With sustainability high on the agenda this week at EBACE, Rolls-Royce (Booth X98) is eager to promote its achievements in bringing greener fuel to its family of business jet engines.
In December, Rolls-Royce and Gulfstream made history by flying the first ultra-long-range business jet with a 100 percent sustainable aviation fuel (SAF) blend. The Rolls-Royce BR725-powered G650 made a 2.5-hour flight from Gulfstream’s Savannah, Georgia headquarters using sustainable fuels from both World Energy in Paramount, California, and Virent in Wisconsin. SAF is currently approved up to a 50 percent blend with jet-A.
The World Energy fuel was derived from waste fats and plant oils using the hydro-processed esters and fatty acids (HEFA) process; the fuel from Virent was synthesized from plant-based sugars using the synthesized aromatic kerosene (SAK) production pathway. These fuels have the potential to reduce net CO2 life cycle emissions by nearly 80 percent compared with jet-A, with the possibility for higher reductions.
James Stoddart, Rolls-Royce’s project engineer for the fleet, described the milestone flight as “perfect,” adding, “This was the first time the BR725 was flown with 100 percent SAF. We repeated the same flight with jet-A1 and the pilots couldn’t tell the difference, which was also supported by engine data analysis of both flights.”
Rolls-Royce’s core market in the business aviation sector includes large-cabin, long-range, and ultra-long-range jets, which will be burning liquid fuel for a long time to come—until other sources of green energy can be developed, Rolls-Royce said. “We see SAF as the opportunity for energy transition in this market and are committed to delivering engines that are compatible with and can run on 100 percent sustainable fuel,” the company acknowledged.
The company’s current-production engines are 100 percent SAF-capable, it said, “So all we are doing this year and next year is proving it by demonstration.”
That box has now been ticked for the BR725. Next in line are the BR710 on the Bombardier Global 5000/6000 -and Gulfstream G500 (previous version) and G550 and the Pearl 15, which powers the Global 6500/5500. The Pearl 700 powering the Gulfstream G700 and G800 business jets and in-development Pearl 10X—which has been selected by Dassault to power its flagship Falcon 10X—have already been ground tested using 100 percent SAF.
“We expect all of our in-production engines to be compatible with a 100 percent SAF blend by the end of the year,” said Rolls-Royce. A decision to pursue a similar SAF strategy for the out-of-production Tay (G350 and G450) and AE 3007 (Cessna Citation X/X+ and Legacy 600/650) has yet to be made.
“We will look closely at these engines, and then we will talk to the airframers and the authorities [which will need to approve the blend],” said Rolls-Royce. “But for now, we are focusing on the in-production models.”
While the industry’s commitment to delivering SAF-ready aircraft is undiminished, the price and availability of synthetic fuel still remain obstacles. “These are, of course, challenges,” said Rolls-Royce. SAF is more expensive than jet-A, but that is largely due to a lack of availability. Rolls said it is “doing its bit” to help stimulate demand and encourage higher levels of production.
“At our sites in Bristol and Derby in the UK and Dahlewitz, Germany, we purchase a 10 percent SAF blend supplied by Air BP for our testbeds,” the company noted.
“We could sit back and say, ‘Well, we have proven our engines can run on 100 percent SAF,’ but we are also actively advocating for the necessary enabling environment to make it widely available,” said Rolls-Royce. “High production rates and widespread deployment are essential to decarbonize medium-and long-haul air travel.
“Key to this strategy is showing investors in petrochemicals that there is not a barrier to adoption at high rates and there is a path to net zero, which the aviation industry is committed to achieving by the 2050 deadline,” said Rolls-Royce.
To demonstrate its dedication to sustainable fuels, Rolls-Royce signed a memorandum of understanding late last year with Alder Fuels covering the flight testing of new SAF being developed by the U.S. clean-tech firm.
Based on Alder’s proprietary technology—which turns waste biomass from forestry and agriculture into what it calls “Greencrude”—the SAF is being readied for global rollout as a drop-in replacement for jet-A and should be commercially available from 2024. Flight tests, scheduled to begin this year, will see the SAF used to run on an undisclosed Pearl engine—likely the Pearl 15 or 700.