Waste and Biodiesel: Feedstocks and Precursors for Catalysts 0128239581, 9780128239582

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WASTE AND BIODIESEL

WASTE AND BIODIESEL Feedstocks and Precursors for Catalysts

Edited by

BHASKAR SINGH Department of Environmental Sciences, Central University of Jharkhand, Ranchi, India

ABHISHEK GULDHE Amity Institute of Biotechnology, Amity University Maharashtra, Mumbai, India

Elsevier Radarweg 29, PO Box 211, 1000 AE Amsterdam, Netherlands The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States Copyright © 2022 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. ISBN: 978-0-12-823958-2 For Information on all Elsevier publications visit our website at https://www.elsevier.com/books-and-journals Publisher: Charlotte Cockle Acquisitions Editor: Peter Adamson Editorial Project Manager: Aleksandra Packowska Production Project Manager: Sojan P. Pazhayattil Cover Designer: Victoria Pearson Esser Typeset by Aptara, New Delhi, India

Foreword The recently held climate conference (COP 26) at Glasgow, and the pledges taken by most participating countries to shift 100% to renewables as soon as possible, has once again highlighted the importance of renewable fuels, especially biodiesel. A very attractive feature of biodiesel is that its “neat” form (B100) can be blended to the extent of upto 20% with mineral diesel and the blend can be used to run existing engines with little or no modifications. But there are several challenges associated with the large-scale deployment of biodiesel. The raw materials needed for it — vegetable oils and animal fats — not only have strongly competitive uses as food, feed, and industrial raw materials but also need large areas of arable land and large volumes of irrigation quality water which both are becoming increasingly precious. These factors make biodiesel prohibitively costly as well. To get round these hurdles strong R & D thrusts are being made across the world to utilize waste materials as feedstocks in biodiesel generation. The present book is the result of the compilation, collation, and syntheses of all existing knowledge in this exceedingly important area of energy technology.In the first five chapters the entire gamut of biodiesel production from different forms of waste has been covered, encompassing waste animal fats, municipal waste lipids, microalgae, fungi, bacteria, and yeast. In the next four chapters, the roles of all possible waste-derived catalysts have been documented in speeding up and enhancing of biodiesel generation. The penultimate chapter expresses the state-of-the-art of the integration of flue gas biomitigation with biodiesel production. The concluding chapter addresses the crucial, but rarely covered, aspect of the environmental impacts associated with biodiesel and the legal limits prescribed in that context. The editors Dr. Bhaskar Singh and Dr. Abhishek Guldhe have both had a highly meritorious research career, distinguished by their copious output of sustained excellence. With close to 10,000 citations between them, the writer duo is now among the foremost scientists in this field. Their wealth of expertise is reflected in the meticulous planning of the book, selection of the most appropriate of the contributions, and ensuring that all chapters meet the highest standards of comprehensiveness, cogency, and clarity. I am sure this book will blaze a trial. Kudos to Elsevier for undertaking this project at the right time and to the author for their impeccable transcreation of the concept into reality. S. A. Abbasi INSA Emeritus Professor Pondicherry University India https://vidwan.inflibnet.ac.in/profile/61966 xiii

Preface

Biodiesel has emerged as a promising alternative renewable fuel. Several feedstocks and processing techniques have been studied and developed by researchers across the globe. Despite the sustainability and environmental benefits attributed to biodiesel, a high production cost is the major bottleneck for commercialization of biodiesel. The major contributors towards the production cost are feedstock procurement, oil extraction and oil to biodiesel conversion process. Researchers and policy makers of nations worldwide have recently advocated towards incorporate waste materials in the biodiesel production process to reduce the production cost. Waste materials can be used as feedstock or in other processing steps such as synthesis of catalysts for conversion of oil to biodiesel. In other approach, waste material can be used as resource to develop potential feedstock or catalysts. This book, Waste and Biodiesel: Feedstocks and Precursors for Catalysts aim to critically evaluate the emerging trends of utilizing waste in various stages of biodiesel production process. Chapters in the book include overview of waste utilization in biodiesel production process, critical evaluation of waste animal fats, municipal waste derived lipids and biowastes as biodiesel feedstock, biodiesel production from microalgae, oleaginous fungi, yeast and bacteria biomass produced by using waste substrates as nutrient medium. Chapters also include recent trends and advancements in synthesizing catalysts used for biodiesel production from waste derived from organic origin, such as waste shell, fish and animal waste, and inorganic materials. A chapter deals with whole cell enzyme catalyst for production of biodiesel. A chapter also discusses integration of flue gas mitigation in biodiesel production process. Integration of waste in biodiesel production process provides economical as well as environmental benefits and leads towards the sustainable production of biodiesel. Bhaskar Singh Abhishek Guldhe

xv

Contributors

Mai O. Abdelmigeed Chemical Engineering Department, Cairo University, Giza, Egypt Omar M. Abdeldayem Environmental Engineering Program, Zewail City of Science and Technology, Giza, Egypt Wiury C. Abreu Federal Institute of Maranhão, Buriticupu, MA, Brazil Adewale Adewuyi Department of Chemical Sciences, Faculty of Natural Sciences, Redeemer’s University, EDE, Osun State, Nigeria Shahrukh N. Alam Department of Environmental Sciences, Central University of Jharkhand, Ranchi, India T.C Aniokete Department of Chemical Engineering, Faculty of Engineering, Enugu State University of Science and Technology, Enugu, Nigeria Naveen K. Arora Department of Environmental Sciences, Babashaheb Bhimrao Ambedkar University, Lucknow, India Eslam G. Al-Sakkari Chemical Engineering Department, Cairo University, Giza, Egypt Rifat Azam Department of Environmental Sciences, Babashaheb Bhimrao Ambedkar University, Lucknow, India Rachael J Barla Department of Chemical Engineering, Birla Institute of Technology and Science (BITS) Pilani, Rajasthan, India Deovrat N. Begde Department of Biochemistry & Biotechnology, Dr. Ambedkar College, Deekshabhoomi, Nagpur, Maharashtra, India Daria C. Boffito Chemical Engineering Department, Polytechnique Montreal, Montreal, Canada Jean C.S. Costa Federal University of Piaui, Teresina, PI, Brazil M.O. Daramola Department of Chemical Engineering, Faculty of Engineering, Built Environment and Information Technology, University of Pretoria, Pretoria, South Africa

ix

x

Contributors

Sumit H. Dhawane Department of Chemical Engineering, Maulana Azad National Institute of Technology, Bhopal, India Alaaeldin A. Elozeiri Environmental Engineering Program, Zewail City of Science and Technology, Giza, Egypt Ayodeji J Fatehinse Department of Chemical Sciences, Faculty of Natural Sciences, Redeemer’s University, EDE, Osun State, Nigeria Kajol Goria Department of Environmental Sciences, Central University of Jammu, Jammu, Jammu and Kashmir, India Abhishek Guldhe Amity Institute of Biotechnology, Amity University Maharashtra, Mumbai, India Suresh Gupta Department of Chemical Engineering, Birla Institute of Technology and Science (BITS) Pilani, Rajasthan, India Zaira Khalid Department of Environmental Sciences, Central University of Jharkhand, Ranchi, India Richa Kothari Department of Environmental Sciences, Central University of Jammu, Jammu, Jammu and Kashmir, India Blaz Likozar Department of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry, Ljubljana, Slovenia Khushal Mehta Department of Biology, SRM University-AP, Andhra Pradesh, India Carla V.R. Moura Federal University of Piaui, Teresina, PI, Brazil Edmilson M. Moura Federal University of Piaui, Teresina, PI, Brazil Marwa M. Naeem Chemical Engineering Department, British University in Egypt, Cairo, Egypt Mahmoud Nasr Environmental Engineering Department, Egypt-Japan University of Science and Technology (E-JUST), P.O. Box 179, New Borg El-Arab City, Alexandria 21934, Egypt; Sanitary Engineering Department, Faculty of Engineering, Alexandria University, P.O. Box 21544, Alexandria 21526, Egypt Imran Pancha Department of Biology, SRM University-AP, Andhra Pradesh, India Smita Raghuvanshi Department of Chemical Engineering, Birla Institute of Technology and Science (BITS) Pilani, Rajasthan, India

Contributors

Shubham Raina Department of Environmental Sciences, Central University of Jammu, Jammu, Jammu and Kashmir, India O.O Sadare Department of Chemical Engineering, Faculty of Engineering, Built Environment and Information Technology, University of Pretoria, Pretoria, South Africa Anjali Singh Institute of Microbiology, Algatech Centrum, Czech Academy of Science, Trebon, Czech Republic Bhaskar Singh Department of Environmental Sciences, Central University of Jharkhand, Ranchi, India Har Mohan Singh School of Energy Management, Shri Mata Vaishno Devi University, Jammu, Jammu and Kashmir, India Poonam Singh Institute of Plant Molecular Biology, Biology Centre, Czech Academy of Science, Czech Republic Kiran Toppo CSIR-National Botanical Research Institute, Lucknow, Uttar Pradesh, India V.V. Tyagi School of Energy Management, Shri Mata Vaishno Devi University, Jammu, Jammu and Kashmir, India

xi

CONTENTS

Contributors

ix

Foreword Preface

xiii xv

Acknowledgments

xvii

1. Biodiesel and an overview of waste utilization at the various production stages

1

Shahrukh N. Alam, Zaira Khalid, Abhishek Guldhe and Bhaskar Singh 1.1 Introduction 1.2 Biodiesel production process 1.3 Integration of waste into biodiesel production process 1.4 Waste material as feedstock 1.5 Feedstocks generated using waste material 1.6 Challenges and future prospects References

2. Prospects of biodiesel production from waste animal fats

1 2 3 4 9 11 11

17

T.C Aniokete, O.O Sadare and M.O. Daramola 2.1 2.2 2.3 2.4 2.5

Introduction Biodiesel production from waste animal fats Transesterification of waste animal fat to biodiesel Technoeconomic feasibility of biodiesel production from waste animal fats Challenges/recent studies for large-scale production of biodiesel from waste animal fats via transesterification Conclusions and outlook References

3. Efficacy of municipal waste derived lipids in production of biodiesel

17 21 32 38 38 39 40

45

Mahmoud Nasr 3.1 Introduction 3.2 Overview of lipids/biodiesel production from municipal solid waste reported in literature 3.3 Types of municipal solid waste available for biodiesel production 3.4 Waste-to-energy conversion techniques Conclusions Acknowledgements References

45 47 51 54 55 55 55 v

vi

Contents

4. Wastewater grown microalgae feedstock for biodiesel production

59

Poonam Singh, Imran Pancha, Anjali Singh, Khushal Mehta and Kiran Toppo 4.1 Introduction 4.2 Assimilation mechanism of nutrients by microalgae 4.3 Feasibility and potential of wastewater based microalgal cultivation 4.4 Challenges for biodiesel production 4.5 Biorefinery approach for biodiesel production from wastewater grown microalgae Conclusion References

5. Biodiesel from oleaginous fungi, bacteria, and yeast produced using waste substrates

59 60 61 63 66 69 69

73

Har Mohan Singh, Kajol Goria, Shubham Raina, Rifat Azam, Richa Kothari, Naveen K. Arora and V.V. Tyagi 5.1 Introduction 5.2 Oleaginous microorganisms 5.3 Technologies involved in biodiesel 5.4 Challenges and perspectives Conclusion References

6. CaO derived from waste shell materials as catalysts in synthesis of biodiesel

73 74 80 83 86 86

91

Carla V.R. Moura, Wiury C. Abreu, Edmilson M. Moura and Jean C.S. Costa 6.1 Introduction 6.2 CaO derived from plant residues 6.3 CaO derived from animal waste 6.4 CaO derived from mineral waste Conclusion References

7. Fish and animal waste as catalysts for biodiesel synthesis

91 92 102 106 113 113

119

Eslam G. Al-Sakkari, Alaaeldin A. Elozeiri, Omar M. Abdeldayem, Blaz Likozar and Daria C. Bofitto 7.1 7.2 7.3 7.4 7.5 7.6 7.7

Introduction Sources of fish and animal waste-based catalyst Preparation of fish and animal waste-based catalyst Transesterification kinetics over waste-derived heterogeneous catalysts Current status of fish and animal waste-based catalyst Remarks on process feasibility and greenness Scaling-up: opportunities and limitations

119 120 121 124 126 130 131

Contents

Conclusions References

8. Inorganic wastes as heterogeneous catalysts for biodiesel production

131 132

137

Eslam G. Al-Sakkari, Mai O. Abdelmigeed, Marwa M. Naeem and Sumit H. Dhawane 8.1 Introduction 8.2 Inorganic wastes Conclusions and future perspectives References

9. Whole cell enzyme catalyst production using waste substrate for application in production of biodiesel

137 144 156 156

163

Deovrat N. Begde 9.1 9.2 9.3 9.4 9.5

Introduction Transesterification - conventional and emergent strategies Whole-cell biocatalysts - advantages and limitations Organisms as whole-cell biocatalyst Industrial waste as potential feedstock/nutrient medium for whole-cell enzyme catalysts production 9.6 Other potential sources for whole-cell biocatalyst production 9.7 Stabilization and optimization of whole-cell biocatalyst for biodiesel production 9.8 Genetic and metabolic engineering of whole-cell biocatalyst for biodiesel production Concluding remarks and future prospects References

10. Process integration for the biodiesel production from biomitigation of flue gases

163 164 165 167 172 177 177 178 179 180

191

Rachael J Barla, Smita Raghuvanshi and Suresh Gupta 10.1 Introduction 10.2 Flue gas mitigation by microbial species 10.3 Process intensification study for biodiesel production Conclusion and future prospects References

11. Bio-waste as an alternative feedstock for biodiesel production: Current status and legal environmental impacts

191 193 200 209 209

215

Adewale Adewuyi and Ayodeji J Fatehinse 11.1 Introduction Reference Index

215 241 247

vii

Acknowledgments

At the outset, I thank the Almighty for the opportunity I got to edit the book. I thank Dr.Aleksandra Packowska,Editorial Project Manager and the entire team of Elsevier who have been very supportive from the beginning till the end of the edition of book. It was a pleasure working with them. I acknowledge and thank all the authors who contributed their work in the book. The authors submitted the work very timely even in the period of difficult time due to the prevailing pandemic. I am very grateful to Dr. Abhishek Guldhe which whom I coedited the book. It has indeed been an enriching experience working with Dr. Abhishek with whom I have several current and previous collaborations in research. I am grateful to Prof. Manoj Kumar, Head, Dept. of Environmental Sciences for supporting and motivating us toward academic and research. I am thankful to my departmental colleagues (Dr. Purabi Saikia, Dr. Kuldeep Bauddh, and Dr. Nirmali Bordoloi) at Central University of Jharkhand, Ranchi for their support and the laughter and cheerfulness they bring. I am thankful to my PhD scholars (Dr. Dipesh, Ms. Rupam, Ms. Sweta, Mr. Shahrukh, and Ms. Zaira) who got their thesis awarded and are presently under my supervision who work enormously hard and with team spirit and keep me inspiring with their thoughts and ideas. I would like to acknowledge the support and love of my parents (Shri Sachchida Nand Singh and Smt. Usha Kiran), my wife Ragini and other members of family. I acknowledge the love of my five years old daughter, Riyansika that rejuvenates me to work and sit for long hours. (Bhaskar Singh) I acknowledge and thank all the authors who contributed their expertise content to the book. I am also thankful to all the people who provided their valuable suggestion and coordination throughout the editing of the book. I am especially grateful to my coeditor Dr. Bhaskar Singh for his support, motivation, and constant encouragement. I am grateful to Prof. Faizal Bux, Durban University of Technology for his continual guidance and encouragement. I am thankful to my colleagues at Central University of Jharkhand, Ranchi and Amity University Maharashtra, Mumbai for their support. I would like to acknowledge Department of Biotechnology, Government of India for the award of prestigious Ramalingaswami Fellowship. I thank the team of Elsevier for their support, without the excellent work of this team it would not have been possible to publish this book. Finally, I would like to acknowledge the support and love of my family – my parents (Mr. Sanjay Guldhe and xvii

xviii

Acknowledgments

Mrs. Ratna Guldhe), My wife (Mrs. Tanushri Guldhe), my son (Shivraj Guldhe) and brother (Mr. Yash Guldhe). Their patience, encouragement, and affection inspired and kept me going through the publication journey of this book. (Abhishek Guldhe)

CHAPTER 1

Biodiesel and an overview of waste utilization at the various production stages Shahrukh N. Alam a, Zaira Khalid a, Abhishek Guldhe b and Bhaskar Singh a a

b

Department of Environmental Sciences, Central University of Jharkhand, Ranchi, India Amity Institute of Biotechnology, Amity University Maharashtra, Mumbai, India

1.1 Introduction Fossil fuel reserves throughout the world are declining at an exponential rate mainly attributed to population explosion. Above all, the extensive burning of fossil fuels for transportation, energy, industrial application creates negative environmental issues, such as global warming, continuous CO2 emission, and green house gas emission. Global energy consumption has already doubled between 1971 and 2001 and it is estimated that energy demand by 2030 is to be called for additional increase by 53%. Since, the fossil fuels are nonrenewable and as per British Petroleum’s (BP) annual report, 2013 it will get exhausted in around 50 years if the current pace continues. Consequently, sustainable fuel alternatives are becoming a high priority for many countries and are bound to play a major role in the fuel industry in the immediate future. Liquid biofuels are being advocated as one of the most sustainable alternatives to deal with ever-increasing demand and to tackle environmental concerns, including diminishing fossil fuel reserves and global warming. Biodiesel has been identified as one of the best alternative nonpetroleum based sustainable fuel consisting of alkyl esters derived from either the the esterification of free fatty acids (FFAs) or transesterification of triglycerides (TGs) or with short-chained alcohols. Production of biodiesel from biological renewable sources, such as vegetable oils, animal fats, waste oils and recently lignocellulosic materials are being reviewed widely. Many advantages of biodiesel over conventional petroleum diesel are: it has low emissions and hence safer, renewable, biodegradable, better lubricity, nontoxic, it contains no sulfur and biodegradable. Biodiesel is the only alternative fuel to complete the health effects test requirements of the Clean Air Act Amendments 1990. Currently, it is not among the popular alternative fuel globally mainly because of its higher cost when compared with conventional petroleum diesel. The major problem in the widespread commercialization of biodiesel is the availability of the feedstock, which makes the cost of production a bit high, thereby raising the overall price. However, the recent advancements in using the Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00005-7

c 2022 Elsevier Inc. Copyright  All rights reserved.

1

2

Waste and biodiesel

Figure 1.1 Transesterification reversible reaction.

cheap raw material instead of pricy refined vegetable oil and fat is showing promising results in making biodiesel more economical. This chapter addresses an overview of utilization of various waste materials, such as waste cooking oil, waste animal fats, agricultural wastes, waste coffee grounds, etc., and the challenges and other prospects of using these wastes material.

1.2 Biodiesel production process The direct use of any kind of vegetable oil or fat or its blend for the purpose of running an engine has been deemed impractical, mainly due to its characteristics like high viscosity, free fatty acid content and acid composition of such oils. These types of oils and fats also have the problem of gum formation because of polymerization and oxidation while storing and combusting. Additionally, thickening of unprocessed oil with time and deposition of carbon are two more issues which make it unfit for direct application (Fukuda et al., 2001). Keeping in view, the problems mentioned the oils and fats needs to undergo conversion processes to make or convert them into viable biodiesel form suitable for conventional diesel engine. Transesterification of vegetable oils or fats with alcohol (with one to eight carbon atoms) is the most widely adapted and preferred method for biodiesel production. Basically, there are two transesterification methods, one is performed with catalyst and the other is performed any without catalyst. The utilization and selection of type of catalyst is depended on type of the feedstock. Generally the use of catalysts improves the rate and yield of biodiesel and is preferred over the other depending on the feedstock being used for producing biodiesel. According to Otera (1993) transesterification reaction can be defined by three reversible reactions where excess alcohol shifts the whole equilibrium to the product side as depicted in Fig. 1.1. First step involves the reversible reaction of changing of triglycerides to diglycerides, then the second reaction is changing of diglycerides to monoglycerides, similarly followed by conversion of monoglycerides to glycerol. All the reactions yield one molecule of methyl ester per mole of glyceride at every step (Noureddini et al., 1998). Sometimes,

Biodiesel and an overview of waste utilization at the various production stages

Figure 1.2 Transesterification process depicting methanolysis of triglyceride.

esterification prior to the transesterification process is the most common method for reducing the feedstock’s free fatty acid (FFA) content. The complete reaction involved in transesterification process is: As depicted in Fig. 1.2, R1, R2, and R3 are long chains of hydrocarbons and carbon atoms called fatty acid chains, which may be same or different with CH3 and C2 H5 attached. The transesterification reaction is based on one mole of triglyceride reacting with three moles of methanol to produce three moles methyl ester (biodiesel) and one mole glycerol. Several kinds of alcohols can be incorporated in this reaction, such as ethanol, butanol, propanol, or methanol. However, methanol is most commonly used based on the lowcost, several physicochemical benefits (high polarity and shortest alcohol chain (Ma and Hanna, 1999). The transesterification reaction involves few important parameters which significantly impacts the final yield. Some of the most important variables are: reaction time, free fatty acid content in the oil, reaction temperature, water content in the oil, type and amount of catalyst, molar ratio of alcohol to oil, use of cosolvent and mixing intensity.

1.3 Integration of waste into biodiesel production process Current biodiesel industry mostly employs edible oilseed as feedstock and strong base and acid based homogenous catalyst mainly due to high conversion rates. However, high costs of these type of feedstocks, catalyst, and other expensive process, such as purification of final product or separation of catalyst makes the whole cost of biodiesel expensive and impractical (Santosa et al., 2019). In order to reduce the production cost, research involving the incorporation of waste materials in several biodiesel production stages is being favored. There are various advantages in utilizing or reusing the waste materials with disposal and recycle issues. Instead of just throwing away the waste materials where it may damage the environment, utilizing it in biodiesel solves multiple problems including

3

4

Waste and biodiesel

employment generation for a large number people in waste recovery and production stages. Waste materials have been incorporated in various biodiesel production stages viz. as feedstock for biodiesel production or using heterogeneous catalyst derived from several waste materials instead of homogenous catalyst. The heterogeneous catalyst have several economical and environmental advantages in addition to low production cost, such as it can be easily separated at the end of the biodiesel production processes by centrifugation or filtration and also they can be reused several times (Gotcht et al., 2009). These heterogeneous catalysts are much safer to handle, less corrosive, and more ecofriendly (Lam et al., 2010). Recent studies show several kinds of wastes ranging from lignocellulosic wastes, shell wastes, and others have been successfully used as catalyst for biodiesel production. Including various types of CaCO3 based wastes as catalyst, such as waste egg shell (Bharti et al., 2020), waste shell (Yuliana et al., 2020), waste fish scales (Chakraborty et al., 2011), waste animal bones (Farooq et al., 2015), waste coral fragment (Roschat et al., 2012), and others. Similarly various lignocellulosic biomass has also been investigated for low cost catalyst such as sugarcane baggase (Akinfalabi et al., 2020), rice husk ash (Hindryawati et al., 2014), bamboo (Zhou et al., 2016), palm shell (Baroutian et al., 2010), etc. Several wastes utilized as biodiesel feedstock like waste oil, animal fat, agricultural waste, municipal waste, lignocellulosic waste, etc., have been discussed in detail below.

1.4 Waste material as feedstock The increased energy demand, growing concern for the environment and the possible shortage of petroleum fuels in future have incentivized the research toward finding alternative sustainable fuel (Pagliano et al., 2017). Biodiesel has come forward as a promising alternative to petroleum fuel with similar physicochemical properties as diesel that can be used as its substitute in diesel engines without any need for modification (Mardhiah et al., 2017). Biodiesel is most commonly synthesized from oilseeds which strongly influence the global food security while increasing the price of edible oils thereby shifting the focus towards non-edible as well as waste cooking oil (Patil et al., 2011). The incorporation of municipal, domestic, and agroindustrial waste feedstock for biodiesel production makes the process sustainable and eco-friendly (Aboelazayem et al., 2018). 1.4.1 Waste oil Biodiesel are ethyl or methyl esters extracted from different feedstocks through the process of transesterification (Sharma et al., 2013). The availability of waste feedstock creates an attractive option of overcoming the energy crisis by conversion of these feedstocks to biofuel. Waste cooking oil (WCO) presents itself as a promising biofuel

Biodiesel and an overview of waste utilization at the various production stages

Table 1.1 Fame yield of waste cooking oil (WCO) under different catalysts. S. No.

Feedstock

Fame Yield (%)

Catalyst used

Reference

1. 2. 3. 4. 5. 6. 7. 8. 9.

WCO WCO WCO WCO WCO WCO WCO WCO WCO

79.7% 81.0% 83.08% 88% 90% 90% 91.7% 94% 97.8%

Sr/ZrO2 ZS/Si CaO/KI/ᵞ-Al2 O3 Lipase Novozyme 435 H2 SO4 KOH/Al2 O3 Purolite D5081 Acid-based catalyst

Omar and Amin, 2011 Jacobson et al., 2008 Asri et al., 2015 Saifuddin et al., 2009 Haigh et al., 2012 Wang et al., 2006 Noiroj et al., 2009 Haigh et al., 2012 Ouachab and Tsoutsos, 2013

feedstock since it is a waste that is readily available from household kitchens, restaurants, and cafeterias. The utilization of waste materials for biodiesel production will be helpful in mitigation of pollution.WCO which is generally disposed off as waste can be exploited as a feedstock making the whole process economical (Arshad et al., 2018; Tangy et al., 2016). The production of biodiesel from WCO is deemed to be cost effective, technically viable and environmentally benign (Farooq et al., 2013). It is estimated that United States of America, Japan, China, Europe, and Malaysia together accounts for 15 million tonnes of WCO generation per year on an average. India is one of the largest producers of WCO with an estimate of 9.2 million tons per annum (Bharti et al., 2020; Kolhe et al., 2017). Che et al., (2012) used olive pomace oil for the production of fatty acid methyl ester (FAME) via acid esterification process with sulfuric acid as catalyst. Reduction in free fatty acid (FFA) by 50% at low methanol to oil ratio while for high methanol to oil ratio over 80% reduction was observed. Furthermore, Ouachab and Tsoutsos (2013) also used olive pomace oil for the production of FAME through esterification process achieving a yield of 97.8% (Table 1.1). The process of transesterification has eliminated durability and operational problems while reducing the viscosity of vegetable oil. Biodiesel blend of WCO in performance characteristics are close to diesel fuel (Abed et al., 2018). Mohod et al. (2013) in their study compared B5 and B10 blends of WCO biodiesel with diesel fuel by using it in a single cylinder diesel engine. The biodiesel blend resulted in reduction of thermal efficiency by 2.8% and increase in specific fuel consumption by 4%. Muralidharan and Vasudevan (2011) tested four blends of diesel-WCO biodiesel; diesel fuel, B5, B20, and B30 in diesel engine and found higher fuel consumption load in biodiesel blends since heating value of biodiesel is lower when compared with diesel fuel. The WCO biodiesel fuel synthesized by transesterification process is similar to diesel fuel in its physical and chemical properties. The ongoing studies focus on the functioning of biodiesel blend of WCO with diesel fuel in the operation of diesel engine without any alteration in hardware (Abed et al., 2018).

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Waste and biodiesel

1.4.2 Waste animal fats Meat processing facilities produce animal fats as a by-product. Recently a lot of attention is paid on the economically sustainable feedstock, animal fat waste (AFW) being one of them (Habib et al., 2020). The animal fat derived from the meat processing facility mainly include white grease and lard from pork, tallows from cattle, poultry fat from turkey, chickens, ducks, and other birds. Oils and fats derived from leather industry waste and fish processing plants are also deemed to be a viable feedstock for biodiesel (Alptekin et al., 2012). Currently, animal fat for the most part is used as raw material in soap and cosmetics industries making the market demand for AFW very limited. AFW offers environmental, economic as well as food security benefit over the conventional edible vegetable oils when used as a feedstock for biodiesel. Additionally, the cost for transesterification of AFW i.e., $0.4-0.5/liter is cheaper than the transesterification cost of vegetable oil which is $0.6–0.8/liter (Bankovi´c-Ili´c et al., 2014). Some AFW, such as chicken, tallow, lard fats are already in use for biodiesel production at industrial scale (Bender, 1999; Schörken and Kempers, 2009). AFWs require complex techniques for biodiesel production since they contain high levels of free fatty acids (FFA) and saturated fatty acids which results in lower chemical and physical quality of biodiesel. Despite that, AFW’s low unsaturation of fatty acids has numerous advantages, such as high cetane number, high calorific value, and high oxidation stability (Alptekin et al., 2012). Since, AFW contains high quantity of FFA and water resulting in reduced yield of biodiesel as well as increased production cost, pretreatment is essential which alleviates the problem of separation and purification (Gebremariam and Marchetti, 2018). The production of biodiesel takes place through the process of transesterification which involves reaction of fat in the presence of a catalyst with short chain alcohol. There are many catalysts available for use in the production of biodiesel (Toldrá-Reig et al.,2020).Catalysts,such as potassium hydroxide, potassium amide, potassium methoxide, potassium hydride, sodium hydroxide, sodium amide, sodium methoxide, sodium hydride, sulfuric acid, phosphoric acid, hydrochloric acid, organic sulfonic acid, lipase, zirconias, silicates, and nanocatalysts, are some of the most widely used alkali, acidic, generous, and complex catalysts used in transesterification reaction (Ma and Hanna, 1999). The use of alkali catalyst in AFW transesterification results in a faster reaction rate (4000 times faster) in comparison with acid catalysts. The other benefit of using alkali catalysts is that it is readily available and less expensive. Various studies have been conducted using AFW for the production of biodiesel, few of which are mentioned in Table 1.2. 1.4.3 Agricultural waste Agricultural crop residues or agricultural wastes can be broadly classified into two types: 1. Field residues: Materials which are left in plantation areas or agricultural land after harvesting. Field residues generally include stalks, rice bran, stems, seed pods, etc.

Biodiesel and an overview of waste utilization at the various production stages

Table 1.2 Biodiesel production from different animal fat feedstock. Sl. No.

Feedstock

Catalyst

Yield (%)

Reference

1.

Chicken fat

H2 SO4 NaOMe Nano CaO AC/CuFe2 O4 encapsulated with CaO CaO/CuFe2 O4 Composite membrane & NaOMe KOH KOH KOH 35%CaO/zeolite Supercritical methanol Immobilized lipase from Candida antartica Lipase from Candida sp. Lipase from Candida antartica Lipase from Candida antartica KOH Immobilized lipase from Burkholderia cepacia Surfonated polystyrene KOH MgO-KOH H2 SO4

99.01 88.5 88.5 95.6

Bhatti et al., 2008 Alptekin and Canakci, 2010 Keihani et al., 2018 Seffati et al., 2019

94.5 98.1

Seffati et al., 2020 Shi et al., 2013

82.0 91.4 98.0 90.9 89.9 96.8

Chavan et al., 2017 Mata et al., 2014 He et al., 2020 Lawan et al., 2020 Shin et al., 2012 Adewale et al., 2016

87.4 74

Lu et al., 2007 Lee et al., 2002

97.2

Huang et al., 2010

90.8 89.7

Mata et al., 2014 Da Rós et al., 2010

75 95 98.00 93.2

Soldi et al., 2009 Moraes et al., 2008 Liu et al., 2007 Bhatti et al., 2008

2.

3.

4.

Lard

Beef tallow

Mutton tallow

2. Process residues: The leftover materials after the crop is processed to some usable resource are called process residues. These process residues may include husks, roots, bagasse, seeds, and deoiled cakes of edible and nonedible oil seeds. Of which corn stover, rice, and wheat stalks and mostly deoiled cakes of edible and nonedible oil seeds have been studied as potential feedstocks for producing biodiesel mainly because of the remaining oil content after processing in them. Global estimation shows that 38.5 million metric tons of rice bran from 482 million metric tons of rice is produced annually (Pattanaik et al., 2019). Roughly this rice bran contains around 17.5% oil and unrefined rice bran oil with 8% FFA content shows great potential for the production of biodiesel. Since the rice bran has high FFA content, it requires certain level of pretreatment. Kattimani et al., (2014) in their study showed biodiesel production in the range of 60%–80% after acid catalyzed esterification with sulfuric acid followed by

7

8

Waste and biodiesel

transesterification. Similarly, Zhang et al. (2013) conducted simultaneous esterification and transesterification reaction from rice bran oil with 40% FFA to obtain biodiesel yield of 92% using chlorosulfonic acid modified zirconia as catalyst. Whereas, Jitputti et al. (2006) performed transesterification of rice bran oil with solid acid catalyst and stated that solid acid catalyst can perform better than mineral acid mainly attributed to its reproducibility and heterogeneous characteristics. Deoiled cakes of edible and nonedible oil seeds like olive deoiled cake have recently gained much attention due to their potential for biodiesel production. The olive deoiled cake in average contains 19.75% oil content and hence has been used in two step processes to produce biodiesel. The olive deoiled cake primarily contains 24.5% FFA which needs esterification reaction to reduce the FFA content to around .52% followed by transesterification to yield biodiesel in the range if 40 to 65% (Al-Hamamre, 2011). 1.4.4 Wastewater as biodiesel feedstock Wastewater contains numerous microorganisms that exploit the inorganic and organic compounds present in the waste water for carbon, nutrients and energy (Dufreche et al., 2007). It is an obvious fact that the production of wastewater sludge is in large quantity. It has been reported that dry sludge obtained from the wastewater contains 5%–20% lipid w/w which is as good as plant seeds (Wang et al., 2016). It has been estimated that because of the use of sludge as a lipid source the biodiesel production cost will be reduces immensely since sludge is a free material. Since wastewater sludge is rich in nitrogen, phosphorus, and carbon, it can be used as a medium for cultivation of microorganisms. Microorganism such as Lipomyces starkeyi, Rhodosporium toruloides, and Trichosporon oleaginosus have been recognized for their capability of assimilating waste for production of lipid (Xavier et al., 2017). Dufreche et al., (2007) through in situ transesterification process found the yield of the dry sludge to be 6.23%. Sharma et al., (2020) investigated two microalgal consortia grown in sewage water and found the lipid content of one to be increased by 31.3% over the other as well as desirable fatty acids for the production of biodiesel were also observed. Arora et al., (2020) observed high microalgal biomass in wastewater as well as enhanced lipid content of about 31% dry cell weight. 1.4.5 Waste coffee ground residue Coffee is one of the most extensively consumed beverages throughout the world and has been since 1000 years. The consumption of coffee worldwide around 2015–1016 was more than 9 million tons according to the International Coffee Organization (ICO,2016). Coffea Arabica and Canephora/Robusta are two species of coffee with great economic importance (Blinová et al., 2017). Worldwide there are top ten producers of coffee beans, with Vietnam and Brazil being accountable for almost half of the total production

Biodiesel and an overview of waste utilization at the various production stages

(Dang and Nguyen, 2019). Spent coffee ground (SCG) is a waste residue that has gained interest as a potential biodiesel feedstock as well as a sustainable waste reduction. The extraction of coffee oil from defective coffee beans and coffee grounds was found to be cost effective as well as of high quality for biodiesel production. The SCG feedstock due to its high content of antioxidant exhibit higher stability is less expensive and pleasant smelling (Haile, 2014). The production of biodiesel from SCG involves collection of the coffee ground and its transportation, drying, extraction resulting in biodiesel production. The content of oil varies based on the coffee source from 11–20 wt%. The oil yield from defective coffee bean ranges from 10-12 wt% on the basis of dry weight while SCG produce 10–15 wt% (Al-Hamamre et al., 2012).

1.5 Feedstocks generated using waste material Utilization of waste material for the production of microbial lipids for the biodiesel synthesis, such as nutrient-rich wastewater, can provide low cost medium for the production of valuable feedstocks. Microbial lipids produced in wastewater also helps in removal of excess nutrients (such as phosphorus and nitrogen), avoiding disposal of wastewater into water bodies because phosphorus and nitrogen cause eutrophication of rivers and lakes thereby also helping in protecting environment. 1.5.1 Microalgae cultivation using wastewater Currently, microalgae is considered one of the promising alternate feedstock for producing biodiesel mainly due to rapid growth rate, high lipid concentration and high GHG fixing capacity (Alam et al., 2012). Cultivation of microalgae requires large amount of nutrition which makes it a fairly energy extensive and expensive process and therefore researchers are studying various methods to reduce the production cost. One of the most prominent being microalgae cultivation using wastewater which incorporates production of microalgae and removal of nutrients from wastewater simultaneously. This method serves multiple purpose of saving large amount of water requirement for microalgae cultivation and nutrients from going to waste by converting the nutrient available in wastewater (particularly nitrogen and phosphate) into microalgal biomass thereby sequestering large amount of carbon dioxide as well (de la Noüe et al., 1992). Most of the microalgae species have the ability to grow fairly well under nutrient rich wastewater by absorbing the nutrient and metal from the wastewater. Several species of green microalgae have been used in existing wastewater treatment ponds for treating the wastewaters of industrial, agricultural, and municipal sources making them an appealing means of lowcost and sustainable wastewater treatment alternative. Therefore, the green microalgae are considered as ideally suited for dual role of biomass production and phytoremediation by converting nutrients present in wastewater to carbohydrate and lipids (Rawat et al., 2011).

9

10

Waste and biodiesel

Table 1.3 Biomass productivity of microalgae cultivated in different types of wastewater. Sr. No.

Microalgae specie

Wastewater type

1.

Chlorella vulgaris

2.

Scenedesmus sp.

3.

Chlorella vulgaris

4.

Chlorella vulgaris

5. 6. 7.

Gonium sp. Scenedesmus obliquus Chlorella pyrenoidosa

8.

C. pyrenoidosa

Aquaculture wastewater Industrial wastewater Poultry litter wastewater Municipal wastewater Textile effluent Urban wastewater Piggery wastewater Soybean processing wastewater

Biomass productivity/day

Reference

42.6 mg L-1

Gao et al., 2016

900 mg L-1

Jebali et al., 2015

127 mg L-1

Markou, 2015

0.251 g L-1

Gao et al., 2014

0.53 g L-1 380 mg L-1 0.3 g L-1

Boduro˘glu et al., 2014 Ruiz et al., 2013 Wang et al., 2012

1070 mg L-1

Hongyang et al., 2011

Several kinds of wastewater which has been investigated for the production of microalgal biomass are depicted in Table 1.3. 1.5.2 Oleaginous fungi grown using wastewater Some filamentous fungi have the potential to accumulate high content of lipids for the production of biofuels are called oleaginous fungi. Examples of some oleaginous fungi include Mucor circinelloides (Song et al., 2001), Cunninghamella echinulate (Fakas et al., 2009), Mortierella alpina (Wang et al., 2011), Umbelopsis isabellina (Harde et al., 2016), etc. These oleaginous fungi species are currently attracting much attention mainly because of high concentration of long-chain polyunsaturated fatty acids (PUFAs). Different kinds of wastewaters have been incorporated by several researchers for the production of oleaginous fungi advantage being utilization of waste as nutrient source for growing the feedstock. Such as Muniraj et al., (2015) showed that potato processing wastewater can be effectively used for the cultivation of two oleaginous fungi namely Aspergillus flavus and Mucor rouxii with high lipid content. Similarly, Muniraj et al., (2013) also used potato processing wastewater for the production of microbial lipid using filamentous oleaginous fungus specie Aspergillus oryzae. The result showed subsequent amount of fatty acids, such as oleic acid, palmitolic acid, palmitic acid, etc. In a different study, Subhash and Mohan, (2015) investigated the potential of two lignocellulosic wastewater of corncob waste liquor and paper mill effluent by using oleaginous fungi specie Aspergillus awamori. Results showed that availability of simple monomeric carbon

Biodiesel and an overview of waste utilization at the various production stages

compounds in the selected lignocellulosic wastewater greatly influenced both lipid productivity and fungal growth.

1.6 Challenges and future prospects Currently, the biodiesel industry is mostly based on the availability of oilseed for the production and the utilization of waste in different stages of biodiesel production reduces the associated cost. However, the production process most of the times are not as efficient as that with oilseed. Therefore a lot of research is still required firstly to search more compatible waste derived feedstock and optimize the overall production process to compete with the oilseed biodiesel production. The prospect of utilizing a waste material to synthesize heterogeneous catalysts surely is a promising alternative to homogenous catalysts eliminating various disadvantages of homogenous catalysts. Therefore, second is exploration of more waste derived catalyst which can reduce the overall production cost and increase the production efficiency. Furthermore, a lot of investigation of waste based feedstock and waste-derived catalyst are necessary to improve the overall performance for biodiesel production in comparison to conventional feedstock and catalyst as well as other chemical processes involved.

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Biodiesel and an overview of waste utilization at the various production stages

Shin, H.-Y., Lee, S.-H., Ryu, J.-H., Bae, S.-Y., 2012. Biodiesel production from waste lard using supercritical methanol. J. Supercrit. Fluids 61, 134–138. Soldi, R.A., Oliveira, A.R.S., Ramos, L.P., Cesar-Oliveira, M.A.F., 2009. Soybean oil and beef tallow alcoholysis by acid heterogeneous catalysis. Appl. Catal. A Gen. 361, 42–48. Song, Y., Wynn, J.P., Li, Y., Grantham, D., Ratledge, C., 2001. A pre-genetic study of the isoforms of malic enzyme associated with lipid accumulation in Mucor circinelloides. Microbiology 147, 1507–1515. Subhash, G.V., Mohan, S.V., 2015. Sustainable biodiesel production through bioconversion of lignocellulosic wastewater by oleaginous fungi. Biomass Convers. Biorefinery 5, 215–226. Tangy, A., Pulidindi, I.N., Gedanken, A., 2016. SiO2 beads decorated with SrO nanoparticles for biodiesel production from waste cooking oil using microwave irradiation. Energy Fuels 30, 3151–3160. Toldrá-Reig, F., Mora, L., Toldrá, F., 2020. Developments in the use of lipase transesterification for biodiesel production from animal fat waste. Appl. Sci. 10, 5085. Wang, H., Xiong, H., Hui, Z., Zeng, X., 2012. Mixotrophic cultivation of Chlorella pyrenoidosa with diluted primary piggery wastewater to produce lipids. Bioresour. Technol. 104, 215–220. Wang, H., Yang, B., Hao, G., Feng, Y., Chen, H., Feng, L., Zhao, J., Zhang, H., Chen, Y.Q., Wang, L., 2011. Biochemical characterization of the tetrahydrobiopterin synthesis pathway in the oleaginous fungus Mortierella alpina. Microbiology 157, 3059. Wang, Y., Feng, S., Bai, X., Zhao, J., Xia, S., 2016. Scum sludge as a potential feedstock for biodiesel production from wastewater treatment plants. Waste Manag. 47, 91–97. Wang, Y., Ou, S., Liu, P., Xue, F., Tang, S., 2006. Comparison of two different processes to synthesize biodiesel by waste cooking oil. J. Mol. Catal. A Chem. 252, 107–112. Xavier, M.C.A., Coradini, A.L.V, Deckmann, A.C., Franco, T.T., 2017. Lipid production from hemicellulose hydrolysate and acetic acid by Lipomyces starkeyi and the ability of yeast to metabolize inhibitors. Biochem. Eng. J. 118, 11–19. Yuliana, M., Santoso, S.P., Soetaredjo, F.E., Ismadji, S., Angkawijaya, A.E., Irawaty, W., Ju, Y.-H., TranNguyen, P.L., Hartono, S.B., 2020. Utilization of waste capiz shell–Based catalyst for the conversion of leather tanning waste into biodiesel. J. Environ. Chem. Eng. 8, 104012. Zhang, Y., Wong, W.-T., Yung, K.-F., 2013. One-step production of biodiesel from rice bran oil catalyzed by chlorosulfonic acid modified zirconia via simultaneous esterification and transesterification. Bioresour. Technol. 147, 59–64. Zhou, Y., Niu, S., Li, J., 2016. Activity of the carbon-based heterogeneous acid catalyst derived from bamboo in esterification of oleic acid with ethanol. Energy Convers. Manag. 114, 188–196.

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Abstract Cost effective production is requisite for biodiesel production to realize its potential as alternative renewable fuel. Conventional feedstocks and catalysts used for conversion are the major contributors towards the production cost of biodiesel. The cost of production can be reduced by integration of waste material as a feedstock, utilization of waste for generation of feedstock and using inexpensive waste derived catalysts in the process. Recently researchers are identifying potential waste materials and developing strategies for incorporation in biodiesel production process. Waste feedstocks such as waste cooking oil and animal fats are gaining popularity. Promising feedstocks such as microalgae and oleaginous fungi can be cultivated using waste streams and material. Several waste materials such as animal bones, egg shells and plant residues have been studied for synthesis of catalysts used in transesterification reaction. These strategies not only make biodiesel production process economical but also offer environmental benefits in terms of waste utilization and management.

Keywords Biodiesel; Waste; Wastewater; Feedstock; Catalyst

CHAPTER 2

Prospects of biodiesel production from waste animal fats T.C Aniokete b, O.O Sadare a and M.O. Daramola a

a Department of Chemical Engineering, Faculty of Engineering, Built Environment and Information Technology, University of Pretoria, Pretoria, South Africa b Department of Chemical Engineering, Faculty of Engineering, Enugu State University of Science and Technology, Enugu, Nigeria

2.1 Introduction Energy is key to the comforts of our modern world (Martínez-Molina et al., 2016). The supply of energy from production and transportation to storage and consumption has consistently drawn profound attention of global energy experts on sustainable energy forms and systems. Nowadays, clean, renewable, reliable and economically realistic substituent fuels are the drumbeats of the world’s future energy systems (UCS, 2017). Biodiesel is one such sustainable, nontoxic, biodegradable diesel fuel replacement to the conventional fossil fuels which can potentially be utilized currently for diesel car infrastructure without major modifications in the internal combustion engine (Demirbas, 2007). The substituent biodiesel fuels have significant added value compared to petrodiesel fuel-based due to the improved properties, including reduced carcinogenic particle matter emission and enhanced lubricity as well as better handling, transport, and storage (UCS, 2008). The great quest for an energy paradigm shift is anchored on the dwindling fossil energy reserve resources, unabated rising fuel cost, intolerable environmental concerns ranging from global warming, greenhouse gas (GHG) emission to climate change, destruction of land topography, ecological systems and most importantly, the negative health impacts, such as carcinogenic diseases via air and water pollutions. On the other hand, biodiesel life cycle must be environmentally sustainable, economically viable, and socially acceptable. National Renewable Energy Laboratory (NREL) conducted a life-cycle assessment (LCA) of biodiesel and reported that the reduction of carbon dioxide emissions by 78% is promising with biodiesel compared to petrodiesel (Babcock et al., 2008). In the context of integrated approach, use of various sources of feedstock for biodiesel production had been extensively investigated. It was observed that sustainability and economic feasibility are crucial criteria in biomass-based feedstock for biodiesel production. Among the popular feedstocks for biodiesel production are edible oils which had been affected adversely by the food-related controversies (Freedman et al., 1984). Apart from this, other issues associated with edible oils include feedstock procurement, Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00002-1

c 2022 Elsevier Inc. Copyright  All rights reserved.

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cost of feedstock, transportation, and length of a time limit of storage for vegetable oils. However, a credible raw material for producing biodiesel is waste animal fats (WAF). WAF has been considered as advantageous in lieu of its potentials to avoid the utilization of food resources for energy production. For instance, about 17% of rendered beef tallow constitute the feedstock of produced biodiesel in Brazil (Kirubakaran and Selvan, 2018). As demonstrated in a two-biodiesel blend from a beef tallow and soybean oil used to study their methyl ester properties, Teixeira et al.(2010) and Jeong et al.(2009) found that the cost of the vegetable oil and alcohol utilized accounted for 75% cost of the biodiesel production and that proved more expensive than the cost of producing an equivalent amount of petrodiesel fuels used in diesel engines. Nevertheless, the advantage of biodiesel fuels compared to petrodiesel fuels in conventional diesel engines on account of cost is that no modifications are required (UCS, 2008). It also displays reduced emission profile for particulate matter, sulphur content and minimized carbon to hydrogen ratio (Bhatti et al., 2008). In developing countries such as India, energy demand annually astronomically rises due to the exploding population. The increasing population is a global phenomenon that attracted the strategic policy of Indian government to tap into the large-scale exploitation of about 77,000 tonnes of chicken fats discarded as waste materials. The accumulation was expected to increase with time. These wastes constitute a public environmental nuisance, and at the same time, were generated from 700,000 tonnes of chicken consumed each year (Tiwari et al., 2007). Similarly, in other developed countries such as the United States, EU and the UK, China, Canada, Japan and South America, huge metric tonnes of waste animal fats including chicken fats, pork fat or lard, beef tallow, fish oils, mutton fats, duck tallow are generated annually and harnessed for biodiesel production. Ultimately, this potentially leads to affordable energy and energy security. Besides, these waste animal fats are not suitable for human consumption; the utilization of these wastes leads to low-cost, ecologically supportive and non-food crop renewable energy sources. Furthermore, it is of a more recent trend in the advancement of production of biodiesel and can in turn save the fossil fuel reserves for more decades. In exploring the various sources and techniques of biodiesel production, waste chicken fat was found to be the best option from various WAFs due to its lowest price. Moreover, it has added viability due to process simplicity and readily available market. According to Bankovic-Ilic et al. (2014), successful industrial biodiesel production significantly depends on the manufacturing cost derived from the feed stock, the applied technology and plant capacity as well as the quality of glycerol by-product. Therefore, by using waste animal fats as a lipid resource, a more sustainable biodiesel production process could be developed to achieve large scale production capacities on a long-term basis without adverse effects on the food chain. 2.1.1 Biodiesel as a renewable source of energy Modern research is focused on alternative renewable sources of energy to replace fossil fuels. Biodiesel is a feasible replacement biofuel to petrodiesel fuels. Global warming,

Prospects of biodiesel production from waste animal fats

climate change, and health issues are some of the major concerns associated with the pollutants from nonrenewable fuel resources (Feddern et al., 2011). The cheap source of catalysts and the technology are aimed at reducing costs of producing biodiesel and have upper stake in energy discourse globally (Aniokete et al., 2019). Besides, the substitute biofuel must be technically viable, obtainable and of high conformity to international pollution standards. Biodiesel, among other advantages over petrol diesel, has significant added values, including fewer carcinogenic particulate matter emissions, increased lubricity, higher cetane number, and flash point. Furthermore, it has compatibility with current diesel engine infrastructure without major modifications of the distribution systems in the transportation industry (Luque et al.,2010).Biodiesel is easy to handle,transport,and store under various conditions. However, the life cycle must be environmentally supportive, economically feasible, and socially tandem in a multidimensional mechanism of its full potential applications. Full-scale industrial production of biodiesel is well established, but the feedstock availability has remained a critical challenge and has urgent concern to research (Chu and Majumdar, 2012). Current research shows that feedstock is responsible for over 80% of the overall biodiesel production cost mainly due to the restriction on the use of food-related feedstocks (Shunich et al., 2014). Nevertheless, the sustainability of biodiesel production to drive this frontier in the transportation sector would rely on well-developed nonedible feedstock flow mechanism through exceedingly more innovating, blending, and evolution of efficient production technologies (Karatzos et al., 2014). Consequently, biodiesel could offer a ray of hope for the world embraced by declining oil supplies, pollution, and global warming. However, biodiesel is affected by growing pains and threat of unsustainable production, particularly in the developing world. Biodiesel could be a sought-after fuel by millions with the successful utilization of sustainably cheap and readily available feedstocks, such as WAFs (Charles, 2007). 2.1.2 Feedstock for biodiesel production Several varieties of feedstocks mentioned in the literature have been used for producing biodiesel. These include vegetable oils (edible, for example, canola oil and sunflower oil; inedible vegetable oils such as Jatropha oil, Pongamia oil, Castor oil, etc.), waste cooking oil, animal fat wastes, and algal oils (Adewale et al., 2015). One of the major factors affecting biodiesel commercial production is the quality of renewable material, the cost and availability of feedstocks (Atadashi et al., 2012). The price and distribution of feedstocks vary according to their regional endowment globally (Balat, 2011). Biodiesel producing nations will, therefore, grapple with the different prevailing circumstances in terms of price and availability of feedstocks. For example, Canada’s biodiesel production trend has been based on the country’s most endowed edible canola oil which unfortunately faces the food controversy (Adewale et al., 2015). Other nations such as the United States and Europe that also depend on such edible vegetable oils grown as feedstocks would go through serious food security and ethical issues.

