Iron-Rich Slag Enables Efficient Carbon Sequestration

Why It Matters

The technology offers a low‑energy, circular‑economy pathway for a high‑emitting industry, allowing miners to cut net emissions while monetizing waste through carbon credits.

Key Takeaways

• Iron‑rich slag captured up to 99.5% CO₂ in lab tests
• Sample S2 sequestered ~1,073 g CO₂ per tonne of slag
• High alkalinity and low moisture boosted carbonation efficiency
• Carbonated slag stabilizes heavy metals, reducing leachate risk

Pulse Analysis

The metals and mining sector, responsible for roughly 8% of global greenhouse‑gas output, has struggled to find cost‑effective decarbonization routes. Mineral carbonation—mirroring natural silicate weathering—offers a promising alternative to energy‑intensive solvent or amine‑based capture. By leveraging alkaline residues such as steel slag, the industry can tap into abundant, low‑cost feedstock that sits near emission sources, cutting transport emissions and capital costs.

In the recent study, researchers exposed two iron‑rich slag samples to a 10% CO₂ atmosphere under varying moisture regimes. The coarser S2 material, with a pH of 10.04, achieved a remarkable 99.5% removal rate, translating to about 1,073 g of CO₂ per tonne of slag. Notably, optimal performance occurred at 25% moisture, indicating that the process can function with minimal water—a critical advantage for remote mining sites where water is scarce. The formation of multiple carbonates (CaCO₃, MgCO₃, FeCO₃) confirms robust mineral trapping, ensuring long‑term stability of the captured carbon.

Beyond emissions, slag carbonation delivers tangible business benefits. Stabilized carbonates lock in potentially leachable metals, reducing environmental liability and improving tailings management. The resulting carbon credits can offset operational costs, while the low‑energy footprint aligns with investors’ ESG expectations. Scaling this technology will require pilot‑scale reactors, lifecycle assessments, and regulatory frameworks that recognize mineral‑based sequestration. If successfully commercialized, iron‑rich slag could become a cornerstone of the mining sector’s net‑zero roadmap.