Overpacking isn't exactly an option for trips into space, even for longer trips like an eventual manned mission to Mars. There isn't enough room to carry a swag of spare parts just in case you need them, and some essential nutrients don't have a long enough shelf life to survive the journey. Now, researchers are recruiting microorganisms to solve both of those problems, by engineering them to make nutrients and 3D-printable plastics out of human waste.

The journey to Mars will be littered with hurdles, and NASA has already mapped out how it plans to start overcoming them. Astronauts on the ISS have the benefit of regular cargo shuttles to resupply them, but a crew bound for the Red Planet would need to be self-sufficient, either carrying what they need or producing what they can along the way and on arrival.

"If astronauts are going to make journeys that span several years, we'll need to find a way to reuse and recycle everything they bring with them," says Mark Blenner, lead researcher on the new project. "Atom economy will become really important. Having a biological system that astronauts can awaken from a dormant state to start producing what they need, when they need it, is the motivation for our project."

Already, 3D printing is proving invaluable for making parts in space on demand. Of course, the raw material still takes up room, but at least it can be shaped into whatever is needed, rather than lugging up spares of every type of screw and tool in case one of them breaks. But that plastic is a finite resource that will also need to be restocked at some point during the journey.

Blenner's team has developed a way to recycle waste products into useful materials using a yeast species called Yarrowia lipolytica. This microorganism feeds on nitrogen and carbon, and the researchers found that human waste can provide both of these elements. Untreated urine contains urea which, in turn, contains nitrogen, and the carbon can be sourced from the CO2 that astronauts exhale, or eventually, even from the Martian air.

The yeast can be engineered to spit out different end products. One strain produced monomers, and then linked them together to make polyester polymers, which then can be used to 3D print new parts. Another strain created omega-3 fatty acids, an essential nutrient with a short shelf-life.

For now, the yeast doesn't produce much of those materials, but the researchers are working on improving the output. They're also tweaking the plastic-producing microorganisms so they can make different types of polymers for different purposes.

The researchers presented their work this week at the 254th National Meeting & Exposition of the American Chemical Society, and they explain the process in the video below.