Search

The valorisation of the organic fraction of municipal solid waste (OFMSW) in the circular economy context is of outmost importance. This review aimed to examine the state-of-the-art valorisation technologies of OFMSW as resource for bioethanol and biodiesel. Firstly, feedstock mapping was performed, where high fluctuation of parameters was revealed. Considering the mean values, the stoichiometries of mechanically and source-sorted OFMSW are C 22 H 44 O 28 N and C 20 H 36 O 16 N, respectively. The substrate's mean carbohydrates (50%) and lipids (13%) contents reflect its potential in bioethanol and biodiesel production, respectively. As far as bioethanol is concerned, this paper critically reviewed the existing variance of second-generation bioethanol production methodologies from OFMSW revealing that high bioethanol yields (over 80%) could be achieved if the treatment steps of pretreatment, enzymatic hydrolysis and fermentation are synergistically compiled. To this end, bioethanol yield could benefit from suitable enzymatic blends. Furthermore, this paper discussed about different ways of oil extraction from OFMSW and various biodiesel production techniques. Soxhlet extraction combined with alkaline transesterification emerged as the most widely applied biodiesel production line from OFMSW. The novelty of this literature review lies in the integration of both bioethanol and biodiesel production processes, in a biorefinery concept that would allow the production of both biofuels along with that of biogas. This integration scenario rendered an energy efficiency expressed as energy content in products per energy in raw materials equal to 68%, proving that OFMSW is a feedstock that could meet the sustainability criteria for biofuels production. Image 1 • Up to date information on the composition of OFMSW. • Bioethanol production from OFMSW; pretreatment, hydrolysis, fermentation, stillage. • Biodiesel production from OFMSW; oil extraction, transesterification. • Bioethanol, biodiesel, biogas production from OFMSW under the biorefinery concept. • Integrated biorefinery exhibits various technical and energy benefits. [ABSTRACT FROM AUTHOR]

Increasing in oil consumption and ridiculous prices has caused the urgency for the main global oil industry players to search new alternative fuels which is biofuels. Biodiesel is better option to replace the crude oil due to its similar characteristics and sustainable. This paper will review the biodiesel produced and implementation from palm oil in Malaysia and current engine research that related to palm oil. Precedency given to the palm oil as it is main raw stock for biodiesel produced in Malaysia. Among scopes of this paper are to discuss current issues related to the palm biodiesel production and specific use in diesel engines. Another issue that arisen for Malaysia is to promote the palm oil as the alternative fuel that meets the stringent regulations and standards in Europe and North America. This paper also briefly covers the continuous global biodiesel consumption trend including the constraints that faced by Malaysia for leading the global biodiesel market with the benefits and drawbacks of palm oil biodiesel as an alternate fuel compared to the other common biodiesel sources. [ABSTRACT FROM AUTHOR]

The present study provides firstly a comprehensive review of studies on measuring the impacts of different biodiesel blends on exhaust emissions characteristics of urban busses under real-world operating conditions. Secondly, this paper discusses the errors that can be made in conducting case studies. Thirdly and finally, it shows lessons learned and provides guidelines to setup case studies, conduct the measurements, perform the statistical analysis and report the results to policy makers and the wider audience. To achieve climate change mitigation targets, using alternative fuels, e.g., biodiesel, hydrogen or electricty (EVs) for the urban fleets requires an in-depth analysis of the impacts under real-world operating conditions. Such experiments are generally very complex as numerous factors could directly or indirectly interfere with the results produced and potentially jeopardize the integrity of the research and the conclusions drawn. Results of the present research show that some vital parameters were ignored by many of the studies performed including the statistical uncertainties, driving cycle uncertainties and fuel uncertainties. Lack of appropriate experimental designs or clear assertions about the level of significance for differences in emissions/fuel consumption between alternative fuels (i.e. biodiesel) and the reference fuel used (i.e., diesel) could be regarded as the main weaknesses. Moreover, many other overarching and very influential factors (e.g., covariates/confounders) can interfere with the research outcomes as these were mostly overlooked by the reviewed studies. A careful and complete experimental design for assessments of alternative fueled vehicles (are critical when conducting real-world operating condition tests. The study findings help to formulate the guidelines for assessing real-world operating condition experiments to achieve the most feasibly and meaningful research outcomes that will have significant implication for local and global policy makers. The guidelines are of use for all types of research studies that want to evaluate the effects of alternative fuels for any transportation fleet. Image 1 • Real-world driving tests on urban buses were examined and discussed. • Key issues were uncertainties related to statistical design, driving cycle, and fuel. • Lack of appropriate experimental design was the main weakness in most studies. • Covariate/confounder factors were mostly overlooked. • Guidelines to perform more complete real-world diving test studies were presented. [ABSTRACT FROM AUTHOR]

