Microbes may help astronauts transform human waste into food

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 per cent protein and 36 per cent 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.
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 per cent protein and 7 per cent 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 per cent protein and 16 per cent 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.