Efficiency does not “decarbonise” aviation

A common industry misconception is that flying can be decarbonised by making aircraft more efficient every year, often expressed in misleading statements such as: “since the advent of jet technology, carbon-dioxide emissions from aviation have reduced by 80%”.¹

It’s correct that these improvements have resulted in emissions reductions per passenger-km flown. Coupled with tax breaks and subsidies, and increasing purchasing power of the global population, this has resulted in a rapid growth of air traffic (doubling every 15 years) and of CO2 emissions that has far outstripped the efficiency savings. [see infographic]

As aircraft efficiency improves, some airlines simultaneously reduce their per seat efficiency by increasing the number of more profitable business or first class seats. They also fly further (ultra long-haul) which burns more fuel, even in efficient aircraft. A new generation of supersonic aircraft are also being developed² that would require up to nine times more energy per passenger-km than subsonic aircraft.³ Private/business jet use has also been increasing; they are 5-14 times more polluting than commercial aircraft due to low passenger density or higher flight speeds.⁴

The earth’s atmosphere isn’t affected by emissions per passenger-km, but instead by total emissions produced. This has been rapidly increasing, rather than decreasing.

In a poorly-regulated industry, efficiency improvements may facilitate market growth and increase total emissions, not reduce them. This is known as Jevon’s Paradox.⁷ Thus, efficiency gains alone cannot be relied upon to decarbonise the industry – we also need regulations to limit air traffic.

A method of limiting aviation emissions would be to increase the cost of jet fuel in order to incentivise reduced consumption. Additionally, a frequent flyer levy or air miles levy could incentivise people to fly less.⁸ There are historic examples of jet fuel price increases: e.g. the OPEC oil crisis in the 1970s-80s, during which it was seen that aircraft technology development actually accelerated, as there was a larger incentive to reduce fuel burn (e.g. flight testing of “Open Rotor” concepts). These designs were shelved when the oil price decreased again in the 1990s and are yet to re-emerge due to low fuel prices.⁹ This example demonstrates that reality does not match the narrative presented to us by airlines and the aviation industry.¹⁰ Financial restrictions on airlines such as increased pricing or fuel taxes wouldn’t reduce spending on new technologies and processes as claimed by airlines¹¹; rather, they would increase the industry’s desire to chase greater efficiency improvements.

End Notes & Literature

¹ The Engineer (2019): https://bit.ly/interview-newby
² BBC (2021): https://bit.ly/bbc-supersonic
³ Kharina, A et al. (2018): https://bit.ly/icct-supersonic
⁴ Murphy, A et al. (2021): https://bit.ly/TE-PrivateJets
⁵ Airbus (2019): https://bit.ly/AirbusMarketForecast
⁶ ATAG (2020): https://bit.ly/atag-report
⁷ Wikipedia: https://bit.ly/JevonsParadox
⁸ Stay Grounded (2018): https://bit.ly/FFL-AML
⁹ Wikipedia (2021): https://bit.ly/Propfan
¹⁰ Further reading: Peeters, P et al. (2016): https://bit.ly/myths-tech
¹¹ Flightglobal (2020): https://bit.ly/KLM-tax-claim

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Electric aircraft will NOT be “zero emissions” any time soon

“Fully-electric” aircraft are powered by batteries, and if the batteries are charged using only renewable electricity, the aircraft operation can be considered “zero emissions”. However, we are a long-way from decarbonising electricity generation, and adding additional load from other energy-intensive activities, will make it harder to move away from fossil fuels. Also, manufacturing the vehicles and batteries has significant social and environmental impacts, due to mining the necessary materials such as lithium and cobalt and producing the components. As such, even “fully-electric” aircraft cannot yet be considered “zero emissions”.

“Hybrid-electric” aircraft burn jet fuel, and so still produce CO₂ and other greenhouse gas emissions during operation. They are therefore not “zero emissions”. These hybrid-electric systems unlock potential new aircraft and engine architectures, such as “distributed propulsion” which could provide aircraft-level aerodynamic improvements, although such improvements can often be negated by the additional complexity of designs.

