Carcass Disposal

Livestock Carcass Disposal

Disposing of livestock carcasses is an important part of animal agriculture. Wisconsin law says that carcasses must be properly disposed of within 24 hours from April through November and within 48 hours from December through March.

Rendering, burial, burning and landfilling have been the typical means of disposal, but these are becoming less and less practical. Burial and burning create biosecurity hazards and threats to water and air quality. Rendering remains the best choice to protect the environment, public health, and animal health, but it is becoming more expensive and less available.

Cattle carcasses in particular are becoming more difficult and expensive to send to rendering because of federal regulations. The Food and Drug Administration, which regulates animal feed and pet foods, now prohibits using parts from cattle 30 months or older in any food for animals unless the spinal cord and brain are first removed.

We recommend composting carcasses to overcome these problems. Remember that composting is an active process. Putting a carcass in the woods or on the back 40 to rot and/or be eaten by scavengers is not composting and:

  • Risks disease transmission to your livestock and your neighbors’, and to wildlife.
  • May contaminate water sources – including your well and your neighbors’ wells.
  • Invites vermin and pests, including coyotes, that may transmit disease and prey on your livestock.
  • Alienates neighbors and generally casts farmers in a bad light.
  • Is illegal.

Benefits of composting
What is composting?
What you need
Site selection
Bulking agents
How to compost
Winter composting

Benefits of composting

  • Biosecurity – It provides immediate, year-round disposal of carcasses so disease isn’t transmitted; does not require off-farm vehicles that may bring disease to your property; and kills disease-causing organisms as it decomposes the carcass.
  • Environmental soundness – Done right, compost piles give off little odor and do not contaminate groundwater, and turn waste into a resource.
  • Cost-effectiveness – Start-up and operating costs can be minimal, and you can often use facilities and equipment you already have.

The following information is digested from Composting Animal Mortalities, a publication of the Minnesota Department of Agriculture in cooperation with the Minnesota Board of Animal Health and the University of Minnesota Extension Service. You can download the entire 32-page booklet here.

Note: Composting is for the normal, incidental livestock deaths that occur on any farm. If you have a mass die-off, you will need to work with state and local authorities to dispose of the carcasses. In such an event, it is likely that the Department of Agriculture, Trade and Consumer Protection would already be involved and could work with you on disposal.

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What is composting?

When you compost carcasses, you put them in a bin between layers of sawdust or other material and let micro-organisms break them down. You can compost animals from chickens to cattle. Depending on the size of the carcass, the process can take 2 to 6 months. At the end of it, you have a material that looks like black soil that you can land-spread as fertilizer or use as your bulking agent for other carcasses.

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What you need

  • Carbon – This is where the sawdust or other carbon-rich “bulking agent” comes in. The carbon in the bulking agent balances the nitrogen in the carcasses to provide the right environment and food for microorganisms.
  • Air flow – The microorganisms need oxygen to work, and carbon dioxide and water vapor need to be released.
  • Moisture – You need enough to allow microorganisms to survive, and not so much that it slows oxygen flow, which slows them down and creates odors.
  • Heat – The warmer the pile, the faster the microorganisms work, which produces more heat and enough heat to speed decomposition and kill pathogens.

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Site selection

You can build a new structure; use an existing one, such as a three-sided shed, a machine shed, corn crib, hoop structure; or use open piles. If using open piles, you will need to protect them from dogs and other animals, and from rain and snow. Regardless, you need to consider -- 

  • Water quality – Well-drained, at least 1,000 feet from lakes and streams and 300 feet from wells.
  • Biosecurity – Don’t locate compost right next to production areas
  • Prevailing winds and public view – Don’t antagonize neighbors or passers-by.
  • Traffic flow – You’ll need all-weather access to move carcasses, bulking agent, and finished compost, and you’ll need to avoid buried and overhead utility lines.
  • Access to water – Locate within one hose length of a water source so you can add water if necessary.

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Bulking agents

You need an organic material. Sawdust is good because it absorbs odors well. You can also use hay and straw, but drier hay or hay with more grasses than legumes will work better, because it has more carbon. Crop residues like wheat straw or corn stalks can be used, but may need to be shredded. Once you get started, finished compost is a good bulking agent, too, for up to half the bulking agent needed.

Factors to consider in choosing a bulking agent 

  • Availability – Choose a bulking agent that you can get in sufficient quantities from one or more source year-round.
  • Cost – Using materials you already have on-farm is normally the most inexpensive, but you can also find low-cost other low-cost materials, especially if they are considered waste, such as sawdust and wood shavings.
  • Physical characteristics – Besides finding an agent with the right carbon ratio, you also need one with particles large enough to let air flow, but not so much that the pile cools and slows or stop decomposition.

