I can't help but recall the image of an old Blackfoot I met in Montana, many moons ago. LeRoy O'Bennon believed in "Turdology;" the idea that everything is basically sh!t that recycles eternally in a closed system. We eat stuff that was fertilized with manure; we poop; we die; microorganisms eat us and poop, and it becomes new life. This simply adds an economic layer to something that already exists... acknowledging the value of it.
At the same time, it feels a bit like a sort of rehearsal for going on fully self-contained spaceships that travel between the stars... all we need is some poop!
=^..^=