Dead Livestock Composting facilities can be built with or without a roof.  The idea is to bury your dead livestock in a compost pile and let the animal deteriorate over time.  The different bins allow you start a new pile while others process.  Most farmers build an extra bin on their facility to store the fresh saw dust.

Composting Mortality Principles and Operation

Basics of Composting

Composting is a natural process where bacteria and fungi decompose organic material in a predominantly aerobic environment. During the composting process, microorganisms break down organic materials into a stable mixture called compost. The compost resembles humus, and is an ideal soil amendment.

Under controlled conditions, composting is usually done in two stages, primary and secondary composting. In the primary stage, a high rate of biological activity results in rapid composting and high temperatures in the pile. This is where most of the organic breakdown occurs. The secondary stage has lower biological activity resulting in slower composting and lower pile temperatures. The secondary stage allows the compost to complete the biological activity and stabilize, also called curing.

While composting occurs naturally, the process requires proper conditions to occur rapidly, minimize odor generation, and prevent nuisance problems. Conditions that must be controlled in the composting process are the material mix, moisture levels, porosity, and temperature.

Material Mix

The proper compost mix requires both carbon and nitrogen at the proper C/N ratio. The proper C/N ratio will result in a composting process that generates little odor, yet offers an environment where microorganisms can flourish. Generally, a C/N ratio that is higher than 25:1 is satisfactory. Most waste materials have a C/N ratio that is too low to compost. In order to compost these materials, amendments that contain a high C/N ratio must be added. Plant materials such as wood chips, sawdust, or straw are ideal amendments for on-farm composting.

Moisture Levels and Porosity

Proper moisture levels and a stable porous structure for the composting mass are two other conditions required in the mixture of materials for proper composting. Like all living things, bacteria need water. To encourage bacterial growth and rapid composting, the mixture should be 50 to 60% moisture. If the mixture feels moist, yet when a handful is squeezed no water drips from it, the mixture probably has adequate moisture.

Second, the bacteria that are encouraged to grow in a compost pile are aerobic (require oxygen). Open spaces must be maintained to provide oxygen and allow air to penetrate and move through the pile. Ideally 35 to 50% of the pile volume would be small open spaces to allow air through the pile.

Temperature

The aerobic bacteria that are of interest for the composting process grow at two temperature ranges: mesophilic bacteria (middle temperature bacteria, up to 100^oF), and thermophilic bacteria (high temperature bacteria, up to 150^oF). As the bacteria begin to break down the materials in the pile, heat is generated and the pile heats up. As the pile warms up, different bacteria will flourish with higher temperatures. As temperature increases, the mass of composting material will be more active and be broken down faster. Above 150^oF, the rate of composting will decrease as bacteria are inactivated, or even destroyed by the excessive temperatures.

As the pile heats up, warm air within the mixture will rise and move out of the pile, while fresh air will be drawn in to replace it. This process exhausts carbon dioxide (CO₂) created in the pile, and maintains an aerobic environment for the bacteria. In addition, temperatures that remain above 130^oF for three days will destroy disease causing bacteria within the pile. Internal pile temperature is an indication of the current biological activity within the mixture and how well the pile is composting.

The composting process will generate and regulate its own temperature. However, to maintain high temperatures, the pile must have some insulation. A layer of inactive material (sawdust or finished compost) placed over the entire pile will insulate the pile. The insulation layer should be a foot or more in depth.

Dead Animal Composting, Reality

Discussions and articles on composting dead animals almost always gravitate towards principles of satisfying the following:

1. Carbon/nitrogen balance
2. Temperature
3. Moisture
4. Porosity, i.e. oxygen level in the pile

Unfortunately, strict application of those standards should only be done when dealing with a consistent, thoroughly mixed pile. The reality is that a pile in which a dead animal is composted is an inconsistent mixture. Therefore, composting a dead animal must be approached in a slightly different way.

Composting dead animals can be visualized as an above-ground burial in a biofilter (primary stage). The compost pile in this case is an inconsistent mixture with a large mass of material (the pig carcass) having a low C/N ratio, a high moisture content and nearly zero porosity. This mass is surrounded by a material (the carbon amendment) with a high C/N ratio, moderate moisture levels, and good porosity.

The decomposition process is anaerobic (lacking oxygen) in and around the animal carcass. But as gasses and liquids are produced and diffuse away from the carcass, they enter an aerobic zone. Here the gasses are trapped in the surrounding material, ingested by the microorganisms, and degraded to CO₂ and H₂O. Thus the surrounding material supports bacteria to form a biological filter, or a biofilter.

With this scenario, turning the pile is to be avoided until the carcass has been decomposed. For swine composting this period is generally three months after the last pig has been placed into the pile. After this time, the compost is moved to a secondary area where it is allowed to cure for an additional 3 months. Moving the pile introduces air back into the pile and mixes the contents of pile.

With larger animals, some bone fragments will remain after completion of the composting process. However, these bone fragments will be quite brittle and pose no health risks or danger to tractor tires or other equipment when land applied.

Data Collection

In order to monitor the composting process, it is necessary to measure and record temperatures of the compost pile. Pathogen kill can be confirmed by monitoring the internal pile temperature. Progress of the pile can also be surveyed from temperature records. Temperatures should be taken at several points near the pigs placed in the pile. Temperature recording can be done easily with a three-foot probe thermometer (1/4 inch probe diameter is recommended). Data recorded should include date, size, number of animals added, and the internal temperature of the pile.

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