ABSTRACT Biodiesel is a non-toxic, biodegradable and renewable fuel with the potential to reduce engine exhaust emissions. The methyl ester of jatropha oil, known as biodiesel, is receiving increasing attention as an alternative fuel for diesel engines. The biodiesel is obtained through transesterification process. Various properties of the biodiesel thus developed are evaluated and compared in relation to that of conventional diesel oil. In the present investigation neat jatropha oil methyl ester (JME) as well as the blends of varying proportions of jatropha oil methyl ester (JME) and diesel were used to run a CI engine. A four stroke diesel engine having compression ratio of 17.5: 1 and developing 5.2 kW at 1500 rpm was used. Experiments were initially carried out on the engine at all loads using diesel to provide baseline data. Significant improvements in engine performance and emission characteristics were observed for JME fuel. The addition of jatropha methyl ester (JME) to diesel fuel has significantly reduced HC, CO, CO 2 and smoke emissions but it increases the NO X emission slightly. The maximum reduction in smoke emission was observed by 35 % in case of neat biodiesel operation as compared to diesel. The unburned hydrocarbon emission was drastically reduced by 53 % for neat biodiesel operation. KEYWORDS Biodiesel, jatropha oil methyl ester, diesel engine, performance, emissions. INTRODUCTION The concept of using biomass based fuel specifically, vegetable oil based methyl ester, as a diesel fuel alternative is not new. Rudolf Diesel himself demonstrated that his engine could run on vegetable oil fuels. Since then various vegetable fuels and their ester has been tested as a diesel fuel alternatives. With the increased availability of petroleum based fuels, studies on biomass-based fuels decreased. During the oil shock era of the 1970s, interest in these fuels again resurfaced. Diesel engines are widely used as power sources for heavy and medium duty applications because of their good fuel economy and low emissions of unburned hydrocarbons (HC) and carbon monoxide (CO). However, diesel engines usually exhaust higher amounts of particulate matter (PM) than spark ignition engines. Many alternative diesel fuels have been shown to have better exhaust emissions than traditional diesel fuel. Alkyl esters of vegetable oils and animal fats, called biodiesel, hold promise as fuel alternatives for diesel engines. A number of researchers have shown that biodiesel has fuel properties and provides engine performance that is very similar to diesel fuel. The primary incentive for using biodiesel is that it is a nontoxic, biodegradable, and renewable fuel. Further advantages over petroleum-based diesel fuel include a high cetane number, low sulfur, low aromatics, low volatility and the presence of oxygen atoms in the fuel molecule. These features of biodiesel lead to its greatest advantage, which is its potential for emission reduction including CO, HC, solid carbon particle
