Efficacy of a microbial additive in reducing odor, ammonia, and hydrogen sulfide emissions from farrowing-gestation swine operation

Abstract

To mitigate odor and gas emission concern, different management practices and treatment technologies are available. In this study, the effectiveness of the Digest3+3© microbial additive was evaluated for reducing odor and pollutant gas emission from a swine gestation-farrowing operation in North Dakota.  In this experiment, one of the deep pits in the facility was left untreated (GC) and the other deep pit was treated (GT) with the Digest 3+3 (22.68 kg/month).  Similarly, shallow pits in one of the farrowing units were treated (FT) with the microbial additive, while another unit was untreated (FC as the control).  Air samples were collected from exhaust fans using a vacuum chamber and Tedlar bags.  Odor detection threshold values were determined using a dynamic dilution olfactometer, and ammonia and hydrogen sulfide (as total reduced sulfur) concentrations were measured using the Dräger^TM CMS and a Jerome^TM meter, respectively.  Air flow rates from exhaust fans were measured using a portable thermo-anemometer and ventilation rate was determined as the summation of air flow rates of all fans.  The average odor concentrations for the GC and GT barn were 954 ± 423 and 908 ± 416 OU/m³, respectively.  Ammonia concentrations ranged from 3.0 to 27.0 ppm in the GC barn, and from 3.1 to 43.0 ppm in the GT barn.  In the shallow pit system, ammonia concentrations varied from 2.0 to 15.9 ppm in the FC barn and from 2.0 to 15.2 ppm in the FT barn.  The average NH₃ emission, over the entire sampling period, at the GC and GT barn were 28.96 ± 20.69 g d^-1 AU^-1 and 33.10 ± 14.24 g d^-1 AU^-1, respectively, whereas they were 2.85 ± 1.28 and 3.51 ± 1.67 g d^-1 AU^-1 in the FC and FT barn, respectively.  The average H₂S concentration over the entire sampling period at the GC and GT barn were 0.64 ± 0.42 ppm and 0.87 ± 0.41 ppm, respectively.  Similarly, H₂S concentrations in the FC and FT barn were 0.45 ± 0.21 ppm and 0.42 ± 0.21 ppm, respectively.  Average H₂S emissions were 3.25 and 5.59 g d^-1 AU^-1 in the GC and GT barns, respectively, and they were 0.36 and 0.43 g d^-1 AU^-1 in the FC and FT barns, respectively.  No significant differences in terms of odor, ammonia, and hydrogen sulfide concentrations and emissions were found between treated and untreated units.  Overall, the microbial treatment had very little effect in reducing odor, ammonia, and hydrogen sulfide emission.