Global warming potential assessment of municipal solid waste management in Greater Lisbon

This study assesses the global warming potential (GWP) of municipal solid waste (MSW) management in the Greater Lisbon area using a system-level life cycle assessment (LCA). The current management system is evaluated alongside alternative scenarios aligned with European Union waste targets, including the preparation for reuse and recycling (PRR) target of 65% and the landfill disposal target of 10%. Process-level results indicate that landfill disposal is the largest contributor to GWP, while the climate performance of waste-to-energy (WtE), organic valorization (OV), and sorting processes is strongly influenced by waste composition and residual fractions (RF) flows. At the system level, landfill diversion emerges as the most effective mitigation strategy, with additional reductions associated with increased plastic recovery and OV. The current MSW management system exhibits a GWP of approximately 261 kg CO₂-eq/t MSW. The lowest GWP (140 kg CO₂-eq/t MSW) is achieved in a scenario prioritizing plastic recovery and OV, while meeting the PRR target. Plastic recovery reduces fossil CO₂ emissions from WtE but also decreases the energy content of the incineration feed, potentially limiting energy recovery and highlighting a trade-off between recycling performance and operational efficiency in WtE-dependent systems. All valorization processes remain net positive in emissions, partly due to RF sent to landfill or incineration, underscoring the need to reduce contamination and improve processes efficiencies. Overall, the results emphasize the need for integrated MSW management strategies that balance material recovery, energy recovery, and operational feasibility to support effective climate mitigation.