How Pasco sewage sludge gets recycled to fuel Benton County wheat farms
Once a year in September, hundreds of wet tons of sludge get moved out of a storage area at the Pasco wastewater treatment plant.
Sewage byproduct, also called biosolids, is loaded into trucks and driven away to two wheat farms in Benton County. Farms pay by the nitrogen value per pound of biosolids.
The wheat fields are fertilized with the biosolids to reach the right balance of nitrogen in the soil.
Pasco entered a new five-year agreement this week with a Sunnyside-based company that sends processed biosolids to farms across the state, and also fertilizes its own grass and wheat fields.
From sewer to field
The company behind the biosolids is Natural Selection Farms. It’s been in business since 1992.
Biosolids are rich in nutrients like nitrogen. They are treated at the wastewater treatment facility, making them safe to apply to agriculture fields. The Washington State Department of Ecology regulates treatment.
Cities are required by the Department of Ecology to send “Class B” biosolids for land application.
If biosolids don’t meet the department’s health standards, they get disposed of in a landfill where they take up space. Storing in landfills also costs the city more.
When biosolids are added to soil, they help with water retention and add organic matter.
Farms that apply biosolids say they have higher yields compared to farms that don’t.
It will cost the city up to $500,000 over the next five years for Natural Selection Farms’ services. Pasco already has worked with Natural Selection Farms for more than 10 years.
Natural Selection Farms is the only biosolids facility in the region, about 50 miles away from the city. It’s approved and monitored by the Department of Ecology.
The facility also collects biosolids from Kennewick, Prosser and West Richland. Richland sends its biosolids to the city landfill where it is applied to land and mixed into soil.
