Development and validation of a dynamic mathematical model of ammonia release in pig house

A dynamic mathematical model of Carbon-dioxide Accelerated Ammonia Release (CAAR) was developed based on the known knowledge of the chemistry of ammonia (NH3) in liquid solution, mass transfer inside liquid and across liquid-gaseous interface, and a new concept of CAAR. It calculated the NH3 concentration, release and emission at transient and steady state conditions related to a mechanically ventilated pig house. One field experimental data set was used for estimating the proportionality coefficient in the model. Another field data set was used for model validation. The ammonia concentration and emission rate calculated in the model validation were compared with the field measurement values. R2 of 0.861 and 0.947 were obtained for NH3 concentration and emission rate, respectively. In the model validation, the pH in manure surface was found to increase from 8 at initial condition to 8.85 at dynamic equilibrium due to the co-release of CO2 from the manure. This pH change accelerated the NH3 release by 6.1-fold. The model provided a quantitative description of some new understanding of the mechanism of NH3 release in the pig house and entailed suggestions of two new techniques of NH3 emission abatement: the reduction of CO2 release and the new ventilation control strategy.