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]

The dwindling of natural resources such as crude oil, coal etc. has made it essential to switch over to biodiesel. Biodiesel has a number of properties which are beneficial to the environment. The main advantage of biodiesel is that it's carbon neutral and it does not create carbon dioxide (CO 2 ). In addition, it leads to a decrease in pollution by reducing the emission of harmful and hazardous substances to the atmosphere and greatly improves the engine performance. This paper puts forward a comprehensive assessment of biodiesel production from various non-edible oils such as waste fried oil, pyrolysis oil, preheated palm oil, waste cooking oil, jatropha oil, karanja oil etc. It also serves as an index to measure combustion, performance and emission characteristics in a variable compression ratio (VCR) diesel engine, where biodiesel is blended with diesel. The need for switching over to VCR engine is that it provides better fuel efficiency, up to 30% reduction in fuel consumption, better control at peak cylinder pressure, ability to use multi-fuel and reduction in the exhaust emissions when compared to that of a constant compression ratio diesel engine. [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]

In the rapidly growing global energy consumption, diesel engines play the key role. Usage of diesel fuel contributes to harmful air pollution exhausted from combustion chamber. To overcome these serious issues, the biodiesel extracted from many feedstocks have been studied and implemented for the past few decades. The combustion characteristics of diesel are not same as the biodiesel blends due to the discrepancy in physio-chemical properties of biodiesel. Enormous studies have been focused on inadequate combustion profiles of biodiesel in compression ignition engines. This review paper analyzes the previous researches concerning the consequences of proposed effective strategies including the variation in engine operating parameters like fuel injection timing and injection pressure for enhancing combustion characteristics of biodiesel implementation. This study focuses its light on the advancement and retardation methods of injection timing and injection pressure to treat the engine combustion indicators such as in-cylinder pressure, peak cylinder pressure, heat release rate, ignition delay period and combustion duration, finally a comparative evaluation has been developed and the relevant reasons for the variation of combustion characteristics have been conversed. The review concludes that the advancement in injection timing and higher injection pressure are best in amplifying the combustion phenomena of biodiesel fuelling. [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]

Abstract: This paper presents a study based on the Systems Thinking and Scenario Planning (STSP) method, focusing the biodiesel production chain of Rio Grande do Sul State. The aim of the study was to identify key elements to comprehend the systemic structure of interaction among the ties of this chain. The study was held by a team of specialists over five months, including 15 meetings. Discussions were based on quantitative and qualitative data and a systemic map was constructed and refined. Based on this modeling, four different prospective scenarios were comparatively analyzed in order to propose strategic actions to promote the sustainability and competitiveness of the chain. The results were then presented to two different groups of external specialists in order to validate the conclusions drawn and the proposals. Both groups agreed with the ideas presented. The paper is constructed as follows: a brief introduction focusing on contextual elements of the biodiesel production in Brazil and in Rio Grande do Sul; some background material regarding agroindustrial production chains and an overview of the biodiesel production chain of interest; a description of the method used to perform the research; main results and discussion; and conclusions. With this paper the authors also hope to contribute to the discussion regarding competitiveness and sustainability of biofuel chains in Brazil. [Copyright &y& Elsevier]

In search of alternative fuels for CI engines, many experimental studies have been carried out and posted in the literature during the last few decades. This paper presents a comprehensive review on the production, performance and emissions from a compression ignition engine using biodiesel as alternate to fossil based diesel fuel. The properties of biodiesel produced from different sources and their fatty acid composition have also been described. The experimental set up used by different researchers for the investigations and their findings regarding performance and emissions with respect to mineral diesel have been presented in short for a large number of studies. For better illustration of the facts, results of a few experimental studies available in the literature have been presented in the form of different graphs for selective important performance and emission parameters as case studies. The overall impression is that the performance of the engine slightly deteriorates with the use of biodiesel partially or fully instead of diesel, but the environmental aspects are significantly improved. [ABSTRACT FROM AUTHOR]

