Mortality composting for horses

Researchers are working to evaluate an often-overlooked but practical and environmentally friendly method for disposing of a horse’s body.

Nearly every horse owner eventually confronts the uncomfortable question of how to dispose of a horse’s body. Now, researchers at the University of Minnesota are working to evaluate a practical, environmentally friendly answer: “mortality composting.”

“Horse owners have limited mortality management options, which include burial, incineration, rendering, and composting,” says Minnesota graduate Hannah Lochner. “Most prefer burial over other methods. However, site restrictions to protect water and soil quality and lack of feasibility during winter months in Northern climates can present barriers to burial.” In addition, many renderers (plants that process carcasses) no longer accept chemically euthanized animals.

Nearly every horse owner eventually confronts the uncomfortable question of how to dispose of a horse’s body. (Adobe Stock)

Composting—allowing a horse’s body to naturally break down above ground under controlled conditions —is an option many horse owners have never considered. Though composting is common in other livestock industries, “it is less familiar in the horse industry,” says Lochner. “Therefore, research and education around equine mortality composting address a need for horse owners seeking an economical and environmental mortality management practice.”

An often-cited concern of equine mortality composting is that the euthanasia agent, such as sodium pentobarbital, will leach into surrounding groundwater or sicken animals who might scavenge a carcass. In a recent study, however, the Minnesota researchers found that proper composting technique can address both of those concerns.

Is mortality composting safe?

For the study, researchers monitored the decomposition of eight horses euthanized with sodium pentobarbital. In the fall and spring, four euthanized horses were composted on a bed of wood chips, covered with a 2:1 mixture of stall waste and cattle manure. The compost piles were sampled for levels of sodium pentobarbital and nutrient composition approximately 50 days later and again at 216 days. Analysis showed that about seven months after composting began, the quantities of sodium pentobarbital had been reduced by 94 percent.

 “Bioactive conditions achieved during the composting process significantly reduced quantities of sodium pentobarbital,” explains Lochner. There are no recommendations for minimum acceptable levels of sodium pentobarbital in finished compost, but “the small amounts remaining present a low risk to animals,” she says.

Odor is another concern. But Lochner says proper construction and management of the compost pile can reduce or eliminate that problem. “A thick carbon base composed of coarse and fine particles, such as 18 to 24 inches of playground wood chips [topped with] a three-inch layer of pine shavings, absorbs moisture and prevents leaching. Odor in our study was managed by covering the carcass with two feet of manure mixture. This cover acts as a biofilter, binding and trapping odorous compounds within the pile.”

For those interested

Horse owners interested in mortality composting will need to do a bit of research and preparation, says Lochner. “First, state and local governments usually regulate carcass management. Secondly, there are general recommendations for selecting a compost site, [regarding] drainage and slope and easy access for heavy operating equipment. Thirdly, [proper construction and management] of piles plays a key role in protecting the environment/animals and promoting microbial activity during composting.”

A conversation about mortality composting can be difficult to have but is ultimately worthwhile, says Lochner. “End-of-life planning altogether is emotionally difficult for many horse owners, myself included. However, many understand that preparation can help ease the transition of losing a horse.” Click here for more information about mortality composting.

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