Findings of a new study offer a potential solution to one of the challenges of long-duration space travel. Researchers at Penn State have shown that human waste could be a valuable source of food for astronauts on deep-space mission.
Penn State geosciences professor Christopher House and colleagues created an enclosed, cylindrical system where they placed artificial solid and liquid waste used in waste management tests and select species of bacteria.
The bacteria broke down the waste using anaerobic digestion, a biological process in which microorganisms break down biodegradable materials without oxygen.
The researchers said that anaerobic digestion of human waste readily produced methane, which could be used to grow a different microbe currently used as animal feed. The researchers produced Methylococcus capsulatus made up of 52 percent protein and 36 percent fats.
The researchers said that this process of microbial growth offers a potentially feasible way of producing nutritious food for astronauts in space.
"On the surface of the [filter] material are microbes that take solid waste from the stream and convert it to fatty acids, which are converted to methane gas by a different set of microbes on the same surface," House explained.
High-Heat And Alkaline Microbes
House and colleagues also attempted to grow microbes in either a high-heat or alkaline environment. They found that the bacteria Halomonas desiderata could thrive when the system's pH level is increased to 11. This microbe is 15 percent protein and 7 percent fats.
The researchers were also able to grow the edible Thermus aquaticus at 158 degrees Fahrenheit. The temperature is high enough to kill most pathogens. Thermus aquaticus consists of 61 percent protein and 16 percent fats.
"This work demonstrates the feasibility of rapid waste treatment in a compact reactor design, and proposes recycling of nutrients back into foodstuffs via heterotrophic (including methanotrophic, acetotrophic, and thermophilic) microbial growth," the researchers wrote in their study, which was published in the November 2017 issue of the Life Sciences in Space Research.
Recycling Human Waste
Scientists continue to conduct studies to find more efficient ways to feed astronauts in space amid plans for a manned mission to planet Mars. Researchers, for instance, are on the search for crops that can grow in extraterrestrial world.
The study shows bacteria can also help in providing nutrients needed by humans in space missions. Recycling human waste is not new. ISS astronauts already recycle a portion of the water they use from their urine.