<oL> <LI> To determine the role of C:N ratio on inactivation of E. coli O157:H7 and Salmonella during composting of animal manures. <LI> To investigate the potential impact of different carbon feedstocks on the composting process and subsequent inactivation of E. coli O157:H7 and Salmonella spp. <LI> To discern the ability of moisture to serve as a control variable in the inactivation of E. coli O157:H7 and Salmonella spp. at surface locations of compost mixtures. <LI> To characterize the role of sunlight on inactivation of E. coli O157:H7 and Salmonella spp. at surface locations of compost mixtures. <LI> To evaluate the repercussions of treatments applied to minimize odors in compost piles on the inactivation of E. coli O157:H7 and Salmonella spp. <LI> To develop expanded guidelines for proper composting of animal manures.
NON-TECHNICAL SUMMARY: This project will focus on the relative contribution of non-thermal factors (pH, ammonia, organic acids, light, and moisture) to inactivation of pathogens in animal manure-based compost mixtures. To address these factors, inactivation of pathogens (Escherichia coli O157:H7 and Salmonella spp.) will be monitored in response to manure type, carbon feedstock, carbon:nitrogen ratio, moisture, and sunlight using compost bioreactors, compost trays housed in environmental chambers, and static compost piles in the field. Data collected will assist in the development of expanded guidelines for compost operations where manure is used as an ingredient.
APPROACH: Three different systems will be used to evaluate inactivation of pathogens in animal manure-based compost mixtures: bioreactors, trays housed in environmental chambers, and field static piles. To track the pathogens in any of these systems, the pathogens will be labeled with a green fluorescent protein. Using bioreactor systems, experimental variables that will be addressed include: initial carbon:nitrogen ratio of compost mixture (ranging from 20:1 to 40:1); type of carbon amendment (straw, peanut hulls, and pine needles); pathogen type and relative stability (Escherichia coli O157:H7 versus Salmonella spp.); and inclusion of odor suppression amendments (horseradish peroxidase and hydrogen peroxide). Environmental chamber composting studies will simulate surface samples of compost piles. They are designed to investigate experimental variables (light, temperature, and moisture) in an environment where they may be controlled. Field composting studies are designed to investigate variables in the field and will be representative of farm situations where minimal labor and resources are available. Hence, the piles once formed, will not be turned throughout the experimental study. Experimental variables to be explored with static piles are: initial C:N ratio of compost mixture; surface moisture level (10-70%); and type of carbon feedstock. In addition to monitoring pathogen populations over time, all experimental systems will be monitored for pH and moisture while selected systems will also be monitored for ammonia and organic acid content.