Biorefinery Production of Fuels and Platform Chemicals E-Book
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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
BIOREFINERY PRODUCTION OF FUELS AND PLATFORM CHEMICALS From the selection and pretreatment of raw materials to design of reactors, methods of conversion, selection of process parameters, optimization, and production of various types of biofuels to the industrial applications for the technology, this is the most up-to-date and comprehensive coverage of liquid biofuels for engineers and students. Massive use of fossil-based fuels not only create environmental pollution, but these sources are already diminishing. Waste biomass can aid in the production of biobased energy and chemicals. This book is a complete collection of chapters on biofuel and biochemical production presented in a sustainable way. Biorefineries are the need of the day, because they have the potential to produce fuels and chemicals in an environmentally sustainable way, to eventually fully displace production based on fossil resources such as petroleum, coal and natural gas. Algal cells are also a suitable fit for the production of both fuels and chemicals replacing conventional sources. In this book, several chapters summarize how algal biomass can be processed for the production of bioenergy and biochemicals. This volume is essentially a roadmap towards thermochemical, biochemicals, bioengineering and bioprocessing. Written and edited by authors from leading biotechnology research groups from across the world, this exciting new volume covers all of these technologies, including the basic concepts and the problems and solutions involved with the practical applications in the real world. 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.
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Table of Contents
Cover
Series Page
Title Page
Copyright Page
Dedication
List of Contributors
Preface
1 Biofuels: Classification, Conversion Technologies, Optimization Techniques and Applications
1.1 Introduction
1.2 Classification of Biofuels
1.3 Commonly Used Conversion Technologies
1.4 Commonly Used Optimization Techniques
1.5 Application of Biofuels in Transportation Sector
Conclusion
References
2 Technical Challenges and Prospects of Renewable Fuel Generation and Utilization at a Global Scale
2.1 Introduction
2.2 Biofuel Synthesis
2.3 Challenges for Bioenergy Generation
2.4 Conclusions
Abbreviations
References
3 Engineered Microbial Systems for the Production of Fuels and Industrially Important Chemicals
3.1 Introduction
3.2 Microbial Systems for Biofuels and Chemicals Production
3.3 Conclusions
References
4 Production of Biomethane and Its Perspective Conversion: An Overview
4.1 Introduction
References
5 Microalgal Biomass Synthesized Biodiesel: A Viable Option to Conventional Fuel Energy in Biorefinery
5.1 Introduction
5.2 Diesel
5.2.1 Biodiesel
5.3 Production of Biodiesel
5.4 Harvesting of Microalgae
5.5 Conclusion
Abbreviations
References
6 Algae Biofuel Production Techniques: Recent Advancements
6.1 Introduction
6.2 Technologies for Conversion if Algal Biofuels
6.3 Production of Biodiesel from Algal Biomass
6.4 Genetic Engineering Toward Biofuels Production
6.5 Summary
References
7 Technologies of Microalgae Biomass Cultivation for Bio-Fuel Production: Challenges and Benefits
7.1 Introduction
7.2 Challenges Towards Algae Biofuel Technology
7.3 Biology Related with Algae
7.4 Algae Biofuels
7.5 Benefits of Microalgal Biofuels
7.6 Technologies for Production of Microalgae Biomass
7.7 Impact of Microalgae on the Environment
7.8 Advantages of Utilizing Microalgae Biomass for Biofuels
7.9 Conclusion
References
8 Agrowaste Lignin as Source of High Calorific Fuel and Fuel Additive
8.1 Agrowaste
8.2 Lignin
8.3 Lignin as Fuel
8.4 As Fuel Additive
8.5 Conclusion
References
9 Fly Ash Derived Catalyst for Biodiesel Production
9.1 Introduction
9.2 Coal Fly Ash: Resources and Utilization
9.3 Composition of Coal Fly Ash
9.4 Economic Perspective of Biodiesel
9.5 Biodiesel from Fly Ash Derived Catalyst
Conclusion
References
10 Emerging Biomaterials for Bone Joints Repairing in Knee Joint Arthroplasty: An Overview
10.1 Introduction
10.2 Resources and Selecting Criteria
10.3 Reasons for Bone Defects of Tibia Plateau
10.4 Classification of Bone Defects of Medial Tibia Plateau
10.5 Different Biomaterials for Tibial Plateau Bone Defects (Figure 10.1, Table 10.1)
10.6 New Biomaterials to Repair Bone Defects in Tibia Plateau
10.7 Conclusion
References
About the Editor
Index
Also of Interest
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Advantages and disadvantages of bioethanol [10].
Table 1.2 Advantages and disadvantages of biodiesel [10].
Table 1.3 Parameters and product description for different gasification techno...
Table 1.4 Common parameters for different pyrolysis modes.
Chapter 2
Table 2.1 Bioenergy from different biomasses with different microbial synthesi...
Table 2.2 Biofuel synthesis with biomass hydrolysis challenges using pretreatm...
Chapter 3
Table 3.1 List of some engineered microorganisms and productivities of fuels a...
Chapter 5
Table 5.1 Physical characteristics of petro-diesel [24, 25].
Table 5.2a Amount of extracted oil by using varying volumes of chemical solven...
Table 5.2b Amount of oil extracted by using varying weights of dried algae in ...
Table 5.3a Amount of oil extracted by using different sizes of algal biomass [...
Table 5.3b Oil extracted by using different contact time with solvents and alg...
Chapter 7
Table 7.1 Groups of microalgae on basis of colour.
Table 7.2 Contents of oil present in microalgae.
Table 7.3 Algal species used for production of biofuel with experimental condi...
Chapter 8
Table 8.1 Structure, chemical composition, and bonding between lignin in bioma...
Table 8.2 Types of lignin.
Table 8.3 Various uses of lignin.
Chapter 9
Table 9.1 Chemical composition of fly ash produced in different countries [26]...
Table 9.2 Average composition of coal derived fly ash [27].
Table 9.3 Elemental analysis of SFA and FA [54].
Chapter 10
Table 10.1 Traditional biomaterials used for repairing bone defects.
List of Illustrations
Chapter 1
Figure 1.1 Various forms of biomass.
Figure 1.2 Process of production of 1
st
generation biofuels.
Figure 1.3 Transesterification process.
Figure 1.4 Conversion of lignocellulosic biomass to biofuel.
Figure 1.5 Feedstocks and products.
Figure 1.6 Production process of third-generation biofuels.
