Abstract
A microbial evaluation was performed at a composting facility where all mechanical agitation of composting materials was performed in an enclosed, negatively pressurized structure in which air is filtered before being discharged into the atmosphere. The objective of this evaluation was to determine if bioaerosol emissions from the composting processes were effectively contained within the enclosed facility. Aspergillus fumigatus was the dominant fungus in settled dust and compost in the facility. The Gram-negative bacteria concentration in compost exceeded 1011 cfu/g. Air sampling in and around the composting facility was performed by spore trap for molds and by polycarbonate filter cassettes for endotoxins. The highest concentrations of airborne spores (by spore traps) and endotoxin within the facility were about 105 spores/m3 and 102 endotoxin units/m3. By contrast, much lower concentrations of fungal spores (range from about 40 to 800 spores/m3) and endotoxins (< 1.0 endotoxin units/m3) were found in ambient air both upwind and downwind of the facility. Penicillium and Aspergillus spores were present in only about 20% of both upwind and downwind ambient air samples. The results indicated that composting within the enclosed facility does not add to the bioaerosol burden in nearby ambient air.