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Researchers study composting for safe disposal of livestock carcasses

by 5m Editor
19 August 2003, at 12:00am

DES MOINES - Researchers are testing whether composting can be used to safely dispose of large numbers of livestock carcasses during an outbreak of a disease such as foot-and-mouth.

Emergency cattle composting research to expand at Iowa State University - Preliminary studies at Iowa State University have opened the door for a second year of research on the environmental impacts and biosecurity of composting to dispose of animal carcasses in the event of a cattle disease outbreak.

The project got underway last fall at the request of the Iowa Department of Natural Resources (IDNR). "We were asked to study the feasibility and safety of using on-farm composting for emergency disposal of beef or dairy animals in the event of a foot-and-mouth disease outbreak in Iowa," said Tom Glanville, project coordinator and associate professor in ISU's agricultural and biosystems engineering department.

If Iowa experiences a contagious livestock disease outbreak resulting from natural causes or bioterrorism, large numbers of diseased animal carcasses and large amounts of infected feed and bedding would need to be disposed of rapidly. "Burial and mass open burning were used during the foot-and-mouth outbreak in Great Britain. But shallow water tables, bedrock and frozen soils rule out mass burial in Iowa at many locations or during the winter. And IDNR officials have concluded open burning could cause widespread air pollution," Glanville said.

Past ISU research showed composting can be a flexible, low-cost method for environmentally sound disposal of normal production losses in the swine and poultry industry. This project will determine if composting also can be used for disposal of large numbers of larger animals with a contagious disease. "The idea is to test the composting process, and monitor impacts on air and water quality, under critical seasonal conditions," Glanville said.

Work during the first year provided a preliminary assessment of the practicality and environmental acceptability of composting practices that could be used in an animal disease emergency. "The composting process seems to work well," said Tom Richard, associate professor of agricultural and biosystems engineering. Monitoring showed reasonably high temperatures within the test compost piles even during the winter, and preliminary excavations indicate nearly complete decomposition of full-sized cattle in six months or less.

Odor production has been minimal. Odor threshold data for samples collected from the surfaces of the composting test piles are measured in the ISU olfactometry laboratory. "With an adequate depth of cover material, odor from the trials conducted so far has been minimal, and odor thresholds often are similar to those from silage or hay stockpiled on most cattle farms," said Jay Harmon, associate professor of agricultural and biosystems engineering.

The ability of composting to retain and inactivate disease-causing agents that could spread to healthy animals is a major component of the study. Results of preliminary work conducted under the direction of Don Reynolds, professor of veterinary microbiology and preventive medicine, have been encouraging. Viruses placed in the composting test piles generally have not survived more than three weeks, even during adverse winter weather when composting temperatures were reduced. Viruses also appear to be retained by the composting system. None of the blood samples drawn from pathogen-free poultry housed in cages nearby have shown an immune response to vaccine viruses placed in the piles.

"We hope we never need to use composting during an animal disease emergency in Iowa," said Glanville. "But based on data collected so far, we think information gained during this project will be useful in developing guidelines for both emergency and non-emergency use of composting by producers." A second year of funding is provided through a continuing grant from IDNR with supplemental funds from the U.S. Department of Agriculture.

Iowa State University - College of Agriculture - 31st July 2003

5m Editor