Disposal pits, trench burial, incineration, and rendering are common methods for disposing of the mortality. Recently, composting has been added to the list of available disposal options.

The best method for a particular farm depends on a number of factors, such as cost, ability to meet design requirements, and suitability for the flock size and management system. For example, burial on the farm and placement in disposal pits are poor options in areas with a high water table or shallow rock formation because it would be difficult to meet design requirements. Landfill disposal is a poor option in most areas of the state because of new regulations and limited landfill capacity.

This publication presents information on mortality disposal regulations and on the design, construction, and management of a mortality composter. Information on mortality, disposal methods other than composting is provided in Poultry Science and Technology Guide No. 19, Proper Disposal of Dead Poultry.

Composting techniques have recently been adapted to provide sanitary degradation of poultry carcasses. In the composting process, organic materials such as dead poultry and litter are decomposed by the natural action of microorganisms. Whole turkeys and chickens, except for a few bone fragments and feathers, can be degraded within a few weeks. The composting process subjects the carcasses to temperatures high enough to destroy pathogenic bacteria normally associated with poultry disease, making the composting system biosecure. The resulting compost has chemical and physical characteristics similar to poultry litter and can be used as crop fertilizer.

Poultry composters are currently being approved on a permit basis to assure proper design and attention to environmental considerations. Poultry producers interested in constructing a mortality composter should send a written request for a permit to the state veterinarian. The request should provide information on the composter design, flock size and type, grid number and county of the farm, producer's address, location of the composter (marked on a topographical map), and name of the contracting company if the flock is under contract.

Disposal of dead birds is also regulated by the Division of Environmental Management, an agency of the North Carolina Department of Natural Resources and Community Development, whose objective is to protect air and water quality.

Farm mortality records can be used as a basis for mortality calculations, particularly in cases where marketing programs or other factors make weights different from normal industry standards. Table 1 shows the average mortality and weights for various types of poultry. These data can be used with the information in Table 2 to estimate the size of the composter required. It is advisable to design a safety factor into the composter to accommodate unusually high mortality rates that may occur at times. For example, multiplying the mortality in pounds per day by 1.5 would accommodate 50 percent higher mortality than normal. Emergency capacity should also be designed into the storage section.

Table 1. Anticipated Mortality for Various Types of Poultry.

Table 2. Estimated Primary and Secondary Bin Capacity for Mortality Composting Per 1,000 Birds and Standard Size Units for Various Types of Poultry.

Allowing 2.0 cubic feet for combined primary and secondary composter volume per pound of bird mortality, the required composter capacity in cubic feet per thousand birds in the flock is estimated in Table 2. Based on these estimates, the number of 5-foot by 5-foot by 8-foot bins for standard sizes of North Carolina poultry units is given in the far right column of Table 2. Storage capacity for the compost that has gone through two heat cycles as well as storage for litter, straw, and other supplies should be designed as part of the facility. Storage space must be provided to allow the compost to go through a third heating. The required volume will vary greatly, depending on how often the compost will be utilized and removed from storage, but it is recommended that space be provided for storing at least a three-month supply. The formulas and an example of how to calculate composter size are given in the box at the right.

Figure A. Formulas and Example Calculations for Sizing of Mortality Composters.

A few construction features are essential to ensuring that the eomposting process will work consistently and to assure compatibility with environmental and nuisance concerns.

• Roof. A roof is necessary to prevent rainwater from reaching the compost because moisture promotes fly breeding and creates unsatisfactory composting conditions. The roof will also prevent water runoff from the compost, thus protecting groundwater and surface water. A roof overhang of 2 feet with "uttering is recommended if compost bins are located at the sides of the building.
• Foundation and Floor. An impervious weight-bearing foundation of a material such as concrete is critical for an all-weather operation. Concrete also makes it easier to sweep up spilled litter ingredients and compost, which is important in preventing these materials from entering runoff water during rains. A concrete floor also assists in rodent control.
• Building Materials. Pressure-treated lumber should be used for bin constrcetion because it resists the rotting process that the eomposting activity encourages.

Figures 1, 2, and 3 are layout drawings of composters constructed as freestanding units or as an extension of an existing building. Copies of these drawings and material listings are available from county Cooperative Extension Centers. As discussed earlier, the size of the composting building should be based on the size and number of composting bins needed. The cost of materials for composters varies considerably. Materials to construct the composter shown in Figure 1, which is sized for a 25,000-turkey operation, are estimated to cost $3,500.

