Composting May Be the Answer to Rising Rendering Costs

by Nancy Carver Singleton

Cattlemen are starting to join the growing number of poultry and pork producers who use composting for their dead stock. This form of composting is growing in popularity as many rendering companies start charging fees or go out of business. Disposal also became more difficult as some states prohibit or severely restrict long-used disposal methods such as burning and burial due to environmental concerns.

The January closing of a rendering plant in northeast Colorado led some feedlots to start composting, said Tim Stanton, an extension beef specialist there. "My guess is that a pretty significant number of feedlots in Colorado are doing that." He has heard of pick-up charges ranging from $30 to $80 for cattle, with more charged for bigger animals.

Some of the Colorado feedyards composting mortalities were already composting manure. "So composting livestock was the logical next step since they had the equipment. Then there are others who have not bought expensive equipment, but are still doing it basically using a front-end loader," Stanton said.

Rich McKee, executive director of the feedlot division for the Kansas Livestock Association, knows of "just a handful" of feedlots composting mortalities. Some did so because renderers stopped picking up animals taken in the past, such as those that had been dead awhile.
Brent Auvermann, an agricultural engineer at the Texas A&M University Agriculture and Extension Research Center at Amarillo, Texas, said there is a "tremendous amount of interest" in composting. That interest is spurred largely by rendering charges, which he's heard are $8 to $12 a head for cattle around Amarillo. Composting is not yet widely used in his area though.

It is a big commitment for a large feedlot to compost animals, Auvermann said, citing the management and space needed. It is much easier for a small operation such as a stocker producer to try composting because their investment and deaths are less. Auvermann has set up three large animal composting demonstrations through a USDA water quality grant. He plans to have six to 12 demonstrations in different parts of Texas.

Tom Glanville, a professor of agriculture and biosystems engineering at Iowa State University, believes rendering truck pickup is the most ideal way to handle livestock deaths. "It makes the best use of those materials. It is really unfortunate that the rendering business is on the decline."

ISU began a cow composting project this fall that is an off shoot of earlier studies with poultry and swine. Glanville, who heads the study, is aware of only several Iowa cattlemen who compost mortalities. "We wanted to get data and help new adapters maximize their potential for success," Glanville said. Mortality composting is on the "cutting edge" in the beef industry and little research has been done.

ISU's cow composting project was also initiated because of the Iowa Department of Natural Resource's, request to study procedures that might be used during a livestock disease outbreak.

Cover material is a key component of composting, said Tom Richard, another ISU professor of agriculture and biosystems engineering working on the study. This material blocks easy access by varmints and helps trap odors. Skimping on it can lead to saturation, odors, leaching and cold internal temperatures. At least 18 inches of cover are put on top, between and below carcasses for this study. ISU researchers monitor the soil under windrows to see if nutrients leach and how much rainfall the cover material absorbs.

The three cover materials studied in this project -- corn stalks, silage and yard waste compost -- were chosen because of quick availability during an emergency,
Richard said. Iowa has 80 companies that process yard waste. One of the study's objectives is to evaluate the performance and thickness of the three covers.

Auvermann said it is challenging in Texas to find cover materials that are good sources of the carbon needed for composting. Since so much cover is used, it needs to be available at little or no cost. The composting demonstrations he works with urge producers to form partnerships with those who have carbon sources. For example, producers might haul away wood shavings and horse manure from the horse barn at a county fair, which would save the fairboard landfill fees. Cotton gin trash, peanut hulls and waste hay are other low-cost carbon sources in Texas.

Temperature and moisture are also important in composting. Glanville said producers can use a long-handled composting thermometer to check temperatures, with ISU recommending temperatures over 130 degrees F.

But temperatures higher than 165 kill desirable bacteria and can temporarily stop the decay process.

ISU researchers are trying to develop a "recipe" that producers can use to calculate the amount of moisture needed for composting to occur. "The real key is you have enough material underneath to absorb the liquid released as carcasses break down. That liquid will essentially activate the base material and help heat up the pile," Richard said.

Glanville said composting is more complicated in states like Iowa that typically have heavy rainfall in the spring and early summer. Most of the cow composting he has heard about takes places in areas with little precipitation. Although he strongly advises pork producers to compost in bins under a roof, that is impractical for larger animals.

"With larger species, you are forced into an open windrow situation. That makes the operations somewhat more vulnerable to saturation during wet weather. There's going to be a need for additional management, particularly during the wet seasons," he said.

"I think it has good potential for cattle, but we will know a lot more by the end of next June. We structured the research to help us understand the performance in seasons we think are most difficult," Glanville also said.

Although little or nothing is left of hogs after composting, some large bones will remain from cows. Glanville said the largest bones may need to be removed from the finished compost since they could interfere with equipment when the compost is spread on fields.

Some of ISU's work in composting is available at www.abe.iastate.edu/pigsgone/ Although this site focuses on swine, many of the general principles also apply to cattle. The "More Composting Resources" option brings up livestock composting fact sheets from several other universities. ©