Coal and oil-fired power plants are the largest source of mercury emissions in the United States, currently accounting for approximately 50% of the country's mercury emissions. With this statistic in mind, U.S. EPA issued a proposed rule on March 16, 2011, which would create emissions standards for all Hazardous Air Pollutants ("HAPs") emitted from coal and oil-fired power plants, including mercury, arsenic, dioxin and hydrochloric acid.
U.S. EPA has been grappling with how to best regulate HAP emissions from power plants for over a decade. In 2000, U.S. EPA determined that it was appropriate and necessary to regulate power plant HAP emissions, particularly mercury emissions, under Section 112 of the Clean Air Act ("CAA"). U.S. EPA changed course in 2005, finding that is was neither appropriate nor necessary to regulate power plant HAP emissions under Section 112, instead establishing a mercury emission cap and trade program under Section 111 of the CAA. This change of course was challenged in court, resulting in a consent decree that required U.S. EPA to promulgate air toxics standards for power plants under Section 112 of the CAA. Under the consent decree, U.S. EPA was required to issue a proposed rule by March 16, 2011, and issue final standards by November 16, 2011.
The proposed rule would establish numeric emission limits for mercury and other metal air toxics for coal and oil-fired power plants. The rule would also establish numeric emission limits for hydrogen chloride, as a surrogate for acid gases, and require work practice standards to reduce organic air toxics emissions such as dioxin. According to U.S. EPA, these new standards will affect 1,350 coal and oil-fired units at 525 power plants across the country, and will prevent 91% of mercury in coal from being released into the air.
More information about the proposed rule can be found at U.S. EPA's website: http://www.epa.gov/airquality/powerplanttoxics/actions.html.