Ann Althouse discusses new "green" corpse-disposal technologies that are either fascinating or creepy or both, depending on how you're wired. And she asks the laconic question:
Isn't old-fashioned burial greener? It's carbon sequestration, right?
Sure. Assuming you have the space for it.
It's a problem all civilized societies have had to deal with: when half your population lives in and around cities (or more than three quarters, in the case of the US), what do you do with all the corpses? Vast necropoli extending along the main roads into town went out with the Romans*. And people today expect their graves to be eternal resting places, so you can't do the old trick of burying people until their soft tissues decay, then rotating graves and efficiently stacking the bones in catacombs.
If you want a permanent receptacle for the dead, close to home, immediately after the time of death, you have to resort to mechanical corpse-ensmallening. If your tribe has developed a fire-taboo that rules out cremation, well, then... Your options are basically to ship the body to a cemetery outside your usual range, pay a fortune for the vanishingly limited urban burial space, or resort to weird high-tech methods involving caustic chemicals or liquid nitrogen.
[* - ETA: I am shamed. It turns out the correct plural of necropolis is necropoles or necropoleis, depending on whether you're following Latin or Greek. "Necropoli" is faux Latin, like "octopi".]