Effects of solid pre-treatment towards optimizing supercritical methanol extraction and transesterification of Jatropha curcas L. seeds for the production of biodiesel

Experimental studies for in situ extraction and transesterification of oil seeds had been carried out recently for the process intensification of biodiesel production. As opposed to the conventional method, the solid oil seeds would be in direct contact with the transesterification reagent. Both the oil extraction and subsequent transesterification process to biodiesel will occur simultaneously. Consequently, solid pre-treatments would play a critical role to ensure that the oil seeds are in a state for optimal oil extraction. Apart from obtaining a higher yield, this could also ensure that the oil extraction phase would not bottleneck the entire in situ extraction and transesterification process. However, solid pre-treatments could be both cost and energy intensive and therefore should be carefully selected for optimum advantages. In this experimental work, ground Jatropha curcas L. seeds were subjected to pre-treatments processes including de-shelling, sieving, drying and heat treatment at five different temperatures (45–105 °C) and two different durations (12 and 24 h) before undergoing single-step supercritical methanol extraction and transesterification. Conventional two-step extraction and transesterification was also performed as comparison to the single-step process. The effects of each pre-treatment were analyzed and optimized towards two responses (extraction and FAME yield). The highest extraction and FAME yield for the two-step and single-step processes were 66.82% w/w, 114.87% w/w and 68.50% w/w, 128.78% w/w respectively. Single-step supercritical methanol extraction and transesterification was found to be able to provide a higher extraction and FAME yield for the production of biodiesel with less pre-treatment stages and intensity as compared to the conventional two-step process. Therefore, this is a highly promising approach to reduce the high biodiesel production cost which is currently impairing the industry.

► Inter-relation of pretreatment processes are investigated for biodiesel production. ► Effect of de-shelling, sieving and drying are studied extensively. ► Higher biodiesel yield can be achieved with optimal pre-treatment stages. ► Supercritical reactive extraction has higher efficiency than conventional process.