The legend about the origin of the word sabotage is that French workers being put out of a job by bosses installing new machinery would drop their wooden clogs (called "sabots" in French) into the machinery's gears, thus damaging it.
Like most meat, actually composting bodies would require a very hot composting temperature, constant mixing, and you'd want to put it through a grinder first, or else it won't properly mix. Especially in the case of bones, those really need to be ground down so they can properly decompose.
Everything coming out of an oil refinery is going to burned either way. So while a big fire at one of those wouldn't be good for the environment, it wouldn't be any worse than it continuing to operate normally.