Use of a Mini-Composter for Disposing of Farrowing House Mortality

Livestock Update, May 2000

Mark Estienne, Swine Research Physiologist,
and Allen Harper, Extension Animal Scientist, Swine
Virginia Tech Tidewater AREC

Still born rates of one pig per litter are common, even on swine farms exhibiting good performance. Of the pigs born live, 11% die before weaning (Murphy et al., 1995). Thus, a 500-sow unit producing 1.8 litters per sow per year and 10 pigs born live per litter, looses approximately 1800 pigs annually. In addition, there is a considerable amount of afterbirth that must be disposed of after each sow farrows. For the manager of the swine farm, a pertinent question becomes "What do I do with the dead pigs and afterbirth tissue?"

Existing methods of dead pig disposal all have serious limitations (Murphy et al. 1995). For example, the number of renderers has decreased dramatically, and the few farmers that have access to this service may pay excessive handling fees. The potential spread of diseases from farm to farm, by renderer personnel and their vehicles is also an important consideration. Incinerators are expensive to purchase and operate and may generate air pollution and odors. Finally, problems with pit burial include odor from, and the attraction of scavengers to, "dead pits" that are not properly covered. There also is the possibility of significant ground and surface water contamination, for which producers may be held liable.

At the Tidewater Agricultural Research and Extension Center (TAREC), we are investigating composting as an option for the disposal of dead pigs. In this issue of the Livestock Update we describe the use of a "mini-composter" for disposal of farrowing house mortality.

What is Composting?
The action of aerobic, thermophilic bacteria convert the combination of nitrogen-rich (e.g., dead pigs) and carbon-rich (e.g., sawdust) materials into humic acids, bacterial biomass, and organic residue called compost. During the process, heat, carbon dioxide and water are generated.

How Do I Compost Dead Pigs?
Details for constructing a mini-composter were described by Murphy (1992). Briefly, a mini-composter consists of a box made of four, 40 x 36-inch screen and lumber panels filled with sawdust. The mini-composter is loaded by first forming a v-shaped trough in the sawdust. Dead pigs and/or placentas are then added to the bottom of the trough. The ideal moisture content in a mini-composter employing sawdust is 50 to 60%. Sawdust that has a damp appearance and feel is near the proper moisture content for composting. Very dry sawdust may require the addition of 1.5 gallons of water per cubic foot of sawdust to obtain proper moisture content.

After addition of tissue and water, the tissue is covered with sawdust and a minimum covering depth of 6 inches is ensured. The tip of a long-stemmed thermometer is placed immediately below the tissue.

Temperatures in the range of 130 to 160º F are indicative of a high level of microbial activity and decomposition of placed carcasses. Carcasses are rapidly reduced, leaving only bones that are easily crumbled. The resulting product is free from harmful pathogens and is nutrient-rich.

Typically, 30 pounds of tissue can be added to a mini-composter daily until a total addition of approximately 800 pounds of tissue has been achieved. At that point, the mini-composter is emptied and the contents used as fertilizer.

Operation of a Mini-Composter at TAREC
Figure 1 depicts the loading and temperature characteristics for the mini-composter in use in the farrowing house at the TAREC swine facility. Dead pigs and placentas were added at various times throughout the five-week period. Temperature of the compost pile increased from less than 60º F to over 120º F within one week and high temperatures were maintained for the remainder of the period. During the first two weeks of operation, a total of nearly 60 lbs. of tissue was added to the mini-composter. After two weeks, we sifted through the compost pile and were able to recover only 6 lbs. of easily crumbled bones. No insect activity or noxious odors were detected during the experimental period.

Summary
The mini-composter appears to be a good option for disposing of farrowing house mortality. We are in the process of building a large composting unit that will provide sufficient space to process market hogs, sows and boars. The Virginia Agricultural Council is providing funds for this project. Research to be conducted in the new facility will include an evaluation of various carbon sources (peanut hulls, cotton gin trash, etc.) for use in composting units and the agronomic properties of the final product.

References
Murphy, D.W. 1992. Minicomposter Dead Bird Disposal. Fact Sheet No. 642 available from the Lower Eastern Shore Research and Education Center, 1190 Strickland Dr., Princess Anne, MD 21853-1247, or phone (410) 651-9111.

Murphy, D.W., M.J. Estienne, C.N. Dobbins, Jr. and K.A. Foster. Disposing of Dead Swine. Purdue University Cooperative Extension Service. Pork Industry Handbook Fact Sheet No. 133 available from the Virginia Tech-Tidewater Agricultural Research and Extension Center, 6321 Holland Road, Suffolk, VA 23437, or phone (757) 657-6450, ext. 114.

Figure 1.	Daily Temperature and cumulative weight of porcine tissue added to a mini-composter at the TAREC swine unit. On Day 14 (indicated by vertical arrow), sawdust from mini-composter was sifted and only 6 lbs. of tissue was recovered.

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