Garry Porter remembers being at Mount Everest’s south base camp in 2003, watching Sherpa porters haul down blue barrels filled to the brim with human feces. “What they do is, they have a poop barrel, and they haul it to a teahouse village,” Porter said, explaining how Sherpas in Nepal deal with the waste left behind by the estimated 700 climbers and guides who spend two months on Everest every climbing season.