Oh man, we had a guy do almost the same thing at our garden two summers back. Here is the thing nobody tells you, a fridge is mostly metal and foam and freon, so the actual compostable part is tiny, like the shelves and the crisper drawers if they are the cheap plastic kind. The metal shell will just sit there for years and leach who knows what into your soil, and if there is still freon in the lines you are basically poisoning your whole plot. You have to take the fridge to a scrap yard or call the city for a bulk pickup, and they will drain it proper. For the plastic inside, it has to be cut up small and even then most of it is not the kind that breaks down, so it just turns into microplastic in your beds. Tell the guy to stick to veggie scraps and coffee grounds, and if he wants to get rid of a fridge he should haul it to the dump like a normal person.