Exhaust emission from transportation sector affects the human health. It is the main contributor to degrade the air quality. Biofuel is promising alternative to maintain both human health and environment quality better by reducing harmful emission from biofuel runs diesel engines. This study explores the global and Australian greenhouse gas (GHG) emission scenario along with the contribution of transportation sector to the GHG emission in Australia. Besides, the world biofuel standard with the target and mandate taken by the government of different countries to use biofuel are also discussed in the paper. This review indicated that engine emission is dependant on some factors such as engine operating condition, biofuel types, blending etc. Both biodiesel–diesel and ethanol–biodiesel–diesel blending plays a significant role in reducing the exhaust gas emission such as carbon monoxides (CO), hydrocarbons (HC), particulate matter (PM). But ethanol–biodiesel–diesel and biodiesel–diesel blends produce higher carbon dioxides emission, which is absorbed by the crops and considered as lower net CO 2 emission. Finally, about 5–10% of ethanol with 20–25% biodiesel can be added with petro-diesel effectively and efficiently to reduce global GHG emission, thus to maintain environment and human health better. [ABSTRACT FROM AUTHOR]

Biodiesel is a renewable, nontoxic, eco-friendly and sustainable alternative fuel for compression ignition engines. In spite of having some application problems, biodiesel, in recent times, being considered as one of the most promising alternative fuels in internal combustion engine. It has been proven that the pollutants in the vehicular emissions have significant impacts on the ecological systems and on the health of human beings. Thus there is an increasing demand on tightening the emission standards of motor vehicles, as well as an ever increasing need for developing means of reducing emissions from in service motor vehicles. Biofuel, such as alcohol and biodiesel, could partly replace petroleum fuel, reduce toxic emissions and more importantly restrain the life-cycle emission of CO. In the present paper, earlier studies have been collected and analyzed. The aim of the present study is to evaluate the feasibility of biodiesel in automobiles, with special emphasis on emission aspects. Few aspects on durability and performance are also included. Evaluation is done on both conventional and CRDI engines, though literature on the latter are few and insufficient when compared to the former. Biodiesel use, when compared to diesel as a fuel, in conventional diesel engines with little or no modification leads to the substantial reduction in particulate matter (PM), hydro carbon (HC) and carbon monoxide (CO) emissions. This is accompanied by a light power loss, increase in fuel consumption and an increase in nitrogen oxide (NO x ) emission. [ABSTRACT FROM AUTHOR]

The recent energy independence and climate change policies encourage development and utilization of renewable energy such as bioenergy. Biofuels in solid, liquid, and gaseous forms have been intensively researched, produced, and used over the past 15 years. This paper reviews the worldwide history, current status, and predictable future trend of bioenergy and biofuels. Bioenergy has been utilized for cooking, heating, and lighting since the dawn of humans. The energy stored in annually produced biomass by terrestrial plants is 3–4 times greater than the current global energy demand. Solid biofuels include firewood, wood chips, wood pellets, and wood charcoal. The global consumption of firewood and charcoal has been remaining relatively constant, but the use of wood chips and wood pellets for electricity (biopower) generation and residential heating doubled in the past decade and will increase steadily into the future. Liquid biofuels cover bioethanol, biodiesel, pyrolysis bio-oil, and drop-in transportation fuels. Commercial production of bioethanol from lignocellulosic materials has just started, supplementing the annual supply of 22 billion gallons predominantly from food crops. Biodiesel from oil seeds reached the 5670 million gallons/yr production capacity, with further increases depending on new feedstock development. Bio-oil and drop-in biofuels are still in the development stage, facing cost-effective conversion and upgrading challenges. Gaseous biofuels extend to biogas and syngas. Production of biogas from organic wastes by anaerobic digestion has been rapidly increasing in Europe and China, with the potential to displace 25% of the current natural gas consumption. In comparison, production of syngas from gasification of woody biomass is not cost-competitive and therefore, narrowly practiced. Overall, the global development and utilization of bioenergy and biofuels will continue to increase, particularly in the biopower, lignocellulosic bioethanol, and biogas sectors. It is expected that by 2050 bioenergy will provide 30% of the world’s demanded energy. [ABSTRACT FROM AUTHOR]

