Biofuel Extraction Techniques E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 1038

Veröffentlichungsjahr: 2023

Beschreibung

BIOFUEL EXTRACTION TECHNIQUES The energy industry and new energy sources and innovations are rapidly changing and evolving. This new volume addresses the current state-of-the-art concepts and technologies associated with biofuel extraction technologies. Biofuels are a viable alternative to petroleum-based fuel because they are produced from organic materials such as plants and their wastes, agricultural crops, and by-products. The development of cutting-edge technology has increased the need for energy significantly, which has resulted in an overreliance on fossil fuels. Renewable fuels are an important subject of research because of their biodegradability, eco-friendliness, decrease in greenhouse gas (GHG) emissions, and favorable socioeconomic consequences to counteract imitations of fossil fuels. Different extraction techniques are used for the production of biofuel from renewable feedstocks. A good example is biodiesel, a promising biofuel which is produced by transesterification of plant-based oils. Extraction of oil includes traditional methods, solvent extraction, mechanical extraction, microwave-assisted and ultrasonic-assisted methods. Many innovative techniques are also used to overcome the limitations of conventional methods. Microwave-assisted and ultrasonic-assisted are some of the new techniques which include the pre-treatment of the raw material using either ultrasonic waves or radio waves which helps in increasing the efficiency of the extraction of oil and improves the final quality of the oil. Written and edited a team of experts in the field, this exciting new volume covers all of these technologies with a view toward giving the engineer, scientist, or other professional the practical solutions for their day-to-day problems. It also contains the theory behind the practical applications, as well, making it the perfect reference for students and engineers alike. Whether for the veteran engineer or scientist, the student, or a manager or other technician working in the field, this volume is a must-have for any library.

Leseprobe

Table of Contents

Cover

Series Page

Title Page

Copyright Page

Preface

1 Plant Seed Oils and Their Potential for Biofuel Production in India

1.1 Introduction

1.2 Background

1.3 Non-Edible Oil as Feedstock for Biodiesel

1.4 Fuel Qualities

1.5 Conclusion

Author Contributions

References

2 Processing of Feedstock in Context of Biodiesel Production

2.1 Introduction

2.2 Feedstock in Context of Biodiesel

2.3 Processing of Oilseeds

2.4 Oil Extraction Methods

2.5 Catalyst

2.6 Production Process of Biodiesel

2.7 Techniques for Biodiesel Production

2.8 Advantages & Disadvantages of Using Biodiesel

2.9 Current Challenges and Future Perspectives of Biodiesel

2.10 Summary

References

3 Extraction Techniques for Biodiesel Production

3.1 Introduction

3.2 Direct Use and Blending

3.3 Microemulsion

3.4 Pyrolysis

3.5 Transesterification

3.6 Intensification Methods for Biodiesel Production

3.7 Conclusions

References

4 Role of Additives on Anaerobic Digestion, Biomethane Generation, and Stabilization of Process Parameters

4.1 Introduction

4.2 Anaerobic Digestion Process

4.3 Metallic Additives

4.4 Alkali Additives

4.5 Biological Additives

4.6 Carbon-Based Additives

4.7 Nanoparticles

4.8 Other Natural Additives

4.9 Conclusions

Acknowledgment

References

5 An Overview on Established and Emerging Biogas Upgradation Systems for Improving Biomethane Quality

5.1 Introduction

5.2 Available Biogas Upgradation Techniques

5.3 Microbial Methane Enrichment

5.4 Bioelectrochemical System

5.5 Photosynthetic Biogas Upgradation

5.6 Techno-Economics of Biological Biogas Upgradation Technologies

5.7 Conclusion

Acknowledgement

References

6 Renewable Feedstocks for Biofuels

6.1 Introduction

6.2 Sugar Containing Plant Crops

6.3 Crops

6.4 Oilseed

6.5 Lignocellulosic Waste

6.6 Sea Waste

6.7 Liquid Waste

6.8 Conclusion

References

7 Extraction Techniques of Gas to Liquids (GtL) Fuels

7.1 Introduction

7.2 History and Origin of Gas to Liquid Technology

7.3 What is Gas to Liquids (GtL) Fuel?

7.4 Need and Benefits from Gas to Liquid Technology

7.5 Extraction or Conversion Techniques of Gas to Liquid Fuels

7.6 Advancements in Gas to Liquid Technology

7.7 Conclusions

References

8 Second Generation Biofuels and Extraction Techniques

List of Abbreviations

8.1 Introduction

8.2 Pre-Treatment of Lignocellulosic Biomasses

8.3 Extraction of Biofuel from Lignocellulosic Biomass

8.4 Bioethanol

8.5 Biodiesel Production from Fatty Acids

8.6 Levulinic Acid (LA)

8.7 Conclusions

References

9 Bio Alcohol: Production, Purification, and Analysis Using Analytical Techniques

9.1 Introduction

9.2 Biomethanol Extraction

9.3 Bioethanol Extraction

9.4 Biopropanol Extraction

9.5 Bioglycerol Extraction

9.6 Bioethylene Glycol Extraction

9.7 Branched-Chain Bioalcohols Extraction

9.8 Purification of Bioalcohol

9.9 Quantification of Bioalcohols

9.10 Recent Perspective of Bioalcohol Production

9.11 Conclusion and Future Trends of Bioalcohol

References

10 Studies on Extraction Techniques of Bio Hydrogen

10.1 Introduction

10.2 Bio-Hydrogen Production Process

10.3 Bio-Photolysis

10.4 Microbial Electrolysis Cell

10.5 Conclusion

References

11 Valorization of By Products Produced During the Extraction and Purification of Biofuels

11.1 Introduction

11.2 Biodiesel Production Process and Its Byproducts

11.3 Biorefinery Concept Based on Utilization of Whole Oilseed Plant

11.4 Valorization of Byproducts Obtained in the Bioethanol Fermentation Process

11.5 Valorization of Byproducts Obtained in Anaerobic Digestion Process

11.6 Conclusion

Acknowledgment

References

12 Valorization of Byproducts Produced During Extraction and Purification of Biodiesel: A Promising Biofuel

List of Abbreviations

12.1 Introduction

12.2 Glycerol

12.3 Glycerol Carbonate

12.4 Conclusions

References

13 Biofuel Applications: Quality Control and Assurance, Techno Economics and Environmental Sustainability

13.1 Introduction

13.2 Solid Fuel

13.3 Liquid and Gaseous Biofuel

13.4 Conclusion

Acknowledgment

References

14 Role of CO

2

Triggered Switchable Polarity Solvents and Supercritical Solvents During Biofuel Extraction

