Could Astronauts Harvest Nutrients From Their Waste?

A new study suggests that modified yeast feeding on human waste can make useful byproducts for long missions in space

Mars Urine
Astronauts traveling to Mars may be able to pack a little lighter with microbes that could make nutrients and the building blocks of plastic. Pat Rawlings / NASA

There's no doubt that the journey to Mars will be a feat of both engineering and logistics. But a few basic human waste products could actually help in the venture, providing not only  vital nutrients, but also materials that could be used to make tools.

In a presentation given this week at the American Chemical Society's National Meeting and Exposition, a scientist from Clemson University explained how genetically engineered yeast could feed on the astronaut's urine and carbon dioxide to produce valuable byproducts like omega-3 fatty acids and compounds commonly found in plastics, reports Andrew deGrandpre for the Washington Post.

"If astronauts are going to make journeys that span several years, we’ll need to find a way to reuse and recycle everything they bring with them,” biomolecular engineer Mark Blenner said in a statement before his presentation. “Atom economy will become really important.”

This is an urgent problem. NASA is hoping to start human settlements on Mars in the next 20 years, and private space companies are pushing for even faster colonization. But this will be no easy feat. Mars is just over 30 million miles from Earth, and the people that eventually make the trip must be protected and nourished throughout the journey.

Every supply brought on board adds to the total mass of the craft flung into space. Not to mention each extra tool takes up space in what will likely already be a cramped environment. But without adequate provisions and tools, astronauts on board the Mars-bound craft would be doomed before they even left Earth.

To help get around this problem, NASA has been funding Blenner since 2015 to scrutinize a strain of yeast called Yarrowia lipolytica, reports Catherine Caruso for STAT. Blenner has used the yeast strain, a close relative of baker's yeast available in grocery stores, as a template that he then modifies with genes from algae and phytoplankton. These alterations allow the microbes to produce the omega-3 fatty acids necessary for healthy metabolism in humans.

This yeast can also be genetically engineered to produce monomers, the basic building blocks of polymers that could be used by 3D printers to create new tools on the spacecraft or on Mars, reports Becky Ferreira of Motherboard.

But the yeast still need fuel to produce these products. That's where the astronauts, and their waste, come in. The microbes can use the nitrogen in human urine and carbon dioxide from their breath to create useful compounds. 

This work is still in its very early stages, notes Nicola Davis of the Guardian. Blenner still needs to tweak the yeast so that it produces useful quantities of the nutrients and monomers. There's also the question of whether the microbes could survive in the low-gravity, high-radiation conditions of a trip to Mars.

If it all works out, however, future settlers on the Red Planet might not have to live solely off potatoes.

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