric pressure and temperature of 50°C–65°C which is usually carried out in 1–4 h [6]. In order to improve the biodiesel quality to meet certain intentional standards, downstream purification of the methyl ester is required prior to its use as biodiesel. This could be achieved by removing impurities such as catalyst and glycerol by hot water washing. It should be noted that such further purification processes generate enormous amounts of wastewater [15]. Thus, replacing

64  Biodiesel Technology and Applications conventional homogeneous catalysts with environmentally friendly heterogeneous catalysts seems to be essential for the benefit of lower production costs and environmental considerations.

2.6 Heterogeneous Catalyst for Biodiesel Production Due to environmental concerns, the interest in biodiesel production is currently been directed toward heterogeneous process. This approach allows catalyst removal after the reaction without extensive downstream purification processes. Other advantages are in the reusability potential of the catalyst and the less corrosive character of heterogeneous catalysts [22]. They can also be formulated to exhibit better activity, selectivity and stability [13]. Solid catalyst can also be divided into two groups, i.e., acid catalysts and base catalysts. It has been reported that acidic heterogeneous catalysts usually show weak activity and react at relatively higher temperature with longer reaction time as compared to basic heterogeneous catalysts [23]. Various types of heterogeneous catalysts for transesterification process have been reported by several researchers. Alkaline and alkaline-earth metal compounds were recently used in biodiesel production to replace conventional homogenous catalysts [5]. Alkaline and alkaline-earth metals supported on other materials such as alumina and silica can be considered as potential catalysts for the transesterification reaction. Zeolites are another group of catalysts studied for the transesterification process [24]. Clay minerals such as hydrotalic, chrysotile, and sepiolite are considered to be the next group. These minerals belong to the group of modest or weakly basic catalysts. In the recent years, heterogeneous base catalysts are gaining popularity for biodiesel production due to their benefits. Yet, there are still a lot more to understand about the natures of these catalysts. Clarifying the nature of the interaction between the support and the catalytically active component in the process is still worthy of further investigation. In this new process, the catalyst is expected to promote the transesterification reaction without experiencing catalyst loss. Yet, it is known that solid base catalysts can be easily poisoned by water or carbon dioxide. Poisoning is a phenomenon responsible for loss of catalytic activity that stems from strong chemisorption of certain substances on the active sites in the reaction system. When solid bases are used in liquid phase organic reactions, the reaction rate may decrease due to the diffusion of reactants and products. One of the main drawbacks of heterogeneous catalysts is lower catalytic activity as compared to that of homogeneous ones such as KOH [6]. Consequently,

Ultrasound-Assisted Biodiesel Production  65 higher reaction temperature and pressure than those in homogeneous processes are required with an excess of methanol. This will certainly result in higher production costs. Therefore, more research endeavor is required to make this technology more economically interesting and environmentally favorable.

2.7 Immiscibility of the Reactants Alcohol and triglycerides as the reactants in the transesterification process are mutually immiscible. This reaction is therefore a mass transfer-limited one due to their immiscibility [25]. The rate of the reaction is very much dependent on the mixing ability of the reactants providing a better contact or interface area. The reason for poor rates of reaction of transesterification process is the mass transfer limitations between the reactants that often create immiscible phases in the reactor [26]. To overcome this problem, researchers have recently introduced new methods to make rigorous mixing in the system. One of the techniques is the use of cavitation which results in conditions characterized by local intense turbulence. These effects are capable of improving the rates of chemical reactions which are limited by mass transfer resistances by increasing the interfacial area between the two phases [27]. Ultrasonic irradiation is one of the approaches that have attracted much attention in this respect to overcome the poor immiscibility of the reactants [28, 29]. Ultrasound is defined as any sound pressure with a frequency above the upper limit of hearing by human. As a matter of fact, the upper limit varies depending on individual. However, about 20 kHz has been established as the upper limit for healthy, young adults. As such, this level usually serves as a lower limit for the definition of an ultrasound. Figure 2.2 shows the approximate frequency ranges of sounds with rough guide of some sources of the sound and common applications [30]. Sonochemical reacting system is an innovative approach in which ultrasonic wave is used to create an oxidative environment by means of cavitation bubbles that are formed during the rarefaction period of the high frequency sound. The creation, propagation, and implosion of cavitation bubbles caused by the sonic waves will cause high local temperature and pressure rises. These rises are considered the responsible mechanism for the acceleration of chemical reactions in a sonochemical system. This leads to the increase in the reaction rate and shortened the time required for complete reaction or to reach equilibrium [31]. In an aqueous system, three different regions have been postulated for the reaction to occur, i.e.,

66  Biodiesel Technology and Applications 20 kHz Sonic

Infrasonic

Hypersonic

Utrasonic

Hz 0

10

102

103

Human hearing

104

105

106

107

108

109

1010

Plastic welding Cleaning

Aircraft Earthquake

Dog Violin

Sonochemistry Bat Dolphin

Chemical analysis Medical diagnostic Non-destructive testing

Figure 2.2  Approximate frequency ranges of sound with rough guide of some sources or applications.

(i) the bulk solution, (ii) the interface between the bulk solution and the cavitation bubbles, and (iii) the gaseous interiors of cavitation bubbles [32].

2.8 Ultrasound-Assisted Biodiesel Production Process 2.8.1 Fundamental Aspects of the Process Lately, the potential of ultrasonic energy in biodiesel production process has attracted the attention of many researchers [2, 27]. Because of the poor immiscibility of a liquid-liquid heterogeneous system, the interaction between alcohol and oil is just limited to the interface of the two phases [9]. Vigorous mechanical stirring is conventionally used to homogenize the reactants to enhance the interfacial area between the two phases [5]. In a conventional stirring method to achieve high yields (>90%), a temperature of 50°C–65°C in presence of catalyst 0.5%–3.0% and the reaction should also be extended to 2 h or more [6]. Kalva et al. [9] concluded that the rate of reaction was influenced by the interfacial contact between the two reacting phases. In addition, the creation of alcohol anions would initiate the methyl ester formation reaction. The use of ultrasonic energy as the source of mixing has become a great interest by two different ways. It will intensively create a virtually homogeneous mixture and at the same time, it can create heating effect to increase the biodiesel production yield. The application of ultrasound in biodiesel production process can be done in several options. It can be directly used to mix the immiscible reactants while they are fed into a continuously flow

Ultrasound-Assisted Biodiesel Production  67 reactor as marked as Option 1 in Figure 2.3. This approach is highly effective as direct contact between the ultrasonic transducer with the reacting mixture is allowed. Then, the desired effects of the ultrasonication are passed directly to the reacting mixture. Ultrasonic cavitation will also result in a localized temperature increase in the phase boundary leading to enhanced reaction rate. However, it also causes unnecessary stress to the ultrasonic system as high temperature could disrupt its normal operation. In addition, metal transducer might also not so stable to the prolonged exposure to acidic condition at high temperature. This is especially true in the case of acidic catalysts used to process high FFA content feedstock [33]. Alternatively, ultrasonic processor can also be used to create microdroplets (~50 microns in diameter) of the alcohol and pre-mix them with the oil to create a homogeneous dispersion to be fed into the reactor as given in Option 2 in Figure 2.3. Ultrasonic irradiation has been demonstrated to Ultrasonicator

Oil

Methanol Option 1

Ultrasonicator

Product Separation

Option 2

Product Separation

Figure 2.3  Different options of ultrasound application for biodiesel production.

68  Biodiesel Technology and Applications be beneficial in accelerating an immiscible reaction system through the generation of cavitation bubbles [2]. The disruption of the phase boundary will then result from the asymmetric collapses of the cavitation bubbles to create micro jets of the liquid. In turn, this will lead to the mixing effect of the system, especially at the interphase. Consequently, the stable emulsion mixture is created to allow accelerated reaction rate in the reactor. It has been reported that the use ultrasound in conjunction with homogeneous catalyst in the biodiesel process can lead to a shorter reaction times of 10–40 min with two to three times lower amount of catalyst needed as compared to those in normal mechanical stirring reactor [34]. The main principle of ultrasound that leads to an efficient mixing of different viscosity reactants is the creation of cavitation bubbles at the interfacial area between molecules of reactants [35]. The molecules would experience a significant vibration which causes the weakening of the attraction force to create gap between liquid. At an ultrasonic wave of >20 kHz, microscopic and macroscopic bubbles will be formed, and they are beneficial in enhancing the mass transfer limitation [36]. The increased vibration of the bubbles at the boundary layer eventually produces acoustic cavitation that increases the mixing rate of the liquid reactants [37, 38]. The cavitation bubbles would then collapse due to vigorous breakdown when exceeding the limitation point. This might generate localized pressure increase to as high as 2,000 atm with the internal temperature approaching 5,000 K, thus initiating the transesterification and esterification reactions [39]. The intense internal heat and pressure generation would extensively provide severe mechanical agitation enticing a homogeneous mixing between oil and alcohol. Thus, the immiscibility and emulsification limitation would be minimized. Overall, the principle of ultrasound acoustic cavitation bubbles is summarized in Figure 2.4. Kalva et al. [9] concluded the desired effects of ultrasound-assisted biodiesel production system based on chemical and physical phenomena. The chemical reaction would be accelerated by transient implosive of the bubbles collapse and a homogenize mixture would formed due to radial motion of the bubbles that can generate micro-turbulence. The collapse of the bubbles can cause transient implosive that would eventually produce H+ and OH− ions that will sequentially accelerate the chemical reaction. Ultimately, the production of biodiesel will technically and economically undergo a massive improvement with the intensification of ultrasound irradiation processing with advanced catalytic system. With recent studies on various types of catalytic system based on the use of ultrasound, a biodiesel process with an accelerated reaction rate is foreseeable in the near future [36, 40].

Ultrasound-Assisted Biodiesel Production  69 Ultrasonication >20kHz

-Shockwaves -Microjets -4,000++ K hot spots -1,000++ atm Emulsified mixture

Bubble Formation

Bubble Growth

Critical Bubble Bubble Size Implosion Transesterification reaction

Alcohol Triglyceride

Fatty acid methyl esters

Figure 2.4  Principle of ultrasound-induced acoustic cavitation bubbles.

2.8.2 Homogeneously Catalyzed Ultrasound-Assisted System Studies on ultrasound-assisted biodiesel production process started with the application of homogeneous catalysis system. Both acid and base homogeneous catalysts have been used in previous works that are tabulated in Table 2.1. Sulfuric acid is the most often used acid homogeneous catalyst in homogeneous biodiesel production [46]. It is highly active during the reaction and gives FAME results of up to 99% [41, 42]. In conventional mechanical stirring method, acid homogeneous catalyst is 4,000 times slower than base homogeneous catalyst [47]. However, it is highly beneficial in achieving high FAME yield production from high FFA feedstock. Acid catalyst is capable of handling FFA and triglycerides by conducting simultaneous esterification and transesterification reactions [46]. Thus, high FAME yield with high purity product is expected to be produced. This is main attributed to milder reaction conditions needed to achieve significantly high reaction rates. However, the resistance of the ultrasonic transducer that has prolonged direct contact with the acidic medium could be the drawback of the ultrasound-assisted process. Mostly, basic homogeneous catalytic processes were carried out by using alkaline metal hydroxides [42, 44]. The transesterification reaction could occur at a sufficiently fast rate and the FAME yield might achieve nearly 100% [42]. Alkaline earth metal hydroxides are also available at low cost. However, they are also sensitive to the presence of FFA in feedstock. Saponification reaction would take place and impedes the formation

60

9:1

Soybean oil

Pottasium hydroxide, KOH

30–80

Pottasium hydroxide, KOH

25

4:1–12:1 (methanol and ethanol)

Rapeseed oil

p-toluenesulfonic acid

3:1–9:1 (Methanol)

60

Silybum marianum oil

FFA from Oreochromis niloticus

Sulfuric acid, H2SO4

9:1 (Methanol)

T (°C)

45

Soybean oil

Sulfuric acid, H2SO4

Alcohol to oil ratio

3.3:1 (Methanol)

Feedstock

Catalyst

1

0.25–2

1

1

1

Wcat (%)

Reaction conditions

60

5–70

180

90

60

Time (min)

Table 2.1  Performance of ultrasound-assisted homogeneous biodiesel production systems.

24

40

20

40

24

Frequency (kHz)

99

96

12

98

90

Biodiesel yield (%)

(Continued)

[41]

[44]

[43]

[42]

[41]

Reference

70  Biodiesel Technology and Applications

Feedstock

Soybean oil

Peanut oil

Fish oil

Catalyst

Sodium hydroxide, NaOH

NaOCH3

C2H5ONa

6:1 (ethanol)

3:1-9:1 (Methanol)

3:1–9:1 (Methanol)

Alcohol to oil ratio

20–60

25

29

T (°C)

1

1

1

Wcat (%)

Reaction conditions

30

60

30

Time (min)

20

20

40

Frequency (kHz)

Table 2.1  Performance of ultrasound-assisted homogeneous biodiesel production systems. (Continued)

>98

90

100

Biodiesel yield (%)

[45]

[28]

[42]

Reference

Ultrasound-Assisted Biodiesel Production  71

72  Biodiesel Technology and Applications of ester. Thus, the activity of the catalyst might decrease and poor reaction yield will result. Besides alkaline earth metal hydroxides, some other catalysts have also been reported as base homogeneous catalysts such as NaOCH3 and C2H5ONa [28, 45]. The use of these catalysts usually showed tremendous reaction yields of up to 98%. Unfortunately, the use of homogeneous catalyst has many drawbacks especially with regards to the product quality problem and environmental concerns. It also requires an additional complicated product separation unit to obtain high purity product. To avoid such problem, another alternative has been explored in which heterogeneous catalysts would be the best candidates to replace the role of homogeneous catalysts in biodiesel production.

2.8.3 Heterogeneously Catalyzed Ultrasound-Assisted System 2.8.3.1 Heterogeneously Acid Catalyzed System Some works focusing investigating the potential of solid acid catalyst in an ultrasound-assisted biodiesel production are tabulated in Table 2.2. Heteropolyacid, i.e., tungstophosporic acid (TPA) was used by Badday et al. [33, 37, 48] to create acidic sites in different kinds of support including gamma alumina, cesium, and activated carbon. The use of 25% TPA loading in gamma alumina resulted in the FAME yield of about 64.3%. After the reaction conditions were mathematically optimized (60% ultrasonic amplitude at 20 kHz, a methanol:oil ratio of 19:1, 65oC, 60 min), the FAME yield successfully increased to 84%. Higher TPA loadings (above 25%) reduced the FAME yield and it was attributed to partial blockage of catalytic pores by the acidic component that eventually reduced the accessibility of reactants into pore sites. Small leaching of TPA was unfortunately reported owing to the partial dissolution of the catalyst in the polar substances in the mixture and it was accelerated by the ultrasonic effect during the reaction. Significantly higher yield was reported by Maneechakr et al. [49] with higher ratio of alcohol to oil. Next, a heteropolyacid-doped cesium (Cs) was used in the ultrasound-assisted biodiesel production [37]. The effect of different Cs exchange levels was investigated with the highest FAME yield obtained of about 81.3%. The reaction was reported to be insensitive to the addition of FFA as the acid sites in the catalyst dominantly converted FFA directly to FAME. However, high content of FFA caused the reduction of FAME yield as water that was produced from the esterification of FFA could also allow acid hydrolysis

5:1–25:1

Jathropa oil

Jathropa oil

Waste cooking oil

Oleaginous scenedesmus sp.

Heteropoly acid supported on alumina

Caesium doped heteropoly acid

Sulfonated carbon

Tungstated zirconia (WO3/ ZrO2)

30:1–60:1

20:1–40:1

5:1–25:1

20:1

Jathropa oil

Heteropoly acid supported on activated carbon

Alcohol to oil ratio

Feedstock

Catalyst

40-60

50-150

65

65

56

T (°C)

2–4

5–15

2.5–4.5

2.5–4.5

4

Wcat (%)

Reaction conditions

20

2–14

10–50

10–50

40–60

Time (min)

22.5

25

20

20

20

Frequency (kHz)

Table 2.2  Ultrasound-assisted biodiesel production processes catalyzed by heterogeneous acid catalyst.

71%

90.8

81.3

64.3-84

87.33

Biodiesel yield (%)

[50]

[49]

[37]

[48]

[33]

Reference

Ultrasound-Assisted Biodiesel Production  73

74  Biodiesel Technology and Applications of the ester. High porosity also caused the catalyst to become unstable and eventually deactivated the catalyst. Maneechakr et al. [49] attempted the use of carbon as the support for acid heterogeneous catalyst in an ultrasound-assisted biodiesel production. The carbon was previously sulfonated by contacting with H2SO4 and it resulted in FAME yields of up to 90.8% under optimum conditions. The sulfonated catalyst was very active, and it showed low activation energy of 11.64 kJ/mol. However, the catalyst showed a significant reduction in FAME yield after being used in successive reactions (12 cycles) without regeneration with H2SO4. The reduction might due to the deactivation caused by the deposition of polymerized products and appreciable acid loss that might occur during the reaction. The disappearance of Na and K elements after the fourth cycle was also reported. A successful work toward activity improvement of phosphotangestic acid as the active catalytic component has been demonstrated by Nikseresht et al. [51]. Guldhe et al. [50] highlighted the role of tungstated zirconia in producing biodiesel from Oleaginous scenedesmus sp oil. The extraction of lipid was carried out in a single step together with transesterification to biodiesel under ultrasound system. In such system, ultrasonic effect was used to extract lipid and a catalyst was used for converting lipid to FAME. The use of acid catalyst often subjects to some difficulties in which the acid strength could affect the activity of the catalyst and it was unlikely to create a uniform porous catalyst [46]. As such, another alternative especially basic heterogeneous catalyst is worth investigation for use to replace acidic heterogeneous catalyst for biodiesel production.

2.8.3.2 Heterogeneous-Based Catalyzed Ultrasound-Assisted System Recent biodiesel research works utilizing ultrasound-assisted systems catalyzed by various heterogeneous base catalysts are tabulated in Table 2.3. In their works, Mootabadi et al. [52] and Chen et al. [54] highlighted the effectiveness of oxides of alkaline earth metals in converting palm oil to biodiesel. CaO showed the highest activity with yields of up to 95% in 1 h. Clearly, the alcohol to oil ratio requirement was lower than those commonly reported for acid-catalyzed biodiesel production. Heterogeneous base catalysts have also shown their applicability for biodiesel production with a wide range of feedstock. These include rarely found feedstock such as Silybum marianum oil [55] and sesame oil (Sesamum indicum L.) [56]. Malani et al. [40] even investigated mixed non-edible oil. In the study on biodiesel production from Silybum marianum oil, a series of TiO2 doped C4H4O6HK catalysts differed by the catalyst preparation

8:1–18:1

4:1–8:1

Used cooking oil

Palm oil

Silybum marianum oil

Waste cooking oil

Sesame (Sesamum indicum L.) oil

Calcium diglyceroxide

CaO

TiO2 doped with C4H4O6HK

Commercial potassium and sodium phosphate

Barium hydroxide

4.5:1–7.5:1

3:1–15:1

6:1–14:1

3:1-15:1

Palm oil

CaO, SrO, BaO

Alcohol to oil ratio

Feedstock

Catalyst

25–35

30–60

40–70

60

45–65

65

T (°C)

1–2

1–4

1–9

3–10

0.5–1.25

3

Wcat (%)

Reaction condition

20–40

0–120

10-40

60–180

0–40

60

Time (min)

20

50

40

20

20

20

Frequency (kHz)

98.6

92.0

90.1

92.7

93.5

95.0

Biodiesel yield (%)

Table 2.3  Performance of ultrasound-assisted heterogeneous base-catalyzed processes for biodiesel production.

(Continued)

[56]

[20]

[55]

[54]

[53]

[52]

Reference

Ultrasound-Assisted Biodiesel Production  75

4:1–12:1

5:1–7:1

Used cooking oil

Jatropha and soybean oil

Coal fly ash

Magnetic (Na2SiO3@ Fe3O4/C)

Alcohol to oil ratio

Feedstock

Catalyst

48–8

70

T (°C)

1–9

3–11

Wcat (%)

Reaction condition

20–100

0.5–2.5

Time (min)

20–25

20

Frequency (kHz)

Soybean: 97.9 Jathropa: 94.7

95.6

Biodiesel yield (%)

[58]

[57]

Reference

Table 2.3  Performance of ultrasound-assisted heterogeneous base-catalyzed processes for biodiesel production. (Continued)

76  Biodiesel Technology and Applications

Ultrasound-Assisted Biodiesel Production  77 procedure were investigated [55]. In this study, TiO2 impregnated with potassium bitartrate and calcined for 6 h at a temperature of 600°C showed the highest activity by producing 90.1% of biodiesel yield. Barium hydroxide was used in a similar reaction system to convert sesame oil into biodiesel [56]. In the optimization study performed using an artificial neural network (ANN) approach, it was found that the catalyst loading was the most influential parameter that significantly determined the FAME yield. The maximum FAME yield recorded was 98.6%. Pukale et al. [20] and Gupta et al. [53] investigated the production of biodiesel with waste cooking oil as the feedstock and catalyzed by commercial PO4 and calcium diglyceroxide, respectively. By using various commercial PO4 catalysts doped with alkaline metals like potassium and sodium, waste cooking oil was successfully converted to biodiesel with K3PO4 demonstrated the best catalytic performance. The high catalytic activity was retained until the fourth cycle and it only started to drop in the fifth to the eighth cycles, observed as the gradual reduction in the FAME yield to 65%. They also demonstrated significant leaching of the catalyst during the reaction. Meanwhile, the use of calcium diglyceroxide was also beneficial in biodiesel production with a maximum yield was 93.5% using an ultrasound-assisted system [53]. However, the catalyst also experienced a severe leaching problem and the FAME yield sharply reduced to 50.5% in the third cycle. This might due to the partial solubility of calcium diglyceroxide in glycerol-methanol mixture in the successive reaction cycles. Heterogeneous base catalysts have also been prepared using coal fly ash as reported by Xiang et al. [57]. With nowadays requirement for the advanced catalysis system for biodiesel production, such a material could potentially conduct good transesterification reaction with low quality feedstock such as used cooking oil. Coal fly ash possibly contains some amount of silicon dioxide, calcium oxide and magnesium oxide. The optimal FAME yield could achieve 95.57% under the right process conditions. Excellent reusability potential was also demonstrated by the catalyst in which it could withstand up to eight reaction cycles under ultrasonic condition with only minimal reduction in the catalytic activity. Zhang et al. [58] came up with a unique heterogeneous catalysis system by combining ultrasound with magnetic stirring. Ultrasound served to create emulsified mixture between the reactants while the conventional stirring’s role was to ensure the emulsified mixture was distributed to the whole reacting volume. The removal of the catalyst was achieved by means of magnetic method. Soybean oil and Jathropa curcas oils were tested and both feedstocks demonstrated high FAME yields of 97.9% and 94.7%, respectively. The combination of magnetic stirring and ultrasound

78  Biodiesel Technology and Applications successfully improved the catalytic activity and prevented the reduction in the catalytic activity after several successive reaction cycles.

2.8.3.3 Influence of Reaction Parameters In an ultrasound-assisted system, the FAME yield can be influenced by a few reaction parameters such as the ratio of alcohol to oil, reaction time, reaction temperature, catalyst amount, and ultrasonic amplitude. These parameters should be taken into consideration to run the reaction at its optimum conditions to obtain highest possible FAME yield. Based on mechanism of transesterification reaction, alkoxide ion produced from alcohol is required to initiate the reaction. Lower alcohols (methanol, ethanol, etc.) are usually preferred for biodiesel production [59]. The alcohol amount used should be stoichiometrically higher than oil to push the equilibrium forward to form more FAME as the oil transesterification reaction is in fact a reversible reaction [20, 53]. In excess alcohol condition, adequate production of alkoxide ion is ensured and high reaction rate will be achieved [55]. However, higher amount of alcohol might significantly dilute the product leading to an initiation of reversed reaction to decrease the FAME yield [20]. In this respect, intensified reaction with the use of ultrasound could lower the alcohol to oil requirement to the benefit of the high biodiesel yield. Reaction temperature is another important factor influencing biodiesel production. In an ultrasound-assisted system, only low reaction temperature is needed as the cavitation effect will also produce internal heating effect during the reaction. An increase in the reaction temperature would facilitate the solubility and miscibility of oil in alcohol and increase the diffusivity of three-phase reaction mixture (oil, alcohol, and catalyst) [20, 53, 55]. Besides, it also increases the kinetic energy of molecules that will significantly increase the collision between reactant molecules hence increasing the reaction yield [53]. However, higher reaction temperature also leads to the supersaturated formation of vaporized alcohol bubbles [20]. It causes cushioning of the collapse of bubbles resulting in low implosion intensity and eventually decreases the mass transfer [53, 60]. Basically, ultrasound-assisted system effectively increases the rate of biodiesel production through cavitation effect; hence, only short reaction time is needed to achieve high reaction yield. Additional time is needed to ensure the reversible reaction can achieve its equilibrium. In the first 10 min, the reaction was observed to start with slow reaction rate due to inadequate agitation effect and reactant mixture was not homogeneously mixed yet [55]. Thus, sufficient time was required to complete the conversion

Ultrasound-Assisted Biodiesel Production  79 of triglycerides to yield FAME. However, the reaction needed is usually significantly shorter than that required by conventionally stirred reactor system. In a biodiesel production reactor system, the amount of catalyst used in biodiesel production should be correctly determined. The ideal amount of catalyst might result in high FAME yield and minimizes wastage of pricy catalyst. At the same time, it contributed to lower impurity level that could be possibly introduced into the biodiesel product. Takase et al. [44] highlighted that less amount of catalyst would beneficially increase the FAME yield while excess of catalyst might cause more saponification reaction to occur to form excessive formation of soap. In addition, higher amount of catalyst often leads to the formation of viscous reactant mixture that requires higher energy to provide adequate stirring effect. Besides, it might also give a negative impact of energy dissipation due to scattering on sound wave [53]. With the intensified reaction rate made possible with the use of ultrasound, same level of biodiesel yield will be achievable with significantly less amount of catalyst. The impact will be significant on the perspectives of process economy, safety, and product quality.

2.9 Conclusions Biodiesel is the most potential biofuel to replace petroleum diesel. Chemically, it is made up of fatty acid methyl esters that are derived mainly from many vegetable oils through either a transesterification or an esterification reaction with alcohols, particularly methanol. Slow reaction biodiesel production process is associated with rather small interfacial area between the two immiscible reactants. Heterogeneous catalysts are greener alternatives to conventionally homogeneous ones but they are often subject to low specific surface area for sufficient interaction with reactants and poor internal mass transfer, leading to poor rate of reaction. Ultrasoundassisted biodiesel production can be potentially used to enhance the transesterification and/or esterification reactions with aid of advanced heterogeneous catalytic system. With the cavitation effect provided by ultrasonic irradiation, the emulsification and mass transfer limitation between the two immiscibility reactants could be effectively minimized. Improved internal mass transfer and hot spots generated during the ultrasonication will allow high methyl ester to be made possible under milder process conditions. Hence, the transesterification reaction might reach its equilibrium in shorter reaction time while lower catalyst loading and alcohol to oil ratio are needed. Many aspects of this new process are yet to be fully

80  Biodiesel Technology and Applications investigated such as behavior of the ultrasonic-mediated process, the roles of ultrasound on the reactants and the catalysts, effects on biodiesel quality, optimization of the reaction based on different aspects, and also the kinetic modeling of the reaction. Influence of ultrasonication to the reaction in terms of reaction temperature requirement, product separation and purification, and methyl ester quality also deserves further research attention. It is also necessary to evaluate the biodiesel quality parameters to make sure that ultrasonic cavitations have no adverse effect on the biofuel quality to make it not suitable engine use.

Acknowledgement This oleochemical research work is made possible by a Fundamental Research Grant Scheme (6071366) provided by the Ministry of Education of Malaysia and a Research University grant (8014059) provided by Universiti Sains Malaysia.

References 1. Rezania, S., Oryani, B., Park, J., Hashemi, B., Cho, J., Review on transesterification of non-edible sources for biodiesel production with a focus on economic aspects, fuel properties and by-product applications. Energ. Conver. Manag., 201, article ID 112155, 2019. 2. Santos, F.FP., Rodrigues, S., Fernandes, F.A.N., Optimization of the production of biodiesel from soybean oil by ultrasound assisted methanolysis. Fuel Proc. Technol., 90, 312-316, 2009. 3. Tan, K.T., Lee, K.T., Mohamed, A.R., Production of FAME by palm oil transesterification via supercritical methanol technology. Biomass Bioenerg, 33, 1096-1099, 2009. 4. Trakarnpruk, W., Porntangjitlikit, S., Palm oil biodiesel synthesized with potassium loaded calcined hydrotalcite and effect of biodiesel blend on elastomer properties. Renew. Energ., 33, 1558-1563, 2008. 5. Arzamendi, G., Arguiñarena, E., Campo, I., Zabala, S., Gandía, L.M., Alkaline and alkaline-earth metals compounds as catalysts for the methanolysis of sunflower oil. Catal. Today, 133-135, 305-313, 2008. 6. Kawashima, A., Matsubara, K., Honda, K., Acceleration of catalytic activity of calcium oxide for biodiesel production. Bioresour. Technol., 100, 696-700, 2009.

Ultrasound-Assisted Biodiesel Production  81 7. Monteiro, M.R., Ambrozin, A.R.P., Lião, L.M., Ferreira, A.G., Critical review on analytical methods for biodiesel characterization. Talanta, 77, 593-605, 2008. 8. Abdullah, A. Z., Razali, N., and Lee, K. T., Optimization of mesoporous K/SBA-15 catalyzed transesterification of palm oil using response surface methodology. Fuel Proc. Technol. 90, 958-964, 2009. 9. Kalva, A., Sivasankar, T., Moholkar, V.S., Physical mechanism of ultrasound-assisted synthesis of biodiesel. Ind. Eng. Chem. Res., 48, 534-544, 2009. 10. Hanh, H.D., Dong, N.T., Okitsu, K., Maeda, Y., Nishimura, R., Effects of molar ratio, catalyst concentration and temperature on transesterification of triolein with ethanol under ultrasonic irradiation. J. Japan Petr. Inst., 50, 195199, 2007. 11. Abdullah, A. Z., Razali, N., Mootabadi, H., and Salamatinia, B., Critical technical areas for future improvement in biodiesel technologies. Environ. Res. Lett., 2, 1-5, 2007. 12. Tan, S.X., Lim, S., Ong, H.C., Pang, Y.L., State of the art review on development of ultrasound-assisted catalytic transesterification process for biodiesel production. Fuel, 235, 886-907, 2019. 13. Liu, Y., Xin, H.I., Yan, Y.J., Physicochemical properties of stillingia oil: Feasibility for biodiesel production by enzyme transesterification. Ind. Crops Prod., 30, 431-436, 2009. 14. Jeong, G.T., Yang, H.S., Park, D.H., Optimization of transesterification of animal fat ester using response surface methodology. Bioresour. Technol., 100, 25-30, 2008. 15. Sakai, T., Kawashima, A., Koshikawa, T., Economic assessment of batch biodiesel production processes using homogeneous and heterogeneous alkali catalysts. Bioresour. Technol., 100, 3268-3276, 2009. 16. Abukhadra, M.R., Salam, M.A., Ibrahim, S.M., Insight into the catalytic conversion of palm oil into biodiesel using Na+/K+ trapped muscovite/phillipsite composite as a novel catalyst: Effect of ultrasonic irradiation and mechanism. Renew. Sust. Energ. Rev., 115, article ID 109346, 2019. 17. Wong, K.Y., Ng, J.H., Chong, C.T., Lam, S.S., Chong, W.T., Biodiesel process intensification through catalytic enhancement and emerging reactor designs: A critical review. Renew. Sust. Energ. Rev., 116, article ID 109399, 2019. 18. Ma, F., Hanna, M.A., Biodiesel production: A review. Bioresour. Technol., 70, 1-15, 1999. 19. Meher, L.C., Sagar, V., D., Naik, S.N., Technical aspects of biodiesel production by transesterification-A review. Renew. Sust. Energ. Rev., 10, 248-268, 2006. 20. Pukale, D.D., Maddikeri, G.L., Gogate, P.R., Pandit, A.B., Pratap, A.P., Ultrasound assisted transesterification of waste cooking oil using heterogeneous solid catalyst. Ultrason. Sonochem., 22, 278-286, 2015.

82  Biodiesel Technology and Applications 21. Kojima, Y., Takai, S., Transesterification of vegetable oil with methanol using solid base catalyst of calcium oxide under ultrasonication. Chem. Eng. Proc., 136, 101-106, 2019. 22. Dossin, T.F., Reyniers, M.F., Marin, G.B., Kinetics of heterogeneously MgOcatalyzed transesterification. Appl. Catal. B Environ., 62, 35-45, 2006. 23. Xie, W., Peng, H., Chen, L., Transesterification of soybean oil catalyzed by potassium loaded on alumina as a solid-base catalyst. Appl. Catal. A Gen., 300, 67-74, 2006. 24. Albuquerque, M.C.G., Cavalcante, C.L., Torres, A.E.B., Azevedo, D.C.S., Parente, E.J.S., Transesterification of castor oil using ethanol: Effect of water removal by adsorption onto zeolite 3A. Energ. Fuel, 23, 1136-1138, 2009. 25. Cintas, P., Mantegna, S., Gaudino, E. C., Cravotto, G., A new pilot flow reactor for high-intensity ultrasound irradiation. Application to the synthesis of biodiesel. Ultrason. Sonochem., 17, 985-989, 2010. 26. Kelkar, M.A., Gogate, P.R., Pandit, A.B., Intensification of esterification of acids for synthesis of biodiesel using acoustic and hydrodynamic cavitation. Ultrason. Sonochem., 15, 188-194, 2008. 27. Deshmane, V.G., Gogate, P.R., Pandit, A.B., Ultrasound-assisted synthesis of biodiesel from palm fatty acid distillate. Ind. Eng. Chem. Res., 48, 7923-7927, 2009. 28. Fan, X., Wang, X., Chen, F., Ultrasonically assisted production of biodiesel from crude cottonseed oil. Int. J. Green Energ., 7, 117-127, 2010. 29. Hingu, S.M., Gogate, P.R., Rathod, V.K., Synthesis of biodiesel from waste cooking oil using sonochemical reactors. Ultrason. Sonochem., 17, 827-832, 2010. 30. Novelline, R., Squire’s Fundamentals of Radiology, 5th/ed. Harvard University Press, 1997. 31. Ghodbane, H., Hamdaoui, O., Intensification of sonochemical decolorization of anthraquinonic dye Acid Blue 25 using carbon tetrachloride. Ultrason. Sonochem., 16, 455-461, 2009. 32. Wongwuttanasatian, T., Jookjantra, K., Effect of dual-frequency pulsed ultrasonic excitation and catalyst size for biodiesel production. Renew. Energ., 152, 1220-1226, 2020. 33. Badday, A.S., Abdullah, A.Z., Lee, K.T., Transesterification of crude Jatropha oil by activated carbon-supported heteropolyacid catalyst in an ultrasound-assisted reactor system. Renew. Energ., 62, 10-17, 2014. 34. Thanh, L.T., Okitsu, K., Sadanaga, Y., Takenaka, N., Maeda, Y., Bandow, H., Ultrasound-assisted production of biodiesel fuel from vegetable oils in a small scale circulation process. Bioresour. Technol., 101, 639-645, 2010. 35. Parkar, P.A., Choudhary, H.A., Moholkar, V.S., Mechanistic and kinetic investigations in ultrasound assisted acid catalyzed biodiesel synthesis. Chem. Eng. J., 187, 248-260, 2012. 36. Murillo, G., Ali, S.S., Sun, J., Yan, Y., Fantozzi, F., Ultrasonic emulsification assisted immobilized Burkholderia cepacia lipase catalyzed transesterification

Ultrasound-Assisted Biodiesel Production  83 of soybean oil for biodiesel production in a novel reactor design. Renew. Energ., 135, 1025-1034, 2019. 37. Badday, A.S., Abdullah, A.Z., Lee, K.T., Ultrasound-assisted transesterification of crude Jatropha oil using cesium doped heteropolyacid catalyst: Interactions between process variables. Energ., 60, 283-291, 2013. 38. Quah, R.V., Tan, Y.H., Mubarak, N.M., Khalid, M., Nolasco-Hipolito, C. An overview of biodiesel production using recyclable biomass and non-biomass derived magnetic catalysts. J. Environ. Chem. Eng., 7(4), article ID 103219, 2019. 39. Zhao, S., Niu, S., Yu, H., Ning, Y., Han, K., Experimental investigation on biodiesel production through transesterification promoted by the La-dolomite catalyst. Fuel, 257, article ID 116092, 2019. 40. Malani, R.S., Shinde, V., Ayachit, S., Goyal, A., Moholkar, V.S., Ultrasoundassisted biodiesel production using heterogeneous base catalyst and mixed non-edible oils. Ultrason. Sonochem., 52, 232-243, 2019. 41. Guo, W., Li, H., Ji, G., Zhang, G., Ultrasound-assisted production of biodiesel from soybean oil using Brønsted acidic ionic liquid as catalyst. Biores. Technol., 125, 332-334, 2012. 42. Santos, F.F.P., Malveira, J.Q., Cruz, M.G.A., Fernandes, F.A.N., Production of biodiesel by ultrasound assisted esterification of Oreochromis niloticus oil. Fuel, 89, 275-279, 2010. 43. Lifka, J., Ondruschka, B., Influence of mass transfer on the production of biodiesel. Chem. Eng. Technol., 27, 1156-1159, 2004. 44. Takase, M., Feng, W., Wang, W., Gu, X., Zhu, Y., Li, T., Yang, L., Wu, X., Silybum marianum oil as a new potential non-edible feedstock for biodiesel: A comparison of its production using conventional and ultrasonic assisted method. Fuel Proc. Technol., 123, 19-26, 2014. 45. Armenta, R.E., Vinatoru, M., Burja, A.M., Kralovec, J.A., Barrow, C.J., Transesterification of fish oil to produce fatty acid ethyl esters using ultrasonic energy. JAOCS, 84, 1045-1052, 2007. 46. Veljković, V.B., Avramović, J.M., Stamenković, O.S., Biodiesel production by ultrasound-assisted transesterification: State of the art and the perspectives. Renew. Sust. Energ. Rev., 16, 1193-1209, 2012. 47. Baêsso, R.M., Costa-Felix, R.P.B., Miloro, P., Zeqiri, B., Ultrasonic parameter measurement as a means of assessing the quality of biodiesel production. Fuel, 241, 155-163, 2019. 48. Badday, A.S., Abdullah, A.Z., Lee, K.T., Ultrasound-assisted transesterification of crude Jatropha oil using alumina-supported heteropolyacid catalyst. Appl. Energ., 105, 380-388, 2013. 49. Maneechakr, P., Samerjit, J., Uppakarnrod, S., Karnjanakom, S., Experimental design and kinetic study of ultrasonic assisted transesterification of waste cooking oil over sulfonated carbon catalyst derived from cyclodextrin. J. Ind. Eng. Chem., 32, 128-136, 2015.

84  Biodiesel Technology and Applications 50. Guldhe, A., Singh, B., Rawat, I., Bux, F., Synthesis of biodiesel from Scenedesmus sp. by microwave and ultrasound assisted in situ transesterification using tungstated zirconia as a solid acid catalyst. Chem. Eng. Res. Des., 92, 1503-1511, 2014. 51. Nikseresht, A., Daniyali, A., Ali-Mohammadi, M., Afzalinia, A., Mirzaie, A., Ultrasound-assisted biodiesel production by a novel composite of Fe(III)based MOF and phosphotangestic acid as efficient and reusable catalyst. Ultrason. Sonochem., 37, 203-207, 2017. 52. Mootabadi, H., Salamatinia, B., Bhatia, S. Abdullah, A.Z., Ultrasonic-assisted biodiesel production process from palm oil using alkaline earth metal oxides as the heterogeneous catalysts. Fuel, 89, 1818-1825, 2010. 53. Gupta, A.R., Yadav, S.V., Rathod, V.K., Enhancement in biodiesel production using waste cooking oil and calcium diglyceroxide as a heterogeneous catalyst in presence of ultrasound. Fuel, 158, 800-806, 2015. 54. Chen, G., Shan, R., Shi, J., Yan, B., Ultrasonic-assisted production of biodiesel from transesterification of palm oil over ostrich eggshell-derived CaO catalysts. Bioresour. Technol., 171, 428-432, 2014. 55. Takase, M., Chen, Y., Liu, H., Zhao, T., Yang, L., Wu, X., Biodiesel production from non-edible Silybum marianum oil using heterogeneous solid base catalyst under ultrasonication. Ultrason. Sonochem., 21, 1752-1762, 2014. 56. Sarve, A., Sonawane, S.S., Varma, M.N., Ultrasound assisted biodiesel production from sesame (Sesamum indicum L.) oil using barium hydroxide as a heterogeneous catalyst: Comparative assessment of prediction abilities between response surface methodology (RSM) and artificial neural network (ANN). Ultrason. Sonochem., 26, 218-228, 2015. 57. Xiang, Y., Wang, L., Jiao, Y., Ultrasound strengthened biodiesel production from waste cooking oil using modified coal fly ash as catalyst. J. Environ. Chem. Eng., 4, 818-824, 2016. 58. Zhang, F., Fang, Z., Wang, Y.T., Biodiesel production directly from oils with high acid value by magnetic Na2SiO3@Fe3O4/C catalyst and ultrasound. Fuel, 150, 370-377, 2015. 59. Singh, A.K., Fernando, S.D., Transesterification of soybean oil using heterogeneous catalysts. Energ. Fuel, 22, 2067-2069, 2008. 60. Choudhury, H.A., Chakma, S., Moholkar, V.S., Mechanistic insight into sonochemical biodiesel synthesis using heterogeneous base catalyst. Ultrason. Sonochem., 21, 169-181, 2014.

3 Application of Catalysts in Biodiesel Production Anilkumar R. Gupta and Virendra K. Rathod* Department of Chemical Engineering, Institute of Chemical Technology, Matunga (E), Mumbai, India

Abstract

Biodiesel has emerged as a potential substitute for petroleum diesel due to its superiority in terms of renewable, biodegradable, and non-toxic nature. It can be produced from a wide range of feedstock using acid and base catalyst or biocatalyst. Catalysts play a vital role in the economical production of biodiesel, as base catalysts are only useful for high-quality feedstock, and low-quality feedstock requires acid pretreatment followed by base catalysis. While using biocatalyst, simultaneous esterification and transesterification reaction can be carried out; however, its high cost is of primary concern. Therefore, this chapter describes different catalysts such as homogeneous acid (e.g., H2SO4 and H3PO4) and base (e.g., KOH and NaOH) catalysts, heterogeneous acid (e.g., sulfated zirconia and alumina, and cation-exchange resins), and base (metal oxide, hydrotalcite, etc.) catalyst, and immobilized biocatalyst (immobilized lipase onto magnetic nanoparticles, resins, etc.) with respect to their synthesis, mechanism, catalytic activity, effect on biodiesel yield or conversion, and their reusability. Keywords:  Biodiesel, heterogeneous catalyst, homogeneous catalyst, biocatalysis, catalyst synthesis, transesterification, esterification

3.1 Introduction Globally, energy demand is continuously increasing due to economic growth and the rapid rise in the population [1]. The liquid fossil fuel is *Corresponding author: [email protected] Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (85–136) © 2021 Scrivener Publishing LLC

85

86  Biodiesel Technology and Applications one of the primary sources used in transportation, agricultural, and industrial sectors to meet their energy demand [2]. However, the burning of fossil fuel emits harmful gases like carbon dioxide, nitrogen oxide, volatile organic compounds, and hydrocarbons, which are responsible for global climate change [3]. Apart from the environmental problem, it also impacts the economic growth of major developing countries because of the dependence on the import of crude oil. Being non-renewable is another disadvantage as it will be exhausted soon. Considering all these points, biofuel, such as biodiesel, may be found as one of the alternatives to liquid fossil fuel. Biodiesel is monoalkyl esters of long-chain fatty acids produce using edible or non-edible oils feedstock and alcohol (methanol or ethanol) or esters (methyl acetate, ethyl acetate, and dimethyl carbonate) in the presence of a catalyst [4–6]. It can be used in the compression ignition (diesel) engine (CIG) without any significant modification. Biodiesel appears as an attractive biofuel because of renewable and biodegradable nature, free from sulfur, aromatic compounds, and other harmful chemicals that harm the environment [7]. It shows a high flash point and cetane number, better lubricating properties, and similarities in physicochemical properties with conventional petroleum diesel [6] and can be used as B100 (pure biodiesel) or as a blend with petroleum diesel (B5–B20) in CIG [8]. Generally, edible vegetable oils such as sunflower oil, palm oil, soybean oil, peanut oil, linseed oil, and coconut oil [9] have been used for the biodiesel production, but, due to continuous rise in the price and competing with the food, raise the concern for the economic feasibility of biodiesel. Non-edible oils (Jatropha curcas, Karanja, Neem, Madhuca indica, Rubber seed oil, etc.), waste cooking oil (WCO), palm fatty acid distillate (PFAD) [10], and animal fats (tallow, chicken fat, and a by-product of fish oil) [9] can be the possible options to reduce the price and eliminate the competition with food. Furthermore, it also helps in solving waste disposal (animal fats and waste oil) problems and reduction in the usage of arable land. In recent times, microalgae become third-generation feedstock due to the effective conversion of sunlight, water, and carbon dioxide into algal biomass. The yield of algae oil per hector is 15 times higher than the secondbest oil, i.e., palm oil [11]. Therefore, there are different options available to select the best available feedstock to reduce the cost and eliminate the competition with food. The different feedstock used by the country has been listed in Table 3.1 [12–14]. Biodiesel production can be carried out either by using a catalytic or non-catalytic process. In the non-catalytic process, transesterification of vegetable oil occurs well above the critical temperature of alcohol (513-K

Catalyst for Biodiesel  87 Table 3.1  Different biodiesel feedstock used by the respective country in the world. Country

Biodiesel feedstock or raw material

Argentina

Soybean, Sunflower, Crambe abyssinica, Jatropha oil, Macrocarpa

Australia

Waste cooking oil, Animal fat

Bangladesh

Pongamia Pinnata, Rubber seed oil

Brazil

Soybean oil, Palm oil, Caster oil

Canada

Canola, Sunflower, Soybean

China

Rapeseed oil, Waste cooking oil

Cuba

Jatropha oil, Neem oil, Moringa oil

Europe

Rapeseed oil, Sunflower oil

Finland

Rapeseed oil, Animal fat

France

Rapeseed oil, Sunflower oil

Germany

Rapeseed oil

Ghana

Palm oil, Coconut oil

Greece

Sunflower oil, Cotton seed oil, Rapeseed oil

India

Jatropha oil

Indonesia

Palm oil

Ireland

Animal tallow, Waste cooking oil

Italy

Rapeseed oil

Japan

Waste cooking oil

Kenya

Castor oil

Malaysia

Palm oil

Mali

Jatropha oil

Mexico

Animal fat, Waste cooking oil

Peru

Palm oil, Jatropha oil

Philippine

Coconut oil, Jatropha oil (Continued)

88  Biodiesel Technology and Applications Table 3.1  Different biodiesel feedstock used by the respective country in the world. (Continued) Country

Biodiesel feedstock or raw material

Russia

Rapeseed oil, Soybean oil, Sunflower oil

South Africa

Canola oil, Sunflower oil, Soybean oil

South Korea

Waste cooking oil

Spain

Sunflower oil

Sweden

Rapeseed oil

Tanzania

Jatropha oil

Thailand

Palm oil, Jatropha oil,

Turkey

Sunflower oil, Rapeseed oil

USA

Soybean oil

Zimbabwe

Jatropha oil

methanol and 514-K ethanol) and pressure of 10–45 MPa [15]. This process is not economically viable as energy consumption is too high due to the requirement of high temperature and pressure. Therefore, catalytic biodiesel synthesis is the most preferred process over the noncatalytic process [16]. In the catalytic process, chemical catalysts or biocatalysts are used to transform the triglyceride (TG) molecule into fatty acid alkyl esters (FAAEs). The chemical catalysts exist in homogeneous (alkali and acid) and heterogeneous (solid base and acid) form. Traditionally, homogeneous catalysts like sodium hydroxide (NaOH) and potassium hydroxide (KOH) are used as it shows high catalytic activity for the transesterification of vegetable oil. However, it generates an ample amount of wastewater during downstream processing, and being corrosive also enhances the cost due to the requirement of costly corrosive resistance equipment [17]. The use of heterogeneous catalysts is an alternative to overcome the problem associated with a homogeneous catalyst with an advantage of recyclability. The use of biocatalysts—free or immobilized form—is another option for the transesterification process. It is beneficial over the chemical catalyst in terms of producing high purity biodiesel, along with being environment-friendly [18]. However, its higher cost is a significant obstacle to employ on a commercial scale. The different catalytic methods used for

Catalyst for Biodiesel  89 Homogeneous Chemical catalysis Heterogeneous Catalytic methods Free enzyme Biocatalysis Immobilized enzyme

Figure 3.1  The different catalytic methods for the biodiesel production.

biodiesel production have been shown in Figure 3.1. This chapter concentrates on trends and current development in the field of catalysis for biodiesel production.

3.2 Homogeneous Catalysis for the Biodiesel Production In general, biodiesel is produced by using a homogeneous catalyst owing to the number of benefits like faster reaction rate, high selectivity, ease of its application, and optimization. The homogeneous catalysts are acids (sulfuric acid, hydrochloric acid, phosphoric acid, aluminium chloride, zinc chloride, etc.) and bases (sodium hydroxide, sodium methoxide, potassium hydroxide, potassium methoxide, etc.). For scaling-up, the homogeneous catalyst is preferred as it requires milder reaction conditions. However, the major drawback of the utilization of homogenous catalysts is that it produces a vast amount of wastewater during the purification of the crude biodiesel. However, studies have been carried out to solve this issue by introducing newer technologies. Some of the selective homogeneous catalysts used for biodiesel production with their reaction conditions have been tabulated in Table 3.2.

