Effect of Low Temperatures on Blends of Jet A-1 Aviation Kerosene and FAME Biofuel—Case Study

Growing pressure to decarbonize aviation has accelerated the search for alternative fuels to replace conventional Jet A-1 kerosene, with renewable biofuels attracting significant interest. While early demonstrations of kerosene–biofuel blends have been successful, they also introduce new operational challenges. This study examines the influence of low temperatures on blends of Jet A-1 and FAME (fatty acid methyl ester), focusing on clear point, cloud point, and density—parameters critical for maintaining reliable fuel flow in cold environments. The measurements demonstrate a consistent trend in which greater FAME fractions raise the clear point from 0.5 °C (0% FAME) to 5.8 °C (40% FAME) and the cloud point from −29.3 °C to −23.4 °C over the same range. Mixture density also increases with higher FAME content, from 810 kg·m−3 for pure Jet A-1 to 883 kg·m−3 for 100% FAME. Additionally, density rises as temperature decreases, with an increase of 6–16 kg·m−3 when the temperature drops from 8 °C to −8 °C. These shifts may impair stable fuel delivery to aircraft engine combustion chambers at low temperatures. The findings confirm that higher FAME content elevates clear and cloud point temperatures and increases density, indicating that such blends may be unsuitable for aviation use in polar and subpolar regions.