Cars and Climate: What Can EPA Do to
Control Greenhouse Gases from Mobile
Sources?
James E. McCarthy
Specialist in Environmental Policy
April 20, 2009
Congressional Research Service
7-5700
www.crs.gov
R40506
CRS Report for Congress
P
repared for Members and Committees of Congress
Cars and Climate: What Can EPA Do to Control Greenhouse Gases from Mobile Sources?
Summary
As Congress considers legislation to reduce the greenhouse gas (GHG) emissions that contribute
to climate change, attention has focused on “cap-and-trade” legislation. Such legislation would
set a national cap on GHG emissions, with allowances (permits) to emit limited amounts of the
gases distributed or auctioned to affected parties. Recently, there has also been discussion of taxes
on greenhouse-gas-emitting substances (generally referred to as a “carbon tax”), which
proponents argue would provide greater transparency and a clearer price signal.
However the arguments over these options play out, enacting greenhouse gas controls is not
simply a choice between cap-and-trade and carbon tax options. A third set of options, using the
more traditional regulatory approaches of the Clean Air Act (CAA), is available. Unlike a cap-
and-trade system or a carbon tax, regulation under the Clean Air Act does not require new
Congressional action. The ability to limit GHG emissions already exists under various CAA
authorities that Congress has enacted, a point underlined by the Supreme Court in an April 2007
decision (Massachusetts v. EPA).
Thus, controlling GHGs could follow a two-track approach, with Congress and the
Administration pursuing new legal authority (for cap-and-trade, carbon tax, or whatever) at the
same time that the Administration, through the Environmental Protection Agency (EPA),
exercises existing authority under the Clean Air Act to begin regulation of greenhouse gas
emissions.
The key to using the Clean Air Act’s authority is for the EPA Administrator to find that GHG
emissions are air pollutants that endanger public health or welfare. Administrator Jackson
proposed such an endangerment finding, April 17. A 60-day public comment period will begin
upon publication of the draft finding in the Federal Register. Once an endangerment finding is
finalized, the agency can proceed to regulate emissions from various sources of GHGs.
EPA has received eight petitions asking that it make such findings and proceed to regulate
emissions from mobile sources, including motor vehicles, aircraft, ships, nonroad vehicles and
engines, and fuels, under Title II of the Clean Air Act. This report discusses EPA’s authority under
Title II and provides information regarding the mobile sources that might be regulated under this
authority. Among these sources, motor vehicles (passenger cars and light trucks, including SUVs)
are assumed to be the most likely initial targets for regulation, both because a petition addressing
these sources began EPA’s consideration of the endangerment issue, and because these are the
most significant GHG emission sources among those covered by Title II.
Regulation of GHGs from mobile sources might also lead the agency to establish controls for
stationary sources, such as electric power plants. That option, the authority for which would come
from different parts of the Clean Air Act, is not addressed in this report.
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Cars and Climate: What Can EPA Do to Control Greenhouse Gases from Mobile Sources?
Contents
Introduction ................................................................................................................................ 1
Option 1: Cap-and-Trade................................................................................................. 1
Option 2: A Carbon (or GHG) Tax................................................................................... 2
Option 3: Regulation Under Existing Authority ............................................................... 2
The Entry Point: Massachusetts vs. EPA...................................................................................... 3
The ANPR ...................................................................................................................... 3
Going After Mobile Sources: Title II Authorities ......................................................................... 4
New Motor Vehicles........................................................................................................ 6
Ships............................................................................................................................... 9
Other Nonroad Engines ................................................................................................. 11
Aircraft ......................................................................................................................... 13
Fuels ............................................................................................................................. 14
Summary of Mobile Source and Fuel GHG Emissions .................................................. 15
Figures
Figure 1. Motor Vehicle Greenhouse Gas Emissions.................................................................... 8
Tables
Table 1. Petitions for Regulation of Greenhouse Gas Emissions Under the Clean Air Act............. 5
Table 2. Motor Vehicle GHG Emissions, 2007, by Source Category ............................................ 9
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 and Climate: What Can EPA Do to Control Greenhouse Gases from Mobile Sources?