Figure 1.7 Line diagram of gasification.
Figure 1.8 Setup diagram of pyrolysis reactor unit.
Figure 1.9 Multi-response optimization results using RSM.
Figure 1.10 Optimization process using GA.
Figure 1.11 Biofuels market value (2018 – 2026).
Chapter 2
Figure 2.1 Biogases from anaerobic digestion of complex biopolymers from diffe...
Figure 2.2 Different types of biofuels showing structures that are different g...
Chapter 3
Figure 3.1 Various objectives of microbial system engineering for the producti...
Figure 3.2 Bioengineering of various microbial systems for production of diver...
Figure 3.3 Metabolic pathways for production of various biofuels and chemicals...
Chapter 5
Figure 5.1 Various forms of oil or lipids (sources from higher plants) used fo...
Figure 5.2 Plant biomass sources for energy & edible products & biomass synthe...
Figure 5.3 Microalgal species used for various types of biofuels including bio...
Figure 5.4 Schematic diagram for production of biodiesel from algal lipid or o...
Figure 5.5 Transesterification processes for biodiesel synthesis used for conv...
Figure 5.6 Chemical reactions occurred in transesterification reaction for bio...
Chapter 6
Figure 6.1 Conversion processes of algae biomass to biofuel.
Chapter 7
Figure 7.1 Life cycle of algae.
Figure 7.2 Classification of microalgae.
Figure 7.3 Schematic diagram for production of microalgae biomass systems.
Chapter 8
Figure 8.1 Monomers of lignin derived from alcoholic precursors.
Figure 8.2 Applications of lignin.
Figure 8.3 Overview of lignin utilization for bio-fuel or chemicals production...
Figure 8.4 Depolymerization of lignin by chemical methods and its use in produ...
Figure 8.5 Processes used to produce bioethanol; Bio-residue called lignin is ...
Chapter 10
Figure 10.1 Bone Defects in Tibial Plateau and Treatment Methods. (a) During s...
Guide
Cover Page
Series Page
Title Page
Copyright Page
Dedication Page
List of Contributors
Preface
Table of Contents
Begin Reading
About the Editor
Index
Also of Interest
WILEY END USER LICENSE AGREEMENT
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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Biorefinery Production of Fuels and Platform Chemicals
Edited by
Prakash Kumar Sarangi
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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Library of Congress Cataloging-in-Publication Data
ISBN 9781119724728
Cover image: Ethanol Plant: Gloria P. Meyerle | Dreamstime.com,Flower Field: ID 181127767 © Jochenschneider | Dreamstime.comCO2: Pop Nukoonrat | Dreamstime.com, Renewable Resources: Mario Kelichhaus | Dreamstime.comCover design by Kris Hackerott
Dedication
List of Contributors
Abbhijith HDepartment of Mechanical Engineering, Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, India
Anushri KeshriInstitute of Biotechnology, Amity University Chhattisgarh, Raipur, Chhattisgarh, India
Balasubramanian VelramarInstitute of Biotechnology, Amity University Chhattisgarh, Raipur, Chhattisgarh, India
Harshini G VDepartment of Mechanical Engineering, Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, India
Harit JhaDepartment of Biotechnology, Guru Ghasidas Vishwavidyalaya, Bilaspur, Chhattisgarh, India
Krushna Prasad ShadangiDepartment of Chemical Engineering, Veer Surendra Sai University of Technology, Burla, Odisha, India
Meenakshi JhaInstitute of Biotechnology, Amity University Chhattisgarh, Raipur, Chhattisgarh, India
Musunuri Shanmukha VardhanDepartment of Mechanical Engineering, Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, India
Neha BothraDepartment of Biotechnology, GIT, Gandhi Institute of Technology and Management (GITAM) Deemed to be University, Rushikonda, Visakhapatnam, India
Neha NamdeoDepartment of Biotechnology, Guru Ghasidas Vishwavidyalaya, Bilaspur, Chhattisgarh, India
P. ManiharikaDepartment of Biotechnology, GIT, Gandhi Institute of Technology and Management (GITAM) Deemed to be University, Rushikonda, Visakhapatnam, India
Pamidimarri D. V. N. SudheerInstitute of Biotechnology, Amity University Chhattisgarh, Raipur, Chhattisgarh, India
Prakash Kumar SarangiCollege of Agriculture, Central Agricultural University, Imphal, Manipur, India
Rajesh K. SrivastavaDepartment of Biotechnology, GIT, Gandhi Institute of Technology and Management (GITAM) Deemed to be University, Rushikonda, Visakhapatnam, India
Shankar Swarup DasDepartment of Farm Machinery and Power Engineering, College of Agricultural Engineering and Post-Harvest Technology (Central Agricultural University), Ranpool, India
Sakthivel RDepartment of Mechanical Engineering, Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, India
Shalini PandeyInstitute of Biotechnology, Amity University Chhattisgarh, Raipur, Chhattisgarh, India
Shivam PandeyInstitute of Biotechnology, Amity University Chhattisgarh, Raipur, Chhattisgarh, India
Sneha KumariInstitute of Biotechnology, Amity University Chhattisgarh, Raipur, Chhattisgarh, India
Sushma ChauhanInstitute of Biotechnology, Amity University Chhattisgarh, Raipur, Chhattisgarh, India
Tanushree Baldeo MadaviInstitute of Biotechnology, Amity University Chhattisgarh, Raipur, Chhattisgarh, India
Trinath BiswalDepartment of Chemistry, Veer Surendra Sai University of Technology, Burla, Odisha, India
Vargobi MukherjeeInstitute of Biotechnology, Amity University Chhattisgarh, Raipur, Chhattisgarh, India
Preface
Economic growth through extensive use of fossil resources is generally considered as unsustainable and has irreversible adverse climatic impacts. An alternative is to use renewable biomass resources for fuels and chemicals. A biorefinery uses various types of renewable biological feedstocks to produce fuels and chemicals. Furthermore, sustainability of society is dependent on sustainable use of renewable resources including waste biomass. The book covers all the key topics relating to sustainable use of waste biomass resources along with biomass sources and characteristics, bioconversion technologies, processes for producing platform chemicals from biomass, and other biotransformations. Also, this book explains the process protocol for biochemical production. One chapter is dedicated to biomaterial production that can help in biorefinery processes. This book highlights new state-of-the-art aspects based on sustainable bioprocess technology involved in various sectors like industries, transportation, etc. This book will justify the needs of a majority of academicians and researchers around the globe in the field of biofuels and platform chemicals towards sustainability. I always accept suggestions and motivational inspirations from my parents for preparation of a manuscript. I express my sincere thanks to all my family members for providing me solid support and in time cooperation towards the completion of book manuscripts. I express our hearty thanks to Mr. Phil Carmical, Scrivener Publishing, LLC for his kind and timely help supplying full logistic support towards publication of this book.
