Scientists want to make plastics in space from recycled human waste

Astronauts could turn their bodily waste into useful plastics on long-distance space journeys, say scientists.

“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,” said Mark A. Blenner, an assistant professor at Clemson University, South Carolina. “Atom economy will become really important.”

He and his team are studying ways of repurposing waste molecules from breathing, eating and using materials, and converting them into products the astronauts might need, such as polyesters and nutrients.

Essential nutrients such as omega-3 fatty acids, important for health, only last a couple of years, and so they will have to be made en route during longer journeys to Mars and beyond. “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,” said Blenner.

Genetically engineered yeast – which feeds on nitrogen (obtained from urine) and carbon (from carbon dioxide in exhaled breath) – can be used to churn out monomers and link them together to make plastic polymers. These could then be used in a 3D printer to generate new plastic parts.

For now, only small amounts can be made, but scientists are working on boosting output.

Janet Scott, a leading chemist at the University of Bath who was not involved in the research, told Professional Engineering that it was an “interesting approach”.

“The production of omega fatty acids and polyhydroxyalkanoate (polyester) plastics using organisms is well known, and both technologies have been conducted at large scale (albeit with different organisms) here on Earth, but it is interesting ‘out of the box’ thinking to use wastes from space travellers to feed the ‘bacterial biofactories',” she said.

Scott said ‘industrial biotechnology’ was a growing sector on Earth, with 'heaps' of approaches being developed. “Using wastes as feedstocks is a good way to close the loop, and so to keep materials cycling in the ‘circular economy'," she said. “Thinking about closed systems is an absolute must in space exploration.”

Antoine Buchard, who is working with Scott on similar work turning sugars into plastics, told PE that a mixture of biological and chemical solutions might be best. "Both have their advantages," he said. "Microorganisms are miniature chemical factories, which can carry out several complex chemical steps without the need for intermediate purification and can keep working as long the microorganisms are fed. On the other hand, the chemical approach we are taking is easy to modify to tune the material properties, depending on needs. So the perfect plan would be to have both systems in a spacecraft!"