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2.1.3 Biodiesel production from waste material sources Natural and renewable sources of lipids have been the basis of producing alternative diesel fuels from vegetable oils and fats (Lee et al., 1995). Studies have shown that the production cost of edible vegetable oils is highly priced than non-edible vegetable oils due to their connection with food chain controversy. The nonedible oil feedstocks are sustainable noncropped grown plants of low cost. Waste cooking /frying oil, brown/yellow grease, and inedible animal fat oils are potential renewable low-cost biodiesel sources of interest. However, as it pertains to inedible animal fat oil, very scanty information is available in the literature as compared to vegetable oils due to the inherent precarious properties of animal fat such as the tendency to solidify at ordinary temperature. This is because of the state of degree of its long-chain fatty acid saturation (Singh and Singh, 2010). It has been shown that the most popular renewable and sustainably promising sources for biodiesel fuel with the lowest-price production cost in the globe compared to the edible and nonedible oil sources are waste fat and oil (Olkiewicz et al., 2016; Skaggs et al., 2018). Moreover, these fat and oil sources are attractive due to their high fatty acid content and high fatty acid methyl ester (FAME) conversion efficiency when appropriate homogeneous or heterogeneous catalysts are applied (Lam et al., 2010). Furthermore, these waste materials yield high fuel properties of international standard and pose no food security issues (Alptekin et al., 2014). However, properties may vary depending on the oil used and the catalyst option during transesterification, and this will in turn affect the quality of the final product (Encinar et al., 2010). 2.1.4 Waste animal fats and the environment Waste animal fats are products of highly centralized generation in the slaughterhouses or meat processing facilities. They are historically low-priced but have potentials for high value-added energy, which can be environmentally and economically exploited (Nelson and Schrock, 2006). The generation of waste animal fats spans the various sources of meat processing and rendering facilities around the world. Animal fat wastes are essentially derived from tallow by processing the meat from cattle. Swine is also processed to derive the lard as well as white grease while the poultry fat wastes are derived from the processing of chicken, turkey, or other bird oil wastes (Toldrá-Reig et al., 2020). Other animal fats/oils include fish oils by processing fishes, fleshing oils from leather industry fleshing (Jayasinghe and Hawboldt, 2012). In the European Union (EU), for example, animal residues are generated via human consumption as food waste, or from butchering and livestock, as an animal by-product (Rosson et al., 2020). The animal residue generation is sustained by the consumption of about three hundred and twenty-two million pigs, sheep, goats, beef, and dairy cattle (Toldrá-Reig et al., 2020). Also, six billions of slaughtered poultry and 2.45 million tonnes of fallen stock collected by farmers are produced every year in the EU (Rosson et al., 2020). However, there

Prospects of biodiesel production from waste animal fats

are two hazardous categories of the animal waste residues classified according to the EU regulations 2008/98/EC which placed the high-risk ones to be used as starting materials for biofuels production.This in turn relieved the environment of solid waste and particulate pollutants by landfill or incineration. With the enabling legislative provision as demonstrated by the EU and other developed biodiesel producing nations in the waste animal fats management restrictions/disposal, the use of animal residues in meeting the growing quest for biofuels is forecast to be sustainable. Furthermore, the quantity of waste animal fats produced and the need to replace edible vegetable oils for these purposes will reduce intensive land exploitation consequently. However, an impediment of using waste animal fats as a source of raw material for producing biodiesel is due to the presence of impurities which may affect the course of purification reactions involved in biodiesel production (Avagyan and Singh, 2019). There is growth in WAF availability and processing technologies will improve as well as vary from a particular region to another globally. In addition, the effluents are channelled safely to the appropriate marine, landfill, and incineration sites. The waste animal fat processing plants equipped with fish plant discards recover the crude and waste fats/oils in-situ.

2.2 Biodiesel production from waste animal fats The use of animal fat oils and its inedible waste has not been widely studied as the vegetable oils, nonedible oils, and waste cooking oils. This could be attributed to, for instance, at room temperature; the oil is solid and does not offer encouraging flexibility for investigation as compared to other inedible vegetable oils. All the same, with improved process and catalyst technologies, the efforts of researchers have become progressively significant attracting attention. Moreover, there are well-established large-scale cattle ranches, piggery, poultry, sheep and goatery, fishery, etc., and sophisticated abattoirs or renderers as well, which provide low-cost and sustainable inedible waste animal fat oil sources globally flourishing, and there is the increasing promise to develop the feedstock for biodiesel production (Meeker, 2006). A documented report by Ramos et al. (2019) has compared the annual increasing potentials of animal fat feedstock with fresh waste cooking oil in biodiesel production in Portugal from 2010–2018. Within the eight years, animal fat has tremendously shown promising feedstock availability in Portugal probably due to increasing awareness campaign and improved method of collection. It has also been shown by Demirbas (2008) that about top 10 oil and fat feedstock distribution in developed countries with self-sufficiency potential in 2006, that animal fats alone contributed 52%, soybean oil 20%, rapeseed oil 11%, palm oil, sunflower, and other vegetable oils consisting 6%, 5%, and 5% each, respectively. In 2018, a similar study was conducted in the United States by IHS (2018). The study shows that current oil and fat feedstocks for biodiesel production globally are driven

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by Indonesia, China, Malaysia, India, European Union, Africa, Brazil, Argentina, United States, and Central America. Animal fats, including tallow, grease, butter, and lard are steadily increased in recent years in the United States due to health concerns with higher saturated acids or cholesterol content (IHS, 2018). Tallow and grease are produced in high volumes in the United States and this competes with soybean oil as a feedstock for biodiesel production. This analyst believes that world fats and oil consumption annually increase by 2.5%–3.0 % mainly by Asia, the United States (US), and European Union (EU). A review of scanty studies in the literature based on catalyst technology of biodiesel production from animal fat oil indicates that although several transesterification of waste animal fat processes had been conducted successfully by researchers, these reactions were mainly catalyzed by homogeneous acid/alkaline 1 or 2-step processes, only a few was catalyzed by heterogeneous acid/alkaline one-step waste-derived lowcost processes. There is a tremendous opportunity of fortune for biodiesel production in this direction via incorporation of waste-derived heterogeneous catalysis of highly FFA content waste animal fat transesterification processes. These waste-derived solid catalysts had proven to exhibit high tolerance for FFAs and presence of moisture among other benefits than the currently used homogeneous acid/alkaline catalysts (Aniokete et al., 2019). 2.2.1 Stages involved in the process In biodiesel production processes, pretreatment of feedstocks represents a critical downstream activity determining the economic value of the produced fuel. Waste animal fats are derived from a host of several sources and the pretreatment processes are necessary to improve both physical and chemical characteristics of the feedstocks for producing biodiesel that meets the International Standards and Specifications. The improper separation and purification of biodiesel result in a higher content of impurities that could affect engine performance (Suthar et al., 2019). This implies that these raw materials contain undesirable constituents or impurities that must be removed or modified before incorporation into a proper transesterification reaction. During homogeneous acid catalyzed pretreatment reaction, the esterification reaction can be represented by the following schematic process Tyson (2002) (Fig. 2.1). The figure shows that sulfuric acid catalyst can react with the free fatty acids of the feedstock to convert the FFA to fatty acid methyl ester (FAME) directly (Tyson, 2002). The sulfuric acid catalyst thus demonstrates high FFA and moisture tolerance and avoids extra process unit for esterification. It simultaneously performs esterification and transesterification reactions. It also avoids soap formation and separation complication, thereby saving costs (Abbaszaadeh et al., 2012). The operational separation and purification sequence for biodiesel production from waste animal fats was studied (Suthar et al., 2019). The presented sequence was a simulation study which indicates that separation operation

Prospects of biodiesel production from waste animal fats

Figure 2.1 Acid-catalyzed esterification reaction of high FFAs.

based on the recovery of unreacted excess alcohol, glycerol-rich phase separation, and removal of impurities and purification of crude biodiesel is imperative to a given process of biodiesel production (Suthar et al., 2019). It typically represents the conventional and separation techniques which account for major reasons of uneconomic biodiesel production in the downstream processing. The simulation from the various processes of biodiesel production points to the fact that separation and purification steps in the downstream processing from any feedstock are critically valuable. Fig. 2.2 displays the summary of the stages involved in producing biodiesel from waste animal fat sources via pretreatment stage, reaction, separation to storage. The storage technique usually depends on the feedstock used in the produced biodiesel. For example, biodiesel produced from waste animal fats is prone to the presence of high FFA content. FFA content of waste animal feedstocks is very high compared to other waste/inedible oil sources (ToldráReig et al., 2020). The profile of FFA content has remained a key factor (more carbon to carbon double bonds and fewer hydrogen molecules on the fatty acid chain). The higher the polyunsaturated fatty acids the more chances issues arise with the oxidation or degradation of produced biodiesel in storage (Sendzikiene et al., 2004). In addition to the FFA content, the conditions of storage offer positive effects for degradation into ketone and aldehydes. To maintain positive storage practices, it is advised to avoid the following: metal containers, exposure of the purified product to sunlight and air (heat, light, and oxygen) (McCormick et al., 2007). It is helpful to add antioxidants such as butylhydroxytoluene or dibutyl hydroxytoluene (BHT), store biodiesel in highdensity plastic barrels that maintain air-tight conditions devoid of the presence of water. Air-tight storage containers should ensure an air space or headspace (Sendzikiene et al., 2004). In the following section, different methods of producing biodiesel from waste animal fats are discussed. 2.2.2 Methods for producing biodiesel from waste animal fat Nowadays, the rational step necessary for sustainable renewable energy supply, especially in the transportation sector is through waste management generally, and food processing industries, particularly urban meat rendering facilities/restaurants. By applying the “reuse” principle the abundantly sustainable waste stocks of animal fat oils emanating

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Figure 2.2 Stages involved in the production of biodiesel from waste animal fats.

therefrom are harnessed for their low-cost, quality and high free fatty acid content (Aniokete et al., 2019). Transesterification occurs through an exchange of an alcoholic functional group of an ester compound with that of another. The transesterification reaction is represented chemically by the following reaction (Fig. 2.3): For example, animal fat oil, in this case, is considered as acidic alcohol and when reacted with methanol or ethanol (another alcohol) leads to the exchange of functional groups of the ester compound. A process flow diagram (PFD) of biodiesel production

Prospects of biodiesel production from waste animal fats

Figure 2.3 Transesterification reaction of animal fat oil (R = alkyl group) (Ma et al., 1998).

Figure 2.4 Process flow diagram of animal fat oil biodiesel production catalyzed by waste-derived hydroxy sodalite (Aniokete et al., 2019).

from high acidic animal fat oil using a high cost-efficient heterogeneous catalyst technology is presented in Fig. 2.4. Fig. 2.4 represents the process flow diagram for the production of animal fat oil biodiesel fuel catalyzed by a waste-derived hydroxy sodalite catalyst without esterification of the high free fatty acid content (Aniokete et al., 2019). Heterogeneous catalysis studies of inedible animal fat oils are still unfolding from its threshold as compared to the edible or inedible vegetable oils. The commonly available catalysts are alkaline or acid homogeneous phased catalysts for transesterification of vegetable oil feedstocks. The

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choice of catalyst type is dependent on several factors such as high contact surface area, ease of separation, low preparation time, cost efficiency and type of material used (Bohlouli and Mahdavian, 2019). Two of the three categories of catalysts homogeneous and heterogeneous are highly favored by the above-mentioned factors during transesterification reactions. Some major advantages of heterogeneous catalysts in preference to homogeneous catalysis are but not limited to low amount of catalyst used during the reaction, a moderately low temperature of reactions, moderate time of reaction, and high tolerance to free fatty acid (FFA) content in lipid feedstock (Thangaraj et al., 2019). The catalysts are highly separable from the reaction mixture and can be reused for several cycles without loss of catalytic performance thereby maximizing cost and amount of catalyst used. Though, some heterogeneous catalysts may leach in solutions and thus deactivate timeously (Thangaraj et al., 2019), they are noncorrosive to the reaction vessel, environmentally friendly (Refaat,2010) and has no provision for wastewater spillage,there is no esterification unit during the processing of biodiesel which in turn saves costs due to the catalyst’s high tolerance to FFA (Kiss and Bildea, 2011). Moreover, heterogeneous catalysis processes are pro-higher yield and quality biodiesel. 2.2.2.1 Nonthermal methods The dire needs for process improvement/modification and optimization have prompted an arching drive toward economical route for biodiesel production from waste animal fats. Besides, this need must satisfy the set standard physical qualities resembling that of fossil diesel. Microwave irradiation energy process is one of the non-thermal promising methods that are rapid, energy-efficient, cost-saving, and environmentally safe for sustainably quality biodiesel (Alajmi et al., 2018). As opposed to the inefficient conventional heating methods, considering microwave energy approach, energy conversion efficiency, and utilization lead to cost minimization and ultimately low biodiesel production cost. Microwave energy is a non-conventional heating method utilized in biodiesel production in two main stages namely extraction and chemical transesterification reaction (Gude et al., 2013). The nonthermal method of biodiesel production employing microwaveaccelerated heating conversion has viability advantages including more effective heating, fast heating of catalysts, reduced equipment size, faster response to process heating control, faster start-up, increased production, and above all, elimination of process steps (ChematDjenni et al., 2007). 2.2.2.2 Thermal-based methods Generally, biodiesel can be produced by techniques other than transesterification. These include thermal cracking of fats, microemulsions, and direct blending of fat with diesel (Raghavendr and Jambulinga, 2018). However, these methods are least opted for due to their impacts on the physicochemical properties of the produced fuel (Schwab et al.,1987).On the other hand,Figs.2.5 and 2.6 display the process flow diagram

Prospects of biodiesel production from waste animal fats

Figure 2.5 Process flow diagram (PFD) of thermal biodiesel production from waste animal fat (WAF) adapted from Alptekin et al. (2014).

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Figure 2.6 Modified nonthermal microwave-accelerated heating process for biodiesel production from WAF adapted from Nomanbhay and Ong (2017).

that contrasts thermal (conventional methods) and nonthermal methods (microwavemediated) for producing biodiesel from waste animal fats, respectively. Most commercial biodiesel production adopts the thermal heating process as demonstrated by Fig. 2.5 (conventional method). The nonthermal microwave-assisted heating process for producing biodiesel is uniquely new and novel as shown in Fig. 2.6. It has potentially many advantages over the thermal heating methods and advances a promising viable method for the future of biodiesel production from renewable feedstocks. 2.2.2.3 Reactors for biodiesel production from waste animal fat The increasing demand for petroleum oils and the fast-diminishing reserve for fossil fuel energy have made it vital for the continued search for a replacement fuel. The

Prospects of biodiesel production from waste animal fats

Figure 2.7 A typical batch reactor for the transesterification process.

thrust currently placed on biodiesel as a suitable candidate in this scenario has gained immense relevance. Oil feedstocks for sustainable biodiesel production are processed via various reactor shapes/configurations and types. These include batch, continuous, ultrasonic/sonochemical, supercritical, membrane, and many other types. Some of these reactors are efficiently in use in biodiesel production industry. The subsequent section discusses in details these reactors for biodiesel production from waste animal fat. 2.2.2.4 Batch reactors Essentially, batch reactors are vessels or tanks fitted with mixing devices to blend the reactants be it oils/fats, alcohols, and catalyst (liquid/solid). Fig. 2.7 shows a representative batch reactor system for the transesterification reaction. A batch reactor is commonly described as a noncontinuous and perfectly mixed closed process vessel equipment that provides a holding space for chemical reactions to take place, depending on reaction time of study (Ranganathan et al., 2008). Batch reactors are remarkably neither nonentering nor leaving flows with liquid contents completely well mixed. Several batch reactor transesterification reactions are replete in the literature

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Figure 2.8 A continuous flow reactor for heating and cooling.

using different oil feedstocks. However, batch reactor systems are inherently associated with issues of increasing production capacity by increasing the physical size of plant and which is cost intensive. These days, the use of continuous reactors is preferred due to saving of cost of plant and achieving of higher throughput by increasing the feed rate or shortening the reaction time. 2.2.2.5 Continuous reactors Continuous stirred tank and fixed bed reactor (CSTR and FBR) are typical reactors in this category. Fig. 2.8 shows a characteristic flow fixed-bed reactor for biodiesel production. A CSTR is equipped with suitable agitation mechanism for uniform composition and temperature distribution. Adequate control and monitoring are essentially required for CSTR facility. At steady state, the concentration of all the chemical species involved in the CSTR system is ideally the same or constant. CSTRs are widely used in chemical processes. However, the associated disadvantages include decreasing kinetic rate with increasing conversion and lower product composition is obtained for isothermal CSTRs

Prospects of biodiesel production from waste animal fats

Figure 2.9 (A) A conventional and (B) integrated membrane reactor system.

(Gutiérrez-Limón et al., 2012). In terms of larger CSTR volumes compared to other reactors,the energy of agitation required in the tank increases the operating costs.Current designs are integrated with efficient mixing performance which reduces residence time. As shown in Fig. 2.8, FBR is a tubular-shaped continuous flow system packed with solid catalyst particles 3. In FBRs or packed bed reactors (FPRs), the solid catalyst particles are fixed in an enclosed volume and randomly packed. There is no regular packing structure for fluid flow. Reactions take place over the exposed active sites of catalyst inside the pores. The reactants consist of methanol and animal fat oil that flows through the bed and subsequently is converted into products (biodiesel and glycerol) collectable via the product exit. In an industrial scale, the FBR offers lower operating costs and higher efficiencies due to the non-interference of a catalyst replacement for new ones during catalytic reactions. 2.2.2.6 Catalytic membrane reactors for production of high-purity biodiesel from waste animal fats Membrane reactor is a device for simultaneously performing a chemical reaction such as reforming, dry reforming, autothermal reforming and so on, as well as a membrane based-separation within the same physical device (Takht Ravanchi et al., 2009). Fig. 2.9 shows the two basic membrane reactor configurations (Lipnizki et al., 1999). The membrane reactor has an excellent potential for commercial application in the purification of biodiesel. Currently, the purification of transesterified product at the commercial level still poses a major issue. Technology involving the use of membrane reactor has demonstrated an effective way of achieving optimum yields and minimizing energy costs for biodiesel production.

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2.2.3 Downstream processing/product purification in biodiesel production from waste animal fats In Section 2.1 above,the stages involved in the conversion of WAF to biodiesel via transesterification were given a detailed discussion including aspects of downstream processing. This section still refers to the schematic steps illustrating the various downstream processes of the produced WAF methyl esters elaborated in Fig. 2.2. The recovery and purification of crude biodiesel from WAFs, including the processing stages are economically sensitive activities that greatly affect both the product quality and the production cost of fuel. Methyl esters are recovered from the crude biodiesel after undergoing purification processes such as several washing steps, drying, impurity removals such as unreacted lipids, methanol, glycerine, soap, residual catalysts are costly and complicated processes. 2.2.4 Biodiesel from waste animal fat versus the standard biodiesel Biodiesel produced should comply with the EU guidelines of EN14214 and the US ASTM6751-3 (Toldrá-Reig et al., 2020). Significant benefits of using biodiesel produced from waste animal fats includes reduction of polycyclic aromatic hydrocarbons emission by 75%–90% and total unburned hydrocarbon by 90% compared to conventional diesel. Sulfur dioxide and CO, particulate matter, and nitrous oxides emissions are also reduced.

2.3 Transesterification of waste animal fat to biodiesel In the previous sections, a detailed discussion of methods of producing waste animal fat biodiesel was schematically presented using two visually laid out process flow diagrams (Figs. 2.5 and 2.6). Fig. 2.5 shows the detailed PFD for transesterification of high FFA animal fat wastes from various sources with emphasis on pretreatment, reactions, and storage on the conventional heating method. Fig. 2.6 represents the non-thermal microwave-mediated novel method of producing biodiesel from waste animal fat (WAF) assembled from various sources. It demonstrates a huge advantage over the conventional or thermal method of transesterification. In the next sections, critical consideration setting out criteria for transesterification and methods of analysis, catalysis, and types as well as the kinetics of the reaction with WAF are discussed. 2.3.1 Criteria for transesterification of waste animal fats to biodiesel and methods of analysis Production of biodiesel via transesterification of WAF is one of the several reasons for the increased utilization of fatty chemicals for industrial application. As a criterium in transesterification, fat or the oil reacts with alcohol to form a reversible reaction with the alcohol in excess used to drive the reaction toward the right for complete conversion. In the same technical situation, a successful transesterification reaction is

Prospects of biodiesel production from waste animal fats

signified by the separation of the methyl ester (biodiesel) and glycerol layers after the elapsed reaction time. The physically observed denser co-product, glycerol, settles out. The glycerol by-product is a value-added product after purification for other industrial applications (pharmaceutical, cosmetics and detergents). As a condition, separation and purification step by the producer is imperative to ensure that before biodiesel utilization, the crude heavy glycerine phase is separated from the crude-light biodiesel. The methods of analysis of biodiesel produced via transesterification reactions establish that produced biodiesel viscosity should be like that of petrodiesel. Furthermore, the analysis methods must be consistent with the ASTM and the EU biodiesel standards. 2.3.2 Homogeneously catalyzed versus heterogeneously catalyzed methods In most commercial biodiesel production, homogeneous catalyzed transesterification of vegetable oils (edible and inedible), animal fats (inedible) and waste cooking oils had been used for the past decade. Common alkaline homogeneous catalysts such as sodium and potassium hydroxides are the most reactive catalysts for transesterification at mild reaction conditions of temperature, pressure, and time. In heterogeneous catalysis, the solid phases are available in alkaline and acidic types. The overall advantage of heterogeneous catalysts over the homogeneous catalysts lies in the different phases of the reaction mixture during transesterification. These types of heterogeneous catalyst (alkaline and acidic) are easily separable from the reaction mixture and fully recoverable for potential recycle or reuse into the transesterification process. 2.3.2.1 Homogeneously catalyzed transesterification Transesterification reaction processes homogeneously catalyzed for biodiesel production include one-step/direct step and two-step. The one-step process is also considered as direct acid homogeneously catalyzed. It is a reaction of strong acids (sulfuric or sulfonic acids, etc.) in the presence of low molecular alcohols such as methanol or ethanol and high free fatty acid (FFA) inexpensive feedstocks, such as waste animal fats or waste oils (Rosson et al., 2020). The two-step process involves the esterification step with acid and the base catalysis of the transesterification of the esterified fat. 2.3.2.1.1 Type of catalyst Homogeneous catalysts are considered in two categories for catalyzed transesterification reactions, namely the acid types consisting of hydrochloric acid (HCl), sulfuric acid (H2 SO4 ), phosphoric acid (H3 PO4 ), organic sulfonic acid (HSO3 R), etc. The other alkaline types consist of sodium hydroxide (NaOH), sodium methoxide (NaOCH3 ), sodium ethoxide (NaOCH2 CH3 ), sodium butoxide (NaOC4 H9 ), potassium hydroxide (KOH), and potassium methoxide (KOCH3 ). Alkaline catalyst transesterification processes form soap or emulsion in the presence of moisture and high FFA content

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resulting in complicated separation issues and high cost of production. The homogeneous alkaline catalysts are most commercially in use for biodiesel production than the acid homogeneous catalysts. In this category, the typically available catalysts include sodium hydroxide, sodium methoxide, potassium hydroxide, potassium methoxide, sodium amide, sodium hydride, and potassium amide and potassium hydride. The literature data has depicted undeniable fact that KOH and sodium methoxide are proven to be popular homogeneous alkaline catalysts for the conventional two-step transesterification processes for waste animal fat conversion to biodiesel. It also indicates specific ranges of reaction conditions under which maximum catalytic efficiency can be obtained with different waste animal fats. However, very important factors that adversely affect the performance or catalytic efficiency of alkaline or homogeneous base catalysts during transesterification of waste animal fats to biodiesel must be explained. Firstly, the presence of water and high FFA content in the waste animal fat feedstock drastically incapacitates the catalytic performance of the base homogeneous catalysts (Toldrá-Reig et al., 2020). Other factors include the homogeneous catalyst concentration, alcohol, fat molar ratio, reaction time and reaction temperature. 2.3.2.1.2 Factors affecting the reaction The specific factors affecting the acid and base homogeneous catalyzed transesterification reaction processes which inimically derail effective conversion of waste animal fats to biodiesel are critically examined in this segment. By contrast, the two catalyst systems, both acid and base homogeneous catalysis have several transesterification processing issues. Previous studies reported that base homogeneous catalyzed transesterification exhibits high cost of biodiesel production due to large amount of energy required in the downstream refining processes of the produced fuel. Still on the base-catalyzed transesterification processes, Ferella et al. (2010), stated that the use of KOH catalyst leads to saponification reaction by neutralizing the FFAs. Besides, there exist tendencies to produce soap, mono, and diglycerides in the process of transesterification by the direct employment of sodium and potassium alkylates as catalysts. As a result, this has been an issue of concern to the industrial sector. Therefore, the saponification process which results in the formation of gels complicates separation and purification of biodiesel. 2.3.2.1.3 Kinetic study Experimentally reported kinetic studies on homogeneous catalysts for transesterification reaction processes of major oils and fats have been carried out widely with alkaline homogeneous catalysts compared to acid homogeneous catalysts. For example, a transesterification of soybean oil was conducted using two alcohols (methanol and butanol) with an alkali and acid homogeneous catalysts (Freedman et al., 1986). The experimental result indicated that alkaline-catalyzed transesterification progressed with considerably faster reaction rates compared to the acid homogeneous catalyzed transesterification reactions.

Prospects of biodiesel production from waste animal fats

It was further noted that the obtained kinetic coefficients evaluated at 60°C for the homogeneous alkaline-catalyzed transesterification was in the order of two to fourfolds greater than the acid homogeneous catalyzed transesterification. Due to this excellent edge demonstrated by the homogeneous alkaline-catalyzed transesterification over the acid homogeneous catalysts, alkaline homogeneous catalysts had become popularly applied in commercial biodiesel production. Besides, alkaline homogeneous catalysts are widely reported to be less corrosive to reaction facilities and therefore, are potentially a lot more cost-saving than the acid homogeneous catalyzed systems (Nomanbhay and Ong, 2017). The extensively applied homogeneous alkaline catalysts include sodium alkoxide, sodium hydroxide, and potassium hydroxide. However, sodium and potassium hydroxides are less popular compared to sodium alkoxide,which are reported to be more efficient but more cost-intensive (Nomanbhay and Ong, 2017). From kinetic studies carried out with various feedstocks so far, all had been with vegetable oils (edible and inedible), including waste oils but none of the studies had been studied with waste animal fats catalyzed by homogeneous acid-base catalysts (Bankovi´c-Ili´c et al., 2014). 2.3.2.2 Heterogeneously catalyzed transesterification One major area that has greatly sustained the economy of the catalytic transesterification processes involving homogeneous alkaline catalysts is the possession of high accelerated reaction rates. However, there have been numerous issues including uneconomically intricate catalyst separation from the reaction medium which have impaired high prospects of biodiesel competing and surmounting the challenges with petroleum baseddiesel fuel along homogeneous based catalysis route. Heterogeneous catalysis technology has emerged to overcome these problems and has been described as the most appropriate replacement for homogeneous catalysts in biodiesel production. Heterogeneous catalysts have potential reduction capacity to CO2 emission-quality and reduced production cost profile (Serio et al., 2008). Compared with the homogeneous catalysts, heterogeneous catalysts are in a different phase with the reaction system during activity thus, permitting easy removal of catalysts at convenient biodiesel processing stages. The discreteness of heterogeneous catalysts enhances high purity of glycerine and biodiesel recovery as well as recovered catalyst reusability. On the other hand, the separation operations, waste, and the use of large quantities of water are minimized drastically and overall cost-effectiveness of biodiesel production (Refaa, 2010) are feasible with heterogeneous catalysis. It has also been reported that these catalysts have a high tolerance for high FFA content and moisture. With the outstanding replacement potentials of heterogeneous catalysts, one of the difficult challenges is finding a catalyst with comparable activity to that of homogeneous catalysis that can operate at the same temperature and pressure as well as having no leaching tendencies. The following section, therefore, discusses the various heterogeneous catalysts and systems applicable for biodiesel production with tailored applications in converting waste animal fats to biodiesel efficiently.

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2.3.2.2.1 Type of catalysts Development in heterogeneous catalysis indicates new catalysts can be recovered, regenerated, and reused for biodiesel production (Toldrá-Reig et al., 2020). Catalysts of this nature are considered integral in certain harsh conditions such as high temperature and pressure. They are also capable of withstanding tough working stress in aqueous treatment steps and are also amenable to a modification to achieve excellent activity, selectivity, and longer catalyst lifetimes (Thangaraj et al., 2019). Heterogeneous catalysts can be designed to meet specific needs such as bringing out grafting and entrapment of the active molecules on the surface or inside the pores of solid support, such as silica and alumina. Typical examples and types include alkali earth metal oxides, transition metal oxides, mixed metal oxides, ion exchange resins and alkali metal compounds supported on alumina or zeolite. They are involved in different chemical reactions such as isomerization, aldol condensation, oxidation and transesterification (Liu et al., 2008). It was noted that whereas the homogeneous acid catalysts possess few Bronsted or Lewis sites, the solid acid heterogeneous catalysts possess multiple sites with different strength of Bronsted or Lewis acidity. Previous studies had proven that heterogeneous solid acid catalysts possess strong capacity to substitute homogeneous acid catalysts to effectively eliminate separation, corrosion and environmental issues associated with homogeneous acid catalysis. This investigation cuts across different solid acid heterogeneous catalysts to produce biodiesel from highly acidic FFA feedstocks, such as waste animal fats and waste cooking oil. 2.3.2.2.2 Factors affecting the reaction Mostly for heterogeneous alkaline and acid catalysts, the influencing factors are related to the presence of FFA content in the waste animal fats. For reactions in which the presence of FFA content is low in the waste animal fats, such a transesterification process is best catalyzed by solid base heterogeneous catalysts (Dias et al., 2012). In the case of solid acid heterogeneous catalysts, their application in producing biodiesel fuels from waste animal fats with high FFA content such as up to 45 wt.% is advised (Bankovi´c-Ili´c et al., 2014). Another critical factor affecting solid base heterogeneous catalyst performance efficiency during the transesterification of waste animal fat is the preparation method. Preparation of solid base catalysts could be in many techniques including wet impregnation and hydrothermal methods. Wet impregnation method requires the addition of an aqueous solution of KOH over MgO or Al2 O3 and the calcination step of the impregnated catalyst at elevated temperature. On the other hand, the hydrothermal technique involves using a mixture of anhydrous sodium metasilicate (Na2 SiO3 ), sodium hydroxide (NaOH), anhydrous sodium aluminate (NaAlO2 ), and deionized water (Makgaba et al., 2018). The mixture is subjected to several hours of ageing mixing to obtain a consistent gel and subsequently treated to hydrothermal

Prospects of biodiesel production from waste animal fats

crystallization, cooling, washing, drying, and calcination. Hydrothermal treatments cause much more intensive transformation of alumina structure and this favours alumina base solid heterogeneous catalysts for waste animal fats transesterification processes to biodiesel. Both methods yield nanostructure crystal particles of the solid base catalysts that would guarantee reactivity and increased surface area of nanosized oxides. Mixed oxides prepared from the calcination of hydrotalcite demonstrated high surface area and pore volumes (Liu et al., 2007). 2.3.2.2.3 Kinetic study As compared to the kinetics of oils and fats with homogeneous catalysts, the transesterification reactions of oils and fats with heterogeneous catalysts (acid and base) are still not diversified. Most heterogeneous catalysis kinetic transesterification processes focused on edible and non-edible vegetable oils with a few kinetic studies based on waste animal fats. Sustainable biodiesel production from diverse feedstocks including waste animal fats will secure competitive biodiesel dominance for the future over petrol diesel fuels. These commonly industrially available waste feedstocks such as tallow, lard and chicken fats compared to the commonly used edible vegetable oils frequently offer economic advantages due to their low cost. Currently, among the most economical options, producing biodiesel from the above-mentioned feedstocks cost US$0.4–0.5 per liter, while transesterification of vegetable oils presently costs around US$0.6–0.8 per liter (Balat, 2011). Development studies are ongoing in this direction to provide guidelines for further experimental work and predict the effect of the composition of feedstocks on the quality of the biodiesel product. For example, a model could predict how the FFA content of or the water content of a feedstock can affect the reaction conversion and therefore,the yield as well as the quality of produced biodiesel fuel.A novel heterogeneous waste-derived hydroxy sodalite (HSOD) base catalyst had been studied to understand the kinetic behavior of the transesterification of waste animal fat to biodiesel in a batch reactor (Aniokete et al., 2019). The catalyst was synthesized from coal fly ash and waste industrial brine via hydrothermal treatment. The transesterification of animal fat was conducted under the following reaction set values: reaction temperature of 49–62°C, reaction time 120 min, fixed methanol/fat ratio 9:1, and wt. % of HSOD catalyst based on fat wt. was 3 and reaction stirring speed of 300–500 rpm. Experimental result revealed a first order reaction rate, the activation and preexponential factor of 585554.65 Jmol−1 and 2.83 min−1 , respectively were obtained. The authors observed that the reaction is endothermic and for efficient transesterification, minimum activation energy of 58.55KJ would be required to effectively mobilize collision of reacting molecules at a frequency of 2.83 min−1 . The highest animal fat methyl ester yield was 90 % which corresponded to the 93 % feedstock conversion at 62°C after 120 min of reaction time with the produced fuel quality meeting the International Standard tests.

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2.4 Technoeconomic feasibility of biodiesel production from waste animal fats Proven and sustainable availability of waste animal fat feedstocks for biodiesel production has been reported in the literature (Raghavendr and Jambulinga, 2018). This section explores the technoeconomic evaluation of producing biodiesel from waste animal fats as well as offering an insightful guide for biodiesel investors to tap into opportunities in the fuel industry’s business. Generally, waste animal fats such as beef tallow, pork lard, chicken fat, mutton fat and other animal fat waste generation from slaughterhouses and tanneries are economic and ecological alternative transesterification processes for biodiesel production. These feedstocks have economic issues with presence of FFA and water in the feedstocks. The content of FFA and water decreases the catalytic activity of alkaline catalysts and multiply separation stages. Besides, raises the production/operating costs significantly higher than that of conventional fossil fuel prices. Prices of biodiesel from waste animal fats are not fully controlled by normal market forces. As waste animal fats, they are assessed for negative excise duty. It is reported that minimum consumption of waste-produced biodiesel is determined by government law or regulation that favors the market position of producers compared to fossil fuel vendors (Malinauskaite et al., 2017). The structure of the case study considered the unique and bright future of bioenergy development integrating government, public and private sector roles in the commercialization of biomass-derived fuels in developing economies. This comes through a 10 % gap of exploitation of fossil fuels with an annual 5 % increase renewable energy mix for biofuels in South Africa. Report of this nature using waste animal fat feedstock from the South African Scenario is lacking in the literature and this instigates the current effort to explore an economic evaluation based on a sustainable and continuous process technology options. Two production scenarios were reviewed to produce biodiesel from waste animal fat, and the economic feasibility of using them was appraised. The catalyst and biodiesel production process conditions and other criteria employed for the assessment are fully elaborated in our work currently in the press.

2.5 Challenges/recent studies for large-scale production of biodiesel from waste animal fats via transesterification This section discusses recently conducted research on pilot-scale production of diesel from waste animal fats and the challenges encountered and the solutions addressing the setbacks. Alptekin et al. (2014) explored corn oil, chicken fat and fleshing oil as animal fats feedstock in the pilot-scale production of methyl ester. The fuel properties of methyl esters produced in the biodiesel pilot plant were characterized and compared to EN 14214 and ASTM D6751 biodiesel standards. Results show that the yield of methyl ester obtained from animal fat was slightly lower than that obtained for corn oil. Also, corn

Prospects of biodiesel production from waste animal fats

oil is a high-cost feedstock from cropped source. As a result, the production cost of corn oil methyl ester was higher than those of animal fat methyl esters. The fuel properties of produced methyl esters from animal fat and corn oil were similar. The measured fuel properties of all produced methyl esters met ASTM D6751 (S500) biodiesel fuel standards. Quality of produced biodiesel from waste vegetable oil on a pilot scale was similar to the result obtained from the laboratory scale experiment conducted by Torres et al. (2013). The overall yield of FAME was about 90%. In a pilot-scale study by Carlini et al.(2014) operating conditions for the production of biodiesel from waste cooking oils was investigated with an acid value of 2.12 mg KOH g_1 . Two different catalyst types, NaOH and H2 SO4 , at varying concentrations and alcohol concentrations were compared. The best yield of 94.3 % was attained at 0.5 % of NaOH and a 100% excess of methanol. More studies need to be conducted and reported on challenges facing pilot-scale production of biodiesel from waste animal fats.

Conclusions and outlook Based on the wide review on the prospects of biodiesel production from waste animal fat, it was shown that by adopting the strategy of feedstock diversification, the following conclusions and outlook are made: r Use of high FFA content waste animal fats for biodiesel production is more economically viable and an ecological alternative which impacts will depend on the type of catalyst system employed. r Biodiesel can be conveniently produced from low-quality feedstocks using heterogeneous acid catalysts requiring a higher amount of alcohol molar ratios. r The conversion of FFAs was found to increase the yield of biodiesel and simplify the separation of catalyst from crude biodiesel mixture. r Biodiesel produced from waste animal fats is more cost-effective than plant-grown vegetable oils. r Alkaline catalysis is still preferred at industrial plants in producing biodiesels from waste animal fats than acid-catalyzed transesterification due to its higher rate of reaction and cheapness. r Heterogeneous catalysis was evolved to overcome the numerous issues associated with homogeneous catalyzed transesterification processes. r Heterogeneous catalytic production of biodiesel from waste animal fats, microwaveassisted heating, and enzymatic catalyzed, non-catalytic supercritical condition transesterification reaction processes offer unique cost reduction steps and high-quality biodiesel yields. The outlook for biodiesel production from waste animal fats portends a bright one. This is strengthened by the fact that there is growing strategic and viable measures for feedstock availability via centralized waste animal fat management system powered by

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government regulatory policies. For example, the well-promoted energy mix policy in South Africa aimed at gradual commercialization of biodiesel in the country is spurring heavy flow of investment and development into the industry. This is a critical boost for market growth for biodiesel production from waste animal fats since advanced biodiesel technologies are available. More importantly, the use of heterogeneous catalysts specially derived from waste sources and applied in continuous process technologies as demonstrated in the techno-economic assessment of biodiesel production from waste animal fats in this work is one of the innovative efforts to make the transesterification processes economic and attractive thereby counter environmental issues. Furthermore, the utilization of heterogeneous catalysts derived from waste sources presently reduces costs when compared to the use of commercially available solid base heterogeneous catalysts and brings about an overall cost of biodiesel production drastically reduced. It is pertinent to mention that the future performance of biodiesel production from waste animal fats also rests on the various reactors and the associated configurations developed for waste animal fat transesterification processes. In this work, issues relating to reactors for producing quality fuels for the future were critically examined touching on the need to reduce capital cost, energy and water consumption, space requirement, reaction time, waste streams and environmental burdens. It further delved into ensuring improved biodiesel quality and boosting conversion efficiency. Finally, it is proposed that biodiesel production from waste animal fats can develop more profoundly under biorefinery concept to address a great deal of the controversial contending issues linked with largescale downstream processing while offering some environmental and huge economic returns. Waste animal fats provide a veritable fuel sourcing strategy for sustainable biodiesel production. However, this requires elaborate management system for realistic feedstock collection.

References Abbaszaadeh, A., Ghobadian, B., Omidkhah, M.R., Najafi, G., 2012. Current biodiesel production technologies: a comparative review. Energy Convers. Manag. 63, 138–148. Adewale, P., Dumont, M.-J., Ngadi, M., 2015. Recent trends of biodiesel production from animal fat wastes and associated production techniques. Renew. Sustain. Energy Rev. 45, 574–588 May. Alajmi,F.S.M.D.A.,Hairuddin,A.A.,Adam,N.M.,Abdullah,L.C.,2018.Recent trends in biodiesel production from commonly used animal fats. Int. J. Energy Res. 42 (3), 885–902. Alptekin, E., Canakci, M., Sanli, H., 2014. Biodiesel production from vegetable oil and waste animal fats in a pilot plant. Waste Manag 34 (11), 2146–2154 Nov. Aniokete, T.C., Ozonoh, M., Daramola, M.O., 2019. Synthesis of waste-derived hydroxy sodalite catalyst from coal fly ash (CFA) and industrial waste brine for transesterification of waste cooking oil (WCO) to biodiesel. Int. J. Renew. Energy 9 (4), 1924–1937. Aniokete, T.C., Mbhele, S., Mdlalani, V., Ozonoh, M., Daramola, M.O., 2019. Kinetic study of waste-derived solid hydroxy sodalite catalyst during transesterification of animal fat oil to biodiesel in a batch reactor. J. Phys. Conf. Ser. 1378, 032081. Atadashi, I.M., Aroua, M.K., Aziz, A., A., R., Sulaiman, N.M.N, 2012. Production of biodiesel using high free fatty acid feedstocks. Renew. Sustain. Energy Rev. 16 (5), 3275–3285.

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Avagyan, A.B., Singh, B., 2019. Biodiesel from plant oil and waste cooking oil. In: Avagyan, A.B., Singh, B. (Eds.), Biodiesel: Feedstocks, Technologies, Economics and Barriers: Assessment of Environmental Impact in Producing and Using Chains. Springer, Singapore, pp. 15–75. Babcock, R.E., Clausen, E.C., Popp, M., Schulte, W.B., 2008. Yield characteristics of biodiesel produced from chicken fat-tall oil blended feedstocks. Natl. Acad. Sci. Eng. Med. 1, 1–44. Balat, M., 2011. Potential alternatives to edible oils for biodiesel production – a review of current work. Energy Convers. Manag. 52 (2), 1479–1492. Bankovi´c-Ili´c, I.B., Stojkovi´c, I.J., Stamenkovi´c, O.S., Veljkovic, V.B., Hung, Y.-T., 2014. Waste animal fats as feedstocks for biodiesel production. Renew. Sustain. Energy Rev. 32, 238–254. Bhatti, H.N., Hanif, M.A., Qasim, M.Ata-ur-Rehman, 2008. Biodiesel production from waste tallow. Fuel 87 (13), 2961–2966. Bohlouli, A., Mahdavian, L., 2019. Catalysts used in biodiesel production: a review. Biofuels 0 (0), 1–14. Carlini, M., Castellucci, S., Cocchi, S., 2014. A Pilot-Scale Study of Waste Vegetable Oil Transesterification with Alkaline and Acidic Catalysts. Energy Procedia 45, 198–206. Chemat-Djenni, Z., Hamada, B., Chemat, F., 2007. Atmospheric pressure microwave assisted heterogeneous catalytic reactions. Molecules 12 (7). Chu, S., Majumdar, A., 2012. Opportunities and challenges for a sustainable energy future. Nature 488 (7411). Demirbas, A., 2007. Importance of biodiesel as transportation fuel. Energy Policy 35 (9), 4661–4670. Dias, A.P.S., Bernardo, J., Felizardo, P., Correia, M.J.N., 2012. Biodiesel production over thermal activated cerium modified Mg-Al hydrotalcites. Energy 41 (1), 344–353. Demirbas, A., 2008. Biodiesel: A Realistic Fuel Alternative for Diesel Engines. Springer London, London. Encinar, J.M., González, J.F., Pardal, A., Martínez, G., 2010. Rape oil transesterification over heterogeneous catalysts. Fuel Process. Technol. 91 (11), 1530–1536 Nov. Feddern, V., Cunha Jr, A., De Prá, M.C., de Abreu, P.G., dos Santos Filho, J.I., Higarashi, M.M., Sulenta, M., Coldebella, A., 2011. Animal fat wastes for biodiesel production. Biodiesel-Feedstocks and Processing Technologies. InTech Europe University Campus STeP Ri Slavka Krautzeka 83/A 51000 Rijeka, Croatia- InTech China Unit 405, Office Block, Hotel Equatorial Shanghai No.65, Yan An Road (West), Shanghai, 200040, China. Ferella, F., Mazziotti Di Celso, G., De Michelis, I., Stanisci, V., Vegliò, F, 2010. Optimization of the transesterification reaction in biodiesel production. Fuel 89 (1), 36–42. Freedman, B., Butterfield, R.O., Pryde, E.H., 1986. Transesterification kinetics of soybean oil. J. Am. Oil. Chem. Soc. 63, 1375–1380. Freedman, B., Pryde, E.H., Mounts, T.L., 1984. Variables affecting the yields of fatty esters from transesterified vegetable oils. J. Am. Oil Chem. Soc. 61 (10), 1638–1643 Oct. Gude, V.G., Patil, P., Martinez-Guerra, E., Deng, S., Nirmalakhandan, N., 2013. Microwave energy potential for biodiesel production. Springer Nat 1 (5), 1–31 May. Gutiérrez-Limón, M.A., Flores-Tlacuahuac, A., Grossmann, I.E., 2012. A multiobjective optimization approach for the simultaneous single line scheduling and control of CSTRs. Ind. Eng. Chem. Res. 51 (17), 5881–5890. IHS, M., Major fats and oils industry overviewChemical Economics Handbook (CEH). California, USA, 2018. Jayasinghe, P., Hawboldt, K., 2012. A review of bio-oils from waste biomass: focus on fish processing waste. Renew. Sustain. Energy Rev. 16 (1), 798–821. Jeong, G.-T., Yang, H.-S., Park, D.-H., 2009. Optimization of transesterification of animal fat ester using response surface methodology. Bioresour. Technol. 100 (1), 25–30. Karatzos, S., University of British Columbia, Canada. James D. McMillan National Renewable Energy Laboratory, USA, and Jack N. Saddler University of British Columbia, Canada. First electronic edition produced in 2014. A catalogue record for this Report is available from the British Library. ISBN: 978-1910154-07-6 (electronic version) Published by IEA Bioenergy. Kirubakaran, M., Arul Mozhi Selvan, V., 2018. A comprehensive review of low cost biodiesel production from waste chicken fat. Renew. Sustain. Energy Rev. 82, 390–401. Kiss, A.A., Bildea, C.S., 2011. Integrated reactive absorption process for synthesis of fatty esters. Bioresour. Technol. 102 (2), 490–498.

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Lam, M.K., Lee, K.T., Mohamed, A.R, 2010. Homogeneous, heterogeneous and enzymatic catalysis for transesterification of high free fatty acid oil (waste cooking oil) to biodiesel: a review. Biotechnol. Adv. 28 (4), 500–518. Lee, I., Johnson, L.A., Hammond, E.G., 1995. Use of branched-chain esters to reduce the crystallization temperature of biodiesel. J. Am. Oil Chem. Soc. 72 (10), 1155–1160. Liu, Y., Lotero, E., James, G., Goodwin, J.G., Mo, X., 2007. Transesterification of poultry fat with methanol using Mg-Al hydrotalcite derived catalysts. Applied Catalysis A: General 331, 138–148. Luque, R., Lovett, J.C., Datta, B., Clancy, J., Campelo, J.M., Romero, A.A., 2010. Biodiesel as feasible petrol fuel replacement: a multidisciplinary overview. Energy Environ. Sci. 3 (11), 1706–1721. Ma, F., Clements, L.D., Hanna, M.A., 1998. Biodiesel fuel from animal fat. Ancillary studies on transesterification of beef tallow. Ind. Eng. Chem. Res. 37 (9), 3768–3771. Makgaba, C.P., Aniokete, T.C., Daramola, M.O., 2018. Waste to energy: effect of reaction parameters on the transesterification of animal fat oil to biodiesel over a solid hydroxy sodalite catalyst. Progress in Industrial Ecology, an International Journal 12 (4), 331–344. Martínez-Molina, A., Tort-Ausina, I., Cho, S., Vivancos, J.-L., 2016. Energy efficiency and thermal comfort in historic buildings: A review. Renew. Sustain. Energy Rev. 61, 70–85. Meeker,D.L.Ed.,2006.Essential Rendering:All About the Animal By-Products Industry.National Renderers Association: Fats and Proteins Research Foundation: Animal Protein Producers Industry, Alexandria, VA. Nelson, R.G., Schrock, M.D., 2006. Energetic and economic feasibility associated with the production, processing, and conversion of beef tallow to a substitute diesel fuel. Biomass Bioenergy 30 (6), 584– 591. Nomanbhay, S., Ong, M.Y., 2017. A review of microwave-assisted reactions for biodiesel production. Bioengineering 4 (2). Olkiewicz,M.,Torres,C.M.,Jiménez,L.,Font,J.,Bengoa,C.,2016.Scale-up and economic analysis of biodiesel production from municipal primary sewage sludge. Bioresour. Technol. 214, 122–131. Raghavendr, G., Jambulinga, R., 2018. Comprehensive study on biodiesel produced from waste animal fats a review. J. Environ. Sci. Technol. 11 (3), 157–166. Ramos, M., Dias, A.P.S., Puna, J.F., Gomes, J., Bordado, J.C. “Biodiesel production processes and sustainable raw materials,” Energies, vol. 12, no. 23 2019. Ranganathan, S.V., Narasimhan, S.L., Muthukumar, K., 2008. An overview of enzymatic production of biodiesel. Bioresour. Technol. 99 (10), 3975–3981. Refaat, A.A., 2010. Different techniques for the production of biodiesel from waste vegetable oil. Int. J. Environ. Sci. Technol. 7 (1), 183–213. Rosson, E., Garbossa, P.S., Pedrielli, F., Mozzon, M., Bertani, R., 2020. Bioliquids from raw waste animal fats: an alternative renewable energy source. Biomass Convers. Biorefinery 11, 1475–1490. Schmidt Charles, W., 2007. Biodiesel: cultivating alternative fuels. Environ. Health Perspect. 115 (2), A86–A91. Schwab, A.W., Bagby, M.O., Freedman, B., 1987. Preparation and properties of diesel fuels from vegetable oils. Fuel 66 (10), 1372–1378. Sendzikiene, E., Makareviciene, V., Janulis, P. Original research oxidation stability of biodiesel fuel produced from fatty wastes. 2004. Serio, M.C., Tesser, R., Pengmei, L., Santacesaria, E., 2008. Heterogeneous Catalysts for Biodiesel Production. Energy Fuels 22 (1), 207–217. Shunichi, N., Deger, S., Dolf, G., 2014. Global bioenergy supply and demand projections: a working paper for REmap 2030. Int. Renew. Energy Agency 1, 88. Singh, S.P., Singh, D., 2010. 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. 14 (1), 200–216. Skaggs, R.L., Coleman, A.M., Seiple, T.E., Milbrandt, A.R., 2018. Waste-to-Energy biofuel production potential for selected feedstocks in the conterminous United States. Renew. Sustain. Energy Rev. 82, 2640–2651. Suthar, K., Dwivedi, A., Joshipura, M., 2019. A review on separation and purification techniques for biodiesel production with special emphasis on Jatropha oil as a feedstock. Asia-Pac. J. Chem. Eng. 14 (5), e2361. Takht Ravanchi, M., Kaghazchi, T., Kargari, A., 2009. Application of membrane separation processes in petrochemical industry: a review. Desalination 235 (1), 199–244.

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Teixeira, L.S.G., et al., 2010. Characterization of beef tallow biodiesel and their mixtures with soybean biodiesel and mineral diesel fuel. Biomass Bioenergy 34 (4), 438–441. Thangaraj,B.,Solomon,P.R.,Muniyandi,B.,Ranganathan,S.,Lin,L.,2019.Catalysis in biodiesel production— a review. Clean Energy 3 (1), 2–23. Tiwari, A.K., Kumar, A., Rahama, H., 2007. Biodiesel production from Jatropha carcus. L. as source of production of biofuel in Nicargia. Bioresour. Technol. 31, 569–575. Toldrá-Reig, F., Mora, L., Toldrá, F., 2020. Trends in biodiesel production from animal fat waste. Appl. Sci. 10 (10), 1–17. Torres,E.A.,Cerqueira,G.S.,Ferrer,T.M.,Quintella,C.M.,Raboni,M.,Torretta,V.,Urbini,G.,2013.Recovery of different waste vegetable oils for biodiesel production: a pilot experience in Bahia State, Brazil. Waste Management 33 (12), 2670–2674. Tyson, K.S., 2002. Brown grease feedstocks for biodiesel. Natl. Renew. Energy Lab. 1, 34. UCS- Union of concerned Scientists REPORTS & MULTIMEDIA/EXPLAINER Benefits of Renewable Energy Use, Published Jul 14, 2008. Updated Dec 20, 2017. UCS- Union of concerned Scientists REPORTS & MULTIMEDIA/EXPLAINER Environmental Impacts of Renewable Energy Technologies, Published Jul 14, 2008. Updated Mar 5, 2013.

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Abstract This chapter gives a systematic exploitation of the residual fatty materials of the globally produced waste animal fat (WAF) from the meat and fish processing industries for biodiesel production. A short overview of generation, sources and the trend in the development of its technologies is discussed. Biodiesel production from waste material sources, WAF and the environment, biodiesel from WAF with highlights on the stages, methods, reactors, downstream processing techniques and the question of ‘biodiesel from WAF versus standard biodiesel’ is examined. Furthermore, a critical consideration of the transesterification of WAF to biodiesel with insights into criteria for transesterification and methods of analysis, catalytic methods, factors affecting the reactions and the kinetics is presented. The chapter analyzed a preliminary techno-economic feasibility of biodiesel production from WAF weighing the challenges of large-scale production from WAF via transesterification concludes by elucidation of the outlook for biodiesel production from WAF.