By extensively reviewing the current state of knowledge, this paper explores the sustainability implications of palm oil biodiesel in Southeast Asia, with a focus on Indonesia, Malaysia and Thailand. Both ecological and environmental vitality as well as socio-economic equity are emphasized in the authors? exploration of sustainability in the three country cases. The article observes that the main environmental sustainability considerations of palm oil biodiesel include its capacity to reduce carbon dioxide emissions, its carbon debt and its repercussions on forestry, biodiversity, and soil and water quality. Issues surrounding socio-economic sustainability encompass how palm oil biodiesel affects food security in Southeast Asia, along with the impact of palm oil production on rural livelihoods and land-tenure. The authors firstly explore the origins, drivers and current technologies surrounding palm oil biodiesel development in the region. They then present the three country cases in order to concentrate on the particular policies, challenges and opportunities that uniquely impact the sustainability of biodiesel development in each locale. [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]

Biodiesel is eco-friendly, less toxic and one of the most researched biofuels in recent years to reduce our reliance on fossil fuels and minimize emissions. The various problems associated with batch-type reactors are longer residence time, higher operating costs, and energy consumption with low production efficiency. Researchers are now focusing on continuous flow biodiesel production techniques to overcome problems in batch reactors. This paper highlights various reactors used in continuous flow biodiesel synthesis, catalyst mechanism, hybrid reactors technique and separation methods. Various continuous flow reactors used in biodiesel production have been discussed and the microreactor was intensively elaborated. Compared to traditional reactors, microreactor technology exhibits higher efficiency, improved mixing, high heat and mass transfer rates due to a high surface-area-to-volume ratio and short diffusion distance. The parameters that influence the liquid-liquid phase flow patterns in the microreactors include mixer type, channel size, internal configuration reaction time, reaction temperature, and alcohol to oil ratio. Post-treatment techniques help to improve the quality of the biodiesel and utilization of by-products has been discussed. The limitations and practical implications prevailing in the microreactors help improve the reactor techniques forward in large-scale production. Finally, the review addresses future directions in bridging the gap in current research on microreactors for better yield and high biodiesel quality. [Display omitted] • A review of the various continuous flow reactors used for biodiesel production was presented. • Biodiesel production using continuous-flow microreactors and their significance was intensively discussed. • Advances required to improve the improve mass transfer rate and conversion of biodiesel was presented. • The importance of the post-treatment techniques to improve the quality of biodiesel was briefly discussed. [ABSTRACT FROM AUTHOR]

Abstract: To be an alternative to fossil fuel, biodiesel should provide a positive energy benefit and a sustainable energy income. Based on the principles of Life Cycle Analysis and using the energy benefits of exploiting Pistacia chinensis in China as a case study, this paper presents a quantitative evaluation of the energy consumed throughout the six-phase life cycle process, which includes planting, fruit transport, oil production, biodiesel production, biodiesel transport and biodiesel combustion. The results show that during the life cycle process, the total energy consumption of the biodiesel production and transformation phase is the greatest and that energy consumption during the plantation phase second greatest. The results indicated that the potential maximum gross annual production is approximately 162.19billion MJ per year for suitable land and 117.20billion MJ per year for lands classified as fairly suitable, which could produce 6.35million t of biodiesel. Considering the net energy production and output potential for P. chinensis based biodiesel at the provincial level, Yunnan Province has the most amount of production potential, while Beijing City has the least amount of production potential. The annual output value created by P. chinensis based bio-fuel is 3007.83million Yuan in China. [Copyright &y& Elsevier]

