An ethanol plant in central Illinois has stopped injecting carbon dioxide (CO₂) into the ground after a potential leak was discovered on the property for the second time this year. The problems at the Archer Daniels Midland (ADM) plant raise questions about the safety of about 150 other carbon capture wells proposed across the U.S., most with taxpayer funding.

The ADM plant in Decatur, Illinois, processes corn into ethanol fuel. To lower the carbon footprint of ethanol production, ADM captures the CO₂ before it can be emitted into the atmosphere and injects it underground. This injection process is meant to permanently isolate the CO₂ in a contained underground reservoir, like a glass bottle sealed with a cork.

However, ADM’s problems show that the reality may not be so simple. On September 24, tests at one of the monitoring wells, used to verify that the CO₂ is being stored as expected, revealed unexpected fluid movement 5,000 feet below the ground that may indicate a hole in the CO₂ storage reservoir.  

Details are still scarce while ADM conducts more tests. But the company has already confirmed a leak earlier this year. In March, ADM discovered that corrosion in a different monitoring well had allowed CO₂ into an unauthorized area. The company estimates less than 8,000 metric tons of CO₂ – about 2 percent of the amount stored in 2022 – escaped its confines. EPA inspected the well in June, but the public was not informed until September.  

If the CO₂ migrates out of its reservoir, it can make its way back into the atmosphere or into a source of drinking water. CO₂ injection can also displace brine, the fluid often found in underground spaces. Brine is salt water – often even saltier than seawater – but can also contain highly toxic chemicals like heavy metals. If the increased pressure caused by CO₂ injection pushes brine into groundwater or soil, it could have devastating effects on the environment.

While EPA believes the leak poses no threat to groundwater, the agency issued a violation notice to ADM on August 14 alleging that ADM did not follow the operating, monitoring, and emergency response requirements laid out in their permit.  EPA’s proposed enforcement order,  which has not yet gone into effect, requires the company to assess the extent of the migration and come up with a corrective action plan. It did not require any pause in injection. The draft text of the order is available on EPA’s website, and public comments will be accepted until October 21^st.  

But experts have pointed out that the order does not contain any consequences for violating the terms of their permit. “All [EPA] is doing is ordering them to comply with their permit” said  Jenny Cassel, a senior attorney with Earthjustice. “They should be assessing penalties. To me, this falls far short of what real, meaningful enforcement should look like.”

Carbon dioxide is a highly corrosive material. When mixed with water, it forms carbonic acid, which can eat through many types of metals. The materials used in the injection and monitoring wells at ADM, which are standard in the oil and gas industry, are supposed to be resistant to such corrosion. However, new information indicates that the monitoring well began malfunctioning as early as September 2020, less than four years after the project was permitted. ADM discovered the corrosion last October, five months before the leak. EPA has since notified other companies seeking injection well permits that the type of steel used is “not suitable for construction of these wells in most instances.”

With ADM’s letter to EPA last week confirming a second leak, both monitoring wells have now experienced issues.  

Like any well that may puncture the storage formation – including abandoned oil and gas wells – monitoring wells can become a pathway for CO₂ leakage and therefore must be monitored carefully. But Dominic DiGuilio, who worked at EPA for more than 30 years and helped develop EPA’s rules for carbon injection, said monitoring wells are necessary to be able to detect escaped CO₂. According to DiGuilio, the corrosion at the ADM well reflects a “technology issue” that will need to be resolved. But that takes time, and several injection projects are already awaiting approval from EPA while the problem remains unresolved.  

ADM was the first company to receive a carbon injection well permit from EPA in 2017, after a successful pilot program sequestered roughly a million metric tons of CO₂ over three years. The project was proof of concept for carbon capture and sequestration as a method to reduce CO₂ emissions. The company has received $281 million in federal grant money and is also eligible for tax credits based on the amount of CO₂ they store.

With the 2022 Inflation Reduction Act, the Biden administration expanded tax credits for CO₂ storage up to $180 per metric ton, bringing carbon capture to the forefront of the administration’s strategies to combat climate change. Many companies have announced their own plans to sequester their emissions and are moving quickly to take advantage of the subsidies.  

Since ADM received their permit, EPA has approved three more injection wells and is currently reviewing applications for 50 additional projects with 150 wells. ADM also applied for another permit at the Decatur plant in March 2023, which is still in the technical review phase. The additional well is expected to inject 1.1 million metric tons of CO₂ per year on average, more than double the current rate of injection at the existing well.

But the problems at ADM cast doubt on the safety and effectiveness of these projects.  

“We should first figure out what went wrong before any additional permits are issued,” said Jenny Cassel. “We should make sure there are all the more protections in place if and when something does go wrong.”

EPA, which is expected to issue final permits for seven more wells in the coming months, has not announced any pause in its review of injection well permits. It is unclear how many permit applications currently under review intend to use the same materials as the ADM well, though it is likely that many of them do. The cause of the second leak is also yet to be determined. . Until these questions are resolved, uncertainty around how these projects can be safely implemented and how well they will work will remain.

“There’s so many different places where it could go wrong. It’s so technically complex,” said Cassel. “They’re really only just starting to understand the science.”

Lead photo: The Archer Daniels Midland Company plant in Decatur, Illinois. Photo by the Associated Press.