Analysis: UK’s ‘jet-zero’ plan would allow demand for flying to soar 70%

As the UK sweltered in record-breaking 40C heat on Tuesday, the UK government quietly released a new aviation plan that could allow the number of flights to soar in coming decades.

The UK’s “jet zero” strategy promises to “deliver net-zero aviation” by 2050, while allowing passengers to travel by air “guilt-free”.

It prioritises largely undeveloped technologies, such as “sustainable aviation fuels” and zero-emission flights – while skirting recommendations from its own climate advisers to reduce demand for flying.

Under the strategy’s plans, the UK aviation sector will not reach net-zero by 2050, but instead will still be emitting 19m tonnes of CO2 equivalent (MtCO2e). For the UK to reach its legal net-zero target, these emissions will need to be removed from the atmosphere.

The plans will also see passenger numbers increase by 70% from 2021 to 2050, representing an additional 200 million passengers. 

In this article, Carbon Brief examines the details of the government’s plan to address emissions from aviation, including through its big bets on new technologies.

• UK’s ‘jet zero’ plan
• Reducing flight demand
• Sustainable aviation fuels
• Carbon pricing
• Non-CO2 emissions
• ‘Zero-emissions aircraft’

UK’s ‘jet zero’ plan

International and domestic aviation only accounts for 3% of the UK’s greenhouse gas emissions, but flights have an outsized role in some – normally relatively wealthy – people’s carbon footprints. Therefore, this is one of the areas where individual actions can have a considerable impact.

The sector has been repeatedly highlighted by government advisers the Climate Change Committee (CCC) as a gap in the government’s climate strategy, which the “jet zero” plan is supposed to fill.

The strategy, whose “jet zero” tagline states it will “deliver net-zero aviation” by 2050, has gone through a couple of rounds of consultations and drafts.

It plans for flight demand to increase by 70%, which would see aviation emissions rising from 38MtCO2e in 2019, before the Covid-19 pandemic, to 52MtCO2e by 2050.

The strategy goes on to suggest that a series of interventions – chiefly based on untested technology – could then reduce the impact of demand growth, bringing the sector’s emissions total down to 19MtCO2e in 2050.

This is shown in the chart below, which highlights that, even in the government’s targeted “high-ambition” scenario, residual emissions from aviation would remain higher in 2050 than they were in 1990 – and a long way from the pledged “net-zero”.

These 19MtCO2e of residual emissions would need to be removed from the atmosphere, if the sector – and the nation overall – is to hit its net-zero targets. Removal technologies are still in their infancy and there is uncertainty about whether they will scale up sufficiently.

UK international and domestic aviation emissions (red) and proposed savings against expected future demand growth under the government’s central “high-ambition” scenario (shades of blue), millions of tonnes of CO2 equivalent. Source: Department for Transport. Chart by Carbon Brief using Highcharts.

(It is worth noting that the CCC’s main net-zero pathway leaves more residual emissions than the jet zero strategy, some 23MtCO2e in 2050. However, it relies far more on demand reduction, which it says is more reliable than new technologies such as zero-emission aircraft – see below.)

The government also sets out two additional scenarios, one involving a “breakthrough in sustainable aviation fuels” and the other a “breakthrough on zero-emission aircraft”. These still result in residual emissions in 2050, albeit at lower levels of 8.6MtCO2e and 11.3MtCO2e, respectively.

The CCC has said both of these technologies represent “major risks” to the government’s climate plans and may not deliver sufficient emissions reductions.

Besides setting its proposed “CO2 emissions reduction trajectory” for aviation, based on its “high-ambition” pathway, the government also includes a “five-year delivery plan” that will be periodically reviewed to assess progress. 

However, the majority of the aviation sector’s cumulative emissions cuts under the strategy’s “high-ambition” scenario – some 251MtCO2e of the 357MtCO2e total – are not expected to take place until after 2040.

Within the overall plan, there is also a specific target for UK domestic flights to reach “net-zero by 2040”, although these only account for 4% of the nation’s aviation emissions. 

There will be a new consultation on how to achieve this in 2023 and the strategy says it could include “requiring airlines to buy greenhouse gas removal credits”.

