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Cars, Trucks, and Climate: EPA Regulation of
Greenhouse Gases from Mobile Sources
James E. McCarthy
Specialist in Environmental Policy
May 4, 2010
Congressional Research Service
7-5700
www.crs.gov
R40506
CRS Report for Congress
P
repared for Members and Committees of Congress
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Cars, Trucks, and Climate: EPA Regulation of Greenhouse Gases from Mobile Sources
Summary
As Congress and the Administration consider new legislation to reduce the greenhouse gas
(GHG) emissions that contribute to climate change, the Environmental Protection Agency has
simultaneously begun to exercise its existing authority under the Clean Air Act to set standards
for GHG emissions. The Administration has made clear that its preference would be for Congress
to address the climate issue through new legislation. Nevertheless, it is moving forward on
several fronts to define how the Clean Air Act will be used and to promulgate regulations.
On April 1, 2010, EPA used existing authority under Section 202 of the act to set the first national
GHG emission standards: the standards will control emissions from new cars and light trucks
beginning in model year 2012. The standards will require cars, SUVs, minivans, and other light
trucks to meet combined emissions levels that the agency estimates will average 250 grams/mile
of carbon dioxide (CO2) in model year 2016, about a 30% reduction in emissions compared to
current levels. The standards will be gradually phased in, with the first reduction targets set for
model year 2012. As part of an agreement brokered by the White House, EPA’s standards were
issued jointly with fuel economy (CAFE) standards developed by the National Highway Traffic
Safety Administration, and the state of California agreed to harmonize state-level GHG emission
standards, so that the auto industry would have a single national set of standards to meet.
The key to using the Clean Air Act’s authority to control greenhouse gases was for the EPA
Administrator to find that GHG emissions are air pollutants that endanger public health or
welfare. Administrator Jackson promulgated such an endangerment finding in December 2009.
With the endangerment finding finalized, the agency can proceed to regulate emissions from
motor vehicles of all kinds. Medium- and heavy-duty trucks are next in line: EPA expects to
propose GHG emission standards for them in the summer of 2010.
EPA has received 10 petitions asking that it make endangerment findings and proceed to regulate
emissions of greenhouse gases. Nine of the 10 petitions address mobile sources: besides motor
vehicles, the petitions cover aircraft, ships, nonroad vehicles and engines, and fuels, all of which
are covered by Title II of the Clean Air Act. In addition to describing the motor vehicle
regulations, this report discusses the range of EPA’s authority under Title II and provides
information regarding other mobile sources that might be regulated under this authority.
Regulation of GHGs from mobile sources will lead the agency to establish controls for stationary
sources, such as electric power plants, as well. Stationary source options, the authority for which
comes from different parts of the Clean Air Act, are addressed in CRS Report R40585, Climate
Change: Potential Regulation of Stationary Greenhouse Gas Sources Under the Clean Air Act
and CRS Report R41212, EPA Regulation of Greenhouse Gases: Congressional Responses and
Options.
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Cars, Trucks, and Climate: EPA Regulation of Greenhouse Gases from Mobile Sources
Contents
Introduction ................................................................................................................................ 1
Massachusetts vs. EPA and Its Effects ......................................................................................... 1
Standards for New Light-Duty Motor Vehicles ............................................................................ 3
Other Mobile Sources ................................................................................................................. 5
Medium and Heavy-Duty Trucks........................................................................................... 6
Ships..................................................................................................................................... 9
Other Nonroad Engines ....................................................................................................... 11
Aircraft ............................................................................................................................... 13
Fuels ................................................................................................................................... 14
Conclusion................................................................................................................................ 15
Figures
Figure 1. Motor Vehicle Greenhouse Gas Emissions.................................................................... 4
Figure 2. Growth of GHG Emissions from Mobile Sources, 1990-2007....................................... 8
Tables
Table 1. Petitions for Regulation of Greenhouse Gas Emissions Under the Clean Air Act............. 6
Table 2. Motor Vehicle GHG Emissions, 2007, by Source Category ............................................ 7
Table 3. Nonroad Sector CO2 Emissions, 2007, by Source Category .......................................... 12
Table 4. Categories of Sources Whose GHG Emissions Could Be Regulated Under Title
II of the Clean Air Act ............................................................................................................ 16
Contacts
Author Contact Information ...................................................................................................... 17
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Cars, Trucks, and Climate: EPA Regulation of Greenhouse Gases from Mobile Sources
Introduction
Although much of the debate on climate legislation has focused on cap-and-trade1 and tax
options,2 establishing greenhouse gas controls is not simply a choice between those two
alternatives. A third set of options, using the more traditional regulatory approaches of the Clean
Air Act (CAA), is available. These regulatory approaches might be modified through new
legislation, but unlike a cap-and-trade system or a carbon tax, regulation does not require new
congressional action: the ability to limit GHG emissions already exists under various Clean Air
Act authorities that Congress has enacted, a point underlined by the Supreme Court in an April
2007 decision, Massachusetts v. EPA.
Thus, while Congress and the Administration are continuing to discuss new legal authority (for
cap-and-trade, carbon tax, and/or targeted emission controls) the Administration, through the
Environmental Protection Agency (EPA), is proceeding to exercise existing authority under the
Clean Air Act to begin regulation of greenhouse gas emissions.
The agency has already taken several steps to regulate GHG emissions. Nevertheless, EPA
Administrator Jackson and others in the Administration have made clear that their preference
would be for Congress to address the climate issue through new legislation. In an April 2009
press release, for example, the agency stated, “notwithstanding this required regulatory process,
both President Obama and Administrator Jackson have repeatedly indicated their preference for
comprehensive legislation to address this issue and create the framework for a clean energy
economy.”3 Similar statements have been made on several occasions since that time; in the
meantime, though, the agency has concluded that current law, including a 2007 Supreme Court
decision discussed below, compels the agency to act.
This report focuses on EPA’s recent and potential actions regarding regulation of GHG emissions
from mobile sources under Title II of the Clean Air Act. We begin with a brief discussion of the
petitions and court action that have led to EPA’s regulatory decisions.
