ITHACA, N.Y. – Farmers caught in the middle – between the recent federal ban against “downer” animals and rising costs for disposing of cattle that can’t walk to slaughter – could consider a composting alternative.
‘Natural’ rendering. Natural rendering, or composting of whole animal carcasses on the farm, is economical and environmentally sound for all downer cattle that do not show signs of neurological disease, say compost researchers at the Cornell University Waste Management Institute.
The heat generated by thermophilic composting, 130-160 degrees Fahrenheit, reduces most pathogens entering the compost pile, said researcher Jean Bonhotal.
“But we doubt that composting destroys the prions associated with mad cow disease, so we emphasize this important exception: Animals showing signs of neurological disease must be reported to authorities and disposed of in the manner they recommend.”
Gone in six months. Livestock that are composted with the approved technique are reduced to clean bones in four to six months and to a usable soil amendment in a year.
The Cornell study placed carcasses on a bed of wood chips and completely covered them with high-carbon material such as sawdust or silage and more wood chips.
The same technique works with butcher “residuals,” the 60 percent of slaughtered livestock that is not salable meat, according to Bonhotal.
Legal option. “Most people don’t realize that composting is a legal and acceptable way of disposing of these materials,” Bonhotal said.
Composting of dead livestock can be accomplished in compliance with environmental regulations in most states, she added.
Whale of an idea. She offered an example to make farmers’ problems seem trivial.
A 300,000-pound whale that died off the coast of New Jersey was obtained by a museum, trucked to Ithaca and covered with horse manure.
After 12 months the compost pile was opened by museum workers, who separated bones from composted soil and assembled the whale skeleton for display at the Paleontological Research Institution’s Museum of the Earth.
“If natural rendering works on a 15-ton whale, it won’t have a problem with a 1,200-pound steer,” Bonhotal said.
Growing problem. Even before the Dec. 30, 2003, order by USDA banning downer cattle from the human food supply, dealing with the estimated 150,000 disabled animals a year in the United States was becoming a problem.
Sending downer cattle to rendering plants had become more costly because of declines in price and demand for hides, tallow, bone meal and other commodities produced from carcasses.
Some rendering plants closed altogether and others hiked the fees to pick up carcasses from farms, while more farmers resorted to burying carcasses in shallow pits or leaving them to decay above ground.
Soil amendment. None of those problems should occur with a properly managed compost operation, the Cornell expert said.
The finished compost can either be used as a base for the next cycle of natural rendering or can be used as a soil amendment for hay, field corn, winter wheat or tree plantations.
Although it is particularly rich in the plant nutrients nitrogen (N), phosphorus (P) and potassium (K), compost from animal carcasses should not be used to fertilize crops that will be consumed by people, the Waste Management Institute recommends.
Get the details
* The bulletin Natural Rendering: Composting Livestock Mortality and Butcher Waste is available at
* Cornell Waste Management Institute
Rice Hall, Cornell University, Ithaca, N.Y. 14853
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