There is no best way to
dispose of swine mortality carcasses. While some methods may work well for
managing routine mortalities, due to capacity issues, they may not adapt to
times when catastrophic mortalities occur. The optimum system for any
particular farm location is based on a number of criteria, including the
current state of the protein/oil market, the biosecurity required, the distance
to processing sites, the local public's perception, the government regulations
that apply to that location, the environmental conditions, and the ability of
the farm to carry out the different procedures.
The death losses at a
farm can be classified broadly as one of two types: routine or catastrophic mortalities. Routine
mortalities represent a small proportion of the herd and occur throughout normal
production. Catastrophic mortality events involve high death losses within a
distinct time. Four predominant methods of routine swine mortality disposal are
burial, incineration, rendering, and compositing. Catastrophic losses present
unique challenges because of handling large amounts carcasses within a short
time (and if losses are due to disease, a higher biosecurity risk).
Burial
Burial can occur either
on site or via transport of carcasses to approved landfills. Typically, on-farm
burial of routine mortalities is performed using a trench method, which
involves excavating a narrow and shallow trench, placing a single layer of
carcasses in the trench and then covering with soil. Pigs slowly decompose
until they are unrecognizable, generally after a few years. One concern is that
burial can have negative environmental impacts if the sites are not selected
carefully. In particular, depth to groundwater or sanding soils where leachate
transport to groundwater is more likely. This method is not available when the
ground is frozen and predators can uncover carcasses not buried deep enough.
Typically, for routine management of mortalities, this method is often reserved
for smaller operations.
In terms of catastrophic
mortality, disposal burial is more common. With emergency disposal burial, the
number of carcasses placed in a location is typically greater, increasing the
potential for leachate, making location selection critical. The use of modern
engineered landfilled equipped with leachate collection and treatment
significantly reduces the risk of leachate concerns. The utilization of the
landfill relies on the owner’s copperation and the transport of carcasses. Efforts
to support bio-secure transport are required in cases where mortality is from a
transmittable disease.
If mass burial is
required on site, the combination of topographic, geologic, soil, and water
resource data should be used to identify and map burials sites. Farms should
work to identify locations for on-farm burial as part of emergency preparedness
plans.
Shallow Burial
Shallow burial is a bit different, almost a cross between
composting and burial. Often burial decomposition is slowed by lower oxygen
concentrations and the fear of leachate movement. Shallow burial tries to
address this by leaving the carcass near the surface.
The process is something like this – dig a long narrow
trench approximately 20-inches deep by the width of an animal body for the
length you need. You’ll want to put in a layer of organic material, like wood
chips, approximately 12-inches thick. This absorbent material will help absorb
any potential leachate from the animals and also can help facilitate air
exchange and keep the zone aerobic.
The next step is to get the animals in the trench, one layer
thick. The animals are probably mostly even with the ground. What we are trying
to do with this approach is keep them in an area with high soil microbial
activity to help promote decomposition. At this point, put the removed soil
back on top, plant grass or perennial vegetation to keep it in place, and let
nature help with the circle of life.
It will take a little time, but most work has shown in about
a year, the animal’s decomposition will be nearing completion.
If you are looking into what you might need to get started
on the process Michigan State has a spreadsheet to help you plan sizes and
material needs. https://www.canr.msu.edu/resources/spartan-emergency-animal-tissue-composting-planner-v1-04.
