A cradle-to-gate life cycle assessment of mechanochemical recycling of poly(ethylene terephthalate) waste

The increasing accumulation of plastic waste in landfills and the natural environment poses significant environmental and human health challenges. Mechanochemical depolymerization, a solvent-free process that utilizes mechanical energy for size reduction and chemical reactions, has emerged as a promising plastics recycling technology. In this study, we present a comprehensive, prospective life cycle assessment (LCA) of the mechanochemical depolymerization of poly(ethylene) terephthalate (PET) waste, starting with unsorted PET as feedstock and resulting in recycled PET resins. We quantify the contributions of individual processing steps and compare the overall environmental impacts to those of virgin terephthalic acid (TPA) and PET production, as well as to alternative PET recycling pathways. Our results indicate that mechanochemical depolymerization route outperforms virgin TPA and PET production in all considered impact categories, with primary environmental burdens attributed to the chemicals used throughout the recycling process. Sensitivity analyses are conducted, varying key process design parameters, energy sources, and LCA co-product handling methods, revealing that the mechanochemical depolymerization route exhibits lower environmental impacts compared to virgin production, even when considering worst-case scenarios. Moreover, the mechanochemical depolymerization route shows similar or lower GWP values compared to competitive chemical recycling technologies. Overall, this study provides a detailed environmental evaluation of the mechanochemical depolymerization recycling route, supporting the advancement of sustainable solutions for plastic waste management. • First LCA of PET recycling via mechanochemistry (MCR) across seven impact categories • MCR shows lower impacts than virgin TPA and PET in all categories. • Chemical usage and polymerization are the main contributors to total impacts. • MCR outperforms virgin production even in pessimistic scenarios. • MCR is a scalable and circular solution for PET waste management