Indiana University Research & Creative Activity

Sustainability

Volume 31 Number 1
Fall 2008

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John Rupp
John Rupp
Photo by Barbara T. Hill, Photography and Imaging, Indiana Geological Survey

Maria Mastalerz
Maria Mastalerz
Photo courtesy Indiana University

Long before the industrial revolution blackened the skies with the byproducts of iron foundries and cotton mills, Bronze Age tribes in Wales burned coal to cremate their dead, and Roman blacksmiths used it for smelting. Pollution caused by burning coal is nothing new. In 1272, King Edward I  , without much success , banned the burning of sea coal, as it was known, because of the stinking fog of smoke it formed in London. In the centuries that followed, Richard III and Henry V tried to get citizens to cut back on their use of coal, but as the population of Britain grew and forests were depleted because of the use of wood for construction and fuel, the reliance on coal increased — with unpleasant results. Diarist John Evelyn summed up the effects of coal burning on the city of London in this treatise, written in 1661: 'And what is all this, but that Hellish and dismall Cloud of SEACOALE, so universally mixed with the otherwise wholesome and excellent Aer, that her Inhabitants breathe nothing but an impure and thick Mist accompanied with a fuliginous and filthy vapour ... ?'
--from FUMIFUNGIUM: or the Inconvenience of the Aer and Smoake of London Dissipated, 1661

Cleaning Coal

by Anne Kibbler

"People will probably always find some use for coal. Any substance versatile enough to pierce ears in Neolithic China, accessorize togas in ancient Rome, smoke out snakes in Dark Ages Britain, darken paint in prehistoric Pennsylvania, and transform itself chemically into goods ranging from pesticides to perfume, from laughing gas to TNT, probably still has undreamed-of future uses. But will coal still be a significant source of energy in the decades ahead?" -- From Coal: A Human History (2003) by Barbara Freese

Beneath the surface of southwestern Indiana lies an enormous deposit of potential energy in the form of high-quality bituminous coal. Hoosiers have a long history with the black stuff, going back to the first organized excavation of coal in the 1830s, and they rely on coal for more than 90 percent of their electricity needs. They could continue the relationship for another 500 years if they tap into the 17 billion tons of coal that could be recovered using current technology.

But there's a problem. Burning coal to produce electricity breaks the hydrogen-carbon bond that took millions of years to solidify as fossil fuels were formed. More than any other process, that instant liberation of carbon from burning coal has upset the balance of the carbon cycle, releasing an overload of carbon dioxide (CO2) into the atmosphere and contributing to a dramatic increase in Earth's temperature.

So there's the dilemma: On the one hand, a ready supply of domestic coal — an estimated 491 billion tons nationally--at a time when the United States wants desperately to reduce its dependence on foreign energy sources; on the other, stark evidence that the continued burning of coal using current energy production techniques is detrimental to the planet.

Energy conservation and the expansion of alternative energy sources, such as wind and water, are two avenues being pursued to decrease carbon emissions. But what if there was a third option--a way to make use of the coal reserve without releasing large quantities of pollutants?

Researchers at the Indiana Geological Survey (IGS), led by Assistant Director of Research John Rupp, are studying how a technique called carbon capture and sequestration  (CCS)  might achieve that aim. Geological sequestration of carbon dioxide means CO2 is captured from a source such as a coal-fired power plant and injected into a deep subsurface environment for long-term storage. To evaluate this technology, the IGS is examining the deep geology of Indiana and providing information for models that will predict what might happen to the carbon dioxide after thousands of years in storage.

"We can't be around to make observations in 10,000 years," Rupp says, "so we have to make informed predictions through simulations and extrapolate what will happen with time."

It's about the science

Carbon sequestration either captures the carbon released into the atmosphere and fixes it in flora by fostering biological systems such as rain forests, which naturally absorb CO2 (so-called "terrestrial sequestration"). Or, it captures CO2 before it is released into the atmosphere and injects it deep underground into the pore spaces of the rock for secure storage (called "geological sequestration"). As experts on the geology of the state, IGS researchers are working with many others to evaluate the technical feasibility of using Indiana's subsurface geology to store large amounts of CO2.

Indiana and its neighbor states, which are among the nation's leading coal producers and consumers, are ideally suited to test this kind of sequestration, partly because these states have a vested interest in the coal industry, and partly because the geology of the region lends itself to various kinds of underground sequestration.

There is immense public interest in the topic these days, both on the international level — CCS was the subject of talks at the most recent G8 summit — and at the community level. In southern Indiana, for instance, Duke Energy is poised to implement carbon sequestration on a large scale for the first time at a coal gasification plant it is constructing at Edwardsport, about 20 miles northeast of Vincennes. Emotions are running high, with critics claiming the technology is unproven and expensive.

As a member of two regional CCS research groups, the survey is supporting Duke's attempt to deploy the technology at this site by providing technical information about the characteristics of the local geology and its potential ability to serve as an effective storage system. For the IGS, it's all about the science: "observations, measurements, and inferences" says Rupp, and how that scientific information can be used by the policy and economic development communities to make decisions about deploying CCS.

