In 2021, the UK aviation industry made a commitment to be net zero carbon by 2050. The challenge ahead is immense but with credible plans in place, the industry hopes the target can be delivered with the right support.
Broad Support for the Net Zero Goal
The UK Government’s broad vision for decarbonising the aviation sector is outlined in its Jet Zero Strategy. The Jet Zero Council (JZC) – a partnership between industry and Government – has an overarching ambition to decarbonise aviation in a way that preserves the benefits of air travel and maximises the opportunities that decarbonisation can bring.
The Jet Zero Strategy, published in July 2022, implements a pathway to lower emissions but, as the then Transport Secretary Grant Shapps acknowledged, “…there are multiple different solutions needed in order for us to get there.”
Some specific policies in the strategy include making domestic aviation and airports net zero by 2040 and mandating at least 10% of sustainable aviation fuels be blended into traditional aviation fuels by 2030. However, such policies fall under six broader measures to ensure the 2050 net zero goal is met. These measures are:
- Improve the efficiency of our existing aviation system
- Build a thriving UK sustainable aviation fuel industry
- Develop zero emission aircraft
- Implement carbon markets and greenhouse gas removal technologies to compensate for residual emissions
- Influence consumers to make sustainable aviation travel choices
- Address non-CO2 impacts that affect climate and local air quality
Below, we consider measures two and three in more detail and outline the key technological developments on the horizon for more efficient, carbon-cutting aircraft propulsion systems. The key focus of this article, however, is to consider any necessary energy and ground infrastructure enabling works that will support these breakthrough aviation technologies.
The UK is making the transition towards Sustainable Aviation Fuels (SAF), electric, and hydrogen-powered aircraft, but what does the adoption of each of these fuel types mean for airport infrastructure?
Sustainable Aviation Fuel (SAF): What is it?
Modern aviation uses kerosene as fuel and in 2019, worldwide flights produced 915 million tonnes of CO2 out of the c.43 billion tonnes of CO2 humans produced globally. This meant the global aviation industry was responsible for around 2.1% of all human-induced CO2 emissions. However, more sustainable fuel types that produce fewer emissions and are less harmful to the atmosphere are now gaining traction.
Sustainable Aviation Fuel (or SAF) is a ‘biofuel’. It is produced from sustainable feedstocks but is very similar in chemistry to traditional fossil jet fuel. However, it has a much smaller carbon footprint than conventional jet fuel. SAFs are known as ‘drop-in’ fuels, meaning they can be blended into fossil-based aviation fuel and used in existing aircraft without modification.
SAF, therefore, is seen as a transitionary step towards net zero carbon aviation. According to Sustainable Aviation, SAF can achieve lifecycle emissions savings of over 70% compared with conventional jet fuel, when fully replacing kerosene. However, SAF comes at a cost premium of around three to six times the market rate for traditional aviation fuel – one of the reasons why SAF comprises less than 1% of all jet fuel used globally.
SAF fuels are available now. Indeed, Virgin flew its first commercial flight using recycled aviation carbon fuel in 2018, but availability is not at the scale to decarbonise the sector. For that, many more SAF production plants are needed.
10% of SAF by 2030: what this means
Currently, only one plant in the UK is producing SAF at scale, but the SAF it does produce is already being supplied via the existing pipeline infrastructure that feeds directly to UK airports. In early 2022, British Airways became the first airline in the world to use SAF produced in the UK, but wider take-up of SAF is being limited by a lack of production capacity.
To help address shortfalls in SAF refining capacity, £180m of new funding has been committed between 2022-25 under the Jet Zero Strategy to support the commercialisation of SAF plants and fuel testing in the UK. This is in addition to £400m of funding through a Government partnership to drive investment in next generation green technologies. To give a sense of the anticipated scale of the planned domestic SAF fuel industry, the Jet Zero Strategy anticipates that by 2035 production of sustainable fuels could support up to 5,200 UK jobs and provide a GVA (gross value add) of up to £2.7bn from UK production and global exports.
According to Sustainable Aviation, the UK has the potential for 14 plants producing sustainable aviation fuel by 2035 and the recently published Jet Zero Strategy commits to having at least five of these commercial-scale, UK SAF plants under construction by 2025. This will enable UK aviation to meet its mandated target of having at least 10% SAF in the UK aviation fuel mix by 2030. The UK is evidently intent on building a thriving SAF production industry, but production is currently limited given the high capital costs and the fact that the technology is relatively unproven at scale.