Electric flight is NOT efficient

Flying is a fundamentally inefficient mode of transport and difficult to electrify. It should not be favoured over more efficient ground transport options that are easier to electrify. This is because aircraft use large amounts of power to take-off and climb and are more sensitive to the weight of batteries and electrical systems¹. Where infrastructure allows: lower energy- and emissions- intensive ground-based public transport options such as rail, coach, or ferry services should be favoured at the short distances where electric aircraft are viable.

There are a large number of relatively small start-up companies attempting to develop and certify electric aircraft over the next decade. Many of the concepts receiving early investment are electric Vertical Take-Off & Landing (eVTOL) aircraft². These aircraft are designed to take-off and land on helicopter pads or short runways, in order to enable versatility of operation from a range of locations. However, these aircraft are even more inefficient than conventional fixed-wing electric aircraft, as they have higher take-off and landing power requirements and higher weight and drag during the rest of the flight. They should not be considered a positive environmental development.

Decarbonisation will be severely limited by aircraft range and payload

Current batteries and electrical systems are far too heavy to displace most jet fuel and combustion engines.

The Chief Technology Officer of Airbus has stated that “even assuming huge advances in battery technology, with batteries that are 30 times more efficient and ‘energy-dense’ than they are today, it would only be possible to fly an A320 airliner for a fifth of its range with just half of its payload”³. It is therefore not foreseeable that this type of aircraft which is the most common in airports for short-haul flights could become electric in the short or even medium term. Only very small, short-range aircraft will be electric. This is reflected by the fact that most companies attempting to certify electric aircraft during the 2020s are developing aircraft carrying less than 10 passengers which do not fit the current configuration of most airports. In addition, unlike a fuel tank where the weight decreases as fuel is burned during the flight, a battery does not become lighter during the trip. These issues further impact the payload and range capability of the aircraft⁴.

Currently this means that electric aircraft will only be viable for short flights under 1,000 km by 2050 which account for only 17% of aviation CO₂ emissions⁵. However, the scope to decarbonise overall aviation emissions is even more limited because, although electric aircraft can be justified for some niche cases in regions where ground transport options are poor, everywhere else short flights can be substituted by more efficient train, coach or ferry services.

Large electric aircraft won’t be here soon

Improvements in the weight of battery technology will not overcome their disadvantages any time soon. The Chief Technology Officer of United Technologies declares:
“Unless there is some radical, yet-to-be invented paradigm shift in energy storage, we are going to rely on hydrocarbon fuels for the foreseeable future”⁶. In its recent “Net Zero by 2050” report⁷, the International Energy Agency (IEA) sees the adoption of commercial battery electric and hydrogen aircraft from 2035, but expects that these aircraft would account for less than 2% of global aviation energy consumption in 2050. Hence, we should not allow the talk of electric flight to distract us from the priority of reducing aviation emissions today.

End Notes & Literature

¹ GreenBiz (2018): https://bit.ly/electric-airplanes
² FlightGlobal (2021): https://bit.ly/eVTOL-aircraft
³ BBC (2019): https://bit.ly/BBC-E-flight
⁴ Airbus (2019): https://bit.ly/airbus-electric
⁵ CleanSky2&FCH (2020): https://bit.ly/report-hydrogen
⁶ BBC (2019): https://bit.ly/BBC-E-flight
⁷ IEA (2021): https://bit.ly/iea-NetZero, p.136

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Hydrogen aircraft unable to meet climate targets in time and quantity

Even if the aggressive schedule announced by Airbus in 2020 is met, it will be too late for the climate. According to the United Nations Environment Program (UNEP), worldwide GHG emissions must be reduced by 55% by 2030 and 90% by 2050 in order to not exceed the globally agreed 1.5°C heating limit⁴. The design of a whole range of aircraft and the conversion of the fleet to hydrogen would start too late and take too long to meet this goal. Aircraft have a typical lifetime of 25 years.

