Aviation and the Environment
Strategic Framework Needed to Address Challenges Posed by Aircraft Emissions Gao ID: GAO-03-252 February 28, 2003Although noise has long been a problem around airports, the anticipated growth in demand for air travel has also raised questions about the effect of airport operations on air quality. Aviation-related emissions of nitrogen oxides, which contribute to the formation of ozone, have been of particular concern to many airport operators. A federal study at 19 airports estimated that, by 2010, aircraft emissions have the potential to significantly contribute to air pollution in the areas around these airports. GAO agreed to review efforts in the United States and other countries to reduce emissions at airports and the effect of improvements in aircraft and engine design on emissions.
Many airports have taken measures to reduce emissions, such as converting airport ground vehicles from diesel or gasoline to cleaner alternative fuels. While the actual impact of these measures is unknown, some measures (such as shifting to cleaner alternative fuels) have the potential to significantly reduce emissions, such as nitrogen oxides. In some cases--such as at Los Angeles and Dallas/Fort Worth airports--the emission reduction measures have been imposed by federal or state agencies to bring severely polluted areas into attainment with the Clean Air Act's air quality standards or to offset expected increases in emissions from airport expansion projects. Many industry and government officials that GAO contacted said that new, stricter federal air quality standards that will go into effect in 2003, combined with a boost in emissions due to an expected increase in air travel, could cause airports to be subject to more federal emission control requirements. In 1998, a group of government and industry stakeholders was established to develop a voluntary nationwide program to reduce aviation-related emissions; however, thus far, the group has not agreed to specific objectives or elements of a program. Other countries use many of the same measures as the United States to reduce emissions at airports. Two countries have imposed landing fees based on the amount of emissions produced by aircraft. However, U.S. officials question the effectiveness of these fees. Research and development efforts by the federal government and the aircraft industry have improved fuel efficiency and reduced many emissions from aircraft, including hydrocarbons and carbon monoxide, but have increased emissions of nitrogen oxides, which are a precursor to ozone formation. As a result, many new aircraft are emitting more nitrogen oxides than the older aircraft they are replacing. For example, GAO's analysis of aircraft emission data shows that the engines employed on the newest models of a widely used jet aircraft, while meeting current standards for nitrogen oxide emissions, average over 40 percent more nitrogen oxides during landings and takeoffs than the engines used on the older models. Technologies are available to limit nitrogen oxide emissions from some other newer aircraft models. Many state and federal officials GAO contacted said that, in the long term, nitrogen oxide emissions from aircraft will need to be reduced as part of broader emission reduction efforts in order for some areas to meet federal ozone standards.
RecommendationsOur recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.
Director: Team: Phone:GAO-03-252, Aviation and the Environment: Strategic Framework Needed to Address Challenges Posed by Aircraft Emissions
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Report to the Chairman, Subcommittee on Aviation, Committee on
Transportation and Infrastructure, House of Representatives:
United States General Accounting Office:
GAO:
February 2003:
Aviation and the Environment:
Strategic Framework Needed to Address Challenges Posed by Aircraft
Emissions:
GAO-03-252:
GAO Highlights:
Highlights of GAO-03-252, a report to the Chairman, Subcommittee on
Aviation, House Committee on Transportation and Infrastructure:
Why GAO Did This Study:
Although noise has long been a problem around airports, the
anticipated growth in demand for air travel has also raised questions
about the effect of airport operations on air quality. Aviationrelated
emissions of nitrogen oxides, which contribute to the
formation of ozone, have been of particular concern to many airport
operators. A federal study at 19 airports estimated that, by 2010,
aircraft emissions have the potential to significantly
contribute to air pollution in the areas around these airports.
GAO agreed to review efforts in the United States and other
countries to reduce emissions at airports and the effect of
improvements in aircraft and engine design on emissions.
What GAO Found:
Many airports have taken measures to reduce emissions, such as
converting airport ground vehicles from diesel or gasoline to cleaner
alternative fuels. While the actual impact of these measures is
unknown, some measures (such as shifting to cleaner alternative fuels)
have the potential to significantly reduce emissions, such as nitrogen
oxides. In some cases”such as at Los Angeles and Dallas/Fort Worth
airports”the emission reduction measures have been imposed by federal
or state agencies to bring severely polluted areas into attainment with
the Clean Air Act‘s air quality standards or to offset expected
increases in emissions from airport expansion projects. Many industry
and government officials that GAO contacted said that new, stricter
federal air quality standards that will go into effect in 2003,
combined
with a boost in emissions due to an expected increase in air travel,
could cause airports to be subject to more federal emission control
requirements. In 1998, a group of government and industry stakeholders
was established to develop a voluntary nationwide program to reduce
aviation-related emissions; however, thus far, the group has not agreed
to specific objectives or elements of a program.
Other countries use many of the same measures as the United States to
reduce emissions at airports. Two countries have imposed landing fees
based on the amount of emissions produced by aircraft. However, U.S.
officials question the effectiveness of these fees.
Research and development efforts by the federal government and the
aircraft industry have improved fuel efficiency and reduced many
emissions
from aircraft, including hydrocarbons and carbon monoxide, but have
increased emissions of nitrogen oxides, which are a precursor to ozone
formation. As a result, many new aircraft are emitting more nitrogen
oxides
than the older aircraft they are replacing. For example, GAO‘s analysis
of
aircraft emission data shows that the engines employed on the newest
models
of a widely used jet aircraft, while meeting current standards for
nitrogen
oxide emissions, average over 40 percent more nitrogen oxides during
landings
and takeoffs than the engines used on the older models. Technologies
are
available to limit nitrogen oxide emissions from some other newer
aircraft
models. Many state and federal officials GAO contacted said that, in
the long
term, nitrogen oxide emissions from aircraft will need to be reduced as
part
of broader emission reduction efforts in order for some areas to meet
federal
ozone standards.
What GAO Recommends:
GAO recommends that the Federal Aviation Administration
(FAA) develop a strategic framework that addresses the
need for information on the extent and impact of emissions, identifies
reduction options, establishes goals and time frames for
achieving needed reductions, and defines the roles of government
and industry in developing and implementing reduction programs.
Contents:
Letter:
Results in Brief:
Background:
Airports and Airlines are Taking a Variety of Actions to Reduce
Emissions, Although Specific Impact of These Actions Unknown:
Two Countries Have Introduced Emission-Based Fees:
Improvements in Aircraft and Engine Design Have Reduced Many Aircraft
Emissions, but Nitrogen Oxide Emissions are Increasing:
Conclusion:
Recommendation for Executive Action:
Agency Comments:
Appendixes:
Appendix I: Objectives, Scope, and Methodology:
Appendix II: Types, Amounts, and Impact of Emissions from
Aviation-related Sources:
Aviation-Related Emissions and Sources:
Health and Environmental Impact of Pollutants:
Appendix III: Federal, State, and International Responsibilities
for Controlling Aviation-related Emissions:
Appendix IV: Efforts by Three States to Reduce Aviation-related
Emissions:
California:
Texas:
Massachusetts:
Appendix V: Airports‘ and Airlines‘ Efforts To Reduce Emissions:
Aircraft:
Ground Support Equipment:
Providing Electric Power at Gates:
Passenger Vehicles:
Other Measures:
Appendix VI: Overview of Aircraft Fuel, Noise, and Nitrogen
Oxide Reduction Technologies:
Appendix VII: Additional Information on Our Analysis of Aircraft
Emissions:
Appendix VIIIComments from the National Aeronautics and
Space Administration:
Appendix IX: GAO Contacts and Staff Acknowledgments:
GAO Contacts:
Staff Acknowledgments:
Tables:
Table 1: Aircraft Turbine Engine Emission Amounts during Cruising Per
1000 Grams of Fuel Burned:
Table 2: Comparison of Emissions during Landing/Takeoff for Older and
the Newest Model Boeing 737s:
Table 3: Comparison of Boeing 747 and 777 Emissions on a Per Aircraft
Basis:
Table 4: Comparison of Boeing 747 and 777 Emissions on a Per Seat
Basis:
Table 5: Comparison of Power, Engine Operating Pressures, and Nitrogen
Oxides Emissions for Two Models of Boeing
737s:
Table 6: Health and Environmental Effects of Air Pollutants:
Table 7: Emission Information for Older Boeing 737s during Landing/
Takeoff:
Table 8: Emission Information for Newest Boeing 737s during Landing/
Takeoff:
Table 9: Additional Information on Comparison of Older and Newest Model
Boeing 737 Landing/Takeoff Emissions:
Table 10: Additional Information on Comparison of Boeing 747 and 777
Emissions on a Per Aircraft Basis:
Table 11: Comparison of Power, Engine Operating Pressures, and Nitrogen
Oxides Emissions for a Boeing 737-300 and Its Most Common Replacement:
Figures:
Figure 1: Examples of Activities to Reduce Emissions:
Figure 2: NASA‘s Planned Funding for Nitrogen Oxide Research:
Figure 3: Major Components of a Turbofan Engine (Two-Shaft High Bypass
Engine):
Abbreviations:
DOT: Department of Transportation:
EDMS: Emissions and Dispersion Modeling System:
EPA: Environmental Protection Agency:
FAA: Federal Aviation Administration:
GAO: General Accounting Office:
ICAO: International Civil Aviation Organization:
NASA: National Aeronautics and Space Administration:
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copyrighted materials separately from GAO‘s product.
United States General Accounting Office:
Washington, DC 20548:
February 28, 2003:
The Honorable John L. Mica
Chairman
Subcommittee on Aviation
Committee on Transportation and Infrastructure
House of Representatives:
Dear Mr. Chairman:
Although aviation-related activities result in the emission of
pollutants that account for only about 0.5 percent of total air
pollution in the United States, these pollutants are among the most
prevalent and harmful in the atmosphere and are expected to grow. The
Federal Aviation Administration (FAA) expects the demand for air travel
in the United States to recover from the events of September 11, 2001,
and then continue a long-term trend of 3.6 percent annual growth. This
expected growth has heightened concerns among some communities,
environmental groups, and others that airport operations will have an
increasingly detrimental effect upon the environment. Although, to
date, these groups have focused primarily on the noise generated by
aircraft operations, they are becoming increasingly concerned about
aviation‘s impact on air quality. Our August 2000 report found that the
operators of the nation‘s 50 busiest airports considered that air
quality issues would become a bigger concern and challenge for them in
the future than any other environmental issue.[Footnote 1] Airport
operators were particularly mindful of the effects on air quality of
the increases in emissions due to airport growth. The emissions of most
concern to many airport operators, as well as to many state and local
air quality authorities, are nitrogen oxides, which are a primary
contributor to the formation of ozone, a major pollutant in many
metropolitan areas.
You asked us to provide information on how the aviation community is
addressing current and future concerns about air quality. Specifically,
you asked the following questions: (1) What efforts are being
undertaken to reduce emissions from airport activities, and what are
the outcomes of these efforts? (2) What additional efforts are being
undertaken in other countries to reduce aviation-related emissions? and
(3) How have improvements in aircraft and engine design affected
aircraft emissions?
To address these questions, we reviewed the results of environmental
reviews conducted over the past 3 years at major airports located in
areas (called nonattainment areas) that have not attained air quality
standards required by the Clean Air Act; surveyed air quality officials
from the 13 states that have major airports in nonattainment areas; and
visited seven airports. To identify trends in aircraft emissions, we
analyzed aircraft landing and takeoff data for the U.S. commercial
aircraft fleet in 2001 using a computer model developed by FAA. In
addition, we interviewed and gathered information from officials
representing FAA, the Environmental Protection Agency (EPA), the
National Aeronautics and Space Administration (NASA), the International
Civil Aviation Organization (ICAO), airlines, aircraft manufacturers,
and state and local governments. We also reviewed previous reports on
aviation emission issues and available information on international
efforts to reduce aviation emissions. We conducted our work from
September 2001 through February 2003 in accordance with generally
accepted government auditing standards. See appendix I for additional
information on our objectives, scope, and methodology.
Results in Brief:
Many of the nation‘s busiest airports and airlines have taken actions
to reduce the emissions from airport activities, such as converting
shuttle buses to alternative fuels, decreasing the taxiing time of
aircraft, and providing electricity to aircraft parked at gates,
thereby allowing aircraft to turn off their more polluting power units
while crews prepare the aircraft for the next flight. Although the
actual impact of these measures is unknown, some measures have the
potential to significantly reduce emissions from certain sources. For
example, an initiative at Dallas/Fort Worth International and Houston
airports to convert ground service equipment from diesel and gasoline
to electric and alternative fuel engines is expected to cut nitrogen
oxide emissions from such equipment by up to 75 percent. In some cases,
federal or state agencies have imposed emission reduction measures on
airports located in severely polluted areas (called nonattainment
areas) to help bring these areas into attainment with the air quality
standards of the Clean Air Act, or to offset expected increases in
emissions from airport expansion projects. In other cases, airports or
airlines have voluntarily undertaken the measures. For example, the
ozone pollution in the Los Angeles metropolitan area has prompted the
state to require emission reductions from all sources, including
airports. State and local air quality agencies have negotiated with
airlines that use five local airports, including Los Angeles
International, to replace older, highly polluting ground support
equipment--such as baggage handling and food service vehicles--with
newer, less polluting equipment. State officials expect this action to
reduce emissions from ground support equipment at the five airports by
80 percent. In addition, our analysis of the environmental reviews
conducted by FAA at major commercial airports located in nonattainment
areas found that most proposed airport construction projects were not
required to institute any emission reduction measures to comply with
emission standards. However, FAA officials told us that in the future,
approval of some projects in these areas may be less likely because of
several factors, including increased focus on air quality by
communities that oppose airport development. In addition, in 1998, a
group of government and industry stakeholders was established to
develop a voluntary nationwide program to reduce aviation-related
emissions however, thus far the group has not defined specific
objectives or established time frames for achieving emissions
reductions. In 2003, EPA plans to begin implementing stricter ambient
air quality standards for ozone and other pollutants, which could make
it more difficult for some localities to achieve or maintain the
standards. Many in the aviation industry as well as federal and state
officials believe that the new standards, combined with the boost in
emissions expected from increases in air travel, could cause airports
to be subject to more federal emission control requirements in the
future. Currently, 26 of the 50 busiest U.S. airports are located in
areas that are not attaining the current 1-hour ozone standard;
however, that number could increase to 38 under the stricter 8-hour
ozone standard, according to EPA estimates.
Other countries use many of the same measures to reduce emissions at
airports as the United States and, in addition, two countries have
imposed landing fees based on the amount of emissions produced by
aircraft. Switzerland and Sweden recently implemented emission-based
landing fee systems as incentives for air carriers to reduce emissions
from aircraft using airports in those countries. It is too soon to
determine whether the fee systems have reduced emissions at these
airports, although FAA officials question the effectiveness of such
fees in reducing emissions. One U.S. airport, Boston Logan
International, considered emission-based landing fees in 2001, but
decided they would not be a practical option for reducing emissions--
particularly nitrogen oxides--because the fees would probably be too
low to influence carriers‘ use of lower-emitting aircraft.
Research and development by NASA and aircraft and engine manufacturers
have led to engine and airframe improvements that have increased fuel
efficiency and yielded environmental benefits, such as reduced carbon
monoxide and other emissions. However, trade-offs among several
factors, including engine performance, have also led to increases in
emissions of nitrogen oxides, which are a precursor to ozone formation.
As a result, some of the newest aircraft are emitting more nitrogen
oxides than the older, noisier, and less fuel-efficient aircraft they
are replacing. For example, our estimate of emissions produced by the
U.S. commercial aircraft fleet in 2001 indicates that the engines used
on the newest Boeing 737 models, which are widely used for domestic
flights, average over 40 percent more nitrogen oxide emissions during
landings and takeoffs than the engines primarily used on older-model
Boeing 737s. Technologies are being introduced that limit nitrogen
oxide emissions from some other newer aircraft models. Many state and
federal officials we contacted stated that, in the long term, nitrogen
oxide emissions from commercial aircraft will need to be reduced as
part of broader emission reduction efforts in order for some areas to
meet ozone standards. Both the environmental and aviation communities
have also voiced concerns that emissions from aircraft, particularly
nitrogen oxides, need to be further reduced. NASA, in association with
the aviation community, is working on technologies to reduce emissions
of nitrogen oxides, but it is unclear if such technologies can be
introduced on commercial aircraft in the foreseeable future.
To address the growing impact of aviation on air quality and the lack
of progress by the stakeholders group, we recommend that FAA develop a
strategic framework that examines the extent and impact of nitrogen
oxides and other aviation-related emissions; considers the
interrelationship among emissions and between emissions and noise;
includes goals, time frames, and options for achieving emission
reductions; and specifies the roles of other government agencies and
the aviation industry in developing and implementing emission reduction
programs. FAA, EPA, and NASA generally agreed with our findings, and
FAA agreed with our recommendation.
Background:
Although aviation-related activities currently account for only 0.5
percent of total air pollution in the United States, the types of
pollutants emitted by these activities are among the most prevalent and
harmful in the atmosphere, and are expected to grow over time. The
major sources of aviation-related emissions are aircraft, which emit
pollutants at ground level as well as over a range of altitudes; the
equipment (such as vehicles that transport baggage) that services them
on the ground at airports; and vehicles transporting passengers to and
from the airport. The amount of emissions attributable to each source
varies by airport. A 1997 study of mobile source emissions at four
airports found that ground access vehicles were the most significant
source (accounting for 27 to 63 percent of total mobile source
emissions), followed by aircraft (15 to 38 percent of the total) and
ground service equipment (12 to 13 percent of the total).[Footnote 2]
The emissions produced by these sources include carbon monoxide; sulfur
dioxide; particulate matter; toxic substances (such as benzene and
formaldehyde); and nitrogen oxides and volatile organic compounds,
which contribute to the formation of ozone, a major pollutant in many
metropolitan areas. In addition, aircraft emit carbon dioxide and other
gases that have been found to contribute to climate change due to
warming. According to the United Nations‘ Intergovernmental Panel on
Climate Change, global aircraft emissions accounted for approximately
3.5 percent of the warming generated by human activities. (The types,
amounts, and impact of emissions from aviation-related sources are
described in detail in appendix II.):
Although only limited research has been done on the impact of projected
growth in air travel on emissions, indications are that emissions are
likely to continue increasing. FAA reported in June 2001 that the
number of commercial flights is expected to increase about 23 percent
by 2010 and about 60 percent by 2025.[Footnote 3] Each flight
represents a takeoff and landing cycle during which most aircraft
emissions enter the local atmosphere. In addition, an EPA study of 19
airports projected that the proportion of mobile-source emissions of
nitrogen oxides attributable to aircraft in the areas adjacent to these
airports will triple from a range of 0.6 to 3.6 percent in 1990 to a
range of 1.9 to 10.4 percent in 2010.[Footnote 4] Such projections,
however, do not consider recent industry changes, such as airlines‘
increased use of smaller aircraft and the financial uncertainties in
the aviation industry. A recent report by the Department of
Transportation indicated that the September 11, 2001, terrorist
attacks, combined with a cut-back in business travel, had a major and
perhaps long-lasting impact on air traffic demand.[Footnote 5]
A number of federal, state, and international agencies are involved in
controlling aviation-related emissions. The Clean Air Act[Footnote 6]
mandates standards for mobile sources of emissions such as aircraft,
ground service equipment, and automobiles. As mandated by the act, EPA
promulgates emission standards for aircraft, and has chosen to adopt
international emission standards for aircraft set by ICAO, which was
chartered by the United Nations to regulate international aviation and
includes the United States and 188 other nations. As the United States‘
representative to ICAO, FAA, in consultation with EPA, works with
representatives from other member countries to formulate the standards.