Introduction
In the 111th Congress, both the House and Senate committees of jurisdiction are expected to give
climate change legislation high priority. With the inauguration of President Obama, there is a
proponent of greenhouse gas (GHG) legislation in the White House, as well, markedly improving
the prospects for enacting some sort of legislation to reduce GHG emissions. The President has
said that a new energy, environment, and climate policy will be "a leading priority of my
presidency, and a defining test of our time."1
Not all parties are in agreement that controls on GHGs are desirable. Some argue that the science
behind climate change is too uncertain; they oppose controls unless, at some future time, more is
known about trends in climate variables and the impact of specific pollutants. Others, who agree
in principle that the science dictates GHG reductions be made, raise a number of arguments,
including issues concerning international commitments and the timing of a control regime (e.g.,
whether a major regulatory initiative is appropriate during the worst economic climate since the
Great Depression). Still others can be expected to raise objections about the form and substance
of specific legislative proposals, many of which are among the broadest regulatory measures that
Congress has ever considered.
Proponents of legislation counter that the threat of climate change is too important for action to be
delayed, and that energy-efficiency and lower GHG emissions can be the building blocks of a
program to restore the economy as well as to protect the environment.
Option 1: Cap-and-Trade2
As debate has proceeded, attention has focused primarily on cap-and-trade legislation3 that would
set a national cap on emissions. Under a cap-and-trade program, the government would either
distribute (most likely on the basis of historic emissions) or auction off allowances to emit
greenhouse gases; a combination of these approaches, in which some allowances are distributed
and some auctioned is also possible. Over time, the cap on emissions and hence the number of
allowances available would be reduced, forcing sources to reduce their emissions or buy
allowances from an ever-shrinking, and presumably more expensive, pool. The shrinking cap and
rising price of allowances would provide incentives for utilities and energy companies to develop
less-carbon-intensive energy supplies, for manufacturers to develop more energy-efficient
production processes, for the transportation sector to be made more fuel-efficient, and for greener
residential, commercial, and institutional buildings.
Although cap-and-trade has drawn the most attention (and appears to be the choice of most
congressional leaders and the Obama Administration), others have suggested that this approach is
1 Remarks of President-Elect Barack Obama, as prepared for delivery at the announcement of his Energy and
Environment Team, December 15, 2008, Chicago, Illinois, at http://change.gov/newsroom/entry/
president_elect_barack_obama_announces_key_members_of_energy_and_environmen/.
2 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.
3 Now also being called “cap-and-tax” by some opponents, or “cap-and-dividend” by some supporters.
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overly complicated. It would require the development of an entirely new administrative structure.
Its costs are uncertain: the experience with emission allowance markets to date suggests that there
may be substantial allowance price volatility. And the markets it creates may not be transparent: it
could give rise to an array of financial instruments and trading mechanisms that would reward
traders and would require strong regulatory oversight to mitigate potential market manipulation.
Option 2: A Carbon (or GHG) Tax4
Many cap-and-trade critics suggest that a carbon (or greenhouse gas) tax may be a more
straightforward approach. By imposing a tax tied to the global warming potential of various fuels
and greenhouse gas emissions, there would be clear signals to utilities, manufacturers, other
businesses, government agencies, and consumers, leading them to lower-carbon choices. If the
tax were imposed “upstream” (i.e., on fuel producers and importers, utilities, and/or major
emitters of other GHGs), the additional cost could then be passed through to consumers of all
kinds.
A carbon tax has critics of its own. The principal argument against it is that it is an instrument
designed to fix the price of GHG control, whereas a cap-and-trade system establishes the quantity
of GHGs emitted. If the chosen price (i.e., the tax level) insufficiently reduces emissions,
Congress or a regulatory authority would need to adjust the tax level, thus negating one of the
tax’s supposed advantages, its cost certainty. With consensus forming among proponents of GHG
control that emissions need to be ratcheted down as much as 80% over a 40-year period, the tax
would need a transparent escalator provision to create additional emission reduction incentives.
From a political point of view, Congress has found it difficult to impose new taxes or to adjust
those in place. Yet carbon tax proponents presume that if the tax is ineffective, it will be adjusted.5
It is also unclear how a carbon tax would mesh with the international commitments to limit
emissions that are expected to be negotiated later this year at Copenhagen: if a treaty is agreed to,
it is likely to establish numerical limits on emissions, not specify the cost of an effective limit.
