The global path to reaching our climate goals by 2050 has placed Carbon Capture and Storage (CCS) at the center of the conversation. While reducing emissions at the source remains the priority, the Intergovernmental Panel on Climate Change (IPCC) has made it clear that carbon dioxide (CO2) removal and permanent storage are essential to offset hard-to-abate sectors and remove “legacy” carbon already in the atmosphere.
Typically, CCS has relied on injecting CO2 into deep sedimentary basins; trapping it as a gas or fluid. However, another permanent and secure alternative is emerging: mineral carbonation, or mineralization. Unlike traditional storage, which requires specific sedimentary “traps,” mineralization uses reactive rock formations to chemically bind CO2 into solid rock.
What is Carbon Mineralization?
Carbon mineralization is a process where CO2 reacts with alkaline minerals (i.e.., magnesium or calcium-bearing silicates) in rocks to form stable, solid carbonates. These carbonates permanently store the CO2 in a mineral form. This process is similar to rock weathering, which is a naturally occurring carbon sink.
Rock weathering can take hundreds to thousands of years to complete naturally. However, by optimizing process conditions, researchers and scientists have been able to accelerate the carbon mineralization process dramatically through two technology-based approaches:
- Ex-situ mineralization: This is an approach to accelerate rock weathering, taking place at the surface, where CO2 reacts with crushed rock containing alkaline minerals such as magnesium or calcium. When the CO2 reacts with the minerals, it solidifies and forms stable carbonates. To speed up the process, the rocks can either be ground to increase their surface area, or spread across land, or a combination of both processes. Ex-situ mineralization can also be completed in industrial reactors, where CO2 reacts with suitable industrial by-products such as certain mine tailings, steel slag and cement kiln dust, or integrated into construction materials like concrete or cement to produce low-carbon building materials.
- In-situ mineralization: This method involves injecting CO2 into deep underground formations composed of mafic or ultramafic rocks rich in magnesium and calcium. The CO2 can be dissolved into water and injected as carbonic acid into these formations. The CO2 could also be compressed to a supercritical state and injected into basalt formations. When injected in a supercritical state, the CO2 takes more time to convert into carbonates than when it’s injected as a carbonic acid. Either way, when CO2 is introduced into these formations, it moves into the rock and reacts with the minerals to form solid carbonates, securely storing the CO2.
The in-situ mineralization process involves three main steps. First the CO2 is dissolved in water to form a weak carbonic acid (H2CO3). This can be done either before injection, or through injecting water into the formation after the CO2, or through the formation having suitable water in place. Next, the acid reacts with the alkaline minerals in rocks. Solid carbonates are formed through the precipitation process, creating stable solid minerals that store the CO2.
Depending on how mineralization is applied, it can be classified as a carbon removal, as a utilization pathway, or as a form of storage. Mineralization can be defined as a removal, when ex-situ mineralization captures CO2 directly from the ambient air; it can be defined as a use, when integrated into construction materials like concrete or cement; or it can be defined as storage, when injecting CO2 either from a direct air capture project or point source capture project. Currently the use in concrete is the only one eligible under the CCUS Investment Tax Credit.
Differences Between Mineralization and Sedimentary Storage
The fundamental difference between mineralization and sedimentary storage is how quickly the carbon stabilizes.
In sedimentary storage, CO2 is typically injected in a supercritical state into the pore space within underground geological formations. This storage method relies on structural trapping, where an impermeable layer of caprock prevents the buoyant CO2 from coming back up to the surface. Monitoring, measurement and verification (MMV) throughout a project is similar regardless of storage type, starting with characterizing the formation, then injection monitoring, and finally post-closure monitoring. Determining the storage location for mineralization requires more geochemical modelling than for sedimentary storage. During the injection period, the MMV is similar, operators monitor the pressure and temperature in the reservoir, as well as the caprock, if present. They also monitor the injection well and complete integrity testing periodically. For post-closure, MMV assesses storage performance, tracks the CO2 plume’s movement, and confirms the CO2 is behaving as expected. For sedimentary storage, post-closure MMV can be required for decades, which can add significant costs to the project. MMV of a mineralization project is much shorter, since the CO2 becomes carbonates faster, however it can be very expensive and reactivity rates vary based on the geochemistry.
