The objective of the STSM was to exchange knowledge and technical experience in the area of modelling ammonia emission from livestock houses, especially on factors affecting ammonia release from emitting sources depending on the airflow pattern and the ventilation rate within the barn using Computational Fluid Dynamics (CFD). The mission focused on Ground Channel Ventilation (GCV). One of the most popular ventilation designs in the Netherland and Belgium associated with draught on pigs in cold seasons and the direct flow of incoming air into the slurry pit due to displacement flow patterns in GCV barns. Consequently, causing undesirable pen fouling and driving ammonia out of the slurry pit, potentially increasing ammonia emissions.
Description of activities
During the STSM, indoor NH3 and CO2 emission models were developed and validated using field measurement results at the ILVO/UGent pig campus, Merelbeke, Belgium including indoor temperature and air velocity. The STSM also used experimental results of pig urine puddle/slurry pH and TAN concentrations at Wageningen University and Research, Wageningen, the Netherlands in the NH3 emission model. The STSM then assessed the impact of different ventilation rates and inlet temperatures, slurry depth (at 0.135 m (D1) and 0.635 m (D2) of 1.0 m deep slurry pit) and three pig arrangements on air distribution and ammonia emission in the validated model.
The CFD model predicted similar airflow patterns as in the real pig compartment during a smoke test and pit headspace temperature and NH3 distribution (Fig. 1). As expected, NH3 emission increased with increasing ventilation rate (Fig. 2). At slurry depth of 0.635 m, there was a clear increase in mean air velocity and turbulent intensity above the slurry surface, as well as the increase in slurry pit exchange rate as ventilation rate increased. However, at slurry depth of 0.135 m the mean air velocity and turbulent intensity above the slurry surface remained relatively constant with increasing ventilation rate.