Livestock Composting as an Alternative Disposal Method
and Matt Jorgensen
NDSU Carrington Research Extension Center
and University of Wisconsin-Extension
Composting is a naturally occurring process in which bacteria, fungi, and other microorganisms convert organic material into a stabilized product termed compost. This means that the microorganisms do the work for you. Your role in managing the composting process is to make sure that the microorganisms have the environment they need to do their work quickly and effectively.
The essential elements for the microorganisms involved in composting are carbon (C), nitrogen (N), oxygen (O2) and moisture (H2O). If any of these elements are lacking, or if they are not provided in the proper proportion to one another, the microorganisms will not flourish and will not provide adequate heat. The proper compost mix requires both carbon and nitrogen at the proper C:N ratio. The proper C:N ratio will result in a composting process that generates little odor, yet offers an environment where microorganisms can flourish. Optimum C:N ratio for composting is within a range of 25-40:1
Livestock compost row with newer animals buried in foreground using straw as bulking material.
Materials and Methods
Bulking materials for composting include chopped straw, sawdust, corn stalks, mixture of manure and straw/sawdust. Sawdust is the easiest to utilize because it is used 1:1 with animal mortalities; if you use other bulking materials, more of the material may be needed to achieve the proper C:N ratio. Short particle length is also important when selecting the bulking material.
Many factors affect where a compost area is set up. While convenience is important, you will not be accessing this area on a regular basis. Therefore, the compost area can be located away from other buildings on the farm site. Other selection issues are:
Pick an area that is well-drained and has all-weather access to roads and work areas. Areas to avoid are 1,000 feet from streams and lakes, and 300 feet from wells.
Avoid locating the compost structure directly next to production units and use appropriate cleaning procedures on transportation vehicles.
Consideration needs to be given to prevailing winds and public view in choosing a site. Provide limited or appealing view for neighbors or passing motorists and consider aesthetics and landscaping. Hauling animal mortalities on roadways may not be the sight you want for your farm.
Consider access and traffic patterns required for moving mortalities and bulking agent to the compost site and removing finished compost, as well as other farm traffic. Ensure all weather access. Locate safe distances from buried and overhead utilities.
Access to Water
Consider the distance between a water source and the bulking agent storage or the composting bins. If you need to add moisture to your composting materials, consider locating the structure within 100 feet of a hydrant that is at least 200 feet from the well.
To avoid the risk of pest problems, some type of structure around the livestock compost pile may be needed. The structure can be as simple as plastic wrapped-round bales. Others have constructed a compost facility similar to a commodity shed with a mono-slope roof and concrete sidewalls. There will be some leachate from the compost. A concrete floor is not necessary, but an all-weather base is important for access and to control ground seepage. Leachate will not generally be a problem, especially if the composting facility is under cover or drainage flows into a grass waterway.
If livestock are composted without a facility, it is best to build the compost in row fashion, adding animals and bulking material in succession of oldest to newest. That way, the row can be turned in order of oldest to newest. It is not recommended to add fresh animals on top of older animals by making a stack since they need to be turned at different times.
Generally, three bins or load areas are used. Bins need to be sized so you can easily place animal mortalities inside. The size of your turning machine (skid steer, tractor with loader) also needs to be considered. Use 100 to 400 square feet per bin as a general rule of thumb. Remember that the pile can become five to eight feet in height; as the material composts, size will decrease. Filling flow of the bins is diagramed below. This chart is dated for adult cattle. Bins for calves and swine can be cycled in 30 day increments. Times may vary due to season and other factors.
To build a base, use two feet of bulking material to start the pile, place the mortalities on top of the base material. Cover the carcass with two feet of bulking material and if using a bin, the carcass must be placed at least one foot from the bin wall. For intensive management, check the temperature daily using a thermometer with at least a 32 inch probe and turn when the pile reaches 103 to 150° F. At turning, add one foot of bulking material next to the row or in an empty bin. Turn compost on to this new layer of bulking material. After turning the compost, make sure that the mortalities are completely covered with at least one foot of bulking material. During winter, turning may not be necessary since too much cold air may be incorporated into the pile causing the decay process to cease
Compost turner in action. When a compost turner is used for livestock row composting vs. mixing with a loader, very few large bones remain in finished compost
Mortalities are able to degrade over time because of sufficient catalytic bacteria and enzymes which are able to break up the carcasses to useful organic material. Warm mortalities degrade faster and will have better ending results. Therefore, it is essential to place the carcasses in the compost pile quickly. The compost pile destroys disease causing bacteria and viruses and reduces flies if done properly. Immediate burial of the livestock mortalities will also reduce the chance of odor. For large animals of 750 to1500 pounds you can expect the primary composting process to be complete in 70 to 90 days with some turning. Most large bones can be easily broken up but if they are still too hard they can be added to the next pile for further decomposition.
Mortality Composting in Wisconsin, Dan Short, UW-Extension Swine Specialist http://cdp.wisc.edu/ppt/Compost_files/Compost.ppt
Composting Animal Mortalities: D. E. Morse, MN Dept of Agriculture, http://www.mda.state.mn.us/composting/compostguide.pdf