CFM56-7B engine undergoing biofuel ground testing (photo: CFMI)
Mon 22 Mar 2010 – Aircraft and engine manufacturers have reported that after successful air and ground fit-for-purpose testing, jet biofuels blended 50/50 with conventional jet kerosene are likely to be certified for commercial airline use before the end of 2010, or early next year at the latest. A key ASTM research report compiled by Boeing, UOP and the US Air Force was sent earlier this month to the FAA, Airbus and engine manufacturers for review and comment. The report marks a final stage in the ASTM D4054 certification process before reaching the ASTM ballot and review procedure and the final fuel specification. Approval of biofuel blends is seen as a major hurdle to overcome in the commercialization and scaling up of aviation biofuel production.
Data from the test flights undertaken by Air New Zealand, Continental Airlines and Japan Airlines have been included in the ASTM research report along with data from laboratory and engine ground testing by manufacturers GE/CFMI and Honeywell, and material compatibility testing by the US Air Force. The fit-for-purpose tests used a range of feedstocks – jatropha, camelina, tallow, algae, halophytes, soybean, canola, palm and coconut – in various blends.
The results indicate that the jet biofuels – Bio-SPKs (bio-synthetic paraffinic kerosene) or HRJs (hydrotreated renewable jet), to give them their technical terminology – tested often exceeded the current jet fuel specification. Their advantages include a lower freezing point, higher temperature thermal stability and higher energy density.
Darrin Morgan, who heads up Boeing’s biofuels strategy, said the standards process was crucial to the supply chain. “If we do not get technical certification we will not be able to use these fuels and the finance to develop them will not be forthcoming,” he told delegates to last week’ World Biofuels Markets in Amsterdam.
Morgan and Paul Nash, Head of New Energies at Airbus, confirmed the two aircraft manufacturers had set aside their rivalry to form a broad strategic alignment for the development of jet biofuels.
“This is not a competitive concern for us,” said Nash. “This issue is critical and we realize that if we don’t do something together and we don’t adopt a cross-industry approach, then we’re not going to move the business forward.”
Dr Jim Kinder, Technical Fellow at Boeing and also Chair of the new ASTM Emerging Fuels Task Force, described the ASTM D4054 certification process as “very rigorous”. He explained: “The 140-page research report will be reviewed by the aircraft and engine manufacturers to see if there are any gaps or holes, or if there is any additional research they would like to see. If it’s approved by the manufacturers then it goes to the full ASTM fuels committee for voting and balloting. Once it goes to the ballot you have the full ASTM community comprised of people with different expertise all looking at the report with a critical eye – for example, pipeline or distribution companies might have their own concerns. All inputs, positive and negative, have to be addressed.”
Kinder said the testing and the report itself was ‘feedstock agnostic’ in that no choice or preference was made between the range of Bio-SPKs tested, which came from five different producers – UOP, Syntroleum, Energy & Environmental Research Center, ENEOS and Neste Oil. Synthetic fuels supplied by SASOL, Shell and Syntroleum, and produced using the Fischer-Tropsch process – called FT-SPKs – were also tested and compared. FT-SPKs have already been certified for commercial use in 50% blends.
Describing the importance of the test flights undertaken by Air New Zealand, Continental and JAL at the beginning of last year, Kinder said up until then the processes to make Bio-SPK fuels were only at a laboratory stage in a US military funded research programme and it had been important to take them out and test a variety of feedstocks under flight conditions. He said it had also been essential to conduct tests with all the major engine manufacturers in order to help them gain experience in Bio-SPK fuels and engage with them in the test process.
Another objective of the test flights, he said, was to start talking to the various regulatory authorities around the world “so they too could get comfortable with the new fuel”.
Tedd Biddle, Fuels Technology Manager at engine manufacturer Pratt & Whitney, told delegates that as challenging as it was to develop a new fuel, it was equally challenging to get it approved. He said the ASTM D7566 new fuel specification for alternative aviation fuels – which, for now, applies only to FT-SPK fuel blends until Bio-SPKs are approved – was the first for 50 years.
“The speed at which aviation biofuels have come on in such a short space of time has been amazing,” he added. “If someone had asked me just three years ago when a blended biofuel could be approved for use in a jet engine, I would have said 2015 at the earliest, and now we’re talking about the end of this year.”
He said the process had been largely driven by Boeing and also by the US Air Force, which had alternative fuel requirement mandates in place and had shown a willingness to work with anyone who could supply them with fuel samples.
Biddle stated engine manufacturers had three basic requirements of a potential biofuel: it had to have a high energy content; it must be a drop-in fuel invisible to the engine in that it required no redesign of the engine, component development or re-certification of the engine; and had no impact on safety, durability, reliability or performance.
Paul Nash of Airbus said an important technological challenge the industry had to face concerned the aromatic content of Bio-SPK fuels. Aromatics are hydrocarbons found naturally in fossil-based fuels and were a necessary component for conventional jet fuels, forming around 25% of their volume. They are not found in biomass sourced fuels and this restricts the use of jet biofuels to 50% blends in order to guarantee aromatic content.
“We have to assess whether zero-percent content of aromatics is an issue for us or whether we have to look at synthetic aromatics,” he said.
Nash said the current target for running aircraft on 100% Bio-SPK fuel was 2013.
He said another issue facing the industry as a whole was over sustainability and life-cycle emissions criteria of aviation biofuels, given the different feedstocks and processes involved. “For us it is sometimes difficult to decide which life-cycle analysis to use and which is key in terms of sustainability analysis. We would like a harmonized industry approach on this.”
Victoria Junquera of the Swiss-based Roundtable on Sustainable Biofuels, an international initiative which Airbus, Boeing and the Sustainable Aviation Fuel Users Group are working with, announced at the conference that it was developing a tool for measuring greenhouse gas emissions from different biofuels and also a standard for sustainability criteria.
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