Currently Regulated Emissions

The pollutants of primary interest and currently regulated in the power generation industry include sulfur dioxide, nitrogen oxides, and particulate matter. Although pollutants such as carbon monoxide and volatile organic compounds (which lead to the production of ozone when reacted with nitrogen oxides) are important and are tracked nationally, no specific control technologies exist for these pollutants as they are formed from incomplete combustion in the boiler. Power plants are minor contributors to nationwide carbon monoxide emissions. Similarly, power plants are insignificant contributors to nationwide hydrocarbon emissions. Carbon monoxide and hydrocarbon emissions are discussed in Chapter 4 (Coal-Fired Emissions and Legislative Action in the United States).

Emissions of sulfur dioxide, nitrogen oxides, and particulate matter in the United States have been dramatically reduced over the last ~30 years due to legislative mandate and technological advances achieved through federal, state, and industrial efforts. This decline is illustrated in Figures 6-1 and 6-2, which show the decreases in overall as well as individual emissions despite increases in the use of coal for power generation. The steady decrease in emission rates is clearly shown in Figure 6-1, where the emission rates (given on a per billion kWh basis) are reported in 5-year increments [1]. The decrease in the emission rates of these three pollutants is also shown in Figure 6-2, along with projected near-term emission rates [2]. The emission rates in Figure 6-2 are compared with the coal use for power generation for the same time periods and illustrate how pollutant emissions per unit of coal burned have decreased significantly while at the same time coal use has increased. The technologies that are being used to achieve these reductions are discussed in the following sections.

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