It would make sense to try and recycle body waste, so, why don't we?
The most obvious thing to repurpose would of course be urine or faeces, maybe as plant fertiliser or as a biomass energy source...
But what about things like toenail clippings, hair and skin? I know that people who have a lot of hair cut off can send or sell it to a wigmaker, but what about smaller sections of hair, and underarm hair, for example? And what about the thick, rough skin on your heel, and all those fingernail and toenail clippings? I mean, we produce so much of that material in the course of a lifetime. Isn't there any purpose that it can be put to? Does it have to go to waste?