If you plan to make a habit out of murder, I recommend taking up pottery. Building a kiln in your backyard is a relatively easy and highly rewarding experience, and they can easily exceed 2000 degrees f. That's more than adequate to incinerate bone. If you've got an oil or gas fired kiln you can get it even hotter.
Additionally, combine it with a potter's wheel and your investment will support two great hobbies (killing people and making things). Plus, think of the morbid satisfaction you'll get if you become talented and begin selling wares that have your victims' ashes baked into the glaze on your pieces.