Simulation of Air Quality and Operating Cost to Ventilate Swine Farrowing Facilities in the Midwest U.S. During Winter

Abstract. We have developed a time-dependent simulation model to estimate in-room concentrations of multiple contaminants, i.e., ammonia (NH₃), carbon dioxide (CO₂), carbon monoxide (CO), and dust, as a function of increased ventilation with filtered recirculation for swine farrowing facilities. Energy and mass balance equations were used to simulate the indoor air quality (IAQ) and operating cost for a variety of ventilation conditions over a three-month winter period for a facility located in the Midwest U.S., using simplified and real-time production parameters, and results were compared to field data. The model was improved by minimizing the sum of squared errors (SSE) between modeled and measured NH₃ and CO₂. After optimizing NH₃ and CO₂, other IAQ results from the simulation were compared to field measurements using linear regression. For NH₃, the coefficient of determination (R²) for simulation results and field measurements improved from 0.02 with the original model to 0.37 with the new model. For CO₂, the R² for simulation results and field measurements was 0.49 with the new model. When the makeup air was matched to hallway air CO₂ concentrations (1,500 ppm), simulation results showed the smallest SSE. With the new model, the R² for other contaminants were 0.34 for inhalable dust, 0.36 for respirable dust, and 0.26 for CO. Operation of the air cleaner decreased inhalable dust by 35% and respirable dust concentrations by 33%, while having no effect on NH₃ and CO₂, in agreement with field data, and increasing operating cost by $860 (58%) for the three-month period.