The combination air cleaners on pig farms that are supposed to reduce both the stench and ammonia levels perform much worse than thought, according to research by Wageningen Livestock Research.
Combination air filters do not remove 81 percent of the aromas from the air in a barn, as has been believed, but only 40 percent. Photo Hollandse Hoogte.
About 45 percent of all air cleaners used in Dutch pig farms are combination cleaners. But they only capture 40 percent of the aromas in the air in pig sheds, rather than 81 percent as was thought. On top of that, they only remove 59 percent of the ammonia in the air, rather than the expected 85 percent. This has consequences for the legislation, says the state secretary for the Environment, Stientje van Veldhoven. The government plans to assume much higher levels of odour and ammonia emissions for sheds with these air cleaners. Pig farmers will therefore have to take more measures to reduce the stench and ammonia levels.
The Livestock Research scientists paid unannounced visits to 48 pig farms and performed odour and ammonia measurements on 16 chemical air cleaners, 3 biological cleaners and 29 combination air cleaners. This showed that the efficiency of the chemical and biological cleaners was close to the values assumed in the legislation. But the combination air cleaners were much less effective in practice than on paper.
Wageningen Livestock Research gives three possible explanation for the fact that the combination cleaners remove far fewer aromas from the air in practice than according to the standard values. Firstly, the standard values are based on German studies in aroma labs that use a different measurement method to the Dutch labs. Furthermore, the German tests of the combination cleaners were under different conditions. Finally, the efficiency of the cleaners on the farms may have fallen over time due to poor maintenance, say the researchers.