What is Biodiesel?
It is a bunch of chemicals called fatty acid alkyl esters. They’re slightly different to vegetable oil because it’s undergone transesterification. Most of the chemicals are fatty acid methyl esters because one of the reagents in its manufacture is methanol. There are also fatty acid ethyl esters if the reagent is chosen to be ethanol.
This page has a fantastic diagram showing its production: http://biofuelsassociation.com.au/biofuels/biodiesel/how-is-biodiesel-made/