I’ve composted meat and bone. Meat breaks down very rapidly. It’s moist which is key, and everything likes to eat it from bug larva to bacteria. You can expect a nice cut of meat to be unrecognizable a week or two after you place it in the core of a healthy compost heap. I even had the opportunity to try this with human tissue: we saved and froze the placentas from my kids births and I composted them. They melted away very quickly.
Bone is another story entirely. My first year composting I decided to throw the bones from a rib family dinner into my pile. Thereafter I kept finding them when I’d turn my pile or sift out finished compost, and I would just throw them back in to take another turn.
It’s now about 12 years after that and I still occasionally find a rib. At first I tried breaking them up with a hammer but that was a bad idea because they shatter everywhere and turn into sharp shards that don’t break down any better :D Now I just throw them in the garbage when I find them.
So you would have a daily easy time getting down to a skeleton but then you’d be stuck with that AFAIK forever.
I guess I’d say first that I don’t have anything on hand to do that with, and I have a lot of shop and garden tools.
If you can turn a skeleton into powder, it’ll no longer be recognizable as a skeleton. It has nothing much to do with composting though. It’s debatable whether the powder would undergo any chemical change by microorganisms. Eggshells for example go into a compost pile and ride along into the soil eventually where they make minerals available to plants, but eggshells don’t get significantly broken down by the composting microorganisms.
