Preliminary study of effects of anaerobic digestion of manure on VFA content and Odor concentration

In this study, the potential reduction of odor of anaerobic digestion has been evaluated in three commercial facilities located in Belgium, Luxembourg and Germany. Odor concentrations were measured by olfactometric analyses in two different situations: at normal conditions and after the stirring the odor source. Parallel to these measures, representative samples were taken for digested and untreated manure and other co-substrates present in the facilities. Volatile solids, total solids, total suspended solids, volatile suspended solids, soluble chemical oxygen demand, ammonia nitrogen, total kjeldhal nitrogen, volatile fatty acids, and pH were determined in laboratory. The performance of anaerobic digestion in terms of VFA concentration reduction achieved values of 77-96%. Odor concentration was reduced by anaerobic digestion in the two studied scenarios: at normal conditions and after the stirring the odor source. No significant effect of anaerobic digestion on chemical analyses was observed, except for an increase in the ammonia nitrogen content. Significant correlations were found between the logarithm of odor concentration and different odor compounds (VFA, acetic, butyric, isobutyric, isovaleric). Correlations between odor concentration, VFA and other parameters (VS, VSS and pH) were also obtained. These results confirm that anaerobic digestion may reduce odor annoyance potential and VFA concentrations. In addition, odor concentration seems to be related with other chemical parameters, therefore more research is needed to obtain further conclusions.