Often, trends in this industry seem to move in see-saw fashion: up and down, up and down, with no apparent progress being made. In the 1980s, for example, a large number of power plants switched from burning oil to
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burning coal because the price of oil became too high. Then the plants switched from coal to natural gas because of environmental restrictions.
Over the last 10 years, many coal-fired power stations switched to a low-sulfur coal available from a vast mine and reserve known as the Powder River Basin (PRB) in Wyoming. This is an energy source that is relatively cheap to mine but expensive to transport. In fact, more than two-thirds of the cost of a typical trainload of PRB coal goes to the railroad company, not the coal supplier.
In many ways, this switch has proven to be a Faustian bargain. Plants managed to postpone the cost of expensive pollution controls, but usually this coal has less energy content than the coal it replaced, and more pollutants that were not as tightly regulated at the time. In fact, the reason why the coal has less energy is because it contains more water—roughly 30 percent of the material is water. So, put two and two together. We're paying to transport huge quantities of water that eventually end up as water vapor (also a global warming gas, by the way) discharged through the power plant smokestacks.
The tonnage of the coal—and the water—is impressive. In Coal: America's Energy Future, the National Coal Association reports that in 1990 (the year the Clean Air Act Amendments were enacted) shipments of PRB coal were 200 million tons. By 2004, they had more than doubled, to 420 million tons. In 1970, PRB production was a mere 10 million tons. Have you ever waited at a railroad crossing for a coal unit train to go by? That represents around 10,000 tons of coal. Each year, more than 40,000 unit trains carrying PRB coal move around the country. The diesel fuel to power those trains also represents a significant energy impact. Look at it this way: One third of that diesel fuel is moving water because one third of the load is moisture in the coal!
PRB coal supply has not only greatly extended the supply lines for U.S. power stations, it has reduced the efficiency of the plants that burn it and causes them to run in a derated condition, meaning that the plant cannot achieve the electricity output it was designed for. It is common knowledge in the industry that the freight rail system is strained trying to accommodate the demand for PRB coal, and some coal-fired plants are having difficulty maintaining adequate inventory of coal at the plant site. Coal shipments now account for more than 40 percent of the nation's railroad freight by tonnage; 58 percent of the coal-fired power stations in the United States are fed only by rail lines, 12 percent by rail and another mode of transportation (truck, barge).
The larger point I am making is that the electricity you enjoy at your home or business is dependent on a vast infrastructure: railroads in the case of coal, pipelines in the case of natural gas, and pipelines and ocean tankers in the case of LNG. All in all, it is apparent that there are key energy and environmental impacts avoided—many of them delineated in Chapter 14—when you closely couple a power station to its source of coal. To me, that means whenever possible, locate a power station adjacent to the mine (Figure 10.4) and shipping the coal "by wire."
The other point I want to stress is that the supply lines for coal were greatly extended for one reason: reduction of sulfur. Better decisions could surely have been made if the other impacts described here had more "value" to utility executives, and the electricity consuming public. Short-term economic gain is often long-term pain in other important areas.
Perhaps there may be a silver lining here. Recent changes to the emissions laws for coal-fired power stations mean that many large coal-fired plants could switch back to sources of coal that are located closer to them. Many large coal-fired plants east of the Mississippi are adding highly efficient flue-gas desulfurization units that remove up to 98 percent of the sulfur dioxide. That means they can source coal from eastern mines, once abandoned because the coal's sulfur content was too high.
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