- Ex-situ mineral carbonation is a process that involves capturing carbon dioxide (CO₂) from industrial or atmospheric sources and reacting it with minerals in a controlled, off-site setting to form stable carbonates.
- This process mimics natural geological carbon sequestration but accelerates it significantly through engineered conditions. It is considered a promising carbon capture and storage (CCS) strategy to mitigate climate change by permanently locking CO₂ in solid mineral form, thereby preventing its release into the atmosphere.
- In ex-situ mineral carbonation, suitable feedstock minerals, such as olivine (Mg₂SiO₄), serpentine (Mg₃Si₂O₅(OH)₄), or industrial byproducts like steel slag or fly ash, are transported to a facility where they are ground into fine particles. These particles are then reacted with CO₂ in aqueous or dry systems. In aqueous carbonation, the mineral is suspended in water, and CO₂ is dissolved under pressure and temperature conditions to promote the formation of magnesium or calcium carbonates, such as magnesite (MgCO₃) or calcite (CaCO₃). This method enhances the kinetics of the reaction, making it more efficient than natural weathering.
- The advantage of ex-situ carbonation lies in the control over reaction conditions, which allows for optimized temperature, pressure, and pH to maximize CO₂ uptake and conversion efficiency. Unlike in-situ methods (where carbonation occurs underground), ex-situ processes can be closely monitored and tailored for different mineral sources. Additionally, the solid carbonates formed are stable over geological timescales, posing minimal risk of CO₂ leakage.
- However, ex-situ mineral carbonation is energy- and resource-intensive, mainly due to the mining, grinding, transportation, and processing of large volumes of minerals. The high energy demand can offset the carbon reduction benefit unless powered by low-carbon or renewable energy sources. Researchers are actively working on improving the process’s economic viability and efficiency by exploring catalysts, pretreatment methods, and the use of waste materials from mining and industry to reduce costs.
- Applications of ex-situ mineral carbonation include its integration with power plants, cement factories, and steel production facilities, where CO₂ emissions are significant. The carbonates produced can potentially be used in construction materials, such as aggregates and fillers, offering a circular approach to CO₂ utilization.
