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Understanding the Geo-Chemistry of Carbon Sequestration

Birds eye view of pollution coming out of several buildings.

Photo by Marcin Jozwiak on Unsplash.

Experts agree that in order to stave off the worst impacts of climate change, it is not only necessary to stop burning fossil fuels, but it’s also imperative to remove carbon dioxide (CO2) from the atmosphere and sequester it safely underground. In fact, the National Academy of Engineering identifies carbon sequestration as one of the 14 grand challenges for engineering in the 21st Century.

Khalid Alshibli.

Khalid Alshibli

CEE Professor and Associate Department Head of Graduate Studies Khalid Alshibli and Larry and Dawn Taylor Assistant Professor of Planetary Geosciences Nicholas J. Dygert in UT’s Department of Earth and Planetary Science are heading up research to study one aspect of carbon sequestration which could help limit the warming of the planet.

Alshibli notes that President Joe Biden is proposing to offer a financial incentive to industries that use carbon capture and storage to reduce their emissions.

“It will take time to phase out industries that use fossil fuel and carbon capture from source points, and sequestering it can offer a viable solution to reduce the adverse impact of CO2,” he said.

Carbon dioxide capture and storage is a process of separating CO2 from industrial facilities and other point sources and injecting it in deep geological formation for long-term storage. With help from a grant from the Institute for Secure and Sustainable Environment, they will study the chemical reaction between CO2 and rocks when it is sequestered deep underground.

Deep saline aquifers, depleted gas and oil fields, and coal mines have been identified as good potential places to store CO2. However, due to the low density of CO2, scientists know that for sequestration to be successful it will need to be injected into porous rocks deeper than 3,000 feet at a pressure higher than 3,000 psi, below thick, low-permeability rock such as limestone, shale, or salt rock (caprock).

Many challenges to safe carbon sequestration remain, including the potential leak of CO2 to the atmosphere and groundwater, or cause for seismic damage and fracture of the caprock. Alshbili and Dygert are specifically interested in identifying whether there is a chemical reaction between CO2 and the caprock, which could compromise the integrity of the rock leading to the leak of CO2 back to the atmosphere.

To accomplish this, they will characterize CO2-caprock geochemical interaction at the micro and nano-scales using world-class analysis tools at the Advanced Photon Source at Argonne National Laboratory.

There, they will image specimens of limestone samples collected from a depth of 800 feet from East Tennessee before and after exposing them to CO2 at 3,000 psi pressure at a temperature similar to field temperature for a long duration.