An IATA report to compare leading decarbonisation roadmaps for the aviation sector has found significant differences regarding how technologies and solutions may evolve in the transition to net zero. Although all roadmaps assume sustainable aviation fuels will be responsible for the greatest amount of CO2 reductions by 2050, their role varies from 24% to 70%. This, says the report, reflects the uncertainties regarding potential supportive government action, the level of investments, cost of production and profit potential, as well as access to feedstocks. This first analysis undertaken to provide a holistic review of 14 major global and regional net zero CO2 emissions by 2050 roadmaps was undertaken by IATA in collaboration with the Air Transport Action Group, the International Council on Clean Transportation, the Mission Possible Partnership and the Air Transportation Systems Laboratory at University College London.

The report, ‘The Aviation Net Zero CO2 Transition Pathways Comparative Review’, compares the selected roadmaps in terms of their scope, key input assumptions, modelled aviation energy demand, respective CO2 emissions and the emissions reduction potential of each mitigation lever or pathway, namely new aircraft technologies, zero-carbon fuels, SAF and operational improvements.

The possible pathways to net zero CO2 emissions by 2050 differ significantly depending on the key assumptions of the roadmap authors regarding how technologies and future fuels may evolve, so the resulting role of particular levers will be more or less important, finds the study led by IATA’s Dr Bojun Wang. In addition, the roadmaps analysed adopted different demand modelling approaches. Some used a top-down approach with pre-determined aviation demand growth rates, and the transition measures were applied on top of this growth as ‘gap fillers’ to reduce the emissions to net zero by 2050, while others used a bottom-up approach where demand growth is modelled to reflect the impacts of different transition measures on demand. This makes it difficult for stakeholders and policymakers to compare the transition pathways and levers of action to achieve net zero, points out the report.

Given that currently there are only a few new aircraft projects under development and the fleet replacement rate is generally low, most of the roadmaps assume, on average, about 1.0% per year improvement in energy efficiency from now until 2050, measured in megajoules per revenue passenger kilometres, although some have more aggressive assumptions, with one forecasting a 2.2% per year fuel efficiency improvement from new types of aircraft introduced from 2035.

All roadmaps assume that energy intensity reduction from operational efficiency gains will be lower than that of technology efficiency improvement, on average 0.1% to 0.2% per year, although one has a greater 0.5% assumption based on higher load factors and traffic efficiency improvements.

If putting the technology and operational levers together for all roadmaps, the total efficiency improvement is about 1.0% to 1.5% per year in most roadmaps.

Sustainable aviation fuel produced from biomass resources (bio-SAF) and those synthetic fuels produced from CO2 and electricity (power-to-liquid or PtL) are assumed to deliver the highest emissions savings in the energy transition of the aviation sector to reach net zero by 2050. SAF volumes only reached 0.5 Mt in 2023 and all roadmaps indicate that to reach the 2050 target, the share of SAF in total aviation energy demand must be at least 5-6% by 2030. ICAO recently set an aspirational goal of achieving a 5% reduction in carbon intensity from international aviation by 2030, and the ICAO LTAG S3 models the highest share of SAF at 21% by 2030 for international aviation.

The report notes that for the higher 2030 SAF use estimates, the speed with which infrastructure can be ramped up is also a key constraint for SAF production, given that the number of SAF facilities planned to be built by then may not meet the high SAF demand.

By 2050, SAF is expected to account for 65% to 100% of the total energy demand for aviation, depending on whether any other clean energy sources, such as green hydrogen-powered aircraft, are considered in the given roadmap.

How fast SAF can penetrate the global aviation energy supply depends on feedstock availability and production costs relative to fossil jet fuel, says the report, and with SAF currently about two to six times more expensive, future prices of SAF remain “highly uncertain”. PtL fuels are assumed to be available only from the mid-2020s or 2030 in the majority of roadmaps. Demand for SAF is projected to accelerate significantly from 2030 to 2050 across all the roadmaps. However, the shares of bio-SAF and PtL in the total SAF consumption vary widely by the corresponding model assumptions.

Hydrogen-powered aircraft, with a limited range, are largely assumed to enter the market in the mid-2030s, while battery-electric aircraft coming in around the same time but serve even shorter-range markets. The estimated emissions savings from these aircraft vary greatly across the roadmaps, depending on whether a strong pro-hydrogen policy is adopted and on whether there is a rapid decline in renewable energy prices that enable swifter uptake of these technologies.

With the exception of one US roadmap, all the global roadmaps suggest the aviation sector will need help from market-based measures (MBMs), such as ICAO’s CORSIA scheme and the EU ETS, and carbon removals to address residual emissions in 2050. “Even if carbon removal technologies are considered an ‘out-of-sector’ mitigation measure, it is still both urgent and critical to develop these technologies as CO2 will be needed as feedstock for producing PtL fuels,” says the report.

IATA’s own roadmap mid-scenario models gross CO2 emissions of 1115 Mt in 2050, which after the implementation of the technology, operational and SAF levers, leaves residual emissions of 465 Mt CO2 to be mitigated by MBMs and carbon removals. This is the largest of all the roadmaps, with the exception of ICAO’s LTAG S2 scenario of 495 Mt from international aviation. The lowest on a global basis, 70 Mt, is forecast in ICCT’s Breakthrough scenario.

Concluding, the authors say: “By comparing these roadmaps, this report is instrumental in helping airlines better understand the potential of reducing CO2 emissions by different mitigation measures. Given that most of the transition measures for the aviation sector are not yet readily available, we believe there will not be a universal path to help the aviation sector reach net zero by 2050.”

Nevertheless, added Marie Owens Thomsen, IATA’s SVP Sustainability and Chief Economist: “This report provides airlines, policymakers and all stakeholders with a useful tool to analyse and improve their policy, investment and business choices.

“It is particularly important for SAF, where strong and urgent public policy support is needed to increase production. Without that, no version of roadmaps will get us to net zero carbon emissions by 2050.”

Image: IATA

Christopher Surgenor

Editor

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Led by non-profit research organisation the International Council on Clean Transportation (ICCT) and Google, a new independent advisory committee has been formed to oversee the Travel Impact Model (TIM), the methodology used for estimating flight emissions by Google Flights, Booking.com, Expedia and elsewhere in the travel industry. Made up of members from academia, airlines, NGOs and government agencies, the committee will oversee future changes to the TIM, including approval of updates to the model by incorporating the latest scientific knowledge in the field of flight emissions forecasting. The ICCT will serve as a technical secretariat to the committee and collate and conduct research on selected topics, plus commissioning studies where needed. Google, which began estimating and sharing air travel-related GHG emissions on Google Flights using the TIM in 2021, will continue to administer its technical implementation.

“Everyone should be able to find reliable, accurate emissions estimates no matter where they’re booking a flight, and we believe the TIM can provide this kind of trusted, universal standard,” said Kate Brandt, Chief Sustainability Officer at Google. “Together with the ICCT and the new advisory committee, we can empower travellers around the world to make more sustainable choices.”

To be widely adopted by consumers, the partners say emissions estimates should be:

• Accurate, as validated by real-world data;
• Precise in distinguishing between low and high emitting tickets;
• Comprehensive of the full climate impacts of aviation;
• Futureproof across new aircraft and fuels;
• Fully transparent in methods; and
• Provide consistent results, both across carriers and booking platforms.

Improvements in the Travel Impact Model are expected to incorporate non-CO2 climate pollutants like contrails and to credit sustainable aviation fuels and zero emission planes. ICCT said its research had shown passengers can reduce CO2 emissions per trip by up to 60% by choosing a lower-emitting itinerary due to differences including aircraft type, seating configuration, load factors and routing. As airlines begin to deploy new low-carbon technologies, even larger emission reductions will be possible, it added.

