Environmental effects of aviation

Source: Wikipedia, the free encyclopedia.
(Redirected from
Environmental impact of aviation
)

CO2 emissions grew from 0.7% to 2.65% of all CO2 emissions.[1]

environmental concerns over their global effects and their effects on local air quality.[2]
contrails
and particulates. Their
radiative forcing is estimated at 1.3–1.4 that of CO2 alone, excluding induced cirrus cloud with a very low level of scientific understanding. In 2018, global commercial operations generated 2.4% of all CO2 emissions.[3]

Jet airliners have become 70% more fuel efficient between 1967 and 2007, and CO2 emissions per revenue

ton-kilometer
(RTK) in 2018 were 47% of those in 1990. In 2018, CO2 emissions averaged 88 grams of CO2 per revenue passenger per km. While the
fuel efficient, overall emissions have risen as the volume of air travel has increased. By 2020, aviation emissions were 70% higher than in 2005 and they could grow by 300% by 2050.[4]

cardiovascular risk
.
Airports can generate water pollution due to their extensive handling of jet fuel and deicing chemicals if not contained
, contaminating nearby water bodies. Aviation activities emit
health hazards. Piston engines used in general aviation burn Avgas, releasing toxic lead
.

Aviation's environmental footprint can be reduced by better fuel economy in aircraft, or air traffic control and flight routes can be optimized to lower non-CO2 effects on climate from NO
x
, particulates or contrails.

ICAO's CORSIA, can lower CO2 emissions. Aviation usage can be lowered by short-haul flight bans, train connections, personal choices and aviation taxation and subsidies. Fuel-powered aircraft may be replaced by hybrid electric aircraft and electric aircraft or by hydrogen-powered aircraft
. Since 2021, the IATA members plan net-zero carbon emissions by 2050, followed by the ICAO in 2022.

Climate change

Factors

Radiative forcings from aviation emissions estimated in 2020[1]

Airplanes emit gases (

hydrocarbons, sulfur oxides, black carbon), interacting among themselves and with the atmosphere.[5]
While the main
jet airliners contribute to climate change in four ways as they fly in the tropopause:[6]

Carbon dioxide (CO2)
CO2 emissions are the most significant and best understood contribution to climate change.[7] The effects of CO2 emissions are similar regardless of altitude. Airport ground vehicles, those used by passengers and staff to access airports, emissions generated by airport construction and aircraft manufacturing also contribute to the greenhouse gas emissions from the aviation industry.[8]
Nitrogen oxides (NO
x
, nitric oxide and nitrogen dioxide
)
In the tropopause, emissions of NO
x
favor
ozone (O
3
) formation in the upper troposphere. At altitudes from 8 to 13 km (26,000 to 43,000 ft), NO
x
emissions result in greater concentrations of O
3
than surface NO
x
emissions and these in turn have a greater global warming effect. The effect of O
3
surface concentrations are regional and local, but it becomes well mixed globally at mid and upper tropospheric levels.[9] NO
x
emissions also reduce ambient levels of methane, another greenhouse gas, resulting in a climate cooling effect, though not offsetting the O
3
forming effect. Aircraft sulfur and water emissions in the stratosphere tend to deplete O
3
, partially offsetting the NO
x
-induced O
3
increases, although these effects have not been quantified.[10] Light aircraft and small commuter aircraft fly lower in the troposphere, not in the tropopause.
Contrails and cirrus clouds
Contrails and cirrus clouds
Fuel burning produces water vapor, which condenses at high altitude, under cold and humid conditions, into visible line clouds: condensation trails (contrails). They are thought to have a global warming effect, though less significant than CO2 emissions.[11] Contrails are uncommon from lower-altitude aircraft. Cirrus clouds can develop after the formation of persistent contrails and can have an additional global warming effect.[12] Their global warming contribution is uncertain and estimating aviation's overall contribution often excludes cirrus cloud enhancement.[7]
Particulates
Compared with other emissions, sulfate and soot particles have a smaller direct effect: sulfate particles have a cooling effect and reflect radiation, while soot has a warming effect and absorbs heat, while the clouds' properties and formation are influenced by particles.[13] Contrails and cirrus clouds evolving from particles may have a greater radiative forcing effect than CO2 emissions.[14] As soot particles are large enough to serve as condensation nuclei, they are thought to cause the most contrail formation. Soot production may be decreased by reducing the aromatic compound of jet fuel.[15][16][17]

In 1999, the IPCC estimated aviation's radiative forcing in 1992 to be 2.7 (2 to 4) times that of CO2 alone − excluding the potential effect of cirrus cloud enhancement.[6] This was updated for 2000, with aviation's radiative forcing estimated at 47.8 mW/m2, 1.9 times the effect of CO2 emissions alone, 25.3 mW/m2.[7]

In 2005, research by David S. Lee, et al., published in the scientific journal Atmospheric Environment estimated the cumulative radiative forcing effect of aviation at 55 mW/m2, which is twice the 28 mW/m2 radiative forcing effect of its CO2 emissions alone, excluding induced cirrus cloud, with a very low level of scientific understanding.[18] In 2012, research from

Chalmers university estimated this weighting factor at 1.3–1.4 if aviation induced cirrus is not included, 1.7–1.8 if they are included (within a range of 1.3–2.9).[19]

Uncertainties remain on the NOx–O3–CH4 interactions, aviation-produced contrails formation, the effects of soot aerosols on cirrus clouds and measuring non-CO2 radiative forcing.[5]

In 2018, CO2 represented 34.3 mW/m2 of aviation's effective radiative forcing (ERF, on the surface), with a high

confidence level (± 6 mW/m2), NOx 17.5 mW/m2 with a low confidence level (± 14) and contrail cirrus 57.4 mW/m2, also with a low confidence level (± 40).[1]
All factors combined represented 43.5 mW/m2 (1.27 that of CO2 alone) excluding contrail cirrus and 101 mW/m2 (±45) including them, 3.5% of the anthropogenic ERF of 2290 mW/m2 (± 1100).[1]

