Odour in composting processes at pilot scale: monitoring and biofiltration

Abstract

Although odour emissions associated with the composting process, especially during the hydrolytic stage, are widely known, their impact on surrounding areas is not easily quantifiable. For this reason, odour emissions during the first stage of composting were evaluated by dynamic olfactometry at pilot scale in order to obtain results which can be extrapolated to industrial facilities. The composting was carried out in a commercial dynamic respirometer equipped with two biofilters at pilot scale filled with prunings (Populus) and mature compost obtained from the organic fraction of municipal solid waste. Given that the highest odour emissions occur in the first stage of the composting process, this stage was carried out in a closed system to better control the odour emissions, whose maximum value was estimated to be 2.78 ou E s −1 during the experiments. Odour concentration, the dynamic respiration index and temperature showed the same evolution during composting, thus indicating that odour could be a key variable in the monitoring process. Other variables such as total organic carbon (C TOC) and pH were also found to be significant in this study due to their influence over odour emissions. The efficiency of the biofilters (empty bed residence time of 86 s) was determined by quantifying the odour emissions at the inlet and outlet of both biofilters. The moisture content in the biofilters was found to be an important variable for improving odour removal efficiency, while the minimum moisture percentage to obtain successful results was found to be 55% (odour removal efficiency of 95%).