Indiana - land of farms, fields and forests - is also home to factories, fertilizer plants and other industries that emit carbon dioxide. The Hoosier state ranks third in the nation in carbon dioxide emissions and 11th in the number of carbon-dioxide-emitting sources.
Indiana, however, could also become a leader in decarbonizing the atmosphere through carbon capture and storage - the capture of carbon dioxide from industry emissions and the storage, or sequestration, of carbon dioxide in deep underground geologic formations. Supported by the U.S. Department of Energy, researchers at the Indiana Geological and Water Survey at Indiana University are working with colleagues from other states to evaluate locations in Indiana and the Midwest where carbon storage in geologic formations could be successful.
Over the past 187 years, researchers at the Indiana Geological and Water Survey have laid the groundwork for carbon capture and storage by mapping in increasing detail the types, thicknesses, depths and properties of rock formations under Indiana. The Indiana Geological and Water Survey maintains a library of hundreds of thousands of feet of rock cores at a facility in Bloomington so researchers from inside and outside the organization can study them as windows into the deep subsurface. Samples collected decades ago are still yielding new information.
"Carbon capture and storage is worth studying because so much of everyday life is still dependent on fossil fuels," said Ashley Douds, co-lead researcher at the Indiana Geological and Water Survey's Center for Energy.
Across the United States, nearly half of all greenhouse gas emissions come from electricity generation or industry. Indiana is home to 220 power plants, nearly half of which run on hydrocarbons. Other significant sources of carbon dioxide emissions in Indiana are landfills, ethanol plants, refineries and facilities that produce industrial materials such as cement or aluminum.
"The ability to store carbon in this state is impactful because we have so many industries that generate CO2, and it's our way of cleaning up the air," Douds said. "The growth in clean energy, such as wind and solar, have been good additions to the energy mix. But hydrocarbons are also a necessary piece of the energy mix, and this is a good way to decarbonize the sector."
In carbon capture and storage, carbon dioxide is made into a supercritical fluid - held at a particular temperature and pressure - and is injected thousands of feet underground into specific types of rock formations. It can be stored in unmineable coal, in natural gas or oil reservoirs, and in other porous sedimentary rocks capped by impermeable rocks. A majority of Indiana is underlain by saline formations consisting of layers of rocks saturated with salty brine water. According to the Department of Energy, these formations have "an enormous potential for CO2 storage."
"In the Indiana-Illinois region, the porosity and permeability of some of the deep reservoirs are ideal for injecting CO2," Douds said. "They are below the 2,600-foot depth threshold so that the CO2 remains in a supercritical state as it is injected, which allows for more CO2 to be stored in a given volume of rock compared to gaseous CO2. They are widespread throughout a big region, and they haven't produced oil and gas, so they're not heavily drilled in that manner."
Douds said people might be surprised to find that deep reservoirs have been used before as injection reservoirs for wastewater, particularly from factories.
"What we're looking for is using the Earth's ability to store these fluids for long periods of time," Douds said. "Natural gas, oil, water, they're all fluids, and CO2 is a fluid in a supercritical state. So the Earth has been storing these fluids for many millions of years. We're looking to take advantage of that natural ability."
The Mount Simon Sandstone, a saline reservoir that underlies Indiana and several adjacent states, was tapped for carbon capture and storage decades ago. In fact, Indiana Geological and Water Survey researchers contributed to that process during the Illinois Basin-Decatur Project at the Archer Daniels Midland ethanol plant in Illinois.
Beginning in 2011, 1 million metric tons of carbon dioxide were injected into the 1,500-foot-thick Mount Simon Sandstone and trapped more than 5,000 feet underground by the caprock. The plant received a second carbon dioxide injection well permit in 2021.
So far, the Illinois Basin-Decatur Project is the only EPA-permitted carbon capture and storage facility in the United States. But 42 projects in 11 states were in the federal permitting process as of mid-February of this year, and three states have been granted the ability to issue permits on their own. In January, the Environmental Protection Agency approved the first two permits for carbon capture and storage wells in Indiana, in Vermillion and Vigo counties.
The Indiana Geological and Water Survey will lead statewide studies to identify areas favorable for carbon dioxide storage, their capacity and any complexities present in the subsurface. The IU Center for Rural Engagement and the Polis Center at IU Indianapolis will provide community engagement and spatial analysis, respectively.
In Lawrence County, researchers are working with the Heidelberg Materials cement plant, which is participating in carbon capture at plants around the world. Working with partners at the Illinois State Geological Survey, Indiana Geological and Water Survey geoscientists assisted with collecting seismic data to characterize the subsurface and select the drilling location.
Once a permit is issued, a stratigraphic test well will be drilled, and core, geophysical logging and other tests will be run to learn more about the possible reservoir and caprock. Broad-scale geologic maps suggest the presence of an unusual type of sand in the Knox Dolomite in that part of Indiana that could serve as a reservoir.
"It has the potential to be a great reservoir target if confirmed by more detailed analysis," Douds said.
While focused on Indiana and the Midwest, the work of Indiana Geological and Water Survey researchers can have an impact across the nation. Whereas some industries in the United States are undertaking their own carbon capture and storage studies, the work of IU researchers is not subject to the same level of proprietary concerns. The study results will be freely available through the Department of Energy.
"Just researching and sharing what we've learned about our subsurface, and what are positive things to look for and things to stay away from, it all adds to the collective knowledge," Douds said.