Volume

By 2018,

ICAO.[20]
The traffic was experiencing continuous growth, doubling every 15 years, despite external shocks − a 4.3% average yearly growth and Airbus forecasts expect the growth to continue.[21] While the
technological advancement and operations improvements, overall emissions have risen as the volume of air travel has increased.[22]
Between 1960 and 2018, RPKs increased from 109 to 8,269 billion.[1]

In 1992, aircraft emissions represented 2% of all man-made CO2 emissions, having accumulated a little more than 1% of the total man-made CO2 increase over 50 years.[10] By 2015, aviation accounted for 2.5% of global CO2 emissions.[23] In 2018, global commercial operations emitted 918 million tonnes (Mt) of CO2, 2.4% of all CO2 emissions: 747 Mt for passenger transport and 171 Mt for freight operations.[3] Between 1960 and 2018, CO2 emissions increased 6.8 times from 152 to 1,034 million tonnes per year.[1] Emissions from flights rose by 32% between 2013 and 2018.[24]

Aviation GHG emissions within the European Economic Area for the EU ETS, showing the top 10 emitters (2013–2019).[25]

Between 1990 and 2006, greenhouse gas emissions from aviation increased by 87% in the European Union.[26] In 2010, about 60% of aviation emissions came from international flights, which are outside the emission reduction targets of the

carbon credits from other industries and projects.[28]

In 1992, aircraft radiative forcing was estimated by the IPCC at 3.5% of the total man-made radiative forcing.[29]

Per passenger

Between 1950 and 2018, efficiency per passenger grew from 0.4 to 8.2 RPK per kg of CO2.[1]

As it accounts for a large share of their costs, 28% by 2007, airlines have a strong incentive to lower their fuel consumption, reducing their environmental footprint.[30] Jet airliners have become 70% more fuel efficient between 1967 and 2007.[30] Jetliner fuel efficiency improves continuously, 40% of the improvement come from engines and 30% from airframes.[31] Efficiency gains were larger early in the

jet age than later, with a 55–67% gain from 1960 to 1980 and a 20–26% gain from 1980 to 2000.[32]

The average fuel burn of new aircraft fell 45% from 1968 to 2014, a compounded annual reduction of 1.3% with variable reduction rate.[33] By 2018, CO2 emissions per revenue

ton-kilometer (RTK) were more than halved compared to 1990, at 47%.[34]
The aviation energy intensity went from 21.2 to 12.3 MJ/RTK between 2000 and 2019, a 42% reduction.[35]

In 2018, CO2 emissions totalled 747 million tonnes for passenger transport, for 8.5 trillion

revenue passenger kilometres (RPK), giving an average of 88 gram CO2 per RPK.[3]
The UK's Department for BEIS calculate a long-haul flight release 102g of CO2 per passenger kilometre, and 254g of CO2 equivalent, including non-CO2 greenhouse gas emissions, water vapor etc.; for a domestic flight in Britain.[24]

The ICAO targets a 2% efficiency improvement per year between 2013 and 2050, while the IATA targets 1.5% for 2009–2020 and to cut net CO2 emissions in half by 2050 relative to 2005.[35]

Evolution

In 1999, the IPCC estimated aviation's radiative forcing may represent 190 mW/m2 or 5% of the total man-made radiative forcing in 2050, with the uncertainty ranging from 100 to 500 mW/m2.[36] If other industries achieve significant reductions in greenhouse gas emissions over time, aviation's share, as a proportion of the remaining emissions, could rise.

Alice Bows-Larkin estimated that the annual global CO2 emissions budget would be entirely consumed by aviation emissions to keep the climate change temperature increase below 2 °C by mid-century.[37] Given that growth projections indicate that aviation will generate 15% of global CO2 emissions, even with the most advanced technology forecast, she estimated that to hold the risks of dangerous climate change to under 50% by 2050 would exceed the entire carbon budget in conventional scenarios.[38]

In 2013, the National Center for Atmospheric Science at the University of Reading forecast that increasing CO2 levels will result in a significant increase in in-flight turbulence experienced by transatlantic airline flights by the middle of the 21st century.[39]

Aviation CO2 emissions grow despite efficiency innovations to aircraft, powerplants and flight operations.[40][41] Air travel continue to grow.[42][43]

In 2015, the Center for Biological Diversity estimated that aircraft could generate 43 Gt of carbon dioxide emissions through 2050, consuming almost 5% of the remaining global carbon budget. Without regulation, global aviation emissions may triple by mid-century and could emit more than 3 Gt of carbon annually under a high-growth, business-as-usual scenario. Many countries have pledged emissions reductions for the Paris Agreement, but the sum of these efforts and pledges remains insufficient and not addressing airplane pollution would be a failure despite technological and operational advancements.[44]

The International Energy Agency projects aviation share of global CO2 emissions may grow from 2.5% in 2019 to 3.5% by 2030.[45]

By 2020, global international aviation emissions were around 70% higher than in 2005 and the ICAO forecasts they could grow by over further 300% by 2050 in the absence of additional measures.[4]

By 2050, aviation's negative effects on climate could be decreased by a 2% increase in fuel efficiency and a decrease in NOx emissions, due to advanced aircraft technologies, operational procedures and renewable alternative fuels decreasing radiative forcing due to sulfate aerosol and black carbon.[5]

Noise

Noise map of Berlin Tegel Airport

cardiovascular risk for airport neighbours.[46] Sleep disruption can be reduced by banning or restricting flying at night, but disturbance progressively decreases and legislation differs across countries.[46]

The

'chevrons' on the back of the nacelle reduce noise.[50]

A

Continuous Descent Approach (CDA) is quieter as less noise is produced while the engines are near idle power.[51] CDA can reduce noise on the ground by ~1–5 dB per flight.[52]

Water pollution

Excess aircraft deicing fluid may contaminate nearby water bodies

Airports can generate significant water pollution due to their extensive use and handling of jet fuel, lubricants and other chemicals. Chemical spills can be mitigated or prevented by spill containment structures and clean-up equipment such as vacuum trucks, portable berms and absorbents.[53]