14.1 Introduction

14.2 Role of Solvent during Bio-Fuel Extraction

14.3 CO

2

Triggered SPS for Extraction of Bio-Fuels

14.4 Supercritical Solvents and Bio-Fuel Extraction

14.5 Challenges and Future Considerations

14.6 Conclusion

References

15 Efficiency of Catalysts During Biofuel Extraction

15.1 Introduction

15.2 Biofuels

15.3 Biodiesel

15.4 Transesterification Reaction

15.5 Catalyst Used for Biodiesel Extraction

15.6 Catalyst Used for Bioalcohol Extraction

15.7 Conclusion

References

16 Microorganisms as Effective CO

2

Assimilator for Biofuel Production

16.1 Introduction

16.2 Microorganisms as Carbon Dioxide Assimilators

16.3 Biofuel Production by Microorganisms Using Carbon Capture

16.4 Recent Advancements in Biofuel Production

16.5 Conclusion

References

17 Global Aspects of Biofuel Extraction

17.1 Introduction

17.2 Biodiesel

17.3 Biogas

17.4 Bioethanol

17.5 Bio-Oil from Biomass

17.6 Conclusion

References

18 New Advancements of Biofuel Extractions and Future Trends

18.1 Introduction

18.2 Extraction and Purification of Biofuels

18.3 Application of Biofuels

18.4 Advantages Associated with Biofuels

18.5 Disadvantages Associated with Biofuels

18.6 Future Trends

18.7 Conclusion

References

About the Editors

Index

End User License Agreement

List of Illustrations

Chapter 1

Figure 1.1 (a) Jatropha flowers. (b) Jatropha fruits. (c) Jatropha seeds.

Figure 1.2 (a) Pongamia flower. (b) Pongamia pods. (c) Pongamia kernels.

Figure 1.3 Effect of FFA during acid catalyzed esterification of high FFA karanja oil.

Figure 1.4 (a) Mahua flowers. (b) Mahua fruits. (c) Mahua seeds.

Figure 1.5 Butyl esterification of mahua oil, effect of FFA on percent of acid catalyst.

Figure 1.6 (a) Nahor flower. (b) Nahor seed. (c) Nahor kernel.

Figure 1.7 Effect of antioxidant concentration on oxidative stability of karanja oil methyl esters.

Chapter 2

Figure 2.1 Oilseed processing.

Figure 2.2 Manual decorticator.

Figure 2.3 Manual decorticator.

Figure 2.4 Improved hand operated decorticator.

Figure 2.5 Hydraulic press [10].

Figure 2.6 Traditional ghani [10].

Figure 2.7 Soxhlet unit [10].

Figure 2.8 Modern screw press [10].

Figure 2.9 Types of catalyst.

Figure 2.10 Techniques used for biodiesel.

Figure 2.11 Transesterification process.

Chapter 3

Figure 3.1 Transesterification TG to biodiesel and glycerol.

Figure 3.2 Biodiesel production by transesterification and reactive extraction.

Figure 3.3 Schematic representation of alkali catalyzed transesterification.

Chapter 4

Figure 4.1 Four stages of anaerobic digestion process [96].

Chapter 5

Figure 5.1 Available biogas upgradation techniques (taken from Khan

et al.

[7]).

Figure 5.2 Microbial methane enrichment methods

(Red Dotted Line: In-situ Method; Green Dotted Line: Ex-situ Method; Blue Dotted Line: Hybrid Method)

.

Figure 5.3 Concept of bioelectrochemical systems for biogas upgradation.

Figure 5.4 Photosynthetic biogas upgradation system concept in anaerobic based wastewater treatment plant.

Chapter 6

Figure 6.1 Classification of renewable feedstocks.

Figure 6.2 Industrial effect of sugar crops.

Figure 6.3 Industrial effect of sugar crops.

Figure 6.4 Bioethanol production from corn.

Figure 6.5 Cassava as feedstock for ethanol production.

Figure 6.6 Schematic diagram of biodiesel production from oil seed.

Figure 6.7 Production of biodiesel from soyabean oil.

Figure 6.8 Biofuel production as renewable energy from palm oil.

Figure 6.9 Production of biofuel from canola seed.

Figure 6.10 Bioethanol production from sunflower oil.

Figure 6.11 Bioethanol production from castor oil.

Figure 6.12 Production of biodiesel from cotton seed oil.

Figure 6.13 Biodiesel extraction from Jatropha.

Figure 6.14 Production of biofuel from jojoba oil.

Figure 6.15 Production of biodiesel from neem oil.

Figure 6.16 Production of biohydrogen from lignocellulosic feedstock.

Figure 6.17 Biofuel production from rice husk.

Figure 6.18 Corn stover as sustainable feedstock.

Figure 6.19 Bioethanol production from wheat straw.

Figure 6.20 Conversion processes of algal biomass for biofuel production.

Figure 6.21 Production of biofuel from glycerol.

Figure 6.22 Production of biofuel as renewable energy from palm oil.

Chapter 7

Figure 7.1 Flow chart of conversion of syngas to gasoline plus (STG+) [77].

Chapter 8

Figure 8.1 Different pre-treatment processes.

Figure 8.2 Different thermochemical processes for production of biofuel and other products.

Figure 8.3 Complete process for the production of bioethanol from different biomasses.

Figure 8.4 Mechanism for base catalysed transesterification process.

Figure 8.5 Mechanism for acid catalyzed transesterification process.

Figure 8.6 Reaction scheme of Levulinic acid production.

Chapter 9

Figure 9.1 Biomethanol extraction from biomass through thermochemical conversion process.

Figure 9.2 (a & c) Crystal structure of membrane-bound particulate MMO having active site residues as Cu, HIS, VAL, PHE, GLU, LEU, and GLN; (b & d) crystal structure of soluble cytoplasmic MMO having active site residues as Fe, GLU, ASP, HIS, and VAL.

Figure 9.3 Classification of methanotrophs based on monooxygenase enzyme exhibit.

Figure 9.4 Analytical tests used for bioethanol identification, exhibit, and its concentration.

Figure 9.5 Synthesis of biopropanol in one-step hydrogenolysis from biomass using catalyst.

Chapter 10

Figure 10.1 Bio-hydrogen production methods.

Figure 10.2 Photo fermentation.

Figure 10.3 Sequential dark and photo fermentation. This is a two-step reaction which is given as:

Figure 10.4 Direct bio-photolysis.

Figure 10.5 Indirect bio-photolysis.

Figure 10.6 Microbial electrolysis of cell.

Chapter 11

Figure 11.1 Parallel waste management in biodiesel production process.

Figure 11.2 Synthesis of useful products from crude glycerol via biological conversion pathway (reconceptualized and redrawn from [52]).

Figure 11.3 Synthesis of useful products from crude glycerol via chemical conversion pathway (reconceptualized and redrawn from [52]).