According to a report produced by the European Commission (EC) in collaboration with key industry partners, hydrogen would be best suited for regional and short- to medium-haul flights. For long-haul flights, which contribute about one third of aviation emissions, hydrogen would not economically compete with synthetic fuels before 20505. By then, for that segment, the industry plans to rely upon alternative jet fuels (biofuels and e-fuels – see Fact Sheets 4 and 5). More recently, Airbus stated that a medium-haul aircraft would not be available before 2050, so, before that time hydrogen could potentially displace less than 20% of CO₂ emissions⁶.

Hydrogen would still have significant non-CO₂ impacts

The EC report takes into account the CO₂ as well as the non-CO₂ impact of aviation on climate, NO_x, water vapour and contrails, considering that the total impact is 3.1 times that of CO₂ alone (see also Fact Sheet on non-CO₂)⁷. It estimates that the total climate impact could be reduced by only 50-75% versus kerosene if hydrogen is burned in turbines and 75-90% if it is used in fuel cells. But this is still highly hypothetical.

Producing green hydrogen would require huge renewable electricity resources

Hydrogen aircraft are part of a new economy of hydrogen aiming at replacing fossil fuels where electricity is not a possible alternative.
In order to be “carbon-free”, hydrogen needs to be produced with renewable electricity (green hydrogen > see infobox).

The challenge is that the energy requirements are huge and will exceed production capacities needed to:

• Replace coal and gas in power plants that supply the electric grid
• Help satisfy new demand for electricity (cars, heating, data, etc.)
• Replace today’s grey hydrogen (produced from fossil fuels) used for industrial processes (e.g. fertiliser production)
• Satisfy new demand for hydrogen for trucks, ships…
• Satisfy new demand for hydrogen for production ofe-fuels for aviation

In a scenario where 40% of the airline fleet would be converted to liquid hydrogen in 2050 and the rest of the fleet would use e-fuels, the resulting electricity demand would be equal to the current total worldwide electricity production and about four times the production of renewable electricity in 2018⁸. As demand for electricity grows so does the risk that renewable electricity supply will not be able to match it, which will increase the risk of using non-renewable power.

Financial support from governments is unjustified: the polluter should pay

Airbus says “support from governments will be key to meet their ambitious objectives with increased funding for research and technology, digitalisation and mechanisms that encourage the use of sustainable fuels and accelerate the renewal of aircraft fleets”⁹.

However: given that most taxpayers rarely or never fly¹⁰ it would be unfair for them to subsidise research and development, particularly as the commercial success of hydrogen is uncertain; timescales are lengthy; and any significant deployment of hydrogen aircraft would be a waste of limited renewable energy resources.

Grey, Blue and Green Hydrogen

This colour code refers to different production methods:

• Grey Hydrogen = produced from methane or coal (both fossil fuels)
• Blue Hydrogen = Grey Hydrogen combined with Carbon Capture & Storage (CCS)
• Green Hydrogen = produced (via electrolysis) from water via renewable electricity

In 2018, the vast majority of the hydrogen production was “grey”, accounting for 2% of total global CO₂ emissions. Only 0.5% of the production was “green”, and a tiny amount was “blue”¹¹. “Blue” hydrogen is unproven at scale, and ultimately still involves the use of fossil fuel and may produce more carbon emissions than simply using “grey” hydrogen¹².

Today, hydrogen is mostly used by industry, for oil refining and for producing ammonia fertilisers. But many sectors, including aviation, are exploring its potential to support clean energy transitions and a new hydrogen economy is being projected.

As new uses for hydrogen develop, there is a major concern that the oil and gas sector will continue with business as usual in order to fulfill new hydrogen demand by extracting it from fossil hydrocarbons, rather than leaving it in the ground.

