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Jun 12, 2023

Everything Farmers Need to Know About Composting Animal Mortalities

Composting is often the best option for dealing with livestock mortality. Now is

Composting is often the best option for dealing with livestock mortality.

Now is the time to compost animal mortalities.

Despite the best intentions and care in animal agriculture facilities, there are occasional animal mortalities.

Dr. David Wolfgang explains that until recently, there was an active rendering industry that would collect dead animals and recycle the carcasses back into useful products.

Changes in economics and the emergence of diseases that must be prevented from circulating in animal herds and flocks have made rendering of carcasses much less attractive or even impossible at times.

Incineration at extremely high temperatures, long-term storage in sealed landfills, and alkaline digestion are the only proven technologies that can destroy transmissible spongiform encephalopathies.

Currently there is an operational incinerator at the Animal Diagnostic Laboratory at Penn State.

The state-owned Pennsylvania Veterinary Laboratory in Harrisburg has provisional approval to operate its incinerator and an alkaline digester.

The University of Pennsylvania's New Bolton Center has an alkaline digester as well.

Certainly for limited numbers of animals where carcass destruction is essential (such as scrapie, chronic wasting disease and bovine spongiform encephalopathy), high-temperature incineration and alkaline digestion would be the preferred methods of carcass disposal.

Burial is permitted by regulation in Pennsylvania as an alternative for carcass disposal for routine animal mortalities. For limited numbers and in certain circumstances, this form of disposal is acceptable.

However, both incineration and burial have considerable limitations based on risk to groundwater, the number and weight of carcasses, and the season.

Incineration and alkaline digestion are also limited by animal numbers, plus the carcasses must be transported to a fixed facility, and such disposal comes at a higher cost than other options.

Composting on site has proved to be a very cost- effective means of carcass disposal. With some proper precautions, composting can be an effective method of safely containing and disposing of animal carcasses.

Numerous Extension and lay publications have described proper techniques for composting of large animals. Composting has been demonstrated as an effective, environmentally sound and relatively easy method of recycling a carcass.

Compost sampled after complete and stable fermentation can be free of pathogenic bacteria and viruses. There is considerable information on the fate of common pathogens in other forms of compost.

In these types of substrates, a relatively uniform composition is achieved, and there is a high level of contact between the substrate and the pathogen. Temperature and pH targets can be accurately and consistently reached. Many plant pathogens are destroyed at temperatures above 95 degrees F, and essentially all vegetative forms of animal pathogens are destroyed at temperatures above 131 degrees.

Large animals have been composted in a variety of substrates from bedded pack manure to leaves, straw, sawdust, shavings and municipal yard waste. Typically a ratio of 25 to 30 parts of carbon substrate to 1 part protein, with a moisture content of approximately 60%, is ideal.

In nearly all cases, surrounding a carcass with a substrate like wood shavings, sawdust (can be from green wood), wood chips or corn silage will achieve satisfactory composting temperatures and conditions.

Since composting is an aerobic process (oxygen is required), the particle size must allow enough space for air to pass into the pile.

A compost pile can be made by finding a level, firm plot of well-drained soil at least 200 feet (some references say 300 feet) from any water source.

The base should consist of a layer of carbon substrate (such as sawdust) at least 2 feet deep and extend 1½ to 2 feet beyond the width of the carcass.

The carcass should be placed in the center of the base layer and buried completely to a depth of 2 feet around the entire carcass. For a single adult cow this means a pile about 7 to 8 feet wide, 8 to 10 feet long and 5 to 7 feet high.

Worksheets are available to help calculate the amount of carbon substrate needed for size and number of animals.

Often piles are left alone for up to six months. Additional substrate can be added on top if needed.

If properly constructed, odor, pathogens, groundwater, flies and disturbance by dogs or other scavengers will not be a problem.

Turning the pile adds oxygen and speeds up the process. Turning large piles as often as every six weeks advances breakdown without the risk of pathogen release into the environment.

Properly composted large animal carcasses will be broken down except for a few parts of the largest, most dense bones in a minimum of 10 months. After 12 months, even the densest bones can be crushed easily.

A concern that has emerged in the last few years is the question of chemicals entering the groundwater near livestock facilities. One issue that has not been resolved is the fate of euthanasia solution in animal mortalities.

A large animal might have 30 to 40 grams of pentobarbital in the carcass. This chemical is quite water-soluble and might persist in the ground following burial for some time.

One safe and environmentally friendly way of reducing agricultural chemicals is bioremediation.

Bioremediation is the use of cells or live organisms to remove, clean up or break down a chemically contaminated site. Composting serves as a means of bioremediation.

In limited preliminary work, data indicate that composting greatly reduces or eliminates euthanasia chemicals and most antibiotics. This is an added ecological advantage of using composting for animal mortalities.

In conclusion, while incineration, burial or tissue digestion are options for carcass disposal, these methods have significant limitations and costs.

In most cases, animal mortalities can be safely and conveniently disposed of by composting. Composting, if done following simple but important guidelines, can be environmentally sound, economical, and safely eliminate pathogens and chemicals.

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In the event of an African swine fever outbreak, researchers believe composting could be a safe, viable way to dispose of infected pig carcasses.

State agriculture and environmental officials are teaming up to perform groundbreaking research on livestock carcass disposal with an eye toward developing a better way to handle mass mortality incidents.

Animal mortality is a fact of life, and in livestock production the challenge is dealing with the number of animals over time and their size.

Leon Ressler is a Penn State Extension educator based in Lancaster County, Pennsylvania.