Unlike hydrogen and electric propulsion technologies, the use of blended and certified SAF should not require any extensive adaptation of aircraft and supply infrastructure. In terms of commercial aircraft, many are already certified to fly using 50% SAF mixed with kerosene, while the likes of Airbus, Boeing and Rolls-Royce are testing emissions performance of 100% SAF use. Initial tests have found no engineering obstacle to engines running on 100% SAF, however the Airport Council International (ACI) has suggested that in its pure form, the use of SAF will require work on existing distribution systems, storage infrastructure and aircraft to make it fully compatible.
However, used as a blended ‘drop-in’ fuel, a key benefit of SAF is that there is no need to invest in new airport infrastructure or aircraft. Unlike hydrogen and electric-powered flight, which will require transformational changes and are still many years away, with SAF airports can use the same storage and refuelling infrastructure. As such, many experts view SAF as the only realistic alternative to kerosene for long-haul flights prior to 2050.
Even with today’s elevated oil prices, SAF costs significantly more to produce than regular jet fuel. The aviation sector therefore has no real business case to invest in SAF other than to reduce emissions, particularly as there are not enough raw materials (eg waste fat from cooking oil) at the moment to supply the industry at a meaningful scale. As more production plants are built and new types of SAF come to the market, prices will inevitably fall. However, outside/Government intervention (such as policies, subsidies, and carbon taxes) will be necessary to make SAF more attractive and scalable in the short to medium-term, or until the cost of SAF aligns with regular jet fuel – something which the World Economic Forum expects will not happen any sooner than the 2030s.
Tim Alderslade, CEO of Airlines UK, recently said that the UK aviation industry “can’t decarbonise long-haul flying without SAF as things stand”.
Alderslade explained that SAF plants will not get built unless producers believe they will get a return on their investment. Any ROI is affected by the price of SAF (which is currently uncertain) and producers, “want to make sure that the price they will get from the airlines for a nascent product is going to provide a solid return”. Accordingly, Alderslade added that support in the form of Government-mandated pricing mechanisms need to be offered to incentivise plant development and production in the short-term.
Are Electric Aircraft the Answer?
According to Sustainable Aviation, in the short to medium-term for short haul flights – and in the long-term for long haul flights – flying will remain jet-fuel based.
Currently, battery technology performance cannot match the performance of liquid hydrocarbon fuels. While research on innovative electric hybrid and full electric propulsion systems is ongoing, these solutions are unlikely to reach commercial production for another 10-20 years and even then will likely be used for only short haul or regional travel. The timescale for electric propulsion technologies becoming viable on long haul flights is expected to be even lengthier, with some sources suggesting a likely development trajectory of 2040-2050.
In short – we will not have electric commercial aircraft until battery technologies improve. Despite making progress on battery chemistries and increasing energy densities, today’s lithium-ion cells would be unable to provide the correct energy-to-weight ratio. Batteries need to get significantly lighter and more energy-dense if they are to replace jet fuels. With an energy density of 9.6kWh/L, jet fuel is about 50 times as dense as today’s best lithium-ion batteries. However, internal combustion engine inefficiencies mean this figure drops to 14 times the energy density of a lithium-ion battery when comparing equal weights of fuel and batteries.
However, with each annual iteration, the energy density of lithium-ion batteries increases by around 5%. Although annual energy density increases have slowed in recent years as battery technology has matured, researchers are looking to the next breakthrough in battery chemistry (eg sodium-ion, lithium-metal, lithium-sulphur and zinc-air) to help make electric commercial flight viable.
Electric Charging Infrastructure
The electrification of aviation would require not only advanced battery technologies on the aircraft itself, but also energy supply equipment and charging infrastructure. Once battery technologies become sufficiently robust, rapid megawatt-level recharging will be required to support a full recharge. Such charging stations will require solutions that consider any physical limitations of the charging infrastructure and energy storage devices.
