Progress Report - Program Basics
Program Basics
Program History
EPA's Power Plant Programs
The 1990 Clean Air Act Amendments launched a new era in environmental protection. New provisions created the innovative Acid Rain Program (ARP) to curtail acid-rain-causing emissions from the electric power sector through a trading program1. The success of the ARP in achieving significant emission reductions in a cost-effective manner led to use of this market-based approach to reduce power plant air pollution emitted in one state that travels long distances to impact air quality in a downwind state, also known as interstate transport of air pollution.2
The Clean Air Act's "good neighbor" provision requires EPA and states to address interstate transport of air pollution that affects downwind states' ability to attain and maintain air quality standards. The Cross-State Air Pollution Rule Programs (CSAPR, CSAPR Update, and Revised CSAPR Update) are designed to address interstate air pollution transport., Both the ARP and CSAPR programs apply to large electricity generating units – boilers, turbines, and combined cycle units – that burn fossil fuel, serve generators with nameplate capacity greater than 25 megawatts, and produce electricity for sale.
In 2011, EPA issued the Mercury and Air Toxics Standards (MATS), establishing national emission standards for mercury and other hazardous air pollutants (HAPs) for new and existing coal- and oil-fired power plants. The power plants affected by these programs include a range of unit types, including units that operate year-round to provide baseload power to the electric grid, as well as units that provide power only on peak demand days.
The ARP, CSAPR, CSAPR Update, Revised CSAPR Update, and MATS have delivered substantial reductions in power sector emissions of SO2, NOX, and hazardous air pollutants, along with significant improvements in air quality and the environment. In addition to the requirements of the power sector emission control programs described in this report, a variety of power industry trends have contributed to further declines of SO2, NOX, and hazardous air pollutant emissions.
Learn more about EPA's Power Sector Programs.
Acid Rain Program (ARP)
- In 2022, the ARP SO2 requirements applied to 3,246 fossil fuel-fired units at 1,146 power plants across the country; 465 units at 216 power plants were subject to the ARP NOX program.
Cross-State Air Pollution Rule (CSAPR), CSAPR Update, and Revised CSAPR Update
- In 2022, there were 2,083 regulated emissions sources at 657 power plants in the CSAPR SO2 programs. Of those, 1,687 (81 percent) were also covered by the ARP.
- In 2022, there were 2,083 regulated emissions sources at 657 power plants in the CSAPR NOX annual program and 2,482 regulated emissions sources at 797 power plants in the CSAPR NOX ozone season programs. Of those, 1,687 (81 percent) and 2,038 (82 percent), respectively, were also covered by the ARP.
Mercury and Air Toxics (MATS)
- In 2022, 387 units at 177 power plants reported hourly mercury emissions to EPA under MATS.
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1 Such trading programs are also known as “emissions trading programs,” “allowance trading programs” or “cap-and-trade” programs.
2 CSAPR refers to the CSAPR, the CSAPR Update, and the Revised CSAPR Update programs.