Down to the ground

State-wide demos teach benefits of composting livestock carcasses

By Dan Lemke

Waseca, Minn. -- Mother Nature does a pretty good job cleaning up after herself. For farmers, one aspect of that cleansing process -- composting -- may be an efficient way to deal with inevitable livestock losses.

In the poultry industry, composting dead birds has been common for years. Now composting's gaining acceptance as a means of disposal for larger animals such as hogs and sheep.

"Composting works," says Jack Johnson, AURI waste utilization manager. "We hope to encourage farmers to adopt composting as a safe, reliable and inexpensive management technique."

To that end, four compost demonstration sites have been established in Minnesota, including a project at the University of Minnesota Southern Experiment Station in Waseca. The sites are cooperative ventures with AURI, the Minnesota Board of Animal Health, the Minnesota Department of Agriculture and the Minnesota Pork Producers.

What do you do with the dead ones?
Animal mortalities are a fact of farming. No matter the species, a small percentage of poultry and livestock die each year. Finding safe and effective methods for disposal is an issue that all livestock producers contend with.

Presently, farmers' disposal choices include sending carcasses to rendering facilities to be converted into industrial fats and fertilizers, burying on-site, or incinerating. While these options are effective, they are not without shortcomings.

Rendering pickup can be unreliable due to geographic or weather challenges. Some producers are also concerned about the disease-spreading potential when trucks travel farm to farm to pick up carcasses.

Burial can be difficult in a northern climate during winter months; it may potentially contaminate groundwater as well. Incineration, on the other hand, works well for small animals, but can become expensive and not as effective with larger animals like market-size hogs.

Producers want to know what benefits composting offers, says Roger Walker, Southern Experiment Station animal scientist. "With composting there is no biosecurity threat from vehicles like rendering trucks. There's the social and visual aspects as well since compost piles are covered, low odor and keep the animals out of sight."

Six months to clean up
"Once you start composting it's remarkable, because it works so well," says Keith Friendshuh, Board of Animal Health veterinarian. "It's hard to believe we haven't used composting all along."

Composting is accomplished by covering an animal carcass with a carbon source such as sawdust and a nitrogen source such as manure. Two activities occur inside a covered pile. First, anaerobic bacteria break down the carcass. It's in this phase where unpleasant odors are generated. Aerobic bacteria, also present in the pile, act as biofilters and convert the smelly gases to water and carbon dioxide. When properly managed, a compost site is odorless, rodent-free and non-polluting.

Small animals like chickens or turkeys are completely composted in three to six weeks. Larger livestock such as hogs or sheep take longer. Walker says those animals should be composted in six to nine months.

Once a compost bin is full, it sits for three months to allow heat to build inside the pile. Natural bacterial activity can raise the internal temperature to as much as 160 degrees; most harmful or pathogenic bacteria are killed at 130 degrees. After the first heating cycle, the pile is turned and allowed to compost for another three months.

"Some large bones may still exist after the first cycle," Johnson says. "Very few are left after the second." When the cycles are completed, the composted material is safe for land spreading.

Composting is an approved alternative for disposing of poultry, goats, sheep and hogs, and no permits are necessary. All that is needed is a covered site with a pad that is impervious to water.

While cattle cannot be composted without special permits, research is underway at Waseca to determine the effectiveness of composting larger animals.