Biodiesel synthesis from sustainable feedstock is gaining importance in
depleting crude oil feedstock and addressing greenhouse emission challenges. A
developing country like India has planned to reduce its 10% dependency on crude oil
by 2022. Synthesis of biodiesel from sustainable edible feedstock has been a concern
for energy vs. food issues. Non-edible feedstock such as Calophyllum innophyllum
Linn, Karanja, Jatropha, Waste Cooking oil, waste engine oil, etc., is gaining
importance. However, biodiesel synthesis from these feedstocks requires higher
processing due to higher initial free fatty content. Intensified techniques can overcome
the shortcoming of higher processing requirements. Spectacular effects associated with
ultrasound and microwave are beneficial for enhancing the rate of processing.
Individual results of microwave and ultrasound have certain limitations. The
intensification of biodiesel synthesis is dependent on the removal of heat/mass barriers
in the transesterification process. Microwave interaction with polar molecules present
in the system enhances the temperature of the reaction at a very intense rate. Microemulsification and the high speed of micro-streaming velocities produced from the
ultrasound during interaction with the aqueous phase are incredibly useful for reducing
the mass transfer barrier in heterogeneous phases. The synergy of microwave and
ultrasound may help enhance the processing rate on a multi-fold basis. The present
chapter has presented an overview of microwave and ultrasound energy effects for
biodiesel synthesis. Process economics has been discussed for future development in
biodiesel synthesis.
Keywords: Biodiesel synthesis, Microwave, Non-edible feedstock, Synergetic effect, Ultrasound.