Abstract: Energy crops constitute significant potential for meeting the future energy need worldwide. In addition, agricultural lands offer an alternative to the agriculture which is referred to as energy farming. The studies on energy crops in biofuel production show that they are quite an economical and environmentally beneficial way of sustainable energy production. Today most of the developed countries use staples such as corn, sugar beet, soybean, rapeseed, and wheat in order to obtain energy. Moreover, bioethanol is mostly produced from sugarcane and corn and biodiesel from oilseed plants. Therefore, these produced raw materials compete with food and feed production. Consequently, the use of those energy crops which are used as food products for biofuel production is an important issue which must be considered in terms of the current food safety. Some energy crops, such as miscanthus, switchgrass and sweet sorghum, that are called C4 crops, can grow with high biomass yield even in infertile land. Thus, these crops are used in energy farming – a new type of agriculture. Furthermore, C4-type crops possess the features of resistance to aridity, high photosynthetic yield and a high rate of CO2 capture when compared with C3 crops. In conclusion, C4 crops tend to produce more biomass than C3 crops. Therefore, these crops are investigated, focused on, and elaborated on in this paper. This study aims to present a comprehensive review on the production of biofuels from lignocellulosic agricultural products and promising energy crops. Thus, the energy crops to be used as raw materials for biofuels today and in the future are investigated. In addition, it is intended to highlight the energy crops used as staples by discussing them in detail for biofuel production. The energy crops which are promising in biofuel production, particularly non-staple miscanthus and sorghum, are presented in detail as they are non-food crops and have a high yield. Furthermore, the energy crops used as raw materials for bioenergy today and their potential are compared both worldwide and in Turkey. [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 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: Microalgae have great potential as renewable fuel sources, but a dire need exists for high-level academic and industrial research into their growth and bioprocessing. New algae strains that efficiently use CO2 and wastes as nutrients, novel oil extraction methods, and industrial-scale designs for fuel production are imperative for long-term energy sustainability. A particular challenge to research in this field is the transition from pilot studies to industrial operations, which often exposes algae cells and their products to hostile environments, reducing yields. Hence, a need exists to integrate algae cell engineering with predictive bioprocess engineering to ensure economic and environmental feasibility and minimize the number of full-scale trials that fail. This review provides a brief overview of biofuel production from microalgal biomass. It highlights the most promising microalgae species for different types of fuel, the proper choice of photobioreactor and process parameters, product extraction techniques, and the main biofuel products. The main goal of this paper is to promote research into energetically- and environmentally-favorable technologies via the development of better algal strains and separation, extraction, and conversion methods. [Copyright &y& Elsevier]

Abstract: Increasing energy demand and environment concerns have prompted an evolution of alternative fuel sources. As an alternative fuel source, biodiesel is attractive because it reduces engine emissions. However, biodiesel produces higher NO x emissions compared to ordinary diesel fuel. Previous researches have established many factors that cause biodiesel to produce elevated NO x emissions. This study reviews the impacts of biodiesel combustion on NO x emissions and their reduction approaches in diesel engines. The first part of this study recaps the NO x formation mechanisms for understanding the kinetics behind the NO x forming reactions. The second part describes the factors affecting on NO x emissions. This paper established that higher NO x emissions are produced for biodiesel combustion which influenced by several factors such as physicochemical properties and molecular structure of biodiesel, adiabatic flame temperature, ignition delay time, injection timing and engine load conditions etc. The final section discusses on the reduction of NO x emissions from biodiesel fuelled engines for both pre and post combustion techniques. The results of reduction approaches of the NO x emissions implies, exhaust gas recirculation (EGR) and retarded injection timing are effective as well as low cost techniques than others. Between these two techniques, EGR reduces the NO x emissions at 5–25% EGR rate adequately in biofuelled engine by controlling oxygen content and combustion peak temperature with slightly decreasing HC and CO emissions. However this technique shows few penalties on smoke and PM emissions as well as brake specific fuel consumption if not perfectly optimized. [Copyright &y& Elsevier]

Abstract: It is a good solution to produce biodiesel by using waste edible oils (WEO), such as waste cooking oils and used frying oils, due to its low cost, disposal problems and potential contamination. Therefore, WEO biodiesels has been gradually produced, and thus applied to study their effects on engine performances and emissions. However, few reviews about these studies have been published to assist understanding and popularization for WEO biodiesels so far. This paper attempts to cite and analyze highly rated journals in scientific indexes about combustion characteristics, engine power, economy, regulated emissions and non-regulated emissions of WEO biodiesels on diesel engine. The use of WEO biodiesels leads to the slight difference in combustion characteristics such as ignition delay, rate of pressure rise, peak pressure and heat release rate, and the substantial reduction in PM, HC and CO emissions accompanying with the imperceptible power loss, the increase in fuel consumption and NO x emission on conventional diesel engines with no or fewer modification, compared to diesel. Although the inconsistent conclusions have been made on CO2 emission of biodiesels from WEO, it reduces greatly from the view of the life cycle circulation of CO2. For non-regulated emissions, the reduction appears for PAH emissions but carbonyl compounds emissions have discordant results for WEO biodiesels. Therefore, WEO biodiesels have the similar combustion characteristics, engine performances and emissions to that of biodiesels from food-grade oils, and the blends of WEO biodiesel with small content by volume could replace the petroleum-based diesel fuel to help in controlling air pollution, encouraging the collection and recycling of waste edible oil to produce biodiesels and easing the pressure on scarce resources to a great extent without significantly sacrificing engine power, economy and emissions. [Copyright &y& Elsevier]