Reducing flight demand

The government’s aviation strategy takes a firm stance against policies that could reduce demand for flights or airport expansion. It instead claims that technologies – many of which remain largely untested (discussed below) – can deliver the necessary emissions cuts, without the need for restrictions on flight numbers.

The strategy says the government “will continue to support sustainable airport growth”, adding:

“Our approach for decarbonising aviation will focus on the rapid development of technologies…Our analysis shows that the sector can achieve jet zero without the government needing to intervene directly to limit aviation growth.”

Under its scenario for how to align aviation with net-zero, it expects passenger numbers to increase by 70% – representing an additional 200 million people flown – from 2018 to 2050. 

On airport expansion, specifically, the strategy says the government will “continue to be supportive of airport growth where it is justified”, adding:

“Our existing policy frameworks for airport planning provide a robust and balanced framework for airports to grow sustainably within our strict environmental criteria. We have also been clear expansion of any airport in England must meet our climate change obligations to be able to proceed.” 

This approach is in conflict with advice from the CCC. Under the CCC’s central pathway for reaching net-zero by 2050, outlined in its “sixth carbon budget” report, aviation demand would be limited to growth of no more than 25% by 2050, when compared to 2018 levels.

In addition, the CCC’s central net-zero pathway allows for no new net airport expansion. According to the CCC, this means that “any expansion” must be “balanced by reductions in capacity elsewhere in the UK”. 

(It is worth noting that seven UK airports currently have formal plans to expand.)

In its most recent progress report, the CCC adds that, given the risks associated with developing new aviation technologies, “as well as risks of under-delivery on emissions reductions in other sectors, the government should actively develop the option to implement policy to manage aviation demand”.

Speaking to Carbon Brief, Helena Bennett, head of climate policy at the thinktank Green Alliance, says the aviation strategy shows a “very blatant disregard for [the CCC’s] recommendation of a demand management framework”.

The UK government’s reluctance to tackle demand also puts it at odds with other countries in Europe. For example, in 2021, France put in place plans to ban domestic flights where the same journey could be made within two-and-a-half hours without flying.

Though the UK strategy rules out measures to tackle flight demand, it does note that “through both our consultations, we received a high volume of responses about the desire for demand management measures to reduce aviation emissions”.

A closer look at the government’s consultation summary document reveals that airport expansion proposals, a potential “frequent flyer levy”, taxing aviation fuel and adding VAT to ticket sales were the most frequently raised topics on the subject of demand management.

A “frequent flyer levy” is a proposal to require those who fly regularly to pay a tax that scales with the number of flights taken each year.

In its most recent progress report, the CCC describes such a levy as a type of fiscal policy that “should be used to increase the price of flying to reflect the high emissions cost of air travel and incentivise low-emission alternatives”.

The idea of a frequent flyer levy also received strong support from the UK’s climate assembly, a consultation of 100 members of the public held in 2020.

As well as failing to address demand, the strategy also appears to offer “contradictory” information on what role consumers should play in reducing emissions from flying, adds Cait Hewitt, policy director at the Aviation Environment Federation.

She notes that the government says it will “support consumers to make sustainable aviation travel choices” and “empower consumers and businesses to make the greenest choices when flying”.

However, a press release accompanying the strategy boldly claims that government plans will enable people to fly “guilt-free”. Hewitt tells Carbon Brief:

“If you’re going to try to encourage people to take responsibility, while at the same time telling them that they don’t have to worry because you’re going to offer them guilt-free flying – that’s completely inconsistent messaging.”

Sustainable aviation fuels

One of the strategy’s largest chunks of emissions cuts by 2050 – some 9MtCO2e – are expected to result from scaling up “sustainable aviation fuels” (SAFs). These are alternatives to kerosene, such as biofuels, or synthetic fuels made from hydrogen.

In its “high-ambition” scenario, the use of SAF in UK flights would reach 10% of overall fuel use by 2030 and 50% by 2050.

These fuels are currently barely used because, as the government acknowledges, they are expensive and their production relies on technology that is “yet to be proven at scale”. 

What is more, as the chart below from the International Council on Clean Transportation’s (ICCT) Dan Rutherford shows, global progress on these fuels has been very slow and has consistently failed to live up to expectations.

