Apr 6, 2018 | By David

A recent study carried out by researchers at the University of Calgary has found a novel solution to two different problems that often face astronauts on long-term space exploration missions. Dr  Mayi Arcellana-Panlilio and colleagues developed a method to dispose of human waste in a sanitary way that will also be useful for the provision of equipment and supplies. Using a special genetically-engineered enzyme, the faeces can be transformed into a special bio-plastic substance, which can then be used as a 3D printing material in order to fabricate new items when necessary.

Figuring out a way to dispose of waste has long been an issue with space travel, as conditions are cramped and water supplies are necessarily limited. The logistics and high costs involved with space exploration projects also mean that an absolute bare minimum of supplies can be taken, as a slight increase in weight can mean a huge increase in fuel is necessary to propel the vehicle into orbit. The Calgary researchers project could provide a solution to both these issues at the same time. As we've previously reported, 3D printing technology has been suggested as a solution to reduce the amount of equipment required, and now it's possible that the materials for the 3D printing might turn out to be even easier to access on-site than the space dust previously suggested.

Courtesy: NASA

The team consulted a number of space industry professionals as part of their research, including Canadian astronauts Dr. Robert Thirsk and Col. Chris Hadfield, Dr. Matthew Bamsey (Chief Systems Engineer at the German Aerospace Center), and Dr. Pascal Lee (Principal Investigator of the Haughton-Mars Project at NASA Ames Research Center and a co-founder of the Mars Institute).

The toilet situation on most spacecraft is similar to aircraft, with a vacuum tube system transporting waste safely and cleanly away into a tank. The researchers proposed introducing extra bacteria into this tank, specially selected for their chemical behaviours through genetic engineering. These bacteria would break down the excrement into further substances, one of which would be recyclable as material for 3D printing.

After being pumped into a tank, the first stage of fermentation of the waste happens naturally. Natural gut bacteria break down the waste so that substances known as volatile fatty acids (VFA) are secreted. VFA is then extracted into a further tank, where the intervention can happen in order to produce the final desired product.

(source: Biorxivv.org)

The researchers made use of E.coli bacteria, pinpointing the exact genes that were responsible for secretion of the desired substance, polyhydroxybutyrate (PHB). These genetically-modified bacteria, fine-tuned in order to secrete large volumes of PHB were then implanted into a second tank containing VFA. This VFA was secreted from the initial tank of artificial human faeces, left to naturally ferment.

The VFA rich stream is continuously fermented in anaerobic conditions. The continuous fermentation is achieved by use of a filter, which can separate out unused bacteria from the resulting PHB stream and recycle it back into the tank to further ferment the VFA. As for the PHB-rich stream, this is further filtered in order to separate out the water, which can then be recycled to go back into the toilet at the start of the waste disposal system.

Remaining solid PHB is then left to dry for a while, after which time no further processing needs to be done and it is ready for use. The PHB can then be used in a Selective Laser Sintering (SLS) 3D printer without the need for additional processing, and this high-precision technology can be used to create all kinds of equipment and supplies that might be needed over the course of a long space journey.



Posted in 3D Printing Materials



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