Investigation of the microbial community structure and activity as indicators of compost stability and composting process evolution

In a bid to identify suitable microbial indicators of compost stability, the process evolution during windrow composting of poultry manure (PM), green waste (GW) and biowaste was studied. Treatments were monitored with regard to abiotic factors, respiration activity (determined using the SOUR test) and functional microflora. The composting process went through typical changes in temperature, moisture content and microbial properties, despite the inherent feedstock differences. Nitrobacter and pathogen indicators varied as a monotonous function of processing time. Some microbial groups have shown a potential to serve as fingerprints of the different process stages, but still they should be examined in context with respirometric tests and abiotic parameters. Respiration activity reflected well the process stage, verifying the value of respirometric tests to access compost stability. SOUR values below 1 mg O₂/g VS/h were achieved for the PM and the GW compost.