Boundary Dam and the other projects operate roughly the same way: Carbon dioxide gas, highly compressed so that it acts like a liquid, is injected into a formation, usually sandstone and often an old oil or gas field. Impermeable rock layers above the storage zone should, in theory, keep the CO2 trapped indefinitely, but because the gas remains buoyant, there is a risk that it will move upward through cracks and eventually bubble back into the atmosphere.
The CarbFix project differs from this conventional approach by using water along with carbon dioxide, and by injecting them into volcanic rocks. The technique is designed to exploit the ability of CO2 to react with the rocks and turn into solid minerals.

“Basically we’re using a natural process and engineering it for climate-change mitigation,” said Juerg Matter, a geochemist at the University of Southampton in Britain and one of the lead researchers on the project. Until last year, Dr. Matter was at the Lamont-Doherty Earth Observatory at Columbia University, a CarbFix partner.