Success is far from assured

Hydrogen flight is unproven, with many technical and safety aspects yet to be understood. There is some skepticism even within the aviation industry. Boeing is not following Airbus¹³ and engine manufacturers have expressed reservations¹⁴. Even Airbus have admitted that hydrogen will not be widely used in planes before 2050, stating that only regional 50-100 seaters would be ready for hydrogen in the 2030s, a small market with a small share of current CO₂ emissions¹⁵. If airlines transition to using a large amount of such aircraft, this will substantially affect their operations and the design of airport infrastructure (e.g. runways, gates, terminals, fuelling and maintenance requirements). It would therefore be sensible to halt aviation expansion plans until we know to what extent hydrogen aircraft will be used.

End Notes & Literature

¹ BBC News (2010): https://bit.ly/bbc-hydrogen
² Airbus (2020): https://bit.ly/airbus-zero
³ Airbus (2020): https://bit.ly/AirbusPod
⁴ UNEP (2019): https://bit.ly/UNEP-EmissionGap, p. 15
⁵ CleanSky2&FCH (2020): https://bit.ly/report-hydrogen
⁶ Reuters (2021): https://bit.ly/hydrogen-limits
⁷ Stay Grounded (2020): https://bit.ly/factsheetClimateImpact
⁸ CleanSky2&FCH (2020): https://bit.ly/report-hydrogen
⁹ Airbus (2020): https://bit.ly/airbus-zero
¹⁰ Gössling, S. et al. (2020): https://bit.ly/Goessling-Global-Aviation
¹¹ IEA (2021): https://bit.ly/IEA-hydrogen
¹² Howarth, R. et al (2021): https://bit.ly/3AZRyqi
¹³ Simple flying (2021): https://bit.ly/Boeing-NoHydrogen
¹⁴ France TV (2020): https://bit.ly/interview-petitcolin
¹⁵ Reuters (2021): https://bit.ly/hydrogen-limits

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Alternative jet fuel can be broadly categorised into two varieties:

• Biofuels – produced from biomass sources (explained below)
• Synthetic electro-fuels (e-fuels) – produced using elec-tricity (see Fact Sheet 5)

Biofuel production can use various sources of biomass as an input. First generation biofuels use agricultural crops. Second generation biofuels aspire to use industrial, agricultural, municipal or household waste, such as: used cooking oil, fat, corn husks, forest resources, or food waste.

Biofuel use is severely constrained by the sustainability and availability of biomass

It is often claimed that aviation would use only second generation biofuels derived from “waste” sources, therefore avoiding any direct or indirect sustainability impacts. Yet the use of first generation biofuels from crops and even entire trees has not been ruled out. There are plans for huge “SAF” refineries in Paraguay using soybeans as a feedstock¹ and such fuels are permitted under the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), which is the only internationally agreed policy and runs until 2035². The threat of scaling up the use of commodities like soy or palm oil with high risk of deforestation is increasing as greater political emphasis is placed on the supposed benefits of “SAF”.

The cultivation of energy crops in large monoculture fields increases the use of fertilisers, pesticides and herbicides; with devastating environmental, biodiversity and health impacts. The expansion of agriculture like soy and palm leads to CO₂ emissions from land use change which can be similar to, or greater, than fossil fuel emissions³ (Fig. 1) It can also result in humanitarian impacts⁴ like land conflicts, labour abuses, rising food prices, water scarcity and chronic disease in neighbouring communities from pollution.

The only process currently able to produce second generation biofuels for aviation at a commercial scale uses “waste oils”, due to its similarity to biodiesel, which is already produced at a limited commercial scale for the road sector. It has been found that when “waste oils” are used to produce large quantities of biodiesel, it displaces their use in other sectors; which then transition to other sources, such as palm oil⁵. This also creates the opportunity for fraud, for example: where fresh palm oil has been sold as “used cooking oil”⁶. Also palm oil or palm oil derivatives are often being used but being disguised by another term.⁷ This indirectly causes an increase in crops for energy with their associated impacts.

Biofuels would compete with other applications

The future quantity of any sustainable biomass “waste” available globally is strictly limited and without fuel production processes having been demonstrated at any significant commercial level. An EU report (contributed to by Airbus, Boeing, BP, Shell, and easyJet) in 2020 stated that “biofuels’ reliance on feedstock, changes in land use, high water use, and/or monoculture (i.e., the production of a single crop) means that the aviation industry will be competing with other interests that need the feedstock for other purposes”⁸.

