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Energy Research

6 ways to get rid of carbon

In Kentucky coal is king: more than 90 percent of our electricity comes from coal. Nationally 50 percent of power production is coal based. Coal is abundant (the United Sates still has 300 billion tons of coal) and cheap (Kentucky has the fourth lowest energy costs in the nation, thanks to coal). Coal puts Kentuckians to work and attracts industries that require cheap power. But coal’s carbon dioxide (CO2) impact is huge: in 2007 the state’s 20 coal-fired electric power plants emitted 90.3 million tons of CO2.

Curbing these CO2 emissions is at the top of the White House’s energy agenda, but what will happen to Kentucky when the proposed limits become law? In 2009 the National Association of Manufacturers and the American Council for Capital Formation released a study asserting that one of the proposed laws would result in a loss of 25,000 to 35,000 Kentucky jobs and a 64 percent increase in electricity rates by 2030.

Scientists at the University of Kentucky’s Center for Applied Energy Research (CAER) and the Kentucky Geological Survey (KGS) are actively seeking solutions to coal’s carbon dioxide-related environmental impact. They are finding short-term fixes that will allow today’s power plants to concentrate CO2 and then bury it underground or convert it with algae, and studying long-term solutions for more efficient, lower emissions power production.

1) Concentrate it

“Energy companies need to know the roadmap before they actually take the journey,” says CAER’s Jim Neathery as he explains that while companies are concerned about the environmental impact of CO2, they are hesitant to choose a new technology to lower emissions before a law is enacted. “In order to keep our electricity affordable, utilities don’t want to pour a huge investment into a technology that won’t get them to the level of the law.” He explains that when the federal guidelines come out, CAER’s Carbon Management Research Group will have the know-how to recommend the right technology for each power plant and make that technology as affordable as possible. This group is a consortium of university researchers, state agencies and power companies—American Electric Power, Big Rivers Electric Corporation, Duke Energy, East Kentucky Power Cooperative, E.ON U.S., and Electric Power Research Institute.

This CAER group is working on chemical capture of CO2 from the flue gas that billows out of a coal-fired power plant. The focus is to create better solvents and catalysts to speed up the chemical process of separating and concentrating CO2 (in order to pipe it for underground storage or convert it to biomass) and recycling solvents to save money. Established with a $1.5 million E.ON U.S. grant, CAER’s two-anda- half story, 0.1-megawatt pilot plant enables the scientists to test their new chemicals, simulating coal-fired power production on a small scale. The group is also studying a long-term solution, a technology called “chemical looping combustion.” This more efficient option takes nitrogen out of the equation, but will require a total redesign of power plants. “It’s a complex system that we still need to work out. It’s 15 to 20 years away,” says Neathery.

2) Bury it

Deep rock reservoirs thousands of feet below Kentucky are a potential burying ground for coal’s CO2 downside. With data on oil and gas drilling that dates back to 1818, the Kentucky Geological Survey (KGS) is leading UK’s research on geologic sequestration of CO2.

With state funding, KGS and its industrial partners chose a test site to inject CO2 underground. In the summer of 2009, an 8,126-foot well was drilled four miles southeast of the Ohio River in Hancock County, Kentucky. The target was a deep, thick rock formation called the Knox Group, found under much of the U.S. Midwest. The Knox Group is dolomite—a fine-grained rock that underlies approximately two-thirds of Kentucky. More than 18,000 barrels of salt water and 300 tons of CO2 were injected into the well. KGS geologist Rick Bowersox says, “The project showed that an industrial CO2 storage well drilled into those subsurface conditions would require about 120 acres to store 1 million tons of CO2, or about 3,500 acres of reservoir to store 30 million tons. Seven to 10 wells like this one would be required to store 30 million tons of CO2.” Such well capacity would have handled 33 percent of the 90.3 million tons of CO2 emitted by coal-fired plants in 2007.

3) Briquette it

“There’s a growing need for green energy from biomass, but there are a lot of problems getting biomass into the market—transportation, low density, capital investment,” says Darrell Taulbee, who has worked at CAER since 1980. How do you overcome these problems? Briquettes. (Think charcoal, medicinal pills, dog and cat food.)

In the process of mining, 20 to 30 percent of the coal generated is “fine coal”—tiny particles with the consistency of flour. Typically this fine coal material is disposed of in sludge-like ponds called slurry impoundments. These impoundments are often hundreds of feet deep and hold millions of gallons of slurry. Kentucky has 500 million tons of fine coal in slurry impoundments. Taulbee says, “We throw away enough each year to run a small industrial country of 10 to 20 million people.”

Instead of throwing that potential energy away, Taulbee and his team are making fine coal/biomass briquettes. They’ve developed ways to process the wet fine coal and combine it with sawdust, agricultural residues (wheat straw and corn stover), energy crops (switchgrass and fescue), and weeds from fields on reclaimed surface mines to make durable, energy-dense briquettes. In December 2008, more than four tons of this so-called “engineered fuel” was combusted for heat at the East Kentucky Correctional Complex in West Liberty, Kentucky. Taulbee says if Kentucky follows the lead of other states and adopts an RPS (Renewable Portfolio Standard), which requires that a specific portion of the electricity consumed in the state come from renewable sources, briquettes would be the cheapest and fastest way to comply.

4) Liquefy it

Burt Davis, who has spent his 30-year career at UK studying clean-fuel technology says, “Today it’s still easier to pump oil out of the ground than it is to dig coal and convert that coal to liquid. But here’s the thing. We—Kentucky and the United States—have much more energy in the form of coal than the world does in petroleum. And we’re finding ways to increase the efficiency of coal conversion.”