Figure 11.4 Synthesis of useful products from crude glycerol via catalytic conversion pathway (reconceptualized and redrawn from [52]).

Figure 11.5 Thermochemical conversion of crude glycerol into value-added products.

Figure 11.6 Biorefinery development based on whole non-edible oilseed plants (reconceptualized and redrawn from [70, 73]).

Figure 11.7 Parallel waste management in bioethanol production process.

Figure 11.8 Parallel waste management in anaerobic digestion process.

Chapter 12

Figure 12.1 Convenient flowchart of biodiesel production [6].

Figure 12.2 Triglyceride and methanol reaction in presence of catalyst [9].

Figure 12.3 Methods for glycerol conversion into value added product [56].

Figure 12.4 Glycerol carbonates synthesis by various techniques using glycerol [122].

Chapter 13

Figure 13.1 Biofuel categorization based on physical state.

Figure 13.2 Biofuel generation categorization based on raw materials [29].

Figure 13.3 Chromatogram sample [44].

Chapter 14

Figure 14.1 Illustration of change in polarity of solvent on addition and removal of CO

2

.

Figure 14.2 Scheme of bio-oil extraction from algal bio-mass using SPS.

Figure 14.3 Composition profile of syngas (H

2

+ CO) obtained at different current densities.

Figure 14.4 Scheme of concept of direct trans-esterification for production of bio-diesel.

Figure 14.5 Scheme of extraction of krill oil from Antarctic krill.

Figure 14.6 Schematic of extraction of algal bio-oil using SC-CO

2

and 1:1 mixture of n-hexane and ethanol.

Figure 14.7 Effect of initial H

2

pressure on bio-oil production, (gas + water) yields.

Chapter 15

Scheme 15.1 Steps involved in transesterification reaction [39].

Scheme 15.2 Hydrolysis of triglycerides [8, 44].

Scheme 15.3 Saponification reaction in homogeneous alkali catalyze transesterification [8, 44].

Scheme 15.4 Mechanism of alkali catalyze transesterification reaction [8, 30, 46].

Scheme 15.5 Mechanism of acid catalyzed transesterification reaction [9, 30, 46].

Scheme 15.6 General mechanism of heterogeneous base catalysed transesterification [10].

Scheme 15.7 Acid catalysed transesterification mechanism [10].

Scheme 15.8 Mechanism of bifunctional heterogeneous catalyst [75].

Figure 15.1 Flowchart of different catalysts used in transesterification reactions [3, 15, 16].

Chapter 16

Figure 16.1 Calvin cycle for sugar synthesis from captured carbon dioxide.

Figure 16.2 Biofuel production from microorganisms through carbon capture.

Figure 16.3 Biofuel classification.

Chapter 17

Figure 17.1 Mechanism of biogas production.

List of Tables

Chapter 1

Table 1.1 Import of major edible oil by India (in Lakh Tons) [s].

Table 1.2 Physico-chemical characterisation of potential non-edible oils for biodiesel feedstock.

Table 1.3 Fatty acid composition of potential non-edible oils for biodiesel feedstock.

Chapter 2

Table 2.1 Quality parameters of oilseeds.

Table 2.2 Quality parameters of oilseeds.

Chapter 3

Table 3.1 Homogeneous alkali catalysts used for transesterification.

Table 3.2 Homogeneous acid catalysts used for transesterification.

Table 3.3 Summary of two-step transesterification of some feedstocks.

Table 3.4 Heterogeneous catalysts used for FAAE production.

Table 3.5 Optimized conditions of biodiesel production in ultrasonic method.

Table 3.6 Optimized conditions of biodiesel production under microwave assisted method.

Chapter 4

Table 4.1 Major functions of few metals in enhancing biogas production.

Table 4.2 Biochar used for enhancement of methane production in anaerobic digestion systems.

Chapter 5

Table 5.1 Comparison of different available biogas upgradation techniques based on performance, energy, and cost requirement (taken from Sahota

et al.

[12]).

Table 5.2 Results of

in-situ

and

ex-situ

biogas upgradation systems from previous studies.

Table 5.3 Likely reactions occurring in bioelectrochemical systems (taken from [6]).

Chapter 8

Table 8.1 Fatty acids transesterification using heterogeneous catalysts and wastes derived catalyst for biodiesel production.

Table 8.2 Steps involved during catalytic cycle of enzymes (Christopher

et al.

, 2021 [187]).

Chapter 9

Table 9.1 Classification of pretreatment technologies and processes exploited for bioethanol extraction from sugarcane.

Table 9.2 Biopropanol generation from various microorganisms, substrate, and different pathways and their yield.

Chapter 11

Table 11.1 Whole oilseed plant-based biofuel production.

Chapter 12

Table 12.1 Physical and chemical properties of glycerol [17].

Table 12.2 Quality parameters of different categories of glycerol [17].

Table 12.3 Global glycerol production and biofuel fraction [21].

Table 12.4 Applications of glycerol as per natural properties [31].

Table 12.5 Physical and chemical properties of glycerol carbonate [63].

Table 12.6 List of glycerol carbonate applications and their utilization [67].

Chapter 13

Table 13.1 Briquette applications [7].

Table 13.2 Specifications for woody and non-woody briquettes according to ISO17225 [9].

Table 13.3 Briquette quality parameters [7].

Table 13.4 Briquetting capital cost for various raw materials [15].

Table 13.5 Cost of briquettes for different raw materials [15].

Table 13.6 Charcoal briquette specification [18, 19].

Table 13.7 Techno-economics of biochar briquettes.

Table 13.8 Specification for anhydrous ethanol for automotive fuel.

Table 13.9 Standard for fuel ethanol as specified for Ed75-Ed85 in the Standard ASTM D5798.

Table 13.10 Evaluation of vehicular emission for different fuels.

Table 13.11 Requirements for biodiesel.

Table 13.12 Biogas specification in various countries.

Table 13.13 Biogas standard according to IS:16087 (2013).

Chapter 14

Table 14.1 Various switchable materials used for extraction of biofuels.

Table 14.2 Applications of various super-critical solvents with involved techniques.

Chapter 15

Table 15.1 Physical characteristics of biodiesel over conventional diesel [8, 16, 31, 32].

Table 15.2 Benefits and limitations of homogeneous catalyst.

Table 15.3 Merits and demerits of homogeneous base catalyst.

Table 15.4 Merits and demerits of homogeneous acid catalyst.

Table 15.5 Effect of process variables in different homogeneous catalyst.

Table 15.6 Characteristics and constraints of using heterogeneous catalyst.

Table 15.7 Significance and shortcomings of heterogeneous catalyst [45, 60].

Table 15.8 Effect of operating parameters on different heterogeneous catalysts for FAME production.