Deicing fluids used in cold weather can pollute water, as most of them fall to the ground and surface runoff can carry them to nearby streams, rivers or coastal waters.[54]: 101  Deicing fluids are based on ethylene glycol or propylene glycol.[54]: 4  Airports use pavement deicers on paved surfaces including runways and taxiways, which may contain potassium acetate, glycol compounds, sodium acetate, urea or other chemicals.[54]: 42 

During degradation in surface waters, ethylene and propylene glycol exert high levels of

dissolved oxygen (DO) in the water column.[55]
: 2–23  Fish,
food-web interactions.[55]
: 2–30 

Glycol-based deicing fluids are toxic to humans and other mammals.[56][57] Research into non-toxic alternative deicing fluids is ongoing.[56]

Air pollution

Aviation is the main human source of ozone, a respiratory

health hazard, causing an estimated 6,800 premature deaths per year.[58]

Aircraft engines emit

ultrafine particles (UFPs) in and near airports, as does ground support equipment. During takeoff, 3 to 50 × 1015 particles were measured per kg of fuel burned,[59] while significant differences are observed depending on the engine.[60] Other estimates include 4 to 200 × 1015 particles for 0.1–0.7 gram,[61] or 14 to 710 × 1015 particles,[62] or 0.1–10 × 1015 black carbon particles for 0.046–0.941 g.[63]

In the

Environmental Protection Agency estimated this released 34,000 tons of lead into the atmosphere between 1970 and 2007.[65] The Federal Aviation Administration recognizes inhaled or ingested lead leads to adverse effects on the nervous system, red blood cells, and cardiovascular and immune systems. Lead exposure in infants and young children may contribute to behavioral and learning problems and lower IQ.[66]

Mitigation

Aviation's environmental footprint can be mitigated by reducing air travel, optimizing flight routes, capping emissions, restricting short-distance flights, increasing taxation and decreasing subsidies to the aviation industry. Technological innovation could also mitigate damage to the environment and climate, for example, through the development of electric aircraft, biofuels, and increased fuel efficiency.

In 2016, the

carbon emissions from 2020 onwards at the same level as those from 2010.[67]
To achieve these goals, multiple measures were identified: more

In December 2020, the UK Climate Change Committee said that: "Mitigation options considered include demand management, improvements in aircraft efficiency (including use of hybrid electric aircraft), and use of sustainable aviation fuels (biofuels, biowaste to jet and synthetic jet fuels) to displace fossil jet fuel."[69]

In February 2021, Europe's aviation sector unveiled its Destination 2050 sustainability initiative towards zero CO2 emissions by 2050:

  • aircraft technology improvements for 37% emission reductions;
  • SAFs for 34%;
  • economic measures for 8%;
  • ATM and operations improvements for 6%;

while air traffic should grow by 1.4% per year between 2018 and 2050.[70] The initiative is led by ACI Europe, ASD Europe, A4E, CANSO and ERA.[70] This would apply to flights within and departing the European single market and the UK.[70]

In October 2021, the IATA committed to net-zero carbon emissions by 2050.[71] In 2022, the ICAO agreed to support a net-zero carbon emission target for 2050.[72]

The aviation sector could be decarbonized by 2050 with moderate demand growth, continuous

CO2 removal to compensate for non-CO2 forcing.[73]
With constant air transport demand and aircraft efficiency, decarbonizing aviation would require nearly five times the 2019 worldwide biofuel production, competing with other hard-to-decarbonize sectors, and 0.2 to 3.4 Gt of CO2 removal to compensate for non-CO2 forcing.[73] Carbon offsets would be preferred if
carbon credits are less expensive than SAFs, but they may be unreliable, while specific routing could avoid contrails.[73]
As of 2023, fuel represents 20-30% of the airlines' operating costs, while SAF is 2–4 times more expensive than fossil jet fuel.[73] Projected cost decreases of green hydrogen and carbon capture could make synthetic fuels more affordable, and lower feedstock costs and higher conversion efficiencies would help FT and HEFA biofuels.[73] Policy incentives like cleaner aviation fuel tax credits and low-carbon fuel standards could induce improvements, and
carbon pricing could render SAFs more competitive, accelerating their deployment and reducing their costs through learning and economies of scale.[73]

According to a 2023 Royal Society study, reaching net zero would need replacing fossil aviation fuel with a low or zero carbon energy source, as battery technologies are unlikely to give enough specific energy.[74] Biofuels can be introduced quickly and with little aircraft modification, but are restricted by scale and feedstock availability, and few are low-carbon.[74] Producing enough renewable electricity to produce green hydrogen would be a costly challenge and would need substantial aircraft and infrastructure modification.[74] Synthetic fuels would need with little aircraft modification, but necessitates green hydrogen feedstock and large scale direct CO2 air capture at high costs.[74] Low-carbon Ammonia would also need costly green hydrogen at scale, and would need substantial aircraft and infrastructure modifications.[74]

In its Sixth Assessment Report, the IPCC notes that sustainable biofuels, low-emissions hydrogen, and derivatives (including ammonia and synthetic fuels) can support mitigation of CO2 emissions but some hard-to-abate residual GHG emissions remain and would need to be counterbalanced by deployment of carbon dioxide removal methods.[75] On 29 March 2003, during a

Senate hearing, hydrogen propulsion proponents like ZeroAvia or Universal Hydrogen bemoaned the incumbents like GE Aerospace or Boeing were supporting sustainable aviation fuel (SAF) because it does not require major changes to existing infrastructure.[76]

An April 2023 report of the Sustainable Aero Lab estimate current in-production aircraft will be the vast majority of the 2050 fleet as

hydrogen aircraft will not be available soon enough : the main decarbonisation drivers will be SAF ; replacing regional jets with turboprop aircraft ; and incentives to replace older jets with new generation ones.[77]

Technology improvements

Electric aircraft

type certificated
electric aircraft on 10 June 2020.

