Biofuel is fuel derived from biomass - which is any recently living organisms or their metabolic byproducts, such as manure from cows. It is renewable unlike any other natural resource such as petroleum, coal, or nuclear fuels.

Some are ethanol fuel, methanol, butanol. Biologically produced oils, sometimes referred to as bio-oils, can be used in diesel engines. Straight vegetable oil, waste vegetable oil, and biodiesel obtained from transesterification of animal fats and vegetable oil, directly useable in petroleum diesel engines.