Composting livestock and poultry carcasses is becoming a more common way to manage mortalities. There are several reasons for this.
Composting is relatively inexpensive when low cost carbon materials are utilized. The high temperatures generated during composting create a very biosecure process which eliminates pathogens and reduces disease transmission when properly managed. Composting is also an environmentally sound method for carcass disposal as it reduces odors as well as carcass leachate by surrounding the carcass with a carbon filter. The composting process creates a beneficial by-product rich in nutrients which can be land-applied as a fertilizer. Composting promotes a positive public perception by adequately disposing of animal carcasses in a sustainable manner without negatively affecting the environment.
Research studies have been done to correlate the temperature of a compost pile containing livestock or poultry carcasses and the amount of pathogen kill achieved at those temperatures. How do you take the temperature of a compost pile? And how does that temperature correlate to pathogen reduction?
Maintaining a temperature of 131 deg F for at least 4 hours assures us that we have reached an appropriate temperature for pathogen reduction. However, to destroy most pathogen and viruses, compost pile should sustain temperature 131 °F or greater for at least 3 consecutive days. The heat is the result of microbial metabolic activity within the compost pile as they are consuming the carcass.
Most bones break down when composting animal carcasses, but a few large bones will usually remain.
With proper composting, the bones will break down over time. This may take several months for larger livestock bones and as little as 60 days for smaller carcasses such as poultry. If large bones remain in the compost pile, they can be added to additional compost piles until completely degraded.
There are many options available for disposing of livestock and poultry carcasses. Rendering is an option in areas where the service is offered, but has some limitations on the type of animals they will pick up.
Compost containing animal carcasses should probably be utilized on crops that are not meant for human consumption for a couple of different reasons.
Disposal of the end product with regard to roadkill compost…we use it on the roadsides and plant vegetation on the roadsides.
With [farm] mortality compost, we want to be careful about where we are putting cows and chickens because we are using it back on the farm. So we may want to remove the large bones [and reuse them as part of the base for the next mortality compost pile]. We do not want to puncture any tires. But the bones do get pitted and will start breaking apart after a couple of cycles of the composting process. We do not want to use this on food crops. We may prefer to use this on field crops where the soil is tilled. We can apply the compost and then till it in. Definitely use it on crops that are harvested above the ground…corn and things like that. Do not use [mortality compost] on root vegetable or on things where we risk contamination if there is a problem.
Mortality compost can also be used in forested areas.
Improperly disposed livestock or poultry carcasses represent a threat to water and air quality.
Proper management of on-farm animal mortalities is vital to every farming operation. Improper disposal of dead animal carcasses can negatively impact surface water and groundwater from carcass leachate. If the animal died of an infectious disease, pathogenic bacteria and viruses may be present within the carcass. These pathogens can be spread by insects, rodents, predators, and subsurface or above ground water movement, as well as through direct contact with other livestock or poultry leading to increased disease transmission risks. Furthermore, many states have rules regulating the proper disposal of livestock and poultry mortalities. Therefore, the purpose of proper mortality disposal is to prevent the spread of infectious, contagious and communicable diseases and to protect air, water and soil quality. Note that regulated AFOs must abide by their animal mortality disposal plan outlined in their nutrient management plan.
Managing dead animals is not pleasant, but is a necessary task for most livestock and poultry farms. This video discusses several options for disposing of carcasses in an environmentally responsible manner.
In most states, commonly approved disposal options include: burial, landfills, incineration, rendering and composting.
Perhaps the most common method of disposal is burial. Most states have regulatory burial guidelines outlining site location, distance from waterways, depth to groundwater, etc. When proper guidelines are followed, burial is a safe option. However, poor site selection, such as sandy soils or areas with high water tables, may pose a threat to groundwater. Furthermore, burial does not convert the carcass into a valuable by-product. Variable equipment and labor costs will influence the economic viability of this disposal option.
Disposing of carcasses at a licensed landfill that accepts animal mortalities is another form of burial. Landfills may require notification before delivery and/or documentation from a licensed veterinarian stating the cause of death. Landfill tipping fees should be assessed and may range from $20 to $30/ton. Other considerations are transportation costs and breeches of biosecurity by moving carcasses off- farm. Similar to burial, a valuable by-product is not produced.
Incineration is a safe and effective means of carcass disposal, especially from the standpoint of biosecurity. The carcass is completely consumed by fire and heat within a self-contained incinerator utilizing air quality and emissions controls. Some states may require air quality permits. Incineration is mainly designed for smaller carcasses and fuel costs should be considered. Due to odor and emission concerns, open air incineration (burning) is not recommended and banned in some states. Furthermore, obtaining complete consumption of the carcass in a timely manner is often difficult to achieve. Burning should only be used in emergencies for controlling infectious or contagious diseases with permission from a regulatory body.
Another recommended carcass disposal method is rendering. This is a heat driven process that cooks the product while killing pathogens and converting it into a value-added product such as an animal feedstuff. These feedstuffs, such as meat and bone meal, are generally used as pet food ingredients. Although rendering is a very effective method, currently, there are few rendering services available. The transportation expense of collecting small volumes creates a financial obstacle for most rendering companies. Some rendering facilities require the producer to transport carcasses to the plant and pay a fee. Biosecurity and disease transmission risks should be considered when allowing vehicles on the farm and when transporting carcasses off-farm.
Composting dead animal mortalities is an inexpensive, biosecure and environmentally sound approach to addressing the issue of carcass disposal. By definition, composting is a controlled biological decomposition process that converts organic matter into a stable, humus-like product. The carcass (nitrogen source) is buried in a bulking agent (carbon source), such as wood shavings, allowing for the proper carbon to nitrogen ratio (C:N) required by microorganisms to successfully decompose the carcass while absorbing excess moisture and filtering odor. The high temperatures achieved through proper composting will destroy most pathogens. Microorganisms will degrade the carcass leaving only a few small bone fragments, which are brittle and break easily. This valuable by-product can then be land-applied as a fertilizer source, adding nutrients and organic matter to the soil or recycled for new compost piles. As with burial, site selection is important. The site should be located in an area that does not pose a risk to surface or groundwater contamination.
Alternative methods are not specifically defined. They may include homogenization, digestion or chemical processes and technologies to recover products from mortalities.
Sometimes, a disease outbreak or natural disaster results in many livestock or poultry carcasses that must be managed. Disposal of these requires additional planning to ensure this is done in an environmentally responsible manner.
During catastrophic events when multiple livestock losses occur, a producer’s routine mortality disposal plan may be inadequate. In these instances, multiple disposal options may need to be considered. Burial, rendering, landfills, composting and incineration or a combination thereof are recommended options. All catastrophic events should be reported to the appropriate state agency. If a catastrophic mortality event is the result of disease outbreak, bio-security considerations may dictate the method of transportation and disposal.
Abandoning animal carcasses and allowing scavengers to dispose of them is risky.
Though dragging off a carcass to the boneyard has been a historical practice, abandonment is NOT recommended and is likely ILLEGAL in most states. Examples include: carcasses abandoned on the surface, in open pits, ditches, water features and sinkholes or in wells. Abandonment promotes extreme biological and disease hazard, threats to water quality, odors, flies, scavengers, rodents and visual pollution.
Reviewers: Shafiqur Rahman, North Dakota State University and Jean Bonhotal, Cornell University
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