Recycling astronaut urine for energy and drinking water

On the less glamorous side of space exploration, there's the more practical problem of waste - in particular, what to do with astronaut pee. But rather than ejecting it into space, scientists are developing a new technique that can turn this waste burden into a boon by converting it into fuel and much-needed drinking water.

Their report, which could also inspire new ways to treat municipal wastewater, appears in the journal ACS Sustainable Chemistry and Engineering.

Eduardo Nicolau, Carlos R. Cabrera and colleagues point out that human waste on long-term journeys into space makes up about half of the mission's total waste. Recycling it is critical to keeping a clean environment for astronauts. And when onboard water supplies run low, treated urine can become a source of essential drinking water, which would otherwise have to be delivered from Earth at a tremendous cost.

Previous research has shown that a wastewater treatment process called forward osmosis in combination with a fuel cell can generate power. Nicolau's team decided to build on these initial findings to meet the challenges of dealing with urine in space.

They collected urine and shower wastewater and processed it using forward osmosis, a way to filter contaminants from urea, a major component of urine, and water. Their new Urea Bioreactor Electrochemical system (UBE) efficiently converted the urea into ammonia in its bioreactor, and then turned the ammonia into energy with its fuel cell.

The system was designed with space missions in mind, but "the results showed that the UBE system could be used in any wastewater treatment systems containing urea and/or ammonia," the researchers conclude.