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This literature review discusses several aspects of biodiesel production from microalgae. This paper elucidates the optimal bioenvironmental conditions for microalgae cultivation, process design of algal biodiesel production, physicochemical properties of lipids extracted from microalgae and the properties of the produced biodiesel fuel, and the transesterification process. On the other hand, this paper illustrates the designs of up-to-date full-scale and lab-scale photobioreactors (PBRs). Furthermore, this paper argues different bioengineering aspects of biodiesel production from microalgae. Eventually, the measurements, calculations, design parameters, Life Cycle Analysis (LCA) of the production process are discussed. [ABSTRACT FROM AUTHOR]

Direct use of Waste Vegetable Oil (WVO) as fuel is very attractive to reduce fossil fuels utilization and increase sustainability. WVO incorrect disposal causes serious damages to sewage systems and wastewater treatment plants. Moreover, if WVO reaches natural ecosystems, such as rivers, aquifers or subsoil, the environmental consequences can be severe. In recent years, the main reuse of WVO has been in biodiesel production, which is remunerative under current tax allowance policies. However, biodiesel production requires complex physical–chemical treatments, while direct use of WVO just needs mechanical treatment. As a consequence, WVO direct use in energy conversion systems lower the impact, from the economic, energetic and environmental points of view, with respect to biodiesel production. Moreover, as concerns the environmental impact, it should be considered that the direct use of WVO as fuel produces less polluting emissions when considering the whole life cycle: carbon dioxide produced during combustion, in fact, can be partially absorbed by crops used for oil production. This paper presents a comprehensive review of the work done to evaluate the effects of direct use of WVO in internal combustion engines. Many authors have shown the advantages of using straight vegetable oils or biodiesel produced from WVO as fuel, while the benefits of WVO direct use have not yet been clearly presented. The available literature still presents few papers about this topic, therefore also the use of vegetable oil, that presents physical chemical characteristics very similar to those of WVO, has been taken into account. After a brief introduction, the characteristics of WVO most affecting its use as fuel have been studied. Then several applications of WVO direct use in internal combustion engines and the available fuel supply technologies have been considered. Finally, the energetic performance and the pollutant emissions reported in literature have been deeply analyzed. [ABSTRACT FROM AUTHOR]

Jatropha curcas L. is a growing feedstock for biodiesel production. The first step in the exploitation of any plant for industrial application is to gather information about its chemistry, biology and all different applications so that the utilization of plant could be used optimized. J. curcas has been the centre of interest for many scientists in the past decade. The purpose of this paper is to present state-of-the-art review of J. curcas research advancement in biological, agronomical and biotechnological areas. This paper gives an overview on plantation science, composition, toxicity and genetics of J. curcas . This review also focuses on all J. curcas uses in agronomical terms. It gives a general idea of agricultural potential, utilizations, medical uses and other molecules that have been extracted from the plant. It finally focuses on the energy production from the crop and the biotechnological improvement of the biodiesel production process. [ABSTRACT FROM AUTHOR]

Abstract: Recently, non-edible vegetable oils have been considered as prospective feedstocks for biodiesel production. This is mainly attributed to their ability to overcome the problems of food versus fuel crisis related to edible oils. Globally, there are more than 350 oil-bearing crops identified as potential sources for biodiesel production. The evaluation of the physical and chemical properties of non-edible feedstocks is very important to assess their viability for future biodiesel production. Therefore, this paper aims to study the properties of some potential non-edible feedstocks. Moreover, the paper studies the physical and chemical properties of these promising crops and compares them with other edible oils. These oils include: crude Calophyllum inophyllum L. (CCIO), Jatropha curcas L. (CJCO), Sterculia foetida L. (CSFO), Croton megalocarpus L. (CCMO), Moringa oleifera L. (CMOO), patchouli (CPO), coconut (CCO), palm (CPaO), canola (CCaO), soybean (CSO) and Pangim edule (CPEO) oils. 14 Different properties have been determined and presented in this study. [Copyright &y& Elsevier]

