Metingen aan twee biologische combi-luchtwassers door twee geurlaboratoria

An earlier field study (Melse et al., 2018b) in the Netherlands showed that the odour and ammonia removal efficiencies of the so called combi-airscrubbers at animal houses were significantly lower than were expected on basis of research and measurements that were done earlier in Germany. Possibly the lower odour removal efficiencies were related to differences in measurement methodology between the Dutch and German odour laboratory involved. Another cause could be differences in dimensioning criteria resulting in larger air scrubbers in German practice as compared to the Netherlands. The aim of this study was to investigate whether the certified performance levels could be reproduced by performing a number of measurements at two farm locations in Germany, each equipped with a certified biological combi-airscrubber. The odour measurements were carried out simultaneously by a German and a Dutch odour laboratory who worked with a different response method, both of which are permitted under EN13725. These are the same two laboratories that also performed the measurements in the earlier research by Melse et al. (2018a). In addition, the removal efficiency for ammonia, the emission of nitrogen oxides and the composition of the recirculation water were determined. The measurements show that the two air scrubbers had a significantly lower average odour efficiency than the efficiency of 85% that was previously assumed on the basis of the earlier German studies. This applied both to the measurements performed by the German laboratory (location 1: 46%, location 2: 31%) and to the measurements performed by the Dutch laboratory (location 1: 49%; location 2: 20%). There are no indications that existing differences in dimensioning and design criteria between Germany and the Netherlands lead to large differences in odour efficiency. Furthermore, it the results show that the reproducibility of olfactometric measurements between laboratories is insufficient. It is recommended to develop a chemical-analytical method and to prepare it for use to quantify odour emissions. The ammonia removal performance that was found for both air scrubbers (90% or higher) was considerably better than the results of the earlier filed study. This may be caused by differences between Germany and the Netherlands in dimensioning and design criteria for air scrubbers and animal house ventilation, or by poor process conditions that occurred at some of the scrubbers in the field study. Finally, the research shows that it is necessary to better define where the pH of the recirculation water is measured (below or above the package) when required minimum or maximum pH values are discussed and set. The occurring differences could have large impact on the emission of nitrogen oxides. The study was commissioned by the Ministry of Infrastructure and Water Management and the Ministry of Agriculture, Nature and Food Quality.