Lithium-ion batteries including packaging and accessories gives a 160 Wh/kg energy density while aviation fuel gives 12,500 Wh/kg.[78] As electric machines and converters are more efficient, their shaft power available is closer to 145 Wh/kg of battery while a gas turbine gives 6,545 Wh/kg of fuel: a 45:1 ratio.[79] For Collins Aerospace, this 1:50 ratio forbids electric propulsion for long-range aircraft.[80] By November 2019, the German Aerospace Center estimated large electric planes could be available by 2040.[81] Large, long-haul aircraft are unlikely to become electric before 2070 or within the 21st century, whilst smaller aircraft can be electrified.[82] As of May 2020, the largest electric airplane was a modified Cessna 208B Caravan
.

For the UK's Committee on Climate Change (CCC), huge technology shifts are uncertain, but consultancy Roland Berger points to 80 new electric aircraft programmes in 2016–2018, all-electric for the smaller two-thirds and hybrid for larger aircraft, with forecast commercial service dates in the early 2030s on short-haul routes like London to Paris, with all-electric aircraft not expected before 2045.[83] Berger predicts a 24% CO2 share for aviation by 2050 if fuel efficiency improves by 1% per year and if there are no electric or hybrid aircraft, dropping to 3–6% if 10-year-old aircraft are replaced by electric or hybrid aircraft due to regulatory constraints, starting in 2030, to reach 70% of the 2050 fleet.[83] This would greatly reduce the value of the existing fleet of aircraft, however.[83] Limits to the supply of battery cells could hamper their aviation adoption, as they compete with other industries like electric vehicles.

Lithium-ion batteries have proven fragile and fire-prone and their capacity deteriorates with age. However, alternatives are being pursued, such as sodium-ion batteries.[83]

Hydrogen-powered aircraft

In 2020, Airbus unveiled liquid-hydrogen-powered aircraft concepts as zero-emissions airliners, poised for 2035.[84] Aviation, like industrial processes that cannot be electrified, could use primarily Hydrogen-based fuel.[85]

A 2020 study by the EU Clean Sky 2 and Fuel Cells and Hydrogen 2 Joint Undertakings found that hydrogen could power aircraft by 2035 for short-range aircraft.[86] A short-range aircraft (< 2,000 km, 1,100 nmi) with hybrid Fuel cell/Turbines could reduce climate impact by 70-80% for a 20-30% additional cost, a medium-range airliner with H2 turbines could have a 50-60% reduced climate impact for a 30-40% overcost, and a long-range aircraft (> 7,000 km, 3,800 nmi) also with H2 turbines could reduce climate impact by 40-50% for a 40-50% additional cost.[86] Research and development would be required, in aircraft technology and into hydrogen infrastructure, regulations and certification standards.[86]

Sustainable aviation fuels (SAF)

Airbus A320 with biofuel
in 2011

An aviation biofuel (also known as bio-jet fuel

environmental impact of aviation.[89] Aviation biofuel is used to decarbonize medium and long-haul air travel. These types of travel generate the most emissions, and could extend the life of older aircraft types by lowering their carbon footprint. Synthetic paraffinic kerosene (SPK) refers to any non-petroleum-based fuel designed to replace kerosene jet fuel
, which is often, but not always, made from biomass.

Biofuels are

The first test flight using blended biofuel was in 2008,and in 2011, blended fuels with 50% biofuels were allowed on commercial flights. In 2023 SAF production was 600 million liters, representing 0.2% of global jet fuel use.[91]

Aviation biofuel can be produced from plant or animal sources such as

tallows, waste oils, palm oil, Babassu, and Camelina (bio-SPK); from solid biomass using pyrolysis processed with a Fischer–Tropsch process (FT-SPK); with an alcohol-to-jet (ATJ) process from waste fermentation; or from synthetic biology through a solar reactor. Small piston engines can be modified to burn ethanol
.

sustainable
by a third-party organisation.

Electrofuels (e-fuels)

The Potsdam Institute for Climate Impact Research reported a €800–1,200 mitigation cost per ton of CO2 for hydrogen-based e-fuels.[93] Those could be reduced to €20–270 per ton of CO2 in 2050, but maybe not early enough to replace

fossil fuels.[93]
Climate policies could bear the risk of e-fuel uncertain availability, and Hydrogen and e-fuels may be prioritised when direct electrification is inaccessible.[93]

Reducing air travel

UK air travel by income quintile through time[94]
Global distribution of aviation fuel use[95]

Aviation is one of three sectors identified in a study where "demand-side options" can have a large effect in "reaching SDS levels".[96] According to a study, the attainment of the 1.5–2°C global temperature goal necessitates substantial demand reductions in the critical sectors of aviation, shipping, road freight, and industry, should large-scale negative emissions not be realized.[97] According to the IMAGE model used to project scenarios aimed at limiting global temperature increases to 1.5°C and 2°C, it is suggested that achieving deep decarbonization within the aviation sector within the specified timeframe is contingent upon a reduction in air travel in certain markets.[97] The decreases in carbon intensity of aviation energy in net-zero scenarios "are heavily dependent on projected changes in aviation demand and energy intensity".[98] The significant challenges of sustainable aviation fuel expansion, including food security, local community impacts, and land use issues, underscore the importance of simultaneous demand reduction efforts.[98] For instance, according to a report by the Royal Society, to produce enough biofuel to supply the UK's aviation industry would require using half of Britain's farming land which would put major pressures on food supplies.[99][100]

Tourism is projected to generate up to 40% of total global CO2 emissions by 2050.[101] Of climate change mitigation consumption options investigated by a review, the consumption options with "the highest mitigation potential advocate reduction in car and air travel".[102] A study projected a potential reduction of "transport direct CO2 emissions by around 50% in the end of the century compared to the baseline" via combined behavioral factors.[103]

Measures

The Taiwan High Speed Rail in 2007

According to the IPCC Sixth Assessment Report, "the greatest Avoid potential" in demand-side mitigation, which consists of Avoid-Shift-Improve (ASI) options, "comes from reducing long-haul aviation and providing short-distance low-carbon urban infrastructure".[104] It lists the following related mobility measures:[104]