Massachusetts vs. EPA and Its Effects
Whether EPA could regulate GHGs through existing Clean Air Act authority was under
consideration at EPA for more than a decade before the agency took action. In 1998, during the
Clinton Administration, EPA General Counsel Jonathan Cannon concluded in a memorandum to
the agency’s Administrator that greenhouse gases were air pollutants within the Clean Air Act’s
1 For a more detailed discussion of cap-and-trade approaches to GHG emission control, see CRS Report RL33799,
Climate Change: Design Approaches for a Greenhouse Gas Reduction Program. For additional information on
allowance allocation methods, see CRS Report RL34502, Emission Allowance Allocation in a Cap-and-Trade
Program: Options and Considerations.
2 For a more detailed discussion of a carbon tax approach to GHG emission control, see CRS Report R40242, Carbon
Tax and Greenhouse Gas Control: Options and Considerations for Congress.
3 “EPA Finds Greenhouse Gases Pose Threat to Public Health, Welfare / Proposed Finding Comes in Response to 2007
Supreme Court Ruling,” Press Release, April 17, 2009, at http://yosemite.epa.gov/opa/admpress.nsf/
d0cf6618525a9efb85257359003fb69d/0ef7df675805295d8525759b00566924.
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Cars, Trucks, and Climate: EPA Regulation of Greenhouse Gases from Mobile Sources
definition of the term, and therefore could be regulated under the act.4 Relying on the Cannon
memorandum as well as the statute itself, on October 20, 1999, a group of 19 organizations
petitioned EPA to regulate greenhouse gas emissions from new motor vehicles under Section 202
of the act.5 Section 202 gives the EPA Administrator broad authority to set “standards applicable
to the emission of any air pollutant from any class or classes of new motor vehicles” if in her
judgment they cause or contribute to air pollution which “may reasonably be anticipated to
endanger public health or welfare.”
Under the Bush Administration, EPA denied the petition August 28, 2003,6 on the basis of a new
General Counsel memorandum the same day, in which it concluded that the CAA does not grant
EPA authority to regulate carbon dioxide (CO2) and other GHG emissions based on their climate
change impacts.7 The denial was challenged by Massachusetts, 11 other states, and various other
petitioners in a case that ultimately reached the Supreme Court. In an April 2, 2007, decision
(Massachusetts v. EPA), the Court found by 5-4 that EPA does have authority to regulate
greenhouse gas emissions, since the emissions are clearly air pollutants under the Clean Air Act’s
definition of that term.8 The Court’s majority concluded that EPA must, therefore, decide whether
emissions of these pollutants from new motor vehicles contribute to air pollution that may
reasonably be anticipated to endanger public health or welfare. When it makes such a finding of
endangerment, the act requires the agency to establish standards for emissions of the pollutants.9
In nearly two years following the Court’s decision, the Bush Administration’s EPA did not
respond to the original petition or make a finding regarding endangerment. Its only formal action
following the Court decision was to issue a detailed information request, called an Advance
Notice of Proposed Rulemaking (ANPR), on July 30, 2008.10
4 Memorandum from Jonathan Z. Cannon, EPA General Counsel, to Carol M. Browner, EPA Administrator, “EPA’s
Authority to Regulate Pollutants Emitted by Electric Power Generation Sources,” April 10, 1998.
5 The lead petitioner was the International Center for Technology Assessment (ICTA). The petition may be found on
their website at http://www.icta.org/doc/ghgpet2.pdf.
6 The agency argued that it lacked statutory authority to regulate greenhouse gases: Congress “was well aware of the
global climate change issue” when it last comprehensively amended the Clean Air Act in 1990, according to the
agency, but “it declined to adopt a proposed amendment establishing binding emissions limitations.” Massachusetts v.
EPA, 549 U.S. 497 (2007).
7 Memorandum from Robert E. Fabricant, EPA General Counsel, to Marianne L. Horinko, EPA Acting Administrator,
“EPA’s Authority to Impose Mandatory Controls to Address Global Climate Change Under the Clean Air Act,” August
28, 2003.
8 Massachusetts v. EPA, 549 U.S. 497 (2007). The majority held: “The Clean Air Act’s sweeping definition of ‘air
pollutant’ includes ‘any air pollution agent or combination of such agents, including any physical, chemical ...
substance or matter which is emitted into or otherwise enters the ambient air.... ’ ... Carbon dioxide, methane, nitrous
oxide, and hydrofluorocarbons are without a doubt ‘physical [and] chemical ... substances[s] which [are] emitted into ...
the ambient air.’ The statute is unambiguous.”
9 For further discussion of the Court’s decision, see CRS Report RS22665, The Supreme Court’s Climate Change
Decision: Massachusetts v. EPA, by Robert Meltz.
10 U.S. EPA, “Regulating Greenhouse Gas Emissions Under the Clean Air Act,” 73 Federal Register 44354, July 30,
2008. The ANPR occupied 167 pages of the Federal Register. Besides requesting information, it took the unusual
approach of presenting statements from the Office of Management and Budget, four Cabinet Departments (Agriculture,
Commerce, Transportation, and Energy), the Chairman of the Council on Environmental Quality, the Director of the
President’s Office of Science and Technology Policy, the Chairman of the Council of Economic Advisers, and the
Chief Counsel for Advocacy at the Small Business Administration, each of whom expressed their objections to
regulating greenhouse gas emissions under the Clean Air Act. The OMB statement began by noting that, “The issues
raised during interagency review are so significant that we have been unable to reach interagency consensus in a timely
way, and as a result, this staff draft cannot be considered Administration policy or representative of the views of the
(continued...)