Abstract: World energy demand is expected to increase due to the expanding urbanization, better living standards and increasing population. At a time when society is becoming increasingly aware of the declining reserves of fossil fuels beside the environmental concerns, it has become apparent that biodiesel is destined to make a substantial contribution to the future energy demands of the domestic and industrial economies. There are different potential feedstocks for biodiesel production. Non-edible vegetable oils which are known as the second generation feedstocks can be considered as promising substitutions for traditional edible food crops for the production of biodiesel. The use of non-edible plant oils is very significant because of the tremendous demand for edible oils as food source. Moreover, edible oils’ feedstock costs are far expensive to be used as fuel. Therefore, production of biodiesel from non-edible oils is an effective way to overcome all the associated problems with edible oils. However, the potential of converting non-edible oil into biodiesel must be well examined. This is because physical and chemical properties of biodiesel produced from any feedstock must comply with the limits of ASTM and DIN EN specifications for biodiesel fuels. This paper introduces non-edible vegetable oils to be used as biodiesel feedstocks. Several aspects related to these feedstocks have been reviewed from various recent publications. These aspects include overview of non-edible oil resources, advantages of non-edible oils, problems in exploitation of non-edible oils, fatty acid composition profiles (FAC) of various non-edible oils, oil extraction techniques, technologies of biodiesel production from non-edible oils, biodiesel standards and characterization, properties and characteristic of non-edible biodiesel and engine performance and emission production. As a conclusion, it has been found that there is a huge chance to produce biodiesel from non-edible oil sources and therefore it can boost the future production of biodiesel. [Copyright &y& Elsevier]

Abstract: Transportation has dominated global fuel consumption and greenhouse gas emissions have risen in an alarming rate. Gasoline and diesel consumption for road transport have a faster growing rate than other sector and the trend appeared to be rapidly moving upwards in the near future. This has caused much concern in many countries including Malaysia to improve the sustainable energy of this sector. The focus of this paper is to analyze the trends of energy pattern and emission of road transport in Malaysia. On top of that, the review of prospective policies such as fuel economy standards and fuel switching to natural gas as well as biodiesel are summarized in this study. The study found that there is an urgent need to adopt suitable energy policy to balance the energy demand and reduce emission in this sector. This study serves as a guideline for further investigation and research in order to implement and improve the transportation sector. [Copyright &y& Elsevier]

Abstract: Energy is a basic requirement for economic development. Every sector of Indian economy-agriculture, industry transport, commercial and domestic needs input of energy. The economic development plans implemented since independence have necessarily required increasing amount of energy. As a result consumption of energy in all forms has been steadily rising all over the country. This growing consumption of energy has also resulted in the country becoming increasingly dependent on fossil fuels such as coal, oil and gas. Rising prices of oil and gas and potential shortage in future lead to concern about the security of energy supply needed to sustain our economic growth. Increased use of fossil fuels also causes environmental problems both locally and globally. In view of the fast depletion of fossil fuel, the search for alternative fuels has become inevitable, looking at huge demand of diesel for transportation sector, captive power generation and agricultural sector, the biodiesel is being viewed a substitute of diesel. The vegetable oils, fats, grease are the source of feed stocks for the production of biodiesel. Biodiesel is an engine fuel that is created by chemically reacting fatty acids and alcohol. This usually means combining vegetable oil with methanol in the presence of a catalyst (usually sodium hydroxide). Biodiesel is much more suitable for use as an engine fuel than straight vegetable oil for a number of reasons, the most notable one being its lower viscosity. The aim of the present paper is to focus on the work done in the area of biodiesel and also the impact analysis of biodiesel on engine performance. [Copyright &y& Elsevier]