His colleague Maria Mastalerz, a research scientist who specializes in coal geology, says the scientists studying carbon sequestration are the biggest skeptics of all. "We try to be as unbiased and objective as we can," she says. "It's not our role or our desire to support one specific way of thinking. I'm concerned about the environment too, but I look at the data, and I know we can do it cleanly. For some people it's hard to accept that. "

Injection exercise

The United States is a world leader in the development of CCS technology. The U.S. Department of Energy is carrying out an ambitious CCS program that aims to have long-term carbon capture and storage technologies ready by 2012. The DOE has formed the Regional Carbon Sequestration Partnerships program to achieve that goal. Two of the nation's seven partnerships — the Midwest Geological Sequestration Consortium and the Midwest Regional Carbon Sequestration Partnership — involve the Indiana Geological Survey. Together, the two consortia have received more than $130 million in federal funding. Rupp says the research is "in hurry-up mode."

The survey has already evaluated areas where CO2 might be stored in deep saline reservoirs, in depleted oil and gas fields, in unmineable coal seams, and in organic shale beds. Each type of reservoir has its pros and cons. The oil and gas fields, widespread throughout MRCSP's research region, have a particular advantage. CO2 injected into these mature fields could displace some remaining petroleum resources out of these reservoirs. Rupp says that using CO2 for "enhanced oil recovery" will be where the first significant carbon sequestration deployments occur.

Unmineable coal fields, as well as organic shale beds, both offer some potential for carbon sequestration. Analysis already conducted in the Appalachian basin of Kentucky, Ohio, Pennsylvania, and West Virginia indicates the basin may have the capacity to store up to 1 billion metric tons of CO2 in its coal beds, with the potential for extracting coal-based methane at the same time. Shale beds also may provide storage for CO2 while allowing for gas extraction.

It's the deep saline reservoirs that have "orders of magnitude larger storage capacity" than other types of reservoirs, but storing CO2 there would be very expensive. "That, of course, is the quandary," Rupp says.

To evaluate the performance of these various types of reservoirs, the partnerships are injecting small amounts of CO2 into them to observe how they behave. Rupp says about 10,000 metric tons of food-grade CO2, purchased from ethanol plants, is being injected into select reservoirs, including four sites in Illinois, to evaluate the performance of these potential storage systems..

"It's fundamentally a field exercise; the operations are very short, very intense, and very expensive," Rupp says. In contrast to these field experiments, an average coal-burning power plant generates millions of metric tons of CO2 annually, meaning the capacities of geological reservoirs will have to be very large. "The biggest challenge to successful implementation of CCS is the scale that will be necessary to make a difference. We as a nation emit almost seven billion tons of CO2 annually. To reduce atmospheric greenhouse gas concentrations and utilize coal sustainably, we are going to have to sequester a lot of CO2".

Poring over pores

With potential reservoirs mapped out and injection of CO2 underground already in progress, IGS researchers are studying the characteristics of rock samples taken from different sites to see how well they might store and confine CO2. At the micro level, the injected CO2 can displace another material, dissolve in salt water found in the pore spaces of rocks, become entrapped in capillary pores, or form carbonate minerals.

"How and when and where the combinations of these four processes are going to take place in a reservoir is of great debate in the scientific community," Rupp says.

Mastalerz, who carries out much of the IGS's research on CCS, is examining the microscopic characteristics of coal from unmineable fields to understand what's happening on a larger scale underground. Mastalerz and her students collect samples in southwest Indiana and bring them back to the lab, where they crush them and form them into shiny quarter-sized pellets embedded in plastic. A machine measures the size of the coal's pores, as well as their adsorption capacity. (Adsorption means that the CO2 firmly attaches onto the walls of the tiny pores found in coal.) Pores less than 2 nanometers in diameter are an ideal size for CO2 adsorption. A gas chromatograph analyzes the CO2 content of the samples. "It turns out that coal as organic matter has a very nice affinity for CO2," Mastalerz says.

Mastalerz sees the good in coal, although she knows there's plenty of opposition to its continued use as a fuel. The technology to sequester carbon exists, she says, but at the moment people just don't want to pay for clean coal. Mastalerz, on the other hand, says the use of coal as part of a portfolio of energy sources is inevitable.

"That's the future of coal," she says. "There's no doubt there will be clean coal technology. We know how to do it, and over the last several years it's become more reliable." So, in answer to Barbara Freese's question, "Will coal still be a significant source of energy in the decades ahead," Mastalerz says, "Yes."

"Because of the demand for energy we cannot find a better solution," she says. "We have to use all the resources we have to provide for people. I do see a significant role for coal in the next 200 years, definitely the next 100."

Anne Kibbler is editor of the IU School of Journalism magazine Newswire and a freelance writer in Bloomington.

MORE INFORMATION

For more information on Indiana Geological Survey carbon sequestration projects, see http://igs.indiana.edu/survey/projects/searchProjectsDetail.cfm?TheID=122