Biofuels can be made from agricultural crops and biomass as alternatives to fossil fuels. First generation biofuels are made from sugar, starch, vegetable oils or animal fats using conventional technology like fermentation of corn into ethanol. Biodiesel is made through transesterification of vegetable oils like soybean, rapeseed or waste cooking oil. Biogas is produced through anaerobic digestion of animal waste and contains methane that can be used for energy. While biofuels provide benefits like reducing emissions, some concerns include high production costs, competition with food crops for land, and sustainability issues depending on feedstock.