Odour evaluation of a dairy farm with anaerobic digestion

The present work focuses on odour evaluation of a dairy farm with anaerobic digestion, located in the Luxembourg province (Belgium). This study pursues three main goals: 1.- To evaluate the effect of the anaerobic digestion process on the odour level in the farm, 2.- To compare field and laboratory odour measurement techniques and 3.-To study the influence of the meteorological observation frequency on the odour plume, through the use of dispersion models. Three different approaches were used to characterize the odour: dynamic and field olfactometry and sniffing team method. Odour emissions from all sources were measured by duplicated through dynamic chamber and olfactometric analysis in two different situations: in normal conditions and after stirring the odour source. Two odour field measurement campaigns were conduced in the surroundings of the farm, and meteorological conditions were recorded two times per minute with a weather station. After comparing odour emissions with field measurements through dispersion modeling, we concluded that the best results were obtained using minimum and averaged odour emission rates. Emission rates measured in stirring conditions overestimated the reach of odour perceived in the field in three field campaigns. Overall odour emitted from the farm increased with the anaerobic digestion process. Although odour emission from digested manure is reduced in comparison with non-treated manure, the presence of agricultural wastes increases global odour emission. Finally, meteorological data were averaged each one, five and fifteen minutes. Odour shape was thinner and more extended with 15-minutes data, whereas it was larger and shorter with 30-secondes records. One minute and 5-minute values showed intermediate situations. In conclusion, different techniques to measure odours were compared in this study and, according to the results, field techniques seemed to be more realistic than dynamic olfactometry.