Validation Methods for the Ammonia Removal of an Air Scrubber on a Poultry House Using the Acid Use and the Process Water Nitrogen Balance

Abstract

Highlights Acid use in an acid air scrubber predicts the ammonia removal of an air scrubber. Nitrogen balance of process and discharge water in an air scrubber predicts ammonia removal of an air scrubber. Long-term monitoring of acid use and/or the nitrogen balance can validate the ammonia reduction of an air scrubber. The two validation methods can support local authorities in granting environmental permits and enforcement. Abstract. Ensured ammonia reduction by novel technologies and guaranteed low ammonia emission from livestock houses is essential for the granting and monitoring of legal permits. This study focuses on methods to underpin the long-term effectiveness of an air scrubber and was done in a commercial poultry house. The measured ammonia removal by an air scrubber with ammonia sensors (method 1) was compared to the acid use for ammonia binding (method 2) and the nitrogen balance over the process water (method 3). Also, the effect of the length of the time period used for the comparison was evaluated, as was the effect of the spatial variation of the ammonia concentration in the house. The overall weekly data showed a clear linear relation between method 1 on the one hand and methods 2 and 3 on the other hand, with regression coefficients close to 1 and a variation of +/- 20% on a 4-weekly basis. The 4-weekly data showed a clearly reduced variation compared to weekly data, due to leveling out of the impact of irregular time events like acid dosage and water discharge. The barn emission assessed by method 1 was significantly (12%) influenced by the spatial aerial concentration differences of ammonia in the house. Taking this into account, method 2 overestimated the emission reduction of method 1 with 16.8% and method 3 was in good agreement with method 1. For method 2, a revised value for acid use per kg of ammonia binding needs to be substantiated in further research. Possible measurement errors influenced calculated ammonia removal with a maximum of +/-2%, but the relative effect on remaining emissions was larger with +/- 15% for method 3. This study shows that monitoring acid use and/or the nitrogen balance can validate the ammonia reduction of air scrubbers and the remaining ammonia emission and support local authorities in granting environmental permits and their enforcement. Keywords: Acid, Air scrubber, Ammonia, Nitrogen balance, Poultry.