Biosolids contain a large percentage of water, so the product is heavy. Spreading it requires large heavy-duty equipment. It is applied after fall harvest, usually in September and October, before the product has a risk of freezing.
By Loretta Sorensen
Biosolids yield greener corn and pocketbooks
Call it biosolids or sewage sludge. Whatever the label, more and more farmers say it’s a valuable economic nutrient. Cities and municipalities are developing waiting lists as biosolid demand grows.
Applying biosolids’ nutrient-rich organic materials—derived from wastewater solids that were stabilized through processing—is comparable in cost to commercial fertilizer. However, some farmers believe it’s more nutrient dense, due to its phosphorus content.
Some cities, such as Fremont, Neb., save residents as much as $160,000 annually by selling biosolids at reduced wastewater treatment fees. Dodge County farmers annually realize about $85,000 in biosolids nutrient value.
"In 2011, farmers began paying for Fremont biosolids, augmenting the city budget by about an additional $40,000," says Dave Varner, a University of Nebraska–Lincoln (UNL) Extension educator in Fremont. "It’s a win-win program for urban and rural citizens."
Farmers complete an application and provide field maps, water drainage maps, well locations, soil types, groundwater depth, flood plain information, crop rotation and a nutrient analysis.
"We also consider the farmer’s relationship with neighbors when determining where biosolids are applied," Varner says. "Our 11-year program hasn’t received any complaints."
Independent agents such as Extension educators and Environmental Protection Agency (EPA) represen-tatives ensure the regulations are observed. Detailed application records are maintained, documenting when, where and how biosolids are applied.
Local utility. "Each city has its own process," says Barb Ogg, a UNL Extension educator in Lincoln. "Most cities have a staff member identifying farmers interested in biosolids and making sure regulations are observed. The city of Lincoln hired the Lancaster County Extension office for that purpose. Some farmers contract to apply biosolids, others apply it themselves."
GPS and GIS technology make it easier to identify exactly where bio-solids are applied. Lincoln has worked with farmers for 20 years to dispose of biosolids. Each year, city officials report to EPA on where biosolids were distributed.
Dave Nielsen’s close proximity to Lincoln’s biosolids storage site got his father thinking about how biosolids might improve their crops.
"We’re all dryland—rolling hills and terraces," Nielsen says. "Our crop rotation is 100% corn and soybeans. Our native soils are especially low in phosphorus and zinc. Biosolids are high in both those nutrients. Dad also liked the biosolids’ slow release of nutrients. He expected it to improve tilth and workability of our soil. It has done that."
Phosphorus is the main nutrient in Fremont’s biosolids—10 tons of material typically includes 250 lb. to 375 lb. of P205 phosphorus fertilizer.
"We constantly hear, ‘Can I get more?’ We limit biosolids application to one field per farmer annually to help spread the material’s value across several operations," UNL’s Varner says.
Most biosolids are hauled to fields during September and October.
"Farmers are billed $10 per ton of material," Varner says. "Hauling accounts for half the cost. The typical application rate is 10 tons per acre."
Biosolids are wet and heavy, which requires larger equipment. Nielsen says it’s difficult to compare biosolid costs with commercial fertilizer.
"When Lincoln started their program, they paid us 50¢ per cubic yard. We applied about 40 cubic yards per acre," Nielsen says. "Now we pay the city. Our cost averages between $20 and $30 per acre with hauling and applying. It’s about a break-even situation. Because it’s building our soils, we believe it’s a good value."
- March 2012