The Fremont plant currently provides Class A biosolids to about a half dozen farmers on about 300 acres every year. It's a combination of dewatered sewage sludge and yard waste that's composted and turned several times. The process heats the material to temperatures high enough and long enough to ensure that pathogens are “burned or cooked out of that product,” says Keith Kontor, superintendent of the Fremont Wastewater Treatment Facility.

Biosolids for that many acres are generated by a combination of sewage sludge from Fremont's 25,000 population, plus sludge from small neighboring sewage plants serving another 2,000 people, according to Kontor. Hence, a population of about 27,000 is providing crop fertility to 300 acres each year — about 90 people for every acre of application — with residual sources of nutrients such as P, sulfur and zinc for several years following application.

These Class A biosolids consist of dewatered sewage sludge, grass clippings and leaves that are composted and turned several times. They reach a minimum temperature of 131° F for 15 days, which eliminates virtually all pathogenic microorganisms, according to Kontor. They are screened to eliminate debris such as pieces of branches and plastic bottles.

County permits for biosolid applications from the Fremont plant allow applications over a five-year period. Biosolids are applied to each acre only once during the permit period.

Farmers receiving the material must agree to go through a county permitting process that includes a number of requirements. Among them is notification of neighbors within 1,000 ft. of the proposed application site, followed by a public hearing. County commissioners then decide whether to approve the application, Kontor says. “In seven years, we've never had a public complaint after it's been hauled.”

Before distribution of waste sludge as biosolids to farmers, the plant spent about $250,000 annually for disposal. Making the biosolids available to farmers costs about half that much, Kontor says — an annual saving of $125,000 to the city.