3.2.1 Homogeneous Acid Catalyst The low quality and non-edible feedstock content large amounts of free fatty acids (FFAs) (5%–40%) [32] which are not suitable for the base-catalyzed

1.5

2.5 5 4

Madhuca indica oil

Waste oil

Hempseed oil

Soybean oil

WCO assisted

Soybean oil with US assisted

WCO

Karanja oil

Fish oil

WCO with micro reactor assisted

Mixed oil pretreatment

Canola oil with THF as co-solvent

Corn oil with dimethyl ether as co-solvent

KOH

NaOH

KOH

NaOH

CH3ONa

KOH

KOH

KOH

KOH

KOH

H2SO4

AlCl3

p-toluene sulfonic acid

a, Catalyst loading (%); b, Temperature (K); c, Molar ratio; d, Reaction time (min).

1.16

0.75

1.25

1.2

1

0.75

1.0

1.2

0.49

a

Feedstock

Catalyst

353

383

333

335.4

343

333

338

333

MW power 750 W

333

316.4

333

333

b

6:1

24:1

6:1

9.4:1

9:1

9:1

6:1

6:1

6:1

6:1

6.4:1

12.2:1

9:1

c

Reaction conditions

120

1080

60

2

60

120

60

6

3

60

63

90

d

100.0

98.0

96.6

98.26

97.11

88.7

93.2

98.0

97.9

90.0

98.5

95.6

91.76

Yield/Conv. (%)

Table 3.2  List of some selective homogeneous catalyst used for biodiesel production with their reaction conditions.

[31]

[30]

[29]

[28]

[27]

[26]

[25]

[24]

[23]

[22]

[21]

[20]

[19]

Ref.

90  Biodiesel Technology and Applications

Catalyst for Biodiesel  91 transesterification reaction as it leads to soap formation as shown in Scheme 3.1. This formed soap not only reduces the biodiesel yield but also prevents the separation of FAAEs and glycerin and thus affects the quality of the biodiesel [33]. Therefore, acid catalysts sulfuric acid (H2SO4), hydrochloric acid (HCl), phosphoric acid (H3PO4), and sulfonic acid have been used to carry out esterification reaction (Scheme 3.2). Among all these homogeneous acid catalysts, sulfuric acid was reported to give a better result for the conversion of FFAs to biodiesel [34]. In most of the cases, acid catalyst only used as a pre-treatment step to reduce the FFAs content ~1% as acid-catalyzed transesterification reaction is 4,000 times slower than the base and requires a large amount of alcohol [9, 35, 36]. The reason for the slower reaction rate for the acid-catalyzed transesterification reaction as compared to base-catalyzed transesterification reaction has been revealed by Lotero et al. [37] through studying both, i.e., acid and base-catalyzed mechanism. In the case of acid-catalyzed transesterification mechanism (Scheme 3.3), the first protonation of the carbonyl oxygen of TG molecule is taken place by Brønsted acid which is the crucial step for the interaction between TG and catalyst. This initial step increases the electrophilicity of the carbonyl carbon, which becomes more susceptible to the nucleophilic attack of the alcohol. In the final step, O R

O +

OH

C

MOH

R

C

Base catalyst

FFAs

OM

+

Soap

H2O Water

M = Na+, K+, etc.

Scheme 3.1  Soap formation in the presence of free fatty acids with the base catalyst.

O R

O OH +

C

R

H Acid catalyst

FFAs

C FAAEs

OR'

R

OH

C

OH

OH OH

C

R'

R'—OH

O

-H

R R'

H

-H

O R

C

O

H

H OR'

OH

C

Alcohol

O R

H

OH -H2O

R R'

C O

OH

H O

R H

R'

C O

O

H

Scheme 3.2  General esterification reaction mechanism in the presence of an acid catalyst.

92  Biodiesel Technology and Applications + OH

O O (i)

R2

R1

O

H+

O R3

O

O R2

O O

O

(ii)

R2

O

O

R1

O O

ROH

R2

O

OH + R O O R H 1

OH O R2

O

O

+ R O H

R1

O

O O R2

R1

OH

O

OR

+

O

R3

O

R3

O

R3 O

(iii)

R3 O

+ OH O

R1

O

O

R3 O

+ H

R1, R2, R3: Long chain fatty acid; R: Atkyl group of alcohol

Scheme 3.3  Acid-catalyzed transesterification of TG (i) Protonation of carbonyl oxygen by acid catalyst; (ii) Alcohol (ROH) attacks on electrophilic carbon; (iii) Proton migration and formation of product (FAAEs). This mechanism repeated two more times to give finally three moles of product.

intermediate break down with the release of the product (FAAEs) and regeneration of catalyst, i.e., H+ ion. Whereas, the base-catalyzed transesterification reaction takes a more direct pathway in which active species alkoxide ion (OR− act as a strong nucleophile) generated initially and attacked to the carbonyl group to transform TG to FAAEs. Thus, the difference in the formation of electrophilic species in the case of an acid catalyst and nucleophilic species for base catalyst is ultimately responsible for the acid and base-catalyzed transesterification reaction rate. Because of aforesaid reason, the feedstock with high FFAs is subjected two-step process, i.e., esterification followed by transesterification. Bouaid et al. [38] carried out the conversion of crude Jatropha oil into biodiesel, where they employed the two-step process. In the first step, Jatropha oil was subjected to esterification using acid catalyst H2SO4 to reduce the % FFAs content from 9.48% to less than 1%, under the optimum condition

Catalyst for Biodiesel  93 of molar ratio of 20:1, reaction temperature of 333 K, and 5 wt% H2SO4 in 60-min reaction time. In the second step, alkaline catalyzed transesterification of Jatropha oil (FFAs < 1%) was performed and obtained more than 98% biodiesel yield. In another study, crude algal oil (5.3 %FFAs) was converted into biodiesel using a similar approach, i.e., esterification followed by transesterification. In the beginning, acid (H2SO4) esterification was performed to reduce the %FFAs from 5.3 to 95%)

Supercritical transesterification

Progress in Biodiesel Production  235

236  Biodiesel Technology and Applications produce biofuels, power, and value-added chemicals from  biomass. The biorefinery approach is related to current petroleum refinery, and it will exhibit products from petroleum and multiple fuels.

7.9 Summary and Outlook In 2020, there is major controversy as regards electric vehicles and biofuel sustainability. Yet, there are much more limitations to run the entire vehicles and system on electric. Nature is always surviving the energy sources with their optimum utilization. If this attention is right, then yes there is huge demand for biofuel production in coming decades. There is need to commercialize the biodiesel plant or refineries widely. The 2018 biodiesel production in a global world report gives progressive future to commercialize the plant for production of biodiesel in a coming decade. The key challenges for biodiesel production are high FFA with desired level of yield, stability, optimized and flexible production, commercialization of feedstock, and environmental friendly cycle. The worldwide region where huge sources of biodiesel feedstock. The only limitation is to construct a biodiesel plant is to complex integration or combine the various feedstock sources of their region-wise and availability for production of a biodiesel. It will solve major obstacles to resolve the commercialization of a biodiesel plant with effective production for biodiesel economy. There is generation-wise report for biodiesel feedstock that has been reviewed. Feedstock optimization with their location are sustainable for biodiesel refinery. Among the all resources, the major productions are that is going on to produce a biofuel are soybean, Moringa oleifera, jatropha, karanja, KP, and genetically optimized microalgae for feedstock. Additives plays major role to boost the efficiency of a biofuel production for a commercialization. Moringa oleifera is a strong potential to produce complex biodiesel feedstock with others resources because of its antioxidant properties. Transesterification by heterogeneous nanocatalysts or biocatalyst is a potential technique to carry out biofuel from biodiesel plant as per the requirements. Catalytic pyrolysis and microwave-mediated transesterification have strong potential to commercialize the biodiesel plant for biodiesel production. Biorefinery is a commercial process for biodiesel and biogas production systems in order to demonstrate higher valuable products that could additionally modify economically and environmentally sustainability of these biomethods. The utilization of renewable sources in few countries has an authorized funding. For the transport sector, accomplished Renewable Energy

Progress in Biodiesel Production  237 Directive (2009/28/EC) is targeting 20% share of alternative energy consumption in the  year of 2020, European Policy Framework with a subtarget of 10% renewables. The collective effort and commitment of research survey as regards feedstocks and commercialization of technology around the globe toward sustainable energy are expressed in terms of accelerating the biofuel economy.

7.10 Conclusion According to biodiesel production technology world, the latest developments in biodiesel are increasing day by day, and the current status of technology is discussed. The existing edible feedstocks have some limitation as regards crime against humanity. Therefore, major role of feedstock sources is to widely available in rich energy of non-edible sources for commercializing production of biodiesel. Among these, well-known high FFA for desired level of yield and stability of a biodiesel and sustainable advanced generation-based feedstock fulfill the criteria for a biodiesel production. As per availability of a number of multiple feedstock grow up the plant or a biorefinery for biodiesel production. Catalytic pyrolysis and microwavemediated transesterification develops desirable characterized biodiesel for revolutionize the commercialization market. The summarized extracted results shows that the evolutionary future to sustain the biodiesel for future of a fuel to run the global world.

References 1. Chakraborty, R., and Sahu, H., Intensification of Biodiesel Production from Waste Goat Tallow Using Infrared Radiation : Process Evaluation through Response Surface Methodology and Artificial Neural Network, Appl. Energy., 2013. 2. Talebian-kiakalaieh, A., Aishah, N., Amin, S., and Mazaheri, H., A Review on Novel Processes of Biodiesel Production from Waste Cooking Oil, 104, pp. 683–710, 2013. 3. Jakeria, M. R., Fazal, M. A., and Haseeb, A. S. M. A., In Fl Uence of Different Factors on the Stability of Biodiesel: A Review, 30, pp. 154–163, 2014. 4. Tabatabaei, M., Karimi, K., Horváth, I. S., and Kumar, R., Recent Trends in Biodiesel Production, 7, pp. 258–267, 2015. 5. Rico, J. A. P., and Sauer, I. L., A Review of Brazilian Biodiesel Experiences A Review of Brazilian Biodiesel Experiences, Renew. Sustain. Energy Rev., 45(September 2018), pp. 513–529, 2015.

238  Biodiesel Technology and Applications 6. Ž, B., Veljkovi, M. V, Bankovi, I. B., Krsti, I. M., Konstantinovi, S., Ili, S. B., Avramovi, J. M., and Stamenkovi, O. S., Risk, Toxicological and Policy Considerations of Biodiesel Production and Use, 79(July 2016), pp. 222–247, 2017. 7. Sha, I., Manaf, A., Embong, N. H., Norha, S., and Khazaai, M., A Review for Key Challenges of the Development of Biodiesel Industry, 185(November 2018), pp. 508–517, 2019. 8. Dieter, B., European and Global View ☆. 2019. 9. Souza, S. P., and Seabra, J. E. A., Integrated Production of Sugarcane Ethanol and Soybean Biodiesel : Environmental and Economic Implications of Fossil Diesel Displacement, Energy Convers. Manag., 2014. 10. Reshad, A. S., Tiwari, P., and Goud, V. V, Extraction of Oil from Rubber Seeds for Biodiesel Application : Optimization of Parameters, Fuel, (February), 2015. 11. Fernandes, D. M., Sousa, R. M. F., Oliveira, A. De, Morais, S. A. L., Richter, E. M., and Muñoz, R. A. A., Moringa Oleifera : A Potential Source for Production of Biodiesel and Antioxidant Additives, Fuel, 146, pp. 75–80, 2015. 12. Niju, S., Balajii, M., Anushya, C., and Niju, S., A Comprehensive Review on Biodiesel Production Using Moringa Oleifera Oil, Int. J. Green Energy, 16(9), pp. 702–715, 2019. 13. Selvaraj, R., Praveenkumar, R., and Moorthy, I. G., A Comprehensive Review of Biodiesel Production Methods from Various Feedstocks, 7269(November), 2016. 14. Bušić, A., Morzak, G., Belskaya, H., and Ivančić, M., Recent Trends in Biodiesel and Biogas Production, 56(2), 2018. 15. Muanruksa, P., Winterburn, J., and Kaewkannetra, P., Of, MethodsX, 2019. 16. Manuscript, A., Sustainable Energy & Fuels. 2020. 17. Jose, T. K., and Anand, K., Effects of Biodiesel Composition on Its Long Term Storage Stability, Fuel, 177, pp. 190–196, 2016. 18. Nongbe, M. C., Ekou, T., Ekou, L., Benjamin, Y. K., Grognec, E. Le, and Felpin, F., AC SC, Renew. Energy, 2017. 19. Liu, Y., Tu, Q., Knothe, G., and Lu, M., Direct Transesterification of Spent Coffee Grounds for Biodiesel Production, Fuel, 199, pp. 157–161, 2017. 20. Mueanmas, C., Nikhom, R., Petchkaew, A., Iewkittayakorn, J., and Prasertsit, K., Extraction and Esterification of Waste Coffee Grounds Oil as Non-Edible Feedstock for Biodiesel Production, Renew. Energy, 2018. 21. Nabi, G., Sajjad, W., Siddique, R., and Hou, H., HAYATI Journal of Biosciences Biodiesel Production From Algae to Overcome the Energy Crisis : A Review, HAYATI J. Biosci., (November), pp. 1–5, 2017. 22. Jena, U., and Hoekman, S. K., Editorial : Recent Advancements in Algae-toBiofuels Research : Novel Growth Technologies, Conversion Methods, and Assessments of Economic and Environmental Impacts, 5(March), pp. 1–2, 2017.

Progress in Biodiesel Production  239 23. Patel, A., Arora, N., Mehtani, J., Pruthi, V., and Pruthi, P. A., Assessment of Fuel Properties on the Basis of Fatty Acid pro Fi Les of Oleaginous Yeast for Potential Biodiesel Production, Renew. Sustain. Energy Rev., 77(April), pp. 604–616, 2017. 24. Martin, A., Ph, F., Researcher, D. S., and Klitkou, A., Energy Research & Social Science A Fuel Too Far ? Technology, Innovation, and Transition in Failed Biofuel Development in Norway, Chem. Phys. Lett., 23, pp. 125–135, 2017. 25. Yesilyurt, M. K., Arslan, M., and Eryilmaz, T., Application of Response Surface Methodology for the Optimization of Biodiesel Production from Yellow Mustard (Sinapis Alba L.) Seed Oil, Int. J. Green Energy, 00(00), pp. 1–12, 2018. 26. Veinblat, M., Baibikov, V., Katoshevski, D., Wiesman, Z., and Tartakovsky, L., Impact of Various Blends of Linseed Oil-Derived Biodiesel on Combustion and Particle Emissions of a Compression Ignition Engine – A Comparison with Diesel and Soybean Fuels, Energy Convers. Manag., 178(August), pp. 178–189, 2018. 27. Sadaf, S., Iqbal, J., Ullah, I., Nawaz, H., and Nouren, S., Biodiesel Production from Waste Cooking Oil : An e Ffi Cient Technique to Convert Waste into Biodiesel, Sustain. Cities Soc., 41(May), pp. 220–226, 2018. 28. Guil-laynez, J. L., and Guil-guerrero, J. L., Industrial Crops & Products Bioprospecting for Seed Oils in Tropical Areas for Biodiesel Production, Ind. Crop. Prod., 128(June 2018), pp. 504–511, 2019. 29. Hossain, N., Mahlia, T. M. I., and Saidur, R., Biotechnology for Biofuels Latest Development in Microalgae ‑ Biofuel Production with Nano  ‑ Additives, Biotechnol. Biofuels, pp. 1–16, 2019. 30. Valdivia, M., and Galan, J. L., Opinion Biofuels 2020: Biore Fi Neries Based on Lignocellulosic Materials. 2020. 31. Khan, I. U., and Yan, Z., Production and Characterization of Biodiesel Derived from a Novel Source Koelreuteria Paniculata Seed Oil. 2020. 32. Gebremariam, S. N., and Marchetti, J. M., Biodiesel Production Technologies: Review, 2017. 33. Biodiesel, O., Singh, M., Ariani, F., Sitorus, T. B., Ginting, E., and Takano, Y., An Overview of Biodiesel Production and Its Utilization in Diesel Engines. 2018. 34. Ogunkunle, O., and Ahmed, N. A., A Review of Global Current Scenario of Biodiesel Adoption and Combustion in Vehicular Diesel Engines, Energy Reports, 5, pp. 1560–1580, 2019. 35. Karmakar, B., and Halder, G., Progress and Future of Biodiesel Synthesis: Advancements in Oil Extraction and Conversion Technologies, Energy Convers. Manag., 182(September 2018), pp. 307–339, 2019. 36. Eddy, A., Imran, A., Ea, B., Seshan, K., and An, B. G., An Overview of Catalysts in Biomass Pyrolysis for Production of Biofuels. 2020.

240  Biodiesel Technology and Applications 37. Kumar, H., Sarma, A. K., and Kumar, P., A Comprehensive Review on Preparation, Characterization, and Combustion Characteristics of Microemulsion Based Hybrid Biofuels, Renew. Sustain. Energy Rev., 117(February 2019), p. 109498, 2020. 38. Lin, J., and Chen, Y., Production of Biodiesel by Transesterification of Jatropha Oil with Microwave Heating, J. Taiwan Inst. Chem. Eng., 0, pp. 1–8, 2017. 39. Martinez-guerra, E., and Gude, V. G., Energy Aspects of Microalgal Biodiesel Production, 4(2), pp. 347–362, 2016. 40. Gude, V. G., and Martinez-guerra, E., Green Chemistry of MicrowaveEnhanced Biodiesel Production. 41. Montcho Papin, S., Konfo, T. R. Christian, Agbangnan, D. C. Pascal, Sidouhounde Assou and Sohounhloue C. K., Comparative Study of Transesterification Processes for Biodiesel Production. Elixir Appl. Chem., 120, pp. 51235–51242, 2018. 42. Thangaraj, B., Solomon, P. R., Muniyandi, B., Ranganathan, S., and Lin, L., Catalysis in Biodiesel Production — a Review, pp. 1–22, 2018.

8 Biodiesel Production Technologies Moina Athar1* and Sadaf Zaidi2 Department of Petroleum Studies, Z H College of Engineering and Technology, Aligarh Muslim University, Aligarh, India 2 Department of Post Harvest Engineering and Technology, Faculty of Agricultural Sciences, Aligarh Muslim University, Aligarh, India

1

Abstract

During the past few years, biodiesel has emerged as a potential renewable source that could replace current petro-diesel. It is a less polluting, biodegradable, and non-toxic that can be simply produced by a transesterification reaction. Vegetable oils, animal fats, waste oil, and microbial oils are the main feedstocks for the production of biodiesel. The current commercial use of edible and refined oils for the production of biodiesel is not feasible and uneconomical due to the high cost of feedstock and priority as a food source. However, non-edible oils which are low-grade and low cost can be a better option but the presence of a high amount of free fatty acids (FFAs) in these oils has been the main problem for their use as potential feedstocks. This chapter is focused to give an overview of the various feedstocks for the production of biodiesel especially non-edible oils. The benefits and constraints of using homogeneous, heterogeneous, and enzymatic catalysts for transesterification of vegetable oil containing a high amount of FFA are discussed in detail. Toward the end of this chapter, a few of the latest intensification techniques for biodiesel production that are capable to manage the mass transfer restrictions of oil and alcohol phases such as supercritical alcohol method, microwave heating, ultrasonic irradiation, and co-solvent method are discussed. Some other techniques that reduce the biodiesel production cost like in situ transesterification, membrane reactor, reactive distillation, static mixers, micro-channel, and oscillatory flow have also been discussed briefly. Keywords:  Biodiesel feed stock, production methods, catalyst, microwave heating, ultrasonic irradiation, co-solvent method, in situ method, static mixture

*Corresponding author: [email protected] Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (241–266) © 2021 Scrivener Publishing LLC

241

242  Biodiesel Technology and Applications

8.1 Introduction Present crises of fossil fuels, hike in crude oil prices, increased environmental pollution, and environmental awareness have changed the world’s focus on the use of alternative fuels [1]. Biodiesel is one of the most eco-friendly, renewable, and promising alternative for diesel engine [2, 3]. Chemically biodiesel is defined as mono-alkyl esters of long-chain fatty acids (FAs) present in vegetable oils or animal fats [4–9] which on combustion produces fewer pollutants like sulfur, carbon dioxide, particulate matters, carbon monoxide, smoke, and unburned hydrocarbons emissions. Complete combustion takes place due to excess oxygen present in biodiesel which also reduces emission [10, 11]. It can be mixed with petrodiesel in any proportion and can be used in the present diesel engine with no or very few engine modifications. The mixtures are represented by acronyms like B20, which signifies a mixture of 20% biodiesel with petro diesel [12, 13]. Biodiesel provides fuel efficiency, torque, and horsepower similar to standard diesel fuel [14].

8.2 Biodiesel Feedstocks Great varieties of feedstocks can be used for biodiesel production. More than 350 oil containing seeds have the potential for biodiesel production [15]. These feedstocks include both edible and non-edible type of vegetable oils, fats of animals, different waste oils, and microbial oils. Table 8.1 shows Table 8.1  Various types of oil and their sources for the production of biodiesel. Type of oil Vegetable oils

Source of oil Edible

Soya bean, mustard, rice bran, sunflower, cottonseed, olive, peanut, sesame, palm, etc.

Non-edible

Jatropha, mahua, jojoba, neem, karanja, milk bush, rubber seed, nagchampa, castor, petroleum nut, silk cotton tree, tung, etc.

Animal fat

Chicken fat, beef tallow, fish oil, pork lard

Waste oil

Waste frying oil, pit oil

Microbial oil

Fungi, microalgae (chlorellavulg), algae (cyanobacteria)

Biodiesel Production Technologies  243 3% 2%

1%

7% Cost of oil Cost of chemical

12%

Depreciation cost Direct labour cost 75%

Energy cost General overhead cost

Figure 8.1  Cost breakup for biodiesel production [7, 21–23].

the various types of oils and their sources that can be used for the production of biodiesel [16–19]. The availability of this vast range of feedstock is one of the major reasons for producing biodiesel [5, 8, 20]. Low production cost and large production scale are the two main demands which should be fulfilled by any of the feedstocks. The feedstocks present in any region or area depending on the geographical locations, regional climate, conditions of soil, and adopted agricultural methods of that country [15]. It was established from various studies that biodiesel feedstock alone contributes to 75% of the total production cost as depicted in Figure 8.1. Hence, the selection of lowcost feedstock is essential for economical biodiesel production. Figure 8.2 shows the various feedstocks used for the production of biodiesel.

8.2.1 Selection of Feedstocks Triglycerides are the basic component of all types of oils used for biodiesel production. Chemically, they are esters of FAs with glycerol and contain several different types of FAs. As the chemical and physical properties of different FAs differ with each other, so they also affect the various properties of the associated oils and fats. Table 8.2 presents the quantities of FA presents in selected fats and oils. At present, edible oils comprise more than 95% of the main feedstocks for biodiesel production worldwide [16]. However, the utilization of edible oils for biodiesel production is uneconomical and impractical because of its high cost and its priority use as food sources. Thus, low quality [high free FA (FFA)] and low-cost non-edible oil that is not being used in human nutrition could be an option. Plants for non-edible oil seeds are easily grown in lands that are not appropriate

244  Biodiesel Technology and Applications

Soyabean y

Sunflower

Mustard

Rice bran

Cotton seed

Palm seeds

Jatropha

Jajoba

j Karanja

Mahua

Neem

Rubber seeds

Animal fat

Waste frying oil

Algal oil

Figure 8.2  Various types of feedstock for biodiesel production.

for edible oil crops with much lower costs [24]. Growing of these plants can also reduce the amount of CO2 in the atmosphere [25]. Apart from all the above-mentioned advantages, the presence of a high amount of FFA, which leads to high production cost, is the major drawback associated with these low-grade non-edible oils [26]. Jatropha is among the most prospective non-edible source for the production of biodiesel in Central and South America, South-East Asia, Africa, and India. Presently, it is the main feedstock of biodiesel in developing countries like India, where its yearly production is around 15,000 t [27]. Jatropha can be cultivated anywhere like on saline and sandy soil, wastelands, in different climatic conditions, with low or high rainfall without

C(12:0) Lauric acid

–

48.8

0.2

–

–

–

–

–

49.2

Feedstock

Algae

Babassu

Beef Tallow

Borage

Camelina Oil

Canola Oil

Castor

Choice white grease

Coconut

18.5

1.3

–

–

–

–

2.9

17.2

0.6

C(14:0) Myristic acid

9.1

21.6

0.9

3.8

5.0

9.3

24.3

9.7

6.9

C(16:0) Palmitic acid

Table 8.2  Fatty acid profile of fats and oils [34].

–

2.8

–

0.3

–

–

2.1

–

0.2

C(16:1) Palmitoleic acid

2.7

9.0

1.1

1.9

2.2

3.8

22.8

4.0

3.0

C(18:0) Stearic acid

6.5

50.4

93.4

63.9

17.7

17.1

40.2

14.2

75.2

C(18:1) Oleic acid

1.7

12.2

4.0

19.0

18.0

38.7

3.3

1.8

12.4

C(18:2) Linoleic acid

–

1.0

0.6

9.7

37.9

26.1

0.7

–

1.2

C(18:3) Linolenic acid

–

0.5

–

–

9.8

–

0.6

–

–

C(20:1) Gadoleic acid

–

0.3

–

–

4.5

2.5

–

–

–

C(22:1) Erucic acid

(Continued)

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Unknowns

Biodiesel Production Technologies  245

C(12:0) Lauric acid

–

–

–

–

–

–

–

–

–

Feedstock

Coffee

Corn

Cuphea Viscosissima

Evening Primrose

Hemp

Jatropha

Linseed

Mustard

Neem

–

–

–

–

–

–

4.7

–

–

C(14:0) Myristic acid

14.9

2.6

4.4

12.7

5.2

6.0

18.2

12.1

11.0

C(16:0) Palmitic acid

0.1

0.2

–

0.7

–

–

–

0.1

0.5

C(16:1) Palmitoleic acid

Table 8.2  Fatty acid profile of fats and oils [34]. (Continued)

20.6

1.2

3.8

5.5

2.4

1.8

3.5

1.8

3.4

C(18:0) Stearic acid

43.9

20.6

20.7

39.1

13.1

6.6

46.9

27.2

70.0

C(18:1) Oleic acid

17.9

20.6

15.9

41.6

57.1

76.3

22.8

56.2

12.7

C(18:2) Linoleic acid

0.4

13.3

54.6

0.2

20.0

9.0

2.3

1.3

0.8

C(18:3) Linolenic acid

–

10.7

–

–

–

–

–

–

0.1

C(20:1) Gadoleic acid

–

25.6

–

–

–

–

–

–

–

C(22:1) Erucic acid

(Continued)

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Unknowns

246  Biodiesel Technology and Applications

C(12:0) Lauric acid

0.2

–

0.1

–

–

–

0.1

0.1

Feedstock

Palm

Perilla Seed

Poultry Fat

Rice Bran

Soybean

Sunflower

Used cooking oil

Yellow Grease

0.5

0.1

–

–

0.3

1.0

–

0.5

C(14:0) Myristic acid

14.3

11.8

4.2

9.4

12.5

19.6

5.3

43.4

C(16:0) Palmitic acid

1.1

0.4

–

–

–

3.2

0.1

0.1

C(16:1) Palmitoleic acid

Table 8.2  Fatty acid profile of fats and oils [34]. (Continued)

8.0

4.4

3.3

4.1

2.1

7.5

2.2

4.6

C(18:0) Stearic acid

35.6

25.3

63.6

22.0

47.5

36.8

16.6

41.9

C(18:1) Oleic acid

35.0

49.5

27.6

55.3

35.4

28.4

13.7

8.6

C(18:2) Linoleic acid

4.0

7.1

0.2

8.9

1.1

2.0

62.1

0.3

C(18:3) Linolenic acid

–

–

–

–

–

–

–

–

C(20:1) Gadoleic acid

0.2

0.3

–

–

–

0.4

–

–

C(22:1) Erucic acid

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Remaining amount

Unknowns

Biodiesel Production Technologies  247

248  Biodiesel Technology and Applications much care and with minimal efforts. The life cycle of the Jatropha plant is 30–40 years, which eliminates its yearly plantation. Although the oil content of Jatropha depends on the type of species as 40%–60% of oil is present in its seeds and 46%–58% is present in kernels [28]. It is a potential alternative to petro-diesel as it has equivalent properties to diesel, like calorific value, cetane number, and does not require any engine modification [27, 29]. While, its toxicity is a serious problem for the people and animals [30]. Among all the new generation non-edible feedstocks, microalgae are being considered to be the most potential one. Microalgae produce oil in the presence of water, sunlight, and carbon dioxide in a more efficient way than crop plants. As different types of algae contain different amounts of oil so among all the species only a few that contain higher amounts of oil are appropriate for the synthesis of biodiesel. The oil content of some microalgae exceeded significantly the oil yield of some of the best oil-producing crops [31, 32]. Moreover, it can be easily grown anywhere, like in sewage or salty water, and no fertile land is needed and most of all its processing needed less energy than it provides [33].

8.3 Biodiesel Production Technologies Polyunsaturated character, viscous, and low volatile vegetable oils are not suitable for diesel engines for direct use [35]. Refinement of these oils is needed to transform them into quality fuel. The principal methods which enable oils and fats to be used in diesel engines are usually direct use by dilution, micro-emulsion, pyrolysis, and transesterification.

8.3.1 Pyrolysis Pyrolysis is defined as chemical change after applying heat without air or oxygen or by using catalyst resulted in chemical bond breakage and production of different small molecules. The changes during pyrolysis take place at a reaction temperature range from 400°C to 600°C using different vegetable or animal oils, naturally accruing FAs or esters of FAs. Process of thermal breakage of triglycerides yields aromatics, alkenes, alkanes, alkadines, and carboxylic acids, which are fuel components for the diesel engine; however, some undesirable components are also produced due to the absence of air during this process [35–37]. Low heating value, incomplete volatility, and instability of the product are some unwanted properties that often limit the use of biodiesel produced through pyrolysis [38, 39].

Biodiesel Production Technologies  249

8.3.2 Dilution The direct use of vegetable oil in an existing diesel engine is limited by its high viscosity, carbon deposits, FFA contents, gum formation by oxidation and polymerization processes, etc. In such situations, dilution of vegetable oils with diesel fuel, solvents, or ethanol is recommended which reduces its viscosity and density [40]. The use of pure oil in an existing petrodiesel engine is not feasible; instead, a mixture of 20% oil and 80% petro-diesel is recommended [41].

8.3.3 Micro-Emulsion It is another effort toward the viscosity reduction of vegetable oils. The process of biodiesel microemulsion is carried out by the use of petro-diesel, alcohol, vegetable oil, surfactant, and cetane improvers in appropriate proportions. Some low molecular weight alcohols like methanol and ethanol are used as additives for viscosity reduction; high molecular weight alcohols can be utilized as surfactants whereas alkyl nitrates are compounds that are used for improving the cetane number [42]. Micro-emulsion reduces the viscosity, improves cetane rating, and introduces excellent spray quality in the biodiesel.

8.3.4 Transesterification Transesterification is the reaction of oil and alcohol with or without a catalyst to produce esters (biodiesel) and glycerol as a product (Figure 8.3). Since the reaction involved is reversible, an extra volume of alcohol is needed to support the forward reaction and to shift the equilibrium to the product’s side [43]. The transesterification reaction is completed in three steps in which the triglyceride conversion to diglycerides is the first step, followed by the subsequent diglycerides conversion into monoglycerides and then to glycerol, producing one ester molecule from each glyceride at each step (Figure 8.4) [44]. CH2

OCOR1

CH

OCOR2

CH2

OCOR3

Triglyceride

Catalyst +

3CH3OH

CHOH CH2OH

Methanol

Figure 8.3  General transesterification reaction.

R1COOCH3

CH2OH

Glycerol

+

R2COOCH3 R3COOCH3

Methyl esters

250  Biodiesel Technology and Applications Triglyceride + R1OH

Diglyceride + RCOOR1

Diglyceride + R1OH

Monoglyceride + RCOOR1

Monoglyceride + R1OH

Glyceride + RCOOR1

Figure 8.4  General mechanism of the transesterification reaction.

The transesterification reaction is carried out in the presence of acidic, basic, or enzymatic catalysts. It can be homogeneously or heterogeneously catalyzed, based upon the catalyst solubility in the reactants. The reaction can be in a single step (by acid or base catalyst) or two steps (acid/base), based on the amount of FFA content of the oil.

8.3.4.1 Homogeneously Catalyzed Transesterification Processes Homogeneous catalysts can be basic or acidic type and their selection mainly depends upon the FFA and water content of the oil.

8.3.4.1.1 Alkaline Catalyst

The alkaline catalysts are used for oils containing a low percentage of FFA (less than 5 wt.%) [45]. Thus, the most common homogeneous alkaline catalysts that have been used and successfully commercialized for production of biodiesel are potassium hydroxide (KOH), sodium hydroxide (NaOH), and sodium methoxide (CH3ONa) [3, 5, 43, 46–48]. Mostly sodium hydroxide and potassium hydroxide are used by biodiesel catalysts. Although the conversions in the presence of sodium and potassium methoxides are better, they are not very frequently used as they are costly. Transesterification by the alkaline catalyst is the fastest and economical method compared to other catalytic methods. It is 4,000 times faster than the acid catalyst of the same amount and achieves a high yield of biodiesel with high purity in less reaction time (30–60 min) [15]. Therefore, it is preferred over the other biodiesel production catalyst.

8.3.4.1.2 Acidic Catalyst

Despite many associated problems like the slower rate of reaction, a higher volume of alcohol requirement, less catalyst activity, and requirement of higher reaction temperature, the acid catalyst has some important advantages for the transesterification reaction [49]. Low sensitivity for the high FFAs present in the non-edible oils (>5%) and the chances for esterification

Biodiesel Production Technologies  251 O R” -C-OH Carboxylic acid

+

Acid catalyst R’-OH Alcohol

O R” -C-OR’ + Biodiesel

H2O Water

Figure 8.5  Mechanism of the esterification reaction.

and transesterification reaction to occur simultaneously are some notable advantages of the acidic catalyst [50]. Esterification is carried out of FFA and alcohol (e.g., methanol) with the help of a strong acidic catalyst to form at least one ester and water as a reaction product (Figure 8.5). The common acid catalyst used for esterification includes sulfuric, hydrochloric, phosphoric, ferric sulfate, and organic sulfonic acid. The yield of biodiesel was reported up to 90% in many studies of transesterification with an acid catalyst, but a much longer reaction time (3–48 h) was required, in comparison to the alkali-catalyst transesterification reaction, except for those carried out with higher reaction temperatures [51–53]. The main variables that influence the transesterification yield are the amount of catalyst, alcohol type, and the reaction time [52]. Hence, the main benefit of using an acidic catalyst is the low-cost production of biodiesel by using high FFA nonedible oil in a single step [54]. However, these acidic catalysts are corrosive and create a handling issue during the operation.

8.3.4.1.3 Two-Step Process

Two-step acid/base catalytic process has been developed to address the drawbacks of single-step homogeneous acid and base catalytic processes for biodiesel production using high FFA non-edible oils. In this twostep method, the first step comprises of acid catalyst esterification of FFA (pre-treatment) for minimizing the FFA below 1% followed by alkali-­ catalyzed transesterification [55]. The acid pretreatment process eliminates the problem of slow reaction rate and soap formation. The higher cost of production is the only problem associated with the two-step transesterification process [49, 56]. Apart from the great advantages of homogeneous catalysts for transesterification, numerous disadvantages like huge energy requirement, the produced soap as a by-product, difficult and costly separation of catalyst, and a large amount of wastewater generation are also associated with them [57, 58].

252  Biodiesel Technology and Applications

8.3.4.2 Heterogeneously Catalyzed Transesterification Processes The catalyst which is not miscible with the reaction mixture is known as heterogeneous. It may be a basic or acidic type and is more conveniently separated from reaction products. Acidic heterogeneous catalysts could be used for transesterification of high FFA oil as they avoid undesirable saponification reaction. Solid heterogeneous catalysts could lead to cheaper production of biodiesel as it can be reused and enable both esterification and transesterification to be carried out simultaneously [59]. However, a slow reaction rate due to difficult diffusion in immiscible phases of oil, alcohol, and catalyst mixture, complex catalyst production method, followed by a considerable effect on the environment are the major disadvantages of heterogeneous catalysts [60]. The basic heterogeneous catalyst commonly used is alkaline earth metal oxides (SrO, BaO, CaO, MgO), alkaline earth metal carbonates (CaCO3), alkaline metal carbonates (K2CO3, Na2CO3), and transition metal oxides (ZnO) [44, 61–63]. However, acidic heterogeneous catalysts for transesterification such as Nafion-NR50 (perfluorinated alkane sulfonic acid resin), Zirconium oxide (ZrO2), sulfated zirconia-­ alumina (SZA), sulfated oxides, cation-exchange resins, and tungstated zirconia–alumina (WZA) are being utilized for the synthesis of biodiesel [64, 65]. Besides, a solid acidic catalyst like sulfated zirconia and tungstated zirconia can be used to support the transesterification as well as the esterification reactions [66, 67].

8.3.4.3 Enzymatic Catalyzed Transesterification Processes Normally, enzymes are a bio-oriented catalyst, primarily natural lipases that are separated from some bacterial species like Pseudomonas fluorescens, Rhizopus oryzae, Thermomyces lanuginosus, Candida antarctica, Pseudomonas cepacia, Candida rugosa, and Rhizomucor miehei [68]. Biodiesel production using enzymes has no problems of washing, purification, neutralization, and saponification, so it is usually recommended from these aspects. It can be used for those non-edible feedstocks having a high amount of FFA and gives appreciable yield. Enzymatic catalysts are typically used in the immobilized form to ensure their stability and reusability. The different ways by which immobilization can be provided are entrapment, adsorption, encapsulation, covalent bonding, cross-linking, and by the process of enzyme embedding on a solid support. These methods are useful to give the stability and recycling of the enzyme and decrease the total expenses on the catalyst that was the main challenge in commercialization [69].

Biodiesel Production Technologies  253

8.4 Intensification Techniques for Biodiesel Production Numerous novel techniques are being used in the past few years for the enhance the biodiesel yield especially from low-cost non-edible oils such as supercritical alcohol method, microwave heating, ultrasonic irradiation, co-solvent method, in situ transesterification processes, motionless mixer technique, and membrane reactors.

8.4.1 Supercritical Alcohol Method Biodiesel production by transesterification method with alcohol (methanol, ethanol, propanol, and butanol) in its supercritical stage with or without catalyst has been considered as the most promising technique. The supercritical method takes very little time to complete the reaction, whereas conventional catalytic transesterification method needs many hours to finish [70]. At conventional processing temperatures, oils (non-polar) and alcohol (polar) form heterogeneous mixture because of the limited miscibility of the polar and non-polar reactants. In a supercritical environment, the alcohol and triglyceride mixture turns into a single homogeneous phase, which will enhance the reaction rate due to the non-existence of any interphase mass transfer. The typical range of operating conditions applied for the supercritical zone has been temperatures of 280°C–400°C and pressures of 10–30 MPa [71]. The supercritical approach is found to be more water and FFA resistant and more easily separated and purifies the biodiesel more than the conventional catalytic transesterification method [72, 73]. Alternatively, in the supercritical condition along with transesterification, esterification of FFA and hydrolysis of triglycerides due to the presence of moisture takes place simultaneously and enhances the yield of methyl ester [72, 74, 75]. The cost of high temperature and pressure reactor is the main drawback that limits its use on a large scale in the industry [76]. Co-solvents, like carbon dioxide [77, 78], hexane [76, 79], propane [80], and calcium oxide [81, 82] with a little quantity of catalyst added during the reaction can reduce the temperature, pressure and the alcohol quantity.

8.4.2 Microwave Heating The transesterification by microwave heating is an effective way for the rapid production of biodiesel. During this process, heat is produced by the friction of molecules due to the alignment of polar alcohol molecules

254  Biodiesel Technology and Applications by the constantly varying magnetic field of microwaves. Due to very effective heat transfer, reactions under microwave heating can take place in a greatly reduced reaction time than those with conventional heating [83, 84]. Microwaves which are of 0.3- to 300-GHz frequency range have both thermal and non-thermal types of effects and generate heat due to its molecular interaction in the sample without changing their structures [85, 86]. Apart from the high yield of biodiesel, microwave heating also reduces the separation and purification time [87, 88]. The microwave heating method has many advantages over the conventional heating method, such as reduction of a thermal gradient, low overheating of surfaces due to contactless heating, energy transfer rather than heat transfer, and heat generation from inside of the mass. In sum, microwave-induced transesterification offers a much-purified product with a high yield and reduces the separation and purification time [87, 88]. Therefore, microwave heating is a more environmentally compatible, more energy-efficient, and favorable technique as compared to conventional heating, where heat transfer mainly takes place by conduction and convection by the walls of the sample container to reach inner materials resulted in inefficient and slow heating due to high thermal gradient because of non-uniform heating [89, 90]. Apart from the enormous advantages of this method, there are also a few drawbacks. The scale-up of microwave technique from laboratory to industrial multi-kilogram production is not very easy. Penetration depth which is only a few centimeters is the major constraint for the scale-up of

Figure 8.6  Microwave reactor.

Biodiesel Production Technologies  255 this technology. The safety is another cause of rejecting microwave heating in the industry [89]. Figure 8.6 shows an open view of a microwave reactor used for laboratory purposes.

8.4.3 Ultrasonic Irradiation The ultrasonic method is a newer mixing technique which is more efficient for the production of biodiesel, compared to the conventional way of agitation. Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. The typical range of hearing is between 16 Hz and about 18 kHz and ultrasound is normally known to be between 20 kHz and more than 100 MHz [91]. The ultrasonic mixing improves the mass transfer among the immiscible oil and alcohol phase, accelerates the chemical reaction and conversion of triglyceride, and reduces the reaction time and energy consumption. One of the types of ultra-sonicator (probe sonicator) that is normally used in laboratories is shown in Figure 8.7. The molecular spacing of the medium gets compressed and stretched on the application of high-frequency ultrasonic sound wave that continuously vibrates the molecules and creates the cavities. The created micro-fine bubbles by sudden collapse and expansion and generate energy for chemical and mechanical effects [92]. Additionally, the phase boundary is disrupted by the collapsed bubbles, and micro-jets are created by the impinging of the liquids, leading to extensive emulsification of the system [93].

Figure 8.7  Probe type ultra sonicator.

256  Biodiesel Technology and Applications

8.4.4 Co-Solvent Method During the transesterification reaction, the oil and methanol phases are immiscible with each other which affects the rate of mass transfer among these phases. This mass transfer constraint could be overcome by the addition of a small amount of co-solvent which is soluble both in methanol as well as in the triglycerides. The addition of the co-solvent increases the transesterification rate because of the elimination of mass transfer resistance between the phases. Many studies have revealed that the presence of co-solvent significantly reduces the reaction temperature, pressure, and quantity of alcohol and enhances the reaction rate [94–96]. Various co-solvents like tetrahydrofuran (THF), hexane, and a mixture of THF and hexane, acetone, propane, heptane, carbon dioxide (CO2), dimethyl ether (DME), and diethyl ether (DEE) have been used in biodiesel production [97, 98]. However, the use of co-solvent increases the cost of biodiesel production due to the extra cost of separation of the co-solvent from the methanol and product phase [99].

8.5 Other Techniques of Biodiesel Production Some other techniques like in situ transesterification, membrane reactor, reactive distillation, static mixers, micro-channel, oscillatory flow have also been used to make the process economical by either improving separation and purification method, reducing equipment cost, or making the process simpler. During the in situ transesterification method, extraction and transesterification of oil take place simultaneously. The used alcohol behaves as a solvent for extraction as well as a reagent for transesterification reaction [100]. After the oil is extracted from the seeds by the alcohol, it is simultaneously converted into ester due to already present alcohol. Hence, this process not only reduces the processing time but also reduces the cost. The only drawback associated is the requirement of a large volume of alcohol as compared to other traditional processes [18]. Membrane reactors combine reaction and separation in a single step which reduces recycling and separation costs and increases conversion due to the enhancement of product inhibited reactions. Inorganic membranes are much better than the organic (polymeric) ones as these are generally more thermally stable [101, 102]. A higher amount of methanol and ultralow catalyst concentration is needed as compared to the conventional production methods [103, 104].

Biodiesel Production Technologies  257 The distillation in which the reaction and the separation of the associated products take place in the same column is known as reactive distillation. Both packed and tray-type columns are suitable for reactive distillation, even though tray columns are recommended for the homogenous type of reactions due to the better liquid hold-up and prolonged retention time [105, 106]. Higher conversion, reduced energy consumption, lower capital cost, better selectivity, none or reduced amount of solvents throughout the reaction, and avoidance of azeotrope formation are some benefits of reactive distillation [107, 108]. The continuous removal of products from the reaction system not only increases the conversion but also helps to reduce capital and investment costs [109, 110]. Static mixers are made up of specially designed static helical mixing part in a hollow cylinder that creates intense mixing and needs less energy in comparison to conventionally used mechanical mixers [111, 112]. They are usually used in continuous processes for biodiesel production. This has no moving elements and therefore carry the benefit of low maintenance and operating costs, along with low space requirements [113, 114]. By static mixer, more fine and uniform droplets of methanol are generated, which enhances the interfacial surface area between raw oil and methanol. Thus, a higher reaction rate and a greater yield of FAME are obtained than that with the mechanical mixer [115, 116]. Apart from the aforementioned technologies, micro-channel [117–120] and oscillatory flow [121, 122] techniques can also improve reaction rate and reduce the alcoholto-oil molar ratio and energy input by the intensification of mass transfer and heat transfer, thus helping in attaining continuous production in the reactor.

References 1. L. Reijnders, Conditions for the sustainability of biomass based fuel use, Energy Policy, vol. 34, no. 7, pp. 863–876, 2006. 2. S. Fernando, C. Hall, and S. Jha, NO Reduction from Biodiesel Fuels, Energy & Fuels, vol. 20, no. 1, pp. 376–382, 2006. 3. L. C. Meher, D. Vidya Sagar, and S. N. Naik, Technical aspects of biodiesel production by transesterification - A review, Renew. Sustain. Energy Rev., vol. 10, no. 3, pp. 248–268, 2006. 4. A. C. Pinto et al., Biodiesel: An overview, J. Braz. Chem. Soc., vol. 16, no. 6 B, pp. 1313–1330, 2005. 5. E. M. Shahid and Y. Jamal, Production of biodiesel: A technical review, Renew. Sustain. Energy Rev., vol. 15, no. 9, pp. 4732–4745, 2011.

258  Biodiesel Technology and Applications 6. G. Kafuku and M. Mbarawa, Biodiesel production from Croton megalocarpus oil and its process optimization, Fuel, vol. 89, no. 9, pp. 2556–2560, 2010. 7. A. L. Ahmad, N. H. M. Yasin, C. J. C. Derek, and J. K. Lim, Microalgae as a sustainable energy source for biodiesel production: A review, Renew. Sustain. Energy Rev., vol. 15, no. 1, pp. 584–593, 2011. 8. J. Janaun and N. Ellis, Perspectives on biodiesel as a sustainable fuel, Renew. Sustain. Energy Rev., vol. 14, no. 4, pp. 1312–1320, 2010. 9. M. Satyanarayana and C. Muraleedharan, A comparative study of vegetable oil methyl esters (biodiesels), Energy, vol. 36, no. 4, pp. 2129–2137, 2011. 10. A. S. Silitonga, A. E. Atabani, T. M. I. Mahlia, H. H. Masjuki, I. A. Badruddin, and S. Mekhilef, A review on prospect of Jatropha curcas for biodiesel in Indonesia, Renew. Sustain. Energy Rev., vol. 15, no. 8, pp. 3733–3756, 2011. 11. M. A. Fazal, A. S. M. A. Haseeb, and H. H. Masjuki, Biodiesel feasibility study: An evaluation of material compatibility; Performance; emission and engine durability, Renew. Sustain. Energy Rev., vol. 15, no. 2, pp. 1314–1324, 2011. 12. D. N. Tziourtzioumis and A. M. Stamatelos, Experimental investigation of the effect of biodiesel blends on a DI diesel engine’s injection and combustion, Energies, vol. 10, no. 7, 2017. 13. S. Islam, A. S. Ahmed, A. Islam, S. A. Aziz, L. C. Xian, and M. Mridha, Study on Emission and Performance of Diesel Engine Using Castor Biodiesel, J. Chem., pp. 1–8, 2014. 14. J. Xue, T. E. Grift, and A. C. Hansen, Effect of biodiesel on engine performances and emissions, Renew. Sustain. Energy Rev., vol. 15, no. 2, pp. 1098– 1116, 2011. 15. A. E. Atabani, A. S. Silitonga, I. A. Badruddin, T. M. I. Mahlia, H. H. Masjuki, and S. Mekhilef, A comprehensive review on biodiesel as an alternative energy resource and its characteristics, Renew. Sustain. Energy Rev., vol. 16, no. 4, pp. 2070–2093, 2012. 16. M. M. Gui, K. T. Lee, and S. Bhatia, Feasibility of edible oil vs. non-­edible oil vs. waste edible oil as biodiesel feedstock, Energy, vol. 33, no. 11, pp. 1646–1653, 2008. 17. P. T. Vasudevan and M. Briggs, Biodiesel production—current state of the art and challenges, J. Ind. Microbiol. Biotechnol., vol. 35, no. 5, p. 421, 2008. 18. I. B. Banković-Ilić, O. S. Stamenković, and V. B. Veljković, Biodiesel production from non-edible plant oils, Renew. Sustain. Energy Rev., vol. 16, no. 6, pp. 3621–3647, 2012. 19. A. Demirbas, Progress and recent trends in biodiesel fuels, Energy Convers. Manag., vol. 50, no. 1, pp. 14–34, 2009. 20. I. M. Atadashi, M. K. Aroua, and A. A. Aziz, High quality biodiesel and its diesel engine application: A review, Renew. Sustain. Energy Rev., vol. 14, no. 7, pp. 1999–2008, 2010.

