Calcium oxide (CaO) acts as a heterogeneous base catalyst. Calcium oxide can be extracted not only from waste materials such as oyster shells, eggshells and crab shells, but also exhibits tolerance to low to moderate oil quality, free fatty acid and water content in raw materials. Calcium oxide can be used in biodiesel production, where it effectively catalyzes the transesterification of vegetable oils or animal fats to produce alkyl esters[1].
