Relation of the Content of Sustainable Components (HEFAs) in Blends with Hydrotreated Straight-Run Kerosene to the Properties of Aviation Fuel

An expected increase in the demand for aviation transport service will result in the deterioration of the environment and human health, respectively, due to extra greenhouse gas (GHG) emissions. Concerns from EU institutions about the issue have led to legislation initiatives and, later, to development of Regulation (EU) 2023/2405 for the reduction of GHG emissions via the substitution of fossil kerosene with an increasing share of sustainable components. Hydroprocessed esters and fatty acids (HEFAs) are the most commercially acceptable sustainable alternative but their influence on aviation fuel properties needs to be further evaluated in terms of all required and extended properties, as per ASTM D1655. The main properties, together with the rarely reported upon existent gum, water separation, corrosion, and the electrical conductivity of HEFAs and their blends with fossil kerosene were quantitatively evaluated in this study. For every increase of 10% (v/v) of HEFAs, the following fuel properties improve: the freezing point decreases by 1.3 °C, the smoke point increases by an average of 3 mm, and the specific net energy increases by 0.08 MJ/kg. The acidity of HEFAs are an order of magnitude higher than that of conventional aviation fuel and, thus, close to the limit. The existent gum of the studied SAF is higher than that of fossil kerosene due to, most probably, the presence of non-evaporated residual material.