Organic Burial Composting of Cattle Mortality
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Karl VanDevender, Biological and Agricultural Engineering,
Jodie Pennington, Animal Science Section,
Merle Gross, Washington County (retired), and
Johnny Gunsaulis, Washington County,
University of Arkansas Division of Agriculture
Cooperative Extension Service
Abstract
Effective May 1, 2004, composting was approved as a method of disposing carcasses or portions of carcasses of large animals (cattle, other ruminants, horses, and swine) unless otherwise directed by the state veterinarian. Previously, the composting option required that the carcasses or portions be limited to 60 lb. In 1995, an exemption from the size restriction was granted for swine composted in bin style composting facilities. Composting of large animals offers a method of dead animal disposal that can be practical, economical, and legal for many cattle producers.
Although rendering, extrusion, and incineration are approved as methods of large animal disposal, burial is the only method other than composting that is feasible for most cattle producers. Burial guidelines designed to protect water quality limit the land available for burial. In addition timely access to equipment to bury mortality is often a challenge.
Introduction
Composting is the decomposition of organic materials under predominately aerobic conditions. While it occurs naturally under a wide range of conditions, in order to achieve rapid decomposition, specific conditions are required. These “proper” conditions are often thought of in terms of the compost “recipe”. The primary consideration in determining the proper recipe is the carbon to nitrogen (C:N) ratio and the moisture content.
Composting is accepted and approved as an environmentally sound method of mortality disposal that also addresses animal health and disease concerns. Normally, composting involves the use of structures with primary and secondary bins located on concrete pads and under roof. To minimize facility size and construction cost active and attentive management is used to achieve maximum “through-put.”
One of the critical features of the disposal of animal mortality is disease control. Composting exposes disease-causing organisms to heat, the toxicity of decomposition products, and the microbial antagonism. Of these, heat is probably the most effective in destroying disease-causing organisms. It is generally considered that temperatures of 122-140#F will kill most viruses. These temperatures also are effective in killing the bacteria that cause anthrax and tuberculosis. It should be noted that while these temperature will kill the anthrax bacteria, it would not kill spores of anthrax or prions associated with bovine spongiform encephalopathy (BSE). Some bacteria such as clostridia can survive these temperatures. For this reason, while elevated temperatures are generally effective in killing bacteria, composting sites should be isolated from the rest of the farm and properly managed. Proper management will help ensure elevated temperatures and prevent the access of disease vectors, such as flies and animals, to the composting mortality.
In the traditional method of determining the ratios of the compost ingredients, the ingredients are assumed to be thoroughly and uniformly mixed. However, when composting animal mortality, it is not practical to grind the mortality to achieve a uniform mixture. Thus, for larger carcasses, there are pockets of low C: N ingredients (the mortality) buried in a larger volume of higher C: N ingredients (the carbon source material). The moisture content within the compost pile also is not uniformly distributed and tends to be highest within and around the mortality.
As a result of these conditions, there are likely to be pockets of anaerobic decompositions in and immediately around the mortality. There also may be a tendency for water from the mortality to saturate the carbon material adjacent to the mortality, resulting in moisture migration to the compost mixture. This means additional carbon material, above the requirements for an ideal C:N ratio, needs to be placed under, to the side of, and on top of the mortality. The extra carbon material serves as a sponge to absorb excess water from the mortality. It also serves as a “biological” filter where odors and objectionable gases are treated prior to being released to the air.
These factors lead to the concept organic burial composting (OBC) as a specialized class of composting for the disposal of large animal carcasses. Here the use of additional carbon material is used minimize the structural and management requirements of traditional animal composting facilities. In concept, OBC is simply the burial of mortality in a sufficient amount of carbon to ensure that decomposition takes place in a manner that is acceptable from an environmental and animal health perspective. The objective of this demonstration was to illustrate to cattle producers and the Arkansas Livestock and Poultry Commission the use of composting as an acceptable method of dead animal disposal.
Demonstration Methods
The total required volume of carbon material for OBC was based on the size of the animal carcass plus additional material to absorb access water and malodors. Design calculations indicated that surrounding a 1,400 lb cow with 18 inches of sawdust exceeded the carbon requirements while providing the necessary moisture and odor control. However, for carbon sources with lower C:N ratios such as rice hulls and straw, a minimum of 24 inches of supplemental carbon source is required to ensure adequate carbon for decomposition to occur and adequate moisture and odor control.
Green sawdust was stockpiled to in preparation of the first mortality. When the mortality became available the participating producer built the compost pile and notified Extension staff who made periodic temperature measurements using an analog compost thermometer.
On September 23, 2002, the carcass of a mature dairy cow was placed on an 18-inch pad of green sawdust. Due to reach limitations of the skid steer being used, it was not possible to place the T-posts and net wire around the carcass as planned. Instead, the carcass was covered without any structure to keep the sawdust from sliding down slope. Then, an existing fence and cattle panels were used to build a fence around the pile. While this approach covered the carcass and prevented large animal access to the pile, it also increased the amount of sawdust needed to cover the carcass. This pile was located outside and exposed to the weather.
