With rendering costs, biosecurity concerns and environmental regulations increasing, composting — where naturally occurring bacteria (microbes) digest carcasses into a humus-like material called compost – could be a viable alternative. It works for manure, too.
The trick, according to Chris Augustin, North Dakota State University Extension specialist in Carrington, is maintaining a carbon:nitrogen ratio of 20:1 to 40:1 (30:1 is ideal).
Look in the May issue of BEEF magazine for an in-depth guide on how to compost carcasses (“Dealing with Deads” at beefmagazine.com/natural-beef/) by Alaina Burt Mousel. Among the highlights:
- Site Selection – Piles should be constructed atop concrete or clay pads to avoid leaching or contaminating ground water. Consider a site with vegetation to reduce the environmental impact of leachate (a flush of liquid) either from the decomposing carcass, or rain and snowmelt filtering through the pile. Most large-animal compost piles are built in long, uncovered windrows, based on the carcass size and volume of material needed to cover them.
- Pile Building – Narrow windrows of carcasses – about two loader-widths wide – are easier to manage than wider piles. Pointed crowns and steep sides are recommended for wet climates to shed moisture, while a flat or concave top can be used in drier climates to accumulate moisture.
“It's important to have the right kind of envelope material under and around the carcasses,” explains Tom Glanville, Iowa State University professor of agriculture and bio-systems engineering.
These materials can vary. Think of things like corn silage, ground cornstalks and feedlot manure capped with ground hay. Base material should be about 2 ft. thick to absorb leachate. The heavier the carcass, the thicker the base should be. Glanville recommends about 2 ft. of material over the top and sides of the carcass. He used 12 cu. yards of cover/base material for every 1,000 lbs. of carcass, equivalent to 1 ton of ground hay or straw, 1.4 tons of ground cornstalks or 3.2 tons of corn silage for large, uncovered and un-turned compost piles.
- Pile Management—Research indicates a 1,000-lb. carcass can be reduced to skeletal remains in four months if the process began in warm seasons, or up to 8-12 months when started in cool seasons.
Turning piles during warm weather will speed the process; doing the same in cold weather can chill the pile and slow things down. Glanville cautions against turning too soon—wait 60-90 days — as it can increase odors and fly problems. Adding more cover material will prevent both.
Be sure to monitor temperature and moisture content of the compost pile throughout the process. If it gets too dry, or wet, it won't compost properly. A properly built pile will reach temperatures of 130-150°F within 2-3 days of construction and remain there for at least two weeks. If the temperature remains below 130°F, the pile is either too wet or too small; the carbon source may be too coarse or fine for adequate oxygen supply. Augustin says the curing process is complete after 4-5 compost turns.