The secret to cheaper gas could lie in cow dung.
The Vehicle Research Institute of Western Washington University in Bellingham, Wash., has been turning cow manure into fuel that can power a natural-gas car. Researchers are not shoveling manure straight into the gas tank but pumping the methane -- a gas created by the manure -- into the car.
They have some hard-working cows at a dairy farm in Lyndon, Wash., to thank for this experiment, which could mean cheaper car fuel for many people.
"We are talking about dairy cows," said Eric Leonhardt, an engineering technology professor and director of the Vehicle Research Institute. "So they are very well-trained. They go in one spot. They feed and do their business in one location. And then that material is pumped into a holding tank."
For 21 days, the manure sits in an underground tank and stews. Then, using regular old garden hoses, researchers siphon floating methane out of the holding tank. They must purify the methane to remove other gases before pumping it into the car.
Every cow can produce enough manure in a day to make a car go about 15 miles. If you take 20 cows, you get 300 miles of gas in your car.
There are not enough cows in the United States to power every vehicle. But Vehicle Research Institute researchers say a natural-car powered by methane could be a great solution for certain rural communities.
The price of cow fuel will put some consumers, well, over the moon.
"The gas is currently being sold at one-fifth the pump price," Leonhardt said.
ABC News' Kate Snow reported this story for "Good Morning America."