Biodiesel Production Technologies  259 21. S. S. Ragit, S. K. Mohapatra, K. Kundu, and P. Gill, Optimization of neem methyl ester from transesterification process and fuel characterization as a diesel substitute, Biomass and Bioenergy, vol. 35, no. 3, pp. 1138–1144, 2011. 22. S. Lim and L. K. Teong, Recent trends, opportunities and challenges of biodiesel in Malaysia: An overview, Renew. Sustain. Energy Rev., vol. 14, no. 3, pp. 938–954, 2010. 23. L. Lin, Z. Cunshan, S. Vittayapadung, S. Xiangqian, and D. Mingdong, Opportunities and challenges for biodiesel fuel, Appl. Energy, vol. 88, no. 4, pp. 1020–1031, 2011. 24. S. A. Basha, K. R. Gopal, and S. Jebaraj, A review on biodiesel production, combustion, emissions and performance, Renew. Sustain. Energy Rev., vol. 13, no. 6–7, pp. 1628–1634, 2009. 25. A. Karmakar, S. Karmakar, and S. Mukherjee, Properties of various plants and animals feedstocks for biodiesel production, Bioresour. Technol., vol. 101, no. 19, pp. 7201–7210, 2010. 26. D. Y. C. Leung, X. Wu, and M. K. H. Leung, A review on biodiesel production using catalyzed transesterification, Appl. Energy, vol. 87, no. 4, pp. 1083–1095, 2010. 27. S. Jain and M. P. Sharma, Prospects of biodiesel from Jatropha in India: A review, Renew. Sustain. Energy Rev., vol. 14, no. 2, pp. 763–771, 2010. 28. A. Kumar and S. Sharma, Potential non-edible oil resources as biodiesel feedstock: An Indian perspective, Renew. Sustain. Energy Rev., vol. 15, no. 4, pp. 1791–1800, 2011. 29. P. Sirisomboon, P. Kitchaiya, T. Pholpho, and W. Mahuttanyavanitch, Physical and mechanical properties of Jatropha curcas L. fruits, nuts and kernels, Biosyst. Eng., vol. 97, no. 2, pp. 201–207, 2007. 30. M. Balat and H. Balat, Progress in biodiesel processing, Appl. Energy, vol. 87, no. 6, pp. 1815–1835, 2010. 31. B. J. Gallagher, The economics of producing biodiesel from algae, Renew. Energy, vol. 36, no. 1, pp. 158–162, 2011. 32. A. E. F. Abomohra, W. Jin, R. Tu, S. F. Han, M. Eid, and H. Eladel, Microalgal biomass production as a sustainable feedstock for biodiesel: Current status and perspectives, Renew. Sustain. Energy Rev., vol. 64, pp. 596–606, 2016. 33. A. Demirbas and M. Fatih Demirbas, Importance of algae oil as a source of biodiesel, Energy Convers. Manag., vol. 52, no. 1, pp. 163–170, 2011. 34. G. R. M. Shannon D. Sanford, James Matthew White, Parag S. Shah, Claudia Wee, Marlen A. Valverde, Feedstock and Biodiesel Characteristics Report, Renew. Energy Group, Inc, pp. 1–136, 2009. 35. A. Srivastava and R. Prasad, Triglycerides-based diesel fuels, Renew. Sustain. energy Rev., vol. 4, no. 2, pp. 111–133, 2000. 36. A. W. Schwab, G. J. Dykstra, E. Selke, S. C. Sorenson, and E. H. Pryde, Diesel fuel from thermal decomposition of soybean oil, J. Am. Oil Chem. Soc., vol. 65, no. 11, pp. 1781–1786, 1988.

260  Biodiesel Technology and Applications 37. R. Saidur, E. A. Abdelaziz, A. Demirbas, M. S. Hossain, and S. Mekhilef, A review on biomass as a fuel for boilers, Renew. Sustain. Energy Rev., vol. 15, no. 5, pp. 2262–2289, 2011. 38. A. Abbaszaadeh, B. Ghobadian, M. R. Omidkhah, and G. Najafi, Current biodiesel production technologies: A comparative review, Energy Convers. Manag., vol. 63, pp. 138–148, 2012. 39. R. French and S. Czernik, Catalytic pyrolysis of biomass for biofuels production, Fuel Process. Technol., vol. 91, no. 1, pp. 25–32, 2010. 40. A. Bilgin, O. Durgun, and Z. Şahin, The effects of diesel-ethanol blends on diesel engine performance, Energy Sources, vol. 24, no. 5, pp. 431–440, 2002. 41. S. P. Singh and D. Singh, Biodiesel production through the use of different sources and characterization of oils and their esters as the substitute of diesel: A review, Renew. Sustain. Energy Rev., vol. 14, no. 1, pp. 200–216, 2010. 42. D. Chiaramonti et al., Development of emulsions from biomass pyrolysis liquid and diesel and their use in engines - Part 1: Emulsion production, Biomass and Bioenergy, vol. 25, no. 1, pp. 85–99, 2003. 43. F. Ma and M. A. Hanna, Biodiesel production: A review, Bioresour. Technol., vol. 70, pp. 1–15, 1999. 44. H. Fukuda, A. Kondo, and H. Noda, Biodiesel fuel production by transesterification of oils, J. Biosci. Bioeng., vol. 92, no. 5, pp. 405–416, 2001. 45. Z. Ilham and S. Saka, Two-step supercritical dimethyl carbonate method for biodiesel production from Jatropha curcas oil, Bioresour. Technol., vol. 101, no. 8, pp. 2735–2740, 2010. 46. J. M. Ã. Marchetti, V. U. Miguel, and A. F. Errazu, Possible methods for biodiesel production, Renew. Sustain. Energy Rev., vol. 11, pp. 1300–1311, 2007. 47. G. Corro, N. Tellez, E. Ayala, and A. Marinez-ayala, Two-step biodiesel production from Jatropha curcas crude oil using SiO 2 Á HF solid catalyst for FFA esterification step, Fuel, vol. 89, no. 10, pp. 2815–2821, 2010. 48. S. Jain and M. P. Sharma, Biodiesel production from Jatropha curcas oil, Renew. Sustain. Energy Rev., vol. 14, no. 9, pp. 3140–3147, Dec. 2010. 49. W. Parawira, Biodiesel production from Jatropha curcas: A review, Sci. Res. Essays, vol. 5, no. 14, pp. 1796–1808, 2010. 50. A. P. Vyas, J. L. Verma, and N. Subrahmanyam, A review on FAME production processes, Fuel, vol. 89, 2010. 51. S. M. P. Meneghetti et al., Biodiesel from castor oil: A comparison of ethanolysis versus methanolysis, Energy and Fuels, vol. 20, no. 5, pp. 2262–2265, 2006. 52. N. Saravanan, S. Puhan, G. Nagarajan, and N. Vedaraman, An experimental comparison of transesterification process with different alcohols using acid catalysts, Biomass and Bioenergy, vol. 34, no. 7, pp. 999–1005, 2010. 53. X. Deng, Z. Fang, and Y. H. Liu, Ultrasonic transesterification of Jatropha curcas L. oil to biodiesel by a two-step process, Energy Convers. Manag., vol. 51, no. 12, pp. 2802–2807, 2010.

Biodiesel Production Technologies  261 54. E. Lotero, Y. Liu, D. E. Lopez, K. Suwannakarn, D. A. Bruce, and J. G. Goodwin, Synthesis of biodiesel via acid catalysis, Ind. Eng. Chem. Res., vol. 44, no. 14, pp. 5353–5363, 2005. 55. M. Canakci and J. VanGerpen, A pilot plant to produce biodiesel from high free fatty acid feedstocks, in Sacramento, CA July 29-August 1, 2001, pp. 1–19. 56. C. Vijaya Lakshmi, K. Viswanath, S. Venkateshwar, and B. Satyavathi, Mixing characteristics of the oil-methanol system in the production of biodiesel using edible and non-edible oils, Fuel Process. Technol., vol. 92, no. 8, pp. 1411–1417, 2011. 57. N. S. Babu, R. Sree, P. S. S. Prasad, and N. Lingaiah, Room-Temperature Transesterification of Edible and Nonedible Oils Using a Heterogeneous Strong Basic Mg/La Catalyst, Energy & Fuels, vol. 22, no. 3, pp. 1965–1971, May 2008. 58. W. Xie and H. Li, Alumina-supported potassium iodide as a heterogeneous catalyst for biodiesel production from soybean oil, J. Mol. Catal. A Chem., vol. 255, no. 1–2, pp. 1–9, 2006. 59. D. E. López, J. G. Goodwin, D. A. Bruce, and E. Lotero, Transesterification of triacetin with methanol on solid acid and base catalysts, Appl. Catal. A Gen., vol. 295, no. 2, pp. 97–105, 2005. 60. I. K. Mbaraka and B. H. Shanks, Advanced Mesoporous Catalytic Materials, JAOCS, vol. 83, no. 2, pp. 79–91, 2006. 61. F. Ma and M. A. Hanna, Biodiesel production: A review, Bioresource Technology. 1999. 62. X. Liu, H. He, Y. Wang, and S. Zhu, Transesterification of soybean oil to biodiesel using SrO as a solid base catalyst, Catal. Commun., vol. 8, no. 7, pp. 1107–1111, 2007. 63. M. Verziu et al., Sunflower and rapeseed oil transesterification to biodiesel over different nanocrystalline MgO catalysts, Green Chem., vol. 10, no. 4, pp. 373–38, 2008. 64. F. Chai, F. Cao, F. Zhai, Y. Chen, X. Wang, and Z. Su, Transesterification of vegetable oil to biodiesel using a heteropolyacid solid catalyst, Adv. Synth. Catal., vol. 349, no. 7, pp. 1057–1065, 2007. 65. D. E. López, J. G. Goodwin, and D. A. Bruce, Transesterification of triacetin with methanol on Nafion®acid resins, J. Catal., vol. 245, no. 2, pp. 381–391, 2007. 66. V. Rathore, B. L. Newalkar, and R. P. Badoni, Processing of vegetable oil for biofuel production through conventional and non-conventional routes, Energy Sustain. Dev., vol. 31, pp. 24–49, 2016. 67. S. Furuta, H. Matsuhashi, and K. Arata, Biodiesel fuel production with solid superacid catalysis in fixed bed reactor under atmospheric pressure, Catal. Commun., vol. 5, no. 12, pp. 721–723, 2004. 68. A. B. R. Moreira, V. H. Perez, G. M. Zanin, and H. F. de Castro, Biodiesel synthesis by enzymatic transesterification of palm oil with ethanol using

262  Biodiesel Technology and Applications lipases from several sources immobilized on silica-PVA composite, Energy and Fuels, vol. 21, no. 6, pp. 3689–3694, 2007. 69. M. K. H. Leung, A review on biodiesel production using catalyzed transesterification A review on biodiesel production using catalyzed transesterification, Appl. Energy, vol. 87, no. 4, pp. 1083–1095, 2009. 70. H. He, S. Sun, T. Wang, and S. Zhu, Transesterification kinetics of soybean oil for production of biodiesel in supercritical methanol, JAOCS, J. Am. Oil Chem. Soc., vol. 84, no. 4, pp. 399–404, 2007. 71. V. F. Marulanda, G. Anitescu, and L. L. Tavlarides, Investigations on supercritical transesterification of chicken fat for biodiesel production from lowcost lipid feedstocks, J. Supercrit. Fluids, vol. 54, no. 1, pp. 53–60, 2010. 72. S. Saka and D. Kusdiana, Biodiesel fuel from rapeseed oil as prepared in supercritical methanol, Fuel, vol. 80, no. 2, pp. 225–231, 2001. 73. K. Bunyakiat, S. Makmee, R. Sawangkeaw, and S. Ngamprasertsith, Continuous Production of Biodiesel via Transesterification from Vegetable Oils in Supercritical Methanol, Energy & Fuels, vol. 20, no. 2, pp. 812–817, 2006. 74. D. Kusdiana and S. Saka, Kinetics of transesterification in rapeseed oil to biodiesel fuel as treated in supercritical methanol, Fuel, vol. 80, no. 5, pp. 693– 698, 2001. 75. D. Kusdiana and S. Saka, Effects of water on biodiesel fuel production by supercritical methanol treatment, Bioresour. Technol., vol. 91, no. 3, pp. 289– 295, 2004. 76. J. Z. Yin, M. Xiao, and J. Bin Song, Biodiesel from soybean oil in supercritical methanol with co-solvent, Energy Convers. Manag., vol. 49, no. 5, pp. 908– 912, 2008. 77. Y. Warabi, D. Kusdiana, and S. Saka, Reactivity of triglycerides and fatty acids of rapeseed oil in supercritical alcohols, Bioresour. Technol., vol. 91, no. 3, pp. 283–287, 2004. 78. Y. Warabi, D. Kusdiana, and S. Saka, Biodiesel Fuel from Vegetable Oil by Various Supercritical Alcohols, Appl. Biochem. Biotechnol., vol. 115, no. 1–3, pp. 0793–0802, 2004. 79. J. Z. Yin, M. Xiao, A. Q. Wang, and Z. L. Xiu, Synthesis of biodiesel from soybean oil by coupling catalysis with subcritical methanol, Energy Convers. Manag., vol. 49, no. 12, pp. 3512–3516, 2008. 80. W. Cao, H. Han, and J. Zhang, Preparation of biodiesel from soybean oil using supercritical methanol and co-sol vent, Fuel, vol. 84, no. 4, pp. 347– 351, 2005. 81. A. Demirbas, Biodiesel from sunflower oil in supercritical methanol with calcium oxide, Energy Convers. Manag., vol. 48, no. 3, pp. 937–941, 2007. 82. Z. Tang, L. Wang, and J. Yang, Transesterification of the crude Jatropha curcas L. oil catalyzed by micro-NaOH in supercritical and subcritical methanol, Eur. J. Lipid Sci. Technol., vol. 109, no. 6, pp. 585–590, 2007.

Biodiesel Production Technologies  263 83. N. Azcan and A. Danisman, Alkali catalyzed transesterification of cottonseed oil by microwave irradiation, Fuel, vol. 86, no. 17–18, pp. 2639–2644, 2007. 84. H. Venkatesh Kamath, I. Regupathi, and M. B. Saidutta, Optimization of two step karanja biodiesel synthesis under microwave irradiation, Fuel Process. Technol., vol. 92, no. 1, pp. 100–105, 2011. 85. R. S. Varma, Solvent-free accelerated organic syntheses using microwaves, Pure Appl. Chem., vol. 73, no. 1, pp. 193–198, 2001. 86. A. A. Refaat, Different techniques for the production of biodiesel from waste vegetable oil, Int. J. Environ. Sci. Tech., vol. 7, no. 1, pp. 183–213, 2010. 87. M. Nüchter, B. Ondruschka, A. Jungnickel, and U. Müller, Organic processes initiated by non-classical energy sources, J. Phys. Org. Chem., vol. 13, no. 10, pp. 579–586, 2000. 88. J. Hernando, P. Leton, M. P. Matia, J. L. Novella, and J. Alvarez-Builla, Biodiesel and FAME synthesis assisted by microwaves: Homogeneous batch and flow processes, Fuel, vol. 86, no. 10–11, pp. 1641–1644, 2007. 89. Y. Groisman and A. Gedanken, Continuous flow, circulating microwave system and its application in nanoparticle fabrication and biodiesel synthesis, J. Phys. Chem. C, vol. 112, no. 24, pp. 8802–8808, 2008. 90. A. A. Refaat, S. T. Sheltawy, and K. U. Sadek, Optimum reaction time, performance and exhaust emissions of biodiesel produced by microwave irradiation, Int. J. Environ. Sci. Technol., vol. 5, no. 3, pp. 315–322, 2008. 91. T. J. Mason, Ultrasound in synthetic organic chemistry, Chem. Soc. Rev., vol. 26, no. 6, pp. 443–451, 1997. 92. J. A. Colucci, E. E. Borrero, and F. Alape, Biodiesel from an alkaline transesterification reaction of soybean oil using ultrasonic mixing, JAOCS, J. Am. Oil Chem. Soc., vol. 82, no. 7, pp. 525–530, 2005. 93. J. Ji, J. Wang, Y. Li, Y. Yu, and Z. Xu, Preparation of biodiesel with the help of ultrasonic and hydrodynamic cavitation, Ultrasonics, vol. 44, no. SUPPL., pp. e411–e414, Dec. 2006. 94. E. Çağlar, Biodiesel Production Using Co-solvent, in Book of Abstracts European Congress of Chemical Engineering (ECCE-6) Copenhagen,16-20 Septembe, 2007. 95. G. Guan, K. Kusakabe, N. Sakurai, and K. Moriyama, Transesterification of vegetable oil to biodiesel fuel using acid catalysts in the presence of dimethyl ether, Fuel, vol. 88, no. 1, pp. 81–86, 2009. 96. S. Sakthivel, S. Halder, and P. D. Gupta, Influence of Co-Solvent on the Production of Biodiesel in Batch and Continuous Process, Int. J. Green Energy, vol. 10, no. 8, pp. 876–884, Sep. 2013. 97. C. Calgaroto, S. Calgaroto, M. A. Mazutti, D. de Oliveira, S. Pergher, and J. de Oliveira, Production of biodiesel from soybean and Jatropha Curcas oils with KSF and amberlyst 15 catalysts in the presence of co-solvents, Sustain. Chem. Process., vol. 1, no. 1, p. 17, 2013.

264  Biodiesel Technology and Applications 98. L. T. Thanh, K. Okitsu, Y. Sadanaga, N. Takenaka, Y. Maeda, and H. Bandow, A new co-solvent method for the green production of biodiesel fuel Optimization and practical application, Fuel, vol. 103, pp. 742–748, Jan. 2013. 99. G. R. Kumar, R. Ravi, and A. Chadha, Kinetic studies of base-catalyzed transesterification reactions of non-edible oils to prepare biodiesel: The effect of Co-solvent and temperature, Energy and Fuels, vol. 25, no. 7, pp. 2826–2832, 2011. 100. G. Knothe, J. Van Gerpen, and J. Krahl, The Biodiesel Handbook, 1st ed. (AOCS Press), 2005. 101. P. Cao, A. Y. Tremblay, M. A. Dubé, and K. Morse, Effect of Membrane Pore Size on the Performance of a Membrane Reactor for Biodiesel Production, Ind. Eng. Chem. Res., vol. 46, no. 1, pp. 52–58, 2007. 102. J. Saleh, A. Y. Tremblay, and M. A. Dubé, Glycerol removal from biodiesel using membrane separation technology, Fuel, vol. 89, no. 9, pp. 2260–2266, 2010. 103. P. Cao, M. A. Dubé, and A. Y. Tremblay, High-purity fatty acid methyl ester production from canola, soybean, palm, and yellow grease lipids by means of a membrane reactor, Biomass and Bioenergy, vol. 32, no. 11, pp. 1028–1036, 2008. 104. L. H. Cheng, S. Y. Yen, L. S. Su, and J. Chen, Study on membrane reactors for biodiesel production by phase behaviors of canola oil methanolysis in batch reactors, Bioresour. Technol., vol. 101, no. 17, pp. 6663–6668, 2010. 105. A. C. Dimian, C. S. Bildea, F. Omota, and A. A. Kiss, Innovative process for fatty acid esters by dual reactive distillation, Comput. Chem. Eng., vol. 33, no. 3, pp. 743–750, 2009. 106. B. B. He, A. P. Singh, and J. C. Thompson, A Novel Continuous-Flow Reactor Using Reactive Distillation For Biodiesel Production, Trans. ASABE (American Soc. Agric. Biol. Eng., vol. 49, no. 1, pp. 107–112, 2006. 107. C. Mueanmas, K. Prasertsit, and C. Tongurai, Feasibility Study of Reactive Distillation Column for Transesterification of Palm Oils, Int. J. Chem. Eng. Appl., vol. 1, no. 1, pp. 77–83, 2010. 108. N. M. Eleftheriades and H. von Blottnitz, Thermodynamic and kinetic considerations for biodiesel production by reactive distillation, Environ. Prog. Sustain. Energy, vol. 32, no. 2, pp. 373–376, Jul. 2013. 109. A. A. Kiss, Novel process for biodiesel by reactive absorption, Sep. Purif. Technol., vol. 69, pp. 280–287, 2009. 110. G. B. Shinde, V. S. Sapkal, R. S. Sapkal, and N. B. Raut, Transesterification by Reactive Distillation for Synthesis and Characterization of Biodiesel, in Biodiesel - Feedstocks and Processing Technologies, Dr. Margarita Stoytcheva, Ed. InTech, 2011, p. 29. 111. H. Noureddini, D. W. Harkey, and M. R. Gutsman, A Continuous Process for the Glycerolysis of Soybean Oil, JAOCS, J. Am. Oil Chem. Soc., vol. 81, no. 2, pp. 203–207, 2004.

Biodiesel Production Technologies  265 112. C. L. Peterson, J. L. Cook, J. C. Thompson, and J. S. Taberski, Continuous flow biodiesel production, Appl. Eng. Agric., vol. 18, no. 1, pp. 5–11, 2002. 113. J. C. Thompson and B. B. He, Biodiesel Production Using Static Mixers, Trans. Asabe, vol. 50, no. 1, pp. 161–166, 2007. 114. M. B. Boucher, C. Weed, N. E. Leadbeater, B. a Wilhite, J. D. Stuart, and R. S. Parnas, Pilot scale two-phase continuous flow biodiesel production via novel laminar flow reactor- separator, Energy & Fuels, vol. 23, no. 14, pp.  2750– 2756, 2009. 115. R. Alamsyah, A. H. Tambunan, Y. A. Purwanto, and D. Kusdiana, Comparison of Static-Mixer and Blade Agitator Reactor in Biodiesel Production, Agric. Eng. Int. CIGR Ejournal, vol. 12, no. 4, pp. 1–12, 2010. 116. P. Sungwornpatansakul, J. Hiroi, Y. Nigahara, T. K. Jayasinghe, and K. Yoshikawa, Enhancement of biodiesel production reaction employing the static mixing, Fuel Process. Technol., vol. 116, pp. 1–8, 2013. 117. N. Chueluecha, A. Kaewchada, and A. Jaree, Biodiesel synthesis using heterogeneous catalyst in a packed- microchannel, Energy Convers. Manag., 2016. 118. Y. Natarajan et al., An overview on the process intensification of microchannel reactors for biodiesel production, Chem. Eng. Process. - Process Intensif., vol. 136, pp. 163–176, 2019. 119. A. Mohd Laziz, K. Z. KuShaari, B. Azeem, S. Yusup, J. Chin, and J. Denecke, Rapid production of biodiesel in a microchannel reactor at room temperature by enhancement of mixing behaviour in methanol phase using volume of fluid model, Chem. Eng. Sci., vol. 219, p. 115532, 2020. 120. H. S. Santana, J. L. S. Júnior, and O. P. Taranto, Numerical simulations of biodiesel synthesis in microchannels with circular obstructions, Chem. Eng. Process. Process Intensif., vol. 98, pp. 137–146, 2015. 121. A. P. Harvey, M. R. Mackley, and T. Seliger, Process intensification of biodiesel production using a continuous oscillatory flow reactor, J. Chem. Technol. Biotechnol., vol. 78, no. 2–3, pp. 338–341, 2003. 122. N. Masngut, A. P. Harvey, and J. Ikwebe, Potential uses of oscillatory baffled reactors for biofuel production, Biofuels, vol. 1, no. 4, pp. 605–619, 2010.

9 Methods for Biodiesel Production M.Gul1,2*, M.A. Mujtaba1,3, H.H. Masjuki1,4, M.A. Kalam1 and N.W.M. Zulkifli1 Center for Energy Science, Department of Mechanical Engineering, University of Malaya, Kuala Lumpur, Malaysia 2 Department of Mechanical Engineering, Faculty of Engineering and Technology, Bahauddin Zakariya University, Multan, Pakistan 3 Department of Mechanical Engineering, University of Engineering and Technology, City Campus Lahore, Pakistan 4 Department of Mechanical Engineering, Faculty of Engineering, IIUM, Kuala Lumpur, Malaysia 1

Abstract

This chapter discusses all types of feedstocks used for synthesizing biodiesel and feedstock’s selection criteria. Moreover, all biodiesel production methods (i.e Dilution with hydrocarbons blending, Micro-emulsion, Pyrolysis, and Transesterification) are also described in detail with their advantages and disadvantages. The major focus is given to the various Transesterification methods because of their simplicity, easy handling, less time consumption, and maximum biodiesel yield. Production methods also include experimental setup layouts, all process parameters, reaction conditions, the latest advancement in reaction processes, and their effects on biodiesel yield. Keywords:  Biodiesel, pyrolysis, transesterification, supercritical methanol

9.1 Selection of Feedstock for Biodiesel There are different types of biodiesel feedstock that mainly comprised of fatty acids (triglycerides) or lipids depending on local soil conditions in different regions and climate. Genetic engineering is also playing important role in growing biodiesel feedstock crops to achieve desired composition *Corresponding author: [email protected] Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (267–284) © 2021 Scrivener Publishing LLC

267

268  Biodiesel Technology and Applications according to application and to overcome their drawbacks. So, selection of feedstock includes fatty acids (lipid) content/oil percentage, free fatty acid (FFA) contents, moisture content, and its availability and productivity per hectare [1]. The major biodiesel producers all over the world are the European Union (EU) (rapeseed, soybeans), the United States (Soybean), Brazil (Soybean), Indonesia and Malaysia (palm oil), and China (rapeseed) that use edible vegetable oil (VO) for synthesizing biodiesel. The following are the kinds of biodiesel feedstock.

9.1.1 First-Generation Feedstock Edible vegetable oils like palm oil, soybeans, rapeseed, coconut, sunflower, safflower, sesame, corn, peanut, groundnut, almond, barley, poppy seed, okra seed, oat oil, camelina (camelina sativa), fish oil, and cottonseed oils are considered as first-generation feedstock for producing biodiesel. Most of the biodiesel are synthesized from edible oils. But, in future, world will face severe malnutrition and serious basic food shortage issues. Growing of crops for getting biodiesel feedstock will utilize land, water, and other energy resources that are also required significantly to fulfil basic food production for human beings.

9.1.2 Second-Generation Feedstock Non-edible oils are defined as second-generation feedstock of biodiesel production that obtained from jatropha tree/ratanjyote (jatropha curcas), jojoba (simmondsia chinensis), neem (azadirachta indica), karanja/honge (pongamia pinnata), desert date (balanites aegyptiaca), koroch seed oil, silk cotton tree (ceiba pentandra), mahua (madhuca indica or madhuca longifolia), pachira glabra nagchampa (calophyllum inophyllum), tobacco seed (nicotiana tabacum L.), sea mango seed (cerbera odollam), rubber seed tree (hevea brasiliensis), aleurites moluccana, croton megalocarpus,  terminalia belerica, babassu tree, euphorbia tirucalli, and rice bran. Significant non-edible oils are getting attention in developing countries as these have no competition and dispute with food. Non-edible oil crops are also environment friendly, efficient, and very economical, can easily grow on wastelands, and reduce deforestation rate. Moreover, animal fats like tallow from beef, sheep and poultry, pork lard, Chinese tallow, waste cooking oils, and grease are also categorized as second-generation feedstocks for biodiesel synthesis. Utilization of these feedstock for biodiesel production also eliminates their disposal problems but collection of waste

Methods for Biodiesel Production  269 oils from scattered sources required logistics and proper infrastructure. Transesterification of some animal fats is not so easy because those have high concentration of saturated fatty acids and exist in solidified form.

9.1.3 Third-Generation Feedstock Recently, microalgae emerged as third-generation promising feedstock for biodiesel production. Microalgae are photosynthetic microorganisms having different varieties that convert CO2 and water into algal biomass by photosynthesis process. Algal biomass has high productivity, faster growth rates, and high yield of oil as compared to VO sources. Microalgae can be grown in farm or in bioreactors that needs high production costs. Moreover, its commercialization requires large-scale bioreactors so more researches are required to explore its production methods in future [2].

9.2 Methods for Biodiesel Production VOs in pure form are not good quality fuels for IC engines because of their polyunsaturated fatty acids characteristics, high viscosity, and low volatility in comparison to diesel fuels. These drawbacks can be resolved by conventional methods like dilution by blending hydrocarbons and micro-­ emulsion. Both of these are physical methods so do not involve any chemical reaction.

9.2.1 Dilution With Hydrocarbons Blending VOs cannot replace diesel fuels completely, so high viscosities of VO can be decreased by blending it with diesel. In addition, 20% VO and 80% diesel blend was successfully implemented in IC engines as described in earlier literatures [3–5]. High percentage blends are not recommended because these do not fulfill ASTM standard limits.

9.2.2 Micro-Emulsion In this method, oils are mixed and blended with immiscible solvents including ionic/non-ionic amphiphiles and methanol, ethanol, butanol, and hexanol to reduce their viscosities. This method ensures the thermodynamically stable colloidal dispersions of micro-phase particles having as small diameter as ¼ part of visible light’s wavelength. As micro-emulsions contain alcohol so give low volumetric heating values in comparison to

270  Biodiesel Technology and Applications diesel fuels, but useful cooling effect developed in combustion chamber because of high latent heat of vaporization of alcohol. These above two methods have improved the viscosity issues and recommended as fuel for short term applications. However, these fuels gave incomplete combustion in diesel engines, premature injection‐nozzle deterioration occurred, and high carbon deposits are observed on the piston lands, intake ports and exhaust valves, and piston ring grooves. These carbon deposits also caused degradation of lubricating oil. So, at present, fuels prepared from pure VOs by dilution and micro-emulsion are not suggested suitable anymore for long term utilization in diesel engines [6]. Some new techniques/methods are adopted to solve all these problems associated with dilution and micro-emulsion. These methods involves pyrolysis, transesterification, and supercritical methanol [7].

9.2.3 Pyrolysis (Thermal Cracking) In pyrolysis heat is used to decompose VOs, fatty acids, and animal fats by using different types of catalysts without oxygen to synthesized suitable potential fuel for DI-diesel engines. Pyrolysis is a chemical reaction taking place by thermal energy that convert triglycerides of VOs into alkanes, alkenes, alkadines, linear and cyclic paraffins and olefins, aromatics, aldehydes, ketones, and carboxylic acids [8], as described in Figure 9.1. O CH3 (CH2)5 CH2 –CH2 CH=CHCH2 –CH2 (CH2)5C–O–CH2R O CH9 (CH2)5 CH2 –CH2 CH=CHCH2 –CH2 (CH2)5C–OH O CH3 (CH2)5CH2•

CH2 =CHCH=CH2

• CH2 (CH2)5C–OH H

CH9 (CH2)3CH2 • + CH2=CH2

DielsAlder

–H2 CH3(CH2)3CH3

O

CH3(CH2)5C–H –CO2 CH3(CH2)4CH3

Figure 9.1  Pyrolysis of vegetable oils into alkanes, alkenes, and aromatics [4].

Methods for Biodiesel Production  271 Saponification and pyrolysis of VOs directly produce the hydrocarbon-­ rich products [9] that are very good alternative of gasoline (a competitive biodiesel fuel) as presented by Equations (9.1) and (9.2) Saponification:

Vegetable oil/fats + NaOH  RCOONa (sodium soap) + Glycerin

(9.1) Pyrolysis of sodium soap:



4 RCOONa + (1/2) O2

R—R (biodiesel) + Na2CO3 + CO2



(9.2)

The products obtained after pyrolysis have good cetane no and low viscosity with acceptable range of copper corrosion value, sulfur, and water content. But, their poor pour point, low higher heating values (HHVs), more carbon residues, and ash content have limited their utilization in specific applications [10].

9.2.4 Transesterification (Alcoholysis) Transesterification is most preferable chemical reaction and considered best method among all other processes because of its simplicity and less cost [4, 11]. Synthesis of biodiesel by transesterification process can be performed by conventional transesterification method or by microwave/­ultrasound-assisted method. Microwave/ultrasound-assisted method  takes very less reaction time and synthesizes biodiesel more quickly at laboratory scale. 9.2.4.1

In Situ Transesterification (Reactive Extraction)

In in situ transesterification process, crop seeds containing oil are crushed and directly reacted with methanol/ethanol (alcohol) and catalyst (acid or alkali based) to produce biodiesel, thereby excluding the need for oil extraction and reducing the intensive running and capital cost of biodiesel synthesis methods [12]. Some co-solvents are also used to speed up the reaction rate [13]. Some significant parameters of in situ transesterification process are moisture content of seeds, oil-to-alcohol molar ratios, type of alcohol, type

272  Biodiesel Technology and Applications and concentration of catalyst, reaction temperature, agitation speed, and size of crushed seeds [12].

9.2.4.2 Conventional Transesterification In conventional transesterification, oils are extracted from seed by crushing, pressing, and solvent extraction (mostly by n-hexane) and then used as raw material. Figure 9.2 shows the difference between in situ and conventional transesterification processes. Conventional process requires crushing and solvent extraction steps so having more cost than in situ. VO is pre-heated at 100°C to evaporate water; then, this VO is transferred into double jacket glass reactor and heated up to desired temperature. Optimized amount of catalyst is dissolved in alcohol and poured into reactor and temperature of mixture is maintained below the boiling point of alcohol (65°C) by using hot water bath. Chemical reaction between oil and alcohols proceeds for 2 hours under continuous stirring. Then, this mixture transferred into separating funnel for 12–20 hours at room temperature; after that, two layers are formed by sedimentation. Conventional transesterification experimental setup for biodiesel production is described in Figure 9.3. Bottom layer of glycerol is removed and top layer containing biodiesel is heated at 80°C to remove excess methanol. At the end, this biodiesel is washed with 40°C warm water to eliminate remaining alcohol, glycerol, and catalyst. Water is absorbed anhydrous Na2SO4 from biodiesel and after filtration purified biodiesel is obtained. There are various types of transesterification process [2] based on different types of catalysts and without catalyst as classified in Figure 9.4. Steps 1. Raw Material 2. Maceration 3. Crushing & solvent extraction 4. Transesterification (oil+alcohol+catalyst) 5. Purification

Conventional method Crop seeds Crushed into small size

In-situ method Crop seeds Crushed into small size

Oil extraction Biodiesel + Glycerol Pure Biodiesel

Biodiesel + Glycerol Pure Biodiesel

Figure 9.2  Comparison between conventional and in situ transesterification.

Methods for Biodiesel Production  273 Stirrer Separating funnel

Condenser Thermometer

Biodiesel Glycerol

Double jacket Circulated Refrigerated glass reactor hot-water bath cooling solvent

Figure 9.3  Conventional transesterification process experimental setup.

Homogeneous Catalysts Catalytic-based process

Heterogeneous Catalysts

Transesterification

Non-catalytic based process

Acidic: H2SO4, HCL, H3PO4 ferric sulfate, and organic sulfonic acid Alkaline: KOH, NaOH, NaOCH3, KOCH3, and K2CO3 etc Enzymes e.g immobilized lipase, Ryzopus oryzae lipase, CH2N2, Titanium silicates, Sulfated Titanium, Alkaline earth metal (MgO, CaO, SrO), Amorphous zirconia, Potassium zirconia

Supercritical Methanol (SCM) Ethanol/Propanol Butanol

BIOX co-solvent Process

Figure 9.4  Classification of transesterification process.

9.2.4.2.1 Catalytic-Based Process 9.2.4.2.1.1 Homogeneous-Acid-Catalyzed-Esterification (Pre-Transesterification Treatment)

If oils have FFA > 3 wt%, then esterification process (pre-­transesterification treatment) is carried out to reduced FFAs less than 3  wt%. FFA can be determined from the acidic values of oils by using Equation (9.3).

274  Biodiesel Technology and Applications



FFA = 0.5% * AV

(9.3)

In pre-transesterification treatment, VO having high FFA is reacted chemically with alcohol (methanol) in the presence of homogeneous acidic catalyst like sulfuric acid/H2SO4 or ferric sulfate which convert the FFA into biodiesel [14] as shown by Equation (9.4) Catalyst

→ FAME (Biodiesel) + H 2O Acid Free Fatty Acids (FFA) + ROH(Alcohol)  (9.4) Then, this mixture is transferred into separating funnel along with cold water and allowed to settle for appropriate time until two phases appeared. Upper layer contains excess of water-methanol fraction that is removed, and bottom layer containing fatty acid methyl ester, VO, and methanol was transferred into evaporator to remove existing methanol, and then, its acid value is determined prior to transesterification process. Then, this obtained biodiesel + VO is purified and neutralized by different kind of methods [15]; most preferable is transesterification.

9.2.4.2.1.2 Homogeneous Alkaline-Catalyzed Transesterification

Most efficient alkaline-catalyzed transesterification is carried out on those oils that have less than or equal to 1–3 wt% range of FFA ≤ 1–3 wt% [16, 17] because presence of more FFAs produce soaps by reacting with alkaline catalyst that makes difficulty in separating the biodiesel and glycerol [18]. It is necessary that FFA content should be less than 3% to achieve greater biodiesel conversion efficiency/yield [19]. Transesterification is the most popular method for producing biodiesel [11, 20]; in this process, short-chain alcohols (methanol, ethanol, propanol, butanol) are reacted chemically with VO (crop seed oils) or fats in the presence of alkali catalysts (like KOH, NaOH, and sodium methoxide) as shown by Equation (9.5). Mostly, methanol is preferred among all other alcohols due to its low cost. VOs have long-chain triglyceride structure of fatty acids. Mostly, methanol is preferable alcohol because of its low cost among other alcohols.



CH2

COOR1

CH

COOR2

CH2 OH Alkaline

CH

CH3 COOR1 OH + CH3 COOR2 CH3 COOR3 OH

+ 3 CH3OH Catalyst CH2 COOR3 CH2 Triglyceride of oil Alcohol (Methanol) Glycerol

Biodiesel (FAME)

(9.5)



Methods for Biodiesel Production  275 The conversion of triglyceride (VO) into diglyceride, monoglyceride, and glycerol along with biodiesel is a reversible three-step process as described by Equation (9.6) [4]. End products of alkaline-catalyzed transesterification process are glycerol and biodiesel (FAME). When this mixture is transferred to separating funnel, then glycerol sinks to the bottom of funnel and biodiesel remains at the top of glycerol. After removing glycerol from bottom, biodiesel is heated and filtered to remove alcohol and catalyst than biodiesel is washed and purified with warm water. Catalyst

1. Triglyceride (Vegetable oil) + ROH (Alcohol) → Diglyceride +FAME (Biodiesel) Catalyst

2. Diglyceride + ROH → Monoglyceride +FAME Catalyst

3. Monoglyceride + ROH → Glycerol +FAME

(9.6)

∴R is alkyl group of hydro- carbons





9.2.4.2.1.3 Heterogeneous-Catalyzed Transesterification

Transesterification process also used heterogeneous catalysts like metal oxides, oxides, mixed metal oxides, hydrotalcites (like aluminum and magnesium hydroxycarbonates, and zeolites), and supported hydroxides. Heterogeneous catalysts increase the biodiesel production, reduce saponification, and easy to recover from biodiesel than homogeneous catalyst. But, these required high temperature and pressure [21]. Alkaline earth metal (CaO, MgO, SrO), titanium silicates, sulfates, titanium, amorphous zirconia, potassium zirconia, and unsupported mixed metal oxides including CaO-La2O3 CaMnOx, BaMnOx, CaFeOx, BaFeOx, CaZrOx, and CaCeOx are the examples of heterogeneous catalyst. Table 9.1 showed the Comparison b/w heterogeneous and homogeneous catalytic transesterification process.

9.2.4.2.1.4 Enzymatic-Catalyzed Transesterification

There are various types of eco-friendly immobilized or soluble enzymatic catalysts that are also suitable for feedstock having more FFA and water under mild reaction conditions [22]. Enzymes include immobilized lipase, ryzopus oryzae lipase, liquid lipase eversa transform, callera trans L lipase, liquid lipolase, lipozyme, novozyme, ZIF-67, novozym 435, lipase immobilized, and CH2N2. Lipases enzymes are synthesized from plant, animal, and microorganism sources. These are relatively costly but require low energy consumption. Some companies are using enzymatic catalysts at industrial

276  Biodiesel Technology and Applications Table 9.1  Comparison between heterogeneous and homogeneous catalytic transesterification process. Heterogeneous catalytic process

Homogeneous catalytic process

Existence of water/free fatty acids

Not sensitive

Sensitive

Cost

Potentially cheaper

Comparatively costly

Reaction rate

Moderate conversion

Fast and high conversion

Catalyst reuse

Possible

Not possible

Post-treatment

Catalyst can be recovered

Acidic catalyst are used in neutralization so cannot be recovered, and produce chemical waste

Factors

levels including Piedmont Biofuel (USA), Sunho Biodiesel Corporation (Taiwan), Lvming Co. Ltd, and Hainabaichuan Co. Ltd (China). Costeffective catalysts can also be synthesized by combining multiple types of enzymes and lipases but alkali or acidic catalyzed transesterification processes are more economical and practical than enzymatic catalyzed.

9.2.4.2.2 Non-Catalytic-Based Process

Non-catalytic transesterification process does not use catalyst, so there is no need of catalyst removal and no saponification occurs, so glycerol is removed easily. It takes very less reaction time because of high solubility between alcohol and triglycerides of oils. Mostly, non-catalytic transesterification is performed by following two routes: (a) supercritical alcohol process and (b) BIOX co-solvent process [4, 23].

9.2.4.2.2.1 Supercritical Alcohol Process

The non-catalytic transesterification of VO can be performed with supercritical alcohols (like methanol/ethanol/propanol/butanol) which requires high temperatures (170°C–350°C), high pressure (10–60 MPa), and high alcohol consumption (molar ratio as 40–42), thereby increasing operational costs. In this process, fats or oils are treated with subcritical water then glycerol is removed from fatty acids (oil) phase by decantation. Fatty

Methods for Biodiesel Production  277 Vegetable oil (Triglyceride + free fatty acids)

Hydrolysis by subcritical water

Phase separation

Oil phase (fatty acids)

Water phase

Transesterification with supercritical alcohol

Phase separation

Phase separation

Alcohol recovery by rotary evaporator

Waste water

Glycerol

Biodiesel

Purification

Biodiesel ready for marketing

Figure 9.5  Supercritical transesterification process.

acid phase reacts with methanol under supercritical conditions to synthesize biodiesel (methyl ester). At the end, unreacted methanol and water is removed to get purified biodiesel as described in Figure 9.5. Schematic experimental setup is also described in Figure 9.6. Supercritical method can also be performed with appropriate co-solvent (CO2, etc.) to lower critical point of alcohol and decrease severity of supercritical reaction condition [24].

9.2.4.2.2.2 BIOX Co-Solvent Process

BIOX co-solvent transesterification is a commercialized approach that decreases the reaction time by enhancing the solubility of alcohol in cosolvent that quickly reacts with triglyceride phase of VO. This process

278  Biodiesel Technology and Applications 4

1. Electric furnace 2. Autoclave 3. Temperature control monitor 4. Pressure control monitor 5. Biodiesel exit valve 6. Condenser 7. Biodiesel collector vessel

3

5 2

6

7

1

Figure 9.6  Supercritical transesterification experimental setup.

requires low temperature. Methyl tert-butyl ether (MTBE) and tetrahydrofuran (THF) are utilized as recycled inert co-solvent to make a one-phase system by solubilizing alcohol in it, and biodiesel is synthesized in very short time of 5–10 min. Mostly, THF are preferred because its boiling point is closer to methanol boiling point. As no catalyst was used, so there is no need of catalyst removal from biodiesel or glycerol.

9.2.4.3 Microwave/Ultrasound-Assisted Transesterification Transesterification can also be performed by 300-MHz to 300-GHz microwaves containing high-frequency radio and infrared waves. These waves accelerate the chemical reaction between alcohol and VO to produce biodiesel [25], thus decreasing the reaction time from hours to few minutes. Similarly, ultrasound waves generate expansion (−ive pressure) and compression (+ive pressure) waves giving eddies/currents that increase the heat and mass transfer in the VO and alcohol mixture. Ultrasound waves vary between low frequency range of 20–100 kHz to high-frequency range of 2–10 MHz [26]. Both of these processes are efficient, economical, and time saving because these require less amount of catalyst. Figures 9.7a and b represent the experimental setup of microwave and ultrasound transesterification. Table 9.2 shows the comparison between different biodiesel production methods.

9.2.4.4 Variables Affecting Transesterification Reaction There are various variables that influence the biodiesel yield and quality but critical variables are moisture and FFA contents, oil-to-alcohol molar ratios, type of alcohol and catalysts, reaction time, and reaction temperature [27]. All these variables have great influence on reaction rate, biodiesel yield, and its conversion efficiency.

Methods for Biodiesel Production  279 Transducer

Water out

Water in

Microwave Oven

Power setting Reactor Time setting

Magnetic stir bar

Ultrasonic generator

Ultrasonic prob Al-foil Glass beaker

Magnetic stirrer

(a)

(b)

Figure 9.7  (a) Microwave assisted transesterification. (b) Ultrasonic assisted transesterification process experimental setup.

Table 9.2  Comparison between biodiesel production methods [7]. Biodiesel production methods Dilution

Advantage

Disadvantage

Simple process, high viscosity, low production, and capital costs

Unsaturated hydrocarbon chains reactivity, gum formation, high free fatty acid (FFA), not good to use in diesel engines directly, poor atomization, high viscosity, bad volatility, bad stability, incomplete fuel combustion, solidification of blend occurs at cold temperatures, injector nozzles plugging, engine durability of engine reduced, higher engine wear, higher engine running and maintenance costs, higher air pollution emission, lubricating oil thickening and deterioration (Continued)

280  Biodiesel Technology and Applications Table 9.2  Comparison between biodiesel production methods [7]. (Continued) Biodiesel production methods

Advantage

Disadvantage

Micro-emulsion

Low viscosity biodiesel formation with no by-product, single phase, lower nitrogen oxide emissions, good atomization of biodiesel

Heavy carbon deposition, incomplete combustion, lubricating oil degradation and thickening, sticking of injector needle

Pyrolysis

Simple process, good for hydro-processing industry, useful by-products like syngas is produced, No-pollution, biodiesel has satisfactory physiochemical properties

Require complex and expensive equipment, high temperature, high production cost, shortchain molecules are produced in biodiesel that are much similar to gasoline than diesel fuel, low purity of biodiesel

Transesterification

The most preferable method for biodiesel production, low cost, Simple equipment, suitable for industrialized production, high conversion yield, glycerol as by-product can be transformed into valueadded products, satisfactory viscosities, biodiesel properties are similar to diesel fuel

Vegetable oils with low free fatty acid and very less water content are required (with base catalyst), reversible side reactions also occurred, high reaction time, obtained biodiesel must be neutralized and washed. Non-catalytic transesterification required complex equipment due to high temperatures and pressure.

(Continued)

Methods for Biodiesel Production  281 Table 9.2  Comparison between biodiesel production methods [7]. (Continued) Biodiesel production methods Supercritical methanol

Advantage

Disadvantage

Good adaptability, no catalyst, high conversion yield, very less reaction time

Equipment cost is high; high energy consumption, high temperature, and pressure are required

For transesterification process, moisture and FFA content should be very low; otherwise, alkali-type catalyst will be consumed in neutralizing FFAs and moisture will produce soap and frothing that will make the biodiesel and glycerol separation difficult. Transesterification is a reversible process so higher alcohol-to-oil ratio is recommended than stoichiometric ratio so that high yield of biodiesel can be achieved in less time. Mostly, in catalytic transesterification, 1:6 oil-to-alcohol ratio is preferred, and in non-catalytic transesterification process, 1:40 oil-to-alcohol is preferred, but it can vary according to type of VO. Among different type of alcohols, methanol is preferred due to its low cost and low boiling point. Many different types of catalysts (acidic, alkali, enzyme, homogeneous, heterogeneous) are available but these are selected according to cost, availability, reaction condition, and type of oil. Concentrations of catalysts are also important but their optimum range should be determined because sometime higher concentrations have no or negative impact on biodiesel synthesis. Conventional transesterification takes more time (120 min), but time can be minimized by using advanced equipment as used in microwave, ultrasound or supercritical methods, etc. As it is reversible process, so it is necessary to suitable biodiesel production time. Similarly, transesterification occurred on different temperatures that influenced the biodiesel yield. In case of conventional transesterification temperature should be sustained below boiling point of alcohol. But, increasing of temperatures in supercritical process also increases the biodiesel yield. Optimum values and quantity of different variables should be determined to get maximum yield of biodiesel form various feedstock having different composition so behave differently. Production optimization for biodiesel synthesis form different VOs should be carried out by varying types/values and quantities of all variables involve in transesterification process.

282  Biodiesel Technology and Applications

References 1. Go, A.W., et al., Developments in in-situ (trans) esterification for biodiesel production: A critical review. Renewable and Sustainable Energy Reviews, 60: p. 284–305, 2016. 2. Atabani, A.E., et al., A comprehensive review on biodiesel as an alternative energy resource and its characteristics. Renewable and Sustainable Energy Reviews, 16(4): p. 2070–2093, 2012. 3. Pramanik, K., Properties and use of jatropha curcas oil and diesel fuel blends in compression ignition engine. Renewable Energy, 28(2): p. 239–248, 2003. 4. Balat, M. and H. Balat, Progress in biodiesel processing. Applied Energy, 87(6): p. 1815–1835, 2010. 5. Ma, F. and M.A. Hanna, Biodiesel production: a review. Bioresource Technology, 70(1): p. 1–15, 1999. 6. Ziejewski, M., et al., Diesel engine evaluation of a nonionic sunflower oil-aqueous ethanol microemulsion. Journal of the American Oil Chemists’ Society, 61(10): p. 1620–1626, 1984. 7. Lin, L., et al., Opportunities and challenges for biodiesel fuel. Applied Energy, 88(4): p. 1020–1031, 2011. 8. Lima, D.G., et al., Diesel-like fuel obtained by pyrolysis of vegetable oils. Journal of Analytical and Applied Pyrolysis, 71(2): p. 987–996, 2004. 9. Demirbaş, A. and H. Kara, New Options for Conversion of Vegetable Oils to Alternative Fuels. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 28(7): p. 619–626, 2006. 10. Sharma, Y.C., B. Singh, and S.N. Upadhyay, Advancements in development and characterization of biodiesel: A review. Fuel, 87(12): p. 2355–2373, 2008. 11. Mujtaba, M.A., et al., Critical review on sesame seed oil and its methyl ester on cold flow and oxidation stability. Energy Reports, 6: p. 40–54, 2020. 12. Kasim, F.H., A.P. Harvey, and R. Zakaria, Biodiesel production by in situ transesterification. Biofuels, 1(2): p. 355–365, 2010. 13. Park, J., et al., Wet in situ transesterification of microalgae using ethyl acetate as a co-solvent and reactant. Bioresource Technology, 230: p. 8–14, 2017. 14. Lee, A.F., et al., Heterogeneous catalysis for sustainable biodiesel production via esterification and transesterification. Chemical Society Reviews, 43(22): p. 7887–7916, 2014. 15. Chongkhong, S., et al., Biodiesel production by esterification of palm fatty acid distillate. Biomass and Bioenergy, 31(8): p. 563–568, 2007. 16. Karmakar, A., S. Karmakar, and S. Mukherjee, Properties of various plants and animals feedstocks for biodiesel production. Bioresource Technology, 101(19): p. 7201–7210, 2010. 17. Kombe, G.G., et al., Pre-Treatment of High Free Fatty Acids Oils by Chemical Re-Esterification for Biodiesel Production: A Review. Advances in Chemical Engineering and Science, Vol.03No.04: p. 6, 2013.

