Scientists say it could be possible to break down solid and liquid human waste in microbial reactors to grow food on future space missions.
The lovely study, published in Life Sciences in Space Research, was led by a team from Penn State University in Pennsylvania. They were investigating whether astronauts on missions to Mars or elsewhere could use their own waste to provide energy to grow food.
"We envisioned and tested the concept of simultaneously treating astronauts' waste with microbes while producing a biomass that is edible either directly or indirectly depending on safety concerns," Christopher House from Penn State, a co-author on the study, said in a statement. "It's a little strange, but the concept would be a little bit like Marmite or Vegemite where you're eating a smear of 'microbial goo.'"
Currently on the International Space Station (ISS), US astronauts recycle their urine (the Russians don’t), but solid waste is sent to burn up in Earth’s atmosphere. While it might be a bit gross, it turns out that solid waste could actually be pretty useful if you’re not near Earth.
In their research, the team didn’t use actual human waste, but instead used an artificial solid and liquid waste often used for waste management tests. They put this inside a cylinder 1.2 meters (4 feet) long, compact enough to fit on a spacecraft, inside which microbes broke it down via anaerobic digestion (without oxygen).
During the digestion process, they found that methane was produced, which could grow another microbe called Methylococcus capsulatus that’s used in animal feed. From this, they produced a M. capsulatus that was 52 percent protein and 36 percent fat, which could be a food source for humans.
They were also able to increase the pH level and temperature to grow two equally nutritious microbes, Halomonas desiderata and Thermus aquaticus, thus also removing any harmful pathogens.
“Based on the results of the study... microbial growth is a rapid option for the production of new foodstuff from the liberated nutrients,” the team writes in their paper.
Whether or not astronauts will be feeding their “solid waste” into a microbial reactor on future space missions, well, we’ll leave that up to NASA to decide.