Methane Emissions of a Western Dairy Manure Storage Basin and Their Correlation with Hydrogen Sulfide Emissions

Abstract

Anaerobic decomposition in manure storage contributes to hydrogen sulfide (H2S) and methane (CH4) emissions. Coincident emission measurements were made of these gases from a western free stall dairy manure storage basin over a two-month period (August and September) as manure filled the basin and dried to assess the similarity or differences in the emissions characteristics. Path-integrated CH4 concentrations were measured from sampled air using photoacoustic spectrometric technology. Half-hourly emissions were determined using a backward Lagrangian Stochastic method utilizing on-site turbulence measurements. The median daily CH4 emission for the basin was 3.5 mg CH4 m−2 s−1 (772 g d−1 hd−1). Aging of the manure over the 44 days of this study did not appear to influence the CH4 emissions. A high correlation between the CH4 and H2S emissions during the study period suggested that the production and transport of these two gases from the basin were influenced by the same factors. Emissions did not appear to be influenced by the above-ground environmental conditions (wind speed, turbulent mixing, air temperature, change in barometric pressure, or vapor pressure deficit) but were likely more a function of the bacterial population present and/or available substrate for bacterial decomposition. Similarity in the CH4 to H2S emission ratio during basin manure filling and drying down to that of a slurry storage in a midwestern US dairy suggested that the bacterial species involved in the decomposition of dairy manure slurry is similar regardless of climate.