Large Animal Carcass Mortality Composting: Impact on Soil Nutrients

Abstract

Livestock producers and environmental agencies have expressed concern about nutrient loss to the soil from routine mortality composting on soil with no cover or site improvement. In 2011, a replicated study of carcasses composted on soil was conducted at the University of Maine’s Compost Research and Education Center. The purpose was to evaluate the potential loss and movement of nutrients to soil from carcass compost piles when constructed on an unimproved site. As carcasses decompose, many nutrients become soluble and are available for leachate losses to ground and surface waters. Most notable among those nutrients are phosphorus and the nitrogen species: ammonia, ammonium, nitrite and nitrate. Six compost piles, approximately 12 cubic yards, were constructed on a fine sandy loam soil (Paxton-Charlton very stony fine sandy loam) on sod similar to a farm field. Three piles had cow carcasses while the other three did not. Feedstock material consisted of a blend of three parts horsebedding and one part waste feed. To determine nutrient movement in the soil profile, soil samples were collected, pre and post pile construction, at 13 cm (6 inches) and 26 cm (12 inches) across a transient of each pile. All samples were analyzed at the Maine Soil and Analytical Lab for nitrogen species and 12 other elements. Composting carcasses on an unimproved site does not appear to contribute significant amounts of nutrients to the soil, providing a cost-effective and environmentally sound method for carcass management.