Esterification using a liquid lipase to remove residual free fatty acids in biodiesel

Abstract Enzymatic catalyzed transesterification has been the subject of many studies during the last decades. Usually an immobilized lipase has been used in the papers to secure re-use of enzyme to save operation costs. Lately, the price on liquid formulated enzymes has been reduced which enable one-time use of these enzymes, and the process is used industrially. However, the transesterification suffers a drawback by leaving 2-3% free fatty acids in the crude biodiesel. This article discusses a second enzymatic esterification step based on lipase B from Candida antarctica and propose two alternative esterification setups that can be developed into full scale operation. The resulting two-step enzymatic biodiesel process - transesterification followed by esterification - provides a is a viable production layout for a large range of oil feedstocks.