Biodiesel at the Crossroads: A Critical Review

The delay in the energy transition, focused in the replacement of fossil diesel with biodiesel, is mainly caused by the need of reducing the costs associated to the transesterification reaction of vegetable oils with methanol. This reaction, on an industrial scale, presents several problems associated with the glycerol generated during the process. The costs to eliminate this glycerol have to be added to the implicit cost of using seed oil as raw material. Recently, several alternative methods to convert vegetable oils into high quality diesel fuels, which avoid the glycerol generation, are being under development, such as Gliperol, DMC-Biod, or Ecodiesel. Besides, there are renewable diesel fuels known as “green diesel”, obtained by several catalytic processes (cracking or pyrolysis, hydrodeoxygenation and hydrotreating) of vegetable oils and which exhibit a lot of similarities with fossil fuels. Likewise, it has also been addressed as a novel strategy, the use of straight vegetable oils in blends with various plant-based sources such as alcohols, vegetable oils, and several organic compounds that are renewable and biodegradable. These plant-based sources are capable of achieving the effective reduction of the viscosity of the blends, allowing their use in combustion ignition engines. The aim of this review is to evaluate the real possibilities that conventional biodiesel has in order to success as the main biofuel for the energy transition, as well as the use of alternative biofuels that can take part in the energy transition in a successful way

Processing of Soybean Oil into Fuels

Abundant and easily refined, petroleum has provided high energy density liquid fuels for a century. However, recent price fluctuations, shortages, and concerns over the long term supply and greenhouse gas emissions have encouraged the development of alternatives to petroleum for liquid transportation fuels (Van Gerpen, Shanks et al. 2004). Plant-based fuels include short chain alcohols, now blended with gasoline, and biodiesels, commonly derived from seed oils. Of plant-derived diesel feedstocks, soybeans yield the most of oil by weight, up to 20% (Mushrush, Willauer et al. 2009), and so have become the primary source of biomass-derived diesel in the United States and Brazil (Lin, Cunshan et al. 2011). Worldwide ester biodiesel production reached over 11,000,000 tons per year in 2008 (Emerging Markets 2008). However, soybean oil cannot be burned directly in modern compression ignition vehicle engines as a direct replacement for diesel fuel because of its physical properties that can lead to clogging of the engine fuel line and problems in the fuel injectors, such as: high viscosity, high flash point, high pour point, high cloud point (where the fuel begins to gel), and high density (Peterson, Cook et al. 2001). Industrial production of biodiesel from oil of low fatty-acid content often follows homogeneous base-catalyzed transesterification, a sequential reaction of the parent triglyceride with an alcohol, usually methanol, into methyl ester and glycerol products. The conversion of the triglyceride to esterified fatty acids improves the characteristics of the fuel, allowing its introduction into a standard compression engine without giving rise to serious issues with flow or combustion. Commercially available biodiesel, a product of the transesterification of fats and oils, can also be blended with standard diesel fuel up to a maximum of 20 vol.%. In the laboratory, the fuel characteristics of unreacted soybean oil have also been improved by dilution with petroleum based fuels, or by aerating and formation of microemulsions. However, it is the chemical conversion of the oil to fuel that has been the area of most interest. The topic has been reviewed extensively (Van Gerpen, Shanks et al. 2004), so this aspect will be the focus in this chapter. Important aspects of the chemistry of conversion of oil into diesel fuel remain the same no matter the composition of the triglyceride. Hence, although the focus in this book is on soybean oil, studies on other plant based oils and simulated oils have occasional mention in this chapter. Valuable data can be taken on systems that are simpler than soybean based oils, with fewer or shorter chain components. Sometimes the triglycerides will behave differently under reaction conditions, and when relevant, these have been noted in the text. Although the price of diesel fuel has increased, economical production of biodiesel is a challenge because of (1) the increasing price of soybean oil feedstocks and reagent methanol, (2) a distributed supply of feedstocks that reduces the potential for economies of scale, (3) processing conditions that include pressures and temperatures above ambient, and (4) multiple processing steps needed to reduce contaminant levels to ASTM specification D6751 limits (Vasudevan & Briggs 2008). Much of the cost of biodiesel production is related to the conversion of the oil to the methyl ester and so there has been an emphasis to research improved methods of converting soybean oil to biodiesel. However, most of these studies have taken place at the bench scale, and have not demonstrated a marked improvement in yield or reduced oil-to-methanol ratio in comparison with standard base-catalyzed transesterification. One aspect that has a short term chance of implementation is the improvement of the conversion process by the use of a continuous rather than batch process, with energy savings generated by combined reaction and separation, online analysis, and reagent methanol added by titration as needed to produce ASTM specification grade fuel. By adapting process intensification methods, recycled sources of soybean oil may also be used for diesel production, taking advantage of a lower priced feedstock material. Even if the economics of production are feasible, biodiesel distribution is complicated by thermal stability and degradation over time, and the physical properties of methyl esters make them undesirable for standard compression ignition engines in concentrations greater than 20% in a blend with diesel fuel. Generation of truly fungible fuel from biomass is now being investigated through a variety of routes. However, it is too early to judge which will become the most viable. The promise of soybean-generated biodiesel is that of a truly fungible, thermodynamically and economically viable technology bringing a biomass replacement to a petroleum product

