Life cycle assessment study on pyrolysis of post-consumer plastic waste
Alatas, Arin (2021)
School of Energy Systems, Ympäristötekniikka
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Plastic polymers have become an essential part of our lives and industries due to their low production cost, widespread application possibilities, and versatility. Driven by economic growth and development, plastic production has been increasing. With the increased production and plastic variety, challenges related to the disposal of plastics have developed. Alternatives to the established end-of-life solutions are investigated to lessen the impacts and manage the challenges of these technologies. One such alternative option for plastic waste management is chemical recycling via pyrolysis. This study uses life cycle assessment (LCA) to compare climate change impacts of pyrolysis, reporting only the global warming potential in kg CO2-equivalent, with the widely practiced end-of-life solutions: mechanical recycling and incineration with energy recovery. Three scenarios were modeled using the GaBi software: incineration with energy recovery (Scenario 1), mechanical recycling (Scenario 2), and pyrolysis (Scenario 3). The pyrolysis temperatures considered in this study were 400°C, 500°C, and 600°C, to observe the effects of temperature on pyrolysis reaction and their impacts. Impacts were estimated using the IPCC AR5 GWP100, excluding biogenic carbon impact assessment method. A sensitivity analysis on mechanical recycling product substitution ratio was carried out. A 1:1 substitution ratio was assumed for the LCA and a 1:0,5 ratio for the sensitivity analysis. The total climate change impacts were 1125 kg CO2-eq. for Scenario 1, -475 kg CO2-eq. for Scenario 2, -238 kg CO2-eq. for Scenario 3 at 400°C, -198 kg CO2-eq. for Scenario 3 at 500°C and -159 kg CO2-eq. for Scenario 3 at 600°C. Pyrolysis has higher climate change impacts compared to mechanical recycling but can recover more of the plastic waste stream. Sensitivity analysis showed that the climate change impacts of mechanical recycling depend on the recyclate quality, and its substitution ratio.