It found that socio-cultural factors promoting a preference for train travel over long-haul flights have the potential to reduce aviation greenhouse gas emissions by 10% to 40% by 2050.[104]

The ICCT estimates that 3% of the global population take regular flights.[24] Stefan Gössling of the Western Norway Research Institute estimates 1% of the world population emits half of commercial aviation's CO2, while close to 90% does not fly in a given year.[105]

Per capita emissions from domestic and international flights

In early 2022, the European Investment Bank published the results of its 2021–2022 Climate Survey, showing that 52% of Europeans under 30, 37% of people between 30 and 64 and 25% for people aged 65 and above plan to travel by air for their summer holidays in 2022; and 27% of those under 30, 17% for people aged 30–64 and 12% for people aged 65 and above plan to travel by air to a faraway destination.[106]

Short-haul flight ban
A short-haul flight ban is a prohibition imposed by
environmental impact of aviation (most notably to reduce anthropogenic greenhouse gas emissions which is the leading cause of climate change). In the 21st century, several governments, organisations and companies have imposed restrictions and even prohibitions on short-haul flights, stimulating or pressuring travellers to opt for more environmentally friendly means of transportation, especially trains.[107]
Flight shame
In Sweden the concept of "flight shame" or "flygskam" has been cited as a cause of falling air travel.[108] Swedish rail company SJ AB reports that twice as many Swedish people chose to travel by train instead of by air in summer 2019 compared with the previous year.[109] Swedish airports operator Swedavia reported 4% fewer passengers across its 10 airports in 2019 compared to the previous year: a 9% drop for domestic passengers and 2% for international passengers.[110]
Personal allowances
Personal carbon allowances (PCAs) where all adults receive "an equal, tradable carbon allowance that reduces over time in line with national targets."[111][112][113][excessive citations] Everyone would have a share of allowed carbon emissions and would need to trade further emissions allowances.[114][importance?] An alternative would be rationing everyone's flights: an "individual cap on air travel, that people can trade with each other".[115]

Economic measures

Emissions trading

European Union Emission Trading Scheme

carbon credits from other companies.[117][118] The Centre for Aviation, Transport and Environment at Manchester Metropolitan University estimates the only way to lower emissions is to put a price on carbon and to use market-based measures like the EU ETS.[119]

Taxation and subsidies

Financial measures can discourage airline passengers and promote other

transportation modes
and motivates airlines to improve fuel efficiency. Aviation taxation include:

  • air passenger taxes
    , paid by passengers for environmental reasons, may be variable by distance and include domestic flights;
  • departure taxes, paid by passengers leaving the country, sometimes also applies outside aviation;
  • banned in the European Union
    .

Consumer behavior can be influenced by cutting subsidies for unsustainable aviation and subsidising the development of sustainable alternatives. By September–October 2019, a carbon tax on flights would be supported by 72% of the EU citizens, in a poll conducted for the European Investment Bank.[120]

Aviation taxation could reflect all its

emissions trading scheme.[121]
International aviation emissions escaped international regulation until the ICAO triennial conference in 2016 agreed on the CORSIA offset scheme.[122] Due to low or nonexistent taxes on aviation fuel, air travel has a competitive advantage over other transportation modes.[123][124]

Carbon offsetting

Money generated by carbon offsets from airlines often go to fund green-energy projects such as wind farms.

A carbon offset is a means of compensating aviation emissions by saving enough carbon or absorbing carbon back into plants through photosynthesis (for example, by planting trees through reforestation or afforestation) to balance the carbon emitted by a particular action.

However, carbon credits

permanence and additionality can be questionable.[73] More than 90% of rainforest offset credits certified by Verra's Verified Carbon Standard may not represent genuine carbon reductions.[125]

Consumer option

Some airlines offer carbon offsets to passengers to cover the emissions created by their flight, invested in

Emirates Airlines, Gulf Air, Jetstar, Lufthansa, Qantas, United Airlines and Virgin Australia.[130] Consumers can also purchase offsets on the individual market. There are certification standards for these,[131] including the Gold Standard[132] and the Green-e.[133]

National carbon budgets

In UK, transportation replaced power generation as the largest emissions source. This includes aviation's 4% contribution. This is expected to expand until 2050 and passenger demand may need to be reduced.

Committee on Climate Change (CCC), the UK target of an 80% reduction from 1990 to 2050 was still achievable from 2019, but the committee suggests that the Paris Agreement should tighten its emission targets.[83]
Their position is that emissions in problematic sectors, like aviation, should be offset by The UK will include international aviation and shipping in their carbon budgets and hopes other countries will too.[134]

Airline offsets

Some airlines have been carbon-neutral like Costa Rican

Harbour Air Seaplanes.[136] Long-haul low-cost venture Fly POP aims to be carbon neutral.[137]

In 2019, Air France announced it would offset CO2 emissions on its 450 daily domestic flights, that carry 57,000 passengers, from January 2020, through certified projects. The company will also offer its customers the option to voluntarily compensate for all their flights and aims to reduce its emissions by 50% per pax/km by 2030, compared to 2005.[138]

Starting in November 2019, UK budget carrier EasyJet decided to offset carbon emissions for all its flights, through investments in atmospheric carbon reduction projects. It claims to be the first major operator to be carbon neutral, at a cost of £25 million for its 2019–20 financial year. Its CO2 emissions were 77 g per passenger in its 2018–19 financial year, down from 78.4 g the previous year.[139]

From January 2020, British Airways began offsetting its 75 daily domestic flights emissions through carbon-reduction project investments. The airline seeks to become carbon neutral by 2050 with fuel-efficient aircraft, sustainable fuels and operational changes. Passengers flying overseas can offset their flights for £1 to Madrid in economy or £15 to New York in business-class.[140]

US low-cost carrier JetBlue planned to use offsets for its emissions from domestic flights starting in July 2020, the first major US airline to do so. It also plans to use sustainable aviation fuel made from waste by Finnish refiner Neste starting in mid-2020.[141] In August 2020, JetBlue became entirely carbon-neutral for its U.S. domestic flights, using efficiency improvements and carbon offsets.[142] Delta Air Lines pledged to do the same within ten years.[143]