EPA and FAA work to ensure that the effective date of emissions
standards permit the development and application of needed technology
and give appropriate consideration to the cost of compliance, according
to FAA officials. The officials also noted that EPA is responsible for
consulting with FAA concerning aircraft safety and noise before
promulgating emission standards. In addition to issuing aircraft
emission standards, ICAO has studied aviation-related emission issues
and issued guidance to its members on ways to reduce these emissions.
States can address airport emissions in plans, known as state
implementation plans, [Footnote 7] that they are required to submit to
EPA for reducing emissions in areas that fail to meet the National
Ambient Air Quality Standards set by the EPA under the Clean Air Act
for common air pollutants with health and environmental effects (known
as criteria pollutants).[Footnote 8] Geographic areas that have levels
of a criteria pollutant above those allowed by the standard are called
nonattainment areas. Areas that did not meet the standard for a
criteria pollutant in the past but have reached attainment and met
certain procedural requirements are known as maintenance areas. The
options available to states for controlling pollution from airports are
limited because most emissions come from mobile sources, such as
automobiles, which are already regulated by EPA, and states are
generally preempted from issuing regulations on aircraft emissions
because of EPA‘s federal responsibility in this area. FAA is
responsible for enforcing the emission standards and for ensuring that
emissions resulting from airport construction projects under their
authority comply with the National Environmental Policy Act, which
requires an environmental review of such projects, and the Clean Air
Act‘s requirement that the projects comply with state implementation
plans for attaining air quality standards. (See appendix III for
additional information on federal, state, and international
responsibilities concerning aviation-related emissions.):
Airports and Airlines are Taking a Variety of Actions to Reduce
Emissions, Although Specific Impact of These Actions Unknown:
Many of the nation‘s busiest airports and airlines that serve them have
initiated voluntary emission reduction measures, such as converting
shuttle buses and other vehicles from diesel or gasoline fuels to
cleaner alternative fuels. While the actual impact of these measures is
unknown, some measures (such as shifting to new cleaner gas or diesel
engines or alternative fuels) have the potential to significantly
reduce emissions, such as nitrogen oxides, volatile organic compounds,
particulate matter, and carbon monoxide. The airports and airlines have
undertaken these efforts for a variety of reasons, including
requirements by states imposed as part of their plans to ensure that
severely polluted areas (i.e., nonattainment areas) achieve the air
quality standards established by the Clean Air Act and to gain federal
approval for airport construction projects. In late 2003, EPA will
begin implementing stricter standards for ozone, which could make it
more difficult for areas to achieve or maintain attainment status.
Representatives from the aviation industry as well as federal and state
officials told us that the new air quality standards, combined with the
boost in emissions expected from increases in air travel, could cause
airports to be subject to more emission control requirements in the
future. In addition, according to FAA officials, approval of some
projects in these areas may be less likely because of several factors,
including increased focus on air quality by communities that oppose
airport development.
Airports‘ and Airlines‘ Voluntary Actions to Reduce Emissions:
Many of the nation‘s busiest airports, in conjunction with the air
carriers that serve them, have implemented voluntary control measures
to reduce emissions from major sources, including aircraft, ground
support equipment, and passenger vehicles entering and exiting the
airport, according to our review of FAA documents and interviews with
airport and state environmental officials. Specific guidelines or
regulations for airports to reduce emissions from these sources do not
exist, but some airports have been proactive in developing programs and
practices that reduce emissions. Although the actual impact of these
measures is unknown, some initiatives have the potential to
significantly reduce emissions from certain sources. For example, a
number of carriers at Dallas/Fort Worth International and Houston
airports have agreed to voluntarily reduce emissions associated with
ground service equipment by up to 75 percent. Figure 1 provides
examples of activities to reduce emissions that have been implemented
at U.S. airports. Appendix V provides more information on some
airports‘ voluntary efforts to reduce emissions.
Figure 1: Examples of Activities to Reduce Emissions:
[See PDF for image]
[End of figure]
Note: The information presented in this chart is not meant to include
all activities for reducing emissions at airports. According to FAA,
there are gaps in understanding how such activities effect various
emissions, including various interrelationships among the emissions and
their effects.
Most States Have Not Included Airports in Their Emission Control
Strategies:
Only 3 of the 13 states with major commercial airports in nonattainment
areas--California, Texas, and Massachusetts--have targeted airports
for emission reductions. The remaining states have not included
emission reductions at airports as part of their strategies for
bringing nonattainment areas into compliance with the Clean Air Act‘s
ambient air quality standards because they have attempted to achieve
sufficient reductions from other pollution sources. Officials from
these states noted that EPA has the authority to set emission standards
for aircraft and nonroad vehicles, including ground support equipment
at airports, which preempts the states‘ regulation of these sources.
California and Texas face major ozone nonattainment problems--
California in the Los Angeles metropolitan area and Texas in the
Dallas-Fort Worth and Houston metropolitan areas. According to air
quality officials from both states, even after imposing all of the
traditional emission control measures available, such as vehicle
emission inspections, the three metropolitan areas still may not be
able to reach attainment status for ozone by the 2010 deadline for Los
Angeles and by the 2005 and 2007 deadlines for Dallas-Fort Worth and
Houston, respectively. Despite potential legal challenges from
airlines, both California and Texas turned to airports for additional
emission control measures. Texas has negotiated an agreement with the
Dallas/Fort Worth International and Houston airports and the airlines
that serve them to reduce emissions attributable to ground support
equipment by 90 percent. California has reached a similar agreement
with the major airlines serving the five commercial airports in the Los
Angeles nonattainment area to reduce emissions from ground support
equipment.
California‘s efforts to cut ground support equipment emissions in the
Los Angeles area are part of a statewide campaign to reduce airport
pollution. In addition to using its limited authority under the Clean
Air Act to implement airport-related emission reductions, the state has
also employed a certification process provided for in federal
law.[Footnote 9] Under this provision, before FAA can approve a grant
for any new airport, new runway, or major runway extension project, the
governor must certify that the project complies with applicable air and
water quality standards. California has developed criteria for
determining whether a proposed airport expansion project would have an
impact on the environment, including air quality. Unlike other states,
California uses the criteria as a mandatory condition for project
certification. If the project exceeds one of the criteria--by
increasing the number of passengers, aircraft operations, or parking
spaces and thereby producing an impact on the environment--the airport
is required to implement emission mitigation measures in order to
attain certification. Thus far, three airports--Sacramento
International, San Jose International, and Ontario International--have
initiated expansion projects that were required to comply with the
certification standards. However, in a legal opinion issued in August
2000, FAA‘s Office of Chief Counsel stated that California has no legal
authority to impose operational limitations on airports through the
certification process. According to FAA, California has not publicly
responded to the opinion. A California air quality official told us
that the state disagrees with the opinion and does not plan to change
its certification process.
In 1999, Boston Logan International Airport began building a new runway
to reduce serious flight delays. As a condition for approving the
project, the state required the airport to cap emissions at 1999 levels
(referred to as a ’benchmark“) because it has determined that the
airport is a significant contributor to Boston‘s serious ozone problem.
To stay within the limit, the airport had considered reduction
strategies that include charging higher landing fees during peak
operating times to reduce congestion and the resulting emissions. Now
that air traffic and emission levels have fallen off since the events
of September 11, 2001, the operator of the Boston airport, the
Massachusetts Port Authority, believes that peak pricing and other
emission reduction strategies will not be needed for several years to
keep emissions below 1999 levels. The Massachusetts Port Authority,
however, continues to work with airport tenants to implement voluntary
emission reduction strategies. More information on states‘ efforts to
reduce emissions appears in appendix IV.
Proposed Airport Projects Have Been Able to Conform to Current Air
Quality Standards:
In addition to facing control measures as part of state strategies to
attain the Clean Air Act‘s ambient air quality standards, airports must
also submit most major construction project proposals for federal
environmental review, which includes an evaluation of the proposed
project‘s impacts on air quality. The National Environmental Policy Act
and the Clean Air Act require that FAA perform environmental reviews of
all airport projects that involve the federal government, such as the
construction of federally subsidized runways. As part of this review
process, FAA must determine that emissions from projects at airports in
nonattainment and maintenance areas do not adversely interfere with
states‘ plans for the areas to reach attainment.
We examined all environmental reviews conducted by FAA at major
commercial airports[Footnote 10] in nonattainment areas during the 3-
year period 1998 to 2001. These reviews include those required by the
National Environmental Policy Act as well as those required under the
Clean Air Act to ensure compliance with state implementation plans for
achieving ambient air quality standards. During the period, FAA
performed such reviews at 24 of the 26 major commercial airports in
nonattainment areas. The projects reviewed included developing runways,
expanding passenger terminals and air cargo and airline support
facilities, and developing roadways and intersections on airport
property.
Our analysis of airport environmental review documents showed that
while air quality issues are a significant consideration for airports
planning major development projects, emissions have not been a major
obstacle in gaining approval for projects; however, FAA is concerned
that increasing emissions from operations could jeopardize the approval
of future expansion projects. In 12 of the 24 cases we examined, the
environmental reviews stated that the airport expansion projects would
not affect air quality in the regions. The environmental reviews for 7
of these 12 projects estimated that emissions would decrease as a
result of improvements in operational efficiency. For example, John F.
Kennedy International Airport expected its proposed passenger terminal,
air cargo, and airline support facilities expansion project to decrease
the emission of nitrogen oxides by 207.2 tons per year by 2010 (about a
5-percent reduction in total airport nitrogen oxide emissions[Footnote
11]) because the project was expected to decrease the amount of time
aircraft take to taxi from the runway to the terminal. For 8 of the
projects, significant project-related emission increases resulted from
construction activities and, although the increases were temporary, the
airports were required, under EPA‘s general conformity rules, to adopt
mitigation measures to allow FAA to determine that the projects
complied with state implementation plans. In only 3 cases, was a
significant permanent rise in emissions expected to result from the
project. Five airports --Atlanta Hartsfield, Dallas/Fort Worth
International, Los Angeles International, San Jose International, and
Oakland International--were required to reduce emissions from other
sources in order to mitigate the effects of the increased emissions
expected from either project construction or operations related to a
project. Atlanta Hartsfield, for example, committed to reduce emissions
associated with construction by requiring construction equipment to be
operated with catalytic converters that would reduce emissions and by
using a massive conveyor system to haul fill material, thereby
minimizing the use of trucks.
Although most recent airport construction projects in nonattainment
areas met the requirements of the Clean Air Act, FAA officials noted
that in the future, approval of some projects in these areas could be
in jeopardy if state implementation plans did not make adequate
allowances for emissions that could result from growth in aviation-
related activities or include provisions for airports to offset future
increases. FAA noted that approval of projects is complicated by the
fact that it is often difficult to determine if a development project
complies with the state implementation plan because some plans do not
contain an aviation emission component, while other plans use a model
or methodology to calculate aviation emissions that is incompatible
with FAA‘s model to determine a project‘s compliance with air quality
requirements. In addition, FAA noted that approval of some projects may
be complicated by an increased focus on air quality by community groups
that oppose airport projects, the insistence of EPA and/or state and
local air quality agencies on mitigation measures when FAA has
determined that proposed projects will reduce emissions, and the
general need to better understand aviation emissions. According to FAA,
approval of airport construction projects may be further complicated by
differences among federal and state air quality standards, especially
when state standards are more restrictive, and differences among EPA
and state/local air quality agencies on the appropriate analysis and
mitigation measures. Also, FAA officials have noted an increasing trend
for communities to demand under the National Environmental Policy Act
that FAA undertake and disclose the effects of air toxics and health
effects studies. Finally, although emissions from construction
activities are temporary, if they are above allowable levels, FAA is
required to undertake and issue a full determination that the project/
activity will conform to the state implementation plan.
Federal and State Programs for Reducing Airport Emissions:
FAA, EPA, and some states have developed programs to reduce emissions
from aviation-related activities and established jointly with the
aviation industry a process that has tried to reach a voluntary
consensus on how to further reduce emissions. For example, as part of
its Inherently Low-Emission Airport Vehicle Pilot Program, required by
Congress in 2000,[Footnote 12] FAA awarded federal grants of up to $2
million to each of 10 airports[Footnote 13] for alternative fuel
vehicles and infrastructure. FAA is using the program to evaluate the
vehicles‘ reliability, performance, and cost-effectiveness in the
airport environment. FAA initially anticipated that the program would
reduce emissions by 22,584 tons of ozone, 314,840 tons of carbon
monoxide, 384 tons of particulates, and 924 tons of sulfur dioxide
during the projected lifetime of the airport equipment. To achieve this
reduction, FAA expected the airports to purchase about 1,600 pieces of
alternative fuel ground support equipment and 600 alternative fuel
ground access vehicles, such as airport cars, buses, and shuttles. As
of October 2002, FAA reported a slower-than-expected start-up of the
program, with only five airports (Baltimore-Washington International,
Dallas/Forth Worth International, Baton Rouge Metropolitan, Sacramento
International, and Denver International) making notable progress on the
program. According to FAA, the effects of the events of September 11,
2001, have caused unforeseen delays and acquisition deferrals for many
low-emission vehicle projects, particularly those that rely on airline
financing to convert ground support equipment to alternative fuels.
Although FAA plans to provide $17.3 million for the Inherently Low-
Emission Airport Vehicle Pilot Program, airports and air carriers
expressed the need for more federal funding to reduce emissions. Some
airports have said that they would like flexibility in how the Airport
Improvement Program[Footnote 14] or passenger facility charge[Footnote
15] funds can be used to mitigate or offset emissions from expansion
projects. For instance, Sacramento Airport officials stated that they
would like the city‘s light rail system to be connected to the airport
to reduce emissions from ground access vehicles. However, Airport
Improvement Program or passenger facility charge funds cannot be used
for emission mitigation projects located outside airport property.
According to FAA, DOT‘s Congestion Mitigation and Air Quality grant
program can be used to finance emission mitigation projects located
outside of airport property.
Some states also have emission reduction assistance programs that are
available to airports. The California Environmental Protection Agency
developed the Carl Moyer Program, which is an incentive-based program
that covers the incremental cost of purchasing airport vehicles with
cleaner engines, including ground support equipment at airports. The
program taps into available new environmental technologies to help the
state advance clean air goals. It provides funds to private companies
or public agencies to offset the incremental cost of purchasing the
cleaner engines. The Texas Natural Resource Conservation Commission
also established incentive funds for emission reduction efforts,
similar to California‘s program. As in California, the funds are not
specifically designated for emission reductions at airports, but air
carriers that are not participating in the agreement with the
Commission to voluntarily reduce ground support equipment emissions can
receive grants to convert their ground support equipment. Airlines that
are part of the voluntary agreement would not be eligible for the
incentive funds.
Some airport operators we spoke with would like EPA to set up a process
in which airports could obtain ’credit“ for the amount of emissions
reduced by their voluntary efforts; the credits can be ’banked“ by the
airport to use at a future date to offset expected increases in
emissions or they can be sold to other nonairport entities in the
region that are required to offset emissions. The airport operators
also indicated that having such a program encourages airport sponsors
to undertake efforts to reduce emissions. Such an emission credit
program is available in Washington State. Airports there can implement
emission reduction efforts and obtain emission credits, which they can
save and use to offset increased emissions from future expansion
projects. Thus far, such a system has been adopted at one location,
Seattle-Tacoma International Airport, which worked with the local clean
air agency to establish a credit program for voluntary emission
reduction actions. If airports are not allowed to save emission
credits, any voluntary reductions will lower their emission baseline,
which is used to calculate the impact of future emissions, and limit
their options for any emission reductions required to obtain approval
for future projects.[Footnote 16] Because of this situation, some
airport officials told us that they have waited to initiate emission
reduction efforts until the efforts are needed to gain approval for an
expansion project. EPA encourages airports to contact their state and
local air quality agencies and negotiate emission credit agreements, as
was done by Seattle-Tacoma International Airport. However, according to
FAA officials, this localized case-by-case approach to issuing emission
credit is inefficient. Instead, FAA supports a consistent national
approach that it believes would lessen the burden on airports to obtain
emission credits from their respective states.
In 1998, FAA and EPA established a process--known as the stakeholders
group--which includes representatives from state environmental
agencies, airports, air carriers, and the aerospace industry to discuss
voluntary efforts to lower nitrogen oxides and other emissions. They
established the process because federal and industry officials told us
that the current approach to reducing emissions--uncoordinated efforts
by individual airports and states--was inefficient and possibly
ineffective from a nationwide perspective. For example, some federal
officials believe the current approach encourages airlines to move
their more polluting equipment to airports that do not require cleaner
vehicles, and the aviation industry is concerned about the impact that
differing state requirements might have on their operations. According
to EPA, another reason for establishing the process was concerns by
EPA, state environmental agencies, and environmental groups about
international emissions standards, particularly standards for nitrogen
oxides.
The stakeholders group decided to focus on achieving lower aircraft
emissions through a voluntary program because this strategy offered the
potential for achieving desired goals with less effort and time than a
regulatory approach. Initially, the group‘s discussions focused on
emission reduction retrofit kits, which could be applied to some
existing aircraft engines, but this was found to not be technically
feasible. However, as the process evolved, the stakeholders expanded
the focus to evaluating various emission reduction strategies for
aircraft and ground support equipment. According to participants, the
group is currently working to establish a national voluntary agreement
for reducing ground service equipment emissions in the nearer term,
similar to the agreement in California. In the longer term, the group
is considering reductions in aircraft emissions through an approach
known as ’environmental design space“ that recognizes the need to
balance such reductions with other competing goals such as noise
reduction, while assuring safety and reliability. FAA also noted that
airport operators used the stakeholders group to highlight the need for
more guidance on the process for ensuring that federal actions, such as
the construction of new runways, conform to the appropriate state
implementation plans. FAA and EPA issued guidance on the process in
September 2002. The group had also commissioned a study to establish a
baseline of aviation-related emissions and another study of options for
reducing them. However, the study will not be completed because of
resource constraints, according to participants.
