DECANTING MANURE BEFORE IT ENTERS LAGOON

REAPS ECONOMIC, ENVIRONMENTAL BENEFITS

(July 24, 2007) – Decanting – the process of separating nutrients in solids from liquids in slurry with a Slurrystore before it enters a lagoon – is gaining steam as a few innovative producers and universities begin to realize its potential economic and environmental benefits.
            Decanting slurry captures more nutrients, allows for more consistent nutrient application to fields, saves on fertilizer costs and cleans up lagoon water to reduce odor and lessen environmental contamination in the event of a leak. And with more stringent environmental regulations on the horizon as homes move closer to agricultural operations and groundwater concerns rise, decanting is one solution that lessens environmental risk while continuing use of a lagoon system.
At the 200-cow Purdue University Dairy Facility, decanting solids out of slurry before it goes into a lagoon is planned to be looked at experimentally for its economic and environmental benefits. And similar systems, all using a Slurrystore to decant solids from slurry, are already in use at a few swine operations with great success.
            Although more research needs to be completed, Purdue aims to reduce the load of solids in the existing lagoons and eventually make the lagoons more functional by decanting solids from slurry into a separate holding container. This container, a Slurrystore®, also allows for better agitation and mixing for greater consistency of nutrients before soil application, says Dr. Al Sutton, Professor of Animal Nutrition and Nutrient Management at Purdue University’s Department of Animal Sciences.
            Presently, the Purdue dairy facility runs lagoon effluent through a center pivot irrigation system onto approximately 500 acres from a two-stage lagoon, with a capacity of approximately 6 million gallons of liquid. Over 20 years, and K soil test levels have built up on the cropland receiving the lagoon effluent.
            Prior to installation of the Slurrystore, the university removed coarse manure-solids with a liquid/solid separator. Liquid plus fine solids went into the first stage of a two-stage lagoon system from a 50,000 gallon-per-day flush system in the free stall area. Liquid from the second stage is used for flushing the free stall barn. When nearly full, the second stage liquid is then land-applied via the center-pivot system. Sludge, extremely difficult to agitate and remove from the first stage, has built up with storage capacity being significantly reduced, Dr. Sutton says. In addition, when pumping the second stage, the facility would run out of flush water and have to add fresh water.
            By decanting, Purdue hopes to correct this shortcoming and send only the cleanest water possible to the lagoon, capture nutrient-rich solids in the Slurrystore and glean a substantial savings in purchased fertilizer costs.
            “We’re just beginning to work with the Slurrystore and do not have an analysis yet,” Dr. Sutton says.
            The Slurrystore structure at Purdue was sold and constructed by Hoosier Harvestore the local authorized Slurrystore dealer.
            Farm Coordinator Larry Underwood says “the plan is that decanting will settle some of the fine particles out of the waste stream that the liquid/solid separator cannot remove. With the 100-foot diameter Slurrystore and agitation equipment located between the liquid/solid separator and the first stage of the lagoon, the finer solids in the tank are settling out and can be removed as thick slurry. This slurry will be hauled with a tanker wagon and knifed into soils needing P and K. In the past, it was extremely difficult to agitate the lagoon.”
            With decanting, “We can now pump much cleaner liquid from the second stage and land apply it through the irrigation system without a build up of nutrients,” Underwood says. “A big problem we faced was that the thicker material could plug the pivot nozzles. With the addition of the Slurrystore, we can handle nutrients more efficiently with less hassle.”