Towards the co-benefits of carbon capture, utilization and sequestration: A life cycle assessment study for steel slag disposal

Achieving decarbonization in the steel industry is of paramount importance for global carbon neutrality. Given the unavoidable generation of calcium-containing steel slag and carbon-rich flue gas emissions in the steelmaking process, steel slag carbonation is considered a CCUS technology capable of achieving pollution and carbon reduction in the steel industry. This study conducts a life cycle assessment (LCA) of the environmental impacts generated within the system boundaries of mainstream hot braising steel slag treatment and a novel carbonation steel slag approach. Results of the research demonstrate that the carbonation route based on carbon capture, utilization, and storage (CCUS) technology reduces the global warming potential (GWP) by 480% compared to the mainstream hot braising route, yielding −76.78 kg CO2 eq./t steel slag. The carbonation route also mitigates the environmental impact of pollutant emissions; however, it introduces a burden shifting associated with energy and resource consumption. Furthermore, to tackle the challenges of industrial application of steel slag carbonation, this study has explored upgrading schemes and proposed a future carbonation steel slag route that achieves process upgrades. By enabling carbonation of flue gas and improving carbonation efficiency, this route is forecasted to elevate the potential of carbon footprint reduction from 5% to 15% throughout the entire life cycle of steelmaking process. The study confirms that steel slag carbonation is a viable carbon-negative technology, delivering a substantiated CCUS solution for achieving co-benefits of pollution and carbon reduction in the steel industry.