Sub-Product

Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with an alcohol, producing a methyl, ethyl or propyl ester by the process of transesterification.

When methanol is used fatty acid methyl esters (FAME) are formed. When ethanol is used fatty acid ethyl esters (FAEE) are created. Other alcohols used for the production of biodiesel include butanol and isobutanol.

Unlike the vegetable and waste oils used to fuel converted diesel engines, biodiesel is a drop-in biofuel, meaning it is compatible with existing diesel engines and distribution infrastructure. However, it is usually blended with petrodiesel (typically to less than 10%) since most engines cannot run on pure biodiesel without modification. Biodiesel blends can also be used as heating oil. The US National Biodiesel Board defines "Biodiesel" as a mono-alkyl ester.

Source: Wikipedia, Biodiesel