Introduction

Power Generation, Transmission, and Use

Markets, Regulation, and Oversight

Impacts of Power Generation and Transmission

Looking Ahead

Appendices

CEIR Report Map

PPRP Home

Maryland Power Plants and the Environment (CEIR-18)

4.1.2 Emissions from Power Plants

Power plants in the U.S. are a major source of air emissions. According to the report Benchmarking Air Emissions of the 100 Largest Electric Power Producers in the United States, power plants in the U.S. contribute about 13 percent of all NOx, 63 percent of SO2, 38 percent of mercury, and about 61 percent of CO2 emissions emitted by the industrial sector, including transportation (based on 2013, the most recently published emissions data).

Air emissions are often discussed in terms of three classes of pollutants: criteria pollutants, hazardous air pollutants (HAPs), and greenhouse gases (GHGs). This section discusses emissions of these classes of pollutants by Maryland’s power plants and compares Maryland’s power plant emissions to those in other states.

Criteria Pollutants:  SO2, NOx, and PM Emissions

Of the criteria pollutants, SO2 and NOx are among the most stringently regulated by EPA because they are the principal pollutants that react with water vapor and other chemicals in the atmosphere to create ozone smog, cause acid precipitation, and impair visibility. Recently, there has also been an increased focus on particulate matter (PM) emissions, both particulate matter less than 10 microns (PM10) and particulate matter less than 2.5 microns (PM2.5), as EPA has recognized that particulates are associated with adverse health effects, including premature mortality, cardiovascular illness, and respiratory illness. EPA continually attempts to better understand which attributes of particles may cause these health effects, who may be most susceptible to their effects, how people are exposed to PM air pollution, how particles form in the atmosphere, and what sources in different regions of the country contribute to PM. This research has allowed EPA to hone its focus over time from regulating emissions of total suspended particulates to PM10 and PM2.5.

Power plants, specifically coal-fired units, are significant contributors of SO2, NOx, PM10, and PM2.5 emissions nationwide and in Maryland. Figures 4-3 and 4-4 show trends in SO2 and NOx emissions, respectively, from power plants with coal-fired units in Maryland during the years 2009 to 2014. Figures 4-5 and 4-6 show trends in PM10 and PM2.5 during the years 2009 to 2014.

Figure 4-3 Annual SO2 Emissions from Coal-fired Power Plants in Maryland

Figure 4-3

Notes:  Emissions reported in Air Markets Program Data (AMPD) (https://ampd.epa.gov/ampd/)
Fort Smallwood consists of the combined Brandon Shores and Wagner generating stations.

Figure 4-4 Annual NOx Emissions from Coal-fired Power Plants in Maryland

Figure 4-4

Notes:  Emissions reported in AMPD (https://ampd.epa.gov/ampd/)
Fort Smallwood consists of the combined Brandon Shores and Wagner generating stations.

Figure 4-5 Annual PM10 Emissions from Coal-fired Power Plants in Maryland

Figure 4-5

Notes:  Emissions reported in MDE Emission Summary Reports.
Fort Smallwood consists of the combined Brandon Shores and Wagner generating stations.

Figure 4-6 Annual PM2.5 Emissions from Coal-fired Power Plants in Maryland

Figure 4-6

Notes:  Emissions reported in MDE Emission Summary Reports.
Fort Smallwood consists of the combined Brandon Shores and Wagner generating stations.

Click to OpenHAA Benefits Emissions of SO2, PM10, and PM2.5 are dependent on the types and amounts of coal combusted at specific generating units and the type, age, and configuration of any air pollution control equipment. Most coal-fired power plants in Maryland installed state-of-the-art pollution control systems to meet requirements of the Maryland Healthy Air Act (HAA). For example, wet flue gas desulfurization (FGD) scrubbers, sorbent injection systems, and fabric filters were installed at Brandon Shores in late 2009, and Wagner switched to burning lower sulfur coal in 2010. With these changes, these two co-located facilities (known collectively as “Fort Smallwood”) have significantly reduced their SO2 and PM emissions. C.P. Crane also switched to burning low sulfur coal in 2010, which decreased its SO2 emissions. Significant SO2 and PM reductions can also be seen at Morgantown, Dickerson, and Chalk Point due to the installation of FGD scrubbers at those facilities. Use of add-on control technologies, with efficient combustion and limits on sulfur content of fuels, are resulting in a decline in PM emissions since 2009. Note that some of the fluctuations in emissions seen from year to year are attributable in part to changes in fuel consumption rates caused by variations in power demand. For example, emissions from Morgantown and Chalk Point in general were reduced in 2013 likely due to a reduced load at these plants in 2013 (see Figure 4-7). The opposite effect is likely to have occurred in Morgantown in 2014. Most emissions from the facility increased in 2014 corresponding to an increased load at that time.