Option 3: Regulation Under Existing Authority
However these arguments play out, enacting greenhouse gas controls is not simply a choice
between cap-and-trade and carbon tax options. A third set of options, using the more traditional
regulatory approaches of the Clean Air Act (CAA) and other legislation, is available. These
approaches could be strengthened through new legislation, but unlike a cap-and-trade system or
carbon tax, regulation does not necessarily 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 (discussed below).
Thus, controlling GHGs could follow a two-track approach, with Congress and the
Administration pursuing new legal authority (for cap-and-trade, carbon tax, or whatever) at the
same time that the Administration, through the Environmental Protection Agency (EPA),
4 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.
5 The reverse assumption, that a cap would not be adjusted even if it caused significant economic dislocation, is
presumed by cap-and-trade proponents. Both assumptions would likely be tested.
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exercises existing authority under the Clean Air Act to begin regulation of greenhouse gas
emissions.
The Entry Point: Massachusetts vs. EPA
The regulatory approach has been under consideration at EPA for more than a decade. In 1998,
EPA’s General Counsel, Jonathan Cannon, concluded in a memorandum to the EPA Administrator
that greenhouse gases were air pollutants within the Clean Air Act’s definition of the term, and
therefore could be regulated under the act.6 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.7 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 contribute
to air pollution which “may reasonably be anticipated to endanger public health or welfare.”
EPA denied the petition in 2003,8 and issued a new General Counsel memorandum the same day,
in which it concluded that the CAA does not grant EPA authority to regulate CO2 and other GHG
emissions based on their climate change impacts.9 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.10 The Court’s majority concluded that EPA must,
therefore, decide whether emissions of these pollutants contribute to air pollution that may
reasonably be anticipated to endanger public health or welfare. If it makes this finding of
endangerment, the act requires the agency to regulate emissions of the pollutants.11
The ANPR
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
6 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).
7 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.
8 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, 127 S.Ct. 1438, 1450-1451 (2007).
9 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).
10 Massachusetts v. EPA, 127 S.Ct. 1438 (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.”
11 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.
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following the Court decision was to issue a detailed information request, called an Advance
Notice of Proposed Rulemaking (ANPR), on July 30, 2008.12
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 Administration.”13 It went
on to state that “... the Clean Air Act is a deeply flawed and unsuitable vehicle for reducing
greenhouse gas emissions.”14 The other letters concurred. The ANPR, therefore, was of limited
use in reaching a conclusion on the endangerment issue, and, in any event, it presents the views of
an Administration no longer in power.
The current Administration made review of the endangerment decision a high priority. On April
17, 2009, EPA proposed a finding that GHGs do endanger both public health and welfare.15
Publication of the proposal in the Federal Register will begin a 60-day public comment period. In
addition, public hearings will be held in mid-May in Arlington, VA, and Seattle, WA.
Going After Mobile Sources: Title II Authorities
Although there are a number of ways in which the Clean Air Act could be used to regulate
greenhouse gas emissions, this report will focus on the authorities in Title II of the act, which
deals with mobile sources of air pollution. As noted in our discussion of Massachusetts v. EPA, it
was a petition to EPA that it control GHG emissions from new motor vehicles that precipitated
much of the discussion of the agency’s Clean Air Act authority to control GHGs, and brought the
issue to the attention of the courts. The Supreme Court dealt with this petition by reversing EPA’s
denial of it and remanding it for the agency to decide whether the pollutants in question endanger
public health or welfare.
12 U.S. EPA, "Regulating Greenhouse Gas Emissions Under the Clean Air Act," 73 Federal Register 44354, July 30,
2008.
13 “Regulating Greenhouse Gas Emissions Under the Clean Air Act,” 73 Federal Register 44356, July 30, 2008.
14 Ibid.
15 Environmental Protection Agency, “Proposed Endangerment and Cause or Contribute Findings for Greenhouse
Gases Under Section 202(a) of the Clean Air Act,” PrePublication Copy, April 17, 2009, at http://epa.gov/
climatechange/endangerment/downloads/GHGEndangermentProposal.pdf.
