Biodiesel is not vegetable oil. Biodiesel is a clean burning renewable fuel made from agricultural co-products and byproducts, animal fats, and other natural oils and greases. It is made through a chemical process converting oils and fats of natural origin into fatty acid methyl esters. Biodiesel is intended to be used as a replacement for petroleum diesel fuel, or it can be blended with petroleum diesel fuel in any proportion. One of the great advantages of biodiesel is that it can be used in existing diesel engines with practically no modifications. Biodiesel is the only alternative fuel to have fully completed the health effects testing requirements of the 1990 Clean Air Act Amendments.