Tomorrow, will planes be flown with used oil or biomass residues? While the performance of batteries limits the use of electrical energy and hydrogen could make its way into planes around 2035, sustainable aviation fuel (SAF) is emerging as a lever. efficient decarbonisation of air transport. Proof of its appeal: Airbus, the German research center DLR, the engine manufacturer Rolls-Royce and the producer of sustainable fuel Neste, announced on Thursday March 18 that they had joined forces to launch the first large-scale study on the subject. What perhaps accelerate a previously confidential use.

For now, the collaboration has already resulted in the launch in mid-March of the first engine tests, including a first flight, carried out at the Toulouse facilities of Airbus. The study will also be conducted on the ground and in flight via an Airbus A350-900 equipped with Rolls-Royce Trent XWB engines, which has started to fly. “These tests will be followed by in-flight emissions tests that will begin in April and resume in the fall, using a DLR Falcon 20-E to perform measurements to study the impact of the use of SAF on emissions.“Says Airbus in a press release. Other ground tests to measure particle emissions are also planned.



Airbus and Rolls Royce take the first steps towards 100 sustainable - Airbus and Rolls-Royce take the first steps towards 100% sustainable fuel flights - L'Usine Nouvelle

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A drop of water in an ocean

For air transport, the issue of large-scale deployment of sustainable fuels could prove to be crucial. The sector represents around 3% of global CO2 emissions and has set itself the goal of reducing its CO2 emissions by two by 2050 compared to those of 2005. These fuels, which can be used by existing aircraft, are the safest means and the easiest way to keep these commitments. France has also established a roadmap in early 2020 targeting 2% incorporation of biofuels in 2025 (160,000 tonnes) and 5% incorporation of biofuels in 2030, or 430,000 tonnes. An initiative coupled with a call for expressions of interest – associating Airbus, Air France, Safran, Suez and Total – aimed at creating an integrated sector.

But for the moment, these fuels are more than discreet in the sky, even though there are seven sectors certified by the ASTM body, most of which provide for an incorporation rate of 50%. In ten years, only some 300,000 flights partially integrating this alternative energy source have been provided. And while a dozen airports distribute them continuously, they only represent around 0.01% of the sector’s total fuel consumption… Their implementation remains sporadic. For its part, Airbus has carried out several test flights with Lufthansa and Air Canada in particular and offers deliveries of aircraft with sustainable fuel from Toulouse, Mobile and Hamburg, with Total and BP as suppliers.

Several shows to follow

First question addressed in the context of this study based on the use of fuel from the HEFA sector (hydroprocessed esters and fatty acids), the most mature from an industrial point of view: what is the impact of sustainable fuels in terms of emissions? It is estimated within the aviation industry that replacing one tonne of conventional kerosene by one tonne of these fuels could reduce CO2 emissions by up to 80% on the basis of the full life cycle of the fuel. Evaluations that the study could make it possible to refine.

1616467514 977 Airbus and Rolls Royce take the first steps towards 100 sustainable - Airbus and Rolls-Royce take the first steps towards 100% sustainable fuel flights - L'Usine Nouvelle

But CO2 is not the only rejection in the crosshairs. “In previous research campaigns, we have already been able to demonstrate the potential for reducing the soot generated by switching from 30% to 50% of alternative fuel blends, and we hope that this new campaign will confirm that this potential is even greater. important“, details in the press release Patrick Le Clercq, within the DLR.”Additional measurements and analyzes for the characterization of particulate emissions during ground testing will be provided by the UK University of Manchester and the National Research Council of Canada“, specify the persons in charge of the project.

Good use of gaskets

Above all, the study launched by Airbus and its associates aims to assess the effect of sustainable fuels on aircraft performance. In other words, ensure that it is possible to exceed the current incorporation rate of 50%, or even reach 100%, paving the way for a greater democratization of their use. Because the behavior of these fuels differs from that of conventional kerosene. “We must ensure the good behavior of these fuels in the aircraft distribution system, in particular related to their lubricity.“, recently explained to L’Usine Nouvelle Steven le Moing, responsible for sustainable fuels at Airbus.

Make sure that sustainable fuels burn the same way as kerosene, explained Nicolas Jeuland, fuel expert at Safran. However, some may have poorer evaporation and cause engine ignition problems. Other questions arise, such as the combustion temperature, for example, which can have an impact on the formation of NOx or the mechanical strength of the combustion chambers. Do they allow good combustion stability to be maintained? Do they have an impact on polluting emissions?“Another point of vigilance: the absence of aromatic rings – a specific arrangement of carbon chains – in these fuels, present in kerosene, tends to reduce the tightness of the joints. Hence the need to develop new ones. elastomers.

Industry advocates the global method

While the new study will undoubtedly provide a better understanding of the use of sustainable aviation fuel, many obstacles still loom on the horizon. First, that of the availability of sources of raw materials, by limiting competition with food needs. “The rise of biofuels will be linked to the sum of local solutions that will succeed in implementing the right resources and the right channels, in each region of the world, in each country.“, for Nicolas Jeuland. In addition, infrastructure will have to be created to transport these fuels, the price of which – between 3 and 10 times higher than kerosene – further limits deployment.

These are all difficulties that push manufacturers to call for support measures, on a European or global scale. Measures which, once put in place, could trigger a virtuous circle of productive investments. “The International Civil Aviation Organization (ICAO) needs to be involved in the democratization of sustainable fuels to avoid fragmentation of recommendations and to avoid market distortions between airlines., according to Steven le Moing. A comprehensive approach is absolutely necessary.“The real take-off of sustainable fuels may take time.

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