Table 15.9 Characteristics and constraints of biological catalyst.

Table 15.10 Different biological catalysts used in biodiesel synthesis from different sources.

Table 15.11 Significance and shortcomings of nano-catalysts.

Table 15.12 Effect of various parameters and reaction conditions on FAME yield using nanocatalysts.

Table 15.13 Effect of reaction parameters on different catalysts [54].

Chapter 16

Table 16.1 Carbon sequestration methods by algae.

Table 16.2 Fatty acid [F. A.] concentrations in microalgal species [30].

Chapter 17

Table 17.1 Overview of biosurfactants.

Guide

Cover

Table of Contents

Title Page

Copyright

Introduction

Begin Reading

Index

End User License Agreement

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Scrivener Publishing

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Publishers at Scrivener

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Biofuel Extraction Techniques

Edited by

Lalit Prasad

Subhalaxmi Pradhan

and

S.N. Naik

This edition first published 2023 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2023 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.

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Preface

Biofuels are viable alternatives to petroleum-based fuel because they are produced from organic materials such as plants and their wastes, agricultural crops, and their by-products. The development of cutting-edge technology has increased the need for energy significantly, which has resulted in an overreliance on fossil fuels. Renewable fuels are the subject of research because of their biodegradability, eco-friendliness, decrease in greenhouse gas (GHG) emissions, and favorable socioeconomic consequences to counteract imitations of fossil fuels.

Depending upon their physical state, biofuels can be classified into solid, liquid, or gas. Examples of solid biofuels are briquettes of biomass and briquetted biochar. Liquid biofuels include bioethanol and biodiesel, and gaseous biofuels include biogas and biomethane, among others. These are only a few examples.

Different extraction techniques are used for the production of biofuels from renewable feedstocks. Biodiesel is a promising biofuel which is produced by the transesterification of plant-based oils. Extraction of oil includes older traditional methods, solvent extraction, mechanical extraction, microwave-assisted, and ultrasonic-assisted methods. The solvent extraction method is more efficient and produces good quality oil. The limitation of this method is time-consuming and very tedious. Many innovative techniques are also used to overcome the limitations of conventional methods. Microwave-assisted and ultrasonic-assisted are some of the new techniques which include the pre-treatment of the raw material using either ultrasonic waves or radio waves which helps in increasing the efficiency of the extraction of oil and improves the final quality of the oil.

This new book covers the prospects and processing of feedstocks for biofuels, extraction techniques, catalysts and solvents used during production of biofuel, optimization of reaction techniques, carbon capturing during biofuel extraction, value addition to biofuel wastes, and their techno-economic and environmental acceptability. A total of 18 chapters are included in this book.

Chapter 1 is an introductory part which covers different plant seeds and their potential for biofuel production.

Chapters 2 and 3 cover the processing of feedstock in context of biodiesel production and extraction techniques for biodiesel production.

Chapters 4 and 5 include biomethane generation, stabilization of process parameters, upgradation systems for biogas and improving biomethane quality.

Chapters 6 and 7 cover renewable feedstocks for biofuels production and extraction techniques of gas to liquids (GtL) fuels respectively.

Chapters 8–10 incorporate bio-alcohol, bio-hydrogen extraction, purification, and analysis.

Chapters 11–13 include valorization of by-products produced during the extraction of biofuels, their purification, quality control, assurance, techno-economics and environmental sustainability.

Chapters 14 and 15 include the role of supercritical solvents and catalysts used during biofuel extraction and their efficiency.

Chapters 16 covers carbon capturing by microorganisms during the biofuel extraction process.

Chapters 17 and 18 include global aspects, new advancements of biofuel extractions and future trends.

It is expected that this book will spark the interest of numerous investigators in the academic universe towards biofuel research. It will provide new information about the recent advancements in the extraction techniques of biofuels, value addition to biofuel wastes and economic and environmental acceptability, sustainability and viability.

1Plant Seed Oils and Their Potential for Biofuel Production in India

L. C. Meher1,2 and S. N. Naik1*

1Centre for Rural Development and Technology, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi, India

2Defence Institute of Bio-Energy Research, DRDO, Haldwani, Nainital, Uttarakhand, India

Abstract

Many tree-borne oilseed plants are grown in India which produce non-food grade oil. Some of these have the potential to produce feedstock for biodiesel. Plants such as Pongamia and Jatropha are found throughout the country, whereas Mahua, Rubber, and Nahor are found in specific regions. The oilseeds are collected to a lesser extent by the local population for traditional uses as medicine, to fuel lamps, etc. and for the preparation of soap in industries. The National Mission on Biofuel has focused to grow Jatropha, whereas the existing tree born oilseeds are also potential sources for biodiesel feedstock. Non-edible oils with their potential as biodiesel feedstock in the country is discussed in this chapter. The oilseed plants less explored for biodiesel have also been discussed.

Keywords: Biodiesel, vegetable oil, non-edible oil, transesterification, methyl esters, jatropha, pongamia

1.1 Introduction

Presently, petroleum fractions are the preferred fuels for internal composition engines used for transport, as well as in the industrial and agricultural sectors. The global consumption of fossil based liquid fuels was above 100 million barrels per day during 2019 and forecasted to continue at the same rate during 2021 [1]. The contribution of CO2 to the atmosphere is about 3.1-3.2 times the consumption of fossil fuel. The exhaust emissions as a result of widespread use of fossil fuel are a global concern for the present time. The level of unburnt hydrocarbon and oxides of nitrogen, along with CO2, are gradually increasing in the atmosphere. The research and development activities have been focused for the last few decades in search of alternative fuel from renewable sources for the nations to be self-reliant for energy sources and much effort is being done by countries with no oil reserves.

Biodiesel is the fatty acid methyl esters derived from renewable lipid feedstocks, such as vegetable oils, as an alternative to diesel fuel. The invention of diesel engines and compression ignition engines dates back to the 19th century and the vegetable oils were used as fuel. The high viscosity and poor volatilities of vegetable oils, as well as the availability of middle distillate, i.e., diesel fuel, did not attract much interest for vegetable oil based fuel during those days.

The research and development activities on vegetable oil based biodiesel were initiated at the beginning of this century. The transesterification of vegetable oil reduces the viscosity by one-tenth, lower molecular weight of the triglyceride molecule by one-third, and improves the volatility along with the physical properties of the biodiesel. Worldwide biodiesel industries are set up and biodiesel blended diesel fuel is technically suitable for use in existing diesel engines with slight or no engine modifications. There is a scarcity of biodiesel feedstock for countries like India where the domestic demand of edible oil is met by import. The present article describes the potential non-food grade vegetable oil sources as feedstock for biodiesel in Indian context.

