Maximizing biodiesel production from high free fatty acids feedstocks through glycerolysis treatment

Abstract The most difficult hindrance to use biodiesel is its expensive price because of the costly edible feedstocks such as soybean oil. Also, the production of biodiesel from edible feedstocks competes with the food supply causing a rise in food prices. Therefore, using the cheap waste feedstocks such as used cooking oil makes the biodiesel price inexpensive. However, the waste feedstocks have great quantities of free fatty acids (FFAs) that form soap and destroy the biodiesel properties while reacting with the base catalyst in the transesterification reaction. Consequently, a treatment step is required to reduce FFAs content below 1 wt %; thus, the base transesterification reaction can be implemented without soap formation. In this work, two types of feedstocks that had 2.82 and 2 wt % of FFAs were treated by the glycerolysis reaction at a temperature of 150 °C using two types of glycerol; the crude glycerol –a by-product in the biodiesel production process after its purification– or the pure glycerol. After the treatment, the FFAs quantity decreased below 1 wt % that was suitable for base transesterification reaction.