March 18, 2002 - Composting an alternative to rendering for small processors

by Bryan Salvage, Meat Marketing & Technology

Sound bite:“Composting, when appropriately managed, offers an environmentally friendly and safe disposal opportunity for meat processors. However, guidelines are needed to enable processors to efficiently compost their waste streams without creating nuisances.” -- Harold M. Keener, associate professor, department of food, agricultural and biological engineering, Ohio Agriculture Research and Development Center, The Ohio State University

No doubt about it, things are tough for small processors. A concentrating industry, large competitors continuing to grow ever larger, increasing insurance and workman's compensation costs and distribution restrictions for plants that are state inspected are among the major challenges they face.

But another new challenge has recently emerged due to the changing business climate in rendering.

“The rendering companies are now charging $25 a pickup,” Vic Caven, vice president of Conover, Ohio-based Caven's Meats Inc., told the Meatingplace.com during the Ohio Association of Meat Processors annual convention in Dayton. “We used to get $2,500 or $3,000 a month that they would pay us and now we're paying them.”

OAMP discovered long ago that issues like this can best be solved if a group tackles the problem versus each individual company trying to tackle it on its own. As a result of this all-for-one philosophy, a session on alternatives to rendering was held during the convention in hopes of helping interested members to defray their rendering costs.

A viable option

“Composting is a viable option for livestock producers and processors in rendering dead animals,” said Harold M. Keener, associate professor, department of food, agricultural and biological engineering, Ohio Agriculture Research and Development Center, The Ohio State University. “Until recently, more than 85 percent of meat processing by-products were rendered. Today, however, processors are looking for alternatives as disposal costs have dramatically increased.

“More recently, composting of animal mortality has been adopted by farmers and has proven to be a very effective means of handling animal mortality,” he added. “Composting, when appropriately managed, offers an environmentally friendly and safe disposal opportunity for meat processors. However, guidelines are needed to enable processors to efficiently compost their waste streams without creating nuisances.”

Keener told his audience that the composting of meat processing by-products can be done efficiently in a windrow system with limited turning and with or without aeration. He participated in a preliminary study, which investigated meat by-products that were added to sawdust in an enclosed pile without forced aeration and with limited turning.

Basics of the study

Two test bins at the OARDC Compost Center were used to compost meat processing by-products (MPBP) from Markey Custom Butchering, West Salem, Ohio. Both bins were filled with sawdust and MPBP on Sept. 26, 2001.

Here are the basics of the study: A sawdust base was constructed in both bins and MPBP from 12, 250-pound hogs and five 1,000+-pound steers were added. Bin 1 received 1,923 pounds , with the MPBP placed on 19.7 inches of sawdust and then covered with another 4.7 inches of sawdust. Bin 2 had 2,043 pounds of by products, which was placed in two layers of 1,000 pounds each separated by 4.7 inches of sawdust. Temperature sensors were located in each bin below and above the waste material.

Based on volumes, mixing ratios were 6:8:1 for sawdust to MPBP. This resulted in an estimated moisture level of 49 percent. Ideally, the sawdust should have been from 45 to 50 percent, which would have raised the mix moisture to 59 percent, Kenner said.

After 21 days, both bins were opened for inspection and resealed. Their bed depths had decreased by 25 percent.

“Some head, gut material and bone trimmings were discernable, but the blood was not,” he said. “No odor was observed during the 21 day test period, but after opening pile two a faint decaying odor was present.”

After both bins were resealed, they were topped with new sawdust to the original depth to provide more insulation for each pile and to ensure odor control.

After 35 days, the compost was removed from both bins, inspected for rendering residues and placed back into the bins. Several leg bones, heads, small quantities of skin and paunch contents were present.

“Very little body tissue remained and no liquids were present,” Kenner said. “Some odor, best described as a 'sweet' decaying small, was present during the removal and refilling phase. Once the bins were refilled and capped with 4 inches of sawdust, the odor dissipated.”

After 70 days, the compost pile was turned for a second time. Some odor was still present during turning. Skull bones with some tissue remained, The compost was mixed and put back into the bones. This time, no fresh sawdust was added for cover.

“Over the course of the next two weeks, odor emanated from the pile and was discernable up to about 25 feet from the bins,” Kenner said. “Removal of the company occurred on Jan 4, 2002, after 100 days.”

Ten samples from each compost bin were collected by the Ohio Department of Agriculture for bio-assay for E. coli and Salmonella ssp. No Salmonella ssp. was detected and E. coli was detected in only two samples at 3.6 MPN/g, Kenner said -- well below current guidelines for safety.

Keener said in looking back at the study, observations on the 35th day indicated paunch material was delayed in breaking down compared to other materials.

“It would be a recommendation to slit the paunch after layering it in the compost pile,” he said. “Some large bones remained at the end of the 100-day process and may require separation and recycling to decalcify to where they would not be an issue if land applied.”

The system used for composting could be either a windrow or bin-type system. The bin would preferably be built on top of a concrete or impervious floor to minimize lecheate concerns.

“Improving air pathways into the base of the composting pile using aeration pipes may decrease decomposition times and odor production, Keener said. “Any reduction achievable in processing the waste stream will reduce the fixed costs of the composting system.”

Be considerate of your neighbors

Aside from meeting regulations on composting, a processor should not have any problems as long as no one complains about odors, said Angel Arroyo-Rodriguez, infectious waste/composting specialist, division of solid and infectious waste management, Ohio Environmental Protection Agency.

“And you will have to test the compost [for safety] if it is sold or given away and not used on your land,” he added.

One person who runs a compost facility in Ohio had one piece of advice to the audience.

“If you don't have neighbors nearby, you eliminate a lot of potential problems,” she said.

Keener also cautioned the audience against charging head-first into composting.

“The process isn't done without management,” he said. “If you decide to do this, you must look at the economics [and regulations].

When the Meatingplace.com asked Keener if adding chemicals to composting to speed up the process was something processors could consider, he said it would add to the costs. Incineration would also be more expensive as a process, particularly when it comes to maintaining the incinerator.

The Meatingplace.com recommends that any readers interested in pursuing composting to first contact their state Environmental Protection Agency to learn about composting facility requirements.

This article reprinted with permission from Meat Marketing & Technology.

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