Best Available Control Technology

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Best available control technology

Best available control technology (BACT) is a standard used in air pollution control in the prevention of significant deterioration (PSD) of air quality in the United States. Under the Clean Air Act , a major stationary new source of air pollution , such as an industrial plant, is required to have a permit that sets emission limitations for the facility. As part of the permit, limitations are based on levels achievable by the use of BACT for each pollutant.

To prevent risk to human health and public welfare, each region in the country is placed in one of three PSD areas in compliance with National Ambient Air Quality Standards (NAAQS). Class I areas include national parks and wilderness areas, where very little deterioration of air quality is allowed. Class II areas allow moderate increases in ambient concentrations. Those classified as Class III permit industrial development and larger increments of deterioration. Except for national parks, most of the land in the United States is set at Class II.

Under the Clean Air Act, the BACT standards are applicable to all plants built after the effective date, as well as preexisting ones whose modifications might increase emissions of any pollutant. To establish a major new source in any PSD area, an applicant must demonstrate, through monitoring and diffusion models, that emissions will not violate NAAQS or the Clean Air Act. The applicant must also agree to use BACT for all pollutants, whether or not that is necessary to avoid exceeding the levels allowed and despite its cost. The Environmental Protection Agency (EPA) requires that a source use the BACT standards, unless it can demonstrate that its use is infeasible based on "substantial and unique local factors." Otherwise BACT, which can include design, equipment, and operational standards, is required for each pollutant emitted above minimal defined levels.

In areas that exceed NAAQS for one or more pollutants, permits are issued only if total allowable emissions of each pollutant are reduced even though a new source is added. The new source must comply with the lowest achievable emission rate (LAER), the most stringent limitations possible for a particular plant.

Under the Clean Air Act, if a new stationary source is incapable of BACT standards, it is subject to the New Source Performance Standard (NSPS) for a pollutant, as determined by the EPA. NSPSs take into consideration the cost and energy requirements of emission reduction processes, as well as other health and environmental impacts. This contrasts with BACT standards, which are determined without regard to cost. Strict BACT requirements resulted in a more than 20% reduction in particulates and sulfur dioxide below NSPS levels.

[Judith Sims ]



Findley, R. W., and D. A. Farber. Environmental Law. St. Paul, MN: West Publishing Company, 1992.

Plater, Z. J. B., R. H. Abrams, and W. Goldfarb. Environmental Law and Policy: Nature, Law, and Society. St. Paul, MN: West Publishing Company, 1992.

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Best Available Control Technology

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