Impacts Impacts

CHAPTEr 3 — IMPACTS Impacts Power Plants and Air Quality Power plants have long been considered one of the more significant contributors to local, regional, and global air quality. In recognition of the potentially significant impacts of power plants on air quality, the U.S. Congress has established numerous provisions to monitor and control the emissions from power plants under the Clean Air Act (CAA). The CAA has been significantly modified twice, first in 1977 and again in 1990. The State of Maryland, and state and local organizations across the United States, develop air quality regulations to address CAA requirements. Some air regulations target power plants specifically, such as the CAA Acid Rain program and the recently promulgated Clean Air Mercury Rule. Other air regulations address specific pollutants that are emitted by power plants, industrial sources, and mobile sources. The following section on air quality describes both statewide, and regional emissions from power plants, trends in emissions from power plants over time, and environmental impacts of these emissions. A review of existing and developing air pollution control systems to reduce emissions from power plants is found at the end of the section. Power Plant Air Emissions Emissions from power plants are often discussed in terms of three classes of pollutants: criteria pollutants, hazardous (or toxic) pollutants, and greenhouse gases. Background on “Criteria Pollutants” The U.S. Environmental Protection Agency (EPA) has established National Ambi- ent Air Quality Standards (NAAQS) for six pollutants, known as criteria pollutants: • Nitrogen dioxide (NO2) – a product of fossil fuel combustion; the nitrogen-based ex- haust product from power plants and other combustion sources is termed nitrogen ox- ides (NOx) and is composed of several compounds such as NO and NO2. NOx emitted by combustion sources is primarily in the form of NO, which is partially converted to NO2 in the atmosphere. In the presence of sunlight and heat, NOx reacts with volatile organic compounds (VOCs) to form ground-level ozone (smog). • Sulfur dioxide (SO2) – also a product of combustion, released when sulfur-containing fuels such as oil and coal are burned. • Particulate matter (PM) – dust, dirt, and liquid droplets that form during combustion of fossil fuels or in the atmosphere by chemical transformation and condensation of liquid droplets. Particulate matter is defined by the size of its particles. PM10, for 3- MARYLAND CUMULATIVE ENVIRONMENTAL IMPACT REPORt — 3TH EDITION example, contains particles smaller than 10 microns in diameter, and PM2.5 is composed of particles smaller than 2.5 microns in diameter. • Carbon monoxide (CO) – formed by incomplete combustion of carbon-based fuels during the combustion process. • Lead – a metal emitted into ambient air in the form of particulate matter. • Ozone (O3) – forms in lower levels of the atmosphere as “smog” when NOx and VOCs react in the presence of sunlight and elevated temperatures. The U.S. EPA has developed both primary and secondary ambient air quality standards for criteria pollutants, representing the maximum pollutant concentrations that are allowable in ambient air. Primary standards are based on health risk assessments and are designed to protect the health of sensitive populations such as asthmatics, children, and the elderly. Secondary standards are set at lower levels designed to protect the public welfare by increasing visibility and preventing damage to crops, animals, and vegetation. Table 3-1 lists the current NAAQS. The U.S. EPA and state and local air regulatory agencies, such as the Maryland Department of the Environment (MDE), monitor concentrations of the criteria pollutants near ground level at various locations across the country. The monitoring locations in Maryland are shown in Figure 3-1. If monitoring indicates that the concentration of a pollutant exceeds the NAAQS in any area of the country, that area is labeled a “nonattainment area” for that pollutant, meaning that Table 3-1 National Ambient Air Quality Standards (NAAQS) Primary Secondary NAAQS* NAAQS* Averaging µg/m3 µg/m3 Criteria Pollutant Period (ppm) (ppm) PM10 (particulate matter Annual 50 50 <10 microns) 24-hour 150 150 PM2.5 (particulate matter Annual 15 15 <2.5 microns) 24-hour 65 65 SO2 (sulfur dioxide) Annual 80 -- (0.03) -- 24-hour 365 (0.14) 1,300 3-hour -- (0.50) NO2 (nitrogen dioxide) Annual 100 100 (0.053) (0.053) Ozone 1-hour 235 235 (0.12) (0.12) 8-hour 157 157 (0.08) (0.08) CO (carbon monoxide) 8-hour 10,000 10,000 (9) (9) 1-hour 40,000 40,000 (35) (35) Lead Quarterly 1.5 1.5 *The NAAQS are expressed in terms of micrograms per cubic meter (µg/m3) or parts per million (ppm). Source: 40 CFR Part 50 3-2 CHAPTEr 3 — IMPACTS the area is not attaining the ambient standard. Conversely, any area in which the concentration of a criteria pollutant is below the NAAQS is labeled an “attainment area” indicating that the NAAQS is being met. The attainment/nonattainment designation is made by states and EPA