Analysis of airborne microorganisms, MVOC and odour in the surrounding of composting facilities and implications for future investigations

Emission and dispersal of microorganisms and odours from composting facilities were studied in a 3-year project at nine different composting facilities in Germany. Measurements were carried out under so-called ‘normal-case’, i.e. typical local climate conditions and working activities within the facilities, and ‘real worst-case’ conditions (‘drainage flow’ conditions) being characterized by the translocation of cold air mostly at night, and containing large amounts of bioaerosols. Highest concentrations of microorganisms were observed during turning of compost with a maximum of 2.4×106 cfu m−3 for thermophilic actinomycetes. Other groups of microorganisms were detected in concentrations of about 105 cfu m−3. During shredding of fresh organic material, the concentrations of all microorganisms reached 104 cfu m−3. Here, odour concentrations turned out to be highest (up to 1,367 odour units (OU) m−3). At facilities equipped with a biofilter (odour reduction), a decrease in OU by a factor of 10 was observed. In the surrounding of the facilities, highest concentrations ranged between 101–103 cfu m−3 upwind and from 101–104 cfu m−3 downwind. The specific local meteorological situations must be considered carefully in advance and during sampling. Especially ‘drainage flow’ situations can lead to high microorganism concentrations (>104–105 cfu m−3 of thermophilic actinomycetes and thermophilic fungi) in the surroundings of composting facilities.