Storing CO2 for the Long Term

(MoneyWatch)  (NOTE: This item is the third in a three-part series on clean-coal technology. For links to other parts of the series, see the end of this item.)

Coal is expected to retain the largest share of the electricity market over the next couple of decades -- which makes curbing its carbon-dioxide emissions a major environmental goal. That's especially true given that most forecasts show a strong surge in coal use in the years to come, especially among large developing economies such as China and India. China alone builds a new coal-fired power plant every seven to 14 days, and its coal supply struggles to keep up with demand.

While government and industry are working on ways to economically capture CO2 from power plants, the question remains: What do you do with all that greenhouse gas? The tentative answer: store it away, a process known as sequestration.

Most carbon sequestration research efforts focus on storing captured CO2 in depleted oil and gas reservoirs, saline aquifers, or the ocean. Some question the permanence of such storage solutions--particularly given the potential for CO2 leakage--and industry's ability to monitor the status of the stored CO2.

Another unanswered question question is whether geological formations have the capacity to handle the CO2 volumes envisioned in most sequestration plans. For what it's worth, the Department of Energy estimates that the U.S. has enough capacity to store 900 years of CO2 emissions, which it describes in great detail in its recent carbon-sequestration atlas.

Seven regional partnerships formed by the DOE, including hundreds of state agencies, universities, and companies, are already at work on a number of CO2 storage projects. One such involves injecting thousands of tons of compressed CO2 captured from a DTE Energy natural gas processing plant into a shale formation 2,600 feet underground. Early results suggest that Michigan's underground rock formations alone could store 80 billion tons of CO2.

StatoilHydro has the granddaddy of industrial CO2 storage projects, having stored CO2 stripped from a North Sea field's natural-gas stream since 1996.

Injecting CO2 underground is nothing new to the oil and gas industry, which has been doing it for decades to enhance recovery of crude oil. A newer twist is using captured industrial emissions of CO2 for that purpose.
Ironically, it may be the oil and gas industry's experience with CO2 that paves the way to a clean coal solution. Encana and Dakota Gasification have been operating a project for nearly a decade that injects CO2 captured from a coal-fired synthetic fuels plant in North Dakota into an oil field across the border in Canada. In addition to injecting the CO2 to boost oil recovery, Encana monitors the CO2 stored underground.

A cost-effective clean coal solution would avoid a future that many utility companies worry would be forced on them and feature unreliable energy at exorbitant costs. A solution can't come soon enough for a world that can't afford either.

BNET Energy on Clean Coal

• Clean Coal: Oxymoron or Magic Bullet?
• Fixing Coal's Carbon-Capture Problem
• Storing CO2 for the Long Term