Technology from the 1920s is finding a new—more efficient—life at CAER, thanks to $5.26 million in federal funds secured by Congressmen Hal Rogers and Geoff Davis. The funds will build a Process Development Unit (PDU) critical for ongoing research in Fischer-Tropsch (FT) synthesis, a process that can convert coal to liquid. To produce liquid fuel, coal must be broken down into its most basic ingredients through gasification—applying heat under pressure to convert coal into a gaseous mixture, primarily hydrogen and carbon monoxide, called syngas. Discovered by two German scientists in the 1920s, the FT process uses a catalyst (a reaction accelerator) to convert syngas to hydrocarbons. The hydrocarbons come out of the FT reactor as wax that is “cracked” (long molecules are chemically broken into shorter ones) to yield 20 percent lower-quality gasoline and 80 percent high-quality diesel. FT diesel is cleaner than traditional petroleum diesel because nitrogen and sulfur are removed in the process, resulting in fewer undesirable emissions.

The PDU will allow CAER to test novel technologies to convert coal, gas, biomass, and coal/biomass mixtures to liquid fuels while reducing the overall carbon footprint of the process. The PDU will be capable of producing a barrel a day of finished products, which will be supplied to other universities and the government for testing in a range of diesel and jet engines.

5) Cement it

A favorite of ancient Rome’s architects to today’s skyscraper designers, concrete is a durable but dirty material. CAER’s Jack Groppo explains, “Concrete is made up of basically three ingredients: coarse aggregate (crushed stone), fine aggregate (sand), and Portland cement which acts as the glue that holds it all together.” For every ton of new Portland cement, one ton of CO2 is released from the kilns that bake it. CAER is looking at ways to replace some of that dirty Portland cement with coal combustion byproducts (CCBs) like fly ash. This ash can be used as a raw ingredient in concrete or as a substitute for around 20 percent of the Portland cement. Groppo says, “The concrete will contain coarse aggregate, fine aggregate, Portland, and fly ash. You need 20 percent less Portland. Since you use less Portland, you produce less CO2 to make the same amount of concrete.” And fly ash has other benefits: it makes stronger, longer lasting concrete.

Groppo’s work is part of the Center for Coal-Derived Low Energy Materials for Sustainable Construction, which is supported with funds secured by Senator Mitch McConnell. The center’s goal is to develop low energy consuming, low CO2 emitting construction materials from CCBs. This research, which will be tested inside a new kiln, is housed at CAER in a building constructed with concrete made from 20 percent fly ash from a Kentucky power plant. Groppo adds, “We are in the process of constructing two new buildings that will most assuredly also require fly ash concrete because we believe in the research we conduct—fly ash makes concrete better.”

6) Convert it

“They’re not plants, and they’re not animals,” CAER scientist Mark Crocker says. He’s talking about algae, in particular a species of pond scum he’s studying that might just be a coal-fired power plant’s CO2 solution. “Our concept is biological sequestration: capturing the CO2 at the power plant site and turning it into biomass. And we’re looking at algae for this purpose because they are the fastest photosynthesizing organisms known to man.” Algae take in carbon dioxide (CO2) and water (H2O), convert it to biomass (a mixture of proteins, carbohydrates and lipids), and exhale oxygen (O2). Energy from sunlight drives these chemical reactions.

Inside a greenhouse at CAER, 144 vertical tubes (called photobioreactors), and numerous PVC pipes make up an 8.5-thousand-liter system that exposes the algae to sunlight in a continuous cycle. Coal-fired flue gas is fed in, it mixes with algae in a nutrient-rich liquid, algae consume the CO2 as they grow, algae are harvested,
and nutrients are recycled. Crocker says everything that comes out of this system can be re-used. The resulting lipids can be converted to diesel fuel. The algae can be sent to an anaerobic digester to make methane gas, which can drive a turbine to generate electricity, or can be chemically converted to make bio-oil. “By making valuable products, this system improves the overall economics of CO2 capture. You use the carbon twice.”

smokestacks in the mountains

In 2007Kentucky’s 20 coal-fired electric power plants emitted 90.3 million tons of CO2.

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pilot plant

Established with a $1.5 million E.ON U.S. grant, CAER’s two-and-a-half story, 0.1-megawatt pilot plant enables the scientists to test their new chemicals, simulating coal-fired power production on a small scale.

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drilling rig far viewWith state funding, KGS and its industrial partners chose a test site to inject CO2 underground. In the summer of 2009, an 8,126-foot well was drilled four miles southeast of the Ohio River in Hancock County, Kentucky.

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drilling rig closeupIt took 63 days to drill the 8,126-foot-deep carbon storage well in Hancock County.

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briquettesDarrell Taulbee and his CAER team have developed ways to process wet fine coal and combine it with sawdust, agricultural residues (wheat straw and corn stover), energy crops (switchgrass and fescue), and weeds from fields on reclaimed surface mines to make durable, energy-dense briquettes.

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Burt DavisIn the basement of the Center for Applied Energy Research, Burt Davis shows off his 16 Fischer-Tropsch (FT) reactors. Thanks to $5.26 million in federal funds secured by Congressmen Hal Rogers and Geoff Davis, CAER will build a new Process Development Unit (PDU) critical for ongoing research in FT synthesis. FT can convert coal to liquid fuels.

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pouring cementFly ash, a coal combustion byproduct, can be substituted for Portland cement—a dirty CO2 emitting material that holds concrete together. Fly ash makes stronger, longer lasting concrete.

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Michael WilsonMichael Wilson, a mechanical engineer who has worked at CAER for 14 months, checks the algae flow in a tube that is part of a massive, 8.5-thousand-liter system that includes 144 vertical tubes (called photobioreactors), and numerous PVC pipes. By exposing algae to sunlight in a continous cycle the scientists are fine tuning a method to capture CO2 at the power plant site and turn it into biomass.

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