Measurement and analysis of ammonia and hydrogen sulfide emissions from a mechanically ventilated swine confinement building in North Carolina

Emissions of atmospheric ammonia–nitrogen (NH3–N, where NH3–N=(1417)NH3) and hydrogen sulfide (H2S) were measured from a finishing swine confinement house at a commercial pig farm in eastern North Carolina. Continuous simultaneous NH3–N and H2S emissions were made for ∼1-week period during four different seasons. The number of pigs contained in the house varied from ∼850 to 900 with average weights ranging from ∼38 to 88 kg. Average NH3–N concentrations were highest during the winter and spring sampling periods, 8.91±4.61 and 8.44±2.40 ppm, respectively, and lower during the summer and fall, 2.45±1.14 and 4.27±0.71 ppm, respectively. Measured average H2S concentrations were 673±282, 429±223, 47±18, and 304±88 ppb during winter, spring, summer, and fall, respectively. Generally, the H2S concentrations were approximately an order of magnitude less than NH3–N during winter, spring, and fall, and two orders of magnitude smaller during the summer season.The average ambient temperature ranged from 5.5 to 22.3 °C while the average barn temperature measured at the outlet fans ranged from 19.0 to 26.0 °C in the winter and summer, respectively. The average fan ventilation rates varied from 253 m3 min−1 during the fall sampling period to 1024 m3 min−1 during summer.Calculated total emission rates for both NH3–N and H2S were highest during the spring, 4519±1639 g N day−1 and 481±142 g day−1, respectively. Emissions were lowest during the fall season for NH3–N (904±568 g N day−1) and the summer season for H2S (82±49 g day−1). Normalized NH3–N emission rates were highest in winter and spring (33.6±21.9 and 30.6±11.1 g N day−1 AU−1, where 1 AU (animal unit)=500 kg) and lowest during summer and fall (24.3±12.4 and 11.8±7.4 g N day−1 AU−1). Normalized H2S emissions were highest during the winter and spring seasons (4.2±2.1 and 3.3±1.0 g day−1 AU−1) and were lowest in summer and fall (1.2±0.7 and 1.7±0.5 g day−1 AU−1).