Researchers say carbon dioxide could be stored underground in Iowa

Ryan Clark of the Iowa Geological Survey made an illustration to show how deep (red dotted line) carbon dioxide would be injected into the ground for sequestration, if this process were to occur in Iowa.

Iowa is at the center of two proposed pipelines that would collect carbon dioxide from ethanol plants and transport it to other states for underground sequestration — a strategy to reduce greenhouse gases that cause climate change.

But Iowa Geological Survey scientists say the state has the underground sequestration infrastructure here, which would allow Iowa companies to keep more of the federal CO2 storage tax credits. and build fewer kilometers of new pipelines.

“It comes down to economics,” said Ryan Clark, a geologist with the Iowa Geological Survey of IIHR – Hydroscience & Engineering at the University of Iowa. “They can get $50 a ton for sequestered carbon, but only if they store it geologically.”

Navigator, a Texas-based company, is proposing a 1,300-mile pipeline that would cross 36 counties in Iowa, including Linn, Benton, Cedar, Delaware and Iowa, capturing carbon dioxide at ethanol and fertilizer plants . The gas would be pressurized, turned into liquid and piped to a site in south-central Illinois.

Summit Carbon Solutions is planning a 2,000 mile C02 pipeline through Iowa to North Dakota. The company announced last week that it had begun drilling test wells at three locations in North Dakota’s Williston Basin.

Why not Iowa?

Elizabeth Burns-Thompson, Navigator vice president of government and public affairs, said in a meeting last week that Iowa is not suited for carbon sequestration.

“We are blessed here in Iowa with many great things,” she said. “This geological profile is not one of them.”

Clark and Keith Schilling, state geologist and director of the Iowa Geological Survey, disagree.

Layers of porous rock topped with non-permeable rock, or capstone, are needed to hold CO2 underground. Iowa has that, Clark said. The Mount Simon aquifer already used to sequester carbon near Decatur, Illinois in a pilot project is also operating under Iowa.

Southwestern Iowa holds particular promise because desirable rock formations are deep enough below the surface — half a mile or more — to provide the pressure needed to keep CO2 from changing from a liquid to a gas, according to Researchers.

The Iowa Geological Survey released a 78-page technical report on the possibility of carbon storage here.

Because Iowa is not an oil-producing state, there hasn’t been a lot of exploratory drilling to collect rock samples from underground. Although geologists know the major underground aquifers, they need to know more about the porosity of sandstone below 2,700 feet – the minimum depth for C02 storage.

“There are more unknowns here in the state,” Schilling said.

Clark and Schilling estimate that it could cost $1 million to drill a 10,000 foot borehole and study the rock samples collected. Seismic surveys and aerial surveys can also provide details of underground rock formations.

That research doesn’t come cheap, but time is probably the biggest concern because companies want to take advantage of federal tax credits, Schilling said. He and Clark approached members of the Iowa Carbon Sequestration Task Force, but didn’t get much traction.

Questions remain

Charles Stanier, professor of chemical and biochemical engineering at User Interface, who is part of the state’s task force, said he did not believe the group had discussed storage in Iowa, but that it should be considered among other options.

“Capture was discussed generally to make Iowa agriculture more competitive, but other than the fact that the CO2 would go into a pipeline to be geologically sequestered (GS) somewhere, the specifics of the location of the GS were not discussed,” Stanier said in an email. . “The absence of a geologist (in a discussion that included sequestration) was an oversight.”

Other questions remain for sequestration — in Iowa or elsewhere, Stanier said.

  • Which agency regulates CO2 injection (short term) and storage (long term)?
  • Who owns the underground porous space where the CO2 is stored?
  • Who does the necessary research before starting such a project, and is this information public?
  • Who monitors leaks and for how long?

“Given that the storage has to hold up for hundreds of years, these fall under a type of regulation and law that has little precedent,” Stanier said in the email.

But Stanier thinks the Iowa-based study is a good example of the type of research needed to see if carbon sequestration is a viable long-term solution.

Seismic movement

Sequestering carbon dioxide in Iowa also means assuming the potential risks of seismic activity — a concern that many Iowans have mentioned in connection with proposed pipeline projects.

Seismic activity has increased at the Decatur CO2 sequestration site – near the end point of Navigator’s proposed pipeline – but not to a level that would cause major earthquakes. The biggest concern is whether movement over existing fault lines could release stored CO2.

Iowa already has at least two sites where companies inject pressurized liquid into underground cavities.

Northern Natural Gas in Redfield, Dallas County stores natural gas in underground sandstone and limestone aquifers. Natural gas is injected under natural domes that have formed on a fault line near Redfield. The company stores the gas during the off-season, then withdraws it during the winter when natural gas is in demand to heat homes and other buildings.

The Mid-America Pipeline Company stores liquid propane underground at a facility off American Legion Road, southeast of Iowa City.

Questions about carbon sequestration

Q: Why are we considering carbon sequestration in the United States?

A: Nations around the world need to reduce atmospheric CO2 dramatically and quickly to keep global warming below 1.5 degrees Celsius, which would prevent some of the worst impacts of climate change, such as the flooding of island nations. Scientists agree that we need a multi-pronged approach, including reducing emissions and storing carbon dioxide. Sequestration can be done by restoring wetlands and forests – which naturally store CO2 – or by capturing carbon dioxide from industrial processes and pumping it into the ground.

Q: How do you transport CO2, a gas, through a pipeline?

A: The gas is captured in ethanol and fertilizer plants and dehydrated. Then the gas is pressurized, so it becomes liquid. The liquid takes up less space than the gas and can be transported by pipeline to a sequestration site.

Q: How does sequestration work?

A: The companies inject the liquid CO2 into rock formations more than half a mile underground. The liquid can be pumped into depleted oil or gas reservoirs or into aquifers containing water too saline to drink. These horizontal pockets are under layers of non-permeable stones, such as shale, which prevent CO2 from returning to the surface. In some cases, the carbon dioxide can turn into minerals and become part of the rock.

Q: Where is CO2 sequestration currently taking place?

A: Pilot projects are underway across the country. ADM and the University of Illinois announced earlier this year that they had successfully captured and stored 1 million metric tons of CO2 over a three-year period at a site near Decatur, Illinois. The CO2, equivalent to the annual emissions of about 1.2 million passenger cars, comes from ADM’s nearby corn processing plant, the partners reported.

Q: Will carbon sequestration cause earthquakes?

A: The United States Geological Survey found low levels of seismic activity at ADM’s Decatur sequestration site, which it began monitoring in 2013. Increased activity along existing fault lines is not considered a significant earthquake hazard, but it is feared that it could create cracks. which would release stored CO2. The U.S. Department of Energy announced nearly $4 million in May for research into predicting and detecting seismic disturbances at carbon storage facilities, as well as groundwater protection.

Q: Why can’t we just plant more trees?

A: While trees absorb carbon dioxide and store it in leaves, bark and roots, we would need to plant more than half a trillion trees worldwide to reduce atmospheric carbon dioxide by 25 %, NASA reported in 2019. Planting that many trees — an area the size of the United States and Canada combined — could take hundreds of years. Reforestation of Cedar Rapids after the 2020 derecho is expected to cost $37 million and take 10 years. Scientists say reforestation should be part of the solution, but it cannot replace emissions reductions or other efforts.

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Bonny J. Streater