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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
Source: U.S. EPA and the petitioning organizations
Since then, the agency has received seven more petitions asking it to regulate GHGs from a wide
variety of mobile sources and their fuels (see Table 1). In addition to new motor vehicles, these
petitions cover aircraft, ocean-going ships and their fuels, 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 an endangerment finding and
decision to regulate GHGs in response to any one of the petitions could trigger regulation in
response to them all. With that in mind, we look at the authorities provided under Title II for the
various categories of mobile sources, and what EPA’s use of these authorities for conventional
pollutants indicates with regard to its ability to regulate greenhouse gases.
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New Motor Vehicles
In general, Title II authorities are better suited to the regulation of GHGs than most other parts of
the act. In Section 202 of the act, the Administrator is directed to “prescribe (and from time to
time revise) ... 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.” The
Administrator can (in fact, must) use this authority to regulate any air pollutant for which she
makes an endangerment finding. There is no need to demonstrate that the regulations will totally
eliminate the danger posed by the air pollution in question. In the case of other air pollutants –
notably, ozone—progressively more stringent standards for motor vehicle emissions have been
promulgated for more than 40 years without the pollutants the regulations addressed being
reduced sufficiently for all nonattainment areas to attain the ambient air quality standards.
For the most part, the pollutants for which standards were set under Section 202 have been either
criteria pollutants16 (carbon monoxide and nitrogen oxides) or emissions that served as precursors
to the formation of a criteria pollutant (ozone) through chemical reactions in the atmosphere.17 In
1986, EPA added emission standards for particulate matter under Section 202; in 2004, the
agency added a standard for formaldehyde, a carcinogen.
The Administrator is given substantial leeway in the design and implementation of motor vehicle
regulations. Except for specific conventional pollutants mentioned in Section 202, there is no
level of stringency (e.g., best available control technology) specified for prospective regulations.
The act also 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, the Administrator 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 previously established different standards for cars
than for SUVs, minivans, and light trucks; often, it 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.
In promulgating its current car and light truck standards, the agency set 11 different emission
levels (some of them temporary), allowing the manufacturers to choose any of these “bins,”
provided that the company achieves a prescribed overall fleet average. Thus, there is precedent
for applying varying requirements to different sized vehicles, for phasing in requirements, and for
the use of fleet averages as opposed to a single standard applied to all models.
16 Criteria pollutants are pollutants that endanger public health or welfare and whose presence in ambient air results
from numerous or diverse sources. Sections 108 and 109 of the act give the Administrator the authority to identify such
pollutants and set national ambient air quality standards for them. There are six criteria pollutants, all of which were
identified in the 1970s.
17 Ozone is not generally emitted directly by emission sources, but forms in the atmosphere as the result of chemical
reactions among precursors in the presence of sunlight. The precursors include the hydrocarbons present in gasoline
(currently termed “non-methane organic gases,” NMOG, in the regulations), as well as nitrogen oxides and carbon
monoxide, which are regulated as criteria pollutants in their own right.
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Although flexible in many respects, motor vehicle standards have nevertheless often been used to
force the development of new technology. In adopting technology-forcing regulations, EPA has
generally followed the lead of California. California, because of its more severe air pollution and
its pioneering role in establishing motor vehicle emission control requirements in the 1960s, is
allowed to adopt standards more stringent than federal requirements. The state must apply for a
waiver of federal preemption 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.”
In the 1970s, California and the federal government used technology-forcing regulations to bring
about the development and introduction of catalytic converters, reducing emissions from new
vehicles as much as 90% in less than a decade. In recent years, California’s Zero Emission
Vehicle and Low Emission Vehicle (LEV2) requirements, though frequently modified, have
stimulated the development of alternative fuel, hybrid, and electric vehicles and led to the
development of the National Low Emission Vehicle program and EPA’s current Tier 2 emission
standards.
Emissions of GHGs from new motor vehicles are the subject of already promulgated California
standards, for which the state has requested that EPA issue a waiver of federal preemption. These
California standards would require gradual reductions of GHG emissions from new passenger
vehicles until they are about 30% below the emissions of the 2002 fleet in 2016. Compliance
would be determined by fleet averages, rather than by the emissions of individual vehicles, and
the regulations provide additional flexibility, including averaging of emissions over a five-year
period, banking, and trading of credits within and among manufacturers. (For a discussion of the
California standards, see CRS Report RL34099, California’s Waiver Request Under the Clean Air
Act to Control Greenhouse Gases From Motor Vehicles.) The California program, if granted a
waiver, might serve as a model for how EPA could regulate motor vehicle GHGs under the Clean
Air Act.