1.2 Background

India ranks third in terms of consumption of fossil fuels after China and the USA. Consumption grew by 2.3% in 2019 with a global share of 5.8%. Petroleum based fuel is the second largest energy source (239.1 million tons oil equivalent) after coal (452.2 million tons oil equivalent). The transportation fuel in India is mainly petroleum based diesel and the consumption is recorded at 83.5 million tons during 2018-19 [2].

The recent BS-VI in India, effective from 2020, is a stringent emission norm for diesel engines. The new pollution norm involves the reduction of NOx by 68% and particulate matter by 82-93% [3]. The fuel for diesel engines should burn clearly, which can be achieved by the inclusion of oxygenated fuel, i.e., biodiesel in petroleum based diesel fuel.

In the global context, the surplus of edible oils such as Rapeseed in Europe, Canola in Canada, Soybean in the USA, and Palm oil in Malaysia and Indonesia are the available feedstocks for biodiesel. In the Indian scenario, the requirement of edible oil is met by import. India imports Palm oil from Malaysia and Indonesia, and Soybean from Argentina and Brazil, and Sunflower from Ukraine and Russia. The import of vegetable oil was 150.02 lakh tons during 2017-18, which increased to 155.49 lakh tons during 2018-19 [4]. The import of edible oils for the last five years is shown in Table 1.1 [5]. The non-food vegetable oils may be a potential source of biodiesel feedstock.

There are over 300 different species of oilseed plants grown in India. Various tree borne oilseed derived oils are not suitable for human consumption due to the presence of toxic components, for example karanjin and pongamol in Pongamia oil, azadirachtin in neem oil, ricin in Castor oil, and phorbol esters in Jatropha oil. These tree-borne oilseeds require agricultural inputs in the initial period and rarely require any expense associated with its maintenance once fully grown. It can also be a cost-effective way to produce oilseed. The production for tree borne oilseed is about 3.0-3.5 million metric tons whereas 0.5-0.6 million tons of seed are collected [6]. The potential non-edible oilseed plants are Jatropha (Jatropha curcas), Karanja (Pongamia pinnata), Mahua (Madhuca indica), Nahor (Mesua ferrea), Rubber (Hevea brasiliensis), Castor (Castor communis), Neem (Azadirachta indica), Sal (Shorea robusta), Undi (Calophyllum inophyllum), Simarouba (Simarouba glauca), etc. Oil derived from tree born oilseed plants such as Neem, Castor, and Sal find specific applications. Neem oil containing azadirachtin is a natural pesticide and emulsifier in the agricultural sectors. The Castor oil with ricinoleic acid in the triglyceride has high viscosity and finds commercial application as a precursor for polyurethane, lubricant, binder, etc. Fat derived from the Sal tree is used as cocoa butter substitute for manufacturing of chocolates. With these exceptions, the rest of the oilseeds may be feedstock for biodiesel.

Table 1.1 Import of major edible oil by India (in Lakh Tons) [s].

Year

Palm oil

Soybean

Sunflower

Crude

Refined

Crude

Refined

Crude

Refined

2015-16

71.1

25.7

39.6

0.0

14.9

0.0

2016-17

53.6

29.4

34.6

0.0

17.3

0.0

2017-18

67.5

27.7

31.5

0.0

22.5

0.0

2018-19

64.2

25.2

31.7

0.3

25.8

2.0

2019-2020 (April-Sept)

30.2

19.0

16.8

0.2

10.8

0.0

Various missions at national and state levels were made to promote the cultivation of oilseed crops. Pongamia and Jatropha were selected as suitable oilseed plants for plantation in the waste and degraded lands, avenue plantations, and perimeter fencing. Massive plantation of Jatropha has been carried out in the Chhattisgarh state and similarly, Pongamia in the Karnataka state of India. These are in addition to the existing potential of oilseed in the country.

1.3 Non-Edible Oil as Feedstock for Biodiesel

The biodiesel derived from vegetable oil should have properties as per EN 14214:2012 A1:2014 or IS 15607:2016 specifications. Properties such as iodine value, linolenic acid methyl ester, and oxidation stability are dependent upon the qualities of the feedstock. The physico-chemical properties of oils are listed in Table 1.2 [7, 8] and their fatty acid compositions in Table 1.3 [7, 9–12]. The saponification value (SV) and the iodine value (IV) are indicative of structures such as chain length of fatty acid and degree of unsaturation of fatty acids in the triglyceride. The cetane index (CI) is related to the saponification value and iodine value as per Equation (1.1) and the cetane number (CN) is related to the cetane index as per Equation (1.2) [9]. The MWoil (weight average molecular weight of the oil) is calculated from the saponification value as per Equation (1.3) and the requirement of methanol for transesterification is calculated based on the MW oil.

(1.1)

(1.2)

(1.3)

Table 1.2 Physico-chemical characterisation of potential non-edible oils for biodiesel feedstock.

Sl. no.

Oil

Physical appearance at room temperature

Acid value

Iodine value

Saponification value

Unsaponifiable matter (%)

1.

Jatropha

Yellowish clear liquid

5-8

93-107

188-196

0.4-1.1

2.

Pongamia

Dark yellow to orange clear liquid

1-11

85-90

185-195

3.0

3.

Mahua

Pale yellow with semi solid fat

Up to 20

58-70

187-196

1-3

4.

Nahor

Dark brown or red viscous liquid

100

87

193-209

2.9

5.

Rubber

Dark brown liquid

84

131-148

190-195

1.83

Table 1.3 Fatty acid composition of potential non-edible oils for biodiesel feedstock.

Fatty acids

Percent fatty acid composition of oils

Jatropha

Pongamia

Mahua

Nahor

Rubber seed

Myristic acid (

C14:0

)

-

-

0.13

2.72

-

Palmitic acid (C

16:0

)

13.4

11.65

19.6

9.76

9.3

Palmitoleic acid (C

16:1

)

0.3

-

-

-

-

Stearic acid (C

18:0

)

5.8

7.50

25.9

13.45

8.4

Oleic acid (C

18:1

)

40.9

51.59

37.3

58.12

25.4

Linoleic acid (C

18:2

)

39.6

16.64

15.8

12.64

41.1

Linolenic acid (C

18:3

)

-

-

-

-

15.3

Arachidic acid (C

20:0

)

-

1.35

0.21

3.14

-

Eicosenoic acid (C

20:1

)

-

-

0.15

-

-

Behenic acid (C

22:0

)

-

4.45

-

-

-

Lignoceric acid (C

24:0

)

-

1.09

-

-

-

The non-edible oils have been reported to have unsaponifiable matters and the lipid associates, as shown in Table 1.2, are required to remove these either by pretreatment or post-transesterification process.

