Washington, DC - In another step forward toward improved scientific understanding of potential geologic carbon dioxide (CO2) storage impacts, a new U.S. Department of Energy (DOE)-sponsored study has confirmed earlier research showing that proper site selection and monitoring is essential for helping anticipate and mitigate possible risks.
The Duke University study, published in the October 26, 2010 edition of Environmental Science & Technology, also provided information that can be used for advanced detection of CO2 in the unlikely event of a leak.
CCS comprises a suite of technologies to separate, compress, transport, and store CO2 produced at power plants and other industrial facilities. Many global experts view the technology - a major focus of research by DOE’s Office of Fossil Energy (FE) - as an important option in a portfolio of strategies for helping reduce the atmospheric buildup of CO2 resulting from human activity as a means of averting potential climate change. A particularly important storage challenge is the ability to conduct CCS without affecting underwater sources of drinking water.
The Duke report, "Potential Impacts of Leakage from Deep CO2 Geosequestration on Overlying Freshwater Aquifers," presented the results of a year-long study investigating the impacts of CO2 injection into different geologic formations and the possible dissolution of metals from specific rocks that naturally contain high concentration of these metals.
The researchers incubated core samples from a variety of freshwater aquifers with CO2 for more than 300 days, and found increased acidity and metals concentrations in water surrounding the samples. They concluded that "the relative severity of the impact of leaks on overlying drinking water aquifers should be considered in the selection of CO2 sequestration sites." This confirms earlier research conducted by FE’s National Energy Technology Laboratory (NETL), several other DOE national laboratories, the U.S. Geological Survey, and others indicating that CCS sites must be carefully selected and monitored.
The Duke researchers also identified three elements--manganese, iron, and calcium--which they suggest should be monitored, along with pH, as geochemical markers of CO2 leaks.
The Duke research project is one of many being sponsored by DOE to investigate the impact of CO2 injection into geologic formations, including the dissolution of metals from rock. This has been recognized for many years as a potential risk in CCS projects and it continues to be a focus of research. The research provides fundamental data that are used to improve risk assessment models and the design of CCS projects and monitoring programs. The risk to drinking water supplies can be mitigated by proper site characterization, having an impervious caprock, and proper construction materials, and by maintaining proper operating conditions as required by the EPA’s Underground Injection Control Program.
Although CCS is an emerging field, it benefits from the experience of oil and gas producers who have more than 40 years of experience injecting CO2 into deep geologic formations to increase the flow of oil and natural gas. This provides a sound base for DOE’s scientific investigations and the development of risk assessment and mitigation strategies.
DOE is committed to continuously supporting research and field projects to make CCS as safe and effective as possible. Through its Carbon Sequestration Research Program, FE is investigating all aspects of CCS, including the risks associated with geologic storage of CO2. Research sponsored by DOE helps to inform future operators, the public, and regulators as they identify safe storage sites, design facilities, and develop plans for a future CCS industry.