The task force at voluntary standards development organisation ASTM International that is compiling a report on bio-derived jet fuels research-a key step to enable commercial production-is waiting for the US Air Force to release its data on materials compatibility testing.
The Air Force must give the task force clearance to include its research findings in the task force report, which is probably 80% complete, says Mark Rumizen, FAA certification and qualification panel leader for the Commercial Aviation Alternative Fuels Initiative (CAAFI), a consortium of aerospace firms, trade groups and the FAA.
ASTM will review the research report as it considers modifying its newly created specification for non-petroleum-based fuels, D7566, to include bio-derived synthetic paraffinic kerosene (SPK) called hydrotreated renewable jet (HRJ).
Earlier this year ASTM passed D7566 to enable the use of up to 50% blends of SPKs derived from the Fischer-Tropsch process, and it modified the existing specification for aviation turbine fuel, D1655, to recognize fuels made with synthetic components.
To move the approval process forward for HRJ SPKs, the Air Force researched how such fuels impact elastomeric materials such as o-rings and seals by soaking the parts in HRJ SPKs.
"You want to confirm that the fuel doesn't do anything unusual to these materials or cause these materials to degrade. We don't anticipate any surprises in that regard for materials compatibility," Rumizen says.
Testing of three sources of HRJ SPKs has been underway for more than a year, with some 10 feedstocks researched including algae, jatropha, camelina, halophyte and animal fat.
In addition to Air Force research, the report will consist of data from sources including the Southwest Research Institute and biofuel demonstration flights performed by Air New Zealand, Continental Airlines and Japan Airlines in December 2008 and January 2009.
Results from chemical properties tests, specification chemical property tests and fit-for-purpose chemical property tests will be included, as well as data from engine tests--turboprops, turbofans and turboshafts--and some component rig testing, Rumizen says.
Once the ASTM HRJ task force finalizes the report by the end of this year or in early 2010, the report will undergo an internal review at ASTM, he says.
Then language will be drafted for modifying D7566 to include up to 50% HRJ blends.
Once the wording is determined, the ASTM aviation fuels subcommittee will vote on the addition.
"We haven't seen anything that would indicate we'll be unable to get it done in 2010," Rumizen says, cautioning that it is difficult to pinpoint a definitive timeline for balloting results to be completed.
A finalised addition to D7566 would set the stage for commercial airlines, private operators and the military to mix up to 50% HRJ SPK blends with petroleum-based fuels.
Operators may be limited to using lower percentage blends of HRJ SPK in order for the fuel to meet property requirements such as density because synthetic fuels are lighter than petroleum-based fuels, Rumizen notes.