When you cremate your remains and then seed the ocean with your ashes, it feeds the bottom of the ecosystem.

CORRECTION Cremated remains have all organic compounds broken down and is a process used to stow or preserve remains (since it’s mostly carbon, it can be used to make an artificial diamond). Also someone I know who planned on this as his return to earth funerary choice was misinformed.

That said, there is a tradition to carve a cadaver up and grind the bones and make sausages for the local wildlife, who will happily partake. In fact part of the ritual is noisy and consistent so as to inform the locals that dinnertime is coming.

Just drop the body into the wilds and the local fauna (mostly invertebrates) will do a fantastic job of utilizing your remains, and reintroducing the material back into the ecosystem. Avoid permafrost places like the Himalayas, seas that are lifeless (like the Dead Sea). Deserts will just desiccate you quickly.

Planting your body under a sapling (without formaldehyde or any other preservatives) will make sure you’re literally worm food.