Exploration

Waste Not! Future Astronauts Might Turn Feces Into Food

Penn State researchers have developed a method for breaking down human waste and turning it into a Nutella-like spread that might be consumed by astronauts.

An illustration of an astronaut on Mars | NASA
An illustration of an astronaut on Mars | NASA

Future astronauts may decide to eat their waste instead of tossing it out of the spacecraft. A new Pennsylvania State University project envisions how space voyagers can use microbes to break down feces and reconstitute it into a healthy, protein-rich "microbial goo." Astronauts could gulp the protein in a smoothie or smear it on their toast like a Nutella spread.

The NASA-funded study was a new direction for co-author Christopher House, a geosciences professor at the university who is familiar with microbes from early Earth and microbes that can survive in extreme environments such as the sea floor. Those research areas are useful for finding out how life evolved and whether microbes are possible on environments such as Mars.

House took on the study as a fun project for his students: It would teach them microbiology, while also helping NASA in its quest to advance the concept of space colonization, he said. While humans won't eat this concoction any time soon, House said there are other studies showing that cows can eat the stuff. "Just don't think about what you're eating," he joked in an interview with Seeker.

Here's how the researchers made the microbial mix.

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First, they used an artificial solid and liquid waste that other studies commonly use to figure out effective waste management. Then they created a 4-foot-long cylindrical microbe-and-waste mixing device with a diameter of 4 inches, which is small enough to fit in a spacecraft and smaller than many similar systems, House said.

Inside the container, the microbes digest the waste in a way that is similar to how humans digest food. Bacteria produce methane during digestion, and the byproduct is sterilized and fed into a carefully separated compartment to breed a different microbe, called Methylococcus capsulatus. Animals can eat this microbe, and in theory, humans could as well. But it will be years before safety approvals will allow astronauts — or really, anybody — to eat the stuff.

House thinks it will work and adds that the waste management system will save astronauts a lot of time — or stinky storage space — in dealing with feces.

"But in this particular scenario, there is a downside: Methylococcus uses oxygen," he said.

"We did think about other microbes too," House added, "and when talking about the future direction to go, we said we haven't yet hit on the right mix of microbes. You need something non-pathogenic, and something you can grow very specifically. Something that is high protein and high lipid [fat]."

A description of the research is published in the journal Life Sciences & Space Research.

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Waste management will be an issue for astronauts heading to Mars, no matter what system they choose. The current practice for astronauts is to put waste on departing cargo spacecraft and burn it up on reentry. That wouldn't be possible on a long Mars voyage in between planets. On Mars, disposed astronaut feces would contain microbes.

That's a possible threat to life on the Red Planet, if there is life there. But, maybe astronauts could grow potatoes in the waste, just like the fictional NASA astronaut Mark Watney did in the book and movie "The Martian." But again – just don't think about what you're eating.

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