The aim of this study was to compare the biodiesel synthesis from waste fish oil (WFO) using the
conventional transesterification and using ultrasonic methods. WFO has 10.5 mg KOH/g oil acidity and
esterification with H2SO4 was utilized to decrease this amount to 0.6 mg KOH/g oil. Ultrasonic and
conventional methods are used for the transesterification of the pre-treated WFO. The results show that
the reaction temperature had more effect on the conventional method than using the ultrasonic. Optimum condition for the biodiesel production is 1% KOH, 55 C, 6:1 alcohol to oil molar ratio and biodiesel
yields were 79.6% and 78% for the ultrasonic and conventional methods respectively. 87% of methyl ester
content in 1 h conventional or 30 min ultrasonic process has been reached.