FAA noted that the progress of the stakeholders group has been impeded
by the impact of the events of September 11, 2001, on the airlines and
the complex nature of addressing all stakeholders‘ viewpoints to
achieve consensus on a framework that can be applied nationally. The
activities of the group were suspended after September 11, but resumed
in May 2002. According to one member of the group, many participants
have been frustrated by the group‘s slow progress, but they hope to
define a nationwide program to reduce emissions from ground service
equipment in 2003 and continue discussion of aircraft emission
reduction options. However, the group has not defined specific
objectives or established time frames for achieving its goal of
reducing aviation-related emissions. Furthermore, the group‘s
activities may be limited by the financial situation of participating
air carriers.
New Air Quality Standards Will Pose a Challenge to Some States and
Airports:
In late 2003, EPA plans to begin implementing a more stringent standard
for ozone emissions, which could require more sources, including
airports, to tighten controls on nitrogen oxides and some types of
volatile organic compound emissions, which contribute to ozone
formation. The new standard calls for concentrations of ozone not to
exceed .08 parts per million over 8-hour blocks of time; the current
standard requires concentrations not to exceed .12 parts per million
over 1-hour blocks of time. Some state air quality officials that we
spoke to believe that the continued growth of aviation-related ozone
precursor emissions, coupled with such emissions from other sources,
may affect their ability to meet to the new standard.
The implementation of the 8-hour standard for ozone could have
significant implications for airports. Currently, 26 major commercial
airports are located in nonattainment areas for ozone. EPA has yet to
designate and classify which areas will not be in attainment with the
8-hour standard. However, the agency estimates that under the 8-hour
standard, areas containing 12 additional airports could be designated
as nonattainment areas. Airports in these areas could be constrained in
their ability to initiate development projects if they did not comply
with the state implementation plans. EPA, however, believes that the
new 8-hour standard provides an opportunity for the airports and the
states that have not addressed airport emissions in their state
implementation plans to identify airport emission growth rates when new
plans are developed under the 8-hour standard.[Footnote 17]
Among the 13 state air quality officials we surveyed, 5 expect that
aviation emissions will somewhat or moderately hinder their state‘s
ability to demonstrate compliance with EPA‘s new 8-hour ozone emission
standard, and 3 stated that aviation emissions will greatly hinder
their ability to comply.[Footnote 18] Some of these officials also said
they are uncertain how their state will meet the new standards. Because
the new 8-hour standard is more stringent, the states will need to
develop more rigorous and innovative control measures for all sources
and may have to rely on the federal government to reduce emissions from
sources over which the state does not have jurisdiction, such as
aircraft engines.
Two Countries Have Introduced Emission-Based Fees:
Other countries use many of the same measures to reduce emissions at
airports as the United States and, in addition, two countries have
imposed landing fees based on the amount of nitrogen oxide emissions
produced by aircraft. Emission-based landing fees and other market-
based methods are currently being studied by ICAO and the former have
been implemented in Switzerland and Sweden.[Footnote 19] Emission-based
landing fees, although considered for Boston Logan International
Airport, have not been implemented at any U.S. airports and many in the
U.S. aviation community question their effectiveness.
ICAO established a working group to identify and evaluate the potential
role of market-based options, including emission charges, fuel taxes,
and emission-trading regimes,[Footnote 20] in reducing aviation-
related emissions. Thus far, the working group has concentrated on
carbon dioxide emissions and has concluded that the aviation sector‘s
participation in an emission-trading system would be a cost-effective
measure to reduce carbon dioxide in the long term. The ICAO Assembly,
the organization‘s highest body, has endorsed the development of an
open emission-trading system for international aviation and has
instructed its Committee on Aviation Environmental Protection to
develop guidelines for open emission trading. The ICAO committee has
also been studying emission charges or taxes as well as evaluating
voluntary programs to reduce emissions. ICAO‘s current policy, adopted
in 1996, recommends that emission-based fees be in the form of charges
rather than taxes and that the funds collected should be applied to
mitigating the impact of aircraft engine emissions.
Switzerland was the first country to implement a market-based system
for reducing aviation-related nitrogen oxides and volatile organic
compound emissions. In 1995, the Swiss federal government enacted
legislation that allowed airports to impose emission charges on
aircraft. In September 1997, the Zurich airport used this authority to
establish emission-based landing fees as an incentive for air carriers
to reduce emissions from aircraft using the airport. The use of
emission-based landing fees has expanded to other airports in
Switzerland and Sweden. The Geneva, Switzerland, airport implemented an
emission-based landing fee similar to the fee scheme used in the Zurich
airport in November 1998. Several Swedish airports also implemented
emission fees after the Swedish Civil Aviation Administration approved
such charges in January 1998. Similar to the system at Zurich airport,
the Swedish airports reduced the landing charges so that income from
emission charges is not considered an additional source of revenue.
The establishment of emission-based landing fees in Switzerland and
Sweden has affected the operations of airlines with frequent flights to
airports in these countries. According to a representative of a jet
engine manufacturer, a Swiss airline purchased a number of new aircraft
equipped with engines designed to emit lower amounts of nitrogen
oxides. The representative said that the airline wanted the engines in
order to reduce its landing fees at Swiss airports. However, the
airline filed for bankruptcy in 2001 and has ceased operations. Only a
few other airlines have expressed interest in equipping their new
aircraft with engines that emit less nitrogen oxides because they are
more expensive and less fuel-efficient and have higher operating costs.
As of December 2002, no other airlines had purchased such engines.
No conclusive studies on the effectiveness of these emission-based
landing fees have been completed. According to the Zurich Airport
Authority, results of the emission-based landing fee can be shown only
in the long term, making it difficult to quantify whether emissions
such as nitrogen oxides or volatile organic compounds have been
reduced. (FAA officials stated that the effects of emission-based fees
can be estimated using existing models. For example, a 2001 ICAO
working paper on market-based options for reducing carbon dioxide
emissions found that enroute emissions charges would be insufficient to
meet reduction targets.) Nevertheless, an aviation expert said that the
emission-based landing fees have caused airlines to begin considering
the cost of nitrogen oxides and volatile organic compound emissions as
part of their business decisions.
Emission-based landing fees have not been introduced at any U.S.
airports. Boston Logan International Airport considered implementing
such fees to reduce emissions, but a 2001 study commissioned by the
Massachusetts Port Authority, which operates the airport, determined
them to be ineffective.[Footnote 21] The study found that emission-
based landing fees would be a small portion of commercial air carriers‘
operating expenses and would be unlikely to affect their operational,
purchasing, or leasing behavior substantially enough for them to
consider using lower nitrogen-oxides-emitting aircraft and engines.
Thus, the study concluded, the emission-based landing fees would not
significantly induce commercial airlines to use aircraft engines
emitting lower levels of nitrogen oxides.
Improvements in Aircraft and Engine Design Have Reduced Many Aircraft
Emissions, but Nitrogen Oxide Emissions are Increasing:
Although research and development efforts by NASA and aircraft and
engine manufacturers have led to engine and airframe improvements that
have increased fuel efficiency and lowered carbon dioxide and
hydrocarbon emissions, trade-offs among several factors, including
engine performance, have also resulted in increased nitrogen oxide
emissions. Our analysis of data on aircraft emissions during landings
and takeoffs indicates that the newest generation of aircraft engines,
while meeting international standards, can produce considerably more
nitrogen oxide emissions than the older versions they are replacing.
Engine options for some aircraft are now being introduced that reduce
nitrogen oxide emissions. Additionally, NASA has ongoing research into
technologies that could reduce nitrogen oxide emissions from jet
engines to well below current standards. However, aviation industry
representatives are unsure whether the technologies will ever be
developed to the point where they can be incorporated into future
production engines because of uncertainties about funding and other
factors. Given the long lifespan of aircraft, even if the technologies
are developed, it could be decades before enough airplanes are replaced
to have a measurable effect on reducing nitrogen oxides. As a result,
both the environmental and aviation communities have expressed concerns
that emissions from aircraft, particularly nitrogen oxides, need to be
further reduced.
Improvements in Aircraft and Engines Have Reduced Fuel Consumption and
Most Emissions:
Improvements in jet engine design have led to increases in fuel
efficiency and reductions in most emissions, particularly emissions
from aircraft flying at cruise altitudes. Historically, the
improvements in fuel consumption for new aircraft designs have averaged
about 1 percent per year. The aviation industry and NASA, which are
developing fuel reduction technologies, expect this rate to continue
for the next two decades. Air carriers‘ desire to control fuel costs
provided the impetus for these efforts. (Appendix VI provides a brief
overview of fuel reduction technologies.):
According to aircraft design experts, fuel consumption is the single
biggest factor affecting the amount of most aircraft emissions. Table 1
shows the amount of emissions produced by a typical aircraft turbine
engine during cruising operations for each 1,000 grams of fuel burned.
Table 1: Aircraft Turbine Engine Emission Amounts during Cruising Per
1000 Grams of Fuel Burned:
Type of emissions: Carbon dioxide; Amount of emissions (in grams):
3,200.
Type of emissions: Water; Amount of emissions (in grams): 1,200.
Type of emissions: Nitrogen oxides (as nitrogen dioxide); Amount of
emissions (in grams): 15.
Type of emissions: Carbon monoxide; Amount of emissions (in grams): 1.
Type of emissions: Sulfur oxides; Amount of emissions (in grams): 1.
Type of emissions: Hydrocarbons (as methane); Amount of emissions (in
grams): 0.20.
Type of emissions: Soot (as carbon); Amount of emissions (in grams):
0.02.
[End of table]
Source: National Research Council.
Note: For Greener Skies, Reducing Environmental Impacts of Aviation
(Washington, D.C.: National Academy Press, 2002).
According to aviation experts, new aircraft designs are reducing carbon
dioxide emissions by about 1 percent per year--the same rate at which
fuel consumption is being reduced. ICAO expects this carbon dioxide and
fuel reduction trend to continue for the next 20 years. Carbon monoxide
and hydrocarbon cruise emissions are declining even faster than the
fuel reduction rates. These emissions, which are formed when a portion
of the fuel is only partially combusted, are much easier to minimize
with the hotter engine temperatures of the new more fuel-efficient
engine designs.
New Aircraft Designs Produce Significantly More Nitrogen Oxides during
Landings and Takeoffs:
A byproduct of the improvements in jet engine design has been an
increase in nitrogen oxide emissions during landings and takeoffs and
while cruising, according to aviation industry experts. The new engine
designs are capable of operating at higher temperatures and producing
more power with greater fuel efficiency and lower carbon monoxide
emissions. However, as engine-operating temperatures increase so do
nitrogen oxide emissions. This phenomenon is most pronounced during
landings and takeoffs, when engine power settings are at their highest.
It is during the landing/takeoff cycle that nitrogen oxide emissions
have the biggest impact on local air quality.
Our analysis of aircraft landing/takeoff emissions shows that newer
aircraft produce considerably more nitrogen oxides than older models.
We identified examples of aircraft models and engines introduced in the
last 5 years and compared their emissions with emissions from older
aircraft they might replace.[Footnote 22] We found, for example, that
although the newer Boeing 737 series aircraft are more fuel-efficient,
are capable of flying longer distances (or with more weight), emit less
carbon monoxide and hydrocarbons, and produce less takeoff noise than
their predecessors, they also produce 47 percent more nitrogen oxides
during landing/takeoff (see table 2).[Footnote 23]
Table 2: Comparison of Emissions during Landing/Takeoff for Older and
the Newest Model Boeing 737s:
Emission: Nitrogen oxides; Average emission (in pounds) per landing/
takeoff: Older Boeing 737: 12.1; Average emission (in pounds) per
landing/takeoff: Newest Boeing 737: 17.8; Change: 47% increase.
Emission: Carbon monoxide; Average emission (in pounds) per landing/
takeoff: Older Boeing 737: 16.8; Average emission (in pounds) per
landing/takeoff: Newest Boeing 737: 10.7; Change: 37% decrease.
Emission: Hydrocarbons; Average emission (in pounds) per landing/
takeoff: Older Boeing 737: 1.2; Average emission (in pounds) per
landing/takeoff: Newest Boeing 737: 1.1; Change: 10% decrease.
[End of table]
Source: GAO.
Note: Landing and takeoff data for U.S. aircraft in 2001 obtained from
AvSoft; emissions calculated using FAA‘s Emissions and Dispersion
Modeling System, version 4.01. See appendix VII for additional
information on our emission calculations and Boeing 737 models and
engines.
Significantly higher emissions of nitrogen oxides during landing/
takeoff for the aircraft introduced in the last 5 years also occur in
the largest aircraft. For example, the Boeing 777, the newest of the
large jets, emits significantly more nitrogen oxides than comparable
older aircraft. Table 3 compares a passenger model Boeing 747-400 with
the Boeing 777 model and engines that it is most comparable to in
seating capacity and range. Even before we adjusted for the greater
seating capacity of the larger Boeing 747-400, we found that the most
comparable Boeing 777--the 200ER model--produces 34 percent more
nitrogen oxide emissions, even though ICAO data shows that the Boeing
777 is quieter and more fuel-efficient than the older aircraft it is
replacing. For example, on a per seat basis, the Boeing 777 can be as
much as 30 percent more fuel-efficient than older model Boeing 747s.
Table 3: Comparison of Boeing 747 and 777 Emissions on a Per Aircraft
Basis:
Emission: Nitrogen oxides; Emission (in pounds) per aircraft during
landing/takeoff: Boeing 747-400: 103.5; Emission (in pounds) per
aircraft during landing/takeoff: Boeing B777-200ER: 124.2; Change: 20
percent increase.
Emission: Carbon monoxide; Emission (in pounds) per aircraft during
landing/takeoff: Boeing 747-400: 47.7; Emission (in pounds) per
aircraft during landing/takeoff: Boeing B777-200ER: 30.4; Change: 36
percent decrease.
Emission: Hydrocarbons; Emission (in pounds) per aircraft during
landing/takeoff: Boeing 747-400: 4.1; Emission (in pounds) per aircraft
during landing/takeoff: Boeing B777-200ER: 2.4; Change: 41 percent
decrease.
[End of table]
Source: GAO.
Notes: Landing and takeoff data for U.S. aircraft in 2001 obtained from
AvSoft; emissions calculated using FAA‘s Emissions and Dispersion
Modeling System, version 4.01. See appendix VII for additional
information on our emission calculations and details about these
aircraft and their contribution to the 2001 U.S. commercial fleet
totals.
The Boeing B777-200ER data is the weighted average (based on 2001
landings and takeoffs) for three different engines. The nitrogen oxides
and other emission characteristics of these engines vary significantly.
As shown in table 4, the percentage increase in nitrogen oxides during
landing/takeoff is 57 percent when the two aircraft are compared on a
per seat basis (the amount of emissions divided by the number of seats
on the aircraft).
Table 4: Comparison of Boeing 747 and 777 Emissions on a Per Seat
Basis:
Emission: Nitrogen oxides; Emission (in pounds) per seat during
landing/takeoff: Boeing 747-400: 0.287; Emission (in pounds) per seat
during landing/takeoff: Boeing B777-200ER: 0.451; Change: 57 percent
increase.
Emission: Carbon monoxide; Emission (in pounds) per seat during
landing/takeoff: Boeing 747-400: 0.132; Emission (in pounds) per seat
during landing/takeoff: Boeing B777-200ER: 0.110; Change: 16 percent
decrease.
Emission: Hydrocarbons; Emission (in pounds) per seat during landing/
takeoff: Boeing 747-400: 0.011; Emission (in pounds) per seat during
landing/takeoff: Boeing B777-200ER: 0.009; Change: 20 percent decrease.
[End of table]
Source: GAO.
Note: Landing and takeoff data for U.S. aircraft in 2001 obtained from
AvSoft; emissions calculated using FAA‘s Emissions and Dispersion
Modeling System, version 4.01. GAO analysis of AvSoft 2001 landing and
takeoff data for U.S. aircraft. Emissions were calculated using FAA‘s
Emissions and Dispersion Modeling System, version 4.01.
EPA and FAA regulate nitrogen oxide emissions and other emissions for
U.S. commercial aircraft by requiring engine designs to meet ICAO
standards for these emissions. Prior to production, all new engine
designs are tested to determine the amount of nitrogen oxides and other
emission characteristics.[Footnote 24] Only engines that meet the
standards are certified for production. ICAO standards for nitrogen
oxides were first adopted in 1981 and more stringent standards were
adopted in 1993 (20 percent more stringent, effective 1996) and again
in 1998 (16 percent more stringent, effective 2004). ICAO working
groups are assessing whether or not the standards for nitrogen oxide
emissions should be made more stringent than the standards that will
take effect in 2004. Options being considered could make the standards
between 5 percent and 30 percent more stringent between 2008 and 2012.
Under ICAO standards, newly designed engines and modified versions of
older designs are allowed to produce significantly more nitrogen oxides
than their predecessors. This is because the ICAO standards recognize
that nitrogen oxides emissions are a function of engine power
capability and operating pressure. Therefore, the standards allow for
higher nitrogen oxide emissions for engines that (1) operate at higher-
pressure ratios, which increase their fuel efficiency and (2) produce
more power. For example, the most common updated Boeing 737-700
aircraft model and engine produces 41 percent more nitrogen oxides
during landing/takeoff than the most common older version it is
replacing (see table 5). Both engines will meet the new ICAO standard,
which will go into effect in 2004 (the old engine betters the standard
by about 15 percent, the new one by about 10 percent). A lower nitrogen
oxide producing engine is available for the Boeing 737-700. This engine
produces 18.5 percent more nitrogen oxides than the older Boeing 737-
700 that it is most comparable to in power and versatility.[Footnote
25] However, this engine is less common in the fleet that then the more
powerful one that offers more aircraft versatility. The database we use
shows that in the U.S. fleet there were 8 Boeing 737-700s with the
lower nitrogen oxides emitting engines and 118 with the more powerful
engines.
Table 5: Comparison of Power, Engine Operating Pressures, and Nitrogen
Oxides Emissions for Two Models of Boeing 737s:
Characteristic: Engine variant; Older model B737-300: CFM56 3B-1;
Newest model B737-700: CFM56 7B-22.
Characteristic: Power (thrust) per engine; Older model B737-300: 89
kiloNewtons; Newest model B737-700: 101 kiloNewtons.
Characteristic: Engine operating pressure ratio; Older model B737-
300: 22.4; Newest model:B737-700: 24.41.
Characteristic: Landing/takeoff nitrogen oxide emissions; Older
model B737-300: 10.72 pounds; Newest model B737-700: 15.08 pounds.
[End of table]
Source: GAO.
Note: Landing and takeoff data for U.S. aircraft in 2001 obtained from
AvSoft; emissions calculated using FAA‘s Emissions and Dispersion
Modeling System, version 4.01. See appendix VII for additional
information on our calculations and details about these aircraft.
