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The rapid depletion of conventional fuel reserves and the increase in environmental pollution prompted the search for a sustainable energy solution. Biodiesel is one of the most promising energy substitutes with similar properties as conventional diesel fuel. Surplus availability of palm oil makes it suitable for biodiesel production. Due to the lack of availability of review articles that cover the entire process of palm biodiesel production and its optimum use in diesel engines, the authors were motivated to write this article. Cultivation parameters of palm trees, extraction of oil, and physicochemical properties of palm oil–based biodiesel are explained in this review. The production of palm biodiesel from raw oil can be done through pyrolysis, micro-emulsification, blending, hydro-esterification, and transesterification processes. For high biodiesel yield and less cost of operation, the transesterification method is adopted. The performance and emission parameters of diesel engines that operated on palm biodiesel and its blends are also explained. There is a decrease in brake thermal efficiency and an increase in brake-specific fuel consumption observed with the use of palm biodiesel in diesel engines. A reduction in CO and HC emissions and an increase in NOx emissions are found due to the oxygenating nature of palm biodiesel. This article provides the scientific approach to find out the optimum parameters for palm biodiesel production and its efficient use in compression ignition engines. [ABSTRACT FROM AUTHOR]

Latest research on fuels focused on exploring better alternatives for compression ignition engines. A large number of studies reported that the properties of biodiesel are comparable with traditional diesel fuel, which makes it a suitable alternative source of energy. Among various available feedstocks, waste cooking oil is considered as the most viable source for biodiesel production. Apart from being economical, it also reduces waste disposal issues. High free fatty acids and water content in waste cooking oil cause the production of biodiesel difficult. In order to overcome this difficulty, two-step transesterification method is preferred for commercial-scale biodiesel production. Several factors like catalyst concentration, alcohol to oil molar ratio, reaction temperature, and time of reaction affect the yield of biodiesel. This article provides a comprehensive review of biodiesel production from waste cooking oil and its use in compression ignition engines. In this review, fatty acid composition, pre-treatment process, catalytic and non-catalytic approaches of biodiesel production with their advantages and limitations are included. The effect of transesterification reaction parameters on biodiesel yield is also covered. The high viscosity of biodiesel than diesel fuel causes an increase in brake specific fuel consumption and a decrease in brake thermal efficiency of engines. Significant reduction in CO, HC, PM, and smoke emissions are identified; however, NO X and CO 2 emissions found increased due to the oxygenating nature of biodiesel. Overall, it could be concluded that biodiesel produced from waste cooking oil serves as a cleaner and economical alternative source of fuel for compression ignition engines. [Display omitted] • Approximately 30% of per capita edible oil consumption is generated as waste. • Two-step transesterification is the most efficient method for biodiesel production. • Yield of biodiesel is most influenced by the type of catalyst and its concentration. • Brake specific fuel consumption increases due to poor atomization of biodiesel. • CO, HC, PM, and smoke emissions from engine exhaust are reduced significantly. [ABSTRACT FROM AUTHOR]

• Classification of biodiesel generations on the basis of the type of feedstocks is covered. • Botanical description and growth condition requirements of jatropha are discussed. • Physicochemical properties and fatty acid profile of jatropha biodiesel are analyzed. • Production of biodiesel from jatropha oil with different techniques is summarized. • Performance and emissions characteristics of C.I. engine fuelled with jatropha biodiesel are reviewed. Due to limited reserves of conventional fossil fuels and their negative impact on global climate and human health, researches are focused to find the alternate energy substitute. Comparable properties of biodiesel make it one of the most promising alternatives of conventional diesel fuel. Jatropha curcas oil (non-edible oil) belongs to the second-generation of biodiesel. In this review, the physicochemical properties, fatty acids distribution, stability of jatropha oil are discussed in detail. The change in fatty acid profile affects the fuel properties, performance and emissions of diesel engines operated on jatropha biodiesel. Oxidation stability of jatropha biodiesel is poor due to the high amount of unsaturated fatty acids. Blending, thermal cracking, micro-emulsification, and transesterification are four basic approaches for production of biodiesel. Transesterification is the most adoptive method due to less expensive operation and high product yield. This article also highlighted the performance and emissions of compression ignition engines operated on jatropha biodiesel and its blends. The lower calorific value of jatropha biodiesel is responsible for the decrease in brake thermal efficiency and an increase in brake specific fuel consumption. High availability of oxygen in jatropha biodiesel reduces HC, CO, and PM emissions, while NOx emission increases significantly. This article provides the most of details of optimum parameters for jatropha biodiesel production and its efficient use in diesel engines. [ABSTRACT FROM AUTHOR]