If you have livestock, you inevitably have dead stock – a reality of animal agriculture. With the rising costs of rendering services and increased concern for biosecurity on farms, producers need to consider all their options for disposing of their dead livestock.
While burial and incineration are still legal disposal options, there is an increasing interest in composting livestock carcasses. Composting can be an environmentally sound way to handle dead livestock – it”s a natural way to recycle organic materials, a properly managed compost pile generates no odors, and the final product is a good soil conditioner for gardening or crops. Proper composting destroys pathogens, weed seeds and insect eggs, as well as reducing the biosecurity risk presented by rendering trucks coming onto farmsteads.
Composting can be a cost-effective disposal alternative – start-up and operating costs are minimal – but composting does require good management.
“Livestock mortality composting is more than dead animals on a pile,” says Dan Short, University of Wisconsin-Madison animal sciences outreach educator and UW-Extension livestock agent for Dodge County. But, he adds, “composting does not have to be high-tech and expensive to be effective.” Short has been working with a low-cost livestock composting demonstration using large square bales at the UW-Madison”s Arlington Agricultural Research Station. A permanent composting facility is planned for construction at this site in 2003.
Composting is defined as the biological decomposition of organic wastes under controlled conditions to a state that allows storage, handling, and land application without harming the environment. The process of composting results in the production of carbon dioxide, water, minerals and stabilized organic matter (humus).
To successfully compost, Short says, you must have a good composting recipe, which entails the correct carbon/nitrogen ratio, the right amount of moisture, and good porosity. The C:N ratio should range from 25:1 to 40:1. A C:N ratio that is too low results in ammonia and other odors. A high C:N ratio results in slow decomposition and low temperatures.
The composting moisture target is 55 percent. If the compost pile is too dry, it results in lower pile temperature and slow decomposition. If moisture levels are too high, putrid odors result and flies are attracted to the compost pile. Porosity is important to the aerobic process of composting. Oxygen levels above 5 percent should be maintained. If porosity is low, decomposition rates slow down, temperatures fall, and odors ensue. Also, if porosity is too high, decomposition rates and temperatures are lower.
Heat is an important byproduct of the bacterial activity that”s responsible for 80 to 90 percent of the decomposition. An effective compost pile should reach temperatures of 130 to 150 degrees F. The increased temperature stimulates rapid growth of heat-loving bacteria growth, which promotes decay. Temperatures above 130 degrees for three days also kill most pathogens and destroy insect larvae and weed seeds.
According to Bob Uphoff of Uphoff Ham and Bacon Farm near Madison, your composting pile “tells” you if the compost recipe isn”t right. The only time a compost pile should have an odor is when it”s being mixed. “If we start smelling an odor, something isn”t right,” Uphoff says, and he knows more straw needs to be mixed into the pile. If there is an odor, he says it”s usually a manure odor from too much moisture from the manure that”s part of their composting recipe.
If carcasses are covered properly, there should be no odor from decomposing livestock. Keeping the carcasses under enough cover also keeps vermin, such as coyotes, out of the pile, though compost piles should still be fenced to help keep unwanted scavengers away. The Uphoffs began composting the dead pigs from their 100-sow herd when their local livestock rendering service closed. Their compost pile end product is used for gardening on their farm.
A livestock composting pile should be located away from livestock housing facilities and away from normal farm traffic, and at least 300 feet from surface water. The pile should have a feedstock base of 1 to 2 feet. The feedstock will vary by farm, but is commonly sawdust, straw, manure, or combinations thereof. Carcasses should be at least 1 foot from the pile”s edge and covered with at least 1 foot of feedstock, with at least 6 inches between carcasses. The rate of decomposition will vary with the level of management and size of the animals being composted.
Regulations pertaining to livestock composting in Wisconsin are minimal, and covered under the administrative code NR 502.12. No license or permit is required to have an on-farm livestock composting site, and these sites are usually only regulated if a complaint is filed. In most cases the Wisconsin Department of Natural Resources would likely work with a cooperative farm owner to correct the situation before considering legal action. According to NR 502.12, compost sites should be operated in a nuisance-free and environmentally sound manner, should have no detrimental affect on surface water or groundwater, and should have no significant adverse affect on wetlands or critical habitat areas.
“Just because you can do something, doesn”t mean you should,” Short says. That is, just because a farm is capable of composting doesn”t mean it”s necessarily the best option for disposing all of a farm”s dead livestock.
He says producers should look closely at the cost of using a rendering service versus composting. Small animals decompose more quickly, and there”s normally a higher mortality rate among young stock than mature livestock. If a rendering service charges, for example, $25 per head picked up, then the cost per hundredweight for having a 100-pound calf picked up is $25/cwt. To have a 1,400-pound cow picked up, the cost per hundredweight drops to $1.79/cwt. If a farm didn”t want to compost all of its dead stock, composting only the smaller young-stock carcasses may be the most cost-effective approach.
For detailed information on composting, including calculating the best compost recipe and pile size for your farm operation, contact your local Extension office or use these resources:
Dan Short, UW-Extension Livestock Agent, Dodge County. (920) 386-3790
“Mortality Composting in Wisconsin” PowerPoint presentation
Click “What”s New” to get to the presentation
“Composting Module” workbook
National Pork Producers Council
“Composting dead livestock: A new solution to an old problem” fact sheet