ADVANCES IN DROP-IN SUSTAINABLE AVIATION FUELS (SAF): PATHWAYS, CHALLENGES, AND FUTURE DIRECTIONS

Drop-in sustainable aviation fuels (SAFs) are critical for reducing the aviation sector's reliance on fossil fuels while utilizing existing infrastructure. This review paper explores various approaches to producing drop-in SAFs, focusing on their technical pathways, compatibility with current engines, and environmental performance. Key technologies include thermochemical processes like Fischer-Tropsch synthesis, hydroprocessed esters and fatty acids (HEFA), and alcohol-to-jet (ATJ), as well as emerging biological and electrochemical conversion methods. These pathways are assessed based on feedstock flexibility, fuel properties, and the ability to meet aviation fuel standards (ASTM D1655). The paper also evaluates the economic and policy challenges hindering large-scale SAF production, including feedstock availability, production costs, and regulatory incentives. Advances in catalyst design, process optimization, and carbon capture integration are highlighted as essential innovations for scaling SAF production. By examining the potential and limitations of each approach, the review aims to guide future research and policy development in sustainable aviation fuel technologies.