There's an interesting concept I saw a few years back of the mushroom body suit: http://grist.org/living/mushroom-burial-suit-turns-dead-bodi.... It's essentially a bag laced with mushroom spores. You put it on an unembalmed body and bury it and the mushrooms use the corpse as fuel. Something like that and a backyard burial is probably the most ecologically friendly way of disposing of a body.