The EU Energy Efficiency Directive (EED), currently Directive (EU) 2023/1791 (recast), is a cornerstone of EU energy and climate policy.

It establishes a framework to reduce energy consumption, promote efficiency as a priority (“energy efficiency first”), and support the EU’s 2030 climate targets (at least 55% GHG reduction vs. 1990) and 2050 climate neutrality.

The EU rules on sustainable aviation fuels (SAF) under ReFuelEU Aviation and related directives (e.g., RED III) could contribute to higher costs and energy intensity for fossil-free aviation fuels, while also exerting upward pressure on biomass demand that indirectly risks higher food or agricultural commodity prices.

SAF is crucial for aviation decarbonization (aviation is hard to electrify for long-haul). Current SAF is 3–10x more expensive than fossil jet fuel, and scaling remains challenging. The EU’s mandates are ambitious, but critics note that prescriptive rules can distort markets and raise costs.

There is a recent study from the Chalmers University of Technology in Sweden, published in the journal Fuel (February 2026).

This study by researchers Johanna Beiron, Simon Harvey, and Henrik Thunman analyze production pathways for synthetic methanol (a building block for sustainable aviation fuel, or SAF). It highlights how EU regulations under ReFuelEU Aviation and the RFNBO (Renewable Fuels of Non-Biological Origin) framework can favor less efficient methods.

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Locked in on RFNBOs – Will EU mandates for drop-in synthetic aviation fuels lead to decreased energy- and cost-efficiency?

This February 2026 paper in Fuel (Beiron, Harvey, Thunman) is a rigorous techno-economic assessment using consistent assumptions: same forest residue biomass input, same methanol output (a key SAF intermediate), and renewable hydrogen.

The study notes this conflicts with EU’s own Energy Efficiency Directive, waste hierarchy, and biomass cascade use principles. It risks lock-in because plants are capital-intensive and long-lived (decades), shaping R&D and infrastructure.

Pure DAC PtL avoids biomass issues entirely and aligns perfectly with RFNBO (very low lifecycle emissions). The rules successfully force progress where market forces alone failed. An early RFNBO review is planned; tweaks (e.g., better efficiency weighting or gasification credit) could help without weakening decarbonization.

Yes, in biomass-involved pathways, the mandates risk decreased efficiency and higher costs due to prescriptive carbon accounting that prioritizes “non-biological” labeling over thermodynamics and system optimization. This is a classic regulatory trade-off: clear, enforceable rules for rapid deployment vs. flexibility for least-cost, high-efficiency solutions. Aviation needs massive SAF scale-up regardless—better policy alignment (e.g., technology-neutral efficiency incentives alongside volume mandates) would reduce waste and improve outcomes. The study provides strong evidence for targeted adjustments.

SAF is crucial for aviation decarbonization (aviation is hard to electrify for long-haul). Current SAF is 3–10x more expensive than fossil jet fuel, and scaling remains challenging. The EU’s mandates are ambitious, but critics (including this study) note that prescriptive rules can distort markets and raise costs. Other analyses highlight feedstock limits, high renewable power needs, and potential competitive disadvantages for EU airlines.

Published: Fuel (2026)

Provided:  Chalmers University of Technology

DOI: 10.1016/j.fuel.2025.137181

Authors: Johanna Beiron, Simon Harvey, Henrik Thunman

Abstract

Decarbonization of the transportation sector implies that fossil fuels must be substituted with sustainable alternatives. Current EU policies incentivize large-scale deployment of synthetic aviation fuel production that can be classified as Renewable Fuel of Non-Biological Origin (RFNBO). Synthetic aviation fuel can be produced from methanol and this work presents a techno-economic assessment of three pathways (two combustion-based and one gasification-based) to produce synthetic methanol from biomass residues and renewable hydrogen. The results show that the gasification-based pathway can produce methanol at a lower cost (820 €/t methanol) and higher energy efficiency (46 %, for conversion of biomass, electricity and heat inputs to methanol) compared to combustion-based options (1,050–1,500 €/t methanol and ∼37 % efficiency). The gasifier route requires less renewable hydrogen, resulting in a 30 % lower electricity demand. However, only 55 % of the gasification-based methanol is compliant with the RFNBO definition, since the regulation stipulates that biofuel cannot be counted towards the drop-in quotas. Furthermore, the findings indicate that RFNBO policies that favor production using CO₂ from combustion processes that supply energy to utility systems (e.g., district heating) risk leading to lock-in in inefficient systems, as electrification of heat supply could be a more efficient option. This work identifies such regulatory inconsistencies that increase risk related to investment decisions.