INFORM April 2025

24 • inform April 2025, Vol. 36 (4)

New enzymatic pretreatment process provides biodiesel feedstock flexibility Rasmus Bøg Alstrup, Mads Agerskov Pedersen, and Lucas Klettenhofer

Demand for renewable fuels is increasing, leading to increased demand for high-quality feedstocks. Such sources have become scarce and expensive. To remain competitive, biodiesel producers need flexibility when it comes to feedstock quality. Flexibility requires pre treatment processes that provide a low-cost means of obtaining optimal feedstocks for biodiesel production. Traditional biodiesel is produced by the transesterification reac tion of glycerides—from vegetable oils, waste oils, and animal fats— with methanol to form fatty acid methyl esters (FAME). However, high amounts of free fatty acids (FFA) in waste feedstocks reduce the effi ciency of the alkaline-catalyzed transesterification reaction by forming soaps while consuming the catalyst. To ensure that feedstocks with higher FFA concentrations can be processed profitably, FFA should be reduced to below 0.2 weight percent prior to transesterification. This specification presents producers with both a challenge and an opportunity for innovation. Enzymatic pretreat ment, as presented here, has proved to be a viable solution for existing biodiesel plants. EXISTING TECHNOLOGIES FOR REDUCING FFA Numerous pretreatment processes exist for reducing FFA concentrations in feedstock, including stripping/deodorization, chemical neutralization, glycerolysis, and acid esterification. Stripping/Deodorization is a robust and widely used pretreatment process, especially for palm oil-based biodiesel with between three and seven weight percent FFA. It is inexpensive to operate at high capacities

• In traditional biodiesel production high concentrations of free fatty acids (FFA) pose a challenge for producers, limiting feedstock flexibility. • A new enzymatic solution reduces and converts up to 20 weight percent FFA to as low as 0.5, enhancing feedstock flexibility and fatty-acid methyl ester (FAME) yield. • It serves as an ideal pretreatment add-on for existing alkaline-based transesterification processes. • The solution can also directly replace acid esterification before transesterification using existing equipment.