As the aviation industry moves toward net zero emissions by 2050, sustainable aviation fuel is one of the many alternatives being developed.
A flying airplane. Image credit: Willy Wo via Unsplash, free license
November 28, 2023, was a landmark day for the international airline industry. It marked the first time a jet airliner powered by 100 percent sustainable aviation fuel flew from London to New York.
The Virgin Atlantic flight, which carried no paying passengers but did have an airline executive, a politician and Virgin founder Sir Richard Branson onboard, flew using a fuel made up mostly of waste fats and plant sugars.
Sustainable aviation fuel is one of the many alternative fuels and propulsion technologies being developed as the aviation industry moves toward net zero emissions by 2050.
After electricity and heat, transport is the sector with the highest carbon dioxide (CO2) emissions. Aviation counts for 2 percent of Co2 emissions globally.
Aviation is crucial not only for global passenger movement but also global supply chains. While civil aviation nearly disappeared during the COVID-19 pandemic, cargo flights distributed much-needed disease controlling equipment and vaccines. The impact of fewer passenger flights was felt across supply chains as a lot of regular cargo is transported as belly capacity in passenger flights.
Aviation bodies such as the International Air Transport Association and International Civil Aviation Organization have committed to decarbonising the industry by 2050.
There are many ways to tackle aviation emissions.
New aircraft designs to reduce noise and pollution have been developed for decades. In recent years, however, new technologies for decarbonising aircraft have been emerging and accelerating.
Sustainable aviation fuels to electric and hydrogen flight, as well as hybrids, are all being researched, designed, tested and commercialised.
Airlines prefer sustainable fuel currently as it can be used in existing aircraft without alterations. But it is not the only long term solution as questions linger over emissions during its production, challenging supply chains, competition for sustainable produced feedstock and worries about deforestation for cultivating feedstock for sustainable fuels.
Sustainable fuels alone will not decarbonise aviation. Other solutions for a more sustainable way of flying are aircraft powered by electricity and hydrogen.
Electric flying
Electric flying has made significant progress with, for example, Pipistrel certifying the first fully electric aircraft, the Velis Electro in 2020. Drones for cargo, and in the future passenger transport, have been betting on electric propulsion as well. Volocopter, a fully electric powered drone for passenger transport, received approval for a production line in 2023.The main challenge for electric aircraft is range due to the limited capacity of batteries.
Electric aircraft can be a solution for short-haul but will not decarbonise medium to long-haul flights. Other important factors to consider with electric aircraft are the production of renewable energies at scale and upgrades of the distribution grid especially in regional and remote areas.
Lifecycle analyses are also needed to consider emissions for the whole life of an electric aircraft, which includes battery production and battery life to determine how much emissions can be reduced in comparison to traditional flight.
Acknowledging the challenges around the short range of electric flight, numerous start-ups are moving to a hybrid model using hydrogen and electricity. Examples include Dovetail Electric Aviation supported by regional airline Rex, and ZeroAvia supported by big names such as Airbus.
Others are looking at an all-hydrogen solution such as Stralis by retrofitting existing aircraft but also designing a new aircraft that would cater for the medium-haul sector with an estimated entry into service in 2030 with a range of 3,000km. In the passenger drone sector, companies such as AMSL Aero are also moving to a hybrid solution with ranges of up to 1,000km.
Hydrogen
An all-hydrogen solution is promising as a long-term long-haul solution for civil aviation but has its own challenges. One is the increase of the size of fuel tanks due to hydrogen’s properties. This not only changes the aircraft designs but also comes with challenges at airports with limited space. Questions about supply chains and possible negative climate effects of contrails are other obstacles.
It is not only the start-ups that are active in sustainable aviation. Manufacturers such as Airbus and Rolls Royce are also working towards more sustainable solutions. Airbus plans to have the first commercial hydrogen-powered aircraft ready by 2035 and Rolls Royce is actively working with partners such as budget carrier easyJet on hydrogen and hybrid propulsion.
Commercial airlines such as easyJet, Air New Zealand and Rex have all made some headway into the market. Rex is an investor in Dovetail Electric Aviation, easyJet is working with Rolls Royce, and Air New Zealand recently bought its first all-electric aircraft. Meanwhile, Emirates and Qantas have established climate funds.
Some of the main challenges with net zero aviation are the sustainable production of the fuel, understanding the lifecycle of emissions, understanding the effect on the climate of other emissions than Co2 and contrails, the limited ranges of electric powered flights, longer aircraft design due to large size hydrogen fuel tanks, infrastructure and sustainable supply chains of electricity and hydrogen especially to more regional and remote areas, high costs of new technology, and skilling up the workforce to work in these emerging fields.
However, with aviation bodies, manufacturers, airlines and entrepreneurs working together on keeping the world moving, one may hope that flying on significantly reduced emissions will be a reality sooner than later.
Source: UNSW