At present, the high cost of biodiesel is the major obstacle to its commercialization. Biodiesel usually costs
over US$0.5/l, compared to US$0.35/l for petroleumbased diesel (Prokop, 2002; Lott, 2002). It is reported
that the high cost of biodiesel is mainly due to the cost of virgin vegetable oil (Krawczyk, 1996; Connemann and
Fischer, 1998). For example, in the United States, soybean oil was sold on average for $0.36/l in June 2002