Bedding and Waste Management

Scrape and Haul

The waste-management system used in your dairy should influence bedding choices. Dairies that use scrape and haul waste-removal system (no lagoon) can use organic or inorganic bedding with little or no problematic ramifications.

Since scrape and haul systems use standard manure spreaders for land-applying the waste, the incorporation of sand (inorganic) and/or organic bedding materials into the waste stream typically does not cause problems. In fact, the incorporation of inorganic bedding on receiving land areas can be advantageous from a soil structure standpoint.

Flush-Style Lagoon Systems

Large dairies, which are becoming typical in Mississippi, often use flush-type waste removal systems. Flush systems use the hydraulic energy of large quantities of water released quickly to wash manure, waste bedding, and urine into the treatment lagoon. These systems have advantages in that they allow free-stall and holding areas to be kept clean by facilitating multiple clean-outs each day. Flush waste-removal systems necessitate the incorporation of a waste-treatment lagoon.

Lagoon-treatment systems (typically anaerobic in the southeastern United States) use naturally occurring bacteria to break down organic substances into simpler substances and water. In addition, some nitrogen volatilization (loss of nitrogen gas to the air) occurs in most lagoons. Lagoons are designed to treat a specific quantity of organic waste such as manure, urine, and limited quantities of other organic materials such as bedding.

Organic Bedding

Organic bedding materials such as shavings and sawdust will break down in the lagoon, but it may take a long time to do so. These materials sometimes float on the surface of the lagoon and may increase surface crusting on the lagoon. Since chunks of bedding and other large debris will be in the lagoon, you must use specialized irrigation equipment (systems with nozzles large enough to pass bulky solids) to land-apply the lagoon wastewater. If you own or have access to a propeller agitator and solids-handling irrigation equipment, the influx of organic bedding into the lagoon should not cause problems.

If you use standard irrigation equipment for land-applying lagoon wastewater, or if the receiving lagoon is undersized, you can install a manure/solids separator upstream of the lagoon to remove most bedding solids. Inclined-screens, screw presses, hydro-cyclones, and drag screens are typical manure/solid separators.

These systems screen large bulk solids, while allowing liquid and smaller manure solids to pass through. These systems are effective in removing organic bedding and some manure solids. Generally these systems will screen enough solids to allow the use of standard (clean water) irrigation equipment. In addition, research indicates that solids removed by these separators can be reused as animal bedding in some instances. The obvious disadvantage of these systems is moving parts. Any mechanical device placed in an animal-waste stream will require upkeep and maintenance.

Sand Bedding

The tremendous hydraulic energy of flush-type manure-removal systems also transports waste sand bedding to the treatment lagoon. In free-stall barns bedded with sand, virtually all of the sand is eventually washed into the lagoon. This is unfortunate, since lagoons are not capable of breaking down inorganic substances such as sand or limestone.

As inorganic bedding (sand) is flushed into the lagoon, the liquid volume of the lagoon is decreased. Since lagoons are designed on a volumetric basis, the addition of large quantities of sand can, over time, severely reduce the lagoon's ability to function as designed. This can result in lagoon overflows and/or odor levels above those normally associated with a properly functioning lagoon.

Fortunately, sand is easy to remove from the flush water with the addition of a sand trap upstream of the treatment lagoon. A sand trap is nothing more than a concrete sump that allows the velocity of the flush water to be reduced such that the sand settles in the trap. Generally, reducing the flush water velocity to 1 foot per second or less, with a retention time of 1 to 2 minutes, is sufficient to trap sand.

Design your sand traps to allow easy access by front-end or skid-steer loaders (access ramps with 10:1 to 12:1 slope are typically sufficient). Base the size of the sand trap on the size of the herd, number of hours of confinement, and clean-out interval. Clean-out interval is a management decision, but should not exceed 2 weeks. Contact the Natural Resources Conservation Service (NRCS) for specific design information.

Design the outlet from the sand trap to handle the largest surge of flush water from the housing facilities or the flow from a 10-year, 1-hour storm event, whichever is greatest. Do not confuse sand traps with gravitational manure/solids settling basins, which are larger and have a much longer retention time (velocity 1 foot per second maximum, retention time 2 hours or more) than sand traps.

Screen-type manure/solids separators, which are excellent for removing organic bedding materials, typically do not remove significant quantities of sand. Dairy producers using sand bedding should not consider these an an alternative to a well-designed sand trap.