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.

They genetically-engineered Escherichia coli bacteria to convert human faeces to a type …