Volume 2: Feedstock-based Biodiesel Fuels

There are four primary research fronts in this section: ‘edible oil-based biodiesel fuels’, ‘nonedible oil-based biodiesel fuels’, ‘waste oil-based biodiesel fuels’, and ‘algal oil-based biodiesel fuels’ with five, four, four, and seven book chapters, respectively.

V: Edible Oil-based Biodiesel Fuels

Chapter 21 (Konur, 2021o) maps the research on ‘edible oil-based biodiesel fuels’ using a scientometric method using the 100 most-cited sample papers and 2,650 population papers. There are two major topical research fronts for these sample papers: ‘edible oil-based biodiesel fuel production" and ‘properties and characterization of edible oil-based biodiesel fuels’ (Table 21.8). There are nine research fronts for the edible oils used for biodiesel production. The most prolific research front is ‘soybean oil-based biodiesel fuels’ with 32 sample papers. This top research front is followed by ‘palm oil-based biodiesel fuels’, ‘rapeseed oil-based biodiesel fuels’, and ‘sunflower oil-based biodiesel fuels’ with 19, 16, and 16 sample papers, respectively. These top four research fronts form 83% of the sample papers in total.

Chapter 22 (Westbrook, 2021) provides an overview of the research on the chemistry of ‘soybean oil-based biodiesel fuels’. He shows that the presence of only five unique methyl ester molecules in a biodiesel fuel is a major simplifying factor in understanding and using detailed chemical kinetic modeling to describe its combustion. He next shows that the number and location of C=C double bonds in these component molecules is a dominant factor in distinguishing soy biodiesel fuel from biodiesel fuels produced from other vegetable oils and for predicting the combustion properties of soybean oil diesel fuel. He finally shows that the monosaturated component of soybean oil, methyl oleate, has an optimal structure as a diesel fuel in terms of minimizing pollutant emissions, maximizing the diesel cetane number of the fuel, and limiting fuel thermal stability.

Chapter 23 (Konur, 202Ip) presents the key findings of the most-cited 25 article papers on ‘palm oil-based biodiesel fuels’. Table 23.1 provides information on the research fronts in this field. As this table shows, the primary research fronts of ‘production of palm oil-based biodiesel fuels’ and ‘properties of palm oil-based biodiesel fuels’ comprise 64 and 44% of these papers, respectively. In the first group of papers, ‘production of crude palm oil-based biodiesel fuels’, ‘production of palm kernel oil-based biodiesel fuels’, and ‘production of waste palm oil-based biodiesel fuels’ form 44, 12, and 8% of these papers, respectively.

Chapter 24 (Konur, 202Iq) presents the key findings of the most-cited 25 article papers on ‘rapeseed oil-based biodiesel fuels’. Table 24.1 provides information on the research fronts in this field. As this table shows the primary research fronts of ‘production of rapeseed oil-based biodiesel fuels’ and ‘properties of rapeseed oilbased biodiesel fuels’ comprise 72 and 28% of these papers, respectively.

VI: Nonedible Oil-based Biodiesel Fuels

There are four chapters in this section. Chapter 25 (Konur. 2021 r) maps the research on ‘nonedible oil-based biodiesel fuels’ using a scientometric method. There are two major topical research fronts for these sample papers: ‘nonedible oil-based biodiesel fuel production’ and ‘properties and characterization of nonedible oil-based biodiesel fuels’ (Table 25.8). There are nine research fronts for the nonedible oils used for biodiesel production. The most-prolific research front is ‘Jatropha oil-based biodiesel fuels’ with 49 sample papers. This top research front is followed by ‘karanja oilbased biodiesel fuels’ and ‘nonedible oil-based biodiesel fuels’ in general, with 16 sample papers each. These top three research fronts form 91% of the sample papers in total.

The other prolific research fronts are ‘castor oil-based biodiesel fuels’, ‘mahua oil-based biodiesel fuels’, ‘polanga oil-based biodiesel fuels’, ‘tobacco oil-basedbiodiesel fuels’, ‘rubber oil-based biodiesel fuels’, and ‘other nonedible oil-based biodiesel fuels’ with five, five, four, four, three, and fourteen sample papers, respectively.

