Regular diesel fuel, as well as crude oil, is made of roughly 75% saturated hydrocarbons and 25% aromatic hydrocarbons. The average chemical formula for common diesel fuel is C12H23, and it ranges from approximately C10H20 to C15H28.
Biodiesel is the term used to describe short chain alkyl (methyl or ethyl) esters. These are transesterified lipids made from animal fat or vegetable oil. The fat / oil is frequently a waste product from food processing, but it can be made from soybeans, corn or other grains. Biodiesel is chemically very different from natural crude oil or petrodiesel fuel. It is possible to burn un-modified vegetable oil in most diesel engines, but a buildup of deposits frequently occurs.
Biocrude is sometimes referred to as BTL (biomass to liquid).