A bit of background: A few years ago I made a compost bin that does a spectacular job of decomposing everything my wife and I toss in. Except for a few weeks in the middle of winter when it freezes solid it's always hot enough to be steaming. Since I also did a good job varmint- and rodent-proofing the bin we've always felt confident to throw our meat scraps, bones and all, into the bin. In the summer chicken and pork bones will be cleaned within a month. Since the bones themselves break down very slowly I pick them out when I'm doing my weekly turn so as to keep them out of my way. This has resulted in a bucket, maybe three gallons big, filled with all kinds of bones from all kinds of animals. My estimation, from older bones I've dug out, is that it takes about three years for a chicken wing bone to degrade to the point it will crumble with the turning action of the shovel. What I'd like to do is turn these bones into bone-meal, or at least find a way to break them down enough that mixing them into my compost bin doesn't create a huge mass of hard-to-shovel-through material. Any suggestions? Edit: Since my wife and I rent we can't have fire, open or closed, on the lawn and there is no fireplace.