The Gulf Coast has the greatest potential of any region in the nation for storing carbon dioxide, according to a study released Wednesday by the Interior Department.
The study, released one day after President Barack Obama announced his own plan to fight global warming by imposing limits on greenhouse gas emissions from power plants, found that the United States has the potential to store 3,000 metric gigatons of carbon dioxide in geologic basins throughout the country.
Two-thirds of that storage capacity — 2,000 metric gigatons — would be in the coastal plains, most of it along the Gulf Coast.
“Yesterday, the president unveiled a bold plan to reduce levels of carbon dioxide,” Interior Secretary Sally Jewell said in a conference call with reporters Wednesday. “Geologic carbon sequestration could play a role.”
Congress authorized the U.S. Geological Survey, the scientific arm of the Interior Department, to conduct the study in 2007.
It considered 36 basins in the United States, looking at currently available technology, pressurization and injection techniques. Geologic carbon storage most commonly involves pressurizing carbon dioxide gas into a liquid and injecting it into subsurface rock layers for long-term storage.
Deputy Interior Secretary David J. Hayes said more research is needed to determine whether carbon sequestration would be economically viable.
The U.S. Geological Survey also is in the midst of studies considering so-called biological carbon sequestration, evaluating how much carbon the nation’s forests and other landscapes absorb.
Brenda Pierce, energy resources program coordinator for the U.S. Geological Survey, declined to define the storage capacity in terms of how many years worth of carbon emissions it could hold. But she noted that the country currently emits 5.5 metric gigatons of carbon dioxide per year.
A metric gigaton is equivalent to a billion metric tons.
While most of the potential storage is along the Gulf, the next largest capacity is in Alaska and the Rocky Mountains-Northern Great Plains regions. The Rocky Mountains-Great Plains region stretches from Mexico to Canada.
Each of the two regions accounts for about 9 percent of potential storage, Pierce said.
She said one reason the Gulf is so attractive is the lack of fresh water — any area with fresh groundwater was eliminated from consideration. In addition, only rock layers deep enough to keep carbon dioxide under sufficient pressure to remain liquid and to prevent it from escaping were considered a good fit.
The study didn’t get into the details of the infrastructure that would be needed to make carbon sequestration work. Pierce noted that the carbon dioxide generally has to be transported by pipeline and then compressed and converted to a liquid before it is injected into the storage well.
Carbon sequestration isn’t new. Oil companies have been using it as a method to enhance oil recovery since the 1980s, flooding the oil reservoir with liquid carbon dioxide to help the hydrocarbons flow more easily, and research on other projects is ongoing.
The Energy Department has helped fund carbon capture projects around the country, including one under construction at NRG Energy’s Parish coal-fired plant in Fort Bend County, to demonstrate the technology while boosting the electricity supply.
“The United States has the ability to store a lot of carbon dioxide,” Jewell said. “If this proves to be economically viable, and that hasn’t been answered in this study, sequestration could help.”