Assessing the CO2 sequestration potential of serpentinized ultramafic rocks in Baie Verte, Newfoundland

Abstract

This study investigated the CO₂ sequestration potential of serpentine from Baie Verte, NL. Serpentinized ultramafic rocks of the Baie Verte Oceanic Tract were tested using two experimental approaches: a two-phase flow-through system, simulating mineral dissolution of near-surface water-rock reactions in serpentinite-rich systems; and a three-phase batch system, simulating surficial carbon dioxide removal (CDR). In both experiments, the fluids were rapidly buffered to basic pH values of ∼10 through the dissolution of crushed serpentine rock. The change in the pH created systems favourable for CO₂ dissolution. CO₂ sequestration from the gaseous-phase to the dissolved-phase was observed in the surficial CDR experiments, with a decrease in CO₂ and an increase in total inorganic carbon (TIC) in the fluid phase. The total CO₂ removed from the chamber of the CDR experiments with MgOH-rich fluids approximately equalled the amount of TIC gained in the fluid. Conversely, in experiments with rocks, the TIC gained in the fluid-phase was approximately five times the amount of CO₂ removed from the gas-phase. The excess TIC likely came from the dissolution of calcite, as predicted by geochemical modelling. With the exception of potentially precipitating dolomite and magnesite, the sequestered CO₂ in our experiments remained in the dissolved-phase. Interestingly, calcite dissolution did not affect the total amount of CO₂ sequestrated or the potential for dolomite or magnesite to precipitate. Therefore, when extrapolating to the field, CO₂ sequestration can still occur in a buffered system where carbonate rocks will dissolve with the addition of water.