A systematic study of the gaseous emissions from biosolids composting: Raw sludge versus anaerobically digested sludge

Volatile organic compound (VOC) and ammonia, that contribute to odor pollution, and methane and nitrous oxide, with an important greenhouse effect, are compounds present in gaseous emission from waste treatment installations, including composting plants. In this work, gaseous emissions from the composting of raw (RS) and anaerobically digested sludge (ADS) have been investigated and compared at pilot scale aiming to provide emission factors and to identify the different VOC families present. CH4 and N2O emissions were higher in ADS composting (0.73 and 0.55 kg Mg−1 sludge, respectively) than in RS composting (0.01 kg Mg−1 sludge for both CH4 and N2O). NH3 and VOCs emitted were higher during the RS composting process (19.37 and 0.21 kg Mg−1 sludge, respectively) than in ADS composting (0.16 and 0.04 kg Mg−1 sludge). Significant differences were found in the VOC compositions emitted in ADS and RS composting, being more diverse in RS than ADS composting.