Keywords Waste animal fats; Waste valorization; Renewable energy; Transesterification; Downstream production; Catalysis; Kinetics

CHAPTER 3

Efficacy of municipal waste derived lipids in production of biodiesel Mahmoud Nasr a,b

a Environmental Engineering Department, Egypt-Japan University of Science and Technology (E-JUST), P.O. Box 179, New Borg El-Arab City, Alexandria 21934, Egypt b Sanitary Engineering Department, Faculty of Engineering, Alexandria University, P.O. Box 21544, Alexandria 21526, Egypt

3.1 Introduction Recently, crucial environmental restrictions, regulations, and guidelines have been announced globally for finding alternatives to fossil-based fuels that can avoid energy security risks (Kirubakaran and Arul Mozhi Selvan, 2018). This action has induced the public and private sectors toward finding alternative eco-friendly and green energy sources (Bankovi´c-Ili´c et al., 2014). For this purpose, researchers are working to enhance the clean and renewable technologies that can cope with the utilization of conventional diesel, that is, also known as the petroleum-based diesel fuels (Patel et al., 2017). This improvement is essential because petro-diesel tends to emit relatively high amounts of pollutants and greenhouse gases (GHG), causing severe impacts to human health, living organisms, and the aquatic and terrestrial species (Mostafa and El-Gendy, 2017). Moreover, the detrimental effects associated with the extensive utilization of conventional fossil fuel have caused serious concerns that face societies around the world (Krishania et al., 2020). Accordingly, there is an urgent need to develop environmentally friendly methods for obtaining efficient and low-pollutant fuel, such as biofuel or biodiesel. The biorefinery concept describes the industrial applications that can utilize wastes as an input feedstock to produce biodiesel and value-added chemical products (Rehan et al., 2018). This green fuel, also known as fatty acid methyl esters (FAME), has been recognized as a strategic, sustainable, and essential energy source, attempting to minimize GHG emissions compared with conventional fossil fuel (Vasaki E et al., 2021). Biodiesel is low-toxic, biodegradable, carbon-neutral, and eco-friendly energy fuel that can reduce an appropriate portion of CO2 released during fuel combustion; i.e., biodiesel can save 2.4– 3.2 kg-CO2 /kg-fuel (Lopresto et al., 2015). Bio-oil can also be mixed with conventional diesel sources to enhance the oxygen content and decrease the carbon to hydrogen ratio in biodiesel (Ito et al., 2012). For instance, Mostafa and El-Gendy (2017) found that blends of microalgae biodiesel and petro-diesel had appropriate physicochemical characteristics (e.g., calorific value, diesel index, viscosity, and flash and initial boiling points), complying Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00006-9

c 2022 Elsevier Inc. Copyright  All rights reserved.

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with the recommended diesel standard specifications. Accordingly, biodiesel has been introduced to the public as the best option for future energy demand regarding utilization efficiency, availability, renewability, and accessibility (Patel et al., 2017). Various waste sources containing fats and oils can be employed to prepare biodiesel (Bankovi´c-Ili´c et al., 2014). The oil used for biodiesel production can be derived from either edible plants (peanut, olive, and palm) or nonedible plants (jatropha, cottonseed, and linseed) (Maneerung et al., 2016). Biodiesel can also be obtained from animal fats (Ben Hassen-Trabelsi et al., 2014) and plastic waste (Tomar et al., 2020) after pyrolysis. For instance, (Karmee et al., 2015) reported that food waste could be utilized as a low-cost feedstock for obtaining lipids. Further, the lipid fraction can be converted into biodiesel or FAME by transesterification (Lee et al., 2015). Their study demonstrated that waste cooking oil,nonedible/vegetable oils,animal fats,and lipid-rich microalgae,which do not compete for food consumption, could be used to produce biodiesel (Karmee et al., 2015). Moreover,(Rehan et al.,2018) investigated the production of biodiesel from various waste sources available in KSA, attempting to provide economic and environmental benefits for maintaining a circular economy in the country. Their study depicted that the fat fraction of MSW would generate 1.41milliontons of biodiesel with an energy potential of 56493TJ and an annual saving of US $72.71million (Rehan et al., 2018). However, various food wastes contain other substances, such as protein, trace elements, carbohydrates, and minerals; hence, a lipid isolation/extraction process is initially required (Mostafa and El-Gendy, 2017). Municipal solid waste (MSW) has been recently selected as a low-cost and possible candidate for biofuel/biodiesel production because it comprises various components with appropriate lipid contents (Abed et al., 2018). Moreover, increased pollution patterns have been associated with the improper management of the large quantities of MSW, that is (Daniel and Perinaz, 2012), reported that the amount of MSW generated from 3 billion residents is 1.3 billion tonnes annually. It’s projected that by 2025, this amount will reach 2.2 billion tonnes per year due to increasing the urban residents to about 4.3 billion (Daniel and Perinaz, 2012). This huge quantity includes various wastes coming from the residential, commercial, educational/institutional, recreational, and municipal areas (Shahzad et al., 2017). Accordingly, MSW is composed of a heterogeneous mixture of waste items, such as food remains, wood pallets, yard trimmings, street cleanings, textiles, grass clippings, plastics, and paper and cardboard (Canakci, 2007). MSW can also compress small quantities of hazardous discards from medicines, heavy metals, and chemicals (Gupta et al., 2018). These items can also be classified into (1) biogenic products obtained from plant, food, or animal residues, (2) nonbiodegradable and combustible products synthesized from petroleum substances, and (3) nonbiodegradable and noncombustible items, such as metals and glass (Mukherjee, 2020). These items can also be categorized into organic (food waste and plant residues) and inorganic (rubber, textiles, and leather) products. The fractions of these components vary among countries

Efficacy of municipal waste derived lipids in production of biodiesel

according to multiple factors, such as climate status, economic prosperity (lifestyles), socio-cultural traditions, fuel source type, and population density (Roy et al., 2019). Proper management of the disposable items of MSW is an essential task to maintain various environmental, economic, and social benefits (Lopresto et al., 2015). The MSW management practices include collection, separation, and reuse/recycling, supporting the waste-to-energy approach (Carmona-Cabello et al., 2019). This framework is assisted by local governments and other public or private organizations acting on their behalf. The primary objective of the MSW management approach is to avoid further discarding the wastes into disposal sites (dumps and landfills) or uncontrolled incineration (Ng et al., 2017). For instance, food and non-industrial solid wastes account for the majority of the organic fraction of MSW, and they contain sufficient amounts of lipids that can be converted into biodiesel (Sikarwar et al., 2017). The conversion of negatively priced and abundant feedstock into biodiesel is in agreement with the basics of the Circular Economy (Vasaki E et al., 2021). Accordingly, comprehensive studies should focus on the proper utilization of MSW for biodiesel production to minimize water resource contamination and emission of large amounts of GHG, in addition, to support the future circular economy strategies for cleaner energy. Hence, this chapter represents an overview of the MSW management for lipid and biodiesel productions, aiming at protecting the environment and minimizing the dependence on fossil fuel. This chapter also gives a brief survey on the SCOPUS database for the recent publications attempting to cover the topic of “waste-to-energy.” The characterization of some MSW items such as food residues, plastic waste, and nonedible animal fats and cooking oil for biofuel/biodiesel generation is summarized. The chapter also gives a brief highlight upon the conversion process of waste into bioenergy, including pyrolysis and transesterification. These objectives provide essential guidance to researchers, policymakers, stakeholders, and several public and private sectors for enabling a sustainable biorefinery application.

3.2 Overview of lipids/biodiesel production from municipal solid waste reported in literature Recently, several studies have demonstrated the production of lipids from wastes, which are subsequently employed for obtaining biodiesel to support multiple industrial and commercial applications. By searching in the SCOPUS database with the keywords “waste,” “lipid,” and “biodiesel,” the cumulative number of documents until 2010 was 63 documents (Fig. 3.1). In 2020, this number significantly (p < 0.05) increased to 1023 documents, suggesting that this topic has attracted several researchers worldwide. Most of these researchers were affiliated by Chinese Academy of Sciences; Ministry of Education China; Korea Advanced Institute of Science & Technology; Centre Eau Terre Environnement; Universiti Teknologi Petronas; Harbin Institute of Technology;

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Figure 3.1 Number of documents recorded in SCOPUS database using the keywords “waste,” “lipids,” and “biodiesel.”

Figure 3.2 Classification of published documents in SCOPUS database using the keywords “waste,” “lipids,” and “biodiesel” based on affiliation.

Indian Institute of Chemical Technology;Indian Institute of Technology Roorkee;Sultan Qaboos University; Prince of Songkla University (Fig. 3.2). These affiliations are relevant to India; China; United States; South Korea; Malaysia; Canada; Brazil; Italy; Thailand; United Kingdom (Fig. 3.3). Moreover, most of the published documents are research articles (78.5%), followed by review articles (10.6%). The remaining documents’ types were distributed among conference paper; book chapter; short survey; editorial; book; note (Fig. 3.4). Additionally, the application of lipid/biodiesel production from waste has multidisciplinary objectives that can be covered by different subject areas. These fields include environmental science; energy; chemical engineering; biochemistry, genetics and molecular biology; immunology and microbiology; agricultural and biological sciences; engineering; chemistry; materials science; pharmacology, toxicology, and pharmaceutics (Fig. 3.5). Accordingly, various guarantors and sponsors have funded the lipid/biodiesel-related projects (Fig. 3.6). The funding sponsors that have been acknowledged in these doc-

Efficacy of municipal waste derived lipids in production of biodiesel

Figure 3.3 Classification of published documents in SCOPUS database using the keywords “waste,” “lipids,” and “biodiesel” based on country.

Figure 3.4 Classification of published documents in SCOPUS database using the keywords “waste,” “lipids,” and “biodiesel” based on type.

uments include National Natural Science Foundation of China; National Research Foundation of Korea; Natural Sciences and Engineering Research Council of Canada; Conselho Nacional de Desenvolvimento Científico e Tecnológico; Bangladesh Council of Scientific and Industrial Research; European Commission; Fundamental Research Funds for the Central Universities; Ministry of Education, Science and Technology; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior; Department of Science and Technology, Government of Kerala. This statistical survey shows the necessity to conduct further researches and projects for waste management, obtaining beneficial products such as biodiesel. This bibliometric analysis gives essential knowledge on the research of microalgaderived biodiesel between 2010 and 2020. Some observations can be highlighted as follows: r Several countries,such as India,Brazil,China,United States,and Malaysia,contributed to the articles’ publications, suggesting that biodiesel has become a popular energy source in developed and developing nations.

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Figure 3.5 Classification of published documents in SCOPUS database using the keywords “waste,” “lipids,” and “biodiesel” based on subject area.

Figure 3.6 Classification of published documents in SCOPUS database using the keywords “waste,” “lipids,” and “biodiesel” based on funding sponsor. r

The number of publications in the literature related to microalgae-biodiesel shows a considerably increased pattern, implying that biodiesel would have broad applications as alternative energy in many fields in the future. r A potential direction of microalga-derived biodiesel in the future would cover (1) preparing efficient microalgae species for biodiesel preparation, (2) achieving environmental and economic goals of microalgae-derived lipid, (3) enhancement of microalgae cultivation, harvesting, and lipid extraction processes, and (4) implementing appropriate design and operation of microalgae growth reactor. r The common microalga species found in this bibliometric analysis are “Chlorella,” “Nannochloropsis,” and “Scenedesmus” because they have appropriate photosynthetic efficiency, high adaptation to the surrounding environment, and a proper ability for N and P uptake.

Efficacy of municipal waste derived lipids in production of biodiesel

r

Several research articles have been identified by linking “Microalgae” with “Wastewater” and “Nutrient Removal,” owing to the high ability of microalgae to grow in wastewater with a subsequent lipid accumulation for biofuel production. r The two keywords “Nitrogen starvation” and “Lipid production” are highly correlated in several articles, assigning to the tendency of microalgae to induce lipid accumulation when nitrogen source is insufficient. r Lipid extraction was performed by previous researchers using either physical methods (e.g., shock waves) to disrupt/rupture the cell walls or chemical protocols (e.g., adding solvents) to penetrate microalgae cells.

3.3 Types of municipal solid waste available for biodiesel production The relatively high cost of biodiesel production has encouraged researchers for finding a cheap and available feedstock such as MSW for lipid extraction (Karmee et al., 2015). MSW is composed of various biodegradable and non-biodegradable products coming from various municipal and urban sources. These sources include households, public facilities (schools, ambulances, health-care centers, etc.), small business entities, and commercial facilities (restaurants, markets, meat roasters, bakeries, etc.). Some MSW items can be converted into biodiesel to make the process economically feasible, which are given as follows: 3.3.1 Food waste Food waste contains noticeable amounts of organic matter that can be utilized to obtain energy, avoiding the incineration and landfill practices (Carmona-Cabello et al., 2018). This waste is collected from food stores, restaurants, cafeterias, markets, hotels, and bakeries (Mukherjee, 2020). Examples of food waste are non-edible fruit and vegetable, dairy products, bakery-based residues, and fish and poultry organs that can be utilized to obtain amino acid, lipid, carbohydrate, and vitamins (Karmee et al., 2015). Recently, several researchers have demonstrated that lipids generated from food waste can be employed as a potential source for biodiesel preparation (Shahzad et al., 2017); (Carmona-Cabello et al., 2018); (Gao et al., 2019). The liquid phase (oil) and the solid portion (fat, wax, and grease) of food waste, which are recognized as unhygienic and zero-value residues, have been considered for lipid generation and biodiesel synthesis (Canakci, 2007). Considering food waste recycling, lipids play an essential role in terms of environmental sustainability and economic viability (Carmona-Cabello et al., 2019). Because food waste contains other soluble bio-chemicals such as carbohydrates, protein, and minerals, lipid isolation (solvent extraction) should be initially conducted. Shahzad et al. (2017) reported that MSW collected from Makkah city contained about 51% food waste, resulting in the release of 64 thousand tons of fat per year. The direct disposal of MSW into the landfills without proper treatment would negatively affect the

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environment, such as soil contamination. Hence, the authors suggested energy recovery from the fat/oil fractions of MSW to attain various economic and environmental benefits. Their study demonstrated that 62.53 thousand tons of biodiesel could be generated in 2014, contributing to the Saudi economy by increasing the total electricity potential from 852 Gigawatt hour (GWh) in 2014 to 1777 GWh in 2050. Carmona-Cabello et al. (2018) found that oil of food waste collected from different restaurants might be mixed and used to produce biodiesel. Their study also demonstrated that some strategies, such as using additives, optimization of transesterification reaction, and/or blending of biodiesel with diesel fuel could be used to improve the quality of biodiesel from food waste. 3.3.2 Plastic waste MSW also contains plastic waste, which imposes harmful environmental externalities upon human health and living organisms if dumped into the environment without proper manner. Over 100 million tons of plastic wastes are accumulating globally; and because plastic has a nondecomposable nature, its management imposes a great challenge to the municipality (Tomar et al., 2020). The idea of waste management is to utilize and recycle plastic waste for generating fuel. Pyrolysis is one of the best and promising pathways that have been broadly employed to transform plastic into oil. In the pyrolysis process via heating at an oxygen-deprived condition, large molecules of hydrocarbons are degraded into smaller molecules like ethane. Further, fractional distillation is employed to separate the smaller hydrocarbon products to be used as chemicals and fuels for different industrial applications. Chintala et al. (2018) demonstrated that municipal mixed plastic waste could be used to obtain plasto-oils, showing comparable performance with diesel fuel for operating compression ignition (CI) engine. The study also showed that the plasto-oils application in the engine was associated with a slight increase in C-related emissions (HC, CO, and smoke), whereas NOx emission was lower, as compared to the diesel operation. Damodharan et al. (2018) used plastic waste to generate waste plastic oil via catalytic pyrolysis.Their study found that 70% of waste plastic oil + 30% of n-pentanol blend could be utilized as a fuel in a direct injection (DI) diesel engine, providing appropriate performance with reduced smoke and CO emissions. Tomar et al. (2020) prepared efficient and low-cost biodiesel blends by adding waste plastic pyrolyzed oil to diesel-waste cooking oil. The biodiesel blends showed also reduced exhaust emissions with a total reduction of approximately 30% for unburnt hydro carbons (UBHC), NOx, and CO emissions. 3.3.3 Oil waste Oil waste can result from cooking and frying food with edible vegetable oil, and it is no longer suitable for human consumption. It is collected from restaurants, household

Efficacy of municipal waste derived lipids in production of biodiesel

kitchens, cafes, and hotels (Carmona-Cabello et al., 2019). The discard of wastewater containing cooking oil waste can increase the potential for blockage formation in the sewer systems (Jaiswal et al., 2019). This oil-based substance has also many disposal problems like water and soil contamination, aquatic ecosystem damage, and human health issues, causing various economic and environmental concerns (El Khatib et al., 2018). Hence, utilizing oil waste for biodiesel production becomes an attractive solution for waste management and environmental pollution reduction (Sahar et al., 2018). Recent researchers have demonstrated that oil waste is an appropriate and low-cost feedstock for sustainable biodiesel production (Verma and Sharma,2016;Abed et al.,2018).For instance, Canakci (2007) succeeded to produce biodiesel from waste grease and vegetable oils of a restaurant via acid catalyst and transesterification processes. Moreover, grease originating from utilized oils (or rendered animal fats) can contain free fatty acids applicable for biodiesel production (Bankovi´c-Ili´c, et al., 2014). For example, Sahar et al. (2018) used waste cooking oil to obtain biodiesel via an alkali catalyzed transesterification process.Their study showed 88.8% for the esterification efficiency of free fatty acids, obtaining biodiesel that contained stearic, linoleic, oleic, and palmitic acids. Abed et al. (2018) investigated different mixtures of waste cookingoil biodiesel and diesel oil for preparing biodiesel blends via transesterification, having comparable physical and chemical characteristics to diesel fuel. The waste cooking-oil biodiesel blends were utilized to operate a single-cylinder diesel engine, showing lower thermal efficiencies, air-fuel ratios, and CO and HC emissions but higher specific fuel consumptions, and exhaust gas temperatures compared to diesel fuel. 3.3.4 Waste animal fats Similar to oil waste, animal fat disposal can cause blockage to drains and sewers and create operational problems for the receiving sewage treatment plants (Kirubakaran and Arul Mozhi Selvan, 2018). Examples of waste animal fats are duck tallow, chicken skin, lard, and mutton and beef fats, which are nonedible and easily available in the restaurant garbage (Rajak and Verma, 2018). Animal fatty wastes are composed of triglycerides, and they are not suitable for the human food chain. Recently, animal fats have attracted attention as one of the raw materials abundantly available to produce biodiesel. Ito et al. (2012) employed the pyrolysis of animal-derived fats for biodiesel production. Their study demonstrated that triacylglycerols and unsaturated fatty acid chains were decomposed to fatty acids and hydrocarbons at 390°C, respectively. Ben Hassen-Trabelsi et al. (2014) used animal-derived fats for bio-oil preparation by pyrolysis at 500°C. The produced bio-oil showed a maximum yield of 77.9 wt.%, and it was characterized by increased aliphatic and oxygenated functional groups. Moreover, the generated bio-oil had low aromatic nature, suggesting its applicability in compression ignition engines.

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3.4 Waste-to-energy conversion techniques Several techniques (solvent extraction, hydrotreating, transesterification, gasification, and pyrolysis) have been reported for energy recovery from oil-based wastes (Singh, 2020). For instance, transesterification utilizes a chemical reaction with animal fat or cooking oils to obtain fatty acid alkyl esters essential for biodiesel production (Carmona-Cabello et al., 2018). Hydrotreating has also been employed to improve the quality of biofuel (biodiesel) by introducing a high pressure of hydrogen gas to the oil for deoxygenation (removing oxygen) and elimination of the undesired impurities (e.g., sulfur and nitrogen) (El Khatib et al., 2018). Solvent extraction, such as the Folch method (FOLCH et al., 1957), has been demonstrated to selectively extract lipids from a complex mixture of organic compounds. Gasification has been employed for the thermochemical processing of lignocellulosic biomass at high temperatures to obtain bio-energy/biofuel (bio-oil and/or syngas) (Sikarwar et al., 2017). Pyrolysis is another thermochemical process that has been widely applied to decompose the organic substances under an oxygen-deprived condition into liquid, carbon-rich solid, and gaseous products (Ben Hassen-Trabelsi et al., 2014). Some examples of the biodiesel recovery mechanisms can be explained as follows: 3.4.1 Transesterification (alcoholysis) Biodiesel is a mixture of alkyl esters that can be prepared through catalytic transesterification of glycerides with short-chain alcohols (Rezania et al., 2019). In brief, the transesterification reaction occurs between triglycerides (derived from waste cooking oil and animal fat) and an alcohol (e.g., methanol) to obtain alkyl ester compound (e.g., biodiesel) in addition to glycerol. The transesterification reaction occurs in the presence of a catalyst, i.e., biological catalysts (e.g., lipase enzyme), homogeneous catalysts (e.g., NaOH and KOH), or heterogeneous catalysts (e.g., metal oxide catalysts). Catalyst

Triglyceride + Alcohol −−−→ Alkyl Ester + Glycerol

(3.1)

Lee et al. (2015) used the transesterification of palm oil assisted by a shell-derived CaO catalyst to produce biodiesel. Their work found that the optimum operational condition was methanol:oil ratio = 12:1, and catalyst amount = 5 wt.% for 6 h, achieving a palm oil conversion efficiency of 86.75%. Lopresto et al. (2015) employed enzymatic transesterification of waste vegetable oils (e.g., frying oils) using Epobond Pseudomonas Cepacia as biocatalyst for biodiesel production. Their study attained 46.32% for the yield in esters at mass ratio biocatalyst/oil of 3% w/w, 200 rpm, and 37°C. Maneerung et al. (2016) investigated the application of transesterification for biodiesel production from waste cooking oil as a feedstock. The transesterification reaction of waste cooking oil and methanol was assisted by an active calcium oxide catalyst prepared from chicken manure through calcination at 850°C under air. At a methanol:oil molar ratio of 15:1,

Efficacy of municipal waste derived lipids in production of biodiesel

catalyst of 7.5 wt% of oil used, and 65°C for 6 h, the transesterification process achieved FAME yield of 90.8%. 3.4.2 Pyrolysis Pyrolysis is the thermal decomposition of waste material (e.g., biomass) in an inert environment at high temperature (300–1000°C) to produce valuable products, that is, solid char (carbon-rich) residues, waxy liquid oil compounds, and incondensable gases (i.e., syngas) (Kumi et al., 2020). Volpe et al. (2015) performed the pyrolysis process at 200–650°C to convert citrus waste (lemon and orange peels) into 2-biofuel (bio-oil and bio-char). Their study demonstrated that the tars extracted from pyrolytic bio-oil had gross calorific values of 19,700 J/g for lemon peel and 17,000 J/g for orange peel. The resultant tar could be utilized as a sustainable raw material source for bio-diesel production through either catalytic or thermal cracking. Ng et al. (2017) employed the pyrolysis process of crude glycerol (as a co-product of biodiesel application) through microwave irradiation assisted by a carbonaceous catalyst. The produced bioenergy from bio-oil and syngas achieved positive energy profits, using pyrolysis temperature= 400– 700°C and N2 (carrier gas) flow rate of 100–2000 mL/min.

Conclusions This chapter revealed the applicability of various MSW items (food waste, plastic waste, waste cooking oil, nonedible oil, and waste animal fats) for biodiesel production. These wastes contain sufficient amounts of lipids that can be converted into biodiesel through a transesterification reaction. Recent achievements have also depicted that pyrolysis is a proper process for the waste-to-energy conversion, such as the thermal decomposition of animal fats into bio-oil under an oxygen-deficient condition. The applicability of biodiesel and bio-oil derived from MSW has been successfully verified as a direct fuel in diesel engines. Accordingly, the waste-to-energy approach could maintain multiple benefits, regarding environmental protection, improvement of diesel blends, and satisfactory fuel properties compared with the ASTM biodiesel standards. Further studies on the feasibility and sustainability of the industrial biorefinery projects (large-scale) using MSW as an input feedstock to produce biodiesel should be conducted.

Acknowledgments The author would like to acknowledge Nasr Academy for Sustainable Environment (NASE).

References Abed, K.A., El Morsi, A.K., Sayed, M.M., Shaib, A.A.E., Gad, M.S., 2018. Effect of waste cooking-oil biodiesel on performance and exhaust emissions of a diesel engine. Egypt. J. Pet. 27 (4), 985–989. https://doi.org/ 10.1016/j.ejpe.2018.02.008.

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Abstract Biodiesel is considered a green fuel that acts as a potential candidate to cope with the increased global energy demand. However, the biodiesel recovery from lipid-based feedstock through thermochemical, biochemical, and physical and/or chemical processes might be costly to some developing countries. Hence, essential efforts should be performed to utilize low-cost and easily available sources (i.e., feedstock) for the biorefinery process. This chapter represents the different elements of municipal solid waste (MSW), such as food waste, plastic waste, and nonedible animal fats and cooking oil, which have been employed for biodiesel production. These MSW components, which are basically triacylglycerols, are subjected to lipid extraction for synthesizing a mixture of fatty acid alkyl esters. The prepared biodiesel and biodiesel blends showed comparable physical and chemical properties to diesel fuel, and they could be employed as a direct fuel in diesel engines. Based on a literature survey in the SCOPUS database by the search strings “waste,” “lipid,” and “biodiesel,” the cumulative number of documents until 2010 was 63 documents, which increased to 1023 documents in 2020. The findings implied that the topic of “biodiesel production from lipid-based waste” attracts the attention of researchers, policymakers, stakeholders, and several public and private sectors. The chapter concludes that this waste-to-energy concept attains multiple environmental and economic benefits, supporting a sustainable biorefinery application. More studies on the largescale application of biodiesel production from waste-derived feedstock are essential to endorse the industrial sector in the future.

Keywords Biofuel; Bio-oil; Municipality; SCOPUS literature; Waste-to-energy

CHAPTER 4

Wastewater grown microalgae feedstock for biodiesel production Poonam Singh a, Imran Pancha b, Anjali Singh c, Khushal Mehta b and Kiran Toppo d a

Institute of Plant Molecular Biology, Biology Centre, Czech Academy of Science, Czech Republic Department of Biology, SRM University-AP, Andhra Pradesh, India c Institute of Microbiology, Algatech Centrum, Czech Academy of Science, Trebon, Czech Republic d CSIR-National Botanical Research Institute, Lucknow, Uttar Pradesh, India b

4.1 Introduction Microalgae have gained lots of attention as alternative source for biofuel production. Fast growth rate, high accumulation of biomolecules (lipid, carbohydrate) makes algae an alternative energy source. Despite of so many advantages, commercialization of the biofuel production of microalgae is still challenging, due to its high production cost. Most expensive process in the microalgae biodiesel production is its cultivation at large scale. Thus, improving the cultivation cost can improve the economy of microalgal biodiesel production. Researchers have suggested to utilize wastewater for microalgal cultivation as it contains all the necessary nutrients for growth as well as it will eliminate the water foot prints. Wastewater, which are rich in carbon, have potential for use as a substrate for microalgae cultivation (Ramsundar et al., 2017), which will greatly reduce the cost involved in nutrients and water supply. The centrate, which is generated from centrifuging of activated sludge (Zhou et al., 2014), may be a viable alternative as the cultivation media for algae. First, the concentrations of carbon, nitrogen, and phosphorus are higher in the centrate than in any other wastewater streams obtained from a wastewater treatment plant, which can provide sufficient nutrients for algae growth. Second, centrate contains a variety of minerals such as K, Ca, Mg, Fe, Cu, and Mn (Li et al., 2011), which are essential micronutrients for algae growth and metabolism. Third, the volume of the centrate produced daily is extremely large with no availability problem all year round, and the centrate need to be recycled to the activated sludge process for further treatment to avoid environmental contamination, which adds extra load for the treatment process, especially the high concentration of phosphorus. Thus, the use of the centrate for algae cultivation could serve the dual role of waste reduction and biomass/bioenergy production. This chapter includes potential wastewater sources for microalgae cultivation,nutrient assimilation mechanism by microalgae, challenges during cultivation of microalgae for biodiesel production, and possible biorefinery approach to improve the cultivation strategy using wastewater (Fig. 4.1). Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00009-4

c 2022 Elsevier Inc. Copyright  All rights reserved.

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Figure 4.1 Integrated diagram of algal biomass production using primary and secondary waste water effluent and their processing to produce biofuel and biocommodities.

4.2 Assimilation mechanism of nutrients by microalgae Understanding mechanism of nutrient assimilation by microalgae is important for algae cultivation. Generally, nutrient remediation by microalgae occurs either by biochemical pathways for uptake of target nutrient into biomass or assimilation into protein and nucleic acid for growth (Kumar and Bera, 2020). Nitrogen is most essential nutrient for microalgal growth. Microalgae utilize nitrogen in the form of ammonium. For this nitrate reduce to nitrite in the cytoplasm which further transported into the chloroplast and again reduced in the ammonia by nitrite reductase (Jiang, 2016). Unlike nitrate, nitrite can be utilized by microalgae as a nitrogen source, thus considered as very important for microalgal metabolism. In a study by Yang et al. (2004), 5 mM nitrite can be used as only nitrogen source for growth and biomass production in Botryococcus braunii.

Wastewater grown microalgae feedstock for biodiesel production

However, high nitrite concentration can be toxic to microalgae which mainly results in photosynthesis inhibition and cell growth (Vollad, 2014). Nitrite assimilation takes place in the chloroplasts of eukaryotic algae. For nitrate assimilation into amino acid cells requires electron electrons from reduced ferredoxin (Fd), which is produced by photosynthetic electron transport, and carbon metabolism. Thus, nitrite assimilation is strictly tangled to photosynthesis, along with the fact that the photosynthetic apparatus is the main site of nitrite action and that may be reason for toxicity of excess nitrite. Phosphate assimilation also occurs via cell membrane and mainly consumed for ribosomal RNA synthesis. Both N and P are considered as macronutrients as they required for basic mechanism of microalgal growth. However, an optimum ratio of N:P concentration is needed for growth of the microalgae. Some studies have shown that a high concentration ratio of N:P can result in the low biomass productivity. Choi and Lee (2015) have studied the impact of N:P ratios on biomass growth of C. vulgaris using municipal wastewater as growth medium. They showed an increase in the N:P ratio (up to 10) first resulted in a continuous increase in the biomass of microalgae which further decreased with very high N:P ratios. Nutrient uptake from microalgae not only dependent on the N:P ratio but also it depends on algal species. Most of the studies on nutrient removal from wastewater have been done with the Chlorophyceae (Whitton, 2015). Microalgal not only assimilation macro nutrient but also it is known for assimilation of polyvalent metals which is also one of the advantages of wastewater utilization for microalgae cultivation. Microalgae accumulates metals by either cell surface sorption which is possible by living cells as well as dead algal cells, or by intracellular accumulation where metals are required for microalgae growth and metabolic activities.

4.3 Feasibility and potential of wastewater based microalgal cultivation Microalgae have versatile nutritional uptake mode, it can grow autotrophically heterotrophically as well as mixotrophically. Different wastewater sources have been used to cultivate microalgae for different applications. 4.3.1 Domestic wastewater based microalgal cultivation The composition and profile of domestic wastewater which depends on the types and region of people habitat. Due to the urbanization concept, people change their lifestyle which result in to consumption of various products, such as cosmetic, plastic materials, and other hazardous chemicals. These things directly contribute into increasing the water pollution (Haung et al., 2010). It can be resolve by applying proper chemical and biological method. Among hazardous material wastewater also contain some organic and inorganic nutrient which can open the way for biological treatment. In terms

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of biological treatment, microalgae becoming bright option for wastewater, it is fulfilling the important concept reuse of domestic water and to generate bioenergy and bioproducts. For selection of the potent microalgae, wastewater indigenous microalgal flora considered as suitable for cultivation. Another option is to use nutritionally versatile potent strain like chlorella, Scenedesmus, Daniella, or Nanochloropsis. However to start microalgal cultivation using wastewater does required some pretreatment strategy, such as sterilization of the waster to avoid microbial load for nutritional competition and supplying additional critical nutrient like nitrate, phosphate, this can trigger the cell proliferation rate and provide dominancy in the environmental condition. There are some remarkable challenges associated with microalgal based wastewater treatment i.e. sometime COD level of domestic waste water is to much higher it can cause difficulty to microalgal cell to grow, also organic matter exudes in water contribute blackish dark color, which can reduce the light availability for microalgae that ultimately affects the photosynthesis and growth.Last one major problem is that initial low inoculum density cause dominancy of other organism which can directly effect on total biomass production (Abinandan et al., 2015). 4.3.2 Industrial wastewater based microalgal cultivation Industrialization plays a major role in water pollution. Depends on types of industry the wastewater profile would be deferred. Paper and pulp industry wastewater contains lignin, hemicellulose, chlorinated, organic halide (Mazhar et al., 2019). Textile industries contains persistent coloring pollutant, surfactant, phenol derivatives, heavy metal, and other transition elements. Organic solvent, additive, catalyst and different form of active pharmaceutical ingredients was found in pharma company effluent water (Deegan et al., 2011). Alcohol distilleries, carbohydrate protein derivatives, and higher potassium found in food industries (Maya-Altamira et al., 2008). Due to the complex organic content and toxic inorganic chemical, the selection of microalgal strain would be difficult. But the nutrient versatile potency of microalgal strain ready for biosorption and bio conversation of waste organic and inorganic effluent pollutant into valuable products (Pancha et al., 2019). Some Chlorella species can decolorize textile wastewater by biosorption and can able azo dye degrade and convert it into innocuous form and microalgal biomass useful for bioproducts and biofuel production. The food industries effluent, suitable for the microalgal cultivation, and it is carried out by indigenous microalgae. The high nutritive ingredient organic matters which can be useful in the bioenergy production (Mohan et al., 2015). Pharmaceutical contaminant can be remediate by the microalgae like Chlorella spp., Scenedesmus spp., working on extracellular (ion interaction by biosorption mechanism) and intracellular (reduction and hydrolysis mechanism) to the contaminant

Wastewater grown microalgae feedstock for biodiesel production

and the produces biomass further utilized to produce biofuel and bioproducts (Xiong and Jeon, 2018). There are several challenges arising during the microalgal cultivation carried out in the industrial effluent water.In case of textile industries there are many persistent phenolic compounds presents in its effluent water which was the not utilizable for microalgae and inhibit the microalgal growth. Another major problem was that, in mixotrophic condition microalgae require organic source along with enough sunlight. Due to the colored effluent cause difficulty to microalgal growth. Pharma company effluent water contains many oxygen reactive species which is creating the disturbance in microalgal cell and arrest the cell growth. Heavy metals and other recalcitrant compound can also accumulate in microalgal cell and which could no degrade by cell stops its growth. Food and dairy industries effluent have high nutritive value, gave another organism to grow along with microalgae, cause that another microbial community invade and dominant on microalgal cell and decrease productivity (Guldhe et al., 2017). 4.3.3 Agriculture wastewater based microalgal cultivation Nowadays traditional farming converting into the modern farming due to the increase utilization of pesticide,insecticide and chemical fertilizer,simultaneously increase demand of that chemical and promote its production which is indirectly affect on the localize water body. Agricultural wastewaters contain biodegradable organic and compound like plant leaves, animal manure (Chiu et al., 2015). Inorganic compound nitrate and phosphate concentration very high compare to other wastewater effluent, which is the suitable for microalgae. Among all these, there are some persistent complex compounds present due to increase the use of pesticide, insecticide, and other chemical fertilizer components. Due to the higher nutrient uptake rate microalgae can easily utilize the nitrogen and phosphorous, which can result in increased biomass production. However, there are certain limitation observed with the cultivation using agriculture waste water used. Due to rich source of nitrogen and phosphorous there might be eutrophication take place of other unwanted organism and it becaome dominant over cultivated microalgae. Sometime this water contain pesticide, insecticide like toxic compound and it can the inhibit the microalgal growth cycle (Gupta et al., 2019).

4.4 Challenges for biodiesel production Despite the fact that wastewater grown microalgal biodiesel production is relatively feasible than the crop plant or lignocellulosic biofuel, there are still several challenges needs to tackle to produce commercial level of biofuel to meet the global energy demand. The main challenges in this regard are low biomass yield, pathogenic contamination, and

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economical as well as efficient harvesting the algae biomass from wastewater. Here we have brifly described these issues. 4.4.1 Low biomass productivity The major hurdle of biofuel production is low biomass yield which is primary source of biofuel and bio-commodities production. Open raceway ponds cultivation of microalgae is best way to scale-up for largescale biofuel and biomass production, but it is very hard to control contamination and constant growth parameter such as light, temperature, pH and aeration. Due to poor light availability, gas exchange/mixing and varying temperature and pH, negatively affect the cell density, diversity, and biomass of desired microalgae (Cho et al., 2015; Narala et al., 2016). Closed photobioreactors (PBRs) could be an alternative of open ponds where constant growth parameters and contaminations can be controlled to achieve high biomass and productivity (Narala et al., 2016). However, PBRs has also few drawbacks like hard to scale-up and high building cost which enhance the overall production cost of biofuel. Another alternative could be selection of strain which can adopt to local environment, grow rapidly with having high lipid content or select genetically engineered strain to overcome the problem of low biomass yield (Aratboni et al., 2019). 4.4.2 Pathogenic contamination Biological contamination is main prevalent problem in large scale microalgal cultivation because nutrient enriched wastewater could be ideal medium for the growth of wide range of organisms such as bacteria, virus, fungi, protozoa, zooplankton and phytoplankton. The diversity and abundance of these organisms in wastewater varies according to the type of wastewater (Guldhe et al., 2017). Besides wastewater inhabiting pathogens, microalgae cultivation at largescale in open pond system has also high chances of contamination (Narala et al., 2016). Due to presence of these pathogens, there will be scarcity or competition for nutrient between pathogens and microalgae, which will negatively affect the growth and productivity of desired microalgae and even sometimes it could be detrimental (Wang et al., 2013). It has been observed that fungal and viral contamination can change/alter the structure, diversity and succession of algal population resulting decrease in their population (Park et al., 2011). To counteract this problem, it is required to reduce the pathogenic organisms load in wastewater medium. Nowadays, removal of microorganism from domestic, industrial and agroindustrial wastewater is major challenge in order to grow microalgae as a source of food, feed, and biodiesel. There are three main types of methods used to reduce these pathogenic contaminations from wastewater such as physical, chemical, and biological treatment. In terms of biological treatments, there are few reports which shows that sometimes microalgae itself reduce or remove the bacterial contamination by producing antibacterial

Wastewater grown microalgae feedstock for biodiesel production

compounds, toxic extracellular substances or by increasing pH and oxygenation of medium (García et al., 2008). Although, this is highly species dependent process and not occur very often. Physical treatments include ultraviolet (UV) irradiation, autoclaving, pasteurization ozonation, and filtration. Few pretreatments methods, such as UV disinfection, autoclaving ozonation, and filtration prior to microalgae cultivation are widely used in recent decades to control the growth of pathogenic organism in wastewater (Markou et al., 2018; Ramsundar et al., 2017). However, all of these processes are not suitable for large scale production because it increases the production cost by time and energy consumption. Along with reducing pathogenic load from wastewater, treatment like ozonation help to eliminate the odors and color of water which increase light transmission of the medium leads to better growth of microalgae (Gan et al., 2014; Kim et al., 2014). Besides physical methods, acidification of wastewater (low pH), increased concentration of ammonia and chlorination by bleach (sodium hypochlorite) were also used as chemical methods to remove the rotifers, protozoa, and zooplanktons contaminations (Larsdotter, 2006). In some cases, chlorination enhance the lipid and biomass productivity by killing the microbes and improving the quality of wastewater (Qin et al., 2014). 4.4.3 Harvesting of wastewater grown microalgae Harvesting of wastewater grown microalgae are generally a two-step process; first step includes the destabilization or bulk harvesting of microalgal culture up to 2%–7% w/w by employing different organic and inorganic coagulants. Inorganic coagulants, such as aluminum or iron salts, are used widely for the sedimentation or floatation of algal cells (Guldhe et al., 2017; Kadir et al., 2018). Along with inorganic coagulants, biopolymer, such as chitosan, used as organic coagulants which increase the floc size of microalgae resulting improved settling efficiency (Matter et al., 2016). Although, second-step includes dewatering (removal of water) or thickening to attain concentrated (15%–25% w/w) volume of microalgae from wet algal sludge biomass by using several energy intensive techniques such as centrifugation or filtration (Kadir et al., 2018). In recent decades most widely used techniques for harvesting are divided into four main categories, such as mechanical, chemical, electrical, and bio-based (Kadir et al., 2018; Mata et al., 2010). Among these, mechanical methods like filtration and centrifugation are very fast but it is costly and energy intensive processes. Even if centrifugation is a proven technology for fast and effective harvesting, its high capital and operation costs make this solution unfeasible when the harvested biomass is used for low-value applications. These techniques required almost one third (20%–60%) of overall production cost, which makes it main snag of bioenergy production (Kadir et al., 2018). Few chemicals like electrolytes or polymers were also used to flocculate the microalgal cells. Although, electrical based harvesting method used rarly, like algal cells having negative charge were also used for

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separating the cells. However, bio-based harvesting method includes microbe-induced, biopolymers-induced flocculation or auto-flocculation which induced by increased pH or calcium ion concentration (Wrede et al., 2014). The flocculation-based method could be best alternative for cost-effective microalgal harvesting (Matter et al., 2016). Economical method for drying and dewatering of algal biomass is also required to maintain the cost-effective biofuel productions (Chen et al., 2015). In fact, in the context of wastewater treatment, only low-cost methods capable of managing large volumes of water and biomass can be suitable. However, usual separation techniques applied in wastewaters, such as conventional sedimentation, have low harvesting efficiencies only (60%–70%) in terms of microalgal biomass. Likewise, low biomass yield in harvesting processes is certainly hampering its efficiency too. Beside these, properties of microalgae (such as shape, size, surface charge, motility, specific gravity, growth phase, presence of appendages and extracellular organic matter [EOM] composition and concentration) and culture medium (pH and ionic strength) can also strongly affect the harvesting efficiency (Henderson et al., 2008). 4.4.4 Pretreatment of wastewater grown microalgae biomass The main challenge of biofuel production is economical biomass harvesting which could be relatively possible by employing few pre-treatment methods like flocculation and sedimentation. Therefore, to accelerate cost-effective biomass harvesting, pretreatment of microalgae biomass has encouraged which mainly include the use of coagulant and recycling of biomass to stimulate bioflocculation followed by sedimentation process. Thus, chemical and natural flocculation is widely used pretreatment method to increase the particle size of algae prior to employing another method for their harvesting. Recently, Zhu et al. (2018) used chitosan as a natural flocculant to harvest Chlorella vulgaris cells which seems quite efficient and convenient method for large scale harvesting (Zhu et al., 2018). The above steps of microalgae harvesting, more precisely in terms of wastewater grown microalgae seems like appropriate choice due to requirement of minimum energy and cost-effective chemicals.

4.5 Biorefinery approach for biodiesel production from wastewater grown microalgae Microalgae are promising alternative to treat wastewater, nutrient recycling and biomass production for sustainable fuel and chemicals production. The high amount of nutrients in wastewater helps microalgae to produce high biomass and other metabolites in the cell. During initial years of microalgal based wastewater remediation research, the main focus was only to reduce the pollution load, but now with recent research outcome, we know that wastewater integrated microalgal cultivation is beneficial in many ways like (1) it

Wastewater grown microalgae feedstock for biodiesel production

reduces the production cost by lower down the cost of nutrients and water, (2) it reduces pollution load in natural environment, and (3) it will produce sustainable green biomass, which can be used for fuel and fertilizer (Guldhe et al., 2017). The success of microalgaebased technology depends on the utilization of each component of biomass, such as pigments, lipids, carbohydrates, and proteins, in a biorefinery manner. However, to date, very little commercialization of microalgal biorefinery is demonstrated. This field is still in its infancy phase due to the low cost of biofuel and cultivation and downstream cost associated with the development of microalgal biorefinery. The application of wastewatergrown microalgae to the biorefinery approach reduces environmental pollution and produces various commercially important products from microalgal biomass (Pancha et al., 2019). Wastewater treatment,biofuel production,and chemical fertilizers synthesis are among the most important issue for present humankind. This issue needs to be addressed immediately and efficiently (Khan et al. 2019). Wastewater integrated microalgal cultivation and subsequent biomass utilization are among the most promising approaches to address these issues. The study carried out by Khan et al. (2019) indicates that microalgae Chlorella, Scenedesmus, and cyanobacterium Nostoc muscorum and their consortium are efficient bioremediation of wastewater and generation of a high amount of lipid which can be easily converted into biodiesel. Additionally, they have calculated that if Chlorella is cultivated for 1 year using wastewater in the pond of 1 ha, that will produce biomass 391111 kgha-1 h-1 . This biomass contains N, P, and K 22,958, 4498, and 1095 kg ha-1 y-1 , respectively, saving 55,840 ha-1 h-1 chemical fertilizers worth 4188 USD (Khan et al., 2019). The study indicates the integration of microalgal-based wastewater remediation and subsequent biorefinery to produce biofuel and biofertilizer to save the country’s environment and economy by reducing waste, greenhouse gases, and chemical use fertilizers. Another recent study indicates a consortium of Chlorella and Scenedesmus reduced 75% nutrients from domestic wastewater and produced 34% lipid, which can be used for biodiesel production (Silambarasan et al., 2021). After lipid extraction, deoiled microalgal biomass is used as fertilizer for Solanum lycopersicum. They have also calculated the total cost for production of 10 kg tomato by 50% deoiled biomass, and 50% NPK is around 0.00067$ (Silambarasan et al., 2021). Like this study, Nayak et al. also reported that microalga Scenedesmus could utilize wastewater from domestic wastewater and CO2 from flue gas (Nayak et al., 2019). Maximum 0.68 g/L biomass and 24.1% lipid is accumulated in the microalga under this cultivation condition. Deoiled biomass was tested for biofertilizer application for rice plants. The results indicate deoiled biomass increase N, P, and K content in the soil and work as best fertilizer for rice plant (Nayak et al., 2019). All this study indicates biorefinery of wastewater grown microalgae reduce our dependency on chemical fertilizers, fossil fuel, and improve the soil quality and agronomic efficiency. Hemalatha et al. (2019) indicate mixed microalgae can reduce 90% total carbon from dairy wastewater and produced 1.4 g/L biomass with 38% and 22

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% of carbohydrates and lipid, respectively, which can be utilized for the production of biofuels in a biorefinery manner (Hemalatha et al., 2019). Various industrial waste water, like dairy wastewater, generally contains a high amount of organic compounds. Microalgae can grow on these organic compounds under heterotrophic and mixotrophic conditions. Even growth, biomass, and metabolite production are significantly higher under hetero and mixotrophic conditions compared to photoautotrophic growth as organic carbon from growth media is directly incorporated into the central metabolism of microalgae (Pancha et al., 2015). Chlorella sorokiniana efficiently grows heterotrophically on aquaculture wastewater, utilizes nutrients from waste, and produces 400mg/L biomass with 39.1 %, 36.1%, and 24.57% lipid, carbohydrates, and proteins, respectively (Guldhe et al., 2017). Generally, most of the wastewater requires some type of physical or chemical pretreatment as most of the wastewater is colored or may contain a high amount of suspended solids. As microalgae are photosynthetic organism light is essential for the growth of microalgae, identification of microalgae which have the ability to grow on wastewater without any pretreatment or less treatment is an advantage and will save a lot of money and resource. Chokshi et al. (2016) indicate microalga Acutodesmus dimorphus have the ability to grow and utilize the nutrient from untreated dairy wastewater and reduced almost 90% od COD after 4 days of mixotrophic cultivation. They also extracted the lipid and carbohydrates from the wastewater grown microalga and reported that if this study is scale-up at 2000 m3 area annually, 53–54 tons of biomass with around 195 g/kg biomass biodiesel and 78 g/kg biomass bioethanol can easily be produced (Chokshi et al., 2016). Further such cultivation also reduced 90410 kg CO2 from the atmosphere, indicating such integration is a win-win strategy to remediate toxic waste and produce renewable energy (Chokshi et al., 2016). Apart from biofertilizers, deoiled algal biomass can be used for pyrolysis or gasification purpose, in this regards, Shahid et al. reported that mixed cultivation of Chlorella sp. and Bracteacoccus sp. in city wastewater produced 1.2 gm/L biomass and reduced 68% and 75% nitrate and phosphate from the wastewater, respectively. Additionally, TGA analysis of de-oiled microalgal biomass indicates activation energy in a range of 182–256 KJ/mol, Gibbs free energy in a range of 159–190 KJ/mol, and entropy 43–81 J/mol indicates excellent pyrolysis characteristics of biomass for production of bio-oil, syngas, and biochar (Shahid et al., 2019). For scale-up and large-scale applications, generally, researchers first perform the techno-economic analysis (TEA) to understand economic sustainability and potential challenges in the process. Along with the techno-economic analysis, the life cycle assessment (LCA) is also performed to understand the impact on the environment by the developed process (Mishra et al., 2019). The development of zero waste microalgal biorefinery from wastewater-grown microalgal biomass is an attractive strategy to minimize environmental hazards and for the generation of clean bioenergy and biofertilizers. However, as mentioned above, to access the sustainability of such integrated biorefinery, TEA, and LCA analysis is very important. A study by Fernandez´ et al. indicates that

Wastewater grown microalgae feedstock for biodiesel production

for production of 200 ton/year of microalgal biomass, 450 ton of CO2 , 25 ton of nitrogen, and 2.5 ton of phosphorous per hectare per is required, utilization of microalgae for wastewater treatment is a good alternative since microalgae recover almost 90% of nutrients from wastewater. However, they have indicated that the current cultivation system, either raceway ponds or other bioreactors, needs development and innovative design to reduce the land requirement and hydraulic retention time. Another recent study by Kiran Kumar et al. indicates that a 1 MLD microalgae-based diary wastewater treatment plant produces 504 tons of annual biomass with approximately 240,000 m3 treated clean water. Additionally, economic feasibility analysis shows 1 MLD plant for 20 years plant life has IRP of 118% and a payback period of 1.9 years (Kumar et al., 2020). Despite the huge potential of microalgae to remediate wastewater and subsequent biomass use for various applications, its commercialization is not widely accepted due to the long cultivation cycle (up to 10–15 days) and land requirement. Optimization of cultivation conditions and photobioreactor design improvement will solve this problem and make microalgal-based wastewater treatment a reality. Further to this lab, scale TEA and LCA analysis will help scale-up the process and demonstrate the large-scale green, sustainable approach for waste remediation, and algal biomass production for various applications.

Conclusion The economic viability of producing biodiesel from microalgae is a major hurdle. Microalgal biomass generated in wastewater, on the other hand, can lower manufacturing costs. The combination of microalgae cultivation with wastewater treatment could enable CO2 sequestration, and low-cost nutrient supply for algal biomass usage, thereby improving the economic outlook of microalgae-based biofuel production systems. The researchers have examined various wastewater sources for algal biomass production. However,there are challenges such as pathogenic contamination,low biomass production, necessity for pre-treatment, and harvesting of algal biomass, all of which can increase the production cost and needs to be addressed. Therefore, a biorefinery system focusing on the usage of wastewater-generated biomass for different applications should be developed.

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Yang, S., Wang, J., Cong, W., Cai, Z., Ouyang, F., 2004. Utilization of nitrite as a nitrogen source by Botryococcus braunii. Biotechnol. Lett 26 (3), 239–243. Zhou, W., Chen, P., Min Min Ma, X., Wang, J., Griffith, R., Hussain, F., Peng, P., Xie, Q., Li, Y., Shi, J., Meng, J., Ruan, R., 2014. Environment-enhancing algal biofuel production using wastewaters. Renew. Sustain. Energy Rev. 36, 256–269. Zhu, L., Li, Z., Hiltunen, E., 2018. Microalgae Chlorella vulgaris biomass harvesting by natural flocculant: effects on biomass sedimentation, spent medium recycling and lipid extraction. Biotechnol. Biofuels 11 (1), 1–10.

NON-PRINT ITEMS

Abstract High energy demand and water crisis are two major concern nowadays. Various alternative energy sources have been searched and suggested from the researchers around the world to address this apprehension. Microalgae biofuel have been considered as future fuel. However economic feasibility of biofuel production from microalgae is still challenging due to high production cost. Utilization of wastewater for algal cultivation can reduce the water demand as well as chemical requirement. This chapter includes different wastewater sources which have been used for microalgae cultivation and challenges associated with it.