There is an ongoing debate between the aviation and environmental
communities over the best method for developing nitrogen oxide
certification standards. Some in the aviation community want to
maintain the current system under which the standards are made more
stringent only when the engine manufacturers have produced engines that
meet the new standards and new standards only apply to newly certified
engines.[Footnote 26] (An industry official identified only two older
types of engines that would not meet the more stringent 2004 nitrogen
oxide standards.) Officials for the aviation industry said that it
would be inadvisable to force more aggressive nitrogen oxide standards
because new engine development programs are already complex and have
many business and schedule risks. These officials added that the
environmental regulatory process lacks cost-benefits data to defend a
more aggressive approach that could result in extreme financial harm
for engine and aircraft manufacturers if the approach delayed a new
program. Further, some believe that if reductions in nitrogen oxides
were to become a higher priority, it would be better to have market-
based incentives that reward lower nitrogen oxide emissions than have
aggressive and rigid pass/fail regulatory barriers.
Moreover, some federal, state, and local environmental officials
believe more incentives are needed to reduce aircraft nitrogen oxide
emissions beyond the ICAO certification standards that are to take
effect in 2004. They say that the current system gives little value to
reducing nitrogen oxides in the many trade-offs among emissions, fuel-
consumption, and other factors made during engine design. They reason
that if there were more incentives to reduce nitrogen oxide emissions
beyond the certification requirements, these incentives would
accelerate innovations that minimize degradations in other engine
performance characteristics such as fuel efficiency.
While NASA and engine manufacturers have made continuous improvements
for decades in technologies that have improved fuel efficiency,
decreased noise, and decreased all emissions including nitrogen oxides,
the design of the newest generation of engines has resulted in trade-
offs that favor fuel efficiency and increase nitrogen oxides. Two
engine manufacturers have responded to this problem by developing
options for several new engines that reduce nitrogen oxides. (General
Electric has developed a ’dual annular combustor“ technology for one of
its CFM56 engines and Pratt Whitney has developed a ’Technology for
Affordable Low NOx“ [TALON] for some of its engines. This TALON
technology is being used on some aircraft in the U.S. fleet.) According
to NASA, about 100 engines using one of these technology options are
currently in service on passenger and cargo aircraft. According to
industry officials, knowledge gained from developing these options is
contributing to ongoing nitrogen oxide reduction research.
Potential Success of Efforts to Reduce Aircraft Nitrogen Oxide
Emissions Uncertain:
NASA, in association with jet engine manufacturers and the academic
community, is working on several technologies to reduce nitrogen oxide
emissions, although it is unclear if they can be introduced on
commercial aircraft in the foreseeable future. If successfully
developed and implemented, these technologies could significantly lower
the emission of nitrogen oxides during landing and takeoff in new
aircraft in stages over the next 30 years. However, the development of
more fuel-efficient engines by NASA and the engine manufacturers, which
are resulting in higher nitrogen oxide emissions,[Footnote 27] and the
lack of economic incentives for airlines to support efforts to reduce
nitrogen oxide emissions make the possibility of reaching these goals
uncertain. In the last several years, increases in nitrogen oxide
emissions from the more fuel-efficient engines have outpaced
improvements made to reduce these emissions. Appendix VI provides more
information on research to reduce nitrogen oxide emissions.
Adding to the uncertainty of introducing technologies to reduce
nitrogen oxides is the limited federal funding for this research
effort. NASA officials told us that in the past they developed their
research to the full engine test level before engine manufacturers
would take over responsibility for integrating the improvements into
production-ready engines. However, budget cuts made in their emission
research programs beginning in fiscal year 2000 have resulted in them
ending their research at the engine component level below full engine
testing. Figure 2 shows the funding for this program.
Figure 2: NASA‘s Planned Funding for Nitrogen Oxide Research:
[See PDF for image]
[End of figure]
Note: GAO analysis of information from NASA. Funding amounts are for
the Ultra Efficient Engine Technology Program.
Industry officials and aviation experts agree on the importance of
NASA‘s research and that NASA is focusing on the right mix of near-term
and long-term technologies, but are critical of the amount of funding
dedicated to nitrogen oxide reduction research. NASA‘s research to
reduce nitrogen oxides is a component of its Ultra Efficient Engine
Technology Program. The goal of this program is to develop technologies
that will enable U.S. manufacturers to compete in the global
marketplace for new commercial gas turbine engines. The current program
is funded at $50 million per year. Industry representatives stated that
shrinking budgets have made it difficult for NASA to maintain a level
of effort at a critical mass for each project within the Ultra
Efficient Engine Technology Program. Furthermore, they added that
engine manufacturers could not afford to work with immature technology
when they are engaged in new engine development projects. This is
because new engine developments are tied into projects with the
airlines, and the engines must meet tight cost, schedule, and
performance goals if they are to win market share.
The Ultra Efficient Engine Technology Program is a scaled-back version
of a larger aeronautical research program that was terminated in fiscal
year 2000. NASA officials said that budget cuts have reduced research
in the current program by about 40 percent from the previous program.
In the previous program, research was typically developed to the point
where the technology was integrated into the full engine system. In the
current program, funding is only available to incorporate the
technology into engine components. The National Research Council has
concluded that the current funding level jeopardizes achieving program
results and does not carry the research far enough for the engine
manufacturing industry to readily adopt it. [Footnote 28]
As a result of the uncertainties surrounding emission reduction
technology research, it is unclear when new production aircraft will,
in the aggregate, start lowering landing/takeoff nitrogen oxide
emissions on a per seat basis during the landing/takeoff cycle. Because
of the 30-year projected life of new commercial aircraft, it could take
decades before future new aircraft can contribute to nitrogen oxide
reductions.
Concerns Over Emissions from Aircraft:
Both the environmental and aviation communities have voiced concerns
about the need to better control the growth of aircraft emissions,
particularly nitrogen oxides. Air quality officials from the 13 states
that have airports in nonattainment areas told us that emission
standards for aircraft should be made more stringent for a number of
reasons. For example, several of those officials said that available
control measures for other air pollution sources have been nearly
exhausted. They noted that aircraft have not been as strictly regulated
as other sources, such as automobiles, and that reductions from
aircraft may be needed in the future for some areas to maintain
attainment of the Clean Air Act‘s standards.[Footnote 29] Likewise, in
2002, the National Academy of Science‘s National Research Council
reported that the advances that have led to increased efficiencies in
individual airplanes are not sufficient to decrease the total emissions
of the global fleet, which is increasing in response to accelerating
demand.[Footnote 30] In the same vein, the Intergovernmental Panel on
Climate Change reported in 1999 that ’although improvements in aircraft
and engine technology and in the efficiency of the air traffic control
system will bring environmental benefits, these will not fully offset
the effects of the increased emissions resulting from the projected
growth in aviation.“:
Concerns about aircraft emissions have prompted calls for an improved
approach for controlling them. For example, the National Research
Council has recommended[Footnote 31] that the U.S. government carry out
its responsibilities for mitigating the environmental effect of
aircraft emissions and noise with a balanced approach that includes
interagency cooperation in close collaboration with the private sector
and university researchers. The Council emphasized that the success of
this approach requires commitment and leadership at the highest level
as well as a national strategy and plan that, among other things,
coordinates research and technology goals, budgets, and expenditures
with national environmental goals. Along the same lines, a recent
industry article on the environmental effectiveness of ICAO emission
standards suggested that a programmatic framework is required to guide
the development of a consensus on policy options for further reducing
aircraft emissions.[Footnote 32] Among the elements of the framework
would be establishing the environmental need, the technical capability,
the economic viability, and the regulatory consistency of each option.
Conclusion:
Aviation‘s impact on local air quality is expected to grow as a result
of projected increases in air travel. In addition, more attention will
be focused on finding additional ways to reduce emissions from airports
to enable localities to meet more stringent ozone standards, which go
into effect in late 2003. In 1998, FAA, EPA, and industry officials
established a stakeholders group to develop and implement a voluntary,
nationwide program to reduce aviation-related nitrogen oxide emissions
because they found the current approach--uncoordinated efforts by
individual airports and states--inefficient for air carriers and
potentially ineffective in reducing emissions nationwide. However, the
stakeholders group has progressed slowly because of the complex nature
of achieving consensus on all issues and, thus far, has not defined
specific objectives or established time frames for achieving emissions
reductions.
Despite its participation in the stakeholder group, FAA has not
developed a long-term strategic framework to deal with these
challenges. Moreover, FAA lacks a thorough study on the extent and
impact of aviation emissions on local air quality. Without such
management tools, FAA cannot assess the status or the effectiveness of
its efforts to improve air quality. The study on aviation emissions
prepared by the Intergovernmental Panel on Climate Change on aviation‘s
effect on the global atmosphere provides a model for a study that FAA
could perform to develop baseline information and lay a foundation for
a strategic framework. Such a study could accomplish the goals of the
study that the stakeholders group commissioned, but never completed, as
well as create an opportunity for making public the substance of its
deliberations and for incorporating this substance in a plan for
reducing emissions. Once completed, such a study would provide baseline
information for setting goals and time frames to measure progress in
reducing aviation-related emissions.
Recommendation for Executive Action:
We recommend that the Secretary, DOT, direct the Administrator of FAA,
in consultation with the Administrator of EPA and Administrator of
NASA, to develop a strategic framework for addressing emissions from
aviation-related sources. In developing this framework, the
Administrator should coordinate with the airline industry, aircraft and
engine manufacturers, airports, and the states with airports in areas
not in attainment of air quality standards. Among the issues that the
framework should address are:
* the need for baseline information on the extent and impact of
aviation-related emissions, particularly nitrogen oxide emissions;
* the interrelationship among emissions and between emissions and
noise;
* options for reducing aviation-related emissions, including the
feasibility, cost, and emission reducing potential of these options;
* goals and time frames for achieving any needed emission reductions;
* the roles of NASA, other government agencies, and the aviation
industry in developing and implementing programs for achieving needed
emission reductions; and:
* coordination of emission reduction proposals with members of ICAO.
Upon its completion, the Administrator, FAA, should communicate the
plan to the appropriate congressional committees and report to them on
its implementation on a regular basis.
Agency Comments:
We provided a draft of this report to the Department of Transportation,
the Environmental Protection Agency, and the National Aeronautics and
Space Administration for review and comment. FAA‘s Director, Office of
Environment and Energy, and senior managers in EPA‘s Office of Air and
Radiation provided oral comments and NASA‘s Deputy Director provided
written comments. (See appendix VIII.) The three agencies generally
concurred with our findings and recommendation and provided technical
corrections, which we incorporated as appropriate. In addition, FAA
indicated that our report provides a helpful overview on the aviation
emissions issue from the perspective of multiple stakeholders dealing
with this important issue. FAA also indicated that it is providing
heightened attention to aviation emissions through multiple efforts
including improving data and modeling, working with the international
community on improved standards, and considering alternative approaches
to encourage reductions in aviation-related, ground-based and aircraft
emissions.
As agreed with your office, unless you publicly announce the contents
of this report earlier, we plan no further distribution until 5 days
from the report date. At that time, we will send copies of this report
to interested congressional committees; the Secretary of
Transportation; the Administrator, FAA; the Administrator, EPA; and the
Administrator, NASA. We also will make copies available to others upon
request. In:
addition, the report will be available at no charge on the GAO Web site
at http://www.gao.gov. Please call me at (202) 512-3650 if you or your
staff have any questions concerning this report. Major contributors to
this report are listed in appendix IX.
Sincerely yours,
Signed by Gerald L. Dillingham:
Gerald L. Dillingham
Director, Physical Infrastructure Issues:
[End of section]
Appendix I: Objectives, Scope, and Methodology:
The Chairman of the Subcommittee on Aviation, House Committee on
Transportation and Infrastructure asked us to provide information on
the nature and scope of aviation‘s impact on air quality and the
opportunities that exist to reduce emissions from aviation activities.
Specifically, our research focused on (1) what efforts are being
undertaken to reduce emissions from airport activities and what the
outcomes are of these efforts, (2) what additional efforts are being
undertaken by other countries to reduce aviation-related emissions, and
(3) how improvements in aircraft and engine design have affected
aircraft emissions.
To address the three questions, we interviewed and collected material
from federal officials at the Federal Aviation Administration (FAA),
Environmental Protection Agency (EPA), and National Aeronautics and
Space Administration (NASA). We also interviewed and collected
information from representatives of aviation associations, airlines,
and aircraft manufacturers. We also interviewed officials from
airports, state and local governments, and nongovernmental
organizations. In addition, we reviewed our previous studies and those
of EPA, the Natural Resources Defense Council, the International Panel
on Climate Control, and other aviation-related environmental studies.
To address the first research question, we identified the nation‘s 50
busiest commercial service airports and determined that 43 of these
airports are located in areas designated as nonattainment or
maintenance with respect to requirements of the Clean Air Act. We
reviewed and summarized environmental review documents submitted from
1997 through 2001 for the 43 airports to identify the nature of
emissions from aviation activities and efforts to mitigate them. We
also reviewed applicable sections of state implementation plans for the
13 states in which the 43 airports are located to identify emission-
related sources and determine the nature of mitigation measures being
undertaken. We also conducted comprehensive computer literature
searches to identify the environmental effects of airport operations.
To also address the first research question and to provide information
on the roles and responsibilities of states in relation to aviation-
related emissions, we identified 13 states with airports located in air
quality problem areas and conducted a telephone survey with state air
quality authorities in these areas to obtain information on oversight/
regulatory responsibilities for airport activities. We selected the
states by first identifying the top 50 busiest commercial service
airports on the basis of the number of air carrier landings and
takeoffs in fiscal year 2001. In those states, 26 airports were
identified as being located in areas designated as nonattainment for
ozone. The 26 airports are located in the following 13 states: Arizona,
California, Georgia, Kentucky, Maryland, Massachusetts, Missouri, New
Jersey, New York, Pennsylvania, Texas, Illinois, and Virginia. We
reviewed applicable sections of the Clean Air Act, the National
Environmental Policy Act, states‘ air quality laws, and International
Civil Aviation Organization (ICAO) policies that defined air emissions
standards applicable to aviation-related activities and agencies‘ role
and responsibilities for administering them.
For the first research question, we also selected seven airports for
case studies--Los Angeles International, Boston Logan International,
Sacramento International, Dallas/Fort Worth International, Chicago
O‘Hare International, George Bush International/Houston, and Atlanta
Hartsfield airports. We selected these airports on the basis of
passenger traffic, air quality status, and initiatives undertaken to
deal with airport-related emissions. At each location, we interviewed
and gathered data from officials representing FAA and EPA regional
offices, airports, state and local governments, and nongovernmental
organizations on efforts to reduce emissions.
To address the second research question, we identified international
efforts to reduce aviation-related emissions through our interviews
with FAA, Department of State, ICAO, airport, airline, and
nongovernmental agency officials. We conducted comprehensive computer
literature searches to identify other international airports and to
gather information on the efforts being undertaken by these airports to
reduce aviation-related emissions. Our searches identified aviation
reduction programs at European airports, including Switzerland and
Sweden. We reviewed materials from Swiss and Swedish federal civil
aviation officials on these efforts. We also reviewed proposed European
Unions policies on reducing aviation-related emissions.
Finally, to address the third research question, we interviewed jet
engine manufacturers, NASA researchers, and a university researcher to
obtain information on efforts to reduce aircraft emissions. In
addition, we calculated the landing and takeoff emissions for every
aircraft model and engine combination in the U.S. 2001 commercial fleet
for which data were available. Next, we looked for emission trends by
identifying instances in which new model/engine combinations had been
introduced in the last 5 years. We then compared the landing/takeoff
emission characteristics of these newer aircraft with the emissions of
the older aircraft they were most likely to replace. We identified
examples of emissions trends for new aircraft. We did not perform a
complete analysis of all trends.
In performing this analysis, we obtained the following information on
every aircraft in the U.S. commercial aircraft fleet:
* specific model and engine,
* year 2001 landing/takeoff counts,
* aircraft age, and:
* seating capacity.
This information came from AvSoft, a company that specializes in
detailed data on commercial aircraft. We summarized this information
for each specific model and engine combination. We then calculated the
landing/takeoff emissions for each of these combinations using the
Emissions and Dispersion Modeling System (EDMS), version 4.01 software
developed by FAA for this purpose.
EDMS software calculates landing/takeoff emissions for four major
criteria pollutants: carbon monoxide, volatile organic compounds,
nitrogen oxides, and sulfur dioxides. The calculations take into
account characteristics of specific aircraft model/engine combinations
as well as airport-specific variations in the landing/takeoff cycle. We
calculated the emissions for a representative ’generic“ airport using
EDMS default values. Key values used in our EDMS calculations were:
* emission ceiling height: below 3,000 feet;
* taxi-time: 15 minutes;[Footnote 33] and:
* takeoff weight: EDMS default value.
To determine the reliability of the software and data we used, we
reviewed FAA‘s and AvSoft‘s quality controls, customer feedback
information, and self-assessments. A weakness AvSoft identified with
the data we used was a tendency to undercount the landings/takeoffs for
smaller aircraft (aircraft with 70 seats or less). In addition, the
EDMS software does not have complete information on some aircraft
models and engines (particularly the less common ones). In addition,
the EDMS software does not have complete information on some of the
less common aircraft models and engines. This weakness, however, did
not affect the trends we identified because of the limited use of these
models and engines. On the basis of our experience working with the
data and the software, we determined that the vendors were providing
reliable products for the purposes for which we used them and that
additional data and software reliability assessments were not needed to
support our conclusions.
During the review, the following aviation experts reviewed our methods
and report drafts for accuracy and balance: John Paul Clarke of the
Massachusetts Institute of Technology; Mary Vigilante of Synergy
Consulting, Inc.; and Ian Waitz of the Massachusetts Institute of
Technology.
[End of section]
Appendix II: Types, Amounts, and Impact of Emissions from Aviation-
related Sources:
Most emissions associated with aviation come from burning fossil fuels
that power aircraft, the equipment that services them, and the vehicles
that transport passengers to and from airports. The primary types of
pollutants emitted by aircraft and airport-related sources are volatile
organic compounds, carbon monoxide, nitrogen oxides, particulate
matter, sulfur dioxide, toxic substances such as benzene and
formaldehyde, and carbon dioxide, which in the upper atmosphere is a
greenhouse gas that can contribute to climate change. When combined
with some types of volatile organic compounds in the atmosphere, carbon
dioxide forms ozone, which is the most significant air pollutant in
many urban areas as well as a greenhouse gas in the upper atmosphere.
Particulate matter emissions result from the incomplete combustion of
fuel. High-power aircraft operations, such as takeoffs and climb outs,
produce the highest rate of particulate matter emission due to the high
fuel consumption under those conditions. Sulfur dioxide is emitted when
sulfur in the fuel combines with oxygen during the combustion process.
Fuels with higher sulfur contents produce higher amounts of sulfur
dioxide than low-sulfur fuels. Ozone and other air pollutants can cause
a variety of adverse health and environmental effects.
