Comparative Carbon Emission Assessment of Waste Plastic Valorization Pathways
The escalating global generation of waste plastics necessitates robust recycling strategies to mitigate environmental impact and advance low-carbon development. This study employs life cycle assessment (LCA) and emission factor methodologies to quantify the carbon footprints of six distinct waste plastic valorization pathways: mechanical recycling, pyrolysis, alcoholysis, co-coking, solid fuel production, and direct incineration. The functional unit is one tonne of waste plastic, with system boundaries encompassing transportation, pretreatment, and resource utilization. The model accounts for indirect emissions from energy consumption, direct emissions from plastic decomposition, and carbon offsets from material or energy recovery. Results indicate that pyrolysis yields the highest carbon offset of approximately -3,024 kgCO2e per tonne, while mechanical recycling achieves an 88% material recovery rate and a net carbon offset of -991.4 kgCO2e. Net carbon emissions per tonne of waste plastic rank as follows: direct incineration (1,104 kgCO2e) > co-coking (185.8 kgCO2e) > solid fuel (115.4 kgCO2e) > alcoholysis (-259.5 kgCO2e) > mechanical recycling (-991.4 kgCO2e) > pyrolysis (-2,592 kgCO2e). These findings demonstrate that pyrolysis offers superior carbon reduction benefits compared to incineration, exhibiting a net-negative carbon footprint across its life cycle. The study provides a scientific basis for selecting low-carbon waste plastic valorization routes and informs carbon trading and emission reduction strategies in the solid waste sector.