Keywords Microalgae; Wastewater; Biomass; Biofuel

CHAPTER 5

Biodiesel from oleaginous fungi, bacteria, and yeast produced using waste substrates Har Mohan Singh a, Kajol Goria b, Shubham Raina b, Rifat Azam c, Richa Kothari b, Naveen K. Arora c and V.V. Tyagi a a

b c

School of Energy Management, Shri Mata Vaishno Devi University, Jammu, Jammu and Kashmir, India Department of Environmental Sciences, Central University of Jammu, Jammu, Jammu and Kashmir, India Department of Environmental Sciences, Babashaheb Bhimrao Ambedkar University, Lucknow, India

5.1 Introduction The high price of fossil fuel is caused of high energy demand. Applications of fossil fuels for energy and transport sectors are raised greenhouse gases (GHGs) emission. This has drawn the global attention toward renewable and sustainable energy sources. The renewable energy sources are environmentally friendly. Bioenergy has a great potential to supply growing energy demand. Among the biofuels, biodiesel is one of the growing fuels that have huge demand in the transport sector. Global warming could be minimized with the use of biodiesel as an alternative fuel due to less emission of CO2 and other GHGs (Azam et al., 2020; Singh et al., 2019). It is a renewable fuel that is produced by transesterification of triacylglycerols (TAGs) containing long-chain fatty acids with shortchain alcohols producing monoalkyl esters (namely, fatty acid methyl esters [FAMEs] and fatty acid ethyl ester [FAEEs]) (Meng et al., 2009; Ahmad et al., 2020). Biodiesel has the advantage that it can be used in currently designed diesel engines without modification, no matter the origin of the feedstock used (e.g., vegetable oil, animal fats, and microbial oils) (Patel et al., 2020). Since, biodiesel is made from biological substances and captures environmental CO2 and sequester it into biomass, a net CO2 emission can be considered as zero. These key features make biodiesel an environment friendly and sustainable fuel. The use of food crops as feedstock for the synthesis of biodiesel on a commercial scale is not recommended as it could trigger severe food scarcity. So, there is a need for exploring non-food based materials that can be used for the synthesis of biodiesel (Patel et al., 2019). Biomass used as feedstock for the production of biodiesel is a promising alternative for fossil-based fuel like diesel.The conventional feedstock of biodiesel include oil seeds, animal fats, spent oils which are being replaced by plants litter and industrial spent (Tsouko et al., 2016). Fungi, bacteria, and yeast are identified as oleaginous microbes which are capable to produce biodiesel. Oleaginous eukaryotic microorganism such as Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00004-5

c 2022 Elsevier Inc. Copyright  All rights reserved.

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fungi, yeast, microalgae, and autotrophic and heterotrophic bacteria are having ability to accumulate TAGs which is oil. The accumulation of TAGs by these microorganisms makes them to be utilized as feedstock for biodiesel.The oil produced by the microorganism is referred to as single-cell oil (SCO). Oleaginous microorganism was firstly reported in 1960s (Dourou et al., 2018). Oleaginous yeasts, when subjected to favorable conditions show high multiplication and growth. Through studies, it has been found that lipid yield could go up to 70% of dry weight under ideal environment. Examples include Trichosporon pullulans, Lipomyces lipofer, Rhodotorula glutinis, Lipomyces starkeyi, Cryptococcus albidun, and Rhodosporidium tortuloides. However, the response of different strains of yeast varies with fermentation conditions. Using conventional sources like food grains can cost high so there is a need to look for materials which can substitute for biodiesel production (Kumar et al., 2019). Generally, lipids obtained from microbes are easier to harvest and have better yield in comparison to plant based oils. The chapter deals with oleaginous microorganisms (namely, fungi, bacteria, and yeast), which are being utilized for the production of biodiesel. Waste substrate, technologies and challenges, and perspective of oleaginous microorganisms for biodiesel production are also discussed.

5.2 Oleaginous microorganisms Various strains of microorganisms, including bacteria, fungi, yeast, and microalgae are known to accumulate lipids higher than 20% (w/w) in their cellular compartments, such microbes are called as oleaginous microbes. The oleaginous microorganisms commonly show to produce oils having 4–28 nonbranched carbon chain; yield of oil can be enhanced up to 70% of their dry cellular weight by changing C/N ratio (Papanikolaou and Aggelis, 2011; Dewick, 2009). Many species of microbes including bacteria, microalgae and yeast are being explored for the production of biodiesel, yet the potential of bacterial species is least among all. TAGs are the major substrates essential for biodiesel synthesis which are produced by microbes like algae, fungi, and yeast (Kumar et al., 2019; Liang and Giang, 2013). The oleaginous microbes like bacteria, algae, fungi, and yeast are known to produce lipids which are known as TAGs producer. SCO yielding oleaginous microbes include fungi, bacteria, yeast, and microalgae. TAG’s have identical properties in comparison to plant oils which are produced by eukaryotic microorganisms like yeast,microalgae,and moulds while bacteria are restricted to the production of few lipids only. Depending on nature of microorganisms, microalgae can be grown in sunlight as well as in dark environmental conditions. In a photoautotrophic medium, sunlight and CO2 is required along with carbon (organic waste, glucose, etc.) for the production of SCO. The physical, chemical, and environmental conditions are the limiting factor for the oleaginous microbes. Rhodococcus and Nocardia are known to produce TAG’s in a large amount and could be used for the production

Biodiesel from oleaginous fungi, bacteria, and yeast produced using waste substrates

of biodiesel. Moulds species, including Aspergillus terreus, Tolyposporium, Claviceps purpurea also yield a good amount of lipids under special environmental conditions. Monounsaturated fatty acids (MUFAs) and saturated fatty acids (SFAs) rich single cell oils are used for the synthesis of biodiesel while oils rich in polyunsaturated fatty acids (PUFAs) can be used for the production of nutraceuticals (Patel et al., 2020). Microorganisms generally produce a varied range of fatty acid profile, including monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), saturated fatty acids (SFAs) having hydrocarbons in the range of C6 to C36. Microbes producing lipids over 20% of their cellular weight could be cultured for the synthesis of biodiesel or nutraceutical products (Patel et al., 2020). Oleaginous microbes are not only energy products for commercial applications but also produce various values added products which have multiple applications for health, food, and medicine. 5.2.1 Fungi Efficient feedstock and substrates selection are depicted as key parameters to ensure the high yield of biodiesel. Generally, microbial biodiesel production demands for availability of lipid content in microbe’s cellular composition. Therefore, microbial organisms comprising lipid content greater than 20% of their body weight are capable of producing biodiesel and are commonly referred as oleaginous microorganisms. Oil or lipid containing fungi called as “oleaginous fungi” has been considered as one of the potential feedstock for biodiesel production. Fungi form a separate kingdom constituting a great diversity of eukaryotic, multicellular (except unicellular yeast) species generally exist as thread-like filamentous (not all fungi) structures called hyphae ranging from 2–10 μm in diameter and up to several centimeters in length or as mycelium (network of hyphae). Structurally, fungi comprise of chitinous cell wall and lacks chlorophyll pigment (achlorophyllous). Therefore, the organism breakdown the organic matter through enzymatic action (lipases) externally before assimilation as it doesn’t possess the ability to digest organic matter inside the body. In the biodiesel production, oleaginous filamentous fungi could offer numerous biotechnological advantages like appropriate fatty acid profiles, capability to utilize carbon rich organic waste as substrate sources, and cost-effective downstream processing (Carvalho et al., 2018). Among the oleaginous fungi, zygomycetes species, such as Mortierella alpine, Umbelopsis isabellina also named as Mortierella isabellina,Mucor circinelloides,and Cunninghamella echinulate have fascinated much interest intended for the higher yield of long-chain polyunsaturated fatty acids. Few of efficient oleaginous fungal strains are given below in Table 5.1 along with their lipid content. Additionally, the substrate for microbial growth plays a key role as it provides nutrients source. There are various molecules available to serves as substrate, rich in nutrients like glucose, nitrogen phosphorus, essential and trace elements necessary for

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Table 5.1 Lipid content present in oleaginous fungi. Oleaginous fungi

Lipid content (%cell dry weight) References

Aspergillus oryzae Mortierella isabellina Humicola lanuginose Mortierella vinacea Cunninghamella echinulata Colletotrichum sp. Fusarium oxysporum Epicoccum purpurascens Phaeodactylum tricornutum Cunninghamella echinulata, Alternaria alternate Rhodotorula glutinis

57 86 75 66 57 73 43 70 57.8 57.5 40.7 47.2

Forde et al., 2014 Bautista et al., 2012 Forde et al., 2014; Meng et al., 2009 Forde et al., 2014; Meng et al., 2009 Bautista et al., 2012 Gao et al., 2016 Chen et al., 2018 Koutb and Morsy, 2011 Xue et al., 2015 Zhang et al., 2017 Bagy et al., 2014 Liu et al., 2015

efficient growth of fungal feedstock that subsequently accumulate lipids for biodiesel production but demands high cost. Therefore, in economic and ecological points of view, usage of organic waste as substrates for biodiesel production from fungi offers a good alternative to costly nutrients enriched substrate. Organic wastes from various sources like municipal solid waste, agricultural waste, industrial waste containing sugars, etc., can fulfill the requirements proficiently. Also, it offers significant cost effectiveness, increased efficiency, waste remediation, and process simplicity. Some of the organic wastes as substrate for biodiesel production from oleaginous fungi have been listed below in Table 5.2. 5.2.2 Bacteria Only a few bacteria like Mycobacterium sp., Nocardia sp., Rhodococcus sp., Streptomyces sp., and Gordonia sp. are known to synthesize lipids required for biodiesel generation under specific environmental circumstances. It is also reported that providing high carbon and low nitrogen conditions to Gordonia sp. and Rhodococcus sp. could increase lipid production up to 80% (Kumar et al., 2019; Miller, 2012; Gouda et al., 2008). Modern technologies could enhance lipid concentration and their quality by genetically altering strains of bacteria to modify their metabolic pathway. Recent researches on modified strains of E. coli have provided similar results in terms of biodiesel production (Liang and Jiang, 2013; Kalscheue et al., 2006). Bacteria can grow exponentially when adequate nutritional conditions are maintained. A considerable proportion of lipid has been reported in a few species of bacteria. Such species of bacteria are being explored by researchers to find a possible mechanism of biodiesel synthesis. For example, E. coli is being genetically modified to obtain the desired traits to get a yield of FAEEs for the production of biodiesel (Bautista and Vicente, 2012). Various species of bacteria are recognized for their high lipid content including Nocardia globerula 432 (Alvarez et al., 2003), Rhodococcus opacus

Biodiesel from oleaginous fungi, bacteria, and yeast produced using waste substrates

Table 5.2 Biodiesel or lipid content accumulation by oleaginous fungi using organic substrate.

Substrate

Corncob waste liquor (lignocellulosic wastewaters) and and a Paper mill effluent (lignocellulosic wastewaters) Deoiled algae extract (cellulosic waste) Deoiled Pongamia seed cake Sugarcane molasses Sugarcane molasses Sugarcane molasses Sugarcane molasses Sugarcane molasses Agro-dairy waste, whey Musa balbisiana cola peels

Fungal strain as feedstock

Biodiesel or FAME yield/lipid content accumulation recorded References

Aspergillus awamori (MTCC 11639)

33.3/16% lipid content (total/neutral)

Subhash and Mohan, 2015

Aspergillus awamori (MTCC 11639)

32.2/15% lipid content (total/neutral)

Subhash and Mohan, 2015

Aspergillus awamori (MTCC 11639) Aspegillus ochraceus MK483340 Aspergillus parasiticus Alternaria alternate Cladosporium cladosporioides Epicoccum nigrum Fusarium oxysporum Aspergillus candidus

35.4/18% lipid content (total/neutral) 28.93% lipid content

Subhash and Mohan, 2015 Jathanna et al., 2020

28.28% lipid content 40.75% lipid content 38.52% lipid content

Bagy et al., 2014 Bagy et al., 2014 Bagy et al., 2014

38.09% lipid content 31.95% lipid content 320 mg total FAME

Bagy et al., 2014 Bagy et al., 2014 Kakkad et al., 2015

Penicillium citrinum PKB20

60.61% lipid content

Bardhan et al., 2019

PD630 (Miller et al., 2012), Streptomyces coelicolor TR0958, Streptomyces coelicolor TR0123 (Arabolaza et al., 2008). However, extraction of biomass from bacterial cells offers high cost that could raise overall cost of corresponding biodiesel production. Various technologies known for harvesting of biomass include centrifugation, flocculation, sedimentation, flotation, filtration, magnetic separation, etc. (Kumar et al., 2019). Putting all the aspects together, the yield of biodiesel production from bacteria is lower in the present scenario but have high potential in the near future (Bautista and Vicente, 2012). Table 5.3 represents biodiesel or lipid content accumulation by oleaginous bacteria using various organic substrates (Qadeer et al., 2017; Behera et al., 2019). The genetic recombination of ethanol production gene and atfA gene (wax ester synthase) of Zymomonas mobilis and Acinetobacter bayiyi respectively is a good option to enhance the FAMEs in E. coli. (Dourou et al., 2018). Gene regulation mechanisms of fatty acid biosynthesis is an advantageous with bacterial community because provides a high rate of replication that produced a significant amount of biomass in a small time. Thus, it is easy to regulate the genetic engineering and metabolic engineering of bacterial cell to enhance its oil accumulation.

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Table 5.3 Biodiesel or lipid content accumulation by oleaginous bacteria using organic substrate. Oleaginous bacteria

Materials used

Lipid/oil Content %

References

Gordonia sp. Streptomyces coelicolor TR0958 Streptomyces coelicolor TR0123 R. opacus DSM 43205 Rhodococcus opacus DSM 1069 Rhodococcus opacus PD630 Rhodococcus opacus Rhodococcus erythropolis Bacillus subtilis

Agricultural wastes Glucose

72 83

Gouda et al., 2008 Arabolaza et al., 2008

Glucose

64

Arabolaza et al., 2008

Biomass gasification wastewater Ethanol organosolv lignin Glucose

65

Goswami et al., 2017

4

Kosa and Ragauskas, 2013

50

Miller, 2012

Dairy wastewater Glycerol

53 14

Gupta et al., 2017 Sriwongchai et al., 2012

Hydrolysate of cotton stalk Kraft hardwood pulp CO2

39

Zhang et al., 2014

46

Kurosawa et al., 2013

45

Qadeer et al., 2017

Rhodococcus opacus PD630 Cynobacterium aponium

5.2.3 Yeast Oleaginous yeast is one of important microorganism having fast growth rate and has potential to accumulate 40%–70% of lipid under various nutrient limiting conditions. However, lipid and fatty acid profile varies from species to species. Candida utilis and Saccharomyces cerevisiae accumulated 5%–10% oil while Rhodotorula sp. and Cryptococcus curvatus accumulated 40%–70% lipid content on the same culture conditions (Meng et al., 2009). Candida, Cryptococcus, Lipomyces, Rhodosporidium, Yarrowia, Trichosporon, and Rhizpus are well known genera of yeast (Thevenieau and Nicaud, 2013). Crptococcus curvatus showed as the most efficient oleaginous yeast which could accumulate >60% of lipid and under nitrogen limiting condition. However, oleaginous yeast and mold accumulated TGA bearing high amount of polyunsaturated fatty acids. Rhodosporidium toruloides Y4 produced long chain fatty acids having 16 and 18 carbon chains. Yeast has the ability to utilize various sources of carbon for the production of biomass and lipid.Starch,xylose,glucose,cellulose,hydrolysates and municipal and various industrial wastes are the main sources of carbon. Nutrients limiting conditions help to accumulate lipid in the yeast cell. Nitrogen is the key element for the biosynthesis of proteins and nucleic acid. In the nitrogen limiting condition, yeast cells continuously assimilates the carbon source that influences the fat storage in the form of lipid and reduced the cell reproduction (Thevenieau and Nicaud, 2013; Dourou et al., 2018).

Biodiesel from oleaginous fungi, bacteria, and yeast produced using waste substrates

Table 5.4 Lipid content accumulation by oleaginous yeast using organic substrate. Oleaginous yeast

Yarrowia lipolytica Lipomyces starkeyi Rhodotorula glutinis

Materials used

Industrial glycerol Glucose and xylose Monosodium glutamate wastewater Lipomyces starkeyi Glucose Lipomyces starkeyi Sweet sorghum CBS 1807 stacks juice Cryptococcus curvatus Waste cooking oil Yarrowia lipolytica Glucose and volatile MUCL 28849 fatty acids Trichosporon Glucose fermentans Rhodosporidium Glucose toruloides Rhodosporidium Crude glycerol toruloides Yarrowia lipolytica Stearin Rhodotorula glutinis Monosodium glutamate and glucose Trichosporon Mannose fermentans Cryptococcus curvatus Glucose Lipomyces stakeyi Flour rich wastewater Lipomyces stakeyi Sweet sorghum bagasse

Lipid/oil content (%) References

43 48 20

Papanikolaou and Aggelis, 2002 Bonturi et al., 2015 Xue et al., 2008

68 30

Angerbauer et al., 2008 Matsakas et al., 2014

70 40

Patel and Matsakas, 2018 Leiva-Candia et al., 2014

62

Zhu et al., 2008

67

Li et al., 2007

41

Kiran et al., 2013

52 20

Papanikolaou et al., 2007 Xue et al., 2008

50

Huang et al., 2009

53 40

Patel and Matsakas, 2018 Qadeer et al., 2017

63

Qadeer et al., 2017

Lipid metabolism of oleaginous yeast has been recognized which is helpful in selecting potential trains and metabolic engineering to increase the lipid production in the yeast cell. S. cerevisiae is well known yeast that has been exploited for metabolic engineering approaches. With the help of metabolic engineering, lipid production can regulate and certain criterion of nutrients concentration alterations such as carbon and nitrogen could be done. However, genetic engineering of yeast is helpful to produce nutraceuticals, such as eicosapentaenoic acid (EPA). Yarrowia lipolytica has been indentified to produce EPA of 161.04 mg/L/Day. Y. lipolytica is considered as “generally recognized as safe.” The cultivation of yeast has advantage to grow on waste products of sugars, glycerol. In order to advance the economic viability, oleaginous yeast strains have been easily fostered on inedible materials,for example,lignocellulosic biomass.Table 5.4 depicts the lipid content accumulation by oleaginouos yeast using various organic substrates (Patel et al., 2020; Qadeer et al., 2017; Behera et al., 2019).

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5.3 Technologies involved in biodiesel Fungi as an oleaginous microbe accumulates oils/lipids, especially triglycerides (TG) or triacyglycerols (TAGs) constituting saturated fatty acids (SFA) like stearic acid (18 carbons, 0 double bonds), palmitic acid (16 carbons, 0 double bonds), monounsaturated fatty acids (MUFA) like oleic acid (18 carbons, 1 double bond), polyunsaturated fatty acids (PUFA) like linoleic acid (18 carbons, 2 double bonds), and linolenic acid (18 carbons, 3 double bonds) in its cellular composition (Tonato et al., 2018; Ghosh and Roy, 2019). These fatty acids are very much comparable with vegetable oils like rapeseed oil, soybean oil, palm oil, etc., exploited for biodiesel production. Major raw material entails carbon rich substrate, alcohol (mostly methanol or ethanol), and acid catalysts (HCl/H2 SO4 ) or base catalysts (NaOH, KOH, CaO, KOH/Al2 O3 , zeolite) or lipase enzymes (Rhizopus oryzae lipase, Candida antartica lipase) (Gujjala et al., 2019) for biodiesel generation from oleaginous feedstock like fungi.Base catalysts are the most commonly used ones due to their low cost, less energy requirement, reusability, rapid reaction rate, and easier separation from product (Ambat et al., 2018). However, the base catalysts suffer with limitations of saponification tendency and large amount of wastewater generation that need to be overcome for process efficiency (Talha and Sulaiman, 2016). With the aim toward economic viability and sustainability in biodiesel production from oleaginous fungi, the process must involve utilization of ideal, low cost organic substrates, such as organic waste rich in carbon and other nutrients. Compatibility of selected microbial/fungal strain with the composition of organic substrates should be considered as not all strains are well-suited for all kind of organic substrates. The technology associated with the exploitation of fungi for biodiesel synthesis by utilizing microbial lipids involves a downstream process with general flow as: Harvesting of fungal biomass > lipid accumulation > lipids extraction from fermentation broth > transesterification of TG/TGA and methanol in the presence of a catalyst into fatty acid methyl/ethyl esters (FAME or FAEE). The group of esters thus obtained is the crude biodiesel which upon purification yield pure biodiesel. In addition, glycerol as a by-product also gets manufactured that requires to be separated from the reaction for methanol recovery and prevention of saponification (Shoaib et al., 2018). The generalized transesterification reaction takes place in biodiesel production process is shown in Fig. 5.1, where R1 , R2 , and R3 are long chains of hydrocarbons (alkyl groups) also known as fatty acid chains. Purification and isolation of crude biodiesel appears to be pretty cumbersome stage subsequent to transesterification as the later produce additional products, such as excess alcohol, soap impurities, unrecovered catalyst, water, free mono-, di-, and tri-glycerides. After 8 to 24 h of transesterification, glycerol settled down at the bottom and separated out from crude biodiesel by filtration, centrifugation or in decantation funnels (Yellapu et al., 2018). Subsequently, excess of alcohol gets removed by distillation or evaporation. Moreover, the other impurities such as soap, catalyst traces, etc., are washed out with

Biodiesel from oleaginous fungi, bacteria, and yeast produced using waste substrates

CH2−OOR1

CH2−OH

R1−OO R’

CH2−OOR2 +

3R’OH +

CH2−OOR3

Alcohol

Triacylglycerol (TAG)

NaOH / KOH Catalyst

R2−OO R’ R3−OO R’ Alkyl ester of fatty acids (Biodiesel)

+

CH2−OH CH2−OH Glycerol

Figure 5.1 Transesterification reaction.

different methods such as wet and dry washing. Wet washing methods involve bubble washing, mist washing, stir or mix washing, but proves not much advantageous as it require large amount of water and drying of excess water in subsequent step. Dry washing involves certain compounds like silica gel, phosphoric acid, starch, cellulolytic derivatives, magnesium silicates, or ion-exchange resins, etc., are also known to wash out or absorb unwanted impurities from the crude biodiesel (Alves et al.,2016;Saengprachum and Pengprecha, 2016). After washing, drying approach is followed so as to remove the water content present in biodiesel. Persistence of water traces in biodiesel might cause problems like corrosion and gelation sufficient enough to damage diesel engine. Therefore, complete water content removal from the biodiesel or concentration below 500 mg/L traces is recommended to boost biodiesel efficiency (Buši´c et al., 2018). Major drying advancements involve heating or chemical treatment. Heat treatment makes use of biodiesel agitation at 90–110°C under vacuum for 20 min to 1 h or 110–120°C for about 20 min to 1 h, while chemical treatment entails utilization of drying agent like anhydrous sodium and magnesium sulfates. Subsequent to drying, distillation as the final step yields biodiesel devoid of any impurity. Overall process of producing biodiesel from oleaginous fungi by making use of waste as substrate is represented in Fig. 5.2. Biodiesel is a clean fuel having less carbon and particulate emissions, which can be prepared from varied source materials, is environmental friendly fuel having high compatibility with present-day diesel engines (Patel et al., 2020; Hill et al., 2006). So there is a need to explore species which can enzymatically break down complex lignocellulosic biomass for the production of biofuels. Different strains of microbes need different environmental conditions, proper feedstock as well as well defined C/N ratio. Waste generated from flour mills and other food industries has a high content of carbohydrates like glucose, xylose, sucrose, etc. which could be exploited as promising biomass for the synthesis of biodiesel. Third generation biodiesel is mainly generated from single cell oils obtained from oleaginous microbes. Using microbes for biodiesel production is a great advancement as it has paved way for land reforms on the areas undesirable for farming

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Figure 5.2 Biodiesel production from fungi by using organic waste substrate.

practices. Production of biodiesel from microbes can be economical on commercialscale as the lipid production rate is much higher than that of plants. Also, microbes could be exploited throughout the year for the same. Sugarcane molasses and plant waste could be used as a source of starch for growing particular yeast species to produce SCO. Advancement in the field of microbial culture is needed in terms of extraction,cultivation, isolation of favorable strains of microorganisms to achieve a high yield (Bharathiraja et al., 2017). Direct conversion of microbial biomass for the synthesis of biodiesel could be achieved in a single step instead of two steps as in the case of indirect transesterification in order to reduce the generation cost as well as to increase the yield of biodiesel. Lipids obtained from microbes are rich in saturated fatty acids while plant and animal-based oils have a

Biodiesel from oleaginous fungi, bacteria, and yeast produced using waste substrates

high content of unsaturated fatty acids. This makes them unfit to be used in conventional engines. However, compounds like carotenoids and tocopherols which are present in them can reduce the corrosive effect of the same (Bautista and Vicente, 2012). Synthesis of biodiesel using plant-based feedstock produces glycerol (10% w/w) as waste which can potentially be utilized as feedstock for biodiesel synthesis by oleaginous microbes. Sewage sludge is also known to be used as feedstock for SCO; however, yield of oil is likely to be lower than other potential feedstock (Tsouko et al., 2016). Synthesis of biodiesel requires transesterification of feedstock which can be a vegetable oil, animalbased oil, or microbial oil. Generally, extraction of microbial oil by disrupting their cell wall is prerequisite prior to transesterification. Proper knowledge for the disruption of the microbial cell wall is required to extract SCO which is later processed for the synthesis of biodiesel. Direct transesterification of microbial oils instead of their extraction could also be achieved in future which may improve the synthesis of biodiesel (Tsouko et al., 2016). There is a probability of improved lipid yield when organic nitrogen source is used instead of inorganic nitrogen sources for the culture of oleaginous microbes as suggested by Zhu et al. (2008). According to Tsouko et al. (2016), yeast, Cryptococcus curvatus showed lipid concentration up to 60% of dry weight by utilizing cheese whey and other food industries spend.

5.4 Challenges and perspectives Currently,biodiesel production at a commercial or large scale involves utilization of edible oleaginous crops like canola or rapeseed (Brassica napus), soybean (Glycine max), sunflower (Helianthus annuus), nonedible energy crops like Jatropha sp. and Pongamia sp. and many other plants capable to extract lipid content around 25% to 35% of their body weight (Bardhan et al., 2019; Chen et al., 2019). However, these feedstock are facing significant public criticism over food security as their cultivation requires arable (Sargeant et al.,2017) or fertile land leading to shortage of fertile land for food crops cultivation. Furthermore, the estimated biodiesel production costs about 1.5 times higher than that of petro-diesel forming one of the major constraints in its commercialization (Gujjala et al., 2019). In contrast, oleaginous microorganisms have convenient and appropriate fatty acid profile, that is, they can accumulate lipid content up to 70% by their body weight (Chen et al., 2019), have rapid growth rate and don’t require fertile crop land for their cultivation growth and development. Currently, feedstock oleaginous microbes like fungi, bacteria, yeast, algae, etc. are evaluated as potential source of lipid accumulation so as to synthesize biodiesel (Bautista et al., 2012). Although these microbes are the promising and renewable oil sources for biodiesel production but requirement of high grade and costly carbon rich source substrates and nutrients is the prime barrier in commercialization of these microbes. Major challenges and their perspectives for biodiesel commercialization can be illustrated through Fig. 5.3.

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Figure 5.3 Current challenges and perspectives in the course of biodiesel synthesis.

The chief restrictive factor associated with large scale biodiesel synthesis evaluated to be the high production cost attributed to feedstock. An appropriate way out to solve the problem of high production cost could be the utilization of low cost substrates for harvesting oleaginous microbes that are supposed to yield microbial lipids. A number of nutrient rich (carbon, nitrogen, sugars) and low cost substrate for are being explored for keeping the process much economical including municipal solid waste, sludge, sewage, agricultural or lignocellulosic waste (wheat or rice straw), waste molasses, sugarcane bagasse, corn stover, soy whey, industrial by products and wastewater, etc. (Patel, et al., 2020). The use of waste as substrate or feedstock may not only reduce the overall production cost but also accounts for waste remediation. Identifying novel high lipid yielding strains or metabolic engineering or manipulation of efficient microbes might enhance biodiesel yield and at a reasonable cost. Critical steps in carbon metabolism affect the lipid accumulation and their regulation in oleaginous microorganisms. Although, low cost feedstock are required for the oleaginous microorganism but low productivity enhances the cost of SCO because of use of high-tech bioreactors

Biodiesel from oleaginous fungi, bacteria, and yeast produced using waste substrates

(Dourou et al., 2018). Genetic manipulation incorporates the alteration in microbial lipids profile and lipid synthesis pathways through molecular engineering techniques, such as deletion or addition of enzyme regulating genes, gene overexpression or coexpression of more genes, gene suppression, gene blocking or knockout, multigene approaches, and many others. One metabolic engineering application has been studied in oleaginous yeast Yarrowia lipolytica that achieved 2 times and 4 times increase of lipid yield on over expression of genes acetyl-CoA carboxylase 1 (ACC1) and diacylglycerol acyltransferase 1 (DGAT1), respectively (Tai and Stephanopoulos, 2013). Another study by Lu et al. (2008) revealed that oleaginous bacteria E. coli increased lipid productivity by about 20 times on over expression of three different genes regulating different enzymes, that is, acetyl-CoA carboxylase (ACC), an endogenous and an exogenous thioesterases along with knockout of gene controlling acetyl-CoA synthetase enzyme. In case of an oleaginous fungi, Mucor circinelloides, lipid content has also been found to improve by 2.5 times on over expression of gene controlling malic enzyme, a key factor providing NADPH for lipid accumulation (Zhu et al., 2020). Furthermore, glycerol effect has also led to major problem due to glycerol production as by-product in case of enzyme catalytic transesterification leading to inactivation of biocatalyst (lipase enzyme) and enhancement of viscosity in the reaction medium (Aguieiras et al., 2015). This inactivation can be inhibited by adding organic cosolvents like hexane, cyclohexane, nheptane, isooctane, petroleum ether tetrahydrofuran, chloroform, and dichloromethane in the reaction medium (Osorio-González et al., 2020) and also viscosity of the reaction medium may get reduced on addition of these solvents. Moreover, presence of water in alcohol and reaction feedstock hampers biodiesel yield by soap formation. In the presence of water, triglycerides and fatty acids as transesterification by-products facilitate excessive saponification (soap formation) by hydrolyzing triglyceride into diglycerides. Saponification induces hindrance in biodiesel production due to solidification of soaps of saturated fatty acids (SFA) that become quite difficult to recover and may lead to reduction in the biodiesel yield (Mosali, 2010). Among the technology advancements, another promising technology that use using nanomaterials (size range 1–100 nm) have emerged to overcome the challenges such as low reaction rate, saponification problems and catalyst inactivation (Ingle et al., 2020). Different kind of nanomaterials used as nanocatalysts in biodiesel production includes (1) metal oxides based nanocatalysts (ZrO2 , SnO2 , Cao, Fe3 O4 , MgO, Ca/Al/Fe3 O4 , KF/Al2 O3 , etc.), sulfated oxides, (2) nanohydrotalcites, (3) zeolites/nanozeolites, and (4) magnetic nanocatalysts (KF/CaO-Fe3 O4 , ZnO/BiFeO3 , etc.) (Zuliani et al., 2018; Ingle et al., 2020). Therefore, development of an ideal catalyst is the need of the hour to prevent saponification for optimum production of biodiesel. Acid catalysts may help to avoid soap formation but not recommended for transesterifiction reaction because of its low reaction rates and other possible side reactions.

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Conclusion Microbes are an integral part of ecosystem and they have a wide diversity. They have the potential to replace biodiesel production from convention crops and easily utilize the waste materials as a feedstock to produce biodiesel. The requirement of biodiesel in bulk amount at commercial level from oleaginous microbes is still a subject of research and development but involvement of low cost is fascinating to solve the challenges of bulk production of biodiesel. Waste materials based substrate might have economic feasibility of lipid production by oleaginous microorganism. Microbial strain and process optimization is a major challenge with oleaginous biodiesel production. Use of advanced bioprocess technology and genetic engineering can promote high production of biodiesel using oleaginous microorganisms.

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NON-PRINT ITEMS

Abstract Climate change consequences are in an alarming stage where a change is required from conventional energy to renewable energy options. Utilization of heat in different industrial sectors and transportation are two major sectors that require huge amount of energy. Biodiesel is mostly produced from food crops which are challenge for current demand of fuel and food. Conventional crops have a long life cycle, require intensive labor, high capital cost investment and could be grown only in a specific season and climate. Oleaginous microorganisms are a promising option for the production of lipid in place of conventional crops because they have a short life cycle, could be easily grown in the lab conditions and have high productivity of lipid. Fungi, bacteria, and yeast are emerging microbes that have potential to fulfil current demand of feedstock needed for biodiesel production. They could easily utilize waste materials for producing biodiesel that can reduce the existing cost of conventionally produced biodiesel. The chapter provides a details discussion of oleaginous microorganisms, fungi, bacteria, and yeast in addition with technologies involved in yielding of biodiesel production and their challenges.

Keywords Oleaginous microbes; Fungi; Yeast; Bacteria; Biodiesel

CHAPTER 6

CaO derived from waste shell materials as catalysts in synthesis of biodiesel Carla V.R. Moura a, Wiury C. Abreu b, Edmilson M. Moura a and Jean C.S. Costa a a

b

Federal University of Piaui, Teresina, PI, Brazil Federal Institute of Maranhão, Buriticupu, MA, Brazil

6.1 Introduction Biodiesel has become a substitute fuel for diesel in recent years, with many countries now using it as a blend with petroleum diesel. It involves several issues: the costs of raw materials, alcohol, catalysts, and water consumption. However, the most considerable cost of production falls on the use of the material, which may be edible or non-edible oils. However, the great controversy would still be whether to use edible oils for fuel production. This raw material is around 70%–95% of the costs of total biodiesel production (Azócar et al., 2010). Industrially, biodiesel is obtained by the transesterification reaction between a vegetable oil or fat and small chain alcohol such as methanol (Fig. 6.1). This reaction takes place through a catalyst that can be basic, acidic, or enzymatic. However, basic catalysts are the most used because they are more convenient in kinetic, thermodynamic, and cheaper terms. The most used homogeneous basic catalysts are NaOH, KOH, and CH3 ONa. When these catalysts are used, some reaction conditions must be obeyed,such as,for example,oil or fat must have a low acid content and low water content, as these factors can lead to the saponification reaction, decreasing the conversion to biodiesel. Therefore, researchers around the world have been using other types of basic catalysts, mainly heterogeneous catalysts. Heterogeneous catalysts can eliminate the formation of soap, improve the separation of the catalyst from the reaction medium, and can be reused (Abreu WC de et al., 2016). Metals, metal oxides, hydrotalcite, TiO2 grafted on silica, vanadyl phosphate, Na/NaOH/γ -Al2 O3 , ion-exchange resin, and SnCl2 , zeolites have been studied as catalysts for the transesterification reaction. Metal oxides most studied as basic catalysts are the alkaline earth metal oxides, such as calcium, magnesium, strontium, mixed oxides, and hydrocalcites. Calcium oxide is the most studied, as it has some advantages over other oxides, for example, longer life, high catalytic activity and requires moderate reaction conditions (Roschat et al., 2016). Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00001-X

c 2022 Elsevier Inc. Copyright  All rights reserved.

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Figure 6.1 Transesterification reaction.

The synthesis of these heterogeneous catalysts involves several steps and a preparation time making them economically and environmentally expensive (Rizwanul Fattah et al., 2020). Therefore, the great challenge is to explore an ideal catalyst, which is solid and basic, highly effective, low-cost, and environmentally friendly for biodiesel production (Di Serio et al., 2008). The use of renewable materials and natural waste from various industries can be the key to solving the problems mentioned above. In this context, the use of basic heterogeneous catalysts derived from residues, has many advantages, for example, ecological, they are cheap, available, quickly recovered from the biodiesel product and reuse (Sharma et al., 2011). Sustainable development is achieved when industries play a role in using innovation processes to use raw materials and the waste generated, thus closing a cycle. Sustainable processes, use of residues from biomass and processing, synthesis of new materials, and production of biofuels, are niches that can be correlated. Calcium oxide (CaO) is a heterogeneous catalyst widely used in transesterification reactions, due to its long life, high activity, the reaction conditions are moderate, the volume and surface area ratio is high, it has a large number of basic sites. Also, CaO can be obtained from various natural sources from agricultural residues, from animals and via the calcination process of the limestone, varying the temperature from 700 to 1000°C. Then, it can be said that CaO is an eco-friendly material (Habte et al., 2019). Table 6.1 summarizes the various sources where calcium oxide can be found (Ling et al., 2019). Table adapted from the article by Ling et al. (2019). In this chapter, we will deal mainly with calcium oxide (CaO) derived from plant, animal, and mineral waste, as it is a cheap raw material, which would be discarded in the environment and use as a catalyst in obtaining biodiesel.

6.2 CaO derived from plant residues Industrial activities, mainly the agricultural industry, generate a considerable amount of waste. The ash generated from biomass is an ecologically correct and economically viable

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

Table 6.1 Natural sources of calcium oxide. Catalyst Heat Treatment

Source

Type

Chicken egg-shell Chicken egg-shell Mud crab Cockle Mussel Clam Turkey bones

1000°C, 2h 900°C, 2 h 900°C, 2h 900°C, 2h 1050°C, 2h 900°C, 3,5 h 909.4°C, 4 h

Wei et al., 2009 Sharma et al., 2010 Boey et al., 2009 Boey et al., 2011 Rezaei et al., 2013 Nair et al., 2012 Chakraborty et al., 2015

350–1000°C, 6 h 600°C, 8 h

Smith et al., 2013 Ghanei et al., 2016

Cemment Dolomite rock Lime mud Red mud

CaO CaO CaO CaO CaO CaO CaO/biological Tri-calcium phosphate (BTCP) CaO CaO/hydroxyapatite (HAP) CaO CaO CaO CaO

450°C, 3 h 800°C 800°C 200°C, 5 h

Palm kernel shell

CaO

800°C, 2h

Wang et al., 2012 Li et al., 2014 Li et al., 2015 Ngamcharussrivichai et al., 2010 Bazargan et al., 2015

Bovine bones Sheep bone

Reference

alternative. The ash composition can vary according to the biomass from which it is produced, but in terms of metals found, the highest levels are Ca, Mg, K, Si, and Al (De Arruda et al., 2016). The calcium content of biomass forest residues (cellulose, paper, and steel industry) can vary in its composition; however, it is one of the most present metals in high quantities. The residues of the calcium-based agricultural industry can be introduced as commercial catalysts for various reactions, mainly the transesterification reaction of vegetable and animal oils and fats. Thus, the destination of agricultural waste for other use contributes to the improvement of the environment (Marwaha et al., 2018). One of the residues of the agricultural industry widely used as a source of CaO in the production of biodiesel is the residues of the palm oil industry. Palm oil cultivation is one of the most relevant agro-industrial activities in humid tropical regions. The palm oil (Elaeis guineensis) is a palm of African origin that grows well in tropical regions with a hot and humid climate. In the world market, the leading palm oil producers are Malaysia, Indonesia, and Nigeria. Brazil represents the 11th oil producer worldwide and is the 3rd in the Americas. The palm coconut can provide two types of oil, the oil extracted from the mesocarp, called palm oil (Palm oil), and the other extracted from the seeds, called palm kernel oil (palm kernel oil), (Fig. 6.2).

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Waste and biodiesel

Figure 6.2 Palm coconut. benefico-ou-malefico.html.

http://bromatopesquisas-ufrj.blogspot.com/2012/04/azeite-dende-

Figure 6.3 Empty bunches and almonds. https://comadrefulozinha.com.br/novo/wp-content/ uploads/2017/06/dende.jpg, https://arevistasociedadedamesa.files.wordpress.com/2015/07/dende. png?w=300.

The production of the oil generates many agricultural residues, being they: 1. Empty bunches and fibers: can be used as fertilizer or as sources of energy in the boilers feed of the oil processing plants themselves. 2. Almonds: the almond shells can be burned to generate energy and the cake after oil extraction can be used as food for domestic animals. 3. Mill sludge and fibers, shells, and palm kernel cake. Fig. 6.3 shows the empty bunches and almonds from the palm oil palm. Many gasification plants that use the palm oil as an energy source produce ashes,which are discarded as waste. These residues can potentially be used as catalysts, to produce biodiesel. The use of these residues would make the biomass gasification processes economically and environmentally more attractive (Bazargan et al., 2015).

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

Ashes from a boiler (Boiler Ash, BA), where empty bunches of palm oil were incinerated,were doped with CaO and used as a catalyst for the transesterification of palm oil. The reaction conditions used in this study were: BA 3%, molar ratio methanol: oil (15:1), the temperature of 60°C and a reaction time of 30 minutes. CaO analytical grade was tested for comparison. As a result of the transesterification reaction, analytical grade CaO exhibited good tolerance up to 3% by weight of water and 4% by weight of FFA (free fat acid), but only 67% of biodiesel yield was produced. In comparison, the addition of CaO laboratory-grade to BA produced a 95% conversion to ester. These results clearly show that CaO and BA combined were more effective as a catalyst. Although BA works very well as a catalyst for transesterification, it is not reusable as the active species in the catalyst tend to leach out of the system during the reaction (Boey et al., 2011). Samples of a mixture of the fiber of the palm oil and the coconut shell burned in a boiler were used as a catalyst in the transesterification reaction of crude palm oil (CPO) under light conditions, Ho et al. (2012). In this case, three boiler ash samples burned at 600°C (bottom ash), 750°C (boiler ash), and the last was called fly ash and is the ash at the boiler head outlet. After being collected, the samples were dried in the oven at 105 ± 1°C for 24 h to eliminate all moisture. These ashes served as support for the impregnation of CaO and CaCO3 . Before being used, CaCO3 was calcined at different temperatures (800, 900, and 1000°C) for 30 min to generate CaO. Adequate amounts of aqueous CaO/CaCO3 solution (stock solution) were loaded separately into the different types of ash, with a concentration of 15% and 30%. The resulting powders were calcined at 900°C. Twenty-four different catalysts were obtained by varying the ash, the amount of CaO and CaCO3 , and the temperature at which CaCO3 was calcined before impregnation. Crude Palm oil biodiesel (CPO) was obtained by testing the 24 types of catalysts, CaO and CaCO3, and the ash separately. The amount of catalyst was kept constant (2%), the alcohol/oil molar ratio was 12:1, and the reaction temperature was 60°C. When using only calcined ash (bottom ash, boiler ash, and fly ash), the conversions into biodiesel were 68.09%, 71.39%, and 73.33%, respectively. However, the best catalysts were those where the ashes have impregnated with CaCO3 . CaO is unstable and easily contaminates with CO2 in the air, becoming CaCO3 . The best results achieved, such as the use of catalysts, were when the CaCO3 catalyst calcined at 800°C was used before being impregnated in ashes. The two best results found in terms of converting oil (CPO) into biodiesel were 94.8% and 82.9% when 15 wt% of CaCO3 calcined at 800°C were loaded onto fly ash and boiler ash, respectively (Ho et al., 2012). The vast quantities of solid waste generated in oil palm factories create an environmental problem. Therefore, it is necessary to recover and reuse them Palm kernel shells (PKS) are the most challenging fraction to break down solid waste. Thus, Bazargan et al. (2015) used the ashes of palm kernel cake biochars (PKCB), after the gasification process to produce a catalyst rich in CaO, without the need for any doping. The PKSB was calcined at 800°C for 2 h under atmospheric pressure (Bazargan et al., 2015).

95

96

Waste and biodiesel

The experiments to obtain biodiesel were carried out using methanol:oil ratio (9: 1), and the amounts of catalyst (PKSB) were 1.0%, 2.5%, 5.0%, and 10% about the mass of the oil. The X-ray diffractogram of ash samples calcined at 450°C shows that the main constituent is calcium carbonate. The TG curve shows a loss of mass between 550 and 670°C, where the authors attributed the transformation of carbonate into calcium oxide. The XRD of the sample calcined at 750°C proves that the calcium carbonate completely decomposes in calcium oxide. According to the literature, the conversion of carbonate to calcium oxide in limestone occurs at temperatures higher than the conversion temperature found in PKSB (Ar and Do˘gu, 2001). The fact may be due to the inhibition of carbonate growth in specific crystallographic orientations of the crystals due to specific functional groups in the plant during the growth phase. Restricted growth can lead to the distorted crystal morphology; in this case, the calcite phase leading to high levels of tension in the crystalline structure. The additional tension contributes to the network’s overall energy and decreases the activation energy necessary for the degradation of calcite that decomposes at lower temperatures (Thompson et al., 2014). The CaO obtained by the ashes of the boiler, where the oil palm shells were burned, converted 98% of the oil into FAME, after 250 minutes of reaction. These results were close to the results obtained with CaO commercial. The best reaction conditions were achieved when the alcohol: oil (9:1) molar ratio, the temperature of 60°C and the amount of catalyst above 5% did not have a significant conversion since the active surface of the catalyst decreases with the increasing the amount of catalyst (Veljkovi´c et al., 2009). In this work, the authors showed an alternative source of waste from gasification plants could be used as a source of calcium for basic heterogeneous catalysts for the transesterification reaction without requiring doping to increase the basicity of the catalyst. Another type of ash derived from a thermal plant, where the fuel was biomass (eucalyptus), was used as a catalyst for the reaction to obtain biodiesel (Vargas et al., 2019). Two types of ash were considered, one heated at 120 °C for 5 h, called FAD, and the other calcined at 700°C for 5 h, called FAC. SEM images (Fig. 6.4A and B) show that the particles of both catalysts (FAD and FAC) have a uniform distribution of irregularly shaped agglomerates. The EDX results show elements such as Ca, Mg, Si, Al, O, K, S, Na, Cl, and P. These elements remained on the solid surface after calcination, as shown in Fig. 6.4B. The diffractograms of the FAD and FAC catalysts showed similar crystalline structures, the main differences being in the peak areas and intensities after calcination. The XRD pattern for FAD showed peaks corresponding to CaO, CaCO3 (major component), KCl, and SiO2 . The FAC XDR shows that the CaCO3 phase was transformed into CaO phase (Ho et al., 2012; Uprety et al., 2016; Maneerung et al., 2015; Chen et al., 2015; Sharma et al., 2012), and this evidence was noted because of the higher intensity of the corresponding peak. The CaO is the major component followed by SiO2 in the FAC catalyst.

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

(A)

(B)

(A)

(B)

Figure 6.4 A – SEM (A) and EDX (B) of FAD catalyst; B – SEM (A) and EDX (B) of FAC catalyst. Order Number: 4881471094556 – Renewable Energy.

The catalysts FAD and FAC were used in the synthesis of biodiesel from a mixture of waste cooking oil (WCO) and refined palm oil (RPO). Five mixtures were prepared as follows: M1 (100% RPO), M2 (75% RPO and 25% RPO), M3 (50% RPO and 50% WCO), M4 (25% RPO and 75% WCO), M5 (100 WCO). The reaction conditions were: temperature of 60°C, molar ratio alcohol/oil (9:1), 10% of the catalyst and time of 180 min. The results of the FAME conversion tests for the different oil mixtures and using the FAD and FAC catalysts are shown in Fig. 6.5. One of the best performances in FFA conversion is related to the FAD catalyst, as it reached values above 96% for all mixtures. However, it was observed that the increase of WCO (waste cooking oil) in the mixtures decreases the FAME yield. In the reactions where the FAC catalyst was used, the yields were lower due to the changes in the morphology of the FAC catalyst (sintering process) and a decrease in the crystalline phases and functional groups. In addition, the most abundant compound in FAD is CaCO3 ,

97

98

Waste and biodiesel

(A)

(B)

Figure 6.5 Performance in terms of FAME conversion of catalisty FAD (A) and FAC (B). Order Number: 4881471094556 – Renewable Energy.

Figure 6.6 Tree and leaves of Tectona grandis. https://images-na.ssl-images-amazon.com/images/I/ 51pF0ynt1GL._AC_.jpg, https://www.worldwondersgardens.co.uk/tectona-grandis-10-seeds-teaktropical-hardwood-tree.

and in FAC is CaO, which may be another reason for the differences observed in the performance of the catalysts. The differences in performance between the catalysts were noticed mainly between oil mixtures, where the amount of WCO was greater than the refined palm oil (RPO). Leaves of the Tectona grandis plant were used to prepare a catalyst that was used in the transesterification reaction of waste cooking oil (Gohain et al., 2020). Tectona grandis is native to South and Southeast Asia, and it is grown extensively in India, Myanmar, Malaysia,Thailand,Sri Lanka,and Bangladesh as its wood is highly valued for its durability and water resistance property. Fig. 6.6 shows the tree and leaves of Tectona grandis plant. The leaves were calcined in a muffle furnace at 700°C for 4 h. The catalyst was called calcined Tectona grandis leaves (CTGL). The XRD of the CTGL showed the presence of

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

oxides and carbonates, such as K2 O, K2 CO3 , CaO, CaCO3 , and SiO2 . Alkali metal oxides of groups I and II (Ca and K) have good activity in the transesterification reaction due to their greater basicity. The EDX study confirmed the presence of 53.25% K, 30.28% Ca, 10.03% Si, 4.77% Mg, and 1.67% Na. Biodiesel was prepared with waste cooking oil, and the best conversion was found with a 6:1 molar ratio of methanol/oil, 2.5 wt% CTGL loading within 3 h. The percentage of catalyst in the conversion was varied from 0.5% to 4.5%. A low conversion was achieved at lower catalyst loading due to the availability of lesser basic sites which is required for conversion of oil to FAME. Low conversions were achieved with a low amount of catalyst, as the amount increased the conversions increased as the number of active sites increased. However, the optimum amount was 2.5%. The following molar ratios (methanol:oil) were tested (2:1, 4:1, 6:1, 8:1, and 10:1), using 2.5 wt% of catalyst for 3 h. The increase in the molar ratio increased the conversion of the oil to FAME, however, an increase above that of the 6:1 molar ratio, showed a reduction in the conversion since a high alcohol/oil molar ratio leads to a reverse reaction that ends up reducing the conversion in FAME (Olutoye et al., 2011; Ma and Hanna, 1999). The reaction time was studied varying from 1 to 5 h of reaction, using the ratio 6:1 of methanol/oil and 2.5% by weight. In the first hour, the conversion was low, reaching around 50%. Meanwhile, with the increase in the reaction time, the conversion to FAME gradually increased until the balance was 3 h. Above that time, the trend was a decrease in conversion to FAME after 5 h (Wan et al., 2014). The reuse of the CTGL catalyst showed that at each cycle, the conversion was reduced. This reduction was attributed to the leaching of the catalyst (Long et al., 2014). Potassium (K) and calcium (Ca) have a greater tendency to be leached into the solution than the other components (Wang et al., 2017). Potassium loss may be one of the main reasons why the catalyst is deactivated, due to the solubility of K2 O in methanol and glycerol. Another reason may be the loss of the catalyst during washing and transfer between cycles. To better understand the results found, a mechanism of action of the CTGL catalyst were proposed, Fig. 6.7. Initially the basic sites present in the catalyst, abstract the acid hydrogen from methanol to form the methoxide. The methoxide, in turn, reacts with the carbonyl group present in the triglycerides,and at the same time,the catalyst is recovered from being used in the next cycle. Ash obtained by air combustion of nutshells were used in the transesterification reaction of sunflower oil. The nutshells were burned in the air to obtain the ashes and then calcined in an oven at 800°C under an air atmosphere for 2 h. XDR analysis showed the presence of CaO, MgO, SiO2 , K2 O, Ca2 SiO4 , KAlO2 , Ca(OH)2 . The observed CaO crystalline phase was also detected in other materials obtained from biomass residues by gasification and calcination (Veljkovi´c et al., 2009). In addition, when a higher calcination temperature is applied, the content of K and Ca in the material increases due to the removal of carbonaceous species and the decomposition of other recalcitrant species in

99

100

Waste and biodiesel

Figure 6.7 Mechanism of transesterification reaction catalyzed by CTGL base catalyst. Order Number: 4881500627462 - Waste Management.

the material (Veljkovi´c et al., 2009). The EDX analysis showed that the highest contents were K (23.55% by weight) and Ca (17.67% by weight). The influence of the catalyst load (0.5, 1.0, 2.5, and 5.0% of the oil weight load) on the FAME content was investigated in the beginning 12:1 methanol/oil molar ratio and the temperature of 60°C reaction. A conversion of 95% of FAME was reached with 2 h of reaction with the amount of 0.5% of catalyst. The additional increase in the catalyst increased the reaction rate and reduced the reaction time needed to reach the maximum FAME content (98%). It was attributed to the pseudo homogeneous nature of the mixture reaction containing nutshell ash. A higher catalyst load provides a higher concentration of catalytic species (Ca2+ and K+ ) in the reaction mixture and a greater dispersion of the basic active sites on the catalyst surface, accelerating the reaction. In addition, increasing the catalyst concentration above 3% reduced the FAME content, which was attributed to the problems of mass transfer (Rizwanul Fattah et al., 2020). To evaluate the alcohol/oil molar ratio, the concentration of 1% of the catalyst was used, due to the amount in 10 minutes, over 50% conversion to FAME was achieved. With a methanol/oil molar ratio of 6:1, the content of 97.87% of FAME was reached in 40 minutes. Increasing the methanol/oil molar ratio to 12:1 increased the FAME conversion rate,and the reaction was completed in 30 min,providing 96.5% FAME. The reaction time to reach the FAME content above 90% in a higher alcohol/oil molar ratio (18:1) was only 10 min.