Abstract With their fast growth rate and ability to accumulate a high percentage of their weight as lipid and carbohydrate, microalgae potentially represent an ideal feedstock for the production of biodiesel and bioethanol. In addition, microalgae offer several environmental benefits, and do not compete with food production for land, fresh water, and nutrients. Therefore, the main goal of this work is to provide a quantitative, systematic and harmonized assessment of current bio-energy potential. The analysis is conducted by considering all the main steps in detail, from cultivation to biodiesel production, and by deriving an overall estimation of energy consumption for biodiesel production. Energy consumption uncertainty is also quantified and discussed. A systematic review of all the main technologies available for all the main processing steps towards the production of biodiesel from microalgae is presented, focusing on the derivation of the Net Energy Ratio (NER) of each combination of technologies, complemented by an uncertainty analysis of the data used and those obtained in the present work. A wide scatter in the data available in the literature has been identified, highlighting the need for an uncertainty analysis. If the average overall energy consumption per unit of biodiesel mass is considered, all the routes adopting a raceway pond have a lower energy consumption, but if the uncertainty on the overall energy consumption is also considered, the minimum value of the range of NER values for some of the routes adopting a photobioreactor is comparable to the NER value obtainable by using raceway ponds. Thus, the present framework proposes a harmonized and comprehensive methodology to compare and contrast technologies for the production of biodiesel from microalgae, and is applied in this paper to identify, with an appreciation of the uncertainty, the most promising combinations of technologies. Highlights • Quantitative, systematic and harmonized assessment of microalgae energy potential. • A step-by-step analysis and overall estimation of energy consumption is given. • A substantial uncertainty on the data in literature has been identified. • The energy consumption uncertainty is quantified and critically discussed. • Derivation of the Net Energy Ratio (NER) for each combination of technologies. [ABSTRACT FROM AUTHOR]

Economically viable microalgal biodiesel production is unrealistic and unsustainable owing to expensive harvesting or dewatering techniques. Hence, immense and meticulous exploration of harvesting process is essential to identify knowledge leads by which suitable harvesting technique could be ascertained for lucrative biodiesel production. With this in view, this review aims to collate and highlight the spectrum of harvesting techniques applied to microalgae, i.e., conventional – modern, high cost- inexpensiveness, energy efficient- energy consuming process. At the outset, global energy outlook and demand had been critically addressed, and the scientific ways to tackle or satiate the fuel demand had also been highlighted in this reveiw. This review manuscript has thrown widespread light on the physical harvesting methods namely centrifugation, sedimentation, filtration, flotation and technical advantages thereof. Due to the energy-intensive and cost barrier of physical harvesting techniques, chemical methods entailing organic, inorganic, and electroflocculation have come to limelight and in this regard, microalgae used, floc recovery and the dose of flocculants have been compared and presented in detail. Further, state of the art harvesting techniques viz., bioflocculation by microalgae/bacteria, flocculation by pH adjustment, and magnetic nanocomposite based microalgal harvesting had been critically articulated. Besides discussing the several methods, this paper has summarized the key challenges in conventional and advanced harvesting techniques and also provided the scope thereof. Hence, the key suggestions and findings given in this manuscript would positively offer a well-defined roadmap in choosing foreseeable harvesting technology for cost-effective microalgal biofuel development. [ABSTRACT FROM AUTHOR]

This paper deals with biodiesel production from corn oil as a feedstock via the transesterification and esterification reactions. To date, corn oil has not been considered a viable biodiesel feedstock because of its high edible value and relatively high price, but some industrial corn processing co-products, such as corn germ and dried distillers grains with solubles (DDGS), have potential for this application after the extraction of corn distillers oil (CDO). Here, after brief discussion of the issues related to corn botany, cultivation, and use, as well as the corn germ and oil composition, properties and use, the methods of corn processing for germ and DDGS recovery are presented. In addition, the mechanical and solvent extraction techniques for oil recovery from whole ground corn kernels, germs, and DDGS are considered. Furthermore, biodiesel production from corn oil, waste frying corn oil, and CDO is critically analyzed. It is expected that further investigation will be directed toward developing simpler, more effective and energy-saving technologies for biodiesel production from corn oil-based feedstocks, especially from CDO. The integration of biodiesel production directly into corn-based ethanol production will advance the overall economy of industrial plants. Furthermore, the fuel properties, performances and exhaust gas emissions of corn-based biodiesel and its blends with diesel fuel are discussed, taking into account the biodiesel quality standards. Finally, issues related to the environmental and socio-economic impacts of corn-based biodiesel production and use are also tackled. [ABSTRACT FROM AUTHOR]