The Production of Green Diesel Rich Pentadecane (C15) from Catalytic Hydrodeoxygenation of Waste Cooking Oil using Ni/Al2O3-ZrO2 and Ni/SiO2-ZrO2

Hydrodeoxygenation (HDO) is applied in fuel processing technology to convert bio-oils to green diesel with metal-based catalysts. The major challenges to this process are feedstock, catalyst preparation, and the production of oxygen-free diesel fuel. In this study, we aimed to synthesize Ni catalysts supported on silica-zirconia and alumina-zirconia binary oxides and evaluated their catalytic activity for waste cooking oil (WCO) hydrodeoxygenation to green diesel. Ni/Al2O3-ZrO2 and Ni/SiO2-ZrO2 were synthesized by wet-impregnation and hydrodeoxygenation of WCO was done using a modified batch reactor. The catalysts were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDS), and N2 isotherm adsorption-desorption analysis. Gas chromatography - mass spectrometry (GC-MS) analysis showed the formation of hydrocarbon framework n-C15 generated from the use of Ni/Al2O3-ZrO2 with the selectivity of 68.97% after a 2 h reaction. Prolonged reaction into 4 h, decreased the selectivity to 58.69%. Ni/SiO2-ZrO2 catalyst at 2 h showed selectivity of 55.39% to n-C15. Conversely, it was observed that the reaction for 4 h increased selectivity to 65.13%. Overall, Ni/Al2O3-ZrO2 and Ni/SiO2-ZrO2 catalysts produced oxygen-free green diesel range (n-C14-C18) enriched with n-C15 hydrocarbon. Reaction time influenced the selectivity to n-C15 hydrocarbon. Both catalysts showed promising hydrodeoxygenation activity via the hydrodecarboxylation pathway. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Development of Biodiesel Production Processes from Various Vegetable Oils

