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Corn+Soybean Digest

Waste Not, Want More

More than 16,000 U.S. wastewater treatment facilities serving more than 220 million people produce sewage sludge, according to a survey cited by the U.S. Environmental Protection Agency (EPA).

A significant portion of that material is turned into biosolids available to farmers for fertilizing crops. And, as commercial fertilizer costs continue to soar, those biosolids are increasingly prized for their ability to reduce crop fertilizer bills by providing nitrogen (N), phosphorus (P) and some secondary and micronutrients for crops. They also provide organic matter.

If you haven't checked into a source of biosolids for your cropland, you may be missing out on a major savings. Among those to contact for availability are: your local wastewater or sewage treatment plant, local Extension educator, farm management consultant or land grant university.

Supply is far from open-ended. You might find yourself on a waiting list, with only limited amounts of biosolids available.

FARMERS BOB CLAUSEN and Ron Bopp in eastern Nebraska accepted biosolids on some of their fields from the municipal wastewater treatment plant at Fremont, NE, several years ago. They were among the first to try the material in their area.

Biosolids were applied at rates required to meet corn N needs, based on soil tests and these farmers' yield goals for their fields, says Ron Schultz of the Pathfinder Company in Fremont. He's the farm manager for their farms.

Commercial N needs on those fields have been met with commercial sources of N for corn in subsequent years. But, the only commercial P for corn and soybeans on those acres since 2002 has been a starter application of 10-34-0. No other P has been needed, say Clausen, Fremont, NE, and Bopp, Hooper, NE. And, that was on fields where soil tests showed low P levels before applying biosolids, says Schultz.

Clausen says corn and soybean yields on those acres — one 50-acre field and another of 40 acres — have equaled or beat corn and soybean yields from his other fields where he usually applies 100 lbs./acre of 11-52-0 annually.

Bopp has experienced similar results on 145 acres of irrigated land, where he had biosolids applied from the Fremont wastewater facility. “I haven't used any (commercial) P since,” he says.

Corn and beans have yielded as well or better than other fields fertilized regularly with commercial fertilizer applied according to soil tests, Bopp says. Biosolids not only cut his fertilizer bill, they improved soil tilth, he adds.

He calls it a “huge savings,” but adds, “The only problem is, there aren't going to be enough (biosolids) to go around.”

The material, Class B, from the Fremont plant is about like potting soil, according to Schultz. It spreads evenly. You don't get the clumps that can occur with livestock manure spread on fields, he says.

Bopp disked in the biosolids he received, which were applied in the fall, and then incorporated further with field cultivation in the spring. Clausen says he incorporated biosolids on some acres and not on other acres, with comparable yield results between the two.

“Environmentally, it's a grand way to get rid of a product from these (municipal wastewater treatment) plants,” Bopp says. And economically, the more fertilizer prices rise, the farther you can transport it for its fertilizer value, he adds.

Clausen and Bopp are among a group of Nebraska farmers who are comparing biosolids processed from municipal sewage sludge for crop production. They participate with the Nebraska Soybean and Feed Grains Profitability Project, an on-farm research program.

Biosolid substitution for commercial fertilizer is just one of many different practices farmers are researching for themselves on their farms. They receive guidance on setting up accurate comparisons from University of Nebraska Extension personnel. (You can review past results at by searching biosolids.)

University of Nebraska Extension Educator Dave Varner in Dodge County, NE — where Clausen and Bopp farm — says farmers receiving biosolids from the Fremont plant have generally enjoyed 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 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.

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