This paper overviews the technological, technical, economic, environmental, social, toxicological and human health risk considerations of biodiesel production and use. The future efforts in the technological domain should be directed towards low–cost and non–edible feedstocks, advanced technologies with reduced overall production costs and profitable production capacity. Process innovations that include new more active and stable catalysts, advanced reactors, continuous operation, lower energy inputs, better energy balance and lower GHG emissions and produce low or no wastes can lead to more efficient biodiesel production. Environmentally sustainable biodiesel production requires that sustainability standards cover direct and indirect impacts on the environment, i.e. soil, water and air. The combination of technological with economic, social and environmental issues will increase biodiesel benefits and may lead to integrated biorefineries capable of producing sustainable biodiesel and other valuable chemicals. Government policies will be the primary driving force for further increases in biodiesel production. Increased cooperation among governments and various stakeholders is needed to develop and apply corresponding sustainability criteria in a consistent way worldwide as soon as possible. [ABSTRACT FROM AUTHOR]

This paper presents a review on microalga Botryococcus braunii ( B. braunii ) with an emphasis on lipid production for possible industrial commercialization in biodiesel production. Summarizing the nature of this alga is fundamental to establish the detail environment conditions for optimal biomass growth and the production of lipids, as well as upstream processing technologies for biodiesel production. This study focuses the attention on identifying possible avenues for further investigation in the design of cultivation systems and the integration of process technologies at industrial scales. The advantages and disadvantages of biodiesel production processes based on these algal lipids are also analyzed. A particularly promising process involving B. braunii combines flue gas and wastewaters to produce lipids, converting them to biodiesel by supercritical (SC) direct trans/esterification (esterification followed by transesterification). We conclude that such processes using B. braunii have considerable potential for the production of cleaner and more efficient biodiesel than current methods, reducing the environmental impact of fossil fuel use. [ABSTRACT FROM AUTHOR]

Developing technologies for the production of alternative fuels from biorenewable resources is a field of interest for many researchers. Adequate substitute to diesel fuel is biodiesel that is synthesized through the transesterification of vegetable oils or animal fats and fulfilled the international standards. Ionic liquids (ILs) and deep eutectic solvents (DESs) have gained tremendous attention for their use in biodiesel production because of environmental benefits and process improvements. The present work overviews the use of ILs and DESs in the reaction and purification steps of biodiesel production processes where they are used as catalysts, cosolvents and extracting solvent. In addition, the possibilities of recycling and reusing of ILs and DESs are pointed out. Moreover, optimization and kinetic studies of biodiesel synthesis in the presence of ILs or DESs are discussed. The use of novel technologies combined with ILs or and DESs are also considered. Therefore, the present paper highlights the promising uses of ILs and DESs in biodiesel production in the future. [ABSTRACT FROM AUTHOR]

Alumina-supported potassium oxides are promising catalysts for the transesterification reaction of vegetable oils for biodiesel production. Various potassium compounds Al 2 O 3 -supported were prepared via impregnation method. Potassium oxide (K 2 O) is a good candidate for a solid base catalyst from an economical point of view. In the present work, we reviewed K 2 O catalyst for the vegetable oil transesterification based on a variety of related research papers. The potassium compounds supported in catalysts, KOH/Al 2 O 3 , KNO 3 /Al 2 O 3 , KI/Al 2 O 3 , KF/Al 2 O 3 and K 2 CO 3 /Al 2 O 3, were optimized through various reaction parameters, such as: amount of catalyst, molar ratio of oil to alcohol, reaction time and temperature. Yields and conversions from various catalytic systems applied for biodiesel production were also compared. Among the catalysts studied, the KF/Al 2 O 3 showed higher catalytic activity and a small amount of catalyst requirement in the transesterification reaction, indicating that it can be applied as a potential catalyst in the industry. [ABSTRACT FROM AUTHOR]

Today, the price of glycerol has dramatically dropped due to its oversupply from biodiesel production as well as oleochemical industry. Thus, it is essential to develop processes to transform bioglycerol into commercially valued products which is important to ensure sustainability in the biodiesel and oleochemical industries. One possibility is to transform it in propanediols, which have numerous applications such as food additives, raw material in pharmaceutical and cosmetic industries. In this paper, methods of conversion of glycerol into 1,3-propanediol are reviewed and discussed in detail. [ABSTRACT FROM AUTHOR]

