Source: University of Minnesota Center for Animal Health and Food Safety
Carcasses and other animal wastes can be a huge burden for sanitation, logistics, and public and animal health. You might remember back to the highly pathogenic avian influenza outbreak in 2015, when tens of millions of poultry carcasses presented a disposal nightmare in the Midwest.

In most mass mortality events, composting is the answer to the carcass conundrum.

Carcasses need to be dealt with quickly in order to protect human and animal health, soil and water quality. Check with your respective state animal health official for specifics for your state.

Why not bury or incinerate the carcasses?
You might think that burial or incineration is an obvious way to cheaply and efficiently dispose of carcasses, but you would only be partially correct.

Burial is inexpensive, fast and effective, but you also have to consider the water table, pit depth, property ownership and purpose and soil composition — criteria that can drastically reduce the practicality of burial.

With incineration, you can’t simply build a bonfire and throw carcasses on it, because you will have to add a high proportion of combustible fuel. Most forms of fuel are expensive, dangerous and have logistical challenges.

How does composting work?
Public perception of carcass composting often assumes that composting means carcasses are piled up to slowly decompose uncontrolled. But composting is actually an accelerated decomposition of animal tissue and waste.

By combining high proportions of protein, moisture and a carbon source, decomposition quickly controls diseases, odors, flies, scavengers and leachate.

The process is really about creating an optimum habitat for microorganisms to thrive and digest flesh. Ideal micro-habitat is created by putting protein-dense, wet carcasses that have a low carbon-to-nitrogen ratio, inside of a pile of relatively dry, porous material with a high carbon-to-nitrogen ratio.

Composting carcasses is important
Composting provides production facilities the advantage of biosecurity and biocontainment by reducing possible transfers of potentially infectious pathogens, especially reducing vehicles that must travel from or to other farms and facilities.

Fire, lightning, barn collapses, power failures, disease outbreaks, floods, fish kills and marine mammal beaching are all situations where composting is a fast and economical disposal option. Composting is a timely solution for any amount of animal carcasses if space and bulking materials are available.

When is composting not ideal?
Composting creates disease destroying heat, but prion diseases such as bovine spongiform encephalopathy, scrapie or chronic wasting disease require a very high temperature to destroy infectious material. Prion-infected carcasses can be composted, but the compost material may need additional disposal treatments after composting.

When animal tissues are eligible for rendering and transporting carcasses does not cause an unreasonable biosecurity burden on other animals or facilities, then rendering is a more ideal disposal method.

When space is limited or when there is not a supply of bulking agents (the carbon source), then composting may not be a timely option.

Resources
Queensland Government Department of Agriculture and Fisheries
Cornell University Department of Crop and Soil Sciences “Composting Animal Mortalities”