Methods for Biodiesel Production  283 18. Ramadhas, A.S., S. Jayaraj, and C. Muraleedharan, Biodiesel production from high FFA rubber seed oil. Fuel, 84(4): p. 335–340, 2005. 19. Dorado, M.P., An Alkali-Catalyzed Transesterification Process for High Free Fatty Acid Waste Oils. Transactions of the ASAE, v. 45(no. 3): p. 525–529, 2002. 20. M. Gul, et al., A review: Role of fatty acids composition in characterizing potential feedstock for sustainable green-lubricant by advance transesterification process and it’s Global as well as Pakistani prospective. BioEnergy Research, 2019. 21. Tabatabaei, M., et al., Reactor technologies for biodiesel production and processing: A review. Progress in Energy and Combustion Science, 74: p. 239–303, 2019. 22. Tan, T., et al., Biodiesel production with immobilized lipase: A review. Biotechnology Advances, 28(5): p. 628–634, 2010. 23. Demirbas, A., Progress and recent trends in biodiesel fuels. Energy Conversion and Management, 50(1): p. 14–34, 2009. 24. Han, H., W. Cao, and J. Zhang, Preparation of biodiesel from soybean oil using supercritical methanol and CO2 as co-solvent. Process Biochemistry, 40(9): p. 3148–3151, 2005. 25. Lidström, P., et al., Microwave assisted organic synthesis—a review. Tetrahedron, 57(45): p. 9225–9283, 2001. 26. Veljković, V.B., J.M. Avramović, and O.S. Stamenković, Biodiesel production by ultrasound-assisted transesterification: State of the art and the perspectives. Renewable and Sustainable Energy Reviews, 16(2): p. 1193–1209, 2012. 27. Meher, L.C., D. Vidya Sagar, and S.N. Naik, Technical aspects of biodiesel production by transesterification—a review. Renewable and Sustainable Energy Reviews, 10(3): p. 248–268, 2006.

10 Non-Edible Feedstock for Biodiesel Production Chikati Roick1, Kabir Opeyemi Otun2, Nkazi Diankanua1 and Gorimbo Joshua2* School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, South Africa 2 Institute for the Development of Energy for African Sustainability (IDEAS), University of South Africa’s College of Science, Engineering and Technology, Florida, South Africa

1

Abstract

Continuous increase in the world’s population and high energy demand together with environmental concerns have called for a sustainable and renewable substitute for fossil fuels. Of all the existing solutions, biodiesel which can be generated from either edible and non-edible sources and these resources have proven to be an appropriate alternative due to its renewable, low toxic, and environmentally friendly nature. However, the use of non-edible feedstocks can be certain to be a sustainable source of biodiesel production because they can be grown on ­abandoned/wasteland, where they do not have competition with food crops, they are relatively cost-effective and produce a similar and sometimes higher yield and fuel properties as the edible feedstocks. This chapter is, therefore, on the potentials of non-edible feedstocks such as non-edible vegetable oils, waste cooking oil, waste animal fats, and microalgae for biodiesel synthesis. Among the highlights of this chapter are the reports relevant to global warming and climate change, modern technology for biodiesel synthesis from non-edible sources including transesterification, fuel properties of the biodiesel produced from non-edible feedstocks, the economic benefits, as well as the environmental concerns. It can be concluded from this chapter that non-edible feedstocks are promising for biodiesel industrialization as they meet the worldwide internationally recognized standards.

*Corresponding author: [email protected] Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (285–310) © 2021 Scrivener Publishing LLC

285

286  Biodiesel Technology and Applications Keywords:  Biodiesel, renewable energy, non-edible feedstocks, global warming, transesterification, climate change

List of Abbreviations IMF MDG AREI SADCC GHG FAME WCO ASTM

International Monetary Fund Millennium Development Goals Africa Renewable Energy Initiative Southern African Development Community Greenhouse gases Fatty acid methyl esters Waste cooking oil American Standards for Testing Materials

10.1 Introduction The 21st century is plagued with series of challenges that cause degradation of our soils, freshwater, oceans, forests, and biodiversity. The scourge of climate change is also not helping the matter as it is even adding more pressure on the resources we rely upon by aggravating the risks connected with disasters, such as droughts and floods. Although, intensive efforts at all levels of governance have contributed greatly in the campaign against climate change. Yet, global warming continues to threaten the ecosystem and the standard of living around the world, and the solutions to mitigate climate change to barest minimum seem not adequate. The major contributor to this is the greenhouse gas emission which contain majorly carbon dioxide. While mitigation policies can help in no small way to mitigate the risks associated global warming caused by human (anthropogenic), increasing the capacity of carbon sinks via reforestation is another great measure. For instance, several approaches have already been adopted to mitigate climate change these include energy use reduction by increasing energy efficiency, using alternative energy source to substitute petroleum-based fuels and removal of carbon dioxide (CO2) from the atmosphere. Biofuel, such as biodiesel and bioethanol, has no significant CO2 contribution to the accumulation of greenhouse gas emission and, hence, can serve as a viable solution to climate change. They are defined as liquid or gaseous fuels which can be sourced from biomass and used chiefly in the transportation sector. As a key replacement to petroleum, biodiesel is considered sustainable and environmentally benign which has elicited a surge

Non-Edible Feedstock for Biodiesel Production  287 of interest from researchers across the globe in the last few years. Biodiesels are esters of long chain fatty acids that range in size from C12 to C24 [1, 2]. By using biofuel produced from biomass for transportation, we can help promote the solution to meeting ever-increasing global energy demands and restoring natural balance of CO2 in the atmosphere. Apart from replacing fossil fuels, the feedstocks employed in producing biofuels require CO2 to germinate and they absorb their food from the atmosphere. So, most, if not all the CO2 released to the atmosphere when biomass is burnt in engines is captured again when new biomass is cultivated to produce more biofuels. Therefore, biofuel is a very effective way of reducing these emissions. The last few years has witnessed a rapid growth in biodiesel production to curb the adverse effects of CO2 emissions. This chapter, therefore, focuses on the reports relevant to global warming and climate change and modern technology for biodiesel synthesis from non-edible sources including transesterification with a view of mitigating the effects of climate change. We also discuss the fuel properties of the biodiesel produced from non-edible sources, their economic benefits, as well as the environmental concerns.

10.2 Reports Relevant to Global Warming and Renewable Energy Renewables may hold the key to a clean energy future. The main goal of climate change mitigation as contained in the Paris Agreement is to limit the world-wide average temperature increase to below 1.5°C above preindustrial levels. To meet this goal, the final energy consumption must have a share of renewable energy that will increase from 19% in 2017 to 65% by 2050. The last few years has witnessed a surge of interests from different nations implementing national or regional plans to mitigate the adverse impact of carbon dioxide (CO2) emissions. Fossil fuels are now considered as an unsustainable source of energy due to contamination of the environment and causing climate changes. Some repercussions of climate change include new weather patterns that continue to exist for considerable amount of time. Renewable energy as a source got attention due to strict environmental regulations. Technologies for renewable-energy production are comparatively cheap and sustainable than the existing coal generation [3]. According to International Monetary Fund (IMF), some governments, local and regional policymakers must bring to a resolution whether to close down or reduce energy production from existing coal plants en route toward decarbonization [4].

288  Biodiesel Technology and Applications Global warming is now a pursuit central to many research laboratories all over the world. Its effects are now visible and a present threat. Our actions and commitments thus far are not good enough. International and regional organizations have been pivotal in awareness and developing policies to curb climate change. For instance, UN is suggesting tax structures and fiscal blueprint to put a stop emission of carbon from fossil fuels. Climate related monitoring reports and agreements such as the IMF [4], Paris Agreement [5], Copenhagen accord [6], United Nations, General Assembly [7], Africa Renewable Energy Initiative (AREI) [8], Renewable Energy and Energy Efficiency Strategy and Action Plan for the Southern African Development Community [9], Millennium Development Goals (MDG) [10], Kyoto Protocol [11] all aim at stabilizing GHG concentrations in the atmosphere. Some of the objectives of the selected agreement and reports, and in response to these, some countries have put through comprehensive governmental climate action schemes to control climate change. Up to the present time, these commitments are still not sufficient to achieve the agreed temperature objectives as per the Paris Agreement; nevertheless, the mentioned agreement draws up the way to further action. Climate researcher and technologist proclaim that carbon emissions must be rapidly reduced with the objective of achieving a net zero by 2050, or earlier [12].

10.3 Biofuels as an Alternative Energy Source Biomass is defined as the plant or animal matter that can be utilized for energy production such as electricity or heat. Biofuels are categorized as natural, primary and secondary biofuels. Generally, natural biofuels are extracted from organic materials, in particular vegetables, waste from animals, and landfill gas. Primary biofuels are fuels from wood usually used for cooking and heating in most rural areas and, in some case, electricity production. Secondary biofuels refers to bioethanol and biodiesel that are sourced from processing biomass. The secondary biofuels are additionally grouped into first-, second-, and third-generation biofuels based on their source, development levels, and the processing technology as shown in Figure 10.1.

10.3.1 First-Generation Biofuels This generation of biofuels  is those fuels originating from what human beings use as food for example sugar, starch, vegetable oil, animal fat, etc.

Non-Edible Feedstock for Biodiesel Production  289

1st Generation

2nd Generation

3rd Generation

4th Generation

• Edible biomass • E.g. sugar beet, corn, wheat, etc.

• Non-edible biomass • E.g. Wood, straw, grass, waste, etc.

• Algal biomass • Microalgae • Macroalgae

Breakthrough Genetically engineered crops and algae

Figure 10.1  Biofuels production sources adapted from [13].

Some examples of the most common types of first-generation biofuels are as follows: • • • • •

vegetable oil, biodiesel, syngas, biogas, and bio-alcohols.

Despite of these first-generation fuels possessing potential to be used in generating carbon neutral biofuels, this approach could have notables economic and political concerns as grain and food prices will go up [13]. Martin (2010) looked at the conflicts of first-generation biofuels and the implications it has on developed and developing economies [14]. The major downside of using the first-generation fuels is the use of arable agricultural lands and as a consequence shortage of land for animal and human food production rendering the food-vs-fuel quandary a moot point.

10.3.2 Second-Generation Biofuels Biofuels under this category are also referred to as advanced biofuels, and these fuels originate from various types of non-food biomass. Lignocellulosic biomasses (such as agricultural waste, and woody crops) are the major feedstocks in the production of second-generation biofuels. Second-generation biofuel feedstock can also be the nonedible

290  Biodiesel Technology and Applications by-product of food crops such as the corn husks or Panicum virgatum (wheat straw) and other variety of plants that are not edible, for instance, switch grass. The technology used allows the plant cellulose and lignin to be separated in order for cellulose to be fermented into alcohol. These biofuels can be sourced from a variety of biomass. A considerable number of companies and research groups are venturing into cost effective processing for producing second-generation biofuels such as ExxonMobil which is pursuing research to determine how these biofuels may best fit into future energy.

10.3.3 Third-Generation Biofuels Beyond second-generation biofuels, engineers and scientists have also looked at the so-called third-generation biofuels, largely derived from algae (microalgae and cyanobacteria) [15, 16]. Different from the firstand second-generation derived biofuels, algae poses no threat to food security. Algae can be grown in brackish water and in some cases seawaters making it human friendly source of biofuel, as it does not put an enormous strain on the freshwater. More so, no agricultural land is used to grow the algae; therefore, little or no competition exist land for food production. Algae are defined as photosynthetic organisms that convert atmospheric CO2 and H2O to oil using light from the sun, and it is the oils that gets converted to biodiesel portion via a series of processes [17]. Also, of interest is the water hyacinth (scientific name Eichhornia crassipes) which has been reported to have a high biomass yield and can grow exponentially. These too can be a potential feedstock for biofuel production and related bioactive ingredients [18]. The advantages of both algae and the water hyacinth is the fact that they are aquaculture, that they reproduce exponentially, and can be cultivated in salty water giving biomass of higher energy content. The amount of oil produced in both systems, however, is a function of parameters such as sunlight exposure times and atmospheric CO2 levels.

10.4 Benefits of Using Biodiesel The advantages of utilizing biodiesel in internal combustion engines are overwhelming and relate to its broader applications based on the following highlights:

Non-Edible Feedstock for Biodiesel Production  291 a. Biodiesel is less toxic and safer to handle than petroleumbased diesel due to its relative high flash point. b. Biodiesel is a sustainable and renewable source of energy with zero harmful emission. c. The simplicity and low capital cost of biodiesel production enhances its wider distribution and use commercially. d. The starting materials for biodiesel synthesis are organic and can be sourced locally. In fact, more biodiesel can be reaped from non-edible and waste oils nowadays. e. In terms of energy conversion and power outputs, generally, diesels engines are more efficient than petrol engines. f. Most countries have adopted biodiesel as a means of foreign exchange. The availability of raw materials for biodiesel production has encouraged local farmers to embark on mass plantation which in turn has created more job opportunities and serves and increasing the production of foreign exchange. g. Biodiesels are clean burning fuels with low emission of greenhouse gases [14, 19].

10.5 Technologies of Biodiesel Production From Non-Edible Feedstock Generally, four main methods have been developed to produce biodiesel to fit in into our conventional engines without any amendments [20]. These are as follows. 1. Direct use or blending (Dilution): This method is the oldest and easiest method of biodiesel production. Vegetable/animal oils are not advisable to use as is in engines because of its high viscosity which may trigger other challenges. To circumvent these challenges, vegetable oils can be blended with diesel oils in some limited ratio. Blend ratios which results in optimum performances in diesel driven engines are generally of less viscosity which is achieved by mixing considerable proportion of petrodiesel (preferably 80%) with lower percentages of renewable vegetable/animal oils (preferably 20%). Carbon deposition in engine cylinder and improper combustion are some of the demerits of this process.

292  Biodiesel Technology and Applications OCOR1

H2C HC

OCOR2

H2C

OCOR3 Triglyceride

+

base

3 CH3OH

Methanol

H2C

OH

H3C

OCOR1

HC

OH

+ H3C

OCOR2

H2C

OH

H3C

OCOR3

Glycerol

Fatty acid methyl esters (Biodiesel)

Figure 10.2  Transesterification reaction for biodiesel production [24].

2. Micro emulsification: This is basically prepared by mixing alcohol, surfactants, vegetable/animal oil, diesel fuel, and cetane improver in different fractions. This process is easy but produces a less volatile, less stable, and highly viscous mixture, which is the main drawback of the process. The challenges associated with the viscosity of vegetable oils can be curtailed by making of microemulsion. It is the solubilization of oils with the aid alcoholic solvents and surfactants [21]. 3. Thermal cracking or pyrolysis: This process involves heating of vegetable or animal oils at high temperature (usually 300 to 1,300°C) in the presence or absence of a catalyst and absence of oxygen. It is simple and produces less waste and less emission. It is very effective when compared with other cracking processes. High installation cost and oxygen removal during pyrolysis are some of the challenges encountered by this process [22]. 4. Transesterification: This is considered as the reaction in which triglycerides (oils/organic fats) are reacted with suitable alcohol in the presence of acidic/alkaline catalyst to yield fatty acid esters (biodiesel) and glycerol. This process produces biodiesels that have comparable features with diesel fuels and is the most promising route for commercial production of biodiesel from the economic point of view [23]. The transesterification process is the most convenient method because it is cheap and simple while the choice of feedstock is key since it contributes a significant seventy percent of the total production cost from edible and non-edible sources [20]. The transesterification reaction is shown in Figure 10.2.

10.6 Biodiesel Production by Transesterification Among the methods previously discussed, transesterification is the commonest and the most preferred method to produce biodiesel because of

Non-Edible Feedstock for Biodiesel Production  293 its simplicity and it has been widely employed in industry to convert oils into biodiesel. It also affords the use of a wide range of feedstocks to produce a biodiesel that greatly resembles conventional diesel in terms of quality. First-generation biodiesel is produced via transesterification of triglycerides from vegetable oils, while second-generation biodiesels are obtained from feedstocks like lignocellulose and non-edible triglycerides. Transesterification involves chemically converting various types of oils into fatty acid methyl esters (FAME) and glycerol in the presence of catalysts [25]. FAME, commonly known as biodiesel, is the monoalkyl esters of long chain fatty acids. Table 10.2 shows the major free fatty acids present in biodiesel production. Type of catalyst, nature of raw material, reaction conditions, type of solvent, reactor type, and solvent to oil ratio are some of the key variables required to obtain optimum yield for biodiesel production via transesterification process [26]. Of all these factors, catalyst type and type of feedstocks are the key parameters for effective biodiesel production because they both determine the price of biodiesel production to a greater extent. These catalysts are divided into two major types, homogenous or heterogeneous: a) Homogeneous catalyst: In homogenous catalysis for transesterification, alkaline or basic catalysts are more preferred to the acid catalysts choice because of their high conversion rate in relatively short time. In addition, basic catalysts do not corrode easily with industrial equipment. The most common examples of homogeneous catalysts for this reaction are KOH, and NaOH (alkaline) and H2SO4 and H3PO4 (acidic). The major demerit of the basic catalysts is their high sensitivity to fatty acids contained in the feedstock. Acid catalysts are also well suited for the transesterification reaction of highly fatty materials present in fats and oil. However, they are slower than base catalyzed reaction and require high temperature and pressure and high amount of alcohols for the esterification reaction. In general, homogenous catalysts is majorly at disadvantage because of the separation of the catalysts from the products and inability to reuse. Removal of catalysts involves several washing steps and activation which increases the total cost of production [27].

294  Biodiesel Technology and Applications b) Heterogeneous catalysts: Heterogeneous catalysts which offers to replace homogeneous catalysts are usually solid materials that can be obtained from renewable materials following pyrolysis at high temperature between 500°C and 900°C [28]. They are better than homogeneous catalysts in the sense that they are easy to separate from the products can be reused, and no side reaction. Moreover, the biodiesel produced from these catalysts yielded about 96% FAME content [28]. The most frequently used heterogeneous basic catalysts are oxides and carbonates of alkali and alkaline-earth metals. c) Enzymatic transesterification: Diesel production via this enzyme-catalyzed transesterification pathway experimented by Dhawane et al. (2018) [29] and Andrade et al. (2017) [30] with the use of lipase enzyme and methanol [31]. It involves hydrolysis and esterification of triglycerides (substrate) to produce FAMEs (diesel). This process is highly promising because of their high conversion rate, ease of separation from the product, good glycerol recovery and high yield when compared with the homogenous and heterogeneous catalysts. Nonetheless, biodiesel synthesis via enzymatic transesterification is expensive because of lipase manufacturing and other intricate stages involved in cellular enzyme synthesis and separation. Table 10.1 gives some of the common free fatty acids in biodiesel production with Figure 10.3 showing a flow chart of biodiesel production process through transesterification process.

Table 10.1  The common free fatty acids in biodiesel production [32]. Entry

Name of fatty acid

Chemical name

Structure

1

Palmitic

Hexadecanoic acid

C16:0

2

Stearic

Octadecanoic acid

C18:0

3

Oleic

Octadecenoic acid

C18:1

4

Linoleic

Octadecadienoic acid

C18:2

5

Linolenic

Cis-9, cis-12, cis-15octadecatrienoic acid

C18:3

Non-Edible Feedstock for Biodiesel Production  295

Alcohol + catalyst

Biodiesel

Drying 350-400ºC, Transesterification 20 h (oil/alcohol ratio) To remove unreacting raw To remove contaminants materials

Washing

t en tm a e l, etr Pr ysica ical, Feedstock Ph olog bi

Glycerol

Figure 10.3  Flow chart of biodiesel production process through transesterification process.

10.7 Non-Edible Feedstocks for Biodiesel Production Mostly, biodiesels can be prepared from two major sources (feedstocks), namely, edible and non-edible feedstocks as shown in Figure 10.4. In 2017, the worldwide biodiesel production was credited to palm oil (31%), soybean oil (27%), rapeseed oil (20%), waste cooking oil (WCO) (10%), animal fats (7%), and others (5%) [33]. Although, the use edible feedstocks may be the cheapest feedstock for biodiesel production for the future, but it is not sustainable to meet the increasing demand for biodiesel [34]. Hence, the use of non-edible feedstocks is a sustainable alternative in the sense

Edible

• Corn, soybean, sunflower, etc

Non edible

• Vegetable oil • Waste animal oil • Waste cooking oil • Algae, lignocellulose, etc

Biodiesel Feedstocks

Figure 10.4  Biodiesel production from edible and non-edible feedstocks.

296  Biodiesel Technology and Applications that it does not compete with the food crops for limited plantation region and has the potentials of reclaiming the wastelands [35]. Based on the data available from the literature, WCO, animal oil, non-edible vegetable oil, waste animal oil, and alga oil are the most promising alternatives for edible oils and are elucidated as follows.

10.7.1 Non-Edible Vegetable Oils The toxic chemicals present in non-edible vegetable oils make them unusable for human consumption. In addition, the threat posed by both the food security and economic issues also make non-edible vegetable oils more preferred than edible vegetable oils in the sense that it does not encourage serious competition over land for food production and for the food supply chain. i) Jatropha is a tropical and drought-resistant plant that can thrive in an abandoned and fallowed farmland [20]. It has been recognized as one of the suitable non-edible sources for biodiesel production due to its physiochemical properties. It is a rich source of hydrocarbons and has picked the interest of researchers all over the world because of the use of its seed oils as alternative feedstock for biodiesel production. There are about 20%–60% oil in the seeds of jatropha plant and contain mainly unsaturated fatty acids likes oleic (42%) as the major component, followed by linoleic (35%) and smaller percentage of palmitic (14%) and stearic acid (6%) [36]. Recently, Salar-Garcia et al. (2016) obtained 99.5% biodiesel production yield from Jatropha oil and 100% conversion rate of triglycerides at 325°C in 90 min [37]. ii) Karanja (botanical name Pongamia pinnata) is another potential non-edible vegetable oil feedstock that can be used to produce biodiesel. Countries like Southeast Asia, US, Australia, New Zealand, India, and China are the main producers of this plant [38]. Interestingly, these trees can grow in many places including roadsides, canals, and boundaries of farmlands. The oil content of its seed ranges between 30% and 40%, and can yield 97% FAME (biodiesel) via transesterification process at a temperature of 65°C using 1 wt% of KOH and alcohol to molar ratio of 6:1 in 2 h. Karanja oil contains stearic acid (up to 8.9%), linoleic acid (up to 18.3%), and oleic acid (up to 71.3%) [39]. iii) Linseed which is also referred to as Linum usitassimum is another potential non-edible feedstock for biodiesel production. Linseed can produce oil up to 47% under optimum conditions [40]. The main fatty acids which are mainly found in linseed oils are linolenic (up to 51%), oleic acid (up to 21%), linoleic acid (up to 15%), and small amounts of

Non-Edible Feedstock for Biodiesel Production  297 Table 10.2  Current research on non-edible vegetable oils as low-cost feedstocks for biodiesel production via transesterification. Non-edible vegetable source

Catalyst

Methanol/ oil

Temperature (°C)

Time (h)

Yield (%)

Ref.

Jatropha curca

KOH, 1 wt%

6:1

60

1

96.1

[42]

Linseed

KOH, 1 wt%

9:1

60

2

95.5

[43]

Karanja

γ-Alumina

1:9

50

0.83

69.3

[44]

Neem

Cu/ZnO nanocatalyst, 10 wt%

10:1

55

1

74%

[45]

Rapeseed

6 wt% Na/FAP

10:1

120

8

98.5

[46]

Cotton seed

KOH, 1 wt%

6:1

25

5 min

-

[39]

Castor

KOH, 1.25 wt%

12:1

60

1

95

[47]

Jojoba

KOH, 1 wt%

6:1

50

1

78.5

[48]

palmitic acid (6%) and stearic acid (5%) [41]. Other non-edible vegetable feedstocks include but not limited to neem, jojoba, desert date, sea mango, rubber, tobacco, and castor, among others. Recent studies on non-edible vegetable oils as sources for the production of biodiesel are shown in Table 10.2.

10.7.2 Waste Cooking Oil WCOs are the left over oils after a deep-frying procedure and the used oil can be a suitable feedstock for biodiesel production. According to Loizides et al. (2019), about 16.5 million tons of WCO is produced annually [49]. The lower solubility of these oils makes their disposal very challenging. Therefore, the conversion of WCO into biodiesel will greatly help to mitigate the disposal problem while helping to solve the energy crisis. WCO can be categorized according to the source such as household, food industry, and non-food industry. Acid, base, and enzymes can be used to promote the conversion of WCO into biodiesel. Recently, it was reported that demonstrated that sulfonated catalysts can effectively convert WCO into biodiesel [50]. The FAME content obtained from pyrolyzed rice straw was around 97.7%, conversion efficiency was 90.4%, and 91.1% free fatty acid conversion rate with 10 wt% catalyst, methanol-to-oil ratio of 20:1 at 70°C

298  Biodiesel Technology and Applications Table 10.3  Recent studies on waste cooking oils as feedstocks for the production of biodiesel via transesterification reaction. Catalyst

Loading (wt%)

Alcohol

Oil/alcohol

Temperature (°C)

Time

Yield (%)

Ref.

KOH/Clinoptilolite

9.1

MeOH

2.25:1

61

13.4 min

97.5

[52]

ZnAl2O4

5

MeOH

1:18

100

3h

94.9

[53]

RS-SO3H

10

MeOH

1:20

70

6h

97.7

[50]

4

MeOH

1:8

65

75 min

98.2

[27]

15

MeOH

1:14

70

3h

94.8

[54]

CaO Kaolinite/K

+

for 6 h [50]. Similarly, Maneerung and co-workers produced biodiesel with 90% FAME yield using calcined chicken manure as a precursor of CaO catalyst [51]. The result was obtained under optimum conditions at 7.5 wt% catalyst, the obtained methanol-to-oil ratio was 1:15 at 65°C [51]. Recent studies on WCOs as feedstocks for the production of biodiesel via transesterification reaction are tabulated below (see Table 10.3).

10.7.3 Algal Oil Algal species, which are regarded as the third-generation feedstock, are a promising non-edible source of biodiesel. Algae can grow in both natural and artificial environment, and they are more economically viable than edible oils. There are about 44,000 species of microalgae and a careful selection of an appropriate algal strain is crucial to the overall performance of biodiesel production [55]. Different microalgae including Chlorella sp., Chlorella vulgaris and Dunaliella salina algae, among others, have been reported to be valuable in biodiesel production (see also Table 10.4). Algal biodiesel has no sulfur and performs just like petroleum diesel, while minimizing the emission of harmful gases like CO, SOx, and NOx. Algal oils have been one of the best choices for researchers as algae provides more oil yield per area of arable land. To make microalgae more economically viable, attention should be shifted to minimizing the cost of feedstocks, inducing the lipid content, improving extraction efficiency, increasing the area productivity, and helps to convert of algal lipids to biodiesel. Of all these, the feedstock alone equals about 80% of the total production cost, which can be drastically lowered by the use of waste and less costly raw materials [56]. Transesterification is the most preferred process to produce biodiesel from algal oil. This process can be economical and time-saving if key factors

Non-Edible Feedstock for Biodiesel Production  299 Table 10.4  Recent studies on algal oils as feedstocks for biodiesel production via transesterification method. Feedstock

Catalyst

Loading (wt%)

Oil/MeOH

Temperature (°C)

Time (min)

Yield (%)

Ref.

Chlorella Vulgaris

NaOH

38

1:600

60

10

96

[57]

Algal lipids

Ca(OCH3)2

3

1:30

80

150

99

[58]

Algal oil

CaO

1.25

1:9

55

-

96.3

[55]

Algal oil

Waste clay/ ZnO

3.5

1:9

60

240

97.4

[59]

Algal lipid

Immobilized C. rugiza lipase

1.39

1:19

70

180

92.03

[60]

like time of reaction, catalyst amount, and oil/alcohol ratio are optimized. Narula et al. (2017) produced 88.9% yield of biodiesel from algal oil via transesterification reaction by using CaO and CaO.Al2O3 as catalysts [55].

10.7.4 Waste Animal Fat/Oil Animal fat is classified under the third-generation feedstock for biodiesel production. The co-product of meat and fishery is animal fat. Examples include beef tallow or mutton and yellow grease. These feedstocks, unlike edible oils, are important for their food security, economic, and environmental benefits. Presently, the co-products obtained from animal fats have a very low market price and hence can be instrumental as an important source of biodiesel production (see Table 10.5). In addition, most animal fats are no longer allowed to be used as food any longer due to the many infections that ravaged animals. For instance, tallow from diseased livestock is a key feedstock for biodiesel production for the same reasons above. However, inconsistent supply poses a great challenge for all these feedstocks because animal fat is not only produced for biodiesel production [61].

10.8 Fuel Properties of Biodiesel Obtained From Non-Edible Feedstock Different factors affect the fuel properties of biodiesel obtained from non-edible feedstock. This includes, but not limited to, quality of raw

300  Biodiesel Technology and Applications Table 10.5  Recent studies on waste animal fat/oil as feedstocks for production of production via transesterification process. Waste animal fats/oils

Catalyst

Loading (wt%)

Oil/MeOH

Temperature (°C)

Time (min)

Yield (%)

Ref.

Animal tallow oil

NaOH

-

1:6

60

180

-

[62]

Mutton fat

KOH/MgO

4

1:22

65

20

98

[63]

Fish oil

CaO-Ca3Al2O6

10

1:12

54

90

96.4

[64]

Waste shark liver

NaOH

5.9

1:6

65

60

96

[65]

Waste chicken fat

CaO/CuFe2O4

3

1:15

70

240

94.52

[66]

materials and fatty acid compositions, method of production, processes involved in refining, and final production conditions [60]. There are different measures to classify fuel properties of biodiesel, the most important of which are: influence of activities taking place in the engine (such as ignition quality, calorific value, combustion of air-fuel mixture, and formation of exhaust gas among others), low temperature properties (like cloud point, pour point, etc.), transportation and storage properties (flash point, oxidation and hydrolytic stability, etc.), wear of engine parts (viscosity, lubrication, etc.) [50]. In addition, these properties must meet the internationally established worldwide standards in order to make the biodiesel useful for commercial purposes, which are American Standards for Testing Materials (ASTM D6751) and European (EN 14214) Standards for biodiesel fuel. In order to obtain high quality biodiesel, as per ASTM and EN standards, optimization of the pretreatment processes, separation of the product, and the final purification steps should be done optimally. Additionally, the free fatty acid contained within the oil blend to a large extent influences quality and the properties of the fuel. The literature reports that factors like cetane number, flash point, viscosity, cloud point, and iodine value are the most important physicochemical qualities of biodiesel and are strongly affected by the composition of FAME [67]. A summary of the physicochemical properties of biodiesel obtained from selected non-edible feedstock vis-à-vis the ASTM and EN standards are given in Table 10.6.

Cetane number

59

54

80

59.64

-

56.1

Non-edible feedstock

Waste cooking oil

Cotton seed

Castor

Jatropha curcas

Chicken fat

Chlorella sp 4.6

5.3

5.65

13.75

4.06

4.63

Viscosity (mm2/s)

113

171

184

149

200

161

Flash point °C

886

858

862

927

850

887

Density Kg/m3

−2.2

18

-

-

−10

-

Cloud point

[24]

[66]

ASTM D6751 ASTM D6751, EN

[37]

[47]

[39]

[25]

Ref.

ASTM D6751

ASTM D6751

EN 14214, ASTM D6751

ASTM D 6751

Standard

Table 10.6  Summary of the physicochemical features of biodiesel produced from non-edible feedstocks.

Non-Edible Feedstock for Biodiesel Production  301

302  Biodiesel Technology and Applications

10.9 Advantages of Non-Edible Feedstocks The various results obtained from different researchers across the globe have shown that non-edible feedstock have the following advantages with respect to biodiesel production [68]. 1. Non-edible feedstocks can be cultivated in marginal land and non-agricultural lands. 2. Non-edible sources do not contend with available agricultural resources. 3. They do not threaten food security because they are inappropriate for human consumption due to the non-toxic components they contain. 4. Most of the non-edible feedstocks are free from pests and diseases. 5. Oils obtained from non-edible feedstocks are readily available, renewable, and biodegradable, with low sulfur and aromatic contents. 6. Non-edible feedstocks produce useful by products. For example, the seed cakes obtained after oil expelling can enhance soil enrichment. 7. Most non-edible feedstocks have a considerable amount of short-chain fatty acids, which gives special features to biodiesel. 8. They are more eco-friendly than non-edible feedstocks. 9. Non-edible feedstocks can be cultivated in wastelands that are not ideal for human food crops. 10. They have the potentials to restore degraded lands and create job opportunities. 

10.10 Economic Importance of Biodiesel Production Capital cost, raw materials cost, process technology, plant capacity, and chemical costs are key economic factors in biodiesel production. Of all, the cost of feedstocks alone is equivalent to 80% of the total production cost, while the cost of catalyst, methanol, and utilities are equally important [69]. For instance, it costs 0.82 USD/litre to make biodiesel from palm oil including the feedstock price of 0.73, while it takes 0.6 USD/litre to produce the same biodiesel from tallow fat including the feedstock cost of 0.4 USD [70]. Most importantly, biodiesel production helps to boost economy

Non-Edible Feedstock for Biodiesel Production  303 in both developing and developed countries by creating job opportunities for the rural community, minimizing greenhouse gas emissions, boosting income tax revenue, and reducing country’s over dependence on crude oils. Recently, the use of non-edible feedstocks that do not contend with the food crops is a reasonable way of improving biofuel production. In terms of socio-economic effects, biodiesel, a sustainable and renewable energy source, is good substitutes for petroleum fuels. Hence, they can help to reduce greenhouse gases that bring about global warming, promotes regional development, and boosts food security and supply. Biodiesel also have health, environmental, safety, and other benefits in addition to economic advantages [3].

10.11 Conclusions In this chapter, we discussed the production pathways of biodiesel from non-edible feedstocks, with respect to their benefits, up-to-date technology, properties of the fuel produced, the economic benefits, and the environmental concerns which provides some key conclusions. Different methods can be used to produce biodiesel from oils. These include pyrolysis, dilution, micro-emulsion, and transesterification. Among these, the most economically viable is transesterification and the produced biodiesel compares favorably with the petroleum-based biodiesel Choice of feedstocks is a crucial factor in the synthesis of biodiesel. Based on the various feedstocks, non-edible oils, algal oils, waste animal fats, and WCOs are promising sources for biodiesel production. Production of biodiesel from non-edible sources has become attractive because they are renewable and sustainable source that guarantees food security, improves local economy, and reduces pollution. Of the various costs of biodiesel production, the feedstock price is almost 80% of the total production cost. A better way of lowering the cost of biodiesel production is to develop technology that will make use of bye products and makes judicious and favorable choice of the feedstocks. The biodiesel made from non-edible sources meet internationally recognized standards.

Acknowledgments The authors are grateful for the financial support provided by the University of South Africa (UNISA), University of the Witwatersrand, National Research Foundation (NRF) of South Africa, and the Institute for

304  Biodiesel Technology and Applications the Development of Energy for African Sustainability (IDEAS) research unit at UNISA.

References 1. G. L. Alexandrino, J. Malmborg, F. Augusto, and J. H. Christensen, Investigating weathering in light diesel oils using comprehensive twodimensional gas chromatography–High resolution mass spectrometry and pixel-based analysis: Possibilities and limitations, J. Chromatogr. A, vol. 1591, pp. 155–161, 2019. 2. F. C. Y. Wang, Comprehensive three-dimensional gas chromatography mass spectrometry separation of diesel, J. Chromatogr. A, vol. 1489, pp. 126–133, 2017. 3. K. Gillingham and J. H. Stock, The Cost of Reducing Greenhouse Gas Emissions, J. Econ. Perspect., vol. 32, no. 4, pp. 53–72, 2018. 4. International Monetary Fund. Fiscal Affairs Dept, Fiscal monitor, How to Mitigate Climate Change. 2019. https://www.imf.org/en/Publications/FM/ Issues/2019/09/12/fiscal-monitor-october-2019, (accessed 15 February 2020). 5. Paris agreement, 2015. https://unfccc.int/process-and-meetings/the-parisagreement/the-paris-agreement, (accessed 15 February 2020). 6. United Nations, Copenhagen accord, 2009. tps://unfccc.int/resource/ docs/2009/cop15/eng/l07.pdf, (accessed 20 February 2020). 7. T. S. United Nations, Transforming our world: the 2030 Agenda for Sustainable Development, 2015. https://sustainabledevelopment.un.org/ post2015/transformingourworld, (accessed 20 February 2020). 8. Africa Renewable Energy Initiative, 2015. Increasing Renewable Energy Capacity on the African Continent, https://unfccc.int/news/africarenewable-energy-initiative-increasing-renewable-energy-capacity-on-theafrican-continent, (accessed 20 February 2020). 9. REEESAP, Renewables Energy and Energy Efficiency Strategy and Action Plan for the Southern African Decelopment Community, 2017. https://www. sacreee.org/document/reeesap-southern-africa-renewable-energy-andenergy-efficiency-strategy-and-action-plan, (accessed 20 February 2020). 10. United Nations, World Economic and Social Survey 2014 / 2015 Learning from national policies supporting MDG implementation, 2016. https:// www.un.org/development/desa/dpad/publication/world-economicand-social-survey-20142015-learning-from-national-policies-supportingmdg-implementation/, (accessed 22 February 2020). 11. B. Ki-moon, Kyoto Protocol Reference Manual, 2008. https://unfccc.int/ resource/docs/publications/08_unfccc_kp_ref_manual.pdf, (accessed 22 February 2020).

Non-Edible Feedstock for Biodiesel Production  305 12. J. R. Millar, Z. R. Nicholls, P. Friedlingstein, and M. R. Allen, A modified impulse-response representation of the global near-surface air temperature and atmospheric concentration response to carbon dioxide emissions, Atmos. Chem. Phys., vol. 17, no. 11, pp. 7213–7228, 2017. 13. F. Alam, A. Date, R. Rasjidin, S. Mobin, H. Moria, and A. Baqui, Biofuel from algae Is it a viable alternative, Procedia Eng., vol. 49, no. 49, pp. 221–227, 2012. 14. M. A. Martin, First generation biofuels compete, N. Biotechnol., vol. 27, pp. 597–607, 2010. 15. C. R. Carere, R. Sparling, N. Cicek, and D. B. Levin, Third Generation Biofuels via Direct Cellulose Fermentation, Int. J. Mol. Sci., vol. 9, pp. 1342– 1360, 2008. 16. S. Khan et al., Biodiesel Production From Algae to Overcome the Energy Crisis _ Elsevier Enhanced Reader, Hayati J. Biosci., vol. 24, no. 24, pp. 163– 167, 2017. 17. G. Dragone, B. Fernandes, A. A. Vicente, and J. A. Teixeira, Third generation biofuels from microalgae, pp. 1355–1366, 2010. 18. S. M. M. Shanab, Water Hyacinth as Non-edible Source for Biofuel Production Water Hyacinth as Non-edible Source for Biofuel Production, Waste and Biomass Valorization, vol. 9, no. 2, pp. 255–264, 2017. 19. N. Matsumoto, D. Sano, and M. Elder, Biofuel initiatives in Japan: Strategies, policies, and future potential, Appl. Energy, vol. 86, no. SUPPL. 1, pp. S69– S76, 2009. 20. H. C. Ong, A. S. Silitonga, H. H. Masjuki, T. M. I. Mahlia, W. T. Chong, and M. H. Boosroh, Production and comparative fuel properties of biodiesel from non-edible oils: Jatropha curcas, Sterculia foetida and Ceiba pentandra, Energy Convers. Manag., vol. 73, pp. 245–255, 2013. 21. J. Yan and Y. Yan, Biodiesel Production and Technologies, vol. 3. Elsevier, 2017. 22. S. Rezania et al., Review on transesterification of non-edible sources for biodiesel production with a focus on economic aspects, fuel properties and by-product applications, Energy Convers. Manag., vol. 201, no. October, pp. 112155, 2019. 23. F. Yaşar, Biodiesel production via waste eggshell as a low-cost heterogeneous catalyst: Its effects on some critical fuel properties and comparison with CaO, Fuel, vol. 255, no. April, pp. 115828, 2019. 24. S. Ghosh, S. Banerjee, and D. Das, Process intensification of biodiesel production from Chlorella sp. MJ 11/11 by single step transesterification, Algal Res., vol. 27, no. March, pp. 12–20, 2017. 25. M. J. Borah, A. Das, V. Das, N. Bhuyan, and D. Deka, Transesterification of waste cooking oil for biodiesel production catalyzed by Zn substituted waste egg shell derived CaO nanocatalyst, Fuel, vol. 242, no. May 2018, pp. 345–354, 2019.

306  Biodiesel Technology and Applications 26. M. E. Günay, L. Türker, and N. A. Tapan, Significant parameters and technological advancements in biodiesel production systems, Fuel, vol. 250, no. September 2018, pp. 27–41, 2019. 27. Z. L. Chung et al., Life cycle assessment of waste cooking oil for biodiesel production using waste chicken eggshell derived CaO as catalyst via transesterification, Biocatal. Agric. Biotechnol., vol. 21, no. September, p. 101317, 2019. 28. M. E. Borges and L. Díaz, Recent developments on heterogeneous catalysts for biodiesel production by oil esterification and transesterification reactions: A review, Renew. Sustain. Energy Rev., vol. 16, no. 5, pp. 2839–2849, 2012. 29. S. H. Dhawane, T. Kumar, and G. Halder, Process optimisation and parametric effects on synthesis of lipase immobilised carbonaceous catalyst for conversion of rubber seed oil to biodiesel, Energy Convers. Manag., vol. 176, no. June, pp. 55–68, 2018. 30. T. A. Andrade, M. Errico, and K. V. Christensen, Influence of the reaction conditions on the enzyme catalyzed transesterification of castor oil: A possible step in biodiesel production, Bioresour. Technol., vol. 243, pp. 366–374, 2017. 31. F. Moazeni, Y. C. Chen, and G. Zhang, Enzymatic transesterification for biodiesel production from used cooking oil, a review, J. Clean. Prod., vol. 216, pp. 117–128, 2019. 32. A. E. Atabani et al., Non-edible vegetable oils: A critical evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, Renew. Sustain. Energy Rev., vol. 18, pp. 211–245, 2013. 33. A. B. Fadhil, E. T. B. Al-Tikrity, and M. A. Albadree, Biodiesel production from mixed non-edible oils, castor seed oil and waste fish oil, Fuel, vol. 210, no. September, pp. 721–728, 2017. 34. A. Arumugam and V. Ponnusami, Biodiesel production from Calophyllum inophyllum oil a potential non-edible feedstock: An overview, Renew. Energy, vol. 131, pp. 459–471, 2019. 35. B. Sajjadi, A. A. A. Raman, and H. Arandiyan, A comprehensive review on properties of edible and non-edible vegetable oil-based biodiesel: Composition, specifications and prediction models, Renew. Sustain. Energy Rev., vol. 63, pp. 62–92, 2016. 36. D. Kumar, T. Das, B. S. Giri, E. R. Rene, and B. Verma, Biodiesel production from hybrid non-edible oil using bio-support beads immobilized with lipase from Pseudomonas cepacia, Fuel, vol. 255, no. February, p. 115801, 2019. 37. M. J. Salar-García, V. M. Ortiz-Martínez, P. Olivares-Carrillo, J. QuesadaMedina, A. P. De Los Ríos, and F. J. Hernández-Fernández, Analysis of optimal conditions for biodiesel production from Jatropha oil in supercritical methanol: Quantification of thermal decomposition degree and analysis of FAMEs, J. Supercrit. Fluids, vol. 112, pp. 1–6, 2016.

Non-Edible Feedstock for Biodiesel Production  307 38. R. L. Patel and C. D. Sankhavara, Biodiesel production from Karanja oil and its use in diesel engine: A review, Renew. Sustain. Energy Rev., vol. 71, no. April 2015, pp. 464–474, 2017. 39. X. Fan, X. Wang, and F. Chen, Ultrasonically assisted production of biodiesel from crude cottonseed oil, Int. J. Green Energy, vol. 7, no. 2, pp. 117–127, 2010. 40. A. Demirbas, Production of biodiesel fuels from linseed oil using methanol and ethanol in non-catalytic SCF conditions, Biomass and Bioenergy, vol. 33, no. 1, pp. 113–118, 2009. 41. M. Taherkhani and S. M. Sadrameli, An improvement and optimization study of biodiesel production from linseed via in-situ transesterification using a co-solvent, Renew. Energy, vol. 119, pp. 787–794, 2018. 42. D. A. Kamel, H. A. Farag, N. K. Amin, A. A. Zatout, and R. M. Ali, Smart utilization of jatropha (Jatropha curcas Linnaeus) seeds for biodiesel production: Optimization and mechanism, Ind. Crops Prod., vol. 111, no. October 2017, pp. 407–413, 2018. 43. R. Kumar, P. Tiwari, and S. Garg, Alkali transesterification of linseed oil for biodiesel production, Fuel, vol. 104, pp. 553–560, 2013. 44. S. S. Kashyap, P. R. Gogate, and S. M. Joshi, Ultrasound assisted intensified production of biodiesel from sustainable source as karanja oil using interesterification based on heterogeneous catalyst (Γ-alumina), Chem. Eng. Process. - Process Intensif., vol. 136, pp. 11–16, 2019. 45. B. Gurunathan and A. Ravi, Process optimization and kinetics of biodiesel production from neem oil using copper doped zinc oxide heterogeneous nanocatalyst, Bioresour. Technol., vol. 190, pp. 424–428, 2015. 46. Y. Essamlali, O. Amadine, A. Fihri, and M. Zahouily, Sodium modified fluorapatite as a sustainable solid bi-functional catalyst for biodiesel production from rapeseed oil, Renew. Energy, vol. 133, pp. 1295–1307, 2019. 47. R. K. Elango, K. Sathiasivan, C. Muthukumaran, V. Thangavelu, M. Rajesh, and K. Tamilarasan, Transesterification of castor oil for biodiesel production: Process optimization and characterization, Microchem. J., vol. 145, pp. 1162– 1168, 2019. 48. A. Bouaid, L. Bajo, M. Martinez, and J. Aracil, Optimization of biodiesel production from jojoba oil, Process Saf. Environ. Prot., vol. 85, no. 5 B, pp. 378–382, 2007. 49. M. I. Loizides, X. I. Loizidou, D. L. Orthodoxou, and D. Petsa, Circular bioeconomy in action: Collection and recycling of domestic used cooking oil through a social, reverse logistics system, Recycling, vol. 4, no. 2, 2019. 50. R. M. Mohamed, G. A. Kadry, H. A. Abdel-Samad, and M. E. Awad, High operative heterogeneous catalyst in biodiesel production from waste cooking oil, Egypt. J. Pet., no. xxxx, 2019. 51. T. Maneerung, S. Kawi, Y. Dai, and C. H. Wang, Sustainable biodiesel production via transesterification of waste cooking oil by using CaO

308  Biodiesel Technology and Applications catalysts prepared from chicken manure, Energy Convers. Manag., vol. 123, pp. 487–497, 2016. 52. M. Mohadesi, B. Aghel, M. Maleki, and A. Ansari, The use of KOH/ Clinoptilolite catalyst in pilot of microreactor for biodiesel production from waste cooking oil, Fuel, vol. 263, no. September, p. 116659, 2020. 53. C. T. Alves et al., Transesterification of waste frying oils using ZnAl2O 4 as heterogeneous catalyst, Procedia Eng., vol. 42, pp. 1928–1945, 2012. 54. M. R. Abukhadra and M. A. Sayed, K+ trapped kaolinite (Kaol/K+) as low cost and eco-friendly basic heterogeneous catalyst in the transesterification of commercial waste cooking oil into biodiesel, Energy Convers. Manag., vol. 177, pp. 468–476, Dec. 2018. 55. V. Narula, M. F. Khan, A. Negi, S. Kalra, A. Thakur, and S. Jain, Low temperature optimization of biodiesel production from algal oil using CaO and CaO/Al2O3 as catalyst by the application of response surface methodology, Energy, vol. 140, pp. 879–884, 2017. 56. A. Xaaldi Kalhor, A. D. Mohammadi Nassab, E. Abedi, A. Bahrami, and A. Movafeghi, Biodiesel production in crude oil contaminated environment using Chlorella vulgaris, Bioresour. Technol., vol. 222, pp. 190–194, 2016. 57. K. A. Salam, S. B. Velasquez-Orta, and A. P. Harvey, Kinetics of fast alkali reactive extraction/in situ transesterification of Chlorella vulgaris that identifies process conditions for a significant enhanced rate and water tolerance, Fuel Process. Technol., vol. 144, pp. 212–219, 2016. 58. S. H. Teo, A. Islam, T. Yusaf, and Y. H. Taufiq-Yap, Transesterification of Nannochloropsis oculata microalga’s oil to biodiesel using calcium methoxide catalyst, Energy, vol. 78, pp. 63–71, 2014. 59. G. Kalavathy and G. Baskar, Synergism of clay with zinc oxide as nanocatalyst for production of biodiesel from marine Ulva lactuca, Bioresour. Technol., vol. 281, no. January, pp. 234–238, 2019. 60. S. Wu, L. Song, M. Sommerfeld, Q. Hu, and W. Chen, Optimization of an effective method for the conversion of crude algal lipids into biodiesel, Fuel, vol. 197, pp. 467–473, 2017. 61. U. Rajak and T. N. Verma, Effect of emission from ethylic biodiesel of edible and non-edible vegetable oil, animal fats, waste oil and alcohol in CI engine, Energy Convers. Manag., vol. 166, no. X, pp. 704–718, 2018. 62. C. Öner and Ş. Altun, Biodiesel production from inedible animal tallow and an experimental investigation of its use as alternative fuel in a direct injection diesel engine, Appl. Energy, vol. 86, no. 10, pp. 2114–2120, 2009. 63. V. Mutreja, S. Singh, and A. Ali, Biodiesel from mutton fat using KOH impregnated MgO as heterogeneous catalysts, Renew. Energy, vol. 36, no. 8, pp. 2253–2258, 2011. 64. D. Papargyriou et al., Investigation of solid base catalysts for biodiesel production from fish oil, Renew. Energy, vol. 139, pp. 661–669, 2019.

