Composting dead sheep
By David L. Greene
Sheep farmer and retired county extension agent
White Hall, Maryland
Since renderers no longer pick up and dispose of sheep, producers have few options in the disposal of sheep and sheep products. Because of the concerns over groundwater pollution, burying sheep is not practical or recommended in most cases. Incineration is the best alternative, but is very costly, therefore not very practical for small and mid-size sheep producers.
Composting is a recycling process where bacteria and fungi decompose organic material in an aerobic (oxygen present) environment. Organic wastes, in this case dead sheep, are transformed by bacteria into a soil-like material similar to humus.
The composting process generally occurs in two stages: primary and secondary. During the primary stage, a higher rate of biological activity results in rapid composting and higher temperatures in the bin. Conversely, the secondary stage has lower biological activity resulting in lower temperatures.
In composting, the material mix is very important. The mix requires the proper balance of carbon and nitrogen. When this balance occurs along with adequate levels of air and water, the composting process results in nearly complete disposal of dead sheep with little odor and run-off. A carbon to nitrogen ratio of 25 to 1 is best, with the sheep supplying most of the nitrogen.
The concentration of oxygen in the mixture is very important. Air is trapped in the material used for composting. As the bacteria multiply, oxygen is used up and additional oxygen must be re-supplied for the composting process to be successful. Turning or mixing the pile after the process slows down will add oxygen and help it to restart the composting process.
The carbon source is also very important in allowing air penetration and holding moisture in the pile. Green (undried) sawdust has been the carbon source of choice in large animal composting. Wood chips will work also, but more attention must be given to monitoring the pile to be certain the correct moisture is present, as chips tend to dry out faster than sawdust. To encourage bacterial growth and rapid composting, the mixture must be 50-60 percent moisture. If a handful feels moist, but no water can be squeezed from it, the mixture is probably okay.
Monitoring the process with a three foot composting thermometer (which can be purchased in most garden supply stores) will show if the pile is heating up properly. When the temperature of the pile declines below 100 F, adding water and stirring to provide oxygen should cause the pile to heat up again. When temperatures remain above 130 F for three consecutive days, disease-causing pathogens within the pile will be destroyed.
After the composting process has completed, usually in 6-8 weeks for active composting and 15 to 20 weeks for inactive, the material can be spread over pastures and crop
fields. A good time to clean out the composter is when the manure is hauled from the barn. A manure spreader does a good job of breaking up some of the larger bones that may not be fully decomposed.
How to Get started
Usually only one bin will be needed for most flocks under 25 to 30 ewes. Bins should be at least six (6) square feet and possibly eight (8) square feet for larger breeds. Do not build bins larger than necessary since larger bins require more carbon material (sawdust, chips, manure etc.). The boards on the sides of the bin should have gaps of one-half to three-fourths inches (? to ?) for proper airflow. Bins should be located close to buildings and a water source, but not in direct contact with the flock. A roof over the bins is recommended, but is not necessary if a tarp can be used during periods of excessive rainfall.
Larger flocks will require two bins. Dead lambs, afterbirth, or material returned from the butchering process can all be composted by this method as well. Begin with at least one (1) foot of sawdust in the bin before placing in the dead animal. Situate the carcass so that at least a foot of carbon material (sawdust in this case) is between the animal and the bin sides. Cover the carcass with one and a half feet of material and monitor every few days. Recent research has indicated that a 120 lb. carcass will require about twelve (12) cubic feet of sawdust.
Personal experience over the last four years has shown this process works well, is a labor saver, is low in cost, has little odor, does not promote the growth of flies or other annoying insects and is environmentally friendly.
For more information, Contact NRAES or 607/255-7654) to purchase "Field Guide to On-Farm Composting" for $14.
This article was written in 2009 by David L. Greene.