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0307 PD: Settling issues with sand-laden manure

Published on 06 March 2007

Leon Weaver hopes new changes to his manure management system cut in half the time and management it currently takes to manage his dairy’s 40 million gallons of manure. Weaver, an owner of Bridgewater Dairy in Montpelier, Ohio, jokingly admits that if his new McLanahan sand separator system works using manure press effluent as wash water, he’ll use the extra time and money he’d otherwise spend managing manure to go fishing.

“A more serious answer to how it will help is that as our system becomes stabilized and repeatable then it becomes more and more amenable for someone other than myself, the owner, to be personally involved in the management,” Weaver says.

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Seven years ago, Bridgewater Dairy had 2,500 cows all bedded on sand. The dairy flushed its parlors and holding pens, trapping that effluent which had low solids, phosphorus and nitrogen levels in a separate lagoon. A central pivot system periodically emptied the lagoon on 300 acres located near the dairy. The rest of the dairy’s manure was scraped into large concrete-lined pits, settling the manure into sand-laden manure and liquid solids. The liquid solids were periodically pumped out and hauled off in Honey Wagons. The rest of the sand-laden manure was hauled away in Knight spreaders.

In the fall of 2005, the dairy expanded from 2,500 cows to 3,900 cows. Weaver knew the dairy couldn’t just add more cows bedded on sand and increase the amount of sand-laden manure going onto his fields each year. So he began consider alternative manure and bedding systems.

“We felt that we needed to look at alternatives to sand bedding as a way to obtain types of manure that could be moved to the field in additional and more efficient ways,” Weaver says.

Eight years ago, the dairy purchased sand for about $4 per ton. Today, the dairy pays more than $8 per ton. Weaver didn’t want to keep paying for sand that would eventually end up on his fields. He knew some other changes for the dairy’s expanded herd would be needed.

So the dairy started bedding some cows on sawdust. In addition, the dairy purchased a FAN manure press and drum dryer. The drum dryer dried enough separated manure solids to bed 1,000 of the dairy’s cows. The remaining manure solids are stacked and hauled to fields for application.

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Weaver and the other dairy managers weren’t convinced they could re-bed with stacks of pressed manure solids that hadn’t gone through the drum dryer system.

“We don’t see the data out there to support the concept of bedding cows with pressed manure solids that haven’t been treated in any way – what some people call green manure.”

Weaver says shortly after the expansion, the dairy began researching digesters.

“The economics of a digester can be made attractive if you say the digester alone would allow you to eliminate sand bedding,” Weaver says.

Between treated manure and sand, Weaver says he’s not convinced which is a better bedding from a production and cow health standpoint. He’d like to give digester technology a bit more time to mature before installing one. Five years’ time might help to provide more answers, he says. But while Weaver was researching digesters, he became aware of another option.

Weaver heard of a few other dairies using effluent from manure presses as wash water for a McLanahan sand separator to separate sand-laden manure. Weaver researched the option last summer and decided it would work for his dairy. He hopes to have equipment installed and be running the system by the end of spring.

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“What it will do is reduce to near zero the amount of sand-laden manure that I have,” Weaver says.

The manure press effluent, he says, should separate the sand efficiently, if the liquid remains at or below 5 percent solids content. The dairy may have to add some of its current flush water back to the effluent or install another treatment system to achieve a workable solids content, but Weaver still believes the system won’t increase the dairy’s total gallons of manure produced.

“What we will accomplish with this new system is that all of the liquid will be available to our drag lines,” Weaver says. “All of that sand-laden portion will be devoid of sand, so we won’t have to scoop it up and haul it out. In fact, we won’t have to haul it out at all.”

The system should reduce the number of manure loads hauled over local roads by up to half. It should also decrease odor when applying on fields, as a greater amount of the manure will be in a liquid form and capable of being injected. In short, the system gives the dairy more flexibility with five forms of manure instead of three, including solids, pressed manure solids, draglines, liquids with some solids and flush water. That flexibility will make it easier to get manure onto the fields given the area’s climate and weather, which Weaver says allows for about 100 days of manure application each year.

“The advantage of getting away from the sand-laden manure is that it’s the hardest material to transport. It’s also the one material that when we put into the fields in the spring takes a long time to dry down,” Weaver says.

Weaver estimates the new system will recapture 95 percent of the dairy’s sand, decreasing significantly the amount of sand the dairy purchases and eliminating the current two semi loads of sand per day that end up on his fields. He believes the system will be able to handle recapturing sand bedding for 2,500 to 3,000 of his cows.

“We’re just going to have to see how many cows we can get through the system,” Weaver says. “We anticipate that there’ll be some fine-tuning and some capital investments to make the system work.”

Throughout the decision-making process, Weaver spoke with other dairymen, product vendors and an engineering firm, Sheff & Sons of Eaton Rapids, Michigan.

“If you own several hundred cows, you probably are the expert because you’ve done it,” Weaver says. “It’s a lot harder in reality than it is on paper. It’s about knowing crop rotations, weather, traffic patterns, the timing of the neighbor’s barbecue, prevailing winds. Someone on your dairy is probably already the expert about moving manure around and applying it to fields.”

Weaver says each dairy will need outside technical assistance, but as nutrient management decisions and capital investments are being made, the on-farm expert needs to be involved in making decisions. He also cautions dairies considering new nutrient management systems or equipment investments take into consideration that future regulations will probably require more record keeping and application limits based on phosphorus or nitrogen levels per acre.

“I’ve known of dairies that have put in sand separator systems without any concern for expanded water volume and higher phosphorus content in the water because where they were located that wasn’t an issue,” Weaver says. “But by the time their concrete dried, it was starting to become a concern.”

As preparations for installation begin, Weaver jokingly says he looks out the window and hopes it will work. However, he honestly says the system should reduce manure management efforts without increasing cost.

“If this plays out, it will take less of my personal involvement to manage neighbor relations, manure spills or road damage,” Weaver says. “It’s more field friendly, too.” PD

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