How to Turn Carbon Dioxide into Rock and Bury It Forever (Hopefully)

Illustration for article titled How to Turn Carbon Dioxide into Rock and Bury It Forever (Hopefully)

What do we do with a problem like carbon dioxide? We want to remove the excess from our atmosphere, but how? In Iceland, geologists are burying the greenhouse gas with water, so that basic chemistry can turn it into solid rock inside what the New York Times calls "a geological soda machine."


Storing carbon dioxide underground is not a new idea, but CarbFix in Iceland uses an unique approach. Conventionally, liquid carbon dioxide is injected into porous rock—like at Sleipner in Norway—where we hope the carbon dioxide will (eventually) turn into carbonate minerals after thousands or tens of thousands of years. Over that long stretch of time, the pressurized gas could escape through cracks into the air, leaving us right back where we started.

CarbFix wants to speed up the process of mineralization, using something as simple as water. But lots of it. Carbonated water is acidic—just like your Diet Coke hence the wonderful phrase "geological soda machine"—which helps release elements like calcium with which carbon dioxide can react. In Iceland's volcanic fields, the carbon dioxide is injected into basalt, where it should turn to calcite.

CarbFix began their first test field injection in 2012, and they're now analyzing their cores of rock for calcite. They've also scaled up their operations to inject 10,000 tons of carbon dioxide captured from a nearby power plant each year. It appears promising, but there is a big dollar sign hanging out next to a question mark over everything. The Times explains why:

But injecting huge amounts of water along with the CO2 — 25 tons of liquid for each ton of gas — adds to the cost. CarbFix scientists have estimated that transportation and injection could cost about $17 per ton of CO2, about twice the cost of transporting and injecting the gas alone. (These costs are on top of the much higher costs of capturing and separating CO2 from a power plant smokestack.)

Without economic incentives, energy companies have no reason to invest in burying their carbon dioxide with water, especially if there are other cheaper solutions. The irony, though, is that over tens of thousands of years, CarbFix's solution might actually be cheaper if it truly works as promised without leaking. But we humans are not so good at thinking in tens of thousands of years. [New York Times]

Top image: Cores containing calcite believed to contain carbon dioxide injected in 2012. Credit: CarbFix




I have a basic carbon sequestration issue. Does it violate the law of Conservation of Energy?

Our energy is created by turning solid or liquid carbon into gas. Sequestration turns carbon dioxide gas back into solid or liquid carbon.

So even if we are 100% efficient, wouldn't we spend as much energy sequestering a ton of carbon dioxide as we got from that carbon when we originally burned it?