What Is the Controversy?
There are two widely varying schools of thought regarding “clean coal.” Some think the concept is a hoax. Others think it is a vitally important economic component of the United States’ plan to fight global warming and achieve energy independence.
The United States has huge coal reserves. Some say they could handle a significant portion of our domestic power generation needs for more than 100 years. Coal is also a major source of jobs and an important part of the economy in coal-producing states. In 2007, Wyoming produced almost 40 percent of the nation’s coal, while the Appalachian states produced almost another 35 percent. For these reasons, many politicians and policymakers believe we must find ways to keep coal in our long-term energy plans.
However, coal produces more carbon dioxide (CO2) per BTU than any other fossil fuel, more than petroleum and almost twice as much as natural gas. As many environmental groups point out, coal has historically been considered the most polluting of energy sources. Pollution from coal plants produces dirty air and acid rain, and contaminates land and water.
According to the Natural Resources Defense Council (NRDC), health problems associated with coal pollution include childhood asthma, birth defects and respiratory diseases. These problems are responsible for the loss of nearly 25,000 lives each year.
There is widespread agreement that since the enactment of the Clean Air Act in 1971, coal plants have reduced emissions significantly; by as much as 70 percent according to some estimates.
For these reasons, researchers in the coal industry and in the government are looking for a means to reduce the CO2 pollution caused by burning coal. However, CO2, unlike other forms of air pollution, is not a minor byproduct of combustion that can be scrubbed (removed) from the process. CO2 is the main product of the combustion of the coal.
Researchers have concluded that the only means to prevent its release into the atmosphere is to capture it and inject it back into the earth. This process is called carbon capture and sequestration (storage), also known as CCS.
The U.S. Department of Energy has been working with the coal industry on the development of this technology for more than a decade. Detractors, such as NRDC and other environmental groups, say “clean coal” is a fantasy. They contend politicians have embraced the idea because the coal industry and its allies spent close to $50 million in 2008 on a campaign to sway public support for more coal-fired power plants.
How Does Carbon Capture and Sequestration Work?
According to the U.S. Environmental Protection Administration (EPA), the CO2 capture and storage (CCS) process is a promising technology for stabilizing atmospheric greenhouse gas concentrations. Instead of releasing CO2 into the atmosphere, geologic sequestration involves separating and capturing CO2 from an industrial or energy-related source, transporting it to a storage location and injecting it deep underground for long-term isolation from the atmosphere. The figures below depict the chain of activities involved in geologic sequestration: capture, transport and injection.
As shown in figures 2 and 3, formations well suited for CO2 storage include the following:
Deep saline formations. Rock units containing water with a high concentration of salts are thought to have the greatest storage capacity.
Depleted oil and gas reservoirs. They have a history of retaining fluids and gases underground for geologic timescales (extremely long periods of time).
Unmineable coal seams. Coal beds that can no longer be profitably mined are well-suited for CO2 storage and have the benefit of enhancing the production of methane, a valuable fuel byproduct that can offset the cost of CCS.
[Figure 1 from http://epa.gov/climatechange/emissions/images/geosequest.gif]
[Figure 2 from http://en.wikipedia.org/wiki/Carbon_capture_and_storage]
Click on above image to view full size diagram
[Figure 3 from http://www.fossil.energy.gov/programs/sequestration/overview.html]
What Are the Risks?
There is limited experience with commercial-scale geologic sequestration. However, according to the EPA, closely related and well-established industrial experience and scientific knowledge can serve as the basis for appropriate risk management strategies.
Key components of a risk management strategy include: appropriate site selection based on thorough geologic characterization; a monitoring program to detect problems during or after injection; appropriate remediation methods, if necessary, and a regulatory system to protect human health and the environment.
Potential pathways exist for CO2 to migrate from the target geologic formation to shallower zones or back to the atmosphere. However, the EPA believes that these conduits for CO2 leakage could be largely avoided through proper site characterization and selection.
In addition to careful site selection, the EPA will require a proper monitoring program to help ensure that CO2 does not escape from the storage site. A monitoring system, they believe, would detect movement of CO2 into shallower formations and allow significant time to take corrective action in order to reduce potential impacts to human health and the environment.
Ground water could be affected by CO2 leaking directly into an aquifer and by saline ground water that enters an aquifer as a result of being displaced by injected CO2. The EPA believes that the risk of these impacts can be minimized through appropriate management strategies.
Underground injection of CO2 for the purpose of sequestration is regulated by the Underground Injection Control (UIC) Program under the Safe Drinking Water Act (SDWA). The UIC program believes it can ensure that injection activities will be performed safely and will not endanger current or future sources of drinking water.
YWC!LI does not at this time take a position for or against the concept of clean coal, its possible benefits or its hazards. Nor do we oppose legislation that funds research and development of carbon sequestration technology. Although we are concerned about the potential environmental impact of sequestration, we realize that sustainable energy solutions are still evolving, and solutions that we cannot envision at this time, including carbon sequestration, may be necessary to stop global warming.