To become carbon neutral by 2050, United Airlines invests to build in the US the largest carbon capture and storage facility through the company 1PointFive, jointly owned by Occidental Petroleum and Rusheen Capital Management, with Carbon Engineering technology, aiming for nearly 10% offsets.[144]

Air traffic management improvements

Air Traffic Control
would allow more direct routes

An improved

air corridors and optimized cruising altitudes, would allow airlines to reduce their emissions by up to 18%.[30] In the European Union, a Single European Sky has been proposed since 1999 to avoid overlapping airspace restrictions between EU countries and to reduce emissions.[145] By 2007, 12 million tons of CO2 emissions per year were caused by the lack of a Single European Sky.[30] As of September 2020, the Single European Sky has still not been completely achieved, costing 6 billion euros in delays and causing 11.6 million tonnes of excess CO2 emissions.[146]

Operations improvements

Economic cost and climate influence relation for transatlantic traffic
Non-CO2 emissions
Besides carbon dioxide, aviation produces nitrogen oxides (NO
x
), particulates, unburned hydrocarbons (UHC) and contrails. Flight routes can be optimized: modelling CO2, H
2
O
and NO
x
effects of transatlantic flights in winter shows westbound flights climate forcing can be lowered by up to 60% and ~25% for jet stream-following eastbound flights, costing 10–15% more due to longer distances and lower altitudes consuming more fuel, but 0.5% costs increase can reduce climate forcing by up to 25%.[147] A 2000 feet (~600 m) lower cruise altitude than the optimal altitude has a 21% lower radiative forcing, while a 2000 feet higher cruise altitude 9% higher radiative forcing.[148]
Nitrogen oxides (NO
x
)
As designers work to reduce NO
x
emissions from jet engines, they fell by over 40% between 1997 and 2003.[50] Cruising at a 2,000 ft (610 m) lower altitude could reduce NO
x
-caused radiative forcing from 5 mW/m2 to ~3 mW/m2.[149]
Particulates
Modern engines are designed so that no smoke is produced at any point in the flight while particulates and smoke were a problem with early jet engines at high power settings.[50]
Unburned hydrocarbons (UHC)
Produced by
incomplete combustion, more unburned hydrocarbons are produced with low compressor pressures and/or relatively low combustor temperatures, they have been eliminated in modern jet engines through improved design and technology, like particulates.[50]
Contrails
cruise altitude with slightly increased flight times, but this would be limited by airspace capacity, especially in Europe and North America, and increased fuel burn due to lower efficiency at lower altitudes, increasing CO2 emissions by 4%.[150] Contrail radiative forcing could be minimized by schedules: night flights cause 60–80% of the forcing for only 25% of the air traffic, while winter flights contribute half of the forcing for only 22% of the air traffic.[151] As 2% of flights are responsible for 80% of contrail radiative forcing, changing a flight altitude by 2,000 ft (610 m) to avoid high humidity for 1.7% of flights would reduce contrail formation by 59%.[152]

