There is no single, clear, sustainable alternative to jet fuel able to support commercial flight, according to a report published today, though some see this as an opportunity for the UK to become the world-leader in net zero aircraft development.
The report suggests there should be a shift in emphasis away from biofuel to novel kinds of aircraft and ways to operate them, according to Prof Guy Gratton, of Cranfield University, co-author.
‘A huge amount of attention is being paid to the potential of biofuels — but these in themselves are not a long-term solution,’ he said, adding there is a window of technological change, shifting to fuels such as green hydrogen, ‘where the UK can be the pioneer.’
‘The report is important in highlighting the importance of understanding the impact of limited resources when developing net zero policy,’ added Prof Rob Miller, Director, Whittle Lab and lead of the Aviation Impact Accelerator global aviation modelling group, which developed a tool to help understand emissions.
‘The report concentrates on the UK, but it shows that we need a better understanding, at a global level, of how different sectors, biodiversity and food requirements will compete for feedstocks. It also shows that a large amount of renewable energy is required for most options. This means that we must focus our research on technologies which can be rapidly scaled after 2035 when the quantity of available renewable electricity increases.’
Through burning kerosene, aviation is a contributor to global heating, including through the emissions of carbon dioxide and the formation of high altitude contrails.
Global aviation carbon dioxide emissions were approximately 1,000 million tonnes per year in 2018/19, representing 2.4% of global emissions, while UK aviation (international and domestic) accounted for 8% of the nation’s greenhouse gas emissions in 2019.
Based on contributions from Royal Society Fellows and 13 UK universities and research institutions, today’s briefing for the public and MPs provides an independent report on decarbonising UK aviation.
The challenge is huge: the report estimates that meeting existing UK aviation demand with energy crops would require around half of UK agricultural land.
Despite increasing investment in ammonia and hydrogen fuels, projected emissions will need to be continually updated as engine data from laboratory, and real-world testing develops.
Though neither produce carbon dioxide, they do however depend on significant renewable electricity: producing ‘green’ hydrogen as a jet fuel would require around 2.4 to 3.4 times the UK’s annual renewable electricity generation in 2020.
Research will also be important to understand the impact of non-CO2 emissions from jet engines, and the formation of contrails, which currently contribute significantly to global heating.
‘Research and innovation are vital tools for the delivery of net zero,’ said Professor Graham Hutchings of Cardiff University, chair of the report working group. ‘But we need to be very clear about the strengths, limitations, and challenges that must be addressed and overcome.’
The UK has committed to scale up manufacturing of sustainable aviation fuels and to make domestic flying net zero by 2040.