A new report prepared by the U.S. Government Accountability Office reveals that older generating units produce a disproportionate amount of emissions. According to the report, which cites data from 2010, older units contributed 75 percent of sulfur dioxide emissions, 64 percent of nitrogen oxides emissions, and 54 percent of carbon dioxide emissions from fossil fuel units. For each unit of electricity generated, older units collectively emitted about 3.6 times as much sulfur dioxide, 2.1 times as much nitrogen oxides, and 1.3 times as much carbon dioxide as newer units.
 
The report finds that the difference in emissions between older and newer units may be attributed to a number of factors. First, 93 percent of the electricity produced by older fossil fuel units in 2010 was generated by coal-fired units.
 
Second, fewer older units have installed emissions controls. Among coal-fired units—which produce nearly all sulfur dioxide emissions from electric power generation—approximately 26 percent of older units used controls for sulfur dioxide, compared with 63 percent of newer units. Controls for nitrogen oxide emissions were more common among all types of fossil fuel units, but these controls vary widely in their effectiveness. Among older units, 14 percent had installed selective catalytic reduction (SCR) equipment, the type of control capable of reducing the greatest amount of nitrogen oxides emissions, compared with 33 percent of newer units. In addition, approximately 38 percent of older units did not have any controls for nitrogen oxides, compared with 6 percent of newer units, the report found.
 
Third, lower emissions among newer units may be attributable in part to improvements in the efficiency with which newer units convert fuel into electricity.
 
The report, which was prepared for Sheldon Whitehouse, Chairman for the Subcommittee on Oversight, is available here.

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