In response to the Massachusetts v. EPA court case and with a new Administration committed to
addressing climate change, EPA has now proposed to find that GHG emissions from new motor
vehicles endanger public health and welfare, which would lead to the proposal and promulgation
of GHG standards for new motor vehicles.
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Figure 1. Motor Vehicle Greenhouse Gas Emissions
Source: U.S. EPA, March 6 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.
Promulgation of an endangerment finding would trigger the development of regulations for
emissions of four greenhouse gases emitted by motor vehicles (CO2, methane, nitrous oxide, and
hydrofluoro-carbons).18 According to EPA, emissions of the four gases from motor vehicles
(passenger cars, light duty trucks, other trucks and buses, and motorcycles) 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 auto air conditioning systems, are
the second most important motor vehicle GHG; but, as the figure shows, they are a distant
second.
Assuming that EPA proceeds with standards for emissions of motor vehicle GHGs, the agency
could either regulate the GHGs as a basket, or regulate them individually. The agency is
proposing the former approach, for several reasons: it follows agency precedent regarding
treatment of other pollutants (volatile organic compounds, particulate matter, etc.); it offers more
flexibility to the regulated community in meeting reduction targets; it eliminates concern about
setting contribution precedents for non-CO2 GHGs, which may be emitted at quite low levels by
some sources; and there is already a well-defined set of CO2 equivalents (CO2-e) that can serve as
the measuring tool for emission reductions. Nevertheless, the proposal states that the
Administrator believes that she could regulate emissions of the GHGs individually: “If the
Administrator defines the air pollutant as the group of greenhouse gases, she believes she would
have the discretion to set standards that either control the emissions of the group as a whole,
18 Two other commonly mentioned greenhouse gases, sulfur hexafluoride (SF6) and perfluorocarbons, are not emitted
by motor vehicles.
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and/or standards that control emissions of individual greenhouse gases, as constituents of the
class.”19 This determination is, like other elements of the proposal, subject to public comment.
As shown in Table 2, cars and light trucks (pickups, minivans, SUVs, etc.) account for three-
quarters of motor vehicle GHG emissions, with medium- and heavy-duty trucks accounting for
most of the rest. If California’s regulations are a model of what EPA might do, it is important to
note that the state’s regulations apply only to cars and light trucks, not to medium- and heavy-
duty trucks.
A further factor limiting the potential effect of motor vehicle emission standards is that both
California and EPA standards would 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.20 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.
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
664.5
40.3%
Light Duty Trucks
561.6
34.0%
Medium- and Heavy-Duty Trucks
410.4
24.9%
Buses 12.4
0.8%
Motorcycles 2.0
0.1%
Total
1650.9
Source: U.S. EPA, Draft Inventory of U.S. Greenhouse Gas Emissions and Sinks, 1990-2007, Table 2-15.
Ships
Three of the eight 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 tonnes of
carbon dioxide, 2.7% 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 tonnes, 3.3% of
19 Environmental Protection Agency, “Proposed Endangerment and Cause or Contribute Findings for Greenhouse
Gases Under Section 202(a) of the Clean Air Act,” PrePublication Copy, April 17, 2009, p. 105, at http://epa.gov/
climatechange/endangerment/downloads/GHGEndangermentProposal.pdf.
20 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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global emissions.21 At these levels, only five countries (the United States, China, Russia, India,
and Japan) account for a higher percentage of the world total of CO2 emissions.22
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 may be somewhat greater than 3%.
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.”23 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. If the
Administrator determines that emissions of GHGs from ships significantly24 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)(3), 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. 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.
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.25 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
21 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.
22 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.
23 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.
24 Section 213 uses the words “significantly contribute,” whereas Section 202 says “cause, or contribute to.”
25 Spector v. Norwegian Cruiseline, 545 U.S. 119 (2005).
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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.”26
EPA did not address these assertions in the ANPR, but it might be that a distinction needs to be
made between operational factors (speed, fuel type, etc.), that are easily amenable to control, and
permanent modifications of the vessel. In its petition, California cites the Clean Air Act’s historic
role in forcing the development of new, cleaner technology, but the Supreme Court opinions in
Spector v. Norwegian Cruiseline and other cases might seem to impose some limits on the degree
to which the act’s authority can be used with respect to foreign-flagged vessels.27
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 are scheduled to go
into effect this year. In addition, on March 27, 2009, EPA proposed that the entire U.S. coastline
except portions of Alaska be designated by the IMO 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 and Section 202 can also be used to regulate other nonroad vehicles and engines. The
language that the act uses in referring to the nonroad sector is similar to that used in the motor
vehicle and ship sections of the act: 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 “cause, or
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 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).
