Ammonia and Hydrogen Sulfide Concentrations and Emissions for Naturally Ventilated Freestall Dairy Barns

Abstract

<abstract> <b><sc>Abstract.</sc></b> Concentrations and emissions of ammonia (NH₃) and hydrogen sulfide (H₂S) data for two naturally ventilated freestall dairy barns, within a one-year window of a two-year measurement effort, are presented in this article. Barn 1 (B1) had a capacity of 400 fresh-lactating Holstein cows, while barn 2 (B2) had a capacity of 850 non-fresh-lactating Holstein cows. The 10 min mean concentrations of NH₃ in the barns ranged from 0.16 to 2.85 ppm, while the concentrations of H₂S ranged from 0.0 to 135.8 ppb. The concentrations of NH₃ and H₂S in the barns were significantly below the OSHA permissible and NIOSH recommended exposure levels with respect to safety and health concerns of farm workers. Air exchange rates ranged from 7 to 74 h^-1 during all measurement periods, which met and exceeded the standard minimum ventilation rate requirements for dairy barns. Ammonia emissions ranged from 15.1 to 36.7 g d^-1 AU^-1 (20.3 to 49.5 g d^-1 cow^-1) with a mean of 21.6 g d^-1 AU^-1 (29.0 g d^-1 cow^-1). Emissions of H₂S, on the other hand, ranged from 0.0 to 1.5 g d^-1 AU^-1 (0.0 and 2.0 g d^-1 cow^-1) with an overall mean of 0.51 g d^-1 AU^-1 (0.69 g d^-1 cow^-1). In general, NH₃ emissions correlated fairly well with temperature (R² = 0.29 to 0.51). However, the relationships between NH₃ emission and wind speed were mixed, ranging from zero to moderately positive (R² = 0.01 to 0.46). Regression analyses did not indicate any significant relationships between H₂S emissions and these environmental parameters.