Energy production and waste reduction from plastics

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Waste water treatment is one of the most important engineering responsibilities managed by Canadian cities. Historically associated with the destruction of pathogens to prevent the spread of disease, waste water treatment plants are now adding resource recovery to their mandate. This is in part due to the higher costs of landfilling waste and energy consumption but also due to the prevalence of plastics in the waste stream. Plastics do not biodegrade but rather fragment into smaller sizes. Sizes that can become mobile in the water systems and affect wild life. Recent trends have also seen an increase of microplastics, particles less than 1 mm, in the consumer market. These plastics are often used in personal care products and naturally end up at the water treatment facility. Systems such as anaerobic digestion are not able to reduce the plastic content of sewage sludge meaning they will either be landfilled or pass through the system. On the other hand, plastics come from natural gas, a fossil fuel, and contain a significant amount of embedded chemical energy. Harvesting this energy for use would provide two benefits, avoidance of plastic release to the environment and recovery of energy from the wastes. The latter will naturally displace additional fossil fuel use and help mitigate climate change risk. To be usable, the plastics must be upgraded using renewable or off peak electricity. In this manner, the plastics become of form of energy storage, taking low demand electricity and turning it into a fuel. This project investigates the feasibility of converting any waste plastics found in wastewater treatment plant residues to usable forms of energy, in particular synthetic methane.