Composting disposal for both confined, pastured cattle

Whether they’re caused by disease or natural disaster, losses can occur, and these mortalities must be managed responsibly to protect the environment and the health of other animals.

Amy Millmier Schmidt

While every livestock producer likely has a method or two to dispose of routine mortalities, developing a mortality management plan can help a producer think through the options available to facilitate prompt and biosecure disposal.

Oftentimes, discussion of mortality disposal is focused primarily on confined livestock, where disease transmission and natural disasters can have a major impact due to the stocking density of animals. However, pastured livestock are subject to losses from natural disaster and diseases as well.

The recent winter storm, Goliath, proved deadly to thousands of pastured cattle – buried alive by excessive snowfall through the Texas-New Mexico border and Midwest.

In the fall of 2013, a similar storm, Atlas, dumped rain and snow accompanied by high winds and severe temperatures on the upper Midwest, leaving several thousand pastured cattle dead.

Losses of this nature can be difficult to manage because of limited access to these animals – possibly for several days. Although some of the options for disposal may be more convenient than others, the chance of groundwater contamination, re-introducing diseases and access to proper facilities can be a major concern.

The benefits of composting

Composting is an effective means of mortality disposal that can be done on any size of livestock operation and with any size of animal. Most farms are already equipped with the necessary materials and implements to construct and manage a compost pile.

Whether used for routine disposal or a catastrophic loss, composting can be a viable option on most operations.

While the sheer volume of animals lost during a catastrophic weather event makes disposal by composting or any other method challenging, the value of planning for such events cannot be overstated.

Knowing ahead of time how and where to obtain carbon material for large-scale composting, who to contact for assistance and how to establish compost piles can help make the disposal process more manageable if the “unthinkable” arises.

Research at a number of universities has shown that animals of any size can be composted – with one East Coast university even composting a beached whale. Demonstration sites in Nebraska organized by USDA-NRCS and the University of Nebraska have demonstrated successful composting of mature cattle, calves, pigs and horses.

The keys to composting

Most people will say the key to composting mortalities is to provide the necessary carbon, nitrogen and moisture to facilitate the decomposition of the pile materials by micro-organisms.

While this is certainly true, having someone dedicated to the success of the composting process is equally essential. Routine monitoring to make sure the pile is heating up and to make adjustments if a problem is identified is critical – especially when first beginning to compost.

Constructing a pile with adequate carbon material is essential to feed the microbes responsible for driving the compost process and to retain heat, minimize odor and discourage scavenging animals from disrupting the pile.

As a general rule, a layer of dry carbon material 24 inches deep should form the base for a mortality compost pile. The base should accommodate the carcass while leaving at least 24 inches of space between the animal and the edge of the pile.

Once the animals are in place, additional carbon material should be added to cover the animal on all sides to a thickness of 24 inches. No part of an animal should protrude from the pile or odors and scavenging animals will likely be an issue.

Moisture is also essential to the composting process and may need to be added depending on the moisture content of the carbon source used. The goal is for the material around the animal to have a “damp sponge” feel. It should clump when squeezed, but water should not drip from the hand.

Material that is too dry should have water added during the pile-building process; throughout the cycle, additional water can be added to the top of the pile. Material that is too wet should be mixed with dry carbon material to reduce the overall moisture content.

When disposing of animals lost to severe winter weather, where frozen ground may make burial impossible and movement of mortalities to a central location may not be feasible, composting in place is recommended.

Though not an ideal pile design, simply covering the animal with 24 to 36 inches of moist carbon material may provide enough insulation to allow heat to be generated by the microbes responsible for driving the composting process. In some cases, soil or snow from the area surrounding the animal may need to be used as a cover for the pile to provide additional insulation and moisture.

While soil can be used as pile cover material when other options do not exist, “sealing” a pile too well with soil can impede air flow within the pile and negatively impact the composting process. Therefore, only a thin layer of soil – perhaps 4 to 6 inches – should be used when needed to provide insulation or to hold carbon material in place under windy conditions.

Most operations with confined livestock will have the necessary material available on-site to construct a pile, while pastured systems might have a difficult time identifying carbon material for the pile. Manure, chopped forages, chopped cornstalks, waste feed and wood chips or shavings all make good compost pile ingredients.

A front-end loader or tractor with a scoop can be utilized to move material and animals to the pile, to build and turn the pile and to remove finished compost for land application. It is important to keep in mind, though, that proper washing and sanitation of equipment used for animal movement or pile management should follow each use, especially if disease was the cause of death.

The varying factors

The length of time required to completely compost an animal is dependent on the size of the animal and, to some extent, weather. While small pigs or poultry may compost in a matter of two or three months, larger animals will require three to six months for each of the two recommended compost cycles.

Likewise, although an animal will begin to compost quicker when warm temperatures support the pile’s heating process, frozen animals placed in a new compost pile have been successfully composted when sufficient carbon material was used.

Temperatures should rise to approximately 130ºF at the core of the pile within a few days of a new pile being established and should stay at this temperature for several days or weeks.

Compost piles can begin to generate heat very quickly even during cold winter weather if the microbes have the appropriate carbon, nitrogen and moisture to survive and thrive.

A long-handled thermometer is ideal for monitoring pile temperature but can be costly for most producers. Without a thermometer, the producer will need to focus on identifying foul odors or other visible issues to address the cause of the problem (pile too wet, animal parts exposed, insufficient pile cover material, etc.).

The determination of when to turn the pile to begin a second compost cycle will need to be based upon recommended time frames for composting the animal based on its size. For those monitoring pile temperature, piles should be turned once the core temperature falls below 120ºF.

Preventing water contamination and ensuring farm biosecurity should be of utmost importance when managing manure and mortalities, no matter the size of the livestock operation.

Information about choosing an appropriate site for composting, pile design and management, nutrient value of compost, cost-share opportunities and biosecurity considerations was recently presented at a UNL mortality composting demonstration event and is available through the Nebraska Extension Animal Manure Management Team’s website.