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Progress Report

Emission Controls and Monitoring

Emission Controls and Monitoring Figures

Last updated: 05/2016

Related Figures

SO₂ Controls in the ARP and CAIR SO₂ Annual Program in 2013
NOₓ Controls in the CAIR NOₓ Annual Program in 2013
NOₓ Controls in the CAIR NOₓ Ozone Season Program in 2013

Key Points

ARP and CAIR SO₂ Program Controls

  • Of all coal-fired generation (measured in megawatt hours, or MWh) from sources participating in the ARP and CAIR SO₂ program, 73 percent was produced in 2014 by units with pollution controls.
  • FGD-controlled units accounted for 51 percent of coal-fired units and 72 percent of coal-fired generation in 2014.
  • In 2014, 77 percent of units, accounting for 38 percent of energy generation, primarily use natural gas, oil, or other fuel sources, and make up 1 percent of SO₂ emissions.
  • In 2014, CEMS monitored over 99 percent of SO₂ emissions from CAIR sources, including 100 percent from coal-fired units.

CAIR NOₓ Annual Program Controls

  • In 2014, the 371 coal-fired units with add-on controls (either SCRs or SNCRs) generated 70 percent of annual coal-fired generation. At oil- and natural gas-fired units, SCR- and SNCR- controlled units produced 71 percent of generation.
  • Although 52 coal-fired units remain uncontrolled, they represent one percent of coal-fired generation under the CAIR NOₓ annual program in 2014.
  • In 2014, CEMS monitored over 99 percent of SO₂ emissions from CAIR sources, including 100 percent from coal-fired units.

CAIR NOₓ Ozone Season Program Controls

  • In 2014, SCR or SNCR accounted for 72 percent of coal-fired generation. At oil- and natural gas-fired units, SCR- and SNCR- controlled units produced 74 percent of generation.
  • Although 63 coal-fired units remain uncontrolled in 2014, they represent 2 percent of coal-fired generation under the CAIR NOₓ ozone season program.

Analysis and Background Information

Continuous Emission Monitoring Systems (CEMS)

Accurate and consistent emissions monitoring is the foundation of a successful cap and trade program. EPA has developed detailed procedures codified in federal regulations (40 CFR Part 75) to ensure that sources monitor and report emissions with a high degree of precision, accuracy, reliability, and consistency. Sources are required to use CEMS or other approved methods to record and report pollutant emissions data. Sources conduct stringent quality assurance tests of their monitoring systems to ensure the accuracy of emissions data and to provide assurance to market participants that a ton of emissions measured at one facility is equivalent to a ton measured at a different facility. EPA conducts comprehensive electronic and field data audits to validate the reported data.

SO₂ Controls

Sources in the ARP and CAIR SO₂ program have a number of SO₂ control options available. These include switching to low sulfur coal, employing various types of flue gas desulfurization technologies (FGDs), or utilizing fluidized bed limestone units. FGDs on coal-fired generators are the principal means of controlling SO₂ and tend to be present on the highest generating coal-fired units. While some units with low levels of emissions are allowed to use other approved methods, the vast majority of SO₂ emissions—over 99 percent—were measured by CEMS.

NOₓ Controls

Sources in the ARP and CAIR NOₓ annual and ozone season programs have a variety of options by which to reduce NOₓ emissions, including advanced controls such as selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR), combustion controls, and others. While some units with low levels of emissions are allowed to use other approved methods, the vast majority of NOₓ emissions—over 99 percent—were measured by CEMS.

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