Plant Power; What's the answer to avgas?

By Dave Hirschman. The original claims describing a bio-fuel replacement for avgas sounded too good to be true.Swift Enterprises, a small start-up firm in Indiana, announced last year that it had developed an unleaded, domestically produced, higher-octane aviation fuel that could be manufactured and produced at a far lower cost than avgas. It promised its bio-fuel would reduce emissions 20 percent and increase aircraft range up to 15 percent.

Laboratory tests by the FAA confirm that Swift’s avgas replacement will work in current piston aircraft engines, even the high-compression, turbocharged varieties that are particularly susceptible to detonation. (Teledyne Continental Motors has begun flight tests using Swift fuel.) The bio-fuel burns cleanly, has acceptable vapor pressures, and even offers some range and performance advantages over traditional avgas. So far Swift has only produced its product in tiny batches. And the unit costs for making it that way are extraordinarily high.

U.S. refiners currently sell about 250 million gallons of leaded avgas a year. That may sound like a lot, but it’s far less than a day’s production of unleaded auto fuel. The world’s aviation emissions—including airlines and military jets—account for about 3 percent of all carbon-dioxide emissions, and general aviation is a tiny fraction of that amount. But avgas is one of the few fuels that still contain lead, and a combination of new regulations, environmental considerations, and economics may soon make leaded fuels untenable.

Swift plans to use switchgrass as its fuel source. An abundant, fast-growing plant that used to cover much of the American heartland before corn, soy, wheat, and other crops took over, switchgrass has a higher energy output than food crops, and using switchgrass in bulk won’t drive up food prices. Swift is building a manufacturing facility near Purdue University Airport in Indiana where company officials hope to prove the merits of high-volume fuel production.

Since Swift fuel is unleaded, it can travel in the same delivery pipelines refiners use to deliver auto gas. Avgas must be segregated from other petroleum products throughout the production and delivery process and stored in separate containers. Trucks, rail cars, and vehicles that carry leaded avgas can’t be used for unleaded fuels. Swift officials say they expect some cost savings based on its ability to use the existing transportation infrastructure for other unleaded fuels. FAA certification of Swift fuel, or any other bio-fuel, is likely to take several years at least. While Swift pursues FAA approval, it’s also selling its specialized fuel to car, motorcycle, and even air racers willing to pay a premium for the added performance they say it brings.

Diesel aircraft engines got a black eye last year when German manufacturer Thielert sought bankruptcy protection after the founder was accused of financial misdeeds. The company’s troubles dealt a serious blow to Diamond Aircraft and other aircraft manufacturers that depended on Thielert for a steady supply of engines and parts, as well as owners of aircraft with Thielert engines. Cessna had already announced plans to manufacture Thielert-powered 172 Skyhawks for the world market when Thielert imploded...

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