Comparative life cycle assessment of end−of−life strategies for post−consumer polylactic acid waste: Environmental trade−offs and uncertainty analysis

The sustainable management of post−consumer polylactic acid (PC − PLA) waste is essential for reducing environmental burdens and advancing circular economy principles. This study presents a novel comparative life cycle assessment (LCA) of five end−of−life (EoL) treatment scenarios for PC − PLA waste, conducted in accordance with ISO 14040:2006 and 14044:2006 standards. The evaluated scenarios include (i) mechanical recycling, (ii) hydrolysis, (iii) methanolysis, (iv) ethanolysis, and (v) incineration. Uniquely, the study accounts for environmental credits associated with replacing virgin PLA with recycled PLA, thereby reducing reliance on both fossil−based and bio − based feedstocks. Results show that all recycling methods outperform incineration in environmental impact reduction, with mechanical recycling offering the lowest net global warming potential (GWP) at −2690 kg CO 2 eq per tonne of PC − PLA waste, owing to its low energy and chemical requirements. While mechanical recycling is energy−efficient and less chemically intensive, chemical recycling enables recovery of monomers with higher material circularity, albeit with increased toxicity and energy demand. Beyond GWP, recycling also significantly reduces agricultural land use, acidification, and eutrophication impacts by avoiding biomass cultivation. However, chemical−intensive recycling methods may introduce toxicity, warranting careful consideration. A sensitivity analysis reveals that energy use and chemical inputs are critical parameters influencing the overall environmental outcomes. Additionally, Monte Carlo uncertainty analysis highlights the variability in results stemming from methodological assumptions, data sources, and process efficiencies. This comprehensive assessment provides insights into optimizing EoL strategies for PC − PLA waste, illustrating the environmental advantages of recycling over incineration while identifying trade−offs and uncertainties to support the circular waste management. • Comparative LCA of five EoL strategies for PC-PLA waste based on ISO standards. • Closed-loop modelling of rPLA production from chemical recycling pathways. • Provides context-specific guidance for applying recycling routes in real settings. • Sensitivity analysis reveals key influence of energy and chemical input variations. • Discusses lab-scale data uncertainty and suggests ways to improve reliability.