The industrial scale of biodiesel production units set up worldwide employs homogeneous catalysts (methoxides or hydroxides of sodium or potassium) for transesterification, which is an efficient and cost-effective method for production of biodiesel in order to meet the fuel qualities as per biodiesel specifications. Among the homogeneous alkali catalytic process, sodium methoxide and potassium methoxide result in higher selectivity of the product with rare formation of byproducts [13]. The methoxide catalyzed transesterification of vegetable oils requires a low reaction temperature, about 60–65oC at atmospheric pressure, and the reaction is completed in a short reaction time. The methoxide catalyzed process results in complete conversion of the triglyceride oil in order to ascertain that produced biodiesel attains methyl ester content > 96.5% and the free glycerol and total glycerol within the limits specified by EN 14214 and IS 15607 biodiesel specifications. The catalytically active species is the methoxide ion, which is generated by dissolution of hydroxides in methanol [9]. The biodiesel feedstock, i.e., vegetable oil for the methoxide catalyzed transesterification mush, have free fatty acid less than 0.1%, moisture less than 0.1%, and phosphorus content less than 10 ppm as per the requirements specified by biodiesel manufacturers such as Lurgi and Desmet Ballestra [9]. The phosphorus content in biodiesel is permissible up to 4 ppm, as per revised specifications, and the pretreated oil should have the phosphorous content accordingly. The required specification of feedstocks may be achieved by pretreatment of the crude vegetable oil. The feedstock of the above mentioned specification, methanol, and catalyst sodium methoxide solution are allowed to act as the reaction vessel for transesterification. The required molar ration of methanol to triglyceride is 3:1, whereas 100% excess methanol is used during the process in order to ascertain the completion of reaction and the excess alcohol is recovered for further use. The completion of reaction is necessary to have methyl ester content above 96.5% and the triglycerides and partial glycerides within the maximum specified limit. The transesterification vessels are designed so that the reaction is accomplished in two or three steps. The glycerol formed in between the steps is removed and as a result, the reaction proceeds towards completion in a short time. The transesterification products are allowed to stand so that glycerol is separated due to high polarity and density and the biodiesel layer containing excel methanol and the residual catalyst is further washed and dried. The B-20 blend of biodiesel and diesel with a volume ratio of 20:80 is being used in the unmodified diesel engines and the targets are made to use B20 fuel as per the National Mission of Biofuels.

1.3.1 Jatropha

Jatropha (Jatropha curcas) is a shrub native to the tropical areas of Mexico and Central America and is presently being naturalized in the different parts of the globe as a potential plant to produce biodiesel feedstock. Jatropha is a small tree that starts flowering after one year and the economic yield starts after the third year of plantation. The plant starts flowering (Figure 1.1a) during summer and monsoon and male and female flowers are produced on the same inflorescence. The green fruits ripen, changing to yellow and are dried to black, contain three seeds, and its shape resembles castor seeds (Figures 1.1b and 1.1c). As an initiative for biodiesel in India, Jatropha plantation was carried out in an area of about 0.5 million hectares of low-quality wasteland [14]. Commercial scale plantations of Jatropha were carried out in low-quality and degraded land in the state of Chhattisgarh and the produced oil is being utilized as feedstock for biodiesel. The oil content in the Jatropha seed varies from 24 to 40%. The major fatty acids are palmitic acid, stearic acid, oleic acid, and linolenic acid, with the last two accounting for more than 80% w/w. The physico-chemical qualities of Jatropha oil are listed in Table 1.2 and the fatty acid composition is shown in Table 1.3. The Jatropha oil contains phorbol esters generally known for tumor promoting activities, making the oil toxic.

The preparation of biodiesel involves pretreatment to remove the fatty acids. The homogeneous alkali-transesterification of pretreated Jatropha oil is conducted where the hydroxide or methoxide of sodium or potassium is used as catalyst. The post transesterification process involves the separation of excess methanol, catalyst, glycerol, and moisture to get the biodiesel. The fuel qualities of Jatropha based biodiesel have been reported to be as per IS 15607 specifications. The high cetane number, favorable fatty acid composition, and fuel qualities as per specifications make the Jatropha a potential candidate for biodiesel feedstock and therefore, massive cultivation has been initiated in the country. The vulnerable qualities of biodiesel are the oxidative stability and the acid value. Processes have been developed to prepare biodiesel with low acid value [15] and enhanced oxidative stability by suitable additives.

In India, the government initiated the National Mission on Biofuels in 2003 and selected Jatropha as a potential biofuel crop since the plant has a low gestation period, hardy nature, is resistant to draught and flood, is not browsed by cattle, and requires a small plant to collect seeds. It has been observed that Jatropha cultivation lead to improved soil fertility, contributed to the reduction of soil erosion, helped in the rehabilitation of lands through greening, and created jobs for the local population in the rural areas.

Figure 1.1 (a) Jatropha flowers. (b) Jatropha fruits. (c) Jatropha seeds.

1.3.2 Pongamia

Pongamia (Pongamia pinnata) or Karanja is a fast-growing medium size evergreen oilseed plant (shrub or tree) found throughout India as well as in the sub-Indian continent. The plant is found in tropical and temperate Asia, including Malaysia, Indonesia, Thailand, Japan, Australia, and the Pacific Islands. The plant is quite hardy and adaptable to dry climates and is used for afforestation in the dry and wastelands in Karnataka state. The plant bears beautiful flowers (Figure 1.2a) and thus is preferred for avenue plantation. The fruiting occurs during April-June (Figure 1.2b). The mature fruits or pods fall on the ground and are also collected from the tree. The ripe pods are elliptic and flat and contain one to two kidney shaped brown kernels (Figure 1.2c). The estimated potential of Pongamia oil has been reported to be 135,000 tons per year [8], whereas large scale afforestation and avenue plantations have not been taken into account. The kernel contains 27-39% oil, the yield is 24-27% in the mechanical oil expeller. The major fatty acids are palmitic acid, stearic acid, oleic acid, and linolenic acid, with the last two accounting for about 70% w/w.

The Karanja oil contains lipid associates, i.e., karanjin and pongamol, and a few more flavonoids which make the oil un-suitable for human consumption. The oil has been reported to treat various skin diseases, to fuel lamps, and for manufacture of soap and fatty acids. The preparation of Karanja based biodiesel has been reported since 1999 [10, 16–19]. The biodiesel preparation from Karanja oil using heterogeneous catalyst was also studied [20–22]. The biodiesel synthesis in pilot scale, fuel characterization, and cross-country trials of Karanja based biodiesel was initiated by IIT Delhi. The free fatty acid FFA present in the Indian non-traditional oilseeds and oils make the oil quality poor for industrial applications. The FFA content depends upon the collection of the condition of seed collection, storage of oilseed, oil extraction process, etc. Karanja oil with high FFA was made by the addition of oleic acid and acid catalyzed esterification was studied. The lowering of FFA during the esterification is shown in Figure 1.3. Further alkali-transesterification produces Karanja oil methyl esters [19].

