Products

The final product

The major process product is PHB (Plyhydroxybuterate) plastic. PHB can be used in SLS 3D printing on Mars and on the ISS. The advantages of producing PHB plastic on Mars are:

• availability of resource for production of urgently needed tools
• the plastic is biodegradable and hence the Carbon-Hydrogen cycle can eventually be closed (once the 3D printed tool is on no use any more)
• Solve the problem of high cost of material shipping to space
• Solve the problem of waste management on Mars

By-product streams:

1. Sludge-like matter
2. Water stream containing some VFAs and PHB stream (plastic for 3D printing)

Treatment of by-products to produce useful materials:

The sludge-like by product can either be fed into the general wastewater processing unit and be combined with the other sludge for treatment, or it can be treated using Torrefaction (mild pyrolysis) technology. The two streams that would leave the torrefaction processing unit (TPU) are water with some VFAs and char - black solid matter. Our team believes that torrefaction is the most efficient approach to treatment of the sludge-like matter as it holds a couple of benefits:

• it is biologically stable - doesn’t support biological activity
• torrefaction allows for production of pyrlytic water – meaning extra water recovery
• char can be used as a building material
• char can be used for radiation shielding
• char can be used as a food substrate
• char can be used as a carbon/hydrogen storage

The torrefaction technology is just emerging and was not yet tested large scale, however a couple of papers (M. Serio, J. Cosgrove, M. Wojtowicz, 2016), (M. Serio, M. Wojtowicz, K. Wignarajah, 2014)) by NASA outline the potential of the system and see it as a promising solution for the sludge management in space and on Mars.

Our team suggests that the water and VFAs by-product stream is fed into one of the final stages of the water processing unit (WPU), where it can be cleaned to the required water quality standard. Such treatment allows to close the water loop in the feces treatment (recycle all the water).