An alternative fuel derived from cultivated algae. Algae biodiesel can be used for cars, airplanes and heating systems. Replacing dwindling fossil fuels with algae-derived oil is among the promising developments in the quest for cleaner, sustainable energy. Algae are plantlike organisms that are easy to grow without disturbing any natural habitats–all they need is water, sunlight and carbon dioxide. They produce an oily substance, commonly seen in pond scum, that can be extracted and made into fuel.