“Climate-conscious consumers understand that which flight you choose matters, but they want and need data to make informed decisions,” said Dr Rachel Muncrief, Executive Director of the ICCT. “We are delighted to partner with Google to help establish the TIM as the global standard for providing accurate, transparent and consistent emissions information to consumers at the point of booking.”

Google is a member of the Travalyst Coalition, through which travel and technological platforms collaborate pre-competitively to drive adoption of the TIM and maximise consumer access to this information. “Google and the ICCT will continue to leverage partnerships such as these to ensure the TIM is widely adopted across the travel industry,” said the two partners.

The advisory committee will do its work through an annual in-person assembly, quarterly virtual meetings and monthly work sessions. It intends sharing recommendations through its public website and provide progress updates at key aviation and climate meetings, including the Aviation Carbon 2023 conference in November.

Representatives on the committee include:

• Jill Blickstein, VP Sustainability, American Airlines
• Tim Johnson, Director, Aviation Environment Federation
• Jane Ashton, Sustainability Director, easyJet
• Achilleas Achilleos, Strategic Programme Officer, European Union Aviation Safety Agency (non-voting board observer)
• Kevin Welsh, Executive Director, Environment & Energy, US FAA (non-voting board observer)
• Dr Marc Stettler, Reader in Transport and the Environment, Imperial College London
• Dr Daniel Rutherford, Aviation Program Director, ICCT (non-voting Secretariat representative)
• Caroline Drischel, Head of Corporate Responsibility, Lufthansa Group
• Prof Steven Barrett, Professor of Aeronautics and Astronautics, MIT
• Andrew Chen, Principal, Aviation Decarbonization, RMI
• Sally Davey, CEO, Travalyst

Image (Travalyst): Flight emissions information consumers see when searching on Google and other platforms

Christopher Surgenor

Editor

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A global levy on frequent flyers could generate significant revenues towards the annual investment of $121 billion that ICAO estimates is required for the aviation sector to reach its 2050 net zero climate target, finds a study by the non-profit research group International Council on Clean Transportation (ICCT). It argues a variable levy based on flying frequency would focus the tax burden on wealthier frequent flyers – those defined in the study as taking more than six flights a year – and help ensure that people with lower incomes are not priced out of air travel because of climate policy. The study looked at two potential models: a flat per-flight tax or a frequent flying levy (FFL). Raising $121 billion in 2019 would have required a flat $25 tax on each one-way flight or a progressive FFL starting at $9 for a person’s second flight to $177 for their twentieth flight within the same year. At the recent COP27 climate conference, the EU’s chief representative suggested a levy on aviation could be a source of finance for the Loss and Damage fund agreed at the talks.

The authors of the study emphasise the inequality of income and uneven participation of those travelling by air is extreme, with the richest 20% worldwide taking 80% of the flights and the top 2% most frequent flyers responsible for around 40% of all flights. They estimate a global FFL would generate 81% of the revenue needed for aviation decarbonisation and 67% from high-income countries, versus 41% and 51% respectively from a flat tax, such as air passenger duty (APD). An FFL would therefore shift the tax burden from occasional flyers to frequent flyers, and from lower-income countries to high-income countries, relative to an APD.

Under an FFL, some high-income countries, such as Norway and Iceland, would almost double the amount of levy revenue collected compared to an APD, while residents in low-income countries would pay a fraction of the APD charges. An FFL could also alleviate the burden on global middle-income country residents compared to a flat levy.

High-income countries generated about 70% of aviation CO2 emissions between 1980 and 2019. “The shift of burden to high-income countries, in particular, is key to ensuring that aviation decarbonisation does not unfairly burden countries with low historical emissions,” says the ICCT report on the study.

Regardless of tax design, the impact of increased cost on travel demand would be moderate, reducing travel by around 7% globally, estimate the researchers, although this would be an extreme case where all decarbonisation costs are passed on to consumers, based on 2019 figures, and the actual impact would likely be even smaller. Demand impact is fairer under an FFL than under an APD as it would be concentrated in the top income brackets and the frequent flyers, they argue.

“Frequent flyers should cover more of the costs associated with clean technologies,” said the study’s lead author, Sola Zheng. “Otherwise, some people could be priced out of flying – those who barely contributed to the climate crisis in the first place.”

Added co-author Dan Rutherford: “Taxing frequent flyers regardless of their passport would align the costs of decarbonisation with historical responsibility for emissions, and it could be done without distorting competition across countries or carriers.”

The concept of an FFL has already been mooted in the UK, which applies one of the highest air passenger duties in the world, and in 2019 the government’s advisory Climate Change Committee identified the potential of an FFL as a fiscal and demand management tool to address the country’s aviation emissions. This was backed by the Parliament’s citizens’ Climate Assembly UK, which came down in favour of the levy. UK polls on the subject have also demonstrated strong public support for an FFL, ranging from 60% to 89% in favour. Following a study conducted on behalf of UK climate charity, Possible, a campaign advocated that everyone should get one tax-free return flight a year each year and that FFL revenues be invested into greener alternatives to flying.

Another study has put forward the concept of an ‘air miles levy’ as a variation of an FFL and based on the distance or carbon emissions of the flight, and factoring in the larger per-person emissions generated by flying business or first class. Since frequent flyers are more likely to purchase premium tickets, a frequency-based levy could reduce emissions by lowering demand specifically for the most carbon-intensive tickets.

The ICCT researchers acknowledge that implementing a global FLL has major challenges, such as establishing an accurate and privacy-protected flying frequency database, distinguishing business trips from personal trips and ensuring effective use of the revenue collected. A real-time, accurate database of the number of flights taken by travellers would need to be set up and maintained by national governments or an international body. This would likely require airlines to collect travel document details at the point of ticket sales, who would then have to charge the appropriate levy retrieved from the database. Travellers may also use different documents for different flights, which would complicate the accounting. Importantly, with the large amounts of data being collected and stored, the database would need to adhere to high privacy protection standards.

Ensuring all governance bodies reinvest the collected revenues into low-carbon aviation technologies would be fundamental to such a plan. The revenues could be managed by individual countries or, better still, pooled internationally so that funds can be prioritised for countries that make the least contribution to climate change but bear the greatest impacts, such as small island developing states.

In a paper released by the Tourism Panel on Climate Change at COP27, Chris Lyle of Air Transport Economics and a former senior official at ICAO, said as well as ‘leakage’ difficulties and data and privacy concerns, achieving a multinational agreement on such a levy and on a common level is “unrealistic given the sovereignty of national taxation jurisdictions.”

ICCT said it plans future workstreams to investigate the implementation logistics and also quantify the emissions impacts of an FFL after further segmenting the flying activities by distance and seating class.

During the negotiations at COP27 on a ‘loss and damage’ fund to help protect vulnerable developing countries against the worst impacts of climate change, the EU’s climate policy chief, Frans Timmermans, said the fund would need to look at innovative sources of finance such as levies on aviation, shipping and fossil fuels, reported Climate Home.

Photo: London Gatwick Airport

A new report by the International Council on Clean Transportation (ICCT) concludes CO2 emissions from aircraft must peak as early as 2025 if the aviation industry is to bring itself in line with Paris Agreement temperature goals. The report, ‘Vision 2050’, uses three scenarios – Action, Transformation and Breakthrough – to assess measures needed to meet global temperature targets of 2, 1.75 and 1.5 degrees Celsius by 2050. The outcomes reflect CO2 reductions of between 9% and 94% below 2019 levels through the use of sustainable aviation fuels, aircraft fleet renewal, improved operational efficiency and the introduction of zero emission planes (ZEPs) powered mainly by liquid hydrogen, reports Tony Harrington. The report comes as ICAO member states meet next month to discuss the establishment of a long-term aspirational goal to limit emissions from international aviation. “One thing is certain,” says ICCT. “Aligning aviation with the below 2-degree Celsius aspiration of the Paris Agreement is possible, but requires significant ambition and investment.”

