To Clean Up Coal, Obama Pushes More Oil Production

Another potential risk is blowouts. Many oil fields that are ideal candidates for carbon dioxide injection have many old and abandoned wells that may or may not be plugged properly.

Denbury Resources has had a series of uncontrolled blowouts in recent years, as the pressure created by injecting carbon dioxide tests the cement plugs in long-shuttered wells. The largest, and one that was responsible for one of the largest environmental fines in Mississippi in the past decade, occurred in 2011 at the Tinsley Field, one of several old oil fields that will receive carbon from Southern Co.'s power plant.

The company paid $662,500 for a blowout that vented carbon dioxide, oil and drilling mud for 37 days. So much carbon dioxide came out that it settled in some hollows, suffocating deer and other animals, Mississippi officials said. The company ultimately drilled a new well to plug the old one, and removed 27,000 tons of drilling mud and contaminated soil and 32,000 barrels of liquids from the site.

The company still claims it's green because of the carbon it is storing as part of its oil production process.