From October 24, 2002 to December, 2003, an additional 14 cows, mostly mature animals with a few heifers, were added to the pile. Initially, more sawdust was added with each additional mortality. After all available sawdust was used, other on farm carbon sources such as waste silage and waste hay were used. Typically the addition of the new mortality was accomplished by partially excavating the pile, adding the mortality, then covering the animal with a blend of existing compost and new carbon material.
Demonstration Results
On October 2, 2002, nine days after the first carcass was placed, the pile temperature was 126 oF. The temperature climbed to a recorded peak of 129 oF on October 7. By October 24, the temperature had dropped to 119 oF. On this date the pile was excavated in four separate locations that included the front leg area, the body cavity area, the tail/hip area, and the head area. In the front leg area only one large leg bone and hoof with some connective tissue was found. In the body cavity area the only identifiable pieces were a few hairs. In the tail/hip area only a few large bones were located. In the head area, the skull and some soft tissue were found. While excavating the pile, no excessive odors or flies were observed. In the 31 days since placement of the carcass, the decomposition process had almost completely processed the mortality.
From September, 2002 to December, 2003, 15 animals had been disposed of in compost pile that had expanded from a 15 ft x 15 ft pile to a 15 ft x 45 ft windrow. The most rapid decomposition took place with the first animal being placed in green sawdust (almost completely decomposed with in 31 days). As more mortality was added to the pile and other carbon sources were used, the rate of decomposition decreased.
On occasion when a fresh carcass was excavated or was not adequately covered, excessive odors did occur. However, when in place, the recommended layer of carbon material did a good job of filtering the odors to background levels.
The fence around the pile consisted of a barbed wire fence on one side and several used stock panels on the other three sides. Therefore, there was easy access to the pile by dogs and wild animals. However, no indication was ever found that animals had dug into the pile.
Due to the concern for water to leach from the pile into ground and surface water, the ground surface down slope from the pile was regularly inspected for signs that the pile was leaching and potentially becoming a source of water contaminates. However, in spite of the fact that the pile was exposed to the weather, no signs of significant water and nutrient movement into the down slope vegetation were ever observed.
One problem that was observed was that the sawdust was prone to blow and slide off of the pile. This was addressed by putting a top layer of waste silage on the sawdust. Of the various carbon sources utilized in the demonstration the green sawdust performed the best in terms of rapid decomposition. However, waste hay, and waste silage also worked but at a significantly reduced rate.
Summary and Recommendations
As a result of this demonstration, effective May 1, 2004 the Livestock and Poultry Commission amended their regulations for the disposal of Large Animal Carcasses to permit Organic Burial Composting for large animals. To provide information to the public the fact sheet “Organic Burial Composting of Cattle Mortality” (FAS 1044) was published.
For infrequent mortality disposal such as on cow calf operations, burial of the mortality in a carbon source such as waste hay at an appropriate site is recommended. This method allows for disposal in a legal, efficient, and economical manner. When composting is exposed to the weather, the compost material (carbon source) may be sawdust, hay, etc., but may not contain manure. When the compost is protected from the weather, compost material (carbon source) for the carcasses may be sawdust, hay, etc., and may contain manure. Composting involving manure must be done in bin(s) that has a concrete floor to provide an all-weather base, roof to exclude excess moisture and rot-resistant bin construction to support the compost material and withstand stresses applied by tractor loader.
There are two basic approaches that apply to the outside composting of large mortality: pile/bin and windrow. Both approaches start as a pile, however in the windrow method, new carcasses are added repeatedly to one end forming a windrow. Both approaches can be done without the use of some type of sidewall, such as fencing or wooden walls. However, the use of sidewalls will reduce the volume of carbon material required, and help to ensure the 24 inches of cover. Walls will also help to prevent pets and other animals from digging into the pile.
Additional information is provided in the fact sheet “Organic Burial Composting of Cattle Mortality” (FAS 1044).
References
Does composting kill contagious disease? Hoard’s Dairyman. January 25, 2002.
Guide D-108, Whole Animal Composting of Dairy Cattle. 2002. M. Looper. New Mexico State University Cooperative Extension Service.
Natural Rendering: Composting Livestock Mortality and Butcher Waste. 2002. J. Bonhotal, L. Telga, J. Petzen. Cornell Waste Management Institute.
NRAES-54, On-Farm Composting Handbook. Editor: Robert Rynk. 1992. Northeast Regional Agricultural Engineering Service. Ithaca, NY.
Ohio’s Livestock and Poultry Mortality Composting Manual. 2000. Ohio State University Extension.
Part 637: Environmental Engineering National Engineering Handbook; Chapter 2: Composting. February 2000. USDA, Natural Resources Conservation Service.
Personal correspondence with Dr. Bill Seekins, agricultural researcher, Maine Department of Agriculture, and member of the University of Maine Compost School. February 2002.
Regulation for the Disposal of Large Animal Carcasses, Excluding Dogs and Cats. Effective May 1, 2004 .Arkansas Livestock and Poultry Commission. Little Rock, AR.
K. VanDevender, J. Pennington. 2004. Organic Burial Composting of Cattle Mortality. FSA1044. University of Arkansas Cooperative Extension Service. Little Rock, AR.