Some solutions currently being considered and developed include:
- Plug-In Charging (installed at the aprons and parking locations for in-situ charging)
- Mobile Charging (a mobile charger, such as a truck with an on-board battery, charges aircraft at the apron)
- Parallel Charging (charging from two separate battery banks)
- Wireless Charging induction based wireless power transfer (or WPT) on the ground and potentially mid-air recharging (MAR))
- Battery Swap (replacing depleted batteries with fully charged batteries at the apron)
- Nano-Electro Fuel Flow Battery Tech (a rechargeable electrofuel that allows ‘spent’ battery fluids to be replaced with charged fluids)
Some of these technologies (eg MAR and nano-electro fuel flow batteries) are in the very early stages of development but have significant potential. Nano-electro fuel flow batteries, for example, work by pumping new liquids into storage tanks which enables the battery to be recharged from a vehicle rather than a single location connected to the grid. These technologies, if developed and deployed successfully, would have huge implications for the charging infrastructure.
Many of these solutions are experimental and have several hurdles to overcome. Wireless charging poses some issues regarding electromagnetic impacts on sensitive aviation and lightning arrest systems. Other problems with the technologies mentioned above include cable cooling, logistical challenges with hooking up charging cables, the need to keep charging infrastructure and/or battery packs on a mobile platform for parking and taxi flexibility, and electromagnetic shielding required for aircraft avionics.
Some of the pros and cons of each charging solution above are outlined in the table below:
Regardless of which solution is utilised, the charge-use-recharge support infrastructure for the solutions above will require megawatt-level charging to support the rapid recharging
Required. All of these solutions will need to consider any physical limitations of the charging infrastructure as well as any associated operational challenges.
Smaller airports in particular are unlikely to have sufficient energy capacity to charge aircraft or ground equipment and so additional infrastructure (eg new substations and network upgrades to increase the capacity of existing electrical connections) will be required, bringing significant cost implications. However, with smaller/lighter aircraft likely to be electrified first, smaller airports will need to provide electrical charging infrastructure ahead of larger commercial airports. For example, in the UK key first adopters are likely to be island airports like Jersey, Guernsey and Highlands and Islands.
If/when airports look to increase their future electrical capacity to meet changing energy demands, the timing of investment will be crucial. Capacity needs to be available ahead of need but not so early that you pay for availability which is not yet required. This will be especially important for smaller airports as financing the installation of charging networks requires a substantial upfront investment and the length of payback (which is linked to revenue earned and passenger fares) is uncertain.
Building Out Electric Infrastructure at Airports: Considerations
Planning the appropriate charging infrastructure will require a joined-up approach. A wide-scale charging station network will be required before the electric aviation industry can take really off (literally and figuratively!). Although we have the recent experience of developing a charging network for EVs, the operational needs of commercial aviation require a slightly different approach. Charging infrastructure on its own will not make financial sense. With the EV market, we saw early adopters install chargers first, then OEMs such as Tesla and now a coalition of public/private investors are planning wider, large-scale installations. For aviation, planning the required infrastructure will require working with utilities and airport planners to bring power to where it will be needed.
Unlike EVs, commercial aviation flies on a schedule and therefore needs fast charging capabilities from the outset to meet short turnaround requirements. Many short haul operators run a model that requires intensive use of aircraft, flying it over the same route multiple times per day with a very short turnaround time. Vast amounts of electrical power would be required during the day to facilitate these quick turn times as well as to handle peak electricity demand airports may need to consider distributed energy resources such as solar PV cells, battery storage and demand management systems – all of which will require working with multiple stakeholders and necessitating the use of a comprehensive strategic roadmap.
Airports around the world are only just starting to electrify their ground-based vehicles, but operators will simultaneously need to consider the electrical needs and longer-term power demands for future electric aircraft against planned regional electrical capacity. Furthermore, airport planners and developers will need to anticipate future demand for air travel as this will determine their electrical needs and how much space will consequently be required for distributed energy generation, charging and even community uses when aircraft charging is not needed.
The potential electrification of aircraft fleets opens up a host of integral questions for airports, such as where the electricity will come from (eg the national grid, local power schemes), how much extra electricity would need to be generated and whether it would make economic sense to, for example, fit solar panels to airport building roofs or on unused land around the airport to generate the electricity for recharging aircraft. Given the long lead times involved in both airport planning and aircraft development, planning to build out the necessary infrastructure to accommodate a rapidly evolving technology will be a difficult task, requiring a strongly coordinated and flexible approach.
 The Phillips 66 Limited Humber Refinery near Immingham is the first plant in the UK to produce SAF at scale. SAF is produced from waste cooking oil and other waste derived oils. Currently the refinery has the capability of producing approximately 20,000 metric tonnes per year, with plans to increase to more than 53,000 metric tonnes per year by 2025.
 A kWh/L is a measure of volumetric energy density.