The National Mission of Biodiesel initiated by the Government of India emphasized this as a potential plant for biodiesel along with Jatropha. The large-scale plantation is carried out in the southern Indian states, i.e., Karnataka, for the purpose of biodiesel. The biodiesel had been used by the state transport corporation with 26 B100 and 1500 B20 buses [23].

Figure 1.2 (a) Pongamia flower. (b) Pongamia pods. (c) Pongamia kernels.

Figure 1.3 Effect of FFA during acid catalyzed esterification of high FFA karanja oil.

1.3.3 Mahua

The Mahua (Madhuca indica) trees are found in the central part of India. The matured plant with an age of about 8-10 years bears the flowers (Figure 1.4a) and the fruits (Figure 1.4b) and continue fruiting up to 60 years. The mature fruits fall on the ground during May-July in northern Indian and August-September in the south. Annual seer yield is 20-40 kg per plant [24]. The ripe fruit contains a fleshy outer coat and 3-5 cm long elliptical seed that is flattened on one side, as shown in Figure 1.3c, that contains 34-37% oil [8]. The estimated potential of Mahua oil is four lakh tons per annum and finds use as an ointment and in rheumatism to prevent and treat cracking skin during cold, for the production of lubricating grease, fatty alcohols, and stearic acid [25]. The fatty acid composition reveals that the oil contains more than 45% saturated fatty acid, i.e., palmitic acid and stearic acid, and the rest is mainly oleic acid and linoleic acid. The saponins present in the oil are the toxic factor that make the oil unsuitable for human consumption. The oil contains up to 20% free fatty acid [26–30] and requires a two-step process where the free fatty acids are esterified to methyl ester using acid catalysts such as H2SO4 followed by alkali transesterification. The Mahua oil methyl esters have high cetane number, 61.5, on the other hand, the pour point is 21oC [27].

Figure 1.4 (a) Mahua flowers. (b) Mahua fruits. (c) Mahua seeds.

Figure 1.5 Butyl esterification of mahua oil, effect of FFA on percent of acid catalyst.

Kumar and Prasad [31] reported a two-step process to prepare Mahua oil butyl ester. The first step involved the acid catalyzed esterification and the free fatty acid FFA value reduced from 19.8% to 1.1%. The variation of FFA with catalyst concentration during the first step is shown in Figure 1.5. It was followed by alkali-transesterification with butanol (alcohol to oil molar ratio 6:1), 1.5% (w/w) KOH as catalyst, reaction temperature 80°C, stirring rate of 500 rpm, and reaction time 90 min as optimized conditions resulting in a 94.8% yield of butyl esters of Mahua oil.

The performance and emission studies on mahua oil methyl ester have been reported with slight modification in the diesel engine. The B20 blend of Mahua based biodiesel with diesel fuel is efficient for the engine [27]. The biodiesel derived from Mahua oil has oxidative stability [31] as per EN14214 and IS 15607 specifications for biodiesel, whereas the biodiesel derived from other non-edible oils require additive, i.e., synthetic antioxidant, in order to attain the oxidation stability in terms of induction period.

1.3.4 Nahor

Nahor (Mesua ferrea) is a beautiful evergreen tree with conical crown found in the forests of north-east India, Karnataka, and Kerala [8]. The fruit contains round or conical brown seeds (Figures 1.6a, b, c). The oil content in the kernel is about 70% and on the base of the seed it is 45%. The estimated annual potential of Nahor oil is 6,200 tons in Assam and 680 tons in Kerala.

Figure 1.6 (a) Nahor flower. (b) Nahor seed. (c) Nahor kernel.

Nahor oil has been used as feedstock for the preparation of biodiesel by alkali-transesterification [16]. The methyl esters from Nahor oil were further subjected to distillation under a vacuum in order to get the methyl esters fraction leaving the triglyceride and other partial glycerides. The transesterification of Nahor oil with short chain alcohol such as methanol and ethanol has been reported in the literature [32, 33]. Lipase-catalyzed transesterification of Nahor oil with methanol has been reported in the literature where the removal of free fatty acid is not required during its conversion to biodiesel since the immobilized lipases are employed for converting free fatty acid as well as triglyceride to methyl esters [34]. The engine performance and emission characteristics from Nahor based biodiesel blended with diesel were studied. The B20 blend (20% Nahor methyl ester with 80% diesel) produced identical results with that of diesel. The B30, B40, and B50 are suitable blends to lower the emission of NOx, CO, and unburnt hydrocarbons.

1.3.5 Rubber

Rubber (Hevea brasiliensis) is native to the Amazon and is being cultivated in the state of Kerala with a potential of 4500 tons per year. The seed resembles Castor in shape and is slightly larger in size. The seed deteriorates quickly and the lipase present in the seed contributes to a sharp rise in the free fatty acid and the acid value [35]. The oil contains lipid associates up to 1.83% [36]. It contains nearly one-fifth saturated fatty acid of C16 and C18, more than 80% unsaturated C18-fatty acids, linolenic acid about 15%, and varies up to 26%. The rubber seed oil contains lipase that causes gradual hydrolysis of the oil during storage resulting in high acidic value of the oil. The oil contains linamarin as a lipid associate, which on decomposition by hydrolysis forms hydrogen cyanide and acetone and the oil is toxic [35].

The two-step process from preparation of biodiesel (methyl esters) from high free fatty acid content rubber seed oil involving acid catalyzed esterification followed by alkaline-transesterification has been reported in the literature [37, 38]. The in situ method for synthesis of biodiesel from rubber seed has been reported to improve the yield of biodiesel up to 91% by acidic catalyst [39] and up to 96% using alkali catalyst [40]. The oil containing 39% free fatty acid has been converted to biodiesel by the use of lipase as a biocatalyst with a yield above 99% at optimized conditions [41]. Studies have been conducted for conversion of rubber seed oil to methyl esters by the use of heterogeneous catalysts [42, 43] in order to reduce the losses due to unwanted reactions. The neat B100 biodiesel has been used as fuel and the emission profiles of CO and CO2 were better compared to diesel fuel. The specific fuel consumption in the case of B100 fuel was 10% higher than diesel fuel and at low engine speed, the break thermal efficiency of B100 was higher compared to that of diesel [44]. The rubber seed oil is a potential feedstock for biodiesel.