Figure 1a. Litter storage shed with compost bins (isometric view).

Figure 1b. Litter storage shed with compost bins (end view).

Figure 2. Delaware two-stage composter.

Composting bins constructed inside the composting building must meet certain requirements to facilitate eomposting and to make it easy to turn the compost. The primary and secondary bins should be 5 feet high. Composter depth should not exceed 6 feet. The width of the compost bins should match the width of the compost-handling equipment but should not exceed 8 feet. Smaller bins make the eomposting process more efficient, particularly for mortality during the early part of the production cycle. The smallest bin recommended measures 3 feet in all dimensions.

Table 3. Recipe for Mortality Composting

Material that has gone through the compost cycle can be substituted in part for the litter, but a carbon source (such as straw or peanut hulls) must be added continu- ously to keep the carbon-to-nitrogen ratio at the optimum level.

Figure 3. Maryland free-standing, two-stage composter.

Figure 4. Compost Layering.

Table 4. Average Nutrient Analysis for Poultry Mortality Compost and Poultry Litter

Much like the daily mortality pickup and disposal to which poultry growers are accustomed, filling the composter is also a daily routine. Once the daily mortality has been picked up, it is weighed, and the other ingredients are weighed and layered in the proper proportions. After the grower gains experience with these weight measurements, the operations can be performed on the basis of volume using buckets and a front-end loader or other equipment. The activity takes one person about 20 minutes a day for a broiler grower with a 100,000-bird capacity or a turkey grower with a brooding capacity of 26,000.

Figure 5 shows the temperature cycle of a turkey composter. Management of the composter includes monitoring the temperature cycle to determine when to turn the compost. The temperature can be measured with a 36-inch probe thermometer. When the temperature during the first heating cycle has reached its peak and has dropped for several consecutive days (for a total drop of approximately 20 degreesF), it is time to transfer and aerate the compost. After a similar temperature sequence during the second heating cycle, the compost should again be turned and aerated. It should then be transferred to a storage area. The compost is ready to spread on fields after going through three heating cycles (including a heating cycle during storage). If it is desirable to break down the ingredients further or to have a more stable compost, the compost can be aerated again in storage; it will go through the heating cycle each time it is aerated.

Figure 5. Temperature profile of a typical turkey mortality composter.

Flies and carrion beetles serve as useful indicators of the overall "health" of the compost. When large numbers of these insects are present, it is likely that the material is not composting properly. Excessive moisture or poorly balanced carbon-to-nitrogen ratios should be suspected in such cases. Once the problem has been identified and corrected, insects will no longer find the compost pile attractive.

In rare cases, insects and other pests can become a problem when compost is spread in the field. This situation generally occurs only if the compost is applied at excessive rates without incorporation and then absorbs enough water to promote fly breeding or if it is applied before the bird carcasses have completely decomposed.

Flies associated with bird mortality composters will always be present at levels similar to the normal back-ground population for the farm. A well-designed and well-managed composter will not contribute to either the number or species of flies already present in the area. The same can be said for other insects and animal pests that may be found in or around composters. The follow- ing suggestions will minimize or eliminate pest problems.

• Design and build the composter in a way that will minimize moisture problems.
• Locate the composter well away from tree lines, ditches, dumps, and areas of heavy brush to discourage easy access by vertebrate pests.
• Construct the bins to be reasonably tight (that is, leave no gaps by which animals can gain access). Bin lids will aid in keeping out larger animal pests, such as raccoons and dogs.
• Keep the site clean. Mow weeds and grass regularly. Keep at least a 50-foot perimeter clear around the site. DO NOT stockpile lumber or store old equipment on or near the site. If replacement lumber or bin planking is kept on the site, it should be stored on racks at least 18 inches above the ground.
• Be observant. Rats and mice often burrow along the edges of concrete pads and into compost bins or into compost that is being held for later use. Bait all rat burrows as soon as they are spotted; place baiting stations or bait bars for mice.
• Follow the 6-inch rule. Be sure that the top layer of birds is covered by at least 6 inches of litter or compost. Place dead birds 6 inches away from the sides of the bin as well. Cover partially decomposed birds with 6 inches of compost when the pile is turned.
• Follow the recommended composting proportions to maintain the proper moisture content and carbon-to-nitrogen ratio for efficient composting.

For more information on insects related to composting see Cooperative Extension Service publication AG-474, Poultry Pest Management.