WASHINGTON – The United States has the potential to store a mean of 3,000 metric gigatons of carbon dioxide (CO2) in geologic basins throughout the country, according to the first-ever detailed national geologic carbon sequestration assessment released today by the U.S. Geological Survey (USGS). The assessment comes on the heels of a national plan to combat climate change announced by President Obama yesterday.
"This USGS research is ground-breaking because it is the first realistic view of technically accessible carbon storage capacity in these basins," said Secretary of the Interior Sally Jewell. "If enough of this capacity also proves to be environmentally and economically viable, then geologic carbon sequestration could help us reduce carbon dioxide emissions that contribute to climate change."
Based on present-day geologic and hydrologic knowledge of the subsurface and current engineering practices, this assessment looked at the potential for CO2 storage in 36 basins in the United States. The largest potential by far is in the Coastal Plains region, which accounts for 2,000 metric gigatons, or 65 percent, of the storage potential. Two other regions with significant storage capacity include the Alaska region and the Rocky Mountains and Northern Great Plains region.
Technically accessible storage resources are those that can be accessed using today's technology and pressurization and injection techniques. The most common method of geologic carbon storage involves pressurizing CO2 gas into a liquid, and then injecting it into subsurface rock layers for long-term storage.
"Today's assessment from the USGS is just the latest example of how the Department of the Interior is applying rigorous, peer-reviewed science to some of our nation's most complex land- and resource-management challenges," said Deputy Secretary David J. Hayes. "Nowhere is this more important than the issue of climate change, and today's new research adds to the USGS's groundbreaking work in biological carbon sequestration to better inform our carbon reduction efforts."
This assessment goes further than all previous assessments in considering the viability of sequestration. For example, all areas with groundwater sources that are considered freshwater by U.S. Environmental Protection Agency (EPA) standards were eliminated from consideration for carbon storage resource potential in this assessment. In addition, the rock layers included in the assessment were limited to those determined to have sufficient natural seals to prevent CO2 from escaping. This assessment also focused only on rock layers located at depths at which CO2 would stay under sufficient pressure to remain liquid.
The study did not evaluate economic viability or accessibility due to land-management or regulatory restrictions for geologic carbon sequestration within these basins.
The assessment is also the first geologically based and probabilistic assessment, estimating a range of 2,400 to 3,700 metric gigatons of CO2 storage potential across the United States. For comparison, the U.S. Energy Information Administration (EIA) estimates that in 2011, the United States emitted 5.5 metric gigatons of energy-related CO2, while the global emissions of energy-related CO2 totaled 31.6 metric gigatons. Metric gigatons are a billion metric tons.
"Today's climate challenges require new, scientifically supported solutions like storing the carbon dioxide created by use of fossil fuels, rather than releasing it into the atmosphere," said Assistant Secretary for Water and Science Anne Castle. "This new study provides the scientific underpinning needed to better manage options related to reducing emissions that contribute to climate change."
Although the scope of sequestration included in this assessment is unprecedented, injecting CO2 into geologic formations is not a new process or technology. Carbon dioxide injection has been one method of enhanced oil recovery since the 1980s. The process works by flooding the oil reservoir with liquid CO2, which reduces the viscosity of the hydrocarbons and allows them to flow to the well more easily.
The USGS project results announced today represent an assessment of storage capacity on a regional and national basis, and results are not intended for use in the evaluation of specific sites for potential CO2 storage.
All sedimentary basins in the United States were evaluated, but 36 were assessed because existing geologic conditions or the available data suggested only these 36 met the assessment’s minimum criteria.
The geologic foundation that underpins the assessment was facilitated by data provided by the U.S. EPA, the U.S. Department of Energy, and State geological surveys. The methodology for the assessment released today was developed by the USGS and consistently applied across all 36 basins, so that results are comparable. This national assessment complements the regional estimates that the Department of Energy includes in their periodically updated Atlas.
The USGS has a long history of assessing national and global oil and gas resources. In 2007, Congress authorized the USGS to conduct the carbon sequestration assessment in the Energy Independence and Security Act of 2007 (Public Law 110-140). In addition to geologic carbon sequestration, the USGS also studies biologic carbon sequestration— sequestration that happens naturally in trees, fields, and different types of ecosystems that store carbon. The USGS has already completed assessments for the Great Plains Region and the western U.S.; reports on the eastern U.S., Alaska and Hawaii will follow.
The geologic carbon sequestration assessment released today has the following publications:
- National Assessment of Geologic Carbon Dioxide Storage Resources—Summary Fact Sheet
- National Assessment of Geologic Carbon Dioxide Storage Resources—Detailed Results
- National Assessment of Geologic Carbon Dioxide Storage Resources—Data