Team:Calgary/Human Practices

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Human Practices

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  Landfills

Figure 1 and 2: Photos from the tour of the wastewater treatment facilities in Calgary in June.

The integration of PHB production in leachate treatment would likely be unfeasible due to low volumes of leachate that are usually produced at landfills. In Calgary, a single landfill generates about 100,000 L of leachate per day. Although COD content in leachate is higher than in wastewater, the estimated amount of PHB produced in Calgary was about 8000 kg/year, based on COD content of 1977 mg/L in Calgary leachate (Kashef & Lungue, 2016). This would result in about $40,000 in revenue, assuming a price of $5 per kg of PHB (Manufacturing and properties of PHB, 2017) . Another member of the team performed similar calculations assuming 0.38 grams of PHB produced per gram of VFA, which resulted in 22,250 kg of PHB per year and a potential revenue of $111,126 per year.The cost of implementing a PHB production process will likely be magnitudes larger. Leachate treatment in China is a more promising alternative. China generates a larger amount of leachate compared to many other countries .("Leachate treatment in China: Technologies and Import Opportunities", 2015) Additionally, the COD content in Hong Kong, China ranges from 15,700 to 50,000 mg/L for young landfills ("Leachate treatment in China: Technologies and Import Opportunities", 2015), which is 8 to 25 times greater than in Calgary. We estimated that about 900,000 - 3,000,000 kg of PHB can be produced per year in Hong Kong depending on COD content and using PHA yield of 0.11 kg of PHA per kg of COD. PHB production from leachate was also considered for Vancouver, which generates 2,225,978 cubic meters of leachate per year (Vancouver landfill 2016 annual report, 2017). Based on our estimates, about 3,100,000 kg of PHB can be produced per year assuming the COD content of about 13,000 mg/L (Tao, Hall & Masbough, 2005)

  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 [14], COD to PHB conversion of 0.11 for mixed cultures and 0.88 for pure cultures (Rhu, Lee, Kim & Choi, 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, Ylikorpi & Pepe, 2015). Reported COD content in feces was found to be 354 mg COD per gram of wet human waste (Rose, Parker, Jefferson & Cartmell, 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, Lee, Kim & Choi, 2003). Another study reported 0.11 kg of PHA produced per kg of effluent COD in a PHA production process from activated sludge (Bengtsson, Werker, Christensson & Welander, 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, Parker, Jefferson & Cartmell, 2015), the COD to VFA ratio of 0.74 (Coats, VandeVoort, Darby & Loge, 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.

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