Is the CO2 really staying underground?

At last public report, monitoring has tracked the injected carbon within the deep sandstone, but EPA records in 2024 noted reported fluid movement at the Decatur site that drew regulator scrutiny. The honest answer is that this is exactly what the monitoring is built to catch, and it is worth watching.

Does this make corn ethanol carbon negative?

It depends on where you draw the line. Capturing the fermentation CO2 removes one large, pure stream, but the full footprint also includes fertilizer, farming, land use, and processing energy. Claims of net removal hinge on those upstream numbers, which disagree.

How deep is a mile, really?

The injection target, the Mount Simon Sandstone, sits roughly 7,000 feet down, more than a mile below Decatur. It lies beneath a thick shale layer meant to act as a seal.

Will a CO2 pipeline run near me?

Maybe, but not soon. Illinois placed a hold on new CO2 pipeline construction in 2024 pending updated federal safety rules, and at least one earlier multistate pipeline was cancelled.

Who regulates all of this?

EPA permits and oversees the injection wells under its Class VI program. The Illinois Commerce Commission reviews pipeline routes, and PHMSA sets the federal pipeline safety rules.

A mile under the cornfields, Decatur buries ethanol's carbon

I.A mile under the cornfields

If you filled a tank anywhere in Illinois this week, roughly a tenth of what you pumped was ethanol, and a good deal of that came from corn grown downstate. The question of what that fuel does to the climate is being tested in a place you can point to on a map: Decatur, about 180 miles southwest of Chicago, where Archer Daniels Midland runs one of the largest corn processing complexes in the country. The carbon from making that ethanol is not going up a stack. It is going down, more than a mile below the prairie.

Here is the plain version of how. When corn sugar ferments into ethanol, it gives off a stream of carbon dioxide that is already almost pure, which makes it cheaper to capture than the diluted exhaust from a power plant. ADM compresses that CO2 and injects it through what the federal government calls Class VI wells (the permit category the Environmental Protection Agency created specifically for storing carbon underground for good) into the Mount Simon Sandstone, a thick, salty rock layer that sits roughly 7,000 feet down. Above it lies a dense shale that is meant to act as a seal, or caprock, holding the gas in place.

II.The honest math

Scale matters here, so start with what has actually gone underground. The first phase, a research project backed by the U.S. Department of Energy, put on the order of 1 million metric tons of CO2 into the Mount Simon over about three years earlier last decade. A second, larger phase was permitted to inject up to roughly 1 million tons a year. Those are meaningful numbers for a demonstration, and still small next to the hundreds of millions of tons the state emits in total.

The harder question is whether capturing fermentation CO2 makes corn ethanol 'carbon negative', a claim you will see in industry materials. It depends on where you draw the boundary. Pulling one pure stream of carbon out of the loop is real, but the full footprint of the fuel also includes fertilizer, tractor diesel, land use, and the energy to run the plant. Whether the arithmetic comes out below zero hinges on those upstream figures, which honest studies disagree about, so treat any single tidy number with caution.

III.Who is watching the wells

Three sets of eyes are supposed to be on this. The EPA issues and enforces the Class VI permits, and its records are public. The Illinois State Geological Survey, part of the University of Illinois, has run much of the underground monitoring, tracking where the carbon plume spreads using sensors in deep observation wells. DOE has funded and reported on the science since the start.

That oversight is not a formality. In 2024, EPA records showed reported movement of fluid at the Decatur site into zones it was not supposed to reach, tied to a problem with a deep monitoring well, and the agency pressed ADM for a response. This desk reads that less as proof the idea failed and more as the monitoring doing its job, which is to catch problems while they are small. Still, it is a live reminder that storage called 'permanent' has to be measured for decades, not declared on day one.

IV.The pipeline fight

Decatur can store its own carbon because the plant sits on top of the right rock. Most other Midwest emitters do not, which is why companies have proposed long CO2 pipelines to gather carbon from ethanol plants across several states and carry it to storage. One large multistate project, Navigator's Heartland Greenway, was cancelled in 2023 after running into landowner opposition and permitting trouble. Another developer, Wolf Carbon Solutions, has floated a line feeding the Decatur area.

In Illinois, the referee for pipeline routes is the Illinois Commerce Commission, the same body that oversees utility rates, and its dockets are open to read. State lawmakers also stepped in: a 2024 Illinois law put a hold on new CO2 pipeline construction until federal safety regulators at the Pipeline and Hazardous Materials Safety Administration finish updated rules, work that has slipped past earlier target dates. For now, the storage is moving ahead faster than the pipes that would feed it.

V.Worth watching this month

1. Watch EPA's Class VI records for the ADM Decatur wells for any new monitoring reports or enforcement updates, which post on no fixed schedule.

2. Check the Illinois Commerce Commission's dockets for any new CO2 pipeline filing near the Decatur area, where routine procedural paperwork is common but a hearing notice would matter more.

3. Follow PHMSA's CO2 pipeline safety rulemaking, since the Illinois construction moratorium is tied to its completion and the federal timeline has slipped before.

4. Look for Illinois State Geological Survey or DOE technical updates on injection volumes and plume tracking at Decatur, usually released as periodic reports rather than news.

5. Track the state's rulemaking under the 2024 carbon sequestration law, which will set much of how storage is permitted and policed in Illinois going forward.