Integrated assessment of resource synergy and emission reduction benefits in iron and steel and cement industries

Industrial symbiosis offers a critical pathway for advancing resource circularity and energy efficiency in hard-to-abate sectors. As the steel and cement industries undergo profound structural transformation toward low-carbon development, this study quantitatively assesses how these transitions affect existing symbiotic networks during 2020–2060 using an integrated assessment model. Three enhanced symbiosis pathways are evaluated, utilizing steel by-products, including process gases, desulfurization gypsum, and steel slag, as alternative energy sources and supplementary materials in cement manufacturing. The model incorporates cleaner production structures, technological progress, and policy instruments such as carbon taxation. Results indicate that transitioning steel production from the Blast Furnace-Basic Oxygen Furnace (BF-BOF) route to Electric Arc Furnace (EAF) and hydrogen-based steelmaking reduces fuel and coke consumption by 61.8% and 84.1%, respectively, from 2020 to 2060, but simultaneously decrease recoverable gases by up to 56.3% and steel slag by 245.3%, constraining traditional symbiotic linkages. Cumulative CO2 emission decreases from 4730.5 Mton in the baseline scenario to a minimum of 3966.8 Mton. While gypsum desulfurization technology initially increases the desulfurized gypsum supply, this subsequently diminishes with BF-BOF phase-out. Conversely, cement quality improvement policies increase fuel and raw materials demand, reinforcing the need for diversified symbiosis pathways. Sensitivity analysis reveals that energy symbiosis represented by recovered gas is substantially more price-sensitive than material symbiosis like steel slag. These findings underscore that that the structural transformation of the steel industry will fundamentally reshape the material basis of steel-cement symbiosis, requiring proactive adaptation and the development of new circular economy linkages to sustain cross-sectoral emission reduction synergies.