During the period from 1 July 2025 to 30 June 2026, 99.6% of the carbon dioxide (CO₂) and all hydrogen sulfide (H₂S) entering the capture system was dissolved in water and sent for permanent storage in the bedrock. Such capture in water is the first stage of carbon dioxide mineral storage, and the results demonstrate the high efficiency of Silverstone, a joint project between Carbfix and ON Power at Hellisheiði.

Accelerating a natural process

The Carbfix method is based on the same natural carbon cycle process that normally takes thousands of years. Through Silverstone, Carbfix technology immediately dissolves the carbon dioxide in water and then transforms it into new minerals within two years by injecting the carbonated water into reactive basalt formation underground. In this way, the operation reduces the climate impact of geothermal power production while also contributing to the safe and cost-effective management of hydrogen sulfide. During the period, more than 19,000 tonnes of CO₂ were injected through older geothermal wells that are now used for reinjection.

Important validation of the technology

ON Power’s Hellisheiði Power Plant has been a global pioneer in reducing emissions from geothermal energy production, and Silverstone plays a key role in that effort. The operational results demonstrate the high efficiency of the capture technology and confirm its effectiveness in continuous operation.

Since the Carbfix method was first implemented at Hellisheiði, a total of more than 120,000 tonnes of CO₂ and more than 50,000 tonnes of H₂S have been permanently mineralized in rock.

Silverstone is led by Carbfix and ON Power, witch received a grant of nearly €3.9 million from the European Union Innovation Fund. This support has been important for the development and expansion of the technology and has contributed to greater knowledge of how Icelandic innovation and engineering expertise can be used to reduce greenhouse gas emissions.