Figure 4-7 Coal-fired Power Plants in Maryland Gross Load

Figure 4-7 - bar chart of power output in MW-h for coal-fired power plants based on years 2009-2014

Notes:  Gross Load reported in AMPD (https://ampd.epa.gov/ampd/)
Fort Smallwood consists of the combined Brandon Shores and Wagner generating stations.

Annual emissions of NOx also depend on the types and amounts of coal burned and pollution control systems in place. However, unlike SO2 and PM emissions, NOx emissions have been regulated more stringently and for a longer period of time, and so there was a less remarkable decrease with implementation of the HAA. NOx emissions from power plants have been declining in previous years due to installation of control equipment and process changes. Fort Smallwood (Brandon Shores and Wagner) began year-round operation of existing state-of-the-art NOx control systems, known as selective catalytic reduction (SCR), in 2009. Previously, the NOx controls operated only during the summer “ozone season.”  Additionally, a selective non-catalytic reduction (SNCR) system was installed on Wagner Unit 2 in 2009. NOx emissions from C.P. Crane and Morgantown decreased prior to 2009 due to process control/process optimization software installed at Crane and SCR installed on both of the large coal-fired generating units at Morgantown. Additionally, SNCR systems were installed on C.P. Crane Unit 1 and Unit 2 and operations of the systems began in 2009. Like SOx and PM emissions, some fluctuation in emissions is seen throughout the year as a result of changes in fuel consumption. Various other factors affect facility emissions throughput the years, including the control type and usage. For example, NOx emission spikes at Fort Smallwood in 2012 were due in part to variability in operation of emission controls at Wagner. The SNCR on Unit 2 was in operation in 2012 only 28% of its potential operating time and did not operate in the ozone season at all. The spike in 2011 may also be from the limited operation of the control device.

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 health or the environment. These pollutants are referred to as hazardous air pollutants, or HAPs. There are currently 187 pollutants on EPA’s list of CAA HAPs. Although some HAPs can occur naturally (such as asbestos or mercury), most HAPs originate from mobile or stationary industrial sources such as factories, refineries, and power plants.

Although fossil fuel-fired power plants emit HAPs, chemical plants and petroleum refineries that use and emit highly toxic compounds have historically been considered more significant sources of air toxics than power plants. Prior to the CAA Amendments of 1990, EPA regulations did not apply to HAP emissions from power plants and even with passage of the Amendments of 1990, power plant HAP emissions were addressed differently by Congress than those from other industrial sources. While many states, including Maryland, have developed toxic air pollutant (TAP) regulations, fuel burning sources in Maryland are exempt from TAP regulations.

Among the HAPs emitted by power plants, mercury is a pollutant of particular concern because of its significant adverse health effects. Figure 4-8 presents annual emissions of mercury from Maryland’s power plants from 2009 through 2014 as reported in EPA’s Toxic Release Inventory (TRI). As show in Figure 4-8, mercury emissions from Maryland’s power plants dropped significantly beginning in 2010 coinciding with installation of controls in response to Maryland’s HAA. Some of the smaller mercury reductions from 2009 through 2014 may be due to the type of control, the type of coal burned, and the date the controls were installed.

Another HAP of potential concern is hydrochloric acid (HCl), which can be emitted in large quantities from coal-fired plants. In response to the Maryland HAA, many of Maryland’s coal-fired power plants installed FGD scrubber systems, primarily for SO2 control; however, the scrubbers also reduce HCl and other acid gas emissions, and so there have been substantial declines in reported HCl emissions from Maryland's coal-fired power plants since 2009. In 2015, both Wagner and C.P. Crane facilities installed dry sorbent injection (DSI) in response to the Mercury and Air Toxics Standards (MATS) for HCl.

