Composting is an acceptable and recommended means of recycling organic
wastes and is rapidly gaining acceptance in the U.S. as a method for stabilizing/sanitizing
animal and municipal wastes. Confined Animal Feeding Operations (CAFO’s)
including dairy, cattle feedlot, poultry and swine operations, generate
more than 136 million metric tons (dry weight basis) of waste products
annually containing significant levels of nitrogen and phosphorous which
threaten surface and below-ground water resources if not managed correctly.
Composting is a totally natural decomposition process, which if performed
under controlled conditions, will produce a quality product that can be
used as a peat moss substitute in greenhouse growing media and can be used
for improving soil texture and soil nutritional level in field situations.
The success of the composting process depends on several basic conditions
including moisture content of the raw material, ability to aerate the compost
mass, degradability of the organic material, and the presence of appropriate
microflora.
Research initiated in 1992 at Texas
A&M University-Commerce (TAMU-C) has resulted in development of
prototype,
pilot-scale, in-vessel, aerobic mechanical composters for decomposing
and stabilizing solid animal wastes. Development of prototype composters
was followed shortly by on-farm
commercial installations of in-vessel aerobic composters for stabilizing
solid dairy
cattle waste. Turning at the rate of three revolutions per hour, the
composter facilitates thermophilic decomposition of solid dairy cattle
waste and produces a quality peat moss substitute in three days for use
in the horticultural industry.
A composter of this type may be of utility in broiler
production facilities as an environmentally appropriate/low management
alternative to static-bin composting of bird carcasses. Composting of mortality,
which will average between 3% and 5% of the total population during the
five to six week growth cycle, is rapidly becoming the preferred alternative
to on-farm burial, landfilling, or incineration.
Preliminary research at TAMU-C has shown that co-composting
of poultry carcasses and poultry
litter from broiler production facilities in in-vessel composters results
in thermophilic stabilization in six days. Carcasses included at the rate
of 25 % (by weight) with 75% broiler
litter will decompose in three to four days.
The composted product with larger
bones remaining, has maintained thermophilic temperatures
for three or more days and is free of coliform and salmonella bacteria.
Composted poultry litter containing 25% mortality tests 24.9% crude protein,
4.0% fat, 15.3% fiber, and 82% total digestible nutrients. Compared to
composted poultry litter alone, co-composting with 25% mortality increases
crude protein by 21.8% and iron by 131.9%. Estimated elevations in fat
content are approximately 300%.
Feeding poultry litter to ruminant livestock is not a new concept,
but inclusion of poultry carcasses in a controlled decomposition process
is new and theoretically improves the value of the resulting product for
use as a pathogen-free ruminant livestock feed ingredient. In-vessel composting
of poultry mortality provides an environmentally appropriate/low management
alternative to the currently recommended static-bin composting or incineration
of carcasses. Co-composting of litter and mortality could be mutually beneficial
to both the poultry and livestock industries, as well as the environment.
This on-going project is supported by the Graduate School, Texas
A&M University-Commerce; and the Texas Department of Agriculture through
the Texas-Israel Exchange (T.I.E.) Program.
