Sequestering carbon dioxide shows promise in studies

EVANSVILLE — Finding a way to capture and use or dispose of carbon dioxide has become essential for utility companies. Given concerns about carbon dioxide's contribution to climate change, utilities are confronted with the possibility that the gas, a byproduct of burning coal at power plants, may face increased regulation.

The gasification process Indiana Gasification would use to turn coal into synthetic natural gas is relatively clean when it comes to emissions of pollutants such as sulfur dioxide and nitrogen oxide. But like conventional coal-fueled power plants, the gasification process results in large amounts of carbon dioxide.

Although gasification plants can remove much of their carbon dioxide more easily than regular coal-fueled power plants, finding a use for such large volumes of it has proved challenging.

The answer, some believe, lies in trapping the gas in porous rock formations and empty oil reservoirs deep underground, possibly in oil fields where it can be used to push out hard to recover oil. The processes are called carbon sequestration and enhanced oil recovery.

The idea has divided environmentalists, with some such as Greenpeace opposing it as too unproven, unsafe and expensive, while others such as the Clean Air Task Force support it as a practical way of addressing global warming.

A report by the University of Toronto last fall warned there still are many hurdles and hazards for the technology, including the cost, the possibility of unexpected leaks, liability issues and the risk of water contamination. It warned that politicians are pushing its development without knowing all the answers.

Dakota Gasification Co.'s Great Plains Synfuels Plant is the only commercial scale coal-to-synthetic natural gas plant operating in the country, and has been cited by Indiana Gasification as an example of what it is seeking to build near Rockport.

The plant captures about 50 percent of its carbon dioxide emissions, said Daryl Hill, a spokesman for Basin Electric Power Cooperative, which owns Dakota Gasification Co. After accounting for the energy used to transport the gas, about 70 percent of it is sequestered, he said.

Dakota Gasification removes the carbon dioxide using a licensed process called Rectisol, which Indiana Gasification developer William Rosenberg said the Rockport plant also would use. It is then compressed into liquid and sent through a 205-mile pipeline to Canada, where it is used for enhanced oil recovery as part of a large-scale study project.

Plano, Texas-based Denbury Resources has signed a contract with Indiana Gasification and the Cash Creek coal gasification project in Henderson County, Ky., to purchase their carbon dioxide for enhanced oil recovery, but the feasibility of building a pipeline to take it to the Gulf Coast is still being studied.

Dakota Gasification sends about 8,000 metric tons of carbon dioxide daily to be sequestered. The project is being observed as part of an eight-year, $80 million project to study the possibilities of carbon sequestration, and is scheduled to be completed in 2011. Much of the carbon dioxide that is injected returns to the surface with oil and water, where it is captured and reinjected into the reservoir, where it is expected to remain permanently stored.

Others are studying carbon sequestration, too. Duke Energy will spend $17 million to study carbon storage at a new power plant it is building near Edwardsport, that will use coal gasification to generate electricity.

A 2007 study on the future of coal by the Massachusetts Institute of Technology concluded that most coal-fired power plants are in regions where there are high expectations for nearby for carbon sequestration sites.

But how well individual areas are suited for it must be studied still.

The Midwest Geological Sequestration Consortium is studying carbon sequestration and enhanced oil recovery in Posey County, Hopkins County, Ky., and Macon County, Ill.

"We're checking to see what kind of storage capacity there is in the subsurface," said Scott Frailey, of the Illinois State Geological Survey. "Part of our job is to prove it can be done safely."

The study uses food-grade carbon dioxide, he said. The carbon dioxide injections will end this summer, but the wells will be monitored for another year to determine if there is any leakage back to the atmosphere or water contamination.

"It definitely looks promising," he said.

Frailey said the study also is considering how seismic activity in the region may affect carbon storage sites, although he said the depth of faults in the area may make it unlikely that there will be much impact.

Gallagher Drilling Inc., an Evansville-based oil company, is supplying the Indiana and Kentucky oil fields being used in the study.

Owner Mike Gallagher said so far the experiment has increased oil production at the Posey County site by about a third, but has had only a slight affect on oil production in Kentucky. But he is encouraged.

"They do this in west Texas, and it obviously does increase oil production," he said. "The next question is can you get it cheap enough where you need it?"