Research Facility Finds Success with Composting Dead Livestock

by Nancy Carver Singleton

As cattlemen search for alternative solutions to dispose of dead animals, many are considering composting. This article is the second in a series of composting livestock.
Composting livestock carcasses works well for the Purina Mills Research Center in Gray Summit, Mo.
Their composting facility, constructed in 1996, is used for small carcasses such as lab rats up to large livestock such as cattle and horses. Joe Cody, manager of operations, said it works well and is efficient in terms of time and money. "The bottom line though is that it is environmentally friendly. Sometimes I step back from it and think 'It is so simple. Why haven't more people been doing this in the past?' " he said.
The American Feed Industry Association in 2000 recognized the innovativeness of Purina's composting operations by presenting it with an environmental award for waste reduction.
Purina Mills Research Center, founded in 1926, most recently incinerated or buried mortalities. In the early 1990s it began examining other options to prepare for changes in environmental regulations. They consulted with Charles Fulhage, extension agricultural engineer at the University of Missouri. Fulhage and his fellow engineers were "very helpful" in working with Purina to design a composting facility and to develop composting procedures, Cody said.
Their structure's floors and walls are concrete. Of the seven bays, three bays are used as primary composting areas, three are secondary composting areas and one is used for sawdust storage. Each bay is 24-feet deep, 12-feet wide, seven-feet high and has 288 square feet. Total area for composting is 1,728 square feet. The design allows carcasses to be loaded into the bays from either side of the building, which helps utilize every cubic foot, Cody said.

At the Purina facility, three bays are used as primary composting areas, three are secondary composting areas and one is used for sawdust storage.

Employees keep a log on the type of animal, weight and date of each mortality placed in the bay. A layer of seasoned hardwood sawdust is put down for the carcass to be placed upon, with the thickness dependent on the animal's size. Smaller animals need only approximately six inches and large animals require two to three feet of sawdust. As the layers grow, new sawdust needs to be placed only on top of carcasses. At least 12 inches is placed on top of all mortalities and a steer would require several feet of sawdust. Moisture and temperatures are monitored in each bay. When medium-to-large animals (such as swine or cattle) are placed upon a layer of sawdust, the body cavity is opened to allow fluids to drain and to enhance composting action.

When he was gathering information on composting, Cody could not find anyone in his part of the country who used it for cows. "But as it turns out, there is no real difference composting large animals compared to small animals except you need to use more sawdust and you need to provide more bin space to accommodate larger animals," he said.

Carcasses compost in the primary bay for three months, then are moved with an end loader to a secondary bay. They are moved from bay to bay every two months until the material has composted for nine months.

By then animals have broken down, with the exception of large bones. Purina staff found that sawdust can be used through three composting cycles. Cody said the microbial action in "used sawdust" seems to better decompose body tissues. After determining that the sawdust is no longer usable, bones are screened out and the material is spread on fields.
The composting facility's visitors have included beef, dairy and pork producers who were thinking of composting. Some were members of cooperative beef feedlots who were gathering information to use on a larger scale for their mortalities. ©