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![handle is hein.crs/govepri0001 and id is 1 raw text is: Congressional Research Service
Informing the IegisI9tive debate since 1914
Updated April 26, 2024
Aviation, Air Pollution, and Climate Change
Some Members of Congress have expressed interest in
addressing air pollution emissions, greenhouse gas (GHG)
emissions, and the climate change effects from domestic
and international aviation. Recent legislative proposals
would provide for sustainable fuel mandates, incentives for
airport efficiency improvements, and GHG emission
targets, among other requirements.
Emssions from Aircraft
The U.S. Environmental Protection Agency (EPA)
estimates that transportation-including passenger cars and
light trucks, heavy-duty trucks, buses, trains, ships, and
aircraft-accounted for 37% of carbon dioxide (CO2, the
principal GHG) emissions in 2021. While CO2 emissions
from passenger cars and light trucks exceed those from
aircraft in the United States, CO2 emissions from aviation
are currently experiencing a faster rate of growth. All
aircraft, including military, commercial, and privately
chartered, accounted for 11% of the U.S. transportation
sector's CO2 emissions and 4% of all U.S. CO2 emissions in
2021. Commercial aircraft, including those operated by
passenger and all-cargo airlines, accounted for 7% of
transportation sector and 3% of all emissions. These
estimates include emissions from U.S. domestic flights and
emissions from international flights departing the United
States, referred to as international bunkering.
In the United States, aggregate CO2emissions from aircraft
have fluctuated due to changes in technology, the economy,
travel frequency, and military activity, among other
reasons. However, since the global financial crisis in 2009,
aggregate CO2 emissions from all aircraft types have grown
steadily, increasing by almost 22% between 2009 and 2019.
This increase makes aircraft one of the faster-growing
sources of CO2 emissions in the U.S. transportation sector
over the past decade. This trend was affected, at least
temporarily, by reduced air travel in 2020 and 2021 due to
Coronavirus Disease 2019 (COVID-19).
The effects of aircraft emissions on the atmosphere are
complex, reflecting differing altitudes, geography, time
horizons, and environmental conditions. Research has
shown that in addition to CO2 emissions, other factors
increase the climate change impacts of aviation. These
factors include the contribution of aircraft emissions to
ozone production; the formation of water condensation
trails and cirrus clouds; the emission of various gases and
particles, including water vapor, nitrous oxides, sulfates,
and particulates from jet fuel combustion; and the high
altitude location of the bulk of these emissions. In
examining the warming and cooling influences of these
factors, the United Nations' Intergovernmental Panel on
Climate Change estimated aviation's total climate change
impact could be from two to four times that of its past CO2
emissions alone.
Aside from GHG emissions, aircraft engines emit a number
of criteria-or common-pollutants, including nitrogen
oxides, carbon monoxide, oxides of sulfur, unburned or
partially combusted hydrocarbons (also known as volatile
organic compounds [VOCs]), particulates, and other trace
compounds. A subset of the VOCs and particulates are
considered hazardous air pollutants.
Emission Reduction Strategies
In an effort to reduce emissions from the aviation sector,
the U.S. government, other nations, and international
organizations have worked together with the aviation
industry toward improving technologies, increasing the
efficient use of aircraft and airport infrastructure, adopting
appropriate economic incentives, and setting standards.
Aircraft Emission Standards: Domest c Process
In the United States, in accordance with Clean Air Act
(CAA) Section 231 (42 U.S.C. §7571), EPA sets emission
levels for specified pollutants, as promulgated in 40 C.F.R.
Part 87, Control of Air Pollution from Aircraft and
Aircraft Engines. EPA sets standards for Federal Aviation
Administration (FAA)-certified aircraft according to the
amount of thrust generated by their engines. Aircraft
emission standards currently exist for fuel venting, and
engine hydrocarbons, carbon monoxide, and nitrogen
oxides. In 2021, EPA promulgated standards for CO2
emissions from aircraft engines. In 2022, EPA finalized
standards for particulate emissions from certain classes of
engines used by civil subsonic jet aircraft (87 FR 72312). In
2023, EPA finalized an endangerment finding for lead
pollution from gasoline-powered, piston-engine aircraft (88
FR 72372). With this final determination, EPA is required
to propose and promulgate regulatory standards for lead
emissions from aircraft engines.
The standard-setting language under CAA Section 231 is
similar to the statutory language for other mobile sources in
the CAA (e.g., cars, trucks, buses). However, compared to
other mobile sources, EPA must meet additional
requirements in setting emission standards for aircraft and
aircraft engines: (1) the EPA Administrator must consult
with the Administrator of the FAA and the Secretary of the
U.S. Department of Transportation (DOT) in developing
emission standards; (2) the EPA Administrator cannot
change standards if doing so would significantly increase
noise and adversely affect safety; and (3) the President
may disapprove any such standards if the DOT Secretary
finds that they would create a hazard to aircraft safety.
CAA Section 232 requires the FAA to enforce the standards
at the time an engine is certified for emissions under 14
C.F.R. Part 34, Fuel Venting and Exhaust Emission
Requirements for Turbine Engine Powered Airplanes.
Since compliance with the federal standards is determined](ViewImageLocal?handle=hein.crs/govepri0001&div=1&collection=&method=preview&ext=.png&size=3)