Friday fun fact: IATA’s new 2030 alternative jet fuel target matches its 2020 target and is 230x current use. https://t.co/FeOagp32UU pic.twitter.com/kal6XNYrCh

— Dan Rutherford (@rutherdan) October 8, 2021

Nevertheless, the government has made the use of SAF central to its jet-zero strategy, with plans for a mandate by 2025 that would oblige fuel suppliers to cut their emissions “by the equivalent of at least 10% SAF use by 2030”.

The government previously conducted a consultation on this topic in which it said the mandate would involve an emissions scheme based on tradable credits. However, it now says there will be a follow-up consultation in autumn 2022 to “refine the practicalities of implementing a mandate, as well as the monitoring and reporting mechanisms”.

Other commitments include having at least five commercial-scale SAF plants under construction in the UK by 2025, a £165m “advanced fuels fund” to scale up new technologies and “up to £1m” to support the delivery of “the first net-zero transatlantic flight running on 100% SAF”.

In its most recent progress report, the CCC noted that the government’s 10% mandate placed a “high reliance on SAF”, something it identified as a “major risk”. It noted: 

“It is essential that supported fuels deliver genuine significant lifecycle emission savings by [2030] and that the resources used do not have adverse impacts on decarbonisation in other sectors (eg land use), in the UK or overseas.”

As SAFs produce emissions when burned, just like kerosene, their advantage – at least in theory – comes from the fact that their production involves removing CO2 from the atmosphere. For example, if they are produced using plants that absorb CO2 as they grow.

In an earlier jet-zero consultation document released by the government, it assumed 100% emissions savings resulting from SAF use, but its final strategy assumed just 70% savings compared to conventional jet fuel.

Matt Finch, interim UK director of NGO Transport & Environment, tells Carbon Brief that fuels made from renewable hydrogen and captured CO2 could result in 100% savings, but they are even less developed than other SAFs.

The strategy’s annex says such fuels will probably need to be deployed at scale to meet its targets and the government’s SAF consultation response last year confirmed it planned to introduce a sub-mandate for these “power-to-liquid” fuels.

🎉A huge win for Green Alliance🎉

A power-to-liquid (PtL) subtarget will be included in the SAF mandate, as per the #JetZero strategy.

✈️This was a key recommendation from our report published earlier this year
➡️https://t.co/SsRGIHoGgI

A thread 1/4 pic.twitter.com/zafej0TkJy

— Green Alliance (@GreenAllianceUK) July 20, 2022

The strategy also includes an important role for fuel-efficiency improvements for aircraft, which are assumed to be 2% per year by 2050 in the high-ambition scenario.

According to the strategy’s “analytical annex”, this is based on an “optimistic” scenario and will be “challenging”, particularly if the aerospace sector cannot afford to invest in modernising its fleet or chooses to invest elsewhere.  

The government says it will work through the UN International Civil Aviation Organization (ICAO) “to ensure a global baseline for fuel efficiency, both through CO2 certification standards and guidance to states on implementing operational efficiencies”.

Carbon pricing

While the government is clear that it is not interested in persuading people to take fewer flights, the biggest chunk of its planned emissions cuts in 2050 – 13.9MtCO2e – comes from carbon pricing, which is meant to cut aviation demand.

The two main means by which the government aims to put a price on aviation emissions are via the UK emissions trading scheme (UKETS), which covers all domestic flights and most flights to Europe, and the UN’s Carbon Offsetting Reduction Scheme for International Aviation (Corsia) for long-haul flights.

When it sent out its consultation, the government referred to the emissions savings resulting from the “demand impact of carbon pricing”, but in the final report this impact is referred to as “ETS and Corsia”. Hewitt tells Carbon Brief:

“Despite all the talk, actually, doing effective carbon pricing, which has an impact on demand, is likely to give you – even in the government analysis – a bigger carbon reduction than any of the new technologies. But I think they’ve relabelled that now so it looks even less like a demand intervention measure.”

As it stands, long-haul flights do not pay a carbon price because they are outside of the ETS, while short-haul flights within the ETS get free allowances, which cover all of the industry’s emissions, offering no incentive to cut emissions. Finch tells Carbon Brief:

“I like carbon pricing, but how are you going to apply it? If the strategy says we are going to have a carbon price and we are going to do that by kerosene tax, that would be great, but it doesn’t say that. In fact, it doesn’t commit to anything more than ‘we will do carbon pricing’.”

