Design and Evaluation of a Regenerating Scrubber for Reducing Animal House Emissions

Abstract

Animal houses can emit substantial quantities of air pollutants. Compared with other pollutants, ammonia is emitted from animal houses in relatively large quantities and can have adverse public health and environmental impacts. This article describes the development and evaluation of a novel scrubber prototype, consisting of an endless polypropylene screen running in a trough of alum solution, that could be used to reduce ammonia emissions from animal houses. When building exhaust ventilation air contacts the screen, ammonia is dissolved in the aqueous solution on the screen and transported into the trough. Low ammonia concentration (<5 mg m-3) evaluations were conducted by connecting the scrubber to a pit ventilation fan in a hog finishing house. Higher ammonia concentration (7.6 to 26.6 mg m-3) evaluations were conducted by placing the scrubber inlet adjacent to a composting bin spiked with urea. Over >66 h of evaluation under low and high concentration conditions, with a weighted average airflow rate of 0.93 m3 s-1 and velocity of 0.52 m s-1, the scrubber reduced ammonia emissions by 58.3%. Compared with commercial spray and packed column scrubbers used in industry, it had a lower pressure drop (~110 Pa). It also had a low water consumption of ~1 mL m-3 treated air. Further evaluation of the scrubber in different types of animal houses and for different pollutants is required. Its design should be improved to increase ammonia removal efficiency and reduce pressure drop, footprint size, and cost. There is also need to model gas transfer in this type of scrubber.