Well, you seem to have a little redundancy in that you've got "biofuels and their feedstock derived from petroleum" in the same list as the feedstock for biofuels, which might need clarifying. But to focus on the bit you're asking about.
We have three items which, without resorting to pronouns, are
- animal and vegetable fats and oils
- biofuels derived from animal and vegetable fats and oils
- feedstock for biofuels
I assume from the way you ask the question, this instance of 'feedstock for biofuels' relates to the 'biofuels derived from animal and vegetable...etc'. You need to make that clear, if so. Making it 'such biofuels' would do the trick.
Using "them" here is reasonably clear, but more clarity would be better. It adds a couple of words, but is still less than writing "animals fats and oils" repeatedly. Well, fewer letters, but it feels less redundant:
"animal and vegetable fats and oils, biofuels derived from such fats and oils, and the feedstock for such biofuels."
That's an Oxford Comma there before the 'and', and I generally advocate them, but it might not be appropriate here, because you say earlier "biofuels and their feedstock derived from petroleum", as if it is one item in the list, so perhaps you want "biofuels derived from such fats and oils and the feedstock for such biofuels" to be seen as one item as well. If you want both instances of biofuels an feedstock to each be "single items" in that way, I would make sure to phrase them equivalently. That would make the bit you're asking about:
"animal and vegetable fats and oils, biofuels and their feedstock derived from such fats and oils"
Though if that is the end of the list in your wider sentence, you need another and:
"animal and vegatable fats and oils, and biofuels and their feedstock derived from such fats and oils."
That's using an Oxford Comma, and this is a good example of why some of us think they are good - it differentiates the "and" compositing two things within a single item in the list from the "and" that appears before the final item in the list.
Alternatively, you might rephrase "biofuels and their feedstock derived from petroleum" to "biofuels derived from petroleum, the feedstock of such [biofuels]", and the last bit of the list can be "animal and vegetable fats and oils, biofuels derives from such oils, and the feedstock of such [biofuels]". The words in square brackets are optional, but aid clarity - so you can decide whether or not to include them.