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Cars, Trucks, and Climate: EPA Regulation of Greenhouse Gases from Mobile Sources
The Obama Administration’s EPA, however, made review of the endangerment issue a high
priority. On April 17, 2009, it proposed a finding that GHGs do endanger both public health and
welfare and that GHGs from new motor vehicles contribute to that endangerment.11 These
findings were finalized in the December 15, 2009, Federal Register.12
Standards for New Light-Duty Motor Vehicles
The proposed endangerment finding of April 2009 was followed in a matter of weeks by an
announcement that the Administration had reached agreement with nine auto manufacturers and
California (which had developed its own GHG emission standards for motor vehicles), as well as
other interested parties regarding the major outlines of a joint greenhouse gas/fuel economy
rulemaking. As announced by the President, May 19, 2009, EPA and the National Highway
Traffic Safety Administration (which administers fuel economy standards for cars and trucks)
would integrate corporate average fuel economy (CAFE) standards for new cars and light trucks
(collectively known as “light-duty motor vehicles”) with national greenhouse gas emission
standards to be issued by EPA. The objective of the joint standards is to achieve GHG reduction
levels similar to those adopted by California, which harmonized its own standards with EPA’s as
part of the agreement.13
Four greenhouse gases are emitted by motor vehicles (CO2, methane, nitrous oxide, and
hydrofluorocarbons).14 According to EPA, emissions of the four gases from motor vehicles
(including trucks) accounted for 23.6% of the total inventory of U.S. GHG emissions in 2006.
Most of the emissions are in the form of CO2 (see Figure 1), which is the product of combusting
any fuel containing carbon. Hydrofluorocarbons (HFCs), the chemicals used as coolants in
vehicle air conditioning systems, are the second-most important motor vehicle GHG; but, as the
figure shows, they are a distant second.
(...continued)
Administration.” (p. 44356) It went on to state that “... the Clean Air Act is a deeply flawed and unsuitable vehicle for
reducing greenhouse gas emissions.” The other letters concurred. The ANPR, therefore, was of limited use in reaching
a conclusion on the endangerment issue.
11 U.S. EPA, “Proposed Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a)
of the Clean Air Act,” 74 Federal Register 18886, April 24, 2009.
12 74 Federal Register 66496. Although generally referred to as simply “the endangerment finding,” the EPA
Administrator actually finalized two separate findings: a finding that six greenhouse gases endanger public health and
welfare, and a separate “cause or contribute” finding that the combined emissions of greenhouse gases from new motor
vehicles and new motor vehicle engines contribute to the greenhouse gas pollution that endangers public health and
welfare.
13 74 Federal Register 49468, September 28, 2009.
14 Two other commonly mentioned greenhouse gases, sulfur hexafluoride (SF6) and perfluorocarbons, are not emitted
by motor vehicles.
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Cars, Trucks, and Climate: EPA Regulation of Greenhouse Gases from Mobile Sources
Figure 1. Motor Vehicle Greenhouse Gas Emissions
Source: U.S. EPA, March 6, 2009 Draft Deliberative Presentation
Notes: Motor vehicles = passenger cars, light duty trucks, other trucks, buses, and motorcycles, including
releases of HFCs from motor vehicle air conditioning. CH4=methane; N2O=nitrous oxide;
HFCs=hydrofluorocarbons.
The EPA/NHTSA joint regulations for light-duty motor vehicles were finalized April 1, 2010.
They require the vehicles (cars, SUVs, minivans, and other light trucks) to meet combined
emissions levels that EPA estimates will average 250 grams/mile of CO2 in model year 2016,
about a 30% reduction in emissions compared to current levels. NHTSA has set corresponding
fuel economy standards, achieving a combined estimated fuel economy of 34.1 miles per gallon
for cars and light trucks by 2016. In both cases, the standards will be gradually phased in, with
the first reduction targets set for model year 2012.
In setting the GHG standards, EPA used the concept of a vehicle’s “footprint” to set differing
standards for different size vehicles. As explained by EPA
These standards are based on CO2 emissions-footprint curves, where each vehicle has a
different CO2 emissions compliance target depending on its footprint value (related to the
size of the vehicle). Generally, the larger the vehicle footprint, the higher the corresponding
vehicle CO2 emissions target. As a result, the burden of compliance is distributed across all
vehicles and all manufacturers. Manufacturers are not compelled to build light vehicles of
any particular size or type, and each manufacturer will have its own standard which reflects
the vehicles it chooses it [sic] produce.15
In general, manufacturers are expected to reduce CO2 emissions by improving the vehicles’ fuel
economy, but they can also take advantage of an option to generate CO2-equivalent credits by
reducing emissions of hydrofluorocarbons (HFCs) and CO2 through improvements in their air
15 “EPA and NHTSA Finalize Historic National Program to Reduce Greenhouse Gases and Improve Fuel Economy for
Cars and Trucks,” Fact Sheet, April 2010, p. 3, at http://www.epa.gov/otaq/climate/regulations/420f10014.htm.
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conditioner systems. Manufacturers will also be allowed to average, bank, and trade emission
credits.16
The light-duty vehicle rule affects a large group of emission sources that accounts for a
significant percentage of total U.S. GHG emissions, but the effectiveness of the standards in
reducing total GHG emissions is limited in that they will apply only to new motor vehicles. The
auto and light truck fleet turns over slowly: the median survival rate for 1990 cars, for example,
was 16.9 years, and that for light trucks was 15.5 years.17 Given this durability, the impact of
GHG standards on the total emissions of the motor vehicle fleet will take a long time to be felt. If
historic experience is any guide, reductions in GHG emissions per new vehicle, unless they are
very aggressive, may be largely offset by growth in vehicle miles traveled.
Other Mobile Sources
The endangerment finding and emission standards for new light-duty vehicles make it likely that
EPA will proceed to set GHG emission standards for other mobile sources of air pollution,
especially medium- and heavy-duty trucks. Since the Massachusetts v. EPA decision, the agency
has received nine petitions asking it to regulate GHGs from other categories, all but one focused
on mobile sources and their fuels (see Table 1). These petitions cover aircraft, ocean-going ships
and their fuels, motor fuels in general, and nonroad vehicles and engines—a category that
includes construction equipment, farm equipment, logging equipment, outdoor power equipment,
forklifts, marine vessels, recreational vehicles, and lawn and garden equipment.
The specifics of the Clean Air Act sections that give EPA authority to regulate pollution from
these sources vary somewhat, but it is generally believed that the endangerment finding and
decision to regulate GHGs in response to the first of the petitions will make it difficult for the
agency to avoid regulating at least some of the other categories. With that in mind, we look at
other mobile source categories, the authorities provided under Title II for each, and what EPA’s
use of these authorities for conventional pollutants emitted by these sources indicates with regard
to its ability to regulate greenhouse gases. (Separate reports, CRS Report R40585, Climate
Change: Potential Regulation of Stationary Greenhouse Gas Sources Under the Clean Air Act,
and CRS Report R41212, EPA Regulation of Greenhouse Gases: Congressional Responses and
Options, by James E. McCarthy and Larry Parker discuss the potential Clean Air Act regulatory
tools for stationary sources.)