An increase in glycerol production is expected because of the increasing use of fuel additives such as methyl esters. This increase can enhance the importance of glycerol as a cheap raw material for producing value-added products. Future scenarios for worldwide glycerol market will mostly be related to the supply and demand of glycerol and its application in other industries. Much research have been developed and continuously investigated to convert low-value glycerol using different strategies and approaches. Due to the unique structure of glycerol, properties and renewability feature of it, new opportunities for the transformation of glycerol into high-valued chemicals have merged in recent years. This paper provides a review on glycerol, global market of glycerol and conversion of glycerol to value-added products. Catalytic etherification of glycerol to value-added products such as polyglycerols is particularly reviewed. [ABSTRACT FROM AUTHOR]

It is well known that energy consumption is rapidly increasing due to population growth, higher standard of living and increased production. Significant amounts of energy resources are being consumed by the transportation sector leading to the fast depletion of fossil fuels and environmental pollution. Biodiesel is one of the technically and economically feasible options to tackle the aforesaid problems. Biodiesel is produced mainly from edible oils. However, it is believed that the extensive use of edible oils for biodiesel production may lead to food shortages in most of the developing countries. Therefore, the aim of this paper is to review the necessity and potentiality of the non-edible oils and to identify the emerging technologies to produce biodiesel. Special attention has been paid to the impact of biofuels on agricultural commodity prices and the food-fuel debate. [ABSTRACT FROM AUTHOR]

Abstract: The story of Jatropha curcas (Jatropha) was started in 2003 when the Planning Commission of India decided 20% blending of Jatropha oil (biodiesel) in petroleum diesel by 2010 and 30% by the year 2030. After that China, Japan, Belgium, Brazil, Tanzania, Mexico, Thailand, Malaysia, Philippines, and East and South Africa have set their own plans to blend Jatropha oil in petroleum diesel. It is not unexpected that almost every paper about Jatropha starts its introduction with the energy, environment and economic benefits and wishful thinking of reducing global warming. Unfortunately, Jatropha could not succeed so far in energy sector as expected, for which it was the most popularized energy crop. Many of the actual investments and policy decisions on Jatropha have convincingly been made without any scientific and technological backup. It has become clear that the positive claims on Jatropha are numerous which have popularized it as a potential source in biodiesel production but many of them still remain as theoretical assumptions and have not been verified yet practically. This letter reports briefly the status of past hopes to ground reality on the basis of what a few scientific studies on Jatropha. [Copyright &y& Elsevier]

Abstract: The demand for petroleum has been rising rapidly due to increasing industrialization and modernization. This economic development has led to a huge demand for energy, most of which is derived from fossil fuel. However, the limited reserve of fossil fuel has led many researchers to look for alternative fuels which can be produced from renewable feedstock. Increasing fossil fuel prices have prompted the global oil industry to look at biodiesel, which is from renewable energy sources. Biodiesel is produced from animal fats and vegetable oils and has become more attractive because it is more environmentally friendly and is obtained from renewable sources. Glycerol is the main by-product of biodiesel production; about 10% of the weight of biodiesel is generated in glycerol. The large amount of glycerol generated may become an environmental problem, since it cannot be disposed of in the environment. In this paper, an attempt has been made to review the different approaches and techniques used to produce glycerol (hydrolysis, transesterification, refining crude glycerol). The world biodiesel/glycerol production and consumption market, the current world glycerin and glycerol prices as well as the news trends for the use of glycerol mainly in Brazil market are analyzed. The technological production and physicochemical properties of glycerol are described, as is the characterization of crude glycerol obtained from different seed oil feedstock. Finally, a simple way to use glycerol in large amounts is combustion, which is an advantageous method as it does not require any purification. However, the combustion process of crude glycerol is not easy and there are technological difficulties. The news and mainly research about the combustion of glycerol was also addressed in this review. [Copyright &y& Elsevier]