Dr. Prakash Kumar Sarangi
Scientist, College of Agriculture Central Agricultural University, Imphal,Manipur, India
1Biofuels: Classification, Conversion Technologies, Optimization Techniques and Applications
Sakthivel R1*, Abbhijith H1, Harshini G V1, Musunuri Shanmukha Vardhan1 and Krushna Prasad Shadangi2
1Department of Mechanical Engineering,Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Coimbatore, India
2Department of Chemical Engineering, Veer Surendra Sai University of Technology, Burla, Odisha, India
Abstract
To combat climate change, many researchers over the past few decades have focused their attention towards adopting and studying biofuels that could not just cause fewer toxic emissions compared to conventional petroleum-based fuel, but are also being generated from a myriad of plant waste, animal waste, etc. In this chapter, the primary study is focused on the classification of biofuels: 1st gen, 2nd gen, and 3rd gen biofuels. Then, different conversion technologies, such as pyrolysis, gasification, hydrothermal processes, and transesterification, which are commonly used in industries and labs to obtain biofuels from a plethora of biomass are studied in detail. After obtaining the biofuel from any one of the aforementioned conversion technologies, they could be used as an alternative power source and studied for emission and performance characteristics. However, to determine the optimal results, a suitable optimization technique would have to be employed. In this chapter, two such optimization techniques, namely Response Surface Methodology and Genetic Algorithm, are described in the view of optimizing engine parameters. Finally, a clear view is given into the application of biofuels in the transportation sector, particularly in the automotive and aviation sectors.
Keywords: Biofuels, pyrolysis, gasification, hydrothermal processes, transesterification, response surface methodology, genetic algorithm
1.1 Introduction
Back in 2005, the petrol price in India was ₹ 59.29 per liter and in 2020 petrol prices are at an all-time high of ₹ 95.53 per liter. The hike in the gap of 15 years is about 62% and it has been concluded that there will be a hike in all fossil fuel-based products in forthcoming years. This trend can be seen all around the world since fossil fuels are being depleting at an alarming rate. Externality means a consequence of an industrial or commercial activity that affects other parties without being reflected in market prices. It is a well-known fact that the usage of fossil fuels causes pollution, but this factor of energy consumption and production of fossil fuels is not considered, hence, making this factor an externality. Under research done by the International Monetary Fund, there is an indication that economic and environmental costs due to fossil fuels add up to $5 trillion [1]. As of now, there is an unprecedented worldwide interest to reduce carbon dioxide emissions which is central to reducing greenhouse gas effects and improving the air quality of the metropolitan cities. In many countries around the globe, the quality of air has been extremely bad in spite of the preventive measures taken by the government. This can be accounted to the over usage of fossil fuels and emissions due to automobiles.
The report submitted by INERA (International Renewable Energy Agency) at the G20 summit to meet the central goals of the Paris climate change agreement showcased that clean energy can achieve up to 90% of energy-related carbon emissions. As of now, 24% of world power generation comes from renewable energy. The primary energy supply stands for energy production plus energy imports, minus energy exports, minus international bunkers, then plus or minus stock exchanges. Right now, in the 24% of available clean energy, 16% accounts for primary energy supply. To achieve desired decarbonization by the year 2050, renewable energy should account for up to 80% and 65% of the primary energy supply. Bringing down the carbon levels in the air can be achieved by only shifting to a clean energy source, or, in other terms, renewable energy. It is important and high time that we move on to adopt and advance renewable energy. Renewable energy is derived from a replenishable source such as the Sun (Solar energy), wind (Wind power), rivers (Hydroelectric power), hot springs (Geothermal power), tides (Tidal power), and biomass (Biofuels). Sunlight is the most abundant form of energy available to us and solar energy is currently constantly seeing a surge in its usage to generate electricity around the world. Solar Photovoltaic (PV) technology can proselytize sunlight to electricity with the use of PV materials. The prices of renewable energy technologies for electricity production in the solar and wind sectors have come down by 70% and 30%, respectively. Denmark has taken up the challenge of transition to 100% clean energy in which wind power is going to play a major role. INERA suggests that biofuel production should increase 10 times by 2050.
It would not be an understatement to say the way forward is renewable energy. Biomass is going to play a major role in the coming future. Biomass is plant or animal materials that can be processed to generate biofuel and such processes could also be used to generate heat and electricity. Biomass was the first method known to man to generate heat as early humans used wood logs to generate heat. There are many types of biomass; if we consider the type of production, it can be chemical or biological, liquid or gas if we consider the type, and heat, current, or transport if we consider the purpose [2]. Biomass is obtained from specific energy crops, agriculture crop residues, forest residue, processed wood residue, algae, municipal waste, etc. Figure 1.1 shows the various forms of biomass. Biofuels are derived from biomass which includes, but is not limited to, animal waste, plants, and algae. Three major benefits from biomass usage are greenhouse gas reduction, low dependence on foreign oil, and an increase of opportunities in forestry and agriculture fields. Ethanol and biodiesel are very well-known biofuels. Biofuels are distinguished into three categories, namely 1st gen. biofuel, 2nd gen. biofuel, and 3rd gen. biofuels. These biofuels can be obtained from different feedstock yields. The given table below lists various biofuel alternative feedstocks currently and long-term yields under the International Energy Agency (IEA).
