https://www.newscientist.com/article/2165731-astronauts-could-3d-print-tools-from-their-own-processed-faeces/

Waste not, want not. A new method for turning faeces into plastic could come in handy for people living on Mars.

Interplanetary travellers face two big challenges: how to transport all the tools and equipment they need from Earth, and what to do with all their waste. Mayi Arcellana-Panlilio at the University of Calgary and her colleagues wondered if they could find a simple solution to both.