SEASTONE: THE FIRST INJECTION OF SEAWATER-DISSOLVED CO2 INTO REACTIVE BASALT

Carbfix has successfully demonstrated carbon storage via mineralization by injecting water-dissolved CO₂ into reactive basalts. Although basaltic formations are widespread, the water demand of this process can restrict its scale-up potential. Seawater, as opposed to fresh water, has the advantage of a lower price, greater availability, and avoidance of potential water use conflicts. Demonstrating that seawater can be effective for CO2 mineralization would unlock carbon storage resources in coastal regions worldwide and take us a step closer to offshore application. Laboratory experiments with seawater have shown CO₂ mineralization rates similar to those in freshwater, and furthermore suggest that the use of seawater could be advantageous providing an additional source of Mg+2 which could be consumed by carbonation reactions. However, the more complex chemistry of CO2-seawater-basalt interaction necessitates a field demonstration before the technology can be commercially exploited.

In CO2SeaStone, the first field injection of CO2 dissolved in seawater is being carried out, monitored, and validated. A test facility, including four wells and a mobile injection system has been constructed in Helguvik Iceland where injection is already taking place. This site provides an onshore/near-shore analogue to offshore basalt environments. For the injection, one thousand tons of CO2 are being captured and transported from a facility in Switzerland in a partner project led by ETH Zurich. The project therefore encompasses the entire CCS value chain. We present the history and status of the SeaStone and describe some of the novel Monitoring, Reporting and Verification (MRV) techniques being tested at the Helguvik facility to advance the field of subsurface mineralization.