16 For additional detail on the EPA/NHTSA joint standards, see CRS Report R40166, Automobile and Light Truck Fuel
Economy: The CAFE Standards, by Brent D. Yacobucci and Robert Bamberger.
17 Oak Ridge National Laboratory, for the U.S. Department of Energy, Transportation Energy Data Book: Edition 27,
2008, Tables 3.10 and 3.11.
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Table 1. Petitions for Regulation of Greenhouse Gas Emissions Under the Clean Air
Act
Date Subject
CAA
Section
Petitioner
10/20/99 New Motor Vehicles
202(a)(1)
International Center for Technology Assessment
(ICTA) and 19 other organizations
10/3/07
Ocean Going Vessels
213(a)(4)
California Attorney General
10/3/07
Marine Shipping Vessels and their
213(a)(4) and
Oceana, Friends of the Earth, and the Center for
Fuels
211
Biological Diversity
1/10/08
New Marine Engines and Vessels
213(a)(4)
South Coast Air Quality Management District
12/5/07
Aircraft
231
States of California, Connecticut, New Jersey,
New Mexico, Pennsylvania, City of New York,
District of Columbia, South Coast Air Quality
Management District
12/5/07 Aircraft
Engines
231(a)(2)(A) Friends of the Earth, Oceana, the Center for
and 231(a)(3)
Biological Diversity, and the Natural Resources
Defense Council
1/29/08
New Nonroad Vehicles and
202(a)(3)(D)
ICTA, Center for Food Safety, and Friends of the
Engines and Rebuilt Heavy-Duty
and 213(a)(4)
Earth
Engines, excluding Aircraft and
Vessels
1/29/08
New Nonroad Vehicles and
202 and
States of California, Connecticut, Massachusetts,
Engines, excluding Aircraft,
213(a)(4)
New Jersey, Oregon, and Pennsylvania
Locomotives, and Vessels
7/29/09
Fuels Used in Motor Vehicles,
211 and 231
NYU Law School Institute for Policy Integrity
Nonroad Vehicles, and Aircraft
9/21/09
Concentrated Animal Feeding
111(b) and (d)
Humane Society of the United States and 8 other
Operations
organizations
Source: U.S. EPA and the petitioning organizations.
Medium and Heavy-Duty Trucks
Section 202(a) of the Clean Air Act, the section that provided authority for the light-duty vehicle
GHG standards, requires the Administrator to set “standards applicable to the emission of any air
pollutant from any class or classes of new motor vehicles or new motor vehicle engines, which in
his judgment cause, or contribute to, air pollution which may reasonably be anticipated to
endanger public health or welfare” (emphasis added). This authority covers medium- and heavy-
duty trucks: in fact, the December 15, 2009, endangerment and cause-or-contribute findings
specifically identified the medium- and heavy-duty truck categories as among those that
contributed to the GHG emissions for which it found endangerment. As a result, EPA has already
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begun work on GHG emission standards for these vehicles, and expects to propose standards in
June or July of 2010.
In addition, in the Energy Independence and Security Act of 2007 (EISA, P.L. 110-140), NHTSA
was directed to set the first-ever fuel economy standards for medium- and heavy-duty trucks,
reflecting the “maximum feasible improvement” in fuel efficiency.18 Thus, as with light duty
vehicles, EPA and NHTSA are cooperating on the setting of standards.
Table 2. Motor Vehicle GHG Emissions, 2007, by Source Category
(million metric tonnes, CO2-e)
Total GHG
% of Motor Vehicle
Category
Emissions
Total
Passenger Cars
664.6
40.3%
Light Duty Trucks
561.7
34.0%
Medium- and Heavy-Duty Trucks
410.8
24.9%
Buses 12.4
0.8%
Motorcycles 2.1
0.1%
Total
1651.6
Source: U.S. EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks, 1990-2007, Table 2-15.
Medium- and heavy-duty trucks are trucks with a gross vehicle weight of 10,000 pounds or more.
The largest emitters, tractor-trailers (Class 8 trucks), account for slightly less than 20% of the
total number of vehicles, but, because they are heavier and are driven longer distances, they
consume 61% of all fuel used by trucks.19 Presumably, they emit about the same percentage of all
trucks’ GHGs. Box trucks, which tend to be lighter and are more frequently used in urban
settings, are a distant second in terms of GHG emissions. As shown in Table 2, medium- and
heavy-duty trucks emitted about 410 million metric tons of GHGs in 2007, about 25% of GHG
emissions from motor vehicles. Between 1990 and 2007, emissions from these trucks grew 80%,
the fastest growth for any major category of GHG sources. (See Figure 2.)
18 Section 102.
19 National Research Council, Technologies and Approaches to Reducing the Fuel Consumption of Medium- and
Heavy-Duty Vehicles, Overview Presentation of Report, March/April 2010, p. 26.
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Figure 2. Growth of GHG Emissions from Mobile Sources, 1990-2007
90%
80%
80%
70%
60%
50%
50%
40%
30%
23%
20%
13%
10%
0%
Aviation
Cars/LDTs
Rail
Trucks
Source: U.S. EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks, 1990-2007, Table 2-15.
The EPA Administrator is given substantial leeway in the design and implementation of motor
vehicle regulations. The act states that the Administrator may establish categories for purposes of
regulation based on “gross vehicle weight, horsepower, type of fuel used or other appropriate
factors.” In addition, she may delay the effective date of regulations as long as she finds
necessary “to permit the development and application of the requisite technology, giving
appropriate consideration to the cost of compliance within such period.” Using this authority in
regulating conventional pollutants, EPA has used weight or power classifications to set differing
levels of emission standards, particularly for trucks; it has given manufacturers as much as four
years lead time to develop emission controls; and it has set different standards based on the type
of fuel an engine uses. Except for specific conventional pollutants mentioned in Section 202, the
act does not specify a level of stringency (e.g., best available control technology) for prospective
regulations.
