Composting Could Be a Viable Alternative for Carcass Disposal

Last year, 94,000 horses were slaughtered--a number that seems to be increasing for 2006--and another 100,000 were euthanatized. With horse slaughter on the edge of extinction in the United States and the practice of carcass rendering on the endangered list, horse owners will need to look at other environmentally friendly ways of carcass disposal. That solution might be composting.

Researchers at West Texas A&M have recently perfected a technique or "recipe" to compost large carcasses, including horses. They said composting could provide an alternative means for horse-carcass disposal if the American Horse Slaughter Prevention Act is passed.

The concept of large-carcass composting had grown to be a more accepted practice among feed yards and dairies in recent years. Researchers contend that composting provides an environmentally friendly way of carcass disposal in addition to burial, rendering, landfill disposal, or incineration, which can sometimes be costly to the owners or unfriendly to the enviornment.

"If they don't go to slaughter, they will have to go somewhere else," Lance Baker, PhD, MS, West Texas A&M University associate professor of animal science, told AgNews.

Last year, Baker, along with Brent W. Auvermann, PhD, MS, assistant professor of Agricultural Engineering, and Laurie Brown, a Texas A&M graduate student, conducted trials in an attempt to refine the process.

Auvermann, who has researched large-carcass composting for about five years, said, "Since we had already done some work with dairy cattle, which weigh about 1,400 pounds, a Quarter Horse at 1,000 pounds wasn't much different. The main thing is: the larger the carcass, the higher the stakes. It is critical that whoever does it, does it right."

Auvermann designed three composting "recipes" to test on horses. They consisted of a 100% stall waste (manure and horse bedding) mixture, a 50/50 mixture of cattle manure and hay waste, and a 50/50 stall waste and cattle manure mix. The group found that either 50/50 mixture worked better than the 100% stall waste.


Stall cleanings from the horse barns at West Texas A&M University are piled over a horse carcass and watered down to begin the composting process.

To compost a single carcass, researchers placed it on a bed of chopped straw before adding other materials. To jumpstart the process, Auvermann advised using pre-composted materials (because it already contains the needed bacteria) before adding the carcass.

The key to any compost pile is the moisture and nutrient content. Excessive moisture in compost creates problems, states Kathy Corwin Doesken, a research associate in the Department of Soil and Crop Sciences at Colorado State University. It can cause compost to leach harmful chemicals into the soil, and it can displace oxygen within the pile, which creates an anaerobic condition that produces an unpleasant odor and phytotoxic (toxic to plants) substances. To check the moisture content in the compost, Doesken said to squeeze the material in your fist. "If it sticks together, it is about 50% moisture and just right," she explains. "If free water can be squeezed out, it is too wet. If the material does not hold together at all, additional water should definitely be added."

The temperature of the compost pile can be a good indicator to determine if the process is working properly. Temperatures in the pile can reach 131ºF-155ºF within 24 hours and should remain there for several weeks to a month.

"Heat generated in composting promotes the growth of the type of microorganisms that begin breaking down the organic material, and kills pathogens, parasites, and weed seeds," Doesken explained.

Auvermann advises using a 48-inch compost thermometer (available online at or to monitor temperatures throughout the pile.

In the study trials, researchers turned the pile with the use of a front loader tractor after three months. At that time, only a few large bones remained. At six months, no identifiable pieces were left.

Baker said the entire process from start to spreading compost on the fields takes about seven to nine months.

"Without renderers to go to, this could become a big market," Baker told AgNews. "If you look at it environmentally and politically, it works. It's the whole circle of life thing. You grow the grass to feed the animals and then turn around and use them to do the same thing for the next generation."

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for .

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