1st generation biofuels are derived from biomass such as sugar, starch, and vegetable oils. To attain 1st generation biofuels, many well-known methods such as fermentation, distillation, and transesterification are used. 2nd generation biofuels are processed through wood, organic, and food waste along with some specified biomass crops. 2nd generation biofuels biomass go through a pretreatment process in which lignin is broken down. This pretreatment consists of thermochemical or biochemical reactions. After the pretreatment, the process is parallel to the production of 1st generation biofuels. The 2nd generation biofuels generate higher energy yields compared to that of 1st generation biofuels. 3rd generation fuels specifically use algae as the feedstock to make biodiesel. The algae’s oils are converted into biodiesel using a similar process as 1st generation biofuels. It is a well-known fact that 3rd generation fuels are highly energy-dense compared to 1st generation and 2nd generation biofuels. Unlike 1st and 2nd generation biofuels, 3rd generation biofuels do not depend on crops, which relieve the stress on water and land. Meanwhile, they can be termed as high-energy, renewable, and low-cost sources of energy. Seaweed is also being reviewed as a possible energy source for 3rd generation biofuels, with the end product being biomethane. The BMP (Biochemical Methane potential) values of seaweed stock vary from 101.7 (L CH4/kg VS-1) to 357.4 (L CH4/kg VS) per the species selected [3]. In the last decade, there has been a lot of research done on fast pyrolysis that can be used to extract high bio-oil yields. In this method, raw biomass is rapidly subjected to heating under inert atmosphere and immediately condensed to obtained liquid product. Pyrolysis is accounted as thermal decomposition of the feedstock with a low level of oxygen [4]. Gasification is also one of the methods to obtain biofuels based on fermentation of the biomass to obtain products like ethanol, butanol, hydrogen, methane, and acetate. After gasification is completed, the obtained syngas is processed into acids and alcohols with the help of specific microorganisms by the fermentation process. Lignocellulosic biomass, after fermentation, goes through size reduction that can be achieved in two methods to obtain biofuels either by pretreatment, hydrolysis, fermentation, and purification or gasification and fermentation. Gasification takes place in a low oxygen environment and fuel abundant conditions with an equivalence ratio of 0.25 (mass of O2/stochiometric mass of O2) [5].
Figure 1.1 Various forms of biomass.
Hydrothermal processes are used for the extraction of third-generation biofuels which must be abstracted from microalgae and macroalgae. One of the main reasons for using hydrothermal processes for 3rd generation biofuels is due to high moisture content in the aquatic biomass. In this method, the biomass is processed wet in hot compressed water. This process is temperature dependent and we get different end products per the operating temperature of the operation. At lower temperatures (less than 200 °C) hydrothermal carbonization (HTC) occurs in which the end product is biochar. At intermediate temperatures (200 – 375 °C) and below the critical point, hydrothermal liquefaction (HTL) occurs giving biocrude as its end product. Finally, above the critical point (above 375 °C) a gasification reaction occurs with syngas as its primary product. The char produced from HTC can be used as manure and it helps to retain nitrogen and sulfur along with reducing the emissions. As known biocrude from HTL helps in upgrading the fuels and chemicals and coming to syngas from the hydrothermal gasification process, it can be either used for combustion or converted to hydrocarbons. In other words, hydrothermal processes stimulate the natural process which occurs in the fossil fuel reserves [6]. The oils obtained from biomass, which was used to run diesel engine cars at the Paris exposition in 1900, had a major flaw in that they were highly viscous. The oils were almost 10 to 20 times more viscous compared to the diesel fuel used. To encounter this problem transesterification was used. This is a chemical conversion process in which the oils are reduced to their corresponding fatty ester form, called biodiesel. This can be a great alternative to conventional fuels used for a compression ignition (CI) engine. A few advantages of biodiesel are they are non-toxic, biodegradable, and free from sulfur and carcinogenic compounds [7]. In the following sections, a detailed study on the above-mentioned processes is given.
1.2 Classification of Biofuels
1.2.1 First-Generation Biofuels
First-generation biofuels are known as conventional biofuels because they are made out of sugar, starch, corn, animal fats, or edible oil. Figure 1.2 shows the production process for 1st generation biofuels. They have a small negative impact on food society as the yield of biofuel is limited [8]. Production of these biofuels includes the processes of transesterification, distillation, and fermentation. The fermentation process includes starches and sugars. Fermentation of these produces primary ethanol, propanol, and butanol. Ethanol has 1/3 the density of energy of gasoline. Transesterification (see Figure 1.3) is the process of producing biodiesel by using plant oil or animal fats. This process occurs in the presence of the catalyst by mixing the plant oil or animal fats with alcohols (methanol). Distillation is the process of separating the main product from its by-products.
The main sources are corn, potatoes, sugarcane, vegetable oil, soybeans, and animal fat. Biodiesel, corn ethanol, and sugar alcohol are the major biofuels produced. A few problems which are faced are limited feedstock (food vs. fuel) and blending compatibility with conventional fuel, but there are a few benefits like environmentally friendliness, economics, and social security [9]. Table 1.1 shows the advantages and disadvantages of bioethanol. Table 1.2 shows the advantages and disadvantages of biodiesel.
Figure 1.2 Process of production of 1st generation biofuels.
Figure 1.3 Transesterification process.
The term sustainable development refers to the methodology that meets the demands of people without compromising the needs of the future. The three major pillars of sustainable development are society, economics, and the environment. Social acceptance, economic feasibility, and environmental impacts are the criteria on which the sustainability of a system is evaluated. To highlight the sustainability challenges, the life cycle of first-generation biofuel production systems can be analyzed. The production chain has several stages like site preparation, feedstock production, transportation, processing facilities, biofuel production, storage and dispensing, and combustion. The feedstock preparation is done with large-scale plantation for large-scale biofuel production of first-generation biofuels. Focussing on the environmental perspective, the benefits in terms of climate change mitigation have been under continuous sustainability discussion [10].
Table 1.1 Advantages and disadvantages of bioethanol [10].
Advantages
Disadvantages
Ethanol burns cleaner than gasoline
About 1.5 times of ethanol is required to produce the same amount of energy as gasoline
Produces fewer greenhouse gases
Corrosive to gasket rubbers
When blended, it increases the octane number of the fuel
Distribution through pipelines is difficult as ethanol absorbs water
Table 1.2 Advantages and disadvantages of biodiesel [10].
Advantages
Disadvantages
Biodiesel is less polluting than fossil diesel
Biodiesel is expensive, 1.5 times more than fossil diesel
Due to the lubricating properties, it increases the life of diesel engines and blending is easy with oils and other energy sources
Harms rubber hoses in diesel engines
1.2.2 Second-Generation Biofuels
Second-generation biofuels are fuels derived from different feedstock, but especially non-edible lignocellulosic biomass. It is plant dry mass that is composed of cellulose and hemicellulose, which are carbohydrate polymers, and lignin, an aromatic polymer. Figure 1.4 shows the conversion of lignocellulose biomass into biofuel. The production of these second-generation biofuels is classified into 3 main categories. They are homogeneous, quasi-homogeneous, and non-homogeneous. Homogeneous includes wood cuttings and white wood chips. Quasi-homogeneous includes agricultural and forest residues and non-homogeneous includes municipal solid wastes, which are low-value feedstock. The cost of this biomass is less than the cost of corn, sugarcane, vegetable oil, and other edible feedstocks [11]. The process of producing second-generation biofuels is more elaborate than first-generation biofuels as this requires pre-treating techniques to release the sugars which are trapped. This process requires more materials and energy. This biomass is more complex for conversion in general and the production is fully dependent on advanced technologies.