Biodiesel is an alternative fuel to petroleum diesel that is renewable and creates less harmful emissions than conventional diesel thus the use of this fuel is a shift toward “sustainable energy”. Biodiesel can be produced from vegetable oil, animal fat, and organisms such as algae or cyanobacteria. Since vegetable oils are the major source for current commercial biodiesel, they are the focus of this thesis. The main objective of this Ph.D. research is to develop processes suitable to produce biodiesel from various vegetable oils especially for those of non-edible oils such as used cooking oil, canola oil from greenseed, and mustard oil. An additional objective is to understand the relationship between the parent vegetable oils and the corresponding biodiesel properties. Used cooking oil was the first vegetable oil investigated in this research. Initially, oil degradation behavior was monitored closely during frying. During 72 hours of frying, acid value and viscosity of the oil increased from 0.2 to 1.5 mgKOH•g-1 and from 38.2 to 50.6 cP, respectively. It was found that ester yield was improved by addition of canola oil to used cooking oil, i.e. addition of 20% canola oil to used cooking oil increased methyl ester yield and ethyl ester yield by 0.5% and 12.2%, respectively. At least 60% canola oil addition is needed to produce ASTM grade ethyl ester biodiesel. The optimum reaction conditions to produce biodiesel are 1% KOH loading, 6:1 alcohol to oil ratio, 600 rpm stirring speed, and either 50°C reaction temperature for 2 hr or 60°C reaction temperature for 1.5 hr for methanolysis and 60°C reaction temperature for 2 hr for ethanolysis. Among non-edible vegetable oils, greenseed canola oil can be used in the most simple biodiesel production process. In this case, an addition of fresh vegetable oil is not required, because chlorophyll contained in this oil did not play a crucial role in the reaction activity. Methyl ester yields derived from greenseed canola oil without and with 94.1 ppm chlorophyll content are 95.7% and 94.8%, respectively. In contrast, erucic acid contained in mustard oil created difficulties in the production process. Ester yield derived from mustard oil using the conditions mentioned above was only 66% due to the present of unconverted monoglyceride. To obtain a deeper understanding on mustard oil transesterification, its reaction kinetics was studied. In the kinetic study, transesterification kinetics of palm oil was also investigated to study the effect of fatty acid chain length and degree of saturation on the rates of the reactions. It is shown in this research that the rates of mustard monoglyceride transesterification (rate constant = 0.2-0.6 L•mol-1•min-1) were slower that those of palm monoglyceride transesterification (rate constant = 1.2-4.2 L•mol-1•min-1) due to its lower molecular polarity resulting from the longer chain of erucic acid. The activation energy of the rate determining step (in this case, conversion of triglyceride to diglyceride reaction step) of mustard transesterification was, however, 26.8 kJ•mol-1, which is similar to those of other vegetable oils as reported in literature. Despite the presence of unconverted monoglyceride, distillation can be used to obtain a high purity ester. Several ester properties are determined by characteristics of the parent oil and choice of alcohol used in transesterification. Chlorophyll contained in greenseed canola oil, for example, has an adverse effect on biodiesel oxidative stability. The induction time for methyl ester derived from treated greenseed canola oil (pigment content = 1 ppm) was enhanced by 12 minutes compared to that derived from crude greenseed canola oil (pigment content = 34 ppm). The optimum bleaching process involves the use of 7.5 wt.% montmorillonite K10 at 60°C and stirring speed of 600 rpm for 30 minutes. In addition, it was found that induction time of treated greenseed canola ethyl ester (1.8 hr) was higher than that of methyl ester (0.7 hr), which suggests a better oxidative stability of esters of higher alcohols. Furthermore, the use of higher alcohols instead of methanol produced materials with improved low temperature properties. For example, the crystallization temperatures of monounsaturated methyl, ethyl, propyl, and butyl esters prepared from mustard oil were -42.5°C, -51.0°C, -51.9°C, and -58.2°C, respectively. In contrast, the lubricity of biodiesel is mainly provided by its functional group which is COOCH3 for methyl ester. The use of higher alcohols in transesterification results in a less polar functional group in the corresponding ester molecule, which leads to reduction in ester lubricity. Methyl ester provided the highest lubricity among all esters produced, i.e. wear reduction at 1% treat rate of methyl ester, ethyl ester, propyl ester, and butyl ester are 43.7%, 23.2%, 30.7% and 30.2%, respectively. The outcomes of this research have been published in several scientific journals and presented at national and international conferences. The published articles and conference presentations are listed at the beginning of each chapter in this thesis

Optimization of Biodiesel and Biofuel Process

Although the compression ignition (C.I.) engine, invented by Rudolf Diesel, was originally intended to work with pure vegetable oils as fuel, more than a century ago, it was adapted to be used with a fuel of fossil origin, obtained from oil. Therefore, there would be no technical difficulties in returning to the primitive design of using biofuels of renewable origin, such as vegetable oils. The main drawback is found in the one billion C.I. engines which are currently in use, which would have to undergo a modification in the injection system in order to adapt them to the higher viscosity of vegetable oils in comparison to that of fossil fuels. Thus, the gradual incorporation of biofuels as substitutes of fossil fuels is mandatory

