Plants --and some algae and bacteria--- already have a highly efficient system for storing solar energy. Through the complex process of photosynthesis, they use sunlight to synthesize organic compounds from carbon dioxide and water. By burning biomass--- organic material, such as plant matter or animal waste---or the liquid fuels derived from it , some of the stored solar energy can be extracted and used to power businesses, homes and cars. The most common types of biofuels in use today are ethanol and biodiesel. Ethanol is an alcohol. It’s typically produced by using yeast to ferment sugars from biomass , such as corn or sugarcane. The yeast cells release ethanol as a byproduct of their metabolism , and the ethanol can be distilled to make it more concentrated. Biodiesel, another common biofuel, is made by combining fats, such as vegetable oils , with alcohols , such as methanol, in the presence of a catalyst. Some researchers are working on producing biofuel from genetically modified algae and bacteria because they will have lower impacts than ethanol or biodiesel , both of which require a lot of farmland to produce.