Effect of ohmic heating as a pretreatment method for biodiesel extraction from microalgae

Microalgae are single cell organisms that have the potential to be developed as feedstock for biodiesel oil. One of the problems of using microalgae as feedstock for biodiesel is in the extraction process. Microalgae extraction requires considerable cost. The purpose of this study was to determine the effect of ohmic heating as a method of pretreatment in microalgae oil extraction. The raw materials used were microalgae paste diluted in two levels cell density, 20 g/L, and 30 g/L. The pretreatment using alternating current (AC) electric with two voltage levels (55 V and 110 V), and the duration of pretreatment was 30 seconds and 60 seconds. The next step was drying and extracting microalgae by solvent extraction method of n-hexane. The results showed that the highest oil yields (14.88%) were obtained by cell density treatment 20 g/L, done for 60 seconds of pretreatment and 110 V voltage. This result was higher than without pretreatment, so the use of pretreatment by ohmic heating can improve extracted oil yield than without pretreatment.