- In-situ carbon mineralization is a natural and engineered process in which carbon dioxide (CO₂) is injected directly into subsurface rock formations, where it reacts with divalent metal ions—such as calcium (Ca²⁺), magnesium (Mg²⁺), or iron (Fe²⁺)—to form stable solid carbonates like calcite (CaCO₃) or magnesite (MgCO₃). This process occurs underground, in situ, meaning the carbon is captured and permanently stored within the geological formations without the need to extract or transport the host minerals. It represents a safe, long-term, and leakage-resistant approach to carbon sequestration and is a promising strategy for mitigating global climate change.
- The fundamental chemistry of in-situ mineralization mimics natural geological processes, such as the weathering of ultramafic and basaltic rocks, which have been removing CO₂ from the atmosphere for millions of years. In engineered systems, the process is accelerated by injecting CO₂-rich fluids (supercritical or dissolved CO₂) into permeable rock formations containing reactive minerals. Over time, chemical reactions between the CO₂ and minerals convert the gas into solid carbonate minerals, effectively locking the carbon in a stable, immobile form for geologic timescales.
- One of the most prominent demonstrations of this method is the CarbFix project in Iceland, where CO₂ from geothermal power plants is dissolved in water and injected into basaltic rock formations. Within just two years, over 95% of the injected CO₂ was converted into carbonate minerals—an impressively fast timeline compared to traditional assumptions that mineralization would take decades or centuries. This showed that in-situ carbon mineralization can be both rapid and efficient under the right conditions.
- The key advantages of in-situ mineralization include:
- Permanent carbon storage with no need for long-term monitoring.
- Minimal risk of leakage compared to conventional CO₂ injection into oil or gas reservoirs.
- Potential for large-scale deployment, especially in regions with extensive ultramafic or basaltic rock formations.
- However, there are technical and logistical challenges. These include identifying suitable geological formations with sufficient reactivity and porosity, ensuring that CO₂ is efficiently dissolved in water (if using aqueous methods), and managing the large volumes of fluid required for injection. Additionally, site characterization, regulatory approvals, and public acceptance are important factors influencing project development.
- In-situ carbon mineralization is particularly promising when integrated with direct air capture (DAC) or industrial point-source capture, creating a closed-loop system where CO₂ is removed from the atmosphere and permanently stored underground. As climate policy evolves and the urgency to reduce emissions increases, in-situ carbon mineralization is gaining recognition as a secure, scalable, and environmentally benign method of carbon storage.