The scenarios addressed by the ICCT study, led by Brandon Graver, examine six key parameters – air traffic, aircraft technology, operations, zero emission planes, sustainable aviation fuels and economic incentives. Against a baseline of continuing current policies, the Action case focuses on technology initiatives by governments and industry to cap aviation’s 2050 CO2 emissions below 2019 levels. The Transformation case is more proactive, with governments and industry transitioning aviation off fossil fuels from 2035, to almost halve 2050 CO2 emissions compared to 2005.  The third and most robust strategy, Breakthrough, relies on “early, aggressive, and sustained government intervention” to encourage widespread investments in zero-carbon aircraft and fuels, “peaking fossil jet fuel use in 2025 and zeroing it out by 2050”.    

Unlike other sustainable aviation roadmaps, the ICCT says its Vision 2050: Aligning Aviation with the Paris Agreement report is focused only on international passenger and freight operations. It also considers aviation’s CO2 emissions on a well-to-wake (WTW) basis, assessing not only direct emissions from flights, but also those linked to the production of conventional Jet A fuel, biofuels and synthetic fuels. “On average, the WTW emissions are 21% higher than the CO2 emitted directly from the aircraft engines,” says the report. “In contrast, other roadmaps typically only account for emissions produced from the combustion of fuel.”

ICCT states the most ambitious scenarios of its roadmap, as well as those published by ATAG (the cross-industry aviation group) and ICAO, are consistent with a 1.75°C future in which aviation does not increase its share of a global carbon budget.

Although the report focuses heavily on the benefits of new technology, it cautions the design and manufacture of new aircraft types are slow, and that efficiency benefits can take years to materialise. “Very few new aircraft projects are currently underway, the Boeing 777X being one example. Hence, we assume that no step-change improvement in the technical efficiency of delivered aircraft will be reflected in scenarios until 2035.”

Under the Action scenario, emission-reducing technologies for 2050 are extended by the introduction of “moderate fuel efficiency standards for new aircraft” and investments in improved airspace management. ICCT predicts these initiatives will reduce fuel consumption per revenue passenger kilometre (RPK) by 36% below 2019 levels. Supported by federal incentives and blending mandates from 2025, 220 million tonnes (Mt) of SAF will be generated by 2050, or around 60% of aviation fuel supply. This scenario estimates a 7% increase in aviation fuel prices in 2030, eventually leading to a 6% reduction in RPKs by 2050 compared to the baseline “status quo” position.

The Transformation case forecasts 2050 fuel consumption per RPK to fall 40% below 2019 levels through accelerated efficiency standards for new aircraft and domestic and intra-EU fuel taxes, supported by the introduction of regional electric aircraft in 2030 and hydrogen combustion fleets from 2035. As well, “aggressive mandates, incentives and fuel taxes” are expected to drive greater uptake of SAF, generating 250 million tonnes of supply in 2050, around 70% of total hydrocarbon demand. This scenario assumes a 17% increase in fuel prices by 2030 and continued rises until 2040, before reductions occur in 2050 as economies of scale are achieved in producing synthetic e-kerosene from renewable electricity.

The most substantial decarbonisation comes from the Breakthrough scenario, in which ICCT predicts a 45% reduction in fuel burn per RPK off the back of a global fuel tax, maximum efficiency standards for new aircraft and breakthroughs in air traffic management.  Under this assessment, hydrogen combustion aircraft enter commercial service in 2035, to comprise half of all regional and narrowbody aircraft sales in 2050, while global fuel taxes and bans on the use of fossil-fuelled aircraft will help to deliver 385 million tonnes of SAF.

The report says all three decarbonisation scenarios deliver 2050 carbon emissions lower than in 2019, with Action cutting CO2 by 9%, Transformation approximately halving 2019 emission levels and Breakthrough reaching near zero (70Mt) emissions in 2050 without the use of out-of-sector measures.

But, it warns: “All scenarios investigated exhaust aviation’s proportional share of a 1.5° Celsius carbon budget in 2030. This suggests that near-term, interim targets will be needed to align aviation with the Paris Agreement.   

“The Baseline case breaches a 2°C carbon budget before 2045. Under the Action scenario, global aviation consumes its share of a 2°C carbon budget by 2050. Under the Transformation case, by the same year, aviation exhausts the share available to it under a 1.9°C carbon budget. By peaking emissions in 2025 and reducing them to near-zero levels by 2050, Breakthrough is consistent with a 1.75°C temperature target.”

The report says only the Breakthrough scenario enables cumulative CO2 emissions to stabilise by 2050.

“For other scenarios, airlines continue to emit substantial CO2 after 2050. Furthermore, aviation could still exhaust its share of a Paris-compatible carbon budget even with deep cuts in CO2 in 2050 if the development of needed technologies is delayed. For a 1.5° C pathway to be maintained without increasing aviation’s share of a global carbon budget, an additional 50% reduction in cumulative emissions (11Gt of CO2) beyond the Breakthrough case would be required. This is equivalent to achieving net zero emissions by 2030 – two decades sooner than the aviation industry has planned in its net-zero commitments.”

Photo: Heathrow Airport

If deployed to their maximum potential, liquid hydrogen-powered aircraft could enable aviation emissions to be capped at 2035 levels, although a 6-12% reduction in CO2e emissions relative to projected 2050 levels is more realistic, finds an ICCT study. However, such aircraft, assuming they enter service by 2035 as targeted by Airbus, are likely to come with performance penalties and much higher fuel costs relative to fossil-fuel aircraft. In 2020, Airbus unveiled three concept hybrid-hydrogen aircraft: two powered by turbofan and turboprop engines and the other a revolutionary blended design with turbofan engines. The new study focuses on the smaller turboprop aircraft targeting the regional market and a narrow-body turbofan aircraft suitable for short and medium haul flights, benchmarked against the ATR 72-600 and Airbus A320neo respectively. Together, the two liquid hydrogen powered aircraft could service 31-38% of all passenger traffic, as measured by RPKs. Another ICCT study just published concludes environmental constraints are likely to severely limit the market for supersonic aircraft.

A significant challenge for hydrogen-powered aircraft design is fuel storage as hydrogen stores 2.8 times the energy on a per unit basis than fossil Jet A. However, its volumetric energy density is significantly lower than that of Jet A and for sufficient hydrogen to be carried in an aircraft, its density needs to be increased. This is achieved by storing gaseous hydrogen (GH2) at high pressure, or by liquefying it and storing the liquid hydrogen (LH2) at very low temperatures. Producing the energy of a unit volume of Jet A requires seven times that volume of compressed GH2 and four times that volume of LH2, so making the latter a superior option from the perspective of improving the payload capacity and range of potential aircraft designs.

The hydrogen study notes that compared to fossil-fuel aircraft, LH2-powered aircraft will still be heavier, less efficient as they have a higher energy requirement per revenue passenger km (RPK) and also have a shorter range. Nevertheless, the LH2-powered narrow-body turbofan could transport 165 passengers up to 3,400 km and the turboprop could transport 70 passengers up to 1,400 km. This represents, estimates ICCT, 57-71% of all RPKs serviced by narrow-body aircraft and 89-97% of all RPKs serviced by turboprops. Aircraft with lighter fuel systems and tighter seating density would provide larger market coverage.

