RALEIGH – North Carolina’s coal-fired power plants have cut their toxic mercury emissions by more than 70 percent since the General Assembly enacted the Clean Smokestack Act in 2002, according to a study the N.C. Division of Air Quality presented Thursday to the state Environmental Management Commission.
The mercury emissions reductions resulted as a “co-benefit” from pollution controls that power plants installed to comply with caps that the legislature set on ozone- and particle-forming emissions in the Clean Smokestacks Act. Those caps required the state’s 14 coal-fired power plants to reduce their nitrogen oxide (NOx) and sulfur dioxide (SO2) emissions by about three-fourths over the following decade.
Power companies achieved those cuts by installing $2.9 billion worth of scrubbers and other equipment aimed at reducing NOx and SO2 emissions, which are the primary contributors to ozone, haze, particle pollution, acid precipitation and other air quality problems.
“We knew that scrubbers and other controls would reduce mercury emissions, but the actual reductions were larger than we expected,” DAQ Director Sheila Holman said. “These cuts show that North Carolina is one of the leading states for reducing mercury emissions and have significant health implications for our residents.”
Mercury is a highly toxic metal that can accumulate in the food chain when it reaches streams, lakes and coastal waters. Eventually it can reach levels in some waters that make top-predator fish unhealthy to eat, particularly for children, pregnant women and women of child-bearing age. Such concerns have prompted the State Health Director to issue advisories about eating large-mouth bass and other top predatory fish caught in waters across North Carolina.
The study found that airborne emissions account for nearly all (98 percent) of the mercury reaching North Carolina waters. Of those emissions, 84 percent comes from out-of-state sources and 16 percent from power plants and other industry located in North Carolina.
Coal-fired power plants account for about half (52 percent) of the mercury air emissions in North Carolina. Large industrial plants account for about one-third (33 percent) of the emissions, and those sources reduced their mercury emissions by about 50 percent over the past eight years. The remaining emissions (15 percent) come from about 600 smaller industrial sources.
Further reductions in mercury emissions are expected over the coming decade due to pending federal regulations on power plants, boilers and other industrial facilities. The state’s two major power companies (Duke Energy and Progress Energy) plan to shut down some of their smaller coal plants and/or convert them to natural gas as part of their plans to comply with new federal and existing state regulations.
Other notable findings in the study include:
Power plants with the most advanced levels of controls cut their mercury emissions by more than 90 percent.
Mercury emissions from coal-fired power plants declined from 3,350 pounds in 2002 to 960 pounds in 2010, a reduction of 71.3 percent.
Mercury emissions from the eight largest industrial sources (other than power plants) declined from 1,950 pounds in 2002 to 890 pounds in 2010, a reduction of 54.4 percent.
A copy of the report and other information about air quality issues can be found at the DAQ website, www.ncair.org/.