Future coal use in the United States will be strongly influenced by environmental concerns. In this appendix, recent trends in U.S. regulatory policy and technology development to address environmental issues are reviewed.
National ambient air quality standards for particulate matter, sulfur dioxide (SO2), nitrogen dioxide (NO2), and photochemical ozone were promulgated under the 1970 Clean Air Act to protect human health and welfare throughout the country. In some regions of the country, additional air quality standards for the ''prevention of significant deterioration" of superior air quality also apply. To achieve air quality standards and to speed the deployment of lower-emission technologies, emission standards for new and existing air pollution sources have been promulgated by federal and state governments over the past two decades. These pollutant-specific emission standards, together with environmental quality standards, have been the primary forces of technology innovation for environmental control. Recent developments in air quality and emission standards for coal-based systems are discussed below.
Ambient air quality standards for SO2, together with federal New Source Performance Standards (NSPS) promulgated in 1971 and 1979, have brought about a profound change in the design of modern coal-fired power plants. Today, SO2 control systems are a necessary component of new coal-based power generation. While air quality standards for SO2 now have been achieved in most regions