Governments will need to use any biomass produced to feed a growing global population whilst also decarbonising the power, heating, agriculture (e.g. replacing fossil fuel fertilisers) and transport sectors. Current government policies will not result in combustion engines being completely phased out of cars, trucks, or ships until after 2040. This means aviation will compete with ground transport for limited quantities of sustainable biofuel over the next few decades and it is recognised that high targets for aviation biofuels may only incentivise the diversion of resources from existing use in the road sector⁹. The UK Government notes that when production facilities produce more aviation biofuel than road biodiesel, their overall efficiency decreases and production costs increase; making “economy-wide decarbonisation more expensive”10. Therefore, the only result would be to shift an emissions saving from one sector to another, whilst decreasing the total emissions saving achieved and increasing costs. There are also dangerous plans to rely heavily on biomass for negative emissions via Bioenergy Carbon Capture & Storage (BECCS) facilities, which is an unproven technology and would increase pressure on scarce global resources and amplify the risk of all the impacts detailed above.

Biofuels would only partially reduce aviation climate impact vs. fossil fuel

The industry claims that “SAF can reduce emissions by up to 80% during its full life cycle”¹¹. However, GHG savings of only 60% have been proposed at national levels as a threshold for “SAF”¹² and fuels eligible under the international CORSIA scheme can have savings as low as 10%.¹³ In addition, aviation also produces non-CO₂ emissions such as contrails which are estimated to cause a greater global warming effect than aviation CO₂¹⁴. Recent studies have shown that while biofuels can contribute to reducing non-CO₂ emissions, they will only be partially reduced¹⁵. So even if fossil fuel were entirely replaced by biofuels, significant emissions would still be generated.

Governments should not subsidise aviation biofuels: the polluter should pay

Even if scaled up further, aviation biofuels will still cost far more than kerosene. Biofuel from “waste oil” is the most cost competitive but still costs double the price and “other conversion processes cost as much as eight times the price”¹⁶. These increased costs would undermine the expansion plans of the industry. The only way the aviation industry can continue to grow whilst using larger quantities of alternative jet fuels such as biofuel, would be to obtain large government subsidies for their production. According to a 2019 study by the International Civil Aviation Organisation (ICAO), 328 new large bio-refineries would need to be built every year by 2035, at an approximate capital cost of US$29-115 billion a year to generate enough biofuel for international aviation only¹⁷. However, investing in bio-refineries would pose a huge risk to public finances as it is unlikely, for the reasons given here, that aviation biofuels can ever be viewed as “sustainable”. This would result in facilities that are likely to turn into “stranded assets” with a large loss of investment. In the end taxpayers, most of whom never or rarely fly, should not be paying for that.

Biofuels cannot be scaled up rapidly enough and neither should this be the goal

Biofuel scale up has been promised by the aviation industry for more than a decade but this has not materialised. Targets have been routinely missed by significant margins and then ambition ratcheted down across successive years. For example, in 2009, the International Air Transport Organisation (IATA) was aiming for 10% biofuels by 2017¹⁸ and in 2011, Air Transport Action Group (ATAG) stated: “We are striving to practically replace 6% of our fuel in 2020 with biofuel. We hope this figure can be higher”¹⁹. However, as of 2021, only less than 0.01% of jet fuel is biofuel²⁰.

Even if we were to accept the industry’s most optimistic future projections of aviation biofuel use, they still do not expect that such fuels will provide a large percentage of total fuel consumption over the next few decades, given their plans for huge growth in air traffic and fuel consumption. For example, the EU has presented plans that will only put them on track to deliver 5% alternative jet fuel (mostly biofuel) by 2030²¹. With limited quantities of biomass available and thus limited biofuel potential, the only way to deliver a greater overall percentage within meaningful timescales would be to decrease total fuel consumption. However, as stated above: even those limited quantities would compete with other applications and bring danger of human rights violations, emissions through land-use change and biodiversity loss. This makes biofuels a false solution on many different levels and a clear threat to meeting climate targets in a just manner.

