Construction of a new source of air pollution or modification of an existing source that causes a significant net increase in emissions of certain pollutants triggers applicability of the Environmental Protection Agency’s (EPA) new source review (NSR) program.  One critical aspect of the NSR program is the requirement that measures to control the emissions be established by the permitting authority before the beginning of construction and be in place before the source commences operations. 

The requirement for Best Available Control Technology, or BACT, applies both to new major sources and to existing major sources undergoing modification.  These requirements apply to all regulated NSR pollutants for which the increase in emissions is “significant.”  The latter term is defined in the federal regulations in two ways.  For most regulated NSR pollutants, EPA has established (at 40 CFR § 52.21(b)(23)(i)) an annual emission rate threshold, in tons per year.  These thresholds range from 0.6 tons per year for lead to 100 tons per year for carbon monoxide.  To date, the thresholds for all regulated NSR pollutants are less than or equal to the major source thresholds (100 tons per year or 250 tons per year of any regulated NSR pollutant, depending on source type), which are the thresholds that establish initial applicability of the NSR program.  The major source thresholds are specified in the statute and may be changed only by amendment of the Clean Air Act in the event CO₂ is subjected to regulation under the NSR program.  If EPA were to establish a “significance” level for CO₂, there is no express statutory prohibition on establishing that level at an emission rate much higher than the major source thresholds, though any such ruling by EPA would almost certainly bring court challenges. 

The second way in which the “significance” level for a regulated NSR pollutant is defined as follows:

Significant means, in reference to a net emissions increase or the potential of a source to emit a regulated NSR pollutant that paragraph (b)(23)(i) of this section, does not list, any emissions rate.

40 C.F.R. § 52.21(b)(23)(ii).  Thus, if EPA first regulates CO₂ emissions through performance standards for mobile sources (e.g., motor vehicles) without simultaneously establishing a significance level in tons per year, any CO₂ emissions increase resulting from construction or modification at a major source will be subject to the BACT requirement.  The administrative burden of such a requirement on both EPA and industry is incalculable.

If, as outlined in the prior installments of this series, EPA determines that greenhouse gases are subject to regulation under the Clean Air Act and, therefore, may trigger NSR, the critical issues becomes what control technology is BACT for the greenhouse gases.  In the next installment, ClimateIntel offers preliminary thoughts on BACT for greenhouse gases.

For further information about this topic, please contact Akin Gump.