There are several different ways to dispose of animal mortalities in a timely manner, both on and off farm.
Which method farmers choose depends on the suitability to the production system, timeliness, biosecurity and potential impact on the environment.
According to the Bodies of Dead Animals Act (BODA) from the Michigan Department of Agriculture and Rural Development, any mortality must be disposed of within 24 hours unless there is a cold storage option, which allows dead animals to be stored for a maximum of seven days at a temperature of 40 degrees F or less. Animals can be frozen up to 30 days if the temperature of storage is below 9 degrees.
After temporary storage, the carcasses will need to be disposed of using one of these options:
• Burial. The first option is burial, which has been commonly used in the past and more recently on small livestock operations. When considering the timeliness of this mortality option, be aware of the weather. Frozen and muddy ground can be difficult to construct a proper grave. So, if possible, it is best to plan burial during warm and dry weather.
The biosecurity risks for burial are relatively low, but farmers should consider the distance from production barns. Environmentally, BODA parameters for burial require that the entire animal carcass is buried at least 2 feet below the surface of the ground and can only be buried with the landowner’s permission.
Furthermore, the carcasses should not come into contact with any bodies of water, which should be assessed if there is a high-water table. This is because every 1,000 pounds of carcass contains about 22 pounds of nitrogen.
It is also required that burial sites are located at least 200 feet from any well. Two types of burial are allowed in the state of Michigan, individual graves and common graves.
For individual graves, no more than 100 per acre are allowed, with a combined total of 5 tons per acre. These graves must be separated by at least 2.5 feet.
For common graves, the weight of all animal carcasses may not exceed 5,000 pounds per acre, and if there is more than one common grave per acre, they must be separated by at least 100 feet.
• Composting. The second option for mortality disposal is composting. The articles, Carcass composting: A mortality management option for Michigan equine owners, E3168, and Carcass composting: A guide to mortality management on Michigan cattle farms, E3197, explain the details of properly composting mortalities on farm.
Bin and windrow composting are two constructed methods for mortality composting. It is important to realize that timeliness of this option can be dependent on the capacity of the pile or bin being used, so creating a windrow compost pile can help alleviate space concerns.
Composting can aid in destroying pathogens that cause disease if the compost pile reaches an internal temperature of greater than 130 degrees for three days, which allows for an additional measure of biosecurity.
To achieve this temperature, the proper carbon-to-nitrogen ratio is needed, and the pile must be turned to allow the outer edges of the pile to be effectively composted. It is ideal to protect the pile from clean water, such as rainwater, by covering the pile to divert the water away. To lessen the impact of surface water runoff and leachates reaching groundwater, a concrete platform can be utilized.
• Incineration. A third option for mortality disposal is incineration or burning of the carcass. Similar to composting, if more mortalities occur than an incinerator can handle, this could delay the process of proper mortality disposal. Consideration may need to be given to composting the carcasses or having a licensed dead animal dealer come in to dispose of it at a rendering plant.
Because of the heat associated with incineration, the biosecurity risk of pathogens decreases. But if the incinerator is overloaded, the operating temperature may not reach the desired level and can allow for pathogen escape.
It is also important to choose a location in which the burning does not cause a public nuisance and follows local ordinances. Additionally, an air use permit is required from the Air Quality Division of the Michigan Department of Environmental Quality. Any residue left from burning the carcass must be either buried according to the BODA standards previously outlined, land-applied at agronomic rates, or disposed of in a landfill licensed by MDEQ.
• Rendering. If a mortality is to be sent for rendering, the rendering services being utilized must be a licensed dead animal dealer. Rendering availability is based on volume and, therefore, used more often by large farms. Proximity to the rendering plant should also be considered. If a small farm has a temporary cold storage, rendering may be economically justifiable.
Biosecurity can become a concern, in some cases, as these trucks move from farm to farm. This makes keeping rendering trucks away from production and livestock barns important. Other than possible odor complaints near the rendering plant, there is very little concern with this option environmentally.
• Landfill. Landfills should be contacted ahead of time to ensure they accept dead animals, as some do not. Distance to the landfill will be an economic factor to consider. Care should be taken when transporting the carcass off the farm and to the landfill due to the biosecurity risk. Although quite convenient, this option is more prohibitive when considering possible breaches in biosecurity.
Michigan State University Extension recognizes and understands that the method of mortality disposal will differ between farm operations and encourages the use of sound practices with all disposal options.
Whether burying, incinerating, composting, rendering, or bringing to landfill mortalities, having a set of standard operating procedures in place will help farm mangers to properly dispose of a dead animal when the time comes. It is also important to remember that records of farm mortality are required in BODA and any increase in mortality not considered normal must be reported immediately to MDARD.