Applied Research Note: Survival of Escherichia coli and temperature development during composting of chicken manure with a typically low carbon/nitrogen ratio and moisture content

The presence of pathogens, e.g., Escherichia coli (E. coli), in chicken manure can potentially lead to serious infections and foodborne diseases when spread on land as organic fertilizer. Therefore, it is essential to inactivate these bacteria before land application. The aim of the present study was to determine the survival of E. coli and the temperature development in compost piles during composting of chicken manure with a typically low carbon/nitrogen (C/N) ratio and moisture content (MC). In a summer and winter trial, chicken manure piles were stacked in 1) uncovered static piles, 2) covered static piles, and 3) periodically turned piles. Samples were inoculated with a nonpathogenic E. coli strain at levels of 10⁷ cfu/g and placed at subsurface and center locations of the piles. Within 24 h, E. coli were undetectable by direct count in all piles and at all sample locations. By d 28, all samples were also negative for E. coli by enrichment. Despite the suboptimal composting conditions with an initial C/N ratio of 10:1 and an MC below 40%, temperatures within all piles mainly exceeded 50°C within the first 24 h. Statistical analyses showed that the sample location and the total hours at temperatures ≥50 and 55°C in the piles had significant influences on the survival of E. coli in the chicken manure compost. The season and manure treatment method had no significant effects on the presence of E. coli.