Underground CO2 storage could contaminate drinking water

Robert B. Jackson, Nicholas Professor of Global Environmental Change and professor of biology at Duke University, published the results of a year long investigation of the varied potentials for carbon sequestration to contaminate drinking water in the online edition of the journal Environmental Science & Technology on November 12, 2010.

Jackson says, "We found the potential for contamination is real, but there are ways to avoid or reduce the risk."

"Geologic criteria that we identified in the study can help identify locations around the country that should be monitored or avoided," he says. "By no means would all sites be susceptible to problems of water quality."

Storing carbon dioxide deep below Earth's surface, a process known as geosequestration, is part of a suite of new carbon capture and storage (CCS) technologies being developed by governments and industries worldwide to reduce the amount of greenhouse gas emissions entering Earth's atmosphere. The still-evolving technologies are designed to capture and compress CO2, emissions at their source -- typically power plants and other industrial facilities -- and transport the CO2 to locations where it can be injected far below the Earth's surface for long-term storage. The U.S. Department of Energy, working with industry and academia, has begun the planning for at least seven regional CCS projects.

"The fear of drinking water contamination from CO2 leaks is one of several sticking points about CCS and has contributed to local opposition to it," says Jackson, who directs Duke's Center on Global Change. "We examined the idea that if CO2 leaked out slowly from deep formations, where might it negatively impact freshwater aquifers near the surface, and why."

Jackson and his postdoctoral fellow Mark G. Little collected core samples from four freshwater aquifers around the nation that overlie potential CCS sites and incubated the samples in their lab at Duke for a year, with CO2 bubbling through them.

After a year's exposure to the CO2, analysis of the samples showed that "there are a number of potential sites where CO2 leaks drive contaminants up tenfold or more, in some cases to levels above the maximum contaminant loads set by the EPA for potable water," Jackson says. Three key factors -- solid-phase metal mobility, carbonate buffering capacity and electron exchanges in the overlying freshwater aquifer -- were found to influence the risk of drinking water contamination from underground carbon leaks.

The study also identified four markers that scientists can use to test for early warnings of potential carbon dioxide leaks. "Along with changes in carbonate concentration and acidity of the water, concentrations of manganese, iron and calcium could all be used as geochemical markers of a leak, as their concentration increase within two weeks of exposure to CO2," Jackson says.

Southern Company, the Parent of Alabama Power has several carbon sequestration projects in Alabama.

Southern Company’s web site notes the following carbon sequestration projects being pursued in Alabama.

The National Carbon Capture Center is a focal point of U.S. Department of Energy's efforts to develop advanced technologies to reduce greenhouse gas emissions from coal-based power generation. The Center, managed and operated by Southern Company in Alabama, works with scientists and technology developers from government, industry and universities who are creating the next generation of carbon capture technologies

Start-to-finish carbon capture and storage at Plant Barry in Alabama. When completed, the facility will be the largest in the world to be connected to a pulverized coal-fired generating plant. Alabama Power and Southern Company, along with the U.S. Department of Energy, Mitsubishi Heavy Industries Ltd., the Electric Power Research Institute and other partners are building the project which will create about 50 construction jobs, and the capture and compression plant will require up to 15 full-time jobs during the life of the demonstration.

A Stratigraphic test well to evaluate and characterize site-specific geology for carbon sequestration is at Alabama Power's Plant Gorgas.

Geologic sequestration, in partnership with the University of Alabama at Birmingham, is evaluating the physical properties of rocks for geologic sequestration and training students in carbon sequestration science and engineering

The Southeast is responsible for 40 percent of the CO2 emissions in the United States according to the Southeastern Regional Carbon Sequestration Partnership (SECARB). The SECARB plans for Alabama are documented here.

The Duke research is to be incorporated into this plan.