Figure 4-8 Annual Mercury Emissions from Coal-fired Power Plants in Maryland

Figure 4-8 - Bar chart of

Notes:  Emissions reported in EPA’s Toxics Release Inventory. Fort Smallwood consists of the combined Brandon Shores and Wagner generating stations.

Greenhouse Gas Emissions

A greenhouse gas (GHG) is broadly defined as any gas that absorbs infrared radiation in the atmosphere. The pollutant “GHG,” as defined in federal air regulations (40 CFR Part 51.21), is the aggregate of six greenhouse gas compounds:  carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). EPA issued a Greenhouse Gas Reporting Rule and other regulations (see Section 5.2 for details) that address GHGs. The principal GHGs that enter the atmosphere due to human activities are:

Click to OpenGlobal Warming PotentialsEmissions of GHGs are reported on a "carbon dioxide equivalent" (CO2e) basis under EPA’s GHG Reporting Rule. CO2e emissions are determined by multiplying the mass amount of emissions in tons per year (tpy), of each of the six individual greenhouse gases by each gas's “global warming potential” or GWP.

Figure 4-9 presents GHG emissions from coal-fired power plants in Maryland, as reported to MDE, for the years 2009 through 2014. Similar to other regulated pollutants, fluctuations in emissions are seen throughout the years as a result of changes in fuel consumption caused by power demand.

Figure 4-9 Annual GHG Emissions from Coal-fired Power Plants in Maryland

Figure 4-9 Bar Chart

Notes:  Emissions reported in MDE Emission Summary Reports.

Maryland Power Plant Emissions Relative to Other U.S. Power Plant Emissions

To put Maryland’s power plant emissions in perspective, Figures 4-10 through 4-13 present a comparison of SO2 and NOx emissions from coal-fired power plants in Maryland in 2009 and 2014 with emissions from coal-fired power plants in other states before and after various pollution control systems were installed in Maryland facilities as a result of the HAA. These figures represent the emissions (in pounds per megawatt-hour of electricity generated) from the lower 48 states as reported in EPA’s Air Markets Program Data (AMPD) for years 2009 and 2014. As seen in Figure 4-10, Maryland’s power plants in 2009 were collectively among the highest SO2 emitting coal-fired plants. In Figure 4-11, the SO2 emissions in 2014 were in line with average emissions nationwide due to the control systems installed in Maryland’s facilities as a result of the HAA. By the end of 2011, 60% of the nation’s coal-fired power plants had FGD scrubbers installed to reduce SO2.

As seen in Figures 4-12 and 4-13, in both 2009 and 2014, Maryland’s NOx emissions were in line with average emissions nationwide due to the installation of SCR, SNCR, and low NOx burners to limit NOx emissions. By the end of 2011, 67% of the nation’s coal-fired power plants had either a SCR or a SNCR installed to reduce NOx.

Figure 4-10 2009 SO2 Emissions from Maryland Coal-fired Power Plants Compared to SO2 Emissions in Other States

Figure 4-10 Bar Chart

Note:  Emissions reported in AMPD (http://www.epa.gov/airmarkets).

Figure 4-11 2014 SO2 Emissions from Maryland Coal-fired Power Plants Compared to SO2 Emissions from Coal-fired Plants in Other States

Figure 4-11 Bar Chart

Figure 4-12 2009 NOx Emissions from Maryland Coal-fired Power Plants Compared to NOx Emissions from Coal-fired Plants in Other States

Figure 4-12 Bar Chart

Note:  Emissions reported in AMPD (http://www.epa.gov/airmarkets).

Figure 4-13  2014 NOx Emissions from Maryland Coal-fired Power Plants Compared to NOx Emissions from Coal-fired Plants in Other States

Figure 4-12 Bar Chart

Note:  Emissions reported in AMPD (http://www.epa.gov/airmarkets).

“M.J. Bradley & Associates. (2015). Benchmarking Air Emissions of the 100 Largest Electric Power Producers in the United States.

