Beyond administrative efficiency: strategic integration of waste-to-energy and industrial symbiosis in Japan’s circular economy transition

Decarbonizing medium‐temperature industrial heat remains a critical challenge for near‐term climate action. Here, we demonstrate that integrating upgraded waste‐to‐energy (WtE) systems with industrial heat demand via industrial–urban symbiosis offers a highly cost‐effective and immediately deployable pathway. We used a multilayered geospatial and technoeconomic model for Ibaraki Prefecture, Japan, to evaluate three 2050 scenarios: business as usual (BaU), decentralized integration with industrial parks (Scenario 2), and prefecture‐scale integration with a petrochemical complex (Scenario 3). Scenarios 2 and 3 cut annual CO₂ by 272 kt and 339 kt, respectively, versus 95 kt in BaU, and they lowered CO2 abatement costs from 24,000 JPY/t (BaU) to 2,310 or 3,090 JPY/t by substituting fossil‐fuel steam with WtE heat and exploiting consolidation economies. Crucially, the binding constraint is institutional scale, not technology. Scenario 3’s wide‐area integration exceeds the coordination capacity of municipality‐based waste governance, functioning as a diagnostic of a governance‐scale mismatch. Unlocking system‐level benefits therefore requires national and prefectural land‐use and industrial‐policy leadership, beyond incremental municipal reforms. The framework generalizes to regions where fragmented waste systems and industrial demand are misaligned, showing how multilevel governance can convert legacy waste assets into scalable climate‐mitigation infrastructure.