Environmental Science

Dissolving CO2 in Brine

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Science  21 Sep 2012:
Vol. 337, Issue 6101, pp. 1435
DOI: 10.1126/science.337.6101.1435-c

Carbon dioxide capture and long-term storage are seen as one way to mitigate and defer global warming. One idea for capturing and storing CO2 is injecting it into the highly saline ground-waters that are common on many continents. These brines are often relics of earlier hydrologic systems and have persisted for millions to tens of millions of years (or longer) because their high salinity makes them denser than shallow freshwater systems. Using thermodynamic modelling of the system CO2-H2O-NaCl-CaCO3, Steele-MacInnis et al. explore what will happen to CO2 when injected as a supercritical fluid into deep saline formations, with a goal of estimating the available storage volume. Initially, injected CO2 will displace the brine, but over time, it will dissolve in the brine. Their thermodynamic analysis shows that this dissolution will yield the most favorable storage conditions and will markedly reduce storage volume requirements. It will also increase the density of the brine, stabilizing it further.

Environ. Sci. Technol. 10.1021/es301598t (2012).

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