AREA'S SEWAGE BECOMES FERTILIZER AT COTTON FARMS.

Byline: Kevin F. Sherry Daily News Staff Writer

Pay attention to what goes down the drain. You may be wearing it next year.

Waste from Thousand Oaks homes eventually becomes fertilizer for 6,000 acres of cotton crops in the Central Valley.

``It's a remarkable material for farming,'' said Jim Willett, president of The Yakima Co. of Edmonds, Wash.

Willett's company hauls sewage sludge from Thousand Oaks, Simi Valley, Camarillo and Los Angeles County to farmers. Willett, who has been hauling urban sludge to farmers for 10 years under contracts with cities, said California is the ideal state for such an operation.

Strict environmental laws force cities to find creative uses for their waste products, and farmers are trying to reduce their dependence on chemical fertilizers. California also has an abundance of large, waste-producing urban areas relatively near major agricultural areas.

``It's almost a perfect marriage,'' he said.

The sewage sludge is the byproduct of every stop that waste water makes in its journey through the Hill Canyon Waste Water Treatment Plant operated by the Thousand Oaks Department of Public Works.

Skimmers and valves remove as many particles as possible. These collect into a mass of sludge, which gets sent to giant holding tanks known as digesters.

Nature takes over with the help of science. The solid mass gets heated and mixed in a 95-degree, oxygen-free environment. During the course of 30 days, the process reduces the size of the waste and produces methane gas, which gets recycled to help heat the digesters.

The final product gets squeezed to remove any remaining water before the pungent sludge is dried.

The plant just completed an 18-month, $6.5 million project to build three new digesters to replace two others that were seismically unsafe, said Don Nelson, Thousand Oaks public works director.

Thousand Oaks pays to have its sludge hauled north to Buttonwillow, a community 20 miles west of Bakersfield. There, solid sludge tumbles out of trucks, and a tractor works the material into the soil.

The city pays $24 a ton to have six tons of sludge hauled out of the plant daily. That compares with the $36 a ton it would cost to dump the stuff into the Simi Valley landfill, Nelson said.

While the city saves money on sludge disposal, farmers are pleased to get the fertilizer.

``We'd like to have more of it. They can't get enough of it,'' Nelson said.

The family that owns the Buttonwillow land has farmed parts of it since 1863, Willett said. But the soil in some portions could not sustain any crops.

``Cotton is hard on soil to begin with,'' he said. ``The farm has an almost unlimited need for soil amendment. They permanently improve the soil through the addition of organic matter.''

Willett noted that the biosolids enrich the soil with nitrogen. ``They act as a slow-release fertilizer. The benefits stay in the soil.''

Cotton farmers prefer sludge to chemical fertilizers that are quickly depleted in the soil and can seep into groundwater, Willett said.

``It's almost a complete fertilizer. The farmer doesn't need to apply anything else.''