Diurnal and seasonal variations of odor and gas emissions from a naturally ventilated free-stall dairy barn on the Canadian prairies.

UNLABELLED

This study characterized the seasonal concentration (C) and emission (E) patterns of odor, ammonia (NH), and hydrogen sulfide (HS) over the course of a whole year and their diurnal patterns in cold, warm, and mild seasons for a naturally ventilated free-stall dairy barn. It was found that seasonal odor and NH and HS emissions varied greatly: from 17.2 to 84.4 odor units (OU) sec AU (AU: animal unit, 500 kg of animal body mass), from 0.27 to 0.92 mg sec AU, and from 3 to 105 μg sec AU, respectively. The overall concentrations of odor and NH were higher in the winter, whereas the emissions were higher in the mild and warm seasons. Diurnal variation was most significant for odor emission (OE) in the mild season when the ratio of maximum (279.2 OU sec AU) to minimum value (60.5 OU sec AU) was up to 4.6. The indoor air quality was also evaluated by considering not only the health effect of individual gases, but also the additive effect of NH and HS. Results showed that the indoor air quality was poorest in cold seasons when NH C could exceed the threshold limit set out in occupational health regulation, and in fact could worsen due to the additive effect of the two gases. Further, it was suggested NH was a good indicator for predicting odor concentration (OC) or OE. The impact of climatic parameters on odor and gases were also examined, and it was found ventilation rate (VR) negatively affected OC and NH C, but positively impacted OE and NH E. Using 70% of the total data, a multilinear model for OE was developed as a function of VR and indoor relative humidity and was validated to be acceptable using the rest of the data.

IMPLICATIONS

Diurnal and seasonal variations of odor, NH, and HS concentrations and emissions were monitored for a naturally ventilated dairy barn in a cold region. The emission factors were calculated and indoor air quality was evaluated. The overall odor and NH concentrations were higher in winter, whereas emissions were higher in the mild and warm seasons. Diurnal variation was most significant for odor emission in the mild season, when the ratio of maximum to minimum value was up to 4.6. The results can be used to estimate odor and gas emissions from other dairy barns in Canada and other cold regions.