Trans-esterification is the most commonly used methods of biodiesel production. In-situ trans-esterification process uses oil (triglycerides) in seeds directly without the need for initial extraction. The in-situproduction of biodiesel from raw castor bean seed with a batch processor was studied at initial catalyst quantity of 0.1, 0.5 and 1.5%, reaction time of 30, 60 and 90 min with a reaction temperature of 600C and alcohol seed ratio of 1:1 using the response surface methodology. Initial catalyst concen-tration and reaction time were subjected to central composite experimental design of the response surface methodology. Initial catalyst quantity and reaction time were found to have significant (P<0.05) effects on the yield of castor biodiesel produced, with increased catalyst quantity giving a negative effect on the yield after an initial amount of between 1.0 and 1.2%. The reaction time had a positive effect on the yield until after 90 minutes after which biodiesel yield reduced with increased time. The CA-Time interactions influence was small and negative, due to the superior effect of initial catalyst quantity by the formation of by-products (soaps) leading to difficult ester separation from glyc-erol. A second-order model was obtained to predict the yield as a function of all factors. The model predicted well the observed data with a R2 value of 0.983. The biodiesel produced had properties com-parable to the standards of ASTM while the specific gravity was higher than the specified standard
