Production of methyl ester from two microalgae by two-step transesterification and direct transesterification.

The efficiency of oil extraction from Chlorella sp. and Scenedesmus sp. using different cell disruption and solvent system was investigated. The ultrasound cell disruption method showed the maximum oil extraction in both algae. Oil extraction with hexane resulted in maximum oil yield for both algae. The kinetic parameters were studied and the extraction followed the first-order kinetics. The activation energy and thermodynamic activation parameters were calculated for both microalgae and the results suggested that the extraction was endothermic, irreversible and spontaneous. The methyl ester yields by two-step transesterification and direct transesterification were 95 and 96% for Scenedesmus sp. and 89 and 92% for Chlorella sp. respectively. Both methods had similar net energy consumption suitable for industrial application. The methyl ester properties were analysed in comparison with those of American Society for Testing and Materials (ASTM) D6751 standards.