Biodiesel refers to fatty acid methyl or ethyl esters produced through esterification of vegetable oils (such as rapeseed oil, soybean oil, peanut oil, corn oil, cottonseed oil, etc.), animal fats (such as fish oil, lard, tallow, mutton fat, etc.), waste oils, or microbial oils with methanol or ethanol. Biodiesel is a clean fuel that can replace conventional petroleum diesel.