Aviation-Related Emissions and Sources:
Aircraft emit pollutants both at ground level as well as over a range
of altitudes. At most U.S. airports, aircraft can be a major source of
air pollutants. The major air pollutants from aircraft engines are
nitrogen oxides, carbon monoxide, sulfur dioxide, particulate matter,
and volatile organic compounds. The burning of aviation fuel also
produces carbon dioxide, which is not considered a pollutant in the
lower atmosphere but is a primary greenhouse gas responsible for
climate change. During the landing and takeoff cycles, and at cruising
altitudes, aircraft produce different levels of air pollutant
emissions. Emission rates for volatile organic compounds and carbon
monoxide are highest when aircraft engines are operating at low power,
such as when idling or taxiing. Conversely, nitrogen oxide emissions
rise with an increasing power level and combustion temperature. Thus,
the highest nitrogen oxide emissions occur during aircraft takeoff and
climb out. In addition, aircraft have mounted auxiliary power units
that are sometimes used to provide electricity and air conditioning
while aircraft are parked at terminal gates and these units emit low
levels of the same pollutants as aircraft engines. When flying at
cruising altitudes, aircraft emissions, including carbon dioxide,
nitrogen oxides, and aerosols that are involved in forming contrails
and cirrus clouds, contribute to climate change.
Ground support equipment--which provide aircraft with such services as
aircraft towing, baggage handling, maintenance/repair, refueling, and
food service--is also a source of emissions at airports. This equipment
is usually owned and operated by airlines, airports, or their
contractors. According to EPA, the average age of ground support
equipment is about 10 years, although some of the equipment can last
more than 30 years with periodic engine replacement. Most ground
support equipment is powered by either diesel or gasoline engines, and
older engines pollute more than newer engines. Emissions from ground
support equipment include volatile organic compounds, carbon monoxide,
nitrogen oxides, and particulate matter. At some airports, airlines and
the airport operators are introducing electric and alternative-fuel
powered ground support equipment.
Emissions from passenger vehicles and trucks, referred to as ground
access vehicles, are an important consideration at airports. Heavy
traffic and congestion in and around airports result from the influx of
personal vehicles, taxis and shuttles discharging and picking up
passengers, and trucks hauling airfreight and airport supplies. Such
traffic generates significant amounts of the emissions including carbon
monoxide, volatile organic compounds, and nitrogen oxides. Several
states that we surveyed indicated that automobiles are the major source
of volatile organic compounds, carbon monoxide, particulate matter, and
nitrogen oxides in areas with air quality problems at airports. This
situation has occurred despite the fact that automobile emissions have
been reduced on a per vehicle basis by 98 percent in the past 25 years.
Other sources of emissions at airports include construction activities,
electric power generating plants, and maintenance operations. The air
pollutants emitted by these activities can include particulate matter,
nitrogen oxides, carbon monoxide, and sulfur dioxide.
The information available on the relative contribution of aviation-
related activities to total emissions in an area is limited, but it
indicates that these activities account for a small amount of air
pollution and the proportion attributed to airports is likely to grow
over time. According to EPA, aircraft, which are the only source of
emissions unique to airports, currently account for about 0.6 percent
of nitrogen oxides, 0.5 percent of carbon monoxide, and 0.4 percent of
the volatile organic compounds emitted in the United States from mobile
sources.[Footnote 34] In cities with major airports, aircraft-related
emissions could be higher or lower. In a 1999 study of 19 airports
located in 10 cities,[Footnote 35] EPA found that the proportion of
nitrogen oxide emissions from mobile sources attributed to aircraft
ranged from 0.6 percent to 3.6 percent in 1990. EPA also found that
aircraft accounted for 0.2 percent to 2.8 percent of volatile organic
compound emissions from mobile sources in the 10 cities during the
period. From information contained in a recent study of emissions at
Dallas/Fort Worth International Airport we estimated that aircraft
produced about 3 percent of the nitrogen oxides and about 5 percent of
the carbon monoxide present in the metropolitan area.[Footnote 36] A
1999 study of emissions at Chicago O‘Hare International Airport found
that aircraft and the airport as a whole emitted about 1.6 percent and
2.6 percent of the total volatile organic compound emissions,
respectively, within a 10-mile radius of the airport‘s terminal area
and that nonairport sources were considerably more important to local
air quality than aircraft.[Footnote 37] In addition, a 2001 report on
an air quality initiative for Boston Logan International Airport stated
that the airport contributed less than 1 percent of the ozone-forming
nitrogen oxides and volatile organic compound emissions in the Boston
area.[Footnote 38]
Little research has been done on how much of total area emissions
(called an emissions inventory) are attributable to ground support
equipment and airport-related road traffic, because they are
categorized as nonroad and onroad mobile sources, both of which are
already accounted for in emissions inventories. However, our analysis
of the Dallas/Fort Worth International Airport emissions inventory
indicated that ground support equipment contributed almost 3 percent of
the nitrogen oxide emissions for the area. When all airport-related
emissions are added together, we estimated that the Dallas/Fort Worth
International Airport was responsible for 6 percent of nitrogen oxides
in the metropolitan area.[Footnote 39]
The amount of emissions attributable to each source varies by airport.
According to a 1997 study of four airports,[Footnote 40] ground access
vehicles were the most significant source of mobile emissions,
responsible for 45 to 68 percent of the airports‘ volatile organic
compounds and 27 to 63 percent of the nitrogen oxides emitted from
mobile sources.[Footnote 41] Aircraft operations were found responsible
for the next largest share of emissions from mobile sources, with total
contributions of 15 to 38 percent and 26 to 37 percent for volatile
organic compounds and nitrogen oxides, respectively. Ground support
equipment accounted for 12 to 13 percent of total emissions from
volatile organic compounds and 14 to 20 percent of total nitrogen
oxides from mobile sources at the airports. The report also found that
auxiliary power units for aircraft contributed a small amount of the
emissions from volatile organic compounds and 9 to 20 percent of total
nitrogen oxide emissions from mobile sources. According to the report,
data on particulate matter emissions is not available for aircraft and
auxiliary power units, but ground access vehicles contribute one type
of particulate matter at 1.3 to 2.7 the rate emitted by ground support
equipment.
Health and Environmental Impact of Pollutants:
Some pollutants associated with aviation activities can increase the
risk of a variety of health and environmental impacts. However,
attributing these impacts to any particular source is extremely
difficult because of the multiplicity of pollution sources in urban
areas and the complexities involved in determining the exact causes of
disease and environmental damage. The limited amount of research
available indicates that the impact of the pollutants associated with
airport activities is no more pronounced in the areas near airports
than it is in other urban areas. Nevertheless, the cumulative impact of
pollution from all sources can affect health and the environment.
The pollutant of most concern in the United States and other industrial
countries is ozone, which is formed when nitrogen oxides, some types of
volatile organic compounds, and other chemicals are combined and heated
in the presence of light in the atmosphere. Ozone been shown to
aggravate respiratory aliments, such as bronchitis and asthma. Research
has indicated that certain levels of ozone affect not only people with
impaired respiratory systems, but healthy adults and children as well.
Exposure to ozone for several hours at relatively low concentrations
has been found to significantly reduce lung function and induce
respiratory inflammation in normal, healthy people during
exercise.[Footnote 42]
In addition, according to EPA, there is growing public concern over
emissions of air toxics, which include benzene, formaldehyde, and
particulate matter, because of their potential adverse effects on
health. Some of these emissions are associated with aviation
activities. EPA‘s 1996 National Toxics Inventory indicates that amounts
of hazardous air pollutants produced by aircraft are small relative to
other sources such as on-road vehicles. However, EPA‘s national
estimates are based on limited data, and very little data is available
on toxic and particulate matter emissions in the vicinity of airports.
A study of emissions at Los Angeles International Airport is expected
to shed some light on the subject. In addition, FAA is involved in a
study on identifying methods to measure aircraft particulate matter
emissions.
In the upper atmosphere, aircraft emissions of carbon dioxide and other
greenhouse gases can contribute to climate change. Greenhouse gases can
trap heat, potentially increasing the temperature of the earth‘s
surface and leading to changes in climate that could result in such
harmful effects as coastal flooding and the melting of glaciers and ice
sheets. According to a 1999 report by the Intergovernmental Panel on
Climate Change, conducted under the auspices of the United Nations,
global aircraft emissions in general accounted for approximately 3.5
percent of the warming generated by human activities.[Footnote 43] Jet
aircraft are also the largest source of emissions generated by human
activity that are deposited directly into the upper atmosphere. Carbon
dioxide is the primary aircraft emission; it survives in the atmosphere
for over 100 years and contributes to climate change. In addition,
other gases and particles emitted by jet aircraft including water
vapor, nitrogen oxides, soot, contrails, and sulfate combined with
carbon dioxide can have two to four times as great an effect on the
atmosphere as carbon dioxide alone, although some scientists believe
that this effect requires further study. The Intergovernmental Panel on
Climate Change concluded that aircraft emissions are likely to grow at
3 percent per year and that the growing demand for air travel will
continue to outpace emission reductions achieved through technological
improvements, such as lower emitting jet engines.
Table 6 summarizes the possible environmental effects of the major
pollutants associated with aviation related activities on the human
health and the environment.
Table 6: Health and Environmental Effects of Air Pollutants:
Pollutant: Ozone; Health effects: Lung function impairment, effects on
exercise performance, increased airway responsiveness, increased
susceptibility to respiratory infection, increased hospital admissions
and emergency room visits, pulmonary inflammation, and lung structure
damage (long term).; Environmental effects: Crop damage, damage to
trees, and decreased resistance to disease for both crops and
ecosystems.
Pollutant: Carbon monoxide; Health effects: Cardiovascular effects,
especially in those persons with heart conditions.; Environmental
effects: Adverse health effects on animals similar to effects on
humans.
Pollutant: Nitrogen oxides; Health effects: Lung irritation and lower
resistance to respiratory infections.; Environmental effects: Acid
rain, visibility degradation, particle formation, contribute toward
ozone formation, and act as a greenhouse gas in the atmosphere and,
therefore, may contribute to climate change.
Pollutant: Particulate matter; Health effects: Premature mortality,
aggravation of respiratory and cardiovascular disease, changes in lung
function and increased respiratory symptoms, changes to lung tissues
and structure, and altered respiratory defense mechanisms.;
Environmental effects: Visibility degradation, damage to monuments and
buildings, safety concerns for aircraft from reduced visibility.
Pollutant: Volatile organic compounds; Health effects: Eye and
respiratory tract irritation, headaches, dizziness, visual disorders,
and memory impairment.; Environmental effects: Contribute to ozone
formation, odors, and have some damaging effect on buildings and
plants.
Pollutant: Carbon dioxide, water vapor, and contrails; Health effects:
None.; Environmental effects: Act as greenhouse gases in the atmosphere
and, therefore, may contribute to climate change..
Pollutant: Sulfur dioxide; Health effects: Respiratory irritant.
Aggravates lung problems, particularly for individuals with asthma.;
Environmental effects: Causes damage to crops and natural vegetation.
In presence of moisture and oxygen, sulfur dioxide converts to sulfuric
acid, which can damage marble, iron, and steel.
[End of table]
Source: EPA and FAA.
[End of section]
Appendix III: Federal, State, and International Responsibilities for
Controlling Aviation-related Emissions:
The federal government and the states have responsibility for
regulating sources of aviation emissions under the Clean Air Act, which
was established to improve and protect air quality for human health and
the environment.[Footnote 44] In addition, a United Nations entity, the
International Civil Aviation Organization (ICAO), establishes
international aircraft emissions standards, studies aviation
emissions-related issues, and provides guidance for controlling these
emissions. ICAO includes 188 member countries, which have agreed to
adopt, to the extent possible, standards set by ICAO.
For aircraft or aircraft engine emissions, the Clean Air Act gives EPA
the authority[Footnote 45] to establish emission standards. EPA, in
consultation with FAA, has chosen to adopt the international emissions
standards established by ICAO. FAA serves as the United States‘
representative to ICAO‘s Committee on Aviation Environmental
Protection, which is responsible for assessing aviation‘s impact on the
environment and establishing the scientific and technological basis for
new gaseous emissions standards for aircraft engines. The committee has
established several working groups to identify and evaluate emissions-
reduction technology and operational measures and market-based options
to reduce emissions. Both FAA and EPA participate in these working
groups. In addition, FAA is responsible for monitoring and enforcing
U.S. manufacturers‘ compliance with aircraft emissions standards, which
it does in part through its process for certifying new aircraft
engines.
In addition, the federal government plays a role in developing
technologies to reduce aircraft emissions. NASA, in partnership with
the aviation industry and universities, conducts research into
improving the capabilities and efficiency of commercial aircraft. Part
of this effort includes developing more fuel efficient and lower
emitting engines. Over the years, NASA has been credited with
contributing to technologies that have significantly lowered the amount
of fuel consumed by jet engines; this in turn has reduced some
emissions, particularly the greenhouse gas, carbon dioxide.
Under the Clean Air Act, EPA has jurisdiction for establishing national
standards for all other mobile sources of emissions, including those
associated with airport operations--such as ground support equipment
and ground access vehicles such as automobiles, trucks, and buses
operating on airport property. In establishing these emissions
standards, EPA is to take into consideration the time it takes to
develop the necessary technology and the cost of compliance.
The Clean Air Act also directs EPA to establish national standards for
ambient air quality, and these standards can affect airport operations
and expansion plans. EPA has set National Ambient Air Quality Standards
for carbon monoxide, lead, nitrogen dioxide, particulate matter, ozone,
and sulfur dioxide. EPA has labeled them criteria pollutants because
the permissible levels established for them are based on ’criteria“ or
information on the effects on public health or welfare that may be
expected from their presence. The criteria pollutants are directly or
indirectly generated by multiple sources, including airport activities.
Local areas not meeting the standards for criteria pollutants are
referred to as nonattainment areas. The act groups nonattainment areas
into classifications based on the extent to which the standards for
each criteria pollutant are exceeded and establishes specific pollution
controls and attainment dates for each classification. The act has set
2010 as the deadline for extreme ozone nonattainment areas to meet the
standards. (California is currently the only state with such an area).
The Clean Air Act also authorizes EPA to set ambient air quality
standards; however, the states, which can adopt EPA‘s or their own more
stringent standards, are responsible for establishing procedures to
attain and maintain the standards. Under the act, states that have
areas in nonattainment, must adopt plans--known as state implementation
plans--for attaining and maintaining air quality standards and submit
the plans to EPA for approval. State implementation plans are based on
analyses of emissions from all sources in the area and computer models
to determine whether air quality violations will occur. If data from
these analyses indicate that air quality standards would be exceeded,
the states are required to impose controls on existing emission sources
to ensure that emissions do not exceed the standards. States can
require control measures on airport emissions sources for which they
are not preempted from regulating, such as power plants and ground
access vehicles, and, to a limited extent, ground support
equipment.[Footnote 46] However, states cannot control emissions from
sources they are preempted from regulating including aircraft, marine
vessels, and locomotives. If a state fails to submit or implement an
adequate implementation plan, EPA can impose an implementation plan.
FAA is responsible for ensuring that its actions supporting airport
development projects--such as providing funding for those projects--
comply with federal environmental requirements, including those
pertaining to air quality. The National Environmental Policy Act of
1969 sets forth a broad national policy intended to protect the quality
of the environment. The act requires that federal actions receive an
environmental review, which includes the impact on air quality, before
federal decisions are made and actions are taken. For example,
federally-funded proposals to construct airport runways require action
by FAA. For airport projects, FAA is the lead agency responsible for
the environmental reviews and for the approval of the airports‘
proposed design. EPA examines the environmental review documents
prepared by FAA and other federal agencies.
The ’general conformity rule“ of the Clean Air Act directs federal
agencies, such as FAA to ensure that federal actions at airports not
delay the attainment or maintenance of ambient air quality standards.
Therefore, FAA must determine, usually as part of the environmental
review, that the estimated amount of emissions caused by a proposed
federal action at an airport comply with the state implementation plan
for meeting the standards. FAA cannot approve an action unless it
complies with the plan. In order to demonstrate compliance, the airport
could be required to implement emission control measures, such as
converting airport vehicles to alternative lower emitting fuels.
To help carry out its responsibilities under the Clean Air Act and the
National Environmental Policy Act, FAA developed the Emissions and
Dispersion Modeling System, which is a computer model that estimates
the amount and type of emissions from airport activities. FAA,
airports, and others use the model to assess the local air quality
impacts of airport development projects. Typically, the model is used
to estimate the amount of emissions produced by aircraft, ground
support equipment, and other sources operating at the airport or in the
nearby vicinity. The model also reflects the way these airport
emissions are dispersed in the atmosphere due to wind and other
factors. The dispersion analysis is intended to assess the
concentrations of the emissions at or near the airport and, thereby,
help to indicate the effect of the emissions on local air quality.
FAA is also engaged in several research projects to improve the
understanding of aircraft emissions and methods for quantifying them.
For example, FAA is working with the Society of Automotive Engineers to
develop a protocol for measuring particulate matter emissions from
aircraft. FAA is also studying ways to increase the accuracy of
aircraft emission dispersion models and is analyzing the air quality
impact of aircraft operations at or above 3000 feet.
[End of section]
Appendix IV: Efforts by Three States to Reduce Aviation-related
Emissions:
Three states with major commercial airports in nonattainment areas--
California, Texas, and Massachusetts--have targeted airports for
emissions reductions.
California:
California has more major commercial airports--seven--than any other
state, and all of them are located in nonattainment areas for ozone.
Although none of the airports are a major source of ozone precursors
such as nitrogen oxides and volatile organic compounds, California air
quality authorities have turned their attention to airports as a source
of reductions needed to reach and maintain attainment of ozone
standards because they believe they have exhausted other sources,
including large sources such as power plants and small sources like
lawn mowers. The Los Angeles region is the only one in the country
classified as an extreme nonattainment area for ozone. According to
state environmental officials, emissions from all airport
activities[Footnote 47] contributed about 1 to 2 percent of the
pollution in the Los Angeles region in 2000, and this is projected to
increase to nearly 4 percent by 2020. State environmental officials
attribute this projected increase in the airports‘ ozone contribution
to an expected doubling of aircraft emissions coupled with a 50 percent
decrease in emissions from other sources. These projections do not take
into account the reductions in aircraft activity as a result of the
events of September 11, 2001, and the financial uncertainties of the
airline industry.
Because of the severity of the nonattainment level in the Los Angeles
area, the state requires reductions from all sources, including
airports, by 2010. Along with Los Angeles‘ local air quality agency,
the California Air Resources Board has negotiated with EPA and airlines
for a memorandum of understanding for voluntary emission reductions
from ground support equipment.[Footnote 48] According to California Air
Resources Board officials, emission reductions would be achieved by
replacing older, high polluting ground support equipment with new
cleaner gas and diesel fueled equipment or equipment operating with
alternative energy sources, such as electricity. In doing so, the
officials expect an 80 percent reduction of emissions from ground
support equipment that are used at five airports--Los Angeles
International, Burbank, Ontario International, Long Beach, and John
Wayne--in the Los Angeles region by 2010.
