Turning Carbon Emissions into Rocks: Use of Saline Water in Geologic Carbon Sequestration by Subsurface In-Situ CO2 Mineralization

The urgent need to mitigate climate change has accelerated the exploration of innovative carbon capture and storage technologies. Among these, in-situ carbon mineralization emerges as a promising technology to store CO2 underground in the form of calcite and magnesite minerals. Carbfix, an Icelandic climate technology company, successfully accelerates the in-situ mineralization process of CO2 by co-injecting carbon dioxide with freshwater into basaltic rock formations using their proprietary technology. Despite the clear techno-economic advantages of this technology, its freshwater demand poses a significant challenge to its large-scale implementation. This paper aims to assess the feasibility of utilizing saline water as a substitute for freshwater in the Carbfix method and to locate the most ideal sites in Iceland and the Pacific Northwest Region (PNW) of the United States where this novel technology can be safely piloted. Review of previous literature supported the feasibility of using saline water as a co-injection fluid with CO2. To test this hypothesis, we ran geochemical simulations to model the pH change of the injection fluid, and carbonate mineralization rates under three different salinity conditions for a typical Columbia River Basalt Group (CRBG) column. We also collected groundwater data and conducted a feasibility analysis based on the hydrogeologic conditions of three potential injection sites selected in CRBG and three injection sites selected in Iceland. The results of this study indicate that saline water is a promising alternative to freshwater to scale the deployment of the Carbfix technology globally. The Project CO2 SeaStone site in Iceland and the Canoe Ridge site in the State of Washington are identified as ideal sites to pilot this novel technology.