Hot topic: biofuels in jet aviation

Two good articles in the New York Times and Scientific American on the current interest in alternative aviation fuels, hooked to this week’s upcoming Continental B737 biofuel flight test.

NYT: Continental plans to have the crew turn off and restart the right engine, the one running on the 50-percent blend of ordinary jet fuel and plant-based fuel. The crew will simulate breaking off an approach and going around, which demands high power from the engines, among other maneuvers. On board will be two pilots, a flight engineer and, because this is an experiment, 157 empty passenger seats.

Although jet fuel prices have dropped with crude oil, industry executives say they are determined to become less dependent on a single source of fuel in case prices rise again.

“It’s hard to plan a business, and buy expensive pieces of equipment that last for 20 or 30 years, when you have total uncertainty about the cost of your biggest expense,” said John P. Heimlich, chief economist of the Air Transport Association, the trade group of the major airlines.

SciAm: “We can use any kind of vegetable oil—palm, jatropha—they all have the same [chemical] backbone,” [says UOP chemist Jennifer Holmgren.] “We just adapted what we tend to do in an oil refinery for this application. This is not rocket science, we feel very comfortable scaling this up.”

She adds, however, that this fuel is not a “drop-in replacement” for Jet A1. That’s because jet fuel from petroleum contains so-called aromatics—hydrocarbon rings—that interact with the seals in current engines, helping swell them shut. “We don’t make aromatics through the vegetable oil route,” she says. “If we wanted to fly on 100 percent [biofuels], there are issues around O-rings and things like that.”

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