Humans have wanted to go to Mars for a long time. NASA says it wants to send people there by the 2030s, while private companies like SpaceX have proposed building colonies on the Red Planet.
There are, of course, a lot of kinks that have to be worked out for us to get there. One of them is living in an enclosed space with a few other people for months on end.
Another is the human need for food. Packing all the food and water for a Mars mission would take up a lot of room and would use lots of fuel. Trying to grow food would use up a lot of energy.
Now, scientists at Penn State think they've found a way for astronauts to create food with help from their own human waste.
Lisa Steinberg, a former postdoctoral astrobiology researcher at the school who now works as a science lab supervisor at Delaware County Community College, told NPR's Scott Simon about how the multistep process works.
"We collect the solid and liquid waste from the astronaut and we put it into a reactor where we have a mixed group of bacteria that break that waste down," she says. "And from that they produce methane, which is a gas. And then that methane can be fed to a second type of bacteria — that it grows up and then the cells themselves have a lot of protein, have a lot of fat."
Penn State News described the model they built:
"They created an enclosed, cylindrical system, four feet long by four inches in diameter, in which select microbes came into contact with the waste. The microbes broke down waste using anaerobic digestion, a process similar to the way humans digest food."
The process can grow a bacterium called Methylococcus capsulatus. It's already in use today as an animal feed.
In the case of the Penn State researchers, their end product looks like a type of "microbial goo," as Steinberg's co-author Christopher House describes it. He told Penn State News that it's similar to the Vegemite or Marmite spreads that people put on toast. The goo has a lot of protein and a lot of fat in it.
The substance "can serve as a supplement to the diet of the astronauts and the life support system," Steinberg says.
It's not quite operational yet.
"To put it in a life support system you would definitely need to have a lot of safety precautions in place," she says. "Astronaut protection would be first and foremost. You would need to make sure that there's no potential of pathogens from the waste getting into the food source."
The researchers didn't actually taste it, Steinberg says. She says people who have tasted the stuff in the past "described it as somewhat bland."
Steinberg has a solution for the good of the astronauts' taste buds, however.
"I recommended just bringing some Sriracha on board," she says, "and that'll make anything taste good."
SCOTT SIMON, HOST:
There's only so much space on a spacecraft, which means limited space for food and water. American crews on the International Space Station recycle their own sweat and urine to produce fresh drinking water - bottoms up. Now new research from Penn State University may have figured out a way to not let another human waste go to waste by turning effluvia into food - got that? Dr. Lisa Steinberg was lead author on the study and joins us now. Thanks so much for being with us.
LISA STEINBERG: Thank you for having me.
SIMON: So I gather microbes do the heavy lifting here, right?
STEINBERG: They sure do. So microbes catalyze most of the major processes on Earth to recycle nutrients, and we're putting them to work in the life-support system to do the same thing.
SIMON: And how's that work?
STEINBERG: We collect the solid and liquid waste from the astronaut, and we put it into a reactor where we have a mixed group of bacteria that break that waste down. And from that, they produce methane which is a gas. And then that methane can be fed to a second type of bacteria that it grows up. And then the cells themselves have a lot of protein, have a lot of fat, and they can serve as a supplement to the diet of the astronauts in the life-support system.
SIMON: And the final product looks and taste like what?
STEINBERG: My collaborator on the project, Dr. Chris House, described it as a marmite or Vegemite-like substance. I'm not familiar with either of those because I don't eat them. But he does and said that the consistency reminded him of that.
SIMON: Kind of - Vegemite and marmite - I've had both. Let's just describe it as kind of a translucent peanut butter except it don't taste like peanuts, OK?
STEINBERG: I'm sure it probably has a much yeasty or richer flavor than, you know, just peanut butter would.
SIMON: Yeah, but you haven't tasted it, right?
STEINBERG: No, so that would have required special permissions that we didn't obtain. So no, we did not taste it. But it has been used for years as a supplemental food for animal husbandry and aquaculture. And at some point, there were some tests done with people who described it as somewhat bland.
SIMON: Oh, that's much better than I was faring. Yeah. All right.
STEINBERG: I recommended just bringing some Sriracha on board, and that'll make anything taste good.
SIMON: (Laughter) Absolutely true. And you know what the French say - as long as the sauce is good. And why is this a great step forward for mankind?
STEINBERG: Well, if we are going to have manned space missions to near-Earth asteroids or Mars - anything that is quite a distance away - it's not going to be feasible at this point to try to pack along all of the food and the water that astronauts would need for the duration of the trip. So we need to have some way of recycling the nutrients from waste material back into food material in a pretty short span of time. So we're hoping that this will make those kinds of manned space missions more feasible in the future.
SIMON: What remains for this to become a reality?
STEINBERG: Well, to put it on a life-support system, you would definitely need to have a lot of safety precautions in place. Astronaut protection would be first and foremost. You would need to make sure that there's no potential of pathogens from the waste getting into the food source. And then beyond that, you would just the system to be incredibly reliable and predictable. Nobody wants surprises in space.
SIMON: So so far, no plans for recipe book?
STEINBERG: No, not for me - I don't even cook at home, so I wouldn't know what to do with this.
SIMON: Dr. Lisa Steinberg, who's a post-doctoral astrobiology researcher at Penn State and lead author of the study - thanks so much for being with us.
STEINBERG: Thank you.
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