Design considerations

Solid waste storage ponds and structures must be designed correctly to ensure desired performance and safety. Considerations include materials selection, control of runoff and seepage, necessary storage capacity, and proper design of structural components, such as sidewalls, floors, and roofs.

The primary materials used in constructing timber structures for solids storage are pressure-treated or rot-resistant wood and reinforced concrete. These materials are suitable for long-term exposure to animal waste without rapid deterioration. Structural grade steel is also used, but it corrodes and must be protected against corrosion or be periodically replaced. Similarly, high quality and protected metal fasteners must be used with timber structures to reduce corrosion problems.

Seepage and runoff, which frequently occur from manure stacks must be controlled to prevent access into surface and ground water. One method of control is to channel any seepage into a storage pond. At the same time uncontaminated runoff, such as that from the roof and outside the animal housing and lot area, should be diverted around the site.

Concrete ramps are used to gain access to solid manure storage areas. Ramps and floors of solid manure storage structures need to be designed so that handling equipment can be safely operated. Ramp slopes of 8 to 1 (horizontal to vertical) or flatter are considered safe. Slopes steeper than this are difficult to negotiate. Concrete pavement for ramps and storage units should be rough finished to aid in traction. Ramps need to be wide enough that equipment can be safely backed and maneuvered.

Chapter 10 Agricultural Waste Management System Part 651

Component Design

Agricultural Waste Management

Field Handbook

Factors to consider in the design of storage facilities

where:

for solids include type, number and size of animals,

VMD

= volume of manure production for animal

number of days storage desired, and the amount of

type for storage period, ft3

bedding that will be added to the manure. Equation

AU

= number of 1,000 pound animal units by

10-1 can be used to calculate the manure storage

animal type

volume:

DVM

= daily volume of manure production for

VMD = AU x DVM x D [10-1]

animal type, ft3ML7day

D

= Number of days in storage period

Figure 10-12 Solid manure stacking facilities

Runoff to storage

Barn cleaner to spreader or tractor stacking

Runoff to storage

Barn cleaner to spreader or tractor stacking

Timber or concrete bucking wall storage

To storage and/or spreader from elevator stacker

Timber or concrete bucking wall storage

To storage and/or spreader from elevator stacker

Figure lO-l3 Roofed solid manure storage

Timber walls Concrete walls with end access with end access

Timber walls Concrete walls with end access with end access

Timber walls with side access

The bedding volume to be stored can be computed using:

where:

FR = volumetric void ratio (ASAE 1982) (values range from 0.3 to 0.5) WB = weight of bedding used for animal type, lb/ AU/day

BUW = bedding unit weight, lb/ft3

Using the recommended volumetric void ratio of 0.5, the equation becomes:

Characteristics of manure and bedding are described in chapter 4. Other values may be available locally or from the farmer or rancher.

Allowance must be made for the accumulation of precipitation that may fall directly into the storage. Contaminated runoff should be handled separately from a solid manure storage facility. Uncontaminated runoff should be diverted from the storage unit.

4. The number of days in storage is entered on line 5. The manure volume (line 7) is calculated using equation 10-1. Add the calculated manure volume for each animal type (VMD) and enter the sum (TVM) on line 8.

Wastewater volume—Because this design example involves a waste stacking facility, it would not be appropriate to include wastewater in the storage facility. Therefore, lines 9, 10, and 11 are not involved in estimating the waste volume for this example.

Bedding volume—The weight of bedding used daily per animal unit for each animal type is entered on line 12. The bedding unit weight, which may be taken from table 4-4, is entered on line 13. The bedding volume for each animal type for the storage period is calculated using equation 10-2 and entered on line 14. The total bedding volume (TBV) is the sum of the bedding volume for all animal types. Sum the calculated bedding volume (BV) for each animal type and enter it on line 15.

Waste volume—The total waste volume (WV) (line 16) is the sum of the total manure production (TVM) and the total bedding volume (TBV). The storage width and depth are known, so the length (line 17) is calculated using the equation:

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