California‘s efforts to cut emissions from ground support equipment in
the Los Angeles area are part of an aggressive statewide campaign to
reduce airport pollution. In addition to using its limited authority
under the Clean Air Act to implement airport related emissions
reductions, the state has also established criteria for issuing air
quality certifications provided for in federal law.[Footnote 49] Under
this law, before federal funds are allocated for projects involving a
new airport, a new runway, or a major runway extension, the state
governor must certify that there is reasonable assurance that the
project will be ’located, designed, constructed, and operated in
compliance with applicable air and water quality standards.“ The state
has developed a unique set of criteria for determining whether a
proposed airport expansion project would have an impact on the
environment. If the project exceeds one of the criteria, the airport is
required to implement emissions mitigation measures in order to attain
certification. For example, the certification for a runway project was
invoked when the Sacramento International Airport planned to increase
the number of parking spaces. The criteria on which the certification
was based included annual increases of more than 7 million passengers
or 139,000 aircraft operations (i.e., landings and takeoffs) or a
permanent increase of more than 4,200 parking spaces. The airport‘s
plans exceeded the number of parking spaces and, as a result, were
required to implement emission mitigation measures in order to build
the parking spaces. According to state officials, California is the
only state to develop such criteria for certifying airport expansion
projects. As of December 2002, three airports in California--Sacramento
International, San Jose International, and Ontario International--have
initiated expansion projects that required state certification.
Texas:
Texas has four regions in nonattainment of national air quality
standards for ozone, but the Houston and Dallas/Fort Worth regions have
required the most extensive emission control measures for reaching
attainment. These two regions contain the state‘s four largest
airports--Dallas/Fort Worth International, Dallas Love Field, George
Bush International/ Houston, and Houston Hobby--all of which are among
the nation‘s 50 busiest airports. The Houston area has one of the worst
ozone problems in the country and has been designated as a severe
nonattainment area, requiring substantial control measures in order to
comply with the Clean Air Act. Dallas-Fort Worth, on the other hand,
has a much less serious ozone problem but has been penalized by EPA for
not meeting its attainment schedule. EPA classified the Dallas/Fort
Worth region as a moderate ozone nonattainment area in the early 1990s,
which meant that the region was required to demonstrate attainment of
the 1-hour ozone standard[Footnote 50] by November 1996. However, air
quality data from the region showed that the area failed to meet the
attainment goal in 1996, which resulted in EPA reclassifying the
severity level of the region from moderate to serious. The downgrading
of the Dallas region‘s classification forced state and local
authorities to develop a new state implementation plan with more
extensive control measures. The state‘s environmental agency, the Texas
Natural Resource Conservation Commission[Footnote 51], included
emissions from airport activities among the top ten highest sources of
nitrogen oxides emissions from nonroad mobile sources in both the
Dallas-Fort Worth and Houston regional areas.
Noting that the emissions inventories for both Houston and Dallas-Fort
Worth placed airports in the top 10 sources for nitrogen oxide
emissions of nonroad mobile sources, which contribute to ozone
formation, the Texas Natural Resource Conservation Commission
determined that control measures for each area were warranted. For
Dallas-Fort Worth, the commission revised the state implementation plan
for the area to include reduction of nitrogen oxide emissions from
ground support equipment at both major commercial airports in the area-
-Dallas/Forth Worth International and Dallas Love Field. The plan
called for a 90 percent reduction of nitrogen oxide emissions from
ground support equipment by 2005. The airline industry challenged the
state rule by filing a lawsuit, citing the Clean Air Act‘s preemption
rule, which it argued prohibited states and local authorities from
regulating ground support equipment. The lawsuit was dropped in October
2000 when the commission, the cities of Dallas and Fort Worth (which
operates the major airports), and the affected airlines--American,
Delta, and Southwest--reached a voluntary agreement to achieve a 90
percent reduction in nitrogen oxide emissions attributable to ground
support equipment or other equipment by 2005. The commission brokered a
similar agreement with the city of Houston as its operator of the
airports and the affected airlines. Under both the Dallas/Fort Worth
and Houston agreements, the affected carriers voluntarily agreed to
reductions equivalent to 75 percent of nitrogen oxides emitted from
ground service equipment and the cities--Dallas-Forth Worth, and
Houston--as the operators of the airports agreed to be responsible for
the remaining 15 percent to achieve the 90 percent reduction.
Massachusetts:
The Boston area is classified as a serious ozone nonattainment area and
state environmental officials are under increasing pressure by
citizens, community groups, and industry to control emissions from
Boston‘s Logan International Airport. State environmental officials
have estimated that while only a small amount of total nitrogen oxide
emissions in the area are attributable to aircraft, these emissions
will continue to increase. They estimate that other emission sources at
the airport, such as ground support equipment, will eventually begin to
decrease as they are replaced by lower polluting equipment. The Boston
airport is also consistently ranked as the airport with the second
highest number of air travel delays in the nation. These air travel
delays add to regional air quality problems because idling aircraft
contribute to pollution. To meet a growing travel demand, Boston
airport officials have proposed building a new runway to allow the
airport to improve operating efficiency, thereby reducing emissions
from idling aircraft. As part of this proposal, the airport also agreed
that emissions would not exceed 1999 levels.
To address airport operation delays and reduce emissions, airport
officials have considered three strategies--peak period pricing,
emissions credit trading, and reducing emissions from ground support
equipment.[Footnote 52] Peak period pricing is a demand management
strategy that raises landing fees during designated air traffic peak
hours, which is expected to induce some air carriers to discontinue or
reduce operations during peak periods. With fewer aircraft waiting to
taxi and land during peak periods, emissions from aircraft would be
reduced and regional air quality would be improved. An emissions credit
trading program is designed to allow facilities to meet emission
reduction goals by trading and transferring air emission credits with
emission sources that surpassed their allotted targets. Used by EPA to
reduce pollutants that contribute to acid rain, the emission credit
trading program allows sources, such as industry, the flexibility to
meet their reduction obligations in a more cost effective manner.
Because emission credits are considered ’additional“ or ’surplus“ to
those that are regulated and otherwise reduced under federal and state
laws, they aid in achieving an overall decline in emissions regionwide,
according to Boston airport officials. Similar to situations at the
major airports in both California and Texas, state and airport
officials have also focused on reducing emissions from ground support
equipment.
In the wake of the events of September 11, 2001, which resulted in a
reduction of flights and emissions at the Boston airport, the airport‘s
operator--Massachusetts Port Authority--believes that peak pricing and
emissions trading will not be needed to keep emissions below 1999
levels for several years. The Port Authority, however, continues to
work with airport tenants to implement voluntary emission reduction
strategies. In addition, in an August 2002 Record of Decision approving
plans for a new runway and taxiways, FAA directed the Port Authority to
develop and submit a plan for peak period pricing or other demand
management strategies to reduce delays, which the Port Authority had
committed to complete this plan as part of the state environmental
review process, before initiating construction. In the Record of
Decision, FAA pointed out that the program would have to comply with
applicable federal constitutional and other requirements.
[End of section]
Appendix V: Airports‘ and Airlines‘ Efforts To Reduce Emissions:
Many of the nation‘s busiest airports, in conjunction with air
carriers, have voluntarily implemented control measures to reduce
emissions by activities that include modifying the operating procedures
of aircraft, using alternative fuels to run ground support equipment,
and reducing the number of passenger vehicles entering and exiting the
airport.
Aircraft:
Although airports have no control over emissions from aircraft, they
can encourage air carriers to reduce emissions as much as possible
through modified operating procedures. For example, limiting the number
of running engines during taxiing of aircraft can reduce the emission
of nitrogen oxides and volatile organic compounds. According to airport
officials at the Boston Logan International Airport, some pilots use
single-engine taxiing with some aircraft to reduce emissions. Another
example is reducing the use of engine reverse thrust to slow an
aircraft to taxi speed after it lands. This procedure reduces nitrogen
oxide emissions, but it may occur at the expense of slightly higher
emissions of volatile organic compounds if the taxi time is increased
because a runway turnoff is missed. Many factors are involved in the
decision to use reverse thrust, including runway length and width,
runway surface and taxiway conditions, weather conditions, and aircraft
type.
Modifying the operating procedures of aircraft does not require
additional equipment or aircraft modifications, but it is done at the
discretion of the pilot. Under federal regulations, the commanding
pilot of the aircraft is responsible for the safety of the passengers,
crewmembers, cargo, and the airplane, and any procedure that modifies
aircraft operation is at the discretion of the pilot. In addition,
modifications to operating procedures may not be feasible in all
weather conditions, with all aircraft, and/or at all airports.
Ground Support Equipment:
Most ground support equipment used by air carriers at airports is
fueled by gasoline or diesel. Replacing that equipment with cleaner-
burning gas or diesel engines or equipment powered by alternative
fuels--such as electricity, liquefied petroleum gas, and compressed
natural gas--could result in reduced emissions. A reliable and
comprehensive database of the ground support equipment in use does not
exist; however, according to FAA, there are about 72,000 pieces of such
equipment in operation. The Air Transport Association estimated that of
the pieces of ground support equipment in used in 1999, about 30 to 40
percent operate on diesel fuel; 50 to 60 percent operate on gasoline;
and about 10 percent use alternative fuels. Several airports we
visited, including Los Angeles International, Sacramento
International, Dallas/Fort Worth International, Boston Logan
International, and Atlanta Hartsfield, provided air carriers with the
infrastructure necessary to operate alternatively fueled ground support
equipment, and some carrier have begun converting their fleets of
ground support equipment to alternative fuels. Los Angeles
International, for instance, provided a varied alternative fuel
infrastructure, including both compressed and liquefied natural gas
refueling stations and electric charging stations, which offered air
carriers different options to use alternative fueled equipment. Airport
officials told us that air carriers have been using the alternative
fuel stations to refuel their ground support equipment.
FAA reported[Footnote 53] that replacing conventionally-fueled ground
support equipment with alternatively-fueled equipment is the most cost
effective way to reduce emissions at airports. Additionally, equipment
originally designed to use the alternative fuels has less impact on the
environment than equipment that is converted from using a conventional
fuel to an alternative fuel; however, it is also more costly up front,
and alternative fuel technology does not currently exist for some types
of ground support equipment. Airports and air carriers use about 24
different types of ground support equipment, such as cargo loaders,
aircraft pushback tractors, baggage tugs, and service trucks; and
according to aviation industry officials, conversion of equipment from
conventional to alternative fuel has had a mixed result in terms of
operating the equipment. According to airline officials, liquefied
petroleum and compressed natural gas vehicles require larger fuel tanks
and are harder to operate; the cost for the alternative fuel
infrastructure engines for ground support equipment is also very
expensive. Air carriers and airports commonly have had to use a mixed
fleet of liquefied petroleum and compressed natural gas and electric
ground support equipment because of limitations of the various types of
alternative fuel sources. For example, electricity has not been
sufficiently powerful to run some of the ground service equipment that
bear significant loads. In addition, some types of electric equipment
do not work well in cold weather conditions. According to the Air
Transport Association, for these and other reasons, no one equipment
size or type fits all airlines‘ needs.
Providing Electric Power at Gates:
A trend at airports is to provide electricity and air conditioning
service for aircraft at the gates, which can permit a reduction in the
use of aircraft auxiliary power units and thereby reduce emissions,
according to FAA. Airports are not required to install boarding gates
that provide electricity to parked aircraft, but an FAA report notes
that some airports have been proactive in reducing emissions and have
invested in these electric gates.[Footnote 54] The report explains that
electric gates operate at greater energy efficiency than auxiliary
power units, which support aircraft with power and ventilation systems
when they are parked at the gates, and can substantially reduce
emissions. Many airports, including Los Angeles International,
Sacramento International, Dallas/Fort Worth International, and Boston
Logan International provide electric power for parked aircraft, which
allows aircraft to turn off their auxiliary power units while
maintenance and cleaning crews prepare the aircraft for the next
flight. However, air carriers are not required to use the electric
gates, and some chose not to use them because they hinder the
efficiency of their operations. For instance, one airline that
specializes in getting its aircraft into and out of airports quickly--
in 20 minutes or less--rarely uses the electricity provided by the
airport, instead running the auxiliary power unit the entire time
aircraft are at the gate, according to officials of that airline. These
officials note that electric gates are only useful for those aircraft
that are parked for 30 to 45 minutes or longer before they take off
because of the time it takes to hook the aircraft up to the system.
Passenger Vehicles:
Although EPA already regulates emissions from most passenger vehicles
and trucks, options are available to further reduce emissions from
theses sources at airports. Vehicles making trips to and from airports
include employee and private passenger vehicles, airport and tenant-
owned fleet vehicles, public transport vehicles and shuttles, and cargo
vehicles for deliveries. All the airports we visited have implemented
or are in the process of implementing emission reduction efforts for
this emissions source. Some emission reduction measures that airports
have applied to such ground access vehicles include the following:
* Dallas/Fort Worth International airport has consolidated its rental
car facilities and, according to airport officials, the consolidation
effort has reduced rental car related emissions by 95 percent. In
addition, the single shuttle service that resulted from consolidating
the rental car facilities uses alternative fuel shuttles. George Bush
Intercontinental/Houston plans to consolidate its rental car
facilities; and Los Angeles International, Atlanta Hartsfield, and
Boston Logan International are also considering the option.
* Dallas/Fort Worth International, Los Angeles International, and
Sacramento International all have promoted some kind of employee/tenant
commuter rideshare program. According to Los Angeles International
Airport officials, about 25 percent of airport employees participate in
a commuter rideshare program.
* Los Angeles International restructured its airport shuttle-van
program in 1999 by reducing the number of shuttle vans authorized to
make passenger pickups at the airport and requiring them to phase-in
alternative fuel vehicles into their fleets. The airport expects all of
the authorized operators to use alternative fuel vehicles by 2003. The
airport is also considering requiring taxicabs serving the airport to
operate on natural gas.
* Both Chicago O‘Hare International and Dallas/Fort Worth International
airports have built an electric automated transport system, also known
as a ’people mover,“ within the airport property to transport
passengers between terminals. Chicago O‘Hare International airport also
offers direct rail service to the city center and provides alternative
transportation to passengers and airport employees entering/exiting the
airport. Los Angeles International provides alternative public
transportation with a bus service that travels between the airport and
the park-and-ride station at the Van Nuys Airport.
Other Measures:
Airports have also reduced emissions from other sources, such as their
on-site utilities plants. Los Angeles International airport‘s central
utilities plant operates under a cogeneration energy saving system,
which simultaneously generates electrical power and steam. Some
electrical power is sold to the local electric company, and the steam
provides heating and air conditioning (by powering steam refrigeration
chillers) for the airport‘s buildings and central terminal area.
According to airport officials, Los Angeles International receives more
than $3 million in emissions credit each year for the emission controls
achieved with its central utilities plant. Dallas/Fort Worth
International airport also generates electricity with its solar power
generators, which produce lower emissions than traditional powered
generators. Airport officials stated that they have the capacity to
build cogeneration plants using solar power and sell the power/surplus
electricity to the state as well. The airport is trying to negotiate
with federal agencies to receive credits for the amount of emission
reductions achieved by using solar power energy and selling surplus
electricity to the state. If successful, the airport could use these
credits to gain approval of future expansion projects that increase
emissions.
[End of section]
Appendix VI: Overview of Aircraft Fuel, Noise, and Nitrogen Oxide
Reduction Technologies:
Fuel efficiency improvements involve every aspect of an aircraft‘s
design. Traditionally, about 40 percent of the improvements have come
from airframe improvements and 60 percent from propulsive and engine
improvements. Airframe improvements include improving the aerodynamic
shape and structural efficiency (for example, reduced aircraft weight).
Propulsive improvements have primarily resulted from increasing the
size of the bypass fan and improving the shape of the bypass fan
blades. Engine improvements have centered on increasing the pressure of
the air that goes through the engine core (the engine operating
pressure). The increased engine operating pressures allow more work to
be extracted from a unit of fuel, thereby improving fuel consumption.
One of the first major technology breakthroughs with commercial jet
engines occurred in the mid-1960s with the introduction of the turbofan
jet engine (see figure 3). This design uses a bypass fan in front of
the jet engine core to move much of the propulsive air and bypass the
core of the jet that contains the compressor, combustor, and turbine.
The primary motivation for this advancement was increased fuel
efficiency. However, the reduced noise of this new design was an
additional benefit. Noise was reduced because the bypass air moves at a
slower speed than the air going through the core. Further noise
reductions have evolved over time by increasing the size of the bypass
fans and improving the shapes of the bypass fan blades. Researchers at
NASA have indicated they are facing diminishing returns as they seek to
reduce noise by further improving bypass fans and aircraft surfaces.
They are also exploring more advanced technologies such as using
electronics to actively control noise.
Figure 3: Major Components of a Turbofan Engine (Two-Shaft High Bypass
Engine):
[See PDF for image]
[End of figure]
NASA, in association with jet engine manufacturers and the academic
community, is working on several technologies to reduce nitrogen oxide
emissions. NASA‘s research to reduce nitrogen oxide emissions is a
component of its Ultra Efficient Engine Technology Program. The goal of
this program is to develop technologies that will enable U.S.
manufacturers to compete in the global marketplace for new commercial
gas turbine engines. An important aspect of this program is reducing
jet engine emissions of nitrogen oxides. NASA has set what it considers
ambitious goals[Footnote 55] for its nitrogen oxide reduction research.
These goals include the following:
* Demonstrate combustion technology, in a NASA test laboratory, that
will reduce nitrogen oxides 70 percent relative to today‘s standard.
This equates to a 20-50 percent reduction compared with the best
engines being produced today.
* Demonstrate these technologies in engine combustor components by
2005.
* Hand off the technologies to manufacturers in a timely fashion so
they can be incorporated in new engines in the 2007-2010 time frame.
* Study long-term concepts that could greatly reduce or eliminate
nitrogen oxides emissions in the 2025-2050 time frame.
According to representatives from jet engine manufacturers, nitrogen
oxide reduction research is complex and time consuming and requires
specialized and expensive test equipment. They also said that basic
research needed to understand the formation of nitrogen oxides in jet
engines and to make significant changes to current engine designs is so
expensive and lacking in marketplace investment rewards that no
significant or sustained basic research in this area would take place
without NASA taking the lead.
Adding to the complexities of this research is the extreme variation in
jet engine designs. Other research and development by NASA and engine
manufacturer is constantly raising engine-operating pressures as a way
of improving fuel consumption and reducing greenhouse gas emissions.
However, these developments tend to increase nitrogen oxide emissions,
and further modifying engine designs to reduce nitrogen oxides has a
direct impact on every other aspect of engine design: safety,
operability, service life, operating costs, maintenance costs, and
production costs. Jet engine manufacturers are taking divergent design
approaches as they research how to maintain these other high-priority
design characteristics while reducing nitrogen oxide emissions. As a
result, NASA divides its resources over numerous projects.
