How Sustainable Aviation Can Reach Net Zero by 2050

Right now, aircraft are powered by fossil fuels. This needs to change.

Flying plays a big role in how we stay connected. It is hard to picture modern life without it. Right now, planes cause about 2.5% of the world’s carbon dioxide emissions.² In the UK, flying makes up 8% of the country’s carbon emissions. Air travel is a very high carbon emitter. These figures demonstrate the challenge for getting to net zero. Net zero cannot be achieved without sustainable aviation.

‘While I welcome the kick-start of a journey to net zero in aviation, the 10% to 22% [SAF] mandate between 2030 and 2040 is a concern…..We want to get to net zero by 2045, but having planes still running on 78% fossil fuels is just not good enough.’[1]
Wera Hobhouse

There are two parallel options for the industry:

1. To leave the aircraft design the same and to change the fuel.

2. To re-design the aircraft to take a very different fuel – for example hydrogen or batteries.

Both options are possible, but the choice is not one or the other. Both can be developed.

Sustainable Fuel vs Aircraft Design

SAFs and e-fuels, can gradually replace kerosene made from fossil fuels. They can be mixed in with existing fossil fuels. Steadily over time sustainable fuels can replace fossil fuels. Scaling up production of SAFs and e-fuels is the challenge.

In contrast, a change in aircraft design will be needed for hydrogen fuel or electric planes. This is because the weight distribution within the plane will change. The fuel and its production need to be fixed at the start. The challenge is that there might be no market for the fuel or the plane until it is approved and licenced ten years or more later.

For a genuine commitment to net zero in aviation, a plane redesign would be considered a long term alternative. Building hydrogen or battery aircraft is an option. However, these are as yet undeveloped and unproven technologies. The technology or designs might not work. Getting to net zero requires more certainty.

The only solution for the next ten to twenty years is to power existing aircraft with sustainable fuels.

A Milestone in Sustainable Aviation

Virgin Atlantic made history on November 28, 2023 by flying its Boeing 787 from London to New York using only first-generation Sustainable Aviation Fuel (SAF).³

The plane didn’t need any changes; the only difference was the fuel used. This trailblazing flight showed what is possible.

Now, it is up to the aviation industry and lawmakers to boost SAF production so air travel can become completely carbon neutral.

The Sustainable Aviation Fuel Order in Parliament

The UK parliament has passed into law the new Labour government’s mechanism for the manufacture and use of sustainable fuels.

This measure was debated as the Renewable Transport Fuel Obligations (Sustainable Aviation Fuel) Order 2024.⁴ on 9^th September 2024.

The mandate puts an obligation on airlines to use increasing amounts of SAF between 2025 and 2040. It also sets penalties if these amounts are not achieved.

In introducing the measure for debate, Mike Kane, the Parliamentary Under-Secretary of State for Transport told the House of Commons:

‘The SAF mandate will require 2% of jet fuel to be made from sustainable sources in 2025, 10% in 2030 and 22% in 2040.’⁵ The government provided more detail on the three different SAFs. The intention of the mandate is to allow vegetable oils and alcohol fuels in the early years, with increasing obligations towards synthetic fuels in later years.

The mandate provides a payout clause. Airlines can pay between £4.70 and £5.00 per litre in lieu of missing the SAF requirement.⁶

In replying to the minister, Wera Hobhouse said:

‘I sense that there is a great deal of consensus across the House on this statutory instrument. There is consensus that the aviation sector is one of the hardest to decarbonise, and probably also that the new technology that is being proposed—SAF, in its different iterations—needs a great deal of technological knowledge. However, the principle of taking the first steps towards creating the SAF mandate—of the requirement for SAF to meet 2% of total jet fuel demand from 1 January, and of increasing that on a linear basis, to 10% by 2030 and to 22% by 2040—has no opposition, and we will absolutely support the Government in that effort.

Virgin Atlantic has already demonstrated that a plane can fly across the Atlantic on 100% SAF[7], but that was just one flight, and there are hundreds of flights every day. That is the challenge. I congratulate Virgin Atlantic on this groundbreaking achievement but we really need to see how industry, the Government and indeed everybody who is developing new technologies can produce sustainable aircraft fuels at the scale that is needed. This needs a great deal of investment.

We know that biofuels are not a long-term solution, as they compete with food production. SAF from waste, the next generation of SAF, is not a long-term solution either. It is obviously part of the solution, but as the shadow Minister has pointed out, the real challenge is to get to the third generation SAFs—that is, synthetic fuels. We need to develop them as soon as possible, and they need a great deal of electricity. Whatever we say about this, direct air capture needs a great deal of electricity. Producing hydrogen in a sustainable way—that is, getting to green hydrogen—will also need a great deal of electricity. The crunch in all this is: where is all that renewable energy coming from, unless we are ultimately overproducing renewable energy? I believe that GB Energy will have a big say in this and will be crucial in developing all the renewable energy that will ultimately help us to decarbonise the aviation sector. This is really the challenge.

While I welcome the kick-start of a journey to net zero in aviation, the 10% to 22% mandate between 2030 and 2040 is a concern for the Liberal Democrats. We want to get to net zero by 2045, but having planes still running on 78% fossil fuels is just not good enough. The UK has the third largest aviation network in the world and the second largest aerospace manufacturing sector. Almost 1 million UK jobs are directly or indirectly supported by the aviation sector. The future of the aviation industry with SAF is obviously a wonderful opportunity and challenge. Making the right choices on SAF will ensure that the UK can continue to be a global leader, and I think that we are as one across the House in wanting this to happen in order to make the UK the global leader in this area.’⁸

Scaling Up e-Fuel Production

Two gases are needed for the manufacture of e-Fuels. These are concentrated carbon dioxide from Direct Air Capture and Storage (DACS) and green hydrogen.