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

(A)

(B)

Figure 6.8 SEM image of the catalyst (RBIW) without calcination (A) and CBIW-800 (B). Order Number: 4877760888660 – Fuel.

According to The United States Department of Agriculture (USDA), beet cultivation tends to increase in both the United States and Mexico. As a result, sugar production from this crop will also increase (McConnell and Olson, 2018). The sugar industry from beet consumes between 2%–6% of lime in the purification of beet and nonsugary materials. This operation uses a large amount of lime, which generates a calcium-rich residue called waste lime cake. The dried waste lime cake is mainly composed of calcium carbonate and magnesium carbonate and traces of other minerals and can be used as a raw material to produce calcium oxide catalyst to produce biodiesel. Abdelhady et al. (2020) investigated the catalytic activity of waste lime cake as a potential source of CaO-based catalyst to produce biodiesel from sunflowers. The catalyst was prepared using Raw Sugar beet agro-industrial waste (RBIW), which was dried in an oven at a temperature of 100°C overnight and then pulverized and calcined at different temperatures (ranging from 600°C to 1000°C), for 2 h. The optimization of the operational parameters of this study was carried out as follows: catalyst quantity (0.1 to 5% about the oil mass), temperature (45, 60, 75, 90 and 105°C), alcohol/oil molar ratio (3:1, 4.5:1, 6:1, 7.5:1, 9:1, and 12:1) and time (30, 60, 120, 240, and 360 min). Based on the results obtained, it can be seen that the optimized reaction conditions are 1% by weight of catalyst load, the temperature of 75°C, the reaction time of 60 min and methanol:oil ratio of 4.5:1. These results led to an oil ± biodiesel conversion of 97 ± 3%. The results of converting oil to FAME were: RBIW (0.0%), CBIW-600 (33%), CBIW-700 (91%), CBIW-800 (99%), CBIW-900 (90%), CBIW- 1000 (94%) (Abdelhady et al., 2020). When the calcination temperature increased, carbonaceous products were decomposed, as shown by the thermogravimetry technique. Thus, the calcium content of the samples increased. The FE-SEM images (Fig. 6.8) showed that depending on the calcination temperature, the CaO morphology varies, showing particles such as spheres

101

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Waste and biodiesel

and aggregates. The shape of the raw and calcined residues was distinguished by smaller crystals attached to the large particles, and the irregularity is a source of high catalytic activity. These aggregates are possibly due to the decomposition of the CaCO3 particles forming finer CaO particles on the order of nanometers (33 nm). The diffraction pattern results of the sample calcined at 800°C, showed only the CaO phase, corroborating the SEM and EDX results. The conversion of sunflower oil into FAME using the CBIW-800 catalyst was 93%, with 1% of the catalyst (by mass), the temperature of 75 °C, molar ratio methanol: oil (4.5:1) for a time of 1 h. The high catalytic activity of this catalyst (CBIW-800) is due to its large surface area (27.9 m2 g−1 ) and small average particle size (33 nm), as well as its high basicity. Because of these results, the catalyst CBIW-800 obtained from the beet agro-industrial residue is active in the transesterification of sunflower oil and it can be used as an inexpensive and ecological source of CaO. The catalyst calcined at 800°C was reused for several cycles, using the optimized conditions in this study. At each cycle, the reaction mixture was centrifuged, and the catalyst was washed after separation, followed by drying for 3 h at 80°C. In total, there were 5 reusability cycles. The results showed that the catalyst maintains its activity for two consecutive cycles.After the 3rd cycle,a considerable loss of catalytic activity was observed, possibly due to the leaching of the catalyst by the glycolic phase of the mixture, which may have led to the formation of calcium glyceroxide, as is highlighted by Kouzu et al. (2009), Leaching decreased the CaO content in the reused catalyst from 74% to 40%. Another factor that can explain the loss of activity is the aggregation of the particles in the reused catalyst (Kouzu et al., 2009).

6.3 CaO derived from animal waste Shell wastes mollusks and bird’s eggs have caused accumulation problems due to increased consumption (Shan et al., 2018). Ecological management of these solids is the synthesis of heterogeneous catalysts for biodiesel production (Chakraborty et al., 2011). This is because the shells are mainly composed of calcium carbonate, initially inactive in the transesterification process, but when treated with temperatures of 600 to 1000°C it forms calcium oxide, an efficient heterogeneous catalyst for the production of biodiesel. (Boey et al., 2011; Kouzu et al., 2008). The work by Nakatani et al. (2009) showed that oyster shells, when calcined at 700°C, provided the formation of calcium oxide. The CaO formed was able to promote the transesterification reaction of soybean oil with a conversion of 73.8%, under the following reaction parameters: methanol: oil (6:1) molar ratio, 65°C, amount of catalyst (25%) and time of 5 h (Di Serio et al., 2008). Freshwater mussel shell wastes, after calcination at 900°C and activation in deionized water at 600°C,was used by Hu and collaborators (2011) as a catalyst for transesterification of Chinese tallow oil. According to the authors, the synthesis procedure was essential to

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

obtain calcium oxide with a high surface area (23.2 m2 g−1 ) and consequently greater catalytic activity. The transesterification experiment under optimized conditions, had biodiesel yield 96%. The catalyst reuse tests took place without subsequent treatment between reactions and showed yields greater than 80% after 12 successive reaction cycles (Hu et al., 2011). CaO was obtained from wastes mussels of the Persian Gulf after calcination at 1050°C. The reaction yield was 94.1% under the conditions of 12% of the catalyst, molar ratio methanol and oil 24:1, 60°C and 8 h. It is interesting to note that the researchers carried out reuse tests following two treatment protocols for the catalyst. In the first protocol, the catalyst, after being separated from the transesterification reaction, was subjected to thermal treatment at 1050°C,repeating the initial calcination.For the second protocol,the catalyst treatment, to be reused, was washing with methanol without calcination. After 5 reaction cycles the yields presented were 59.10% for the methanol-treated catalyst, whereas only 37.13% was obtained for the heat-treated catalyst. The authors justification for the lower yield when using the recalcination protocol is that the catalyst surface area has been reduced (Rezaei et al., 2013). Cockle shells, bivalve mollusks, were heat treated at 900°C for 2 h to produce heterogeneous catalysts active in the palm oil transesterification reaction. Biodiesel with a yield of approximately 97.48% was obtained using the conditions: amount of catalyst 4.9% by weight; mass ratio methanol:oil (0.54:1) and 3 h of reaction. The reuse of the catalyst, after washing process with methanol and n-hexane and recalcination at 900°C for 2 h, was tested and the yield after the 3rd cycle remained above 97% (Boey et al., 2011). Birla et al. (2012) found that from the calcination of the snail shell at 900°C for 3.5 h in a tubular oven, calcium oxide was obtained. Subsequently, when CaO was applied in a transesterification reaction of recycled fried oil, yields greater than 95% were produced under optimized conditions (Birla et al., 2012). Turbo jourdani shells wastes, a species of marine snail, were used as raw material to produce porous calcium oxide catalyst, after 5 h of calcination at 900°C, for the production of biodiesel from palm oil. In the conditions of 10% of the catalyst, molar ratio of alcohol and oil 3:1 and reaction time of 7 h, conversion above 99% was found. Reuse experiments were carried out, and it was observed that the catalyst regeneration process, washing with methanol and drying at 80°C for 2 h, was crucial to obtain yields greater than 90% after 8 reaction cycles (Boonyuen et al., 2018). Waste grooved razor shell, Waste grooved razor shell, was applied as a primary source of CaCO3 by Aitlaalim and researchers (2020). After calcination at 900°C it was found that crystalline CaO was the chemical compound formed mostly and the application in the transesterification of residual frying oil ensured the production of biodiesel with yields above 94% in reaction conditions: 3 h, 65°C, 5% catalyst and molar ratio alcohol and oil 15:1. The reuse of the catalyst was investigated and the yield after the 5th reaction cycle was 87% (Aitlaalim et al., 2020).

103

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Waste and biodiesel

Catalytic activities similar to the materials obtained from mollusks shells were observed when scientific experiments were carried out using bird egg residues (Balakrishnan et al., 2011). The study by Wei et al. (2009), considered by the scientific community to be the first work to report the use of a catalyst derived from chicken eggshells for the production of biodiesel (Shan et al., 2018), reports that the shells are mainly formed by CaCO3 (94%) and 4% organic materials, in addition to MgCO3 and Ca3 (PO4 )2 , which together totaled 2%. The shells when calcined at 1000°C gave rise to CaO which was subsequently applied in the transesterification reaction of soybean oil with molar ratio alcohol and oil 9:1, 3% catalyst, temperature of 65°C and 3 h, obtaining at the final biodiesel with yield greater than 95%. The catalyst reuse was initially carried out in 13 reaction cycles with no apparent loss of activity, however after the 17th cycle the catalyst was completely deactivated. For the authors, this deactivation was caused by the presence of Ca(OH)2 formed from the initial CaO. Sharma et al. (2010) and Chavan et al. (2015) were also successful in obtaining the CaO catalyst from the hen’s eggs shells using calcination at 900°C. In the work of Sharma and coauthors, the transesterification reaction occurred with Pongamia pinnata seed oil. The 95% yield was obtained using the reaction parameters: 65°C, molar ratio alcohol:oil (8:1), 2.5 h and 2.5% catalyst (Sharma et al., 2010). Chavan et al. carried out the production of biodiesel from Jatropha curcas oil with the best result at 90% yield when applying conditions of molar ratio alcohol and oil 8:1, 65°C, 2% catalyst, and 2.5 h of reaction (Chavan et al., 2015). Similar performance to chicken egg shell was observed when using ostrich egg shell as a primary source of CaCO3 by Tan and researchers (2015). Calcium oxide was obtained after calcining the ostrich egg shell at 1000°C for 4 h. The transesterification reaction of the oil used in frying was carried out with 1.5% catalyst, molar ratio alcohol and oil 12:1, temperature of 65°C and 2 h, obtaining a 96% yield. The reuse capacity of the catalyst was tested and even after five reaction cycles the yield remained above 70%. The washing process with n-hexane and recalcination at 700°C became necessary between cycles (Tan et al., 2015). Cho and Seo (2010) obtained calcium oxide from the quail egg shell calcined at 800°C for 2 h. The 98% yield was obtained using palm oil, molar ratio alcohol and oil 12:1, 1.5% catalyst, 65°C, and 2 h (Cho and Seo, 2010). Singh and Verma (2019) researched duck eggs as a precursor to obtain calcium oxide after 720 minutes of calcination at 900°C. When applied in the transesterification of Momordica charantia (L.) oil, the yield was 96.8% when applying reaction conditions: 10% catalyst, 65°C and 80 minutes of reaction (Singh and Verma, 2019). In Table 6.2, present other studies that used shell wastes mollusks and birds eggs as raw materials to obtain active CaO catalysts after heat treatment at temperatures above 600°C. It is also important to present the work carried out by Viriya-empikul et al. (2010) who studied the similarity of the residues of chicken eggshell, golden apple snail shell and Meretrix venus shell. According to the authors, after calcination at 800°C all raw

Table 6.2 Catalysts derived from shell wastes mollusks and birds eggs, applied in the transesterification reaction. Reaction conditions Calcination Catalyst Alcohol and Temperature Shell source Oil Yield (%) (°C) (% weight) oil (mol:mol) Time (h) (°C)

Mustard Palm

3.0 1.0

9:1 9:1

6 2

65 65

93.3 98

Chicoreus brunneus 1100

Rice bran

0.5

30:1

2

65

93

Mussel Snail mud clam Malleus malleus River snail

900 900 900 600 800

Camelina Sativa Soybean Castor Used in frying Used in frying

1.0 3.0 3.0 7.5 3.0

12:1 6:1 14:1 11.85:1 9:1

2 7 2 1.44 1

65 28 60 65 65

95 98 96.7 93.81 92.5

Chicken

1000

Used in frying 5.0

20:1

1.0

65

45.5

Chicken

900

1.61

12:1

4.0

75

90.44

Chicken

900

5.0

12:1

1.5

65

93.5

Chicken

900

1.7

12:1

3.6

75

86.41

Chicken Ostrich Quail

950 800 800

Scenedesmus armatus Semente de Phoenix dactylifera L. Acutodesmus obliquus Colza Palm Soybean

4.0 8.0 3.0

9:1 9:1 9:1

1.0 1.0 4.0

60 60 65

95.12 92.7 94.8

Duck

900

Soybean

10.0

10:1

1.3

60

94.6%

Reference

Boro et al., 2011 Asikin-Mijan et al., 2015 Mazaheri et al., 2018 Perea et al., 2016 Laskar et al., 2018 Ismail et al., 2016 Niju et al., 2020 Kaewdaeng et al., 2017 Farid Fitri Kamaronzaman, 2020 Pandit and Fulekar, 2019 Farooq et al., 2018

Pandit and Fulekar, 2017 Ya¸sar, 2019 Chen et al., 2014 Graziottin et al., 2020 Yin et al., 2016

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

Turbonilla striatula 800 Mereterix mereterix 900

105

106

Waste and biodiesel

(A)

(B)

Figure 6.9 Limestone (A), quicklime (B) https://www.tradeindia.com/fp5008031/White-LimestoneLump.html, https://www.chemtradeasia.com/blog/uses-of-quicklime.

materials gave rise to CaO with high crystallinity. When applied in the transesterification reaction of palm oil, the catalytic activity followed the order: chicken egg shell > golden apple snail shell > Meretrix venus shell. According to the authors, the catalytic activity was justified by the directly proportional relationship of the calcium content, surface area and smaller particle size present in the different oxides (Viriya-empikul et al., 2010).

6.4 CaO derived from mineral waste One of the primary sources of calcium oxide is limestone, having advantages of its availability and low cost. Besides, CaO can be obtained from several inexpensive sources, such as calcium carbonate, calcium acetate, and calcium nitrate, as well as from ores such as dolomite and quicklime (Stojkovi´c et al., 2016). Fig. 6.9 shows limestone and quicklime rocks. Kouzu et al. (2009), proposed the use of crushed limestone as a catalyst in the synthesis of biodiesel from rapeseed oil and two types of cooking oil WCO-A (Waste cooking oil collected after home cooking, filtered before transesterification), and WCOB (Waste cooking oil provided from the restaurant, chemically pretreated to remove free fatty acids after filtration). The oils were transesterified with methanol at 333K under atmospheric pressure in the presence of the calcined catalyst in a laboratory-scale pilot plant in discontinuous circulating flow. The current flow is advantageous for fast feeding, promoting the emulsification of the reagents in the column reactor. The rapeseed oil transesterification operation was repeated successively without changing the catalyst in order to investigate its deactivation. In addition to rapeseed oil and used cooking oil were tested in the pilot plant test. The catalyst called limestone bit was sieved to obtain a size range of 1.0 to 1.7 mm. Then, the particles were packaged in a column steel reactor. The lower and upper spaces of the column were filled with activated carbon. The calcination in the column reactor was carried out at a temperature of 1173K for 2 h in a flow of helium gas of 100 mL min−1 . The column was cooled to a temperature of 333K under an inert atmosphere, and then the vegetable oil and methanol emulsion

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

Figure 6.10 Schematic flow diagram of a laboratory scale pilot plant to transestrify vegetable oil with methanol in the presence of quick lime bit used as catalyst. Order Number: 4878310635283 - Fuel.

was pumped into the column reactor for the transesterification reaction to occur. Fig. 6.10 shows how the transesterification reaction procedure was carried out (Kouzu et al., 2009). In the first attempt to use the scheme shown in Fig. 6.11, the conversion to FAME was 60% in a time of 2 h. Due to this result, the time was extended for another 1 h. Then there was a feeding problem due to the increase in pumping pressure. The mixture of reagents stretched the tube that connected the pump without any feeding in the column reactor. With this problem, it was necessary to disassemble the entire system. With the reactor’s opening, it was attempted to remove the catalyst by gravity, but it did not come out due to the agglomeration of the particles, transforming them into a single block. After removal, an XRD analysis was performed to investigate the reason for this particle agglomeration. The XDR revealed that the catalyst consisted of calcium diglyceride, obtained by combining calcium oxide with glycerol during the reaction (Kouzu et al., 2008). After the transformation, calcium diglyceride functioned as a solid-based catalyst. As a small amount of soluble substance was leached, the authors proposed the following agglomeration mechanism illustrated in Fig. 6.11. Probably, a part of the soluble substance was crystallized under the reaction conditions. Therefore, it was considered that the crystallized substance was formed in fine particles functioning as a binder to agglomerate the catalyst. After checking the problem, the solution was to disperse the catalyst again on the activated carbon and fill the lower and upper parts of the column. This procedure was followed to protect the catalyst against the binder. Thus, the transesterification reaction can be carried out without changing the catalyst. After two reaction times, the conversion increased by about 10%, reaching 70% conversion of the oil into biodiesel.

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Figure 6.11 Possible mechanism for agglomeration of catalyst limestone bit. Order Number: 4878310635283 - Fuel.

A third attempt was made to make the system work. The volumetric proportion of methanol/oil has been increased from 0.5 to 0.78. The increase in volume promotes a higher mass transfer between methanol and oil, which leads to an increase in conversion to FAME (Kouzu et al., 2008). With this change, the result of conversion to FAME rose above 96.5% in 2 h of reaction. The System repeatedly functioned to examine the deactivation of the catalyst. 17 cycles were repeated, and until the 10th cycle, the conversion remained around 96.5%. After the 11th cycle, the catalyst’s efficiency gradually decreased, reaching the 17th cycle with a conversion to FAME of 67%. These results indicated that the catalyst was deactivated during successively repeated transesterifications. The XDR of the catalyst after the 17 cycles showed the presence of calcium diglyceride and calcium hydroxide. In this case, it is considered that its hydration deactivated the catalyst because calcium hydroxide was less active in the transesterification of vegetable oil than calcium oxide and calcium diglyceride (Kouzu et al., 2008; Kouzu et al., 2008).

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

The result of the tests when the WCO-A and WCO-B oils were transesterified was that the conversion to FAME reached 99%. For WCO-B, it should be noted that most of the free fatty acids were esterified with methanol before transesterification in the reactor. On the other hand, the same pre-treatment was not performed for WCO-A due to its low acid value. When the same catalyst was used for the transesterification of rapeseed oil, the efficiency of the reaction was quite low compared to the transesterification of used cooking oil: the conversion to FAME measured after 1 h was 74% for rapeseed oil, 82 % for WCO-A, which was the oil collected after cooking at home and 85% for WCO-B,supplied by a restaurant.In other words,cooking oil residues were more reactive than rapeseed oil. The difference in reactivity probably occurred due to the impurities contained in the used oils. The deactivation test, using 17 cycles, of the catalyst was carried out when using the oils WCO-A and WCO-B. The conversion to FAME of the WCO-A after 2 h was over 96.5% for each run repeated successively. Besides, the FAME yield measured in 1 h has hardly decreased with successive repetition. From these results, it was found that the deactivation of the catalyst was reduced. Probably, the free fatty acids contained in the feed oil released the solid base catalyst from the agglomeration. However,the fine particles formed by the crystallization of calcium diglyceride were transformed into calcium soap, combined with free fatty acids, and the liquid mixture dissolved the soap. As the calcium soap was dissolved, this calcium probably stayed in the soluble mixture, which is produced in the biodiesel produced. The calcium content in the biodiesel was measured, and the values were 201 ppm for the WCO-A biodiesel, the WCO-B biodiesel was 290ppm, and 40 ppm for the rapeseed biodiesel. However, calcium can be reduced in crude biodiesel using a cation exchange resin (Kouzu et al., 2009). Thus, the calcium content in the WCO-B biodiesel decreased from 290 ppm to 9 ppm. Based on all the test data from the pilot plant, the limestone bit was quite promising as a catalyst to perform the catalysis reaction to obtain biodiesel from different oils.However, the present work revealed that the process parameters, such as catalyst/dispersant ratio, reactor size, and feed rate, must be optimized to increase the reaction’s efficiency. The catalyst needs to be modified to protect it from the hydration that was one of the causes for deactivation. The literature shows another work in which the authors used limestone as a source of calcium oxide in the transesterification of Pongamia (Fig. 6.12) oil. The limestone was washed with water to remove impurities on its surface. The limestone pieces were ground to a particle size between 2-3 mm. Then it was calcined at 1000 °C for 4 h in a muffle furnace under static air conditions to transform the carbonates into CaO (Anjana et al.,2016). After calcination, the solid was again crushed into particles between 2-4 mm in size and then stored in an airtight container free from air,so that the oxide would not turn into carbonate or hydroxide. The transesterification reaction was optimized to know which would be the best condition for catalysis. The maximum conversion of oil to FAME was

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Figure 6.12 Pongamia leaves and seeds. https://www.alibaba.com/product-detail/Karanj-forestrytree-Seeds-Pongamia-pinnata_138462514.html.

97.28% when CaO based on limestone was used at a concentration of 12% in relation to the mass of oil, the molar ratio of methanol/oil was 15: 1, the temperature of the reaction was 65 °C and reaction time 3 h (Anjana et al., 2016). Miladinovic et al. (2014) have reported applying limestone as a cheap source of CaO to catalyze the transesterification reaction of sunflower oil in a batch reactor. The authors investigated the influence of the catalyst quantity and the methanol/oil molar ratio on FAME conversion. A study of a kinetic model was proposed and included the mechanism of variable reaction and limitation of the mass transfer of triglycerides (Miladinovi´c et al., 2014).

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

The catalyst was prepared by grinding the lime and then calcining at 550 °C for 4 h under atmospheric pressure. Several reactions have carried out by varying the methanl/oil molar ratio (6:1, 12:1 and 18:1) and the amount of catalyst corresponding to 1.0, 2.5, 5.0, and 10.0% by weight to oil). The XDR result of the calcined catalyst showed CaO and CaCO3 phases. The presence of CaCO3 is due to the reaction of atmospheric CO2 with CaO. However, the CaCO3 signal is fragile and almost imperceptible, which indicates a small CaCO3 content in the calcined sample. SEM micrographs of the calcined catalyst show particles with sharp edges and visible pores. The alkalinity of the basic sites was measured and showed strength in the range of 15.0 to 18.4. This force influenced the activity of the catalyst in the methanolysis reaction. The reaction tests carried out showed that the conversion of oil to FAME followed a sigmoidal variation; that is, at the beginning of the reaction, the conversion rate increased slowly, then accelerated reaching the maximum and becoming constant when the reaction approached completion. Simultaneously with the increase in the FAME content during the reaction, the TAG (triglyceride) content decreased. The concentrations of MAG (monoglycerides) and DAG (diglycerides) were deficient from the beginning to the end of the reaction. The variations in TAG and FAME concentrations during the methanolysis reaction have calculated from the proposed kinetic model compared with the experimental data to verify the proposed kinetic model. The degree of TAG conversion was calculated based on Eq. (6.1) using Polymath Programs. It has found that the relative deviation between the calculated and experimental xA values was ± 4.97% (based on 168 data), confirming the validity of the model kinetic method. dXA (1 − XA )(CRO + 3CA0 XA = Km dt K + CA0 (1 − XA )

(6.1)

K and Km = kinetic parameters,which define the affinity of TAG for the active catalyst sites. CR0 = initial hypothetical FAME concentration corresponding to the active sites on the catalyst surface CA and CR = TAG and FAME concentration (calculated by Eqs. 6.2 and 6.3) XA = conversion rate CR0 = initial TAG concentration CA = CA0 (1 − XA )

(6.2)

CR = 3CA0 XA

(6.3)

The concentrations of TAG and FAME were determined using Eqs. 6.2 and 6.3 based on the calculated values of the degree of TAG conversion. The comparison of calculated and experimental values of TAG and FAME concentrations have shown in Fig. 6.13. The kinetic model agrees well with the experimental data. The results of the study showed

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Figure 6.13 The comparison of calculated and experimental values of TAG and FAME concentrations. Order Number: 4881510858093 - Chemical Engineering Research and Design.

that when the amount of catalyst increases, maintaining the methanol/oil molar ratio (6:1), the reaction time decreases. However, when the molar ratio of 18:1 (methanol/oil) has used, the amount of catalyst greater than 5% did not influence the conversion rate, probably due to the reduction in the available catalytically active surface. Regarding the variation of the methanol/oil molar ratio in the conversion of FAME, the catalyst influenced. When a 1% catalyst was used, and the 6:1 molar ratio increased to 12:1, the reaction became slow. This fact can be explained by the lower concentration of the catalyst in a larger volume of the reaction mixture. With increasing amounts of methanol (i.e in the 18:1 molar methanol/oil ratio), the density and viscosity of the mixture have reduced, and the mixture was more efficient, contributing to a faster mass transfer and better availability of the centers catalytically active for the reaction. As a result, the reaction rate has increased, and the initial slow reaction period has shortened. However, the methanol/oil molar ratio did not influence the duration of the reaction, and the reaction equilibrium was reached almost at the same hour. A slightly higher FAME yield was observed in the higher initial amount of methanol since excess methanol

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

displaces the reaction equilibrium for product formation. The increase in the volume ratio may have caused the reaction rate to decrease due to the decrease in the catalyst concentration, which resulted in an impediment to the access of acylglycerol molecules to the active sites of the catalyst.

Conclusion This study showed that using CaO, a heterogeneous catalyst for biodiesel production to replace homogeneous catalyst viz. NaOH is very promising. In this chapter, the study focused on calcium oxide obtained from minerals, plants, and animals. In addition, the study focused on residues from these sources. Several studies were reviewed that showed that all such residues are very promising and the catalyst derived from it (i.e. CaO) can replace sodium hydroxide (a homogeneous catalyst). Laboratory findings and industrial simulations were reviewed, demonstrating that catalysts from calcium oxide obtained from waste materials(plant residue, animal waste, and mineral waste) can be used as a catalyst to obtain biodiesel with a high yield.

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Nair, P., Singh, B., Upadhyay, S.N., Sharma, YC., 2012. Synthesis of biodiesel from low FFA waste frying oil using calcium oxide derived from Mereterix mereterix as a heterogeneous catalyst. J. Clean. Prod. 29–30, 82–90. https://doi.org/10.1016/j.jclepro.2012.01.039. Nakatani, N., Nakatani, H., Takeda, K., Sakugawa, H., 2009. Transesterification of soybean oil using combusted oyster shell waste as a catalyst. Bioresource Technology 100, 1510-1513. doi:10.1016/j.biortech.2008.09.007. Ngamcharussrivichai, C., Nunthasanti, P., Tanachai, S., Bunyakiat, K., 2010. Biodiesel production through transesterification over natural calciums. Fuel Process. Technol. 91, 1409–1415. https://doi.org/ 10.1016/j.fuproc.2010.05.014. Niju, S., Rabia, R., Sumithra Devi, K., Naveen Kumar, M., Balajii, M., 2020. Modified malleus shells for biodiesel production from waste cooking oil: an optimization study using box–Behnken design. Waste Biomass Valorization 11, 793–806. https://doi.org/10.1007/s12649-018-0520-6. Olutoye, M.A., Lee, S.C., Hameed, BH., 2011. Synthesis of fatty acid methyl ester from palm oil (Elaeis guineensis) with Ky(MgCa)2xO3 as heterogeneous catalyst. Bioresour. Technol. 102, 10777–10783. https://doi.org/10.1016/j.biortech.2011.09.033. Pandit, P., Fulekar, M., 2019. Biodiesel production fromScenedesmus armatususing egg shell waste as nanocatalyst. Mater. Today Proc. 10, 75–86. https://doi.org/10.1016/j.matpr.2019.02.191. Pandit, P.R., Fulekar, MH., 2017. Egg shell waste as heterogeneous nanocatalyst for biodiesel production: optimized by response surface methodology. J. Environ. Manage. 198, 319–329. https://doi.org/ 10.1016/j.jenvman.2017.04.100. Perea, A., Kelly, T., Hangun-Balkir, Y., 2016. Utilization of waste seashells and Camelina sativa oil for biodiesel synthesis. Green Chem. Lett. Rev. 9, 27–32. https://doi.org/10.1080/17518253.2016.1142004. Rezaei, R., Mohadesi, M., Moradi, GR., 2013. Optimization of biodiesel production using waste mussel shell catalyst. Fuel 109, 534–541. https://doi.org/10.1016/j.fuel.2013.03.004. Rizwanul Fattah, I.M., Ong, H.C., Mahlia, T.M.I., Mofijur, M., Silitonga, A.S., Rahman, S.M.A., et al., 2020. State of the art of catalysts for biodiesel production. Front. Energy Res. 8. https://doi.org/ 10.3389/fenrg.2020.00101. Roschat, W., Siritanon, T., Yoosuk, B., Promarak, V., 2016. Biodiesel production from palm oil using hydrated lime-derived CaO as a low-cost basic heterogeneous catalyst. Energy Convers. Manag. 108, 459–467. https://doi.org/10.1016/j.enconman.2015.11.036. Shan, R., Lu, L., Shi, Y., Yuan, H., Shi, J., 2018. Catalysts from renewable resources for biodiesel production. Energy Convers. Manag. 178, 277–289. https://doi.org/10.1016/j.enconman.2018.10.032. Sharma, M., Khan, A.A., Puri, S.K., Tuli, DK., 2012. Wood ash as a potential heterogeneous catalyst for biodiesel synthesis. Biomass Bioenergy 41, 94–106. https://doi.org/10.1016/j.biombioe.2012.02.017. Sharma, Y.C., Singh, B., Korstad, J., 2010. Application of an efficient nonconventional heterogeneous catalyst for biodiesel synthesis from Pongamia pinnata oil. Energy Fuels 24, 3223–3231. https://doi.org/ 10.1021/ef901514a. Sharma, Y.C., Singh, B., Korstad, J., 2011. Latest developments on application of heterogenous basic catalysts for an efficient and eco friendly synthesis of biodiesel: a review. Fuel 90, 1309–1324. https://doi.org/ 10.1016/j.fuel.2010.10.015. Singh, T.S., Verma, TN., 2019. Biodiesel production from Momordica Charantia (L.): extraction and engine characteristics. Energy 189, 116198. https://doi.org/10.1016/j.energy.2019.116198. Smith, S.M., Oopathum, C., Weeramongkhonlert, V., Smith, C.B., Chaveanghong, S., Ketwong, P., et al., 2013. Transesterification of soybean oil using bovine bone waste as new catalyst. Bioresour. Technol. 143, 686– 690. https://doi.org/10.1016/j.biortech.2013.06.087. Stojkovi´c, I.J., Miladinovi´c, M.R., Stamenkovi´c, O.S., Bankovi´c-Ili´c, I.B., Povrenovi´c, D.S., Veljkovi´c, VB., 2016. Biodiesel production by methanolysis of waste lard from piglet roasting over quicklime. Fuel 182, 454–466. https://doi.org/10.1016/j.fuel.2016.06.014. Tan, Y.H., Abdullah, M.O., Nolasco-Hipolito, C., Taufiq-Yap, YH., 2015. Waste ostrich- and chickeneggshells as heterogeneous base catalyst for biodiesel production from used cooking oil: Catalyst characterization and biodiesel yield performance. Appl. Energy 160, 58–70. https://doi.org/10.1016/ j.apenergy.2015.09.023.

CaO derived from waste shell materials as catalysts in synthesis of biodiesel

Thompson, S.P., Parker, J.E., Tang, CC., 2014. Thermal breakdown of calcium carbonate and constraints on its use as a biomarker. Icarus 229, 1–10. https://doi.org/10.1016/j.icarus.2013.10.025. Uprety, B.K., Chaiwong, W., Ewelike, C., Rakshit, SK., 2016. Biodiesel production using heterogeneous catalysts including wood ash and the importance of enhancing byproduct glycerol purity. Energy Convers. Manag. 115, 191–199. https://doi.org/10.1016/j.enconman.2016.02.032. Vargas, E.M., Neves, M.C., Tarelho, L.A.C., Nunes, MI., 2019. Solid catalysts obtained from wastes for FAME production using mixtures of refined palm oil and waste cooking oils. Renew Energy 136, 873–883. https://doi.org/10.1016/j.renene.2019.01.048. Veljkovi´c, V.B., Stamenkovi´c, O.S., Todorovi´c, Z.B., Lazi´c, M.L., Skala, DU., 2009. Kinetics of sunflower oil methanolysis catalyzed by calcium oxide. Fuel 88, 1554–1562. https://doi.org/10.1016/j.fuel. 2009.02.013. Viriya-empikul, N., Krasae, P., Puttasawat, B., Yoosuk, B., Chollacoop, N., Faungnawakij, K., 2010. Waste shells of mollusk and egg as biodiesel production catalysts. Bioresour. Technol. 101, 3765–3767. https://doi. org/10.1016/j.biortech.2009.12.079. Wan, L., Liu, H., Skala, D., 2014. Biodiesel production from soybean oil in subcritical methanol using MnCO3/ZnO as catalyst. Appl. Catal. B Environ. 152–153, 352–359. https://doi.org/10.1016/ j.apcatb.2014.01.033. Wang, J., Xing, S., Huang, Y., Fan, P., Fu, J., Yang, G., et al., 2017. Highly stable gasified straw slag as a novel solid base catalyst for the effective synthesis of biodiesel: characteristics and performance. Appl. Energy 190, 703–712. https://doi.org/10.1016/j.apenergy.2017.01.004. Wang, J.-.X., Chen, K.-.T., Wen, B.-.Z., Ben, L.Y.-.H., Chen, C.-.C., 2012. Transesterification of soybean oil to biodiesel using cement as a solid base catalyst. J. Taiwan Inst. Chem. Eng. 43, 215–219. https://doi.org/ 10.1016/j.jtice.2011.08.002. Wei, Z., Xu, C., Li, B., 2009. Application of waste eggshell as low-cost solid catalyst for biodiesel production. Bioresour. Technol. 100, 2883–2885. https://doi.org/10.1016/j.biortech.2008.12.039. Ya¸sar, F., 2019. Biodiesel production via waste eggshell as a low-cost heterogeneous catalyst: its effects on some critical fuel properties and comparison with CaO. Fuel 255, 115828. https://doi.org/10.1016/ j.fuel.2019.115828. Yin, X., Duan, X., You, Q., Dai, C., Tan, Z., Zhu, X., 2016. Biodiesel production from soybean oil deodorizer distillate usingcalcined duck eggshell as catalyst. Energy Convers. Manag. 112, 199–207. https://doi.org/ 10.1016/j.enconman.2016.01.026.

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Abstract Biodiesel has gained prominence a substitute for diesel in recent years, with many countries having policies to blend it with petroleum diesel. One of the raw materials to produce biodiesel is the catalyst used for its manufacture. The most used catalyst is sodium hydroxide (NaOH). However, the use of this catalyst requires some treatment of the oil before the reaction, which makes the use of certain oils to produce biodiesel difficult. Therefore, replacing sodium hydroxide with other catalysts has been the subject of much research among researchers. CaO is a catalyst that is a good substitute for NaOH, and this catalyst can be obtained from renewable sources and being a heterogeneous catalyst, it can be used in several batches to obtain biodiesel. This chapter deals with several renewable sources, mainly material husk residues, obtaining and using CaO as a catalyst in the synthesis of biodiesel.

Keywords Biodiesel; Shell material; Waste-to-energy

CHAPTER 7

Fish and animal waste as catalysts for biodiesel synthesis Eslam G. Al-Sakkari a, Alaaeldin A. Elozeiri b, Omar M. Abdeldayem b, Blaz Likozar c and Daria C. Boffito d a

Chemical Engineering Department, Cairo University, Giza, Egypt Environmental Engineering Program, Zewail City of Science and Technology, Giza, Egypt Department of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry, Ljubljana, Slovenia d Chemical Engineering Department, Polytechnique Montreal, Montreal, Canada b c

7.1 Introduction Biodiesel or fatty acid alkyl ester, that is, FAME or FAEE, is produced commonly by lipid feedstock’s alcoholysis using homogeneous catalysts soluble in an alcohol phase, for example, NaOH (Thanh et al., 2012) or KOH (Agarwal et al., 2012). Unfortunately, this process involves multiple purification steps of biodiesel and glycerol due to catalyst existence in both phases that hinders process viability. Besides, higher contents of free fatty acids FFAs, i.e. > 2 wt%, and the presence of moisture limit the application of homogeneously catalyzed transesterification (Ibrahim, 2013). Accordingly, heterogeneous catalysis is preferred due to the ease of catalyst separation and its reusability (Muazu et al., 2015). Therefore, the process involves a lower number of purification equipment; for instance, no neutralization is needed for glycerol produced at high purity (Bournay et al., 2005). Additionally, they are tolerant to the high content of FFAs and moisture (Boz and Kara, 2008). Besides, the solid catalyst eliminates soap formation (Buasri et al., 2013). Furthermore, acidic heterogeneous catalyst replaces strong mineral acids such as sulfuric acid. Consequently, neither special materials of construction are needed nor waste acidic effluent will exit from the production facility (Cao et al., 2008). Within the field of heterogeneous catalysis, there is an ongoing trend to produce highly active solid catalysts based on chicken, animal and fish wastes as a way of waste management (Chakraborty et al., 2011; Farooq and Ramli, 2015; Sulaiman et al., 2014; Obadiah et al., 2012; Shah et al., 2014). In addition to being suitable raw materials for solid catalysts preparation, they are also sources of calcium and other useful materials used as fertilizers, supplements, animal feed and nutrients (Gaonkar et al., 2007; McLaughlan et al., 2014; Hemung, 2013). Specifically, fish bones are used in soil remediation (Freeman, 2012); whereas chicken eggshell is a collagen source used in high revenue industries such as cosmetics and pharmaceuticals (King’ori, 2011). The high annual production rate of these wastes should be covered by more waste management or valorization techniques Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00003-3

c 2022 Elsevier Inc. Copyright  All rights reserved.

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Figure 7.1 Type of catalysts reported for biodiesel production.

in various applications to overcome their accumulation in the ecosystem. This is another reason that the utilization of these types of wastes in catalysts preparation is investigated extensively. Studies about waste-derived solid catalysts (WDSC) for biodiesel production covered the selection of feedstock/waste type, Optimization of catalyst preparation conditions, optimization of transesterification or esterification parameters and kinetic modeling of alcoholysis as well. The following is a summary of the recent efforts and attempts done in this field of using fish and bone wastes as a low-cost precursor for catalyst synthesis.

7.2 Sources of fish and animal waste-based catalyst The catalyst type is a critical factor for biodiesel production’s economics; since it controls both the rate and the conversion yields (Etim et al., 2020). As aforementioned, transesterification reaction can be catalyzed by chemical or biological agents (Fig. 7.1). According to their nature, chemical catalysts are either acidic or alkaline. Generally, the acidic catalysts are less sensitive to the feedstock’s FFA and water content compared to the alkaline catalyst (Abdullah et al., 2017). Moreover, acid catalysts promote both esterification and transesterification reactions. However, the alkaline catalysts provide faster transesterification reaction rates under mild conditions (40–65°C) (Joshi et al., 2017). As stated in the introduction section, the biodiesel catalyst is either homogenous or heterogeneous relative to the reaction media. Heterogeneous catalysts are relatively

Fish and animal waste as catalysts for biodiesel synthesis

slower; due to mass transfer limitations. Therefore, homogenous alkaline catalysts, such as KOH or NaOH, are commonly used for industrial production (Putra et al., 2018, Ali and Fadhil, 2013, Talha and Sulaiman, 2016). On the other hand, due to solid catalysts’ merits, stated in details in Section 7.1, they can promote biodiesel production’s economic feasibility (Etim et al., 2020, Smith et al., 2013). However, conventional preparation of those catalysts is costly; since it requires various chemical reagents and multi-steps. Alternatively, non-conventional resources can be used to prepare solid catalyst (Abdullah et al., 2017). In this regard, several waste streams (Fig. 7.1) were investigated for preparing solid catalysts as a more economical and environmentally-benign method. In this chapter, we focus on fish and animal wastebased catalyst (FAWC). FAWC includes animal bones (Smith et al., 2013; AlSharifi and Znad, 2019), fish bones (Madhu et al.,2014),fish scale (Chakraborty et al.,2011),and chicken manure (Maneerung et al., 2016). These sources are renewable and widely available. For example, Labeo rohita production accounts for 23.9% of India’s total fish production (Chakraborty et al., 2011). Moreover, the thin, flexible scales represent about 6% of the wet weight of this species. Therefore, Labeo rohita is an abundant source of fish scale waste. Hydroxyapatite (HAP) is the major component of animal bones and fish scales (Marwaha et al., 2018). HAP transforms to β-tricalcium phosphate (β-TCP) when calcined above 900°C (Chakraborty et al., 2011). In Thailand, bovine bones are valorized by conversion into powdered or particulate forms for porcelain production or land fertilizer (Smith et al., 2013). Due to health hazards, bovine bones are banned as livestock feed in many countries (Seidel et al., 2006). However, applying high-temperature calcination kills the pathogens, producing a nontoxic and safe to handle catalyst. Therefore, using FASC in biodiesel production is a proper management practice for biological solid waste.

7.3 Preparation of fish and animal waste-based catalyst Before being used as catalysts, FAW should be prepared to achieve specific properties that enable them to catalyze transesterification reaction. Generally, the desired properties for these catalyst are (Etim et al., 2020): r Strong, active sites r High surface area r High stability r Ease of separation and recycling/reusing r Low cost These raw materials are already low-cost or even zero-cost ones as they are wastes. In addition, they are solids that are neither soluble nor leachable in the reaction medium. However, to complete the rest of the desired properties, an activation step should be

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Figure 7.2 Steps of catalyst preparation from biomass wastes retrieved from (El-Sheltawy and Al-Sakkari, 2016).

performed, including calcination, loading with active sites through wet impregnation, and pyrolysis. The following is a short summary of these activation methods. 7.3.1 Calcination One of the simplest ways to obtain a waste-derived catalyst having the abovementioned properties is calcination. In this process, the pretreated waste goes through a thermal treatment to remove undesired impurities such as carbon dioxide and moisture. It is most commonly done under air as the main component active for catalysis will not react or burn in presence of oxygen or air. However, the waste sample should be pretreated before the activation step, that is, calcination (Fig. 7.2). In bone preparation,

Fish and animal waste as catalysts for biodiesel synthesis

this thermal treatment decomposes its organic part, i.e. collagen (Figueiredo et al., 2010). Upon this decomposition, pores are generated, and consequently, the specific surface area increases. Besides, carbonate apatite is converted to hydroxyapatite (HAP) between 600°C and 900°C (Figueiredo et al., 2010; Ishikawa et al., 2018). Where HAP is the active site suitable for catalyzing transesterification. As previously mentioned, at temperatures above 900°C, HAP can be converted to β-TCP, which is also active toward catalyzing transesterification. From another perspective, the pretreatment steps help in the removal of other contaminations such as dust. In addition, size reduction and homogenization raise efficiency and enhance the rate of calcination. They also ensure the conversion of all the sample to the desired active components during the calcination step. Besides, these steps increase the specific surface area due to reducing the particle size to the level of millimetres or even micrometres. Moreover, agitation and mixing inside reaction vessels become easier and more homogeneous upon using smaller catalyst particles. This eliminates the external and internal mass transfer resistances and enhances reaction kinetics and this will be shown in more details in Section 7.4. 7.3.2 Wet impregnation method Furthermore, FAW can be mixed or loaded with/on other WDSC or pure active components via wet impregnation method. Simply, this method is done by adding the other active compounds to a considerable amount of distilled water and then this mixture is mixed with FAW. After loading, the solid particles are filtered, dried and calcined as a final activation step. For instance, Volli et al. (Volli et al., 2019) prepared a catalyst based on impregnated fly ash with 10-30 wt% of calcined animal bone powder (CABP). Firstly, sheep bones ground, dried and washed with hot distilled water for contaminants removal. Then, the purified particles were calcined at 900°C for 2 h. After calcination, CABP was added to distilled water and then fly ash was added to this mixture and agitated for 4 h under reflux conditions. To ensure good loading, this mixture was kept at 70°C for 24 h. Finally, solid catalyst particles were filtered, dried and calcined for the second time at 900°C for 2 h. In this case, fly ash acted as support. Moreover, it provides the mixture with a rich source of metal oxides with high thermal stability. The maximum mustard oil conversion to biodiesel was as high as 90%. The conditions applied to achieve it were 5.5:1 methanol to oil molar ratio, 65°C, 6 h and 10 wt.% catalyst loading. Besides, this method is applied for the preparation of other bi-functional WDSC (Etim et al., 2020). The produced solid catalyst has an amphoteric nature, i.e. exhibiting both acidic and basic active site. Such catalysts can be intriguing for high FFA feedstock; since two steps simultaneously achieved in one reactor, i.e. esterification and transesterification. Putra et al. (Putra et al., 2018) adapted this method to prepare a low-cost heterogeneous catalyst CaO/SiO2 based on eggshell and peat clay wastes. While CaO

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catalyzed the transesterification reactions, the silica promoted the esterification reaction. The incorporation of silica as support raised the biodiesel yield to 91% compared to the 78% yield of using CaO alone. Section 7.5 elaborates more on the other studies utilized this method for producing highly active catalysts. 7.3.3 Pyrolysis Generally, pyrolysis can be defined as the thermal treatment of materials in the absence of oxygen to avoid oxidation or combustion. To ensure the pyrolysis atmosphere’s inertness, nitrogen is continuously supplied to the pyrolysis furnace during the decomposition. This process is used to produce biochar from chicken manure to be used as a porous media and catalyst for biodiesel production (Jung et al., 2017; Jung et al., 2018). Biochars produced at 350, 400, 450, 500, 550 and 660°C were added along with silica to a reactor performing pseudo-catalytic transesterification of waste cooking oil (Jung et al., 2018). In this regard,the reaction was performed at high temperatures between 240 and 380°C.The authors observed that using biochars obtained at 450°C enhanced the reaction yield and kinetics compared to those obtained at 350°C.This indicates the increase of their catalytic influence. This is due to the increase in calcium carbonate and calcium oxide contents in biochar. However, at higher reaction temperatures (> 280°C), the yield decreased dramatically due to the thermal cracking of esters. Similarly, upon using biochar obtained at 350°C, the yield started to decrease at temperatures exceeding 350°C. In addition, biochar was loaded with ash derived from the same manure to enhance the yield to reach 90% in some cases. The maximum yield obtained was 95% which was achieved at 350°C using biochar obtained at 350°C.

7.4 Transesterification kinetics of waste-derived heterogeneous catalysts Chemical reactions kinetics is a vital engineering tool, as they can be applied to the modeling, simulation and optimization of processes and their digital twinning. With biodiesel, the kinetics can help understand the rates of adsorption, reaction, and desorption when applying heterogeneous catalysis materials attained from wastes. This can be performed by applying the principles of heterogeneous catalysis kinetic models or mechanisms such as Eley-Rideal and Langmuir-Hinshelwood. However, (trans)esterification kinetics are often simplified to power-law models where they are found sufficient to describe reaction kinetics. Interpolative statistical models are most common and applied for catalysts derived from wastes of different sources, such as shell mixture (Adepoju et al., 2020), clams (Shobana et al., 2017), or scallops (Ramos et al., 2020). Sometimes, kinetics are misinterpreted as only temporal concentration evolution skipping the derivation of models

Fish and animal waste as catalysts for biodiesel synthesis

entirely. Consequently, deducing any reactor dimensioning or scaling would thus be speculative. Besides, some studies only investigate the change of concentrations over time without deducing the rate equations. However, these equations are necessary upon process scale-up to accurately design the reactor and estimate the cost (Yuliana et al., 2020). Mechanistic chemical kinetics try to take into account the underlying reaction series. Nonetheless, in most studies, only the overall reaction is considered instead of the steps of the whole reaction mechanism. For example, when waste goat bone-derived catalyst supported on silica was used (Lani et al., 2020), the only the overall reaction was considered. This yielded, e.g., the order of reaction of 4. However, the best fit model was one of first order as the concentration of methanol did not change significantly. In this case, the reaction was divided into two-time intervals to facilitate the estimation of rate constant. In the first interval, i.e. from 0 to 30 min, the rate was slower and had a constant of 0.0086 min−1 . Whereas, this constant increased to 0.0166 min−1 in the second interval from 30 to 120 min. In other investigations, such as for waste chicken bones (Zik et al., 2020), change in alcohol concentration was also disregarded and the reactions after the conversion of triglycerides. The reaction followed a pseudo-first-order kinetic model; the rate constant ranged from 0.0092 to 0.0151 min−1 in the studied temperature range. Besides, the activation energy had a value of 46.72 kJ/mol. Whereas the value of Thiele modulus was < 2, indicating negligible internal mass transfer resistances. For another chicken bone-derived catalyst, kinetics were simplified to a first-order model where the limiting reactant was triglyceride (AlSharifi and Znad, 2020). The activation energy was relatively low and had a value of 23.2 kJ/mol. The authors confirmed the absence of internal mass transfer limitations via the calculation of the Thiele modulus. A similar observation was detected using catalyst derived from the fish industry wastes to catalyze the methanolysis of jojoba oil, where pseudo-first-order was sufficient to describe reaction kinetics (Sánchez et al., 2015). However, in this study, external mass transfer was limited at the beginning of the reaction and then it was kinetically controlled. In addition, due to the sigmoidal kinetics the Arrhenius constant and activation energy were relatively high and equal to 7292 min−1 and 55 kJ/mol, respectively. On the other hand, pseudo-second-order reaction kinetics was the best model to fit Neem oil transesterification’s experimental data using a heterogeneous catalyst derived from the waste of goat bones (Chukwuemekeulakpa et al., 2019). Where, the activation energy was 90.98 kJ/mol, and the pre-exponential factor had the value of 1.46E10 dm3 / (mol. min). From another perspective, the group of V. Veljkovi´c are known for their detailed studies of the reactions of (trans)esterification. For example, a study using these detailed complex models with chicken eggshell catalysts was published recently (Pavlovi´c et al., 2020). In these studies, internal/external transport phenomena, kinetics and equilibria are often well modelled. Thus, large scale packed bed reactors can be envisaged and an

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extrapolative process modeling upon varying operating conditions or (oil) feedstock. A similar advanced methodology (Likozar and Levec, 2014) also considers the compositions of oil, correlating the glycerides’ structure with kinetics, accounting for various feed concentrations. The latter’s methodology is detailed-wise illustrated in (Likozar and Levec, 2014), where glyceride structure-activity relationships were proved and derived from kinetics. Besides, the physical models describing the reaction medium in the studied systems were considered and discussed. This methodology is believed to model transesterification’s kinetics using catalysts derived from wastes, especially fish and animal wastes, very well and at high accuracy.

7.5 Current status of fish and animal waste-based catalyst Table 7.1 summarizes the attempt done for biodiesel production using different FAWCs. As it can be observed, these catalysts have relatively high activity as the conversion exceeded 90% in most cases. They also exhibit good stability characteristics as most of them can be reused 3 times and more till reaching 7 times in the case of using fishbone (Chinglenthoiba et al., 2020). Surprisingly, this catalyst showed high activity as it converted 98% of waste cooking palm oil in 1.5 h. This activity and stability my be due to the hydrothermal treatment of fish waste bone before calcination at 900°C. This preparation method confirmed its ability to produce good catalyst in another case, that is, raw animal bone utilization (Chingakham et al., 2019). Foe instance, after hydrothermal treatment and calcination at 1000°C, the produced catalyst gave 96% honge raw oil conversion and reutilized for 5 successive cycles. This high conversion was attainable within 2 h at 64°C upon using 12:1 methanol to oil molar ratio MTOR and 2.5 wt.% catalyst loading. On the other hand, the feedstock and reaction conditions play an important role in controlling the maximum conversion upon using the same catalyst. For example, turkey bone calcined at almost 900°C gave 91% mustard oil conversion. The optimum conditions were 70°C, 3h, 5 wt.% catalyst loading and almost 10:1 MTOR (Chakraborty et al., 2015). Nonetheless, this conversion ranged from 92 to 96% at the conditions of 65°C, 2-3h, 4-7 wt.% catalyst loading and 11:1-14:1 MTOR (Ayoola et al., 2018). Where the catalyst origin was also turkey bone but it was calcined at 800°C. It is believed that increasing the methanol content had a good influence on reaction conversion. In addition, the way of heating is also a key parameter in controlling the reaction kinetics. For instance, the only attempt that gave a conversion of 96% within 15 min was that one using microwave heating (Singh and Sharma, 2017). Compared with other attempts, this one was relatively fast as the average reaction time was almost 3 h in the case of conventional heating. Moreover, waste feedstock and activation conditions of FAWC determine its activity and reaction maximum conversion. Some wastes have higher concentrations of active

Table 7.1 A summary of the FASC prepared by calcination for biodiesel production (Tc = calcination temperature, TR = temperature of the transesterification reaction, t = reaction time, CL = catalyst loading, MTOR = methanol to oil molar ratio, C = conversion, [∗ ] refers to an additional hydrothermal process during the catalyst preparation). Catalyst Transesterfication reaction Source Tc [°c] Reusability Feedstock Tr [°c] T [hr] CL [wt% of oil] MTOR C [%] Ref.

