Ohio State University Extension Fact Sheet

Ohio State University Fact Sheet

Food, Agricultural and Biological Engineering

590 Woody Hayes Dr., Columbus, Ohio 43210


Swine Composting
Facility Design

AEX-713-97

Terry Mescher
Ken Wolfe
Steve Foster
Rick Stowell

Changes in the swine industry and larger production facilities have created concern over the disposal of swine mortalities. Traditionally, swine producers had three methods of disposal: burial, incineration, and rendering. Due to concerns of ground water pollution associated with burial, economic and environmental issues of incineration, and the disappearance of rendering services to rural areas, new methods for swine disposal must be developed. Composting swine mortality is a method that has recently been developed and successfully practiced.

Composting offers an economical and environmentally friendly way to dispose of swine mortalities, and recycle nutrients contained in the animal carcass. Composting is a natural process in which the animal carcass is degraded by bacteria in such a way as to avoid air and water pollution.

The process of composting dead animals uses bacteria and fungi to decompose the carcass in an aerobic environment. By providing oxygen, the microbes are able to decompose the animal without the production of objectionable odors and gasses. Composting, when done properly, destroys disease causing bacteria and viruses. In addition, fly and insect production is not a problem, and scavenging animals are eliminated from the composting site.

Ohio's Swine Composting Development Team has identified objectives for composting swine mortalities in Ohio. These objectives are:

  1. Protect ground and surface waters from pollution.
  2. Reduce or eliminate the risk of the spread of disease.
  3. Eliminate nuisances such as flies, vermin, and scavenging animals.
  4. Maintain air quality.

Proper design and sizing of the composting facility is required to properly complete the composting process. The following is a discussion of the design and sizing requirements for swine composting facilities. Included in this fact sheet are worksheets to help size and design composting facilities for any size swine operation.

Design

Two basic composting facility designs can be used for swine mortalities: the static pile (or windrow) and composting bins. Both of these designs work well. However, initial cost and management requirements for the two differ.

The static pile (Figure 1) design allows the composting process to take place in a windrow or a pile. Static piles use a constructed pad on which windrows are built. After the last pig is placed in the windrow, the pile is allowed to compost for a minimum of 90 days. At the end of this primary composting period, the pile is moved to a secondary area where it completes another 90-day composting period. Moving the pile mixes and aerates the compost before beginning the secondary stage. After the windrow is moved to the secondary area, a new primary compost pile can be constructed. In this management system, piles are continually being built and moved onto the composting pad.

Figure 1. Static Pile layout for composting swine mortality.

Figure 1a) Windrow Cross Section

Figure 1b) Composting Pad Layout

Site preparation and runoff control structures are required for a static pile composting system. Runoff from the compost pile may contain organic compounds that could degrade the quality of nearby ground or surface water. To avoid this, all runoff from the composting facility must be collected and treated through a filter strip or infiltration area. In addition, all clean surface water must be diverted away from the composting area. This will minimize the volume of water that must be treated or stored and keep the composting area dry.

Initial costs for a static pile, or windrow composting facility should be less compared to the bin system. However, there will be more intense management demands with the windrow composting facility. Windrows are not protected from cold weather, rain, or wind. This exposes the processes occurring inside the pile to more adverse weather conditions, which may affect the operation of the pile.

Bins can also be used to compost dead swine (Figure 2). Bins consist of a concrete floor with concrete or treated lumber walls. A roof is highly recommended with the use of bins. Management practices for composting swine in bins are much the same as using a static pile. After a primary bin is filled, it is allowed to compost for 90 days. Then the contents of the primary bin are moved to a secondary composting bin where it continues the process for another 90 days. The secondary bin will most often be identical in size and construction. Once the primary bin is empty, it can be filled again.

Figure 2. Bin system for composting swine mortality.

Figure 2a) Bin Layout, Top View

Figure 2b) Bin Isometric

Leachate and runoff concerns are largely eliminated when using the bin system with a roof. A properly managed bin composter will not generate leachate from the pile. This eliminates the need to have a runoff storage or filter area. However, clean water needs to be diverted away from the composting facility. Locate the bins on high ground to meet this need. Bin systems without roofs require a filter strip or infiltration area.

Bin composting also offers aesthetic advantages over a static pile. Bin composting appears to be more controlled and blocks the view of the compost from a distance. This may be important when neighbors are close, or in areas where public perception is important.

While the use of bins to compost will require less intense management, there will be a larger initial investment. When covered with a roof, bins offer protection from rain as well as surface runoff. This greatly reduces the chances of runoff from the compost and adverse affects of weather on the pile's operation. As the resulting facility is less vulnerable to the weather, there are no collection or treatment structures required for runoff control and the system is simpler to manage.

Sizing

Sizing of the composting facility is critical for successful operation. Composting facilities that are undersized will force material through the facility before the process is complete. This can lead to problems with odor and flies. Proper sizing will make the management and operation of the composting process easier.

Sizing for composting facilities depends on the amount of material to be composted on a daily basis. Actual death loss data from the operation should be used in sizing the composting facilities whenever possible. To help design and size composting facilities for individual farms, example worksheets have been completed on the following pages. Sizing of a composting facility is a fairly simple process. The steps to to follow are discussed below (Table 1). The following worksheets are a step-by-step guide to size composting facilities. Use these worksheets to determine the size of the composting area for a windrow system, or the size and number of bins required for a given operation.

Table 1. Design process Review and Explanation.
StepDescription
A

Calculate amount of material to be composted. Use farm records if possible or Table 1 of Worksheet 1.

  1. Pounds of dead swine produced from operations in one year.
  2. Average daily loss in pounds per day which must be composted. Determine the annual sawdust requirements for the farm (Worksheet 2 or 3, step 5).

B

Calculate required volume for the composting facilities. Use Worksheet 2 or 3, step 1. Multiply the average pounds loss per day (from Worksheet 1) by 20. Results are:

  1. Required volume (ft3) for primary composting area.
  2. Required volume (ft3) for the secondary composting area (Note: size and construction of primary and secondary bins are generally identical.)

C

Calculate the dimensions of the compost facility pad, or the bin dimensions and number of bins. Use steps 2-4 in Worksheet 2 or 3. Note the sizing procedures differ between the two composting systems.



Swine Composting Facility Design Worksheets

Worksheet 1. Swine Death Loss Calculations and Sawdust Needs
Worksheet 1(PDF). Swine Death Loss Calculations and Sawdust Needs (Example of Worksheet 1 completed)
Worksheet 2. Swine Composting Worksheet For Bins
Worksheet 2(PDF). Swine Composting Worksheet For Bins (Example of Worksheet 2 completed)
Worksheet 3. Swine Composting Worksheet For Windrows
Worksheet 3(PDF). Swine Composting Worksheet For Windrows (Example of Worksheet 3 completed)


All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.

TDD No. 800-589-8292 (Ohio only) or 614-292-6181



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