Although flexible in many respects, motor vehicle standards have often been used to force the
development of new technology. In adopting technology-forcing regulations, EPA has generally
followed the lead of California. Because of its more severe air pollution and its pioneering role in
establishing motor vehicle emission control requirements in the 1960s, California is allowed to
adopt standards more stringent than federal requirements. The state must apply for a waiver of
federal preemption under CAA Section 209(b) in order to enforce its more stringent standards,
which EPA is to grant if the state meets certain criteria, primarily a showing that the standards are
needed to meet “compelling and extraordinary conditions.” If California is granted a waiver, other
states may adopt identical requirements, thus reinforcing the potential impact of California’s
technology-forcing standards.
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EPA discussed several potential strategies for reducing GHG emissions from medium- and heavy-
duty trucks in its July 2008 Advance Notice of Proposed Rulemaking,20 including:
1. Improvements in Engine Technology. Most trucks, particularly tractor-trailers,
are powered by diesel engines, which are already quite efficient; but EPA thinks
that a number of small improvements (such as better lubricants and higher
cylinder pressure) could increase diesel engine efficiency by up to 20%. For
urban trucks, which engage in stop-and-go driving and may idle frequently in
traffic, hybrid engine technologies show promise of substantial reductions in
emissions.
2. Eliminating Aerodynamic Drag. Aerodynamic drag is an important factor in
fuel consumption, particularly for tractor-trailers. EPA estimates that drag
accounts for 21% of energy consumed by tractor-trailers at 65 miles per hour.
The agency has promoted a number of relatively simple redesigns (high roof
fairings, side skirts, side fairing gap reducers, aerodynamic mirrors and bumpers)
through its SmartWay voluntary program. These measures can have a significant
impact on fuel use.
3. Reducing Rolling Resistance. Tire rolling resistance accounts for about 13% of
energy consumed by tractor trailers, according to EPA. The agency says that 10%
or greater reductions in rolling resistance have already been demonstrated and
continued innovation has the potential to achieve larger improvements. In
addition to better tires with less rolling resistance, tire inflation indicators can
improve fuel efficiency.
4. Addressing Operational Factors. Operational factors refer to a wide variety of
measures that can reduce truck fuel use, including the installation of speed
governors (widely used in Europe and by some fleets in the United States).
According to EPA, vehicle speed is the single largest operational factor affecting
CO2 emissions from trucks: every one mile per hour increase above 55 mph
increases CO2 emissions by more than 1%. Engine idling is another operational
factor affecting fuel consumption and GHG emissions. The addition of auxiliary
power units or truck stop electrification could eliminate the need for extended
idling, reducing emissions.
All in all, EPA stated in its 2008 analysis of the issues, “we see a potential for up to a 40%
reduction in GHG emissions from a typical heavy-duty truck in the 2015 timeframe, with greater
reductions possible looking beyond 2015....”21
Ships
Three of the 10 petitions to EPA asking the agency to control greenhouse gas emissions concern
ocean-going ships (also referred to as marine engines and vessels) and (in two of the petitions)
their fuel. Although there is a wide range of estimates, the International Maritime Organization’s
consensus is that international shipping emitted 843 million metric tons of carbon dioxide, 2.7%
20 U.S. EPA, “Regulating Greenhouse Gas Emissions Under the Clean Air Act,” Advance Notice of Proposed
Rulemaking, July 30, 2008, 73 Federal Register 44453-44458.
21 Ibid., p. 44454.
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of global CO2 emissions in 2007. Including domestic shipping and fishing vessels larger than 100
gross tonnes, the amount would increase to 1.019 billion metric tons, 3.3% of global emissions.22
At these levels, only five countries (the United States, China, Russia, India, and Japan)
individually account for a higher percentage of the world total of CO2 emissions.23
In addition to the CO2 emissions, the low-quality bunker fuel that ships use and the absence of
pollution controls result in significant emissions of black carbon and nitrogen oxides, which also
contribute to climate change. Refrigerants used on ships (hydrofluorcarbons and
perfluorocarbons—HFCs and PFCs) are also potent greenhouse gases when released to the
atmosphere. Thus, the total impact of ships on climate is likely greater than the 3.3% estimate
above.
The authority to control pollution from ships is found in Section 213(a)(4) of the Clean Air Act,
which provides general authority to the Administrator to promulgate standards for emissions other
than carbon monoxide, oxides of nitrogen, and volatile organic compounds from “nonroad
engines and vehicles.”24 Fuels are regulated separately under Section 211 of the act.
The language of Section 213 is similar to that for new motor vehicles in Section 202, except that
in place of the words “cause, or contribute,” Section 213 uses the phrase “significantly
contribute”: if the Administrator determines that emissions of GHGs from ships significantly
contribute to air pollution which may reasonably be anticipated to endanger public health or
welfare, she may promulgate such regulations as she deems “appropriate.” Except for the specific
conventional pollutants mentioned in Section 213(a)(2), there is no level of stringency (such as
best available control technology) specified for prospective regulations. The Administrator may
establish classes or categories of ships for the purposes of regulation. There is no deadline for the
promulgation of standards, and in setting them, the Administrator may take into account costs,
noise, safety, and energy factors associated with the application of technology.
A wide variety of measures might be undertaken to reduce emissions from shipping, from simple
operational measures, such as reducing speed or using cleaner fuels, to various hull and propeller
design features that would increase fuel economy. Reducing speed can save substantial amounts
of fuel. A.P. Moller-Maersk, which operates the world’s largest fleet of containerships, reported
that it reduced fuel consumption by its ships 6% in 2008, compared to the fuel used for the same
level of business activity in 2007. According to the company, “reducing speed 5-10% does
increase the number of days at sea, but reduces both fuel consumption and CO2 emission by more
than 15%.”25 The petitions also mention improved fleet deployment planning, use of shore-side
power while in port, heat recovery systems, the use of sails as supplemental propulsion sources,
and NOx controls, such as selective catalytic reduction (SCR) or exhaust gas recirculation, as
potential emission control measures.
22 International Maritime Organization, Updated Study on Greenhouse Gas Emissions from Ships, Executive Summary
of Phase 1 Report, 1st September 2008, p. 5 at egserver.unfccc.int/seors/attachment/file_storage/6ep77qqvcujba7k.doc.
