The material used to cover the carcasses is an important part of the composting system. The ideal cover material retains heat, absorbs excess moisture, and provides a barrier that helps discourage insects and scavengers. Cover materials also must provide much of the carbon, which is essential to the microbes that decompose animal carcasses. Due to its excellent ability to retain heat and absorb excess moisture, sawdust is generally acknowledged as the best cover material. Unfortunately, sawdust and recycled wood products are in high demand for many other uses, making them increasingly hard to obtain and raising their price substantially in recent years.
Alternative cover materials that are much easier to obtain include chopped cornstalks or straw. Since these tend to be less absorptive and have poorer insulating properties than sawdust, their use requires more care during cold or wet weather. Poultry litter, a mixture of sawdust and poultry manure produced during turkey or broiler chicken production, has been used successfully for carcass composting in the poultry industry. Not only does poultry litter have the desirable characteristics of sawdust, the bacteria and nitrogen added by the manure make this mixture more biologically active than sawdust alone.
Bedding from swine hoop buildings also can be used as cover material. Since the quality of used bedding from hoop
buildings varies considerably, care should be taken to avoid materials that are saturated with liquid or that contain high proportions of manure because these conditions can lead to slow decay and/or excessive odor production.
Another possible source of cover materials to consider is the 70 or so publically operated or industrial composting operations located throughout Iowa. These facilities process municipal yard wastes and industrial organic byproducts, producing a variety of partially- or fully-composted products, some of which could become cover material for animal mortality composting. For a listing of wood byproducts (chips/shaving/sawdust) available throughout Iowa, search the Iowa Waste Exchange database website maintained by the Iowa Department of Natural Resources. Turkey litter, a mixture of wood shavings and turkey droppings, makes an excellent mortality composting cover material that is absorbent, heats quickly, and retains heat. If you are interested in using turkey litter for composting swine losses, contact Gretta Irwin (firstname.lastname@example.org, 515-232-7492) for information regarding turkey growers in your region of the state.