Long-haul flights currently account for over 50% of all aviation CO2 emissions, in the EU and UK, making up only 10% of flights. And despite game-changing technologies, Eurocontrol warns that long-haul flights are still far from decarbonisation.
1. Priority and challenge
While the aviation industry is considering plenty of technological alternatives to counter their environmental footprint, a recent report by Eurocontrol admits that long-haul flights will remain the greatest source of CO2 from aviation. Currently, the only alternative to kerosene is the uptake of sustainable aviation fuels (SAF) yet a massive scale-up is necessary.
Eurocontrol’s report notes that long-haul flights, operating more than 3,000 km or roughly the distance between London and Istanbul, accounted for 9% of UK and EU departures in 2019 but 54% of aviation CO2 emissions — a figure forecast to account for more than 60% by 2050.
High energy density is essential for aviation, especially for long-haul flights. Fuel makes up a significant portion of the weight in certain transport modes. For example, in the Saturn V (3,000 tonnes) and SpaceX Starship (5,000 tonnes) rockets, fuel accounts for more than 93% of the total weight, compared to around 3% in an average passenger car.
2. ”Long way” from decarbonisation
The study, entitled “The challenge of long-haul flight decarbonization”, considers potential alternatives to traditional jet fuel or SAF, including battery, fuel cell, hydrogen, methane, ammonia and solar energy, and what each would involve in powering an aircraft flight from Paris to Singapore.
“Unfortunately, [we are] a long way from being able to use any of these technologies before several decades for any large-size aeroplane,” concludes the report, noting that it will take “several decades” before any of these technologies could be adapted to power a widebody flying long-distance.
Faced with technical limitations, Eurocontrol said it’s vital to make real progress on existing alternatives, namely by massively increasing SAF supply and usage and moving forward with fleet renewal.
3. Alternative technologies
Electric battery-powered aircraft could work efficiently, Eurocontrol says, but only if there is a revolution in battery efficiencies, requiring them to nearly triple in energy density, every decade for the next three decades, to reach the required 5,000Wh/kg energy density.
Another possibility would be fuel cells or liquid hydrogen powered combustion aircraft. However, for that to happen, a set of huge challenges would need to be met in terms of safety, production, distribution, volume, cryogenic tank and global warming effect. Also, today it’s nearly impossible to find extremely powerful fuel cells and electric engines fit for a long-haul aircraft.
The study also assesses liquid methane as a possible thruster for aircraft take-off but it notes that both together with ammonia (LH3) pose additional loss risks. Finally, a solar-powered widebody is considered as an impossibility whatsoever.
“Advances in solving many of the technological challenges outlined in this paper will happen, but significant progress is not expected to take place for decades at the earliest,” concludes the report.