27 In addition to these considerations, U.S. international treaty obligations, specifically international trade agreements,
may be implicated. These issues are beyond the scope of this report.
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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.28 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%).29
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, the agency 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.
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.
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,
28 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.
29 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 (GHG) emissions.30 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.31
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.... ”
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
1999.32 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
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.
30 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.
31 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.
32 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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It is also worth noting that, compared to other mobile sources, EPA’s Clean Air Act authority vis-
à-vis aircraft and aircraft engines contains two principal differences. The first is that 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 change the
standards if doing so would significantly increase noise and adversely affect safety. The second,
and perhaps more significant difference, is that 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.33
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.34
On March 5, 2009, the California Air Resources Board (CARB) proposed the California Low
Carbon Fuel Standard, the goal of which is to reduce GHG emissions from transportation fuels
per unit of energy 10% by 2020.35 The regulations would address emissions from the production,
transportation, and consumption of gasoline, diesel fuel, and their alternatives, including biofuels.
The regulations 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. A public comment period on the proposed standards began with
their release on March 5. CARB hopes to finalize the regulations by 2010.
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.
Regulation of fuels would be a way for CARB or 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 would only gradually affect emission levels from the fleet as a
whole. By requiring low carbon fuels, CARB and EPA could obtain GHG reductions from the
entire fleet more quickly.
33 “EPA Proposal to Bring Certain Aircraft Up to International Engine Standard,” Daily Environment Report,
September 30, 2003.
34 For more information, see CRS Report R40078, A Low Carbon Fuel Standard: State and Federal Legislation and
Regulations.
35 The proposed regulation and supporting information can be found on CARB’s website at
http://www.arb.ca.gov/regact/2009/lcfs09/lcfsisor1.pdf.
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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 is embroiled in a controversy over this issue already,36 as it attempts 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).37 For regulations implementing this
provision, EPA is still developing a methodology to measure the GHG effects of indirect land-use
changes, such as the switching of land from forest to cropland.
Summary of Mobile Source and Fuel GHG Emissions
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 is focusing its efforts on motor vehicles (most likely passenger
cars and light trucks), which, as Table 4 shows, account for the majority of mobile source GHG
emissions. Nevertheless, assuming the agency does issue an endangerment finding for motor
vehicles, it would appear that they could move forward to control GHG emissions from most of
the other categories of mobile sources and/or their fuels by issuing similar endangerment
findings.
Regulation of GHGs from mobile sources might also lead the agency to establish controls for
stationary sources, such as electric power plants.38 That option, which would use authorities in
different sections of the Clean Air Act than Title II, is not addressed in this report. Electric power
plants accounted for 33.6% of U.S. GHG emissions in 2007.
36 For information, see CRS Report R40460, Calculation of Lifecycle Greenhouse Gas Emissions for the Renewable
Fuel Standard.
37 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.
38 In its ANPR last summer, the agency stated: “As part of EPA’s efforts to respond to the Supreme Court’s decision,
the Agency conducted a thorough review of the CAA to identify and assess any other CAA provisions that might
authorize regulation of GHG emission sources. That review made clear that a decision to control any source of GHG
emissions could or would impact other CAA programs with potentially far-reaching implications for many industrial
sectors. In particular, EPA recognized that regulation of GHG emissions from motor vehicles under section 202(a)(1)
or from other sources of GHG emissions under many other provisions of the Act would subject major stationary
sources to preconstruction permitting under the CAA.” 73 Federal Register 44399, July 30, 2008.
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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
Totalb
2073.9
29.1%
Source: U.S. EPA and ICTA
a. Does not include international bunker fuel.
b. Emission reductions from these categories might also be addressed through regulation of the carbon
content of their fuels.
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Author Contact Information
James E. McCarthy
Specialist in Environmental Policy
jmccarthy@crs.loc.gov, 7-7225
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