Figure 1.4 Conversion of lignocellulosic biomass to biofuel.
There are four steps in the lignocellulosic conversion process: (1) Pretreatment, (2) Hydrolysis, (3) Fermentation, and (4) Distillation. The pre-treatment step is done to soften the biomass, thereby breaking down the cell structures. The hydrolysis process is done to increase the complexity of the sugar. The sugar is released from the cellulose part of the biomass. The fermentation process is done to convert these sugars to bioethanol. It is a metabolic process. Common crops used are salmon oil, jatropha, rubber tree, tobacco seed, jojoba oil, and sea mango. Biodiesel feedstocks include restaurant grease, non-edible oil crops, cooking oil waste, beef tallow, and pork lard. Figure 1.5 shows the feedstocks and products obtained in the hydrolysis process. Some of the advantages of second-generation biofuels are it is environmentally friendly and does not compete with food items, so it does not affect people. One main disadvantage of these second-generation feedstocks is there are not enough active advanced technologies for the commercial usage of the waste generated by biodiesel production. Animal fats also contain a high concentration of saturated fatty acids. Those fatty acids increase the complexity of transesterification which is also a notable drawback [12].
Figure 1.5 Feedstocks and products.
In regards to constraints in the production of second-generation biofuels, water scarcity is one of the major problems. The biofuels produced from biomass have an increasing demand, which will intensify the pressure on clean water resources. The reasons for that are (1) certain feedstocks like energy crops are grown with a requirement of large quantities of water and (2) with crop production, agricultural drainage is likely to increase. When specific biomass crops are grown on large-scale land, it affects biodiversity, whereas production of biofuels from crops/forest residues should have less negative impact. Intensification of feedstock production has both positive and negative impacts on biodiversity [13].
1.2.3 Third-Generation Algal Biofuels
Third-generation fuels consist of microalgae, animal fat, fish oil, pyrolysis oil, etc. Third generation feedstocks have an upperhand compared to 1st and 2nd generation biofuels in terms of availability, economic feasibility, affecting of the food chain, and adaptability to climatic conditions. Figure 1.6 details the production of 3rd generation biofuels. Algae can be cultivated at lower costs due to their ability to grow in harsh conditions. Another advantage of the algae is the lipid content; on average the lipid content is about 70% and by enhancing the conditions we can get up to 90% dry weight. Biodiesel can be extracted from waste cooking oil and is also known to be a cost-effective and heterogenous raw material. Increasing the usage of waste cooking oil may also reduce the burden on sewage treatment and water contamination [14].
Figure 1.6 Production process of third-generation biofuels.
Bioethanol from algal biomass is obtained by fermentation. In the process, strain selection and growth play a very important role in yield and property of the biofuel. Algal growth is very much dependent on environmental changes. Biodiesels are obtained by transesterification which are generally methyl or ethyl esters. The required fatty acid esters are obtained when triglycerides from oil feedstock and short-chain alcohol (methanol or ethanol) react along with a catalyst to introduce the alkyl group of the alcohol where glycerol is obtained as a side product [15].
1.3 Commonly Used Conversion Technologies
1.3.1 Gasification
Gasification has been in practice since the 1800s when, from coal, also known as town gas, gases were produced. In the 1900s, European nations employed wood gasification to fuel their cars when there was a paucity of fuel [16]. Gasification is a thermochemical conversion where biomass, or any carbonaceous matter, solid or liquid for that matter, is converted to syngas. The major composition of syngas is CO and H2. There is also substantial heat produced in the process with a temperature range of 600 - 1500°C [17]. An important point to note while doing experiments with gasification is that the oxygen feed must be less than the stoichiometric values since higher oxygen may lead to oxidation of products. For enhancing gasification, gasifying agents are often used such as steam, carbon dioxide, or oxygen. In addition to syngas, tar and char are also obtained. Tar is the liquid phase and char is the solid phase [18]. Before gasification, it is important that we pre-heat the feedstock biomass so that there is no moisture content in it.
Table 1.3 Parameters and product description for different gasification technologies.
Technology → parameters & description↓
Plasma gasification
Melting gasification
Fluidized bed gasification
Supercritical water gasification
Microwave gasification
Ref
Temperature
>2500°C.
2200°C.
600°C.
375 – 500°C.
800°C.
[
17
]
Reactor type
Plasma gasifier
Fixed/Moving bed gasifier
Fluidized bed reactor.
Hydrothermal gasifier
Microwave-assisted
[
17
]
Product Description
There’s a 100% carbon conversion. The syngas quality is very high.
The syngas obtained has to undergo a downstream treatment.
The syngas quality is high and it’s relatively easy to control the operating parameters.
The gasification is carried out in the presence of a large volume of water. The methane in the syngas has to undergo further refinement.
The temperature profile of the syngas is uniform and better yield is observed when we use a catalyst such as Ni.
[
17
]
Common gasification technologies used in the industry include plasma gasification, melting gasification, fluidized bed gasification, supercritical water gasification, and microwave gasification. Given below (Table 1.3) are the subsuming parameters and product description for the aforementioned technologies.
Given below (Figure 1.7) is the line diagram of the gasification process.
1.3.1.1 Factors Influencing Gasification
1. Particle Size
Smaller particle size biomass is preferred to larger sizes because, for the former, the time needed for the heat transfer to the center of the biomass particles from the walls of the reactor is less, therefore, enhancing the rate of chemical reactions. Also, when the particle size of the biomass is less, the H2 concentration is high and the concentration of tar and char is less [18].
2. Moisture Content
The gasification efficiency significantly depends on the amount of moisture content in the biomass. The lower the moisture content, the higher the gasification efficiency. The favorable moisture content is 15% by weight moisture. Moisture content also affects the transportation and handling of biomass fuels. The problem with wet biomass is that some amount of energy is spent in vaporization and as a result of that, gasification temperature decreases [18].
Figure 1.7 Line diagram of gasification.
