The biofuel, made from used cooking oil, could help the aviation industry cut climate-threatening...
Two flying machines partially powered by unblended sustainable aviation fuel, or SAF, performed successful test flights in France this fall.
An Airbus A319neo plane and an Airbus H225 helicopter each fueled one of their two engines with unblended SAF during flights that lasted three and two hours, respectively.
The aviation sector is investigating various kinds of SAFs in hopes of eventually making flying carbon-neutral.
"The same hydrocarbon molecule is present in both SAF and traditional jet fuel. As a result, CO2 emissions of both fuels are not much different. However, the difference between the two fuels is the origin of the carbon," says Massimiliano Materazzi, senior research associate at University College London, who is not involved in the test flight project.
"The carbon in SAF is from biomass. This means the carbon that is emitted is exactly the same that was removed from the atmosphere by the biomass to grow." In other words, the living sources used to produce SAF actually take carbon out of the atmosphere; therefore, burning the material merely represents the return of that same carbon back to the air, making the overall process close to carbon-neutral.
"With the best SAF production pathways, you can have between 80 to 90 percent reduction of CO2 emissions over the fuel's whole life cycle, compared to the traditional aviation fuel," says Nicolas Jeuland, an expert on future fuels and manager at Paris-based aerospace company Safran, which is a part of the test project.
Jeuland says aircraft engines are already certified to use SAF blended with traditional jet fuel at ratios of up to 50 percent, and some airlines currently use SAF at ratios between 10 and 15 percent.
The goal is to measure both on-ground and in-flight SAF emissions, and to study existing engines' compatibility with this type of fuel.
Without sulfur, the emissions are cleaner, and without those aromatic compounds, SAF also emits much less particulate matter than traditional fuel.
Although Jeuland says existing engines should be able to run on unblended SAF without any major modifications, peripheral fuel systems may have to change slightly.