Prospective life cycle assessment of end-of-life pathways for polylactic acid: Evaluating environmental trade-offs and technology learning potential

As the global demand for sustainable materials grows, polylactic acid (PLA) has emerged as a leading bioplastic due to its renewable origin and biodegradability. However, its environmental performance highly depends on end-of-life (EoL) treatment. This study presents a prospective life cycle assessment (pLCA) of five EoL pathways for PLA: industrial composting, incineration, mechanical recycling, chemical recycling with repolymerisation, and chemical recycling without repolymerisation. The pLCA was carried out by factoring shared socioeconomic pathways (SSP1, SSP2) along with a representative concentration scenario (SSP2-RCP1.9) and normative environmental learning rates to map sustainable EoL strategies between 2025 and 2050. Results reveal that mechanical recycling consistently delivers the lowest climate change impact, achieving net-negative emissions (−1.22 to −0.67 kg CO₂-eq/kg PLA), while chemical recycling without repolymerisation performs worst (up to 0.58 kg CO₂-eq/kg PLA). Burden shifting is observed in all pathways, with terrestrial ecotoxicity for composting increasing by 31% and water consumption for recycling rising by up to 49% under ambitious climate scenarios. Normative environmental learning rate analysis reveals that maintaining 2025 impact levels across categories requires annual learning rates of 5–14% for recycling and < 12% for composting and incineration, rates considered feasible. In contrast, achieving net-zero emissions by 2050 would demand high learning rates (>40% per year) for most EoL options, pointing to the need for radical process redesign, integration of renewable energy, and systemic innovation.