Filling the Gaps: Tracing 12 Types of Non-commodity Plastics in China's Plastic Socioeconomic Metabolism.

Recent plastic flow research has largely focused on commodity plastics (PE, PP, PVC, PS, ABS), yet a sizable share of other polymer types remains understudied. These non-commodity plastics suffer from inconsistent definitions, complex classifications, and data gaps, which hinder accurate assessment of their production, use, and end-of-life management. This study develops dynamic material flow analysis to investigate 12 key "non-commodity" plastics in China─including PET, PU, seven engineering plastics, and three thermosetting plastics─and addresses these knowledge gaps. Our results show that in 2022, China produces approximately 85 million tonnes of these polymers, a volume comparable to commodity plastics, with 35% used in plastic products and the remainder in non-plastic applications (e.g., fibers, rubber). PET is predominantly employed in short-lifespan packaging, whereas PU, engineering plastics, and thermosetting plastics find use in longer-lifespan applications, underscoring the need for targeted recycling strategies─particularly chemical recycling for PU and thermoset products. Revisiting the scope of "plastics" using scientific criteria can help mitigate definitional ambiguities and guide more effective policymaking. By improving data availability and tracking this underexplored non-commodity category, our study lays the groundwork for more accurate assessments and interventions to reduce plastic pollution.