EU rules designed to accelerate the use of sustainable aviation fuels may unintentionally favour production pathways that are more energy-intensive and expensive than necessary, according to new research from Chalmers University of Technology in Sweden.
The study examined different methods for producing synthetic methanol — a fuel molecule that can be converted into sustainable aviation fuel — and found significant differences in electricity demand, resource efficiency and production cost between alternative production pathways using the same raw materials.
Researchers said the findings raise broader questions about how EU regulation is shaping investment and technology development in the emerging sustainable aviation fuel sector.
Last year, the EU introduced rules requiring a minimum 2% blend of sustainable aviation fuel at EU airports, with the requirement due to rise progressively to at least 70% by 2050.
Under the legislation, half of the sustainable aviation fuel used by 2050 must come from a category known as RFNBOs — Renewable Fuels of Non-Biological Origin — synthetic fuels produced using renewable hydrogen and captured carbon dioxide.
But the Chalmers researchers argue that the current RFNBO framework risks incentivising less resource-efficient production methods.
“Regulations influence not only industry’s investments in technology, but also which research and development priorities are pursued,” said Henrik Thunman, Professor of Energy Technology at Chalmers and co-author of the study.
“Instead of driving innovation towards the most efficient solutions, we risk locking ourselves into less resource-efficient production methods.”
The researchers compared three technically feasible production pathways for synthetic methanol using biogenic carbon from biomass.
Two of the pathways rely on biomass combustion, where carbon dioxide is captured from flue gases and combined with hydrogen produced separately using electricity. The third pathway uses biomass gasification, in which heated biomass is converted directly into synthesis gas containing both carbon and hydrogen.
According to the researchers, the gasification approach proved substantially more efficient.
“The gasification pathway proved to be the most resource-efficient option in our analysis, with up to 46 percent lower production cost and 30 percent lower electricity demand than the two combustion-based alternatives,” said Johanna Beiron, researcher in Physical Resource Theory at Chalmers and first author of the study.
“The difference shows how large the energy losses can be when biomass is first combusted into carbon dioxide, which is then rebuilt into fuel molecules using large amounts of electricity and hydrogen.”
Despite this, the study argues that EU regulation strongly favours the combustion-based pathways.
Under the current RFNBO framework, fuels produced through combustion-based systems qualify fully under the regulations, while fuels produced via gasification may only partially qualify because the process uses biomass-derived carbon and energy more directly.
The researchers said this creates a policy contradiction, since one objective of the RFNBO framework is to reduce reliance on biomass as a limited resource while increasing renewable electricity production for green hydrogen.
According to the study, the current rules could instead increase demand for biomass-derived carbon dioxide from combustion processes, even where direct gasification would use biomass more efficiently.
“One of the combustion-based alternatives we analysed was the process in combined heat and power plants,” said Beiron.
“It has lower cost and energy efficiency than gasification, even when we include the additional electricity needed to replace, for example, the district heating that the combustion process can contribute.”
The researchers warned that the regulatory framework may ultimately work against broader EU goals around energy efficiency and industrial competitiveness.
“The regulatory framework does not account sufficiently for how efficiently different systems use energy and resources,” said Thunman.
“The study therefore highlights a structural issue in EU energy and industrial policy: regulation risks working against its own objectives when definitions of sustainable fuels are not aligned with fundamental energy principles or with the Union’s broader ambitions for resource efficiency.”
The researchers said the findings highlight the need for greater coordination between climate policy, industrial feasibility and resource efficiency as Europe expands sustainable aviation fuel production capacity over the coming decades.
“It is surprising that EU rules do not provide clearer incentives for the most efficient alternatives,” said Beiron.
“The current regulatory framework risks causing lock-in to combustion-based energy systems, even though technically mature processes already exist that would provide both lower energy use and lower cost – such as gasification and electrification of district heating.”
Thunman added: “Our study shows that some parts of the regulatory framework probably need to be adjusted if the EU is to achieve its long-term goals.”
“Better coordination is needed between climate targets, resource efficiency and industrial feasibility in order to address the uncertainty that currently exists. This uncertainty makes it difficult to make rational investment decisions for the large-scale expansion of sustainable aviation fuels in the coming years.”