End Notes & Literature

¹ Global AG Investing (2019): https://bit.ly/biofuel-paraguay
² T&E (2019): https://bit.ly/Corsia-assessment
³ T&E (2019): https://bit.ly/Biofuels-GHG
⁴ Milieudefensie (2020): https://bit.ly/Neste-biofuel
⁵ Biofuelwatch (2017): https://bit.ly/aviation-biofuels-report
⁶ BBC (2021): https://bit.ly/doubts-biofuels
⁷ Biofuelwatch: https://bit.ly/names-palmoil
⁸ CleanSky2&FCH (2020): https://bit.ly/report-hydrogen, p. 18
⁹ ICCT (2021): https://bit.ly/SAF-feedstock, p 1-4
¹⁰ Department for Transport UK (2021): https://bit.ly/SAF-Mandate, p. 48-49
¹¹ IATA (2021): https://bit.ly/IATA-SAF
¹² Department for Transport UK (2021): https://bit.ly/SAF-Mandate, p. 48-49
¹³ T&E (2019): https://bit.ly/Corsia-assessment
¹⁴ Lee, D et al (2021): https://bit.ly/Aviation-climate-forcing, p.1
¹⁵ Vogt, C et al (2021): https://bit.ly/biofuels-nonco2, p. 1
¹⁶ ICCT (2021): https://bit.ly/SAF-feedstock, p 1-4
¹⁷ ICAO (2019): https://bit.ly/destination-green, p. 20
¹⁸ IATA (2009): https://bit.ly/IATA-projections, p.14
¹⁹ ATAG (2011): https://bit.ly/atag-future-of-flight, p.2
²⁰ FlightGlobal (2020): https://bit.ly/faith-in-SAF
²¹ European Commission (2021): https://bit.ly/refuel-EU, Annex 1, p. 28

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Alternative jet fuel can be broadly categorised into two varieties:

• Biofuels produced from biomass sources (see Fact Sheet 4)
• Synthetic electro-fuels (e-fuels) produced using electricity (explained below)

Synthetic electro-fuels or “e-fuels” can be produced by combining hydrogen with carbon to create a liquid hydrocarbon. In order to minimise emissions, hydrogen must be extracted from water by electrolysis using renewable energy; and carbon must be extracted from the air using a process called ‘Direct Air Capture’ (DAC). These can then be combined, to form a hydrocarbon fuel using Fischer-Tropsch (FT) synthesis¹. The latter processes must also be powered with renewable energy.

E-fuels are also known as “Synfuels” or Power-to-Liquid (PtL) fuels. E-fuels, as well as biofuels, are drop-in fuels that could be blended with conventional fossil jet fuel (kerosene) and used by the existing fleet.

E-fuels cannot be scaled up rapidly enough to meet climate targets

The deployment of e-fuels is likely to be slow and last several decades. Very few countries have concrete plans for implementation. Currently, only the EU is considering a mandate for e-fuels which starts at only 0.7% in 2030² and the NGO Transport & Environment believes that an objective of more than 1% in the EU would be challenging³. This is far behind the emissions reduction pace that must be achieved in order to not exceed the globally agreed 1.5°C heating target: according to the United Nations Environment Program (UNEP), worldwide greenhouse gas (GHG) emissions must be reduced by 55% by 2030⁴.

E-fuels would only partially reduce non-CO₂ emissions

Additionally, aviation should not only reduce CO₂ emissions but also non-CO₂ emissions that have twice as large a climate impact today⁵. Whereas CO₂ emissions of e-fuels could theoretically be reduced to zero if CO₂ is extracted from the air and renewable electricity is used to produce hydrogen and in all the other processes, this is far from being the case for non-CO₂ impacts. Recent estimates indicate that e-fuels will not contribute to reducing non-CO₂ impacts by more than 12% versus kerosene⁶.