Non-Edible Feedstock for Biodiesel Production  309 65. A. S. Al Hatrooshi, V. C. Eze, and A. P. Harvey, Production of biodiesel from waste shark liver oil for biofuel applications, Renew. Energy, vol. 145, pp. 99–105, 2020. 66. K. Seffati, B. Honarvar, H. Esmaeili, and N. Esfandiari, Enhanced biodiesel production from chicken fat using CaO/CuFe 2 O 4 nanocatalyst and its combination with diesel to improve fuel properties, Fuel, vol. 235, no. August 2018, pp. 1238–1244, 2019. 67. P. R. Pandit and M. H. Fulekar, Biodiesel production from microalgal biomass using CaO catalyst synthesized from natural waste material, Renew. Energy, vol. 136, pp. 837–845, 2019. 68. B. Karmakar and G. Halder, Progress and future of biodiesel synthesis: Advancements in oil extraction and conversion technologies, Energy Convers. Manag., vol. 182, no. December 2018, pp. 307–339, 2019. 69. V. B. Veljković et al., Biodiesel production from corn oil: A review, Renew. Sustain. Energy Rev., vol. 91, no. April 2017, pp. 531–548, 2018. 70. S. N. Gebremariam and J. M. Marchetti, Economics of biodiesel production: Review, Energy Convers. Manag., vol. 168, no. May, pp. 74–84, 2018.

11 Oleochemical Resources for Biodiesel Production Gayathri R., Ranjitha J. and Vijayalakshmi Shankar* CO2 Research and Green Technologies Centre, VIT University, Vellore, Tamil Nadu, India

Abstract

Oleochemicals are materials composed of high energy molecules made up of triglycerides (lipids) with more than 96% present inform of MG, DG, and FFA. The energy produced when the oleochemicals heated is nearly 91% close to diesel fuel. The major difference between the oil of fossil fuel and plant oils is due to variation in the percentage of oxygen present in it. The direct usage of triglyceride in diesel engines is possible but it causes lot of problems as result of reduced volatile, thickness, and its properties in cold flow, which will be rectified by improving the properties of plant oil. Non-edible feedstocks including AFW have recently gained high interest due to the quality of biodiesel produced from them and they are low cost, eco-friendly, with reduced emission of NOx and properties such as high cetane number and oxidative stability. Oleochemicals can be used to produce three major biofuels which includes biodiesel, bio-oil, and renewable diesel. The advantages of renewable biofuels are that they are similar to fossil fuels but eco-friendly with reduced emission of greenhouse gases. Keywords:  Oleochemicals, plant oils, animal oils, biodiesel production, optimization, purification, biodiesel properties

11.1 Introduction Biodiesel (FAME/FAEE) is an alternative, inexhaustible, and green energy resource than fossil fuels in order to meet the energy crisis. Utilization of *Corresponding author: [email protected] Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (311–340) © 2021 Scrivener Publishing LLC

311

312  Biodiesel Technology and Applications fossil fuel results in the elevated emission of environmental pollutants/ contaminants including nitric oxides, sulfur oxides, and carbon monoxide and other toxic volatile organic compounds which are the major causes for deforestation, depletion of ozone, global warming, photochemical smog, and Eutrophication of aquatic ecosystem. The amount of the emitted environmental pollutants/contaminants can be highly reduced by replacing the fossil fuel with biodiesel [1]. There are variety of raw materials/feedstocks available for the production of biodiesel which include first-generation feedstock mainly focusing on food crops, second-generation feedstocks are materials that are processed form of first-generation feedstock such as derived products of plants and animals in form of vegetable oil and lignocellulosic materials, animal products including fat, oil, waxes obtained from tallow, and dairy products. These second-generation residues are categorized into four groups. Primary residues are materials obtained while cultivating the desired plants and in the forest. Secondary residue comprises of intermediate and by-products formed during the processing of food crops into their final products (e.g., food processing waste). Tertiary residue includes the final products result from the derivative products of biomass available only after its consumption by humans or animals in form municipal solid waste (MSW) that are further subjected waste water/sewage treatment for proper disposal. The last group involves the utilization of algal biomass. Third-generation feedstocks are materials with high carbon content utilized for biodiesel production and also include chemical and enzymatic conversion of algae [2]. Utilization of used waste frying oil (WFO) for FAME synthesis through process of recycling is a potential and eco-friendly technique. This technique gives promising results in the yield of biodiesel ranging from 60% to 90%. The yield can be increased up to 95% by adjusting some physiochemical and biological parameters during the process of production and simple pre-treatment before subjecting it for biochemical reactions [3]. This method is economically feasible by cutting down the production cost up to 60%–70% [1]. This method is an eco-friendly technique which involves the proper disposal of waste cooking oil (WCO) that is unpalatable because of elevated level of FFA [4]. Recycling of the WCO is subjected for oleochemical production [2].

11.2 Definition of Oleochemicals Chemicals produced from natural oils and fats are called oleochemicals. From the overall production of oils and fats (around 105 million), 80% is

Oleochemical Resources for Biodiesel Production  313 used for human consumption, 5% for animal feed, and 15% for chemical production. For industrial production of chemicals every year 16 million tons of fats and oils were utilized. There are two categories of oils-lauric oils (e.g., coconut and palm kernel) with rich carbon chains involving of 12 and 14 linked carbon atoms, and (tallow and palm) with 16 and18 carbon atoms. Rapeseed, soybean, and sunflower oil are also used for oleochemical production [5]. Oleochemicals are typically derived products of fatty acids (FAs) and glycerol obtained through variety of chemical/biological reactions in which separation of the triglyceride (TG) structure of oil and fats occurs. Oleochemicals can also be synthesized from FA through modification of their carboxylic group. The basic oleochemicals include FA, FAME, fatty alcohols, fatty amines, glycerol/glycerine, and products obtained by hydrogenation of FAME and fatty alcohols. Fatty chemical derivative such as methyl ester (ME) and FAs plays a major role in the field of oleochemistry and oleochemical-based industries [6].

11.3 Oleochemical Types There are five different types of oleochemicals which includes ME, FAs, fatty alcohol, fatty amines, and glycerol. FA is a lipid molecule made up of a long fatty chain combined with a carboxyl group at the end. FAs are present in two forms, the saturated (absence of double bond) and unsaturated FAs (presence of double bond) based on the types of bond present in that FA chain. Lipids such as fats and oil are made up of TGs (single glycerol molecule bounded with three FA chains) and these TGs can be split into FA and glycerol by hydrolyzing the oil/fat and then subjecting it for further reaction under high temperature, pressure, or lipase catalyst under 37°C with controlled pressure and stirring speed. The TGs present in oils and fats are converted into ME by a process called methanolysis. The process was illustrated in Figure 11.1. When oil/fat is subjected to react with methanol and catalyst, the FAs get detached from the glycerol and bond with methanol thus resulting in a compound called MEs and glycerol is recovered as by-product. MEs are reported to be superior than FAs for production of various FA derivatives. Fatty alcohols are long-chain high molecular weight primary alcohols derived from oil and fats (lipids). They are produced by methanolysis process in which the esters react with alcohol after the formation of ME. Fatty amines are derivative products of fatty alcohol and FAs. The production of primary amines is gradually declining, but there is an increased utilization and demand for secondary and tertiary amines.

314  Biodiesel Technology and Applications Animal products Edible products Fish industry waste

Poultry products

Cattle and sheep products

Crushing process Wet Dry crushing crushing

Pressing

Separation of solid and liquid materials

Rendering process Evaporation of liquid Chicken fat

solid waste of fish

Fish oil and Protein meal

solid waste of chicken

solid waste of cattle/sheep

Protein meal

Fish oil, tallow, chicken fat usedas feedstock for biodiesel production

Figure 11.1  Process flow of methyl ester production from animal fat.

Pet feed and tallow

Oleochemical Resources for Biodiesel Production  315 They are used as biocides, mineral oils, corrosion inhibitors, in the oil field as additives (demulsifiers), used in textiles, fibers, industrial dyes and pigments, soft detergents, softening agents, and also used in the following fields, as anti-cracking agents for road construction, etc. Fatty amines containing ca. 25% are used as anti-cracking agents and ca. 75% derived product are used as conditioning agents in cosmetics, amine oxides, and amineEO-adducts [7]. Glycerine occurs as a by-product when oil/fats are subjected for any reactions in which water (hydrolysis), methanol (methanolysis), and acid/base catalyst (saponification) takes place, this due to breaking of glycerol from FAs. Glycerine is primarily used for its viscosity and moisture retaining capacity [1, 4–8].

11.4 Production of Biodiesel The synthesis and utilization of FAME have created a great interest in the financial investment and implementation of biodiesel production plants among various countries. Based on the report of the European Biodiesel Board, the production of Biodiesel by the European Union in 2011 was 24.7 × 109 L yr−1 and 4.16 × 109 L yr−1 by the USA in 2011 [4]. The amount of biodiesel produced by Canada has increased twice when comparing its annual production in 0.210 × 109 L yr−1 (2012) and 0.471 × 109 L yr−1 (2013) [20]. In USA, Europe, and Canada, the biodiesel was produced from rapeseed oil, soybean oil, and canola oil with low content of erucic acid [9]. There is an increased demand for production of biodiesel in Malaysia, Canada, Europe, USA, and China. So, in order to meet the demand, there is a need for use of rendered oils, palm oil (Elaeis guineensis jacq.) and rendered animal fats. The animal fat was classified as feeds by the international market, and their price become low. Hence, the cost of biodiesel will be extremely lowered by the AFWs to increase the production of biodiesel to compete with Petro-diesel. The various feedstocks to produce ME include animal fats and vegetable oils both edible and non-edible oils [10–14]. The two major limiting factors involved in the use of various substrates for the production of biodiesel are their obtainability and price. The industries store their feedstock which serves as a limiting factor for sustainability of biodiesel regardless of their current growth. There are limitations in the sustainability of biodiesel production regardless of its current growth is due to inefficiency of the industries to safely store their cheapest feedstocks. The chief source for the production of FAME in Canada is Canola oil. The feedstocks used by USA and Europe is edible vegetable oil but this leads to an increased demand for

316  Biodiesel Technology and Applications vegetable oil supply that will result in food security, ethical issues, and provoke worldwide arguments regarding the level of effect on the diversity of food crops at global level. This could be sought by replacing the feedstocks that produce good quality biodiesel with low capital cost and not a threat to food safety [15]. The feedstocks that can be used to avoid such issues include chicken fat, tallow, lard, and solid waste materials produced in leather industry, etc. In some regions, the animal fat waste (AFWs) are abundant that result in lowering the cost of feedstocks. The advantage of using waste animal fat for producing biodiesel is that it emits NOX which will be below or equal to vegetable oil biodiesel with a reduced amount of environmental pollutant and thus preventing environmental damage. Quality of the produced diesel fuel is determined by the cetane number. The ratio of saturated FAs is high in AFWs which is the major reason for high cetane number (460) when compared with most of the vegetable oils. The advantage of high cetane number is that it reduces the temperature during the early combustion process resulting in low NOx emission. The presence of saturated FA in the AFWs is responsible for better oxidative stability of biodiesel [16–19]. There is a huge challenge in producing biodiesel by alkali-catalyzed transesterification because of the presence of more free FAs in AFWs. Efficiency of the biodiesel is based on the techniques involved during the construction/ development of the biodiesel plant. Chemical and biological techniques are the two important techniques currently used for the synthesis of FAME from plant oil and animal fats. Synthesis of biodiesel using chemical techniques includes acidic or basic catalytic conversion reactions. Enzymatic conversion of biodiesel takes place in biological technique. Lipase enzyme is mainly used in biological techniques. Other than these two techniques, the use of other techniques such as non-catalytic and superficial temperature conversion methods is still under the process of investigation. Even though chemical-based biodiesel production is widely used in industrial scale, they have certain limiting factors such as high energy, equipment, and alcohol requirements, and the downstream and purification process was complex. Through enzyme catalyzed transesterification process, there is an advantage of overcoming a specific limitation in producing diesel with the feedstock having low FFA content and moisture that are required for chemical techniques. Development of high molar ratio of animal fat and soap required for production of biodiesel during which chemical-based catalysis will be comparatively low in the biological method. Enzyme immobilized techniques made the lipase enzyme reusable and developed high alcohol tolerant lipases; thus, this technique become cost efficient by overcoming the inactivation of enzyme lipase and its higher cost [15, 20].

Oleochemical Resources for Biodiesel Production  317 There are many new techniques emerging for biodiesel production which involves many treatments for maximum yield with the reduced reactor operating time. The microwave-assisted (MA) transesterification and ultrasound-assisted (UA) transesterification are the two major emerging techniques for biodiesel production. The use of cheap reagents, short reaction time, and simple process reactors created a great interest in the UA techniques for biodiesel production. There is also a positive approach toward MA technique due to its great energy efficiency, improved yield, short reaction period, and highly purified products [15].

11.5 Types of Feedstocks 11.5.1 Non-Edible Feedstocks There is a global demand for edible oil and animal fat due to increased population and resulted in elevating their price on the world market that many developing countries had limited the utilization of plant oil and animal fat as fuel. Several studies stated that grease and fat obtained from animal source waste are feasible, good, and eco-friendly feedstocks for FAME production. These materials are easily accessible in many developing countries through placing order in units of teragrams. There is a worldwide availability of non-edible oil plants. But there will be a problem leading to strong debate due to the inaccessibility of land for food crops vs. non-edible oil crops [15].

11.5.2 Non-Edible Vegetable Oil Oil from non-edible sources for synthesizing biodiesel from Oleagnious, Leguminosae, Brassicaceae, and Euphorbiaceae have been under several investigations in recent years. These plants produce oil-rich seeds but their high FFA level made them toxic and inedible for both animals and human consumption. The use of non-edible oil can directly gain opposition with respect to safe and availability of food. Pongamia, Jatropha, Brassica, Madhuca, Gossypium, Cerbera, Nicotiana, Thevettia, Ricinus, and Hevea sps are the common non-edible crops used for the production of biodiesel. The non-edible plants used for the research of biodiesel production and their cultivation varies according to its place of growth. For example, several types of researches mainly concentrating on oleaginous microorganism for lipid-based biodiesel feedstocks are currently going in the USA, Canada, and EU [15].

318  Biodiesel Technology and Applications

11.5.3 Tall Oil Tall oil is the secondary product produced by wood pulp industry. It contains 42% resins and 45% of FAs. Distillation method is used to separate the resin and FAs which are present together and only in the form of free acids [21].

11.5.4 Waste Cooking Oils There is no direct opposition for the usage of WFO as a source for biodiesel concerned with land usage and availability of food. Yellow grease and brown grease are the two groups of waste cooking or frying oil (WFO). WFO is highly concentrated with grease after cooking bacon, meat appetizers, and hamburgers, and this is due to the method used for the extraction of cooking oils. Since the cooking oil is extracted by the melting of fat obtained from AFW and heating of vegetable oil that is used for cooking various foods including meat, fish, and vegetable oils. This is the major reason for the formation of grease after cooking. WFO collected from the restaurant or industrial operations with the presence of less than 15% of FFA in the grease produced from WFO, fats, and oil act as feasible potent and inexpensive raw material for biodiesel production. Restaurants and industries involve the use of grease trap to collect brown grease in order to separate oil and grease from the wastewater for municipal sewage facilities. Grease traps allow floating of light grease and oil at the top of the trap when flushed in the drain and thus facilitating the free flow of wastewater into the water treatment unit. Difficulties in the potential conversion of biodiesel from brown grease with greater than 15% FFA are due to the presence of H2O content in it. The techniques used for conversion of biodiesel from WFO include various types of transesterification process such as acid-catalyzed transesterification, alkaline-catalyzed transesterification, two-step transesterification, enzymatic catalysis, and supercritical temperature processing methods. Heating virgin oils for long duration leads to higher FFA concentration of FFA in WFO. Biodiesel yield from WCO is lowered and involves a complex downstream process during the separation of ME, C3H8O3, and washing H2O, and this is due to the saponification reaction taking place when the alkaline catalyst acts on FFA during the alkaline transesterification process [15].

11.5.5 Animal Fats The by-products of processed and rendered animal meats from facilities are the primary source used for deriving fats from animals. From cattle processing

Oleochemical Resources for Biodiesel Production  319 facilities and rendering process, tallow can be obtained; grease and lard can be obtained from processing the pork, and poultry fat can be obtained from chicken and other birds processing; oil fish industry and waste from leather industry are the major animal fats used for synthesis of FAME. Chicken, tallow, and lard fats are some of the animal fat-based feedstocks used for large industrial scaled biodiesel production. Compared with edible plant oils, AFW used as feedstock for FAME production have economical environmental and food security advantages. Production of FAME from AFWs involves complex techniques when saturated FAs (FFA) is present at a high level, and the resulting biodiesel will have low chemical and physical quality. There are certain advantages in low unsaturated FAs of AFWs such as increased cetane number, increased oxidation stability, and increased calorific value [15].

11.5.6 Chicken Fat During the feather meal preparation, the chicken fat can be produced. Head, intestine, undeveloped eggs, and feet other than feathers are clean carcass available in poultry by-products found in different portions of wet rendered or dry grounded forms. Based on the type of feather used, the fat thus obtained varies from 2% to 12%. Biodiesel has been produced by Guru et al. (2010) [66], with fat from chicken using catalytic process which contains two steps involving catalyst such as CH3OH, H2SO4, and NaOH. The effects on performance in engine and exhaust emission when injected in a diesel engine with produced biodiesel from synthetic Mg additive chicken fat have been reported by the author. The decrease in the viscosity (5.184 to 4.812) and flash point (129°C to 122°C) due to rise in concentration of Mg have been reported by the author. There was a decrease of 7°C pour point in the chicken fat ME with the addition of Mg. Yield of ME was about 87.4% when the conditions for animal fat was optimized by pre-treatment. When converting chicken fat into biodiesel the point at which best TG conversion and glycerol decomposition were obtained at 400°C, 300 bar pressure, 9:1 molar ratio, with 6-min time [15].

11.5.7 Lard Rendered fat of pig is termed as lard. Dry or wet process is used for rendering the pig fat. Wet rendering involves high temperature boiling of pig fat in water/steam and the insoluble lard is formed as an upper layer in the mixture which is skimmed off or centrifuged. Pig fat is subjected to higher heat treatment in the absence of water in oven or pan. These two processes result in the yield of two different products. Lard with a neutral flavor, light color,

320  Biodiesel Technology and Applications and high smoke point can be obtained from the process of wet rendering process and dry rendering results in lard production with brown color and low smoke point. According to Dias et al. [67] on the generation biodiesel by acid transesterification, the lard was pretreated with KOH to enable it to be a potential feedstock for FAME production with suitable quality but the yield is low with only 65% by weight. The yield of biodiesel from waste lard and WFO ranges from 81.7 to 88.0 (wt.%) has been reported from the investigation done on the synthesis of FAME from mixtures of WFO; thus, the yield is low when only WFO and lard have been used as raw materials. Investigations have been done on the conversion of biodiesel from lard using the Candida sp. (fungus) as a biocatalyst in transesterification process shows the optimal condition for the reaction in order to process a gram of lard involves immobilized lipase (0.2 g), 8-ml n-hexane, a ratio of 20% of water to the weight of fat, 40°C and adding CH3OH produced 87.4% of FAME. This investigation gives a detailed report about the effect of biocatalyst used in transesterification of lard involving the parameters such as temperature, water content, the quantity of enzyme used, solvent, in three-step methanolysis process for biodiesel production. The ME production was directly affected by the concentration of catalyst used and agitation speed, and the optimal agitation speed is found to be 600 rpm found in a regression model used to the predict concentration of ME with sufficient experimental parameters. According to the experiment of Shin et al. [68], on production of biodiesel with lard without pre-treatment and using the technique with supercritical without adding the catalyst under optimal reaction conditions produced biodiesel which is similar to biodiesel synthesized from refined lard, although it has free FA and water in it [15].

11.5.8 Tallow Animal by-products from slaughter house can be rendered to produce fat and protein meal. More than 50% of FAs in the tallow are in saturated form. The high melting point and viscosity is because of the presence of palmitic and stearic acid in the tallow leads to makes it solid at room temperature. Edible or non-edible tallow are derivatives of beef or mutton which are mostly used to produce FAME. For alkaline transesterification reaction process, edible tallow acts as a potential substrate having low FFA content. Biodiesel production from beef tallow that was studied and reported conclusively stated that tallow from beef obtained from cattle house remarkably acts as an inexpensive feedstock for FAME production with an immense energy, along with economic and environmental advantages and this report also included the economic feasibility, energy efficiency, and resource availability of beef tallow

Oleochemical Resources for Biodiesel Production  321 and its conversion into biodiesel. The yield of FAME from edible tallow and the effect of catalyst, FFA, water content, and mixing intensities have been investigated by Ma and Hanna and reported that reaction takes place only when NaOH and CH3OH were added and mixed with melted beef tallow with limited stirring speed and also stated that higher stirring speed for a longer period is required to mix the two phases when a blend of sodium hydroxide and methanol solution is added before stirring the melted beef tallow. Biodiesel production from non-edible tallow requires highly expensive processing methods, which leads to higher FFA. Viability of FAME conversion from inedible tallow has also been reported. Based on the report of Bhatti et al. (2008) [69] and their studies on biodiesel production, its reaction parameters for the conversion of 5 grams of tallow waste are 60°C, 1:3 molar ratio, and addition of sulfuric acid (2.5g) [22]. Oner and Altun (2009) have done an experiment in which they directly injected the biodiesel produced from nonedible tallow in a diesel engine and studied its emission and performance. This experimental report clearly shows that there was a significant decrease in the emission of carbon monoxide (15%), NOX (38.5%), sulfur dioxide SO2 (72.7%), and smoke opacity 56.8% for ME (B100) from tallow [23]. Teixeira et al. (2009) did a comparative study on FAME production from beef tallow by using ultrasonic and conventional method and reported that only the time for reaction is reduced but the reaction rate and quality of biodiesel remained the same for both. Kumar et al. (2013) [24] reported the effect of enzyme ns88001with CH3OH and n-hexane used as solvent. This report shows that n-hexane reduced the toxicity of alcohol by stabilizing the enzyme and the NS88001-enzyme is reduced a little bit after 10 cycles [25]. Immobilized PS-30 lipase enzyme used for transesterification of Primary alcohol (methanol) resulted in the effective conversion of biodiesel ranging from 82% to 94% when compared with free lipase enzyme with low conversion efficiency ranging from 47% to 89%, and ME showed poorest yield [15].

11.5.9 Leather Industry Solid Waste Fat Leather industry generates huge amount solid waste fat during various processes. This fat remains solid at room temperature with high H2O content in it. The water content is eliminated by treating the fat at 110°C for 1 hour and insoluble materials are removed by filtering it. A study [26] experimentally proved the utilization of these fuels in engine (without any modifications) and synthesized from the fat produced in tannery fleshing waste. The reaction parameters were studied by Isler et al. (2010) [70] which includes molar ratio (1:6), weight percentage (0.75%), and catalyst and temperature for production of ME from raw fleshing oil through

322  Biodiesel Technology and Applications base-catalyzed transesterification reaction and found that the efficient biodiesel yield can be achieved 1:6 molar ratio, temperature (50°C), 0.75 percentage weight of catalyst, and time of reaction is about 15 min. Evaluation of FAME production from leather industry waste as feedstock in alkaline catalyzed transesterification reaction was reported by Alptekin et al. (2012) [27]. Property of produced ME met the biodiesel standard, and to enhance the cold flow property or cold flow, enhancers can be added to it. Supercritical CH3OH approach in transesterification of leather tanning waste for production of FAME was first applied by Ong et al. (2013) [65]. A model was developed by the author for the kinetic reactions of FAME production from leather industry waste [15].

11.5.10 Fish Oil FAME can be produced from oil-rich waste obtained in a significant amount during the processing of fish from the fish processing industry. Large fraction of the effluent contains oil (6%–11%) will be utilized as a feasible feedstock for FAME production with good yield can be obtained with proper separation techniques. Recovery of fish oil from the effluent involves the following methods such as grinding/­homogenizing of solid fish waste followed by heat treatment for 15–20 min at 95°C–100°C, screw pressing of the solid waste to remove liquids, centrifugation of the liquid to separate oil and remove wastewater, and final polishing of oil by water washing. Colak et al. (2005) [26] investigated production of FAME with fish oil and reported that catalyst concentration gives greater yield and quality of biodiesel. This report shows that optimum condition for biodiesel production is 1 wt.% catalyst and 60 vol% of CH3OH solution. Waste characterization and quality assessment of fish processing plant effluent for FAME production have been investigated by Tanwar et al. (2013) [28] and Jayasinghe and Hawboldt (2013) [29]. The major factors which determine the suitability of the transesterification technique for FAME production are the type and quality of the feedstock used.

11.6 Uses of Oleochemicals 11.6.1 Polymer Applications Linoleum is produced from the linseed oil. The demand for linoleum has been increased from 10,000 tons to 50,000 tons from the year 1975–1998. Epoxidized soybean oil is used for plastic and coating additives, and the

Oleochemical Resources for Biodiesel Production  323 production is around 100,000 tons/year. Industrial production of dicarboxylic acid involves ozonolysis of oleic acid to produce diacids [4]. Hydrocarbons and chlorinated compounds are used in large volume as solvents for coating and other various polymer applications. Ester solvents are the largest groups representing the Green solvents naturally obtained from the FAs and alcohols [5].

11.6.2 Application of Plant Oil as a Substitute for Petro-Diesel Ground nut was used as a fuel for demonstration in 1900 [30]. In 1930s and 1940s, experimental work has been done with plant oil in diesel engine. Due to depleting non-renewable energy and fuel energy crisis during the year 1970–1980 lead to the development of alternatives to petroleum-based fuels. This gives rise to many investigations in finding various alternatives for Petro-diesel and resulted in the production of biodiesel. Currently, biodiesel have become commercial and have a global level demand. Several plant oils were investigated for the production of FAME. FAME production will be determined upon availability of substrates such as palm oil, coconut oil, soybean oil, rapeseed oil, sunflower oil, safflower oil, and some vegetable oil used for cooking. Plant oil directly in diesel engine is still problematic because of its high viscosity; further development is needed to overcome this problem. Following techniques can be applied to maximize the quality of the fuel from plant oil which includes dilution of oil from plant (25 parts) with Petro-diesel (75 parts). The physiochemical properties of biodiesel (FA esters) are similar to Petro-diesel. The production process is simple and the burning efficiency of methyl or ethyl ester of FA in diesel engine does not require any modifications. When compared to microemulsion and dilution techniques, transesterification is a best choice for biodiesel production [5].

11.6.3 Used as Surfactants Oleochemicals are used as surfactants used to bring two different types of compounds together. Oleochemicals with FA chains or long-chain alcohol are used for this purpose. Oleochemical used as surfactant involve compounds such as bio-based hydrophiles including amino acid [31], polysaccharide, and FA chains with carboxylate groups. Bio-based surfactant should have its hydrophobic or hydrophilic group to be derived. Group of bio-based surfactants includes oleochemical-based fatty esters that are used as hydrophobe group to combined with ethylene oxide as hydrophile group. Carbohydrates were used as hydrophilic group of surfactants for

324  Biodiesel Technology and Applications more than half of a century. Carbohydrates such as sorbitol (lignin, lecithin to sugars) are used surfactants. Some surfactant has both the hydrophilic and hydrophobic groups to be bio-based such as sugar and FA, which is beneficial in case of SpanTM 60. Glycerol produced in excess during biodiesel production can be used as a cheap material for the bio-based surfactant production as a precursor. Polymers of glycerol such as such as polyglycerides act as good hydrophobes. Surfactant with polyglycerol properties will be produced either from compound contains epoxide such as glycidol or by polymerization of glycerol. The utilization of surfactants involves various fields. The most important field where more than 50% of surfactants used includes washing and cleansing sector, textile treatment, and cosmetics. Other fields such as mining, protection of crop, paints, coatings, inks, and adhesives also involve the application of surfactants [5].

11.6.4 Oleochemicals Used in Pesticide Plant-based oils and fats act as an important raw material for chemicals industry [32]. Plant-based oleochemicals are more advantageous than mineral oil that they are renewable, biodegradable, and widely available (byproducts from industries). Pesticide formulation is mainly composed of two major components such as inert and active ingredients [33].

11.6.5 Oleochemicals Used in Spray Adjuvants and Solvents Oleochemicals have been used as spray adjuvants due to their high adherence capacity to the leaves of plants or insects. The polyunsaturated nature of this plant oil made them persistent on leaves and insects even after rainfall. Palm olein in liquid fraction from palm oil also used as spray adjuvants. MEs and hydrocarbons act as potential vehicles for transporting pesticides on the surface of plant and insects. This is due to high viscosity and surface tension of methyl eater and hydrocarbons. They are biodegradable with less toxicity and less viscous with better solvency. The solvency property to pesticide is better in ME produced from plant oils [5].

11.7 Methyl Ester or Biodiesel Production Biodiesel (ME) from plant oil and fat resulting with the glycerol release [15]. Conversion of plant oil into biodiesel includes TGs’ reaction such as methanol with catalyst resulting in FAME and C3H8O3. Initially, in

Oleochemical Resources for Biodiesel Production  325 transesterification process, the TGs are converted into DG followed by a series of reactions involving larger glycerides converted into smaller glycerides and finally into glycerol (Figure 11.2), with one ME molecule at the end of each steps of the subsequent reactions [10]. In this reversible reaction, the equilibrium is shifted toward the product side by using excess alcohol [15]. Solubility of alcohol will be improved by the catalyst, thus result in increasing the reaction rate and yield. Utilization of catalyst depends upon the substrate and content of free FA. The FFA and H2O content should be below 0.5 and 0.05 wt.%, to prevent saponification during the reaction [34]. FFA can be converted into FAEE through esterification reaction as a pre-treatment process for effective conversion of oil into biodiesel [35]. The TG and DG can be hydrolyzed into FFA using water. Temperature is an important parameter influencing the rate of reaction, which is fast when the temperature is high [36]. Many techniques were used in the transesterification reaction which includes the usage of catalysts of heterogeneous type (e.g., magnesium oxide, calcium oxide, and sulfated zirconia) [35]. BIOX process is also a noncatalytic transesterification method used for ME production from WCO, animal fat, and vegetable oil [7, 37–39]. For transesterification process, the WCO has to be pre-treated

Step 1 feed stock

oil extraction

Esterification (pre-treatment)

Step 2

Transesterif ication

• addition of methanol/ethanol

Ester recovery

• release of by-product (glycerol)

Biodiesel FAME/FAEE

Figure 11.2  Production of biodiesel by transesterification reaction. Step1. Pre-treatment of oil to treat FFA and water through esterification reaction. Step 2. Transesterification of pre-treated oil to produce fatty acid methyl ester/ fatty acid ethyl ester (biodiesel).

326  Biodiesel Technology and Applications due to presence of high FFA (0.5%–15%) content for proper conversion and yield [36].

11.7.1 Palm Oil Acidic crude palm oil (ACPO) can be utilized as potential substrate for the production of ME production. Cost for production can be lowered by using the by-products of APCO [40]. The catalyst commonly used for the pre-treatment of acidic oils in esterification reaction includes sulfuric acid—conventional catalyst [41] (lipase-biocatalyst, Ferric sulfateheterogeneous catalyst (widely used). Ethane sulfonic acid is a catalyst used for treating high FFA content in industrial ACPO by [41] for esterification process. Methane sulfonic acid (MSA) is a catalyst used for pre-treatment of FFA in APCO by (Adeeb Hayyan et al., 2012) [40]. Materials used in this reaction are APCO, CH3OH 99.8 %, potassium hydroxide pellets 85%, and MSA. Before starting the esterification reaction, the ACPO has to be melted at a 65°C. Then, the FFA content was measured and reported. For FAME production, 200g of ACPO was taken for each experiment in which both transesterification and esterification reactions were involved. Conversion of FFA into FAME through esterification reaction is a preliminary stage. There is a high yield of FAME, and enhanced esterification reaction due to addition of MSA catalyst was observed by Adeeb Hayyan et al. (2012) [40]. The liquid phase of APCO and MSA were found to be responsible for enhanced esterification reaction. It also converted triacylglycerols (TAGs) into FAMEs. In the second reaction, the TAG is converted into FAME by using KOH as a catalyst [40].

11.7.2 Sunflower Oil Production of ME from sunflower oil by alkali-catalyzed transesterification reaction was done by Umer Rashida et al. (2008) [42]. About 500 g of sunflower oil was preheated for setting the temperature that ranges from (30°C, 45°C, or 60°C) [43] with known catalysts and mixed well. Each experiment was subjected for 120 min at 600 rpm. Different molar ratio was used including 3:1, 6:1, 9:1, 12:1, 15:1, and 18:1 [44]. The sunflower oil methyl oil (SOME) was purified by distillation around 80°C in which the left out methanol is removed by subsequent washing with distilled water and Na2SO4 along with filtration. The unreacted catalyst is treated by neutralization with concentrated sulfuric acid and decomposition of soap formed during the reaction. Methanol is recovered by vacuum treatment under 80°C to purify the C3H8O3.

Oleochemical Resources for Biodiesel Production  327 Results reported from this experiment were mentioned in the following: In this experiment, temperature variation has no significant effect on biodiesel yield. After the reaction was completed, it is more than 80% without the influence of temperature change. The yield was reported to be 97.1% at 60°C, 92.8% at 45°C, and 90.9% at 30°C, and this indicates the efficiency of base catalyst to be high nearly to the boiling point of alcohol. Different concentrations of NaOH (0%, 0.25%, 0.50%, 0.75%, 1.00%, 1.25%, and 1.50% w/w) [45] were used among four different catalysts in same experimental conditions mentioned above, and the yield was found to be 97.1% at a concentration of 1.00% NaOH. Six different molar ratios were used in each of the experiments ranging from 3:1, 6:1, 9:1, 12:1, 15:1, and 18:1, and 97.1% was found at 6:1. This experiment shows that the optimal reaction condition for the production of ME from sunflower oil through transesterification was found to be at 60°C,6:1, concentration of catalyst 1.00% with 97.1% yield.

11.7.3 ME From AFW Production of ME from various animal fat sources was explained in Figure 11.3. Guru et al. (2010) [66] reported the production of FAME from chicken fat. They reported that yield of biodiesel to 87.4% with an optimal reaction condition of 20% H2SO4 at 40:1 methanol molar ratio with 13.45% FFA in chicken fat was subjected to reaction for 8 min at 60°C. The yield of FAME was 88% when the lard was subjected under the following reaction conditions: 1-g lard, with 20% H2SO4 based on weight of the fat, 0.2g of immobilized lipase catalyst, and 8 ml of n-hexane. The ME yield was reported to be 93.21% when 5 g of mutton tallow was treated with 2.5g of H2SO4 at CH3OH molar ratio of 1:3 for 24 h under 60°C [15].

11.8 Parameters Affecting the Yield of Biodiesel 11.8.1 Reaction Conditions The production of FAME can be affected by the reaction conditions such as oil to alcohol ratio, temperature, catalyst concentration, and type of reactor used.

11.8.2 Catalyst 11.8.2.1 Alkali Catalyst Saponification reaction reduces the FA yield and forms emulsions which cause difficulties in glycerol and biodiesel separation. Singh et al. reported

328  Biodiesel Technology and Applications Seed storage

Removal of cortex (Decortication)

Size reduction by flaking

Breaking of seeds

Pre-expelling of crude oil

Solvent extraction

Oil cake or oil meal

Crude oil

Oil storage

Refining of oil

Figure 11.3  Process of extraction of vegetable oil (e.g., sunflower seed oil extraction process).

Oleochemical Resources for Biodiesel Production  329 that better yield was obtained when hydroxide catalysts is replaced with methoxide catalysts and sodium-based catalysts replaced by potassium-­ based catalysts [46].

11.8.2.2 Acid Catalyst There is a slow reaction rate when acid catalyst is used and it requires more TGs and high ratio of alcohol; hence, they are usually a best choice for feedstock pretreatment with maximum FFA where conversion of soap into ester is required [15].

11.8.2.3 Biocatalyst Lipase immobilized transesterification is a very slow process and requires more reaction time and temperature ranging from 4 to 40 h and 35°C to 45°C, respectively. But, this process gives promising results only for feedstocks containing high FFA contents. The FA ME produced by using various strains of fungus Aspergillus sp. has been reported to have high biodiesel properties (lubrication and fuel properties) [47].

11.8.2.4 Heterogeneous Catalyst CaO and Ca(OCH3)2 are usually used heterogeneous catalyst for biodiesel production. Slow reaction is seen due to low mass transfer ability and requires a co-solvent with a boiling point similar to methanol for enhanced mass transfer among the reactants and thus resulting in the fast reaction without leaving the catalyst as residue with a reaction period of 5 to 10 min at 30°C. Alkali doped metal oxides were used as an alternative for homogenous catalyst [48].

11.8.2.5 ME Conversion by Supercritical Method Supercritical methanol transesterification is a modified method used to avoid initiation time lag during biodiesel production. The solvents are kept in a temperature and pressure beyond its critical point there will be only liquid phase which facilitates simple, fast, and eco-friendly production of biodiesel. The recovery of glycerol and separation of biodiesel becomes much easier due to the absence of catalyst. This method involves alcohol to oil ratio of 42:1 under 80 atm pressure at 350°C to 500°C in 2 to 4 min [15].

330  Biodiesel Technology and Applications

11.8.3 Properties of Feedstock Quality of produced biodiesel is based on feedstocks used for its production. The factors that affect the biodiesel production are FA contents and its composition present in the selected feedstocks. Other factors such as elimination of unsaponifiables and water and titer property oil also influence the properties of biodiesel produced [15].

11.8.3.1 Composition of FA The FAs present in the feedstock in different compositions highly influence the physical and chemical properties. FAs and its composition of various feedstocks were presented in Table 11.1 [15].

11.8.3.2 FFA These are FAs produced as a consequence of breakage in the long carbon chain in a FA that result in the detachment of TG molecule due to heating/overheating of the oil/fat. Over-heating of oils and fats results in the production of high FFA contents and they present in the ratio of FA wt.% in oil. This FFA leads to saponification reaction during the transesterification process and slow down the biodiesel production [15, 49].

11.8.3.3 Heat The calorific value of feedstock greatly influences the energy content of the biodiesel. Fuels with high saturation give high energy (on weight basis), and high unsaturation provides lower energy content. The fuel has high energy when it is denser. Heat is an important factor that affects biodiesel quality [50].

11.8.3.4 Presence of Unwanted Materials The feedstock contains undesirable materials that hinder the biodiesel production, which has to be eliminated before or in the purification process. Water content and impurities are filterable solids (including solid wastes, bone fragments, and food particles) and unsaponifiable are non-TGs which are incapable of producing mono alkyl fatty esters when subjected for esterification or transesterification process [15].

Soybean oil (wt.%)

10.2

3.7

22.8

53.72

0.1

0.1

8.6

Fatty acids

Palmitic acid

Stearic acid

Oleic acid

Linoleic acid

Lauric acid

Myristic acid

Linolenic acid

0.2

1.0

0.1

10.1

40.5

4.5

42.8

Palm oil (wt.%)

1.5

0.9

–

74.5

35.0

2.9

5.8

Sunflower oil (wt.%)

Table 11.1  Fatty acid contents of vegetable oils and animal fats.

5.9

–

–

55.2

21.2

3.1

8.5

WCO (wt.%)

0.9

2.8

0.1

2.9

42.4

19.4

23.3

Tallow (wt.%)

0.4

1.4

0.1

10.7

44.2

14.2

23.6

Lard (wt.%)

1.9

–

–

19.9

44.0

6.0

23.9

Poultry oil (wt.%)

0.7

6.1

0.2

1.4

15.0

3.0

14.3

Fish oil (wt.%)

Oleochemical Resources for Biodiesel Production  331

332  Biodiesel Technology and Applications

11.8.3.5 Titer Titer is the temperature required for melting of oil from solid into liquid phase. Titer is an important factor which influences the biodiesel production. Oil with high titer leads to high production cost [15].

11.8.4 Characteristic of Feedstock The characteristics of feedstock are directly reflected in the biodiesel obtained from it. Since the transesterification process does not have any effect on the composition of FAs that already exist in the feedstock, this greatly influences the quality and physiochemical properties of the biodiesel. Factors which affect the quality of biodiesel are oil or fat with high FFA content which leads to high production cost, presence of MIU involving additional processing methods including filtration, heat treatment and centrifuge, and some critical parameters like cetane number, cold flow properties, saturation level of FAs, cloud point, flash point, and oxidative stability [15].

11.9 Optimization of Reactions Conditions for High Yield and Quality of Biodiesel 11.9.1 Pre-Treatment of Feedstock 11.9.1.1 Elimination of Water During the transesterification reaction, the water present in the feedstock at high temperature forms FFA by hydrolyzing the TG into DG, and as a result, saponification reaction takes place even a very low amount FFA (less than 1%) is present. To avoid the saponification reaction, the water has to be removed from the feedstock in order to obtain good biodiesel yield from transesterification reaction. Heat treatment and centrifuge are some of the methods used to remove water content from the feedstock [51].

11.9.1.2 Elimination of Insoluble Impurities The feedstock must be filtered before subjecting it to the conversion reaction in order to remove the presence of solid impurities in the form of sand, dirt, fragments, etc., in vegetable oil and small fragments of gums, bones, etc., and in animal fats and WCO [51].

Oleochemical Resources for Biodiesel Production  333

11.9.1.3 Elimination of Unsaponifiables Unsaponifiables are organic compounds such as hydrocarbons, alcohol with high molecular weight, sterols, waxes, and pigments from which soaps cannot be formed during transesterification process. These compounds are removed during refining process of crude oil or with water washing technique during glycerol phase if the crude oil is directly used for biodiesel production [15, 51].

11.9.2 Characterization and Selection of Feedstocks The followings conditions should be taken into account for selection of the feedstock to obtain better yield and quality in biodiesel. FFA content of the feedstock should be low, the FA composition should be considered since it directly influences the properties of the biodiesel, either the feedstock should be free from MIU or pre-treated before subjecting it transesterification reaction, and the saturation level of FAs should be considered for better quality of biodiesel [15, 51].

11.9.3 Selection of Reaction Conditions Biocatalyst is better, and as a pre-treatment step for producing FAAE from FFA, acid catalyst transesterification method is suitable. Heterogeneous catalyst such as calcium methoxide can be used when solvent with boiling point equal to methanol is used. To avoid initiation time lag, supercritical methanol transesterification can be adopted. In order to get a better yield and higher quality biodiesel, reaction parameters have to be optimized by proper selection of feedstock, and reaction conditions play an important role [15, 51].

11.10 Oil Recovery 11.10.1 Alkaline Flooding Method Alkaline flooding is a method used to improve oil recovery from crude oil. NaOH, Na2CO3, and sodium orthosilicate are some of the alkali compounds used for oil recovery [52]. Based on the results reported from the experiment done by Abhijit Samanta et al. (2011) [53], there is conclusive proof that alkali flooding enhances the oil recovery by formation of in situ surfactant. When the alkali slug concentration was increased, the recovery of oil was found to be increased about 15% more than the conventional water flooding in which the recovery of oil is ~50%.

334  Biodiesel Technology and Applications

11.10.2 Additives Hydrocarbon solvents are commonly used for extraction of TG oil directly derived from seeds of feedstocks, e.g., sunflower seeds. Hexane is widely as solvent in plant oil industry [54]. Fishwick and Wright (1997) [55] have experimentally proven that chloroform-methyl alcohol can be used as potential solvent for extraction of plant lipids such as sterol lipids, phospholipids (both bounded and free), and glycolipids. Supercritical carbon dioxide is also used as a solvent for oil recovery [56].

11.11 Quality Improvement of Biodiesel The properties of FAME/FAEE can be enhanced by addition of different types of additives based on the requirements.

11.11.1 Additives for Improving Combustion Ability Barium, platinum, iron, cerium, manganese, and calcium can be used as additives with metal based to enhance the ability to combust and less emission [57, 58].

11.11.2 Additives for Enhancing the Octane Number Oxygenated additives are fuel containing oxygen. It is used for enhancement of octane rating and improving the combustion quality. Commonly used oxygenate additives include alcohols, ether, and ester. Alcohol includes C2H5OH, CH3OH, C4H10O, and C₃H₈O. Ethers used are C5H12O, C6H14O, (C2H5)2O, C2H6O, and C6H14O, etc. [59].

11.11.3 Additives for Improving the Stability Antioxidant additives are used improve the stability and deterioration of biodiesel during storage. Alkyl phenols, hindered phenols, and aromatic diamines are commonly used as antioxidant additives [60–62].

11.11.4 Additives to Enhance Cold Flow Property Ethylene vinyl acetates are used as cold flow improver additives [63].

Oleochemical Resources for Biodiesel Production  335

11.11.5 Additives to Enhance Lubricity These surface-active compounds allow the protective film formation for assisting the solubility of fuel and to improve the lubrication property of biodiesel [64]. Ester, FAs, and amides are used as lubricity improver additives to reverse the lubricity lost during refining of oil [65].

11.11.6 Additives to Enhance Cetane Number Alkyl nitrates especially 2-ethyl hexyl nitrate (2-EHN) is an important cetane number improver additive used to enhance the cetane number. Tertiary butyl peroxide can be used for improving the quality of biodiesel [64].

11.12 Conclusion Oleochemicals are a capable substrate for renewable and production of biofuel and it has advantages over fossil fuels due to its carbon renewability, but there is an issue due to the threating of food safety and security and loss of agrobiodiversity when edible feedstocks are used. Techniques such as transesterification, pyrolysis, and hydrotreatment are the successful process adopted for large-scale biofuel production including biodiesel, bio-oil, and renewable diesel. This would act as an alternative method for glycerol production that, in turn, produces a good impact on biodiesel production. Biodiesel blend that is available commercially has the potentiality to perform as same as Petro-diesel in diesel engines in an eco-friendly manner with reduced emission of greenhouse gases. This production may be increased when there is an increased demand for renewable fuel occurs.

Abbreviations AFW Animal Fat waste ACPO Acid crude palm oil DG Diglyceride FA Fatty acid FAEE Fatty Acid Ethyl Ester FAME Fatty Acid Methyl Ester FFA Free Fatty Acid ME Methyl ester MG Monoglyceride

336  Biodiesel Technology and Applications MSA Methane Sulfonic Acid MSW Municipal Solid Waste PTSA p-toluene sulfhonic monohydrate acid TAG Triacylglycerol TG Triglyceride WCO Waste Cooking Oil WFO Waste Frying Oil

References 1. Sumitkumar  Joshi, Pradipkumar  Hadiya, Manan  Shah,  Anirbid  Sircar, Techno-economical and Experimental Analysis of Biodiesel Production from Used Cooking Oil. Biophy. Econo. Resour. Quality, 4, 2, 2019. 2. Sze Ying Lee, Revathy Sankaran, Kit Wayne Chew, Chung Hong Tan, Rambabu Krishnamoorthy, Dinh-Toi Chu, Pau-Loke Show., Waste to bioenergy: a review on the recent conversion technologies. BMC Energy, 1, 4, 2019. 3. Gemma Vicente, Mercedes Martínez, José Aracil., Comparative Study of Vegetable Oils for Biodiesel Production in Spain. Ene. Fuels, 20, 394–398, 2006. 4. Karlheinz Hill, Fats and oils as oleochemical raw materials. Pure Appl. Chem., 72, 7, 1255–1264, 2000. 5. Jumat Salimon, Nadia Salih, Emad Yousif, Industrial development and applications of plant oils and their biobased oleochemicals. Arab. J. Chem., 5, 135–145, 2012. 6. Richtler, H.J., Knaut, J., Henkel KGaA., Challenges to a Mature Industry: Marketing and Economics of Oleochemicals in Western Europe. JAOCS., 61, 2, 1984. 7. Meira, M., Quintella, C.M., Ribeiro, E.M.O., Silva, H.R.G., Guimarães, A.K., Overview of the challenges in the production of biodiesel. Biomass. Conv. Bioref., 5, 321–329, 2015. 8. Mehdizadeh, A., Handy, L.L., Further investigation of high temperature alkaline floods. SPE. Reservoir. Eng., 171–177, 1989. 9. Gander, K.F., Fats and Oils as Feedstocks for Oleochemicals. JAOCS., 61, 2 February 1984. 10. Balat, M., Potential alternatives to edible oils for biodiesel production–A review of current work. Energy. Convers. Manage., 52, 1479–92, 2011. 11. Sanli, H., Canakci, M., Alptekin, E., Predicting the higher heating values of waste frying oils as potential biodiesel feedstock. Fuel, 2013. 12. Badday, A.S., Abdullah, A.Z., Lee, K.T., Optimization of biodiesel production process from Jatropha oil using supported heteropolyacid catalyst and assisted by ultrasonic energy. Ren. Energy, 50, 427–32, 2013.

Oleochemical Resources for Biodiesel Production  337 13. Kumar, G., Kumar, D., Poonam Johari, R., Singh, C.P., Enzymatic transesterification of Jatropha curcas oil assisted by ultrasonication. Ultrason. Sonochem., 18, 923–7, 2011. 14. Heidrich, J.F., Oleochemicals: Feedstock or Auxiliary, JAOCS., 61, 2 Feb 1984 15. Peter Adewale, Marie-Josée Dumontn, Michael Ngadinn., Recent trends of biodiesel production from animal fat wastes and associated production techniques. Ren. Sustain. Ene. Rev., 45, 574–588, 2015. 16. Tong, D., Hu, C., Jiang, K., Li, Y., Cetane number prediction of biodiesel from the composition of the fatty acid methyl esters. J. Am. Oil. Chem. Soc., 88, 415–23, 2011. 17. Ramírez-Verduzco, L.F., Rodríguez-Rodríguez, J.E., Jaramillo-Jacob, A.d.R., Predicting Cetane number, kinematic viscosity, density and higher heating value of biodiesel from its fatty acid methyl ester composition. Fuel, 91, 102–11, 2012. 18. Adewale, P., Dumont, M.J., Ngadi, M., Rheological, thermal and physicochemical characterization of animal fat wastes destined for biodiesel production. Energy. Technol., 2, 634–42, 2014. 19. Knothe, G., Some aspects of biodiesel oxidative stability. Fuel. Process. Technol., 88, 669–77, 2007. 20. Luković, N., Knežević-Jugović, Z., Bezbradica, D., Biodiesel fuel production by enzymatic transesterification of oils: recent trends, challenges and future perspectives. Alter. Fuel. Tech. Europe., 47–72, 2011. 21. Hanna Brännström, Hemanathan Kumar, Raimo Alén, Current and Potential Biofuel Production from Plant Oils. BioEne. Research., 11, 592–613, 2018. 22. Öner, C., Altun, Ş., Biodiesel production from inedible animal tallow and an experimental investigation of its use as alternative fuel in a direct injection diesel engine., Appl. Energy, 86, 2114–20, 2009. 23. Teixeira, L.S.G., Assis, J.C.R., Mendonça, D.R., Santos, I.T.V., Guimarães, P.R.B., Pontes L.A.M., Comparison between conventional and ultrasonic preparation of beef tallow biodiesel. Fuel. Process. Technol., 90,1164–6, 2009. 24. Kumar, S., Ghaly, A., Brooks, M., Budge, S., Dave, D., Effectiveness of enzymatic transesterification of beef tallow using experimental enzyme Ns88001 with methanol and hexane. Enzyme. Eng., 2, 2, 2013. 25. Hsu, A.F., Jones, K., Marmer, W., Foglia, T., Production of alkyl esters from tallow and grease using lipase immobilized in a phyllosilicate sol–gel. JAOCS., 78, 585–8, 2001. 26. Colak, S., Zengin, G., Ozgunay, H., Sarikahya, H., Sari, O., Yuceer, L., Utilization of leather industry pre-fleshings in biodiesel production. J. Am. Leather. Chem. Assoc., 100, 137–41, 2005. 27. Alptekin, E., Canakci, M., Sanli, H., Evaluation of leather industry wastes as a feedstock for biodiesel production. Fuel, 95, 214–20, 2012. 28. Tanwar, D., Tanwar, A., Sharma, D., Mathur, Y.P., Khatri, K.K., Soni, S.L., Production and characterization of fish oil methyl ester. IJITR., 1, 209–17, 2013.

