Underground carbon sequestration may be less effective than proponents previously believed, according to a study team at MIT’s Department of Earth, Atmospheric and Planetary Sciences.
“Once (CO2 is) injected into the ground, less carbon dioxide is converted to rock than previously imagined,” Daniloff says. “The team studied the chemical reactions between carbon dioxide and its surroundings once the gas is injected into the Earth—finding that as carbon dioxide works its way underground, only a small fraction of the gas turns to rock. The remainder of the gas stays in a more tenuous form.”
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“If it turns into rock, it’s stable and will remain there permanently,” says post-doctoral student Yossi Cohen. “However, if it stays in its gaseous or liquid phase, it remains mobile and it can possibly return back to the atmosphere.”
Cohen and geophysics professor Daniel Rothman are calling for further research to determine the extent of the problem. “There are many factors, such as the porosity and connectivity between pores in rocks, that will determine if and when carbon dioxide mineralizes,” Cohen says. “Our study reveals new features of this problem that may help identify the optimal geologic formations for long-term sequestration.”
