Unraveling the potential of chemical recycling for poly(methyl methacrylate) through pyrolysis: Rigorous modeling, economic, and environmental evaluation

Pyrolysis is considered a promising method for the chemical recycling of waste plastics. While experimental and feasibility studies on the pyrolysis of poly(methyl methacrylate) (PMMA) have been conducted, a comprehensive pyrolyzer model has not yet been established. To address this gap, this study firstly develops a comprehensive and rigorous process model for the pyrolysis of PMMA. The research focuses on a one-dimensional, three-phase entrained bed model for the pyrolysis reactor, which thoroughly examines mass, energy, and momentum balances, as well as pyrolysis kinetics and thermodynamic properties. Subsequently, appropriate separation strategies have been developed for various scenarios of PMMA pyrolysis. For process analysis, a techno-economic evaluation (TEA) determines the minimum required selling price (MRSP) of recycled methyl methacrylate (MMA) monomer, which ranges from 0.76 to 1.1 USD/kg across various sources and with uncertainties in monomer yield. However, the corresponding price is less than half the cost of virgin MMA. Additionally, LCA indicated that chemical recycling of PMMA offers substantial advantages across multiple environmental impact categories compared to incineration and landfill treatments, including global warming potential (GWP), fine particulate matter formation (FPMF), terrestrial acidification (TA), human carcinogenic toxicity (HCT), fossil resource Scarcity (FRS), and water consumption (WC). The findings further indicate that the pyrolysis of PMMA sources containing impurities, as well as any uncertainties associated with monomer yield, may compromise the overall sustainability of the process. Overall, this study provides insights into the potential of PMMA pyrolysis as a sustainable recycling method, contributing to both economic efficiency and environmental sustainability in the polymer industry.