A Method of Central Composite Design (CCD) For Optimization of Biodiesel Production from Chlorella vulgaris

Abstract

The direct transesterification of the oleaginous biomass using chloroform resulted in a high biodiesel yield and FAME content than the chloroform-based extraction transesterification method and the yield was almost 100%. Hexane (89%) and petroleum ether (80%) also produced biodiesel but the yield was low when compared with chloroform. Our study showed that the biodiesel yield and FAME content of the wet biomass in the direct transesterification was significantly lower than those obtained from freeze-dried biomass suggesting that drying the algae was necessary for direct transesterification. The optimization procedures were carried out with algae: ethanol ratio, catalyst amount, reaction temperature and reaction time. The central composite design (CCD) was used to optimize the various processes. The analysis of variance (ANOVA) was also carried out and the results were found to be significant. The ρ value less than 0.0001 indicated that the model was statistically significant. The optimization procedures revealed that a yield of 95% was obtained. The 3D plot was done by keeping two components constant and other two components variable. In GC-MS, the results showed that the main components found were tetradecanoic acid ethyl ester (C14:0) 2-5%, Hexadecanoic acid ethyl ester (C16:0) 26-45%, Hexadecanoic acid ethyl ester (C16:1) 25-38%, octadecanoic acid ethyl ester (C18:0) 1-2%, oleic acid ethyl ester (C18:1) 9-13%, Eicosapentaenoic acid ethyl ester (C20:5) 1.2-5.1%. As the temperature was increased the percentage of C20:5 were decreased to 1.2% which was a good indication for fuel properties.