Rocking the carbon

The conversion of carbon dioxide into stone is actually a very common natural phenomenon. As certain types of rock weather, carbon dioxide in the atmosphere reacts with the exposed rock surface, either directly or after dissolving into water. Over time, this creates new minerals: carbonates, in which carbon dioxide (CO2) becomes part of a new, solid rock. Naturally occurring carbonate minerals include calcite (CaCO3) and magnesite (MgCO3), while limestone is one example of a rock type that contains them. In fact, carbonate minerals constitute the largest carbon reservoir on Earth, storing more than 1,000 times as much carbon as the oceans, all living organisms and the atmosphere combined (Falkowski et al., 2000). 

To mitigate the anthropogenic climate change, this natural weathering is regrettably slow. Common rock types can take thousands of years to react with significant quantities of atmospheric carbon dioxide (Lackner et al., 1995). Fortunately, these reactions between carbon dioxide and suitable minerals can be dramatically accelerated using technology. What takes millennia in nature can be achieved in a matter of hours.

The key lies in choosing the right raw materials and reaction conditions. The first step is to select a mineral that can bind large amounts of carbon dioxide and pair it with the best available source of CO₂. The mineral is ground to increase the surface area available for reactions and, where necessary, the carbon dioxide is purified. The optimal reaction conditions depend on the chosen feedstocks, but may require water, elevated pressure, high temperatures or additional chemicals. All of this requires energy, equipment and the transport of large volumes of material. From the perspective of climate mitigation and broader environmental impacts, it is therefore essential to ensure that the process is efficient and delivers significantly greater benefits than drawbacks. At the end of the process, the carbon dioxide and the original mineral have been transformed into a new rock, from which the carbon is no longer released back into the atmosphere on its own.

Technology presents an intriguing possibility: what kind of stone would we like to create? Powder or blocks? Round or angular?

Modern construction relies heavily on concrete, which can be produced in almost any shape. There is, however, one major difference between carbon dioxide mineralisation and conventional concrete production: carbon dioxide emissions. In cement production, limestone decomposes chemically, releasing large amounts of carbon dioxide both from the fuels used and from the stone itself. Yet if concrete is treated with carbon dioxide as it hardens, CO2 can be bound back into limestone. Curing concrete with carbon dioxide is in fact one of the first commercial methods of carbon dioxide mineralisation. In Finland, the technology has been commercialised by Carbonaide, a company spun out from VTT (Carbonaide, n.d.).

The concrete industry is not the only potential user of minerals made from carbon dioxide. The paper industry has long used precipitated calcium carbonate as a filler and coating material. In plastics, carbonates are used to strengthen materials or as flame retardants. Lightweight aggregates that have bound carbon dioxide are already available for earthworks.

Could all of Finland's annual carbon dioxide emissions, currently around 46 million tonnes (Statistics Finland, 2025), be turned into stone? In theory, yes. But it would produce an enormous amount of stone: well over 160 million tonnes every year. And for several reasons, that would not make sense. Finland’s bedrock does contain plenty of suitable rock, enough in principle to store the country’s carbon dioxide emissions for decades — around 2,000–3,000 million tonnes of CO2 in total (Aatos et al., 2006). But doing so would require massive new mining projects and staggering logistics. Processing virgin rock would also demand huge amounts of energy. The end result would be an enormous surplus of aggregate compared with Finland’s total current use of aggregates, and the quality of the material produced would not meet the requirements of all existing applications.

Instead, it makes sense to look carefully at the mines and industrial processes we already have, and to make use of the side streams they already generate. These can be connected with the nearest sources of carbon dioxide to determine how much of each fraction could realistically be used, and where. This kind of assessment would be particularly important for new mining projects and planned industrial plants, allowing synergies between processes to be identified early. For example, if recovering metals from a particular side stream would not be economically viable on its own, processing that stream may become profitable if the remaining material can also be used cost-effectively as a carbon dioxide storage, creating an additional revenue stream. 

For Finland, carbon dioxide mineralisation could become a significant domestic solution alongside geological carbon dioxide storage abroad. Carbon dioxide that has been permanently turned into stone also does not require the same type of storage-site monitoring as geological storage. Storing carbon dioxide in Finland through mineralisation would require investments, but completed plants would create new circular economy jobs. By exporting Finnish technology, we could extend our positive impact to other regions with ambitious climate policies and mining sectors, such as elsewhere in Europe, Canada and Australia.

However, several more years of development work will be needed before the emissions from the first power plant can be permanently stored in minerals. There are thousands of possible combinations of feedstocks, processes and end-products. Of these, processes based on magnesium silicate minerals, which offer a pathway to large-scale carbon storage, are currently at the demonstration stage at best. At least two commercial facilities are planned in Europe. For now, ensuring both economic viability and positive climate impacts still generally requires replacing an existing emission-intensive product. Nevertheless, low-emission energy, higher carbon pricing and more efficient processes could make turning carbon dioxide into stone a viable standalone storage solution. Advancing and commercialising these technologies will require funding, skilled people and consistent climate policy. Few countries, however, are better placed to seize this opportunity than Finland, thanks to its low-emission electricity system, extensive mining industry and highly educated workforce. 

• Aatos, S., Sorjonen-Ward, P., Kontinen, A., & Kuivasaari, T. (2006). Serpentiinin ja serpentiniitin hyötykäyttönäkymiä [Outlooks for utilisation of serpentine and serpentinite] (Raportti M10.1/2006/3). Geological Survey of Finland (GTK).  
• Carbonaide Oy. (n.d.). Home. Accessed 29 July 2026. https://carbonaide.com
• Falkowski, P., Scholes, R. J., Boyle, E., Canadell, J., Canfield, D., Elser, J., Gruber, N., Hibbard, K., Högberg, P., Linder, S., Mackenzie, F. T., Moore, B., III, Pedersen, T., Rosenthal, Y., Seitzinger, S., Smetacek, V., & Steffen, W. (2000). The global carbon cycle: A test of our knowledge of Earth as a system. Science, 290(5490), 291–296. https://doi.org/10.1126/science.290.5490.291  
• Lackner, K. S., Wendt, C. H., Butt, D. P., Joyce, E. L., Jr., & Sharp, D. H. (1995). Carbon dioxide disposal in carbonate minerals. Energy, 20(11), 1153–1170. https://doi.org/10.1016/0360-5442(95)00071-N  
• Statistics Finland. (2025). Official Statistics of Finland (OSF): Greenhouse gases [online publication]. ISSN=1797-6049. Helsinki: Statistics Finland. Accessed 30 July 2026. https://stat.fi/fi/tilasto/khki