Comparative environmental assessment of biodegradable municipal plastic waste treatment in Finland

As biodegradable plastics (BDPs) become more prevalent in municipal waste streams, their environmental performance depends on how well existing waste management systems can accommodate them. This study evaluates the environmental consequences of nine end-of-life scenarios for BDPs in Finland using consequential life cycle assessment (LCA). The analysis considers biological treatment, advanced sorting and chemical recycling of polylactic acid (PLA), with all scenarios benchmarked against the current practice of energy recovery. The functional unit is the treatment of one metric tonne of post-consumer BDP waste, including the consequential production of heat, electricity, biomethane, and recycled PLA. The results indicate that separating PLA from plastic packaging waste for chemical recycling delivers the most significant environmental benefit, reducing the aggregated score by 39-53% relative to the baseline. These improvements are primarily driven by avoided virgin PLA production, which dominates eutrophication, water use, particulate emissions, and acidification. Biological treatment options offer limited gains: composting provides no system-level advantage due to fugitive emissions and the lack of additional nutrient recovery, while anaerobic digestion with biomethane upgrading performs well in terms of climate change mitigation but generally underperforms compared with recycling in other impact categories. Environmental performance is highly sensitive to the bio-based share of BDPs, their distribution across waste streams, and achievable PLA purity. Increasing PLA capture from plastic packaging waste consistently outperforms diverting BDPs into biowaste. Overall, the findings underscore the importance of prioritising advanced sorting technologies and avoiding fossil-based BDPs to support a more circular and low-carbon waste management system.