“The military has this ‘single battlefield-fuel’ concept,” Aulich says. “They are trying to use a single fuel for aircraft, Humvees, tanks and everything in between.” While this may not sound economical—burning high-quality jet fuel in Humvees—what’s another dollar or two per gallon when the transportation costs are already so high? Furthermore, national security naturally comes into play. Domestic rhetoric pushing for the proliferation of renewable fuels frequently hinges on national security, which is ultimately about preserving a way of life and proactively avoiding interruption if foreign oil shipments should cease.
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“The primary driver for the U.S. military is developing a domestically produced and ideally renewable fuel—a non-oil, nonpetroleum resource—so we aren’t in any way dependent on foreign oil for our military fuel requirements,” Aulich says.
Four years ago, the EERC and U.S. military began working together to develop a biobased aviation fuel. The motivation behind this research was to reduce particulate emissions. “When the aircraft is sitting on the tarmac idling—where the guys are breathing in all of this stuff, and then during take off when they are really putting the pedal to the metal and blowing out emissions like crazy—they wanted to eliminate a lot of that,” says Chris Zygarlicke, EERC deputy associate director of research. “Adding biodiesel was helping to reduce emissions, but cold flow was definitely a problem.” There’s no room for errors when powering a fighter jet traveling five miles above the Earth’s surface at a speed that’s faster than sound. “If you’re flying at 30,000 feet of altitude, you need to have fuel that will flow at 50 degrees below [zero] Fahrenheit,” he says.
Another technical problem prohibiting biodiesel in aviation is that the renewable fuel’s methyl ester chain lengths commonly run 18 to 23 carbons long, which works against its operability in the cold—conventional biodiesel will turn wax solid at minus 50 degrees Fahrenheit. However, jet fuel typically has a carbon count between C9 and C15, with emphasis on C12. Also, the presence of oxygen in biodiesel means its energy density is compromised. DARPA data shows biodiesel contains 25 percent less energy density per mass basis than JP-8 military jet fuel. “In order to meet the military requirements for energy density in our jet fuel (as dictated by the MIL-DTL-83133 specification), we have to remove the oxygen,” Aulich says. Therefore, the EERC was tasked to reevaluate how to produce a renewable fuel that would pass military muster—and one that’s “drop-in compatible” for the propulsion of everything from Humvees to jets.
Bids, Awards, Deliverables
In July 2006, DARPA issued a solicitation under its Biofuels Program for alternative fuels and efficiency options “to reduce the military’s reliance on traditional fuel for aircraft,” the agency said. The EERC was able to put a funding package together and have a project in place with assistance from soybean grower groups and North Dakota’s State Board of Agricultural Research and Education, Zygarlicke says. In December 2006, the EERC announced it was awarded $5 million to develop this renewable JP-8 surrogate. “There were 30 proposals and we were one of three awards,” Aulich says.
Thomas Erickson, associate director of research at the EERC, says, “I would guess the other two are very near to entering agreements with DARPA.” One of the two is General Electric Global Research, according to DARPA. At press time, a third recipient hadn’t been named.
In order to win the bid process, the EERC sufficiently demonstrated its abilities to meet the challenge. “We’ve demonstrated the initial concept viability already,” Aulich says. The center has the necessary lab equipment to process vegetable oils into anaerobic, short-chained and energy-dense renewable aviation fuel.
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