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NOx Reductions Under the Acid Rain Program

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This page provides an overview of how reductions in NOx emissions are to be achieved under the Acid Rain Program.


The Clean Air Act Amendments of 1990 set a goal of reducing NOx by 2 million tons from 1980 levels. The Acid Rain Program focuses on one set of sources that emit NOx: coal-fired electric utility boilers. As with the SO2 emission reduction requirements, the NOxprogram was implemented in two phases, beginning in 1996 and 2000:

The NOx program embodies many of the same principles of the SO2 trading program, in that it also has a results-oriented approach, flexibility in the method to achieve emission reductions, and program integrity through measurement of the emissions. However, it does not "cap" NOxemissions as the SO2 program does, nor does it utilize an allowance trading system.

U.S. Court of Appeals Upholds Acid Rain Program's Phase II NOx Rule

On February 13, 1998, the DC Circuit Court of Appeals issued its decision to uphold EPA's December 1996 rule setting emission limits on nitrogen oxide (NOx) emissions from coal-fired electric power plants for Phase II (starting January 1, 2000) of the Acid Rain Program. A coalition of electric utilities had sought to overturn the NOx limits, but the court denied the utilities' petition in its entirety.

Beginning January 1, 2000, NOx emissions from utilities will be reduced by an additional 15 percent, or 900,000 tons per year, beyond the 1.2 million per year reduction required by EPA's April 1995 rule which set emission limits for Phase I and Phase II.

For additional details, see: Full text of court ruling to uphold Phase II NOx Rule (PDF) (57 pp, 162 K, About PDF)

NOx Control Technology

NOx Control Technology Cost Tool

This tool calculates costs and cost-effectiveness ratios for combinations of NOx control technologies for utility boilers with specified characteristics. It works by taking input from the user, such as which boiler is to be analyzed, and/or what the boiler's characteristics are. Use of the tool requires Microsoft Excel or a compatible spreadsheet program.

To use the tool, download the following zip file which contains the NOx Control Technology Cost Tool (in Excel) and the instruction guide (in Word Perfect): Cost Tool Zip file (Zip, 368 K).

Performance of Selective Catalytic Reduction on Coal-Fired Steam Generating Units (PDF) (238 pp, 2 MB, About PDF)

This 1997 report provides an comprehensive overview of the application and performance of selective catalytic reduction (SRC) as a control technology for NOx for coal-fired steam generating units. This assessment includes information provided by SCR installations on boilers and SCR systems, coal characteristics, NOx control performance, operational experience, and costs. In all, data have been obtained from SCR installations on coal-fired boilers in the U.S., Germany, Sweden, Austria, Denmark, and Finland. The findings indicate that all coal-fired units using SCR have achieved targeted NO emission levels.


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