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A secret to improving cargo ship efficiency: Go fly a kite

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While some of these technologies are promising, none represents a "silver bullet" in reducing fuel use and emissions, says James Corbett, an associate professor of marine policy at the University of Delaware in Newark, Del., who co-wrote last year's report on ship emissions and health as well as a 2000 IMO study of greenhouse-gas emissions from ships.

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"The problem is not simply to choose the best technology or practice, because there isn't a single solution," he says. "Industry and regulators are going to have to look at a variety of solutions and demonstrate the will to take effective action."

While the voyage of the SkySails Beluga has shown kite-power can work, the current design may have only limited usefulness since it appears to operate only at speeds below 17 knots (20 m.p.h.), Dr. Corbett says. "The fastest ships [big container vessels that travel at 20 knots or more] would not yet be able to take advantage of this design."

But even speed can change if the incentive is strong enough. Bunker fuel prices now exceed $450 per ton, and ships already are slowing down to save energy and reduce cost. Just a 10 percent reduction in ship speed saves 25 to 30 percent in fuel burned, Corbett points out.

• Monitor correspondent Tony Azios contributed to this story

Bunker fuel: cheap, but dirty

It can turn as solid as asphalt, but it's considered black gold for oceangoing ships.

Bunkerfuel, also called residual fuel, is what remains after crude oil hasbeen refined into higher grades of fuel, such as diesel.

"Forall intents and purposes, it's a waste product," says T.L. Garrett,vice president of the Pacific Merchant Shipping Association in San Francisco.

After decades of engineering improvements, the colossal marine engines used by cargo ships have learned to love bunker fuel and burn it efficiently. With a price about half that of marine diesel fuel, bunker fuel has proved to be the perfect choice for moving massive ships from continent to continent.

Almost.

That's because the tarlike sludge also is rich in contaminants, from toxic heavy metals to sulfur, which are emitted into the atmosphere and are being linked to health problems.

Two shipping-industry organizations – the International Association of Independent TankerOwners and the Pacific Merchant Shipping Association – and environmental groups, including Friends of the Earth, have called for an end to the use of bunker fuel in cargo ships.

"Bunker fuel is the dirtiest fuel on the planet," a Friends of the Earth spokeswoman told the Associated Press last fall. "Ships are being used as waste incinerators for the oil industry."