Introduction to CDR
Carbon mineralization describes the process of carbon dioxide (CO₂) reacting with certain minerals in rocks to produce solid minerals, called carbonates. In this way, mineralization removes CO2 from the atmosphere and stores it in a stable solid.
Not all minerals can effectively capture CO2. The best ones are those that are most reactive with CO2 and form stable carbonate minerals that durably store the CO2, rather than carbonates that dissolve easily. Often, they are rich in magnesium, calcium and iron.
There is a wide range of ways that mineralization can be used within a CDR method. It can serve simply as the storage mechanism, by taking concentrated CO2 removed from the air by another process and turning it into minerals. Or, the mineralization process can be a complete CDR method on its own, by reacting minerals with the CO2 in the air to form carbonates that store CO2.
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There are two broad categories of mineralization methods:
Ex-situ mineralization
Ex-situ means being away from its natural location. Suitable rock is crushed to increase its surface area and accelerate the natural mineralization process that would otherwise take thousands of years. Ex-situ mineralization can be done through:
Industrial facility mineralization: A concentrated stream of CO2 is combined with crushed rock at industrial sites in a controlled process, often integrated into product manufacturing like concrete production or into mining and metallurgical processes such as ore processing and steel making where industrial byproducts –– mineral wastes and steel slag –– are carbonated.
Enhanced rock weathering: crushed rock is spread on agricultural fields to react with CO2 in the air. Crushing the minerals — which can come from quarry fines or mine tailings, i.e., waste material from the mining process — accelerates the natural weathering process of the rocks. For instance, in Kingston, Ontario, wollastonite is being mined and applied on agricultural land to remove CO2 from the atmosphere.
In-situ mineralization
In-situ means being in the natural location. Thus, in-situ mineralization involves bringing the CO2 to the suitable rocks where they are, deep underground. CO₂ that is captured by other processes is injected deep below the Earth’s surface into natural underground rock formations that are suitable for mineralization. CO2 can be dissolved in water prior to injection or injected separately as a supercritical fluid. Once injected, the mix of CO₂ and water spreads throughout the pores and reacts with the rocks to form solid carbonate minerals that securely lock the carbon underground.
In-situ mineralization is a type of deep geologic CO2 storage that is differentiated because of the mineralogy of rock formation into which the CO2 is injected. With in-situ mineralization, the CO2 is ultimately stored as a solid, whereas with other types of deep underground storage, the CO2 largely remains as a fluid that is trapped underground.
Iceland, for example, has large amounts of basalt, a type of volcanic rock that is suitable for mineralization due to and its high concentration of minerals possessing magnesium, calcium and iron, which are highly reactivity with CO2. Since 2021, CO2 captured from the air has been injected into underground basalt formations.
In a similar manner, Solid Carbon, a carbon dioxide removal initiative in British Columbia, is developing an offshore project that injects CO2 under the ocean — deep below the seafloor — into basalt formations where it mineralizes within the host rock formation.
Last Edited - July 22, 2026