See also

References

  1. ^
    PMID 32895604
  2. ^ "Aircraft Engine Emissions". International Civil Aviation Organization.
  3. ^ a b c Brandon Graver; Kevin Zhang; Dan Rutherford (September 2019). "CO2 emissions from commercial aviation, 2018" (PDF). International Council on Clean Transportation.
  4. ^ a b "Reducing emissions from aviation". Climate Action. European Commission. 23 November 2016.
  5. ^ .
  6. ^ .
  7. ^ .
  8. ^ Horvath A, Chester M (1 December 2008), Environmental Life-cycle Assessment of Passenger Transportation An Energy, Greenhouse Gas and Criteria Pollutant Inventory of Rail and Air Transportation, University of California Transportation Center, UC Berkeley
  9. PMID 12380066
  10. ^ .
  11. ^ "Summary for Policymakers" (PDF), Climate Change 2007: The Physical Science Basis, Intergovernmental Panel on Climate Change, February 2007, archived from the original (PDF) on 14 November 2007
  12. ^ Le Page, Michael (27 June 2019). "It turns out planes are even worse for the climate than we thought". New Scientist.
  13. ^ "Questions & Answers on Aviation & Climate Change". Press corner. European Commission. 27 September 2005.
  14. .
  15. .
  16. .
  17. .
  18. .
  19. .
  20. ICAO
    .
  21. ^ "Global Market Forecast" (PDF). Airbus. 2019.
  22. ^ "Aviation industry reducing its environmental footprint". Aviation Benefits.
  23. .
  24. ^ a b c Timperley, Jocelyn (19 February 2020). "Should we give up flying for the sake of the climate?". BBC.
  25. EEA
    , 2021, p. 24
  26. ^ "Climate change: Commission proposes bringing air transport into EU Emissions Trading Scheme" (Press release). EU Commission. 20 December 2006.
  27. PMID 20225840
    .
  28. ^ Lowy, Joan (7 October 2016). "UN agreement reached on aircraft climate-change emissions". Associated Press.
  29. IPCC
    .
  30. ^ a b c d Giovanni Bisignani, CEO of the IATA (20 September 2007). "Opinion: Aviation and global warming". The New York Times.
  31. ^ Joyce E. Penner; et al. (1999), "9.2.2. Developments in Technology", Special Report on Aviation and the Global Atmosphere, IPCC
  32. ^ Peeters, P. M.; et al. (November 2005). "Fuel efficiency of commercial aircraft" (PDF). Netherlands National Aerospace Laboratory. An overview of historical and future trends
  33. ^ Anastasia Kharina; Daniel Rutherford (August 2015), Fuel efficiency trends for new commercial jet aircraft: 1960 to 2014 (PDF), ICCT
  34. ^ Fuel Fact Sheet (PDF), IATA, December 2019
  35. ^ a b Aviation report, International Energy Agency, 2020
  36. ^ Joyce E. Penner; et al. (1999). "Potential Climate Change from Aviation". The Role of Aircraft in Climate Change-Evaluation of Sample Scenarios. IPCC.
  37. ^ Bows, A.; et al. (2009), "5", Aviation and Climate Change: Lessons for European Policy, Routledge, p. 146
  38. S2CID 233361436
  39. .
  40. ^ Bows-Larkin, A.; et al. (2016), "Aviation and Climate Change – The Continuing Challenge", Encyclopedia of aerospace engineering, Fig. 7
  41. S2CID 55899619
    .
  42. ^ Current Market Outlook, 2014–2033 (PDF), Boeing, 2014, archived from the original (PDF) on 15 October 2014
  43. ^ Flying by Numbers: Global Market Forecast 2015–2034, Airbus, 2015, archived from the original on 15 January 2013
  44. ^ Paradee, Vera (December 2015). Up in the air: how airplane carbon pollution jeopardizes global climate goals (PDF). Center for Biological Diversity (Report). Tucson, AZ.
  45. ^ Pharoah Le Feuvre (18 March 2019). "Are aviation biofuels ready for take off?". International Energy Agency.
  46. ^
    PMID 29192612.{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link
    )
  47. ^ "Reduction of Noise at Source". ICAO.
  48. ^ "Aircraft Noise Levels and Stages". FAA. 1 July 2020.
  49. ^ Peter Coy (15 October 2015). "The Little Gear That Could Reshape the Jet Engine". Bloomberg.
  50. ^ .
  51. (PDF) on 9 November 2008
  52. ^ "European Joint Industry CDA Action Plan". Eurocontrol. 2009.
  53. ^ Sector S: Vehicle Maintenance Areas, Equipment Cleaning Areas, or Deicing Areas Located at Air Transportation Facilities (Report). Industrial Stormwater Fact Sheet Series. Washington, D.C.: U.S. Environmental Protection Agency (EPA). December 2006. EPA-833-F-06-034.
  54. ^ a b c Technical Development Document for the Final Effluent Limitations Guidelines and New Source Performance Standards for the Airport Deicing Category (Report). EPA. April 2012. EPA-821-R-12-005.
  55. ^ a b Environmental Impact and Benefit Assessment for the Final Effluent Limitation Guidelines and Standards for the Airport Deicing Category (Report). EPA. April 2012. EPA-821-R-12-003.
  56. ^ .
  57. ^ "Issues and Testing of Non-Glycol Aircraft Ground Deicing Fluids" (PDF). SAE International. 13 June 2011. Archived from the original (PDF) on 2 February 2013.
  58. ISSN 1352-2310
    .
  59. .
  60. .
  61. .
  62. .
  63. .
  64. ^ "Leaded Fuel Is a Thing of the Past—Unless You Fly a Private Plane". Mother Jones. 10 January 2013.
  65. ^ "Lead-free airplane fuel testing is in progress at Lewis" (Press release). Lewis University. 18 July 2011.
  66. ^ "Fact Sheet – Leaded Aviation Fuel and the Environment". FAA. 20 November 2019.
  67. ^ a b "Sustainable Aviation Fuels Guide" (PDF). ICAO. December 2018.
  68. ^ "Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA)". ICAO.
  69. ^ "The Sixth Carbon Budget: Aviation" (PDF).
  70. ^ a b c "Europe's aviation sector launches ambitious plan to reach net zero CO2 emissions by 2050" (PDF) (Press release). Destination 2050. 11 February 2021.
  71. ^ "Net-Zero Carbon Emissions by 2050" (Press release). IATA. 4 October 2021.
  72. ^ "Climate change: World aviation agrees 'aspirational' net zero plan". BBC News. 7 October 2022.
  73. ^
    S2CID 256449498
    .
  74. ^
    The Royal Society
    . February 2023.
  75. ^ Lewis Harper (22 March 2023). "Carbon removal 'a necessity' for aviation to reach net-zero emissions: IPCC report". FlightGlobal.
  76. ^ Jon Hemmerdinger (30 March 2023). "US aerospace leaders disagree on best path to 'net-zero' carbon emissions". FlightGlobal.
  77. ^ "Bridging the Gap to 2050 - How to Decarbonize Aviation Faster With Today's Technologies". Sustainable Aviation Lab GmbH. Hamburg Investment and Development Bank. April 2023.
  78. ^ Philip E. Ross (1 June 2018). "Hybrid Electric Airliners Will Cut Emissions—and Noise". IEEE Spectrum.
  79. ^ Bjorn Fehrm (30 June 2017). "Bjorn's Corner: Electric aircraft". Leeham.
  80. ^ Paul Seidenman (10 January 2019). "How Batteries Need To Develop To Match Jet Fuel". Aviation Week Network.
  81. ^ "Don't Expect To See Large Electric Planes Until At Least 2040". Simple Flying. 28 November 2019.