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Many or most farms will already have the big-ticket equipment necessary:

  • A front-end or skid-steer loader to move, cover and turn carcasses
  • A manure spreader if you plan to land-spread the finished compost

Ideally, you would also have:

  • A probe thermometer with at least a 36-inch stainless steel stem to monitor the pile
  • A logbook to record dates and weights of carcasses placed in the compost pile, temperature readings, amounts of bulking agent used, when you turn the compost, and dates and amounts of finished compost

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How to compost

If you are using a structure with walls, you will need enough space to maneuver your loader and to keep carcasses at least a foot from any wall.

  • Put at least a foot of bulking agent down to insulate the composting carcass, provide carbon to fuel the process, and absorb liquids.
  • Place the carcass (or carcasses) on the bulking agent. If you’re composting calves or other smaller animals, place them starting at the back in a single layer, at least six inches apart.
  • Cover the carcass(es) with another 12 inches of bulking agent. If the bulking agent does not feel moist, add water before covering the carcass. The bulking agent should feel moist to the hand, but you should not be able to squeeze water out of it.
  • Record the species, weight, date, and amount of bulking material used.
  • Follow the same steps to add more carcasses if necessary until the pile is close to the top of the bin.
  • When the first bin is full or the pile is as tall as you can work with, start a second bin/pile if you have more mortalities.
  • Monitor the first bin daily to be sure the carcasses are covered and check the temperature at several locations. The temperature should increase fairly quickly to between 130 and 150 degrees F. Once the part of the pile that you added last has reached this temperature range, make sure it remains in that range for at least a week.
  • After at least a week has passed, wait until the temperature drops. Then turn the pile:
    • Line the bottom of a third bin or pile (assuming you’ve started a second one) with a foot of bulking agent.
    • Move the partially composted material from the first pile via front-end or skid loader, starting with the topmost/most recently added material and ending with the first added. There may be some odor. If the material does not feel moist, add water as you move it to be sure it is distributed evenly.
    • Cover the fresh pile with a foot of bulking agent.
    • Record the date, bulking agent type and volume.
    • Check the temperature daily. Once it has been over 130 degrees F. for a week and then drops, the compost is probably finished. You should not be able to see any flesh, and the material should be dark and soil-like with little odor. Any bones present will probably be very brittle and easily crushed, or they can be placed on a bone pile that wild animals will consume. If the material is not finished, turn it again.

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Winter composting

  • Do not allow carcasses to freeze before placing them on a compost pile.
  • Do not add carcasses to a pile that has dropped below 60 degrees F.; it will be too cold for microbial activity.
  • Keep a thick layer of bulking material between the carcasses and the floors and walls of the bin.
  • Avoid turning piles on extremely cold days.

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Some common problems you might encounter, especially when you first start composting, are listed below, along with possible solutions. You can also consult some of the resources listed below for advice.

Likely cause
Improper  temperature
  • Too dry
  • Too wet
  • Improper carbon-nitrogen ratio, because of wrong amount of bulking agent, or bulking agent that is too porous
  • Adverse environment for microbes
  • Add water
  • Add bulking agent and turn pile
  • Evaluate bulking agent and adjust amount
  • Ensure there is enough bulking agent to insulate the carcass
Failure to compost
  • Improper carbon-nitrogen ratio
  • Carcasses layered too thickly
  • Carcasses placed on the outside edge of the pile
  • Turn pile and adjust amount of bulking agent
  • Arrange the carcasses in a single layer
  • Maintain one foot of space between carcases and outside edge of bins
  • Too wet
  • Carbon-nitrogen ratio is too low
  • Inadequate cover over carcasses
  • Extended periods of low temperature
  • Add bulking agent and turn pile
  • Evaluate type of bulking agent and/or add bulking agent
  • Maintain one foot of bulking agent near outside of bin. Turn pile.
  • Cover carcasses with one foot of bulking agent
  • Follow steps in temperature section above
  • Inadequate cover over carcasses
  • Poor sanitation conditions
  • Failure to achieve proper temperature
  • Too wet
  • Cover carcasses with one foot of bulking agent
  • Avoid leaching from pile. Maintain a clean, debris-free area near the pile
  • Follow steps in temperature section
  • Open/remove pile contents and add additional bulking agent
Scavenging animals
  • Inadequate cover over carcasses
  • Maintain one foot of bulking agent over carcasses
  • Stop entry with a fence or other barrier

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The three publications listed below provide excellent detailed information about how to compost animal carcasses, as well as background information about why you perform each step to help you trouble-shoot. All are from institutions located in climates similar to Wisconsin’s. Note that each refers to laws in their particular states, however. If you have questions about Wisconsin’s laws, you will need to contact the Wisconsin Department of Natural Resources and/or your local authorities.

Composting Animal Mortalities, a 32-page booklet published by the Minnesota Department of Agriculture in cooperation with the Minnesota Board of Animal Health and the University of Minnesota Extension Service.

Composting dead livestock: A new solution to an old problem, a 12-page document published by Iowa State University Extension, the Leopold Center, and the Iowa Department of Natural Resources.

Natural Rendering: Composting Livestock Mortality and Butcher Waste, a 12-page document published by Cornell Waste Management Institute at Cornell University.

Wisconsin Department of Natural Resources
Rules for on-farm composting

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