Emissions of H2S from Hog Finisher Farm Anaerobic Manure Treatment Lagoons: Physical, Chemical and Biological Influence

Abstract

Hydrogen sulfide (H2S) from hog operations contributes to noxious odors in the surrounding environment and can be life-threatening. There is, however, limited understanding of what influences H2S emissions from these farms. Emissions of H2S were measured periodically over the course of two years at hog finisher farms in humid mesothermal (North Carolina, NC, USA) and semi-arid (Oklahoma, OK, USA) climates. Emissions were determined using an inverse dispersion backward Lagrangian stochastic model in conjunction with line-sampled H2S concentrations and measured turbulence. Daily emissions at the two lagoons were characterized by low emissions on most days with occasional days of high emissions. Mean annual area-specific emissions were much lower for the NC lagoon (1.32 µg H2S m−2 s−1 ± 0.07 µg H2S m−2 s−1) than the OK lagoon (6.88 µg H2S m−2 s−1 ± 0.13 µg H2S m−2 s−1). Mean annual hog-specific emissions for the NC lagoon were 0.75 g H2S hd−1 d−1 while those for the OK lagoon were 1.92 g H2S hd−1 d−1. Emissions tended to be higher during the afternoon, likely due to higher mean winds. Daily H2S emissions from both lagoons were greatest during the first half of the year and decreased as the year progressed and a reddish color (indicating high populations of purple sulfur bacteria (PSB)) appeared in the lagoon. The generally low emissions at the NC lagoon and higher emissions at the OK lagoon were likely a result of the influence of wind on mixing the lagoon and not the presence of PSB.