338  Biodiesel Technology and Applications 29. Jayasinghe, P., Hawboldt, K., Biofuels from fish processing plant effluentswaste characterization and oil extraction and quality. Sustain. Energy. Technol. Assess., 4, 36–44, 2013. 30. Kirakosyan, A., Kaufman, P.B., Plants as Sources of Energy. Recent. Adv. in. Plant. Biotech., 163–210, 2010. 31. Reznik, G.O., Vishwanath, P., Pynn, M.A., Sitnik, J.M., Todd, J.J., Wu, J., Jiang, Y., Keenan, B.G., Castle, A.B., Haskell, R.F., Smith, T.F., Smith, T.F., Somasundaran, P., Jarrell, K.A., Use of sustainable chemistry to produce an acyl amino acid surfactant. Appl. Microbiol. Biotechnol., 86, 1387–1397, 2010. 32. Keng, P.S., Basria, M., Zakaria, M.R., Abdul Rahman, M.B., Ariff, A.B., Abdul Rahman, R.N., Salleh, A.B., Newly synthesized palm esters for cosmetics industry. Ind. Crops. Prod., 29, 37–44, 2009. 33. Abhilash, P.C., Singh, N., Pesticide use and application: an Indian scenario. J. Hazard. Mater., 165, 1–12, 2009. 34. Christopher, L.P., Kumar, H., Zambare, V.P., Enzymatic biodiesel: challenges and opportunities. Appl. Energy., 119, 497–520, 2014. 35. Larissa, P., Lima, Francisco, F.P., Santos, Enio Costa, Fabiano, A.N., Fernandes., Production of free fatty acids from waste oil by application of ultrasound. Biomass. Conver. Bioref., 2, 309–315, 2012. 36. Karmakar, A., Karmakar, S., Mukherjee, S., Properties of various plants and animal feedstocks for biodiesel production. Bioresour. Technol., 101,19, 720110, 2010. 37. Demirbas, A., Biodiesel fuels from vegetable oils via catalytic and non-­ catalytic supercritical alcohol transesterifications and other methods: a survey. Energy. Convers. Manag., 44, 2093–2109, 2003. 38. Abbaszaadeh, A., Ghobadian, B., Omidkhah, M.R., Najafi, G., Current biodiesel production technologies: a comparative review. Energy. Convers. Manag., 63, 138–148, 2012. 39. http://www.bioxcorp.com. BIOX Process., Dec 2008. 40. Adeeb Hayyan, Farouq, S., Mjalli, Mohamed, E.S., Mirghani, Mohd Ali Hashim, Maan Hayyan, Inas, M., AlNashef, Saeed M., Al-Zahrani., Treatment of acidic palm oil for fatty acid methyl esters production. Chem. Papers, 66, 1, 39–46, 2012. 41. Hayyan, A., Mjalli, F. S., Hashim, M. A., Hayyan, M., AlNashef, I. M., Al-Zahrani, S. M., & Al-Saadi, M. A. Ethane sulfonic acid-based esterification of industrial acidic crude palm oil for biodiesel production. Bioresour. Technol., 102, 9564–9570, 2011. 42. Umer Rashida, Farooq Anwara, Bryan R. Moserb, Samia Ashrafa., Production of sunflower oil methyl esters by optimized alkali-catalyzed methanolysis. Biomass. Ener., 32, 1202–1205, 2008. 43. Jeong, G.T., Park, D.H., Kang, C.H., Lee, W.T., Sunwoo, C.S., Yoon, C.H., Production of biodiesel fuel by transesterification of rapeseed oil. Appl. Biochem. Biotechno., 113–116, 747–58, 2004.

Oleochemical Resources for Biodiesel Production  339 44. Antolin, G., Tinaut, F.V., Briceno, Y., Castano, V., Perez, C., Ramirez, A.I., Optimization of biodiesel production by sunflower oil transesterification. Bioresour. Technol., 83, 111–4, 2002. 45. Encinar, J.M., Gonzalez, J.F., Sabio, E., Ramiro, M.J., Preparation and properties of biodiesel from Cynara cardunculus L. oil. Indus. Eng. Chem. Research., 38, 2927–31, 1999. 46. Singh, A., He, B., Thompson, J., Process optimization of biodiesel production using alkaline catalysts. Appl. Eng. Agri., 22, 597–600, 2006. 47. Venkata Subhash, G., Venkata Mohan, S., Sustainable biodiesel production through bioconversion of lignocellulosic wastewater by oleaginous fungi. Biomass. Conv. Bioref., 5, 215–226, 2015. 48. Georgios Karavalakis, Georgios Anastopoulos, and Stamos Stournas., Methyl Ester Production from Sunflower and Waste Cooking Oils Using AlkaliDoped Metal Oxide Catalysts. Ind. Eng. Chem. Res., 49, 12168–12172, 2010. 49. Hayyan, A., Alam, Md. Z., Mirghani, M. E. S., Kabbashi, N. A., Hakimi, N. I. N. M., Siran, Y. M., & Tahiruddin, S., Reduction of high content of free fatty acid in sludge palm oil via acid catalyst for biodiesel production. Fuel. Processing. Technol., 92, 920–924. 2011. 50. Sevil Özgül-Yücel, Selma Türkay, Variables Affecting the Yields of Methyl Esters Derived from in situ Esterification of Rice Bran Oil- parameters affecting ME. JAOCS., 79, 6, 2002. 51. Van Gerpen, J., Shanks, B., Pruszko, R., Clements, D., Knothe, G., Biodiesel Production Technology., Subcontractor Report. Nat. Ren. Ene. Lab./SR., 510–36244, 2004. 52. Mehdizadeh, A., Handy, L.L., Further investigation of high temperature alkaline floods. SPE. Reservoir. Eng., 171–177, 1989. 53. Abhijit Samanta, Keka Ojha, and Ajay Mandal., Interactions between Acidic Crude Oil and Alkali and Their Effects on Enhanced Oil Recovery. Ene. Fuels, 25, 1642–1649, 2011. 54. Kevin, J., Harrington, Catherine, D’Arcy-Evans., Transesterification in Situ of Sunflower Seed Oil. Ind. Eng. Chem. Prod. Res. Dev., 24, 314–310, 1985. 55. Fishwick, M. J and Wright, A. J., phytochemistry, 16, 1507, 1977. 56. Rashedul, H.K., Masjuki, H.H., Kalam, M.A., Ashraful, A.M., Ashrafur Rahman, S.M., Shahir, S.A., The effect of additives on properties, performance and emission of biodiesel fuelled compression ignition engine. Ener. Conver. Manage., 88 348–364, 2014. 57. Kannan, G., Karvembu, R., Anand, R., Effect of metal-based additive on performance emission and combustion characteristics of diesel engine fuelled with biodiesel. Appl. Energy, 88, 3694–703, 2011. 58. Campanella, A., Rustoy, E., Baldessari, A., Baltaná s, M.A., Lubricants from chemically modified plant oils. Bioresour. Technol., 101, 245–254, 2010. 59. Rahmat, N., Abdullah, A.Z., Mohamed, A.R., Recent progress on innovative and potential technologies for glycerol transformation into fuel additives: a critical review. Renew. Sustain. Energy. Rev., 14, 987–1000, 2010.

340  Biodiesel Technology and Applications 60. Joshi, G., Lamba, B.Y., Rawat, D.S., Mallick, S, Murthy, K., Evaluation of additive effects on oxidation stability of Jatropha curcas biodiesel blends with conventional diesel sold at retail outlets. Ind. Eng. Chem. Res., 52, 7586–92, 2013. 61. Karavalakis, G., Hilari, D., Givalou, L., Karonis, D., Stournas, S., Storage stability and ageing effect of biodiesel blends treated with different antioxidants. Energy, 36, 369–74, 2011. 62. Schober, S., Mittelbach, M., The impact of antioxidants on biodiesel oxidation stability. Eur. J. Lipid. Sci. Technol.,106, 382–9, 2004. 63. Hamada, H., Kato, H., Ito, N., Takase, Y., Nanbu, H., Mishima, S., Effects of polyglycerol esters of fatty acids and ethylene-vinyl acetate co-polymer on crystallization behaviour of biodiesel. Eur. J. Lipid. Sci. Technol., 12, 1323–30, 2010. 64. Kumar, H., Enhancing biodiesel stability by using fuel additives–a review. Int. J. Res. Biochem. Process. Eng., 1, 2012. 65. Ong, L.K, Kurniawan, A., Suwandi, A.C., Lin, C.X., Zhao, X.S., Ismadji, S., Transesterification of leather tanning waste to biodiesel at supercritical condition: kinetics and thermodynamics studies. J. Supercrit. Fluid., 75, 11–20, 2013. 66. Gürü, M, Koca, A., Can, Ö., Çınar, C., Şahin, F., Biodiesel production from waste chicken fat-based sources and evaluation with Mg based additive in a diesel engine. Ren.@Energy., 35, 637–43, 2010. 67. Dias, J.M., Alvim-Ferraz, M., Almeida, M.F., Production of biodiesel from acid waste lard. Bioresour. Technol., 100, 6355–61, 2009. 68. Shin, H.Y., An, S.H., Sheikh, R., Park, Y.H., Bae, S.Y., Transesterification of used vegetable oils with a Cs-doped heteropoly acid catalyst in supercritical methanol. Fuel, 96, 572–8, 2012. 69. Bhatti, H.N., Hanif, M.A., Qasim, M., Ataur, R., Biodiesel production from waste tallow. Fuel, 87, 2961–6, 2008. 70. İşler, A., Sundu, S., Tüter, M., Karaosmanoğlu, F., Transesterification reaction of the fat originated from solid waste of the leather industry. Waste. Manage., 30, 2631–5, 2010.

12 Overview on Different Reactors for Biodiesel Production V. C. Akubude1*, K.F. Jaiyeoba2, T.F Oyewusi2, E.C. Abbah1, J.A. Oyedokun3 and V.C. Okafor1 Department of Agricultural and Bioresource Engineering, Federal University of Technology, Owerri, Nigeria 2 Department of Agricultural Engineering, Adeleke University, Ede, Nigeria 3 National Centre for Agricultural Mechanization, Ilori, Nigeria

1

Abstract

Biodiesel is alternative source of energy which has gained wide research input. Notwithstanding, its wide utilization in energy systems like fossil fuel is still facing challenges due to high production cost. This bottleneck can only be eradicated by developing a better cost-effective and productive approach that can lead to affordable end product at the long run. Biodiesel reactor plays a key function in the overall production cost of biodiesel; therefore, a careful selection of a reactor that can help eliminate the challenges faced by convectional reactors is paramount. Batch reactors are widely used for biodiesel production but its disadvantages has led to development of continuous flow reactors and even novel reactors like microreactors. This chapter features the general concept of various configuration of reactors currently been utilized in biodiesel production. Their merit and limitations as well as their properties are captured. Keywords:  Biodiesel, reactor, batch reactors, continuous flow reactors, microreactors

12.1 Introduction Alternative source of energy has been the current center of research in developing countries to provide the global energy need with its rising population and limited source of petroleum. Also, a cleaner, sustainable, and *Corresponding author: [email protected] Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (341–360) © 2021 Scrivener Publishing LLC

341

342  Biodiesel Technology and Applications eco-friendly source of energy [1, 2] is another aim of the research community to reduce the pollution caused by the fossil fuel. Biodiesel is energy product that is gotten from biological sources like animal fat, vegetable, or waste oil. It is derived from chemical reaction between bio-oil and alcohol in the presence of a catalyst [2]. It is a type of biofuel comprising of mono-alkyl esters of long-chain fatty acids produced by transforming vegetable oil via transesterification reaction [3]. It offers lots of advantage to the environment, society, and economy including lower sulfur and aromatic content, non-toxic, renewable, biodegradable, clean burning, reduce greenhouse gas emission, reduce the carbon monoxide, and good lubricity [4–8]. Despite the numerous benefits of biodiesel, it has not gain public acceptance because of the price when compared with fossil fuel. Hence, to make biodiesel more appealing to the society, well-developed strategy that is void of the various problems relating to the production processis essential [9]. Reactor is known as a compartment where chemical conversion takes place during any processing activity. It is a chamber used in transforming raw materials to desired products via chemical reaction. A reactor must provide enough time for chemical reaction to occur [10]. Reactor design should consider the following key factors: construction material, stirring system, size of reactor, hydrodynamics, physical properties of the reactants, and methods for in-take or discharge of heat as this will ensure high effectiveness and productivity [11]. Several configurations of continuous reactors have been developed. This work reviews many technological developments within literature with respect to these reactors.

12.2 Biodiesel Production Reactors Generally, reactors are classified as batch or continuous [12, 13]. The design of the reactor depends on how the biodiesel is produced, either in batches or as a continuous process. Many investigations have been carried out in order to realize the right type of reactor to surmount some technical challenges during production of biodiesel by transesterification. In the recent time, the technical methods or processes in production of biodiesel have improved tremendously with the advent of various types of reactor in different sizes. This study therefore examines several types of reactor such as batch reactors (BRs), continuous stirred tank reactors (CSTRs), fixed bed reactors (FBRs), bubble column reactors (BCRs), microchannel reactors

Different Reactors for Biodiesel Production  343 (MCRs), membrane reactors (MRs), reactive distillation, and hybrid catalytic plasma reactors.

12.2.1 Batch Reactor Batch production of biodiesel via the use of BR is the basic method that has been used for biodiesel synthesis [14] before the emerging of continuous processes [15]. BRs are as simple as tanks with different forms of agitating equipment as shown in Figure 12.1 [16]. The chamber/tank remains occupied with the processing reactants (catalyst, oil, and alcohol) with operation of the agitators for a certain period. In the reactor, the reactants are charged at a predetermined period of time. The chemical structure in the reactor transforms with time along with the product concentration by closing the reactor and then taking it to the required reaction states (pressures, temperatures, and agitation rates). Subsequently, the result of reaction inhibition by reaction products can be reduced. After completion of the reaction time, the chemical substances from the reactor are isolated and sent for consequent processes. One of the major features of BRs is that it begins with unreacted substance, cause it to react, and then finish with reacted substance after a while. Other helpful characteristics of BRs include suitable mixing features and comparative ease of controlling homogeneous catalysts as used in the biodiesel transesterification reaction.

Speed controller

Cooling water

Thermometer and sampling outlet

Condenser

Cooling water Agitator/stirrer Three-neck flask

Hot plate

Figure 12.1  Schematic diagram of batch reactor apparatus [16].

344  Biodiesel Technology and Applications In some literature, reports have mostly focused on maximizing the experimental factors of BRs to obtain high biodiesel yield. Price et al. [17] performed a modeling study on optimal yield of biodiesel in a BR by means of a liquid lipase formulation. A simulated biodiesel yield of 90.8% (wt.) was reported at optimum parameters for the model. Leadbeater et al. [18] reported a typical reaction procedure of a BR which involved two-neck round bottomed flask of 31 containing a stirrer with soybean oil (1 kg), sulfuric acid solution (5% by weight, 27 ml) with 630 ml of butanol. This blend was laid inside hollow of a microwave through an immersion in one side of the flask necks with a glass connector into one another. In addition, an optic’s fiber probe was dipped inside the immersion. This blend was allowed to heat from room temperature to 120°C by means of a preliminary microwave powered at 1,600 W and allowed to stay for 2 min at 120°C. Then, reaction compartment was detached from the hollow of the microwave, and upon cooling to normal temperature, the substance was transferred into another chamber to settle. Thereafter, the substance was rinsed with water followed by brine. By solution of nuclear magnetic resonance spectroscopy with respect to hydrogen (HNMR), the degree of transesterification of oil was measured. The groups of −OCH2in the butylester-chain with α-methylene proton presents inside the triglyceride (TG) by-products of the oil were related signs selected for incorporation. After estimating the conversion completely from the incorporated area of the signal, 93% conversion of biodiesel was the highest reported. However, BRs have drawbacks, for instance, bulky reactor size, wide separation processes, and high cost of labor [19]. More so, the main restriction of BRs is commonly connected near mass transfer control relating the oil and solvent [20]. To rise above these challenges, several forms of reactors were developed with improving usage of solvent, catalyst, and energy; furthermore, to streamline improvement phases by incorporated separation techniques. The extent of mixing in BRs increases as the totality of energy presented from the stirrer increases and vice-versa [11, 12].

12.2.2 Continuous Stirred Tank Reactor Most CSTRs are well configured in order to give room to continuous pumping of the reactants [21] for efficient working of the reactors as shown in Figure 12.2 as given by [22]. At first glance, a CSTR seems to be similar to a BR. Actually, the reactors can be so alike except that CSTR requires some controls to be set up inside the reactor. At the beginning, after loading the continuous reactor with reaction substances, the process is agitated adequately until the reaction is accomplished. The major components in

Different Reactors for Biodiesel Production  345 reactant 1 reactant 2

electronic valve control

level gauge

to vent system floor level

products overflow from reactor

coolant

stirrer

Figure 12.2  Schematic diagram of continuous stiired tank reactor.

CSTRs include the agitation speed and in-out flow rate which influences the residence time, rate of mass transfer, and efficiency of mixing [23]. Thorough mixing is required for assurance of adequate homogeneity of the products; this always caused more energy to be consumed. Thus, many efforts have been made with the use of different kinds of CSTR to exchange the mechanical agitators in order to minimize the energy consumed. So far, CSTR has been extensively employed for production of biodiesel in large scale due to its adequate technologies and wide understanding of operations. While the continuous steady tank reactor worked continuously at a steady condition, the ideal thing is that the concentrations of some chemicals used should be nearly constant all time at everywhere in the reactor. However, this ideal condition is rare to achieve; hence, adjustment needs to be done to working parameters to make sure reaction is completed. It must be noted that, two reactors may be used sometimes. For the two-stage process, almost 80% of catalyst with alcohol can be combined with oil in the first stage of CSTR. After which, the reacted flow passes within glycerol removal phase prior to its entrance to second stage of CSTR. The other 20% of catalyst with alcohol can be placed inside the reactor at the second stage. This process offers an extremely completed reaction with the possibility of

346  Biodiesel Technology and Applications utilizing a smaller amount of alcohol than single phase process. So, due to consistency of quality products required and inadequate capital with operational cost for each product, transesterification by CSTR process is preferable to BR process [24]. When comparing CSTR with BR, CSTR provides quality operation to improve thermal and mass transfer, less production cost, provides a uniformity of product, and supports scale up [25, 26].

12.2.3 Fixed Bed Reactor FBR as shown in Figure 12.3 [16], sometimes, called packed bed reactor, is a cylindrical-tube full of catalytic agents (pellets) packed in a fixed bed with the flowing of the reactants within the bed which are transformed to fatty acid methyl esters (FAMEs). It uses heterogeneous catalysts to simplify actions in improving process since no separation technique common to the catalyst and product is needed. Also, FBR improves the heterogeneous reaction of the catalyst because of the delay in deactivation

stainless steel column (Φ25х450mm)

outlet

water jacket

pump

inlet

pump

accumulation tank feedstock tank

thermostat water bath

Heater

Figure 12.3  Schematic diagram of fixed bed reactor [16].

Different Reactors for Biodiesel Production  347 and longevity in duration of the catalytic agent; hence, there is reduction in cost of production. However, the main parameters in this reactor are amount and size of the catalytic agent, feed flowrate, bed height, molar ratio, and residence time. When comparing with another heterogeneous catalytic reactor, FBR lowers the reaction time and raises the link combining bio-oil and alcohol with catalyst; yet, a greater molar ratio is required. Likewise, the by-product (resultant glycerol) dwells in the bottom most part of the reactor and accumulates on the surface of the catalytic agent. Hence, it lowers the effectiveness of the catalyst which causes a further process removal [27]. Previous works on FBR have been reported by some researchers [28] who extensively examined the production of FAME from esterification of acidified oil alongside methanol in FBR with cation exchange resin, and a better result was attained. Also, esterification of crude triolein with ethanol in FBR was examined at 60-min residence time, and thereafter, about 80% of FAME was achieved [29]. In a recent study, esterification of processed coconut oil using methanol in FBR was carried out with mass transfer as recovery step and 78% conversion rate was obtained [30]. An optimum FBR for biodiesel production using soybean oil in a solvent process of tert-butanol achieved a molar conversion of 83.31%. The FBR can work over 30 days with no meaningful loss noticed in the substrate conversion. Also, the FBR shows the ability for industrial-scale production of FAME utilizing a tert-butanol solvent system. Some common advantages of using FBR are constant discharge of glycerol with excessive alcohol, effectual reuse of enzymes, and preservation of particulate enzymes from mechanical shear stress [31–33]. Conversely, short-term operation of FBR is a big problem; however, using a solvent-free system can operate for 3 to 7 days without reduction in ester yield [34, 35].

12.2.4 Bubble Column Reactor This is broadly used in industrial production of biodiesel. It has been generally utilized for performing gas-to-liquid reaction for many industrial applications. It is a better reactor for production of biodiesel that requires a substantial interaction area for gas-to-liquid mass transfer and effective blending for reacting species. Figure 12.4 [36] gives a schematic diagram of BCR. The heterogeneous somatic scheme in the BCR is classified into two fragments: vapor and liquid phase. Vapor phase contains water vapor and methanol, whereas the liquid phase contains oil, biodiesel, methanol, water and catalyst (H2SO4). For simplicity, both phases are assumed to be well

348  Biodiesel Technology and Applications Gaseous Phase (Unreacted Methanol) Condenser Reactor Vessel (520-620 K, 0.1 MPa) Liquid Phase

Vegetable Oil

FAME (Biodiesel Fuel) Dehydration Column Methanol

Glycerol (By-Product) Heater

Figure 12.4  Schematic view of bubble column reactor for biodiesel production [36].

blended without spatial concentration gradient inside the reactor. Often, BCR makes use of acid catalysts without soap but produces high temperature that boils the methanol. The bubbling methanol produces agitation and removes the by-product water. Production of biodiesel with superheated methanol-vapor occurs under atmospheric pressure and higher temperature between 250°C to 300°C, this necessitates for stainless-steel reactor with insulation [37]. Kocsisova et al. [38] reported that supplying methanol into BCR with operation at temperature greater than 100oC under atmospheric pressure supports water ejection from oil during transesterification that enhances conversion of the final biodiesel. Suwannakaran et al. [39] discovered the viability of utilizing blended feedstocks [TGs and free fatty acid (FFA)] for production of biodiesel using solid catalyst (Calcined Tungstated Zirconia) through BCR at high temperature of 130°C. Conversion of 85% (FFA) and 22% (TG) was achieved under 2 h of reaction. The fairly low conversion rate achieved is on account of the competition between FFA and TG during early protonation of their carboxylic functionality following nucleophilic attack by methanol producing biodiesel. Also, BCR has been operated previously at upper temperatures (250°C to 290°C) by means of palm oil in deficit of catalytic agent to envisage its functionality with increased methanol flow rate but low conversion of 60% was recorded [40]. In a subsequent report, an increased conversion rate of 95% was observed at 290°C but esterification rate increases as temperature increased [41].

Different Reactors for Biodiesel Production  349 In another related development, utilization of BCR in preparing biodiesel was reported by Joelianingsih et al. [40, 41]. The studies established that catalyst free biodiesel can be successfully produced using BCR at ambient pressure. BCR provides the opportunity of achieving vigorous agitation as gas is circulated in a sparger that brings out bubbles through a vertical-ylindrical column [42, 43]. Reduction in enzymes’ wears and tears, and provision of longer duration using a highly viscous and s­ olvent-free system agitated by gas bubbling has been reported by Manman et al. [43]. Benefit of this process is that catalytic agent is not needed; thus, esterification of oil with high FFA substance can be achieved with no initial treatment. Also, methanol bubbles coming up in the reactor provides adequate agitation to permit dispersal of methanol steam to enter the oil phase for reaction; hence, there is reduction in the cost of mechanical agitation [44]. However, the main drawbacks of using BCR in production of biodiesel are the condition for even bubble size dispersal and gas/vapor delay profile. These drawbacks are as a result of somekey factors including column height and diameter, geometry of sparger, liquid phase viscosity, and gas velocity [42]. The problem of improving these factors is the major constraint to the use of BCR for industrial-scale production. Also, it exhibits ill-effect when biocatalyst (enzyme) is used since the enzyme carrier can be broken-down through mechanical agitation thereby deactivate the catalytic activity.

12.2.5 Reactive Distillation Column This is a reactor type in which chemical reactions and product separations occur concurrently in a single unit. Reactive distillation column (RDC) consists of a reactive section, non-reactive rectifying and stripping sections as shown in Figure 12.5 [45]. The product removal and formation happens simultaneously giving rise to its capacity to overbear the equilibrium thermodynamics of the reaction, reaching high conversion and selectivity. Therefore, it can serve as a good option to the conventional combination of reactor and separation units [46–49]. Usually, vegetable oil is fed to the top of the column and alcohol is fed to the bottom as vapor. The product formed (biodiesel) is pumped from the bottom while the water by-­product is distilled from the top [21]. The merits of using this process include maintaining a high alcohol-to-oil molar ratio, reduction in excess alcohol usage, and combination of reactor and separation chamber in a single unit thereby saving cost [50–52]. This technique has been utilized in biodiesel production by researchers [53].

350  Biodiesel Technology and Applications

Rectifying section Feed Reactive section

Stripping section

Figure 12.5  The general configuration of reactive distillation [45].

12.2.6 Hybrid Catalytic Plasma Reactor The potential of the plasma technology is the utilization of high energetic electrons because of a collision between the high energetic electrons and the reaction mixtures. The high energetic electron is generated from a high-voltage power supply through high-voltage electrode. The advantages of this plasma electro-catalysis system only require very short time reaction, do not need a catalyst, do not form soap, and do not produce glycerol as a by-product. However, there was difficulty in regulating the main reaction process during the plasma process due to the action of high energetic electrons [54]. Figure 12.6 shows a schematic diagram of hybrid catalytic plasma reactor [16].

12.2.7 Microreactors Technology They are of different configuration, namely, MCR, MR, microtube microreactor (MM), and oscillatory flow reactors (OFRs). The sizes of these reactors are quite small compared to the conventional types. This will result to reduction in capital cost. MCR as shown in Figure 12.7 [55] is made up of channels whose diameters are very small like less than few millimeters [55]. The merits of MCR are reduced reaction time, fast phase separation, excellent blending,

Different Reactors for Biodiesel Production  351

Oil Tank

AC/DC Voltage Regulator

Methanol Tank flowmeter

High Voltage Generator (AC/DC)

High Voltage Electrode

Settler BIODIESEL PRODUCT

Mixing Tank Ground Electrode Hybrid Catalytic Plasma Reactor

Figure 12.6  A schematic diagram of hybrid catalytic plasma reactor system in the future works [16].

Outlet

Middle Sheet Inlet

Zig-zag Mirochannel (with 90º turn)

Figure 12.7  Schematic diagram of a microchannel microreactor [55].

less cost of scale-up, large surface area–to-volume ratio, effective mass and thermal, and safe and stable operations. Its demerit is limited capacity [21]. MR as shown in Figure 12.8 [9] is a reactor type was reaction, and membrane-based separation occurs concurrently in the same chamber [21, 56]. It has high selectivity and ability to regulate the blending of components between two phases and provide high surface areas per unit volume. The membrane acts as a selective barrier thereby controlling the movement of

352  Biodiesel Technology and Applications Pressure guage Membrane reactor Heat exchanger Back pressure valve

Oil tank Circulating pump

chiller Methanol tank

Mixing tank Biodiesel tank

Methanol recovery unit

Figure 12.8  Schematic diagram of a membrane reactor for biodiesel production [9].

substances using different mass transfer rates. During production process, the membrane isolates the glycerol from the product stream [57, 58] or keeps the unreacted TGs within the membrane [59–61]. Various forms of membrane that have been utilized in biodiesel production include as ceramic carbon membranes, polymeric membranes, and polyethersulfone [59–63]. Study by [56] shows that using ceramic membrane gave a yield of 96.42% under optimal conditions. MM as shown in Figure 12.9 [55] is a type of reactor where heat and mass transfer are expected to remain notably reinforced due to its small High Pressure Pump (HPLC)

Hot Water Tube Containing Microreactor Substrate

Cooling Tube

Mixing Unit (I-Mixer)

Product

Hot Water Inlet

Hot Water Cold Water Cold Water Outlet Inlet Inlet

Methanol+Catalyst

Figure 12.9  Schematic diagram of microtubemicroreactor [55].

Ice-Water Bath

Different Reactors for Biodiesel Production  353 space with a large surface area–to-volume ratio. Resulting in molecular diffusions via the edge and in the two-phase reaction, it should come to be much less considerable [64].

12.2.8 Oscillatory Flow Reactors This is a continuous process reactor type that is made up of tubes enclosing equally spaced orifice plate baffles on a piston that create an oscillatory motion generating recirculation flow pattern that ensures effective blending of fluid inside it, resulting in increased heat and mass transfer. This piston is electrically or pneumatically operated. It helps to enhance the residence time for the reaction [65, 66]. Production of biodiesel using an oscillatory flow biodiesel reactor (OFBR) has been reported to be another effective continuous process [14].

12.2.9 Other Novel Reactors Novel reactors such as sonochemical reactor, cavitation reactor, and microwave reactor have been used as intensification technology for biodiesel production. Cavitation is the formation of small bubbles that grows and collapses resulting in discharge of high level of energy [2, 67, 68], generating very high pressure and temperature gradient which improves the mass transfer rate of the reaction by creating a state of intense violent movement and liquid microcirculation currents in the reactor [67–69]. Sonochemical reactor is a novel reactor that works based on the generation of cavitation using energy from ultrasonic irradiation [68]. The merits include savings on energy and cost, high yield and selectivity, and safer operating conditions [70]. Also, studies report that in ultrasound-assisted process, the operating parameters are meaningfully decreased [71, 72]. However, its demerit is that of erosion and particle shedding at the delivery tip surface because of the high surface energy intensity [2, 68]. Microwave reactor utilizes microwave radiation in conveying energy directly into the reactants and thus speeds up the transesterification process. It plays a vital function in heating of reactants to the desired temperature [73]. It is more advantageous in terms of energy and time saving, steady internal heating, and safe operating conditions. It is easy to regulate and gives higher yield under mild reaction conditions and less environmental pollution [67].

354  Biodiesel Technology and Applications

12.3 Future Prospects BRs are basic mode of biodiesel production. However, several continuous process reactors are emerging with specific benefits to tackle the drawbacks of BRs. Most of the reactors have been utilized at laboratory level and needs a scale up for large-scale production. Therefore, there is need for more research on how to improve on the existing technologies for largescale production. Also, the cost that will be incurred to build the reactors for scale up should be considered carefully as this will have effect on the cost of production of biodiesel.

12.4 Conclusion Biodiesel are produced using reactor which vary in type, configuration, and design. Reactor has a direct effect on the biodiesel produced. The various types of bioreactors include batch, CSTR, FBR, BCR, RDC, hybrid catalytic plasma reactor, microreactors technology, and OFRs. Each configuration of reactor has varying degrees of merits and demerits; most of the reactors have been utilized at laboratory level and needs a scale up for large-scale production thus calling for more research on improvement of existing technologies for large-scale production considering cost of production.

References 1. Rahman, M.M., Hazrat, M.A., Rasul, M.G., Mahmudul, H.M. Comparative evaluation of edible and non-edible oil methyl ester performance in a vehicular engine. Energy Procedia 75, 37–43, 2015. 2. Bhuiya, K.M.M., Rasul, M.G., Khan, M.M.K., Ashwath, N., Azad, A.K. Prospects of generation biodiesel as a sustainable fuel—Part: 1 selection of feedstocks, oil extraction techniques and conversion technologies. Renew. Sustain. Energy Rev. 55, 1109–1128, 2016. 3. Akubude, V. C., Nwaigwe, K. N. Dintwa, E. Production of biodiesel from microalgae via nanocatalyzedtransesterification process: A review, Materials Science for Energy Technologies 2, 216–225, 2019. 4. Atabani A.E., Silitonga A.S., IrfanAnjumBadruddin, Mahlia T.M.I., Masjuki H.H. and Mekhilef S. A comprehensive review on biodiesel as an alternative energy resource and its characteristics. Renewable and Sustainable Energy Reviews, 16, 2070–2093, 2012.

Different Reactors for Biodiesel Production  355 5. Daming Huang, Haining Zhou and Lin Lin. Biodiesel: an alternative to conventional fuel. Energy Procedia, 16, 1874–1885, 2012. 6. Rhoda H. G., Iwekumo W. and OkekogeneEfeonah I E. Simulation model for biodiesel production using nonisothermal (CSTR) mode: Membrane reactor. Chemical and Process Engineering Research, 21–34, 2013. 7. Saxena P., Jawale S. and Joshipura M.H. A review on prediction of properties of biodiesel and blends of biodiesel. Procedia Engineering 51, 395–402, 2013. 8. Coniglio L., Bennadji H., Glaude P.A., Herbinet O. and Billaud F. Combustion chemical kinetics of biodiesel and related compounds (methyl and ethyl esters): experiments and modelling - advances and future refinements. Progress in Energy and Combustion Science 39, 340–382, 2013. 9. Olagunju, O. A. and Musonge. P. Production of Biodiesel Using a Membrane Reactor to Minimize Separation Cost. IOP Conf. Series: Earth and Environmental Science 78, 2017. 10. Gary, F.L. Reactors in Process Engineering, https://www.researchgate.net/ publication/241765470, 2017. 11. Ajala, E., O., Aberuagba, F., Olaniyan, A. M., Ajala, M. A., Sunmonu, M. O. and Odewole. M. M. Design, construction and performance evaluation of a mini-scale batch reactor for biodiesel production: A case study of shea butter, Songklanakarin J. Sci. Technol. 40, 1066–1075, 2018. 12. Gerpen, J. V. Biodiesel processing and production, Fuel Processing Technology, 86,1097–1107, 2005. 13. Knothe, G., Van Gerpen, J. H. and Krahl, J. The biodiesel handbook, AOCS Press, Champaign, Ill, 2005. 14. Azhari T. I. Mohd. Ghazi, M. F. M. GunamResul, R. Yunus, T. C. Shean Yaw. Preliminary design of oscillatory flow biodiesel reactor for continuous biodiesel production from jatropha triglycerides. Journal of Engineering Science and Technology 3, 138–145, 2008. 15. Kraai, G. N., Schuur, B., Van Zwol, F., Van de Bovenkamp, H. H., Heeres, H. J. Novel highly integrated biodiesel production technology in a centrifugal contactor separator device. Chemical Engineering Journal 154, 384–389, 2009. 16. Buchori, L., Istadi, I., Purwanto, P. Advanced Chemical Reactor Technologies for Biodiesel Production from Vegetable Oils - A Review. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (3), 406–430, 2016. 17. Price, J., Hofmann, B., Silva, V.T.L., Nordblad, M. Woodley, J.M. and Huusom, J.K. Mechanistic modeling of biodiesel production using a liquid lipase formulation. Biotechnol. Prog. 30, 1277–90, 2014. 18. Leadbeater, N.E., Barnard, T.M. and Stencel. L.M. Batch and continuous-flow preparationof biodiesel derived from butanol and facilitated by microwave heating. Energy & Fuels. 22(3), 2008. 19. Anton, A. K. and Costin, S. B. (2012). A review of biodiesel production by integrated reactive separation technologies. Journal of Chemical Technology and Biotechnology 87, 861–879, 2012.

356  Biodiesel Technology and Applications 20. Abdurakhman Y.B., Putra Z.A. and Bilad M.R. Aspen HYSYS simulation for biodiesel production from waste cooking oil using membrane reactor. Proceedings IOP Conference Series: Materials Science and Engineering, 180, 2017. 21. KhairulAzlyZahana, Manabu Kano Technological Progress in Biodiesel Production: An Overview on Different Types of Reactors Energy Procedia, 156, 452–457, 2019. 22. Department Of Chemistry of York, UK. The essential chemical industry: chemical reactors http://www.essentialchemicalindustry.org/processes/ chemical-reactors.htm, 2018. 23. Janajreh I. and Al-Shrah M. Numerical simulation of multiple step transesterification of waste oilin tubular reactor. Journal of Infrastructure Systems, 22(4), 2016. 24. Madhu, A., Sunny, S., Kailash, S., Chaurasia, S. P. and Dohare, R. K. Biodiesel YieldAssessment in Continuous-Flow Reactors Using Batch Reactor Conditions, International Journalof Green Energy, 10:1, 28–40, 2013. 25. Eflita, Y., Moh, E. Y., Diyono, I., Aditya M. N., and Ristiyanti P. The development ofthe super-biodiesel production continuously from Sunan pecan oil through the process of reactive distillation. AIP Conference Proceedings, 1737, 2016. 26. Bao-Quan, Q., Dan, Z., Gen, L., Jian-Zhong, Y., Song, X. and Jiao L. Processenhancement of supercritical methanol biodiesel production by packing beds. Bioresource Technology 228, 298–304, 2017. 27. Shinji, H., Ayumi, Y., Naoki, T., Hideo, N. and Akihiko, K. Enzymatic production of biodiesel from waste cooking oil in a packed-bed reactor: An engineering approach to separation of hydrophilic impurities. Bioresource Technology, 135, 417–421, 2013. 28. Feng, Y., Zhang, A., Li, J., and He, B. A continuous process for biodiesel production in a fixed bed reactor packed with cation-exchange resin as heterogeneous catalyst. Bioresource Technology, 102, 3607–3609, 2011. 29. Shibasaki-Kitakawa, N., Honda, H., Kuribayashi, H., Toda, T., Fukumura, T., and Yonemoto, T. Biodiesel production using anionic ion-exchange resin as heterogeneous catalyst. Bioresource Technology, 98(2), 416–421, 2007. 30. Edric, C., Millicent, C., Angelo, J., Diamante, Rainier, L.C. and Raymond, Y.R. Internalmass-transfer limitations on the transesterification of coconut oil using an anionic ion exchangeresin in a packed bed reactor. Catal. Today 174, 54–58, 2011. 31. Royon, D., Daz, M., Ellenrieder, G. and Locatelli, S. (2007). Enzymatic production of biodiesel from cotton seed oil using t-butanol as a solvent, Bioresource Technology, 98(3), 648–653, 2007. 32. Nielsen, P. M., Brask, J. and Fjerbaek, L. Enzymatic biodiesel production: technical and economic considerations,  European Journal of Lipid Science and Technology, 110 (8), 692–700, 2008.

Different Reactors for Biodiesel Production  357 33. Robles-Medina, A., González-Moreno, P.A., Esteban-Cerdán, L. and Molina-Grima, E.Biocatalysis: towards ever greener biodiesel production, Biotechnology Advances, 27(4), 398–408, 2009. 34. Chang, C., Chen, J.H., Chang, C.M. J., Wu, T.T. and Shieh, C.J. Optimization of lipase-catalyzed biodiesel by isopropanolysis in a continuous packed-bed reactor using response surface methodology, New Biotechnology, 26 (3–4), 187–192, 2009. 35. Ognjanovic, N., Bezbradica, D. and Knezevic-Jugovic, Z. Enzymatic conversion of sunflower oil to biodiesel in a solvent-free system: process optimization and the immobilized system stability. Bioresource Technology, 100(21), 5146–5154, 2009. 36. Hagiwara, S., Nabetani, H and M Nakajima. Non-catalytic alcoholysis process for production of biodiesel fuel by using bubble column reactor. Journal of Physics: Conference Series, 596, 2015. 37. Wulandani, D. Determination on CFD Modeling for Bubble Column Reactor to ImproveBiodiesel Fuel Production. SustaiN’2010, 2010: 41–44, 2010 38. Kocsisová, T., Cvengros, J., Lutisan, J. High-temperature esterification of fattyacids with methanol at ambient pressure. European Journal of Lipid Science and Technology, 107(2), 87–92, 2005. 39. Suwannakarn, K., Lotero, E., Ngaosuwan, K. and Goodwin, J. G. SimultaneousFree Fatty Acid Esterification and Triglyceride Tran­ sesterification Using a Solid Acid Catalyst with in Situ Removal of Water and Unreacted Methanol. Industrial & Engineering Chemistry Research, 48 (6), 2810-2818, 2009. 40. Joelianingsih, H.S., Nabetani, H., Sagara, Y., Soerawidjaya, T.H., Tambunan, A.H. and Abdullah, K. Performance of a Bubble Column Reactor for theNon-Catalytic Methyl Esterification of Free Fatty Acids at Atmospheric Pressure. Journal of Chemical Engineering of Japan, 40 (9), 780–785, 2007 41. Joelianingsih, M.H., Hagiwara, S., Nabetani, H., Sagara, Y., Soerawidjaya, T.H., Tambunan, A.H. and Abdullah, K. Biodiesel fuels from palm oil via the non-catalytic transesterificationina bubble column reactor at atmospheric pressure: Akinetic study. Renewable Energy, 33 (7), 1629–1636, 2008. 42. Dyah, W., Fajri, I., Yayan, F., Ahmad, I.S., Hiroshi, N. and Shoji, H. Modification of biodiesel reactor by using of triple obstacle within the bubblecolumn reactor. Energy Procedia, 65: 83–89, 2015. 43. Manman, L., Junning, F., Yinglai, T., Zhen, Z., Ning, Z. and Yong, W. Fast production of diacylglycerol in a solvent free system via lipase catalyzed esterification using a bubble columnreactor. Journal of the American Oil Chemists’ Society (93): 637–648, 2016. 44. Mollenhauer, T., Klemm, W., Lauterbach, M., Ondruschka, B. and Haupt, J. ProcessEngineering Study of the Homogenously Catalyzed Biodiesel Synthesis in a Bubble Column Reactor. Industrial and Engineering Chemistry Research, 49(24), 12390–12398, 2010.

358  Biodiesel Technology and Applications 45. Shinde, G. B., Sapkal, V. S., Sapkal. R.S. and Raut, N. B. Transesterification by Reactive Distillation for Synthesis and Characterization of Biodiesel., https:// www.researchgate.net/publication/221919441, 2011. 46. Giessler, S., Danilov, R.Y., Pisarenko, R.Y., Serafimov, L.A., Hasebe, S. & Hashimoto, I. Systematic structure generation for reactive distillation processes. Computers & Chemical Engineering, 25 (1), 49–60, 2001 47. Pai, R.A., Doherty, M.F. & Malone, M.F. Design of reactive extraction systems for bioproduct recovery. AIChE Journal, 48 (3), 514–526, 2002. 48. Chin, S.Y., Mohamed, A.R., Ahmad, A.L. & Bhatia, S. Esterification of palmitic acid with iso-propanol in a catalytic distillation column: Modeling and simulation studies. International Journal of Chemical Reactor Engineering, 4 (4) 32, 2006. 49. He, B.B., Singh, A.P. & Thompson, J.C. A novel continuous-flow reactor using reactive distillation for biodiesel production. Transactions of the ASABE, 49 (1), 107–112, 2006. 50. Omota, F., Dimian, A.C. & Bliek, A. Fatty acid esterification by reactive distillation. Chemical Engineering Science. 58, 3159–3174, 2003 51. Singh, A.P., Thompson, J.C. & He, B.B. In A continuous-flow reactive distillation reactor for biodiesel preparation from seed oils, ASAE/CSAE Annual International Meeting, Ottawa, Ontario, Canada, 1–4 August, 2004; Ottawa, Ontario, Canada, 2004. 52. Kiss, A.A., Omota, F., Dimian, A.C. & Rothenberg, G. The heterogeneous advantage: biodiesel by catalytic reactive distillation. Topics in Catalysis, 40 (1), 141–150, 2006. 53. MadhuAgarwal, Kailash Singh, S.P. Chaurasia. Simulation and sensitivity analysis for biodiesel production in a reactive distillation column. Polish Journal of Chemical Technology, 14(3), 59, 2012. 54. Istadi, I., Yudhistira, A.D., Anggoro, D.D., Buchori, L. Electro-catalysis system for biodiesel synthesis from palm oil over dielectric-barrier discharge plasma reactor. Bull. Chem. React. Eng. Catal., 9(2): 111–120, 2014. 55. Akansha Madhawan & Arzoo Arora & Jyoti Das & ArindamKuila & Vinay SharmaMicroreactor technology for biodiesel production: a review. Biomass Conversion and Biorefinery, https://doi.org/10.1007/s13399-017-0296-0, 2017. 56. Motahareh V., Mohammad R. S.E. and Kambiz T. A Novel Membrane Reactor for Production of High-Purity Biodiesel European Online Journal of Natural and Social Sciences, 3(3), 2014. 57. Guerreiro L., Castanheiro J.E., Fonseca I.M., Martin-Aranda R.M., Ramos A.M., Vital J. Transesterification of soybean oil oversulfonic acid functionalised polymeric membranes. Catal Today, 118(1–2):166–171, 2006 58. Saleh J., Tremblay A.Y., Dubé M.A. Glycerol removal from biodiesel using membrane separation technology. Fuel, 89(9):2260–2266, 2010. 59. Dubé, M. A., Tremblay A.Y., Liu J. Biodiesel production using a membrane reactor. BioresourTechnol, 98(3):639–647, 2007.

Different Reactors for Biodiesel Production  359 60. Cao P., Dubé M.A., Tremblay A.Y. High-purity fatty acid methyl ester production from canola, soybean, palm, and yellow greaselipids by means of a membrane reactor. Biomass Bioenergy, 32(11): 1028–1036, 2008. 61. Baroutian S., Aroua M.K., Raman A.A.A., SulaimanN.M..N. A packed bed membrane reactor for production of biodiesel usingactivated carbon supported catalyst. BioresourTechnol, 102(2): 1095–1102, 2010. 62. Barredo-Damas S, Alcaina-Miranda M.I., Bes-Piá A., Iborra-Clar M.I., Iborra- Clar A., Mendoza-Roca J.A. Ceramic membrane behavior in textile wastewater ultrafiltration. Desalination, 250(2): 623–628, 2010. 63. Achmadin LM, Misri G, Mohammad N, Mohammad N, Siswa S, Young JY Membrane microreactor in biocatalytictransesterification of triolein for biodiesel production. Biotechnol Bioprocess Eng, 15:911–916, 2010. 64. Afia Mehboob, Shafaq Nisar, Umer Rashid, Thomas Shean Yaw Choong, Talha Khalid and Hafiz Abdul Qadeer. Reactor designs for the production of biodiesel. International Journal of Chemical and Biochemical Sciences, 10(2016):87–94. 65. Mackley, M. R. Process innovation using oscillatory flow within baffled tubes. Trans IchemE, 69(A), 197–199, 1991. 66. Stonestreet, P., and Harvey, A. P. A mixing-based design methodology for continuous oscillatory flow reactors. Institution of Chemical Engineers, 80(A), 31–44, 2002. 67. Qiu, Z., Zhao, L., Weatherley, L. Process intensification technologies in continuousbiodiesel production. Chem. Eng. Process, 49, 323–330, 2010. 68. Gogate, P. R., Kabadi, A. M. A review of applications of cavitation in biochemicalengineering/biotechnology. Biochem. Eng. J. 44, 60–72, 2009. 69. Kelkar, M. A., Gogate, P. R., Pandit, A. B. Intensification of esterification ofacids for synthesis of biodiesel using acoustic and hydrodynamic cavitation. Ultrason. Sonochem. 15, 188–194, 2008. 70. Colucci, J., Borrero, E., Alape, F. Biodiesel from an alkaline transesterificationreaction of soybean oil using ultrasonic mixing. J. Am. Oil. Chem. Soc. 82,525–530, 2005. 71. Deshmane, V. G., Gogate, P. R., Pandit, A. B. Ultrasound-assisted synthesisof biodiesel from palm fatty acid distilate. Ind. Eng. Chem. Res., 48, 7923–7927, 2008. 72. Kalva, A., Sivasankar, T., Moholkar, V. S. Physical mechanism of ultrasoundassistedsynthesis of biodiesel. Ind. Eng. Chem. Res., 48, 534–544, 2008. 73. Barnard, T. M., Leadbeater, N. E., Boucher, M. B., Stencel, L. M., Wilhite, B. A., Continuous-flow preparation of biodiesel using microwave heating. Energy.Fuel. 211777–1781.

