WESTLEY, Calif. (AP) _ The country has billions of unusable tires and an energy company says it has the answer: burn them.

A $41 million plant is being built 90 miles south of San Francisco to consume more than 500 whole tires a minute, non-stop, creating steam for a turbine to generate electricity for 14,000 homes a year. It will be the first such plant in the nation.

''The technology is unique in North America. Nobody's got it but us,'' said Arch Ford, senior vice president of Oxford Energy Co.

State, county and municipal officials have granted approval for the plant, but environmentalists fear its emissions, including carbon dioxide, sulfur dioxide and hydrocarbons.

''We are opposed not because we know it's going to be bad, but because we don't know it's not going to be bad. There's been no complete environmental study,'' said Gordon E. Hart, executive director of Ecology Action, which sued unsuccessfully to stop construction on the Westley facility.

Opponents sued unsuccessfully for an independent environmental study of the plant, which is to open near this farming community of 700 in the summer.

The nation has 2 billion unretreadable tires lying around, with 240 million more being discarded every year, or roughly one per person, according to the Department of Energy.

Many landfills no longer accept tires because they work their way to the surface. Dumps that do must take costly storage measures.

As a result, millions of tires are left along roads or stored at illegal dumps every year.

Other tire disposal practices include building ocean reefs, using shredded rubber chips as asphalt additive for softer roads, adding them to farm waste burners as supplemental fuel, and shipping them overseas for burning or recapping. Some dealers resell tires below U.S. retreading standards to Third World countries, according to Oxford officials.

As fuel, tires hardly can be rivaled, said Ford. Each contains the equivalent of 2.5 gallons of oil, enough to heat an average house for a day. About 18 percent of modern tires are steel, which Oxford will recycle.

Oxford obtained its system through an exclusive arrangement with Gummi- Mayer, West Germany's largest tire retreader, which has run a tire-burning facility since 1973.

Oxford has proposed two additional plants at Sterling, Conn. and Danville, N.H., and three others are in the design stage, Colman said.

After an analysis at Gummi's plant, New Hampshire environmental agencies said in January they found no air quality degredation, no adverse impacts on crops, and no odors.

In Sterling, town leaders embraced the 24-megawatt project, but citizens turned it down in a referendum last February, only to narrowly approve it weeks later in a second referendum which is now being challenged in court.

The Oxford plant is being built in Westley because that's where Ed Filbin's dump is. He began carting tires here for a fee in 1963.

''I always figured that if you collect enough of something, there'll be a market for it sometime,'' Filbin told reporters in 1985, standing next to his 40 million tires that are waiting to be burned.