The air travel sector is responsible for the emission of greenhouse gases, yet numerous projects are currently underway to reduce the environmental impact
Currently, air travel already contributes about one billion tonnes of carbon dioxide equivalent per year, corresponding to just under two per cent of total global emissions.
This impact is set to grow if the sector does not act promptly to meet the UN climate change targets, especially considering that the number of aircraft in circulation is expected to increase to one million by 2050 from the current 600,000.
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The exponential growth of the global aviation fleet
Boeing, the renowned aircraft manufacturer, predicts that the global aviation fleet will have to reach 47,000 by 2040, up from around 26,000 in 2019, to meet the growing demand in the sector.
Confirming this trend, Ryanair, the well-known low-cost airline, has projected ahead by ordering no less than three hundred new models from the American company.
The challenge of making air transport more sustainable
In order to align the air transport sector with the ecological transition, it is necessary to make flying a more sustainable activity.
However, it faces the problem of a lack of clean, successful and readily available technology, similar to electric propulsion for cars.
Electric planes are considered remote solutions by some and unfeasible by others. Due to the limited weight and performance of batteries, especially for long-haul flights.
Hydrogen, a fuel that does not emit CO2 during combustion, is a possibility, but complicated to handle. The remaining options to address emissions directly are efficiency and Sustainable Aviation Fuels (SAF).
Decarbonising the industry with Sustainable Aviation Fuels (SAF)
Sustainable Aviation Fuels (SAF) currently seem to be the best solution for decarbonising air travel. These sustainable fuels are derived from used animal fats and vegetable oils. Since their chemical composition is almost similar to traditional aviation fuels, they can be used in the same existing engines. And refuelling systems without conversion.
SAFs are not carbon-free, but are carbon-neutral. This means that although they emit about 80 per cent less CO2 than paraffin, their combustion still releases CO2. However, when considering the entire life cycle of SAFs, their impact is carbon-neutral as they absorb the same amount of carbon dioxide that was previously absorbed by organic materials that have become waste.
Thus, SAFs offer an immediate solution for reducing emissions in the aviation sector by utilising recycled organic materials.
Hydrogen aircraft: the zero-emission challenge in the future of aviation
By mid-century it is possible that hydrogen aircraft, truly zero-emission solutions, will be ready. Airbus, Europe’s leading aircraft manufacturer, had set 2035 as the release date for its first hydrogen-powered aircraft. Only to go back on its word. Twelve years is too little time. It is not just the technology that is lacking, but the whole context.
Green hydrogen is a key element that is currently lacking, both in terms of abundance and price competitiveness. In addition, airports lack the necessary infrastructure to transport, store and refuel a fuel that is very different from paraffin.
It is important to consider that liquid hydrogen requires storage at extremely low temperatures, as low as -253 degrees Celsius, approaching absolute zero. The planes themselves will have to undergo modifications with much larger cooling systems and tanks, as hydrogen has a lower energy density than paraffin and therefore takes up more space. The allocation of space for fuel means a reduction in passenger space, which is not insignificant.
Electric planes: powerful and light batteries on the way
Third and last option at the moment are electric planes. Which are more complicated to realise because the batteries available now do not contain the same amount of energy per kilo as fossil fuel. And do not allow as many kilometres to be covered. They are too heavy and too underpowered. Which is why the batteries will perhaps power short flights, but not long ones.
In mid-April, however, the Chinese giant Catl announced a battery so powerful that it could, in theory, power an aircraft. It has an energy density of 500 watt-hours per kilo. This is almost twice as much as the latest model developed by the company.
All we know about Catl’s super-battery is that it is a ‘condensed state’ technology and that production (with the idea of using it in electric cars, at least for now) will start this year. It is difficult to speak of a breakthrough until more details are public.
Read also: Swiss hydrogen-powered hypersonic jet will reduce flights from Europe to Australia to 4 hours
