Students at the state university's Vehicle Research Institute have developed a scrubber that removes the corrosive chemicals from the gases released by manure so it can power a natural-gas car.

Eric Leonhardt, director of the institute, said the fuel that he calls "biomethane" is less flammable than gasoline and produces fewer greenhouse gases than manure left to decompose naturally in fields.

He estimates the natural gas would cost about half the current price of gasoline to produce, but emphasizes that is not the real benefit of cow power.

"If we can get farmers to put in anaerobic digesters, that's going to be the environmental impact," he said. "The gas is really an aside. The real impact is getting manure out of the water supply."

This new kind of natural gas isn't ready to be pumped into your car at a service station - yet. Only one farm in Washington has started turning its cow manure into natural gas, although the process is catching on more quickly in some other states where utility companies are helping farmers buy anaerobic digesters.

An anaerobic digester on Darryl Vander Haak's dairy farm in Lynden, Wash., processes manure from about 1,000 cows into electricity to sell to Puget Sound Energy. At full capacity, the digester can produce enough energy to power 180 homes.

The raw biogas contains highly corrosive hydrogen sulfide, so it must be processed before it can be used in motor vehicles that run on natural gas.

Leonhardt says his institute is working on creating a commercially viable bioscrubber to turn that idea into a reality.

One of Leonhardt's students, Matt Wilson, 23, said the scrubber they have developed from PVC pipe and spare parts removes both hydrogen sulfide and carbon dioxide from methane gas. The gas is then compressed before it can be pumped into a special natural-gas-powered car.

Waste produced by 15 cows has been enough to run the institute's natural-gas car for 250 to 300 miles, Wilson said.

Leonhardt said to convert a standard engine to cow power would be an expensive process, possibly costing thousands of dollars.

But Wilson seemed confident biomethane would eventually be a fuel source for cars.

"It's not going to take care of the whole fuel need," he said. "It can't replace gasoline, but it can play a big part in ending our dependency on fossil fuels."