Scientists in Iceland are turning carbon dioxide into stone by injecting it into volcanic rock, and it could redefine the fight against climate change |

Edda Sif Pind Aradottir, a chemical and reservoir engineer and CEO of Carbfix, holds a sample of basalt rock at the Carbfix site in Iceland.

Scientists in Iceland are demonstrating a groundbreaking way to tackle climate change by permanently turning carbon dioxide (CO₂) into stone deep beneath the Earth’s surface. Instead of storing captured CO₂ as compressed gas, researchers dissolve it in water before injecting it into porous basalt, a volcanic rock rich in minerals. Once underground, the dissolved carbon reacts naturally with calcium, magnesium and iron in the basalt to form stable carbonate minerals, effectively locking the carbon away for geological timescales. The process, developed through the Carbfix project, has already shown that more than 95% of injected CO₂ can mineralise within two years, offering one of the most secure and durable forms of carbon storage currently available.

Inside Iceland’s Carbfix project turning carbon dioxide into stone

Carbfix is an Icelandic carbon mineralisation project launched in 2007 as a collaboration between Reykjavík Energy, the University of Iceland, CNRS in France and Columbia University in the United States. The technology is based at the Hellisheiði Geothermal Power Plant near Reykjavík, where carbon dioxide captured from industrial emissions is dissolved in water and injected into underground basalt formations. What began as a research initiative has since grown into one of the world’s leading demonstrations of permanent carbon storage through mineralisation.The process starts by capturing carbon dioxide before it enters the atmosphere. Instead of compressing the gas for underground storage, scientists dissolve it in water, producing carbonated water similar to sparkling water. This solution is then injected hundreds of metres below the surface into porous basalt rock. Because the carbonated water is denser than CO₂ gas, it naturally sinks through the rock rather than rising. As it moves through the basalt, it reacts with naturally occurring calcium, magnesium and iron to form solid carbonate minerals, permanently trapping the carbon inside the rock.

Illustration of the Carbfix process, which turns captured CO₂ into stone inside underground basalt.

Why basalt plays a crucial role

Basalt is one of the most abundant volcanic rocks on Earth and contains large amounts of calcium, magnesium and iron, the essential ingredients needed for carbon mineralisation. These minerals readily react with dissolved carbon dioxide to create stable carbonate rocks such as calcite, magnesite and siderite. Basalt also contains tiny pores and fractures that allow carbonated water to circulate through the rock, speeding up the chemical reactions. Scientists estimate that basalt formations around the world have the potential to store thousands of gigatonnes of CO₂, making them an attractive long-term solution for carbon storage.

From greenhouse gas to solid rock in just two years

Before the Carbfix project, many scientists believed that mineralising carbon dioxide underground would take hundreds or even thousands of years. However, field studies in Iceland produced a surprising result. Monitoring showed that more than 95% of the injected CO₂ was converted into solid carbonate minerals within just two years. This rapid mineralisation significantly reduces the likelihood of carbon leaking back into the atmosphere and has become one of the project’s most important scientific achievements.

A safer alternative to conventional carbon storage

Traditional carbon capture and storage often involves injecting compressed CO₂ into underground reservoirs, where it remains as a fluid and must be carefully monitored to ensure it does not escape. Carbfix takes a different approach by chemically transforming the carbon into solid rock. Once mineralisation is complete, the carbon becomes part of the basalt itself and is expected to remain trapped for thousands to millions of years. This greatly reduces the long-term risk of leakage and minimises the need for extensive monitoring.Although the technology has enormous potential, it cannot be implemented everywhere. Carbon mineralisation requires suitable basalt formations, sufficient underground water and carefully selected geological conditions. Basalt covers about 5% of Earth’s continental surface and much of the ocean floor, providing vast theoretical storage capacity. Researchers are now exploring opportunities to deploy the technology in other volcanic regions while also integrating it with direct air capture systems that remove carbon dioxide directly from the atmosphere.

Scaling up the technology

Despite its success, carbon mineralisation is not a complete solution to climate change. Capturing carbon dioxide from industrial facilities or directly from the atmosphere remains expensive, and transporting the gas to suitable storage sites requires significant infrastructure. The process also uses substantial amounts of water, although scientists are investigating ways to reduce water consumption and adapt the technology for different geological settings. Scaling the approach to remove billions of tonnes of CO₂ annually will require major investment and international cooperation.

A new frontier in permanent carbon removal

As countries seek reliable ways to reduce greenhouse gas emissions, permanent carbon storage is becoming increasingly important alongside renewable energy and emissions reductions. The Carbfix project demonstrates that captured carbon dioxide can be transformed into stable rock rather than stored as gas, offering one of the most secure forms of long-term carbon sequestration available today. While it is not a replacement for reducing fossil fuel emissions, the technology could become an important tool for tackling emissions from industries that are difficult to decarbonise and supporting global efforts to achieve net-zero emissions.