Choosing the right method for carcass disposal is dependent on several issues
Four common methods are: Burial, Incineration, Rendering, Composting
Local regulations need to be considered
Dead animals are inevitable. Methods for carcass disposal vary, but, especially with today's heightened biosecurity concerns, this is an important management decision. There are several options available; each should be carefully considered to find the best method for your operation.
The four methods most commonly used on farms for carcass disposal are:
In addition, there may be alternative methods, depending on your location and circumstances. With all methods of carcass disposal, first check with local authorities regarding regulations and permits for the use of a particular method. Laws vary according to area and species. Carcasses should be disposed of within 48 hours, regardless of the method used.
The burial method is best used for occasional losses and relatively small amounts of material. The general guideline is about 2000 lb or less/pit/acre. This can be an inexpensive method of disposal if the equipment needed is already available. However, some cautions need to be addressed. Careful thought and planning is necessary, because as the carcasses decompose, they release compounds that could potentially pollute ground water. Therefore, site selection is of utmost importance. Take care not to dig any burial pits within 10 feet of the water table. This includes areas that may be seasonally wet, but dry up later. Use the wettest scenario for your figures. Also, keep in mind that in certain areas, it may be difficult to impossible to use burial in the cold winter months. Other methods should be used at this time.
If burial is used, the carcass should be buried without delay. The pit should be at least 100' away from any production facilities, including pastures, and should be filled in with 3-4 feet of dirt. Sites should be identified somehow, to alert workers and other individuals. Open trenches should not be used. Care should be taken to properly cover the burial pit to prevent dogs or wild animals from digging up and dragging off parts of carcasses.
Another option for carcass disposal is incineration. One major advantage of this method is that it is not season- or weather-dependent. However, incineration is quite expensive, especially for large carcasses. Most incinerators work best with carcasses that are 500 lb or less. Initial incinerator cost is substantial. Then there is the fuel cost of running the equipment. A diesel-fueled unit is estimated to use about 1-3 gallons of fuel/100 lb of carcass. Another disadvantage of this method is the potential for odor. This can create difficult neighbor relations, so take wind direction and neighbor's proximity into consideration. If this method is chosen, incinerate daily rather than allowing carcasses to accumulate for days. Choose a unit large enough to handle the expected mortality from your operation and maintain the unit properly. If at all possible, choose a site for the incinerator that is out of public view or find a way to screen it with trees or decorative fencing. Be aware during the warm months that neighbors are more likely to be outside and may notice the odor.
Rendering of livestock mortality is a method that creates a usable feed product and is available year-round. However, because of changes in the animal by-product industry and market, this method is not as popular as it once was and may be more costly. Check with the company to determine their requirements for acceptability. If this method is still available in your area, it is probably to your benefit to get on some kind of a continuous contract, rather than operate on a "per call" basis. Find out if any neighboring farms want to use this method and try to coordinate pick up times and routes.
If you decide to use this method there are a few things to take into consideration. First, you must know if the animal was exposed to any drugs or other substances and what residue issues may be involved. There should be a dedicated off-site pickup area, to avoid disease contamination from the rendering vehicle. The storage site on the farm should be away from the public sight and/or screened. It should be situated at least 100' away from any production facilities. If the rendering company cannot pick the carcass up within 72 hours, you will either have to refrigerate it or find an alternative method of disposal.
Composting is showing great promise as a routine method for disposing of farm mortality. Most of the research to this point has been done with poultry, but composting has been used to dispose of larger carcasses with success. Check into local regulations; composting may be approved for some species and not others.
Composting can be defined as the aerobic breakdown of material by bacteria, fungi and protozoa to produce water, carbon dioxide, heat and organic residue. Carcasses are placed in layers of a carbon source (for example, straw, hay, or sawdust) and allowed to breakdown. The basic elements required for successful composting are moisture, carbon, nitrogen, oxygen and heat. A moisture level of 40-60% is required, as is a carbon:nitrogen ratio of 25:1. If ammonia odor occurs, the nitrogen level is too high, and more carbon needs to be added. The ideal oxygen level is 5%, however, compost requires constant aeration. Decomposition will occur with lower oxygen levels, but it will proceed very slowly. This may be fine if space is not limiting, but that is generally not the case. Additionally, the slower rate of composting may not generate enough heat to kill pathogens.
Turning the pile periodically will ensure adequate oxygen being available. Using at least some large particle size carbon materials (like wood chips) will help pile aeration as well. The heat generated by the pile should be in the range of 120 - 150 degrees Fahrenheit. The bacteria that decompose the pile actually thrive in that temperature range. An internal temperature of 130 degrees for 3 days is required to destroy pathogenic organisms. This is especially important if the compost product will be used as a fertilizer. At the end of this paper are more detailed sources of information about the mechanics and biology of composting.
As with burial, site selection is a very important consideration to the success of composting. It has advantages over burial because the process is more biosecure due to the destruction of pathogenic bacteria by heat. Composting can be done year-round and in the end, the producer has a usable product. Composting requires some kind of a container, with impervious floor, rot resistant walls and a cover to keep out the rain. It is also a method that requires some experience and "feel" to produce a successful product.
In general, to compost livestock mortality, you need to start with a base of carbon material that is about 12 inches deep. Sawdust is most commonly used, but chopped straw, corncobs, silage and wood chips can also be used. Carcasses must be at least 6 inches and preferably two feet from the sides of the container. Layer carcasses with sawdust and cover with at least 12 inches of material. For larger animals, such as cattle, the amount of carbon material required is about 4-6 cubic yards/animal. Record temperature of pile daily. As the temperature begins to decline, mix the pile to generate a new cycle of heat.
Some alternative methods that may be worth looking into are pet food processing, fur farm consumption and lactic fermentation. Check to see if any of these methods are feasible in your local area.
On Farm Composting Handbook. 1992. R. Rynk. Northeast Regional Engineering Services. 152 Riley-Robb Hall. Cornell Cooperative Extension. Ithaca, NY14853.
Disposal Methods of Livestock Mortality.
Cooperative Extension - University of Nebraska-Lincoln.
Best Management Practices - Carcass Disposal.
Minnesota Board of Animal Health.
Carcass Disposal Information.
M. Byers. BiosecurityCenter.
Composting Dead Livestock: a new solution to an old problem.
T. Glanville. Leopold Center for Sustainable Agriculture and Iowa Department of Natural Resources.