- Mineral carbonation is a natural and engineered process through which carbon dioxide (CO₂) reacts with metal-rich silicate or oxide minerals to form stable, solid carbonates, such as calcite (CaCO₃) or magnesite (MgCO₃). This reaction represents a powerful strategy for permanent carbon sequestration, as it transforms gaseous CO₂—a major greenhouse gas—into mineral forms that are stable over geological time scales. Because the resulting carbonates are non-toxic and do not pose a risk of leakage, mineral carbonation is widely regarded as one of the most secure forms of carbon capture and storage (CCS).
- In nature, mineral carbonation occurs very slowly as part of the Earth’s long-term carbon cycle, typically through the weathering of ultramafic rocks such as peridotite and serpentinite, or basaltic rocks. These rocks contain high concentrations of calcium, magnesium, and iron silicates, which can react with atmospheric or dissolved CO₂ in rainwater to form solid carbonates over millions of years. Scientists have sought to accelerate this natural process through artificial means in order to address the urgent need to reduce CO₂ emissions from industrial and power generation activities.
- Engineered mineral carbonation can be classified into two main approaches: ex-situ and in-situ. In ex-situ mineral carbonation, rocks or industrial byproducts are mined or collected, crushed, and reacted with captured CO₂ in a controlled industrial setting. This process allows for optimization of reaction conditions (temperature, pressure, and moisture) but involves significant energy and logistical inputs. On the other hand, in-situ mineral carbonation involves injecting CO₂ directly into underground rock formations where it reacts naturally with the host minerals—offering lower operational demands and more permanent storage, but requiring careful site selection and long-term geological monitoring.
- The general chemical reaction can be represented as:
- Mg,Ca)SiO₃ + CO₂ → (Mg,Ca)CO₃ + SiO₂
- This reaction is exothermic, meaning it releases heat, which makes it potentially energy-efficient under the right conditions. Some implementations also use aqueous solutions to speed up the process by dissolving CO₂ and enhancing its contact with mineral surfaces.
- Mineral carbonation is gaining traction not only for climate mitigation but also for its potential applications in carbon utilization. The resulting carbonates can be used in construction materials, such as concrete aggregates or fillers in cement, contributing to a circular carbon economy. Moreover, mineral carbonation processes are increasingly being tested in mine tailings, industrial waste streams, and cement and steel industries, where reactive materials are already present.
- In summary, mineral carbonation is a scientifically robust and environmentally safe method for long-term CO₂ storage. Although challenges remain—especially in scaling up and reducing the energy cost of industrial applications—it holds significant promise as part of a broader portfolio of climate solutions. Its dual role in both carbon sequestration and carbon utilization makes it a versatile tool in the global effort to achieve net-zero emissions.
