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CHAPTER 15. EMISSIONS ANALYSIS

TABLE OF CONTENTS

15.1 INTRODUCTION ......................................................................................................... 15-1

15.2 APPROACH .................................................................................................................. 15-1
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15.1 INTRODUCTION

The U.S. Department of Energy (DOE) will conduct an emissions analysis as part of the 

notice of proposed rulemaking for electric motors. 

In the emissions analysis, DOE will estimate the reduction in power sector emissions of 

carbon dioxide (CO2), nitrogen oxides (NOX), sulfur dioxide (SO2) and mercury (Hg) from 

potential energy conservation standards for the considered products. In addition, DOE will 

estimate emissions impacts in production activities (extracting, processing, and transporting 

fuels) that provide the energy inputs to power plants. These are referred to as “upstream” 

emissions. Together, these emissions account for the full-fuel-cycle (FFC). In accordance with 

DOE’s FFC Statement of Policy (76 FR 51282 (Aug. 18, 2011)), the FFC analysis includes 

impacts on emissions of methane and nitrous oxide, both of which are recognized as greenhouse 

gases. 

15.2 APPROACH

 DOE may conduct the emissions analysis using emissions factors derived from data in 

EIA’s Annual Energy Outlook 2012, supplemented by data from other sources. EIA prepares the 

Annual Energy Outlook using NEMS. Each annual version of NEMS incorporates the projected 

impacts of existing air quality regulations on emissions.

SO2 emissions from affected electric generating units (EGUs) are subject to nationwide 

and regional emissions cap and trading programs. Title IV of the Clean Air Act sets an annual 

emissions cap on SO2 for affected EGUs in the 48 contiguous states and the District of Columbia 

(D.C.). SO2 emissions from 28 eastern states and D.C. were also limited under the Clean Air 

Interstate Rule (CAIR), which created an allowance-based trading program that operates along 

with the Title IV program in those States and D.C. 70 FR 25162 (May 12, 2005). CAIR was 

remanded to EPA by the U.S. Court of Appeals for the District of Columbia Circuit (D.C. 

Circuit), but it remains in effect. See North Carolina v. EPA, 550 F.3d 1176 (D.C. Cir. 2008); 

North Carolina v. EPA, 531 F.3d 896 (D.C. Cir. 2008). On July 6, 2011 EPA issued a 

replacement for CAIR, the Cross-State Air Pollution Rule (CSAPR; also known as the Transport 

Rule). 76 FR 48208 (August 8, 2011). The AEO 2012 NEMS assumes the implementation of 

the CSAPR.a

 

a

 On December 30, 2011, the D.C. Circuit stayed the new rules while a panel of judges reviews them, and told EPA 

to continue administering CAIR (see EME Homer City Generation v. EPA, No. 11-1302, Slip Op. at *2 (D.C. Cir. 

Dec. 30, 2011)). On August 21, 2012, the D.C. Circuit issued a decision to vacate CSAPR. See EME Homer City 

Generation, LP v. EPA, No. 11-1302, 2012 WL 3570721 at *24 (D.C. Cir. Aug. 21, 2012). The court again ordered 

EPA to continue administering CAIR. AEO 2012 had been finalized prior to this decision, however. DOE 

understands that CAIR and CSAPR are similar with respect to their effect on emissions impacts of energy efficiency 

standards.
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The attainment of emissions caps is typically flexible among EGUs and is enforced 

through the use of emissions allowances and tradable permits. Under existing EPA regulations, 

any excess SO2 emissions allowances resulting from the lower electricity demand caused by the 

adoption of an efficiency standard could be used to permit offsetting increases in SO2 emissions 

by any regulated EGU. In past rulemakings, DOE recognized that there was uncertainty about 

the effects of efficiency standards on SO2 emissions covered by the existing cap-and-trade 

system, but it concluded that no reductions in power sector emissions would occur for SO2 as a 

result of standards. 

 Beginning in 2015, however, SO2 emissions will fall as a result of the Mercury and Air 

Toxics Standards (MATS) for power plants, which were announced by EPA on December 21, 

2011. 77 FR 9304 (Feb. 16, 2012).b In the final MATS rule, EPA established a standard for HCl 

as a surrogate for acid gas hazardous air pollutants (HAP), and also established a standard for 

SO2 (a non-HAP acid gas) as an alternative equivalent surrogate standard for acid gas HAP. The 

same controls are used to reduce HAP and non-HAP acid gas; thus, SO2 emissions will be 

reduced as a result of the control technologies installed on coal-fired power plants to comply 

with the MATS requirements for acid gas. AEO 2012 assumes that, in order to continue 

operating, coal plants must have either flue gas desulfurization or dry sorbent injection systems 

installed by 2015. Both technologies, which are used to reduce acid gas emissions, also reduce 

SO2 emissions. Under the MATS, NEMS shows a reduction in SO2 emissions when electricity 

demand decreases (e.g., as a result of energy efficiency standards). Emissions will be far below 

the cap that would be established by CSAPR, so it is unlikely that excess SO2 emissions 

allowances resulting from the lower electricity demand would be needed or used to permit 

offsetting increases in SO2 emissions by any regulated EGU. Therefore, DOE believes that 

efficiency standards will reduce SO2 emissions in 2015 and beyond. 

CSAPR established a cap on NOX emissions in eastern States and the District of 

Columbia. Energy conservation standards are expected to have little or no physical effect on 

these emissions in those States covered by CSAPR because excess NOx emissions allowances 

resulting from the lower electricity demand could be used to permit offsetting increases in NOx

emissions. However, standards would be expected to reduce NOx emissions in the States not 

affected by CSAPR. Therefore, DOE estimates NOX emissions reductions from potential 

standards in the States where emissions are not capped. 

The MATS limit mercury emissions from power plants, but they do not include emissions caps 

and, as such, DOE’s energy conservation standards would likely reduce Hg emissions. For this 

rulemaking, DOE estimated mercury emissions reductions using emissions factors based on AEO 

2012, which incorporates the MATS. 

Power plants may emit particulates from the smoke stack, which are known as direct 

particulate matter (PM) emissions. NEMS does not account for direct PM emissions from power 

plants. DOE is investigating the possibility of using other methods to estimate reduction in PM 

emissions due to standards. The great majority of ambient PM associated with power plants is in 

 

b On July 20, 2012, EPA announced a partial stay, for a limited duration, of the effectiveness of national new source 

emission standards for hazardous air pollutants from coal- and oil-fired electric utility steam generating units. More 

at: www.epa.gov/airquality/powerplanttoxics/pdfs/20120727staynotice.pdf
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the form of secondary sulfates and nitrates, which are produced at a significant distance from 

power plants by complex atmospheric chemical reactions that often involve the gaseous 

emissions of power plants, mainly SO2 and NOx. The monetary benefits that DOE estimates for 

reductions in SO2 and NOx emissions resulting from standards are in fact primarily related to the 

health benefits of reduced ambient PM.