Biodiesel Production from Scenedesmus sp. through Optimized in situ Acidic Transesterification Process

Biodiesel, one of renewable bioenergy, has been produced from various resources such as vegetable oil, animal fats, used frying oils and microbial oils etc.1–3 Extensive study has been conducted on using edible oils, which limited by the availability of oil inventories, but these materials result in high sensitivity of prices to oil demand from industry.4–7 In order to not compete with edible oils, the lowcost and profitable biodiesel should be produced from low-cost feedstocks such as non-edible oils (used frying oils, animal fats and greases etc.). However the available quantities of waste oils and animal fats are not enough to match the today demands for biodiesel. Therefore, other biofuel feedstock, microalgae, has been focused since it would not much require the agricultural land and has higher energy yields per hectare as well as very short cell cycles (within 24 hours).8 In addition, liquid culture of the microalgae can be controlled easily and even used for a waste treatment as a new source having renewable, environmental and economical sustainability.4,6,9–11 However, in making biodiesel, actually Fatty Acid Methyl Esters (FAME), generally lipid extraction and its transesterification process produce large amount of hazardous solvent waste and are also very cumbersome.6,12,13 Automated extraction equipment such as the Soxhlet apparatus has been designed, but they require the long time of extraction process. To overcome this limitation, one step to make biodiesel, in situ transesterification (or direct transesterification from the biomass) process, has been considered where intact biomas rather than pre-extracted oil directly contacts with acidified or alkalized alcohol that acts as both an extraction solvent and an esterification reagent. This process coul reduce the long process time and also maximize biodiesel yield as well as use of reagents an solvents, etc.13–16 However, overall process of directly producing biodiesel (FAME) from fresh microalgae has not been well investigated and did not identify even key parameters in employing in situ transesterification for microalgae that contain relatively hard and rigid cell membranes, which require longer process time and larger extraction solvents, etc.17 Biodiesel Production from Scenedesmus sp. through Optimized in situ Acidic Transesterification Process