The government says it will ensure Corsia is “fully implemented” in the UK by 2024, the start of the scheme’s “first phase”. It also says it will ensure a “net-zero consistent UKETS cap” and consider the future of the free allocation of credits.

However, there are question marks over the future price that will be set on carbon for aviation emissions under the UK ETS and Corsia. 

The jet-zero scenarios all assume that both the ETS and Corsia price will be £378 per tonne by 2050. This is far higher than most estimates for both of these schemes and Finch says there is no “mechanism” proposed for raising the price. 

In addition, the CCC has previously stated that there are “significant risks that Corsia is not stringent enough and the offsets are of insufficient quality and additionality to be an acceptable contribution to UK carbon budgets”.

The strategy also discusses incentivising greenhouse gas removals, something that will be essential given the 19MtCO2e of remaining emissions from the aviation sector it anticipates in 2050 under the “high-ambition” scenario. 

Under the government’s “delivery pathway” for net-zero, removals will be scaled up to around 23MtCO2 by 2035, from zero today. Any removals will have to cover not only aviation, but also residual emissions from other “hard-to-abate” sectors, such as agriculture.

Plans for the removals sector remain relatively underdeveloped, although the strategy says business models and markets to support its growth will be finalised by 2024. It says the government is also “exploring the role that the UKETS could play as a long-term market for greenhouse gas removals”.

Non-CO2 emissions

The expected large increase in flight numbers under the “jet-zero” strategy means that non-CO2 emissions, such as contrails, emissions of oxides of nitrogen (NOx) and sulphates, will increase unchecked, even if efforts are being taken to curb CO2 emissions.

The strategy emphasises the “uncertainty” around non-CO2 emissions, pledging to “work closely with academia and industry, and monitor global developments in this area”.

While it is true that there are uncertainties around the extent to which these emissions impact the climate, the evidence suggests that they have a strong overall warming effect that is around three times that of aviation CO2. As Finch tells Carbon Brief:

“There are ranges of uncertainty, but we know that the ranges are somewhere between a massive climate impact and an absolutely humongous climate impact – it’s not like this is a little problem and the strategy just lets those drift through.”

Yday was another day with another gvt release of disinformation. They claim to publish a new strategy which shows 2019 the year of ‘peak emissions’ from air travel. What it actually shows is ‘peak carbon (CO2) emissions’ and ignores non-CO2 gases which will likely grow.

— Alex Chapman (@chappersmk) July 20, 2022

The government also says it will “work with the CCC to explore their recommendation for no additional non-CO2 warming from aviation after 2050 and to develop a methodology to monitor the non-CO2 impacts from aviation on a regular basis”. 

It also says that it will “explore” whether and how non-CO2 impacts could be included in the UKETS, as well as “consider” conducting trials flights to examine the impact of different SAFs on levels of non-CO2 emissions.

For its part, the CCC has been clear that “the most effective way of mitigating non-CO2 emissions is through controlling demand for aviation”.

‘Zero-emissions aircraft’

The strategy says the government “will ensure the UK is at the forefront of deploying zero-emission aircraft” with “an aspiration to have zero-emission routes connecting different parts of the UK by 2030”.

Its definition of zero-emission aircraft includes small battery electric aircraft and commercial flights fuelled using hydrogen.

It is worth noting that both types of air transport are still in their infancy – and are currently limited to small aircraft.

In its most recent progress report, the CCC says: “We do not include an indicator on zero- or low-emission aircraft as they are not currently commercially viable.”

The most recent assessment report on how to tackle climate change from the Intergovernmental Panel on Climate Change (IPCC), meanwhile, says that hydrogen “holds significant promise” for emissions reductions in “harder-to-electrify transport segments, such as heavy-duty vehicles, shipping and aviation”. However, it adds that further technological advances are needed for them to play a greater role.

The report adds with “medium confidence” that electrification “could play a niche role for aviation and shipping for short trips”.

For example, the report says that for shorter ranges, flights of light planes carrying up to 50 passengers may be able to use electric power. However, it says that liquid fuels would be needed for most major long distance journeys.