questions in the title

I'd assume not but it probably has some in it

Yes, decomposed fat is primarily made up of various fatty acids and some glycerol, plus some oxidation products.

Fats are mostly made up of triglicerydes.

A triglyceride molecule is glycerol with three long fatty acid chains stuck to it.

Different fats have different fatty acids attached to the glycerol, and in different proportions.

During rotting/fermenting, trigycerides are taken apart and the leftovers float freely (and make up BTO).

To make it more visual:


glycerol:



common fatty acids:




fat (triglyceride):