Livestock Composting as an Alternative Disposal Method
Ron Wiederholt
and Matt Jorgensen
NDSU Carrington Research Extension
Center
and University of
Wisconsin-Extension
Introduction
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 Ingredients
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.
Site Selection
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:
Water
Quality
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.
Biosecurity
Avoid locating the compost
structure directly next to production units and use appropriate cleaning
procedures on transportation vehicles.
Public
Perception
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.
Traffic
Flow
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.
Composting Structure
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.
Rows
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.
Bins
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.
Management
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
Implications
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.
Literature Cited
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