Disposal webinar helps livestock producers with methodology

This isn’t the first time Mark Hutchinson, a professor at the University of Maine, has been called to assist in large-scale herd reductions. Diseases, yes. A pandemic, no.

Hutchinson has been deployed “numerous times for mass carcass mortality disposal incidents throughout the U.S. including in Iowa in 2015,” he said.

Hutchinson spoke during an April 29 webinar hosted by Iowa State University Extension and sponsored by the Iowa Pork Producers Association. Topics included environmentally sound disposal options, how compost works, above-ground burial, carbon feedstocks, windrow construction, and windrow management and troubleshooting.

Much of the information presented is relevant not only to the swine industry, but can be used for poultry, turkeys and cattle.

“You need to evaluate all the different options,” he said. “USDA has a list and that will include rendering, burial, incineration—but there’s a lot of different options on that list.”

Hutchinson focused on the compost and above ground burial. He said some of the best guidance documents can be found on the U.S. Department of Agriculture website at www.aphis.usda.gov/aphis/ourfocus/animalhealth/emergency-management/carcass-management/carcass.

“We have to remember that even though we’re talking about large numbers of animals, the same principles apply as you would on a daily routine management if you’re using composting,” Hutchinson said. “It’s just on a different scale.”

Instead of having to deal with one or two animals in regards to disposal, some producers are facing the disposal of thousands of animals at a time.

“But the basic principles of composting still apply,” Hutchinson said. “It’s important to understand those principles before you actually start building your windrows or start building your piles.”

There’s a science and art to composting, according to Hutchinson.

“We remember that it’s a biological process and we’re really depending on those microbes to do the work that we want to do, and that’s the decomposition of the carcasses,” he said.

One of the ways to know microbes are working in the pile is the heat and temperatures.

“It is the microbial activity that’s really breaking down that tissue and breaking down the bones,” Hutchinson said.

During a disease outbreak, the heat in the compost pile would actually be what is inactivating the disease.

“So, it’s important to track the heat to understand that biological activity and understand the function of the compost pile,” he said. “To take heat in a compost pile we normally take it in two different locations in the pile.”

Those two places are 12 to 18 inches from the outside, and the core. The 12 to 18 inch temp will usually increase first, and the core rising slowly behind that.

“Eventually, those two temperatures will actually invert and the inside temperature at the core will be warmer than the outside temperature at the 12 to 18 inch mark,” Hutchinson said. “And that’s when you know that your pile is functioning properly.”

Also remember this is an aerobic process, meaning microbes need oxygen, and the most efficient composting organisms are aerobic organisms.

“So we have to make sure that the piles are structured so that there is enough airflow to allow the oxygen to get into the to the microbes. There are some requirements for creating an optimal environment for the microbes.”

One of the biggest concerns is moisture around carcasses. When animals have been euthanized, especially poultry, foam is used and the carcasses are very wet.

“So we have to think about how to dry that material out,” Hutchinson said.

Other times when there is natural or disease mortality, the carcass material could be very dry. So pay attention to the moisture content carefully, he advised. In swine situations, depending on what carbon was used to line the pit, consideration must be taken as to how to manage the moisture in those piles.

“Moisture in the pile really has two different functions,” Hutchinson said. “It allows the microbes that feed—because they’re feeding at a molecular scale—they have to excrete digestive enzymes, and then absorb that back in through the fluid or the water around the particles. So it’s important for the microbes to be able to feed.”

The other function is the cooling of the pile.

“As a compost pile functions, the moisture—it’s kind of like us sweating,” Hutchinson said. “It’s a way in which the pile maintains its temperature or cools itself over time.”

If a pile gets too dry and continues to heat, it will never have the opportunity to cool down and it just stays hot without functioning properly. There’s really no way to maintain the temperature if this happens.

Air veracity is the airflow through the pile and how much air is actually moving. The pile structure plays an important part of the process, and it allows for large enough particle sizes so the air can get through the pile and get air to the microbes.

The ratio of carbon to nitrogen helps feed the microbes during the composition process. In most instances, carbon is wood shavings, corn stalks or other types of dried materials.

“This is one that we often talk about in different types of composting scenarios, but not as important in mortality management,” Hutchinson said. “It’s hard to manage that C to N ratio when you are talking about whole carcasses—they’re 300 to 400 pounds (for swine) or 1,200 to 1,500 pounds in cattle.”

The C to N ratio is more important for the cover in the base material than it is for the overall mixture. The base of the windrow needs to be coarse material with a 3-inch minimum size.

“However a lot of ground material is long and stringy which can work also,” he said. “It needs to allow airflow through the pile. On top of this coarse material, I recommend a thin layer of fines to absorb any liquids from the carcasses.”

The shape of the pile matters the most, Hutchinson said.

“We want these to be trapezoid,” he said. “We want to be fairly steep sides. This allows the airflow, or the convection air to move from the bottom of the pile through the chimney.”

The tops shouldn’t be flat. The pile shouldn’t be thin, wide or extremely tall either as those aren’t efficient ways to get air though the piles.

“So shape matters,” Hutchinson said.

There are two types of systems he said. Static—set it and forget it; with very limited management for six to eight months or possibly up to a year before the material is ready to move to another location. The other requires more management, but is a faster process, where the material is turned after a period of time—seven to 12 or 14 days.

“You would go in there and turn that pile and re-blend that material,” Hutchinson said. “This is going to accelerate the compost all by being able to re-blend that material that’s in those windrows.”

When the material is in a compost pile, they allow the air to move in from the side, usually at the bottom, and it moves into the core. Then air moves out to the top of the pile.

“It’s important to keep those air channels so that air can actually move through this and actually feed the oxygen into the core of the pile and allow the microbes to do their work,” Hutchinson said.

He showed an example of a pile where 450 laying hens were put four weeks prior, and all that was left was a few bones and feather quills.

Bones from larger animals will decompose, but time just depends on the age of the animals.

“The decomposition of mammalian bones depends on the degree of ossification,” he said. “With younger animals—less than a year—the bones disappear quickly. For older sows/boars, the head and other larger bones will be around.”

Hutchinson said when burying large numbers of livestock with above ground burial, there’s generally not a lot of odor.

“Once the soil cap is in place, you generally don’t notice any odor at all,” he said. “In about one or two weeks the animals will settle and a few cracks will form on the mound. Some odor can come from these cracks, so it is best to fill these cracks with a hand tool, like a rake.”

To keep predators or scavengers from raiding the piles, the first 2 feet of cover acts like a biofilter to absorb odors.

“If the predator doesn’t smell anything, it won’t raid the pile,” he said. “Lack of cover is probably the number one reason for vector activity. The cover material also needs to have significant fine material for surface area to absorb the volatile organic acids.”

For more information visit the USDA website mentioned earlier in the story. Hutchinson said the most helpful document for him is “Best Management Practices for Large Animal Carcass Composting” by retired Maine Department of Agriculture, Conservation and Forestry agent, Bill Seekins. It can be found at www.maine.gov/dacf/php/nutrient_management/documents/BESTMANAGEMENTPRACTICESforCarcassComposting-2011Complete.pdf.

Kylene Scott can be reached at 620-227-1804 or [email protected].