The trend of “flygskam“, or flight shame, is spreading around the world. In recent years, air travel has not received good press because of its impact on climate change. Indeed, air travel accounts for about 2% of global carbon dioxide (CO2) emissions, according to the International Civil Aviation Organization. Today a plane takes off every second in the world, and the number of aircraft is expected to double and air traffic to triple by 2050. The aviation sector therefore plays a key role in the global economy. A world without planes is unimaginable, so the solution is to make air travel greener.

The aviation industry has committed to halving its CO2 emissions by 2050. What are the innovations that can help the industry fulfil its promises?

Designing greener aircraft

The first solution would be to design planes that use less fuel and emit less greenhouse gases. 3D simulation software can help improve the design of new aircraft. Aircraft manufacturers can test completely new shapes and simulate their impact on the environment.

Delft University and KLM are collaborating on the Flying V project. This partnership has resulted in a futuristic aircraft in the shape of a flying V-wing. Passengers, luggage, and fuel would all be in this large wing. The first successful flight of a 22.5 kg, 3 m wide model powered by an electric motor took place in 2020. The aircraft could potentially consume 20% less fuel. This saving is made possible by its more aerodynamic shape, but also by its reduced weight.

Indeed, manufacturers are increasingly seeking to reduce the weight of aircraft using innovative composite materials. These materials are very light, very strong and not sensitive to corrosion. Carbon fibre, one of the most well-known materials, is as strong as steel but six times lighter. Thanks to these innovative materials, some parts can even be produced using additive manufacturing. Anisoprint, a startup rated by Early Metrics, develops continuous fibre 3D printing systems and materials. The startup can thus produce composite structures that are lighter and less expensive than their metal counterparts, but just as strong.

Drawing inspiration from nature

Other manufacturers are using biomimicry. They take inspiration from the shape of some birds in flight to improve the aerodynamic performance of planes. In 2019, Airbus presented a concept aircraft inspired by a bird of prey. The Bird of Prey was envisioned as a hybrid aircraft, combining electric power and conventional propulsion to fly. These are only concepts today, but these planes could become a reality in the coming years.

Manufacturers can also design environmentally friendly aircraft that are more suitable for short distances. Vertical take-off and landing aircraft are beginning to emerge for intercity travel. Ascendance, a French startup rated by Early Metrics, is developing a plane with hybrid propulsion (kerosene and electric) that takes off and lands vertically thanks to propellers integrated into its wings. This aircraft has a range of 150 km. However, the prototype will not be commercialised before 2025.

Powering aircraft with alternative fuels

Fuel consumption is a key issue in making air travel greener. The green plane of the future will need to use less fossil fuel and more alternative sources of energy. Sustainable aviation fuels (SAF) can be made from:

• vegetable or cooking oils,
• animal fats,
• sugars and starches,
• certain algae
• lignocellulose from wood waste
• and some inedible plants.

Their use could reduce air travel emissions by 70% to 90%. Most airlines are already certified to fly with a 50% SAF blend. However, SAFs accounted for less than 0.1% of the 360 billion litres of fuel used by aviation in 2019.

To encourage the use of SAFs, some countries are introducing specific regulations. In France, kerosene distributors will be required to incorporate 1% of alternative fuels from 2022, then 2% in 2025 and 5% in 2030. For the Air France-KLM group, 1% of SAF mixed with fossil fuel would reduce emissions by around 30,000 tonnes of CO2 per year. This equals to 550 carbon-free flights from Paris to New York.

However, one major obstacle to the general use of alternative fuels is their price. On average, they are four to five times more expensive than conventional kerosene. In addition, they are not available at all airports. The production of alternative fuels needs to be increased to meet the targets set.

The future of fuel

Other niche fuels are beginning to be developed, including an “e-kerosene” produced from hydrogen by capturing CO2 from the atmosphere. This fuel would be almost carbon-neutral. Its production is not limited to the quantity of waste available. However, it is ten times more expensive than traditional kerosene.

Synhelion, a spin-off from the Swiss Federal Institute of Technology in Zurich, is developing a solar fuel. Synhelion uses solar heat to break down CO2 and water molecules injected into a reactor to reconstruct a synthetic fuel. When burned in an aircraft engine, for example, this fuel will emit only the CO2 captured from the air during its production. This 100% renewable fuel is expected to be commercialised in 2030.

Tapping into renewable energy sources

Renewable energies have gained in popularity over the past few years and are now being used in aviation. Wright Electric is working on an electric engine, called Wright 1, with a power of 1.5 Megawatt. The first flight tests of this engine are planned for 2023. The goal is to achieve a 100% electric aircraft by 2030, on flights of one hour or less.

For its part, Dassault took part in the Solar Impulse project. In 2015-2016, an aircraft flew around the world for the first time without fuel or polluting emissions during the flight.

Among these renewable energies, many hopes have been placed in hydrogen. On June 9, 2020, the French Minister of the Economy, Bruno Le Maire, unveiled his plan to support the French aeronautics industry. This plan includes a 15-billion-euro package with the aim of developing a 100% green airliner by 2035. Hydrogen could be used as a fuel, in modified engines or via a fuel cell that produces electricity by reacting with oxygen in the air. However, for a plane to be 100% green, green hydrogen should be used. However, this remains very expensive. Moreover, hydrogen is bulkier than kerosene for the same power. It would therefore be necessary to modify the storage space in the aircraft.

Optimising flight routes

Finally, in addition to designing sustainable aircraft, it seems essential to optimise air traffic. New meteorological tools offer very accurate real-time weather monitoring and allow the pilot to adapt the trajectory as early as possible. For example, the German startup WxFusion anticipates lightning strikes with great accuracy.

These tools can also help avoid areas with high concentrations of contrails. Contrails form at high altitudes after jet engines if the surrounding air is sufficiently cold and moist. They can be problematic because they absorb some of the radiation from the Earth and re-emit it to the ground.

For its part, Safety Line offers software solutions to reduce fuel consumption. OptiClimb optimises fuel consumption during the climbing phase, while OptiDirect provides pilots with shortcuts during the flight. Transavia estimates that it saves 85 kg of fuel per climb thanks to this tool.

Thales has developed a complete flight management system called PureFlyt. PureFlyt acts as a co-pilot and helps the pilot optimise flight routes. It continuously calculates the best trajectory at arrival. The goal is to stay as long as possible at altitude, where the engines consume the least amount of fuel, and then to glide down with the engines at idle.

Working together to make air travel greener

As the consequences of climate change become increasingly visible, creating green aircraft has become an emergency. Technologies can help achieve this by reducing carbon emissions throughout the value chain, from aircraft design to flight. Once again, price is a major barrier to these innovations. Public authorities must therefore become more involved and encourage collaborations between innovative startups and corporates in the aeronautics sector.