Biodiesel is produced from vegetable oils and animal fats (lipids) and is used as an alternative and/or an additive to petroleum derived diesel fuel. Biodiesel production in the U.S. has been increasing from an estimated 0.5 million gallons of production in 1999 to an estimated 250 million gallons in 2006.
Soybean oil (about 2.6 billion pounds, 13 percent of 2006 production) is the principal feedstock used in the U.S., but other virgin vegetable oils (e.g., Canola, castor, peanut, palm, rapeseed, sunflower) and greases and recycled oils (e.g., tallow, yellow grease, trap grease) can also be potentially used depending on their availability and price.
Biodiesel is made by reacting vegetable oils or fats with alcohol in the presence of a catalyst. Glycerol is produced as a by-product. One pound of soybean oil yields approximately 1 pound (0.1 gallons) of biodiesel and 0.1 pounds of glycerol.