The analysis finds fuel costs for a green LH2 (made using additional renewable electricity) will be higher than fossil Jet A-fuelled aircraft but cheaper than blue LH2 (generated from fossil fuels with carbon sequestration) or synthetic e-kerosene for the missions investigated by the study. The price advantage could be smaller or reversed when accounting for the cost of building hydrogen refuelling infrastructure at airports. The cost of e-kerosene production could also increase if more energy-intensive direct air capture, rather than point source carbon capture, is required. ICCT suggests green LH2 will be cheaper than e-kerosene on routes up to 3,400 km.

To make green LH2 cost-competitive with fossil jet fuel, ICCT says taxes will need to be levied on CO2 emissions, with a carbon price of around $250/tonne CO2e needed in 2025 for cost parity in the United States, falling to $100 in 2050. Europe, where renewable hydrogen is expected to be more expensive, may require a higher carbon price.

Using airline route data for 2019, the analysis projected the CO2e mitigation potential of each LH2-powered design running on green hydrogen from 2035 to 2050. ICCT forecasts RPKs to grow at 3% annually, while historical trends suggest the fleet-averaged fuel burn for narrow-body and turboprop aircraft has decreased at 0.5% annually.

Assuming that fleet renewal and growth is sufficient for LH2 designs to cover between 20% and 40% of the addressable market in 2050, there is a mitigation potential of 126-251 million tonnes (Mt) of CO2e in 2050, representing 6-12% of passenger aviation’s CO2e inventory that year. Deployed to their maximum potential (100%), 628 Mt of CO2e could be mitigated in 2050, representing 31% of the projected inventory.

The study, led by Dr Jayant Mukhopadhaya, calls for supportive government policies if LH2-powered aircraft are to succeed, to include carbon pricing, low-carbon fuel standards or alternative fuel mandates to bridge the cost gap with fossil fuel, together with life-cycle accounting to ensure aviation has access to the cleanest sources of hydrogen. An important next step, it recommends, would be to determine where and how to invest in hydrogen infrastructure to maximise the CO2 mitigation potential while minimising cost.

“Even after considering the performance penalties for carrying LH2 as a fuel source, the aircraft modelled in this work can capture a large section of the aviation market,” concludes Dr Mukhopadhaya. “They can provide significant reductions in carbon emissions of the captured market and potentially, at a maximum, cap global passenger aviation emissions at 2035 levels. The aircraft can fit into existing airline route operations but will require significant investment in infrastructure to make them viable.”

Meanwhile, a joint study by ICCT and MIT’s Laboratory for Aviation and the Environment (LAE) has found that both ‘low-boom’ designs and ultralow cost sustainable aviation fuels will be needed for a sizeable supersonic aircraft market to develop. A small number of US aircraft manufacturers, such as Boom Supersonic, which has backing from United Airlines and Japan Airlines, are seeking to develop and reintroduce supersonic transport aircraft (SST). They are pledging to use alternative jet fuels like e-kerosene to address greenhouse gas emissions and contribute to the industry’s net zero target. The US is pushing ICAO to develop international standards that would enable supersonic flights and a meeting of ICAO’s CAEP committee is due to meet February 7 to discuss whether SSTs should have to comply with the same environmental standards as subsonic designs.

ICCT expects SSTs to burn 7 to 9 times more fuel per seat-km than subsonics and e-fuels, despite their ability to reduce life-cycle emissions by around 90% compared to fossil Jet A if made using renewable energy, would only “modestly” reduce CO2 per seat-km compared to today’s aircraft, it says. Additionally, burning low sulphur e-kerosene at the high altitudes SSTs cruise could lead to stratospheric warming and increase the medium-term climate impact of commercial aviation by two-thirds, despite providing only 0.6% of projected available seat kilometres, estimates the study.

“Supersonics and clean aviation fuels mix like oil and water,” contends Dan Rutherford, ICCT’s Aviation Director and co-author of the study. “Supersonics shouldn’t be given weaker environmental standards on the theory that exotic new fuels will clean up the mess.”

The study predicts a market for 130-240 supersonic aircraft in 2035, assuming no environmental constraints, which include overland noise restrictions as well as control of emissions. However, that market falls by 95% to 100% after taking into account overland flight bans and projected e-kerosene costs. Only by using conventional Jet A do the economics work, suggests the study.

“Our modelling confirms that supersonic aircraft will have larger atmospheric impacts per passenger than today’s aircraft,” said Sebastian Eastham, co-author of the study and research scientist at LAE. “We know that fuel composition matters – for the supersonic fleet we evaluated using low sulphur fuel could increase medium-term climate warming without significantly reducing ozone impacts.”

Image: Airbus ZEROe hybrid-hydrogen concept aircraft

As part of its ‘Jet Zero’ strategy to ensure the aviation sector meets the national target of net zero emissions by 2050, the UK government is considering whether to mandate the provision of standard, reliable and accurate environmental information to encourage travellers at the time of booking their flights to choose the greenest option. Such information, says the Department for Transport (DfT) in a consultation launched last month, could help passengers make more informed decisions, increase public awareness of carbon emissions and climate change, and support aviation growth in a sustainable manner. New analysis of US domestic routes by the International Council on Clean Transportation (ICCT), which supports itinerary-level emissions disclosure by airlines at the point of purchase, shows the carbon footprint of different itineraries on the same route varies greatly in terms of CO2 emissions per passenger. On average the most fuel-efficient itineraries emitted 63% less CO2 per passenger than the highest emitting itinerary. Greater efficiency also tends to correlate with lower fares, which is a win-win for consumers and the environment, says ICCT.

In its consultation, the DfT reports the UK Civil Aviation Authority recently carried out a research project with consultancy BritainThinks to explore the feasibility and utility of sharing carbon information with consumers. Most participants in the study thought emissions data should be provided to inform the public about the relative impacts of flying, allow the opportunity for consumers to pick more sustainable flight options and also encourage airlines to reduce emissions. The participants considered the information should be standardised, easily accessible and have third-party vetting to encourage trust and reliability.

ICCT points out that travel search engines like Google Flights, Kayak and Skyscanner have introduced ‘eco-flight’ filters into their platforms, reflecting, it says, growing consumer interest in climate disclosure at the time of purchase.

A study which included a survey of employees at the University of California also found that when presented with hypothetical price and emissions estimates side by side, the employees expressed a willingness to pay more for a lower-emitting flight – representing about $200 per tonne of CO2e saved, which is much higher than carbon offset prices seen today. The emissions information also provided more incentives for the employees to choose direct flights from a non-preferred airport over flights with a layover leaving from a preferred airport.

The ICCT’s own study shows flights with the lowest emissions per passenger are not necessarily the most expensive. “Consumers might worry that lower-emitting flights cost more, but our analysis has shown that in most cases the least emitting flight is among the cheapest tickets on a route,” Sola Zheng, co-author of the study, told GreenAir. “With access to emissions data, consumers can opt for fewer emissions with the same amount of dollars.”

ICCT says although there are a number of online carbon calculators available, including from ICAO, that allow users to estimate CO2 emissions for origin-destination airport pairs, they do not provide specific information on carrier or aircraft type and cannot be used by consumers to choose less-emitting flights.

Its study analysed 20 frequently travelled US domestic routes, 16 of which were selected based on the high number of departures and total revenue passenger-miles in 2019. On the remaining four routes, low-cost carriers accounted for more than 60% of market share and were selected based on the number of departures in 2019 as well as on carrier diversity.

Among the analysed routes, the least-emitting itinerary on average emits 63% less CO2 than the most-emitting itinerary on the same route, with a range from 48% to 80%. The emissions gap between the most and least emitting itineraries is much wider than the airline-level fuel efficiency gap of 26%, reflecting the influence of layovers (direct vs. non-direct flights), aircraft used and variations in operational parameters like load factors. When compared to the route averages, the least-emitting itineraries are on average 22% less carbon-intensive.

