Microalgae - organisms from which a diesel-like fuel can be derived. Cultured in the American southwestern deserts, NREL-developed microalgae may one day produce large amounts of lipids for conversion to biodiesel fuel. A biofuel is a fuel that contains energy from geologically recent carbon fixation, such as plants. These fuels are produced from living organisms. Examples of this carbon fixation occur in plants and microalgae. These fuels are made by a biomass conversion (biomass refers to recently living organisms, most often referring to plants or plant-derived materials). This biomass can be converted to convenient energy containing substances in three different ways: thermal conversion, chemical conversion, and biochemical conversion. This biomass conversion can result in fuel in solid, liquid, or gas form. This new biomass can be used for biofuels. Biofuels have increased in popularity because of rising oil prices and the need for energy security.