confusion with legal terminology, in this chapter we use the terms repair and replacement instead of maintenance and modification.

The main focus here in terms of pollutants is on selected criteria pollutants, especially sulfur dioxide (SO2) and oxides of nitrogen (NOx) but also including carbon monoxide (CO), particulate matter (PM) with an aerodynamic diameter smaller than about 10 µm (PM10), and PM with an aerodynamic diameter smaller than about 2.5 µm (PM2.5). Volatile organic compounds (VOCs), which are ozone precursors, are also included.

With respect to identifying technology options, the focus here is on the current status of emission-source technologies and current options for repair and replacement. However, because technology changes, explicit consideration is given to the process of technology change and the implications for technology change in the future. Furthermore, we consider both pollution control and pollution prevention. Typically, pollution control refers to “end-of-pipe” techniques for removing pollutants from an exhaust gas after they have been formed in an upstream process. For example, in a coal-fired power plant, NOx, SO2, and PM are formed during combustion. Postcombustion control technologies—such as selective catalytic reduction, flue-gas desulfurization, and electrostatic precipitation, respectively—can be used to reduce or capture those pollutants. In contrast, pollution prevention is aimed at reducing or eliminating sources of pollution, typically through feedstock substitutions or process alterations. For example, in the case of a coal-fired power plant, methods that control and stage mixing of fuel and air more carefully can prevent the formation of a portion of NOx that otherwise would have been created, and evaporative VOC emissions can be prevented by substituting water-based solvents for VOC-based solvents in a manufacturing facility. In addition, cost is always a consideration in evaluating and choosing options for repair and replacement. Therefore, cost implications of alternatives for repair and replacement are summarized.


The purpose of this section is to identify and evaluate the frequency of NSR permitting activity with respect to industrial categories for the purpose of determining which emission sources represent the highest priority for assessment. However, a substantial challenge is that there is not a readily available database that summarizes NSR permitting activity. For example, an Environmental Protection Agency (EPA) database1 (EPA 2004d) containing case-specific information on best available control technology (BACT) and lowest achievable emission rate (LAER) does not readily distinguish


The database is referred to as the RACT-BACT-LAER clearinghouse. RACT means reasonably available control technology.

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