A character in Footfall (or was it Oath of Fealty?), by Larry Niven and Jerry Pournelle, composted the inconvenient body of someone he had murdered. I've wondered if that was practical and this article says affirmative. But for purposes of hiding a corpse I'd think it would be painfully slow to decompose. The man-eating pigs in Hannibal or Deadwood seem like a better bet, converting it quickly into fertilizer. But then you have to keep pigs.

Is it legal to feed a human corpse to pigs? Maybe it should be. It would seem to be eco-friendly.