Temporal Variation of Hydrogen Sulfide in a Swine Farrowing Facility.

Large-scale swine production facilities are known emission sources of ammonia (NH₃) and hydrogen sulfide (H₂S). Presented are the results of monitoring H₂S concentrations in a farrowing room at a sow gestation/farrowing farm (~2500 hog permitted capacity) in eastern North Carolina. This farm is one of two swine sites in North Carolina being monitored by the National Air Emission Monitoring Study (NAEMS). Piglets are produced throughout the year in farrowing rooms (20 sows; ~ 240 piglets) where piglets are born and raised during a period of 21 – 28 days. The farrowing rooms have solid walls and are ventilated with three mechanical fans (2 46-cm and 1 61-cm fans). Fresh air enters the room through ceiling baffles along the entire length of the sidewalls. Target temperature range for the farrowing rooms is 26-28°C. Solid and liquid waste accumulates in two shallow pits (~48 cm from floor to bottom of pit) in the room that are flushed and filled with anaerobic lagoon water twice during the 21 – 28 day growth period. As expected, the H₂S concentration of exhaust air measured ~70 cm from the Stage 1 fan was dependent on the total ventilation rate for the farrowing room. However, we also observed an increase in the gas concentrations of H₂S between flushing events of the pits, and a substantial short-term increase in H₂S during actual drainage of the pits (which lasts ~ 10 minutes). During this short period, H₂S concentrations could reach 30 times average observed concentrations in the room, depending on season of the year (colder periods yielding higher peaks in measured H₂S concentrations). Other gases (NH₃ and carbon dioxide) did not exhibit this phenomenon, suggesting that the high measured H₂S concentrations are related to the physical disturbance of the pit liquid. H₂S concentrations were lowest when the pits were filled with fresh anaerobic lagoon liquid. We did not observe these elevated levels of H₂S during flushing of the pits in the breeding/gestation and gestation barns also located at this facility. We continue to investigate this phenomenon to identify the unique characteristics of the farrowing room that result in the elevated concentrations of H₂S.