...the Harper Dry Lake Energy Park seeks to transform manure from bane to blessing, in the form of nearly 50 megawatts of electricity.

CHINO, Calif. — This Southern California valley is at an epochal stage in the ancient and deeply ambivalent relationship between man and cow manure.

The milk flows richly here, thanks to 350,000 dairy cows, one of the world's densest concentrations of cows. But with these animals comes their waste: 1.5 million tons a year.

"Manure is becoming a bigger problem," said Mark Lambooy, 41, one of 260 dairy farmers in this valley of 50 square miles, known as the Chino Basin.

That is because a half-million people and counting live here, too. Downtown Los Angeles is a mere 35 miles away, and Orange County a stone's throw. With this kind of geography in its favor, people will build houses here, no matter how much it smells or how many flies strafe their barbecues.

Not that they are without complaint. The dairy farmers here are already a beleaguered lot, coping with falling milk prices and environmental lawsuits over seepage from unlined waste ponds, among other serious problems. And then there are the new residents who call the local Milk Producers Council from tract homes abutting dairies to ask if it is fly season or if anything can be done about the odor.

One answer, at least for 90,000 of the cows, could be the Harper Dry Lake Energy Park, which seeks to transform manure from bane to blessing, in the form of nearly 50 megawatts of electricity.

Buck Johns, 61, president of Inland Energy Inc., a developer of energy plants based in Newport Beach, Calif., heard about the Chino Basin situation and proposed building a methane digester on 1,900 acres in the high desert country just west of Barstow, in San Bernardino County.

The plant uses technology that heats the cow manure, releasing methane in sufficient quantities to fuel a gas turbine and create electricity. The solid waste remains are used for fertilizer, and the waste water is mostly recirculated, with some used to grow alfalfa around the plant to help feed the cows and provide greenery.

The technology is used worldwide, with animal wastes and with rotting garbage, but nothing close to this scale has been done using livestock manure, according to the Environmental Protection Agency and the International Energy Agency, a Paris organization with 26 member countries.

"This park would allow an economy of scale that makes it profitable to the dairymen," said Robert Feenstra, executive director of the local Milk Producers Council in the Chino Basin. "It would address environmental exposure. Even the barns will be cooled with solar power. Everything the dairyman needs will be there, and he doesn't need to live on site. It's a win for everybody. Once this hits, I think we'll see it everywhere."

Mr. Lambooy is one of a dozen dairy farmers giving serious consideration to Harper Lake. There is a strong temptation, from the flip side of development pressure: escalating land values. Mr. Feenstra said owners of dairy properties were getting offers of $150,000 to $250,000 an acre.

But those who like dairy life say they are not so sure they want to live in an isolated area after having the amenities of the Chino Basin.

"I would consider Harper Lake — the perks are getting the manure converted into electricity," said Art Marquez, 26, a third-generation dairyman. "But living there is better for the cows than it is for me."

The Harper Lake developers plan to build housing for each dairy unit, and have hired Eric Lloyd Wright, an architect who is Frank Lloyd Wright's grandson, to design the project.

Mr. Johns said he hoped to have permits to begin construction in six months, and to have the first cows in place in about a year.

Chino Basin dairies are a billion-dollar industry, responsible for 23 percent of milk production in California, the biggest milk-producing state. This makes them attractive pickings for others states. Iowa, Indiana, Kansas, Nebraska, South Dakota and Texas are trying to lure these dairy farmers to their less populated farmland.

Other dairy farmers are looking north to the San Joaquin Valley, but environmental lawsuits are delaying the process and making it very costly, which is discouraging some from starting the process. For their part, the environmentalists say their objective is not to chase dairy farmers out of California. Indeed, they hope and expect dairies to remain in the Chino Basin for a long time to come.

"Our interest isn't in shifting them from place to place, but in improving their operation," said David Beckman, a senior lawyer for the Natural Resources Defense Council. "It's great that they want to make investments in macro solutions to dairy pollution, like Harper Lake, but that doesn't excuse individual dairymen from polluting their facilities."

Mr. Feenstra finds it ironic that the very concentration of dairy cows that he considers a mistake in the Chino Basin is exactly what is needed to make Harper Lake an economic and environmental coup.

"I used to say to people, someday you're going to love us for our manure," he said, "and now it's true."