 Biofuels are renewable energy sources derived from organic matter such as plants or animals. Ethanol is one of the most popular biofuels, produced from fermenting sugars in plant material like corn or sugarcane. First generation biofuels are made from edible crops, but they cannot meet the global demand for ethanol. Second generation biofuels can be made from non-edible lignocellulosic biomass, while third and fourth generation biofuels can be made from algae and other microorganisms. Biorefining is the process of converting biomass into useful products, including biofuels. This article was authored by Richard Ahorsu, Francesca Medina, and Magda Constanti.