Human Practices

The team focused on evaluating the feasibility of the 4 proposed project applications: production of PHB on Mars from human waste, integrating PHB production in a wastewater treatment plant, integrating PHB production with leachate treatment, and integrating PHB production in developing countries. Our subgroup calculated the approximate amount of PHB that would be expected in each scenario.

  Landfills

Landfill leachate treatment is an avenue that our team considered when looking at possible applications of our project on Earth. Leaches make up feedstock that is rich with organic matter. Leaches are highly toxic waters produced during the decomposition of waste. This waste becomes dangerous to the environment when left untreated and can leak to the groundwater, causing contamination. The impurities found in leachate can be classified into 3 major groups: dissolved organic matter, inorganic macrocomponents, heavy metals and xenobiotic organic compounds. Leachate from young landfills look particularly promising as a choice of feedstock due to its high chemical oxygen demand (COD), which is found to be greater than 10 000 mg/L, while in the older landfills the COD decreases to less than 4000mg/L.

Currently, different conventional treatment technologies are used in leachate treatment. However, none of them includes the production of value-added products and such technologies appear to be concerned with the simple removal of toxic, undesired components. Leachate transfer involves recycling and combined treatment with domestic sewage, biodegradation involves aerobic and anaerobic processes for waste decomposition, chemical and physical methods involve chemical oxidation, adsorption, chemical precipitation, coagulation/ flocculation, sedimentation/flotation and air stripping. Integrating a PHB-producing stage into the conventional leachate treatment would facilitate the production of PHB bioplastic out of the waste, thus allowing the facilities to become profitable or at least cut down the costs of treatment. One problem associated with this feedstock is that it is a nutrient rich-medium, which decreases the rate of PHB production in our bacteria. This would mean that the leachate would have to be treated from phosphates and nitrates prior to entering a bioreactor containing the bacteria.

  Wastewater Treatment Plants

Our project was initially aimed at providing a method by which wastewater treatment facilities could take biological material in wastewater and transform it into value-added product in the form of bioplastic. Part of our integrated human practices included a visit to our local wastewater treatment facility.

For the wastewater treatment plant, we estimated 28,100,000 kg of PHB produced per year. The Pine Creek Wastewater Treatment Plant in Calgary processes about 1 million cubic meters of waste per day. The COD content and PHA yield were assumed to be 1000 mg/L and 0.11 kg of PHA per kg of COD, respectively, for the calculations.

  Developing Countries

In developing countries, we envisioned PHB production incorporated into scaled-down wastewater treatment systems in small communities that lacked established treatment methods. Selling PHB would provide monetary incentive to construct a wastewater treatment system, which, in turn, will reduce diseases due to poor sanitation. Additionally, we wanted to compare PHB production between genetically engineered bacteria and natural bacterial communities in sludge, which have been previously used to feasibly produce PHB. Assuming a community size of 2000 people, solid waste generation of 3.113 x 10^-3 m³/day/person (Palanivel & Sulaiman, 2014), COD content of 601 mg/L, COD to PHB conversion of 0.11 for mixed cultures and 0.88 for pure cultures (Rhu et al., 2003) and a price of $5 per kg of PHB (Choi & Lee, 1997), we found that using pure cultures results in additional $2,000 in revenues. However, the cost of sterilization of waste stream before inoculation with pure culture was estimated at $100,000 (Choi & Lee, 1997).

  Space

We approximated that about 40 - 90 kg of PHB can be produced on Mars per year with a crew of 6 astronauts. A crew of 6 will generate about 6 tonnes of solid organic waste over 2.5 years (Zhang et al., 2015). Reported COD content in feces was found to be 354 mg COD per gram of wet human waste (Rose et al., 2015). One study looking at PHA production from food waste estimated the yield of 0.05 g of PHA per g of COD applied (Rhu et al., 2003). Another study reported 0.11 kg of PHA produced per kg of effluent COD in a PHA production process from activated sludge (Bengtsson et al., 2008). The predicted PHB range was based on COD to PHA conversion. Another member of the team assumed the average COD content in human excretions to be 61.75 g/cap/day (Rose et al., 2015), the COD to VFA ratio of 0.74 (Coats et al., 2011)and the VFA to PHB conversion of 0.38 g PHA/g VFA ,(Coats, VandeVoort, Darby & Loge, 2011) which resulted in 41 kg of PHA per year per crew of 6. According to NASA, the cost of shipping supplies to space using SpaceX Dragon spacecraft is $27,000 per pound. The costs saved by producing 41 kg of PHA in space would then be about $2,440,000. We also contacted a 3D printing company called 4G Vision Tech that uses selective laser sintering (SLS), which can be used to 3D print with PHB (Pereira et al., 2012). Howard from 4G Vision Tech approximated that the predicted amount of PHB can be used to create approximately 50 hydroponic systems and 20 general tools like wrenches, hammers, and scissors.

Engagement

Collaborations

SAFETY