HAA Benefits

The Maryland Healthy Air Act (HAA) adopted in 2006 is the toughest power plant emission law on the East Coast and was implemented with the objective of decreasing emissions from Maryland’s coal-fired power plants, and ultimately reducing ambient air quality concentrations in the State of Maryland. Significant reductions in SO2, NOx, and mercury emissions from coal-fired power plants in Maryland driven by the HAA have helped the State manage three important environmental challenges: maintaining ozone and PM2.5 concentrations at levels below ambient air quality standards, reducing acid rain and mercury deposition, and reducing harmful nutrient loading to the Chesapeake Bay. Based on the EPA’s Air Markets Program Data (AMPD), emissions from the Maryland coal-fired generating facilities in 2014 reflect a reduction in SO2 emissions of approximately 91 percent, and NOx emissions of about 83 percent compared to the 2002 HAA baseline emission levels.

Colored maps of Maryland in the years 1990, 2000, 2010, 2015.

Source: http://www.mde.state.md.us/programs/Air/AirQualityMonitoring/Pages/HistoricalData.aspx “Historical Air Quality Data.” Maryland Department of the Environment Air and Radiation. MDE. Accessed 10 March 2016.

Global Warming Potentials

Global warming potential (GWP) is a measurement of how “effective” individual greenhouse gases are in contributing to warming relative to the most common greenhouse gas, carbon dioxide (CO2). It includes the period of time the gas remains in the atmosphere (lifetime) and its ability to absorb energy (radiative efficiency). CO2, by definition, has a GWP of 1 since it is the gas used as reference. Methane is estimated to have a GWP of 28-36 over 100 years. Even though methane emissions last about a decade in the atmosphere which is less than CO2, it absorbs much more energy than CO2. Both the net effect of the shorter lifetime and higher energy absorption is reflected in the GWP. N2O has a GWP of 265-298 times that of CO2 because it remains in the atmosphere for over 100 years. The GWP for fluorinated gases is in the thousands or tens of thousands because they trap substantially more heat than CO2. The Major Long-Lived Greenhouse Gases and Their Characteristics Table indicates the GHG average lifetime in the atmosphere and the 100-year GWP.

Global Warming Potentials

Greenhouse gas How it’s produced Average lifetime in the atmosphere 100-year global warming potential
Carbon dioxide Emitted primarily through the burning of fossil fuels (oil, natural gas, and coal), solid waste, and trees and wood products. Changes in land use also play a role. Deforestation and soil degradation add carbon dioxide to the atmosphere, while forest regrowth takes it out of the atmosphere. see below* 1
Methane Emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and agricultural practices and from the anaerobic decay of organic waste in municipal solid waste landfills. 12 years 28
Nitrous oxide Emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste. 121 years 265
Fluorinated gases A group of gases that contain fluorine, including hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, among other chemicals. These gases are emitted from a variety of industrial processes and commercial and household uses, and do not occur naturally. Sometimes used as substitutes for ozone-depleting substances such as chlorofluorocarbons (CFCs). A few weeks to thousands of years Varies (the highest is sulfur hexafluoride at 23,500)

This table shows 100-year global warming potentials, which describe the effects that occur over a period of 100 years after a particular mass of a gas is emitted. Global warming potentials and lifetimes come from the Intergovernmental Panel on Climate Change’s Fifth Assessment Report.

* Carbon dioxide’s lifetime is poorly defined because the gas is not destroyed over time, but instead moves among different parts of the ocean–atmosphere–land system. Some of the excess carbon dioxide will be absorbed quickly (for example, by the ocean surface), but some will remain in the atmosphere for thousands of years, due in part to the very slow process by which carbon is transferred to ocean sediments.

Source: https://www3.epa.gov/climatechange/science/indicators/ghg/
“Greenhouse Gases.” Climate Change Indicators in the United States. EPA Climate Change, 24 February 2016. Accessed 16 March 2016.

 

MDE. “A History of Power Plant Controls in Maryland Part 2 – NOx Issues.” PowerPoint file.
“Power plant emissions of sulfur dioxide and nitrogen oxides continue to decline in 2012.” Today in Energy. U.S. Energy Information Administration, 27 February 2013. Web. 17 March 2016.
“Power plant emissions of sulfur dioxide and nitrogen oxides continue to decline in 2012.” Today in Energy. U.S. Energy Information Administration, 27 February 2013. Web. 17 March 2016.