The report looked at all sources of sustainable fuels, including biomass fuels using rapeseed, elephant grass and poplar. 

It said: “In all three example feedstocks, the amount of land needed to replace all the UK’s aviation fuel is over 50% of that available in the UK for agriculture.” The report estimated growing rapeseed to produce the amount of fuel needed would take 68% of all UK agricultural land.

The report, ’Net Zero aviation fuels, resource requirements and environmental impacts’, highlights obstacles to “jet zero” flying, which airlines are aiming for by 2050. It concluded: “Overall, the results of this analysis are uncertain and there is no clear or single net zero alternative to jet fuel.” 

The scientists also examined waste cooking oil as an alternative to kerosene. The report said 250 million litres of used oil was produced in the UK annually, with some recycled for industrial use. It added: “If 100 – 200 million litres of used cooking oil were diverted to jet fuel production, a conservative estimate of 50% conversion efficiency would produce 50 to 100 million litres of jet fuel, which is only 0.3 to 0.6% of the total amount of jet fuel used every year in the UK.”

 
The report estimates kerosene’s cost at £11-£27 per gigajoule, compared to the current £72-£94 for fuel made from direct air capture or another sustainable source.

Professor Graham Hutchings, chair of the working group that produced the report, said aviation was now growing again after the pandemic and a solution needed to be found.

The group looked at alternatives including hydrogen, ammonia, synthetic fuels and biofuels. It examined the resources and costs needed to make each and whether they could be used in existing aircraft and engines. Battery power was not considered as it was “unlikely” to have developed sufficiently in time for commercial flights by 2050.

“The conclusion we’ve come to considering these four alternative fuels is that there’s no clear winner,” Hutchings said.

The report also underlined the urgent need for the UK to play a role in finding alternatives. It said: “In 2019 the UK aviation sector consumed 12.3 million tonnes of jet fuel, a 1% increase on the previous year. 

“When viewed on an international scale, it can be seen that the UK was the second largest consumer of jet fuel during 2019, exceeded only by the USA which had 811 million passengers travelling by domestic flights.”

The report highlighted Heathrow as the largest global user of ‘sustainable’ biofuels but added this accounted “for just 0.5% of the airport’s fuel provision”. 

It concluded: “Despite best endeavours at developing and rolling out alternative fuels, a scenario may arise where the reliance is predominantly on hydrocarbon fuels if the alternatives can’t be manufactured and safely deployed at the scale needed.”