biodiesel, a biofuel made primarily from oily plants and algae and to a lesser extent from other oily sources (such as waste cooking fat from restaurant deep-frying). Biodiesel, which has found greatest acceptance in Europe, is used in diesel engines and is usually blended with petroleum diesel fuel in various percentages. See also renewable energy.
Soybean and oil palm are common plants used in biodiesel production. The use of algae and cyanobacteria as sources for biodiesel holds promise but has been difficult to develop economically. Some algal species contain up to 40 percent lipids by weight, which can be converted into biodiesel or synthetic petroleum. Some estimates state that algae and cyanobacteria could yield between 10 and 100 times more fuel per unit area than plant-based biofuels.