Biodiesel is a type of fuel prepared by changing vegetable oil, animal fat, special types of algae and possibly even sewage. It is considered a type of renewable energy, since it all comes from living plants and animals. It can be used to power an engine, usually for vehicles, including airplanes. It replaces diesel that comes from petroleum, a type of fossil fuel.

Biofuel prepared from biomass is different since it does not start from oil and uses a different chemical process to make the fuel.