Assessment of Nutrients, Bacteria, and Gaseous Emissions in Swine Mortality Composts of Sawdust, Broiler Litter, and Swine Lagoon Effluent.

Disposition of mortalities challenges confined animal feeding operations (CAFOs), especially large sow (farrowing) farms, which experience mortalities daily.  Regulations preclude incineration and high costs make rendering impractical.  Swine CAFOs in the Mid-South US practice mortality composting with sawdust, a forestry and wood products industry byproduct that is available at little or no cost, except for hauling.  Sawdust provides a suitable matrix and C source for mortality composting.  The farm standard practice was to place mortalities on a layer of sawdust (S) in a compost shed, cover the mortalities with additional sawdust, wet the pile with water (W), turn the pile after 100 days, and later remove the compost to an outside storage pile.  In the present study, this compost practice was compared with others where additional C and N were supplied by broiler litter (L) and by replacing water with swine lagoon effluent (E).  Levels of nutrients and bacteria, including some human pathogens, had been documented for broiler litter and lagoon effluent in the region, but little was known of nutrient levels, bacterial survival, or greenhouse gas and ammonia emissions in these composts.  Objectives of the present study were to assess potential risks and benefits of adding these manure sources of C and N, and to determine and compare the levels of nutrients, bacterial pathogens, and gaseous emissions from the composts.  Three replications of four treatments (SW, SLW, SE, and SLE) were compared in microcosms comprising modified 227-L covered heavy-duty plastic recycling bins.  Temperature, water content, and emissions of ammonia, carbon dioxide, methane, and nitrous oxide were measured during composting.  Levels of C, N, P, K, Mg, Mn, Na, Cu, Zn, Clostridium perfringens, Escherichia coli, Listeria spp., Salmonella spp., and staphylococci were measured in mature composts.  Composting offers environmentally sound disposition of these byproducts and manures.