The Mahomet Aquifer, Champaign-Urbana’s primary source of drinking water, is at the center of debate between companies, activists and residents in Illinois over carbon sequestration.

The aquifer spans 15 counties and serves nearly a million people. The EPA designated it a sole source aquifer in 2015, which means many Illinois counties would have no economically feasible alternative for drinking water if the aquifer were compromised.

Carbon sequestration is the process of injecting and storing captured carbon underground. While it aims to reduce carbon dioxide emissions, its long-term sustainability remains uncertain.

“The incentive for carbon sequestration is $85 per metric tonne of CO2 stored in tradable tax credits,” said Andrew Rehn, climate policy director of the Prairie Rivers Network.

The network is a registered nonprofit organization that aims to protect land and water in Illinois.

This federal incentive on carbon sequestration encourages companies to use carbon capture and sequestration techniques to reduce atmospheric CO2 emissions. Proposed carbon sequestration projects under the Mahomet Aquifer involve drilling wells about a mile underground to inject and store the carbon dioxide.

This leaves many pathways for leakage, such as through well casing failures, abandoned wells that are not properly sealed and geological faults and fractures. Leakage could allow sequestered carbon to compromise the aquifer’s water.

This can result in acidification, which can change the aquifer’s chemistry, introducing threats like pollutants that were previously stable, dormant or not chemically reactive.

“The prime region for sequestration stacks up, unfortunately, really nicely with the Mahomet Aquifer,” Rehn said. “There are a number of proposed carbon sequestration projects that would pass through the aquifer.”

One project in particular, One Earth Sequestration, LLC, is proposing to store 90 million tons beneath the aquifer. This scale is much larger than existing pilot projects in Illinois. 

“We feel that, with respect to the aquifer, there are too many uncertainties and too many things that could go wrong, and there should be zero tolerance,” said Pam Richart, co-founder and co-director of Eco-Justice Collaborative.

The collaborative works with the law to fight for ecological sustainability.

Earthquakes can create pathways for CO2 to contaminate aquifers. Sequestration has been known to increase seismic activity, creating an even higher risk of carbon pollution.

“If you put CO2 at high pressure and large volumes for long periods of time, then we’re looking at the potential for inducing earthquakes,” Richart said.

Illinois State Rep. Carol Ammons is working on a legislative bill to ban sequestration under the Mahomet Aquifer. Until then, Prairie Rivers Network and the Eco-Justice Collaborative are pushing for a county-by-county solution. 

“Counties can also ban this,” Rehn said. “Champaign passed a statewide moratorium on sequestration for a year. We don’t need to turn our aquifer into a laboratory.”

The Prairie Rivers Network and Eco-Justice Collaborative are working with Illinois State Sen. Paul Faraci and Ammons to move the bill through the Illinois legislature. 

“It’s the right thing to do,” Richart said. “You don’t mess with people’s water.”

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