Team:Calgary/Products

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Products

Overview

The main product from our process is PHB, which can be used for 3D printing after the PHB extraction step. Water is also recovered from human feces and can undergo additional treatment after PHB extraction to become potable water or to be reused in the vacuum toilet. Lastly, char would be produced as a byproduct of torrefaction to treat the solids separated during the solid-liquid separation step. The resulting primary product and secondary byproducts are summarized in Figure 1.

Figure 1: Diagram of the proposed process indicating primary product PHB and secondary products (water and char).

Desired product: PHB

The major process product is PHB bioplastic. PHB can be used in Selective Laser Sintering (SLS) 3D printing on Mars. The production of PHB from solid human waste is advantageous for the following reasons:

• It addresses the challenge of anticipating every little thing astronauts might need on Mars by providing a resource for production of urgently required tools
• It addresses the issue with high transportation costs
• It reuses solid human waste and does not require an additional feedstock
• It recovers water from solid human waste
• It produces char that can be used for applications that NASA is considering such as fertilizer or radiation shielding
• It produces a plastic that can be biodegraded in a controlled environment to close the carbon-hydrogen cycle

PHB characteristics and properties:

Physical Properties (Manufacturing and Properties of PHB)

• Molecular weight = 2-3×10³ kDa
• Melting point = 173°C at 1 atm
• Crystallinity = 55%

Byproducts: Water and VFA stream

In our process, water is recovered from solid human waste. This water + VFA stream can be treated in the water processing unit (WPU), which is currently implemented on the International Space Station to recycle and clean water. Such treatment allows us to close the water loop in the feces treatment by recycling all of the water.

Byproduct: Char

The sludge byproduct is produced during solid-liquid separation and filtration stages. Sludge can either be fed into the general wastewater processing unit, where it would be combined with the other sludge for storage or treatment, or it can be treated using torrefaction (mild pyrolysis) technology. Torrefaction will produce char which can be a used as a building material, radiation shielding, and as a food substrate. In addition to char, torrefaction will recover more water and VFAs from sludge. To summarize, torrefaction provides the following benefits:

• It produces biologically stable char (no biological activity)
• It recovers pyrolytic water
• It produces char that can be used as a building material, radiation shielding, food substrate and carbon/hydrogen storage

The torrefaction technology is just emerging and was not yet tested large scale. However, literature discusses the potential of the system as a promising solution for sludge management in space and on Mars (M. Serio et al., 2016), (M. Serio et al., 2014).

Works cited

A. Serio, M., E. Cosgrove, J., & A. Wojtowicz, M. (2016). Torrefaction Processing for Human Solid Waste Managment. In 46th International Conference on Environmental Systems (pp. 1-18). East Hartford: Advanced Fuel Research, Inc.

Manufacturing and properties of PHB. Retrieved October 27, 2017, from https://sundoc.bibliothek.uni-halle.de/diss-online/02/02H017/t2.pdf