I did arctic exploration for a decade. We froze all our poo (I'm using this word and giggling like a child -- and blaming the headline). Then we put it Rubbermaid tubs and put them on the supply plane that was bringing us food and fuel. They were disposed of in town at proper waste management facilities.

Bonus photo of one of our toilets -- basically a seat in a bucket in a tent vestibule. The waste froze solid almost immediately so it didn't stink.

Seems the Everest adventures weren't held to the same standards.