on a pollutant-by-pollutant basis. The air quality in an area, therefore, may be designated attainment for some pollutants and nonattainment for other pollutants simulta- neously. Currently, all of Maryland is in attainment with the NAAQS for most of the criteria pollutants (SO2, NO2, PM10, CO, and lead). However, central Maryland counties are not attaining the new PM2.5 standard (see discussion below). In addition, much of the urbanized portion of Maryland is not meeting the NAAQS for ozone. Because ozone is recognized as a regional, rather than local issue, the entire state is treated as an ozone nonattainment area, even though ozone monitoring indicates that many counties are in attainment with the ozone standard. EPA reviews each of the NAAQS routinely and modifies the standards if new data suggest a change is warranted. For example, in 1997, EPA revised the NAAQS for PM10 and added a standard for a new class of particulate matter known as PM2.5, particulate matter less than 2.5 microns in diameter. PM2.5, or “fine particulates,” are of concern because their small size allows them to be inhaled into the lungs. Litigation over the PM2.5 NAAQS delayed the official identification and designation of PM2.5 nonattainment areas until 2004. EPA published its final PM2.5 nonattainment area designations in January 2005. Power Plant Criteria Pollutant Emissions Power plants are significant sources of many of the criteria pollutants. For example, power plants contribute nearly 80 percent of the total SO2 emissions and 30 percent of the total NOx emissions in Maryland annually. The other significant source of NOx emissions in Maryland are mobile sources, primarily automobiles. Figure 3-1 Criteria Pollutant Monitoring Locations in Maryland 3-3 MARYLAND CUMULATIVE ENVIRONMENTAL IMPACT REPORt — 3TH EDITION Figure 3-2 presents NOx emissions from power PM2.5 Nonattainment Areas plants in Maryland during the years 1995 to EPA finalized the designation of nonattainment areas for PM2.5 in January 2004; Figure 3-3 presents SO2 emissions over the 2005. The shaded portions in the figure below represent the nonattain- same time period. NOx emissions from power ment areas in Maryland for PM2.5. plants in Maryland have decreased over time as a result of the increasingly stringent NOx emission limits to which power plants are subject. SO2 emissions, on the other hand, remained fairly constant over the years from 1995 to 2004. The CAA Acid Rain Program capped SO2 emissions from larger power plants in Maryland (and across the country) in two phases that began in 1995 and in 2000. The year-to-year fluctuations since 2000 seen in Figure 3-3 reflect changes in power demand and fuel consumption. Source: EPA Hazardous Air Pollutant Emissions In 1990, Congress amended the CAA to regulate a class of pollutants that cause or might cause an adverse impact to the environment. These pollutants are referred to as hazardous air pollutants (HAPs). There are currently 188 pollutants on the HAP list. HAPs occur naturally, but they may be hazardous to humans and the environ- Emissions Inventories and Databases ment when emitted by man-made sources such as mobile or industrial sources (factories, refiner- There are a wide range of inventories and databases available that contain ies, power plants, etc.). air emissions information on power plants in the United States: • eGRID – EPA Office of Atmospheric Programs' Emissions & Generation Although fossil fuel-fired power plants emit Resource Integrated Database combines emissions, source, and genera- HAPs, power plants have not historically been tion information from several federal agencies into one nationwide considered among the more significant sources power plant database. of air toxics nationally. Chemical plants and • EIA databases – The Department of Energy (DOE) Energy Information petroleum refineries use and emit highly toxic Administration (EIA) collects data on a variety of operational and gener- compounds and are considered a more signifi- ating factors, including EIA-767 (Annual Steam-Electric Plant Operation cant source than power plants. Prior to the CAA and Design Data), EIA-906 (Monthly and Annual Data on Generation and Fuel Consumption at Power Plants), and EIA-860 (Annual Electric Amendments of 1990, EPA regulations did not Generation Report). apply to HAP emissions from power plants. • ETS/CEM – EPA’s Clean Air Act Acid Rain database, referred to as the Many states, including Maryland, have devel- Emission Tracking System/Continuous Emissions Monitoring (ETS/CEM) oped toxic air pollutant regulations; however, in database, includes limited criteria pollutant and carbon dioxide emis- Maryland, fuel burning sources are exempt from sions information on power plants nationwide. these regulations. • NEI – The EPA Emission Factor and Inventory Group’s National Emissions Inventory (NEI) database is the latest version of nationwide emissions Under the CAA Amendments of 1990, Congress information on point, area, and mobile sources.

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