Continental jet 516—a two-engine Boeing 737-800—completed a two hour test flight out of Houston today with one engine powered by a 50-50 blend of regular petroleum-based jet fuel and a synthetic alternative made from Jatropha and algae.

"The properties of the fuel are fabulous, in fact, the bio part of the blend has a lower freeze point than Jet A," says Billy Glover, managing director of environmental strategy at Boeing, which is helping organize similar test flights throughout the world. "The fuels we're testing now have equal or better energy content than the Jet A requirements," of at least 48 megajoules per kilogram (20,700 British thermal units per pound).

In fact, the alternative jet fuel—known as synthetic paraffinated kerosenes—has as good or better qualities than Jet A refined from petroleum: It does not freeze at high-altitude temperatures, delivers the same or more power to the engines, and is lighter, as well. And the refiners, UOP, LLC, a division of Honeywell, can turn almost any plant oil into the alternative jet fuel. "They're all the same as far as we're concerned. We're feedstock agnostic," says chemist Jennifer Holmgren, UOP's general manager of the renewable energy and chemicals business.. "If the feedstock is available, we can process it to make fuels of the same capability."

For this flight, UOP transformed gallons of oil derived from the seeds of the Jatropha plant—an African weedy shrub that can be grown on land that is not being used for food production—provided by Terasol Energy. The Jatropha oil made up the bulk of the biofuel but 2.5 percent of the blend was also derived from 600 gallons (2,270 liters) of algae oil procured by Sapphire Energy from Cyanotech, an algae grower in Hawaii—the first time such algae oil has been used for flight.

"Crude oil is nothing but algae from 10 million years ago during a great algae bloom that got transported underground and today we call it crude oil," says Tim Zenk, vice president of corporate affairs at Sapphire Energy. "We take that process and speed it up by 10 million years and produce green crude."

Of course, making algae oil in any quantity remains a huge challenge, from perfecting the growth of the organism and its oil production to extracting the product in a cost-effective manner. Zenk says the company hopes to produce 300 barrels of oil from algae grown in brackish ponds at its test facility in Las Cruces, N.M., by 2011 and 10,000 barrels a day in five years. It will cost "between $60 to $80 per barrel," he says. "That's with very conservative numbers in terms of oil produced per acre." Companies ranging from Science Applications International (SAIC) in San Diego to San Francisco-based start-up Solazyme are working to produce jet fuel from algae oil as well.

In the meantime, efforts to grow Jatropha—already planted in quantity in Africa and India—may be scaled up, whereas other feedstocks that can be rotated with wheat, such as Camelina—a relative of canola—will play a role. "The way to think about it is that Camelina and Jatropha will be at the correct price point—$80 per barrel or less—within three to five years and algae in eight to 10 years," UOP's Holmgren says.

The next test flight—a Japan Airlines flight scheduled for January 30—will employ a jet biofuel made from Camelina supplied by Bozeman, Mt.-based Sustainable Oils, a joint venture of Seattle biotech company Targeted Growth and Green Earth Fuels in Houston. "It's a nonfood primary crop, can be grown on land that isn't being used, but it fits with existing farm infrastructure," says CEO Tom Todaro of Targeted Growth. "If you're expecting to have hundreds of millions of gallons of jet fuel in the next five years produced from a plant feedstock, it's almost certainly going to be Camelina."

That's because it can be grown on wheat fields that would otherwise be left fallow without harming the soil and in some cases improving it. "You give farmers an opportunity to make money in a year when they weren't going to," Todaro says, and the company is already recruiting farmers to grow the crop as part of plans to produce 1 million gallons (3.8 million liters) of the oil this year. "By 2010, at current wheat prices [of $5.50 per bushel], we can supply oil at $2 per gallon [and] … we could make north of 50 million gallons."

But the commercial aviation industry burns nearly 240 million gallons (945 million liters) of Jet A daily and if oil prices were to approach the $150-per-barrel mark reached last year, the demand for Camelina oil might end up driving farmers to grow less wheat—a staple food crop. "If the incentives are wrong it could displace wheat," UOP's Holmgren says. "We don't want it to be priced above what the price is for food."

That is why the industry is likely to use a variety of different feedstocks—Jatropha, Camelina, algae and others—to create the jet biofuel, Boeing's Glover says. "Different parts of the world will source differently," he adds. "That's another thing we are trying to do with these flights: show that we can use a variety of feedstocks and still get consistent high quality results."

In the near-term, the jet biofuel is likely to be blended with the petroleum-based variety, because the biofuels lack aromatics—hydrocarbon rings—that interact with the seals in current engines, helping swell them shut. "We fully expect that the first fuels will be 50-50 blends or less just due to the supply availability and the conservative nature of the industry," Glover says.

The Continental flight—and the Air New Zealand and Virgin Atlantic flights prior to it—prove that such blends can be effective, or even better than petroleum-based kerosene alone. "We have also found that engines running this mix emit less smoke even than those fueled by traditional jet fuel," said Eric Bachelet, president and CEO of CFM International in a statement.

And with this Continental flight, UOP has proved that blending the biofuels themselves, in this case algae and Jatropha, works well, too. "We have demonstrated two different fuel feedstocks into the same feedtank," Holmgren says. "We're going to use a lot of different feedstocks so if you had to use a different fuel tank for each fuel that would be a big problem."

Already, the first alternative fuel for jets has been certified for use worldwide by the American Society for Testing and Materials International (ASTM)—coal turned to liquid jet fuel by South Africa's SASOL. And the jet biofuel made by the UOP process has the exact same chemistry; the flights are designed to gather enough data so that the jet biofuel can undergo certification as soon as the end of 2010, according to Richard Altman, executive director of the Commercial Aviation Alternative Fuels Initiative.

By 2017, the Air Transport Association, a Washington, D.C.-based industry group, hopes to source 10 percent of all aviation fuel from such sustainable plant sources, both to ease the volatility of fuel prices and to cut the emissions of climate-change causing greenhouse gases from aviation.

Boeing hopes to help such biofuels become a "significant part of the commercial fuel supply by 2015," Glover says. "Three years ago, we started out saying this doesn't look like it's possible. But every day we become more and more convinced it's not only possible, it has huge benefits for industry and the public."