997

6

Soybean oil

70

5

1.01

6.27:1

98

900 800 650 900 850 1000 909 800 900

4 5 4–5 5 1 5 5 – 4

Waste cooking oil Palm oil Soybean oil Waste fish oil Waste cooking oil Honge raw oil Mustard oil Soybean oil Waste cooking oil

65 65 65 55 65 64 70 55 60

4 4 3 2 4–5 2 3 3 4

5 20 8 1.5 7.5 2.5 5 15 5

15:1 18:1 6:1 6.5:1 15:1 12:1 9.9:1 9:1 15:1

89 97 97 95 90 96 91 92 91

900

7

65

1.5

2.5

Fish bone

900

5

65

1.5

2.5

Turkey bone chicken bone Chicken bone, fish bone Guinea fowl bone

800 – 800 3 1000 4

Waste cooking palm oil Pongamia pinnata (Karanja) oil Palm kernel oil Waste cooking oil Waste cooking oil

65 80 65

2–3 3 1.5

4–7 3 2

18:1

96

900

5

Annona squamosa 65 oil

0.25 4

Chakraborty et al., 2011

Farooq and Ramli, 2015 Obadiah et al., 2012 Smith et al., 2013 Madhu et al., 2014 Maneerung et al., 2016 Chingakham et al., 2019 Chakraborty et al., 2015 Ayodeji et al., 2018 Mahmood Khan et al., 2020 9:1 98 Chinglenthoiba et al., 2020 10:1 97 Madhu and Sharma, 2017 11:1–14:1 92–96 Ayoola et al., 2018 3:1 96 Suwannasom et al., 2016 10:1 90 Tan et al., 2019 Singh and Sharma, 2017

Fish and animal waste as catalysts for biodiesel synthesis

Rohu fish (Labeo rohita) scale Chicken bone Animal bone Bovine bone Fish waste Chicken manure Raw animal bone∗ Turkey bone Cow bone Ostrich (Struthio camelus) bones Fish bone∗

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components than others which elevates their catalytic performance. This can be detected from Table 7.1. In the case of using chicken bone (Farooq and Ramli, 2015; Tan et al., 2019) and chicken manure (Maneerung et al., 2016) the conversion is relatively lower than the other wastes. For instance, chicken bones calcined at 900°C gave a waste cooking oil transesterification conversion of 89% (Farooq and Ramli, 2015). This conversion was obtained at 65°C after 4 h of reaction. However, this value was increased to 96% upon operating at 80°C for 3 h (Suwannasom et al., 2016). The activation of the catalyst was done by calcination at 800°C. Raising temperature has a good influence on the conversion as this reaction is endothermic. Nevertheless, these conversions, that is, 8991%, are still high, indicating the good performance of FAWC and the efficiency of calcination to produce such catalysts. In addition, as aforementioned in Section 7.3.2, to enhance the catalytic activity of FAWC, they were loaded by other waste-derived active materials or even pure ones (Table 7.2). Chicken bone impregnated with lithium and calcined at 850°C converted 97% of canola oil to biodiesel at only 60°C (AlSharifi and Znad, 2019). This is a considerable improvement compared to catalysts produced with calcination only (Farooq and Ramli, 2015; Suwannasom et al., 2016; Tan et al., 2019). In addition, the activity of animal bones was enhanced by the addition of KOH and calcination at 900°C (Nisar et al., 2017). As a way of comparison, a conversion of 97% needed 20 wt.% catalyst loading when only calcined animal bones (Obadiah et al., 2012); whereas, upon KOH loading this value was achieved by only 6 wt.%. Moreover, the MTOR decreased from 18:1 to 9:1 and the reaction time was shorter by a value of a one hour. These examples and the others mentioned in Table 7.2 confirm the impregnation method’s ability to prepare more active catalysts operating at milder conditions. On the other hand, recently, a non-catalytic or pseudo-catalytic approach was investigated for transesterification reaction (Kwon et al., 2012). This approach employs a porous substance, such as silica or activated alumina. The porous material facilitates the reaction between the triglycerides (liquid phase) and the methanol (gaseous phase) under supercritical or subcritical conditions. This approach is advantageous for being insensitive to the FFA content in the oil. Moreover, it neither requires catalysts nor produces wastewater. Chicken manure (Jung et al., 2017) is a greener alternative for commercial porous materials. Jung et al. (Jung et al., 2017) produced biochar from chicken manure via pyrolysis at 350°C. By applying this biochar to transesterification reaction, FAME yield reaches 96% at 350°C. However, operating transesterification at high temperatures is limited by the thermal cracking of FAME. This can be mitigated by using a mixture of chicken manure biochar and silica with a ratio of 1:0.8 (Jung et al., 2018). Moreover, the produced biochar’s pore-structure is engineered by controlling the amount of CO2 during the pyrolysis step (Jung et al., 2019). Biochar based on manure/CO2 pyrolysis resulted in FAME yield of 95% at 170°C.

Table 7.2 A summary of the FASC prepared by wet impregnation method for biodiesel production (Tc = calcination temperature, TR = temperature of the transesterification reaction, t = reaction time, CL = catalyst loading, MTOR = methanol to oil molar ratio, C = conversion). Catalyst Transesterification reaction FAWC Tc [°C] Additive Feedstock TR [°C] t [h] CL [wt% of oil] MTOR C [%] Ref.

850 900 600 600 900

Lithium Fly ash K2 CO3 CaO KOH

Canola oil Mustard oil Palm oil Food grade canola oil Nonedible Jatropha oil

60 65 65 60 70

3 6 1.5 5 3

4 10 8 5 6

18:1 5.5:1 9:1 12:1 9:1

97 90 96 95 96

AlSharifi and Znad, 2019 Volli et al., 2019 Chen et al., 2015 Ghanei et al., 2016 Nisar et al., 2017

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Chicken bone Animal bone powder Pig bone Sheep bone Animal bone

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7.6 Remarks on process feasibility and greenness Waste utilization as biodiesel feedstock or even for catalysts preparation increases the opportunity to have a feasible biodiesel production process (Gebremariam and Marchetti, 2018). Hence, waste oil utilization should be the first option for biodiesel production as feedstock price has the biggest share in production cost relative to other parameters (Al-Sakkari et al., 2020). From another perspective, type of waste and its preparation conditions, to be an active catalyst, influence the economics of the whole production process. These conditions differ according to type of waste; however, they are generally within those presented in Fig. 7.1 (El-Sheltawy and Al-Sakkari, 2016). The quality and activity of produced waste-derived catalysts is defined by its physicochemical properties, including particle size, surface area, moisture/impurities contents, types and amount of active sites. All these characteristics are related to the preparation conditions. Thus, insufficient treatment of waste precursor produces inactive or low-activity catalyst which hampers process profitability by lowering conversion and producing side products that increase purification and separation loads to achieve the required ASTM standard quality of biodiesel. On the other hand, operating at severe conditions such as calcination at temperatures over 1000 °C may cause sintering of catalyst particles, decreasing its specific surface area (Yang et al., 2021). In addition, excessive size reduction produces very fine catalyst particles that make the separation and filtration of these particles difficult (Zhou et al., 2019; jie Lv et al., 2018). Moreover, the storage of catalyst in inappropriate conditions such as elevated humidity can deactivate the catalyst, making it in need of additional activation through calcination, which adds more costs to the process (Al-Sakkari et al., 2017). Although, animal and fish wastes are low-cost or even zero-cost raw materials for catalyst synthesis, their purification and pretreatment expenses cannot be neglected. Accordingly, optimization of catalyst preparation conditions is a must to achieve or keep a biodiesel production process. Researchers in future studies should pay more attention and focus on the technoeconomic analysis of using wastes as catalysts and conducting life cycle analysis (LCA) studies to determine the profitability and degree of the production process’s greenness. Optimization of catalyst preparation conditions results in decreasing carbon and water footprints of the whole process. For instance, the catalyst’s high activity will give high lipid conversion, which consequently decreases the load on purification steps, including distillation for methanol recovery. This will decrease the carbon footprint of the process. On the other hand, high catalyst stability where it does not leach or dissolve in reaction products or reactants will result in clean ester and glycerol layers. Hence, washing water needed to remove impurities from the ester layer will be minimized, decreasing the water footprint of the process. Accordingly, to confirm these advantages of water and carbon footprints reduction, complete and detailed LCA studies of using fish and animal wastes for catalyst production should be performed in future investigations.

Fish and animal waste as catalysts for biodiesel synthesis

7.7 Scaling-up: opportunities and limitations Upon scale-up of heterogeneously catalyzed transesterification using waste-derived catalysts there is a promising potential to use cheap material of construction such as carbon steel for building equipment. The need for special materials will no longer exist as the hazards of excessive corrosion will be eliminated, e.g. no mineral acids as catalysts will be added to the reaction medium. In addition, solid catalysts with high stability will not leach in the reaction medium, and consequently, the neutralization step of glycerol byproduct by mineral phosphoric acid will not be performed. This is another reason that the need for a special material of construction will no longer exist. Moreover, high methanol to oil molar ratios will be avoided and thus, the volume of units, including reactor and purification equipment will be reduced. All of these merits should influence process feasibility positively as well by reducing the physical cost of equipment. From another perspective, regarding the mode of reactor operation, both continuous and batch modes can be applied as in the case of conventional process or even the processes using pure solid catalysts. However, on a small industrial scale, batch reaction mode may be preferred. Where, stirred tank reactors (batch or continuous) followed by a filtration system will be a good choice to contain this slurry reaction medium and to perform the transesterification effectively. The packed bed also is an applicable option, but mass transfer resistances will not be negligible in this case. However, till now, only lab-scale investigations were conducted, and no simulations or real studies on the scale-up of these processes were done. Hence, the technical limitations upon scale-up and mitigation methods were not determined because the pilot plant studies and shifting toward this production scale were not considered until now.A possible reason for this issue is the weak connections between researchers and industrial developers and stakeholders in this case. In addition, waste collection (especially in developing countries or regions inside one country),transportation,storage,purification,and thermal treatment of wastes still represent limiting issues for the bigger scale applications. Process safety is also an issue, including the safety during the operation of kilns or furnaces for waste calcination. In this regard, a complete risk assessment should be performed to investigate the possible risks and hazards of the catalyst production unit and to put a comprehensive strategy to mitigate them by reasonable actions. Moreover, one of the most limiting problems for using wastes generally is social acceptance. Thus, increasing awareness about the importance of valorizing waste materials and the creation of job vacancies related to this duty could lessen this problem and make it diminish gradually.

Conclusions This chapter introduced an overview of the utilisation of waste from fish and animals as a raw material for producing new solid catalysts active for biodiesel production. It covered

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all the treatment and preparation conditions of these wastes to be ready for reaction catalysis. In addition, it reported on the optimum conditions for biodiesel production, including the catalyst loading at which maximum yields were obtained experimentally. These conditions differ according to the type of waste-derived catalyst and biodiesel feedstock. Moreover, it summarized the reaction kinetic analysis and modeling studies of different catalytic systems. Fortunately, these wastes proved their ability to be a precursor for catalyst production on lab scale. However, due to a lack of data, more technoeconomic analysis studies should be performed on using such waste-derived catalysts. This will help in making reasonable decisions for the scale-up of the process to be applied on an industrial scale. Additionally, life cycle analysis will determine the degree of process greenness and possible methods for reducing carbon and water footprints,leading to more eco-friendly processes.

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Abstract Biodiesel is produced commonly by alcoholysis of lipid feedstock using homogeneous catalysts (e.g. KOH) soluble in an alcohol phase. Unfortunately, this process involves multiple purification steps of biodiesel and glycerol due to catalyst existence in both phases that hinder process viability. Besides, contents of free fatty acids FFAs > 2 wt%, and the presence of moisture limit the application of homogeneously catalyzed transesterification. Accordingly, heterogeneous catalysis is preferred owing to the ease of catalyst separation as well as its reusability. Within the field of heterogeneous catalysis, there is an ongoing trend to produce highly active solid catalysts based on chicken, animal and fish wastes as a way of waste management. This chapter introduces a review on the use of different fish and animal wastes, including their bones and fish scales, to produce active catalysts for biodiesel synthesis from various feedstocks, e.g. edible and non-edible oils. Besides, kinetic studies will be summarized as an essential aspect for the scale-up of the production process. Moreover, it will mention some of the techno-economic aspects related to the utilization of these wastes in the catalysis of biodiesel production and their impact on process feasibility.

Keywords Fish and animal wastes; Biodiesel; Heterogeneous catalysis; Calcination; Wet impregnation; Kinetics

CHAPTER 8

Inorganic wastes as heterogeneous catalysts for biodiesel production Eslam G. Al-Sakkari a, Mai O. Abdelmigeed a, Marwa M. Naeem b and Sumit H. Dhawane c a

b c

Chemical Engineering Department, Cairo University, Giza, Egypt Chemical Engineering Department, British University in Egypt, Cairo, Egypt Department of Chemical Engineering, Maulana Azad National Institute of Technology, Bhopal, India

8.1 Introduction The consumption of primary energy is increased on a daily basis with the increase of population and modern industries. In 2015, it was reported that the energy consumption was over 150,000,000 GWh and it is predicted that by the year 2050 the consumption will increase by 57% (Hajjari et al., 2017). This drastic growth in energy consumption will ultimately result in more greenhouse emissions hence more environmental problems that directly threatening the survival of humans. Currently, over 80% of total energy usage is generated by fossil fuels, which directly leads to further negative effects on the environment and health of the population globally (Kumar and Sharma, 2016). Hence, to tackle these issues, huge efforts have been underway to find suitable alternatives to fossil fuels, such as biofuels, to limit their negative effects economically and environmentally due to rapid consumption. The emergence of biofuels has proved a potential substitute to the current growing demand in energy market and reduces the threat to the environment. Among the wide array of biofuels, biodiesel has received a great amount of focus due to being an environmentally friendly biofuel as it is biodegradable and renewable having less emissions as compared to the mineral diesel. In addition, it can be used in diesel engines without any modification at a low blend ratio with the petro-diesel (Gaurav et al., 2017). 8.1.1 Global biodiesel production The biodiesel production increased over the last years due to the increase concern about the environmental impact of fossil fuels. For instance, from 2014 to 2017, it increased by almost 30% (i.e. from 27.84 to 35.82 million tons per year). Additionally, the biodiesel production share of different countries all over the world in 2017 was 13.55, 6.1, 3.75 and 2.87 million tons per year for EU, USA, Brazil and Argentina, respectively as illustrated by Fig. 8.1. This represents about 75% of the total global biodiesel production. In addition, Indonesia had the highest Asian share of biodiesel production with 2.92 million tons Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00010-0

c 2022 Elsevier Inc. Copyright  All rights reserved.

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Figure 8.1 Biodiesel capacity of major producing countries in 2017 (UFOP, 2019).

per year. Surprisingly, this rate is greater than the summation of production rates of both China and India which produced 0.44 and 0.15 million tons per year, respectively (UFOP, 2019). 8.1.2 Properties, advantages, and feedstock of biodiesel Biodiesel is considered as one of the new alternative renewable energy sources to petrodiesel. It is produced from biological sources such as the vegetable oil (Baskar et al., 2018) and animal produced fats (Sander et al., 2018). It is composed of a mixture of long chain fatty acids mono-alkyl esters (Ahmad et al., 2019) that offers a competitive replacement of the widely used petro-diesel fuels that is currently used. This prominent renewable fuel has shown to be vastly acceptable in the energy market due to its wide array of features against petro-diesel such as the absence of sulfur, higher flash point, more positive energy balance, higher natural lubricity and cetane number (Elango et al., 2019). In addition, it is compatible with the currently existing fuel systems besides it can be produced from domestic renewable origins. Biodiesel offers a lesser environmental impact than petro-diesel with 20% less hydrocarbons, 30% less carbon monoxide and 50% less smoke emissions (Shamshirband et al., 2016). However, it has some drawbacks as 2% lower brake thermal efficiency and 13% higher specific fuel consumption in comparison with petro-diesel (Datta and Mandal, 2016). Normally, fatty acids used for biodiesel production are long chain ones consist of about 16 to 18 carbons which can be saturated or unsaturated (Fonseca et al., 2019). The alkyl esters, e.g. biodiesel, derived from these long chain fatty acids have almost the same

Inorganic wastes as heterogeneous catalysts for biodiesel production

combustion features of fossil-derived diesel. This similarity is due to the fact that fossil diesel is composed mainly of mixture of 16 carbons straight chain hydrocarbons (Devold, 2013). Alkyl esters produced from various feedstocks can be differentiated according to the amount of unsaturation. Goodness of different fuel characteristics is also dependent on the degree of saturation and amount of unsaturation. For instance, highly saturated chains produce a very stable fuel with respect to oxidation besides offering a very good combustion features.On the other hand,cold flow properties are enhanced by presence of higher amounts of unsaturated chains and vice versa. The higher degree of unsaturation makes the fuel more active hence showing low oxidation stability (Ong et al., 2013). As mentioned before, biodiesel has lower emissions of smoke, unburned hydrocarbons (HCs) particulate matters (PM) and carbon monoxide (CO); this is attributed to 11% oxygen content in its chemical structure which improves the combustion and make it complete (Parida et al., 2016). In addition, it has almost zero sulfur and contains no aromatics. Conventionally, biofuels, including biodiesel, are classified based on their feedstock (lipid source) and production technologies into three different generations. These generations include biofuels produced from, 1) edible oil seeds, 2) non-food oil crops and wastes, 3) algae. In fact, the feedstock supply is considered as the most important challenge in the process of biodiesel production as it represents about 80% production cost of biodiesel (Anuar and Abdullah, 2016). Feedstock availability is another limiting issue as it depends highly on different parameters such as conditions of cultivation region and the available crops nature as well (Ambat et al., 2018). 8.1.3 Production generations 8.1.3.1 First generation In this generation, biodiesel was mainly produced from edible oils (Verma and Sharma, 2016). These oils are rapeseed (Gaidukeviˇc et al., 2018), sunflower (Karthikumar et al., 2014), soybean (Colombo et al., 2019), cottonseed (Gui et al., 2016), corn (Balamurugan et al., 2018), linseed (Taherkhani and Sadrameli, 2018), and coconut (Jiang and Tan, 2012) oils. About 95% of the global biodiesel production come from first generation sources (Balat, 2011). For example, fertile lands and water resources rich countries, edible oils are considered as feasible and sustainable feedstocks for biodiesel production. However, using edible oils for energy production conflict with the global food demand because it reduces the supply of these crops to the food market. Consequently, this contradiction with global food supply was the motivation to develop new nonedible feedstocks in order to mitigate the fuel versus food competition (Gupta et al., 2019). 8.1.3.2 Second generation The biodiesel/food supply competition became a serious issue due to extensive consumption of the edible oil which is a result of the rapid growth in global population. This

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competition has a direct impact on food security which might lead to significant problems, for instance, starvation in developing countries. Consequently, second generation feedstock using nonedible oils have been considered as promising alternative feedstocks for biodiesel production. In addition, the cultivation cost of non-edible crops has been reported to be lower than edible oil plants (Azad et al., 2016). Non-edible oils could be produced or extracted from different crops including castor oil, jojoba oil and jatropha oil (Wan Ghazali et al., 2015). Using nonedible oils as a feedstock for biodiesel production has several advantages over the usage of edible oils (Guil-Laynez et al., 2019). The main advantages include lower aromatic content, availability, lower cultivation cost and elimination of any competition with food industry (Bhuiya et al., 2014). However, there are some drawbacks of producing biodiesel from non-edible oils such as the higher viscosity, higher carbon residue percentage and lower volatility (No, 2011). In addition, there are other second-generation sources, such as animal fats (Awad et al., 2013), including chicken fat (Seffati et al., 2019), yellow grease (Diaz-Felix et al., 2009), and tallow (Vedulla, 2017). The low price of animal fats is considered as the main advantage for biodiesel production. However, it could not be considered for large scale production due to the limited availability. Moreover, animal fats are in solid state at room temperature which creates problems in the production process of biodiesel (Bhuiya et al., 2016). WCO has been considered as a potential second-generation feedstock for biodiesel production (Tran et al., 2016). It eliminates any competition with food industry and it is extensively cheaper than virgin vegetable oil by two to three times. The availability of waste cooking oil could be considered for large scale production where it depends on each country. The type of waste cooking oil depends on the origin virgin oil which is relatively different in each country. The main disadvantage of using WCO as a feedstock for biodiesel production is the contamination of impurities and the high concentration of FFA and water. Accordingly, pre-treatment processes are required for WCO before being processed for biodiesel production which relatively raises the cost of the process (Bhuiya et al., 2016). One of the main issues that should be taken into consideration is the land to be used for the cultivation of non-edible oils trees. These lands should not be suitable for planting trees of edible oil in order to decrease or eliminate the competition with global food production. In addition, cultivation of energy crops by converting rainforest, peatland, savanna, to produce biofuel can release 17-420 times carbon dioxide more than the reductions of greenhouse gases annually which can be achieved by using biodiesel instead of petrodiesel (Gude et al., 2013). Accordingly, new genetically engineered crops that withstand high salinity and temperatures should be developed. New lipids sources that can be cultivated directly on surface of sea water such as microalgae (Pandit and Fulekar, 2019;

Inorganic wastes as heterogeneous catalysts for biodiesel production

Figure 8.2 Transesterification reaction (Feyzi et al., 2017).

Vinoth Arul Raj et al., 2019) should be extensively investigated and used for the production of biodiesel 8.1.3.3 Third generation Microalgae have been considered as the third-generation feedstock for biodiesel production (Sun et al., 2019). The main advantages of using microalgae are the high biomass productivity and high lipid content, where some species can accumulate up to 20–50% TG (Tan et al., 2018) and that there is no agricultural land required (Chen et al., 2018). Recently, microalgae-based biodiesel is considered as a highly promising source of carbon neutral energy. Microalgae have been considered as the only bio-renewable source which can cover all the global demand on fossil-based fuel (Shah et al., 2018). However, the costs of harvesting, drying of microalgae cells and triglycerides extraction, which are essential for biodiesel production, are very high (Wahidin et al., 2014). Lastly, microalgae oil is highly unsaturated which affect their stability negatively in comparison with other feedstocks. These have been reported as the main disadvantages of using microalgae as a feedstock (Živkovi´c et al., 2017) 8.1.4 Biodiesel chemistry and catalysis Biodiesel can be produced through transesterification or esterification reactions based on the feedstock used (Feyzi et al., 2017; Diamantopoulos, 2015). Transesterification is defined as the conversion of oils or lipids into fatty acids alkyl esters as illustrated by Fig. 8.2. Oils main chemical components are triglycerides which consist of a glycerol base linking three different long chain fatty acids (Sahu et al., 2018). When oil reacts with an alcohol it is converted to three different fatty acid alkyl esters, i.e. biodiesel, and glycerol as by product. Different short chain alcohols such as methanol, ethanol, propanol and butanol are sufficient to complete transesterification (Elkady et al., 2015). Methanol is used commonly to convert oils to biodiesel rapidly owing to its short chain which boost reaction kinetics (Keera et al., 2018).

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Figure 8.3 Esterification reaction (Diamantopoulos, 2015).

Whereas, esterification is the reaction between carboxylic acids and alcohols to produce esters and water as side product in the presence of acid catalyst (Fig. 8.3). The most commonly used long chain carboxylic acids are oleic and palmitic acids (Shahidi, 2005). Short chain alcohols are also utilized for biodiesel production through esterification. The alcohol used are preferred to be short chain due to some technological reasons. The first one is related to reaction kinetics; the smaller the chain of alcohol, the faster goes the reaction. The second reason is related to the subsequent separation steps. Long chain alcohols may act as solvents for the reaction mixture (products, reactants and catalyst) (Keera et al., 2018). Accordingly, this heterogeneous mixture will form single phase which seizes the separation process and renders a costly production process. Regarding the used catalyst, there is great interest recently to use heterogeneous catalysts instead of homogeneous ones, i.e. alkalis or mineral acids, specially those derived from wastes (Khemthong et al., 2012; Kumar et al., 2015; Naeem et al., 2021). Solid catalysts including those derived from wastes can be basic or acidic or even they can be functionalized to be acidic, basic or bifunctional (Kumar et al., 2016; Babajide et al., 2012). However, the conventional heterogeneous catalysts have some disadvantages including being expensive as they are prepared from pure chemicals as raw materials (Abdullah et al., 2017). For more elaboration on the characteristics of solid catalysts, Table 8.1 illustrates some remarks on the conventional base and acid catalysts including the drawbacks of both of them. In recent time, the interest of researchers is oriented more and more toward the utilization of low-cost waste-derived catalysts (Chinglenthoiba et al., 2020). In this context, the abundant wastes that can be used includes inorganic wastes and lignocellulosic waste materials which can be converted to biochar or activated carbon (Saputra et al., 2018; Dhawane et al., 2021). These carbonaceous materials can be functionalized to become acidic, basic or bifunctional. In addition, the produced waste-derived catalysts have the advantages of high activity and availability owing to high annual production rate of industrial and lignocellulosic wastes without appropriate use.For instance,annually, different industries, factories, and mills produce large amount of waste worldwide. The major waste generation industries are steel industries, thermal power plants, cement industries, paper and pulp mills, fertilizer and sugar industries (Marwaha et al., 2018). Besides, these catalysts show good physico-chemical characteristics including relatively high surface area. Hence, the utilization of wastes represents a cost-effective way for

Table 8.1 Remarks on conventional heterogeneous catalysts (Abdullah et al., 2017). Catalyst Catalyst description Advantages

- Immiscible in alcohol - Solid phase - Base in nature such as metal oxides (e.g. CaO)

- Eco-freindly catalyst due to not being corrosive - Selective and reusable - Catalyst can be separated easily from reaction medium

Heterogeneous acid catalyst

- Immiscible in alcohol - Solid phase - Acid in nature such as zeolites

- Acid catalyst handels high FFA and moisture contents of feedstocks - Acid catalyst can catalyze both esterification and transesterification

Limitations

- Compared to homogeneous catalyst, reaction rate is significantly slower - This catalyst is sensitive to FFA and moisture contents of feedstock - Expensive and complicated catalyst preparation process - Leaching of active sites is a reason for catalyst deactivation and can lead to soap formation - Has the same problem of slow reaction rate as in the case of base heterogeneous catalyst - Usually operates at elevated conditions and need high excess of alcohol to overcome the mass transfer limitations - Low catalytic activity and high mass transfer resistance - Shares the same problem of costly and complicated production steps with heterogeneous base catalyst

Inorganic wastes as heterogeneous catalysts for biodiesel production

Heterogeneous base catalyst

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catalyst synthesis and a reasonable waste management method under the umbrella of circular economy to achieve a sustainable zero-waste community. This chapter provides an overview on the attempts which were done over the last years to utilize inorganic wastes to produce catalysts active for biodiesel synthesis. It covers the catalyst preparation conditions besides the optimum conditions of biodiesel synthesis using various catalysts and feedstocks.

8.2 Inorganic wastes 8.2.1 Lithium ion battery waste Several studies focus on studying a mixture of metal hydroxide as an innovative source of catalyst for biodiesel production like lithium-potassium (LiOH + KOH) and lithium-sodium (LiOH + NaOH) because of their high consumption and disposal rates (electronic residues of Li-ion batteries) in the last years. One of these studies aims to reach a recycling process that removes Li-ion battery wastes and oily contaminants from the environment and generates a green power source. In this study, Li-ion battery waste catalyzed the transesterification of waste cooking oil, without prior treatment, for biodiesel production at room temperature. The biodiesel yield was 90% by using 5 wt.% LiOH with 95 wt.% NaOH or KOH catalysts. The physico-chemical properties of the produced methyl esters samples are checked where the tests proved their matching with ASTM biodiesel standards (Brito et al., 2020). 8.2.2 Bauxite processing wastes (red mud) Bayer process is about the production of alumina through the refining of aluminum ore (bauxite). The red mud is insoluble slurry waste that contains different types of oxides. Tremendous amount of this slurry is disposed every year (Marwaha et al., 2018). Aluminum, silicon, iron, and calcium oxides are the main oxides that form the red mud (Liu et al., 2011). Liu et al. achieved 94% biodiesel yield within 3 h by using the red mud as a base catalyst at 65°C, a catalyst amount of 4 wt.% and an alcohol to oil molar ratio of 24:1 (Liu et al., 2013). The highest activity for the red mud is achieved at calcination temperature of 200°C for 5 h. In another study done by Senthil et al., Madhuca indica oil is used as feedstock with the red mud and the results are compared with that of KOH (Senthil et al., 2016). B50 blend of red mud-derived biodiesel proved to have better performance characteristics when tested on a real 4-stroke diesel engine. Thus, scrap red mud can be employed as potential catalyst for decreasing the cost of biodiesel production for industrial application. 8.2.3 Calcium-rich wastes 8.2.3.1 Dolomite rock wastes Dolomite rocks is highly basic and low cost material that mainly consist of CaCO3 and MgCO3 . Several studies focused on using dolomite as a heterogeneous catalyst for

Inorganic wastes as heterogeneous catalysts for biodiesel production

transesterification reactions. In one of these studies, 10 wt% calcined dolomite at 800°C was used as a catalyst with methanol to oil molar ratio of 15:1 to produce biodiesel with a yield of 99.9% after 3 h. However, the yield decreased to reach < 20% in the fifth cycle of catalyst reuse (Ngamcharussrivichai et al., 2007). In a further study done by the same team, the reusability of catalyst is improved and managed to achieve a yield of 98% by using palm kernel oil methyl ester with only 6 wt% dolomite catalyst, temperature at 60°C, and 30:1 molar ratio in 3 h. The catalyst gave a methyl ester yield of > 80% even after 10 cycles of reuse (Ngamcharussrivichai et al., 2010). Furthermore, calcined dolomite at 850°C catalyzed canola oil conversion where a maximum yield of 91.78% was obtained (Ilgen, 2011). The optimum conditions were 3 wt% catalyst amount, almost 68°C reaction temperature, 6:1 methanol to oil molar ratio, and 3 h reaction time. Fortunately, > 90% yield was maintained even after 3 cycles of reuse. 8.2.3.2 Cement kiln dust and lime kiln dust Cement kiln dust (CKD) is an abundant inorganic waste that is produced at high annual rates from cement industry. It consists mainly of calcium oxide (46 wt.%) besides other metal oxides as well as a considerable amount of alkalis accounts for almost 8 wt.% (AlSakkari et al., 2017). As a trial for using it for catalyzing the methanolysis of soybean oil, a conversion of 70% was obtained at the conditions of 15:1 methanol to oil molar ratio and 2 wt.% catalyst loading at 65 °C within 6 h (Al-Sakkari et al., 2017). In a more recent study, CKD calcined at higher temperature of 840 °C for 2 h was effectively used for the treatment of waste cooking oil with high free fatty acids (FFAs) (Al-Sakkari et al., 2020). The maximum conversion of FFA into fatty acid methyl esters FAME was 98.8% which was obtained at the conditions of 65°C, 6 h, 18:1 methanol to oil molar ratio and 2 wt.% catalyst loading. Fortunately, the catalyst at these conditions was able to convert over 90% of triglycerides into FAME as well. On the other hand, lime kiln dust (LKD) also proved its ability for the transesterification of virgin oils to be converted to biodiesel (V.S. et al., 2009). For instance, a transesterification conversion of almost 95% was achieved upon utilizing 8.7 wt.% LKD loading and 12:1 methanol to soybean oil at 71 °C within 2 h. 8.2.3.3 Marble wastes Marble slurry (MS) is a source of natural calcium carbonate that is found worldwide such as in the USA, India, Belgium, Italy, Spain, Brazil, Greece, and Portugal. In marble plants, through the size reduction processes around 15–30% of the marble rock turns into marble sand. Handling of marble sand is not easy because of being an environmental pollutant that possesses health hazards. Besides, this wastes is normally disposed near living areas (Gencel et al., 2012). Hence, a good management strategy should be applied to avoid these hazards. Accordingly, waste marble slurry was investigated as an inexpensive heterogeneous catalyst for biodiesel production using soybean oil as a raw material

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(Gupta et al., 2018). The used marble slurry was converted to two active forms before reaction, i.e. hydroxyapatite and calcined marble slurry. The highest biodiesel yield of 94% was provided by hydroxyapatite owing to highest basicity (13.30 mmol/g) and basic strength. The optimum reaction conditions were 3 h, 65 °C, 6 wt.% catalyst loading, and 9:1 methanol to oil molar ratio. The catalyst was stable and maintained high catalytic activity and biodiesel yield up to five runs of reuse. In an earlier study, marble waste in the powder form was used to catalyze soybean oil transesterification heterogeneously (Balakrishnan et al., 2013). The maximum observed yield was 88% where the catalyst loading and the reaction time were 3 wt.% and 3 h, respectively. 8.2.3.4 Pulp mills waste (lime mud) The major component of lime mud is calcium carbonate and it is produced mainly as a waste from the pulp mills. Lime mud calcined at 800°C, to convert it to CaO, was used as a transesterification heterogeneous catalyst and its activity was compared with that of commercial CaO (Li et al., 2014). In this study, the optimum conditions for biodiesel production were 6 wt.% catalyst loading, 15:1 molar ratio, 3 h, and 64°C that gave almost 94% biodiesel yield.In addition,calcined lime mud successfully reused 5 consecutive time. In addition, calcination temperature was found as a very important condition that affects maximum conversion. For instance, the conversion decreased at calcination temperatures higher than 800°C because of catalyst sintering. When the same waste was calcined at 700°C it was active enough to give a yield of 88% as a result of catalyzing peanut oil methanolysis within 2 h (Li et al., 2015). The optimum conditions at which this yield was obtained were 64°C, 8 wt.% catalyst loading and 15:1 alcohol to oil molar ratio. This study stated that catalyst hydration and carbonation are fundamental reasons for catalyst deactivation. This means that moisture content and carbon dioxide concentration during catalyst handling and storage are key players in controlling catalytic activity. Doping with other active components is another vital factor for controlling mud lime activity. For example, 99% peanut biodiesel yield was achieved upon using calcined mud doped with potassium fluoride KF (Li et al., 2014). Catalyst preparation conditions were size reduction of lime mud to achieve 0.125 mm particle size followed by calcination at 800°C and doping with potassium fluoride at a percentage of 20 wt%. Finally, the doped particles were further calcined at 600°C. On the other hand, the optimum transesterification conditions were 64°C, 8 wt.% catalyst loading, 12:1 methanol to oil molar ratio and 2 h. 8.2.3.5 Carbide lime waste Carbide lime waste is rich in calcium and that is why it is used as a base catalyst for transesterification of palm oil (Subramaniam et al., 2018). Different types of catalysts

Inorganic wastes as heterogeneous catalysts for biodiesel production

were prepared from this waste via different methods including calcination at 850 °C for 4 h and mixing with ammonium carbonate followed by calcination. As a result, 75% oil conversion was obtained as the highest percentage conversion by using calcined carbide lime waste catalyst at an initial catalyst/oil mass ratio of 9 wt%. 8.2.3.6 Constructional sites wastes Limestone supplied from construction sites was crushed to reach a particle size below 2 mm and then calcined at 900°C to catalyze the transesterification of both virgin and waste oils (Kouzu et al., 2009). The maximum yield obtained through this study was > 96% within 2 h. The derived catalyst was stable enough to catalyze 10 consecutive runs without activity drop. Another study was done to test constructional lime waste as a heterogeneous base catalyst to convert waste cooking oils to biodiesel where a 94% conversion of waste frying oil was achieved (Ghanei et al., 2013). Production conditions were 1 wt.% catalyst loading, 12:1 alcohol to oil molar ratio, 65°C, and 5 h. Fortunately, the calcined constructional could overcome the limitation of high free fatty acids FFAs content in the used feedstock as the used waste cooking oil contained 2.2 wt% FFAs. In a more recent study, production of biodiesel from non-edible Karanja oil was investigated using demolition and construction waste materials as heterogeneous catalysts. These wastes are accumulating in landfills because of their limited recycling and reusability applications. There are several steps that are performed on the local collected concrete and mortar before their use as transesterification catalysts like washing, drying, grinding, sieving and calcination at 850 °C for 3 h. The catalytic activity of cementitious waste materials has been compared with that of cement and commercial grade CaO. Among all cementitious materials tested, cement was the most efficient one in catalyzing Karanja oil transesterification which gave a conversion of 76 %. This conversion was obtained at 60°C, methanol to oil molar ratio of 30:1 and catalyst loading of 2.5 wt.%. These results were then used to conduct an economic analysis of a 50000 ton/year biodiesel production facility where the estimated total biodiesel production cost was $1.23 /kg (Kumar et al., 2018). In addition, calcined waste concrete was investigated to catalyze the conversion of soybean oil into biodiesel (Wang et al., 2012). In this study, waste concrete calcined at 650°C under air for 3 h had the ability to convert 98% of oil within 3 h at 65°C using almost 33% catalyst loading and 24:1 methanol to oil molar ratio. 8.2.3.7 Sugar industry waste In a very recent investigation, waste sludge from a sugar beet manufacturing facility was utilized as a raw material for calcium oxide catalyst production and tested to catalyze sunflower oil methanolysis (Bedir and Do˘gan, 2021). Firstly, the wastes were collected and dried for 5 h at 100°C. After drying, solid materials were ground to reach the average size

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of 240 microns where they were calcined at 900°C for 3 h.The resultant catalyst consisted mainly of active calcium oxide and had high basicity which made it ready to catalyze transesterification. As a result of this activation, upon conducting transesterification, a biodiesel yield of > 87% was obtained within 2 h at 60°C using 15:1 alcohol to oil molar ratio and 5 wt.% catalyst loading. The catalyst was able to be reused three successive times giving a yield of 80% in the last cycle. Table 8.2 summarizes selected cases from the abovementioned attempts as a way of comparing the activity of different catalysts derived from each calcium-rich waste. 8.2.4 Different slags 8.2.4.1 Gasified slag Gasified slags is produced as a residue of biomass gasification and comes in different forms. For instance, waste straw gasified slag proved its ability to catalyze rapeseed oil transesterification where biodiesel yield exceeded 95% within 2 h (Wang et al., 2017). The optimum conditions at which this yield was obtained were catalyst/oil mass ratio of 20 wt%, alcohol to oil molar ratio of 12:1 and reaction temperature of 200°C. It is highly basic due to presence of leucite and åkermanite besides being extremely stable as it kept a conversion of >80% even after 30 cycles of reuse. 8.2.4.2 Carbide slag Carbide slag is produced as a waste from calcium carbide hydrolysis. It has high calcium content which enabled it to be a good basic catalyst active for transesterification after calcination to form calcium oxide CaO (Niu et al., 2014). For instance, it catalyzed soybean oil methanolysis where 91% yield was observed after calcination at 650°C (Li et al., 2015). This high yield was attainable at 65°C, 9:1 alcohol to oil molar ratio and 1 wt% catalyst loading after 30 min (Li et al., 2015). Additionally, peanut oil transesterification was performed successfully with a conversion >92% over carbide slag catalyst activated at 650°C (Liu et al., 2014). The optimal transesterification conditions were 60°C, 3 wt% catalyst loading, and 15:1 methanol to oil molar ratio. Moreover, this catalyst was stable and reusable as it was able to achieve >85% yield after being reused 5 times. The activated calcined carbide slag produced (Niu et al., 2014) was able to convert 90% of the oil being transesterified by methanol. However, the transesterification time was longer i.e. 180 min. (Li et al., 2015). Whereas, the remaining conditions were 20:1 alcohol to oil molar ratio, 5.5 wt.% catalyst loading and 54°C. 8.2.4.3 Blast furnace and metal slags Blast furnace slag is a mixture of various metals, metal oxides, alumina and silica produced from iron ore melting (Marwaha et al., 2018). It is believed to be a good alternative for conventional base catalysts as well as its derivatives. For instance, blast furnace slag was

Table 8.2 Comparison between the catalysts derived from calcium-rich wastes. Catalyst activation Optimum (trans) Optimum yield or Type of waste Feedstock conditions esterification conditions conversion

Dolomite rocks

Calcination at 800°C Palm kernel oil

CKD

Calcination at 840°C Waste cooking oil for 2 h

Sugar industry Waste

Soybean oil

Peanut oil

Ngamcharussrivichai et al., 2010

Al-Sakkari et al., 2020

Gupta et al., 2018

Li et al., 2014

Palm oil

9 wt.% catalyst loading 75% oil conversion Subramaniam et al., 2018

Soybean oil

24:1 alcohol to oil 98% oil conversion Wang et al., 2012 molar ratio, 3 h, 65°C, 33 wt.% catalyst loading 15:1 alcohol to oil molar > 87% yield Bedir and Do˘gan, 2021 ratio, 2 h, 60°C, 5 wt.% catalyst loading

Calcination at 900°C Sunflower oil for 3 h

Inorganic wastes as heterogeneous catalysts for biodiesel production

Waste marble slurry Calcination and conversion to hydroxyapatite Pulp mills waste Calcination at 800°C + doping with KF followed by Calcination at 600°C Carbide lime waste Calcination at 850°C for 4 h + mixing with ammonia Constructional sites Calcination at 650°C wastes (concrete) for 3 h

30:1 alcohol to oil 98% yield molar ratio, 3 h, 60°C, 6 wt.% catalyst loading 18:1 alcohol to oil molar 98.8% FFA ratio, 6 h, 65°C, 2 conversion > wt.% catalyst loading 90% total conversion 9:1 alcohol to oil molar 94% yield ratio, 3 h, 65°C, 6 wt.% catalyst loading 12:1 alcohol to oil molar 99% yield ratio, 2 h, 64°C, 8 wt.% catalyst loading

Reference

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used to produce hydrocalumite as an economical heterogeneous base catalyst through calcination at 800°C in air (Yasutaka Kuwahara et al., 2012). This catalyst had the ability to convert soybean oil at 97% yield where the optimum conditions were 1 wt.% catalyst dose, 12:1 methanol to oil molar ratio, 6 h, and 60°C. Moreover, waste slag produced from metal magnesium manufacturing plant was used to derive MgO-CaO/SiO2 solid catalyst to facilitate the methanolysis of rapeseed oil (Zhang and Huang, 2011). This catalyst was very active toward transesterification due to having elevated basic strength that allowed it to achieve 98% oil conversion.The optimum conditions were 6.5:1 alcohol to oil molar ratio, 3.5 wt.% catalyst loading, 68°C, and 3.5 h. It is worth noting that the catalyst preparation included pre-treatment with nitric acid, gelation of filtrate by ammonia, drying and calcination under nitrogen at 600 °C. The merits of high catalytic activity, low cost, and abundant storage make the waste slag a promising catalyst in the production of biodiesel. 8.2.5 Waste metals In a recent study, waste-iron-filling was used to produce an efficient acidic catalyst able to convert waste cooking oil with high free fatty acids content to biodiesel (Ajala et al., 2020). In this study, waste-iron-filling was utilized as a cheap source to prepare hematite α-Fe2 O3 via co-precipitation then the produced α-Fe2 O3 was calcined at 900°C followed by sulfonation to produce the solid acid catalyst. Waste cooking oil having free fatty acids content of 6.1 wt.% was used as a feedstock. Surprisingly, 92% biodiesel yield was achieved at 80°C, 6 wt.% catalyst loading, 12:1 methanol to oil molar ratio, and 3 h. In addition, the developed acid catalyst maintained a good stability with this dirty feedstock till the third cycle of reuse. 8.2.6 Different ashes Besides, different research studies were done on usage of biomass ashes, that is, fly ash and bottom ash,as an inorganic waste catalysts active for the production of biodiesel (Manique et al., 2017). Organic compounds composed naturally of carbon, oxygen, hydrogen in addition to relatively small amount of mineral salts containing alkali metals such as potassium, sodium, magnesium and calcium. By applying combustion or gasification on these organic materials, carbon, hydrogen and oxygen contents diminish. Whereas, the oxides of potassium, sodium, calcium and magnesium besides alumina, silica and oxides of heavy metals remain as ashes in the bottom of gasification or combustion chamber (Ojha et al., 2005; Kumar et al., 2015). These alkali metal oxides are the main active substances in ashes. The high basicity of these metal oxides possesses higher catalytic capability required for biodiesel production. For instance, Ofori-Boateng and Lee (Ofori-Boateng and Lee, 2013) stated that potash has the potential to be a good catalyst to produce biodiesel. The common sources of potash are potassium chloride and potassium carbonate. These two

Inorganic wastes as heterogeneous catalysts for biodiesel production

components are usually found in the biomass combustion by-products. Potash derived from inorganic materials proved to have high catalytic activity as a base catalyst toward catalyzing transesterification. Yet, the production process of ashes is considered somehow environmentally unfriendly and lacks sustainability. Besides, it is a risky process due to combustion at high temperature and the possibility of releasing some hazardous gases. Despite having the same catalytic abilities, the biomass-derived potashes successfully overcome the previously stated drawbacks of inorganic-derived potash. In addition, Chakraborty et al. (Chakraborty et al., 2010) reported that fly ashes having significantly high silica and alumina quantities afford high catalytic performance and cheaper way for catalyst production compared to the ordinary one. Thus, the total biodiesel production performance was improved drastically. For instance, the authors of this study loaded calcium oxide on fly ash and calcined the composite for 2 h at 1000°C to have an active transesterification basic catalyst. It is worthy to note that the feedstock was virgin soybean oil and the source of calcium oxide CaO was waste egg shell. The maximum oil conversion was 97% which was obtained by using 6.9:1 methanol/ oil molar ratio and 1 wt.% catalyst loading; where the fly ash catalyst was loaded by 30 wt.% CaO that showed good stability over 16 successive runs. However, by the time of this study (2010), only few studies were performed on using biomass ashes as a heterogeneous transesterification base catalyst. These ashes were derived from empty palm bunch, husk of coconut and husk of cocoa pod and biomass residues used as fuel materials in boilers of thermal power stations. For example, one of these studies used boiler ash as a basic transesterification catalyst after being loaded with potassium nitrate (Kotwal et al., 2009). In this study, the loaded parent ash was calcined at 500°C to be active for sunflower oil transesterification. After activation, the optimum transesterification conditions were 170°C, 15 wt.% catalyst loading and 15:1 alcohol to oil molar ratio at which the oil maximum conversion was 87% that was achieved within 8 h. Rice husk was also utilized as a source of active ash. For instance, ash silica derived from rice husk was impregnated by lithium, sodium and potassium and catalyzed waste cooking oil transesterification where the resulted catalysts gave an average conversion of 97% (Hindryawati et al., 2014). In this attempt, the composite catalysts were activated after impregnation through calcination for 3 h at only 500°C. This high conversion was attainable after only 1 h at 65°C upon using 9:1 methanol to oil molar ratio and 3 wt.% catalyst dose. The catalysts remained stable for three successive runs. However, unfortunately, they were not very tolerant to FFA and moisture contents such as other heterogeneous catalysts developed from waste materials. In another study, the tolerance toward moisture was enhanced besides the resistance against carbonation through treating ash silica derived from rice husk by lithium carbonate (Chen et al., 2013). The developed catalyst was tested to convert soybean oil to biodiesel where a conversion of > 99% was obtained after 3 h at 65°C. Whereas, the optimum catalyst loading and alcohol to oil molar ratio were 4 wt.% and 24:1, respectively. It should be noted that the high basicity and stability of the catalyst

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was attainable after blending lithium carbonate with parent rice husk at 1.23:1 lithium carbonate to rice husk mass ratio followed by calcination under air for 4 h at 900°C. In addition, another type of ashes, which is gasification residues of palm kernel shell in the form of powder biochar, was used as a transesterification catalyst (Bazargan et al., 2015). For the purpose of activation toward the methanolysis of sunflower oil, the residues were calcined for 2 h at 800°C to have ashes rich in calcium oxide. As a first investigation, the transesterification reaction was conducted at 60°C for 5 h with 9:1 methanol to oil molar ratio and 5 wt.% catalyst loading; where, 99% conversion was obtained. In a further study using the same system, transesterification conditions were optimized to give the same oil conversion at 65°C using 9:1 methanol to oil molar ratio and 5 wt.% catalyst loading within 4 h (Kosti´c et al., 2016). Furthermore, in an earlier study, bottom ash produced from gasification of woody biomass was selected as a source of calcium oxide as an active basic catalyst for palm oil transesterification (Maneerung et al., 2015). Ash thermal activation by calcination at 800°C for 4 h was sufficient to give a biodiesel 96% yield at 65°C, 5 wt% catalyst dose, and 20:1 methanol to oil molar ratio within 6 h. In another earlier investigation,calcium oxide loaded on fly ash derived from another type of palm oil biomass wastes,i.e.palm oil mill waste,as a way of increasing the calcium ion content in the catalyst (Ho et al., 2014). The feedstock in this study was crude palm oil and the catalyst was prepared through loading calcium carbonate on fly ash at a mass ratio of 0.45:1 then thermally activated at 850°C for 2 h. The maximum observed biodiesel yield was 79% that was attainable at 45°C after 3 h using 6 wt% catalyst dose and 12:1 alcohol to crude palm oil molar ratio. However, this catalyst was not resistant against saponification or leaching and these were the significant reasons of its deactivation after being used only twice. Same problem of deactivation by leaching was reported elsewhere (Kosti´c et al., 2016). On the other hand, jatropha oil was utilized as a non-edible feedstock to prepare high quality biodiesel over ashes derived from different biomass wastes (Yaakob et al., 2012; Sharma et al., 2012). For instance, empty fruit bunch ash showed high activity as it gave 98% jatropha-based biodiesel yield after impregnation with 20 wt.% KOH followed by calcination at 550°C (Yaakob et al., 2012). Whereas, transesterification conditions were 15:1 methanol to jatropha oil molar ratio, 15 wt.% catalyst loading, 90 min and 65°C. In another study, wood was selected as the precursor to produce ash. This ash was calcined for 3 h at 800°C and then activated chemically by calcium and potassium carbonates to catalyze jatropha oil transesterification (Sharma et al., 2012). The highest oil conversion obtained in this study was 99%. Due to high activity of different ashes, the utilization of these types of catalysts is attracting researchers attention and the investigation in this area is still an ongoing process (Mendonça et al., 2019; Rajkumari and Rokhum, 2020; Pathak et al., 2018). For instance, in a recent study, banana trunk was utilized as a raw material for transesterification ash catalyst production (Rajkumari and Rokhum, 2020). Firstly, banana trunk waste was collected, washed and then dried by solar heating. After that, the dried trunk was crushed

Inorganic wastes as heterogeneous catalysts for biodiesel production

to small particles where these particles were combusted totally and the remaining ashes were ground to be ready for the catalysis of soybean oil transesterification. A conversion of 98% was obtained at room temperature within 6 h by using 6:1 methanol to oil molar ratio and 7 wt.% catalyst loading. The same procedure of ash catalyst preparation was applied on banana peel biomass waste; as a result, upon catalyzing transesterification, the conversion of soybean oil to biodiesel reached almost 99% (Pathak et al., 2018). The optimum conditions applied to have this high conversion were the same as in (Rajkumari and Rokhum, 2020) except that the reaction time was 4 h. It is worth noting that this type of ash catalyst proved its ability to catalyze other reactions rather than transesterification such as Henry reaction (Rajkumari et al., 2019). This is due to having high basic strength which makes it very active toward these reactions. Aside from demonstrating high activity (Table 8.3) and stability, ashes possess the merits of being green and low-cost catalysts which make them very attractive. 8.2.7 Water treatment unit wastes Wastes from water treatment units proved their ability to be a good solid catalysts for transesterification (Moradi et al., 2015; Moradi et al., 2016; Moradi and Ghanadi, 2019). For instance,due to being a mixture of calcium and magnesium carbonates,demineralized (DM) water treatment precipitate was used to catalyze waste cooking oil methanolysis (Moradi et al., 2015). A maximum conversion of 84% was obtained at 75°C after 8 h using 9 wt.% catalyst loading and 22.5:1 methanol to oil molar ratio. Whereas, the activation steps of the wastes were grinding them to the level of microns (125-250 μm) followed by drying at 110°C for 18 h and finally calcination at 900°C for 2 h. Increasing the temperature of calcination above 900°C was not favorable. In addition, this catalyst maintained high stability by being able to be reused five successive times. It should be noted that the waste oil was treated through esterification using acidic catalyst before transesterification. The same DM water treatment precipitate-derived catalyst was also used in another study where soybean oil was the feedstock instead of waste cooking oil (Moradi et al., 2016). Similar optimum transesterification conditions resulted in a maximum biodiesel yield of 82% except that the temperature was lower, i.e. 60°C instead of 75°C. In both studies (Moradi et al., 2015; Moradi et al., 2016) the activity of catalyst was dropped after 5th cycle of reuse because of CaO leaching in the methanol phase. 8.2.8 Waste clay Wastes of peat clay are a good source of silica which contributes positively in catalyzing esterification of free fatty acids.Putra M.D.et al.,extracted silica from peat clay and loaded it with eggshell-derived CaO as a low-cost bi-functional catalyst (Putra et al., 2018). For silica extraction, the authors firstly washed the clay to remove impurities and then dried it to be ready for size reduction. The particles then went through calcination at 700°C

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Calcination at 1000°C for 2 h followed by loading with eggshell-derived CaO Boiler ash Calcination at 500°C + loading with KNO3 Silica ash derived Loading with Li, Na from rice husk and K + calcination at 500°C for 3 h Rice husk ash silica Doping with Li2 CO3 followed by calcination at 900°C for 4 h Gasification Calcination at 800°C residues of palm for 2 h kernel shell

Waste and biodiesel

Table 8.3 Different ashes as active catalysts for biodiesel production. Catalyst activation Optimum (trans) Optimum yield or Type of waste Feedstock conditions esterification conditions conversion

Reference

Soybean oil

6.9:1 alcohol to oil molar ratio, 1 wt.% catalyst loading

Sunflower oil

15:1 alcohol to oil molar 87% total Kotwal et al., 2009 ratio, 8 h, 170°C, 15 conversion wt.% catalyst loading 9:1 alcohol to oil molar 97% oil conversion Hindryawati et al., ratio, 1 h, 65°C, 3 2014 wt.% catalyst loading

Waste cooking oil

Soybean oil

Sunflower oil

97% oil conversion Chakraborty et al., 2010

24:1 alcohol to oil >99% oil Chen et al., 2013 molar ratio, 3 h, conversion 65°C, 4 wt.% catalyst loading 9:1 alcohol to oil molar 99% oil conversion Bazargan et al., 2015 ratio, 5 h, 60°C, 5 wt.% catalyst loading (continued on next page)

Bottom ash from Calcination at 800°C Palm oil wood gasification for 4 h to have active CaO Fly ash

Banana peel ash

Maneerung et al., 2015

Jatropha oil

15:1 alcohol to oil molar 98% ratio, 1.5 h, 65°C, 15 wt.% catalyst loading

Yaakob et al., 2012

Jatropha oil

12:1 alcohol to oil molar 99% ratio, 3 h, 65°C, 3 wt.% catalyst loading

Sharma et al., 2012

Soybean oil

6:1 alcohol to oil molar 98% oil conversion Rajkumari and ratio, 6 h, room Rokhum, 2020 temperature, 7 wt.% catalyst loading 6:1 alcohol to oil molar 99% oil conversion Pathak et al., 2018 ratio, 4 h, room temperature, 7 wt.% catalyst loading

Crude palm oil

Biomass combustion Soybean oil after drying and size reduction

Ho et al., 2014

Inorganic wastes as heterogeneous catalysts for biodiesel production

Loading with CaCO3 + Calcination at 850°C for 2 h Empty fruit punch Impregnation with ash KOH followed by Calcination at 550°C Wood ash Calcination at 800°C for 3 h + chemical activation with CaCO3 and K2 CO3 Banana trunk ash Biomass combustion after drying and size reduction

20:1 alcohol to oil 96% yield molar ratio, 6 h, 65°C, 5 wt.% catalyst loading 12:1 alcohol to oil molar 79% yield ratio, 3 h, 45°C, 6 wt.% catalyst loading

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for 4 h followed by extraction by NaOH aqueous solution. The filtrate was then treated by 1 N HCl to precipitate silica which is then dried to be ready for being a support. The produced silica was then impregnated by eggshell-derived calcium carbonate then dried and finally calcined at 900°C for 2 h. Presence of silica with CaO increased the yield of waste cooking oil-derived biodiesel from only 78% to 91%. This relatively high yield was obtained at 60°C within 90 min. Authors confirmed that silica support catalyzed esterification while CaO catalyzed the transesterification of triglycerides.