Chapter 26 (Banapurmath et al., 2021) presents and discusses the research on the use of ‘Jatropha oil-based biodiesel fuels’ for modern diesel engine applications. They focus on the approaches to nanofluid preparation using ultrasonic probes and bath sonication methods, the stability improvement of nanofluids by the addition of surfactants, numerous characterization techniques to estimate the nanoparticle shape and size, dispersion stability, and the chemical bonding of nanoadditives in liquid fuel. Jatropha oil was subsequently converted into its biodiesel called ‘Jatropha oil methyl ester’ (JOME) and blended with diesel to obtain its B20 blend. Further improvement in fuel properties of the B20 blend was realized with the addition of graphene as a fuel additive with the varying doses of 15, 20, and 30 mg respectively. Accordingly, JOMEB20Gr20 represents a B20 blend of JOME with a 20 mg dosage of graphene nanoparticles. The stability of the nanoadditive fuel blends resulted in their improved thermophysical properties. Further, their use in high-pressure-assisted ‘common rail diesel injection' (CRDI) diesel engines resulted in a higher heat transfer rate and higher in-cylinder pressures, while ‘brake thermal efficiency’ (BTE) increased and ‘brake specific fuel consumption' (BSFC) reduced, with the exhaust emissions of carbon monoxide, unburned hydrocarbons, and nitrogen oxide decreasing, depending on the dosage of graphene in the fuel.

Chapter 27 (Dandu et al., 2021) reviews the research on the effects of additives with ‘Calophyllum inophyllum methyl ester’ (CIME) in CI engine applications. Calophylluni inophyllum have several advantages including abundant availability in nature and comprising superior properties with a modest extraction process. The application of CIME and their blends in diesel engines are reported to have better characteristics in all respects of the engine as compared to that of base diesel fuel. In order to enhance the properties of the CIME fuel, various additives are identified and added to achieve improved characteristics of the engine. The additives generally suitable for CIME blends are oxygenated additives like ethers, alcohols, and nanoparticles. All the experimental results projected slightly poor performance and better emission behaviors due to the reduction in net heat content. CIME fuel performance was highly improved on a par with the BTE of diesel fuel. On the other hand, the general drawback of CIME fuel, namely NOX emission, is easily eradicated by the addition of more alcohols.

Chapter 28 (Niju and Janani, 2021) reviews the research on the Moringa oleifera oil as a potential feedstock for sustainable biodiesel production. Moringa oleifera, with a high cetane number, appreciable oxidation stability, and a low iodine value, along with wide availability, confers the potential to utilize it for biodiesel production. Though the pour point, cloud point, and ‘cold filter plugging point’ (CFPP) are higher, it is possible to reduce them appreciably with a ternary blend of diesel, bioethanol, and biodiesel; ultrasonication-mediated esterification has been experimentally proven to be a cutting edge technology that reduces the acid value from 81.5 mg KOH/g of oil to 2.78 mg KOH/g of oil with a volumetric ratio of 0.6:1 methanol to Moringa oleifera oil and a 1.5 vol% of concentrated H2SO4 for 40 min at 60°C.

VII: Waste Oil-based Biodiesel Fuels

There are four chapters in this section. Chapter 29 (Konur. 2021s) maps the research on ‘waste oil-based biodiesel fuels’ using a scientometric method through the use of the 100-most-cited sample papers and 2,150 population papers.

There are two major topical research fronts for these sample papers: ‘waste oilbased biodiesel fuel production’ and ‘properties and characterization of waste oilbased biodiesel fuels’ (Table 29.8). There are three primary research fronts for the waste oils used for biodiesel production. The most-prolific research front is ‘waste oil-based biodiesel fuels’. This top research front is follow'ed by ‘animal fat-based biodiesel fuels’ and ‘other waste oil-based biodiesel fuels’.

