Biodiesel is made from vegetation (usually rapeseed or palm) and methane.
The vegetation must be harvested crushed and turned into vegetable oil.
The methane reacts in a steam methane reformer and/or O2 blown POX/secondary reformer to produce syngas followed by a highly exothermic tubular reactor that has a large recycle and produce a lot of relatively low pressure steam as a by product.
The simplest part of the process occurs when the vegetable oil created from processing vegetation and the methanol produced from natural gas then react in a stirred tank reactor to form an Ester called "biodiesel" and glycerin. Why don't you do an Exergy (aka available energy) analysis on the whole process instead of one of the simplest steps?