Five McLanahan sand separators (four shown) pull the manure up their 36"-diameter augers to reclaim coarse sand particles.
The Disneyland of Manure. The Manure Factory. Manure Mecca. Call it what you will, but the manure processing facility at the Rosendale Dairy is a jaw-dropping, $6 million–plus operation that has to be seen to be believed. Yes, it’s that impressive.
With manure flowing into the facility from 8,000 cows 24/7, it has to be. That’s especially true for Wisconsin’s largest single-site dairy, which faced bitter local opposition when it was first proposed some five years ago.
In operation since November 2008, the facility is living up to its promise of being an environmentally responsible neighbor while providing work for more than 80 employees and buying feed from 18 local growers.
Milk Source, the largest dairy producer in the state, owns the facility and milks 17,500 cows on three sites. Rosendale Dairy, near the village of Pickett in east central Wisconsin, is its largest. A fourth facility, with 4,300 cows, is being planned for the Central Sands region of the state.
The manure processing facility at Rosendale was designed to allow sand-bedded stalls to optimize cow comfort in the cross-ventilated barn. The extraordinary effort to process the manure involved "building a facility to reduce odors and capture and utilize manure nutrients without having to land-apply sand-laden manure," says Bill Eberle, operations manager.
The system not only reclaims 90% to 95% of the sand, it also segregates manure solids from the waste stream. One load of separated manure solids is equal to four loads of processed "tea water." In turn, solids separation reduces manure hauling and wear, tear and traffic on local roads. That’s not insignificant, since Rosendale reaches out as far as 10 miles for
Sand-laden manure is scraped from freestall alleys three times a day, each time cows are milked. It is scraped into cross augers, which carry it to the collection pit in the manure processing building. The building, 200'x250', is insulated and heated for year-round operation.
From the collection pit, five McLanahan sand separators pull the manure up their 36"-diameter
augers to reclaim coarse sand particles, which account for roughly two-thirds of the reclaimed sand.
From the separator screws, the remaining liquid, solids and sand moves to three McLanahan Hydro Cyclones, which remove finer particles of sand through high-speed centrifuge action. In total, the two-step process removes between 90% and 95% of the sand.
The reclaimed sand is then moved outside by front-end loader to a 170'x429' concrete pad with concrete walls. Here, sand is allowed to seep moisture for three to four weeks before it is re-used.
"A dairy our size would normally use about sixty 20-ton truckloads of new sand per week," says Bill Harke, public relations specialist with Milk Source. "We now normally bring in less than six truckloads per week of new sand."
Such re-use saves $700,000 to $800,000 annually in new sand purchases for an 8,000-cow dairy, based on a cost of $12 per ton.
"It really isn’t about saving money but more about environment and neighbor relations," Harke adds. "Savings in sand costs are used for the system itself. By separating the sand—which is a higher grade than we would use if we were not separating it—we can reduce truck runs as well as clean up the manure/fertilizer enough that we can use the new underground pipe system we have.
"That allows us to reach about 1,000 acres and reduce about 6,000 loads per year that normally would go by truck," Harke says. "In addition, the new pipeline proposed for 2011 will cover 2,000 acres and reduce truckloads by 10,000."
Back in the processing building, the remaining manure solids and liquid are pushed through four FAN squeeze press separators to remove coarse manure fibers from the mix. The remaining "tea water" slurry still contains 4½% to 5% solids.
The slurry is then pumped to two large dissolved air flotation (DAF) tanks to remove additional solids. In the DAF system, polymer is added while tiny air bubbles are injected into the solution. The manure solids attach themselves to the bubbles, which float solids to the top of the system, where they are harvested over a weir.
The DAF float material is spun through a horizontal centrifuge to remove much of the remaining solids. These solids are then incorporated with the other manure solids removed by the FAN presses.
"The solids are stacked, hauled on semis during spreading season and land-applied. The material has a 3-1-3 nutrient analysis per ton," Harke says. "Some solids may go as far as 25 miles to growers with a specific fertilizer need. We have about twice as many acre requests as we have manure/fertilizer available."
The final manure liquid, or tea water, is pumped out to a three-stage lagoon system. The nutrient analysis is typically 9-2-14, and it still contains 3% to 3½% solids.
The three-stage lagoon system—11 million gallons, 27 million gallons and 31 million gallons—is designed to further settle out the remaining solids. Settling and denitrification off the uncovered lagoons brings the nutrient analysis down to 4-1-7 in the third-stage lagoon. (Before any processing, the typical analysis is 10-4-20.)
But Eberle can pull tea water from any of the three lagoons, depending on the crop he’s fertilizing. "If a grower is planting wheat and needs only 50 units of nitrogen, we would apply tea water from waste storage facility [WSF] 3. A grower fertilizing for corn might need 120 units and would likely get the more nutrient-dense WSF 1 tea water," he explains.
The low-solids tea water will allow Rosendale Dairy to pump the liquid to fields four to five miles away. The Wisconsin Department of Natural Resources recently permitted the facility to do so, using 10" pipe.
The solids separation adds one more huge benefit: Reduced phosphorus loading through the liquid manure.
"On most of our soils, nitrogen rules impact spreading rates before phosphorus [P]," Eberle says. "But given the system we now have, which lowers the P in our manure, we should never run into our P loading limits."
- February 2011