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Photo A. A Brown Bear 24C
compost turner fitted to a skid-steer drive unit turns compost
inside a high-rise layer structure. |
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High-rise, Caged Layer Facilities
The standard structure design for high-rise, caged layer facilities
involves housing poultry in offset-stacked cages in the upper floor
of the structure. Manure from the cages is directed with plastic
sheeting into the storage area below (Figure
1). Manure may accumulate for several months or more before
buildings are cleaned out.
Automated fans housed in the lower portion of the structure control
ambient temperatures in the cage area by drawing air in through
evaporative cooling screens located in the roof and expelling it
through the walls in the manure storage area. The fans also serve
to vent ammonia and other gasses from the building, and to accelerate
manure drying. Fly control is normally achieved by supplying a feed-based
larvicide to laying hens coupled with topical applications of insecticides
on the manure as needed to control outbreaks. Odor and fly complaints
are commonly associated with the clean-out process when accumulated
manure is disturbed for loading and transport.
An Overview of In-House Composting
Composting is possible inside high-rise facilities using equipment
sized to fit in the manure accumulation area of the structure. Cooperators
at the sites where this SARE research was conducted used a Brown
Bear model 24C compost turner [2
] fitted to a skid-steer drive unit to aerate the materials (Photo
A). The skid-steer is the same power unit that, when fitted with
a loader bucket, is used to remove material from the buildings.
To prepare for a compost cycle, a carbon source such as straw or
sawdust is spread on the floor after cleaning out a building. Manure
is allowed to accumulate on the carbon bed for 2 to 4 days before
forming the material into windrows with the turner. The material
is turned (aerated) every two to four days, depending on the size
of windrows and material temperature.
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| Figure 1. Photograph and schematic of a high-rise
layer structure. Fans in the wall of the structure draw air
out under negative pressure (suction). This pathway of air flow
serves to vent ammonia and other gasses out of the structure,
minimizing exposure of poultry. |
Aerating promotes rapid decomposition by microorganisms. The metabolic
heat produced by the microorganisms is capable of generating temperatures
in the compost above the lethal limit for fly larvae (110o F). Aerating
also rotates fresh manure into the center of the pile where high
temperatures kill new fly larvae. Material is removed when the volume
exceeds the operational capacity of the turner.
In-house composting differs from traditional composting. Since
manure is being added continuously, the product at the end of a
cycle is not finished compost. However, as a result of frequent
mixing and partial decomposition, the material is more uniform and
has a lower moisture content and less odor than fresh poultry manure.
If desired, finishing can occur outdoors in a conventional composting
system, or partially composted material can be land-applied without
finishing. Practitioners should check with state and local officials
regarding regulations on composting facilities and compost quality
standards before marketing the products of this process as compost.
An essential component of in-house composting is the negative pressure
ventilation system that vents ammonia and other gasses from the
composting area. This reduces the exposure of poultry and employees
to potentially toxic gasses produced during composting. High concentrations
of harmful gasses may still be present in the composting area, so
employees working there should be equipped with appropriate monitoring
and respiratory safety devices. Also, practitioners should be aware
of impending air quality rules designed to regulate ammonia emissions
from poultry farms. Careful attention to composting conditions,
particularly the carbon to nitrogen (C:N) ratio of the material,
can limit ammonia emissions. There is also some evidence (cited
later) that chemical amendments can be used to reduce ammonia volatilized
from composting manure.
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