Conclusions and future perspectives The above mentioned review confirms inorganic wastes activity toward catalyzing transesterification and esterification reactions. This high activity makes them promising materials to be utilized on larger scales, that is, pilot and industrial scales. Besides, they are abundant, cheap and some of them are very eco-friendly which makes them more promising from the economical and environmental point of views. As it can be observed, each system has its optimum (trans)esterification and catalyst preparation conditions. Accordingly, all these experimental data should be compiled with simulations and process designs as a step forward in the way of process scale-up. Tecnoeconomic analysis combined with Life Cycle Assessment studies will give a complete vision about process viability, profitability and environmental impacts before implementing the large scale units.

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NON-PRINT ITEMS

Abstract The consumption of primary energy gets enhanced on a daily basis with the increase of population and modern industries. In 2015, it was reported that the energy consumption was over 150,000,000 Gigawatt hour (GWh) and it is predicted that by the year 2050 the consumption will increase by 57%. Fortunately, the emergence of biofuels has proved a potential substitute to the current growing demand in energy market and reduces the threat to the environment. Among the wide array of biofuels, biodiesel has received a great amount of focus due to being an environmentally friendly biofuel as it is bio-degradable and renewable having less emissions as compared to petrodiesel. From another point of view, regarding the catalysis of biodiesel production, there is great interest recently to use heterogeneous catalysts, specially those derived from wastes, instead of homogeneous ones. This chapter provides an overview on the attempts which were done over the last years to utilize inorganic wastes to produce catalysts active for biodiesel synthesis. It covers the catalyst preparation conditions besides the optimum conditions of biodiesel synthesis using various catalysts and feedstocks.

Keywords Biodiesel; Heterogeneous catalysis; Waste valorization; Inorganic wastes

CHAPTER 9

Whole cell enzyme catalyst production using waste substrate for application in production of biodiesel Deovrat N. Begde Department of Biochemistry & Biotechnology, Dr. Ambedkar College, Deekshabhoomi, Nagpur, Maharashtra, India

9.1 Introduction Having a sustainable and environmentally friendly way of fuel production has been the research focus for over a decade now. Leveraging bio-based processes for meeting our fuel requirements is increasingly attracting scientific and industrial interests considering the negative environmental impact associated with conventional fuel production technologies (Straathof, 2014; Wachtmeister and Rother, 2016). Traditional chemical based technologies, although, have delivered high-yields, their byproducts often lead to toxic environmental fates and thus also involve further downstream processing, elevating the overall cost of production. Emergence of whole cell biocatalysts (WCB) has revolutionized the field of biofuel production due to their ease of operation and exceptional advantages over chemical methods (Lee, 2006). All improved genetic and metabolic manipulation technologies, high-selectivity, catalytic efficiency and environmentally friendly nature of WCB, provide unique advantages for improved deliverables during biofuel production (Ladkau et al., 2014; Lee and Kim, 2015; Sunna, 2021). The efficiency and specificity of biocatalysis is not new to the scientific world but the conceptual developments of WCB have opened a whole new array of possibilities in the field of biofuel production (Gehring et al., 2016). Despite the successful application of free enzymes, their natural response to substrate or product inhibition has always been a major hurdle for the wide industrial use and enhanced product yield. Whole cell biocatalyst approach provides the necessary solution to eliminate this drawback to certain extent. With the advantage of recent cell-surface display technology, engineered cells can be made to express different heterologous enzymes on the cell surface creating a biological assembly line for sequential modification of enzymatic products yielding a final desired outcome (Ye et al., 2021). Broadly one can classify the whole cell biocatalysis approach into two types of bioprocesses. The first being, the traditional way of fermentation wherein the fermentation Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00011-2

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broth is supplemented with the growth substrates which proceed through the host organism’s original metabolic pathways to deliver the final product. The fermentation approach involves the challenges associated with the metabolic intermediates separation which often contaminate the final product. The second approach of biotransformation takes care of this challenge associated with metabolic intermediates and hence is slightly better evolved compared to the traditional fermentation approach. In biotransformation the process of enzyme synthesis by the host and the substrate transformation steps are segregated from each other. Thus, the resting cells equipped with all the enzymes are employed here for the production of desired products minimizing the accumulation of intermediate metabolite contaminants (de Carvalho, 2017). The exceptional capacity of WCB to use cheap and abundant raw materials for enzyme production and catalyze multi step reactions makes them stand out of the conventional chemical catalysis scheme. Bioengineering of microbial factories for fermentation is a conceptually different process when compared to the principles employed for the designing of WCB. Careful section of simple or complex, single or multi step biosynthetic reactions for obtaining product of our interest from cheap raw material, with a focus to design a whole cell catalyst having fully functional one organism and not its individual product delivering enzyme, is the ultimate aim for achieving the desired product production in a cost effective way (Chen et al., 2015; Lin et al., 2013; Guo et al., 2017; Ma et al., 2015; Ricklefs et al., 2016). Targeted enrichment of a single organism to deliver the desired product can thus be envisioned as the primary aim of whole cell biocatalysis. When this is achieved using cheap and readily available feedstock for production of highly-valued products can be done with substantial ease, nothing more can be expected by the industries to obtain such products in an environmentally friendly and affordable way. This chapter will steer the readers through the conventional and emergent strategies for development of whole cell enzyme catalysts particularly produced using waste substrates, useful in biodiesel production. It will summarize the fundamental reactions involved in biodiesel production and discuss the applications of whole cell catalysis in the same.

9.2 Transesterification - conventional and emergent strategies Renewable and environmental friendly biodiesel production largely depends upon the process of triglyceride (TG) transesterification to generate fatty acid methyl/ethyl esters (FAM/EEs). Vegetable oils and animal fats which form the major source of TGs are routinely subjected for transesterification to obtain FAM/EEs necessary for biodiesel production (Moazeni et al., 2019). There are many ways other than transesterification such as blending the oil with conventional diesel, micro-emulsion, thermal cracking (pyrolysis) or catalytic cracking for obtaining biodiesel, however transesterification has become more popular (Juan et al.,2011).Overall,the process of transesterification involves

Whole cell enzyme catalyst production using waste substrate for application in production of biodiesel

the reaction of TGs with primary alcohol in presence of a catalyst to yield FAM/EEs or biodiesel (Demirbas, 2005). There is sequential conversion of TGs to diglycerides, diglycerides to monoglycerides which are finally converted to glycerol with release of FAM/EEs at every step. These reversible conversions are favoured by addition of external catalysts, however, the process has been tried even without any catalyst addition but under critical conditions. Application of catalysts during transesterification is still a much more popular way of obtaining biodiesel than doing the same without a catalyst. A comparative summary of different catalytic options available to achieve transesterification of TGs with their advantages and drawbacks under different conditions is compiled in the Table 9.1

9.3 Whole-cell biocatalysts - advantages and limitations A single,customized,whole cell biocatalyst equipped with all the necessary set of enzymes present in an optimally favourable cellular environment offers a unique stereo, region, and enantiomeric specificity advantage with virtually negligible by-product contamination in the production line of desired compound (Ricca et al., 2011; Shi et al., 2018). Such tailormade microorganisms provide the important enzymes with essential co-enzymes and the much required protection from the unfavorable environmental conditions routinely associated with media formulations used for biodiesel synthesis (Lin and Tao, 2017; de Carvalho, 2017). No matter how conceptually appealing is the application of whole cell biocatalyst, in the field of biodiesel production, there are substantial challenges involved in the complete process, right from generation of these microbes till obtaining the maximum yield. The rate of catalysis is significantly lower in the whole cell when compared with a free enzyme catalysis model (Wachtmeister and Rother, 2016; Rudroff, 2019). Bioavailability of the precursors is another limitation considering the hydrophobic nature of most of the substrates used in biodiesel production. Although, the lipophilicity of the substrates is conducive for membrane permeability, the same factor limits their media solubility and hence reduces the bioavailability of the substrate (McAuliffe, 2012). There have been many efforts done to improve the bioavailability of substrates either through inclusion of some miscible organic solvents, addition of surfactants or by giving physical stress to the organism. Most of these procedures however increase the risk of compromised membrane integrity of the organism causing leakage of intracellular metabolites, thereby, adding to challenges associated with downstream processing (Krauser et al., 2013). Of all these strategies, use of organic solvents have been widely recommended for their considerable advantages viz. ease of management, wide range of solubility for lipophilic substrates, improved bioavailability for biocatalysis (Krauser et al., 2013; Wachtmeister and Rother, 2016). Organic solvents often enhance the cell membrane permeability and can be used as a supplementary solvents but the percentage of these is essentially decided as per the organism’s tolerance and considering

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Table 9.1 Comparison of the different catalytic processes of transesterification for biodiesel production.

Factor Reaction rate Biodiesel yield Catalyst recovery/ recycle Processing methodology Water/FFA presence Cost Recovery of glycerol

Purification of biodiesel Biodiesel yield

Homogeneous catalysts (Polshettiwar et al., 2011, Ma and Hanna, 1999, Fukuda et al., 2001, Marchetti et al., 2007) Fast Normal Not possible

Absence of catalysts (Demirbas, 2005, Demirba¸s, 2002, Heterogeneous Deslandes et al., nanocatalysts 1998, Kusdiana and Heterogeneous (Polshettiwar et al., Saka, 2004, Yin et catalysts (Fukuda et al., 2011, Wen et al., al., 2008, Han et al., 2001, Xie et al., 2007, 2010, Thangaraj et 2005, Alenezi et al., ˙Ilgen and Akin, 2009, al., 2015, Venkat 2010, Ilham and Wan et al., 2009) Reddy et al., 2006) Saka, 2009) Moderate High High Moderate Higher Higher Easy Easy Difficult

Limited use of continuous methodology Sensitive Comparatively costl Difficult

Continuous fixed- bed operation possible Not sensitive Potentially cheaper Easy by filtration method

Continuous process

Repeated washing Normal

Lipase catalysts (Fukuda et al., 2001, Marchetti et al., 2007, Zhang et al., 2012, Li et al., 2007, Li et al., 2013, Naranjo et al., 2010) Low Higher Difficult

Immobilized lipase catalysts (Li et al., 2012, Iso et al., 2001, Yagiz et al., 2007, Du et al., 2005) Low Higher Easy

Whole Cell Biocatalysts (Chen et al., 2017, Almyasheva et al., 2018, Chatzifragkou et al., 2011, Munch et al., 2015) Moderate Higher Very easy

Continuous process

Continuous process

Continuous process

Continuous process

Not sensitive Much cheaper Easy

Not sensitive Medium Ill-favoured

Not sensitive High Difficult

Not sensitive Moderate Easy

Easy

Easy

Easy

Easy

Easy

Not sensitive Moderate Easy/can be utilized for further biodiesel synthesis Easy

Moderate

Higher

Higher

Higher

Higher

Higher

Whole cell enzyme catalyst production using waste substrate for application in production of biodiesel

the adverse environmental impact they cause, their wide scale industrial application is still not recommended (Zheng et al., 2010; Li et al., 2018). The most promising application of WCB is pertaining to their reusability as biocatalysts which reduces the expense related to purification and recycling as is seen in case of free enzymes. This becomes extremely important when one considers a multi step biochemical pathway for rapid and bulk production of a highly valued commercial product, using free enzymes over WCB could prove extremely expensive (Ladkau et al., 2014). WCB offers an effortless mode for controlled modification of all the pathway intermediates, no matter the extent of their chemical complexity, with abundant supply of rate limiting coenzymes, leading to efficient delivery of desired products (Lin et al., 2013, McAuliffe, 2012) Thus WCB provides an inexpensive alternative to free enzymes, their cofactors and regulators with high reactant transformation efficiency due to their close proximity during catalysis as an inherent advantage attributed to WCB (McAuliffe, 2012). Apart from free enzymes, immobilized enzymes are also being used industrially for biotransformation processes. WCB excels even here in comparison to immobilized enzymes on the expense front. The process of purification and chemical immobilization of industrially useful enzymes while being an expensive affair on one hand also does not cater for any cofactors supply, nor does it ensure long term stability of such enzymes in comparatively harsh reaction conditions. Furthermore, the cost involved in multi step biotransformations using immobilized enzymes can be exorbitant. Despite the fine tuning, the opportunities offered by immobilized enzymes such as in selectivity, activity and high volumetric loading, WCB engineered to deliver the same can be far more efficient and affordable (Barbosa et al., 2013; Rodrigues et al., 2013; Verma et al., 2013; Yan et al., 2014). When addressing the biotransformation using WCB, it involves two steps: Step one addresses the growth of the biocatalyst,and the step two is associated with carrying out the substrate conversion. For the culture of WCB, the growth media is optimized for cellular multiplication and hence contains all the essential nutrients required for the growth of the target organism. When a desired cell mass is reached, the cells can be harvested, washing off all the unwanted metabolites produced as the byproducts by the organism during its growth and the cells are essentially provided with the substrate for obtaining the product of interest. Removal of nutritional supplements halts the growth of the WCB directing them to utilize the provided substrate to the fullest, delivering the products with minimal unwanted metabolite contamination thereby easing out on the downstream processing costs (McAuliffe, 2012).

9.4 Organisms as whole-cell biocatalyst The limitations associated with enzymatic applications in the biotransformation process lead to considerable research focus being shifted in analysis of WCB application in

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this aspect. Realization of extraordinary ability of microorganisms in display of biocatalytically useful proteins on their cell surface does away with the intricacies of the enzyme immobilization strategies otherwise used in biotransformations. Also, if needed, with minimal effort one can immobilize any desired biocatalyst on organisms like the filamentous fungi, making these WCB exceptionally advantageous in commercial applications (Nakashima et al., 1990). Apart from the filamentous fungi, yeast and genetically engineered bacteria also provide distinct technical advantages under specified conditions and thus are also popular in certain setups. Another approach is to harness natural abilities of certain environmentally tamed microorganisms, isolated through application of genome mining and metagenomic screening (Ferrer et al., 2005; Wilkinson and Micklefield, 2007; Lorenz and Eck, 2005; FernándezArrojo et al., 2010). Further improvement in such microorganisms, if desired, can be brought about via metabolic engineering and biosynthetic engineering methods that utilize genetic engineering techniques for optimization of cellular processes or to completely create a bioproduction pipeline either non-existent in nature or specific to the microorganism which is being developed as WCB (Fisher et al., 2014; Turconi et al., 2014). For efficient development of optimally functional whole-cell factories enabled to deliver the desired product, a design-construction-evaluation-optimization (DCEO) biotechnology concept came into existence. It involves a conceptual and technological interface to newly construct or evolve the existing metabolic pathways to best utilize the substrate and to obtain the desired product through an optimized workflow (Chen et al., 2018). The major hurdle in the engineering of a metabolic pathway is associated with the stringently and intricately woven natural design of the pathway, which still remains a challenge. Few researchers have proposed to incorporate measures of regulatory disruption or introduction of heterologous pathways in the endogenous metabolism to cut down the cellular regulatory framework in a rational manner (Nielsen and Keasling, 2016). This technique of design-build-test-learn cycle (DBTL) can be considered an evolved version of the DCEO concept and has proven to be effective in some recent studies (Nazhand et al., 2020). The rationale behind this approach is to enrich the knowledge about the organism’s intracellular environmental dynamics, regulatory circuits, ways of coping with the heterologous intermediates, stability features and coenzyme flux in response to the tweaking. The availability of such knowledge in the scientific domain can further pave the way for development of more efficient cellular factories. Combination of metabolomics and enzyme kinetics put together through mathematical modelling has been found to deliver vital details to narrow down to the most essential aspects of engineering for successful WCB production (Milker et al., 2017). Nevertheless, the field is attracting considerable scientific attention and is open for active research to furnish more information in near future.

Whole cell enzyme catalyst production using waste substrate for application in production of biodiesel

9.4.1 Fungal whole-cell biocatalyst Very early during the testing of WCB in biodiesel production, the use of a filamentous heterothallic microfungus, Rhizopus oryzae, made its mark (Ban et al., 2001). Since then several filamentous fungi (e.g., Aspergillus niger, Penicillium expansum, Rhizomucor miehei, and Thermomyces lanuginosus) have been used in the biodiesel industry essentially for lipase production. There has been an increasing awareness now about the potential utility of oleaginous fungi belonging to the genera Alternaria, Aspergillus, Chaetomium, Colletotrichum, Cunninghamella, Epicoccum, Mortierella, Mucor, Thamnidium, and Zygorhynchus in advanced biodiesel production (Third generation biofuel). Previously, fungi were looked upon only to be a rich source of enzymes necessary for biodelignification and resistant cellulase production. However, recently, the realization developed in the field of biodiesel production that fungal lipases can be utilized in an efficient and environmental friendly manner for biodiesel production in a better way when compared to chemical acid-base catalysis.Conventionally, substrates rich in triglycerides such as plant oils and animal fats were preferred for biodiesel production through subjecting them to lipase treatment to yield biodiesel which contains monoalkyl esters with long-chain fatty acids (Tabatabaei et al., 2019). The conflict around these substrate sources on the ground of world food security, and taking into account the considerable fuel demands, requirement of extensive land mass for cultivation of such oil feedstock was another concern raised (Tabatabaei et al., 2019). Analyzing some novel oil feedstocks excluded from food security standards made researchers concentrate on lipid synthesizing and storing microorganisms e.g. algae and fungi, oils from these sources are commonly known as single cell oils (SCOs). Ease of cultivation, high lipid to biomass content,no food vs fuel concern provided SCOs an edge over the conventional feedstocks (Panahi et al., 2019). The application of filamentous fungi, both wild-type as well as recombinant, have been tried out successfully for achieving optimal yield during biodiesel synthesis. It has been identified that the best results are delivered when biomass support particles (BSPs) are used to immobilize the lipase-expressing filamentous fungi. Triglyceride lipase producing wild-type Rhizopus oryzae’s ability has been explored to the fullest in such an immobilized system and is found to be one of the most suitable WCB for biodiesel production (Arai et al., 2010; Koda et al., 2010). Similarly, genetically engineered, Aspergillus oryzae, when is made to express different forms of lipases from other microorganisms like Fusarium heterosporium, Candida antarctica, etc., can be used for enhanced and efficient production of biodiesel using a wide variety of substrates (Arai et al., 2010; Koda et al., 2010). Despite a wide range of lipase availability in the commercial market, its industrial application in biodiesel production is still limited. But at the same time, whole cell lipase immobilized using the BSPs has been found to deliver much better and industrially scalable results. Some studies even claim to reach almost 90% biodiesel

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yield using the whole cell Aspergillus sp. lipases in similar setups (Rakchai et al., 2018, Regner et al., 2019). Usually the fungi producing lipases can be grown easily on waste substrates such as agricultural wastes and crop residues, which provide a solid support and also serve as a cost effective nutritional source for the growth and simultaneous lipase expression, thereby making such a scheme industrially prudent for biodiesel (Razak et al., 2012; Thamvithayakorn et al., 2019; Oliveira et al., 2018). Plant oil refinery waste such as palm oil decanter cake waste has also been found to be useful for elicitation of fungal lipase expression as well as its potential utility in the biodiesel industry (Oliveira et al., 2018; Cheirsilp et al., 2021). In this context, there have been several attempts to isolate such industrially relevant fungi from a variety of natural sources, which can be conditioned and nurtured to deliver efficiently (Spencer et al., 2020; Kadhim and Alrubayae, 2019). Moreover, some proven studies also emphasize the importance of WCB immobilization on waste materials such as palm oil mill effluent to be a good alternative to routinely used BSPs (Rachmadona et al., 2021). Lipase producing plant endophytic fungi can also open completely new avenues in the field of WCB (Reis et al., 2020; Rocha et al., 2020). It has been observed in some previous studies that fungal isolates from oil extraction waste material can deliver astonishing results when their lipase dependent biodiesel capacity is evaluated (Elhussiny et al., 2020; Elhussiny et al., 2020). Furthermore, filamentous fungi have also been found useful when coupled with some bacteria to harvest most expensive oleaginous microalgae for cost effective utilization of microalgae biodiesel production at industrial scale (Jiang et al., 2021). 9.4.2 Yeast as whole-cell biocatalyst Yeast has been a popular organism of choice in a variety of industries and the biofuel industry is no exception. The ease of application of this organism has made it a popular choice among the investigators. Utilization of yeast as WCB by its immobilization on agricultural waste has proven to be effective in the delivery of biodiesel from oleaginous algae (Surendhiran et al., 2014). And at the same time oleaginous yeasts have also been explored for their potential to convert lignocellulosic agricultural waste, brewery industrial and some other wastes to microbial oil reserves which could later on serve as precursors for biodiesel production (Sitepu et al., 2014; Leiva-Candia et al., 2014; Ryu et al., 2013). Since, these microbial oils resemble plant oils and their production and use for biodiesel synthesis is also environmentally friendly in every sense, several studies were done in this direction recently (Leiva-Candia et al., 2014; Galafassi et al., 2012; Huang et al., 2012). Moreover, the biodiesel industry itself faces the challenge of excessive glycerol waste that is produced as a by-product of biodiesel synthesis. Even this waste glycerol has been found to be efficiently utilized by certain yeast such as Rhodotorula sp. and Rhodosporidium sp. to produce some value-added metabolites, including microbial oils that in turn can be used in biodiesel synthesis (Chatzifragkou et al., 2011; Munch et al., 2015). The

Whole cell enzyme catalyst production using waste substrate for application in production of biodiesel

extensive potential of these oleaginous yeasts have taken the research focus in this field to another level in the past few years and that will be discussed in greater detail in next section. Both wild type and recombinant yeasts have been widely employed in biodiesel synthesis. Yeasts provide a uniquely easy genomic modification route for intracellular and cell surface expression of heterologous proteins. It is not surprising that the first attempts for overproduction of lipase were done in Saccharomyces cerevisiae. A S. cerevisiae MT8-1 strain was engineered in 2001 to over produce Rhizopus oryzae lipase, IFO4697 (ROL) (Matsumoto et al., 2001). Despite overproduction of lipase, this system appeared to be ineffective due to its intracellular localization, thus limiting the mass transfer of substrates. Improvement in substrate permeabilizing attempts to enhance the delivery outcome from this intracellular lipase started attracting scientific attention thereafter. But, soon with the emergence of surface display technology, the same group pioneered the fusion of cell wall anchoring domain of Flo1p protein with ROL to have a surface display of overexpressed lipase on S. cerevisiae MT8-1 cell membrane (Matsumoto et al., 2002). Since then, there has been a great improvement in yeast cell surface display technology (Tanaka et al., 2012; Smith et al., 2015). A similar strategy was tested in other yeasts as well such as in Pichia pastoris for combined expression of Candida antarctica lipase B (CALB) and Rhizomucor miehei lipase (RML) to improve solvent compatibility of lipase during biodiesel production (Jin et al., 2013). Also the same group tried expression of thermostable (Thermomyces lanuginosus) lipase in Pichia pastoris and its application in biodiesel production (Yan et al., 2014). Recent advances recommend Pichia pastoris as a more promising organism for recombinant protein expression in industrial setups perhaps due to its smaller size in comparison to S. cerevisiae, which theoretically implies more surface area for protein display in P. pastoris (Pekarsky et al., 2018; Zakhartsev and Reuss, 2018; Zhu et al., 2019). Despite these advancements in yeast genetic engineering, researchers are still trying to isolate environmentally conditioned strains of yeasts preferentially from oil rich or agricultural wastes (Salgado et al., 2020; Maria de Fátima et al., 2021), perhaps due to their better adaptivity features. 9.4.3 Bacteria as whole-cell biocatalyst When it comes to WCB, the bacterial cells are thought to be very obvious choice of being utilized for the purpose. However, direct application of bacterial cells for FAM/EEs synthesis was not that simple. It was only when E. coli was genetically engineered to coexpress heterologous enzymes from two different organisms: one for ethanol production from Zymomonas mobilis and the other being Acinetobacter sp. ADP1 strain’s acyl-coenzyme A: diacylglycerol acyltransferase, the de novo synthesis of FAEEs was made possible (Kalscheuer et al., 2006; Stöveken et al., 2005). This study counts as the first recorded

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report of recombinant E. coli producing biodiesel provided an exogenous source of free fatty acids (FFAs) is available. Soon the studies attempting overproduction of FFAs within E.coli followed to make this organism self-sufficient, as a biodiesel yielding cellular factory (Lu et al., 2008; Steen et al., 2010). Also, attempts were made to transform the E. coli cells to produce hemicellulases for obtaining simple sugars to be used for direct production of FAM/EEs, fatty acid alcohols, and waxes utilizing hemicellulosic biomass (Steen et al., 2010). Very soon, there was this pilot study documenting the introduction of a “p(microdiesel)” plasmid in E. coli, perhaps providing it with all the arsenal required for biodiesel production but with an external source of lipids (Elbahloul and Steinbüchel, 2010). Authors of this study have also given a direction for further improved utility of the similar plasmids if introduced into some oleaginous bacterial strains or their coculture with oleaginous fungi. Some researchers even tried as many as six alterations in E.coli and attempted optimization of culture conditions in fed-batch reactors with their scale-up strategies to demonstrate the practical applicability of recombinant E. coli in biodiesel production using lignocellulosic materials (Duan et al., 2011; Wang et al., 2012). Such studies and arguments presented herein guided the research endeavours to explore the possibilities of biodiesel production in bacteria with inherent ability of excessive neutral lipid synthesis capabilities. The extraordinary development in the fields of metabolic engineering and computational biology has brought this distant dream within the reach of the scientific community (Hollinshead et al., 2014; Röttig et al., 2015; Wang and Wu, 2020). Despite these tools and successful laboratory reports the commercial biodiesel production using only bacteria is still in its infancy. Only a few encouraging reports in this direction explore the biodiesel production utilizing bacterial lipids with bacterial lipase (Khosla et al., 2017). Perhaps, the major bottleneck is limited bacterial capacity to produce and accumulate lipids that can be used for biodiesel production. Only a few species of bacteria except actinomycetes (Kalscheuer et al.,2006) show excessive fatty acid accumulation favorable for biodiesel synthesis. Therefore, a co-culture of recombinant bacteria with microalgae seems to be a more promising strategy that can be scaled up to industrial level (Zhang et al., 2020). Also, the efficiency of recombinant bacterial strains to synthesize and accumulate excessive lipids derived essentially from non-lipid or unconventional precursors namely, lignocellulosic hydrolysates seems to be a more rewarding approach in the field of commercial biofuel production (Zuccaro et al., 2020; Chintagunta et al., 2021) using bacteria.

9.5 Industrial waste as potential feedstock/nutrient medium for whole-cell enzyme catalysts production The effluents from a variety of industries contain waste products with potential nutrients that can still be used by some microorganisms for their growth. Isolation and characterization of such microorganisms may provide some clues about their application in

Whole cell enzyme catalyst production using waste substrate for application in production of biodiesel

biofuel synthesis, perhaps using the same waste materials as the feedstock. Investigations carried out in this direction has led to some encouraging results, like the palm oil decanter cake waste from the oil mills has been found to be a useful source, support and nutrient medium to harbour some industrially useful whole-cell lipase producing fungal species (Rakchai et al., 2018; Oliveira et al., 2018; Rachmadona et al., 2021). Even certain bacterial species with lipase expression have been isolated from oil mill wastes and oil contaminated mill soil (Mohan et al., 2008; Gayathri, 2021; Sirisha et al., 2010; Kumar et al., 2012). Other lipid rich wastes from industries which could serve to nourish the growth of microorganisms includes dairy waste. Soil contaminated with dairy waste has been screened for lipase producers, Aspergillus aculeatus strain with substantially high lipase expression was isolated whose application in biodiesel production still needs to be done (Roy et al., 2021). Even, non-dairy creamer industrial waste has been documented to contain the same organism with highest lipase expression (Triyaswati and Ilmi, 2020). All these studies validate the presence of potential whole-cell enzyme catalysts in industrial wastes which could be further exploited for biodiesel synthesis. A more focused research regime is thus needed for screening and evaluation of lipid rich industrial wastes to isolate some environmentally conditioned microorganisms to be employed as whole-cell catalysts in the biodiesel industry. Lipid rich industrial waste as well as agro-industrial waste is being presently utilized extensively for the growth and propagation of oleaginous microorganisms (Leiva-Candia et al., 2014). These oleaginous microorganisms are used as the feedstocks for biodiesel production thereby leading to the complete bioremediation of industrial waste into a valuable fuel substitute (Louhasakul et al., 2020; Sae-ngae et al., 2020). A variety of yeast species have been found to be useful in this regard (Arous et al., 2016; Arous et al., 2017; Ayadi et al., 2018). The industrial wastes such as paper mill sludge, lignin-like dyes in textile waste water have been valorized by oleaginous yeasts and have been brought to use as feedstock for biodiesel synthesis (Deeba et al., 2016; Ali et al., 2021). Application of microalgae, either alone or in combination with yeast, in lipid production utilizing industrial wastes to ultimately serve as feedstock for biodiesel production has also been investigated (Cheirsilp et al., 2011; Jayakumar et al., 2017). Apart from industrial wastes, there are other domestic wastes which are also reported to be the rich sources of microorganisms capable of being employed as WCB in biodiesel synthesis (Emmanuel, 2021; Nehal et al., 2019). All the wastes, whether solid or liquid can therefore either be valorized or can be used as a source of industrially important microorganisms (Ren et al., 2021; Gaonkar and Furtado, 2021; Louhasakul et al., 2016). Agricultural wastes are also being increasingly employed as BSPs for immobilizing WCBs (Musa et al., 2018). Nevertheless, essential strategies need to be devised for successful isolation and identification of natural lipase producer microorganisms as well as oleaginous microorganisms from different sources to achieve a fully sustainable and environmental friendly biodiesel production.

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Table 9.2 List of industrially relevant bacteria with a potential WCB application isolated from different environmental sources. Industrially relevant Bacteria Source Reference characteristic

Pseudomonas, Acinetobacter, Enterobacter, Bacillus, and Terribacillus Microbacterium sp.

High transesterification potential

Oil mill waste

Escobar-Nino et al., 2014

Methanol tolerant

Tripathi et al., 2014

Kocuria flava ASU5 (MT919305), Bacillus circulans ASU11 (MT919306) Haloarcula sp. G41

Thermotolerant and methanol-tolerant

Sludge Pulp and Paper Mill Cooking oil waste

Saline soil

Li and Yu, 2014

Salt lake saline soil

Li et al., 2014

Mushroom Spring

Christopher et al., 2015

Idiomarina sp. W33 Geobacillus thermodenitrificans AV-5

Halophile and organic solvent-tolerant Organic solvent-tolerant Thermo-alkaline

Najjar et al., 2021

9.5.1 Strategies for isolation and culture Lipase production is one of the most crucial aspects in screening of naturally occurring microorganisms for their application in the biodiesel industry (Hama et al., 2018). Owing to the fundamental difference in culture habits of microorganisms belonging to different groups viz. bacteria, fungi, yeast and algae, screening and isolation strategies are often distinct and target group specific. Serial dilution of the collected sample source and plating on tributyrin agar is a routine strategy to screen the lipolytic bacteria. Among these, the highest lipase producing strains are imperative and were found routinely belonging to the Bacillus sp., Staphylococcus sp. and Pseudomonas sp. (Mohan et al., 2008; Gayathri, 2021; Sirisha et al., 2010; Kumar et al., 2012; Chary and Devi, 2018). However, recently, researchers have emphasized upon analysis of transesterification activity analysis of lipolytic bacteria to be more certain about their utility in biodiesel production. This is usually tested based on transesterification of para-nitrophenyl palmitate (pNPP) in ethanol without water to form para-nitrophenol (p-NP) which can be assessed spectrophotometrically (Escobar-Nino et al., 2014). Few industrially relevant bacterial strains can thus be found using this strategy, as listed in Table 9.2.

Whole cell enzyme catalyst production using waste substrate for application in production of biodiesel

Filamentous fungal strains are considered to be the best suited source of microbial lipase and are found to be most adaptable for the whole-cell catalysis applications (Garzón-Posse et al., 2018). Previously, where only some studies were conducted with a purview of isolation of industrially relevant fungal WCBs which recognized just few fungi with high capacity of lipase expression, Fusarium sp (Maia et al., 2001), Rhizopus sp. (Idrees and Rajoka, 2002) and Trichoderma sp. (Ülker et al., 2011), the recent efforts has dynamically upgraded this list of fungi (Elhussiny et al., 2020). There is evidence that fungi belonging to the order Mucorales have an impeccable record as whole cell lipases for potential industrial application in biodiesel synthesis (Andrade et al., 2014; Arumugam and Ponnusami, 2014; Athalye et al., 2013; Carvalho et al., 2015; He et al., 2016; Kantak and Prabhune, 2015). Bioinformatics tools come in handy to check for screening of the potential lipase genes in the genome (Zan et al., 2016). Also, there have been attempts for improving lipase activities through the mutagenesis approach in some industrially relevant fungi (Peña-García et al., 2016; Jiang et al., 2020). For screening of natural lipase producers, a usual strategy is to subject the source samples for serial dilution followed by plating on Potato Dextrose Agar and sometimes modified Czapek Dox agar (mDOX), routinely supplemented with olive oil as the carbon source (Nevalainen et al., 2014). As has been stated previously for bacterial whole cell lipase screening, even the fungal whole cell lipase and its prospects in the biodiesel industry cannot be predicted unless evaluated for its transesterification potential (Elhussiny et al., 2020). Researchers have also successfully tried chemical mutagenesis for bringing about improvement in the lipolytic as well as transesterification abilities of certain isolated fungi species to enhance their applicability in the biodiesel industry (Elhussiny et al., 2020; Sharma and Bhati, 2019). Considering the ease of isolation and comparatively simpler culture requirements, several yeast species have also been explored for their potential application in the biodiesel industry. Lipase expression being the prerequisite criteria, some yeast genera were the ones to get identified first in this exploratory period and the prominent amongst them were, Zygosaccharomyces, Saccharomyces, Kluyveromyces, Pichia, Lachancea, Candida, and Torulaspora (Romo-Sánchez et al., 2010; Vakhlu and Kour, 2006; Divya and Padma, 2015). Industrially applicable lipases were however secreted only by a handful of yeast species like Candida cylindracea, Candida antarctica, Geotrichum candidum and Yarrowia lipolytica (Goldbeck and Maugeri Filho, 2013). Soon the quest began to screen environmental sources for industrially relevant yeasts with stable lipase expression (Divya and Padma, 2015). Also, researchers started focusing on advantages of whole cell catalysis during biodiesel synthesis prompting them to work on isolation of cell bound lipase expressing yeast species (Goldbeck and Maugeri Filho, 2013). To meet the demands of industry it was evident that yeasts, coupled to their lipase expression must also harbor transesterification and esterification activities for improving their biodiesel production yields (Srimhan et al., 2011). And this paved the way for explorers to isolate and characterize a variety

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of non-conventional yeast species which delivered some or the other added characters proving their suitability for industrial biodiesel production (Divya and Padma, 2015; Srimhan et al., 2011; Salgado et al., 2020; Baloch et al., 2021). A wide range of sources, as diverse as oil mill contaminated soil and/or wastewater, grease, fruits, sludge and spoiled desserts, were also screened for such important environmentally acclimatized yeast species (Salgado et al., 2020; Raj et al., 2016; Dias et al., 2020; Sakpuntoon et al., 2020; Tangsombatvichit et al., 2020; Wang et al., 2020). A routine screening strategy for lipase producing yeasts include cultivation of diluted source in YM broth and/or plating on an isolation medium for yeasts (IMY) usually supplemented with 1-2% olive or palm oil and rhodamine B, to see the halo created by lipase producing pink-red colonies of yeast under UV illumination. Often the yeast isolates with maximum lipase expression are further subjected to esterification and transesterification activity evaluation in presence of oleic acid:methanol (1:3) and palm oil:methanol (1:3) substrate containing reaction mixtures respectively and FAME with other products of the reaction can be analysed by TLC (Srimhan et al., 2011). Despite the advent of cutting edge surface display technology for heterologous protein expression on yeast surface, the importance of environmental sources for yeast isolation has remained unaffected thus keeping the scope and interest in this research aspect still alive (Moura et al., 2015; Raoufi and Gargari, 2018). Microalgae, in contrast to all of the above, are essentially utilized for lipid synthesis and accumulation so that they can be used as a feedstock for biodiesel production (Gong and Jiang, 2011; Behera et al., 2015; Goh et al., 2019). This is an indirect route to valorise the industrial waste and put it to use for sustainable fuel production (Jayakumar et al., 2017; Idris et al., 2018; Cheah et al., 2018; Wu et al., 2017). Therefore, strategies for isolation and culture of microalgae from industrial wastes are significantly focussing around identification of species with a potential to utilize specific industrial waste for microbial oil production (Cheah et al., 2018; Wu et al., 2017). 9.5.2 Oleaginous microorganisms with lipase production serving dual purpose The convenience with which microorganisms can be employed to valorize industrial wastes and a guided approach to analyze their ability to synthesize and accumulate lipids even from non-lipid sources has invited scientific interests toward oleaginous microorganisms (Louhasakul et al., 2020; Sae-ngae et al., 2020; Ayadi et al., 2018; Kumar et al., 2017). Another intriguing facet of these organisms was uncovered when an approach about intracellular FAME production was floated by some researchers in microorganisms with dual ability to accumulate lipids and at the same time express lipases (Vyas and Chhabra, 2017). Despite being a lucrative research concept, very few studies were actually initiated in this direction (Dias et al., 2021). Oleaginous microorganisms with proven ability of transforming a variety of industrial wastes into single cell oils can be used to engineer a cellular factory with a capacity for intracellular biodiesel synthesis

Whole cell enzyme catalyst production using waste substrate for application in production of biodiesel

via expression of heterologous lipases and defined transesterification capabilities. With substantial progress and cutting edge tools available to carry out desirable metabolic pathway alterations and high-throughput genetic engineering approaches put to test, the development of certain oleaginous yeasts or bacterial species into a skillfully transformed single cell biodiesel factory can be brought to reality. Such pilot studies, if carried out, can bring about a paradigm shift in the field of environmental protection and sustainable fuel production (Cho and Park, 2018; Patnaik et al., 2022; Archanaa et al., 2019). This approach can not only cater to the ever increasing fuel demands but can also solve global warming issues if carbon dioxide sequestering oleaginous bacteria or microalgae are employed for such purposes (Archanaa et al., 2019; Kumar et al., 2017; Kumar et al., 2017).

9.6 Other potential sources for whole-cell biocatalyst production Apart from lipid rich industrial wastes, some non-conventional sources have also been analyzed for presence of potential WCBs.Lipase being an industrially useful enzyme,even before its application was sorted in the biodiesel industry, the organisms producing lipase were isolated from different environmental sources (Kokusho et al., 1982; Mittelbach, 2015). Even some novel endophytic fungal species isolated from a diverse variety of plants have been tried in biodiesel synthesis (Saranya and Ramachandra, 2020; Oliveira et al., 2012). All such organisms could be considered to be the potential WCBs provided they are tolerant to the solvent stress that is inevitable during biodiesel synthesis (Srimhan et al., 2011). Thermotolerant, psychrophiles, mesophiles and other extremophiles with lipase expression, whether secretory or cell bound, can be theoretically useful for industrial application during biodiesel synthesis (Divya and Padma, 2015; Duarte et al., 2013; Ovando-Chacon et al., 2020). Environmentally tamed stress tolerant microorganisms can much easily adapt to the industrial conditions and can deliver more rewarding outcomes with less technical and revenue investments. But, at the same time there could be some inherent challenges associated with environmental isolates which might limit their scaleup potential. Here, the technical advancements in genetic engineering can come in handy to construct and design WCBs which are best fit to suit your requirements (Lin and Tao, 2017).

9.7 Stabilization and optimization of whole-cell biocatalyst for biodiesel production WCBs stability is crucial during the catalysis process to deliver the expected outcome (Garzón-Posse et al., 2018). Only high lipase expression profile of any microorganism does not testify its suitability for application in biodiesel synthesis. Often the stability of an organism in the reaction mixture as well as preservation of its lipase activity with sustained transesterification and esterification potential are the deciding factors for

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ensuring eligibility to optimal biodiesel productivity. An organism can only stand its ground as WCB for industrial biodiesel production if it excels on all the above mentioned criteria. Some common approaches used for screening of microorganisms were given in the previous section.Affirmation of an organism’s ability for its WCB application depends upon the stabilization and optimization standards used after its screening is done. These standards depend upon the type of microorganism being optimized to meet the purpose. For instance,in the studies documented for bacterial whole cell catalysis,once the relevant bacterial strain is identified and found suitable as per its lipase expression, the cell mass is first allowed to build up using a favourable bacterial growth medium. In the second step, the pre-decided number of bacterial cells are exposed to oil:alcohol mixture in the oil phase and supplemented with an emulsifying solvent usually n-hexane. Allowing a desired duration of incubation time in a sealed vessel the biodiesel yield is quantified to calculate the percent volumetric yield which can be further optimized on five point or higher parameter scale, usually targeting temperature, agitation speed, oil:alcohol ratio, n-hexane, etc. keeping the incubation time and cell count constant and assessed on the popular Plackett-Burman design. Further to this, often a central composite design approach is preferred for assessment of optimization of significant variables obtained by Plackett-Burman design. The impact of these variables on biodiesel yield is routinely studied using a response surface methodology and optimization is done for such variables to reach the maximum yield mark (ul ain et al., 2019; Haq et al., 2020). For example, with whole cell catalysis often alcohol content with respect to oil can start to limit the biodiesel yield, when increased beyond a particular level, thus the organism’s tolerance to alcohol and the biodiesel delivery needs to be balanced for optimizing the yield. Many times organism immobilization of BSPs might help improve over such limiting factors and usually done with fungal WCBs (Tabatabaei et al., 2020). Such stability features need to be analysed prior to optimization to have an effective study design.

9.8 Genetic and metabolic engineering of whole-cell biocatalyst for biodiesel production Recent developments in the area of genetic and metabolic engineering has lead to the advancements in yeast (Raoufi and Gargari, 2018; Fan et al., 2020) and bacterial surface display technology (Schüürmann et al., 2014). A lot could be achieved through laboratory manipulations, thereby, cutting down upon the tedious stability and optimization testings applicable to the wild type isolates. Surface display is a preferred choice to overcome methanol/solvent driven enzymatic inactivation routinely a point of concern during the biodiesel synthesis process (Lotti et al., 2018). The surface display technology has greatly influenced biodiesel synthesis and even unconventional substrates like agro-industrial wastes have been successfully used in biodiesel production (Sena et al., 2021). In this approach, a well characterized lipase previously tested for its enzymatic activity and

Whole cell enzyme catalyst production using waste substrate for application in production of biodiesel

stability for biodiesel synthesis is routinely expressed in organisms more suitable for whole-cell biocatalysis purposes (Huang et al., 2012; Jia et al., 2021). Another interesting facet put to test is the rerouting of the metabolic pathways for maximizing single cell microbial oil production to be used as rapid and inexpensive feedstock for biodiesel production (Zhang et al., 2011; Majidian et al., 2018; Das et al., 2020; Adegboye et al., 2021; Yan et al., 2017). For extensive product pipeline and sequential modification of substrates to desired products, a revolutionary strategy of controlled and sequential expression of required heterologous enzymes on microorganism cell surface has been tried in yeast for the purpose of biofuel synthesis (Fan et al., 2020; Dong et al., 2020). Utilizing such powerful consolidated bioprocessing approaches, one can think of innumerable possibilities for sustainable biodiesel and biofuel synthesis from a diverse variety of wastes and unconventional substrates (Rachmadona and Ogino, 2021). With extensive advances in the field of genetic engineering due to advent of CRISPR like genome editing handy tools, any suitable organism with a potential to be used as single cell factory for expression and display of multitude of different proteins, can be further exploited for a dual purpose of single cell oil synthesis and simultaneous intra/extracellular biodiesel synthesis as envisioned in a previous study (Vyas and Chhabra, 2017). However, some concerns need to be paid attention to before putting up such approaches to practice. There could be many potential uncertainty issues associated with such genetically and metabolically engineered organisms which are not usually considered by researchers in a haste of producing industrially rewarding organism transformations. Factors such as long term environmental impact assessment for these hugely distinct and modified organisms, the transformed organism is entitled to attain some undesirable characteristics perhaps with time, for example, some microalgae strains are pathogenic and serious toxin producers and their application in valorization of waste might be disastrous (Johanningmeier and Fischer, 2010; Adamczak et al., 2009; Chisti, 2007). Taking the same lead forward, one might never know that in a haste of creating industrially favorable organisms, we might produce certain strains that could challenge our own existence. Therefore, a cautious use of these genetic tools is warranted.

Concluding remarks and future prospects Sprawling reports on application and production of whole-cell biocatalysts and their extraordinary potential in biodiesel synthesis highlight the extensive research interest in this area of sustainable fuel research. However, a more focused and well articulated research effort is needed to take these laboratory proven concepts to industrial level. Despite the huge advantage of their recycle potential, WCBs still lag behind due to their slow reaction rates compared to non-biological catalysts. Bringing the WCBs at par to the chemical catalysis is still out of reach. Efforts of heterologous expression of widely tolerant enzymes on organisms to produce efficient WCBs do show some

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signs of hope for their industrial applicability. A more promising approach is to deploy some extremely versatile WCBs in waste valorization and microbial oil synthesis that can further pave the way for biodiesel production from microbial oils leading to a sustainable waste to fuel path. Another environmental friendly way could be utilizing oleaginous microorganisms to sequester nonedible waste oil from the industrial effluents to its intracellular transformation into biodiesel through the application of metabolic engineering approach. A judicious combination of WCBs and nanocatalysis can also provide some fruitful and industrially relevant alternatives. Nevertheless, the investigatory journey exploring the enormous potential of WCBs in biodiesel synthesis is still underway and much needs to be done in this direction to convert the sustainable fuel dream into reality.

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NON-PRINT ITEMS

Abstract Emergent strategies for biofuel production have revolutionized the field of sustainable and ecofriendly energy generation. With decades of research inputs, scientists have now successfully started employing greener alternatives to traditional chemical syntheses. Green technological intervention in biofuel production largely relied on application of enzymatic biotransformation reactions, which essentially faced challenges of enzymatic availability, stability, reproducibility, cost-effectiveness and limited reusability. Technological advances coupled with handy molecular tools of metabolic and genetic engineering led to the development of robust whole-cell catalysts which removed the bottle-necks of free enzyme catalysis bringing a paradigm shift in biofuel technology. Fatty acid alkyl esters derived from transesterification of natural triglycerides, and commonly known as biodiesel, could largely be obtained by application of stable extra- and/or intracellular expression of lipases and transesterification capabilities attributed to new generation whole cell biocatalysts. Recently, the screening and isolation of such organisms suitable for application as whole cell catalysts in biodiesel production is focussed on sources usually considered to be wastes largely dumped in the environment. Organisms thriving on such waste materials are considered to be robust and are frequently tamed naturally to be tolerant to the conditions which are otherwise contemplated to be toxic for most other life forms. This chapter provides a comprehensive summary of research attempts being made for the development of whole cell catalysts obtained from a variety of wastes for their efficient application in biodiesel production.

