Aspergillus fumigatus in windrow composting: effect of turning frequency

Abstract

The influence of the windrow turning frequency on the pro liferation and dispersion of Aspergillus fumigatus (AF) at a classic, open-air windrow composting site was investigated. Independent of the turning frequency, the intially high con centrations of AF (>106 cfu/gDW ) were strongly reduced already after 2 weeks of composting in the center of all exper imental windrows, as well as at the surface of those being turned frequently (daily). Surface AF counts, however, remained elevated (>10 4 cfu/gDW ) for the less frequently (weekly to monthly) turned windrows. Also, in this case, con centrations of AF dispersed in the air were higher. Tempera ture, the main factor for eliminating AF, rose faster, more homogeneously, and reached higher values in the more fre quently (daily and/or weekly) turned composts than in those turned less frequently. Significant differences were seen between daily and weekly turnings of material with high a C/N ratio (40: 1), but not for the more nutrient rich composts (C/N 30:1), where temperatures were generally higher.