On-farm composting of animal carcasses is typically done in simple uninsulated bins constructed outside of livestock production buildings. Composting also can be done either in outdoor windrows, but in Iowa where frequent precipitation can lead to excessive moisture content (resulting in slow decay, odor, and seepage) bins with a roof are preferred. By keeping a large mass of material in a compact form, bins also help to retain internal heat, thereby promoting rapid decay. Bins also reduce blowing and scattering of compost materials and make carcasses less accessible to predators and rodents.
Composting facilities intended for long-term use are usually built from treated lumber or concrete. Like the simple structure pictured above, pole-shed construction is typical. Though not required by the Iowa Department of Natural Resources (IDNR) rules, a roof over the bins is recommended to prevent excess moisture accumulation that can lead to production of undesirable odors and leachate. An all-weather base constructed from compacted soil, compacted granual aggregates, asphalt, concrete, or similar relatively impermeable material is required by IDNR rules to minimize contamination of surface and groundwater.
Bins for swine carcass composting are typically 5 - 6 feet high. Bin widths of 8 - 10 feet are common, but vary with the width of the equipment used to load and unload them. Bin lengths are adjusted to obtain the desired bin volume. For further information on bin sizing, go to Designing a Composter for YOUR Operation.