13 Patents on Biodiesel Azira Abdul Razak, Mohamad Azuwa Mohamed* and Darfizzi Derawi Department of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM Bangi, Malaysia

Abstract

Biodiesel is a renewable fuel that is made from edible or non-edible feedstock and it has high potential to compete with the diesel fuel. In this paper, the published patents from 2003 to 2018 related to biodiesel were reviewed, and they were retrieved from Justia Patent Database. This paper is divided into five sections: started with the introduction to biodiesel, the generation of biodiesel that depends on the feedstock used, the development of catalysts, the latest method for biodiesel production, and the technology of reactor used to produce biodiesel. The second generation of biodiesel has gained interest as it can be produced from waste which lowering the production cost. The use of a catalyst can facilitate the reaction, but it is crucial to choose the best type of catalyst. There are various methods used to produce biodiesel, and the most common method used is transesterification due to its simplest and efficient method for biodiesel production. To produce biodiesel in large amounts, the reactor’s technology is used and it was found that continuous stirred tank reactor is a more practical and simpler reactor that can be used. Keywords:  Biodiesel, feedstock, catalyst, production method, reactor technology

13.1 Introduction The change in the global climate is one of the most serious problems faced by the world nowadays. The major contribution to this problem is the high utilization of fossil fuel, where the burning of them leads to the release of carbon dioxide (CO2) to the atmosphere and cause global warming [5]. Based on the data obtained by International Energy Agency, the utilization *Corresponding author: [email protected] Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (361–376) © 2021 Scrivener Publishing LLC

361

362  Biodiesel Technology and Applications of energy continues to increase within the years, and it is reported that the energy demand for oil showed the highest amount, where it has increased from 3,232,737 kiloton (1990) to 4,449,499 kiloton (2017). High demand for fossil fuel not only becomes the environmental issue, but it is also a non-renewable source of energy. If the consumption continues to increase, then fossil fuel is expected to be completely used up by 2050 [1–3]. To overcome the problems discussed earlier, biofuels show a high potential to be an alternative solution to replace the usage of fossil fuels as energy and expected to satisfy the global energy demand. Biofuels are known as liquid or gaseous fuels produced through a biological and chemical process or derived from biomass of living organisms such as microalgae, plants, and bacteria and used for transport sectors [2]. Biodiesel is one of the types of biofuel that most commonly used in European Countries. Biodiesel can be produced by converting fats or oils from animal fat and vegetable oil chemically to esters because they have similar properties to mineral diesel. U.S. Energy Information Administration indicated that the United States (U.S.) showed the highest amount of biodiesel production, which is 6.9 billion liters [4]. Indonesia has become the leading for Asian Countries, which produced 4.0 billion liters of biodiesel and fall as the third-highest production of biodiesel in 2018.

13.2 Generation of Biodiesel Biodiesel can be classified into different generations depending on the feedstock used either edible, non-edible, or waste oil which determines the qualities of biodiesel produced. It also depends on the major sources of feedstock from the countries to produce biodiesel. For example, the common feedstock used in the U.S. is refined vegetable oil such as soybean and canola oil. However, they also produced biodiesel from used cooking oil and animal fats to cut the production cost [4]. The patent for biodiesel production from first to the fourth generation, which is still in an early stage. The first generation of biodiesel is quite popular at the beginning of the biodiesel era, where edible oil used as feedstock to produce biodiesel. For E.U. and U.S., rapeseed oil and soybean oil are widely used, while for Asian countries such as Malaysia and Indonesia, palm and coconut oil is the most common feedstock used. The difference in feedstock used will affect the production process, quality, and cost because the produced biodiesel depends on the types of fatty acid that attached to the triglycerides molecules [6]. Saka and Kusdiana (2001) have proposed the transesterification of rapeseed oil in supercritical methanol without catalyst consumed.

Patents on Biodiesel  363 They  found that by using the new supercritical methanol, the process became shorter in time and has a simpler purification procedure [7]. However, there is a limitation for this generation because of the competition between food supplies that increase the production cost is the main drawback for edible oil-based biodiesel. The disadvantages showed by the first generation of biodiesel caused the development of the second generation of biodiesel. The feedstock for second-generation biodiesel is non-­ edible oil such as Neem oil, Jatropha oil, Karanja oil, Rubber seed oil, and waste oil. This type of biodiesel has advantages compared to the first generation because there is no competition between the food supply and also less production cost [8]. However, there is still a need for land for growth which causes competition between food and fiber production. The high competition will lead to limited nutrient supply for the land and it will be hard to maintain the quality of oil produced [9]. Algae-based biodiesel, known as third-­generation biodiesel, has gained much attention to overcome the disadvantages of the first and second generation of biodiesel. They could produce less greenhouse effect, elevated growth rate and productivity, lesser struggle toward farming land, and a higher amount of oil. However, the limitations for third-generation biodiesel are higher production cost, high need for sunlight, need to produce on large scale, and difficult for oil extraction.

13.3 Development of Catalyst Catalyst is a substance that facilitates a chemical reaction, which makes the reaction go faster without itself being consumed in the reaction. Catalysis can be divided into three categories, which are homogeneous, heterogeneous, and bio-catalysis. A homogeneous catalyst involves the reaction between a catalyst and the substrate in different phases. Recently, the heterogeneous catalyst is preferable over the homogeneous catalyst in the production of biofuels. This is because it is easier to separate from the mixture after the reaction process by filtering [10], their reusability, and low production cost due to a single-step reaction [11]. The catalyst used for industrial production of biodiesel is the alkali-based catalyst method, where Sodium Hydroxide and Potassium Hydroxide are commonly used as a homogeneous catalyst. By using alkali catalyst, the reaction can be carried out in mild temperature and pressure condition. However, this process requires additional steps of separating and removing the catalyst used. The free fatty acid (FFA) produced also will react with the alkali catalyst to form soap which will be lowering the function of the catalyst [12].

364  Biodiesel Technology and Applications

13.3.1 Homogeneous Catalyst Homogeneous catalyst refers to a catalytic reaction involving catalyst and reactant within the same phase that can be divided into two types which are alkali and acid catalyst. Alkali catalyst (NaOH, KOH) for biodiesel production is widely used because they are cheap and readily available. Transesterification of low-grade safflower oil with methanol in the presence of alkaline-catalyst (NaOH) has produced a high yield of methyl ester [13]. However, the utilization of sodium or potassium hydroxide as an alkaline catalyst caused the decrease of biodiesel yield. This is due to the presence of the hydroxide group originally attached from triglyceride, which will dissolve with glycerol [14]. An acid catalyst such as sulfuric, sulfonic, and hydrochloric acid is the most common acid catalyst used in transesterification and preferable because it can produce a high yield of the product. However, the reaction rate when using an acid catalyst is too slow and the heat is required to accelerate the reaction which makes it unsuitable for larger-scale production [15]. Other than that, the homogeneous catalyst also difficult to be separated from the reactant which makes it unsuitable to reuse and presence acid could lead to corrosion. The present invention for the homogeneous catalyst is to provide a neutral, non-corrosive homogeneous catalyst for transesterification of triglycerides. The design for the catalyst is based on organometallic compounds that contain at least one −OCH3 functional group that will catalyze the transesterification and esterification efficiently to produce biodiesel. This invention made to solve the disadvantages of using a homogeneous catalyst by offering a non-basic and non-acidic homogeneous catalyst [16].

13.3.2 Heterogeneous Catalyst A heterogeneous catalyst is the type of catalysis that involves different phases of catalyst and reactant which contrast with homogeneous catalyst. A heterogeneous catalyst is widely used in many industries such as chemical, petrochemical, agrochemical, and pharmaceutical industries. The most important factors in choosing good catalysts are the choice of catalyst support, type of supported catalyst, and interaction between catalyst and support [17]. In the previous study, several types of heterogeneous catalysts have been developed for biodiesel production such as Amberlyst 36, Purolite CT482, Purolite CT275DR, Amberlyst-15, and Sulfuric Silica-Acid. In a study by Kuzminnska et al. (2014), they found that Amberlyst 36, Purolite CT482, and Purolite CT275DR were able to

Patents on Biodiesel  365 produce biodiesel from Trimethylolpropane (TMP) and Oleic Acid [18]. In another study, Akerman et al. (2011) produced heterogeneous catalysts such as Amberlyst-15 and Silica-Sulfuric Acid for biodiesel production from TMP and Oleic Acid. They found that the Silica-Acid catalyst shows better properties and efficient catalysts compared to Amberlist-15 [19]. The present invention provides a heterogeneous catalyst that has high tolerance toward the presence of water and FFAs in the production of biodiesel. The catalyst is designed by a class of zinc and lanthanum oxide heterogeneous catalysts, with different ratios of the metal. The metal catalyst will give effect to both esterifications of fatty acid and transesterification of oil simultaneously [20].

13.4 Method Producing Biodiesel The present invention to produce biodiesel and/or glycerine from feedstock includes pre-treatment process, esterification of FFA, and transesterification of triglycerides. The pre-treatment process involves the separation of biodiesel feedstock from impurities such as sulfur, phosphorous, phosphatides, gums, sterols, metals, and other color bodies. As for esterification, the FFA content in biodiesel feedstock will react with methanol in the presence of a catalyst to form biodiesel and water. Meanwhile, transesterification involves the reaction between triglycerides of biodiesel feedstock with methanol in the presence of a catalyst to produce biodiesel and glycerine [21]. Other methods used for biodiesel production, such as direct use and blending of oils and pyrolysis methods, also will be discussed further under this topic.

13.4.1 Pre-Treatment Process According to U.S. Patent No. 20090071063 (2009), by applying the pre-treatment process, low quality of feedstock could be used as a source of FFA to produce good quality of biodiesel. The pre-treatment process involves the filtration and distillation process, which first started by heating to 43°C, followed by filtering the feedstock from solid particles to provide filtrate, which then further distilling repeatedly until the final distillate is obtained [22]. This process is important to ensure all the impurities are removed completely from the feedstock before they are used to produce biodiesel. The production of low-cost biodiesel is a necessity to compete with petroleum-based diesel. Utilizing waste such as waste cooking oil, brown greases, and crude corn oil as feedstock could be a better alternative

366  Biodiesel Technology and Applications for more practical and economical biodiesel. However, high FFA content in these wastes will become the obstacle which is the reason why the pre-treatment process becomes necessary to produce biodiesel [23].

13.4.2 Direct Use and Blending of Oils Direct use of vegetable oils as biodiesel is not preferable because of their properties due to the effect of cold temperature, which not suitable to be used as fuel. Therefore, vegetable oil usually will be blended with biodiesel with a certain concentration. The amount of biodiesel blending with diesel varies depending on the country which used biodiesel. The most common are B5 (5% of biodiesel) and B20 (6%–20% of biodiesel). An invention by U.S. Patent No. 20180223202 proposed four stages of principle which apply for biodiesel blending. The first principle is an automated method of blending that provides a distillation stream, separation of distillate, provides target pf biodiesel content, and measure of actual biodiesel content. The second principle is an automated system for blending, which applies the same principle with the addition of an analyzer for measuring actual biodiesel content. The third and fourth principles are automated methods and systems for blending, which provide a blending of biodiesel not to exceed the maximum biodiesel content [24]. Another invention by U.S. Patent No. 7458998 proposed a method of blended biodiesel by heating the biodiesel and diesel at a temperature above the cloud point of the first blended. Then, the heated biodiesel will be added to the unheated diesel to provide the second biodiesel blend. The blended biodiesel produced by this method is maintained in a heated environment which compatible with fuel purposes [25]. It is important to ensure that the blended fuel meets the standard requirement of diesel in terms of its kinematic viscosity, density, and the flashpoint of the blend. Arabi et al. (2017) studied the characteristics of palm oil-biodiesel-diesel fuel blend, where they found that the fuel properties for the blended oil showed no significant difference compared to diesel fuel up to 30% of the volume of biodiesel of palm oil [26].

13.4.3 Esterification of FFA Biodiesel can be produced via an esterification reaction between fatty acid and methanol with the presence of a catalyst. The most common catalyst used in esterification is liquid acid such as sulfuric acid, hydrochloric acid, and p-toluenesulfonic acid (p-TsOH). Esterification is considered as an attractive method for producing biodiesel because it allows the use of FFA which can

Patents on Biodiesel  367 O H2C

O

HC

O

H2C

O

O O

R R

Hydrolysis 3

Esterification

O R

OH

+ 3 R

OH

3

O R

O

R

+ H2O

R

Triglycerides of Oil

Fatty acid

Alkyl Ester (Biodiesel)

Figure 13.1  General reaction for esterification.

be obtained from refinement of vegetable oils and waste oil such as animal fats and waste frying oil. The use of low-value fatty acid gives the advantage for biodiesel produced, where it could compete with diesel in terms of their low cost. Figure 13.1 illustrates the general reaction for esterification. The invention for the production of biodiesel by esterification of FFA using niobic acid as a heterogeneous catalyst has been proposed. Long chain of carboxylic acid-containing 6–24 carbon atoms is used to react with short-chain alcohol (methanol and ethanol), which act as esterifying agents. Before the niobic acid catalyst is used in the reaction, it must be calcined to maximize the acid strength of the catalyst [27]. An invention by U.S. Patent No. 20080289248 proposed a process of producing biodiesel by involving the contact of lipid material with alcohol in the presence of Zirconium (IV) metal salt conjugated to the solid support. The temperature for the process is between 25°C and 75°C, in which the esterification process runs within the lipid material. The purpose of this invention is to enhance the conversion of fatty acid and efficiently producing biodiesel [28].

13.4.4 Transesterification of TAG Transesterification of TAG in biodiesel feedstock is the most common and widely used method to produce biodiesel, as shown in Figure 13.2. Transesterification is a reversible reaction, where triglyceride of oil reacted with short-chain alcohol with the presence of catalyst either a strong base or strong acid to produce Fatty Acid Alkyl Ester, which is the biodiesel. In transesterification, the most preferable alcohol used is methanol and ethanol, especially methanol because of its low cost, polar solvent, and the shortest chain of alcohol [29]. If methanol is chosen, then the product generated is Fatty Acid Methyl Ester (FAME), which is the biodiesel that has been well established in the oleo-chemical industry. The present invention for the transesterification of biodiesel is by controlling the removal of glycerin, which is the major by-product in biodiesel

368  Biodiesel Technology and Applications O H2C

O

HC

O

H2C

O

O O

R +

R

3 R

OH

3

O R

O

+

R

R Alkyl Ester (Biodiesel)

Triglycerides of Oil

H2C

OH

HC

OH

H 2C

OH

Glycerol

Figure 13.2  General reaction for transesterification.

production. The removal of glycerin can be done in a reaction vessel, either continuous, semi-continuous, or batch reaction. By removing glycerin from the biodiesel product, the reaction can be carried out with lower ratios of alcohol to oil and will increase the rate of production for biodiesel [30].

13.4.5 Pyrolysis Pyrolysis is defined as a thermochemical reaction which involved reaction at high temperature (280°C–850°C), with the absence of an oxidizing agent to produce different products such as solid (biochar), gaseous (biogas), and liquid (bio-oil) [31]. High oxygen content in biodiesel from the transesterification reaction has become a disadvantage as it could lead to corrosion. In contrast, biodiesel from pyrolysis appears as the solution as no oxygen involved in the reaction and also it produced hydrocarbon diesel [32]. An invention by U.S. Patent Application 20070144060 proposed a method of producing biodiesel from triglycerides feedstock by pre-treating with thermal cracking or rapid pyrolysis. By applying this method, the contaminants from the biodiesel can be removed and will produce distillate fraction that rich in FFA content [33]. The general reaction of pyrolysis is shown in Figure 13.3. O H2C

O

HC

O

H2C

O

O O

R

R

+ CO2

R R

Triglycerides of Oil

Figure 13.3  General reaction for pyrolysis.

R

+ CO + H2O

Hydrocarbon

Patents on Biodiesel  369 Table 13.1  Comparison between the pyrolysis method by operating parameters and product yield [34]. Pyrolysis method

Temperature (°C)

Residence time (s)

Heating rate (°C/s)

Slow

Medium-High (400–500)

Long (450–550)

Fast

Medium-High (400–650)

Flash

High (700–1,000)

Product yield (%) Oil

Char

Gas

Low (10)

30

35

35

Short (0.5–10)

High (100)

50

20

30

Very short (500)

75

12

13

The pyrolysis method is considered a complex process because of two reactions condition, which is temperature and non-reactive atmosphere that must be kept simultaneously within the reaction. The reaction involved the breakdown of long chains of carbon, hydrogen, and oxygen compounds in biomass into smaller molecules. Pyrolysis can be classified into three main categories: slow, fast, and flash pyrolysis. Among the methods, fast and flash pyrolysis is considered a better method for producing biodiesel because these methods are able to produce high yield of biodiesel with 50 and 75% respectively, in a high reaction temperature but within a very short residence time as stated in the Table 13.1 [34]. By referring to Takuya (2012), triglycerides of oils decomposed to fatty acid chains and further decomposed to the hydrocarbon chain at 390°C. By increasing the reaction temperature and heating rate, the product yield of oil can be increased [35].

13.5 Reactor’s Technology for Biodiesel Production General reactors used for biodiesel production are batch reactors, semicontinuous-flow reactor, and continuous-flow reactor. Reactor becomes an important technology for producing biodiesel on a large scale with more economic value. By referring to U.S. Patent No. 20080282606, a biodiesel reactor is a material that consists of a housing enclosing chamber that contains four parts. The part in a biodiesel reactor is an inlet (for the inflow of raw material), stir bar (inner part for stirring), baffle (partially segmenting chamber for mixing), and outflow (for the outflow of the reaction mixture). It is also stated that the process for producing biodiesel started by selecting the feedstock oil and followed by measuring alcohol and catalyst need to

370  Biodiesel Technology and Applications be used. Then, the feedstock, alcohol, and catalyst are mixing in the reactor to form a mixture. The product and by-product will be separated from the mixture and further distillate to purify the biodiesel product [36]. For current status, there are various types of reactors used nowadays to increase biodiesel production, which will be discussed further within this topic.

13.5.1 Continuous Stirred Tank Reactor A continuous stirred tank reactor (CTSR) is an advanced technology for a reactor that applies the same fundamental processing mechanism as a batch reactor. CTSR allowed the continuous production of biodiesel in a simple step, which makes the production cost become lowered. There is two important part in CTSR: the reactor and phase separator. The first past of the reactor involved the conversion of alcohol and triglycerides into biodiesel. The process followed by the removal of glycerol from the reaction mixture in the second stage of CTSR. The second stage: phase separator used to promote the reaction of transesterification through chemical equilibrium shifting. CTSR has proved to produce a high yield of biodiesel, which is about 97.3% yield [37]. CTSR has been used widely in industrial scale due to the simpler and deep understanding operation of CTSR. An invention from U.S. Patent No. 2005052103 provides an improved process for the preparation of biodiesel using modified CTSR. The feedstock oil is taken into the modified reactor equipped with the alcohol recycle/recovery system, condenser, thermometer, and feeding funnel. By using the CTSR, two layers are formed, and the mixture is allowed to settle for four hours and the top layer is taken for further processing [38].

13.5.2 Fixed Bed Reactor Fixed bed reactor (FBR) involved the flowing of oil and solvent through a cylindrical tube filled with catalyst pellets, which packed in static bed for the conversion of biodiesel shown in Figure 13.4. A heterogeneous catalyst is used in FBR because of their simple recovery steps which do not involve any separation process between product and catalyst. Other than that, the heterogeneous catalyst used in FBR would enhance the reaction due to slow deactivation and longer durability of the catalyst. By offering these advantages, the production cost can be reduced. However, the higher molar ratio is needed during the process due to the remaining glycerol (by-­ product), which will remain at the bottom of the reactor and will adsorb on the surface of the catalyst. This condition will affect the catalyst efficiency and an additional removal process will be needed [39].

Patents on Biodiesel  371 Condenser

Thermometer Sampling Biodiesel Separator

Feedstock oil

Alcohol and catalyst

Reactor Glycerol Heating and Stirring

Figure 13.4  Schematic diagram of a single reactor CTRS. Reproduced with permission from [37]. Copyright 2019 Elsevier.

The invention proposed by U.S. Patent No. 2011/0245551A1 introduced the process for hydroprocessing an acidic biomass feedstock in a guard bed, which aims to prevent undesired polymerization from occurring. The guard bed reactor is used to saturate the olefins with hydrogen and prevent the olefins and other compounds from polymerizing. The reactor, which can be either a noble metal or non-metal catalyst, is run at low temperatures and able to recycle back the product into the reactor [40].

13.5.3 Micro-Mixer Reactor Micro-mixer reactor also known as micro-reactors and microstructured reactors has been used widely in biodiesel production. The micro-mixer reactor uses numerous channels with millimeter range in diameter, which allowed better separation of oil. This is because of high surface-to-volume ratios and low distance between heat and mass transfer for diffusion. An invention from U.S. Patent No 8.404,005 stated the method and system to produce biodiesel using an improved catalytic transesterification process. In this process, the first and second reactant is dispersed to form a laminar slug flow pattern within the micro-channel of microreactor and both of them become immiscible. The mixing between the reactant will trigger the reaction between them to produce biodiesel and glycerol [41].

372  Biodiesel Technology and Applications

13.6 Conclusion This paper has discussed and analyzed patents related to biodiesel, and the following conclusion can be made. The demand for fuel energy continues to increase each year and biodiesel has become a solution to replace diesel fuel for a more sustainable and greener environment. The use of feedstock for biodiesel production must come from non-edible feedstock to avoid the competition between food and fuel. For the current status of biodiesel production, the second generation of biodiesel, which is from waste, is more preferable because it does not only produce low-cost biodiesel but also helps in properly managing waste. In biodiesel production, the use of catalyst is crucial to fasten the reaction and to produce a better quality of biodiesel. A heterogeneous catalyst is more suitable to use as it is easier to separate after the reaction and it can be reused for five to six cycles of reaction. There are few methods for biodiesel production that have been discussed, and most of the patents have been made for the transesterification process. This shows that the trend nowadays is more to using transesterification as a method to produce biodiesel due to the easier reaction which will lower the production cost. Lastly, the utilization of the reactor in producing biodiesel is very helpful for the industrial scale. Among the reactor used, the CTSR has been used by many biodiesel industries because of the operation method is more practical.

References 1. Abideen. A., Sustainable biofuel production from non-food sources-An overview. Journal of the Science of Food and Agriculture., 26 (12), 1057–1066, 2014. 2. Rodionova. M.V et al., Biofuel production: Challenges and opportunities. International Journal of Hydrogen Energy., 42, 8450–8461, 2017. 3. International Energy Agency, Data and Statistic, https://www.iea.org/ data-andstatistics?country=WORLD&fuel=Energy%20supply&indicator=Total%20primary%20energy%20supply%20(TPES)%20by%20source, 2017. 4. U.S. Energy Information Administration, Biodiesels produced from certain feedstocks have distinct properties from petroleum diesel, https://www.eia. gov/todayinenergy/detail.php?id=36052, 2018. 5. Alalwan, H. A., Alminshid, A.H & Aljaafari, H. A. S, Promising Evolution of Biofuel Generations. Subject Review. Renewable Energy Focus., 28, 127–139, 2019. 6. Ho, D.P., Ngo, H.H., Guo, W., A mini review on renewable sources for biofuel. Bioresource Technology., 169, 742–749, 2014.

Patents on Biodiesel  373 7. Saka, S., Kusdiana, D., Biodiesel fuel from Rapeseed oil as prepared in supercritical methanol. Fuel., 80(2), 225–231, 2001. 8. Singh, D., Sharma, D., Soni, S.L., Sharma, S., Sharma, P.K., Jhalani, A., A review on feedstocks, production processes, and yield for different generations of biodiesel. Fuel., 262, 2020. 9. Sims, R.E.H., Mabee, W., Saddler, J.N., Taylor, M., An overview of second generation biofuel technologies. Bioresource Technology., 101, 1570–1580, 2010. 10. Martinez, A., A novel green one-pot synthesis of biodiesel from Ricinus communis seeds by basic heterogeneous catalysis. Journal of Cleaner Production., 196, 340–349, 2018. 11. Gopinath, S., Efficient mesoporous SO4 2/Zr-KIT-6 solid acid catalyst for green diesel production from esterification of oleic acid, Fuel., 203, 488–500, 2017. 12. Y. Ueki and M. Tamada, Catalyst for Production of Biodiesel and Its Production Method, and Method for Producing Biodiesel, US Patent No 20100170145, 2011. 13. Math, M.C., Chandrashekhara, K.N., Optimization of Alkali Catalyzed Transesterification of Safflower Oil for Production of Biodiesel. Journal of Engineering., 8, 86–92, 2016. 14. Vyas, A.P., Shukla, P.H., Subrahmanyam, N., Production of Biodiesel using Homogeneous Alkali Catalyst and its Effect on Vehicular Emission. International Conference on Current Trends in Technology., 382–481, 2011. 15. Zheng, S., Kates, M., Dube, M.A., Acid-catalyzed production of biodiesel from waste frying oil. Biomass Bioenergy., 30(2), 67–72, 2006. 16. S. C. Yang, J.R. Chang, M.T. Lee, T. B. Lin, F.M. Lee, C.T. Hong and J.C. Lee, Homogeneous Catalysts for Biodiesel Production, US Patent No 8624073, assigned to CPC Corporation, Taiwan, 2014. 17. Bailie, J. E., Hutchings, G. J., O’Leary, S., Supported Catalysts. Encyclopedia of Materials: Science and Technology, pp. 8986–8990, 2001. 18. Kuzminska, M., Backov, R., Gaigneaux, E.M., Complementarity of Heterogeneous and Homogeneous Catalysis for Oleic Acid Esterification with Trimethylolpropane Over Ion-Exchange Resins. Catalysis Communication., 14, 566–736, 2014. 19. Akerman, C.O., Gaber, Y., Ghani, N.A., Lamsa, M., Kaul, R.H., Clean synthesis of biolubricants for low temperature applications using heterogeneous catalyst. Journal of Molecular Catalysis B: Enzymatic., 72, 263–269, 2011. 20. S. Yan, S. O. Salley and K. Y. S. Ng, Methods and Catalysts for making Biodiesel from the Transesterification and Esterification of Unrefined Oils, US Patent No 8163946, assigned to Wayne State University, 2012. 21. G. Shah and S. Francisco, Transesterification of Biodiesel Feedstock with Solid Heterogeneous Catalyst, US Patent 8580119, assigned to Menlo Energy Management, 2013.

374  Biodiesel Technology and Applications 22. M. J. Perrier, Process and System for producing biodiesel fuel, US Patent 20090071063, assigned to Next Energy System, 2009. 23. Tafesh, A., Basheer, S., Pre-treatment Methods in Biodiesel Production Processes. Green Energy and Technology., pp. 417–434, 2013. 24. R. Fransham and C. Robbins, Controlled Blending of Biodiesel into Distillate Streams, US Patent 20180223202, 2018. 25. K. Copeland, R. Hardy, J. Johnson, C. Selvidge and K. Walztoni, Blending Biodiesel with Diesel Fuel in Cold Locations, US Patent 7458998, assigned to Flint Hills Resources, 2008. 26. Arabi, R., Amin, A., Morsi, A.K., Ibiari, N.N., Diwani, G.I., Study on the characteristics of palm oil–biodiesel–diesel fuel blend. Egyptian Journal of Petroleum., 27(2), 187–194, 2017. 27. A. T. Pereira, K. A. Oliveira, R. S. Monteiro, D. A. G. Aranda, R. T. P. Santos and R. R. Joao, Production Process of Biodiesel from the Esterification of Free Fatty Acids, US Patent 20070232817, applied to Companhia Brasileira De metalurgia E Mineracao, 2007. 28. Y. Gao, Immobilized Esterification Catalyst for Producing Fatty Acid Alkyl Esters, US Patent 20080289248, applied to Southern Illinois University Carbondale, 2008. 29. Keera, S.T., Sabagh, S.M.E., Taman, A.R., Transesterification of vegetable oil to biodiesel fuel using alkaline catalyst. Fuel., 90, 42–47, 2011. 30. J. Crawford, J. Crawford and R. Crafts, Transesterification of Oil to form Biodiesel, US Patent 20070232818, applied to Domestic Energy Leasing, 2007. 31. Gopal, P. M., Sivaram, N. M., Barik, D., Paper Industry Wastes and Energy Generation from Wastes Energy from Toxic Organic Waste for Heat and Power Generation, 7, 83–97, 2019. 32. Abdelfattah, M.S.H., Osayed S.M.AA., AbdElmawla, E., Marwa, A., On Biodiesels from Castor Raw Oil using Catalytic Pyrolysis. Energy., 143, 950– 960, 2017. 33. M. Ikura, Production of Biodiesel from Triglycerides via a Thermal Route, US Patent Application 20070144060, 2007. 34. Jahirul, M.I., Rasul, M.G., Chowdhury, A.A., Ashwath, N., Biofuels Production through Biomass Pyrolysis-A Technology Review. Energies., 5, 4952–5001, 2012. 35. Takuya, I., Yusuke, S., Yusuke, K., Motoyuki, S., Katsumi, H., Biodiesel production from waste animal fats using pyrolysis method. Fuel Processing Technology., 94:47–52, 2012. 36. J. P. Plaza and B. L. Goodall, System and Process for Producing Biodiesel, US Patent Application 20080282606, 2008. 37. Wong, K.Y., Han, N.J., Chong, C.T., Lam, S.S & Chong, W.T., Biodiesel process intensification through catalytic enhancement and emerging reactor designs: A critical review. Renewable and Sustainable Energy Reviews., 116, 109399, 2019.

Patents on Biodiesel  375 38. Velappan, Kandukalpatti, Chinnaraj, Saravanan, Subramani, Vedaraman, Nagarajan, Paruchuri and Gangadhar, an Improved Process for the Preparation of Bio-Diesel, US Patent 2005052103, 2003. 39. Zahan, K.A., Kano, M., Technological Progress in Biodiesel Production: An Overview of different types of Reactor. Energy Procedia., 156, 452–457, 2019. 40. T. L. Marker, P. Height, T.A. Brandyold, A. Height and C.P. Leubke, Use of a Guard Bed Reactor to Improve Conversion of Biofeedstocks to Fuel, US Patent 2011/0245551A1, assigned to UOP LLC, 2011. 41. B. H. Dennis, R. E. Billo, C. R. Oliver, J. W. Priest, E. S. Kolesar and E. Kolesar, Methods and Systems for Improved Other Publications Biodiesel Production, US Patent 8.404,005, assigned to Board of Regents, The University of Texas System, 2009.

14 Reactions of Carboxylic Acids With an Alcohol Over Acid Materials J.E. Castanheiro

*

MED, DQ, ECT, Universidade de Évora, Évora, Portugal

Abstract

Biodiesel is an alternative to fossil diesel. It is biodegradable and non-toxic. The production of biodiesel is carried out by transesterification and/or esterification reactions. Usually, reactions between a carboxylic acid with an alcohol are carried out using sulfuric and phosphoric acids. Mineral acids (e.g., sulfuric acid) have some problems, such as the separation of reaction mixture. Heterogeneous catalysts can used to replace the homogenous ones. These catalysts have been used for biodiesel production. Recently, acid solids, such as heteropolyacids, activated carbons with sulfonic acid groups, and cation-­ exchange resins, have been used as catalysts on esterification of free fatty acids (FFAs). This present work is a review about the esterification reactions of carboxylic acid (fatty acid) with an alcohol over solid materials. Keywords:  Fatty acids, esterification, heterogenous catalysts, biodiesel

14.1 Introduction Traditionally, the biodisel is obtained by reaction between one molecule of triglyceride in conjunction with three molecules of an alcohol, using NaOH as catalyst. However, if the quantity of carboxylic acid presents in fat is high, processes will become inefficient, due to the soap formation. It is necessery an esterification reaction step before the transesterification.

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Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (377–388) © 2021 Scrivener Publishing LLC

377

378  Biodiesel Technology and Applications Esterification of a molecule of free fatty acid (FFA) with a molecule of alcohol (methanol or ethanol) yields an ester molecule and water molecule. Figure 14.1 shows a scheme of a fatty acid esterification with an alcohol (methanol, ethanol, 1-propanol, and 1-butanol) [1, 2]. R1– COOH + R2 – OH ↔ R1 – COOR2 + H2O

Figure 14.1  Scheme of reaction between a carboxylic acid and an alcohol.

where R1 represents a carbon atoms and R2 represents an alkyl group of the alcohol. The reactions of carboxylic acids with a alcohol are performed using homogeneous substances (one phase formed with reactants and catalyst) and heterogeneous catalysts (two phases: the catalysts are solid and the reactants are liquid) [1, 2]. To become the biodiesel production as a “eco-friendly processes”, the traditional sulfuric acid has been substituted for solid catalysts. The homogeneous catalysts are corrosive, and it is neutralized after reaction. The heterogeneous catalysts are more environmentally friend and can be reused [3–5]. This chapter focuses on solid acid materials on esterification of FFA.

14.2 Zeolites Zeolites are aluminosilicates crystalline with micropore system. These catalysts have an important propriety: shape selective. Due to the surface acidity, the zeolites can be used as heterogenous catalyst in the synthesis of different areas such, fine chemistry, and petrochemical industry [6–8]. However, only zeolites with large porous are applied on reactions between carboxylic acids with alcohols. The zeolite’s activity improves with the increases of the ratio silicon to aluminum, which can be an indication that the zeolite reactivity is influenced by the hydrophobic/hydrophilic balance of its surface The activity of zeolites for esterification reactions is affected by the aluminum amount present in its framework [6–9]. The reaction between hexadecanoic acid and methanol was done over four zeolites (H-Y, ZSM-5) as catalysts [10]. When the reaction was carried out without zeolite (Blank), the conversion was lower than with zeolite. With H-Y-60 zeolite, a conversion of 100% was obtained. This behavior was explained due to difference on zeolite’s porous system. H-ZSM-5 contains medium-sized micropores, with avarege pore size (5.6 Å × 5.3 Å channels) lower than H-Y zeolite (7.4 Å). The reaction over H-ZSM-5

Reactions of Carboxylic Acids  379 zeolites, probably, occurs at the external surface area, due to the molecular size of ester. In contrast, H-Y zeolites offer high surface and porous volume. The H-Y-60 catalyst showed the highest catalytic activity for this reaction. Under optimazed reaction conditions, a 100% conversion was obtained. The H-Y-60 zeolite can be recycled [10].

14.3 SO3H as Catalyst The reaction between oleic acid and ethanol was performed using sulfonated polystyrene [11]. This reaction without polystyrene yielded only about 10% of the ethyl oleate. When it was used sulfonated polystyrene, the yield increased from 30% to 90%. The optime reaction conditions were found to be amount of ethanol (219.0 mmol), amount of oleic acid (7.45 mmol), and amount catalyst (25 mg). Under this reaction conditions, the ethyl oleate yield was about 90%. These catalysts can be reused several times [11]. When octadec-9-enoic acid reacted together with methanol over Amberlyst-15, using a continuous reactor, over of Amberlyst-15, the conversion increased with reaction temperature [12]. The reaction conditions were as follows: methanol flow 6.4 ml/h, oleic acid flow 9.0 ml/h, and bed height of 10 cm, and the temprature was 80°C, 100°C, and 120°C. Under this conditions, the yields were 69.9%, 72.7%, and 84.0%. It was observed that the catalyst does not loss activity during the reaction [12]. The esterification of palmitic acid with methylic alcohol was done over PVA cross-linked with sulphosuccinic acid (SSA) and PS cross-linked with divinylbenzene containing −SO3H [13]. It was observed that the PVA catalysts showed high activity than the PS. PVA_SSA40 material showed a good stability [13]. This reaction was also studied over chitosan with sulfonic acid [14]. Catalyic actvity of these materials increased when the amount of sulfonic groups increases, until a maximum (sample CT4). The catalyst sample CT4 showed a good catalytic stability [14]. The reaction of octadec-9-enoic acid and n-butanol was done over polystyrene-modified organosilicas with sulfonic acid groups [15]. These materials demonstrated high activity. The optimal conditions were T = 130°C, catalyst amount = 2 wt%, and molar ratio oleic acid to n-butanol 1:1.4, which led a oleic acid conversion about 92% [15]. Activated carbons with −SO3H have been utilized as material for reactions between carboxylic acids with alcohols. These materials can be obtained from sugar, starch, or cellulose [16, 17]. The reaction between octadec-9-enoic acid and octadecanoic acid and ethanol were performed using activated carbons prepared from d-glucose

380  Biodiesel Technology and Applications with −SO3H. The materials exhibited high activity, probably by the high quantity of −SO3H groups [17]. The reaction between octadec-9-enoic acid and ethyl alcohol was done over carbons (CMK) with −SO3H [18]. A yield of ethyl oleate about 60% was obtained, after 6 h of reaction, at 353 K, when it used 0.005 mol of ­octadec-9-enoic acid and 0.05 mol of ethyl alcohol. After four uses, high catalytic activity was observed [18]. These reaction was studied over activated carbon prepared from bamboo with sulfanilic acid [19]. The optimized conditions were as follows: m activated carbon = 12%; octadec-9-enoic acid: ethyl alcohol = 7, T = 85°C; t = 3 h. In these conditions, a catalytic efficiency of 91% was obtained [19]. The reaction between octadec-9-enoic acid and methyl alcohol was done on activated carbons [20]. These catalysts are mesoporous materials, and sulfonic acid groups were introduced in its surface. The performance of these materials was greater than Amberlyst-15 [20]. The same reaction was studied using ordered mesoporous carbons (OMCs). The catalysts showed a methyl oleate yield of 96.25%. After nine reuses, the catalyst is active [21]. The esterification of fatty acid was performed using sulfonated mesoporous carbon catalysts [22]. After eight cycles, the FFA conversion was >91% [22].

14.4 Metal Oxides The reaction between n-octanoic acid and methyl alcohol was carried over metal oxides (tin and zirconia) sulfated. The sulfated tin material revealed high performance for the esterification, which can be explained due to its strong acidity [23]. The reaction between of octadecanoic acid and methyl alcohol was performed over aerogel sulfated zirconia (A-SZr) and xerogel sulfated zirconia (X-SZr) [24]. A-SZr catalyst has greater textural properties, like total porous volume than X-SZr material. After 7 h of reaction, the A-SZr catalyst showed 88% yield to product. The activity of aerogel material was better than xerogel. A-SZr catalyst was reused [24]. The reaction of octanoic acid and ethyl alcohol was performed using zirconia catalysts. The SZ500 material exhibited high performace for this reaction [25]. The reaction between octadec-9-enoic acid and methy alcohol was done using titanium oxide [26]. It was observed that the catalyst [TiO0 /SO42− ] showed the greatest performed of all material used in the esterification

Reactions of Carboxylic Acids  381 (after 3 h, about 82.2% oleic acid conversion) [26]. This reaction was also studied over WOx immobilized on MCM-41 [27]. It was prepared materials with several WO3 amount. It was observed a conversion near 100% with catalysts loading of WO3 higher than 10 wt%. The catalyst with 15 wt% WO3 can be reused [27]. This reaction was studied over sulphated Zr-KIT-6 (x) material [28]. Under optimized conditions (T = 393 K, methy alcohol: octadec-9-enoic acid = 20:1, mcatalyst = 4 wt%, t = 6 h), it was obtained an ester yields of 95%. The catalyst was reused. After three cycles, it was observed that the material has a good activity and stability [28]. The reaction between octadec-9-enoic acid and n-butyl alcohol has been studied using zirconium sulphate immoblized on silica (ZS) [29]. It was observed that the performance of ZS was greater than ZS not immobilized. The catalytic activity increased with amount of ZS. However, when the ZS amount is high, the catalytic activity decreased. The octadec-­ 9-enoic acid conversion increased with the amount of solid. Molar ratio of ­octadec-9-enoic acid:n-butyl alcohol was also optimized. The conversion of octadec-9-enoic acid enhanced with the molar ratio. Silica-supported ZS was reused [29]. The reaction between octadec-9-enoic acid and ethyl alcohol was done over oxides of tin sulfated [30]. At T = 353 K with molar ratio 1:10, the octadec-9-enoic acid conversion improved with the acidity. The material can be recycled [30]. This reaction was also studied over mesoporous SnO2/WO3 [31]. The reaction was permormed using three temperatures: 313, 333, and 353 K. The octadec-9-enoic acid conversion increases with the reaction temperature. Also, the catalyst loading was studied. It was observed that increases with the amount of catalyst. The catalyst can be reused, after regeneration [31]. The reaction between octadec-9-enoic acid and ethyl alcohol was done over WO3 supported on a USY zeolite [32]. Catalysts with different amounts of WO3 (from 2.5% to 20.5% WO3) were prepared. It was observed that the WO3/USY catalysts were more active than USY. The material perormance enhanced with quantity of WO3 supported on USY, until the top (11.4% of WO3). After this activity maximum, when the amount of WO3 increases the catalytic activity decreases. The material could be recycled [32]. The reactions between octadec-9-enoic acid, octadecanoic acid and dodecanoic acid and methyl alcohol, and ethyl alcohol and butyl alcohol was carried out over niobium materials [33]. The reaction between dodecanoic acid and butyl alcohol was studied over niobic acid and niobium phosphate, being phosphate material that showed the best performance. The dodecanoic acid conversion improved with the temperature. The

382  Biodiesel Technology and Applications effect of carbon chain legth was also studied. The conversion reduce from dodecanoic acid (97%) to octadecanoic acid (94%). The octadec-9-enoic acid conversion was smallest of all carboxylic acids. The niobium phosphate catalyst was reused without loss its activity [33]. The reaction between octanoic acid and ethyl alcohol was carried out over SO24− /Fe x Al1− x PO4 acid catalysts [34]. The presence of Fe on this materials improved the conversion of octanoic acid. This materials can be recycled [34].

14.5 Heteropolyacids These materials (HPAs) are polyoxometalates, which are catalysts of different reactions. The HPAs have got a low surface area. The heteropolyacids have been supported on different materials like silica, zeolites, zirconia, and polymers [35, 36]. The reaction between octadec-9-enoic acid and ethyl alcohol was carried out in the presence of H3PW12O40 immobilized in ZrO2 [37]. Catalysts with different amount of heteropolyacids were prepared. The octadec-9-enoic acid conversion enhanced with the amount of H3PW12O40 immobilized on zirconia. Optimum reaction conditions were obtained with mcatalyst = 20 wt%, T = 100°C, t = 240 min, and an octadec-9-enoic acid:ethyl alcohol= 1:6. In these conditions, it is obtained a 88% of octadec-9-enoic acid conversion. This material can be recycled [37]. The reaction between acid hexadecanoic (0.01 mol) and methanol (2.5 mmol) was performed using insoluble HPA salts with Cs [38]. The optimum activity was obtained over a material with Cs equal to 2.3. Material Cs2.3H0.7PW12O40 was reused [38]. This reaction was studied using heteropolyacids in SiO2 [39]. The materials activity reduced in the following order: HPMo-SiO2 < HSiW-SiO2 < HPW-SiO2. Different catalysts with HPW immobilized in SiO2 were made. The catalyst PW-silica2 reveals the greatest reation rate. The material was reused [39]. This reaction was studied over differents amount of HPW (5% to 30% wt) immobilized on niobia [40]. The conversion of acid hexadecanoic increases with HPW quantity supported on Nb2O5. High conversion was obtained with material (HPW)25%/Nb2O5. When amount of HPW increases, the conversion do not change to much. The conversion of acid hexadecanoic increased when the temperature increased as well. Material (HPW) 25%/Nb2O5 was recycled [40, 44]. This reaction was studied over different heteropolyacids (HPW, HPMo, and HSiW) immobilized on SBA-15 [41]. Material HPW1

Reactions of Carboxylic Acids  383 showed highest conversion of all prepared materials. It was also made materials with various HPW quantity. The acid hexadecanoic conversion improved when the quantity of heteropolyacid supported on silica until a maximum, which was obtaind using HPW3-SBA-15 catalyst (6.7% wt). The effect of catalyst loading (HPW3-SBA-15) on esterification was also studied. The acid hexadecanoic conversion improved when the catalyst quantity improved. The HPW3-SBA-15 catalyst could be reused [41]. The reaction between hexadecanoic acid, octadecanoic acid, octadec-9-enoic acid, and ethyl acohol was done in the presence of HPW immobilized in SBA-15 (12.5% wt) [42]. The highest conversion was obtained with hexadecanoic acid. This material could be recycled [42]. The reaction between hexadecanoic acid and methyl alcohol was done over HPW on MCM-41 [43]. Materials with various quantities of HPW were made. The hexadecanoic acid conversion enhanced with quantity of HPW anchored to MCM-41. However, for catalysts with high amount of HPW (for 30% and 40% loading), the palmitic acid conversion did not increase significatively. The material with 30% loading of HPW (HPW3/ MCM-41) was used for optimize the reaction conditions. Under optimized conditions (T = 333 K; mcatalyst = 0.1 g; t = 360 min; hexadecanoic acid:methyl alcohol = 1:40), a 90% of hexadecanoic acid conversion was achieved. Catalyst can be reused [43]. This reaction was also done over 12-tungstophosphoric acid on SnO2 [44]. Material with 15 wt% of 12-tungstophosphoric acid supported on SnO2 revealed the greatest conversion. Material was reused. After five reaction cycles, the hexadecanoic acid conversion stayed high level [44]. The reaction between octadec-9-enoic acid and methyl alcohol was done over HPW anchored to SBA-15, as catalyst [45]. Under optimized condition (octadec-9-enoic acid: methyl alcohol = 1:40; mcatalyst = 0.1 g; T = 313 K; t = 240 min), the conversion of octadec-9-enoic acid was 90%. Materials could be recycled [45]. The reaction between hexanoic acid and methyl alcohol was done on HPA supported in Nb2O5, ZrO2, and TiO2 [46]. These materials demonstrated higher performance than Amberlyst-15, H-Beta, and HY zeolite. Under optimized condition (hexanoic acid:methyl alcohol = 1:20, mcatalyst = 0.1 g, T = 333 K), a 53.2% conversion was obtained [46]. The reaction between dodecanoic acid and ethyl alcohol was done over H3PW12O40 (HPW) immobilized on Ta2O5 support [47]. The TOF of HPW (1.62 min−1) is lower than the TOF of HPW/Ta2O5 (5.58 min−1), which is an indication that the HPW immobilized on Ta2O5 shows more activity than the HPW. The catalysts showed high stability [47].

384  Biodiesel Technology and Applications

14.6 Other Materials The reaction between dodecanoic acid and ethyl alcohol was done over clay mineral (montmorillonite STx1-b) as catalyst [48]. Under optimized condition (dodecanoic acid: ethyl alcohol = 1:6; mcatalyst = 10 wt%; T = 453 K; t = 1.5 h), the conversion of octadec-9-enoic acid was 90%. Catalyst STx1-b can reused. After four cycles, a good catalytic activity was observed [48]. This reaction was also done over Zr-MOF [49]. These materials showed performance similar to other solids [49]. The reaction between dodecanoic acid, octadecanoic acid, octadec9-enoic acid, and ethyl alcohol was preformed using montmorillonite K10 as catalyst [50]. Under optimized conditions (carboxylic acid:ethyl alcool = 1:12, mcatalyst = 12%, T = 453 K, t = 240 min), high conversions (about 90%) were achieved [50]. The reaction between octanoic acid, dodecanoic acid, octadecanoic acid, octadec-9-enoic acid, and methyl alcohol was carried out over Brazilian smectite natural clay [51]. The acid treatment of material gave a catalyst with high catalytic activity. Under optimized condition (carboxylic acid: methyl alcohol = 1:3; mcatalyst = 10 wt%; T = 373 K; t = 240 min), the conversion of octanoic acid, dodecanoic acid, octadecanoic acid, and octadec-9-enoic acid was 99%, 98%, 93%, and 80%, respectively. The material could be recycled [51].

14.7 Conclusions The reaction between a carboxylic acid (like octanoic acid, dodecanoic acid, octadecanoic acid, and octadec-9-enoic acid) and an alcohol is an important step in biodiesel production. The existence of high amount of free carboxylic acids in raw material (like waste cooking oil and animal fat) can complicate the process of transesterification of triglycerides, which is done with KOH or NaOH. An alternative to produce biodiesel from oils or fats with high level of carboxylic acids, it is a esterification of carboxylic acids before transesterification reaction. Reactions between carboxylic acids and alcohols are carried out over homogenous catalysts, which have some environment problems. In order to become the process as a “environmentally friendly process”, sulfuric acid can be substituted by solid materials. Some materials like zeolites, heteropolyacids, materials with sulfonic groups (MCM-41, SBA-15, activated carbons, organic polymers), and modified inorganic mixed oxides have been applied on this type of reaction.

Reactions of Carboxylic Acids  385

References 1. Gerpen; J.V., Biodiesel processing and production. Fuel Process Technol., 86, 1097, 2005. 2. Avhad, M.R., Marchettin, J.M., A review on recent advancement in catalytic materials for biodiesel production. Renew. Sust. Energ. Rev., 50, 696, 2015. 3. Kulkarni, M.G., Dalai, A.K., Waste Cooking Oils-An Economical Source for Biodiesel: A Review, Ind. Eng. Chem. Res., 45, 2901, 2006. 4. Lam, M.K., Lee, K.T., Mohamed, A.R., Homogeneous, heterogeneous and enzymatic catalysis for transesterification of high free fatty acid oil (waste cooking oil) to biodiesel: A review. Biotechnol. Adv., 28, 500, 2010. 5. Karmakar, B., Halder, G., Progress and future of biodiesel synthesis: Advancements in oil extraction and conversion technologies, Energy Convers. Manag., 182, 307, 2019. 6. Serrano, D.P., Melero, J.A., Morales, G., Iglesias, J., Pizarro, P., Progress in the design of zeolite catalysts for biomass conversion into biofuels and bio-based chemicals, Catal. Rev., 60, 1, 2018. 7. Venuto, P.B., Organic catalysis over zeolites: A perspective on reaction paths within micropores, Microporous Mater., 2, 297, 1994. 8. Burton, A., Recent trends in the synthesis of high-silica zeolites, Catal. Rev., 60, 132, 2018. 9. Kiss, A.A., Dimian, A.C., Rothenberg, G., Solid Acid Catalysts for Biodiesel Production-Towards Sustainable. Energy. Adv. Synth. Catal., 348, 75, 2006. 10. Prinsen, P., Luque, R., González-Arellano, C., Zeolite catalyzed palmitic acid esterification. Microporous Mesoporous Mat., 262, 133, 2018. 11. Grossi, C. V., Jardim, E.O., de Araujo, M.H., Lago, R.M., Silva, M.J., Sulfonated polystyrene: A catalyst with acid and superabsorbent properties for the esterification of fatty acids. Fuel, 89, 257, 2010. 12. Son, S., Kimura, M. H., Kusakabe, K., Esterification of oleic acid in a threephase, fixed-bed reactor packed with a cation exchange resin catalyst. Bioresour. Technol., 102, 2130, 2011. 13. Caetano, C.S., Guerreiro, L., Fonseca, I.M., Ramos, A.M., Vital, J., Castanheiro, J.E. Esterification of fatty acids to biodiesel over polymers with sulfonic acid groups. Appl. Catal. A: Gen., 359, 41, 2009. 14. Caetano, C.S., Caiado, M., Farinha, J., Fonseca, I.M., Ramos, A.M., Vital, J, Castanheiro, J.E., Esterification of free fatty acids over chitosan with sulfonic acid groups, Chem. Eng. J., 230, 567, 2013. 15. Morales, G., van Grieken, R., Martín, A., Martínez, F., Sulfonated polystyrene-modified mesoporous organosilicas for acid-catalyzed processes. Chem. Eng. J., 161, 388, 2010. 16. Zong, Z., Duan, W., Lou, T.J., Smith, H. Wu, Preparation of a sugar catalyst and its use for highly efficient production of biodiesel, Green Chem., 9, 434, 2007.