NASA‘s Ultra Efficient Engine Technology Program is scheduled to
complete research and technology on aircraft engine combustor
refinements that reduce the formation of nitrogen oxides so that the
refinements can be introduced on aircraft by 2010. Because of the 30-
year projected life of commercial aircraft, it could take decades
before enough lower emitting aircraft are introduced in the commercial
fleet to contribute to significant reductions in nitrogen oxides.
NASA‘s nitrogen oxides research under the Ultra Efficient Engine
Technology Program is centered on developing lean-burning rather than
rich burning combustors that are in commercial service today. These
lean-burning combustors will increase fuel/air mixing rates that, when
combined with the lean fuel/air ratios, will reduce temperatures
locally in the combustor and thus reduce the nitrogen oxide emissions
generated. Because of funding constraints, NASA does not plan to
implement the next phase of development, which is to examine the
combustor improvements in a full engine test environment. NASA is
relying on the engine manufacturers to implement this full engine
development. Both NASA and aviation industry engineers said that this
full engine development phase will be far more complex and involve many
more design trade-offs than the combustor development phase.
Additionally, they acknowledged that some of the nitrogen oxide
reductions achieved during the combustor development phase would be
lost during the full engine development phase. NASA researchers
indicated these losses could be particularly severe because engine
manufacturers are concurrently making other design changes to their
engines to minimize fuel consumption and these changes will increase
nitrogen oxide emissions. Consequently, NASA researchers are not sure
how many of the improvements they expect to achieve by 2005 will
survive as the engine manufacturers take over responsibility for
completing the development of these improvements in a full engine test
environment and then integrate these improvements into production-ready
engines.
NASA is also working on a long-term revolutionary jet engine design
that could significantly reduce all emissions including nitrogen oxides
while also reducing fuel consumption. Under its ’intelligent
propulsions controls“ design concept, engine functions are more
precisely controlled using computers. For example, with this design,
the number of ports delivering fuel to the engine combustion chamber
would be greatly increased, and each port would be computer controlled.
NASA officials are optimistic about the potential of this concept, but
they added that research is in the early stages and that it will
probably take 20 years or more to develop. NASA‘s overall long-term
research plan calls for spending about $20 million per year over the
next 5-year period to explore improved fuel burned and nitrogen oxide
emission reduction technologies.
NASA researchers are also studying the possibility of developing zero
emissions (except water) hydrogen-fueled aircraft with an electric
propulsion system. While they note that there would have to be many
breakthroughs in hydrogen storage and fuel cell technologies and high-
powered lightweight electric motors before a hydrogen-fueled commercial
airliner is feasible, they believe many of the needed breakthroughs
could occur in the next 50 years.
NASA[Footnote 56] is also researching nonengine methods that will
indirectly reduce nitrogen oxides (and all other emissions) by reducing
fuel consumption. This work includes more efficient airframes through
aerodynamic improvements, structural improvements (i.e., reducing
aircraft weight), and operational efficiencies (i.e., more fuel
efficient flight routes, reduced taxi time). Historically, 40 percent
of aviation fuel improvements have come from such efficiency
improvements. Aviation emission experts emphasize that it is important
that research into these types of improvements continue along with the
engine research. The advantage of these improvements is that all
emissions are reduced simultaneously without having to make emission
trade-offs.
[End of section]
Appendix VII: Additional Information on Our Analysis of Aircraft
Emissions:
Using the Emissions and Dispersion Modeling System (version 4.01)
computer model developed by FAA and fleet data obtained from AvSoft, we
calculated the landing/takeoff emissions for every aircraft model and
engine combination in the U.S. commercial aircraft fleet during 2001.
(See appendix I for additional information on our methodology.) Tables
7 and 8 provide additional information on our comparison of older and
newest model Boeing 737s. As shown below, older model Boeing 737s,
produced in 1969-1998, averaged 12.1 pounds of nitrogen oxides per
landing/takeoff (see table 7), while the newest model Boeing 737s,
produced in 1997-2201, averaged 17.9 pounds of nitrogen oxides per
landing/takeoff (see table 8). Tables 9, 10, and 11 provide additional
information about the calculations and commercial fleet for data
presented earlier in this report.
Table 7: Emission Information for Older Boeing 737s during Landing/
Takeoff:
Model: 737-200; Engine: JT8D-15; Pounds
NOx per LTO[A]: 13.361; Pounds CO
per LTO[A]: 9.912; Pounds VOC
per LTO[A]: 1.296; Number
in U.S. fleet in 2001: 55; Number
of LTOs in 2001: 101,887; Oldest in fleet: 1977; Newest
in fleet: 1985; Average
number
of seats: 113.1; Pounds takeoff
weight: 105000.
Model: 737-200; Engine: JT8D-15A; Pounds
NOx per LTO[A]: 11.835; Pounds CO
per LTO[A]: 10.475; Pounds VOC
per LTO[A]: 1.479; Number
in U.S. fleet in 2001: 65; Number
of LTOs in 2001: 85,577; Oldest in fleet: 1980; Newest
in fleet: 1988; Average
number
of seats: 113.7; Pounds takeoff
weight: 105000.
Model: 737-200; Engine: JT8D-17; Pounds
NOx per LTO[A]: 14.804; Pounds CO
per LTO[A]: 9.574; Pounds VOC
per LTO[A]: 1.165; Number
in U.S. fleet in 2001: 21; Number
of LTOs in 2001: 31,620; Oldest in fleet: 1976; Newest
in fleet: 1987; Average
number
of seats: 106.6; Pounds takeoff
weight: 105000.
Model: 737-200; Engine: JT8D-17(Q); Pounds
NOx per LTO[A]: 14.804; Pounds CO
per LTO[A]: 9.574; Pounds VOC
per LTO[A]: 1.165; Number
in U.S. fleet in 2001: 1; Number
of LTOs in 2001: 879; Oldest in fleet: 1976; Newest
in fleet: 1976; Average
number
of seats: 128.0; Pounds takeoff
weight: 105000.
Model: 737-200; Engine: JT8D-17A; Pounds
NOx per LTO[A]: 12.801; Pounds CO
per LTO[A]: 10.421; Pounds VOC
per LTO[A]: 4.204; Number
in U.S. fleet in 2001: 5; Number
of LTOs in 2001: 8,632; Oldest in fleet: 1983; Newest
in fleet: 1985; Average
number
of seats: 117.0; Pounds takeoff
weight: 105000.
Model: 737-200; Engine: JT8D-7B; Pounds
NOx per LTO[A]: 11.207; Pounds CO
per LTO[A]: 10.424; Pounds VOC
per LTO[A]: 2.326; Number
in U.S. fleet in 2001: 1; Number
of LTOs in 2001: 181; Oldest in fleet: 1969; Newest
in fleet: 1969; Average
number
of seats: 56.0; Pounds takeoff
weight: 100000.
Model: 737-200; Engine: JT8D-9A; Pounds
NOx per LTO[A]: 12.079; Pounds CO
per LTO[A]: 10.591; Pounds VOC
per LTO[A]: 2.042; Number
in U.S. fleet in 2001: 55; Number
of LTOs in 2001: 128,673; Oldest in fleet: 1968; Newest
in fleet: 1988; Average
number
of seats: 114.5; Pounds takeoff
weight: 100000.
Model: 737-200C; Engine: JT8D-15; Pounds
NOx per LTO[A]: 13.361; Pounds CO
per LTO[A]: 9.912; Pounds VOC
per LTO[A]: 1.296; Number
in U.S. fleet in 2001: 1; Number
of LTOs in 2001: 2,139; Oldest in fleet: 1974; Newest
in fleet: 1974; Average
number
of seats: 111.0; Pounds takeoff
weight: 105000.
Model: 737-200C; Engine: JT8D-17; Pounds
NOx per LTO[A]: 14.804; Pounds CO
per LTO[A]: 9.574; Pounds VOC
per LTO[A]: 1.165; Number
in U.S. fleet in 2001: 7; Number
of LTOs in 2001: 17,428; Oldest in fleet: 1979; Newest
in fleet: 1984; Average
number
of seats: 111.1; Pounds takeoff
weight: 105000.
Model: 737-200C; Engine: JT8D-17A; Pounds
NOx per LTO[A]: 12.801; Pounds CO
per LTO[A]: 10.421; Pounds VOC
per LTO[A]: 4.204; Number
in U.S. fleet in 2001: 5; Number
of LTOs in 2001: 12,750; Oldest in fleet: 1983; Newest
in fleet: 1985; Average
number
of seats: 111.6; Pounds takeoff
weight: 105000.
Model: 737-200C; Engine: JT8D-9A; Pounds
NOx per LTO[A]: 12.075; Pounds CO
per LTO[A]: 10.590; Pounds VOC
per LTO[A]: 2.042; Number
in U.S. fleet in 2001: 1; Number
of LTOs in 2001: 3,373; Oldest in fleet: 1980; Newest
in fleet: 1980; Average
number
of seats: 112.0; Pounds takeoff
weight: 100000.
Model: 737-300; Engine: CFM56-3B-1; Pounds
NOx per LTO[A]: 10.720; Pounds CO
per LTO[A]: 19.197; Pounds VOC
per LTO[A]: 1.201; Number
in U.S. fleet in 2001: 380; Number
of LTOs in 2001: 842,336; Oldest in fleet: 1984; Newest
in fleet: 1997; Average
number
of seats: 130.8; Pounds takeoff
weight: 122000.
Model: 737-300; Engine: CFM56-3B-2; Pounds
NOx per LTO[A]: 12.496; Pounds CO
per LTO[A]: 17.811; Pounds VOC
per LTO[A]: 0.991; Number
in U.S. fleet in 2001: 137; Number
of LTOs in 2001: 244,395; Oldest in fleet: 1984; Newest
in fleet: 1992; Average
number
of seats: 126.3; Pounds takeoff
weight: 122000.
Model: 737-300; Engine: CFM56-3C-1; Pounds
NOx per LTO[A]: 14.195; Pounds CO
per LTO[A]: 16.766; Pounds VOC
per LTO[A]: 0.859; Number
in U.S. fleet in 2001: 9; Number
of LTOs in 2001: 12,355; Oldest in fleet: 1993; Newest
in fleet: 1998; Average
number
of seats: 126.9; Pounds takeoff
weight: 122000.
Model: 737-400; Engine: CFM56-3B-2; Pounds
NOx per LTO[A]: 12.496; Pounds CO
per LTO[A]: 17.811; Pounds VOC
per LTO[A]: 0.991; Number
in U.S. fleet in 2001: 56; Number
of LTOs in 2001: 97,791; Oldest in fleet: 1988; Newest
in fleet: 1992; Average
number
of seats: 144.9; Pounds takeoff
weight: 122000.
Model: 737-400; Engine: CFM56-3C-1; Pounds
NOx per LTO[A]: 14.350; Pounds CO
per LTO[A]: 16.771; Pounds VOC
per LTO[A]: 0.861; Number
in U.S. fleet in 2001: 41; Number
of LTOs in 2001: 71,175; Oldest in fleet: 1989; Newest
in fleet: 1999; Average
number
of seats: 138.9; Pounds takeoff
weight: 133000.
Model: 737-500; Engine: CFM56-3B-1; Pounds
NOx per LTO[A]: 11.617; Pounds CO
per LTO[A]: 19.278; Pounds VOC
per LTO[A]: 1.204; Number
in U.S. fleet in 2001: 26; Number
of LTOs in 2001: 77,823; Oldest in fleet: 1990; Newest
in fleet: 1998; Average
number
of seats: 121.3; Pounds takeoff
weight: 122000.
Model: 737-500; Engine: CFM56-3B-2; Pounds
NOx per LTO[A]: 13.578; Pounds CO
per LTO[A]: 17.894; Pounds VOC
per LTO[A]: 0.994; Number
in U.S. fleet in 2001: 3; Number
of LTOs in 2001: 5,188; Oldest in fleet: 1990; Newest
in fleet: 1990; Average
number
of seats: 104.0; Pounds takeoff
weight: 122000.
Model: 737-500; Engine: CFM56-3C-1; Pounds
NOx per LTO[A]: 15.451; Pounds CO
per LTO[A]: 16.852; Pounds VOC
per LTO[A]: 0.862; Number
in U.S. fleet in 2001: 119; Number
of LTOs in 2001: 197,140; Oldest in fleet: 1990; Newest
in fleet: 1998; Average
number
of seats: 106.5; Pounds takeoff
weight: 122000.
Model: Weighted averages[B]; Pounds
NOx per LTO[A]: 12.123; Pounds CO
per LTO[A]: 16.798; Pounds VOC
per LTO[A]: 1.221; Number
in U.S. fleet in 2001: [Empty]; Number
of LTOs in 2001: [Empty]; Oldest in fleet: [Empty]; Newest
in fleet: [Empty]; Average
number
of seats: [Empty]; Pounds takeoff
weight: [Empty].
Model: Total; Engine: [Empty]; Pounds
NOx per LTO[A]: [Empty]; Pounds CO
per LTO[A]: [Empty]; Pounds VOC
per LTO[A]: [Empty]; Number
in U.S. fleet in 2001: 988; Number
of LTOs in 2001: 1,941,342; Oldest in fleet: [Empty]; Newest
in fleet: [Empty]; Average
number
of seats: [Empty]; Pounds takeoff
weight: [Empty].
Model: Percentage of total U.S. commercial fleet; Number
in U.S. fleet in 2001: 12.7%; Number
of LTOs in 2001: 17.6%; Oldest in fleet: [Empty]; Newest
in fleet: [Empty]; Average
number
of seats: [Empty]; Pounds takeoff
weight: [Empty].
[End of table]
Legend
CO=carbon monoxide
LTO= landing/takeoff
NOx=nitrogen oxides
VOC= volatile organic compounds:
Source: GAO.
Notes: Landing and takeoff data for U.S. aircraft in 2001 obtained from
AvSoft. Emissions were calculated using FAA‘s Emissions and Dispersion
Modeling System, version 4.01. The following variables were assumed to
be the same for all aircraft: (1) taxi-time: 15 minutes, (2) auxiliary
power unit time: 26 minutes, and (3) ceiling height for emissions
mixing with local air: 3,000 feet. The model‘s default was used for
takeoff weight.
[A] Pounds of emissions per one landing/takeoff (LTO), which includes
emissions for takeoff, climb to 3,000 feet, approach, taxi, and
auxiliary power unit.
[B] The average was computed by weighting the emissions for a specific
model/engine combination by the number of landings/takeoffs for that
combination in 2001.
Table 8: Emission Information for Newest Boeing 737s during Landing/
Takeoff:
Model: 737-700; Engine: CFM56-7B-20; Pounds NOx[A] per LTO: 12.702;
Pounds CO per LTO: 12.178; Pounds VOC per LTO: 1.370; Number in U.S.
fleet in 2001: 8; Number of LTOS in 2001: 3,176; Oldest in fleet: 1998;
Newest in fleet: 2001; Average number of seats: 123.9; Pounds takeoff
weight: 122000.
Model: 737-700; Engine: CFM56-7B-22; Pounds NOx[A] per LTO: 15.078;
Pounds CO per LTO: 11.269; Pounds VOC per LTO: 1.183; Number in U.S.
fleet in 2001: 118; Number of LTOS in 2001: 218,184; Oldest in fleet:
1997; Newest in fleet: 2002; Average number of seats: 136.9; Pounds
takeoff weight: 122000.
Model: 737-700; Engine: CFM56-7B-24; Pounds NOx[A] per LTO: 16.971;
Pounds CO per LTO: 11.229; Pounds VOC per LTO: 1.185; Number in U.S.
fleet in 2001: 55; Number of LTOS in 2001: 72,337; Oldest in fleet:
1998; Newest in fleet: 2001; Average number of seats: 123.1; Pounds
takeoff weight: 122000.
Model: 737-700; Engine: CFM56-7B-26; Pounds NOx[A] per LTO: 20.280;
Pounds CO per LTO: 9.926; Pounds VOC per LTO: 1.001; Number in U.S.
fleet in 2001: 5; Number of LTOS in 2001: 2,435; Oldest in fleet: 2001;
Newest in fleet: 2001; Average number of seats: 124.0; Pounds takeoff
weight: 122000.
Model: 737-800; Engine: CFM56-7B-26; Pounds NOx[A] per LTO: 20.280;
Pounds CO per LTO: 9.926; Pounds VOC per LTO: 1.001; Number in U.S.
fleet in 2001: 193; Number of LTOS in 2001: 208,950; Oldest in fleet:
1998; Newest in fleet: 2002; Average number of seats: 151.5; Pounds
takeoff weight: 122000.
Model: 737-800; Engine: CFM56-7B-27; Pounds NOx[A] per LTO: 22.181;
Pounds CO per LTO: 9.663; Pounds VOC per LTO: 0.934; Number in U.S.
fleet in 2001: 54; Number of LTOS in 2001: 33,181; Oldest in fleet:
2000; Newest in fleet: 2002; Average number of seats: 157.0; Pounds
takeoff weight: 122000.
Model: 737-900; Engine: CFM56-7B-26; Pounds NOx[A] per LTO: 20.030;
Pounds CO per LTO: 11.221; Pounds VOC per LTO: 1.065; Number in U.S.
fleet in 2001: 16; Number of LTOS in 2001: 8,285; Oldest in fleet:
2001; Newest in fleet: 2002; Average number of seats: 161.7; Pounds
takeoff weight: 122000.
Model: Weighted averages[B]; Pounds NOx[A] per LTO: 17.883; Pounds CO
per LTO: 10.651; Pounds VOC per LTO: 1.097; Number in U.S. fleet in
2001: [Empty]; Number of LTOS in 2001: [Empty]; Oldest in fleet:
[Empty]; Newest in fleet: [Empty]; Average number of seats: [Empty];
Pounds takeoff weight: [Empty].
Model: Total; Engine: [Empty]; Pounds NOx[A] per LTO: [Empty]; Pounds
CO per LTO: [Empty]; Pounds VOC per LTO: [Empty]; Number in U.S. fleet
in 2001: 449; Number of LTOS in 2001: 546,548; Oldest in fleet:
[Empty]; Newest in fleet: [Empty]; Average number of seats: [Empty];
Pounds takeoff weight: [Empty].
Model: Percentage of total U.S. commercial fleet; Pounds VOC per LTO:
[Empty]; Number in U.S. fleet in 2001: 5.75%; Number of LTOS in 2001:
4.96%; Oldest in fleet: [Empty]; Newest in fleet: [Empty]; Average
number of seats: [Empty]; Pounds takeoff weight: [Empty].
[End of table]
Legend
CO=carbon monoxide
LTO=landing/takeoff
NOx=nitrogen oxides
VOC=volatile organic compounds:
Source: GAO.
