Composting animal mortalities
Livestock mortalities are an inevitable aspect of any operation. To make matters even more difficult, the number of options available for carcass disposal has dwindled. In recent years, fewer and fewer rendering plants are accepting single animals from producers.
In some areas, burying the carcass may not be an option due to the geology of the land and its proximity to springs, streams and other water sources. Agricultural experts state carcasses left to decay above ground can also create problems. This process attracts predators and can spread disease.
However, there are steps producers can take to protect their operation. “Mortality management is a critical part of a livestock operation, and if done properly will help minimize the transfer of disease from within their herd or to a neighboring herd,” Troy Chockley, Environmental Engineer with Missouri Natural Resources Conservation Service (NRCS), said.
Many livestock producers are turning to composting as an avenue for mortality management. Poultry and swine producers are the operators most commonly utilizing mortality composting. Although, large animal producers will implement the process from time to time.
The composting process used for animal mortalities is similar to composting food waste. “If it is an organic substance, it can be composted,” Chockley stated. “The size of the organic particle or nitrogen source of the compost, in this case it’s the carcass, has a direct impact on how rapid the composting process proceeds.”
Types of Composting
A static pile composter is the most frequently used method of mortality composting throughout the Ozarks. A static pile composting system is used on many poultry operations.
Producers build concrete bins, add sawdust or other carbon material, put in a layer of poultry carcasses and then add another layer of sawdust. These steps continue until the bin is full. Producers will maintain numerous bins, all at different stages of composting.
When producers add compost that has come out of a compost mortality bin to start a new bin, the process is accelerated.
The active fungus and bacteria in the later stage compost jumpstarts the composting process in the new bin.
If producers follow the protocol, monitor the temperature of the compost and reaerate the material when needed, then the process should be successful. “The carbon material and the nitrogen material have to be well mixed and well aerated at the proper moisture content and if all that occurs composting proceeds very efficiently,” Chockley added.
The temperature in an efficient static pile will fluctuate between 100 to 140 degrees. The composting process for poultry takes 30 to 45 days.
A similar system can be set up for larger animals. However, since the need is far less frequent in cattle operations, a temporary mortality composting site can be created. In these situations, large round bales are lined up to create a bin like structure. Producers create a thick base layer of carbon material like sawdust, then place the carcass on the base layer, and add more carbon material.
A static pile composter that is properly managed should have minimal issues with odor. “If you do everything correctly it will not attract predators or other types of critters that want to eat that carcass,” Chockley explained. “That is the case because part of the carbon material will form what is a called a biofilter over the top of the carcass. So, as the process proceeds it is helping to minimize the odor transmission from that pile.”
The finished compost from static pile composting can be applied to fields as fertilizer. Typically, it contains a low numeric value of nitrogen, phosphorus and potassium. In addition, there is carbon material remaining in the compost that can be beneficial to pastures.
Producers implement other forms of mortality composting as well. Some operations use incinerators that operate at a high temperature and reduce the carcass volume by 97 percent. Incinerators are an expense to purchase, operate and maintain.
Another mortality composter utilized by some operations is an in-vessel composter. These are typically large-diameter drums that rotate. The compost is kept at constant ideal composting conditions in order to speed up the process. The in-vessel system requires a secondary composting stage, that is usually done through static piles.
Engineers and experts with NRCS, along with specialists at state university extension offices, help producers create and execute mortality management plans. Local specialists can also guide producers looking for funding assistance with morality management expenses.