Enzymatic biodiesel production: an overview of potential feedstocks and process development.

The increased global demand for biofuels has prompted the search for alternatives to edible oils for biodiesel production. Given the abundance and cost, waste and nonedible oils have been investigated as potential feedstocks. A recent research interest is the conversion of such feedstocks into biodiesel via enzymatic processes, which have considerable advantages over conventional alkali-catalyzed processes. To expand the viability of enzymatic biodiesel production, considerable effort has been directed toward process development in terms of biodiesel productivity, application to wide ranges of contents of water and fatty acids, adding value to glycerol byproducts, and bioreactor design. A cost evaluation suggested that, with the current enzyme prices, the cost of catalysts alone is not competitive against that of alkalis. However, it can also be expected that further process optimization will lead to a reduced cost in enzyme preparation as well as in downstream processes.