3. Gasifying Agent
Gasifying agents are a vital medium for biomass gasification. The most commonly used gasifying agent is air. This is because it is cheap and is readily available. Despite these advantages, when air is used as a gasifying agent, in the synthesis gas predominantly N2 is formed, which is not desirable. We could also use O2 and steam as gasification agents but they are costly and have high operation costs [18].
4. Gasification Temperature
For reactions, high gasification temperatures are favored. This is because, at high temperatures, the decomposition of tar and char is high and the overall gas yield is also high. For exothermic reactions such as methanation and water gas shift reactions, lower temperatures are preferred [18].
5. Operating Pressure
The operating parameter is an important parameter because pressurized gasifiers generate gases of high pressure which are then fed into turbine coupled generators for the production of electricity. If the operating pressure is greater than the atmospheric pressure, we could store them in small volumes. The amount of heat transfer also increases when we used pressurized gasifiers. The disadvantages of pressurized gasifiers include complex construction, high operation costs, and difficulty in maintaining a constant flow rate of the biomass that is fed into the reactor [18].
1.3.2 Pyrolysis
Pyrolysis, also known as destructive distillation, is a thermochemical process where organic matter, in the absence of oxygen, undergoes decomposition. This process started in ancient Egypt for the production of tar. Later on, research of pyrolysis was expanded using a myriad of feedstock ranging from coal to wood to biomass. Biomass is the most common feedstock used these days in an industrial setting [19].
1.3.2.1 Production of Bio-Oil from Pyrolysis
First, the appropriate feedstock (rice husk, peanut shell, etc.) chosen for study must be ground into fine particles. Then, the particles must, using a screw feeder or a vibratory feeder, be fed into the reactor through the hopper. The mass flow rate of the biomass that is fed into the reactor is controlled using screw feed. It is also a good practice to pre-heat the biomass before it is fed into the reactor to remove the moisture content. To create an inert atmosphere inside the reactor, gases (usually N2) are passed into the reactor. A heating coil is placed around the reactor core and it escalates the temperature of the reactor core. To improve the yield, in addition to the feedstock, catalysts such as Zirconium, Zinc, etc. can be used. Due to the high temperature in the reactor which is provided by the heating coil, the feedstock undergoes a phase change from the solid to the gaseous phase. The gases emanating are then passed through a freeboard where it expands and enters the cyclone separator. The separator takes advantage of gravity and allows the pyrolysis vapors to pass through and the solid char particles go down the spiral structure. The resultant pyrolysis vapors then enter a condenser, usually a shell and tube type, where it condenses to bio-oil. The following diagram (Figure 1.8) explains the pyrolysis process discussed.
Depending on the heating rate, the pyrolysis temperature, and the residence time of the biomass particles in the reactor, there are three types of pyrolysis, namely: slow pyrolysis, fast pyrolysis, and flash pyrolysis. Table 1.4 shows the various parameters for the different pyrolysis modes mentioned above.
Figure 1.8 Setup diagram of pyrolysis reactor unit.
Table 1.4 Common parameters for different pyrolysis modes.
Parameters → Pyrolysis mode ↓
Temperature (
°
C)
Residence time
Heating value
Commonly used reactor
Slow Pyrolysis
300-550°C
5-30 minutes
10°C/min
Drum, Auger-type, and Rotatory kilns
Fast Pyrolysis
500-600°C
0.5-2 sec.
10-1000°C/s
Fluidized bed and microwave reactors
Flash Pyrolysis
900-1300°C
<0.5 sec.
>1000°C/s
Fluidized bed reactors
1.3.3 Hydrothermal Processes
These are the processes where an intricate organic waste, for instance lignocellulose biomass, is transmuted to simple organic compounds such as biochar, water, carbon dioxide, etc. The most commonly used type of wastes in hydrothermal processes are municipal solid wastes (MSW). This process occurs in an environment aided by high temperature and pressure where the organic wastes solubilize. To further aid the process, different oxidizing agents such as hydrogen peroxide (H2O2), are used. In the processes discussed previously, one of the key issues is that wet feedstock is not desirable and in case we are in need to use them, it is better to preheat the biomass before feeding it in the appropriate reactor. But, in hydrothermal processes, the processing of wet wastes can be achieved without the need for adopting energy-intensive dewatering steps. It is an advantage that hydrothermal processes have compared to thermochemical conversion techniques such as pyrolysis or gasification.
Based on the operating pressure and temperature, hydrothermal processes can be classified into three categories. They include a) Hydrothermal carbonization, b) Hydrothermal Liquefaction, and c) Hydrothermal gasification. Let’s study each of the aforementioned processes in detail.
1.3.3.1 Hydrothermal Carbonization
Hydrothermal carbonization, also called wet torrefaction, is the process of converting organic solid wastes that are cellulose-rich, such as bagasse, straw, corn stover, plastics, etc., into useful products such as biochar. The energy density of the bio-char is very high. The operating conditions for hydrothermal carbonization are as follows: 180-250°C temperature and 2-10 MPa pressure. The reason for maintaining the low temperature is to prevent gasification or liquefaction so that only char (desired product) is produced. There are three steps in hydrothermal carbonization: decarboxylation, dehydration, and aromatization. In decarboxylation, carboxyl groups are removed and in dehydration the OH groups are removed. As a result of this, the oxygen/carbon ratio or O/C ratio, is reduced significantly and the final product has high energy density. No catalyst is needed for hydrothermal carbonization. The downside of hydrothermal carbonization includes heat loss, high residence time, unrestrained side reactions, etc. [20].
1.3.3.2 Hydrothermal Liquefaction
Hydrothermal Liquefaction (HTL) is a thermo-chemical process where wet biomass is converted into fuel. The feedstocks used in this process include, but are not limited to, algae and lignocellulose biomass. For woody biomass, it is advisable to reduce the particle size before the operation. The operating conditions for hydrothermal carbonization are as follows: 200-375°C temperature and 5-20 MPa pressure. There are three steps in hydrothermal liquefaction: depolymerization, decomposition, and recombination. During depolymerization, depending on the chemical and physical properties of the biomass feedstock, the macromolecules undergo a sequential dissolving process. In short, the long polymer chain gets broken down into a shorter hydrocarbon chain. In decomposition, oxygen is removed from the biomass and there is a formation of water and carbon dioxide. In recombination, the hydrogen fragments recombine and form a compound of high molecular weight, also known as coke [21]. Some advantages of HTL include a huge percentage of carbon recovery and high energy outputs [22].
