Biofuels are biomass (organic matter) or biomass products used for energy production. Energy created from the use of biofuels is often termed bioenergy. Biomass crops grown for the primary purpose of use in biofuels are called energy crops. Biofuels include wood and wood wastes, domestic wastes, agricultural crops and wastes, animal wastes, peat, and aquatic plants. Almost any type of combustible organic matter can potentially be used as an energy source.

Plants store solar energy by photosynthesis. During photosynthesis, carbon dioxide (CO₂) and water (H₂O) in the presence of light are converted into glucose (C₆H₁₂O₆) by the following chemical equation: Further processes in the plant make more complex molecules from the glucose. The exact makeup of biomass varies with type, but in general it has the chemical formula of (CH₂O)_n and on average is about 75 percent carbohydrates or sugars and 25 percent lignin, a...