Catalytic Transfer Hydrogenation Reactions of Lipids

Catalytic transfer hydrogenation (CTH) of lipids was investigated using 2-propanol as hydrogen donor for producing liquid hydrocarbons, e.g. jet fuels. The main sources of lipids selected in this study were waste cooking oil (WCO) and oil-laden algae-derived biofuel intermediate (BI). Two different catalysts were employed in this study, namely activated carbon and trimetallic-doped zeolite. The CTH reaction was between WCO and 2-propanol in a continuous flow reactor over a packed-bed activated carbon at near atmospheric pressure. Results revealed a high level of alkenes and aromatics compounds, which are not stable and are not environmentally unfriendly. To reduce these compounds in the liquid fuel, trimetallic catalyst was prepared and the reaction was by optimizing the reaction variables (temperature, pressure, weight hourly space velocity, and oil-2-propanol ratio). Results from the second study were better than that of the first, as the level of aromatics and alkenes was lower in the second study. However, the amount of branched and cyclo-alkanes (high octane rating compounds) was insignificant. Lipids from algae-derived oil-laden BI were extracted by 2-propanol and without evaporation of alcohol; the pregnant 2-propanol was subjected to CTH over the prepared trimetallic catalyst in a batch reactor. The liquid fuel product from this third study produced significant branched and cyclo-alkanes (serendipity). Finally, technoeconomic analysis (TEA) and life cycle assessment (LCA) of CTH reaction were conducted. The results were compared, with a conventional hydroprocessed renewable jet fuels (HRJ) process. Results showed that the economic performance of CTH was lower than that of HRJ, due to the large volume of 2-propanol employed in the CTH. However, the environmental performance of CTH was very impressive, compared to that of HRJ. Chapter 1 of this study describes the rationale for selecting WCO and 2-propanol as the potential hydrogen donor. In Chapter 2, 2-propanol was used the react with waste cooking oil by considering four reaction parameters: temperature, oil flow rate, WHSV, and pressure. Finally, the kinetics of the reaction were ascertained, in order to estimate reaction order, activation energy, and kinetic rate constant. Chapter 3 employed commercial catalyst doped with transition metals which catalyzed the reaction between waste cooking oil and 2-propanol. Optimization of the reaction was studied by varying temperature, WHSV, pressure, and oil-2-propanol ratio. The percent of transition metal employed remained constant. Chapter 4, on the other hand, explored the possibility of using oil-laden biofuel intermediate from flash hydrolyzed algae. The purpose was to utilize 2-propanol as oil extract and hydrogen donor in CTH reaction of the oil. Finally, Chapter 5 thoroughly discussed the technoeconomic and environmental performance of the CTH reaction of waste cooking oil and 2-propanol

A comprehensive review on biofuels from oil palm empty bunch (Efb): current status, potential, barriers and way forward

Biomass is an important renewable energy resource which primarily contributes to heating and cooling end use sectors. It is also a promising alternative source of biofuels to replace the depleting supply of fossil fuels. Surprisingly, few writers have been able to draw on the feedstock significance for oil palm empty fruit bunch (EFB) as the biomass resource for biofuels compared to the other types of biomass waste. Therefore, this paper presents a comprehensive review of EFB as a biomass resource presented in four major parts. First, the introduction covers the demand for bio-oil and describes the different kinds of feedstock, the relevance and potential of EFB biomass. Sec-ond, the characteristics of biomass are explained before it is upgraded as biofuel, drawing similarities and contrasts between EFB and other sources of biomass. Pyrolysis processes and reactors used for EFB conversion are described, and the factors affecting the bio-oil yield and quality are dis-cussed. Major reactor parameters are summarized and reactor optimization is discussed. Third, comparison on the properties of the bio-oil vs. petroleum in transportation, power generation, and heating are compared followed by prioritizing the bio-oil properties from the most to least critical, revealing the most promising methods for upgrading. Fourth, the environmental impact, including CO2 emission, of the use of EFB as a promising renewable energy resource and a cleaner alternative fuel is recommended. This paper has comprehensively reviewed the conversion of oil palm empty fruit bunches into biofuels, including the similarities and differences between biomasses, the best reactors, its comparison with fossil fuels, and bio-oil upgrading methods. The upgrading mapping matrix is created to present the best upgrading strategies for the optimum quality of biofuels. This paper serves as a one-stop center for EFB conversion into biofuels