Direct Air Capture and Storage (DACS) is a process that removes carbon dioxide from the air and stores it underground or reuses it in fuels.

Green Hydrogen is produced using renewable energy and electrolysis, making it carbon neutral.

Both technologies are well established but are only done at a small scale. Scaling up will require investment. This investment can be underpinned by the Renewable Transport Obligation. The opt out granted to airlines is a worry. This opt out will allow airlines to buy themselves out of this new fuel. The risk to investment in eFuels might be felt to be too high as the product manufactured could find no buyers.

The government should review the mandate. It needs to be much more ambitious between 2030 and 2040. If there is no review, there is a chance that airlines will decide to pay off the extra cost as a £5.00 per litre penalty. On the current figures, this would affect the price of just 10% of their whole fuel usage in 2030. This would rise to only 22% of their whole fuel usage in 2040. It is easy to see that airlines could absorb the extra cost.⁹

Government will need to drive the change

Airlines, with some possible exceptions, are unlikely to be the drivers of decarbonising aviation. They are unlikely to be the direct supporters of the new DACS and green hydrogen industries as they won’t be buying these products at any scale. Blue hydrogen and carbon capture is already a more appealing choice for the existing fuel suppliers. The disincentives for fossil fuels and the incentives for SAFs are still not in place.

The pathway to 100% Sustainable Aircraft Fuel

At her keynote speech at the Solar and Storage Live show at the NEC on 25^th September 2024, Wera Hobhouse said:

We must get to 100% renewables for electricity generation. We must also overproduce at certain times to open the pathway for making green hydrogen and synthetic fuels.’

One of the blocks to progress in the UK has been the policy to limit the growth of renewable electricity. The policy has been designed to keep a place for fossil fuels in electricity generation for as long as possible.

Examples of this have been by limiting Contracts for Difference only for large scale renewable installations. The ban on onshore wind has only been lifted in 2024. There is still no price guarantee for smaller scale renewable energy, including community energy. Investment in the grid is full of delays.

There is a clear pathway for the government to upscale the production of e-Fuels. A deliberate and massive rollout of renewables in this parliament is the first step. Next will be to build new Direct Air Capture and Storage (DACS) and green hydrogen industries. If these new factories are built in the right places, the overproduced renewable energy will go straight into these electricity intensive industries. These industries can scale up and down as national electricity demand fluctuates.

For example, a scaled-up expansion of solar in the UK can directly feed into DACS and green hydrogen production in the daytime summer months when solar is at its most productive. Not only SAFs but other chemicals can be made on the same basis, using cheap or excess electricity.

This can replace the ridiculous market distortion currently in place. Renewable energy producers are sometimes paid to turn off their wind turbines.¹⁰

The grid problem

The UK’s national electricity grid needs to be redesigned. At the moment it is set up to distribute electricity from a small number of power stations. Renewable electricity generation is, at its best, a network of a million power stations. The grid design needs to change.

Even now, coal and gas power stations are ramped up and down to manage variable demand. Owners of wind turbines have been paid to turn them off when supply exceeds demand.

With a million small power stations on the way, we should use this to our advantage. When renewable power is over-produced we should use that power, not turn it off.

At a small scale we can do this with battery storage. At a middle level we can create mini-grids on one side of a substation, providing up to full power in a small network of hundreds of homes and businesses. At a large scale, big producers can be connected into green hydrogen and DACs facilities. Downstream chemical factories, for example making synthetic fuels, can be built alongside.

The green transition will be to build new industries powered directly by renewables.

Conclusion

The planes can be the same. The lifestyles of travellers needn’t change. What needs to change is the fuel.

Aviation is, by its very nature, international. It is not taxed, and it is, like all business, price sensitive. Without effective disincentives, airlines will continue to use fossil fuels.

The UK is pledged in law to get to net zero by 2050.¹¹ With the right incentives, 100% sustainable aviation is possible by then. The Renewable Transport Fuel Obligations (Sustainable Aviation Fuel) Order 2024 will not achieve that on its own.

FAQs

What are the biggest challenges to making air travel net zero?

If we make and use sustainable aircraft fuels, air travel will become net zero. The challenges are to scale up production of these fuels and to encourage or require airlines to buy them. The UK has made a start on this.

Will flying become more expensive with sustainable aviation?

There is no yes or no answer to this question. The price of sustainable flying will depend on the investment government and private companies are prepared to make into new fuels and the subsidies available. Government money and private investment needs to shift from fossil fuels to the net zero fuels of the future.

How can we get airlines to fly with sustainable fuels?

Governments control the taxes and supply of aircraft fuel within their countries or groups of countries. If governments mandate the use of sustainable fuels in their own countries, this will support the shift into their use worldwide.

What is Sustainable Aviation Fuel (SAF) and how does it work?

a) Biofuels: Made from natural materials like vegetable oils or alcohol.
b) Waste-Derived Fuels: Created from various waste products.
c) Synthetic Fuels (e-Fuels): these are made from green hydrogen and captured carbon dioxide. Producing them requires a lot of renewable electricity.

All three SAFs can be mixed with kerosene and used as a percentage of the fuel in an aircraft.

How Sustainable Aviation Can Reach Net Zero: The Role of SAF, Hydrogen & e-Fuels