The quest for a guilt-free flight may have been called off by a wide-ranging study that concluded “there is no clear or single net-zero alternative to jet fuel.”
According to the Royal Society Academy of Sciences review, the four most viable alternatives “provide some carbon reductions, but are not ideal”.
For example, replacing jet fuel with biomass would require half the UK’s farmland to sustain current passenger traffic.
But the government plans to soar that level by 70 per cent, or 200 million more passengers, by 2050.
The switch to sustainable fuels is key to its “Jet Zero” strategy to turn aviation green, touted as a plan to deliver “guilt-free flight”.
Flying is responsible for 8% of UK emissions and around 2.4% globally, and also releases other forms of pollution.
As the world works towards net-zero emissions by 2050, a lack of alternatives makes carbon-intensive industries among the hardest to decarbonise.
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“The requirements for an alternative jet fuel, kerosene, are energy density, must be sufficient to sustain short- and long-haul flights, must be mass-produced globally, must be cost-competitive, and must be implemented by 2050” report Working Group Chair Graham Professor Hutchins said.
Other options, such as hydrogen, ammonia and synthetic fuels, require massive increases in renewable energy production, are either expensive, or require major modifications to existing aircraft.
Producing enough green hydrogen – which is produced by splitting water molecules into oxygen and hydrogen using renewable electricity – would require more than doubling or tripling the UK’s renewable energy capacity.
Fuel from biomass could be used in the same aircraft engine, but there are concerns about its sustainability.
Suitable crops could be rapeseed, fast-growing poplar and miscanthus, the Royal Society said.
But because of how much land it takes to grow them, there’s growing interest in using biological waste like used cooking oil.
The UK is “highly dependent” on imports of biofuel raw materials, or feedstocks, importing 423 million liters of used cooking oil from China in 2021 alone.
Converting waste from the 250 million liters of vegetable oil produced in the UK would produce only 0.3% to 0.6% of the UK’s annual jet fuel needs.
The government hopes to have five ‘Sustainable Aviation Fuel’ (SAF) plants under construction by 2025.
A Department of Transport spokesman said its SAF program was “one of the most comprehensive in the world”.
“Our Jet Zero strategy sets out how we can achieve net zero emissions from the UK aviation industry by 2050 without directly constraining aviation demand.
“Sustainable aviation fuel and hydrogen are key elements of this and we will ensure there is no impact on food crops.”
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The Royal Society report did not consider battery-powered aircraft because they are “unlikely to be developed to provide the energy density required for most commercial flights within the timeframe available to reach net-zero emissions by 2050”.
A spokesman for British Airways, the industry’s trade body, said there was “no silver bullet”.
“However, it can be achieved by modernizing the airspace to improve flight efficiency, by introducing new zero-emissions technologies such as hydrogen aircraft, and by expanding the use of sustainable aviation fuels within this decade.”
The “elephant in the room” is “the need to reduce flying,” said Kate Hewitt, policy director at the campaign group Aviation Environment Federation.
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