Both estimates exclude emissions from naval vessels.
23 Oceana, Shipping Impacts on Climate: A Source with Solutions, p. 2, at http://www.oceana.org/fileadmin/oceana/
uploads/Climate_Change/Oceana_Shipping_Report.pdf.
24 CO, NOx, and VOCs are regulated under Section 213(a)(3), which requires the imposition of best available control
technology, and set a deadline for such regulation.
25 See Preparing for the Future, The A.P. Moller – Maersk Group’s Health, Safety, Security and Environment Report
2008, pp. 28-30, at http://media.maersk.com/da/PressReleases/2009/Documents/Maersk%20HSSE%202008_Final.pdf.
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A complicating factor in the regulation of emissions from ocean-going vessels would be that, for
the most part, their GHG emissions occur in international waters, and the sources (the ships) are
not registered in the United States: according to California’s petition, 95% of the fleet calling on
U.S. ports is foreign-flagged. The petitioners assert that these factors are not a bar to EPA
regulation, however, citing as precedent a Supreme Court case that held that the Americans with
Disabilities Act could be applied to foreign-flagged cruise ships so long as the ADA-required
accommodations did not interfere with the ships’ internal affairs or require major, permanent
modifications to the ships.26
In addition to petitioning for regulation of emissions from ships, the petitions from California and
from Oceana et al. stated that EPA should regulate the composition of marine shipping vessel fuel
to control global-climate-change-related emissions, or should require use of marine diesel fuel oil
instead of bunker fuel. The purpose would be to limit the sulfur content of marine fuels and
reduce NOx emissions. We discuss EPA’s authority to regulate fuels in a separate section below,
but note here that EPA, the state of California, and the International Maritime Organization are all
moving forward with regulations to limit the sulfur content of bunker fuel for the purpose of
reducing conventional pollutants. California’s low sulfur fuel requirements went into effect July
1, 2009. In addition, on March 26, 2010, the International Maritime Organization approved an
EPA proposal that the entire U.S. coastline except portions of Alaska be designated as an
Emission Control Area, subject to lower sulfur limits in bunker fuel.
Sulfur emissions form fine particles of sulfate in the atmosphere, with significant impacts on
public health and welfare. (For a further discussion of these impacts, see CRS Report RL34548,
Air Pollution and Greenhouse Gas Emissions from Ships.) Although harmful as a conventional
pollutant, sulfur emissions are thought by most experts to be beneficial or at least neutral in the
climate context. Sulfates have a cooling effect on the atmosphere, since the particles tend to
reflect solar radiation back into space rather than absorbing it. On the other hand, removing sulfur
might be necessary to prevent the fouling of pollution control equipment that reduces other
pollutants that do lead to warming.
Other Nonroad Engines
Section 213 can also be used to regulate other nonroad vehicles and engines. A similar
endangerment finding would first be required, following which the Administrator may
promulgate such regulations as she deems appropriate to control emissions from the classes or
categories of nonroad engines that she determines “significantly contribute” to the air pollution
that endangers public health or welfare. The Administrator is to take into account costs, noise,
safety, and energy factors in setting standards. There is no deadline for setting standards.
26 Spector v. Norwegian Cruiseline, 545 U.S. 119 (2005). In addition, according to the California petition, the United
States can and does enforce pollution standards on ships in its territorial waters, “as can be seen by the fact that the
National Park Service has imposed air pollutant emissions controls on cruise ships, including foreign-flagged cruise
ships (the vast majority of such ships are foreign-flagged), that sail off the coast from Glacier Bay National Park, in
Alaska.” See People of the State of California Acting by and Through Attorney General Edmund G. Brown, Jr.,
“Petition for Rule Making Seeking the Regulation of Greenhouse Gas Emissions from Ocean-Going Vessels,” October
3, 2007, p. 13. The cited regulations are at 36 CFR 13.65(b)(4). The Federal Register citation is 61 Federal Register
27008, 27011 (May 30, 1996).
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The nonroad sector is a broad category that includes construction equipment, farm equipment,
forklifts, outdoor power equipment, lawn and garden equipment, and recreational vehicles.27 This
group accounted for 199.7 million metric tons of CO2 emissions in 2007, according to the two
petitions requesting regulation (see Table 3), 3.3% of total U.S. emissions of CO2 in that year.
According to the ICTA petition, GHG emissions from the nonroad sector increased 49% between
1990 and 2005, a higher rate of emissions increase over the same period than for on-road vehicles
(32%), aircraft (3%), boats and ships (36%), and rail (32%).28
Table 3. Nonroad Sector CO2 Emissions, 2007, by Source Category
(million metric tonnes)
Category CO2 Emissions
% of Nonroad Total
Construction and Mining
63.9 32.0%
Equipment
Agricultural Equipment
39.6
19.8%
Industrial Equipment
27.8
13.9%
Lawn and Garden Equipment
23.8
11.9%
Commercial Equipment
16.4
8.2%
Pleasure Craft
15.8
7.9%
Recreational Equipment
9.4
4.7%
Logging Equipment
1.9
1.0%
Airport Equipment
1.0
0.5%
Railroad Equipment
0.2
0.1%
Total
199.7
Source: ICTA et al., Petition for Rulemaking Seeking the Regulation of Greenhouse Gas Emissions from Nonroad
Vehicles and Engines. According to the petition, the emissions data were compiled by the Western Environmental
Law Center using EPA’s nonroad emissions model.
Given their smaller impact on overall emission levels, EPA has been slower to regulate
conventional (criteria) pollutants from nonroad engines than from motor vehicles. Many of these
engines had few emission control requirements for as many as 25 years after the regulation of
automobiles. In the last decade, however, often following the lead of California, EPA has
promulgated standards for many nonroad categories. Some of these standards, particularly for
diesel-powered equipment and for lawn and garden equipment, have been technology-forcing.
Others, such as for snowmobiles, have been less so.
In general, given the wide variety of engine types and sizes and the configurations of the
equipment itself, the agency has based its standards on a review of individual subcategories and
the technologies available to reduce emissions from specific types of machinery or equipment,
27 Locomotives are also considered nonroad engines, but the authority to regulate them (in Section 213(a)(5)) is
separate from that applicable to the rest of the category, and does not appear to give the Administrator the authority to
set GHG standards. Thus, they were not included in either of the two petitions EPA received requesting regulation of
nonroad GHG emissions.
