How Drinking Urine, And Pee-Powered Spacecraft, Will Help Humans Reach Mars

By Ben Wolford on April 12, 2014 2:45 PM EDT

Astronaut Chris Hadfield drinks from a water bag inside the International Space Station. That water was probably urine at one point. (Photo: NASA)

Astronaut Chris Hadfield drinks from a water bag inside the International Space Station. That water was probably urine at one point. (Photo: NASA)

Lugging water into space is extremely expensive and perhaps, in the case of future missions to Mars, impossible. Urine, however, comes free of charge.

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That's why scientists are keen to increase the efficiency of urine filtration and to find new ways to recycle every last drop. Urine actually contains about 3,100 individual compounds, according to this extensive database of pee components, compiled and maintained by Canadian scientists. Not all of them are useful (yet), but chemists and NASA officials have been trying to figure out what compounds are. One recent study even shows how pee can be turned into power.

The water, however, is still the most precious of urine's components for astronauts. The residents of the International Space Station treat water like gold, because it practically is. To launch a gallon of water into space costs about $125,000, according to Eduardo Nicolau, a chemist at the University of Puerto Rico, Rio Piedras, who spoke recently with Science. So the astronauts up there do everything they can to conserve. There are no water faucets for washing; instead they dab a little water on a washcloth. On Earth, we use around 50 liters of water to take a shower; in the ISS, they use about four, NASA reports.

NASA tries to capture every drop or vapor of water to shuffle it through the onboard filtration system, which resembles a 1950s film version of what future computers would look like. There's humidity inside the space station from the astronauts' breath, and machines condense it and reuse it. All the astronaut pee gets piped through the filter, which uses osmosis to create pure water. "The water that we generate is much cleaner than anything you'll ever get out of any tap in the United States," says Layne Carter, who's in charge of water processing at the Marshall Space Flight Center. And that's good because the lab rats' urine also goes into the filtration system.

Several groups are trying to send humans to Mars. NASA, of course, has made Mars a priority, with the goal of a manned mission by 2030. Private groups are also interested, Mars One probably the most famous of these. "Our astronauts will be settling on Mars indefinitely. It's not feasible to send water, oxygen, and food from Earth to the astronauts: they will produce those on Mars," Mars One says on its website. One source will be recycling urine; another, they claim, will be extracting it from the Martian soil. And water isn't just for drinking — NASA and Mars One plan to break down water into oxygen to breathe.

With current technology, only about three-fourths of the water in urine is recaptured. Much of it goes to waste as brine. Plus, the ISS loses water through its air locks, its oxygen-converters, and through its carbon dioxide filters. But according to Science, NASA is working on increasing urine filtration efficiency to 100 percent.

Meanwhile, other scientists, including Nicolau in Puerto Rico, are working on other uses for human waste. The other major compound of urine is urea, a compound of hydrogen, nitrogen, and oxygen that can be converted into ammonia. According to a recent study published in Sustainable Chemistry and Engineering, Nicolau and his colleagues describe how they could feed that ammonia into an electrochemical cell to spark electricity. "It is estimated that in future long-term space missions, human wastes such as urine will contribute more than 50 percent of the total waste," Nicolau writes. His process converts an estimated 86 percent of the urea to ammonia.

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