Just google "Natural Burial".
It's become a bit of a "movement". Warren Zevon, Alevasholem, was buried naturally in Oregon. There is a Natural Cemetery about five miles from me in Maine.
Thr eason we have, in this country, the "vault thing" is to prevent the embalming chemicals from entering the water supply. They're toxic as all get out and take a long time to break down. Even their broken-down components are toxic.
I would go for it, except I prefer to be cremated. I'm not worried about the "zombie thing" like some others, (wink), but I want a pyre. Actually, the burning-ship modal of the Norse is quite cool, but I'll just take the pyre. Or, being put into one of those vulture-towers in Bangra...