EU sustainable aviation fuel rules may hinder energy-efficient investments, research suggests

European Union rules meant to speed up the use of sustainable aviation fuel could end up steering investment towards production routes that waste more energy and cost more than necessary, according to research from Chalmers University of Technology.

The Swedish study examined several ways of making synthetic methanol, a key intermediate that can be turned into aviation fuel, and found wide gaps in electricity use, resource efficiency and production cost even when the same raw materials were used. In one comparison, the most efficient route delivered up to 46% lower production costs and 30% less electricity demand than the combustion-based alternatives.

That matters because the EU’s aviation fuel mandate is tightening quickly. Airlines operating from EU airports must now use at least 2% sustainable aviation fuel, with the requirement set to rise steadily to 70% by 2050. Under the same framework, half of the fuel used by mid-century must come from Renewable Fuels of Non-Biological Origin, or RFNBOs, a category covering synthetic fuels made with renewable hydrogen and captured carbon dioxide.

The Chalmers researchers argue that the present definition may not reward the most resource-efficient technologies. Their analysis compared three technically viable routes for producing methanol from biogenic carbon in biomass. Two depended on biomass combustion, where carbon dioxide is captured from exhaust gases and then combined with separately produced hydrogen. The third used biomass gasification, in which biomass is converted directly into synthesis gas containing both carbon and hydrogen.

According to the study, the gasification route came out ahead on both cost and energy use. Johanna Beiron, the paper’s first author, said the difference showed how much energy can be lost when biomass is first burned into carbon dioxide and then rebuilt into fuel using large volumes of electricity and hydrogen.

The researchers also warned that the current RFNBO rules may be creating a contradiction inside EU policy. On one hand, the bloc wants to reduce pressure on limited biomass supplies and expand renewable electricity for green hydrogen. On the other, the framework can favour combustion-based systems that rely more heavily on biomass-derived carbon dioxide, even where direct gasification would use the same feedstock more efficiently.

Henrik Thunman, a professor of energy technology at Chalmers and co-author of the study, said regulation affects not just industrial investment but also the direction of research and development. In his view, poorly designed rules risk locking the sector into less efficient production methods.

The paper also noted that one combustion-based option, using combined heat and power plants, remained less efficient and more expensive than gasification even after accounting for the electricity needed to replace district heating that such plants can supply.

For Europe’s emerging sustainable aviation fuel industry, the findings add to a growing debate over whether policy design is encouraging the right technologies, or merely the ones easiest to classify. The researchers say more careful alignment is needed between climate targets, industrial practicality and resource efficiency if the EU is to build large-scale SAF capacity without embedding unnecessary costs into the system.

Beiron said it was striking that the rules did not more clearly reward the most efficient options. Thunman added that some parts of the regulatory framework may need adjustment if the EU wants to meet its long-term goals without undermining its own ambitions for energy efficiency and industrial competitiveness.