Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
3/6/00
Contacts:
Tom Glanville, Department of Agricultural and Biosystems
Engineering, (515) 294-0463, tglanvil@iastate.edu
Sherry Hoyer, Iowa Pork Industry Center, (515) 294-4496,
shoyer@iastate.edu
Composting is Convenient Carcass Disposal Method
AMES, Iowa -- As rendering services increase in price and decrease in availability, more livestock producers are turning to the low-cost option of composting. This on-farm method of animal carcass disposal will work on most farms, according to Tom Glanville of Iowa State University's Agricultural and Biosystems Engineering Department.
"Composting can be done on nearly any scale, as long as you pay attention to the four basic needs of the microbes that break down organic matter: temperature, moisture, food and oxygen," Glanville said. "Under proper conditions, the microbes can reproduce at a rate sufficient to decompose small animal carcasses in as little as four to six weeks."
Thermophiles, the heat-loving microbes responsible for most of the actual composting action, do their fastest work in piles with temperatures between 120 -150 F. Besides aiding in quicker composting, these temperatures also help kill harmful bacteria and weed seeds.
Moisture is a critical factor in composting. Keep moisture content between 30-65 percent for optimum conditions, Glanville said. "How can you determine moisture level? Compost should be slightly damp, but if you're able to squeeze water from a handful of compost, add drier materials to keep the bacteria healthy and productive."
Bacteria need a balanced diet to do their best work. Ideally, this happens when carbon levels are 20-30 times higher than nitrogen. If carbon-nitrogen ratios are too low, ammonia odors may become a problem, particularly when the compost is turned. Adding more sawdust or other high carbon material to the mixture will bring carbon levels back up. If nitrogen levels are too low, the rate of decomposition will be slow, a problem that also is characteristic of inadequate moisture. If moisture levels seem adequate, but decomposition just isn't happening, try adding some manure to the compost mixture to bring nitrogen levels up to desired levels, Glanville said.
With a sufficient oxygen supply, aerobic bacteria will do most of the composting. That's preferable because they produce more heat and fewer odor-causing byproducts than anaerobic bacteria. One easy method to help maintain oxygen in a compost pile is to cover carcasses with coarse sawdust or wood chips that allow air to diffuse into the compost mixture. Turning the pile occasionally also improves available oxygen and speeds decay, he added
For more information on planning a composting operation that meets Iowa Department of Natural Resource regulations, contact any ISU Extension county office and ask for the publication, SA 8, "Composting dead livestock: A new solution to an old problem." This publication is also available on the Web at http://www.extension.iastate.edu/Publications/SA8.pdf.
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