According to a NASA-approved study out of Penn State University...it's poop.
There would be a recycling procedure involving mixing the good portion of the waster with microbes to create something edible.
Penn State geosciences professor Christopher House describes the product as "a smear of microbial goo."
Kinda makes those potatoes Matt Damon ate in The Martian not so bad, right?
What's the worst item you've ever eaten?