The Spacefaring Power of Pee. Credit: ACSReaction
Besides water, which is the main component, urine also has a small percentage of nitrogen and carbon (in the form of urea), as well as mineral ions like potassium, calcium, and sodium. There are many ways to recover water from urine, but purifying urine in space is a different ball game. It started out as a method to cut costs and increase efficiency. After all, transporting tons of water from the Earth to space is not cheap. In 2009, American astronauts began recycling urine using a system called a Urine Processor Assembly, which could reclaim 75 percent of the available water. NASA's engineers have since improved urine-recycling efficiency. The secret ingredient is called Alternate Urine Pretreatment solution. With only a few milliliters dispensed into the toilet during each flush, the system has been proven to recover a greater portion (up to 90%) of water on the International Space Station. The success of the improved process paves the way for long-duration space travel, because the water reclamation system is essential to creating a closed life support system when the Earth is far out of reach.
Of course, there is more to urine recycling in space travel than just recovering water. A NASA-funded research team from Clemson University announced recently that they have found a way to turn urine into plastic and omega-3 fatty acids by harnessing the unique metabolic nature of a genetically engineered yeast known as Yarrowia lipolytica.
This unique creature likes to consume urea to obtain nitrogen. Interestingly, when the research switched from working with just urea solution to human urine , the yeast not only showed good tolerance of the other components in the urine, but it grew even better. The other critical step is to create sugar using carbon dioxide (from astronauts breathing). The team turned to photosynthetic cyanobacteria for help: the microbes can utilize carbon dioxide and light to produce sugars, which are fed to the yeast. The yeast uses the sugars and human urine to produce plastics and fatty acids.
“Developing plastics and omega-3 fatty acids from astronaut waste shows the possibility of what can be made in space from things that are already there,” said Dr. Mark Blenner the team leader. "We don't view this as the holy grail of how we're going to enable space travel, but it's certainly an interesting part of the equation.