Carbon Storage Studies Grapple with Politics, Geology
Follow the Hudson River a few miles north of New York City and look west across the water, and you’ll see a series of cliffs called the Palisades, made of dark gray volcanic rocks called diabase.
Thousands of feet underground below those cliffs may be clues for how carbon dioxide could be stored, or sequestered, near numerous sources of carbon dioxide emissions not far from the largest population center in the country. Carbon capture and storage is one solution the U.S. Department of Energy is researching for reducing the volume of climate change-fueling greenhouse gas emissions that are released into the atmosphere from coal-fired power plants throughout the region.
Columbia University earth and environmental sciences professor Paul Olsen examines the rock core samples drilled from beneath the university's Lamont-Doherty Earth Observatory in New York in August.
Credit: Bobby Magill
It is here atop the Palisades at Columbia University’s Lamont-Doherty Earth Observatory where earth and environmental sciences professor Paul Olsen and several other researchers are part of a national series of DOE-funded studies of subsurface rock formations that will help scientists find the best places to capture and store carbon dioxide.
These studies are just a few currently underway that attempt to help determine the feasibility of large-scale carbon sequestration efforts and are part of a national discussion grappling with the political, economic and technical challenges they pose. The projects are contributing to the emerging debate about the costs of storing carbon, the risks of leakage from carbon dioxide storage sites and whether the gas should be stored on land or offshore where it is more distant from population centers and possibly more secure — all issues that require more study.
The DOE's goal is bigger than just locating the underground rock formations that may have potential for storing carbon dioxide and learning how much carbon dioxide they can hold. The agency wants to prove that 99 percent of carbon dioxide injected underground will stay there permanently because there's wide concern that carbon dioxide stored beneath the ground could eventually leak into the atmosphere through wells or fractures in the subsurface rock, potentially wreaking havoc on air and water quality and negating some of the climate benefits of storing carbon dioxide in the first place.
To gain a better understanding of the geology that might be ideal for carbon sequestration, Olsen and his team are looking deep beneath the Palisades to study the little-understood Stockton formation — sandstone bedrock in the Newark Basin west of the Hudson River. The DOE estimates the Stockton formation can hold up to 1 metric gigatonne of carbon dioxide, possibly an ideal location to store carbon dioxide emitted from the many coal-fired power plants that are scattered throughout the Northeast.
“This is the best hope for a major reservoir onshore and close to sources of carbon dioxide,” Olsen said.
He and his team drilled 2,000 feet below the surface of the Lamont-Doherty campus in late August to retrieve rock core samples from the Stockton formation, suspected to be composed primarily of sandstone, conglomerate and shale. The granules of that sandstone could be spaced just far enough apart — scientists are aiming for about 15 percent porosity — for carbon dioxide to be stored in the rock.
But the geology of the Stockton is tricky because scientists are unsure where exactly the formation exists beneath the surface of the Northeast. Much more study is needed before it can be determined whether a carbon sequestration operation can be viable there, Olsen said.
Chances are one won’t be, said Olsen’s colleague on the project, Lamont-Doherty geophysics and marine geology professor David Goldberg.
The Lamont-Doherty team’s research will tell scientists how rocks similar to those beneath the Palisades are able to hold carbon dioxide all along the East Coast, not just near New York City, Goldberg said.
But, greenhouse gas emissions are an “immense” problem, “and the answer is equally immense, and that is offshore,” said Goldberg, one of only a handful of advocates for sub-oceanic carbon storage.
The subsurface rocks off the coast of the Northeast U.S. are similar to those beneath the Palisades, and the study could give scientists clues about how to store carbon beneath the Atlantic without having to deal with the politics of residents onshore worried about any environmental or security challenges that might arise from storing carbon dioxide thousands of feet beneath their homes and cities, he said.
One of the biggest advantages of storing carbon dioxide beneath the Atlantic is that the ocean water keeps the carbon dioxide under a lot of pressure, keeping the gas dissolved in solution, while also being buried beneath possibly thousands of feet of siltstone or mudstone in addition to being locked into the same rock formations found beneath the Palisades, Goldberg said.
All of those things reduces the opportunities for the carbon dioxide to leak, he said.
“There's basically impermeable mud and water working to your advantage,” Goldberg said.
Plus, in the event of a major leak, storing carbon dioxide beneath the ocean keeps damage to people and property at a minimum because it would be far away from population centers — a major political advantage for sub-oceanic carbon sequestration, he said.
But many scientists involved in related rock characterization studies are looking for carbon dioxide storage reservoirs onshore, and they say it’s critical that they do.
“It’s part of the solution, it’s not the solution,” said Hannes Leetaru of the Illinois Geological Survey, principal investigator of an evaluation of the carbon sequestration potential of rocks in the Illinois and Michigan basins, one of 10 studies, including the Lamont-Doherty study, funded through the DOE with a $50 million American Reinvestment and Recovery Act appropriation.
Large cavities up to 2 feet in diameter — a series of “pipes” ready for carbon dioxide injection — were discovered deep underground in the Illinois Basin near the central part of that state, and scientists are running computer simulations of the formation to learn where the gas would go if it were injected there, Leetaru said.
“Not every state or every area has rocks that you can put carbon dioxide into,” he said, adding that the point of doing these studies is to see if large-scale carbon dioxide storage onshore is feasible in the first place.
Robert Finley, director of the Illinois Geological Survey, is working on a study that might prove how technically feasible carbon sequestration will be in Illinois.
Finley and his team on the study he is directing, the Illinois Basin-Decatur Project, are planning to inject 1 million tons of carbon dioxide 7,000 feet into the ground beneath central Illinois. So far, they’ve injected more than 570,000 metric tons and plan to complete the process in 2014.
If the sandstone layer the team is studying proves to be a viable carbon dioxide reservoir, emissions from coal-fired power plants and ethanol plants in Illinois, Indiana and Kentucky could eventually be stored there, Finley said, adding that the study’s results could show that carbon sequestration is a safe way to isolate carbon dioxide from the atmosphere.
“It’s important to have demonstration projects like we have in Decatur so we can show what does happen . . . to have those results available to people,” he said.
Leetaru said such demonstration projects are a step toward earning the public's support for carbon sequestration onshore.
“What we don't want is people going and saying, 'not in my backyard,' like what's happening with shale gas and fracking,” Leetaru said.
Other rock characterization projects funded alongside the Lamont-Doherty study are being conducted in Colorado, Wyoming, South Carolina, Kansas, Alabama and off the shores of California and Texas. All are expected to be complete by next year.
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