Mercury Emissions Decline in North Carolina

The surprising results of an air quality study in North Carolina confirm that airborne mercury emissions are actually a great deal less than what was recorded in previous years.

Specifically, in the past decade mercury emissions have dropped by about 70 percent according to a North Carolina Division of Air Quality (DAQ) study. The lower emissions have been credited to actions taken by the state’s coal-fired power plants to reduce emissions in order to comply with the N.C. General Assembly’s 2002 Clean Smokestacks Act.

The state’s 14 coal plants invested $2.9 billion in order to comply with the act. The money spent on air scrubbers and additional technologies actually aimed at reducing nitrogen-oxide (NOx) and sulfur-dioxide (SO2) from the exhaust entering the atmosphere and causing acid rain, ozone problems, and other pollution. The lower mercury emissions were actually a peripheral benefit.

“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 in a DAQ press release. “These cuts show that North Carolina is one of the leading states for reducing mercury emissions and have significant health implications for our residents.”

South Carolina’s DAQ predicts additional emission benefits for the next decade as plans move forward to close smaller coal plants. The smaller plants are currently owned and operated by Duke Energy and Progress Energy and may give way to natural gas plants in their stead, according to the DAQ.

As mercury and coal become more and more unpopular with the Environmental Protection Agency (EPA) and with various state agencies like the N.C. DAQ, more coal plants could be replaced with natural gas plants, which burn with much lower emissions: roughly 800 pounds of carbon-dioxide (CO2) per megawatt-hour compared with coal’s nearly 2,000 pounds per megawatt-hour.

The EPA set new standards earlier this year limiting the amount of CO2 new coal plants could produce: less than 1,000 pounds per megawatt-hour. Coal plants have to invest in emission-limiting technologies, and thus, many coal plants in the United States have closed or have converted to natural gas. Since 1990, 77 percent of new power plants in the United States burn natural gas to supply electricity compared to only 6 percent that use coal, according to a Bloomberg Government study published this May.

According to the DAQ study on mercury emissions, airborne mercury accounts for 98 percent of the mercury that ends up in the lakes, rivers, and other waters of North Carolina. The mercury eventually makes its way into the fish population, which can be eaten by people or wildlife and cause various health problems.

Of that 98 percent airborne mercury, only 16 percent comes from power plants located within North Carolina. The other 84 percent comes from outside the state. Further reductions are expected with more federal regulations being placed on industrial and power producers.

Coal-fired power plants contribute 52 percent of mercury air emissions, while 33 percent comes from large industrial complexes. The remaining 15 percent comes from approximately 600 smaller industrial complexes.

According to the DAQ study, North Carolina mercury emissions decreased from 3,350 pounds in 2002 to 960 pounds in 2010, which yields a reduction of 71.3 percent. Additionally, power plants with the most advanced emissions control systems cut their mercury emissions by 90 percent.

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