The CO2 Fixation into Basalt at Hellisheidi Geothermal Power Plant, Iceland

Abstract

The reduction of anthropogenic CO2 emissions is considered one of the main challenges of this century. Capturing CO2 from various sources and injecting it into carefully selected deep rock formations with large potential storage capacity might help to mitigate climate change.
More than 90% of Iceland’s crust is composed of basalt. Basaltic rocks are one of the most reactive rock types in the Earth’s crust and contain reactive minerals and glasses with high potential for CO2 sequestration. At Hellisheidi Geothermal Power Plant a mixture of water and steam was harnessed from 2000-3000 m deep wells. The steam contained geothermal gases, with CO2 accounting for about 85 % of these gases. CO2 from the geothermal plant will be dissolved in water at elevated pressures and then injected into wells with depths of 400-800 m, just outside the boundary of the geothermal system. The liquid will react with minerals such as magnesium and calcium from the basalt to form solid carbonates. This process occurs naturally in basaltic volcanoes that host geothermal systems, and the carbonates are stable for thousands of years. The proposed CarbFix pilot project aims to accelerate these natural processes.