note 5-composting chicken carcasses v2

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slower and less effective. Low C:N ratios tend to produce more ammonia, which
inhibits breakdown. High C:N ratios may also inhibit breakdown through limited
available nitrogen. This can be remedied by using a substrate with a higher nitrogen
content or by adding granular nitrogen fertiliser. Adequate oxygen must be available
to keep the pile aerobic.

Heat retention

The temperature inside properly sized and maintained compost piles should reach
50- 65 oC. This temperature stimulates the growth of the thermophilic bacteria that
promote decay. It also helps to destroy disease-causing microorganisms. For a
meat chicken farm this improves biosecurity and produces a product that is safe for
land application. Compost piles are likely to be cooler close to the edge, so
carcasses should be kept at least 300 mm from the edge of the pile.


Compost Bin Design
Compost bins can be as simple as large round or large square hay bales configured
into an open-fronted bay. They need to be set up on an impermeable pad
(compacted clay or preferably concrete). Many of the carcass composting operations
in the United States are conducted in open sheds. This design allows for improved
environmental control, by excluding rainfall. The sidewalls of these shed structures
can be constructed of timber, concrete or plywood with timber supports. Bins are
generally 2 m deep and approximately 2.5 m wide. The width needed depends on
the implements available for turning (front-end loader, bobcat etc).




CHICKEN COMPOST SHED COMMONLY USED IN THE UNITED STATES

Size of Operation

A 100,000 bird operation with 4% mortality rate will produce approximately 5 t of
mortalities per batch or an average daily mortality of about 100 kg for the batch. An
average daily bird loss of 100 kg/d will require approximately 12.5 m3 of bin capacity
(6.25 m3 for the primary bin and 6.25 m3 for the secondary bin).

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Operating Principles and Management

The compost pile should be started with a 150 mm layer of clean bedding material
(sawdust, shavings etc.) on the base to absorb any leachate that may be released
from the pile. Next, place 150 mm layer of co-composting material (dry spent litter).
Carcasses are then placed in single layers on top of these base layers. All
carcasses should be at least 250 mm from the side walls to ensure adequate
coverage for aerobic decomposition and to avoid leachate exiting the pile.

Each layer of birds is covered with at least 150 mm of co-composting material. This
procedure is continued until the bin is full. The top layer of birds should be covered
with at least 300 mm of co-composting material to ensure there is no scavenging or
fly breeding. This cover will also ensure little odour is released during the operation.

The pile should heat up to 55-60oC within 24-48 hours. If this does not occur, it will
generally be due to a lack of or an excess of moisture. After the bin is full, it needs to
undergo a primary composting phase of 10-14 days. During this time, the microbial
action will deplete the oxygen and the temperature will fall with a slowing of the
decay process.

After this primary cycle, the partially composted material is removed and placed in a
secondary bin. The moving of the pile aids in mixing, which redistributes excess
moisture and introduces more oxygen. This promotes further composting and
decomposition. After another 14 days the composting process should be complete.
For heavier carcases (exceeding 3kg), a third composting phase may be required.
The composted product can then be stored for further curing or be available for use
as a nutrient rich by-product. It is important that the compost piles are either turned
or moved during the process to introduce new oxygen and avoid odour generation.




COMPOSTING CHICKEN CARCASSES IN OPEN BAYS




This Meat Chicken Technical Environmental Note was produced as part of the
RIRDC – Meat Chicken Program project “National Environmental Management
System for the Meat Chicken Industry, Project No. FSE-1A.