Geologic Carbon Sequestration: Key Technology for Clean Coal Power

Coal lay in ledges under the ground since the Flood, until a laborer with pick and windlass brings it to the surface. We may well call it black diamonds. Every basket is power and civilization. For coal is a portable climate. It carries the heat of the tropics to Labrador and the polar circle: and it is the means of transporting
itself whithersoever it is wanted.
  ~Ralph Waldo Emerson

	Courtesy of U.S. Environmental Protection Agency

When American essayist and poet Ralph Waldo Emerson christened coal “a portable climate” in his 1860 essay “Wealth,” he was not referring to global climate change. And yet his statement that coal “carries the heat of the tropics to Labrador and the polar circle” may be truer than he knew. For the combustion of coal to produce electricity emits vast volumes of greenhouse gases—especially carbon dioxide (CO₂)—and these gases are believed to be changing the world’s climate.

Consider the evidence: In 1860, when Emerson wrote his essay, the concentration of CO₂ in the atmosphere was about 290 parts per million (ppm); today it is more than 370 ppm, and rising steadily. Over the same period of time, the global temperature has increased about a degree Centigrade, or almost two degrees Fahrenheit.

Are the rising concentration CO₂ and rising global temperatures cause and effect? Many scientists think so—and others, who remain skeptical, recognize that it may be wise to proceed as if it’s true. Because, if climate change is real, and human actions are the cause, the window of time in which we have to act—before land and species and habitat and homes are destroyed—is small. The science that will satisfy all of the skeptics may take more time than we have.

Turning Knowledge Into Action
It is one thing to understand a problem; it is something quite different to solve it. And climate change is a megaproblem that will require many solutions. As individuals, we can reduce the amount of CO₂ emissions that we cause—our “carbon footprint”— by buying a hybrid car, turning back the thermostat, switching to fluorescent light bulbs, or taking public transportation. But individuals are only one part of the solution.

Another part of the solution, one on which that the Department of Energy and its National Energy Technology Laboratory (NETL) are working hard, is finding ways to permanently store or sequester CO₂. Because the reality, at least in the United States, is that we are going to continue to burn large amounts of coal for a very, very long time.

Coal provides more than half of our nation’s electricity—and, according to the Energy Information Administration, this percentage is projected to rise to 60 percent by 2030. That “black diamond” is our country’s most abundant energy resource; it is estimated that there is more energy contained in U.S. coal reserves than in all the oil in the Middle East. Since America cannot, at present, meet its energy demand without coal, innovative technologies are needed that will allow us to burn coal without increasing CO₂ concentrations in the atmosphere.

One way to do this is through terrestrial carbon sequestration—enhancing the storage of carbon in natural surroundings. Every sixth grader learns that plants take up CO₂ and emit oxygen. The simple act of planting trees, or of not cutting them down, reduces CO₂ in the atmosphere. Scientists at NETL are exploring ways to improve carbon uptake in forests and agricultural lands, deserts and wetlands.

Another way to keep from increasing atmospheric CO₂ is through geologic carbon sequestration. This type of carbon storage can be thought of as a twist on the old saying, “What goes up must come down.” In geologic sequestration, what would go up—CO₂ emissions from large point sources such as power plants—does go down, far below the Earth’s surface. This is another realm of active research at NETL.

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Criteria are stringent for choosing sites for CO₂ storage; sequestration is useless if injected CO₂ bubbles to the surface or, worse, if it “burps” in a massive release. To be acceptable, and accepted, CO₂ storage must be effective and cost-competitive, safe and stable, and have no negative environmental impact.

In choosing a site, intensive geologic studies must first be completed to prove the site’s integrity. Then careful monitoring and verification must be undertaken to ensure that the CO₂ stays put. It is thought that, over time, the injected CO₂ will dissolve into the brine and hydrocarbons present underground, and chemical reactions will mineralize some of it. Both the dissolved and the mineralized CO₂ would then be permanently fixed in place. Scientists believe that a well-chosen sequestration site should safely contain the carbon for thousands of years.

To accomplish the many tasks involved in developing carbon capture and storage technologies, NETL takes two tacks: the laboratory conducts sequestration research onsite and it collaborates on research with other organizations. An important effort in this latter category is the NETL-managed Regional Carbon Sequestration Partnerships program. Through the program, seven regional partnerships, spanning most of the United States and part of Canada, conduct laboratory and modeling studies, as well as field tests, to develop sequestration options appropriate for their respective regions. More than 350 organizations have joined the partnerships to date, including governmental agencies, Indian nations, private industry, and colleges and universities.

Among the partnerships’ many accomplishments is the publication earlier this year of the groundbreaking Carbon Sequestration Atlas of the United States and Canada. In the atlas, the partnerships identify stationary sources, including power plants, that emit 3.8 billion tons of CO₂ a year. To put this number in context, consider that, in 2005, the total amount of CO₂ emitted from all U.S. sources was 6.1 billion tons. In other words, the sources described in the atlas, which are all candidates for geologic sequestration, account for more than half of all CO₂ emissions.

Addressing the other half of the sequestration equation, the atlas also identifies potential sites for geologic storage with a combined capacity of more than 4,000 billion tons of CO₂. These sites could, in theory, permanently store all of the CO₂ the United States produces over hundreds of years. It is likely that we would run out of coal before we run out of places to store the CO₂ its combustion creates.

The Power Plant of Tomorrow

Carbon capture and sequestration are important goals for the FutureGen plant, which is intended to be a “living laboratory” for researchers to test and validate new technologies as the plant produces 275 megawatts of power with almost no greenhouse gas emissions. Planned for FutureGen are advanced technologies for coal gasification, electricity production, emissions control, CO₂ capture and geologic storage, and hydrogen production at a commercial scale.

“One of our most exciting projects is FutureGen,” Secretary of Energy Samuel Bodman said last February. “[This is] a project aimed at designing and building the world’s first commercial scale, coal-fired power plant that produces no significant emissions of carbon or pollutants into the atmosphere. This is an international partnership that will allow the rapid deployment of these new emissions-free technologies around the globe so that the entire world can harness the power of clean coal.”

The German playwright and poet Johann Wolfgang von Goethe said, “Knowing is not enough; we must apply. Willing is not enough; we must do.” NETL is taking this to heart. Through onsite research, and work with the regional partnerships and other research partners, the laboratory is developing sequestration options to enable the continued use of coal, that “portable climate,” while combating climate change.