In general, the data confirmed that a nonstop flight is likely to emit less CO2 per passenger than an itinerary with layovers. However, found the study, there can be relatively fuel-inefficient nonstop flights that emit more than some one-stop itineraries on the same route, so the number of stops does not always identify lower-emitting itinerary options.

The correlation between itinerary emissions and aircraft deployed is also complicated, says ICCT. Comparing the combined fuel efficiencies of multiple aircraft based on their types alone yields high uncertainties and is not easily done by an average consumer. Even for nonstop flights, the relative emissions of different itineraries using the same aircraft type vary depending on operational factors and on the other types of aircraft flown on the route. Itineraries on the same aircraft can be low-emitting on one route but high-emitting on another.

The carrier that operates the aircraft also matters. An airline may carry more passengers on a given flight, either by operating at higher load factors or via a single class service, leading to lower per-passenger emissions than other carriers flying the same aircraft on that route. “Load factors, aircraft age, congestion at a hub airport and many other factors also contribute to the different outcomes for the same aircraft type,” says the study. Despite the variation across routes, however, flights using the newest generation of aircraft types are likely to be less emitting regardless of other factors.

The study also found the lowest-emitting itinerary by a carrier sometimes emits more than the route average, indicating that loyalty to a single airline could lead a consumer to choose a higher-emitting itinerary than necessary. “There is no one carrier that operates only low-emitting itineraries (better than route average) across all the analysed routes on which it operates,” it explains. “An airline can also emit much less than airlines on one route but show the opposite emissions pattern on another route. Some airlines have more fuel-efficient operations than others on average but there is no one ‘greenest’ airline when evaluated at the route and itinerary level.”

Said Zheng: “There are no golden rules when it comes to selecting lower-emitting flights based on aircraft type or airline. For two flights from Los Angeles to Hawaii, for example, one may emit 63% less CO2 than the other on a per passenger basis but consumers currently have no access to this kind of information. Directly disclosing emissions by itinerary would be the most helpful to them.”

Emissions disclosure by airlines would raise awareness among consumers of their carbon footprint and, more importantly, reward airlines that operate more fuel-efficient flights through strategies such as deploying newer, more fuel-efficient aircraft and improving load factors, argue the authors. “Eventually, as technologies such as sustainable aviation fuels and zero emission planes fuelled by electricity and/or hydrogen become mature, emission reductions due to fuel switching and cleaner aircraft could be rewarded as well,” they add.

While in principle airlines could disclose the carbon intensity of their flights voluntarily on their own websites or other booking platforms, the authors suggest public policy would help to ensure accurate and standardised disclosure from all airlines. For example, policymakers could require carriers to disclose previous-year emissions by route and aircraft on their websites, with third-party booking sites also choosing to display independently validated and credible information to consumers.

“The flip side of voluntary behaviour change by consumers is to internalise the environmental costs of flying into ticket prices through taxation policies or market-based emissions regulations,” say the authors. “While effective, experience suggests that these policy instruments are politically difficult and may take a long time to craft and implement. Emissions disclosure, on the other hand, could conceivably be implemented in a shorter period with fewer resources because it is politically less fraught.”

Photo: Skyscanner’s ‘Greener Choices’ labels flights it believes to emit less CO2 compared to the average

In 2009, the International Air Transport Association (IATA) committed to capping aviation emissions at 2020 levels and to reducing them 50% from 2005 levels by 2050. Fast forward more than a decade and a lot has changed. The amount of attention paid to the environmental impact of flying has increased and the Covid-19 pandemic decimated demand. The previous Director General of IATA, Alexandre de Juniac, stated last month the organisation is considering a revision of its previous goals, and that it will be up to the new head, former International Airlines Group CEO Willie Walsh, to determine the next steps, writes Brandon Graver.

The obvious first item to address is the goal of capping aviation emissions at 2020 levels. The trade group asked the International Civil Aviation Organization (ICAO) to change the baseline for its Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) from an average of 2019 and 2020 emissions to only 2019 emissions. This is because the sharp decline in air travel in 2020 due to the pandemic led to a sharp decline in emissions, which would significantly lower the overall baseline. The ICAO Council agreed, and international emissions above the 2019 level will need to be offset in future years. As IATA is forecasting that commercial aviation emissions in 2021 will be higher than 2020, I expect IATA will change its goal to capping emissions at 2019 levels.

That leaves the long-term goal of reducing net emissions by 50% compared to 2005 levels by 2050. The amount of CO2 emitted from commercial aviation in 2005 was 650 million tonnes (Mt), so 2050 emissions will have to be 325 Mt or less. The plan for most airlines is to reduce emissions as much as possible using aircraft technology, alternative fuels and operational improvements, and then use carbon offsets to cover the remainder. A number of airlines have now announced their own, more stringent climate goals. The roadmap is the same in many cases, but instead of using carbon offsets to cover shortfalls from reaching a 50% reduction in emissions, some airlines will use them to achieve a 100% reduction, or net-zero. It should be noted, however, Scott Kirby, CEO of United Airlines, has made it abundantly clear that for them, carbon offsets don’t work, calling them “a fig leaf for a CEO.”

Figure 1 depicts the share of 2019 commercial aviation emissions (914 Mt) from airlines that have made net-zero commitments. In theory, once enough airlines set a net-zero goal and their total 2019 emissions exceed 65% (reduced from 914 Mt to 325 Mt), IATA’s ‘net 50 by 50’ goal is moot. This is depicted by the red dashed line.

Figure 1. Share of 2019 commercial aviation CO2 emissions by airlines with public 2050 net-zero commitments.

Last month, the trade group for the 10 largest US airlines, Airlines for America, announced that all of its members committed to net-zero emissions by 2050. Earlier in the year, a group of industry stakeholders, including Airlines for Europe and the European Regions Airline Association, released Destination 2050, a roadmap for the decarbonisation of European aviation. The emissions associated with airlines in the United States and Europe are illustrated by the red and yellow blocks of Figure 1.

Net-zero committed airlines in other geographic regions, including those in the oneworld airline alliance, are depicted by the blue block. The assumption is that CO2 emissions from airlines that have since ceased operations will not return, especially if industry caps emissions at 2019 levels. As of March 31, 2021, 50% of commercial aviation emissions from 2019 are apportioned to airlines that have set goals of net-zero emission by 2050.

While numerous airlines have set net-zero by 2050 targets, and there will inevitably be more, IATA does not believe the industry as a whole will be able to make the same commitment. Instead, the head of environment at IATA stated that 2060 is a more reasonable deadline. Figure 2 depicts emissions from commercial aviation (solid blue line) and where IATA’s goals lie (assuming the 2020 cap on emissions is now a 2019 cap on emissions).

Figure 2. Commercial aviation CO2 emissions and reduction goals 1990-2060 (source data: ATAG and IATA)

There are some clear pathways to achieve the 65% threshold. If both SkyTeam and Star Alliance members make net-zero commitments, then more than 70% of CO2 emissions from commercial aviation in 2019 are accounted for. Alternately, if airlines operating in all countries that have made national net-zero targets also set net-zero goals, that would also be enough to push the industry over the threshold.

So, what does this all mean for the new IATA Director General? Clearly, now is the time to announce ambitious climate goals for the association’s members, and there are many upcoming forums to do so. My suggestion is to make a net-zero commitment at the COP26 meeting in Glasgow this November and adopt the net 50% reduction as a mid-term target. In addition, the association should push ICAO to secure a net-zero goal from international aviation by 2050 at the 41st General Assembly in September 2022. By establishing bold targets for reducing aviation emissions and ensuring other airlines do their part, Mr Walsh can make a big impact in his new position.

