Direct biodiesel production from wet microalgae assisted by radio frequency heating

Rapid growth, fixation of carbon dioxide, and little competition with food plus some species possessing high lipid content make microalgae a suitable feedstock to produce biodiesel. However, high cost related to dehydration, lipid extraction and conversion to biodiesel hampers industrialization of biodiesel production from microalgae. The objective of this study was to develop a biodiesel production procedure directly from wet microalgae. The system was operated under atmospheric pressure without requiring any specific apparatus. Wet microalgae (Chlorella vulgaris) was pretreated by radio frequency (RF) heating to disrupt cell walls first, followed by esterification and transesterification with relatively small amount of methanol and catalyst (either HCL or NaOH) assisted by RF heating at 55 °C for only 20 min. The fatty acid methyl esters (FAME) yield reached as high as 79.5 ± 3.0%. The two major factors impacting biodiesel yield are catalyst and methanol. Also, scanning electron microscope (SEM) was used to investigate morphology of the algae before and after the RF heating pretreatment. The SEM images visually verified the significant effect of cell disruption by the pretreatment. Although this pathway was developed for Chlorella vulgaris, it can be applied to any other microalgae which are rich in both free fatty acids and triglycerides.