Carbon Dioxide Sequestration through Steel Slag Carbonation

Steel slag carbonation harnesses the alkaline by-products of steelmaking to capture and permanently lock away carbon dioxide as stable carbonate minerals. In this process, steel slag—rich in calcium, magnesium and iron oxides—is exposed to CO₂ under controlled temperature, pressure and moisture conditions. The reactive oxides in the slag bind with CO₂ to form solid carbonates, notably calcite and magnesite, leading to significant reductions in greenhouse‐gas emissions. Beyond sequestration, the carbonated slag exhibits enhanced material properties, offering pathways to produce low-carbon binders, high-strength aggregates and supplementary cementitious materials. This approach thus transforms a major industrial waste stream into a resource for construction, aligning with circular-economy principles and contributing to global decarbonisation efforts.

Research from Nature Portfolio

Recent studies have demonstrated an integrated waste-to-resource supply chain by directly mineralising flue-gas CO₂ with electric-arc furnace slag. High levels of calcite precipitation were achieved rapidly, converting CO₂ into stable carbonate phases that suppress heavy-metal leaching and volume instability. The resultant carbonated slag was successfully blended into cement mortars, where it functioned as a green supplementary binder. Life-cycle estimates suggest that widescale deployment of this route could abate on the order of 10⁸ tonnes of CO₂ annually, while valorising steel-industry residues into construction products of comparable performance to conventional materials.

Carbon Dioxide Sequestration through Steel Slag Carbonation publication trend

The graph below shows the total number of articles in carbon dioxide sequestration through steel slag carbonation across all publications each year (not limited to Nature Index journals).

Technical terms

Steel slag: A solid residue rich in metal oxides generated during steelmaking, often comprising free CaO, MgO and silicates.

Mineral carbonation: A chemical process whereby CO₂ reacts with metal oxides to form stable carbonate minerals.

Accelerated carbonation: A controlled treatment using elevated CO₂ concentrations, pressures or temperatures to speed up the formation of carbonates in alkaline materials.

CO₂ uptake: The mass of CO₂ permanently fixed per unit mass of reactive material, often expressed in g CO₂/kg slag.

Supplementary cementitious material (SCM): A non-cementitious ingredient that, when used with Portland cement, contributes to the properties of the hardened concrete through hydraulic or pozzolanic activity.

References

1. Research progress of hydrogen production and CO2 fixation in molten slag cooling process. Carbon Neutralization (2024).
2. Accelerated carbonation and performance of concrete made with steel slag as binding materials and aggregates. Cement and Concrete Composites (2017).
3. CO2 Mineralization and Utilization using Steel Slag for Establishing a Waste-to-Resource Supply Chain. Scientific Reports (2017).
4. Accelerated Carbonation of Steel Slag Compacts: Development of High-Strength Construction Materials. Frontiers in Energy Research (2015).
5. Carbonated steel slags as supplementary cementitious materials: Reaction kinetics and phase evolution. Cement and Concrete Composites (2023).