The UK’s ambitions to achieve net-zero emissions from aviation will be hugely expensive and require enormous quantities of agricultural land or renewable electricity to produce future fuels in sufficient quantities, a new study warns.

In its report – Net zero aviation fuels: resource requirements and environmental impacts – the UK’s Royal Society says “there is no single, clear, sustainable alternative to jet fuel able to support flying on a scale equivalent to present day use”.

Environmental impact of airline emissions

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To meet the UK’s existing aviation demand solely through the production of “energy crops” for biofuel would require almost half of the country’s existing agricultural land, it estimates.

The production of green hydrogen at scale is no less challenging: to meet aviation demand the UK would need to more than double or even triple the electricity it generated in 2020 from renewable sources, it calculates.

Four fuel types are examined in the study – green hydrogen, biofuels (those generated from energy crops and waste), ammonia and synthetic efuels. In addition to the resource challenges, it also explores likely costs, life-cycle impacts, infrastructure requirements and outstanding research questions.

“Research and innovation are vital tools for the delivery of net zero,” says Professor Graham Hutchings FRS, Regius Professor of Chemistry, Cardiff University, and 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 if we are to scale up the required new technologies in a few short decades.”

The UK has committed to ensure that all domestic flights are net-zero by 2040.

To meet the environmental targets, renewable energy generation would need to rise by 2.4-3.4 times over 2020 levels for green hydrogen production, by 2.5-3.9 times for ammonia, and by an extraordinary 5-8 times for synthetic fuels. Biofuel production would require more than 50% of the UK’s agricultural land for the growth of energy crops, the report adds.

In addition, the cost of future clean fuels – including the need for expensive storage methods at airports – is likely to be significantly higher than standard fossil-based jet fuel. The report calculates that hydrogen will come in at £34.4-£41.3 per gigajoule (GJ), ammonia £32-62.1/GJ and efuels £72.7-£94.5/GJ. In comparison, conventional jet fuel is £11-£27/GJ.

It also notes that more research is required into the impact of non-CO2 emissions from jet engines and different fuel types, alongside contrail formation.

Other potential barriers to the adoption of new fuel types include the requirement to develop new airframes or powertrains, refuelling infrastructure, plus safety and certification standards.