Top photo: oneworld member airlines have already committed to a net-zero by 2050 goal

About the author

Brandon Graver

Brandon is a Senior Aviation Researcher at the International Council on Clean Transportation (ICCT). His reserach identifies, refines and promotes policies to reduce the environmental impacts of commercial aviation. He can be reached at b.graver@theicct.org.
This article was first published as a blog post on the ICCT website.

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Views expressed in Commentary op-ed articles do not necessarily represent those of GreenAir.

Analysis by the International Council on Clean Transportation (ICCT) shows there are sufficient sources of sustainable feedstock to support the production of 3.4 million tonnes (Mt) of advanced sustainable aviation fuels (SAF) annually in the EU by 2030, around 5.5% of projected EU jet fuel demand. Waste oils is the most technically mature SAF pathway at present and could produce up to 2% of the share although this resource is highly constrained and largely consumed by the road sector. Moving beyond 2% of SAF deployment will require targeted support by the EU for more conversion pathways such as lignocellulosic biofuels and electrofuels, which come with more challenging economics and uncertain production timelines, says ICCT. Current volumes of SAF are below 0.1% of EU annual jet fuel consumption. The European aviation industry’s recent Destination 2050 roadmap estimates SAF deployment of 3 Mt in 2030, rising to 32 Mt – equal to 83% of total jet kerosene consumption – in 2050 if given strong political support.

Ahead of the forthcoming launch by the European Commission’s ReFuel EU Aviation policy initiative, the study by ICCT evaluates the resource base that could support SAF production in the EU from 2025 to 2035, focusing only on the potential volumes available from sustainably available feedstocks. It also takes into account sustainable harvesting limits, existing other uses of feedstock materials and SAF conversion yields.

Deploying SAF requires overcoming even greater economic and technological constraints than deploying alternative fuels to the road sector, cautions the study. The vast majority of biofuels up till now have come from first-generation, food-based production, although the EU is transitioning away from these fuels. By targeting the deployment of advanced SAFs from non-food feedstocks early on, the developing SAF industry can avoid the controversies around food-based biofuels, it argues, although there will be limiting factors around economic viability, feedstock supply and pace of technology advances.

Waste oils, including used cooking oil, animal fats and other fatty acids, offer the cheapest and easiest means for producing SAF with current technology. In 2018, hydrogenated esters and fatty acids (HEFA), which can be blended up to 50% by volume with petroleum-based kerosene, were the most common alternative drop-in jet fuels with about 360,000 tonnes of capacity in the EU. Their advantage is that infrastructure is already in place to support large production volumes and are likely to be the cheapest source of SAF in the near term. Production costs are around twice the cost of fossil-based jet fuel production, while other conversion processes may be as much as eight times higher.

Lignocellulosic feedstocks from agricultural and forestry residues and from municipal and industrial waste are more technically challenging to convert than waste oils due to their physical properties. However, these feedstocks are more abundant than waste fats and, when converted into SAF, generally have higher GHG savings than food-based SAF pathways. Feedstock conversion pathways include gasification with Fischer-Tropsch synthesis or by upgrading ethanol or isobutanol into drop-in fuel quality or alcohol-to-jet fuels. The delays in building compatible biorefineries have so far slowed down the commercialisation of lignocellulosic biofuel pathways.

ICCT estimates 76.5 Mt of feedstocks from agricultural residues, 5.1 Mt from forestry residues and 21.2 Mt of municipal and industrial waste will be available for biofuel production in 2030.

Cover crops, which are grown during the winter and harvested in the spring before sowing of principal crops, could also provide additional feedstock for SAF production, though their future contribution is uncertain. Cover cropping is relatively uncommon in Europe so in theory there is the possibility to expand the practice without substantial negative environmental or market impacts. Potential cover crops could include oilseeds such as rapeseed and carinata. ICCT estimates cover crops could provide an additional 7.15 Mt of lignocellulosic feedstocks for SAF production in 2030.

The study also looks at non-biological pathways for producing SAF such as electrofuels (e-fuels), also called power-to-liquid (PtL) fuels. This is a potentially low-carbon yet resource-intensive pathway involving splitting water into hydrogen and oxygen via electrolysis, with the hydrogen then synthesised in a reactor with carbon dioxide to produce liquid or gaseous hydrocarbons or alcohols. To ensure these fuels are both sustainable and low-carbon, renewable electricity used in SAF production should not be diverted from other uses.

The amount of PtL that could be theoretically available for SAF is very large, says the study, but the potential is unlikely to be met in the timeframe, given the high cost and time required to commercialise an emerging industry. For the most economical scenario, using grid-connected wind electricity and industrial CO2, it would require policy support of €2 per litre, which, according to the study, is very high compared to current alternative fuel subsidies and other forms of European policy support. However, at that incentive level and if SAF is a high political priority, then PtL aviation fuels could conceivably be provided in the 2030 timeframe in quantities estimated at 0.006 Mt in 2025 to 0.15 Mt by 2030 and 0.23 Mt by 2035.

Achieving higher production quantities would be possible, says ICCT, with greater policy support, such as a sub-mandate for e-fuels, and especially with more time for industry commercialisation and when the price of renewable electricity declines.

The final source of feedstocks examined by the study that could play a part in 2030 EU SAF production is industrial flue gases, which are captured, fermented and upgraded into SAF, a process developed by LanzaTech for steel mills. The process produces an ethanol intermediate which is then converted to a synthetic hydrocarbon. Assuming steel production remains near 2018 levels, the study estimates industrial flue gases would yield 3.3 Mt of ethanol for further upgrading to transport fuels, contributing an additional 0.76 Mt of alcohol-to-jet SAF in 2030.

Estimated 2030 SAF production and contribution to overall EU jet fuel demand by feedstock (source: ICCT)

ICCT’s central estimate of EU jet fuel demand, based on a 4.5% growth rate in conjunction with a 2.0% annual fuel efficiency improvement and without accounting for the Covid-19 pandemic, is 55.5 Mt in 2025, 62.8 Mt in 2030 and 71.1 Mt in 2035. Although there is a sufficient resource base to theoretically support peak production of 12.2 Mt of SAF a year, it says with deployment and feedstock constraints in place there is a maximum potential for 3.4 Mt, or 5.5% of 2030 jet fuel demand. Without any targeted support for more challenging pathways, the actual SAF potential could be closer to 1.9%, primarily drawn from easier-to-convert HEFA fuels.

“Expanding SAF beyond today’s production levels will require substantial financial incentives to overcome the economic and technical barriers that have thus far kept production low,” concludes the study. “Absent strong policy support and long-term commitments to advanced fuels, it will be difficult to do more than divert waste oils from other sectors. High blending targets in the absence of complementary policies may instead open the door to higher use of food-based biofuels in aviation.

“Even with strong policies in place, the limited availability of the best-performing feedstocks suggests that SAF production alone cannot achieve the EU aviation sector’s long-term GHG reduction obligations.”

Photo: Air BP

US environmental groups say the proposal by the Environmental Protection Agency (EPA) to adopt the ICAO CO2 standards for aircraft into US regulations violates the nation’s Clean Air Act because it fails to reduce greenhouse gas emissions despite the EPA’s findings that such emissions endanger public health and welfare. Moreover, they say, the proposal’s failure to consider the statutory factors laid out in the Act or analyse the costs and benefits of a range of possible emission standards, and refusal to select an alternative based on the evidence before the agency was “arbitrary and capricious”. The groups were responding to a public comment period just closed on the proposal, which has been largely supported by US aerospace and airline sectors. Although the majority of aircraft will not be subject to the standards until January 2028, the industry is calling for finalisation of its domestic adoption by the end of this year.

