One of the challenges currently facing the aviation industry is to reduce its impact on the environment. Immediate solutions include the European Commission, which proposes obliging short-haul airlines to use a minimum amount of environmentally friendly fuel, and the millions of dollars invested by airlines to compensate for the emission of polluting gases. The problem with the current approaches is that they are only a stopgap until the technology arrives that will allow the industry to complete the revolution towards sustainability.
There are several sustainable aviation proposals under development that are expected to be operational over the next decade. Among the proposals already under development are biofuel, hydrogen and the electric motor.
Biofuel is a sustainable aviation fuel (SAF) obtained from biomass or waste. There are two types of this fuel: first-generation, which is obtained from vegetable oils, and advanced, which is obtained from agri-food and forestry waste or the organic fraction of urban waste. First generation biofuels reduce CO₂ emissions by 60% and advanced biofuels can exceed 85%.
The main advantage of biofuels is that they considerably reduce the environmental impact of air travel without having to make structural changes in either airplanes or airports, since practically the same technology currently in use could be used.
The main disadvantage is that, at present, there is little production, and this translates into higher prices for airlines. For their production, in the case of first-generation fuels, production in developing countries also comes into play, where jungle is deforested to grow crops for biofuel production.
Ecological fuels are a promising option if they can be produced in an eco-friendly way, which is why the European Union demands that the production of biofuel used in its airspace be sustainable, and therefore biofuels cannot come from crops where there was previously a natural area, whether a forest, a jungle or a wetland.
The hydrogen-powered aircraft is one of the strongest bets of companies such as EasyJet, which has an agreement with Airbus and hopes, by 2035, to be able to manufacture the first passenger aircraft with zero polluting emissions.
The main advantage of the liquid hydrogen engine (in cryogenic state) is that it has a density three times lower than kerosene per unit volume and stores three and a half times more energy than kerosene, which gives it much more power than the traditional kerosene engine.
The main disadvantage is that the hydrogen tanks are huge cylinders, which differs from the traditional method of storing fuel in aircraft, so their location in the aircraft must be changed, and this change conditions the design and aerodynamics.
In addition to changing the structure of the aircraft, Airbus also warned that, if the hydrogen engine is to be functional, airports would have to invest in changing the refueling infrastructure.
Although the challenge is enormous, the hydrogen-powered aircraft is one of the strongest and most hopeful proposals, which is why Airbus has already presented the concept of the three zero-emission airplanes that it wants to produce.
Finally, the alternative that the automotive industry has been betting on: the electric motor. In the aeronautical sector, Wright Electric has already presented its electric motor with power of up to two megawatts, but although the prototype is ready, it still has to go through several development phases before it can fly.
The main advantage of the electric motor, apart from being sustainable, is that it is a reality. In addition to the Wright Electric engine, Rolls Royce has also presented a functional engine for ultralight aircraft models.
The main disadvantage is that the power density must be solved. Current electric-powered aircraft have between 3 and 4 kW per kilogram of weight, but a conventional airliner needs a power density of more than 12 kW per kilogram. The current problem with power is that to cover long distances, this peak power is needed continuously to reach the destination with guarantees.
The electric motor is at the most advanced stage, however, it still faces challenges and technological advances to become the future of sustainable aviation.
The aeronautical industry in general, and the air transport sector, is particularly challenged in the development of new technologies that increase efficiency and ensure a lower impact on the environment. It is no coincidence that the sector’s activity takes place almost entirely in the atmosphere, which is one of the main players in the process of climate change we are experiencing.
Initiatives such as Clean Sky, a joint venture between the European Commission and the European aeronautics industry to finance and develop research and development activities to accelerate the progress of aeronautics towards sustainability, are a good example of these concerns that will undoubtedly lead to great advances in the short and medium term, not only in aircraft but also in airport infrastructures and services, making them more sustainable. Barely a hundred years separated the Wright brothers’ tiny aircraft from the colossal Airbus A380, so let’s get ready for the formidable advances to come!