Frequently Asked Questions - Composting
What is required in Minnesota for a carcass compost facility?
Board of Animal Health rules require that composting facilities be constructed on an impervious pad using rot resistant materials. For best results, facilities should be covered with a roof and moisture levels should be maintained between 45 and 50 percent. Carcasses and litter should be layered so that a carbon:nitrogen ratio is established between 15:1 and 35:1 (optimal 23:1). To ensure pathogen reduction, compost piles must go through at least two heat cycles of greater than 130 degrees Fahrenheit.
What ingredients are used for composting carcasses?
Carbon and nitrogen are the key ingredients in the composting process. In most cases, sawdust, wood shavings, chopped straw, or similar plant material is used to provide the carbon source. Carcass material, with the possible addition of small amounts of manure, will generally provide adequate nitrogen.
Two sample recipes for composting carcasses are presented below. Ingredients may be altered depending on the availability and cost of the carbon source, but the carbon:nitrogen ratio must be kept near 23:1. The advantage of using sawdust is that it is clean, absorbent, and provides a large surface area for bacterial contact. Poultry litter has the added advantage of higher moisture and nitrogen content. If straw or corn stalks are used, they should be ground to create more surface area.
| Compost Recipe #1 | Compost Recipe #2 | |
|---|---|---|
| Carcasses | 100 lbs carcasses | 100 lbs carcasses |
| Carbon Source | 150 lbs poultry litter 10 lbs straw |
200 lbs sawdust |
| Water | 4 gallons water | 10 gallons water or liquid manure |
| Time | 30 - 90 days/bin | 30 - 90 days/bin |
How do I start a compost pile?
Primary compost piles are started by placing 12 inches of sawdust or litter on the floor of the compost facility. Carcasses are then placed in a single layer on top of the sawdust and at least 12 inches away from the walls of the facility. The carcasses are covered with another 12 inches of sawdust and the pile is ready for the next layer. Each additional layer of carcasses is covered with another layer of sawdust. In order to add a large sow or boar to the pile, a trough can be dug into the existing layers to accommodate the carcass. Water is added to each layer as needed to maintain the proper moisture level.
Once a compost site is fully operational, finished compost may be recycled back into the primary bins in equal proportion to new sawdust. This helps to conserve on raw materials, accelerates bacterial activity, and provides needed heat when new piles are started in the winter. Temperatures should be continuously monitored and the piles should be turned to add air when the temperatures start to drop below 130 degrees Fahrenheit. Each time the pile is turned, internal temperatures will rise and the composting process will accelerate.
How often should I turn my compost pile?
Compost piles should be turned every 30 - 90 days. With each turn the composting process accelerates, yielding improved results.
How long does it take to complete the composting process?
Speed of carcass decomposition depends on the size of carcasses, the frequency that the pile is turned and the ratios of nutrients in the compost pile. Under ideal conditions, most compost material will be suitable for land application in 60 to 180 days.
What do I do with finished compost material?
Once the compost is finished, it may be land spread at the proper agronomic rates for the crop being grown. On a wet basis, a ton of finished compost consists of approximately 1000 pounds of dry matter, 20 pounds of nitrogen (4 pounds from ammonia), 2 pounds of phosphate, and 6 pounds of potash.
Does composting material have an unpleasant odor?
Carcass compost facilities should emit very little odor if properly operated. This is because the products of aerobic microbial digestion are mostly carbon dioxide and water.
Are flies and rodents a problem around compost sites?
Flies are not a problem around compost piles because internal temperatures above 130 degrees Fahrenheit will kill existing fly larvae. Also, when piles are covered by at least 12 inches of sawdust or litter, flies and rodents are not attracted to the area.
Does composting kill bacteria and viruses?
Studies have shown that proper composting of animal carcasses will destroy most viruses and bacteria common in livestock operations. Viruses such as avian influenza, Newcastle disease and pseudorabies virus are completely inactivated by the end of the second stage of composting. Similarly, bacteria such as Salmonella enteritidis, Pasteurella multocida, Erysipelas rhusiopathiae and Salmonella cholerasuis have been successfully destroyed by the composting process.
For additional information refer to Composting Animal Mortalities or contact the Board of Animal Health at 651-296-2942.