Size Reduction of Ammonia Scrubbers for Pig and Poultry Houses: Use of Conditional Bypass Vent at High Air Loading Rates

In The Netherlands, both acid and biological air scrubbers are used for removal of ammonia from exhaust air at pig and poultry houses. Current regulations require that scrubbers are dimensioned for treating the maximum airflow rate that may occur, so on average these systems are overdimensioned and underloaded. A new approach is introduced that is based on bypassing airflow peaks untreated. As a result, the air loading rate in m3 [air] m−3 [scrubber] h−1 and ammonia loading rate in kg [NH3] m−3 [scrubber] h−1 of the scrubber are more constant in time and average loading rates increase. By model calculations and analyses of measurement datasets it was demonstrated that the application of such a scrubber significantly decreases the required scrubber size while ammonia emission levels are only slightly increased (e.g. where the bypass is operated at 50% of the maximum ventilation rate and the scrubber volume is reduced by 50%, the bypass venting systems only allows 10–20% of the total ammonia load to be vented untreated). As a result, both the efficiency of scrubber utilisation in kg [NH3 removal] m−3 [scrubber volume] and the cost-effectiveness of air scrubbing for ammonia removal in kg [NH3 removal] €−1 are increased.