Biodiesel is a prominent biofuel.
Plant oils and/or animal fats are put through a process of “transesterification”; a chemical reaction in which the triglycerides of the oil are broken apart and combined with an alcohol (usual methanol) to produce fatty acid methyl (or ethyl) esters, with glycerine as a by-product. Pure biodiesel is safe to use in diesel engines, and is generally cleaner and better for the engine (the original diesel engine was designed to run on peanut oil). As biodiesel has a slightly lower energy content than petroleum diesel most commercial product is a “blend”. This blend is most commonly 80% biodiesel and 20% petroleum diesel.