386  Biodiesel Technology and Applications 17. Takagaki, A., Toda, M., Okamura, M., Kondo, J.N., Hayashi, S., Domen, K., Hara, M., Esterification of higher fatty acids by a novel strong solid acid. Catal. Today, 116, 157, 2006. 18. Peng, L., Philippaerts, A., Ke, X., van Noyen, J., de Clippel, F., van Tendeloo, G., Jacobs, P.A., Sels, B.F., Preparation of sulfonated ordered mesoporous carbon and its use for the esterification of fatty acids. Catal. Today, 150, 140, 2010. 19. Geng, L., Wang, Y., Yu, G., Zhu, Y., Efficient carbon-based solid acid catalysts for the esterification of oleic acid. Catal. Commun., 13, 26, 2011. 20. Niu, S., Ning, Y., Lu, C., Han, K., Yu H., Zhou, Y., Esterification of oleic acid to produce biodiesel catalyzed by sulfonated activated carbon from bamboo. Energy Convers. Manag., 163, 59, 2018. 21. Gao, Z., Tanga, S., Cuia, X., Tian, S., Zhang, M., Efficient mesoporous carbon-based solid catalyst for the esterification of oleic acid. Fuel, 140, 669, 2015. 22. Zhang, M., Sun, A., Meng, Y., Wang, L., Jiang, H., Li, G. High activity ordered mesoporous carbon-based solid acid catalyst for the esterification of free fatty acids. Microporous Mesoporous Mat., 204, 210, 2015. 23. Furuta, S., Matsuhashi, H., Arata, K., Biodiesel fuel production with solid superacid catalysis in fixed bed reactor under atmospheric pressure. Catal. Commun., 5, 721, 2004. 24. López, D.E., Goodwin Jr., J.G., Bruce, D.A., Furuta, S. Esterification and transesterification using modified-zirconia catalysts. Appl. Catal. A: Gen., 339, 76, 2008. 25. Saravanan, K., Tyagi, B., Bajaj, H.C., Nano-crystalline, mesoporous aerogel sulfated zirconia as an efficient catalyst for esterification of stearic acid with methanol. Appl Catal B: Env., 192, 161, 2016. 26. Jimenez-Morales, I., Santamaria-Gonzalez, J., Maireles-Torres, P., JimenezLopez, A., Zirconium doped MCM-41 supported WO3 solid acid catalysts for the esterification of oleic acid with methanol. Appl. Catal. A: Gen., 379, 61, 2010. 27. Juan, J.C., Zhang, J., Yarmo, M.A., Structure and reactivity of silica-supported zirconium sulfate for esterification of fatty acid under solvent-free condition. Appl. Catal. A: Gen., 332, 209, 2007. 28. Gopinath, S., Kumar, P.S.M., Arafath, K.A.Y., Thiruvengadaravi, K.V., Sivanesan S., Baskaralingam, P., Efficient mesoporous SO24− /Zr-KIT-6 solid acid catalyst for green diesel production from esterification of oleic acid. Fuel, 203, 488, 2017. 29. Ropero-Vega, J. L., Aldana-Pérez, A., Gómez, R., Niño-Gómez, M.E., Sulfated 2− titania [TiO2 /SO4 ]: A very active solid acid catalyst for the esterification of free fatty acids with ethanol. Appl. Catal. A: Gen., 379, 24, 2010. 30. Moreno, J.I., Jaimes, R., Gómez, R., Niño-Gómez, M.E., Evaluation of sulfated tin oxides in the esterification reaction of free fatty acids. Catal. Today, 172, 34, 2011.

Reactions of Carboxylic Acids  387 31. Sarkara, A., Ghosh, S.K., Pramanik, P., Investigation of the catalytic efficiency of a new mesoporous catalyst SnO2/WO3 towards oleic acid esterification. J. Mol. Catal. A: Chem., 327, 73, 2010. 32. Costa, A.A., Braga, P.R.S., Macedo, J.L., Dias, J.A., Dias, S.C.L., Structural effects of WO3 incorporation on USY zeolite and application to free fatty acids esterification. Microporous Mesoporous Mat., 147, 142, 2012. 33. Bassan, I.A.L., Nascimento, D.R., Gil, R.A.S.S., Silva, M.I.P., Moreira, C.R., Gonzalez, W.A., Faro Jr., A.C., Onfroye, T., Lachter, E.R., Esterification of fatty acids with alcohols over niobium phosphate. Fuel Process. Technol., 106, 619, 2013. 34. Liu, B., Jiang, P., Zhang, P., Bian, G., Li, M., Preparation and characterization of SO24− /FexAl1− x PO4 solid acid catalysts for caprylic acid esterification. Catal. Commun., 99, 49, 2017. 35. Sanchez, L.M., Thomas, H.J., Climent, M.J., Romanelli, G.P., Iborra, S., Heteropolycompounds as catalysts for biomass product transformations. Catal. Rev. 58, 497, 2016. 36. Patel, A., Narkhede, N., Singh, S., Pathan, S. Keggin-type lacunary and transition metal substituted polyoxometalates as heterogeneous catalysts: A recent progress. Catal. Rev. 58, 337, 2016. 37. Oliveira, C.F., Dezaneti, L.M., Garcia, F.A.C., de Macedo, J. L., Dias, J.  A., Dias, S.C.L., Alvim, K.S.P., Esterification of oleic acid with ethanol by 12-tungstophosphoric acid supported on zirconia. Appl Catal. A:Gen., 372, 153, 2010. 38. Narasimharao, K., Brown, D. R., Lee, A.F., Newman, A.D., Siril, P.F., Tavener, S.J., Wilson, K., Structure–activity relations in Cs-doped heteropolyacid catalysts for biodiesel production. J. Catal., 248, 226–234, 2007. 39. Caetano, C.S., Fonseca, I.M., Ramos, A.M., Vital, J., Castanheiro, J.E. Esterification of free fatty acids with methanol using heteropolyacids immobilized on silica. Catal. Commun. 9, 1996, 2008. 40. Srilatha, K., Lingaiah, N., Devi, B.L.A.P., Prasad, R. B. N., Venkateswar, S., Prasad, P.S.S., Esterification of free fatty acids for biodiesel production over heteropoly tungstate supported on niobia catalysts. Appl. Catal A: Gen., 365, 28, 2009. 41. Tropecêlo, A.I., Casimiro, M.H., Fonseca, I.M., Ramos, A.M., Vital, J., Castanheiro, J. E., Esterification of free fatty acids to biodiesel over heteropolyacids immobilized on mesoporous silica. Appl. Catal A:Gen., 390, 183, 2010. 42. Castanheiro, J.E., Fonseca, I.M., Ramos, A.M., Vital, J., Tungstophosphoric acid immobilised in SBA-15 as an efficient heterogeneous acid catalyst for the conversion of terpenes and free fatty acids. Microporous Mesoporous Mat., 249, 16, 2017. 43. Brahmkhatri, V.; Patel, A., Biodiesel Production by Esterification of Free Fatty Acids over 12-Tungstophosphoric Acid Anchored to MCM-41. Ind. Eng. Chem. Res., 50, 6620, 2011.

388  Biodiesel Technology and Applications 44. Srilatha, K., Kumar, C.R., Devi, B.L.A.P., Prasad, R.B.N., Prasada, P.S.S., Lingaiah, N., Efficient solid acid catalysts for esterification of free fatty acids with methanol for the production of biodiesel. Catal. Sci. Technol., 1, 662, 2011. 45. Brahmkhatri, V.; Patel, A., 12-Tungstophosphoric acid anchored to SBA-15: An efficient, environmentally benign reusable catalysts for biodiesel production by esterification of free fatty acids. Appl Catal A: Gen., 403, 161, 2011. 46. Alsalme, A., Kozhevnikova, E.F., Kozhevnikov, I.V., Heteropoly acids as catalysts for liquid-phase esterification and transesterification. Appl. Catal. A: Gen., 349, 170, 2008. 47. Xu, L., Yang, X., Yu, X., Maynurkader, G.Y., Preparation of mesoporous polyoxometalate–tantalum pentoxide composite catalyst for efficient esterification of fatty acid. Catal. Commun. 9, 1607, 2008. 48. Santos, P.R.S., Wypych, F., Voll, F.A.P., Hamerski, F., Corazza, M.L., Kinetics of ethylic esterification of lauric acid on acid activated montmorillonite (STx1-b) as catalyst. Fuel, 181, 600, 2016. 49. Cirujano, F.G.; Corma, A.; Llabrés, F.X.; Xamena, I., Zirconium-containing metal organic frameworks as solid acid catalysts for the esterification of free fatty acids: Synthesis of biodiesel and other compounds of interest. Catal. Today, 257, 213, 2015. 50. Kanda, L.R.S., Corazza, M.L., Zatta, L., Wypychc, F., Kinetics evaluation of the ethyl esterification of long chain fatty acids using commercial montmorillonite K10 as catalyst. Fuel, 193, 265, 2017. 51. Rezende, M.J.C., Pinto, A.C., Esterification of fatty acids using acid-activated Brazilian smectite natural clay as a catalyst. Renew Energ., 92, 171, 2016.

15 Biodiesel Production From Non-Edible and Waste Lipid Sources Opeoluwa O. Fasanya1, Aishat A. Osigbesan1 and Onoriode P. Avbenake2,3* Petrochemical and Allieds Department, National Research Institute for Chemical Technology, Zaria, Nigeria 2 Chemical and Petroleum Engineering Department, Bayero University, Kano, Nigeria 3 School of Science & Technology, Pan-Atlantic University, Ibeju-Lekki, Nigeria

1

Abstract

Biodiesel has become a very popular renewable/alternative fuel. The popularity of biodiesel is driven by the relative ease of synthesis and the wide array of feedstock from which it can be produced. These include vegetable oils, animal fats, and other sources of biomass. Vegetable oils are the main feed stock that have been used for biodiesel synthesis. To the extent that oils meant as food for humans and animals are being diverted for biodiesel production. To stop this unsustainable practice, nonedible vegetable feedstocks are constantly identified, researched, and cultivated. Much progress has been made over the last few years in this especially in terms of oils from seeds of plants such as Jatropha curcas, Calophyllum inophyllum, Azadirachta indica, Hevea brasiliensis, and Ricinus communis, among others. In addition, waste vegetable oils are also being harnessed for the purpose of biodiesel production, rather than being discarded once they degrade. Furthermore, the use of microalgae, a third-generation source of biodiesel, was equally discussed, owing to their popularity among researchers. The increased interest is a consequence of the speed and ease of cultivation and to a larger extent the quantity of oil that could be harvested. As a matter of fact, fourth-generation biodiesel is now being derived from genetically modified algae strains which contain even more oils. Accordingly, this chapter aims to critically review a portion of the numerous developments concerning biodiesel from non-edible sources.

*Corresponding author: [email protected] Inamuddin, Mohd Imran Ahamed, Rajender Boddula, and Mashallah Rezakazemi (eds.) Biodiesel Technology and Applications, (389–428) © 2021 Scrivener Publishing LLC

389

390  Biodiesel Technology and Applications Keywords:  Biodiesel, lipids, renewable energy, waste utilization, methyl esters, fuel, non-edible oils, deacidification

15.1 Introduction The ever increasing energy requirements in the world today have placed a large demand on limited quantity of fossil based fuels in the world at large. The increase in energy demand is due to technological advancement, industrialization, and population growth all over the world. The International Energy Agency (IEA) estimates that 50% more energy will be required in 2030 when compared with present energy consumption [1]. There is no gain saying that copious levels of environmental pollution particularly crude oil spills and CO2 emissions are associated with extraction and use of fossil fuels. Coupled with fluctuating crude oil prices, there is pertinent need of generating alternative sustainable fuels for energy consumption. Some alternate sources of fuel that have generated a lot of interest include solar cells [2], fuel cells powered by hydrogen [3], ethanol [4], methanol [5], and diesel derived from biological materials or biomass. Biomass as a source of fuel is quite advantageous because it is renewable and also has relatively low carbon foot print during synthesis of fuels. This guarantees some measure of environmental stability while energy requirements are being met. Globally, the United States of America, Brazil, and European Union are the main consumers of bio-based fuels. As at 2000, annual biodiesel production was recorded to be about 0.8 million tons [6]. In 2007, Germany alone marketed 3.2 million tons of biodiesel [7]. Despite this production rate, the IEA claims that global biofuel production rate is not able to keep up with the present demand for the product. As at 2018, renewable energy met only 3.7% of transportation fuel demand [1]. The IEA have, however, predicated that between 2019 and 2024, a 25% production increase corresponding to approximately 190 billion litres would be achieved. Diesel produced from biomass is popularly referred to as biodiesel. It is a fuel which is made up of monoalkyl esters of long-chain fatty acids derived from biomass which are sourced from plants or animal fats. Better combustion efficiency has been observed in biodiesel synthesized by this route [8]. The International Association for Testing and Materials (ASTM) has set out criteria in the ASTM D6751 (Table 15.1) which lists out properties that a fuel must possess to be called biodiesel. Inherent advantages of biodiesel use include its blending capacity with other energy sources, lubricity which could invariably help extend engine lifespan, higher flash point, and lack of toxicity [9, 10].

Biodiesel Production From Non-Edible Sources  391 Table 15.1  Biodiesel specifications and their limits. Properties

EN 14214

ASTM D6751

Composition of biodiesel

C12-C22

C12-C22

Esters content

Greater than 96.5% (m/m)

–

Density at 15°C

860–900 kg m−3

–

Viscosity at 40°C

3.5–5.0 mm2 s−1

1.9–6.0 mm2 s−1

Flash point

≥101°C

≥ 130°C

Sulphur content

≤10 mg kg−1

50 mg kg−1

Carbon residue

≤0.3% (m/m)

≤ 0.05 (m/m)

Cetane number

≥51

≥ 47

Sulfated ash

≤0.02% (m/m)

≤ 0.02% (m/m)

Water content

≤500 mg kg−1

≤ 0.05% (v/v)

Corrosion

–

3h

Oxidative stability 110°C

4h

3h

Acid value

≤0.50 mg KOH g−1

≤ 0.50 mg KOH g−1

Iodine value

130 g I2/100 g

–

Methanol content

≤0.02% (m/m)

–

Monoacylglycerols content

≤0.8% (m/m)

–

Diacylglycerols content

≤0.2 (m/m)

–

Triacylglycerols content

≤0.2 (m/m)

–

Free glycerine

≤0.02% (m/m)

≤ 0.20% (m/m)

Total glycerrin

≤0.25% (m/m)

≤ 0.25% (m/m)

Pour point

–

−15 to −16°C

Phosphorous amount

≤4 mg kg−1

≤ 0.001% (m/m)

Cloud point

–

−3 to 12°C

Adapted from Fonseca et al. (2019) [11].

392  Biodiesel Technology and Applications Generally, biodiesel is produced by transesterification of triglycerides with a short chain alcohol in the presence of a catalyst to form fatty acid alkyl esters and glycerol as products. The reaction scheme is shown in Figure 15.1 and in Equations 15.1 to 15.3. Transesterification is a relatively simple and cost-effective process [12]. Though some challenges with separation of the final products from catalyst may occur depending on whether homogenous or heterogeneous catalysts are employed. Transesterification catalysts could either be acidic [13], basic [14, 15], or enzymatic [16]. While homogeneous catalysts such as NaOH and KOH are generally more effective, separation after reaction requires thorough washing with large amounts of water to ensure complete removal of the catalyst. This challenge was resolved with use of solid catalysts such as CaO. Though these are not quite as reactive and are often prone to deactivation or single digit limited cycles of use. Strides have made to develop stable heterogeneous catalysts which are resistant to rapid deactivation.



Triglycerides + Methanol = diglycerides + FAME

(15.1)

Diglycerides + Methanol = Monoglycerides + FAME (15.2)



Monoglycerides + Methanol = Glycerol + FAME

(15.3)

For oils with high free fatty acid (FFA), an initial pre-treatment step is required where esterification of the oil with methanol in the presence of an acid catalyst (usually sulphuric acid) is carried out as seen in Equation 15.4



FFA + Methanol = FAME + Water

(15.4)

One major point of concern in biodiesel synthesis is the biomass feedstock. Globally, oil-bearing plants have been widely explored for biodiesel production. Typically, plants with seeds that yield high amounts of oil are usually preferred as starting triglyceride sources, since these would result in large volumes of biodiesel being produced. Economically, this is the route H2C

COO

R1

HC

COO

R2 + 3CH3OH

H 2C

COO

Triglyceride

Catalyst

R3 Methanol

CH3

COO

CH3

COO

R2

CH3

COO

R3

R1 +

Fatty acid methyl ester

H2C

OH

HC

OH

H2C

OH

Glycerol

Figure 15.1  Transesterification reaction showing reaction of methanol and triglyceride to form Fatty acid methyl ester (FAME) and glycerol.

Biodiesel Production From Non-Edible Sources  393 to follow. The challenge, however, is that edible oils which are in large demand as food sources such as palm oil [17, 18] and soybean oil [19, 20] are being used to produce the fuel. This has led to unhealthy competition between use of oil as food or fuel. Inadvertently, resulting in global depletion of edible oils for food and consequently affecting the price of food and fuel dependent on these oils. It is expected, therefore, that this would birth major economic crisis in future [12]. Available arable land for agricultural cultivation would reduce and lose nutrients due to large volumes of plants constantly being cultivated to meet the ever increasing energy and food requirements. Edible biodiesel feedstocks are generally termed first-generation feedstock. They were initially explored for large-scale production. Currently, it is estimated that over 90% of current biodiesel production is from edible vegetable oils [21]. Palm oil, sunflower oil, coconut, groundnut, and soybean [19] oils all fall in this category [12]. To forestall the impending crisis associated with the use of edible crops, attention has been focused on utilization of non-edible oils. These are generally classified as second-generation biodiesel feedstock. Some of which include but not limited to Jatropha curcas, Hevca brasillenis, and Azadirachta indica. Biodiesel from waste oil is also considered to be second-generation feedstock. Using these types of feedstock offers the advantage of reducing pollution concerns and costs associated with safe disposal. It is estimated that production costs can be reduced by as much as 70% when non-edible oils are utilized [22]. There are numerous reviews on the use of non-edible oils for biodiesel production [6, 23–27]. Atadashi discussed the effect of using high FFA oils, many of which are not fit for human consumption [28]. The review by Balat discussed about trends in non-edible feedstock that were gaining traction as of 2011 [29]. Discussions were oils derived from Jatropha curcas, Pongamia pinnata, Madhucca indica, and microalgae among others were reviewed. Although there are now more recent reviews highlighting developments using micro-algae [30], some of which we will discuss here. The review by Sajjadi and co-workers contained prediction models for parameters such as viscosity, density, flash point, cetane number, and heating value of both edible and non-edible based biodiesels [31]. Pereira and co-workers also reviewed models but their focus was on thermos-physical models to estimate melting points of fats and cold flow properties of biodiesel [32]. While Kirubakaran and Selvan focused their review on using waste chicken fat [33]. Some other reviews are location specific, highlighting potential feedstock and production strategies [34, 35]. In the end, the choice of non-edible feedstock for biodiesel production will be highly location dependent. Such as in the case of Jatropha,

394  Biodiesel Technology and Applications Callophyllum innophyllum, and neem which are native to India. Another important property that would determine choice of feed for biodiesel production is its ability be grown rapidly and under a wide variety of conditions. This will definitely reduce competition on the use of arable land for cultivating crops for energy for plant based sources. For animal-based sources feeds with low FFA or with FFA that can be reduced with ease are feedstock of choice. This chapter highlights both plant and animal-based sources feedstock that are non-edible and shows progresses made in utilizing them for biodiesel production.

15.2 Non-Edible Plant-Based Oils 15.2.1 Jatropha curcas Jatropha curcas is a drought resistant crop that is capable of growing in fallowed land. It has the ability to withstand a variety climatic zones and soil conditions. In addition to these, its short gestation period and fast growth have led to its widespread cultivation. It is a highly suitable crop for biodiesel production in developing countries especially in the tropical and subtropical parts of the world [36]. Commercial growth of the crop has, however, experienced setbacks all over the world due to poor understanding of the crop [37]. Recently, detailed studies have, however, shown that optimum growing conditions such as an excess of 700-mm rainfall annually, soil pH ranging between 6 and 9, and annual temperature between 16°C and 28°C are required for commercial Jatropha plantation [38]. A lot of attention is given to its cultivation as it is responsible for 36%–44% of the biodiesel selling price depending on where it is planted [37, 38]. Deliberate J. curcas plantations are currently being grown in Rwanda [39], China, Ethiopia, India, Nepal, and Tanzania [38]. Its combustion and emission properties closely resemble that of petroleum diesel. Properties such as flash point and ignition point are higher for J. curcas derived fuels [36]. As far back as World War II, J. curcas oil was used was blended with diesel and used as a fuel alternative [28]. A number of authors have maintained that it is the best non-edible oil for biodiesel production [36, 39, 40]. The oil content of the seed appears to be dependent on location and probably variety as values seen in literature fall between the range of 25% to 59% [28, 36]. Oil from J. curcas can also be used for producing soaps and candles. The use of Jatropha for biodiesel has been widely investigated. Its high FFA usually entails that a two-step production process is often required.

2

1

2.1

100

97.7

85.3

Na2SiO3@Ni/ JRC

KF supported 92.2 on red mud

98.54

Zn8FeC

nano CaO

SO2−4/TiO2

24

4

2

99.6

Sr+2 - CaO/ MgO

4

94

Time (hours)

CaSO4/ Fe2O2-SiO2

Catalyst

Yield (%)

0.2

Atm

Atm

Atm

4.5 MPa

Atm

Atm

Pressure (MPa)

140

60

75

65

160

65

120

Temperature (°C)

4

2

7

7

7

5

12

Catalyst loading (wt %)

9

5.15

21

9

40

9

9

Acidic

Basic

[64]

[63]

[62]

[61]

[41]

[60]

[42]

Ref.

(Continued)

Alkaline

Not stated

Esterification

Basicmagnetic

Amphoteric

Basic

Amphoteric

Esterification

None

Not stated

None

Methanol oil Catalyst ratio Pre-treatment type

Table 15.2  Different catalysts, reaction conditions, and yield during synthesis of biodiesel from Jatropha seed oil between 2015 and 2019.

Biodiesel Production From Non-Edible Sources  395

3

2.5

3

–

99

90

96.91

98

96.1

Al-SBA-15

Fe-Zn-1

Na2ZrO3

Cs-Na2ZrO3

Ca-La-Al

Si-MMT-PhSO3H

Calcined animal bones

1

1

4

24

99

Catalyst

Time (hours)

Yield (%)

Atm

Atm

Atm

Atm

Atm

Atm

4

Pressure (MPa)

70

110

150

65

65

160

180

Temperature (°C)

6

6

15

15

30

4

6.5

Catalyst loading (wt %)

9

5

7

3

3

10

12

None

Basic

Basic

Acidic

Acidic

Methanol oil Catalyst ratio Pre-treatment type

Table 15.2  Different catalysts, reaction conditions, and yield during synthesis of biodiesel from Jatropha seed oil between 2015 and 2019. (Continued)

[67]

[66]

[44]

[20]

[20]

[65]

[43]

Ref.

396  Biodiesel Technology and Applications

Biodiesel Production From Non-Edible Sources  397 The discovery and use of amphoteric catalysts has been suggested as a way of combining the esterification and transesterification step into one. The use of Zn-FeC catalysts resulted in as much as 100% biodiesel yield with extremely high stability [41]. Other studies using amphoteric catalysts have given yield of 94% after 4 hours of reaction [42]. Table 15.2 contains data on recent catalyst developments for biodiesel synthesis from Jatropha. Interestingly, one report has shown that under the right conditions some transformation can occur without the use of catalysts [43]. Jatropha still remains one of most widely researched oils for biodiesel production. As can be seen from Table 15.2, there is still a lot of room for research especially in terms of catalyst development. Reusability of catalysts for multiple runs remains a challenge. Though some work has shown reusability of up to five times with just a 5%–10% drop in FAME yield [44].

15.2.2 Calophyllum inophyllum Calophyllum inophyllum is a perennial plant that grows predominantly in Australia, Sri Lanka, India, and Southeast Asia. It is a mangrove plant with oil containing seeds [45]. The relatively high oil content in its kernels has also made the plant attractive for biodiesel production in parts of the world where its growth is prevalent. About 46%–60% of toxic non-edible oil can be extracted from its kernels [45, 46]. Apart from biodiesel synthesis, the oils have been found to have properties which can be used to treat skin diseases, arthritis, and burns, to salve wounds, and many others [47]. Biodiesel from C. Inophyllum generally has high oxidation stability but it is improved further with the use of additives such as Butylated hydroxytolune, 4-methyl-6-tert-butyphenol and antioxidant extracted from pongamia leaf [48]. As with other oils previously discussed, the biodiesel yield is dependent on reaction conditions and catalyst type with yields of over 85% reported by different groups [49, 50]. Various reports have also been written describing its performance in diesel compression engines [51–54].

15.2.3 Mesua ferrea Mesua ferrea L. also known as Nahar or Ceylon ironwood [55] is a non-­ edible evergreen timber plant native to Sri Lanka and rather abundant in Northeast India [56, 57]. It also grows freely in Nepal, Indonesia, Vietnam, Cambodia, and Singapore [58]. Its seeds containing between 55% and 57% of oil [56]. The timber plant is its unsaturated fatty acid content is between 65.85% and 68.31% [56]. With regard to biodiesel production, this plant is relatively underutilized but this trend is changing. The reason for this is

398  Biodiesel Technology and Applications attributed to some shortfalls experienced in Jatropha yield over the last few years [58]. When tested on compression injection engines, results obtained were comparable with conventional diesel [58, 59]. Suggesting that the biodiesel from this oil is suitable for blending or as a complement to Jatropha derived biodiesel.

15.2.4 Jojoba Oil Simmondsia chinensis (linn) Schneider (commonly identified as jojoba but is also called deer nut, oat nut, wild hazel, and coffee berry) is a promising oil seed crop for the economic development of the arid and semiarid land all over the globe. The jojoba plant is a monogenetic dioecious gray-green shrub belonging to Simmondsiaceae family. It is native to the North American deserts, especially those of south western states in the United States (California, Arizona, and Utah) and Northwestern Mexico (Baja California and Sonora). Jojoba oil became widely known through the Spanish missionaries of the 18th and 19th centuries. Native Americans used the crushed seed oil for skin care and medicinal purposes. The Spanish missionaries became aware of its uses and introduced it to other parts of the world. The plant has been cultivated for more than 30 years in many countries worldwide, such as India, Mexico, Chile, Argentina, Australia, Tunisia, the Palestinian territories, Saudi Arabia, and Egypt, due to its promising economic value [3], with the United States considered the largest jojoba oil-producing country, followed by Mexico. The jojoba oil has been reported previously as having potential capabilities for the cosmetics and skincare industry [68]. The oil extracted from Jojoba seeds is golden colored and odorless with relatively high viscosity which is much higher than petroleum fuels [69, 70]. It has wax-like unsaturated esters, consisting of a straight chain of fatty acids and higher alcohols. It has been stated severally that wax and not oils are extracted from Jojoba due to their peculiar nature [71, 72]. The main constituent of these FFA is gondoic acid (C20:1) with a concentration of 59.5%. Other components as reported by Shah and co-workers include oleic acid, erucic acid, and arachidonic acid with concentrations of 10.7%, 12.3%, and 9.1%, respectively [68].

15.2.5 Azadirachta indica Oil can be extracted from seed kernels of the Azadirachta indica (Neem tree). Depending on the source, neem seeds could have as low as 30% oil [73] or between 40% and 45% oil [74]. It has been found to have diverse

Biodiesel Production From Non-Edible Sources  399 applications. One of the main uses of neem seed oil (NSO) has been widely used as a pesticide due to the presence of Azadirachtin [75, 76]. Due to the presence of this compound and other similar ones, neem oil is toxic to humans. Children are especially more vulnerable to neem oil poisoning [77]. NSO has been reported to have high levels of FFA. Like Jatropha and other high FFA oils, this invariably requires a two-step pre-treatment during biodiesel synthesis [78]. This involves the use of an acid catalyst for esterification with methanol to reduce the FFA. This is then followed by transesterification with a base or acid catalyst to produce the required methyl ester. H2SO4 has been predominantly used to reduce FFA but solid catalysts are also being explored. Solid acid catalysts have the advantage of easy separation after reaction though activity at times may not be comparable to homogenous catalysts [13]. Recently, solid catalysts with improved activity are being reported. The use phosphoric mordenite was reported to result in a 92% reduction on neem oil FFA after just 60 minutes of reaction [73]. The performance of biodiesel from neem oil has been evaluated either as a blend or as a standalone fuel. It was reported that methyl esters from NSO blended with diesel gave better performance provided the concentration was below 20% [79]. Higher blends resulted in increased NOx emissions though engine performance was marginally better. Besides, catalytic converters are currently being employed to reduce emissions from neem oil derived diesel [80].

15.2.6 Rubber Seed Oil Rubber tree (Hevea brasiliensis) is one of the abundant natural resources found in humid tropical countries. Seed yield from rubber plantations varies from 100 to 150 kg/ha, depending on soil fertility and crop density. Extensive plantations can be found in Nigeria [81], Malaysia, India [82], Indonesia, Liberia [83], Thailand [84], and China [85]. As at 2009, plantations in Malaysia produced more than 1.2 million hectares producing roughly 1.2 million tons of seeds per year [86]. It is primarily grown for latex production as a source of foreign exchange, though its usefulness is not maximally explored. The tree produces oil-bearing seeds with oil content far more than that obtainable from the likes of Jatropha and Karanja seeds. Yields of kernel from rubber seeds range from 57% to 63% [87]. This leads to yield about 5,500 tons of rubber seed oil and about 6,000 tons of defatted protein meal for animal and human consumption [81].

13.37

15.6

Jatropha Oil

mango seed

pentandra

Ceiba

maackii

Euonymus

grounds

seed

Spent coffee

22.37

14.5

32.4

26.4

Yellow

oleander

18.1

Neem seed oil

oil

1.3

9.1

3.8

3.1

7.5

3.86

18.1

30.2

6.1

1.2

5.6

23.24

49.8

10.1

39.4

44.5

48.2

41.71

3.6

24

(18:1)

(C18:0)

(C16:0)

Castor oil

oil

Rubber seed

acid

acid

acid

Oleic

Stearic

Palmitic

33.63

29.3

43.1

27.03

18.3

6.9

36.42

4.6

46.2

(C18:2)

acid

Linoleic

0.9

0.2

–

0.4

14.2

(C18:3)

acid

Linolenic

9.14

–

–

–

–

–

–

–

–

acid

Malvalic

Table 15.3  Comparison of FFA composition of selected non-edible oils.

–

–

–

–

–

88.9

0.9

Ricinoleic

0.07

3.1

1.1

0.8

–

Arachidic

2

0.82

(C16:1)

Palmitoleic (C12:0)

Lauric (C14:0)

acid

Myristic

(Continued)

[99]

[98]

[97]

[96]

[95]

[94]

93]

[92,

91]

[21,

[84]

Ref.

400  Biodiesel Technology and Applications

Tobacco

Karanja

odollam

Cerbera

armeniaca

Prunus

Mesua Ferrea

oil

speciose

Attalea

24.86

3.31

13.63

5.79

1.625

13.65

52.82

71.76

50.71

16.1

(18:1)

(C18:0)

(C16:0)

8.5

acid

acid

acid

Oleic

Stearic

Palmitic

13.65

20.19

19.47

(C18:2)

acid

Linoleic

1.03

0.316

1.4

(C18:3)

acid

Linolenic acid

Malvalic Ricinoleic

1.3

Arachidic

Table 15.3  Comparison of FFA composition of selected non-edible oils. (Continued)

0.75

0.087

(C16:1)

Palmitoleic 44.0

(C12:0)

Lauric

15.4

(C14:0)

acid

Myristic

[102]

[30]

[101]

[100]

Ref.

Biodiesel Production From Non-Edible Sources  401

402  Biodiesel Technology and Applications The extracted oil from rubber seed is non-edible and rich in unsaturated FFA(roughly 80%) [88], and this is a property essential to making it a prominent raw material for biodiesel production [89]. This, in turn, gives more economic value to growth of rubber plantations. It becomes imperative to obtain specific data for sample of rubber seed oil from a particular area because there is a range of variation in the physicochemical parameters of the oil due to environmental factors such as rain-fall, soil fertility, agronomic practices, maturation period, and genetic substitution [89, 90]. For biodiesel production, the foremost characterization to consider is the FFA composition and value of the oil. A freshly extracted rubber seed oil (RSO) has a total acid value of about 47% [90]; this implies FFA of 23.5% comprising of the saturated and unsaturated acids. The fatty acid composition of RSO along with other oils is captured in Table 15.3. Saturated fatty acids are responsible for higher cloud point, cetane number, and general stability of the oil and diesel synthesized from it [103]. As with other non-edible oils the high FFA of RSO requires that it under goes acid esterification before transesterification to FAME. This is a problem that is encountered even when utilizing continuous flow setup invariably making a system as proposed by Sai and coworkers a semi batch process [104]. Some authors have proposed the use of co-solvents during transesterification as a way of getting higher ester yield at with relatively milder transesterification conditions. One such report indicates that using acetonitrile as co-solvent, 99% ester yield was obtained at 40°C after 30 minutes of reaction [105].

15.2.7 Ricinus communis as Feedstock (Castor Oil) The castor plant, which has numerous varieties, bears seeds that contain between 40% and 55% oil. Castor oil has a relatively low cost but it is of immense value as it can be utilized in a number of different applications. It is utilized in production of pharmaceuticals [106], paints [107], polymers [91], and for fuel production [108]. As of 2015, the estimated average castor oil seed worldwide was put down as 1.1 tons ha−1 [21]. This value is expected to grow exponentially. It is said that the plant is able to thrive under harsh conditions. It is believed to originate from either Africa or Asia. Castor oil is inedible and is composed of mostly ricinoleic acid, between 80% and 90% [108] depending on location and variety of the seeds from which the oil is extracted. It has a yellow-green hue and the biodiesel from castor oil is viscous and is usually blended with fossil fuel derived diesel. Castor oil is rather peculiar in the sense that it possesses high

Biodiesel Production From Non-Edible Sources  403 OH 18

16 17

O

14 15

10 13

12

9

11

OH

5

7 8

6

3 4

2

1

O

O O

OH

O O

Figure 15.2  Chemical structure of riconelic acid, major component of castor oil [106].

concentration of riconelic acid which has an OH group as seen in the structure in Figure 15.2. As a result of riconoleic acid, castor oil is highly viscous and the biodiesel produced from it also has high viscosity. Nevertheless, blending with fossil derived diesels and others with very low viscosity usually results in overall improved characteristics [109]. Biodiesel from castor oil has been heavily researched over last two decades [108–114]. Recent focus has however been geared towards process optimization, intensification and the development of more efficient catalysts. One such development is the one-step transesterification process which has been proposed with varying degrees of success. The use of sulphonated phenyl silane montmorillonite catalyst was reported to have 89% conversion of castor oil to FAME after 300-minute reaction time [66]. Moradi and Ghanadi [113] evaluated the feasibility of producing biodiesel directly from castor seed in a one-step route. Their model developed using centre composite design predicted a 91% FAME yield.

15.2.8 Other Non-Edible Oils Oils from plants such as Thevetia peruviana have also been explored as a potential biodiesel feedstock. The plant is highly toxic in nature [115] and is commonly known as yellow oleander or milk bush. However, the seeds can also be used to treat cardiac problems, skin issues, and asthma [96]. The oil content of the seeds ranges from 60% to 65% and can grow in a variety of arid areas [116] where it is usually used for decorations. Interestingly, a yield of 96 wt% biodiesel has been reported by Deka and Basumatary [116] after

404  Biodiesel Technology and Applications reaction for 3 hours at room temperature. The duo carbonized the trunk of Musa balbisana plant and used it as catalyst for transesterification with methanol. Other groups who have used the same plant report 90 wt% yield after 75 minutes at 70°C using 2.8 (w/v)% of CaO as catalyst [96]. The efficacy of spent coffee grounds (SCG) as potential biodiesel feedstock has also been investigated. The drawback with this feedstock is the high moisture content which the spent grounds possess as a result of brewing. In addition to this, they also are characterized by high FFA content ranging between 21 and 38 w/w % [97]. Some other authors have proposed in situ transesterification of the seeds as a way of improving process economics of production from SCG [117]. Also, Silybum marianum L., a wild plant native to Iraq, Iran, Syria, and some parts of China on the Asian continent, produces seeds which have oil content of between 23% and 45% depending on the variety. Esterification of high FFA oil from S. Marianum using a sulfonated acid carbon catalyst resulted in low FFA oil [118]. They utilized 6% w/w of the carbon acid catalyst, 68°C reaction temperature, and 15:1 methanol-to-oil ratio with a reaction time of 180 minutes resulted in FFA reduction of over 90% from an initial value of 20.0 mg KOH/g. Transesterification with KOH at 60°C gave ester yield of 96.69% after 75 minutes of reaction. Table 15.4 contains physico-chemical properties of different oils. There are so many other plants which have not been discussed in this list. In different regions of the world, scientists are investigating different oils to see which contain the appropriate esters and which have high oil concentration [119]. These factors greatly affect the economics of the biodiesel synthesis process and are key to ensuring reduced dependence on fossil derived diesels.

15.3 Waste Animal Fats Animal fats (tallow) have also been considered as potential biodiesel sources. There are challenges when dealing with this feedstock which result in necessary pre-treatment steps before conversion to biodiesel. The major challenges include (1) high moisture content, (2) high FFA, and (3) fats that are solid at room temperature. Nevertheless, research is exploring ways to harness the tallow as an economically viable feedstock. Different animal fats have been investigated on. Some of which include duck [123], beef [124, 125], sheep [126], and chicken fats [127]. Similar to other high FFA feedstock, esterification with methanol in the presence of an acid such as H2SO4 is a method that has been explored but

Biodiesel Production From Non-Edible Sources  405 not as extensively as with vegetable oils. However, water content should be less than 0.1 wt% before the reaction is carried out as water hampers the reaction. Laboratory scale studies have been successfully carried out using microwaves to shorten the esterification time [128]. The cost of utilizing microwaves at an industrial scale may lead to increased price of biodiesel due to larger energy requirements.

15.4 Expired and Waste Cooking Oils Vegetable oils after being used for extensive frying are classified as inedible. The oils have been said to degrade, due to harmful compounds which are produced during frying. Initially, the oils were sold as feed to the animal industry which has now been banned by the European commission in 2002 [129]. This is to forestall consumption of these chemicals which could contaminate the meat of animals which consumed. Generally, waste cooking oils (WCO) are generated in bulk by households, hotels, and the food industry. To illustrate this, in 2015, 69% of the 77,000 tons of WCO generated in Portugal came from hotels and food catering services, while domestic use accounted for 25% [130]. The use of expired and waste vegetable oils as feedstock for biodiesel is timely as these oils are usually discarded into sewage systems which invariably become a problem for wastewater treatment plants [131]. To this end, many developed countries have established laws prohibiting and penalizing disposal of WCO during sewage systems [132]. Consequently, utilizing WCOs in biodiesel production reduces pollution and gives them added value. The potential for waste cooking oil (WCO) biodiesel is much higher in European and American countries where copious amounts of WCOs are generated [133]. The source of WCO may not particularly have an effect on the final biodiesel produced. Studies have shown that properties such as acid value and density may have appreciable effect on the biodiesel synthesis process [134]. Therefore, to obtain higher acid value oils a two-stage reaction process is required: first is esterification and then followed by transesterification. Some authors have also suggested that FAME yields with WCOs are marginally lower due to some of these compounds formed as oils degrade while cooking/frying [11]. Purification of WCO before use in biodiesel synthesis presents a challenge in some situations. Food debris and water often pose problems as contaminants, which could have adverse effects in the synthesis process. Filtration or gravity settling may be employed to remove debris that may accompany the WCO.

406  Biodiesel Technology and Applications Also, the level of saturation of the WCO used is apposite. Although degradation is certain, it is not possible to predict the exact level of degradation that will take place. Generally, degradation of the oil while cooking results in the oils becoming more saturated due to FFA. As a result, FFA content of most WCO typically ranges between 2% and 10% [135] which has a negative effect on the viscosity of the final biodiesel [135]. For bench scale synthesis, this can be overlooked. It, however, is a major challenge in plant design, as a flexible system which can cater for oils with a wide range of FFA would be required.

15.5 Algae/Microalgae Harnessing algae for biofuels production is gaining widespread attention. Initially, algae were used for just lipid and protein production. But, it was since discovered that a good portion of the lipids were suitable for production of biodiesel. Fuel applications exploiting algal components include transesterification of lipids to biodiesel, saccharification of carbohydrates to ethanol, gasification of biomass to syngas, cracking of hydrocarbons to gasoline, and biosynthesis of hydrogen gas [136]. This is due to the expanding use of fossil fuels, increasing CO2 emission into the atmosphere, and consequently contributing to climate change. With depleting fossil fuel reservoirs coupled with global clampdown on greenhouse gases spur the motivation for the development of renewable energy sources such as algae/ microalgae [136]. Algae require carbon dioxide, sun light, and water for growth in non-arable land, arid land, and in waste water. They grow very fast in a short period, producing as much as double their mass in few hours. The lipid content of algae is higher than that of seed plants, producing not less than 30 times more oil per acre than seed plants [137]. Algae can be subdivided into microalgae and macroalgae; either of them has different metabolic behaviors during their growth. These include (1) autotrophic behavior where algae make use of light solely as a source of energy where the light energy is converted to chemical energy using CO2 via photosynthesis; (2) mixotrophic behavior allows algae to perform photosynthesis using both organic compound and CO2 in the presence of light energy for growth; (3) heterotrophic behavior where algae utilize only organic compounds as energy and carbon source; and (4) photoheterotrophic behavior makes algae use light as well as organic compounds as carbon source [136, 138]. They can change the metabolic pathway according to the changes in the environmental conditions. The ability of algae to fix CO2 is a method

Biodiesel Production From Non-Edible Sources  407 of removing CO2 from flue gases of power plants, thereby reducing emissions of greenhouse gases [9]. Photoautotrophic means of algae cultivation is recommended for when growing algae for biodiesel production. This ensures cost reduction and CO2 sequestration [139]. Figure 15.3 shows the pathways of biodiesel production from microalgae and by products of the production process. Large scale growth of algae is conducted either in open ponds or photobioreactors [140]. The photobioreactors reportedly have higher algae yield as cultivation conditions can be controlled to maximize production. It has been established that oil yields from microalgae can be as much as 31 to 72 times that obtainable from Jatropha [30]. The bottleneck in biodiesel production from algae is to identify the strains with high oil productivity and to develop cost-effective growing and harvesting systems [141]. There is a disagreement on exact quantity of algae strains that have been identified in the world today. There are possibly between 44,000 and 100,000 different algae strains depending on the source of the information [140, 142].

Harvest & Drying Lipid extraction

CO2 + Nutrients

Biodiesel

Animal feeding

Cosmetics

Glycerol

Figure 15.3  Microalgal biodiesel refinery producing multiple products from algal biomass [136].

Habitat

Fresh Water

Fresh Water

Fresh Water

Fresh Water

Fresh Water

Fresh Water

Fresh Water

Marine water

Fresh water

Strain

Chlorella vulgaris

Chlorella vulgaris

Chlorella vulgaris

Chlorella pyrenoidosa

Chlorella vulgaris

S. obliquus (YSL02)

Spirulina sp

Aurantiochytrium sp. (KRS101)

Chlamydomonasreinhardtii na

Defined medium

Zarrouk’s medium

Bold’s basal medium

Bold’s basal medium

Bold’s basal medium

Modified basal Medium

Soy Whey

Thin Stillage

Nutrients

2

6.69

1.37

1.84

1.65

0.106

2

1.6

2.5

Biomass production (g/L/day)

Table 15.4  Some selected algae strains and their production data.

na

31.8

na

na

na

na

8

6.3

9.8

Biomass yield (g/L)

0.505

Na

0.66

0.53

0.44

0.019

0.6

0.2

1.1

Lipid production (g/L/day)

25.25

38.1

20

29

26

29.68

27

11

43

Total Lipid extracted (wt% of biomass)

[150]

[149]

[148]

[147]

[147]

[146]

[145]

[145]

[145]

Ref.

408  Biodiesel Technology and Applications

protothecoides)

(Chlorella

From microalgae

dimorphus)

(Scenedesmus

From microalgae

tricornutum)

(Phaeodactylum

From microalgae

oculata)

(Nannochloropsis

From microalgae

protothecoides)

(Chlorella

From microalgae

NA

na

na

NA

–0.99

–4.6

7.8

–4.8

–13

(°C)

KOH/g)

0.29

plugging

Cold filter

(mg

Acid value

NA

0.91

0.89

0.88

0.88

m3)

(kg/

15°C

Density

4.63

3.74

4.2

4.43

5.6

NA

95.7

54.57

32.9

47.3

55

NA

(h)

4.52

110°C

(mm2/s)

g)

stability

40°C

(g I2/100

Oxidation

viscosity

Kinematic

value

Iodine

Table 15.5  Some properties of biodiesel synthesizes from microalgae.

Saponification

point

Cloud point

Pour

[153]

[152]

[152]

[152]

[151]

Ref.

(Continued)

number

Cetane

Biodiesel Production From Non-Edible Sources  409

1.69

Micractinium sp.

0.873

0.875

–9.66

Chlorella sorokiniana

0.9

m3)

0.83

NA

4.6

2.58

3.55

(°C)

KOH/g)

(kg/

15°C

Density

spirulina

vulgaris)

(Chlorella

From microalgae

vulgaris)

(Chlorella

From microalgae

(Chlorella salina)

From microalgae

emersonii)

(Chlorella

From microalgae

plugging

Cold filter

(mg

Acid value

28.33

48.411

88.5

5.07

4.9

2.9

4.5

(h)

7.4

44

49.93

54.24

110°C

(mm2/s)

g)

stability

40°C

(g I2/100

Oxidation

viscosity

Kinematic

value

Iodine

Table 15.5  Some properties of biodiesel synthesizes from microalgae. (Continued)

233.71

Saponification

17.19

13.58

9.2

point

Cloud

3.1

point

Pour

61.48

59.68

44.55

50

number

Cetane

[156]

[156]

[155]

[154]

[153]

[153]

[153]

Ref.

410  Biodiesel Technology and Applications

Biodiesel Production From Non-Edible Sources  411 The oil content of each algae strain varies with Colonial, Capsoid, Coccoid, Palmelloid, Filamentous, and Parenchymatou as some of the various forms of algae. Chlorella zofingiensis, Chlorella protothecoids, and Schizochytrium limacinum have been identified as strains with large oil production capacity [143]. Table 15.4 lists some strains with their growth per day and lipid content, and extensive lists can be found in literature [144]. Table 15.5 shows the properties of biodiesel synthesized from different algal strains.

15.6 Insects as Biodiesel Feedstock The use of insects as biodiesel feedstock is still a relatively virgin area of focus. They had hitherto been mainly considered as a source of protein for animal feed [157]. They have been identified as viable sources of fats for biodiesel production but there is a lot that is yet to be researched upon using this feedstock. Insects offer the advantage low cost of rearing, large insect yield, and relatively small space is required for cultivation [158]. Of which, methods of improving insect yields are constantly being developed [159]. As with other feedstock, there are criteria to be considered when selecting an insect as feed for biodiesel production. These include fat content usually of larva, speed of completion of insect life cycle, space requirements, and feeding costs. Detailed discussions on this can be studied in the review by Manzano-Agugliaro et al. [160]. At their larva stage, metabolic reserves for non-feeding periods are developed. These reserves are majorly composed of high quantities of fat, in addition to glycogen and proteins [160]. Insects which have shown high lipid content include Musca domestica, Hermetia illucens, and Rhynchophorus sp. with lipid contents of approximately 21%, 29%, and 43%, respectively [161]. Table 15.6 shows acid content of biodiesel produced from some larva, while Table 15.7 presents properties of some biodiesel synthesized from insects. The use of insect larva is also seen as a means of tackling environmental pollution. The larva can feed on residual food grease, animal waste, sewage sludge, and other such contaminants [162], effectively reducing cost of purchasing feed. This was demonstrated in the work of Zheng et al. [163] who were able to increase biodiesel yield and reduce food grease considerably by using it as feed for the larva. With regard to process economics, important factors to consider asides from oil content and cultivation of the larva include extraction temperature, solvent types, and quantity of solvent required. The use of microwaves has been studied and recommended as a means of increasing the rate of lipid extraction [158].

9.36

2.2

3

5.01

32.74

28.4

28.2

27.14

Zophobas morio

Musca domestica L. (grown on poultry manure)

Musca domestica L. (grown on kitchen waste)

Musca domestic (food waste and wheat bran)

0.2

18.9

Boettcherisca peregrine

5.1

18.2

Stearic acid (C18:0)

Hermetia illucens

Palmitic acid (C16:0)

24.54

22.9

24.1

29.43

44.5

27.1

Oleic acid

13.45

18.8

18.1

22.53

4.1

7.5

Linoleic acid (C18:2)

0.36

1.4

1.1

0.85

7.6

Linolenic acid (C18:3)

Table 15.6  Fatty oil composition of diesel derived from insect larva.

5.96

2.91

3.3

1.4

3.7

Myristic (C14:1)

17.4

20.6

20.1

2.16

18.3

9.4

Palmitoleic (C16:1)

1.21

23.4

Lauric (C12:0)

1.6

1.8

Capric (C10:0)

[167]

[166]

[166]

[165]

[164]

[163]

412  Biodiesel Technology and Applications

1.25

1.1

0.15

0.62

0.884

0.875

0.871

5

10

Acid value

Zophobas morio

50

62

% Cata

0.875

KOH

NaOH

Temperature

Density @ 15°C

Musca domestica L. (poultry manure)

Boettcherisca peregrine

Hermetia illucens

Catalyst

MeOHtooil ratio

159

166

130

143

Flash point

Table 15.7  Fuel properties of biodiesels synthesized from insect larva.