|Fig. 1: Oil Extraction from Jatropha seeds. (Source: Wikimedia Commons)|
According to the statistics presented by the International energy outlook 2011, the world energy consumption in the year 2008 was 505 quadrillion British thermal units (Btu) and is expected to rise to 770 quadrillion Btu by 2035.  Out of the total energy consumed, majority of energy supply comes from non-renewable energy sources like coal, natural gas, petroleum and other liquid fuels etc. With depleting coal and oil reserves, attention is turning to the use of alternative renewable sources of energy. In the light of the rampant crisis, Jatropha has received significance as a source of usable biodiesel.
Jatropha plant (botanical name: Jatropha Curcas) was classified by a Swedish botanist Karl von Linne. It is a flowering plant having a Latin American origin. However, it has been widely found in many tropical and subtropical regions of the world. Although there are several small uses of the parts of Jatropha plant, it is most widely known for its oil bearing seeds. Jatropha bears seeds containing 30 to 50% inedible oil and comprise of myristic, palmitic, stearic, arachidic, oleic and linoleic fatty acids, making it rich in oil content. 
Jatropha oil is extracted from its seeds mechanically using rams or screw presses, chemically or enzymatically using a novel technique called aqueous enzymatic oil extraction (AEOE) and converted into biodiesel by a process called trans-esterification. Crude Jatropha oil has a higher number of carbon atoms per molecule than diesel oil which imparts a higher viscosity and hence a lower cetane number to it.  Large viscosity may give rise to improper atomization and incomplete combustion in the engine. To improve its combustion characteristics, Jatropha oil has to be trans-esterified. Trans-esterification is the process of converting a triglyceride or complex fatty acid, neutralizing the free fatty acids, removing the glycerin and creating an alcohol ester.  A mixture of methanol and NaOH, which acts as a catalyst is added to heated Jatropha oil and stirred continuously. The mixture is then allowed to settle under gravity. Jatropha oil methyl ester (biodiesel) formed forms the upper layer along with other impurities which are removed by distillation process.
According to a research paper by P.K. Sahoo and L.M. Das, experimental studies carried out on a single cylinder four stroke internal combustion engine using biodiesel obtained in a laboratory scale setup shows that the properties of diesel oil and Jatropha biodiesel are relatively similar.  The proximity in the values of the biodiesel blends (JB20, JB50 and JB100) with conventional diesel oil shows that current diesel engines can be used without significant modification in the hardware. However, more research is required for a better idea of the long terms effects on engine and combustion characteristics of biodiesel. The following table gives an overview of the comparison between properties of conventional diesel Jatropha biodiesel and its blends.
|Table 1: Properties of biodiesel from Jatropha (JB) and its blends. |
It was also observed during investigations conducted on a duel fuel engine rig that by optimizing the fuel inlet temperature, Jatropha biodiesel has the potential to reduce CO, HC emissions with a slight increase in CO2 emission compared to conventional diesel oil while maintaining other functional parameters of engine operation nearly constant. 
Daimler Chrysler AG, Daimler Chrysler India undertook the Jatropha biodiesel project with Central Salt and Marine Chemical Research Institute (CSMCRI), India and the University of Hohenheim, Stuttgart, Germany. A part of the investigation involved the comparison of the properties of Jatropha oil methyl ester with the European EN 14214 standard for diesel oil. Jatropha oil methyl ester was found to have a desirable cetane number and emission properties. 
|Table 2: Comparison of Jatropha oil with EN 14214 standard for diesel oil. |
Jatropha Curcas is also estimated to have a positive impact on the environment through effective reduction of greenhouse gases (GHG). Firstly, since Jatropha oil is poisonous and can be grown in arid, stony regions and is resistant to diseases, it does not compete with food crops for land and water. Dry waste lands can also be used for its cultivation, thus helping in reducing carbon debts. Apart from these, Jatropha has numerous secondary benefits like provision of animal feed after detoxification of extracts, chemicals for medical and pharmaceutical applications and more importantly means of livelihood for poor farmers and labourers especially in the developing countries.
In the view of current energy crisis, Jatropha oil seems to be an attractive alternative source of energy. Along with properties comparable to that of conventional diesel oil, Jatropha oil proves to be more environmentally friendly and comes with supplementary benefits for the farmers. Hence it seems worthwhile to conduct extensive research on the use of Jatropha oil as an alternative automobile fuel and observe its long term impact on the engine performance.
© Chaitali Dalvi. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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