Ultrasonic enhancement of lipase-catalyzed transesterification for biodiesel production from used cooking oil

This work investigated the ultrasonic irradiation-enhanced transesterification using lipase from the viscera of Nile tilapia (Oreochromis niloticus) to produce biodiesel from used cooking oil (UCO) and methanol. The effects of processing conditions such as irradiation time, ultrasonic frequency, and temperature on biodiesel yield were investigated. Results showed that the use of ultrasound decreased the reaction time from 28 to 3 h with ultrasonic frequency of 16 kHz, methanol to oil molar ratio of 4:1, lipase concentration of 30 kUnit, and reaction temperature of 40 degrees C. The efficacy of ultrasound was compared with conventional mechanical stirring operated at optimum conditions, and the ultrasonic irradiation coupled with stirring enhanced the transesterification with the highest yield of 97.59%. The fuel properties of the produced biodiesel in this study desirably met the recommended biodiesel standards as prescribed by EN 14214 and ASTM D 6751, suggesting the biodiesel obtained from ultrasound-assisted lipase-catalyzed transesterification of UCO with methanol is a promising alternative for conventional biodiesels and diesels.