Plastic and contaminant flow dynamics in the German building and infrastructure sector: Current and future challenges and opportunities for recycling

Satisfying the growing demand for plastics while pursuing climate neutrality requires a surge in recycling. Despite being Germany’s second-largest plastics use sector, the circularity potential of plastics in buildings and infrastructure (B&I) remains largely unexplored. This study investigates plastic flows, stocks, and legacy contamination for major product groups in Germany’s B&I sector from 1950 to 2100, using high-resolution dynamic material flow modeling (six products, eight polymers, seven legacy substances). Results show that plastic stocks are anticipated to increase from 62.9 million metric tons (Mt) in 2023 to 89.5–163.1 Mt in 2100, depending on future consumption scenarios. End-of-life flows were 66 % lower than consumption in 2023 but are projected to at least double by 2100. Achieving high recycling rates is constrained by contaminant thresholds, as demonstrated for DEHP, Pb, HBCD, and (H)CFCs in various products. Consequently, contaminant detection and removal in recycling are crucial for safe and circular plastic use.