Environmental Engineering Reference
In-Depth Information
The advantage of western coal is that it contains less than a quarter of
the amount of pollutant sulfur that eastern coal has. Lower ranks of
coal, in addition to being less effective producers of heat, also leave more
ash residue when they burn.
Coal Use
Ninety percent of coal use is to generate electric power. The United States
uses 3.7 trillion kilowatt-hours of electricity per year, about 23 percent
of total world use.
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A small percentage of coal is used as a basic energy
source in industries such as steel, cement, and paper. Only 7 to 8 percent
of America's coal was exported in 2008, but the percentage is growing
rapidly because world coal consumption is growing by more than 4
percent annually. It grew 30 percent between 2001 and 2007, twice as
fast as any other energy source.
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There were 1,470 coal-fi red power plants operating in the United
States in 2007, and as of January 2009, 28 more were under construction,
7 additional ones had been approved and were about to start construc-
tion, and 13 more had applied for permits to build.
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But power plants
that burn coal are increasingly unpopular because coal is the world's dirti-
est fuel. The 48 percent of power plants that are fueled by coal account
for 93 percent of the emissions from the electric utility industry.
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About 8 percent of electricity generation in the United States comes
from cogeneration, an integrated energy system that produces both elec-
tricity and heat (combined heat and power, CHP). The heat is recycled
to provide another energy service. Most of America's CHP capacity is in
industry rather than in power plants because of the relative constancy
of industrial power needs compared to those of power plants. The United
States has the potential to produce between 110,000 and 150,000 mega-
watts of electricity with CHP systems. Thermal heat is lost rapidly when
transported, so CHP plants must be located near the point of use to be
most effective.
Coal emits twice as much carbon dioxide as natural gas for the same
amount of energy produced, ninety times the sulfur dioxide, and nine
times the nitrogen oxides. Because of this, natural gas is currently the
fuel of choice in new construction despite its much higher cost. Electricity
produced using natural gas increased by 9 percent between 1997 and
2007. Two-thirds of the new generating capacity added in 2006 was
fueled by natural gas. Using coal to generate electricity costs about $0.90
per 1 million BTUs, petroleum $7.00, and natural gas about a dime more
than oil.
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Economics rules.