Chapter 30 (Siddique and Rohani, 2021) reviews the research on biodiesel production from ‘municipal wastewater sludge’ (MWWS). Biodiesel production from MWWS is a promising alternative to reduce biodiesel production cost, to meet growing future energy demand, and to facilitate waste management for increasing sludge generation. Although MWWS is readily available free of cost, biodiesel production from it involves challenges in processing the sludge, extracting lipid, and producing biodiesel. However, there is significant progress being made in sludge processing, lipid extraction, and biodiesel production processes. The use of oleaginous substances to cultivate the secondary sludge along with the use of an ultrasonic technique would offer a promising improvement towards biodiesel production from MWWS. A mixture of polar and nonpolar solvents, especially hexane or chloroform and methanol, can greatly enhance lipid extraction efficiency and biodiesel yield. It is important to scale up biodiesel production and characterize the biodiesel produced following ‘American Society for Testing and Materials’ (ASTM) standards.

Chapter 31 (Castanheiro, 2021 ) reviews the research on heterogeneous acid catalysts for biodiesel production from ‘waste cooking oils’ (WCO). Biodiesel production is performed using homogeneous catalysts, which can cause some problems such as difficulty in removing the catalyst from the reaction mixture and possibility to soap production and corrosion. The use of heterogeneous catalysts can overcome these problems. Different heterogenous acid catalysts (zeolites, heteropolyacids, metal oxides, materials with sulfonic acid groups) have been employed in biodiesel production from waste cooking oil.

Chapter 32 (Satyannarayana et al., 2021) reviews the research on ‘microbial biodiesel fuel production’ using microbes such as algae, fungi, and yeasts. These feedstocks have their own advantages and disadvantages that are discussed in detail in this chapter. The selection of microbial species depends on the type of feedstock used and their culture conditions. These microbial sources promise effective biodiesel production in less time and the use of biodiesel which leads to a safer environment. The chapter also focuses on the methods to accumulate high lipids and lipid extraction techniques. Further, selection and analysis of various essential biodiesel parameters like pH, salinity, temperature, and feedstock are discussed. However, there is much scope for future research on the optimization of these parameters for obtaining high-quality biodiesel.

VIII: Algal Oil-based Biodiesel Fuels

There are seven chapters in this section. They include a scientometric review of the research on ‘algal oil-based biodiesel fuels’, ‘algal biomass production for biodiesel production’, ‘algal biomass production in wastewater for biodiesel production’, ‘algal lipid production for biodiesel production’, ‘biooil production from microalgae’, ‘extraction of algal neutral lipids for biofuel production', and ‘microalgal biodiesel production’.

Chapter 33 (Konur, 20211) maps the research on ‘algal biomass’, ‘algal biooils’, and ‘algal oil-based biodiesel fuels’ using a scientometric method through the use of the 100-most-cited sample papers and over 15,000 population papers.

There are three major research fronts for these sample papers: ‘algal biomass production’, ‘algal biooil production’, and ‘algal biodiesel production’ (Table 33.8). There are three research subfronts for the top research front: ‘algal biomass production in general’, ‘algal biomass production and nutrient removal in wastewaters’, and ‘CO, bioremediation by algal biomass’, with 48,14, and 7 sample papers, respectively.

There are six research subfronts for ‘algal biooil production': ‘algal lipid production in general’, ‘algal lipid production in wastewater’, ‘algal biomass pyrolysis’, ‘algal biomass liquefaction’, ‘algal lipid extraction', and ‘algal lipid characterization’.

Chapter 34 (Konur, 202lu) reviews the research on ‘algal biomass production for biodiesel production’. This chapter presents the key findings of the 25-most-cited article papers, in five pragmatically distinct research streams in this field.

These prolific studies provide valuable evidence on cultivation engineering in general, cultivation engineering in wastewater and nutrient removal, cultivation engineering and CO, bioremediation, life-cycle analysis of algal biomass production, and techno-economic studies of algal biomass production. There are also two more distinct research fields: photobioreactors and cell biology, and omics studies of algal biomass production, although there are no papers for these research streams in the table of the top 25 papers.

All these research streams contribute significantly towards improving algal biomass productivity, mostly in microalgae. It is apparent that it is highly desirable to enhance both biomass productivity and lipid productivity such as through the use of a two-phase cultivation strategy where, first, biomass growth is ensured in a nutrient (N, P) replete mode and then followed by a nutrient-deficient phase.

It is then apparent that the use of wastewater and flue gases is of critical importance to reduce the production costs as well as to reduce the adverse environmental impact of algal biomass production. It is also apparent that the studies on omics and cell biology studies complement the primary cultivation processes by providing valuable tools to understand and assess them.

