Biodiesel is chemically similar to petroleum diesel

Biodiesel consists of chemicals known as fatty acid methyl esters (FAME). Biodiesel can be used as a substitute for petroleum diesel fuel or as an additive to petroleum diesel fuel.

A biodiesel refinery in Wisconsin

Source: Stock photography (copyrighted)

Biodiesel can be made from a variety of materials

Most biodiesel in the United States is produced from vegetable oils, but it is also made using other feedstocks (raw materials) like waste animal fats from processing plants or recycled cooking oil and grease from restaurants.

Biodiesel can be made from virtually any feedstock that contains an adequate amount of free fatty acids, which are the raw materials that are converted to biodiesel through a chemical process called transesterification. FAME are a type of fatty acid esters that can be produced by an alkali-catalyzed reaction between fats or fatty acids and methanol. The molecules in biodiesel are primarily FAME.

Researchers are working to harvest algae for biodiesel production, because algae contain fat pockets that help them float. This fat can be collected and processed into biodiesel. Continued biodiesel production and use will help the United States meet biofuels consumption levels mandated by the U.S. Renewable Fuel Standard.

In addition to biodiesel derived from FAME, it is possible to make a diesel fuel substitute from cellulosic material like bark or switchgrass. This fuel, sometimes called renewable diesel, also counts toward meeting the U.S. Renewable Fuel Standard mandate. Like cellulosic ethanol, the commercial viability of renewable diesel has yet to be demonstrated.