Life Cycle Assessment of Polystyrene (PS) and Low-Density Polyethylene (LDPE) Waste-to-Energy Co-Pyrolysis Process Through Design of Experiment

Synthetic plastic has seen a significant increase in production, extensive use, and improper waste disposal in recent years. Pyrolysis is an emerging thermochemical treatment method that converts plastic solid waste (PSW) into basic petrochemicals for energy recovery and char production. Although it is considered environmentally beneficial over combustion and gasification due to minimized plastic-associated carbon footprint, the process still uses energy and emits chemical components back into the environment. This study investigated the environmental impact of the waste-to-energy co-pyrolysis process with Polystyrene (PS) and low-density polyethylene (LDPE) waste as feedstock, life cycle assessment (LCA) as the environmental impact assessment method, and Design of Experiment (DOE) as the framework for the methodology and analysis. Through literature review and domain expertise, it was hypothesized that PS and LDPE feedstock mass in co-pyrolysis could significantly influence the global warming potential (GWP) impact score. A 2k Full Factorial Design resulted in 8 randomly generated runs, wherein PS and LDPE feedstock mass varied between 1 kg and 5 kg. The same openLCA model was used throughout the study to limit errors and uncertainties. Analysis of variance verified that PS and LDPE feedstock significantly affect GWP impact scores independently, while the interaction between the two factors is insignificant. A regression model best explains the linear relationship between GWP impact scores and the two factors.