Assessing the environmental footprint of plastic pyrolysis and gasification: A life cycle inventory study

Abstract

Chemical recycling is a promising technology that can help alleviate the environmental burdens of plastic waste. This paper developed a comprehensive, scenario-based life cycle assessment (LCA) to quantify the environmental profile of different management options to treat polyethylene (PE) and polypropylene (PP), including landfill, pyrolysis, and gasification. Using a system expansion method and inventory data from various sources, the result showed that the recovery of ethylene and propylene monomers for plastic re-manufacturing, which resembled closed-loop recycling systems, offered the highest environmental benefits. Most notably, fossil fuel depletion, climate change, and human toxicity impacts were 36,761%, 1063%, and 329% lower than those of landfill disposal, respectively. Open-loop recycling scenarios, such as high-value chemical (HVC) and energy recovery from pyrolysis and gasification, were also investigated. Amongst these scenarios, pyrolysis for HVC recovery was the most environmentally favourable, followed by HVC recovery using gasification. Energy recovery scenarios offered limited benefits and had worse results than landfill in terrestrial acidification, freshwater and marine eutrophication impact categories. The main driver of impacts during end-of-life treatment using chemical recycling is the energy consumption needed to achieve appropriate temperature for the necessary reactions to take place. In terms of material consumption, the use of nitrogen gas to purge the reactor is the biggest contributor for pyrolysis whereas zeolite usage accounts for the majority of material impacts for gasification.