28 International Center for Technology Assessment, et al., “Petition for Rulemaking Seeking the Regulation of
Greenhouse Gas Emissions from Nonroad Vehicles and Engines,” January 29, 2008, p. 5.
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rather than applying one across the board standard. Presumably, any GHG standards for this
sector would take the same approach.
Aircraft
EPA has also received petitions to regulate GHG emissions from aircraft and aircraft engines. In
the United States, aircraft of all kinds are estimated to emit between 2.4% and 3.4% of the
nation’s total greenhouse gas emissions.29 When other factors are considered, the impact of U.S.
aviation on climate change is perhaps twice that size. These factors include the contribution of
aircraft emissions to ozone formation, the water vapor and soot that aircraft emit, and the high
altitude location of the bulk of aircraft emissions. (For additional information on aircraft GHG
emissions, see CRS Report R40090, Aviation and Climate Change.)
As noted in Table 1, two December 2007 petitions requested that EPA address aircraft GHG
emissions. Specifically, the petitions asked that EPA make a finding that aircraft GHG emissions
endanger public health or welfare, and that the agency adopt regulations that allow a range of
compliance approaches: these might include emission limits, operational practices, fees, a cap-
and-trade system, minimizing engine idling time, employing single engine taxiing, or use of
ground-side electricity measures to replace the use of fuel-burning auxiliary power units at airport
gates.30
EPA has authority to regulate emissions from aircraft under Section 231 of the Clean Air Act. The
language is similar to that for other mobile sources. It requires the Administrator to issue
standards for the emission of any air pollutant from any class or classes of aircraft engines which,
in her judgment, causes or contributes to air pollution which may reasonably be anticipated to
endanger public health or welfare. The regulations are to take effect “after such period as the
Administrator finds necessary ... to permit the development and application of the requisite
technology, giving appropriate consideration to the cost of compliance.” But compared to other
mobile sources, EPA’s Clean Air Act authority vis-à-vis aircraft and aircraft engines contains an
important difference: the Administrator must consult with the Administrator of the Federal
Aviation Administration and the Secretary of Transportation in developing emission standards,
and is not allowed to impose new standards if doing so would significantly increase noise and
adversely affect safety.
Unlike ships, aircraft operating in the United States are generally registered here: EPA has cited
data that foreign carriers accounted for only 3% of major carrier operations in the United States in
1999.31 Thus, whether GHG regulations could be applied to foreign flag carriers might seem to
pose less of an issue, at least in terms of whether any potential regulations would address the bulk
of the sector’s U.S. emissions. On the other hand, international air travel is extremely
29 The lower percentage includes CO2 emissions from consumption of fuel by military aircraft, general aviation, and
domestic operation of commercial aircraft. The higher estimate includes CO2 emissions from international air travel
originating in the United States, as well.
30 For a brief discussion of the petitions, see 73 Federal Register 44460, July 30, 2008. Some of these measures, such
as minimizing engine idling time, employing single engine taxiing, and use of ground-side electricity measures to
replace the use of fuel-burning auxiliary power units, are already widely used by the airlines as fuel-saving measures.
31 U.S. EPA, Office of Air and Radiation, Emission Standards and Test Procedures for Aircraft and Aircraft Engines,
Summary and Analysis of Comments, November 2005, p. 10, at http://www.epa.gov/oms/regs/nonroad/aviation/
420r05004.pdf
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competitive, and issues of whether regulations can be imposed on foreign carriers have already
been raised in the context of the European Union’s adoption of cap-and-trade requirements for
international aviation. U.S. airlines generally maintain that the imposition of requirements on
foreign-flag airlines (i.e., themselves, in the European Union) violates international trade
agreements. Their preference is that any controls be negotiated through the International Civil
Aviation Organization (ICAO) and be applied equally to all carriers.
EPA has rarely regulated emissions from aircraft without first negotiating international
agreements through ICAO. ICAO’s regulation of conventional pollutants from aircraft, unlike
EPA’s regulation of the same pollutants from motor vehicles, has consistently avoided forcing
technology. The most recent standards for nitrogen oxides, for example, essentially ratified what
the principal aircraft manufacturers had already achieved.32
Fuels
Fuel regulation, whether of bunker fuel, gasoline, or any other type of fuel, is authorized under
Section 211 of the Clean Air Act. Section 211 gives the Administrator authority to control or
prohibit the manufacture and sale of any fuel or fuel additive if she concludes that its emission
products may endanger public health or welfare, or if they will impair to a significant degree the
performance of emission control devices. As with the regulation of engines and vehicles, the
Administrator is given substantial leeway in the design and implementation of fuel regulations
and there is no deadline for their promulgation even after an endangerment finding is made.
GHG emissions from fuels have already been targeted for regulation by the state of California.33
On April 15, 2010, California’s Office of Administrative Law approved regulations to implement
the California Low Carbon Fuel Standard, which has been under development since 2007. The
standard’s goal is to reduce GHG emissions from transportation fuels per unit of energy 10% by
2020. The regulations address emissions from the production, transportation, and consumption of
gasoline, diesel fuel, and their alternatives, including biofuels. They envision compliance both
through the use of lower carbon fuels and through the development of more efficient, advanced-
technology vehicles, such as plug-in hybrids, electric vehicles, and hydrogen fuel cells.
As has been the case with motor vehicles, California has often led the way in the development of
cleaner conventional fuels through technology-forcing regulation, with U.S. EPA later adopting
similar standards. Thus, many view the Low Carbon Fuel Standard as the prototype of another
possible use of existing Clean Air Act authority to regulate greenhouse gas emissions nationally.
On July 29, 2009, the Institute for Policy Integrity at NYU Law School petitioned EPA to
establish a cap-and-trade system to limit greenhouse gas emissions from fuels used in motor
vehicles, nonroad vehicles, and aircraft.
Regulation of fuels would be a way for California or U.S. EPA to obtain reductions from existing
vehicles and engines. As noted earlier, the slow turnover of the vehicle fleet means that emission
reductions from new vehicles will only gradually affect emission levels from the fleet as a whole.