  82. ^ Chris Baraniuk (18 June 2020). "The largest electric plane ever to fly". Future Planet. BBC.
  83. ^ a b c d e f g Kerry Reals (7 January 2019). "Don't count on technology to save us". Flightglobal. Retrieved 20 October 2020.
  84. ^ Guy Norris (4 February 2021). "Boeing Moves Forward With Airbus A321XLR-Competitor Plan". Aviation Week.
  85. ^ "Hydrogen instead of electrification? Potentials and risks for climate targets" (Press release). Potsdam Institute for Climate Impact Research. 6 May 2021.
  86. ^ a b c Hydrogen-powered aviation (PDF) (Report). EU Clean Sky 2 and Fuel Cells and Hydrogen 2 Joint Undertakings. May 2020.
  87. ^ "Sustainable aviation fuel market demand drives new product launches". Investable Universe. 4 December 2020. Retrieved 12 December 2022. Note: Investable Universe>About
  88. .
  89. ^ "Developing Sustainable Aviation Fuel (SAF)". IATA.
  90. CiteSeerX 10.1.1.170.8750
    .
  91. ^ IATA (December 2023). "Net zero 2050: sustainable aviation fuels – December 2023". www.iata.org/flynetzero. Archived from the original on 24 February 2024.
  92. ^ Mark Pilling (25 March 2021). "How sustainable fuel will help power aviation's green revolution". Flight Global.
  93. ^
    S2CID 233876615
    .
  94. .
  95. .
  96. .
  97. ^ .
  98. ^ .
  99. ^ "Green flights not in easy reach, warn scientists". BBC News. 28 February 2023. Retrieved 3 March 2023.
  100. ^ "UK net zero aviation ambitions must resolve resource and research questions around alternatives to jet fuel | Royal Society". royalsociety.org. Retrieved 3 March 2023.
  101. ISSN 0959-6526
    .
  102. .
  103. .
  104. ^ .
  105. .
  106. ^ "2021–2022 EIB Climate Survey, part 2 of 3: Shopping for a new car? Most Europeans say they will opt for hybrid or electric". European Investment Bank. 22 March 2022.
  107. ^ Wabl, Matthias; Jasper, Christopher (9 June 2020). "Airline bailouts point to greener travel—and higher fares". BNN Bloomberg. Retrieved 13 June 2020.
  108. ^ Haines, Gavin (31 May 2019). "Is Sweden's 'flight shame' movement dampening demand for air travel?". The Daily Telegraph. Retrieved 1 June 2019 – via www.telegraph.co.uk.
  109. ^ Kerry Reals (6 September 2019). "'Flight shaming' is changing the face of travel". Flightglobal.
  110. ^ "'Flight shame' a factor in Swedish traffic decline". Flightglobal. 10 January 2020.
  111. S2CID 237101457
    .
  112. ^ "Pandemic and digitalization set stage for revival of a cast-off idea: Personal carbon allowances". phys.org. 16 August 2021.
  113. ^ "Opinion: We Need Cap-and-Trade For Individuals As Well As Companies". Bloomberg. 25 August 2021.
  114. ^ "How personal carbon allowances can help normal people fight climate change". Popular Science. 28 August 2021.
  115. ^ Sodha, Sonia (9 May 2018). "Opinion: A radical way to cut emissions – ration everyone's flights". The Guardian.
  116. ^ "International Civil Aviation Day calls for the greening of aviation" (PDF) (Press release). ICAO. 30 November 2005.
  117. ^ Reducing the Climate Change Impact of Aviation (PDF), European Commission, 2005
  118. ^ "Climate change: Commission proposes bringing air transport into EU Emissions Trading Scheme" (Press release). European Commission. 20 December 2006.
  119. Centre for Aviation, Transport and the Environment
  120. ^ Kate Abnett (10 March 2020). "Ban short-haul flights for climate? In EU poll 62% say yes". Reuters.
  121. ^ ICF Consulting (1 February 2006). "Including Aviation into the EU ETS: Impact on EU allowance prices" (PDF).
  122. ^ "Resolution A39-3: Consolidated statement of continuing ICAO policies and practices related to environmental protection – Global Market-based Measure (MBM) scheme" (PDF). ICAO. 15 February 2019.
  123. ^ "Study: Aviation tax breaks cost EU states €39 billion a year". euractiv. 25 July 2013.
  124. Transport and Environment
    . 24 July 2013.
  125. ^ Greenfield, Patrick (18 January 2023). "Revealed: more than 90% of rainforest carbon offsets by biggest certifier are worthless, analysis shows". The Guardian. Archived from the original on 14 February 2023.
  126. ^ British Airways Carbon Offset Programme, British Airways, retrieved 2 May 2010
  127. ^ Continental Airlines Carbon Offset Programme, Continental Airlines, archived from the original on 2 March 2012, retrieved 2 May 2010
  128. ^ Continental Airlines Carbon Offset Schemes, Bloomberg, archived from the original on 28 March 2008, retrieved 2 May 2010
  129. ^ easyJet Carbon Offset Programme, easyJet, retrieved 2 May 2010
  130. ^ 11 Airlines That Offer Carbon Offset Programs
  131. ^ How to Buy Carbon Offsets(subscription required)
  132. ^ The Gold Standard
  133. ^ Find Green-e Certified Carbon Offsets
  134. ^ "UK to include aviation in carbon emissions targets". CAPA - Centre for Aviation. 27 April 2021.
  135. UN
    News. 20 November 2008.
  136. ^ "Corporate Responsibility > Going Green". Harbour Air.
  137. ^ "flypop plans to be first international carbon-neutral airline" (Press release). flypop. 17 July 2019. Archived from the original on 26 November 2020. Retrieved 2 December 2020.
  138. ^ "Air France to proactively offset 100% of CO2 emissions on its domestic flights as of January 1st, 2020" (Press release). Air France. 1 October 2019. Archived from the original on 9 February 2023. Retrieved 3 January 2020.
  139. ^ David Kaminski-Morrow (19 November 2019). "EasyJet to offset carbon emissions across whole network". Flightglobal.
  140. ^ "BA begins offsetting domestic flight emissions". Flightglobal. 3 January 2020.
  141. ^ Pilar Wolfsteller (6 January 2020). "JetBlue to be first major US airline to offset all emissions from domestic flights". Flightglobal.
  142. ^ "All JetBlue Flights Are Now Carbon Neutral Within The US". simpleflying.
  143. ^ "Delta burns tons of jet fuel - but says it's on track to be carbon neutral. What?". CNN. 14 February 2020.
  144. ^ Jon Hemmerdinger (10 December 2020). "United to invest in 'direct air capture' as it makes 2050 carbon-neutral pledge". Flightglobal.
  145. .
  146. ^ Sam Morgan (22 September 2020). "Corona-crisis and Brexit boost EU air traffic reform hopes". Euractiv.
  147. .
  148. .
  149. .
  150. .
  151. .
  152. Imperial College
    .

Works cited

Further reading

Institutional
Concerns
  • "airportwatch.org.uk". AirportWatch. oppose any expansion of aviation and airports likely to damage the human or natural environment, and to promote an aviation policy for the UK which is in full accordance with the principles of sustainable development
Industry
Research
Studies