Community Manure Management

Dane County led the development of two community manure digesters based on recommendations from the Community Manure Feasibility Study (PDF). The primary goal of the digesters is to remove phosphorous from manure resulting in reduced phosphorus runoff and improving water quality. Removed phosphorus can then be recycled and relocated to areas where phosphorus is needed. There are currently two community digesters in operation, one north of the Village of Waunakee and the other near the City of Middleton in the Town of Springfield.

Waunakee

In 2010, Dane County commissioned its first community manure digester located just north of the Village of Waunakee. The digester serves as a centralized collection and processing facility for 35 million gallons per year of manure generated from three nearby farms. The manure is pumped from the farms into three 1.25 million gallon digester tanks where it undergoes anaerobic digestion. After digestion, fiber and solids containing phosphorus are removed through a combination of centrifuges and screw presses. These solids can then be used for bedding or as a fertilizer and soil amendment for area cropland. The liquid fraction, which contains nitrogen and potassium, is then returned to participating farms where it is used as a fertilizer for growing crops.

Another by-product of the manure digester process is the generation of methane gas during anaerobic digestion in the three digester tanks. The gas is collected, cleaned, and transported to the Dane County Renewable Natural Gas Processing and Offloading Station where it is sold and injected into the Interstate Pipeline to be distributed throughout the United States as natural gas for residential and industrial use.  

Middleton

The second digester, located northwest of the City of Middleton, was commissioned in 2013 and collects manure from three nearby farms. Two farms use semi-trucks to transport manure to and from the facility while the third farm is located close enough to the facility to pump manure through a pipe. More than 26 million gallons of manure are processed at the facility each year using screw press and centrifuge technology, similar to the Waunakee community digester, to separate fiber and solids containing phosphorus,. This facility converts the methane gas generated on site directly into more than 2,000 kW of electricity.

This location also includes a 71,000 square foot building and turner for composting the separated solids and a 15 million gallon manure storage facility to store the separated liquids. These structures improve the ability to manage the end products of the digester and to buffer facility malfunctions. The facility is also designed to accommodate further treatment technology including nutrient concentration systems.

June of 2020 marked the completion of additional manure treatment and commissioning of Dane County’s first Nutrient Concentration System at the Middleton community digester. In this system, the liquid fraction of the separated manure is pumped through ultrafiltration and reverse osmosis membranes, oxygenated and adjusted for pH, before being discharged to the North Fork of Pheasant Branch Creek. The system has the capacity to treat up to 100,000 gallons of manure each day while returning as much as 50,000 gallons of clean water back to the stream.

In addition to returning clean water to the environment, the system also reduces the volume and concentrates the nutrients within manure leading to:

• Cost efficiency in hauling manure longer distances to nutrient- deficient crop fields,
• Reduced equipment and truck traffic on local roads,
• Increased flexibility in the timing of nutrient applications as a result of increased storage capacity, and
• Customizable manure nutrient streams to meet a wider variety of cropping systems.

Additional Information:

• 9/15/2020 Dane County Cuts Ribbon on Cutting-Edge Technology that Turns Cow Manure into Drinkable Water

Composting is a naturally occurring process in the environment which recycles organic material and nutrients back into the soil. From an agricultural perspective, the practice has been documented going back thousands of years to prehistoric farming peoples and was commonly used up until the twentieth century when synthetic fertilizers were introduced in order to increase food production for a growing population. However, synthetic fertilizers do not provide the same soil conditioning benefits that compost does. With an increased focus on soil health, as well as a desire to manage nutrients such as phosphorus, composting is coming back as a low technology (though high management) alternative to managing manure while benefiting the soil and reducing nutrient runoff. Making composting work on today’s farms means finding ways to improve handling efficiency and working together to achieve economies of scale.

Over the past few years, Dane County has supported the efforts of Yahara Pride Farms and Endres Berryridge Farms to explore composting as a manure management tool. This includes supporting the purchase of a compost turner and compost spreader to be used in the Mendota Watershed.

The benefits of composting manure and having the right equipment include:

• Reducing the amount of manure spread during high runoff risk periods.
• Insuring adequate heat is generated through regular turning for pathogen reduction.
• Reducing the weight and volume of material to be hauled.
• Reducing soluble phosphorus levels from manure to compost.
• Providing more accurate spreading methods of compost on fields.
• Improving soil organic matter and soil health in crop fields.