1.3.6 Lesser Explored Non-Edible Oils for Biodiesel Feedstock in India

In addition to the above discussed oilseed plants, there are many known oilseed plants like Simarouba, Undi, Kukum, etc. Simarouba (Simarouba glauca) originated from Central and South America and has been introduced in India by the National Bureau of Plant Genetic Resources in 1960, as the oil content in the seed is 60 to 75%. Flowering has been observed 4-6 years after plantation. The tree has the potential to produce 20002500 kg oil per hectare per year. Calophyllum inophyllum (Undi) is an evergreen plant of the tropics and grown in southern coastal India. The five year old plant produces about 11-12 kg seed per year and gradually increases to about 100 kg once the plant is 20 years old. The oil content in the kernel is about 70%. Salvadora (Pilu) is a shrub that is grown in the tropics of Asia and Africa. It matures in 8-12 years and produces 47,000 tons of seed per year. The kernel of Salvadora contains 35-50% oil and is rich in saturated fatty acid, revealed from iodine value ~10 g iodine per 100g. Kokum (Garcinia indica) is a small evergreen oilseed plant found in the forests of Western Ghats from Konkan to Mysore. A matured plant produces 60-80 kg seed per tree per year and the seed contains about 44% oil. Kusum (Schleichera trijuga) is another oilseed plant that grows to a medium to large sized tree. The estimated annual potential of Kusum is 66,000 tons and the oil content is 51-62% in the seed. Similarly, many less explored oilseed plants are in India which may collectively be a potential source for biodiesel feedstock.

1.4 Fuel Qualities

The qualities of biodiesel listed in the specifications include the physical characteristics as well as a few properties specific to vegetable oils. These properties and their limits in the latest specification IS 15607:2016 is discussed under this section. The specifications for vegetable oil-based properties specified in IS15607:2016 are similar to those of EN14214:2012 + A1:2014.

1.4.1 Cetane Number

The cetane number of biodiesel should be at least 51. As discussed above, the cetane number is dependent upon the structure of fatty acid methyl esters derived from the oil, i.e., saponification value and iodine value of the oil. The cetane number of Jatropha based biodiesel is above 57 and expected to be higher in the case of Pongamia, Mahua, and Nahor oil-based biodiesel. The biodiesel from rubber seed oil may not satisfy the cetane number and the oil blended with an oil with low iodine value may serve as a biodiesel feedstock.

1.4.2 Acid Value

The acid value is a parameter that is liable to increase and even exceed its specified limit upon storage for long times. The acid value of the biodiesel should be less than 0.50 mg KOH/g, whereas the value is kept between 0.30-0.35 mg KOH/g at the site of production. The acid value of biodiesel is dependent upon the acid value of the feedstock before transesterification. The pre-treatment of the oil should be done in order to lower the acid value of the oil below 0.2 mg KOH/g to get biodiesel with the same or slightly higher acid value. The acid value has been lowered up to 0.1 mg KOH/g in case of Jatropha based biodiesel [45] and is possible with the rest of the feedstocks.

1.4.3 Ester Content, Glycerides, and Glycerol

The methyl ester content of the biodiesel should be at least 96.5% and the same is being achieved in the industrial scale biodiesel manufacturing units. It ascertains the formation of methyl esters, as well as the conversion of triglycerides. The maximum permissible level of triglyceride, diglyceride, and monoglycerides in the biodiesel are specified to be 0.7, 0.2, and 0.2% respectively. The maximum limits of free glycerol and the total glycerol are specified to be 0.02 and 0.25%, respectively. All these parameters are achieved during the transesterification and post-transesterification processes.

1.4.4 Phosphorus Content

The phosphorus content of biodiesel is specified to be less than 4 ppm. The phosphorus content in the feedstock oil can be reduced by the process of refining, involving degumming. The industrial process, i.e., degumming using phosphoric acid is practised to efficiently reduce the phosphorus content.

1.4.5 Iodine Value

Iodine value of biodiesel is an important parameter and should be less than 120g iodine/100g. The iodine value of the oil remains unchanged during the conversion to biodiesel. The iodine value is an important parameter related with the cetane number and oxidative stability. The iodine value of rubber seed oil is higher than the required level and the oil needs to be blended with low iodine value oil to make the feedstock suitable for production of quality biodiesel. The other oils discussed have iodine value in accordance with the requirement.

1.4.6 Oxidation Stability

The induction period should be more than or equal to 8 hours when the biodiesel is subjected to 110oC at an air flow of 10 litre per hour. The stability is dependent upon unsaturation in the methyl ester since the allylic hydrogen are reactive and initiate free radical reactions. Suitable synthetic antioxidants such as pyrogallol, propyl gallate, tert-butylhydroxyquinone, 3-tert-butyl-4-hydroxyanisole, and 2,6-di-tert-butyl-4-methyl-phenol are required to achieve the required oxidative stability.

Figure 1.7 Effect of antioxidant concentration on oxidative stability of karanja oil methyl esters.

The effect of synthetic antioxidants on the oxidative stability of Karanja oil has been reported by Meher et al. [46]. The biodiesel was prepared at the optimized reaction conditions of catalyst 1% KOH, methanol/oil molar ratio 6:1, reaction temperature 65°C, and rate of stirring 600 rpm, which yielded 97 to 98% of methyl esters. The oxidative stability has been improved significantly in the case of pyrogallol as the additive and 50 ppm of pyrogallol is sufficient to attain required stability, as depicted in Figure 1.7.

1.4.7 Linolenic Acid Methyl Esters

The linolenic acid methyl esters should be less than 12% in biodiesel and this is related to the stability of the product. The same is nil in the case of Jatropha, Pongamia, Mahua, and Nahor oil, whereas rubber seed oil contains up to 15.3%.

1.4.8 Polyunsaturated (≥ 4 Double Bonds) Methyl Esters

The polyunsaturated fatty acids having double bonds more than or equal to four are nil in the case of the non-edible oils discussed in this article and all these oils satisfy the maximum permissible limit. The parameter is specified as it is related with ensuring the oxidative stability.

1.5 Conclusion

The Indian non-edible oils discussed here are suitable feedstocks for biodiesel. The oils from Jatropha, Pongamia, Mahua, and Nahor are suitable feedstock for biodiesel, whereas the feedstock with iodine value >120 g iodine/100g and linolenic acid content >15% needs to be blended with low iodine value feedstock such as Palm stearin (Iodine value 35 g iodine/100g) or Mahua oil to make a feedstock technically suitable to prepare biodiesel in order to achieve qualities as per the specifications. In terms of large-scale use, the non-edible oils are supposed to have less importance and should be collected in order to be used as biodiesel feedstock. The activities of collection of these oilseeds are labour intensive. Most of these tree borne oilseeds mature during or before monsoon, resulting in the wastage of these oilseeds. The further plantation of these oilseed plants should be done in the low-quality wastelands. The activities starting from plantation to maintenance and harvesting requires manpower at the local rural level and it will improve the socio-economic status of the rural populace.