Introduction
Due to the energy crisis, several oil-bearing crops have become
of interest for use as a raw material for biofuel. While there are
more than 350 types of oil-bearing crops, the ones that have
been commercialized to date include soybean (Glycine max), rapeseed
(Brassica napus), sunflower (Helianthus annuus), and oil palm
(Elaeis guineensis) (Ayhan, 2005). However, to be useful either for
food or energy, first the oil must be extracted from the plants’
seeds. Vegetable oil can be extracted by several methods including
mechanical and solvent extraction. Solvent extraction is a conventional
method that is widely used at a large-scale production
for obtaining vegetable oils from their seeds, i.e. peanut (Arachis
hypogaea), soybean, sunflower, corn (Zea mays) and palm kernel
(Mattil et al., 1964). However, hexane extraction, the most common
type of solvent extraction, requires expensive equipment to
handle the solvent and to ensure worker safety measure because
hexane is a highly volatile solvent. Hexane is classified as a hazardous
air pollutant by the US Environmental Protection Agency
and they thus consider vegetable oil extraction plants to represent