Evaluation of HIGFLY Jet Fuel Properties and Compliance with Specifications

The report Evaluation of Jet Fuel Properties and Compliance with Specifications, conducted by SkyNRG, provides a comprehensive analysis of HIGFLY´s jet fuel produced through novel sustainable aviation fuel (SAF) pathways. The primary aim was to assess the quality of these fuels and their compliance with established American Society for Testing and Materials (ASTM) standards, which are essential for ensuring aviation fuel safety and performance.

The aviation industry depends on stringent fuel quality standards to maintain operational safety and minimise environmental impact. The most widely recognised standards for commercial aviation turbine fuels are ASTM D1655 for conventional jet fuels and ASTM D7566 for SAF. At present, there are eight ASTM-approved SAF production pathways. Any new pathway must undergo a rigorous qualification process under ASTM D4054 to gain approval.

The HIGFLY project, which aimed to develop new technologies for producing SAF from under-utilised five-carbon sugars derived from biorefinery waste streams, used two distinct routes to develop jet fuel precursors: (1) the condensation of furfural with acetone and (2) the self-condensation of cyclopentanone (CPO). As these pathways are not yet approved by ASTM, a thorough evaluation was conducted to establish early-stage confidence in the fuel’s properties and its suitability as a jet fuel.

Methodology and Testing Programme

The research employed a detailed testing programme, designed to maximise insights while considering the limited sample volumes available. Samples were tested using ASTM-prescribed methods and evaluated against relevant ASTM standards. The testing programme was divided into two rounds:

• Preliminary testing, which provided feedback for process optimisation.
• Final testing, which assessed jet fuel quality and determined the potential blending percentage.

Key Findings

Furfural-Acetone Pathway

The evaluation revealed certain performance and compositional characteristics that must be optimised to meet aviation fuel standards. In particular, the fuel’s freezing point exceeded typical specification thresholds, indicating the need for further refinement. Improvements were also recommended to reduce the presence of oxygenated compounds that may impact fuel stability under operational conditions.

CPO Self-Condensation Pathway

This pathway yielded a predominantly cycloparaffinic product with molecular structures contributing to elevated freezing and flash points, as well as higher density values. While these results fall outside current specifications for sustainable aviation fuels, targeted testing and process adjustments were proposed to enhance fuel quality and address the presence of specific impurities.

Conclusions and Future Work

The evaluation indicated that both pathways have the potential to become viable jet fuels, though specific technical challenges must be addressed. Future efforts will focus on demonstrating the complete value chain, producing larger volumes for more extensive testing, and using real feedstocks to introduce additional complexity, thereby refining fuel quality and performance.

This report establishes a solid foundation for further development of HIGFLY’s novel SAF production pathways. By addressing the identified challenges and optimising production processes, these pathways could significantly contribute to the SAF industry, expanding available feedstocks and technology options for sustainable aviation fuel production.