A five-level-four-factor central composite design (CCD) with 54 assays was employed to study the effect of catalyst concentration (NaOH), reaction temperature, reaction time, and methanol/oil molar ratio on the methyl esters yield from Jatropha curcas oil (JCO) during its transesterification. Using response surface methodology (RSM), a quadratic polynomial equation was obtained for Jatropha curcas biodiesel (JCB) yield by regression analysis. Verification experiments confirmed the validity of the predicted model. The high free fatty acids (FFAs) (14.6%) of JCO could be reduced to 0.34% by acid-catalyzed esterification and a JCB yield of 98.3% was obtained with methanol/oil ratio (11？:？1) using NaOH as catalyst (1% w/w) in 110？min time at 55°C temperature. The predicted value of JCB yield is found to be in good agreement with the experimental value at the optimum level of input parameters. The properties of the biodiesel, thus, produced conform to the ASTM and IS specifications, making it an ideal alternative fuel for diesel engines. The model can be effectively used in oil industry to maximize the biodiesel yield from given oil. 1. Introduction The rapid increase in energy demand and fast depletion of fossil fuel resources has led to the search for alternative energy sources. Biodiesel, a renewable and biodegradable fuel, has generated considerable interest as a substitute to petrodiesel in recent years. Presently, the main focus is being placed to explore the nonedible oil resources like Jatropha, Pongamia, Mahua, and Neem as a potential source for biodiesel. Jatropha curcas L. oil (JCO) has been assigned top priority by the Government of India as feedstock for biodiesel production, and accordingly, Jatropha curcas plantations are cultivated on about 400,000？ha of land under National Biodiesel Mission of the Government of India, and the oil is expected to be available for biodiesel production in the coming years. The oil can be converted to biodiesel using transesterification, but the type of transesterification to be adopted depends on the free fatty acid (FFA) content of the oil. For the conversion of high FFA JCO, two-step acid-base catalyzed method has been-developed [1] which consists of acid-catalyzed pretreatment/esterification step to reduce the FFA to less than 1% using H2SO4 as acid catalyst and transesterification of pretreated oil to biodiesel using alkali catalyst. Its basic objective is to maximize the yield of biodiesel and to achieve higher conversion efficiency of biodiesel production. Different oils are found to contain varying amount
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