Do RFNBO regulations promote exergetic efficiency in sustainable aviation fuel production? A comparative exergoeconomic analysis

Journal article, 2026

Decarbonizing the aviation sector will require deployment of sustainable aviation fuels (SAF) compatible with existing infrastructure. To accelerate this transition, the EU’s Renewable Energy Directive (RED III) has established increasing SAF drop-in quotas covering aviation biofuels and Renewable Fuels of Non-Biological Origin (RFNBO), with a specific drop-in quota for RFNBO. Although these policies aim to support emission reduction in the sector, they risk incentivizing energy-intensive production pathways at the expense of other pathways with comparable emission reduction. This raises the question of whether current regulatory definitions promote pathways aligned with the Energy Efficiency Directive (EED).
To address this, the study evaluates three SAF production pathways in terms of exergetic efficiency and production costs. Exergoeconomic analysis is combined with a regulatory assessment to compare SAF production pathways under RED III using carbon sourced from combustion (RFNBO-compliant), reforming or gasification processes (aviation biofuel-compliant) to produce methanol as an intermediate for SAF production, for both stand-alone and refinery-integrated configurations.
The results show that the RFNBO-compliant pathway exhibits lower exergetic efficiency (58%) compared to reforming (68%) and gasification (86%), while leading to higher production costs. Reforming and gasification pathways reduce the levelized fuel production cost by 45% and 59%, respectively. Refinery integration reduces the efficiency penalty by 18% and production costs by 30–50% while providing flexibility to meet RFNBO requirements.
This study highlights a misalignment between EU policies (RED III and the EED), as RFNBO aviation fuel compliance requirements are not technology-neutral, favoring pathways with lower exergetic efficiency and higher levelized production costs.