Hydrotreated renewable jet fuel close to certification but scale-up challenges remain

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Commercial production of jet biofuels could find authorisation in December under fuel specification amendments being considered by certificating body ASTM International.

Enormous investments and economies of scale are far behind testing that consistently confirms the safety and performance of hydro­treated renewable jet (HRJ) fuel, a term used to describe any feedstock or process that leads to fuel that is chemically identical to crude oil-based kerosene.

Fresh test reports supporting a new ballot to revise ASTM D7566-09 and allow HRJ production are being examined by the 160 members of ASTM International Committee D02's Subcommittee J. Negative responses are not expected after seven negatives led to the withdrawal of a similar ballot in June. Those objections were no surprise, with engine manufacturers already asking for safety and performance tests that are now complete.

A USAF Boeing F-15 flew in late October on a 50/50 HRJ blend, adding to its F100 powerplant ground tests. Picture: US Air Force
"The biggest hurdle is getting it out of the aviation committee," says Jim Kinder, chairman of the ASTM emerging fuels task force and technical fellow at Boeing. "Then it has to pass Committee D02. Generally that's just a formality." But unforeseen concerns could spell months of delay. Both meetings are due on 5-9 December in Jacksonville, Florida.

ASTM specifications are specific and demanding, but jet fuel is jet fuel no matter what feedstock was grown, mined or pumped to make it. "No fuel samples are exactly the same from every manufacturer every day," notes Kinder. "They all fall within a range, and these bio SPKs [synthetic paraffinic kerosenes] all fall within the same range. This is just the beginning. The next one that's coming up is probably an alcohol route to jet fuel. The other one is fuel from a pyrolysis route, and there are other guys working on microbes and all kinds of things."

Every fuel must undergo ASTM's strict analysis and fall under a specification before it can be produced commercially. "It's not anything very radical," says George Wilson, senior research scientist with Southwest Research Institute and chairman of the emerging fuels group. "It's really important, because aviation is life and death. With flight safety you can't make casual errors. There are going to be a series of different types of synthetic fuels, and each one has an annex telling us how it's used in the main part of D7566 [jet fuel specification] to blend the finished product."

Acceptance and testing of HRJ has been simple compared with the plethora of tests and research preceding the September 2009 publication of ASTM D7566-09. That annex allows production of 50% blends of synthetic kerosene from coal and natural gas through the Fischer-Tropsch process. The US Air Force tested its entire turbine fleet to prove that Fischer-Tropsch fuels work well. So well, in fact, that USAF testing of HRJ depends on only three "pathfinder" airframes to represent and certificate the fleet.

Betty Rodriguez, chief engineer of the alternative fuels certification office at Wright-Patterson AFB in Ohio, says the process is much faster than predicted three years ago. "We have become a lot more effective in terms of planning our testing, working with different original equipment manufacturers and different platforms. We're a lot smarter now in terms of what kinds of tests, what kinds of properties we're testing for."

The USAF initiative has paid off, notes Rodriguez, with private fuel producers and engine manufacturers increasing their testing commitments. "The navy is also joining the group and we're sharing data back and forth. You can see the efficiencies multiply every time you see the new requirement."

HRJ was blended with JP-8 and then with Fischer-Tropsch fuel for Boeing C-17 flight tests in late August, says Jeff Braun, director of the USAF alternative fuels certification office. ASTM members were eager for data on that test, as well as data on Pratt & Whitney F100 and General Electric F110 engine tests. Their team worked "feverishly with our OEMs and test agencies to prepare reports that are suitable", he says.

Braun adds that the Boeing F-15 flew in late October on a 50/50 HRJ blend, adding to its F100 powerplant ground tests. "Testing remains on the [Lockheed Martin] F-22 in February or March," he says. "We'll test the [Lockheed Martin] F-35 in late February and we are looking to test the [Northrop Grumman] Global Hawk aircraft in the very late spring or early summer."

HRJ fuels are being proved in USAF aircraft. Picture: US Air Force 
Global Hawk availability has been the most serious challenge to meeting the USAF goal of certificating its turbine fleet on Fischer-Tropsch fuel by 2011. "The Global Hawk F-T effort has been delayed, delayed, delayed," he says.

New tests have value even with ASTM balloting already under way. "We need to make sure our fuels can perform in a challenging environment like the F-22," Braun explains. "In terms of endurance testing, we push it to the limit. Sometimes we keep our airframes for 60 years."

The USAF has worked with P&W, GE and Rolls-Royce on Fischer-Tropsch and HRJ tests. "The FAA is not directly conducting HRJ testing," says Mark Rumizen, FAA aviation fuels specialist in the aircraft certification service and its senior member of ASTM International D02.

"However, we just issued a broad agency announcement to solicit proposals for some additional engine testing of HRJ fuel to expand our knowledge base of this new fuel. If we accept any of the proposals, then we will fund a contractor to perform this testing and to make the data available," he adds. "The FAA's main concerns are with the qualification process and to make sure that we have a safe and well-controlled fuel when completed. And we are confident that the ASTM community can accomplish this."

The FAA's other members of ASTM are Mark Orr, an aerospace engineer from the small airplane directorate, and Dave Atwood, a research project manager from the FAA technical centre.

"We are eager to see the comments submitted by the ASTM members," says Rumizen. "That doesn't mean we won't get negative votes. That's part of the process and is important for driving the specification to an acceptable form."

Neither technical nor safety concerns are the main obstacle to widespread commercial availability of HRJ, he adds. "Without question, it's the production scale-up. We've proven that we can make these fuels and we know how to evaluate them to ensure they are safe and well controlled. But we need some breakthroughs relative to feedstocks and high-volume production to finally have the impact necessary to achieve our goals."

At ASTM meetings Rumizen also represents the Commercial Alternative Aviation Fuels Initiative. "CAAFI is engaged in many commercialisation activities intended to spur the production scale-up of HRJ fuel," he says.

Dozens of research laboratories and start-ups have formulas and plans to produce and sell HRJ, but immense investments supporting enormous production facilities are needed for economies of scale. Any carbon-based jatropha and camelina oils will go mainstream before algae does, but each chemical process to convert every feedstock has refinement ahead.

AltAir Fuels remains in the lead for HRJ production, but is not sharing updates on construction of a facility that could begin operation in 2012 and produce 380 million litres (100 million USgal) of HRJ a year. AltAir says it "has been holding off on providing any exact details about the status of the project" because it is "still negotiating with airlines and still in discussion with funders".

The Seattle-based company was formed in 2008 and in December 2009 announced a memorandum of understanding with 14 major airlines from the USA, Mexico, Canada and Germany to negotiate the purchase of up to 2.8 billion litres of HRJ.

This would represent 10% of the fuel consumed annually at Seattle Tacoma International airport. The plan is to convert camelina oil into HRJ and diesel at a Tesoro oil refinery in Anacortes, Washington. The facility will need to prove that its overall environmental impact is smaller than that of traditional jet fuel. This is the snag keeping USAF from purchasing Fischer-Tropsch fuels.

"We can buy F-T for the same price as JP-8, but we're not allowed to buy it because it's perceived as less clean than JP-8," says Braun, pointing to Section 526 of the 2008 Energy Act.

"After we complete the certification effort and put the bow around it and say 'we're done', then it's up to the politicians whether they're going to allow F-T, or any other alternative fuel, to be integrated into military operations," Braun adds.