The aircraft CO2 standards were adopted by the ICAO Council in March 2017 and are contained in Annex 16 of the Chicago Convention. It applies to new aircraft type designs from 2020 and to aircraft type designs already in production as of 2023. Those in-production aircraft which by 2028 do not meet the standards will no longer be able to be produced unless their designs are sufficiently modified. The EPA and FAA represented the United States on ICAO’s environmental protection committee CAEP, which drew up the standards.

After legal challenges by environmental groups, in 2016 the EPA issued findings that within the meaning of section 231 of the Clean Air Act, elevated concentrations of greenhouse gas (GHG) emissions in the atmosphere endangered the public health and welfare of current and future generations, and that GHG emissions from certain classes of engines used in certain aircraft are contributing to the air pollution that endangers public health and welfare.

As such, the EPA is proposing to regulate GHG emissions from covered airplanes through the adoption of domestic GHG regulations that match ICAO’s international CO2 standards. Covered airplanes are civil subsonic jet aircraft with a MTOM greater than 5,700 kgs and larger civil subsonic turboprop airplanes with a MTOM greater than 8,618 kgs. It proposes to adopt the ICAO CO2 metric, which measures fuel efficiency, for demonstrating compliance with the GHG emissions standards. The metric is a mathematical function that incorporates the specific air range (SAR) of an airplane/engine combination – a traditional measure of airplane cruise performance in units of km/kg of fuel – and the reference geometric factor (RGF), a measure of fuselage size.

To measure airplane fuel efficiency, the EPA is proposing to adopt the ICAO test procedures whereby the SAR value is measured in three specific operating test points, and a composite of those results used in the metric to determine compliance with the proposed GHG standards. In order to be consistent with the current annual reporting requirement for engine emissions, the EPA is also proposing to require the annual reporting of the number of airplanes produced, airplane characteristics and test parameters.

The EPA says US manufacturers have already developed or are developing technologies that will allow affected airplanes to comply with the ICAO standards, in advance of its adoption, and it anticipates nearly all affected airplanes to be compliant by the respective dates for new type designs and for in-production airplanes. This includes the expectation that existing in-production airplanes that are non-compliant will either be modified and re-certificated as compliant or will likely go out of production before the production compliance date of 1 January 2028.

“For these reasons, the EPA is not projecting emission reductions associated with these proposed GHG regulations,” it states in the executive summary of the proposed rule.

The EPA held a virtual public hearing on September 17, with participation from aircraft and engine manufacturers, aerospace and airline industry associations, environmental organisations and other interested parties. Over 120 written public comments have been submitted in response to the proposal by the October 19 closing date.

A coalition of environmental groups that first filed a suit against the EPA over a decade ago to force the agency to address GHG emissions from aircraft said the proposal violated section 231 of the Clean Air Act (CAA) as it failed to reduce GHG emissions from aircraft despite the EPA’s own endangerment findings.

“Moreover, the proposal’s failure to consider the statutory factors laid out in section 231, over-reliance on factors outside the statute, failure to analyse the costs and benefits of a sufficient range of possible emission standards, and refusal to select an alternative based on the evidence before the agency are arbitrary and capricious,” says the submission by Earthjustice, Center for Biological Diversity, Sierra Club, Friends of the Earth and Natural Resources Defense Council.

“These flaws cannot be remedied in a final rule. Instead, EPA must replace the proposal with one that meets its duties under the Clean Air Act. The final regulations must employ strong mechanisms to reduce emissions from aircraft and protect the public health and welfare and in doing so, EPA must consider the full panoply of available measures, including declining fleetwide emissions averages and operational and design improvements.

“To avoid catastrophic climate change, EPA must implement standards that far exceeds ICAO’s standards in both stringency and scope.”

The submission dismisses the EPA’s argument that US manufacturers would be at a competitive disadvantage if the US failed to adopt standards in line with ICAO’s. “EPA provides no legitimate basis for this assertion. Nothing prevents the US from adopting standards that are more stringent than ICAO’s and EPA has responsibility to do so if that is what public health and environmental protection require.”

Commenting on its own submission, Annie Petsonk, International Counsel for the Environmental Defense Fund, said: “As EPA’s own analysis indicates, the proposed standards will not drive emissions down. It simply embodies what the industry has already baked in. To justify its approach, EPA relied on a problematic estimate of the costs of doing nothing, arbitrarily ignoring the real costs of climate pollution that people across the country are facing every day.

“As the aviation industry tries to bounce back from Covid, it must put addressing the climate crisis at the core of its recovery, and government needs to lead the way. A stringent aircraft pollution standard would mean jobs building the aircraft and creating the fuels of the future. Instead, EPA’s proposed aircraft rule ignores the science and contravenes laws that require it to protect public health and the environment.

“We urge EPA to replace its proposal with standards that will actually reduce aircraft emissions, as one key element of a broader package of carrots and sticks to get the aviation industry to take real steps to cut climate pollution.”

In its submission to the EPA, the non-profit environmental research organisation International Council on Clean Transportation (ICCT) said its analysis showed new deliveries of commercial aircraft in 2019 were on average 6% more fuel efficient than required by the ICAO standards.

With some caveats, the industry response to the EPA’s proposal is supportive of legislation in line with ICAO CO2 standards, which it sees as meeting the criteria set out in the CAA’s section 231.

“Adopting the standards into US law will ensure US-manufactured aircraft and engines are available to US airlines, while fostering global competition and enabling our airlines to acquire aircraft and aircraft engines at market-driven, competitive prices,” says a joint submission by Airlines for America and the Air Lines Pilots Association International. “Especially given that, as the agency itself notes, other ICAO member states that certify airplanes have already adopted the ICAO CO2 standards, the agency needs to act to put US manufacturers on the same footing as their foreign counterparts.”

The two trade bodies said the ICAO standards would achieve GHG emissions reductions, support US policies to combat climate change and provide international uniformity. “Aircraft and the international airspace system simply could not function if aircraft and aircraft engines were subject to disparate regulatory requirements and standards.”

However, they asked the EPA to clarify in its rulemaking that the proposed US standards did not apply to in-service aircraft and disagreed with the agency’s conclusion that there could be no costs or benefits attributable to the standards.

A submission by the Aerospace Industries Association (AIA) said its members had already taken steps to ensure compliance with the proposed standards, including making plans to end production of the least fuel-efficient aircraft.

“The majority of aircraft will not be subject to the standards until 1 January 2028. Nevertheless, we urge the EPA to finalise the domestic adoption of these rules by the end of this year,” said the AIA. “Airlines purchase aircraft several years in advance. They are currently deciding on aircraft that will be delivered through the end of this decade. When making these decisions, airlines will require assurances that aircraft meet the standards to operate in international markets.

“Without domestic regulations in place, the FAA would be unable to certify an aircraft as meeting the ICAO CO2 standards. In this situation, US manufacturers would be at a serious competitive disadvantage if airlines were to seek greater regulatory certainty by opting to purchase aircraft manufactured elsewhere that meet the requirements of their certifying authority’s equivalent rules, which have already been implemented in some cases.

“If this was to occur, it could jeopardise tens of billions of dollars in sales for the US aerospace industry.”

Engine manufacturer GE said the proposed rule would provide the global aviation industry with much-needed certainty and consistency as it faced the Covid crisis and its adoption would satisfy US obligations under the Chicago Convention by ensuring compliance with ICAO standards.

GE also argued that more stringent GHG standards were not appropriate and would potentially violate the Clean Air Act.