The ecological, techno-economic, and environmental benefits from using wastewater for these purposes are significant. The use of wastewater would make biodiesel production more competitive in relation to petrodiesel fuels in reducing the feedstock costs and reducing environmental burdens significantly.

It would also help with the treatment of wastewater. Another beneficial effect of using wastewater for algal biomass accumulation and nutrient removal would be the lessening of the volume and harmful effects of algal blooms, which have created a significant ecological disaster in recent years.

The production of algal biodiesel fuels in competition with petrodiesel fuels would also help in shifting biodiesel production from edible-oil-based biodiesel fuels, which has been associated with public concern over ‘food security’ and the destruction of forests for the expansion of palm oil plantations, the destruction of ecological biodiversity, the significant increase in CO, emissions, and finally, the exploitation of local communities.

Chapter 35 (Konur, 202 Iv) presents the key findings of the 25-most-cited article papers in ‘algal biomass production in wastewater for biodiesel production’. These prolific studies provide valuable evidence on algal biomass production and nutrient removal from wastewater by algae as well as lipid production and biodiesel production.

Chapter 36 (Konur, 2021 x) reviews the research on algal lipid production for biodiesel production. This chapter presents the key findings of the 25-most-cited article papers, in five pragmatically distinct research streams in this field. These studies provide valuable evidence on cultivation engineering in general, cultivation engineering in wastewater and nutrient removal, cultivation engineering and CO, bioremediation, algal lipid analysis and imaging, and omics and cell biology studies in lipid production.

All these research streams contribute significantly towards improving lipid content and productivity in algae, mostly high-lipid microalgae. It is apparent that it is highly desirable to enhance both biomass productivity and lipid productivity, such as through the use of a two-phase cultivation strategy w'here, first, biomass growth is ensured in a nutrient (N, P) sufficient mode and then follow'ed by a nutrient-deficient phase.

Chapter 37 (Koley et al., 2021) reviews the research on biooil production from microalgae through the hydrothermal liquefaction of algal biomass. The direct conversion of biomass to biocrude could be a viable solution. Alongside this, it enables the biooil produced to meet the characteristics of petrocrude, and to be refined in established petroleum refineries. To further enhance the economics of biofuel production, the by-products of direct conversion, i.e. the aqueous phase and biochar, are rich in nutrients and can be used as fertilizers. Biooil production can also be helpful if simultaneous production of biodiesel and biocrude is carried out from the same biomass. The defatted biomass following the extraction of lipid can be again subjected to hydrothermal liquefaction for the production of biocrude. Nevertheless, there is enough space to fill the gaps and improve the economics of biooil production from microalgal biomass for obtaining a sustainable substitute to fossil fuels.

Chapter 38 (Krishnan et al., 2021) provides an overview of the diverse conventional and advanced extraction methods used as efficient approaches for lipid extraction from algae for biofuel production. Lipids represent a major algal biochemical with an extensive range of applications, including biodiesel synthesis. Biodiesel constitutes ‘fatty acid methyl esters’ (FAMEs) from the transesterification of lipids. Among algal lipids, neutral or true lipids such as triacylglycerides are important for generating high quality and stable biodiesel fuel with enhanced calorific value. New and improved physicochemical lipid extraction methods are highly critical for enabling the selective generation of true lipids from algal biomass. The authors, finally, discuss the impact of nanotechnology on enhanced lipid extraction.

Chapter 39 (Sivaramakrishnan and Incharoensakdi, 2021) provides an overview of the research on algal biodiesel fuel production. Microalgae have a high growth rate and a high lipid content. Moreover, microalgal biodiesel production is less energy intensive and economically feasible. However, the commercialization of microalgal biodiesel production is still confronted with numerous challenges in practice. The selection of microalgae is very important for achieving high biomass and lipid yield. A microalgal cultivation system is one of the crucial factors to achieve sustainable microalgal production, which can undoubtedly affect the biomass and lipid yield. The authors focus on the lipid extraction and biodiesel production methods. The discussion and suggestions based on the findings could be well described as a roadmap for acquiring knowledge amendable for microalgal biodiesel production and future microalgal biodiesel development.

 
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