Abstract: This paper aims at the assessment of the methods of production of biodiesel from different types of used cooking oil. Researches into the productive chain of this type of biofuel were performed in Brazil while several scientific studies approaching processes of pretreatment and transesterification of waste cooking oil were analyzed with their possible variations: alkaline catalysis, acid catalysis, enzymatic catalysis and non-catalytic conversion techniques, highlighting the main advantages and disadvantages of each analyzed route. The use of alkaline catalysts in transesterification is the most common technique employed by the industry, being the KOH the most recommended catalyst for the reaction with waste cooking oil. When water and acidity contents are high, pretreatment techniques and other types of catalysts such as solid acids are recommended. Moreover, the economic benefits provided by used cooking oil were analyzed, indicating reductions of up to 45% of direct production costs compared to virgin oils, even with the additional costs of the pretreatment. Finally, the availability of raw materials was estimated, indicating that the used cooking oil would have potential to supply up to 13% of the demand for biodiesel in Brazil. [Copyright &y& Elsevier]

Abstract: This paper assesses 13 different inputs for biodiesel production and shows that the highest cost currently associated with the processing of residual resources, as well as their small production scale, are compensated by their smaller procurement costs, by their immediate availability in the urban centers and by their larger potential for greenhouse gas emission reduction. Biodiesel production from residues can meet all technical international specifications, even the esterification process. Data Envelopment Analysis (DEA), the methodology used in this study, allows for the building of an efficiency index up through linear programming with multiple inputs and outputs, enabling the integration of sustainable development dimensions. The experts' conclusions were arrived at through restrictions on virtual weighting, with findings that allow the grading of alternatives. [Copyright &y& Elsevier]

Abstract: Glycerol is a valuable byproduct in biodiesel production by transesterification, soap manufacturing by saponification as well as hydrolysis reaction. The purity of glycerol obtained is low due to the presence of impurities such as remaining catalyst, water, soaps, salts and esters formed during the reaction. Purification of glycerol as well as the conversion of glycerol into valuable products has attained growing interest in recent years due to the dramatic growth of the biodiesel industry. This paper reviews different methods of producing crude glycerol as the major by-product. Purification of glycerol was reported as well as value-added products produced from glycerol. [Copyright &y& Elsevier]

Abstract: Biodiesel production through transesterification of vegetable oils and animal fats is rapidly increasing due to strong governmental policies and incentives. However, corresponding increase in the production of crude glycerol causes mixed effects. Sustainable biodiesel production requires optimization of its production process and drastic increase in the utilization of glycerol. High biodiesel yields and low environmental impacts, with respect to needless waste streams are mandatory. As such, upgrading of crude glycerol to highly pure glycerol and subsequent utilization of the product in producing value-added products are emerging research areas. International crude glycerol market is still at an early and very unstable stage. Globally, future conditions for an international market will largely be decided by supply and demand of glycerol for its utilization in conventional and newly developed industries. This paper highlights the current scenario on glycerol production from biodiesel industry, its global market and its new emerging outlets as commodity chemicals. [Copyright &y& Elsevier]

Abstract: As the fossil fuels are depleting day by day, there is a need to find out an alternative fuel to fulfill the energy demand of the world. Biodiesel is one of the best available resources that have come to the forefront recently. In this paper, a detailed review has been conducted to highlight different related aspects to biodiesel industry. These aspects include, biodiesel feedstocks, extraction and production methods, properties and qualities of biodiesel, problems and potential solutions of using vegetable oil, advantages and disadvantages of biodiesel, the economical viability and finally the future of biodiesel. The literature reviewed was selective and critical. Highly rated journals in scientific indexes were the preferred choice, although other non-indexed publications, such as Scientific Research and Essays or some internal reports from highly reputed organizations such as International Energy Agency (IEA), Energy Information Administration (EIA) and British Petroleum (BP) have also been cited. Based on the overview presented, it is clear that the search for beneficial biodiesel sources should focus on feedstocks that do not compete with food crops, do not lead to land-clearing and provide greenhouse-gas reductions. These feedstocks include non-edible oils such as Jatropha curcas and Calophyllum inophyllum, and more recently microalgae and genetically engineered plants such as poplar and switchgrass have emerged to be very promising feedstocks for biodiesel production. It has been found that feedstock alone represents more than 75% of the overall biodiesel production cost. Therefore, selecting the best feedstock is vital to ensure low production cost. It has also been found that the continuity in transesterification process is another choice to minimize the production cost. Biodiesel is currently not economically feasible, and more research and technological development are needed. Thus supporting policies are important to promote biodiesel research and make their prices competitive with other conventional sources of energy. Currently, biodiesel can be more effective if used as a complement to other energy sources. [Copyright &y& Elsevier]