Keywords Lipase; Transesterification; Whole-cell biocatalysts

CHAPTER 10

Process integration for the biodiesel production from biomitigation of flue gases Rachael J Barla, Smita Raghuvanshi and Suresh Gupta Department of Chemical Engineering, Birla Institute of Technology and Science (BITS) Pilani, Rajasthan, India

10.1 Introduction Petroleum-based fuels are on the threshold, reaching their exhaustion limit due to the intensifying energy demand. The Environmental issues such as global warming, ozone depletion, air pollution, deforestation, and acid rain have directed the development of alternate and renewable energy sources. Alternative fuels such as biofuel or biodiesel are one of the possible ways to meet the increasing energy demand. Biofuels are classified into four generations: (1) the first generation consisting of edible biomass, such as starch, vegetable oil, and sugar, (2) the second generation, which is derived from the non-edible feedstock, including municipal waste, agricultural lignocellulose, and forest, (3) the third generation which are derived from the algal biomass, and (4) the fourth generation which are made up of crops and consume a large amount of CO2 from the atmosphere (Lage et al., 2018). These plants are genetically engineered and follow complex processes such as gasification, pyrolysis, and genetic manipulation of microorganisms. Plants and microorganisms are excellent sources of renewable fuel due to their abundance and the capacity to replenish and store energy (Cuellar-Bermudez et al., 2015). Biodiesel is a refined, diesel-equivalent, and renewable fuel derived from biological sources for diesel engines. Biodiesel is made from fats and natural oils through a chemical reaction called transesterification reaction, and it is also referred to as monoalkyl esters (Pai and Lai, 2011). The production of biofuels of the first and second generation is termed as unsustainable. The overall process requires large areas of cultivation and is not found to be cost-effective. The biofuels of the third and fourth generations have a promising option to generate renewable fuels. Microorganisms such as algae and bacteria can survive almost anywhere in the presence of little to no sunlight. Photosynthesizing organisms such as microalgae are fast-growing and can complete their growing cycle in few days (Solimeno and García, 2017; Lage et al., 2018). Microalgae have higher productivity than conventional forests and crops due to the short harvesting cycle and the potential to Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00007-0

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double their masses in less than 24 hours. The microorganisms require less freshwater than terrestrial plants and can even cultivate in marine, brackish, or wastewater and lessen the pressure on freshwater resources (Mansourpoor and Shariati, 2014; Hundt and Reddy, 2011). Different fuels and biodiesel can be produced depending upon the microalgae biomass. For example, methane can be produced from marine green algae Ulva, Chaetomorpha, and Cladophora (Hansson et al., 1983). Ethanol can be produced from naturally occurring microalgae Saccharomyces cerevisiae, and hydrogen can be produced from the algal biomass with their processes from numerous species such as Phaeodactylum tricornutum, Micromonas pusilla, and Volvox carteri (Hossain et al., 2015; Sharma and Arya, 2017). These species also have the ability to deliver high-value composites such as natural dyes, pigments, proteins, polyunsaturated fatty acids, antioxidants, and polysaccharides (Lage et al., 2018). Microalgae can also take up phosphate, nitrate, and ammonium ions from wastewater. Microalgae can biologically store these components and later be utilized as the source of valued biomaterials such as live feed, medicines, and fertilizers (Choi, 2019). Unlike fossil fuels, biomass is a renewable energy source with negligible flue gas emissions, including sulphur dioxide, nitrogen oxides, carbon dioxide, and ash. Microalgae can produce up to 70% of the dry-weight biomass concentration of lipids, rising by 90% when exposed to proper nutrients (Lage et al., 2018). Microalgae can produce up to 94,000 L of biofuel per hectare of land per year, while crop plants can produce about 560 L per hectare of land per year (Hossain et al.,2015).The possibility of culturing microalgae in wastewater during sewage bio-treatment combined for producing valued biomass and reduction in greenhouse gas emissions can be explored. Industrial-scale biofuel production using microalgae coupled with wastewater treatment can be implemented as an economically viable option (Lage et al., 2018). Feedstock comprised of 70-80% of the total cost of biodiesel production. The biomass obtained from microalgae is one of the critical ways to minimize the fuel output’s initial price (Mansourpoor and Shariati, 2014). Microalgae can be cultivated according to the requirement of the manufacture of biofuels. It can be grown from a shallow pond of wastewater or a specially designed open pond called the racetrack design. The only difficulty faced in these methods is its efficiency in harvesting the algae from the ponds and the selection of a pond’s specific location. An alternate and more feasible choice for harvesting algae biomass is the algae closed photo-bioreactor (Hundt and Reddy, 2011). The adequate sunlight is supplied via series of transparent tubes to the water and algae for the adequate growth of algae. The closed system overcomes the majority of the open system’s disadvantages, which makes the harvesting of the biomass easy. The photo-bioreactor can be located near the power plant’s emission system. Being a closed system, the probability of the algae being contaminated is eliminated. It is estimated that growing algae in a photo-bioreactor

Process integration for the biodiesel production from biomitigation of flue gases

system can produce approximately 42000 kg of biofuel in 1 year on one hectare of land (Dineshkumar et al., 2015). Bacterial microorganisms have the ability to mitigate flue gas completely into natural compounds such as ethanol, methanol, and biomass. Glycerol is produced abundantly as a co-product during the production of biodiesel by the bacteria (Sathianachiyar and Devaraj, 2013). The production of biodiesel by bacteria is classified into two different approaches: i) indirect production by in-vitro transesterification reaction from oleaginous microbes, and ii) direct production from redesigned cell factories. With the advancement of technology, metabolically modified microbes can produce higher fatty acid rates (Shi et al., 2011). Many valuable co-products are produced containing fatty acid soaps, glycerol, and residual fatty acid methyl esters during the manufacture of biodiesel. This idea of obtaining valuable co-products further supports the conversion of biomass into biodiesel. The capability of synthesizing biodiesel production depends upon the bacterial strain being used (Ashby et al., 2004). Bacteria are capable of fermenting carbohydrateenriched feedstocks even under anaerobic conditions. There are two types of anaerobic bacteria: facultative and obligate, which consume organic substances to produce biodiesel (Rodionova et al., 2017). Many bacterial species have the advantageous properties to produce biodiesel; however, no single species possess all the required characteristics to produce specific biofuel. Genetically engineered organisms prove to be more efficient in sustainability and biofuel production (Gronenberg et al., 2013). Hence the book chapter covers extensive details on biofuels, microbial production systems and, extraction & processing of the biomass. The intensive study of the microbial species’ metabolic pathways right from its growth stage to converting the flue gas components (SOX , NOX, and CO2 ) into valuable bio-products is also discussed. The various process integration implemented till date for biodiesel extraction and processing by different industries are included. This chapter highlights the validity of the entire method of intensification of biodiesel production from the bio-mitigation of flue gases.

10.2 Flue gas mitigation by microbial species Flue gas mitigation generally refers to the treatment of flue gas emitted from the exhaust of industries. The conventional techniques which can treat flue gas include chemical absorption, membrane separation, and physical adsorption. Biomitigation is the treatment of flue gas through biological routes by utilizing micro-algae or bacterial species. The drawbacks of physicochemical methods’ are more consumption of energy, costly processes,and costly solvent recovery process.The biomitigation process overcomes several limitations of conventional techniques, and it has been proven to be an efficient process.

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10.2.1 Composition of flue gas Flue gas is considered an air pollutant which refers to the combustion of exhaust gases produced by various industries. The major component of the flue gas generated from fossil-fuel combustion is nitrogen and oxides of nitrogen, such as nitrogen oxide, nitrogen dioxide, and nitrogen trioxide. Flue gas contains around 10−25 % (v/v) of CO2, followed by water vapour (H2 O) in volume, which is formed due to the combustion of hydrogen in the fuel with atmospheric oxygen. The flue gas is also comprised of SO2 and SO3, which depends on the chemistry of sulfur in the fuel. Trace amounts of heavy metals, chlorine, fluorine, and its compounds are also present in the flue gas. The flue gas characteristics generated from various industries and flue gas emission standards for different industries in India are given in Tables 10.1 and 10.2. 10.2.2 Flue gas mitigation 10.2.2.1 By microalgae Lee and Lee, (2003) have identified Chlorella HA-1, a freshwater alga from the paddy field for CO2 fixation from flue gas. The study reported removing 4.44 g CO2 L-1 day-1 with a cell concentration of 6.8 g/L, which indicated the effective removal of CO2 from the LNG thermal power plant’s gas stream. The removal rate of flue gas was 2-3 times higher in the raceway reactor than in the small tubular reactor. A bench-scale hollow fiber membrane photo-bioreactor (HFMPB) operated with 2-15% CO2 supply indicated 85% removal efficiency for removing CO2 using spirulina platensis from the flue gas released from the steel plant. The HFMPB was used to examine the increased interfacial contact area available for gas transfer through the membrane, treat wastewater, and produce algal biomass used as a biofuel (Kumar et al., 2010). Cheng et al., (2019) inculcated a new strain, Chlorella sp. Cv, through adaptive evolution for 138 days and showed that it could tolerate the simulated flue gas and achieved a maximum CO2 fixation rate of 1.2 g L-1 d-1 . In a comparison of different microorganisms, the maximum CO2 fixations from gas emitted by industrial plants were demonstrated by Chlorella vulgaris and Scenedesmus obliquus. Nannochloropsis salina, Desmodesmus sp., Chlorella fusca, and Spirulina sp were also found to be effective microorganism for the removal of NOX , SOX, and VOCs and production of biomass for conversion to biofuel (Doucha et al., 2005; Yen et al., 2015; Kroumov et al., 2016; Singh et al., 2019). Wang et al. (2008) tested the microalgae, Scenedesmus obliquus, and Chlorella kessleri separated from waste treatment ponds of thermoelectric power plants and have shown good tolerance to higher CO2 concentration. Chlorella kessleri showed maximum specific growth rates (μmax ) and biomass productivity of 0.267 per day and 0.087 g l−1 per day, respectively, when cultivated with 6% (v/v) CO2 . The maximum specific growth rates (μmax ) and biomass productivity of 0.22 per day and 0.14 g l−1 per day, respectively, for

S. No. Industry 1. Coal-fired power plant Gas-fired power 2. plant 3. Cement Plant 4. Coal-fired power generation plant

Flue gas composition SO2 NOx CO2 H2 O O2 SO3 120-200 ppm 150-250 ppm 10%–11% (v/v) 20%–23% (v/v) 4-5% (v/v) -

CO -

N2 -

-

-

-

76 mol%

25 mg/Nm3 400 ppm

250 mg/Nm3 17.8 mol% 400 ppm 7–15 mol%

4 mol%

8 mol%

12 mol%

-

18.2 mol% 5–15 mol%

7.5 mol% 1470 mg/Nm3 2–12 mol% 1–12 ppm -

Reference Aouini et al., 2014

Arachchige et al., 2012 56.5 mol% Schakel et al., 2018 65–75 mol% Wattanaphan et al., 2013

Process integration for the biodiesel production from biomitigation of flue gases

Table 10.1 Flue gas characteristics of different industries.

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Table 10.2 Flue gas emission standards for different industries in India.∗ Emission standards (mg/nm3 ) S. No. Industry SO2 NOX CO PM H2 S Hg NH3 Cl2

1 2 3 4 5 6 7 8 9 10

Thermal power plant 100 100 Caustic soda 50 350 Petroleum oil refinery 50 250 Dye and dye intermediates 200 Cement 200 500 Iron and steel 800 500 Pesticides 200 Rotary kiln Up to 213.63 (kg/hr) Ceramic 400 600 Foundry 300 400

30 150 10 150 100 5 150 100 50 150 1% (vol/vol) 50 100 50 5 1% (vol/vol) 50 150 150 -

0.03 75 30 30 -

10 5 100 -

Scenedesmus obliquus,when cultivated with the same 6% (v/v) CO2 .The above-mentioned studies reveal the fact that microalgae can be efficiently utilized for CO2 mitigation. 10.2.2.2 By bacterial species A bio-tricking filter with an inlet concentration of 100-500 ppm of NOx and 0-10% of O2 was used for the experimental elimination of NOx from the inlet gas stream. The flue gas removal efficiency of 91.94-96.74% was reported using Pseudomonas aeruginosa, which is an aerobic bacterial denitrifying strain. More than 95% removal efficiency signifies the bacterial strain’s ability to mitigate NOx from the flue gas (Zheng et al., 2016). A thermophilic biofilter containing a desulfurizing bacterial strain was utilized for the removal of SO2 at 60°C. The biofilter achieved a removal efficiency of more than 90% and reached a maximum elimination power of 50.67 g m-3 h-1 at a steady state. The thermophilic biofiltration of SO2 by bacterial species at such high temperatures makes it a promising option for treating SOx in flue gas (Zhang et al., 2015). A halotolerant bacterium, Pseudomonas aeruginosa, was used for CO2 sequestration in a biofilter, and it showed a removal efficiency of 92.37% (Mishra et al., 2017). Pandey et al. (2005) conducted experiments for the conversion of SO2 from gaseous waste streams to H2 S by D.desulfuricans in a two-stage indirect process by oxidizing ferrous iron to ferric iron by Thiobacillus ferrooxidans. The process, besides being efficient in removing SO2, also produces high-quality reusable elemental sulphur. 94% NO can be removed from the gaseous stream by Pseudomonas putida under the microoxygen conditions of 2% O2, and 79.3% removal efficiency was noted at 20% O2 concentration in the simulated flue gas. It demonstrated the feasibility of removing NO by the aerobic denitrifying process (Jiang et al., 2009). Bharti et al. (2014) studied the mitigation of CO2 using chemolithotrophs to produce biodiesel as a by-product. The bacterium produced 0.487 mg mg-1 per unit cell dry

Process integration for the biodiesel production from biomitigation of flue gases

weight of hydrocarbons and 0.647 mg mg-1 per unit cell dry weight of lipids. The hydrocarbons produced were within the range of C13-C24, making it equivalent to light oil. Faridi and Satyanarayana, (2016) studied the characteristics and applicability of CO2 sequestration in flue gas by the poly extremophilic bacterium Bacillus halodurans. Its thermal stability, efficiency, and good tolerance to SOX , NOX, and CO2 make it a robust catalyst for bio-mitigation. It demonstrated a unique property of stimulation by SO4 2− , and it remains unaffected by SO3 2− , NOx, and most other components present in the flue gas. Consistent removal of NO between 64-95% was given by Klebsiella sp., Pseudomonas sp. from a coal-fired power plant’s flue gas with a gas flow rate of 120-240 m3 /h (Jiang et al. 2009). A deep-sea sulphur- oxidizing bacterium, Sulfurovum lithotrophicum exhibited a CO2 fixation rate of 0.42 g per cell per h when the concentration was varied from low to high (Kwon et al., 2015). Thermophilic denitrifying bacteria removed 85% NO from a simulated wet-scrubbed combustion gas with three different packing materials (compost, perlite, and bio-foam) (Flanagan et al., 2002). Pseudomonas stutzeri was capable of aerobic denitrification of NO with a removal rate of 11.66 mg L-1 h-1 (Zheng et al., 2014). In a micro-oxygen condition of 2% O2 and an inlet NO concentration of 535.7 mg/m3 , Chelatococcus daeguensis bacterium gave a removal efficiency of 93.7%. In contrast, at 8% O2 concentration, it gave an efficiency of 80% when the inlet concentration varied between 133.9-669.6 mg/m3 (Liang et al., 2012). 10.2.3 Factors affecting mitigation of flue gas The microorganisms are exposed to a multitude of physicochemical influences in the natural ecosystem. These are affected by the actions of many other microorganisms in the same environment (Gottschal, 1993). The effect of the influencing parameters is discussed in the subsequent sections: 10.2.3.1 Temperature Temperature is an essential factor in determining the performance of the cells of the microorganisms. At the optimal growth temperature, the growth rate of the cells doubles every 10◦ C rise in the temperature. Moreover, anything above the optimal temperature causes thermal death or decreased growth rate (Østlie et al., 2005). Y. Zhang and Shen (2006) showed that the variation of temperature had shown a significant shift in the metabolic pathways. It is directly related to the bioactivity of the microbial species. The maximum specific growth rate is a strong function of temperature (Volkering et al., 1992). It also affects the rate-limiting step in the fermentation process as, at higher temperatures, the rate of bioreaction becomes higher than the rate of diffusion. The cells’ maintenance requirements also increase at a higher temperature. The maintenance described in the literature is the energy required for all other cell functions other than creating new cell materials. It covers everything related to the non-growth component (Zhang et al., 2015).

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Low temperatures of 15°C and 20°C with the salinity of 10 and 20 respectively proved to be better conditioned for the growth of C. ellipsoidea. On the contrary, high temperatures of 25°C and 30°C with a high salinity of 30 were better conditions for N. oculata (Cho et al., 2007). Price and Sowers (2004) suggested that an increase in the energy requirement is caused due to the decrease in the specific growth rate at a temperature higher than optimum temperature. Adamberg et al. (2003) observed that the highest specific growth rate of 2.2 h-1 was observed at 44◦ C by S. thermophilus. The growth yield increased to a maximum of 17 g dry weight mol-1 of ATP at a temperature of 41◦ C, but a slight decrease was also observed when the temperature was above 45◦ C. Higher temperatures showed an increased number of bacteria attached to the packing material in a packed bed reactor (McCaulou et al., 1995). 10.2.3.2 pH Changes in the medium’s pH induce changes in the ionic structure of the active site and enzyme activity and, thus, in the enzyme’s reaction rate (Van Den Hende et al., 2012). The maintenance energy requirements increase when the pH differs from the optimal value (Ferella et al., 2010). In the reactor studies, the nutrients such as nitrogen and sulphate accumulate in the circulating nutrient solution, and the pH value dropped with an increase in the time of the process. The varying values of pH do not affect the removal efficiency of the flue gases as it is maintained at different levels with the activity of the microorganisms. Adamberg et al., (2003) suggested that there is a drastic effect on the decrease of the external pH on the growth, higher the maximum growth rate of the strain is. A decrease in the growth yield (YATP ) and the specific acid production rate (QATP ) were observed with decreased pH. The most tolerant strain to pH change having the lowest μmax was L. paracasei E1H3 in the study. In the case of green algae, the biomass production is significantly affected by the pH at which the cultures were preserved in the laboratory. The pH tolerance limits of the microalgae are administered by the metabolic effects on the cells and the chemical influence of the growth medium (Azov, 1982). pH is the main determining factor of relative concentrations of water carbonated system organisms and can impact the supply of carbon to intensive cultivation for algal photosynthesis (Solimeno and García, 2017). Antoniou et al. (1990) reported that the flue gas’s removal efficiency was not affected by the microorganisms’ varying pH values. The optimum rate of nitrification is obtained in the pH range of 7-8.5 and was found to be an increasing function of temperature. The acid or biofuel production due to the activity of microorganisms results in the lowering of the pH (Lou and Nakai, 2001). 10.2.3.3 Concentration of growth medium Several factors are known to impact the lipid content or biomass of the microalgae, such as high salinity, nitrogen deficiency, phosphate limitation, and the iron content in the growth medium (Yeesang and Cheirsilp, 2011). The significant components of algae

Process integration for the biodiesel production from biomitigation of flue gases

growth components include CaCl2 , NaCl, NaNO2 , MgSO4 , KH2 PO4, and K2 HPO4 . The trace mineral composition includes FeCl3 , MnCl2 , ZnCl2 , CoCl2, and Na2 MoO4 (Blair et al., 2014). There are primarily two types of growth media: first is the specified media or defined media, which consists of pure chemical complexes with a known chemical composition in a fixed quantity. Second is the complex media, which is composed of natural complexes, and the chemical compositions of this media are unknown. Defined media contains (NH4 )2 SO4 ,KH2 PO4, and MgCl2, whereas complex media contains yeast extract, peptone, and molasses (Vasumathi et al., 2012). (Liebeke et al., 2009; Rathnayake et al., 2013). The primary advantage of a complex medium is that it can provide the necessary growth factor, hormones, vitamins, and trace elements, which results in yielding higher cell concentration compare to a defined medium. Moreover, the complex medium is usually less expensive than the defined medium. The advantages of the defined medium are that it gives more reproducible results and better controls the fermentation process. Furthermore, the product’s recovery and purification are more accessible and cheaper in a defined medium (Arumugam et al., 2013). 10.2.4 Extraction and processing of microbial biomass The inefficiencies in industrial bioprocesses of microorganisms are the physiology, the conditions in cultivation, and the recovery quality of cells and materials. The microorganisms’ lipids are brought into various use, e.g., medicines, foods, and biofuels. Their purpose shall be to take into account the quality and concentration of the products to be obtained. Critical values are required in order to achieve high biomass, lipid yields, and productivities for the bioengineering development of lipids. The processes of cell separation and lipid discharge from the culture medium must also be practical and commercially viable (Sathish et al., 2014; Menegazzo and Fonseca, 2019). 10.2.4.1 Media Preparation The medium or medium of cultivation is a gel or fluid that helps microorganisms or cells to expand. Different media for the cultivation of different species or cells are available. Nutrient broth or agar is one of the most popular types of media. Some of the commonly available media for microalgae and bacteria are given in Tables 10.3 and 10.4. 10.2.4.2 Process flow diagram of enrichment, isolation, and lipid production of microbes A general process flow diagram of processing the lipid from biomass for FAME analysis is depicted in Figs. 10.1 and 10.2. An overview of the whole process has been briefly described for the microalgae as well as bacterial route, starting from the isolation of the microorganism to performing the analytical and statistical studies and the, at last, the quantification of the derived fatty alcohols.

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Table 10.3 Standard culture media used for the cultivation of microalgae. S. No. Media type Medium pH

1 2 3 4 5 6 7 8 9 10

Freshwater media

Saltwater media

CHEV Diatom Allen BG-11 Desmid J medium Erdschreiber’s BG11+1%NaCl solution BG11+0.36%NaCl solution Enriched seawater SS Diatom

6 < pH 8 6 < pH 8

Table 10.4 Standard culture media used for cultivation of bacterial cells. S. No. Media type Medium Species

1

Basal

i. Nutrient Broth ii. Nutrient Agar iii. Peptone Water

2

Enriched

3

Selective

4

Indicator or Differential

5

Transport

i. Blood agar ii. LowensteinJensen i. MacConkey agarTellurite ii. LowensteinJensen i. Blood agar ii. MacConkey agar i. Cary-Blair ii. Amies iii. Stuart

6

Storage

i. Egg saline medium ii. Chalk cooked meat broth

Staphylococcus, Enterobacteriaceae, and many common bacteria Streptococci

Reference

John et al., 2011

Venkataraman, 1969

Reference

Microbiology: Canadian Edition, Wendy Keenleyside, 2008

Escherichia coli, Salmonella, Vibrio

Streptococcus pyogenes, Viridans streptococci Used when specimen cannot be cultured soon after collection For storing the bacteria for an extended period

10.3 Process intensification study for biodiesel production Organic fuels derived from plants, microorganisms, or vegetable fats are called biodiesel or bioethanol gasoline. Biofuel is an essential liquid fuel used in the transport field. These biofuels can be employed as only fuel in the automobile or as an additive mixed with diesel or petrol. Biofuels have the property of blending with diesel or petrol to improve

Process integration for the biodiesel production from biomitigation of flue gases

Figure 10.1 Process flow diagram for the production of biodiesel from microalgae.

Figure 10.2 Process flow diagram for the production of biodiesel from microalgae.

the fuel’s oxygen content.These blends further decrease the release of contaminating gases into the atmosphere (Gutiérrez et al., 2009). Biofuels can be beneficial as an alternative to crude oil-based fuels due to the prevailing depletion of fossil fuels. Feedstock, including soya, canola, a sunflower, is a well-known source of biodiesel production. Microorganisms such as algae and bacteria can convert flue gas into biomass and can be utilized to develop biodiesel and fertilizer (Pokoo-Aikins et al., 2010; Dineshkumar et al., 2015).

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10.3.1 Optimization of the culture conditions Algae, which is a vast and diversified community of single and multicellular organisms, require sunlight, water, and carbon dioxide for the photosynthetic growth (Pokoo-Aikins et al., 2010). In this study, the microalgal strain was cultured in a nitrate deficient, welloptimized bold basal media (BBM). The temperature was set at 28◦ C with a 350 μmol m-2 s-1 light intensity. The culture could tolerate a higher concentration of carbon dioxide ranging from 0.03% to 15% (Fulke et al., 2010). Bagchi and Mallick (2016) utilized the microalgae, Scenedesmus obliqus for biodiesel production by reducing greenhouse gases. The culture was maintained at 25°C in N11 medium at a pH of 6.8 in a culture room with light and dark cycles at a ratio of 14:10 hours. During the light cycle, the light intensity of 75 μmol m-2 s-1 was maintained. The culture was preserved under photosynthetically active radiation (PAR). Cabello et al. (2017) experimented in a bubble column photo-bioreactor, in which another microalgal strain, Scenedesmus obtusiusculus, was introduced for carbon dioxide mitigation and lipid accumulation. The pH and temperature of 7.5 and 30◦ C respectively were maintained in the reactor. A BG 11 mineral media with a persistent irradiance of 96 μmol m-2 s-1 was utilized to inoculate the species in a photo-bioreactor. The strain was efficient in treating 3.8% of CO2 . The cultivated microalgae, Haematococcus pluvialis, was used for treating industrial flue gas. It was grown in a photo-autotrophic NIES-C medium comprised primarily of essential salts. The pH was adjusted to 7.5, and an average temperature of 23◦ C was maintained throughout the experiment. Light intensity was retained between 30 to 50 μmol photons m-2 s-1 throughout the growth cycle and between 300 and 500 μmol photons m-2 s-1 during the induction step (Choi et al., 2017). Duarte et al. (2017) studied two algal strains, Chlorella fusca and Spirulina sp., which were isolated from a coal power plant for bio-fixation of CO2 . The culture medium used for the Chlorella fusca algae was BG 11, and Zarrouk was used for the Spirulina sp. microalgae. Chlorella sp., a high tolerant microalgal strain, exhibited proper growth at 10–30% CO2 concentration. It was used for the bio-mitigation of CO2 and instantaneous production of biodiesel in the airlift photo-bioreactor. The culture was grown with a 100 μmol photon m-2 s-1 of light intensity in the tubular photo-bioreactor, and the temperature was maintained as 28°C (Cheng et al., 2019). Similarly, chemical and physical factors such as temperature, humidity, pH, and oxygen level affect bacterial growth. A chemolithotrophic bacteria, Serratia sp. ISTD04, collected from the marble rocks region, was kept in the chemostat at 30◦ C. The pH was maintained at 7.6 for the minimum salt media (MSM). The bacteria species were enriched in the chemostat with 20-150 mM sodium bicarbonate concentration. The bacteria adapted better at a higher salt concentration (150mM) (Bharti et al., 2014). Pseudomonas putida was used in a biotrickling filter to remove nitric oxide from flue gas, which was inoculated

Process integration for the biodiesel production from biomitigation of flue gases

at a temperature of 30◦ C. Enrichment medium (EM) and bromothymol blue medium (BTB) were the two mediums used for inoculation. The biofilter’s pH was maintained between 7 to 7.6 (Jiang et al., 2009). A new Pseudomonas stutzeri PCN-11 isolated bacterial strain reduced N2 O and NO emissions by aerobic denitrification (Zheng et al., 2014). Enrichment medium with necessary salts and trace elements solution were utilized for bacterial enrichment. The basal denitrification medium (DM) was used to cultivate and evaluate the efficiency of the bacteria. The bacterial strain was immobilized in an aerated biological filter maintained at a temperature of 30◦ C, and the pH was adjusted to 7.5 (Zheng et al., 2014). In another study, the Bacillus sp. was used to yield a biosurfactant by sequestering carbon dioxide (CO2 ). The temperature was fixed at 30°C, while the pH was kept at 8, and the minimal salt media was continuously fed to the chemostat. For the sequestration process, 5% gaseous CO2 was used. (Sundaram and Thakur, 2015). 10.3.2 High lipid productivity from the biomass Microorganisms such as algae and bacteria contribute to the formation of a significant amount of lipid. The quality and quantity of lipid production depend not only on the strains but also on the culture’s conditions (Pruvost et al., 2011). The desirability for maximizing lipid development requires rapid growth, intense environment growth, broad environmental tolerance, shear force, contaminants tolerance, and no self-inhibiting excretion. An additional aspect of biodiesel production is the suitability of lipids for biodiesel in terms of the form and amount produced by a species. These factors greatly influence the quality of biodiesel production (Griffiths and Harrison, 2009). Lipid productivity is defined as average lipid mass production and depends on the biomass productivity of the microorganism and its biomass lipid value. The efficiency of lipids can be calculated in terms of surface area as grams per square meter per day (g m-2 d-1 ) or as grams per liter per day (g L-1 d-1 ) volumetrically (Xu and Boeing, 2014). A viable locally isolated, microalgal strain, Nannochloropsis sp., was cultivated as sterilized seawater enriched with Guillard media. The salinity of the seawater was 35 ppt, which was determined by the analytical salt refractometer. The dry biomass weight and the biomass concentration were obtained,and the lipid analysis was performed by FAME analysis to determine the fatty acid composition. The FAME yield of the microalga in the open raceway pond was reported to be 133 mg L-1 , which indicated the presence of an organic substrate resulted in higher fatty acids production (Das et al., 2011). The lipid efficiency is directly affected by various external conditions, such as nutritional stress, temperature, pH, photoperiod, and light intensity. Research on nutrient stresses (Nitrogen, Phosphorus, and Iron) on lipid production was performed using the oleaginous microalgal strain Ankistro desmus folicatus (Arumugam et al., 2013). The highest lipid content of 59.6% and the highest productivity of 74.07 mg L-1 d-1 were achieved

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at a modest nitrogen concentration of 750 mg L-1 and an iron concentration of 9 mg L-1 . The lowest lipid content of 27.74 % and the productivity of 3.37 mg L-1 d-1 were obtained in the presence of 40 mg L-1 phosphorous and 6 mg L-1 of iron in deprived nitrogen conditions. Response surface methodology analysis revealed the fact that nitrogen and iron are the most influential factor for lipid productivity, while phosphorous shows no significant influence (Singh et al., 2015). In the co-culture of microalgae, Chlorella Vulgaris and Leptolyngyba sp., growth, lipid, and biomass productivity were studied. Mixotrophical growth with sodium acetate addition at a C: N ratio of 15:1 achieved the maximum biomass productivity of 134 g m-3 d-1 and lipid productivity of 24.07 g m-3 d-1 . The productivities were 1.47 and 3.10 times, respectively, higher than autotrophic growth (Silaban et al., 2014). In few literature studies, as reported, an attached system for algal cultivation offers numerous advantages over the suspended system for mass biodiesel production. In an attached algal culture, the raceway pond consisted of various species such as Scenedesmus, Chlorella, Pediastrum, Nitzschia, Cosmarium, and filamentous microalgae. Biomass productivity and lipid efficiency of 13.5 g m-2 d-1 and 3.7 g m-2 d-1 in the given system. The suspended system’s overall biomass productivity was obtained as 6.1 g m-2 d-1 , and lipid productivity was obtained as 1.2 g m-2 d-1 , making the attached algal system more productive. (Lee et al., 2014). Methods for lipid extraction from microalgae, such as Botryococcus sp. and Vulgaris Chlorella was examined to test the most successful cell disruption method. Some of the comparison methods were autoclaving, bead-beating, microwave oven technique, sonication, and a 10% NaCl solution method using a chloroform and methanol blend (1:1). The organisms’ lipid content using the techniques was 5.4-11.9, 7.9-8.1, 10.0-28.6, 6.1-8.8, and 6.8-10.9 g/L, with the maximum oleic acid productivity of 5.7 mg L-1 d-1 with the microwave process (Lee et al., 2010). 12 different microalgae strains were developed to assess the biodiesel fuel properties and bioprospecting for the volumetric lipid productivity. The productivity of lipid for various strains ranged from 22.61 mg L-1 d-1 to 204.91 mg L-1 d-1 . The highest lipid volumetric productivity was observed for Chlorella (204.91 mg L-1 d-1 ) and Botryococcus strains (112.43 mg L-1 d-1 ). According to their potential for biodiesel production, the FAME profiles discriminated against the algae groups (Nascimento et al., 2013). More such studies compared the fatty acid profile and productivity of 11 different nitrogen-repressed microalgae species. The response to the weakened state of nitrogen was species-specific. The lipid’s yield was highest at 150 mg L-1 nitrate concentration. The most promising species tested for lipid content were freshwater algae, Scenedesmus and C. Vulgaris (Griffiths et al., 2012). 10.3.3 Transesterification reaction for biodiesel production Transesterification reactions are used in the processing of biodiesel, catalyzed with chemical catalysts, and it produces fatty alkyl esters. There is currently no commercial use of the enzymatic transesterification process and is limited due to its high lipase costs

Process integration for the biodiesel production from biomitigation of flue gases

and its long reaction duration. A catalyst is selected to maximize the products’ value and minimize waste generation in a catalytic transesterification reaction.NaOH and KOH are the main catalysts for biodiesel development and offer higher yields quickly. Biocatalysts are more efficient than chemical catalysts because they decrease waste production (Leung et al., 2010; Amini et al., 2017). Several lipases from microbial strains such as Pseudomonas fluorescens, Pseudomonas cepacian, Rhizopus oryzae, Candida rugosa, and Thermomyces lanuginosus have been evaluated for active transesterification; the photosynthesis process is crucial and is given as reaction 1 (Vasudevan and Briggs, 2008). 6CO2 + 12H2 O + photons → C6 H12 O6 + 6O2 + 6H2

(10.1)

The method of extraction of wet lipids (WLEP) was successful when 79% of transesterifying lipids were extracted utilizing acid and base hydrolyses (90°C and atmospheric pressure) from wet microalgae biomass (84% moisture). The extracted lipids were further processed and transformed into FAMEs. The process prevents chlorophyll contamination by precipitation of the lipid extract. It can minimize organic solvents and produce feedstock for high-value bioproducts. Chlorella sp. and Scenedesmus sp. were used for the process and have developed 60% transesterifiable lipid (Sathish and Sims, 2012). Another successful method was explored for lipid extraction from microalgae which is known as microwave fragmentation technology. The process’s catalysts were prepared under different conditions and are characterized by BET and XRD. GC had determined the conversion of transesterification catalyzed by other stimuli. The experimental results showed that many microalgae lipids could be extracted of about 30 wt% by n-hexane and iso-propanol solvents. The conversion of 76.2% was obtained by the heating performance for transesterification under 68 with 3 wt% LiSO4 and oil/methanol molar ratio of 1:18 for 4 hours (Dai et al., 2014). Total lipids were extracted using chloroform/methanol (2/1 v/v), and GC-MS was used to investigate the organic material. The transesterification method was accomplished by treating hexane extracted triglycerides with ethanol in KOH’s presence as a catalyst. The biomass acid value was estimated to be 0.4 mg KOH/g, with calorific value of 40 M.J./kg, and density of 801 kg/m3 (Vijayaraghavan and Hemanathan, 2009). In conjunction with methanol or ethanol, the P. pastoris recombinant strain was used to catalyze microalgal oil to produce biodiesel using the n-hexane solvent process. More than 90% of the conversion rates were achieved over 24 hours for two essential biodiesel types, fatty acid methyl ester (FAME) and fatty acid ethyl ester (FAEE). The thin-layer chromatography (TLC) or the gas-chromatographic (GC) examination of microalgae oil derived from the chloroform/methane (1:2). The extracted microalgae oil contained 508.26 mg of fatty acids (Huang et al., 2015). Research has shown that biodiesel recovery was decreased substantially by algal biomass with a moisture content of more than 20%.

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However,a rise in catalyst or methanol in response improved the recovery of algal biomass (Sathish et al., 2014). Transesterification on marine microalgae, Nannochloropsis sp. was carried out directly in a study. The methanol: n-hexane (1:1) volume ratio, the molar ratio of lipids: methanol (1:400), and the 4 hour reaction time provided 90.9% biodiesel. The saturated fatty acid content reached 52.72% (Dianursanti et al., 2015). A simple procedure was developed to obtain biodiesel from wet microalgae, Nannochloropsis gatidana (25 wt% dry biomass, and 11.1 wt% saponifiable lipids). With the direct catalyzed methylation of the SLs in biomass and FAME extraction with hexane, the synthesis of fatty acid methyl esters was maximized. The best yield has been recorded with a methanol/SL ratio of 171.1 mL/g, 5% (v/v) concentration of acetyl chloride (catalyst) at 100°C and 105 minutes of reaction time. FAME’s purity improved from 74.5 to 82.7 wt% by treating bentonite adsorption (Macías-Sánchez et al., 2015). In the presence of methanol as a precursor, triglycerides can form diglycerides, monoglycerides, and, subsequently, glycol; The transesterification process consists of multiple reversible reactions, which are represented in reactions 2, 3, and 4. The R in reaction denotes the short alkyl group of alcohol (Ramachandran et al., 2013). CH2 − O − CO − R1 CH2 − OH | | CH − O − CO − R2 + CH3 OH ↔ CH3 − O − CO − R1 + CH − O − CO − R2 | | CH2 − O − CO − R3 CH3 − O − CO − R3

(10.2) CH2 − OH− CH2 − OH | | CH − O − CO − R2 + CH3 OH ↔ CH3 − O − CO − R2 + CH − OH | | CH2 − O − CO − R3 CH2 − O − CO − R3

(10.3) CH2 − OH− CH2 − OH | | CH − OH + CH3 OH ↔ CH3 − O − CO − R3 + CH − OH | | CH2 − O − CO − R3 CH2 − OH

(10.4)

In the Direct transesterification analysis, the energy usage of the lipid extraction process was decreased by 75% using ethanol as a co-solvent such as petroleum ether, nhexane, ethyl ether, n-butanol, and increase the conversion rate of biodiesel. The reaction

Process integration for the biodiesel production from biomitigation of flue gases

state of n-hexane at 75% ethanol volume ratio 1:2, the temperature of 90°C, the reaction time of 2 hours, and the catalyst volume of 0.6 mL gave a high conversion rate 90.02 ± 0.55 wt% (Zhang et al., 2015). Heterotrophic bacteria, Schizochytrium limacinum, were tested to generate high biomass and total fatty acid levels. Frozen biomass was used to generate crude bio-diesel at a rate of 57% and a FAME content of 66.37% as a feedstock in a two-phase process (oil extraction, followed by transesterification) (Johnson and Wen, 2009). Chlorella pyrenoidosa, which comprises about 90% of the water, was used to turn the wet oil-bearing microalgae into biodiesel in a one-stage process. The research results have shown that below 90◦ C temperatures, it has a detrimental effect on biodiesel production. The yield dropped from 91.4% to 10.3% as the water content increased from 0 to 90%. The biodiesel yield was over 100% without any adverse effect at around 150°C temperature. The biodiesel yield was 92.5% and a FAME content of 93.2% (Cao et al., 2013). Tetraselmis sp., a green marine micro-alga, was used to transform lipid into biodiesel at varying nitrate concentrations. The lipid was extracted using a solvent of chloroform-methanol and quantified using the Nile Red method. The highest lipid content of 508.42 mg L-1 was obtained in the absence of nitrate than in the presence of nitrate (Teo et al., 2014). 10.3.4 Reactor studies for biodiesel scale-up production Research interests are inclined to develop clean and renewable diesel fuels such as biodiesel to resolve environmental concerns. The challenges in large-scale biodiesel production are high costs over conventional diesel production.The viability of microalgae oil processing depends economically on optimizing the whole system (Ríos et al., 2013). Blending and direct application, microemulsion, pyrolysis, and transesterification are the four primary processes used to manufacture biodiesel. The conventional chemical reactors used in biodiesel production include revolving reactors, plug-flow reactors, microwave reactors, cavitation reactors, and simultaneous separation-reaction reactors. Among these reactors, few are used at the industrial scale and others at the pilot-scale (Tabatabaei et al., 2019). Lipid quality and lipid efficiency of Micractinium sp. with a concentration of 20% (v/v%) of vinasse, grown in a 2 L flask, was calculated. Lipid content was found to be 4.13±0.12 (%w/w) and lipid productivity 1.08±0.03 g L-1 day-1 . The same experiment was replicated with a 5 L bioreactor scale. In identical bioreactors, microalgae were grown with 10.7±0.57% lipid content and 3.4±0.20 g L-1 day-1 lipid productivity. The high productivity of lipids in the 5 L reactor results from high biomass productivity, as lipid productivity incorporates productivity of biomass with lipid content (Engin et al., 2018). The experiment was carried out using Chlorella sp. for biodiesel development; in two phases; the first stage was to provide necessary information on microalgae’s performance using an autoclaved center. Moreover, it was focused on the viability of algae production

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using a raw core in the second stage. The scale-up biodiesel production output in the 25-L coiled reactor has also been checked with a raw center. The scale-up tests were initially performed for 7 days in batch mode, followed by continuous mode upgrades. The FAME content was 11.04%, and biodiesel production was obtained as 0.12/L (Li et al., 2011). A comparative analysis was conducted on algal growth for surface-attached biofilm and suspension culture. The biomass was naturally concentrated and easily collected in a surface-attached biofilm. It has been a cheaper method of removing biomass and less expensive for the downstream biofuel production process. The observations were tested in an 8 L bench scale and 8000 L pilot scale of the novel rotating algal biofilm reactor (RABR). Biomass productivity of 5.5 g m-2 day-1 was achieved for the bench-scale reactor, and pilot-scale productivity of 31 g m-2 day-1 was achieved (Christenson and Sims, 2012). A compost-coal mixture of (4:1) weight ratio was filled in a continuous bed bioreactor. Coal particles were cleaned with de-ionized water and dried in a hot air oven for a 24-hour duration of 100°C to eliminate the pollutants. The analysis confirmed a combined volume of carbon and compost of 0.88 kg and 3.52 kg. The macronutrient manure (nitrogen, phosphorus, potassium) and organic substances in the compost mixture promote microbial development (Liebeke et al., 2009). The analysis used a combination of coal and compost. The packaging height was 90 cm. The airflow rate was 1 LPM, and the flow rate was 0.05-0.2 LPM. The necessary nutrient supply was provided for the proper growth of microorganisms; MSM was supplied to the top column at a rate of 5 mL min-1 for 15-30 minutes per day. The enriched microbial population was introduced from the top of the column, and leachate was taken from the bottom of the column after 2 hours.The leachate extracted was manually recirculated into the bioreactor.The process was carried out for 15 days. MSM was inducted from top to top at 5 mL min-1 flow rates and provided the necessary supply of nutrients for the growth of the microorganism (Mishra et al., 2016, 2018b, 2018a). Research has been performed on the technical aspects of the reactors used for the manufacture of biodiesel. Factors influencing the process of transesterification in the reactor were reviewed on the basis of the types of solvents and the types of catalysts used. Batch reactors were unproductive in biodiesel development due to the large volume of reactors, high labour costs, and comprehensive reaction/separation processes. In contrast, the continuous reactors were proved worthy due to the optimization of solvent, catalyst, and catalyst and simplification of recovery stages by integrated techniques. Continuous reactors offered better performance, uniform quality products, and reduced production costs (Zahan and Kano, 2019). A comparison was then made between different reactors based on the reactor’s economics at a commercial scale. Commercial reactors such as open raceway ponds, tubular photo-bioreactors, and flat-panel photo-bioreactors were compared on their operational characteristics. The productivity was maximum in a

Process integration for the biodiesel production from biomitigation of flue gases

flat-panel reactor of 64 (ton per hectare) and the lowest 32 (ton per hectare) in an open pond reactor. The unit biomass production cost was lowest in a tubular reactor with 990 cts kg-1 DW and highest in the open raceway pond with 1772 cts kg-1 DW (Norsker et al., 2011).

Conclusion and future prospects The four critical points can be made regarding the mitigation of flue gas by microalgae and biofuel production from microalgae. First is the biological route of treating flue gas components has proven beneficial and economical in the past few years of research. Biomitigation is an eco-friendly method, and the recent developments in this field indicate the emerging status of the process.The process has been proven successful at a bench-scale experiment and can be taken to a pilot-scale or commercial level. The second conclusion which can be drawn is the extraction and processing of the biomass produced by the microalgae. The rigorous experiments being conducted suggest that a large quantity of biomass can be obtained with the proper growth of the microalgae. The flue gas components are used as a substrate to nourish the microbial growth and hence solving two purposes: abatement of polluting flue gas and production of many valuable by-products. The third is that the biomass produced from microbial species shows excellent potential to be used as a biofuel source. Given the depleting natural resources’ current scenario, we need to tap onto alternative fuel sources. Producing biofuel from microbial biomass is a promising option. The clean technology benefits of biofuels include the potential to use waste sources, decreased effects on the atmosphere, fast growth rates, and higher oil content. Since the local ecosystem has a significant number of microalgae and bacteria, external feeding costs can be avoided. The easy availability of the flue gas substrates from the waste streams of the stacks of different industries. Fourth is biofuel production technology, which is a new and unexplored area. The production of biofuel from biomass depends entirely on microbial efficiency, harvested biomass, and the processing system. The output of FAME’s is successful at bench-scale experiments as it can produce a decent amount of by-products. This technology is still to be upgraded and applied at the commercial level to handle large biomass quantities and make commercially equivalent bio-fuel.

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NON-PRINT ITEMS

Abstract The bacterial routes for the mitigation of flue gas from the industries are a groundbreaking approach for biofuel production. Commonly found microalgae and bacteria are incorporated in the series of experiments which eventually leads to the creation of many FAME’s. These valuable products can be utilized in medicine, perfume, food industries as well as in automobiles. The composition of the exhaust flue gas is different for different industries. Many factors are taken into account in selecting the microorganism for the bio-mitigation process. The whole work process, starting from isolating the microorganisms from a natural environment to conducting rigorous experiments and analysis, gives a thorough output in reproducing the biofuel. Various reactors are used for the mitigation process ranging from the bench-scale reactor to industrial scale. With an extended period of research, the bio-mitigation method had been impactful when compared to the other conventional methods in the field of biofuel production and utilization.

Keywords Flue gas; Bio-mitigation; Microalgae; Bacteria; Biomass; Lipid; Transesterification reaction; Bioreactor; Biodiesel

CHAPTER 11

Bio-waste as an alternative feedstock for biodiesel production: Current status and legal environmental impacts Adewale Adewuyi and Ayodeji J Fatehinse Department of Chemical Sciences, Faculty of Natural Sciences, Redeemer’s University, EDE, Osun State, Nigeria

11.1 Introduction The quest for alternative source and form of energy has become high as the global economy grows. As of today, fossil fuel still plays a key role as a source of energy globally. Although, several nations of the world are alternating with substitutes, the demand is still high. Despite the success achieved with fossil fuel, there are issues of sustainability and environment, which has created concerns with health, environmental pollution, and reserve depletion (Hoekman, 2009; Kiran, Kumar and Deshmukh, 2014). These concerns have led to the search for alternatives and complementary sources of energy (Demirbas, 2010 ; Shafiee and Topal, 2009). The world is currently faced with challenges caused by continuous use of fossil fuel. Several attempts have been made in developing replacement for fossil fuel in form of renewable energies. However, among the renewable energies, priority is given to liquid biofuels since their use reduces emission of greenhouse gases, environmental hazard, and dwindling price of global energy (Demirbas, 2009). Biowaste reduction and its application to real-time issues are current global approaches toward transformation from fossil fuel to renewable energy. This concept of biowaste-to-fuel is encouraged because it will help manage the large chunk of biowaste continuously generated globally. As the world population increases, more biowaste are generated, which can serve as feedstock to meet the ever-increasing demand for energy. They can serve as the source for the global quest for clean and benign energy. The biofuel generated from the biowaste may be grouped into first (from edible food crops), second (from agricultural, industrial and municipal solid wastes) and third (waste cooking oil and microalgae) generation biofuels. Agricultural wastes, waste cooking oils and waste microalgae have proved to be promising feedstock for biofuel production. Among the biofuels, biodiesel has been of important benefit to the economy due to its energy sustainability and strategy for cleaner energy development mechanism. Biodiesel, also Waste and Biodiesel: Feedstocks and Precursors for Catalysts DOI: https://doi.org/10.1016/B978-0-12-823958-2.00008-2

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known as fatty acid methyl ester (FAME) (as methanol is the commonly used alcohol in its production) is mainly produced from vegetable oil, which is from a renewable plant source. It is considered a green source of energy for the transportation sector and electrification. It is a replacement for liquid fossil fuel, that contributes high amount of greenhouse gas and other toxic pollutants to the environment. Though, derived from a renewable plant source, biodiesel has a density which is comparable to the fossil sourced liquid fuels, making it an outstanding resource. The vegetable oil may be virgin vegetable oil or waste vegetable oil such as waste animal fats or cooking oil. The vegetable oil may be edible or non-edible oil. The use of edible oil in the production of biodiesel has the disadvantage of competing with the use of such oil as food. Previous report showed that the use of highly refined oil and edible oil is expensive; the cost of production is about four times higher than the cost of diesel production (Banapurmath et al., 2008). However, the nonedible oils have great benefit of not being used as food, which makes them cheaper and readily available when compared with the edible oils. The commonly used nonedible oils for biodiesel production include cotton oil, karanja oil, jatropha oil, polanga oil, etc. Studies have reported the production of biodiesel from underutilized seed oils (Adewuyi et al., 2012). Several methods have been used, which may be biological, chemical or thermochemical (Ranganathan et al., 2008). Focus has shifted toward the use of nonedible oils, as they do not compete with food. Some of them have shown high potential as sustainable sources for biodiesel production with high product yield and outstanding product quality. Moreover, vegetable oils are biodegradable with capacity to produce biodiesel, which can biodegrade up to more than 90% within 21 days (Leung et al., 2006). 11.1.1 Chemistry of biodiesel production from vegetable oils and animal fats Transesterification is an established globally acceptable chemical reaction route used in the production of biodiesel. The process involves the use of catalyst that has an important role to play in production process. The catalyst can either be homogeneous or heterogeneous, in the case of homogeneous catalysis, production cost is higher when compared with heterogeneous catalysis due to difficulty in catalyst separation and the fact that additional steps may be required,which increases production cost.Current research works have considered the use of biocatalyst for biodiesel production. Despite this, there is need to develop efficient and cheap catalyst to promote the course of biodiesel production.The quality of biodiesel produced depends on the type and chemical composition of feedstock used.The triglyceride,diglyceride,and monoglyceride contents of the oil varies (Endalew et al., 2011; Helwani et al., 2009); other composition such as free fatty acid, phospholipids, glycerol, glycolipid, and other impurities also varies. The composition of vegetable oil may depend on storage condition of seed and oil, oil extraction method, cultivation method, and geographical growing conditions (Akbar et al., 2009). These compositions

Bio-waste as an alternative feedstock for biodiesel production: Current status and legal environmental impacts

Table 11.1 Physicochemical properties of some selected vegetable oils for biodiesel production. Yield Oil AV SV IV PV SG Viscocity Reference (%)

Seasame Dacryodes Moringa Cashew Canola Castor Cotton Jatropha Karanja Mahua Safflower Baobab

48 20.92 40.6 49.34 – – – – – – – 22.5

5.049 44.88 0.51 0.84 0.31 0.94 0.3 9.81 13.92 22.8 0.22 3.14

Lannea kerstingii Rice bran

57.85 0.64 4.36 28

98.56 126.8 182.89 169.42

21.51 110.43 68 48.45 109.3 85.3 119.1 100.2 87.4 71.7 162.69 142.3 186 82.58

10.32 8.3 5.82 3.45 – – – – – – 2.81 10.15

189.73 60.72 0.99 156 72 31

0.95 1.056 – – – – – – – – 0.917 –

1.35 2.86 – – 34.7 239.7 35.4 35 37.1 32.8 45.6 –

– –

– –

Eze, 2012 Eze, 2012 Saeed et al., 2015 Saeed et al., 2015 Giakoumis, 2018 Giakoumis, 2018 Giakoumis, 2018 Giakoumis, 2018 Giakoumis, 2018 Giakoumis, 2018 Katkade et al., 2018 Birnin-Yauri and Garba, 2011 Ouilly et al., 2017 Oluremi et al., 2013

- = Not reported AV = Acid value (mg NaOH/g of oil), SV = Saponification value (mg KOH/g of oil), IV = Iodine value (g I2/100 g of oil), PV = Peroxide value (Meq/kg), SG = Specific gravity (g/cm3 ).

O R' C OCH3

O H2 C

O

H C

O

H2 C O

C R' R" C O C R"' O

+

3 CH3OH Catalyst Methanol

Triglyceride

H2 C OH H C OH H2 C OH Glycerol

+

O R'' C OCH3 O R''' C

OCH3

FAME

Figure 11.1 Transesterification of triglyceride to FAME.

as well as the catalyst go a long way in determining method used, yield and purity of biodiesel produced. The physicochemical properties of some selected vegetable oils for biodiesel production are presented in Table 11.1. However, the fatty acid composition is important as this forms the FAME. The type of fatty acid involved in FAME production is important in understanding the properties exhibited by the biodiesel. Examples of major fatty acid composition of some selected oils for biodiesel production is shown in Table 11.2. Transesterification converts triglyceride and short chain alcohol in the presence of a suitable catalyst to alkyl ester and glycerol.This involves 3 moles of methanol reacting with 1 mole of triglyceride to produce 3 moles of FAME and 1 mole of glycerol as described in Fig. 11.1. There may be need for pre-treatment steps if the oil contains

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Table 11.2 Major fatty acid composition of some selected vegetable oils for biodiesel production. Oil 16:0 (%) 18:0 (%) 18:1 (%) 18:2 (%) 18:3 (%) Reference

Cotton Neem Jatropha Karanja Castor Mahua Canola Rice bran Sunflower Seasame Khaya senegalensis

32.47 16.32 14.39 10.82 1.36 22.23 4.52 16.2 5.62 9.38 8.23

9.05 23.87 5.83 7.92 1.11 22.49 1.99 1.5 4.26 5.07 12.54

19.05 48.12 42.05 53.73 91.44 39.01 60.43 52.1 25.61 40.06 68.46

37.32 9.37 35.9 20.68 4.82 14.89 21.19 22.1 62.45 43.77 8.33

– – 0.23 1.97 0.56 0.1 9.42 1.5