Producing e-fuels would require huge quantities of renewable electricity that would deprive all other sectors that need to decarbonise

E-fuels could be part of a new economy of hydrogen aiming at replacing fossil fuels where electricity is not a possible alternative. But their production would require huge quantities of renewable electricity: not only must hydrogen be produced from electricity with significant energy loss, but making synthetic fuels from hydrogen requires further process steps with even higher energy losses. Hydrogen needs to be combined with CO₂ and the resulting fuel must be processed and purified to make it usable by aircraft engines. CO₂ must be extracted from the atmosphere using “Direct Air Capture” (DAC) at high energy cost due to its dilution. No more than about 10 % of the electricity spent would be converted into thrust to move an aircraft⁷.

Using renewable electricity to make e-fuel therefore looks like a crazy idea because energy requirements would be huge, whereas renewable electricity is crucially needed to decarbonise the global economy and can be used with a far higher efficiency in most other applications. For example, electricity powering a battery-electric coach results in an approximate 77% power-to-motion efficiency⁸, which is 8x better than if used for an e-fuel powered flight in an aircraft!
For the decades to come, the production capacity of renewable electricity will still not be enough to:

• Replace fossil fuel in power plants that supply the electricity grid
• Help satisfy new demand for electricity (cars, heating/cooling, data, etc.)
• Replace today’s grey hydrogen (produced from fossil fuels) used for industrial processes e.g. fertiliser production
• Satisfy new demand for hydrogen for trucks, ships, aviation…

Governments should not subsidise aviation
e-fuels: the polluter should pay

The complex process and the huge energy requirements will result in high costs: e-fuels cost six to nine times the price of kerosene in 2020 and would still cost 2 to 3 times more in 2050¹⁰. Governments will therefore be asked for subsidies. These would keep flying artificially cheap which would result in more air traffic and emissions than if the industry were to pay the costs themselves. Taxpayers, most of whom never or rarely fly, should not be paying for that.

Other lesser known issues

The industry is facing a dilemma over the production of the CO₂ required: achieving the highest climate impact reduction (60%), would mean extracting diluted CO₂ from the atmosphere at very high energy expense, when concentrated CO₂ is still available in large quantities from industrial exhaust/chimneys (cement, steel, refineries…). However, if CO₂ was to be extracted from factory exhausts, this would just be using fossil fuel a second time and still result in additional emissions ending up in the atmosphere. The climate impact reduction would then drop down to 30%¹¹.

Another rarely mentioned issue is that the manufacturing process produces a mix of hydrocarbons, of which only 50-70% is suitable for aviation¹². This means that about 30-50% of the renewable electricity used in the process would be wasted for by-products that could be obtained in more efficient ways or for which there are better alternatives.

E-fuels will long be a precious commodity, rare and expensive, that should not be widely used in the future to replace kerosene in quantities much larger than today if the industry keeps growing.

End Notes & Literature

¹ The Royal Society (2019): https://bit.ly/policy-briefing-e-fuels
² European Commission, (2021): https://bit.ly/refuel-EU, Annex I, p. 28
³ T&E (2021): https://bit.ly/TE-E-kerosene
⁴ UNEP (2019): https://bit.ly/UNEP-EmissionGap, p. 15
⁵ Stay Grounded (2020): https://bit.ly/factsheetClimateImpact
⁶ CleanSky2&FCH (2020): https://bit.ly/report-hydrogen
⁷ Ausfeder, F. et al (2017): https://bit.ly/analysis-sektorkopplung
⁸ T&E (2020): https://bit.ly/briefing-e-fuels
⁹ CleanSky2&FCH (2020): https://bit.ly/report-hydrogen, p. 44
and IEA: https://bit.ly/iea-data-statistics
¹⁰ CleanSky2&FCH (2020): https://bit.ly/report-hydrogen, p. 48
¹¹ CleanSky2&FCH (2020): https://bit.ly/report-hydrogen, p. 21
¹² Novelli, P. ONERA, (2021): https://bit.ly/decarbonising-aviation

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