Biomass Processing for Biofuels, Bioenergy and Chemicals

Biomass can be used to produce renewable electricity, thermal energy, transportation fuels (biofuels), and high-value functional chemicals. As an energy source, biomass can be used either directly via combustion to produce heat or indirectly after it is converted to one of many forms of bioenergy and biofuel via thermochemical or biochemical pathways. The conversion of biomass can be achieved using various advanced methods, which are broadly classified into thermochemical conversion, biochemical conversion, electrochemical conversion, and so on. Advanced development technologies and processes are able to convert biomass into alternative energy sources in solid (e.g., charcoal, biochar, and RDF), liquid (biodiesel, algae biofuel, bioethanol, and pyrolysis and liquefaction bio-oils), and gaseous (e.g., biogas, syngas, and biohydrogen) forms. Because of the merits of biomass energy for environmental sustainability, biofuel and bioenergy technologies play a crucial role in renewable energy development and the replacement of chemicals by highly functional biomass. This book provides a comprehensive overview and in-depth technical research addressing recent progress in biomass conversion processes. It also covers studies on advanced techniques and methods for bioenergy and biofuel production

Biodyzelino ir vandenilio bendro degimo proceso slėginio uždegimo variklyje tyrimas

Increasing environmental pollution, concerns about oil price, traffic related health effects and depletion of fossil fuel resources are forcing humanity to limit the consumption or to look for new forms of energy. The cleanest power suitable for the road trans-port would be the electric energy produced of the clean sources such as solar, hydro, wind power and stored in batteries or extracted from hydrogen using fuel cell technology. However, the limitted range of driven distance are the obstacle for today battery electric cars. The lack of hydrogen fuelling stations, high price of hydrogen and expensive materials, limits the outbreake of the fuel cell technology. According to experts, hybrid systems including both electric and internal combustion engines consuming the renewable fuels would be the main power plant of vehicles decreasing the exhaust emissions of the internal combustion engine remains the important research subject for the time beeing. This dissertation work presents the study of performance, efficiency and ecological indicators of the co-combustion process of hydrogen with various renewable biomass based biofuels and their blends in the compression ignition engine. Experimental investigation and numerical simulation methods were applied in order to have a complex understanding of biodiesel fuels and influence of hydrogen on the engine work cycle. Introductory chapter presents the formulation of the problem, object and importance of the thesis, aim and the tasks of the work. The scientific novelty, theoretical and practical value of results obtained during experiments, and the list of published scientific publications by the author are presented. The scientific literature according to the theme of the thesis overviewed in the first chapter. The composition of biomass based biofuels with transestherification and hydrotreatening processes, heating values of the fuel and other features were reviewed according to other scientist’s works. The influence of the main parameters on CI engine efficiency and emission parameters were discussed. The second chapter represents the set-up of engines used at experiment, its methodology, calculations of heating values of the fuel mixtures used in experiment, calculations of hydrogen energy share according to the biodiesel flow rate, calculation of mass fraction burned, theoretical analysis of the rate of heat release, numerical simulation of performed experiments are discussed. The results of experiments obtained during tests of biodiesel and hydrogen fuel mixtures, numerical analysis and simulation of mentioned fuel mixtures presented in the third chapter. Research of various hydrogen energy share revealed that, higher engine efficiency and lower exhaust gas emissions in CI engine can be achieved. 11 scientific papers focused on the subject of the doctoral thesis have been published: 2 – in publications of the Clarivate Analytics Web of Science database with citation index; 1 – in Conference Proceedings publications of the Clarivate Analytics Web of Science database; 5 – in publications of other international database; 3 – in publications of other reviewable scientific publications.Dissertatio