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Smart Energy Summer Archive |
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Coal Glossary
 The coal industry likes to call America the Saudi Arabia of coal. By some estimates we sit atop a 250-year supply. But, while coal may be abundant, it's also dirty to burn, dangerous to mine, and a major contributor to global warming.
While the Bush administration sees coal as our destiny, many others fear it could be our demise. One thing is certain: If we want to weigh in on the energy debate, we need to know a few things about coal and the terminology attending to it.
Coal: A solid fossil fuel derived from ancient vegetation that has been compacted, hardened, and chemically altered by heat and pressure over geologic time. Coal is mined from the earth and used primarily to create steam in order to generate electricity. Generally thought of as the fuel of the Industrial Revolution, coal is still the largest single source of electricity in the world, as well as the United States, where coal-fired power plants account for half of the total electricity generated. Coal combustion is the largerst single producer of carbon dioxide emissions, which are the leading cause of global warming. Acid rain is another byproduct of burning coal.
Mercury pollution: a potent neurotoxin, mercury is a byproduct of coal combustion. Coal-fired power plants in the U.S. release an estimated 48 tons of mercury into the atmosphere annually. In the environment, methyl mercury accumulates in the tissues of fish and other animals and makes its way into humans via the food chain. Methyl mercury has been linked to birth defects and developmental disorders.
Mountaintop-removal mining: A method of surface mining in which mountain tops are removed by blasting and excavation in order to get at coal seams. This type of mining operation is especially prevalent in Appalachia where the process of decapitating peaks has resulted in the deforestation of hundreds of thousands of acres and the destruction of more than 1,000 miles of streambed.
Clean coal – a promotional slogan in the coal industry, designed to re-cast a nineteenth-century fuel as our "economic destiny" and the answer to our future energy needs. Clean coal is widely considered to be an oxymoron. That said, some coal technologies are cleaner than others.
Coal-fired power plant: A conventional power plant that burns pulverized coal to produce steam which, in turn, powers a turbine to produce electricity. The more efficient a plant is, the less coal it requires to produce energy, and there are considerable differences between plants which are rated as sub-, super-, and ultra-super-critical. "Super-critical" plants are capable of removing up to 96 percent of coal's sulfur dioxide (SO2) content and 80 percent of its nitrogen oxide (NOx) content – both of which are major air pollutants. Super-critical plants also reduce carbon dioxide emissions by 27 percent and can, theoretically, be fitted with technology to capture and sequester the remaining CO2. Ultra-super-critical plants are even cleaner, but while there are currently a few of them operating in Japan and Europe and one under construction in China, there are currently none in the U.S.
Integrated Gasified Combined Cycle (IGCC): A modern power plant technology in which pulverized coal is not burned directly but mixed with oxygen and water in a high-pressure gasifier to make "syngas," a combustible fluid that produces extremely low emissions of sulfur, nitrous oxides, mercury and particulates. IGCC plants can also concentrate carbon-dioxide emissions, making CO2 easier to capture and store. IGCC plants are 10 percent more efficient than conventional coal plants, use 40 percent less water, and burn almost as cleanly as natural gas-fired plants. Only two first-generation IGCC plants are currently operating in the U.S., partly because the cost to produce electricity is 15 to 20 percent higher than for conventional coal-fired plants and partly because the gasifier technology is, according to U.S. utilities, unreliable.
Carbon Tax: A tax levied on energy sources that emit carbon dioxide into the atmosphere. Since fossil-fuel burning imposes severe health and environmental costs that aren't factored into the current market system, a carbon tax would correct this failure by reflecting the real cost of CO2 emissions — and thereby making cleaner energy more financially viable. No such tax currently exists anywhere in the world yet, but the European Union is actively debating one. The head of Duke Energy, one of the U.S.'s largest utilities, announced in April that he will lobby for a carbon tax to help combat climate change.
Carbon-Dioxide Capture and Storage: Scientists are hopeful that CO2 can be stored (or "sequestered") deep in the ocean or in underground coal seams and deep saline reservoirs. According to the National Academy of Sciences, as much as 40 percent of human-made CO2 "could be removed from the atmosphere and tucked safely away." The oil industry has been injecting CO2 into the ground for years in order to increase oil production, so the technology has a track record. But the capture and storage of CO2 from the world's coal-fired plants would be on a much larger scale. Moreover, there are concerns about CO2 escaping to the surface; a sudden large release of CO2 would pose immediate risks to life. Economics are potentially a bigger hurdle, as carbon capture and storage would be costly and add to the price of energy. However, a carbon tax would change the financial picture considerably. Carbon capture and storage technology works best with IGCC plants; retrofitting old plants would be more costly and would lead to significantly reduced efficiency.
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