Strategies for evaluating the sanitary quality of composting.

AIMS To evaluate different strategies for description of the sanitary quality of industrial-scale composting. METHODS AND RESULTS The investigation included microbiological analyses of waste at different stages during the process (spot test analysis), as well as physical and chemical parameters. The elimination of indicator organisms was also investigated by means of direct process evaluation, based on inoculation of the waste. At the four investigated facilities, the sanitary process was very efficient when evaluated by the direct process evaluation, indicated by an efficient elimination of Escherichia coli and Enterococcus faecalis inoculated into the waste. The sanitization was poor when evaluated by spot test analysis at the two windrow facilities, while good agreement was found at the two in-vessel facilities. CONCLUSIONS The direct process evaluation is a valuable tool for identifying parameters for process optimization in different zones and for measuring elimination patterns of pathogens not normally present in the waste, but it is unreliable for evaluating the overall sanitary process. SIGNIFICANCE AND IMPACT OF THE STUDY The spot test analysis is an accurate method for the analysis of the sanitary process. In addition, it is simple and inexpensive to perform, which makes it very cost-effective for supervision of the sanitary quality of industrial-scale composting.