1.3.3.3 Hydrothermal Gasification
Hydrothermal gasification is biomass gasification in hot compressed water. The water usage is two-pronged. First, the water is used as a solvent and second, it could be a reaction-aid. This is one of the most efficient technologies adopted for wet biomass gasification, as the reaction is short. The operating conditions for hydrothermal carbonization are as follows: 350-700°C temperature. The main products obtained include H2, CO2, and CH4. Due to high operating temperatures, the decomposition is faster and complete. To take advantage of hydrothermal gasification, wet feedstocks are often used. Dry feedstocks could also be used, but for that we could adopt the regular gasification techniques discussed previously. Hydrothermal gasification usually involves the following steps: aqueous phase reforming, methane catalyzation, and supercritical water gasification. In aqueous phase reforming, biomass is mainly gasified to form hydrogen and carbon dioxide in the presence of a heterogeneous catalyst. In methane catalyzation, biomass is mainly gasified to form methane and carbon dioxide in the presence of a heterogeneous catalyst. The temperature range is between 350°C for methane production in the liquid phase and 400°C for production in the supercritical state. In supercritical water gasification, biomass is mainly gasified to form hydrogen and carbon dioxide without the presence of a solid catalyst [23]. The advantage of gasification includes not having tar in the product and a high heating value of the product.
1.3.4 Transesterification
Biodiesel is one of the most prominently used alternative fuels for diesel traction. Biodiesel is the fatty acid alkyl ester produced from vegetable or animal oils produced by transesterification reaction. Some of the common sources for biodiesel production explored by the current research community include Jatropha, canola, rapeseed, Calophyllum inophyllum, sunflower, castor, moringa, coconut, animal fat, pyrolysis oil, etc. [14]. The salient features of these feedstocks have been discussed in the previous topics. Transesterification is mainly carried out to convert raw fatty acid components of the feedstock into esters, using alcohol and base. This conversion ensured the reduced viscosity and enhanced combustion properties of the resulting biodiesel. During the reaction stage, the glycerides (mono, di, and tri) react with alcohol (preferably methanol) to produce esters and glycerol as main products. The alkyl group (R) alcohol is completely replaced by the alkyl ester (R’) group. It should also be noted that oils with high free fatty acid (FFA>5) should be subjected to acid esterification and then followed by transesterification to avoid the formation of soap in the process. The overall transesterification reaction is consecutive stages, as shown in Scheme 1.1.
where TG is Triglycerides, GLY is Glycerol, DG is Diglycerides, MG is Monoglycerides, MET is Methyl Esters, and FAME is Fatty Acid Methyl Esters.
In the course of the transesterification process, a base is commonly employed as a catalyst to fasten up the ester formation. The recent decade witnessed utilizing different types of catalyst to enhance the transesterification reaction for producing biodiesel. The catalyst can be classified as enzymatic, homogeneous, or heterogeneous based on their formulation and material. Bio-catalysis is yet another booming area in the field of biodiesel production, which used enzymes as a catalyst.
Moving on to the experimental conditions that affect the transesterification reaction, it was observed that the alcohol to methanol molar ratio, catalyst concentration, reaction temperature, and reaction time played a vital role in the yield of biodiesel. In general, varying the process conditions affects the yield and composition of biodiesel. The addition of catalyst to the reaction increases the conversion rate, to some extent, whereas excessive catalyst concentration has the potential to reverse the transesterification reaction. Meanwhile, high temperature and reaction time subdues the reaction rate and reduces the yield. The addition of methanol above the optimized point supports the formation of glycerol rather than biodiesel yield. Also, a higher methanol level degrades the rate of reaction owing to the physical dilution and flooding of active catalyst sites. So, it becomes inevitable to optimize the reaction conditions for the production of biodiesel to increase the yield which is given by Equation 1.1.
Some of the experimental studies carried out to optimized the transesterification conditions to produce better biodiesel fuel are discussed. Raj et al. [24] modeled and optimized the reaction conditions for the production of biodiesel from Nannochloropsis salina with nanocatalysts derived from eggshell waste. The authors employed techniques like RSM and ANN for the optimization studies. The maximum FAME conversion was found to be 86% under the catalyst load of 3% (v/v), reaction temperature (60° C), time of 55 min, and oil to methanol ratio 1:6 (v/v). Rajendiran and Gurunathan [25] optimized the transesterification reaction parameters for biodiesel production from Calophyllum inophyllum oil. The zinc-doped CaO nanocatalyst was employed to enhance the yield and quality of biodiesel. A maximum conversion efficiency of 91.95% was recorded at 9.66:1 methanol to oil ratio, 5% catalyst load, 81.31 min reaction time, and 56.71°C reaction temperature. The overall green chemistry value has been evaluated as 0.873. Transesterification of soybean oil with ionic liquid catalyst is carried out by Panchal et al. [26]. The ANOVA results suggested 1:2 v/v of oil to methanol, 8% catalyst load, 4 h reaction time, and 300 rpm agitation as an optimized condition to obtain the maximum yield of biodiesel. The overall results of these optimization studies reveal that proper selection of reaction parameters not only affects the yield, but also the properties of biodiesel fuel produced.
1.4 Commonly Used Optimization Techniques
1.4.1 Response Surface Methodology
Response surface methodology (RSM) is one of the popularly known statistical tools which is gaining much importance in the renewable energy sector for optimizing energy production processes. It is a combination of mathematical techniques used in optimization and approximation of real-life stochastic models. RSM was presented by Box and Wilson in the early 1950s, commonly addressed as Box-Wilson methodology. RSM applies statistical techniques based on the factorial design aspects of central composite design (CCD) and Box-Behnken design (BBD). Apart from determining the optimized conditions from the least experimental trials, RSM also provides the information to evaluate the results of the experiments in the view of designing a process [27]. Due to this positive aspect, RSM is widely employed in the biofuel production process for optimizing particular responses associated with several variables. The response variable can be mathematically expressed by Equation 1.2 where the response ‘y’ depends on independent variables x1 and x2 with an error of ‘e’.
In the recent optimization processes in the energy sector, both I and II order response surface models are utilized. The approximation of response of I order models are represented by a linear function having independent nature of variables. Equation 1.3 represents a simple I order model where β0, β1, and β2 are regression coefficients.