32 “EPA Proposal to Bring Certain Aircraft Up to International Engine Standard,” Daily Environment Report,
September 30, 2003.
33 For more information, see http://www.arb.ca.gov/regact/2009/lcfs09/lcfs09.htm. For additional background, see
archived CRS Report R40078, A Low Carbon Fuel Standard: State and Federal Legislation and Regulations, by Brent
D. Yacobucci.
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By requiring low carbon fuels, California and EPA could obtain GHG reductions from the entire
fleet more quickly.
On the other hand, measuring the carbon content of fuels is more complicated than it may seem,
particularly if one considers the life-cycle emissions, including indirect impacts of production.
EPA has been embroiled in a controversy over this issue already, as it attempted to develop a
methodology for measuring greenhouse gas emissions from biofuels, as required by the Energy
Independence and Security Act of 2007 (P.L. 110-140).34 For regulations implementing this
provision, EPA developed and later modified a methodology to measure the GHG effects of
indirect land-use changes, such as the switching of land from forest to cropland.35
Conclusion
Table 4 summarizes EPA’s existing authorities over mobile source GHG emissions and the
emissions of each of the sectors discussed in this report. Given the Supreme Court’s remand in
Massachusetts v. EPA, the agency has focused its efforts on motor vehicles (first of all, passenger
cars and light trucks), which, as Table 4 shows, account for the majority of mobile source GHG
emissions. Having finalized these standards, the agency has now moved on to the development of
GHG emission standards for medium- and heavy-duty trucks, the next largest category of
emissions. Both of these categories were covered by EPA’s December 15, 2009, endangerment
finding.
By issuing endangerment findings similar to the one it issued for motor vehicles, EPA could move
forward to control GHG emissions from other categories of mobile sources and/or their fuels. On
the other hand, once the agency has completed the setting of emission standards for passenger
cars, light duty trucks, and medium- and heavy-duty trucks, it will have addressed the categories
responsible for about 80% of all mobile source GHG emissions. The next largest category,
aircraft, has rarely been the subject of EPA regulation unless the International Civil Aviation
Organization (ICAO) has first agreed on standards. Other mobile source categories are less
significant: each accounts for less than 1% of total U.S. emissions.
Thus, EPA seems more likely to follow up its car and truck standards in two ways: (1) by
considering a new round of emission standards for light duty vehicles, and (2) by expanding its
focus to stationary sources. On April 28, 2010, EPA Administrator Jackson, at a House Energy
and Commerce Committee subcommittee hearing, indicated that the agency might begin “soon”
to craft a second round of regulations for GHG emissions from cars and light trucks, applicable to
model years 2017 and later.36 The Administrator made her statement in response to questions
from Representative John Dingell, who expressed concern that the agency needed to provide the
auto industry sufficient lead time before implementing additional standards. As has often
happened in the development of auto emission standards, EPA will likely be following the lead of
California, which expects to adopt GHG emission standards for 2017-2025 model year cars and
34 Section 202 of the act mandates the use of “advanced biofuels”—fuels produced from non-corn feedstocks and with
50% lower lifecycle greenhouse gas emissions than petroleum fuel—starting in 2009. Of the 36 billion gallons of
renewable fuel required in 2022, at least 21 billion gallons must be advanced biofuel.
35 For information, see CRS Report R40460, Calculation of Lifecycle Greenhouse Gas Emissions for the Renewable
Fuel Standard (RFS), by Brent D. Yacobucci and Kelsi Bracmort.
36 See “Feds Eye Next Round of Auto Standards,” Environment And Energy Daily, April 29, 2010.
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light trucks by the end of 2010.37 The California standards would require a waiver of federal
preemption from EPA in order to take effect.
Table 4. Categories of Sources Whose GHG Emissions Could Be Regulated Under
Title II of the Clean Air Act
(assuming an endangerment finding for the category)
Estimated 2007
GHG Emissions
CAA Authority
(million tonnes
% of Total U.S.
Category
(Section #)
CO2-e)
GHG Emissions
Passenger Cars
202
664.5
9.3%
Light Duty Trucks
202
561.6
7.9%
Medium- and
202 410.4 5.8%
Heavy-Duty
Trucks
Aircraft (domestic
231 189.4 2.7%
operation)
Construction and
213 63.9
0.9%
Mining Equipment
Agricultural
213 39.7
0.6%
Equipment
Ships and Other
213 33.7
0.5%
Boatsa
Industrial
213 27.8
0.4%
Equipment
Lawn and Garden
213 23.8
0.3%
Equipment
Commercial
213 16.4
0.2%
Equipment
Pleasure Craft
213
15.8
0.2%
Buses 202
12.4
0.2%
Recreational
213 9.4
0.1%
Equipment
Motorcycles 202
2.0 <0.1%
Logging Equipment
213
1.9
<0.1%
Airport Equipment
213
1.0
<0.1%
Railroad
213 0.2
<0.1%
Equipment
Totala
2073.9
29.1%
Source: U.S. EPA and ICTA
a. Does not include international bunker fuel.
37 See “California Seeks to Lead in Strengthening Future Fuel Economy, Emissions Standards,” Daily Environment
Report, April 30, 2010, p. A-6.
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Emission reductions from these categories might also be addressed through regulation of the
carbon content of their fuels.
Meanwhile, EPA can be expected to expand its focus to stationary sources, which account for
nearly 70% of the nation’s GHG emissions, and within that group to electric power plants. Power
plants account for about one-third of all U.S. GHG emissions, a higher percentage of the nation’s
total than all mobile sources combined. New and modified power plants will automatically be
subject to permit requirements and the imposition of Best Available Control Technology as of
January 2, 2011, under EPA’s interpretation of Section 165 of the Clean Air Act. The agency also
appears likely to develop New Source Performance Standards for GHG emissions from electric
power plants in the 2011 time period. (For additional discussion, see CRS Report R41212, EPA
Regulation of Greenhouse Gases: Congressional Responses and Options, by James E. McCarthy
and Larry Parker.)
Author Contact Information
James E. McCarthy
Specialist in Environmental Policy
jmccarthy@crs.loc.gov, 7-7225
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