Ammonia Fate and Transport Mechanisms in Broiler Litter

Abstract

Ammonia (NH3) emission from poultry houses is a major air quality concern. In poultry litter, uric acid converts to urea which hydrolyzes to NH3, a fraction of NH3 protonates to ammonium (NH4+). Moisture content (MC), dissociation constant, and Henry's law constant affect NH3 partitioning among solid, liquid, and gas phases. The dissociation constant (Kd) and Henry's Law constant (Kh) that are so well known for dilute aqueous solutions may not apply to broiler litter which has much higher ionic concentration. We quantified Kd, Kh, and NH3 sorption at different MC in broiler litter in replicated lab experiments. Dissociation constant in litter slurry was 1.02 × 10−10, 20 % of the dissociation constant in aqueous solution, which may be due to NH3/NH4+adsorption and reduced activities of the dissolved ions. Henry's Law constant (0.0158 atm/M) in litter slurry was 4 % lower than Kh in dilute aqueous solution. Ammonia sorption increased linearly with MC from 0 to 55 %, whereas 0 % MC litter adsorbed 5 % of its background total ammoniacal N (TAN) concentration as NH3, litter with 55 sorbed 266 % its background TAN concentration mostly as NH4+. We have improved the understanding of NH3 sorption in litter as function of MC. However, improved sensors that can measure TAN and pH in unsaturated matrices are required to improve quantification of N fate and transport.