On the other hand, the functions with 2 variables can be approximate3d by the II order model which also considers all cross-product and quadratic terms along with I order interaction models. A typical II order model can be mathematically expressed as Equation 1.4:
Meanwhile, the analysis of variance (ANOVA) is inevitable to evaluate the significance of models proposed by RSM. The P-value in ANOVA results plays a vital role to identify the model significance. In biofuel research, RSM plays a significant role in the optimization of conditions for fuel synthesis and engine parameters for fuel utilization. The optimization of the biofuel production process is already discussed in the previous section, due to which the engine parameter optimization is discussed here. Generally, engine operating parameters such as compression ratio, injection timing, load, and biofuel concentration are the most commonly optimized input parameters that respect output parameters such as thermal efficiency, fuel consumption, and emissions. The desirability function determines the optimal parameter in the multi-objective optimization problem. A typical representation of optimal parameter estimation from a multi-response problem is given in Figure 1.9.
Baranitharan et al. [28] optimized the engine attributed of DI-diesel engine fueled with Aegle marmelos pyrolysis oil blends using RSM and ANN. The authors observed that both the compression ratio (CR) and engine load affected the performance and emission attributes of the engine to a greater extent. The value of average correlation coefficient (R=0.998) and coefficient of determination (R2=0.99) showed that the CR=17.5 and load=100% gave optimum engine operation for the selected fuel blend. Meanwhile, a similar engine study using Calophyllum inophyllum seed cake pyrolysis oil has been carried out by Sakthivel et al. [29]. In the research work, the authors optimized three different parameters, namely, CR, load, and biofuel concentration. The CR and load directly affect the performance of the engine, whereas biofuel concentration affects the emission to a greater extent. The optimized values are found to be CR=18, blend ratio 20%, and load =100%. The reduction in NOx at exhaust with an increase in blend ratio [30] is attributed to lower combustion temperature by the authors [31]. On the other hand, Narayanan et al. [32] optimized NOx emission by varying injection holes, biodiesel blends, and loads. The variation in holes may vary wall impingement effects thereby reducing NOx. The maximum composite desirability of 0.715 was observed for input conditions of 6 kg load, 20% blend and 6 nozzle holes for optimum engine operation.
Figure 1.9 Multi-response optimization results using RSM.
1.4.2 Genetic Algorithm
Genetic algorithm (GA) is one of the most widely used heuristic optimization techniques which mimics the natural evolution process by altering the population of an individual set of solutions required for a specific problem. GA operates on string structures that evolve with time using randomized but structured data exchange. The evolution takes place by the rule of survival of the fittest. Due to this, a new set of strings are generated for every new generation from the fittest old member sets. Some of the salient features of GA are given below:
GA does not work directly on parameters, instead, it works with the coding of the parameter set.
The search will be conducted from a population rather than a single point.
GA utilizes payoff information rather than derivates.
GA uses probabilistic transition rules.
GA is generally used for optimizing the parameters of a typical engineering system that is too complex to be solved by traditional methods. The advantage of GA comes from its capability to obtain information from previous solution sets and focused to enhance the performance of future solutions. GA works on selecting random individuals in the present population as parents and utilizes them to generate children for the next generation of solutions. By continuing the procedure, an optimal solution is attained since “good” parents create “good” children and then the bad points are rejected from the entire generation. Owing to the probabilistic approach, GA produces assorted solutions in different runs which leads to the requirement of multiple runs for deducing optimal solutions. The new population is usually generated by GA based on three important genetic operators, namely reproduction, crossover, and mutation.
The reproduction operator eliminates “bad” solutions from the population by duplicating the “good” solutions. Tournament and ranking selection are the two vital methods in reproduction operators. The prior one compared the two solutions and makes the best one survive, whereas the latter lists the entire population based on fitness values. Unlike reproduction, the crossover operator generates new solution sets by mating two parents to form a new child in a random mating pool. The “good” parent will always generate “good” children. The mutation operator is very much similar to the crossover operator in terms of generating a new population. The difference is that the new solutions will jump out from the local optimum. The optimization flow using GA is given in Figure 1.10.
Shirneshan et al. [33] optimized effects of biodiesel-ethanol blends in the operation of a diesel engine. The optimization is carried out using RSM and GA. The authors observed an increase in brake power by 30% with increased ethanol concentration in the blend. In the emission aspects, ethanol reduced smoke and NOx by 38% and 17%, respectively. The GA optimization results showed fuel blend (94.65%), speed (2800 RPM), and load (65.75%) as optimal conditions. Singh et al. [34] employed adaptive neuro-fuzzy interference system (ANFIS) along with ANFIS – GA method to optimize the engine operation fueled with Kusum biodiesel. Input variables such as FIP, FIT, blend, and load are optimized based on the engine performance and emission response. The results obtained from both the techniques were on par with each other. The ANFIS-GA method showed a more precise prediction of engine parameters as compared to ANFIS alone. The dual fuel combustion of diesel/gasoline in a CI engine was optimized by Xu et al. using computational fluid dynamics (CFD) and GA. The authors took seven inevitable operating parameters and optimized them in terms of fuel efficiency, NOx, and soot emissions. GA showed that about 45% of indicated thermal efficiency can be achieved by maintaining the emissions under Euro 6 level during the prescribed operating conditions [35]. Liu et al. [36] optimized operating parameters of a diesel engine fueled with natural gas in dual fuel mode using GA. The optimization objectives selected in the study are ISFC, NOx, and methane emissions. From the results, it was observed that all the solutions meet soot limitations provided by Euro 6, whereas partial solution sets satisfied the NOx norms laid by Euro 5.
Figure 1.10 Optimization process using GA.
1.5 Application of Biofuels in Transportation Sector
1.5.1 Automobile Sector
As the demand for automobiles is constantly increasing, there is a huge threat of an increase of greenhouse gases accompanying it. Biofuels have a very promising application in the automobile sector. Using biofuels is not a new idea; in the 1990s ethanol was launched by blending it with conventional gasoline in two different concentrations, 10% and 85%, named E10 and E85 respectively. Interestingly, the Ford Model T (1908) was designed to run a mixture of gasoline and low level ethanol. Due to the increase of concern towards greenhouse gases, the prominence of the usage of biofuels has seen an exponential growth in the transportation sector. First-world countries already assessed their policies, costs, and outcomes for the usage of biofuels. Biofuel production has also been increasing constantly over the period. Biofuels can either be blended with fossil fuels for lower emissions or replace conventional fuels. Brazil, the European Union, and Nigeria are some examples of countries that made biofuels blending mandatory. Figure 1.11
