Sustainable Aviation Fuel (SAF) is a lower-carbon alternative to traditional jet fuel, made by blending conventional fuel with up to 50% Synthetic Blending Component (SBC) derived from renewable feedstocks like waste oils and biomass. SAF is produced through 8 approved pathways, or annexes, under ASTM D7566. Common pathways include HEFA (Hydroprocessed Esters and Fatty Acids) and Fischer-Tropsch (FT), which produce Synthetic Paraffinic Kerosene (SPK), and Alcohol-to-Jet (ATJ), which produces SPK-A from alcohols like ethanol. These fuels meet ASTM D7566 standards, ensuring both performance and sustainability while significantly reducing aviation’s greenhouse gas emissions. SAF can reduce lifecycle carbon emissions by up to 80% compared to conventional jet fuel, depending on factors such as the type of renewable feedstock, the production process, and the efficiency of the supply chain to the airport.
WHY IS TESTING IMPORTANT?
SAF laboratory testing ensures that critical fuel properties, such as energy density, thermal stability, and freezing point, meet ASTM D7566 standards. With lower aromatic content reducing seal swelling, thorough testing is essential to confirm that SAF performs reliably in existing aircraft engines. Additionally, testing safeguards key factors like thermal stability (to prevent fuel breakdown at high temperatures) and freezing point (to ensure SAF remains fluid at high altitudes), guaranteeing both safety and optimal engine performance.
WHAT TESTING IS REQUIRED AND WHEN?
Each of the 8 approved production pathways (or ‘Annexes’) for SAF under ASTM D7566 includes strict testing protocols including unique requirements for each production pathway. Table 1 of each annex specifies the key technical requirements for the Synthetic Blending Component (SBC), including testing for critical properties such as aromatics content, freezing point, viscosity, density, and flash point. These tests must be conducted before blending to ensure the SBC meets performance and safety standards.
Table 2 of each annex outlines the Management of Change (MoC) testing, which are required only when significant changes occur in the production process, such as alterations in feedstock or technology. Testing at both stages ensures that the final blended fuel complies with ASTM D1655, the standard for conventional jet fuel, safeguarding performance, safety, and sustainability.
Table 1 Required Testing is required whenever a batch of SAF is produced and blended with conventional jet fuel. The testing must be completed before the fuel can be certified as meeting the specifications for use in aviation. At that point, the fuel is no longer treated as “synthetic” or “blended” under ASTM D7566, but as conventional ASTM D1655 Jet A or Jet A-1, meaning it can be handled, stored, and used just like any other certified conventional jet fuel.
WHY PARTNER WITH AMSPEC?
AmSpec is a trusted global leader in fuel testing, inspection, and certification, with a robust network of locations that deliver fast, reliable service wherever our clients operate. Our expertise and strategic presence position us at the forefront of the renewable fuels sector. We empower our clients to navigate the complexities of ASTM D7566 standards, ensuring compliance and operational success.
In addition, we offer consulting services for ASTM D4054, helping streamline the approval process for new Sustainable Blending Component (SBC) technologies. From technical guidance to advocacy, we are committed to driving innovation and supporting our clients every step of the way.
What Components Make Up ASTM D7566 Testing
- Table AX.1 Tests are routine and required for all SBC batches before blending.
- Table AX.2 Tests are triggered only by significant changes in feedstocks, processes, or equipment to ensure continued compliance.
- Table 1 Required Testing is performed after the synthetic blending component (SBC) is blended with Jet A or Jet A-1 fuel to confirm that the final blended product meets ASTM D7566 standards, ensuring it can be reclassified as ASTM D1655 jet fuel for safe use in aviation.
Table 1 Required Testing
- Physical Properties
- Density
- What It Tests: Measures the mass of fuel per unit volume.
- Why It’s Important: Ensures accurate fuel load and burn rate calculations, critical for range and safety.
- Distillation
- What It Tests: Determines the boiling range of the fuel.
- Why It’s Important: Confirms proper vaporization at altitude, ensuring safe combustion and consistent fuel performance.
- Viscosity
- What It Tests: Evaluates the fuel’s resistance to flow.
- Why It’s Important: Ensures smooth fuel flow, particularly in cold temperatures, which is crucial for engine reliability.
- Appearance
- What It Tests: Examines the fuel’s clarity and cleanliness.
- Why It’s Important: Ensures there are no visible contaminants, which could block fuel filters or injectors.
- Density
- Safety Standards
- Electrical Conductivity
- What It Tests: Measures the fuel’s ability to dissipate static electricity.
- Importance: Prevents static buildup and discharge, lowering ignition risks, especially during refueling operations.
- Flash Point
- What It Tests: Identifies the lowest temperature at which fuel vapors ignite.
- Why It’s Important: Determines the temperature at which fuel can ignite, vital for fire safety during storage and handling.
- Freezing Point
- What It Tests: Determines the temperature at which fuel begins to crystallize.
- Why It’s Important: Prevents fuel line blockages and ensures reliable engine performance in cold-weather or high-altitude conditions.
- Existent Gum
- What It Tests: Measures residue buildup after fuel evaporation.
- Why It’s Important: Ensures clean combustion and reduces deposits in fuel injectors and engine components.
- Electrical Conductivity
- Performance Metrics
- Net Heat of Combustion
- What It Tests: Measures the energy released during fuel combustion.
- Why It’s Important: Measures energy output, ensuring the SAF blend provides enough power for efficient flight range.
- Thermal Stability (JFTOT)
- What It Tests: Evaluates the fuel’s resistance to thermal degradation at high temperatures.
- Why It’s Important: Prevents the formation of deposits in fuel injectors, ensuring consistent fuel flow and reducing risks of engine malfunctions or shutdowns.
- Smoke Point
- What It Tests: Measures the height of the flame during combustion.
- Why It’s Important: Confirms clean burning of the fuel, minimizing soot emissions and ensuring compliance with air quality standards.
- Net Heat of Combustion
- Chemical Composition
- Aromatic Content
- What It Tests: Determines the concentration of aromatic hydrocarbons in the fuel.
- Why It’s Important: Maintains lubrication for seals in aircraft fuel systems; insufficient aromatics may lead to leaks, impacting safety and reliability.
- Sulfur/Mercaptan Sulfur Content
- What It Tests: Measures the amount of sulfur present in the fuel.
- Why It’s Important: Low total sulfur reduces engine corrosion, protects critical components, and minimizes harmful emissions, improving environmental compliance.
- Naphthalenes
- What It Tests: Measures the concentration of naphthalene compounds, which are aromatic hydrocarbons with two fused benzene rings.
- Why It’s Important: High naphthalene levels can lead to soot formation, carbon deposits in engines, and reduced combustion efficiency, impacting engine performance, maintenance, and safety.
- Aromatic Content
- Durability and System Integrity
- Copper Strip Corrosion
- What It Tests: Assesses the fuel’s reactivity with metal components.
- Why It’s Important: Prevents corrosion in critical fuel system parts, reducing the risk of component failure during flight.
- Water Separation Index
- What It Tests: Measures how effectively the fuel separates from water.
- Why It’s Important: Prevents water contamination, which can freeze at high altitudes, clogging fuel lines and risking engine failure.
- Copper Strip Corrosion