In 2006, global production of coal rose 4.5%, while oil consumption rose a mere 0.7%, according to BP plc. While coal is an abundant resource in many parts of the world, it is generally burned in a manner that creates significant amounts of air pollution. The consumption of coal produces 37% of the world’s fossil fuel-related emissions of carbon dioxide, one of the chief culprits in greenhouse gas. In the U.S., coal produces over 50% of the electricity used but 81% of the carbon dioxide related to power generation. On a global scale, coal provides 24% of the energy used and 40% of all electricity, but produces more carbon dioxide than any other fossil source. “Clean coal” technologies are in the works, but such technologies are difficult for small projects or Third World nations to afford.
Coal in the U.S. comes from several different regions. The Northern Appalachian area of the Eastern U.S. and the Illinois basin in the Midwest produce coal that is high in sulfur, which produces more pollutants, especially carbon dioxide. In contrast are the enormous stores of coal in Wyoming and Montana, which burn at lower temperatures and produce less energy than high-sulfur coal, but create fewer pollutants. In existing mines, the U.S. has an about 250 billion tons of recoverable coal, which would fulfill the country’s electricity needs for two centuries. Combined with coal seams outside of mines, the U.S. has 500 billion tons of recoverable coal.
The market for higher-sulfur coal is on the rise, since filtering units called scrubbers are in use by a growing number of utility companies. Scrubbers are multistory facilities that are built adjacent to smokestacks. They capture sulfur as the coal exhaust billows through the smokestack and sequesters it for storage before it can be cleaned.
In a similar vein, scientists at the University of Texas are developing a new technology that blasts sound waves into the flue ducts of coal-fired power plants. The noise, which registers at more than 150 decibels (about as loud as a jet engine at takeoff) causes tiny ash particles in the emission stream to vibrate and stick to larger ones, thereby making larger particles that are easier to capture by pollution control equipment like scrubbers.
Yet another technology to reduce emissions is the use of photosynthesis to capture exhaust gases, such as CO
2, from power plants. A company called GS CleanTech (
www.gs-cleantech.com) has developed a CO
2 Bioreactor that converts a concentrated supply of carbon dioxide into oxygen and biomass in the form of algae, which can then be converted into fuel. Competitor GreenFuel Technologies (
www.greenfuelonline.com) uses a different method of recycling carbon dioxide from flue gases but with the same end result: algae. An early test of GreenFuel’s reactor at the Massachusetts Institute of Technology promised the removal of 75% of the carbon dioxide in the exhaust sampled. Further tests are being conducted by Arizona Public Service, a state power utility.
Coal is the largest source of power in the U.S. It provides more than half of the country’s electricity needs, which are growing at a steady clip. The Energy Information Administration reports that electric power generation has grown 26% since 1995, and will continue to increase by 1.8% per year through 2020. With today’s skyrocketing oil and gas prices, clean coal technologies and growing demand should encourage increased coal production.
Clean coal or coal-gasification plants will be a major trend for electric generation plant construction over the long term. Such plants use a process that first converts coal into a synthetic gas, later burning that gas to power the electric generators. The steam produced in the process is further used to generate electricity. The process is called Integrated Gasification Combined Cycle (IGCC). While these plants are more expensive to construct than traditional coal-burning plants, they produce much less pollution. Since the coal isn’t actually burnt, these plants can use lower-cost coal that is high in sulfur. In addition, such plants reduce the amount of mercury emitted from the use of coal by as much as 95%. Today, a 1,200-megawatt clean coal plant might cost about $1.2 billion, which is 20% more than the cost to build a traditional coal-burning plant. American Electric Power, a Columbus, Ohio electric utility, reached an agreement in late 2005 with General Electric and Bechtel to design an IGCC plant that could be operating by 2010.
An additional step that can be added to IGCC plants is the capture or “sequestration” of carbon. The technology to do so already exists, as Norway’s Statoil has used it for years at its natural-gas wells in the North Sea. The sequestered carbon can be pumped underground, under the sea or mineralized for burial. It can also be used by oil and gas companies to force oil out of wells. However, the process of sequestration is extremely expensive, adding as much as 50% to the overall cost of a coal plant.
South African fuel company Sasol Ltd. has had great success in making liquid fuel from coal that powers gasoline, diesel and jet engines. The Nazi party first used the technology, which is called Fischer-Tropsch after the German scientists who developed it, during World War II. In the decades since then, the technology has been refined and improved to the point that Sasol provides 28% of South Africa’s fuel needs and is expanding with gas-to-liquids plants in Qatar and Nigeria.
Many U.S. utility companies are waiting for federal regulations that require limited emissions before expending the capital on new plants that are capable of carbon sequestration. For example, Dallas, Texas-based utility company TXU planned to build 11 coal-burning plants in Texas by 2011 hoping to avoid costly restrictions on coal plant emissions and/or enjoy “allowances” due to the fact that the plants are to be built before the restrictions take effect. However, in 2007, eight of the 11 plants were scrapped when private investors acquired TXU for $45 billion. The reason? Traditional plants emit too much carbon dioxide and clean coal technology is too expensive. In a similar vein, more than 20 coal plant projects in several U.S. states have been cancelled since 2006, according to the National Energy Technology Laboratory in Pittsburgh.
An interesting side note to the use of coal is the recent use of jet fuel that is derived from coal. The U.S. Air Force, which spends about $4.5 billion per year in jet fuel, tested a blend of conventional petroleum-based jet fuel and synthetic fuel derived from gasification in a B-52 aircraft in late 2006. The Air Force planned to test the concept on a C-17 cargo plane by late 2007. These tests are a crucial step toward using a coal-to-liquid fuel.
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