“The CAA does not require the EPA to ‘technology force’ at the risk of flight safety,” said the submission. “[It] requires EPA to refrain from changing aircraft emission standards if such a change would adversely affect safety. To maintain the trust and confidence of the flying public, it is imperative that EPA not adopt standards that could in any way be perceived as sacrificing aviation safety. The perception of the flying public matters and EPA should endeavour to avoid any erosion of public confidence in the safety of aviation. This objective is best achieved by EPA remaining aligned with the ICAO analytical criteria of technical feasibility, environmental benefit, cost effectiveness and impacts of interdependencies, which have helped ensure the continuation of aviation’s impressive safety record.

“Moreover, when preparing this proposal, EPA carefully analysed the impacts of two more stringent alternatives. These analyses show that the alternatives would lead to minimal reduction in GHG emissions, while imposing significant costs associated with deviating from the ICAO standards. Consequently, EPA appropriately decided against proposing either of these alternatives.”

While supportive of aligning EPA regulations with the ICAO CO2 standard, both Boeing and Airbus are opposed to the reporting requirements laid out in the proposal. Boeing said they were unnecessary as they were duplicative of FAA reporting requirements, “and unwise because they pose unnecessary risks to Boeing’s confidential business information and potentially the nation’s security.”

The concerns are centred on fears the EPA could make public manufacturers’ specific air range data.

“SAR data is highly sensitive, treated by Boeing and other airplane manufacturers as a trade secret and protected zealously from disclosure to competitors and the public,” says the Boeing submission. “because of the strategic value of SAR data, it can also be subject to federal export controls and sanction regimes.

“There is also a risk that someone could wrongly argue that SAR data should be considered to be emissions data or ‘related technical information’ that EPA must disclose. EPA should not collect SAR data … and should not require reporting of that data. If it nonetheless requires reporting of SAR data then EPA must ensure that data is protected from public disclosure.

“EPA need not collect SAR data to track airplane CO2 emissions performance and verify compliance. ICAO agreed to the use and public reporting of an aircraft’s [fuel efficiency] metric value for this purpose because it is sufficient by itself to enable assessment of compliance with the CO2 emissions standard, while continuing to maintain the confidentiality of manufacturers’ SAR data. Significantly, ICAO does not require public reporting of RGF – an important element of SAR data – precisely because it can be used to derive an airplane’s SAR.”

Airbus too said SAR data and the reference geometric factor were highly commercially sensitive information. It also questioned the EPA’s authority to request such information when a large number of airplanes delivered around the world would never operate within the United States.

“ICAO is the right body to create international standards,” said the Airbus submission. “Airbus believes that in the absence of a worldwide harmonisation process, regional requirements could produce unintended consequences that would harm the aviation industry. We therefore urge the EPA to adopt the proposed ICAO rule with no additional requirements.”

The ICAO Aircraft CO2 standards are contained in Volume III to Annex 16 of the Chicago Convention and were adopted in Europe by the European Parliament and Council in July 2018 (Regulation (EU) No. 2018/1139). The European Union Aviation Safety Agency (EASA) published certification specifications concerning the standard in August 2019.

Photo: Boeing

In its first analysis of the carbon impact of premium (first and business) class seating, the International Council for Clean Transportation (ICCT) estimates nearly 20% of emissions from commercial aviation were attributable to premium passengers in 2019, higher than the 15% coming from air freight transport. Premium seating was estimated to be up to 4.3 times more CO2 intensive than economy seating. The ICCT study for the years 2013, 2018 and 2019 also found global commercial air traffic increased nearly four times faster than fuel efficiency improvement between 2013 and 2019, with passenger aircraft CO2 emissions increasing by a third during the period. The three largest aviation markets – the United States, the European Union and China – were together responsible for 55% cent of CO2 emissions in 2019.

Merging data from ICAO, OAG and individual airlines using Lissys’ Piano 5 software, ICCT’s Global Aviation Carbon Assessment model calculated commercial aviation (passenger and cargo) CO2 emissions rose from 706 million tonnes (Mt) in 2013 to 920 Mt in 2019, figures close to the industry’s own estimates. Passenger transport accounted for 785 Mt, or 85%, of commercial aviation CO2 emissions in 2019, with the remaining 15% (135 Mt) from freight carriage that was divided between belly freight on passenger aircraft (8%) and dedicated freighter operations (7%).

The top five departure countries for passenger aviation-related carbon emissions in 2019 were the United States (with a 23% share), China (13%), the United Kingdom (4.1%), Japan (3.3%) and Germany (2.9%). While still the largest, the US market is growing more slowly over time than the rest of the world and is the most carbon intensive of the major markets, emitting 12 per cent more CO2 per RPK than the global average.

Globally, two-thirds of all flights in 2019 were domestic but only accounted for around one-third of global RPKs and 40% of global passenger transport-related CO2 emissions. CO2 emissions from international flights increased by 35% between 2013 and 2019, outpacing the 30% increase in emissions from domestic flights.

Between 2013 and 2019, the total number of flight departures worldwide increased by 23%, RPKs increased 50% and passenger transport-related emissions by 33%. ICCT’s analysts found that RPKs correlate well with CO2 emissions after accounting for improvements in fuel efficiency. That RPKs increased faster than emissions during this period suggests that fuel efficiency improved, resulting in a 12% decrease in carbon intensity.

On average, global commercial aircraft operations emitted 90 grams of CO2 per RPK in 2019, which was 2% lower than in 2018 and 12% lower than in 2013. While domestic operations are included, the change is in line with ICAO’s aspirational goal of 2% fuel efficiency improvement annually for international aviation.

Flights within the regions of Asia/Pacific and Europe saw the largest intra-region increase in passenger CO2 emissions since 2013, at 50% and 35% respectively. Emissions in several regions grew slower than the global average: Middle East, 27%; Africa, 21%; and Latin America/Caribbean, 19%. The smallest growth in passenger emissions for a major market, 16%, was observed for flights within North America.

The least efficient route groups between 2013 and 2019 were flights within Africa and within the Middle East, emitting more than 30% more CO2 to transport one passenger one kilometre than the global average. This was primarily due to the use of older, fuel-inefficient aircraft and low passenger load factors. However, there were improvements in fuel efficiency of 4-5% for these route groups from 2018 to 2019, higher than the global average yearly increase in fuel efficiency between 2013 and 2019.

The largest gains in fuel efficiency between 2013 and 2019 were for flights between the Asia/Pacific and Latin America/Caribbean regions, which can be credited to the replacement of Airbus A340 and Boeing 767 aircraft with more fuel-efficient Boeing 787 Dreamliners. Flights departing a US airport had an average CO2 intensity 6% higher than the global average.

Around 61% of passenger transport emissions in 2019 came from international aviation, although domestic flights made up two-thirds of all departures. Together, the United States and China were responsible for 185 Mt of CO2 from domestic flights, or over 60% of emissions from global domestic operations in 2019, which was an increase of 31% since 2013.

Responsible for 39% of global passenger CO2 emissions, domestic aviation falls outside the jurisdiction of ICAO and the report’s authors suggest national and regional measures and policies are needed to curb emissions from this important part of the air transport sector.

They say the study highlights the significant differences in the carbon intensity of flights at all levels: market, aircraft class, aircraft type and seating class.

“Better emissions disclosure, for example requiring airlines to disclose the carbon intensity of each itinerary to consumers at the time of purchase, would help consumers steer their business to lower emitting carriers,” they recommend.

Additionally, they suggest carbon pricing for aviation could be improved and made more equitable by properly reflecting the emissions due to premium travel, with fees graduated based upon seating class so that premium travellers pay more and help generate revenue for climate mitigation in a progressive way.