Notes: Landing and takeoff data for U.S. aircraft in 2001 obtained from
AvSoft. Emissions were calculated using FAA‘s Emissions and Dispersion
Modeling System, version 4.01. The following variables were assumed to
be the same for all aircraft: (1) taxi-time: 15 minutes, (2) auxiliary
power unit time: 26 minutes, and (3) ceiling height for emissions
mixing with local air: 3,000 feet. The model‘s default was used for
takeoff weight.
[A] Pounds of emissions per one landing/takeoff (LTO), which includes
emissions for takeoff, climb to 3,000 feet, approach, taxi, and
auxiliary power unit.
Table 9: Additional Information on Comparison of Older and Newest Model
Boeing 737 Landing/Takeoff Emissions:
Emission: Nitrogen oxides; Average emission per landing/takeoff: Older
Boeing 737 (pounds): 12.1; Average emission per landing/takeoff: Newest
Boeing737 (pounds): 17.8; Changes: 47% increase.
Emission: Carbon monoxide; Average emission per landing/takeoff: Older
Boeing 737 (pounds): 16.8; Average emission per landing/takeoff: Newest
Boeing737 (pounds): 10.7; Changes: 37% decrease.
Emission: Hydrocarbons; Average emission per landing/takeoff: Older
Boeing 737 (pounds): 1.2; Average emission per landing/takeoff: Newest
Boeing737 (pounds): 1.1; Changes: 10% decrease.
[End of table]
Source: GAO.
Notes: Landing and takeoff data for U.S. aircraft in 2001 obtained from
AvSoft. Emissions were calculated using FAA‘s Emissions and Dispersion
Modeling System , version 4.01. The following variables were assumed to
be the same for all aircraft: (1) taxi-time: 15 minutes, (2) auxiliary
power unit time: 26 minutes, and (3) ceiling height for emissions
mixing with local air: 3,000 feet. The model‘s default was used for
takeoff weight.
The U.S. 2001 commercial fleet included 988 older Boeing 737s. They
accounted for 17.6 percent of this fleet‘s landings and takeoffs and
13.4 percent of this fleet‘s nitrogen oxides emissions during landing
and takeoffs. The U.S. 2001 commercial fleet included 449 newer Boeing
737s. They accounted for 5.0 percent of this fleet‘s landings and
takeoffs and 5.5 percent of this fleet‘s nitrogen oxides emissions
during landing and takeoffs. See table 2 also.
Table 10: Additional Information on Comparison of Boeing 747 and 777
Emissions on a Per Aircraft Basis:
Emission: Nitrogen oxides; Emission per aircraft during landing/
takeoff: Boeing 747-400 (pounds): 103.5; Emission per aircraft during
landing/takeoff: Boeing B777-200ER (pounds): 124.2; Changes: 20 percent
increase.
Emission: Carbon monoxide; Emission per aircraft during landing/
takeoff: Boeing 747-400 (pounds): 47.7; Emission per aircraft during
landing/takeoff: Boeing B777-200ER (pounds): 30.4; Changes: 36 percent
decrease.
Emission: Hydrocarbons; Emission per aircraft during landing/takeoff:
Boeing 747-400 (pounds): 4.1; Emission per aircraft during landing/
takeoff: Boeing B777-200ER (pounds): 2.4; Changes: 41 percent decrease.
[End of table]
Source: GAO.
Notes: Landing and takeoff data for U.S. aircraft in 2001 obtained from
AvSoft. Emissions were calculated using FAA‘s Emissions and Dispersion
Modeling System, version 4.01. The following variables were assumed to
be the same for all aircraft: (1) taxi-time: 15 minutes, (2) auxiliary
power unit time: 26 minutes, and (3) ceiling height for emissions
mixing with local air: 3,000 feet. The model‘s default was used for
takeoff weight. See table 3 also.
The Boeing B77-200ER data is the weighted average (based on 2001
landings and takeoffs) for three different engines. The nitrogen oxides
and other emission characteristics of these engines vary significantly.
The 58 Boeing 747-400s in the 2001 U.S. fleet have PW4056 engines and
average 361 seats per aircraft. The 101 Boeing 777-200ERs in the 2001
U.S. fleet have the following engines: PW4090
(37 aircraft averaging 302 seats), GE90-90B (16 aircraft averaging 283
seats), and TRENT 892B-17 (48 aircraft averaging 249 seats). The three
engine types for the Boeing 777-200ERs emit 138.6, 123.6, and 112.3
pounds of nitrogen oxide emissions per landing/takeoff, respectively.
Table 11: Comparison of Power, Engine Operating Pressures, and Nitrogen
Oxides Emissions for a Boeing 737-300 and Its Most Common Replacement:
Engine variant; Older model: B737-300: CFM56 3B-1; Newer model: B737-
700: CFM56 7B-22.
Power (thrust) per engine; Older model: B737-300: 89 kiloNewtons;
Newer model: B737-700: 101 kiloNewtons.
Engine operating pressure ratio; Older model: B737-300: 22.4; Newer
model: B737-700: 24.41.
Landing/takeoff nitrogen oxides emissions; Older model: B737-300:
10.72 pounds; Newer model: B737-700: 15.08 pounds.
[End of table]
Source: GAO.
Notes: Aircraft engine emissions data obtained from ICAO. Calculations
made using FAA‘s Emissions and Dispersion Modeling System, version
4.01. Landing/takeoff emission computations assume typical conditions
of 3,000 foot mixing height, 15-minute taxi, and 26 minute auxiliary
power unit usage and 122,000 pound takeoff weight. See table 5 also.
Other details: B737-300 B737-700
Takeoff weight used for comparison: 122,000 lbs. 22,000 lbs.
Average seat count: 131 137
Number in 2001 commercial fleet: 380 118
Production years for U.S. fleet: 1984-1997 1997-present
Percent of 2001 commercial fleet landings/takeoffs: 7.7% 2.0%
Other landing/takeoff emissions in pounds:
Carbon monoxide improved 41%: 19.20 lbs. 11.27 lbs.
Hydrocarbons improved 1.5%: 01.20 lbs. 01.18 lbs.
[End of section]
Appendix VIII: Comments from the National Aeronautics and Space
Administration:
National Aeronautics and Space Administration:
Office of the Administrator Washington, DC 20546-0001:
February 27, 2003:
Gerald L. Dillingham, PhD. Director, Civil Aviation Issues U S. General
Accounting Office 441 G. St. N. W.
Room 2T23 Washington, DC 20548:
Dear Dr. Dillingharn.:
Thank you for giving us the opportunity to review and comment on (GAO)
Draft Report: Aviation and the Environment: Strategic Framework Needed
to Address Challenges Posed by Aircraft Emissions.
We concur with the report‘s conclusion that the Environmental Protect-
ion Agency and the National Aeronautics and Space Administration (NASA)
should work together under the Federal Aviation Administration‘s
leadership to develop a strategic framework for addressing emissions
from aviation-related sources.
Comments on the report‘s content relative to NASA programs are provided
in the enclosure. If we can be of further assistance, please do not
hesitate to call Terrence Hertz at 358-4636.
Signed by Frederick D. Gregory:
Frederick D. Gregory Deputy Administrator:
Enclosure:
[End of section]
Appendix IX: GAO Contacts and Staff Acknowledgments:
GAO Contacts:
Gerald L. Dillingham (202) 512-3650
Teresa Spisak (202) 512-3950:
Staff Acknowledgments:
In addition to the individuals named above, Carolyn Boyce, Joyce Evans,
David Hooper, David Ireland, Art James, Jennifer Kim, Eileen Larence,
Edward Laughlin, Donna Leiss, Jena Sinkfield, Larry Thomas, and
Gail Traynham made key contributions to this report.
FOOTNOTES
[1] U. S. General Accounting Office, Aviation and the Environment:
Airport Operations and Future Growth Present Environmental Challenges,
GAO/RCED-00-153 (Washington, D.C.: Aug. 30, 2000).
[2] Energy and Environmental Analysis, Inc. for Industrial Economics
submitted to EPA Analysis of Techniques to Reduce Air Emissions at
Airports (Draft Final Report) (Washington, D.C.: June 1997).
[3] Federal Aviation Administration, FAA Long-Range Aerospace Forecasts
Fiscal Years 2015, 2020 and 2025, FAA-APO-01-3 (Washington, D.C.: June
2001).
[4] ICF Consulting Group, Evaluation of Air Pollutant Emissions from
Subsonic Commercial Jet Aircraft, EPA420-R-99-013 (Washington, D.C.:
April 1999). In this report, which was prepared for EPA, the agency
acknowledged that some groups, including the air transport industry
were critical of the growth projections, fleet turnover assumptions,
and emissions estimates used in the report. As a result, these groups
believe the report overstates the amount of emissions generated by
aircraft.
[5] Department of Transportation, Office of the Inspector General,
Airline Industry Metrics (Washington, D.C.: January 7, 2003).
[6] 42 U.S.C. 7401-7626.
[7] State implementation plans are based on analyses of emissions from
all sources in the area and computer models to determine whether air
quality violations will occur. If data show that air quality standards
will be exceeded, the states are required to impose controls on
existing emission sources to prevent this situation.
[8] The criteria pollutants are carbon monoxide, lead, nitrogen
dioxide, particulate matter, ozone, and sulfur dioxide.
[9] 49 U.S.C. section 47106.
[10] Major commercial airports are the 50 busiest airports in 2001,
based on air carrier operations at those airports.
[11] The reduction was calculated using total nitrogen oxide emissions
from John L. Kennedy International and LaGuardia Airports for 1999.
[12] 49 U.S.C. section 47136.
[13] The 10 airports are Atlanta Hartsfield, Baltimore Washington
International, Baton Rouge Metropolitan, Denver International, Dallas/
Fort Worth International, New York John F. Kennedy International, New
York LaGuardia, Chicago O‘Hare International, San Francisco
International, and Sacramento International.
[14] FAA‘s Airport Improvement Program provides grants to airports for
capital development. FAA allocates most grants on the basis of a
legislated formula tied to the number of passengers an airport enplanes
and categories earmarked for specific types of airports and projects.
[15] Most airports are able to charge passengers a boarding fee, called
a passenger facility charge, to help pay for their capital development
projects. The program is managed by FAA, which approves an airport‘s
application to participate and the specific projects to be funded.
[16] For example, if an airport produces 100 tons of nitrogen oxides
per year and then voluntarily initiates a project that reduces the
amount by 10 tons, the baseline becomes
90 tons. If an expansion project then results in a 10-ton yearly
increase in nitrogen oxides, the airport might have to initiate new
mitigation measures that will compensate for the increase.
[17] In September 2002, FAA and EPA issued guidance for airports
developing early emissions reduction programs.
[18] The 13 states encompass all 26 of the top 50 busiest commercial
airports located in areas designated as not in attainment for ozone.
[19] Market-based options are rewards or inducements to reduce
emissions. They can be in the form of charges, emission credit-trading
regimes, and voluntary measures. According to ICAO, market-based
measures are policy tools that are designed to achieve environmental
goals at a lower cost and in a more flexible manner than traditional
emission reduction measures.
[20] Emissions trading is a market based approach to reducing
emissions. As practiced in the United States, a ’cap“ or limit is set
on the amount of emissions allowed from regulated sources, such as
power plants. The cap is set lower than historical emissions to cause
reductions. Sources are then given an allowance, which authorizes them
to emit a fixed amount of a pollutant. Sources whose emissions are
lower than their allowance, can sell the remainder of their allowance
on the open market to sources that have exceeded their allowance.
[21] Massachusetts Port Authority, Air Quality Initiative for Boston
Logan International Airport (March 2001).
[22] To the extent possible, we compared aircraft that can be used
interchangeably to fulfill the same mission (same number of passengers,
same range). In instances where aircraft fly the same routes but have
different seating capacity, we made comparisons on a per seat basis.
The most straightforward comparison of newest versus older aircraft
emissions involves the various Boeing 737 models. This family of
medium-sized jets made
22.6 percent of all landings and takeoffs in the 2001 U.S. aircraft
fleet. Furthermore, all models in this family have been updated in the
last 5 years with improved airframes and engines.
[23] The U.S. 2001 commercial fleet included 988 older Boeing 737s.
They accounted for
17.6 percent of this fleet‘s landings and takeoffs and 13.4 percent of
this fleet‘s nitrogen oxides emissions during landing and takeoffs. The
U.S. 2001 commercial fleet included
449 newer Boeing 737s. They accounted for 5.0 percent of this fleet‘s
landings and takeoffs and 5.5 percent of this fleet‘s nitrogen oxide
emissions during landings and takeoffs.
[24] Almost all that is known about the emission characteristics of a
particular engine comes from these certification tests, which cover
four modes of the landing/takeoff cycle (taxi in/taxi out, takeoff,
climb out, and approach). Landing/takeoff emissions are derived from
computer models that combine the engine certification emission data
with characteristics of specific aircraft.
[25] The ICAO Engine Exhaust Emissions Data Bank lists the power of the
CFM56 3B-1 engine (used on the Boeing 737-700) at 89.4 kiloNewtons. The
CFM56 7B-20 (used on the Boeing 737-700) is rated at 91.6 kiloNewtons.
[26] According to FAA, this approach has produced an aircraft fleet
that is about 65 percent more fuel efficient than in 1970 and aircraft
engines with a high safety record.
[27] The new fuel-efficient engines are operating at increasingly
higher engine operating pressures. The nitrogen oxides emissions
standards allow for increasing emissions as this pressure increases.
[28] National Research Council, For Greener Skies, Reducing
Environmental Impacts of Aviation (Washington, D.C.: National Academy
Press, 2002).
[29] According to FAA official, aircraft are more heavily regulated
than other mobile sources in terms of design, maintenance, and
operation and have safety and noise regulations that other mobile
sources lack.
[30] National Research Council, For Greener Skies, Reducing
Environmental Impacts of Aviation (Washington, D.C.: National Academy
Press, 2002).
[31] Ibid.
[32] Howard G. Aylesworth, Jr. and Peter Newton, ’Qualitative Standards
of the Environmental Effectiveness of International Civil Aviation
Organization Emissions Standards and Recommended Practices,“ Handbook
of Airline Strategy: Public Policy, Regulatory Issues, Challenges, and
Solutions (Washington, D.C: Aviation Week, 2001).
[33] ICAO‘s analyses use 26 minutes as the default value for taxi-time.
Our analysis of information provided by FAA indicated that 15 minutes
was a more appropriate value for the large number of U.S. airports in
our analysis.
[34] Environmental Protection Agency, National Air Quality and
Emissions Trends Report, 1999, EPA 454/R-01-004 (Washington, D.C.:
March 2001).
[35] ICF Consulting Group, Evaluation of Air Pollutant Emissions from
Subsonic Commercial Jet Aircraft, EPA420-R-99-013 (Washington, D.C.:
April 1999). In this report, which was prepared for EPA, the agency
acknowledged that some groups, including the air transport industry
were critical of the growth projections, fleet turnover assumptions,
and emissions estimates used in the report. As a result, these groups
believe the report overstates the amount of emissions generated by
aircraft.
[36] Dallas/Fort Worth International Airport, Inventory of Air
Emissions (July 1998).
[37] The City of Chicago, Findings Regarding Aircraft Emissions: O‘Hare
Airport and Surrounding Communities (December 1999).
[38] Massachusetts Port Authority, Air Quality Initiative for Boston
Logan International Airport (March 2001).
[39] Our estimates were developed from information contained in Dallas/
Fort Worth International Airport Emissions Inventory (July 1998) and
emissions inventories for the Dallas/Forth Worth metropolitan area
contained in that area‘s State Implementation Plan.
[40] Energy and Environmental Analysis, Inc., Analysis of Techniques to
Reduce Air Emissions at Airports, (Arlington, VA: June 1997). The four
airports included in this study, which was conducted for EPA, were
Baltimore-Washington International Airport, Boston Logan International
Airport, Los Angeles International Airport, and Phoenix Sky Harbor
International Airport.
[41] According to EPA, mobile sources are moving objects that release
pollution; mobile sources include cars, trucks, buses, planes, trains,
motorcycles, and gasoline-powered lawn mowers. Mobile sources are
divided into two groups: road vehicles, which include cars, trucks and
buses, and nonroad vehicles, which include trains, planes, and lawn
mowers. Mobile sources are distinguished from stationary sources, which
are places or objects from which pollutants are released and which do
not move around. Stationary sources include power plants, gas stations,
incinerators, houses, etc.
[42] Environmental Protection Agency, Environmental Fact Sheet: Adopted
Aircraft Emissions Standards (EPA 420-F-97-010, April 1997) and Federal
Aviation Administration, Air Quality Procedures For Civilian Airports
and Air Force Bases (Washington: April 1997).
[43] Intergovernmental Panel on Climate Change, Aviation and the Global
Atmosphere (1999).
[44] 42 U.S.C 7401-7626. The amendment to the Clean Air Act in 1990
provided for a number of related programs designed to protect health
and control air pollution. The 1990 amendments established new programs
and made major changes in the ways that air pollution is controlled.
See U.S. General Accounting Office, Air Pollution: Status of
Implementation and Issues of the Clean Air Act Amendments of 1990, GAO/
RCED-00-72 (Washington, D.C.: Apr.17, 2000).
[45] See 42 U.S.C. 7571 of the Clean Air Act.
[46] California is authorized, under section 209(e)(2)(B) of the Clean
Air Act to enact and enforce nonroad engine standards, which apply to
ground support equipment. States with nonattainment areas can
promulgate standards identical to those of California. Otherwise, the
federal standard applies. In November 2002, EPA adopted emissions
standards for nonroad large spark emissions engines such as those used
in much of the ground support equipment currently in service at
airports.
[47] The airports in the Los Angeles region include Burbank, Long
Beach, Los Angeles International, John Wayne (Orange County), Ontario
International, and Palm Springs International.
[48] The California Air Resources Board has reached agreement with the
major carriers in Southern California to reduce emissions from ground
support equipment.
[49] 49 U.S.C. 47106.
[50] The 1-hour ozone standard is the average amount of ozone allowed
by EPA in the lower atmosphere during a one-hour period.
[51] The agency‘s name was recently changed to the Texas Commission on
Environmental Quality.
[52] Air carrier representatives have noted that the airport‘s proposed
strategies could be subject to legal challenge if they are implemented.
[53] Federal Aviation Administration, Air Quality Procedures For
Civilian Airports and Air Force Bases (Washington, D.C.: April 1997).
[54] Federal Aviation Administration, Air Quality Procedures For
Civilian Airports and Air Force Bases (Washington: April 1997).
[55] NASA officials told us that their nitrogen oxide research goals
are more ambitious than what they expect to actually achieve when their
research is incorporated into production ready engine designs. This is
because designs that work well during component level research testing
will undergo modification as the complete engine design is refined to
meet safety and operability requirements and fuel-efficiency goals.
[56] FAA, the aviation industry, and universities also participate with
this research.
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