The benefit of mineralization is that it shifts the storage mechanism from physical containment to chemical transformation. When CO2 interacts with mafic or ultramafic rock formations, it undergoes a phase change from a gas or fluid to a solid mineral, known as mineral trapping. This phase change happens sooner than in sedimentary formations and reduces the risk of leakage because the CO2 has essentially become part of the bedrock.
Also, the mafic and ultramafic rock formations are in different places in Canada compared to sedimentary formations, opening up storage opportunities that wouldn’t otherwise be available.
Challenges and the Path Forward
Mineralization is still in the early development stages, facing several technical and economic hurdles that must be overcome for it to reach a gigaton-scale impact. For ex-situ mineralization, one of the primary technical challenges is the reaction kinetics required to accelerate the natural mineralization process. This requires energy-intensive steps such as crushing rock to increase its surface area or high energy requirements to heat the reactants in industrial reactors to convert CO2 into stable carbonates. The reactivity rate is also impacted by the ambient temperature and soil conditions. The cost per tonne of CO2 stored may be higher than traditional sedimentary storage. For in-situ mineralization, injecting the CO2 into underground mafic or ultramafic rock formations requires a delicate balance of fluid pressure to avoid clogging the rock’s natural pathways as new minerals precipitate and expand. In addition to this, there can be logistical concerns regarding water consumption, as many mineralization processes require significant volumes of water to act as a transport medium for the dissolved carbon.
To address these challenges, the future potential of mineralization lies in the development of hybrid energy systems that use waste heat from industrial plants or dedicated renewable sources to power the carbonation reactors. Research is currently pivoting toward the use of seawater instead of freshwater and the refinement of “passive” mineralization techniques in mine tailings, which could turn existing industrial waste sites into massive, low-cost carbon sinks without the need for extensive new infrastructure.
Mineralization in Canada
Canada is uniquely positioned to lead the global shift toward mineralization due to its vast geological critical mineral belts and a high concentration of reactive rock formations. Mineralization projects need rocks rich in olivine, serpentine, or brucite, which are present in many areas in Canada, especially in British Columbia and Quebec. However, further studies and long-term observations are necessary to confirm the site-specific suitability of these formations for large-scale carbon sequestration.
The Canadian landscape is currently playing host to some of the world’s most advanced mineralization projects. In British Columbia, Arca is partnering with mining operations to transform ultramafic mine tailings, naturally reactive waste rock, into carbon sinks. Their proprietary technology, which includes advanced microwave activation, accelerates the natural carbonation process, effectively turning an environmental liability into a climate asset.
Further east, UNDO has partnered with Canadian Wollastonite in Ontario to deploy enhanced rock weathering on farms in Eastern Ontario, and Deep Sky has completed Quebec’s first geological injection of captured CO2 into the ultramafic formations of Thetford Mines in December 2025.
Complementing these storage and removal efforts is the utilization pathway pioneered by Halifax-based CarbonCure. By injecting captured CO2 into concrete during the mixing process, CarbonCure creates a reaction with calcium ions in the cement to form nano-sized carbonate minerals. This not only provides a permanent storage solution but also improves the compressive strength of the concrete, allowing for a reduction in cement usage.
Together, these companies represent a diversified portfolio of mineralization strategies; from surface waste treatment to deep geological injection and industrial utilization, positioning Canada as a global hub for CO2 mineralization.
Future of Carbon Mineralization
While traditional carbon capture and storage in sedimentary basins remains the current industrial standard, mineralization represents a transformative and novel alternative for the captured CO2. However, as an emerging field, the transition from successful pilot projects to global-scale deployment requires extensive further study and long-term observation. Projects continue to investigate the secondary effects of large-scale mineral precipitation on underground fluid flow and pressure, as well as the lifecycle energy requirements of surface-based mineralization.
Moreover, establishing standardized MMV protocols is essential to quantify the exact amount of carbon sequestered for the carbon credit markets. Continued interdisciplinary research combining geochemistry, structural engineering, and environmental policy will be essential.
The CCUS Insight Accelerator (CCUSIA) is a partnership between the Government of Alberta and the International CCS Knowledge Centre to accelerate and de-risk CCUS by sharing knowledge and developing insights from projects.