Astronauts who participate in deep space travel may soon have to rely on a very unappealing way to conserve food supplies.

A research team at Penn State in the US believes it is possible to use microbial reactors to convert human waste into new food. Any spacecraft can only hold so much food for a trip and given the distance and time it takes to travel, the team believes recycling human waste would provide an adequate food source.

Geoscience professor Christopher House admitted the concept was rather unconventional. "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," House said, according to phys.org.

"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'."

The system has been tested with artificial waste. Microbes managed to break down the substance in a similar way that stomach acid digests food. "Anaerobic digestion is something we use frequently on earth for treating waste," House said. "It's an efficient way of getting mass treated and recycled."

"What was novel about our work was taking the nutrients out of that stream and intentionally putting them into a microbial reactor to grow food."

While a "microbial goo" may not sound appealing, the team believes it will provide a nutritious food source for lengthened space flight. It will be predominantly a mix of protein (52%) and fat (36%).

The system works on the principle of an aquarium, slightly adapted for methane production, House said. Astronauts already drink water partially recycled from urine. Solid waste has proved a more energy consuming task.

The Penn State team's new system would be able to cut solid waste recycling times from a few days to around 13 hours. "Each component is quite robust and fast and breaks down waste quickly," House said. "that's why this might have potential for future space flight. It's faster than growing tomatoes or potatoes."