Hydrogen sulfide emissions from waste lagoons of bread-to-wean hog operations

Hydrogen sulfide (H2S) is often viewed as a major contributor to odor from livestock farms and is a reported gas under the Emergency Planning and Community Right-to-Know Act (EPCRA) of 1986. However, relatively little is known about H2S emissions from animal waste lagoons. Hydrogen sulfide emissions were measured periodically over the course of two years at two hog waste lagoons representing operations in humid-subtropical (North Carolina, NC), humid continental (Indiana, IN) and semi-arid steppe (Oklahoma, OK) climates. The North Carolina farm had monthly mean air temperatures ranging from 24 oC to 3 oC with the lagoon surface never freezing during the winter. The Oklahoma farm had monthly mean air temperatures ranging from 27 oC to 1 oC with the lagoon surface freezing periodically during the winter. The Indiana farm had monthly mean air temperatures ranging from 24 oC to -3 oC with the lagoon surface freezing for extensive periods during the winter. Hydrogen sulfide concentrations were measured around each lagoon with a pulsed-florescence analyzer drawing air from two line sampling systems on opposite sides of the lagoon. Turbulence was measured using a three-dimensional sonic anemometer located on the lagoon berm. Hydrogen sulfide emissions were calculated at ½ h intervals using the measured H2S concentrations and turbulence statistics in a backward Lagrangian stochastic model (WindTrax). The highest median monthly emission at the OK farm was 5.05 ug H2S m-2 s-1 (3.4 g H2S d-1 hd-1) in January, declining progressively through the Fall. The highest monthly median emission at the IN farm was 6.26 ug H2S m-2 s-1 (4.6 g H2S d-1 hd-1) in May. The monthly median emissions at the NC farm were small throughout the year but highest in February at 0.30 ug H2S m-2 s-1 (0.3 g H2S d-1 hd-1). As expected, emissions were negligible when ice covered the lagoons since the microbiological formation of the H2S occurs in the sludge of the lagoon. Emissions were strongly influenced by wind speed but were not sensitive to the loading, lagoon temperature, pH or oxidation-reduction potential. The lower emissions in North Carolina compared to Oklahoma were likely due to the combined effects of low winds and the microbiological activity in the upper phototropic regions of the lagoon.