njoyed successes similar to those that Clausen and Bopp have experienced. Many farmers trying biosolids have posted yields equal to or better than yields from crops where nutrient needs were met with commercial fertilizer. There's a long waiting list of farmers who want their turn at receiving this material, he adds.
Qualifying to receive it requires meeting certain federal, state and local environmental requirements, such as frequency of application, distances from streams and wells, slopes and application rates.
A little more than 7 million dry tons of biosolids were used or disposed of in 50 states in 2004, according to EPA. The 3,300 largest U.S. facilities generated more than 92% of the wastewater solids in the U.S., according to that survey. About 55% (3.9 million dry tons) of biosolids from those plants were applied to soils for various agronomic purposes (row crops, forestry, land restoration, etc.), according to EPA. Even so, the EPA estimates biosolids are applied to only 0.1% of U.S. agricultural land currently under cultivation each year.
Farmers like Clausen and Bopp applied biosolids at rates based on crop N needs. But, because of the composted material's higher P content, application rates are now based on crop P needs. In Nebraska, they are applied subject to limitations similar to those in effect for livestock waste applications, says Varner. He coordinates the biosolids program between farmers and the Fremont treatment plant.
That plant provides Class A biosolids. Using estimated commercial fertilizer prices, he calculates that a typical 10-ton/acre application of composted biosolids might be worth more than $500 of crop nutrients over a five-year period. The material is about 30% moisture.
Not all municipal wastewater biosolids are Class A. Class B can range from a liquid (2-5% solids) to dried products (80% solids), according to EPA.
CLASS B BIOSOLIDS are also processed to reduce pathogens, and can be safely applied to agricultural land, according to Varner. But, they are subject to greater application restrictions on such things as distances from streams and wells. Biosolids with higher moisture content may represent higher hauling and spreading costs.
The city of Omaha has provided Class B biosolids to farmers for more than 30 years, according to Varner. Omaha's program delivers about 70,000 wet tons annually to farmers in eight counties. There is usually a waiting period of two to three years to enroll in the program.
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