Deep pit beef cattle barn ammonia and carbon dioxide concentrations

Roofed beef cattle finishing facilities with under-floor deep pit manure storage are increasing in number, despite limited data on the gas production and concentration conditions for this style of housing and manure management. This paper presents ammonia (NH3) and carbon dioxide (CO2) concentration distributions for three finishing beef cattle barns (Barns F, H and R) with under-floor deep pit manure storage, for summer, fall and spring weather conditions in Midwest US. The three barns were variable in size and layout, roof style, stocking density and management practices. On each of the three sampling days per barn, three sets of air samples were collected in Tedlar bags to represent the concentrations above the manure surface, at floor level, at nose level, and in the north and south wall openings for four pens. The effect of pen, sampling location, season and interactions were analyzed for each individual site. Location and season were significant factors affecting ammonia and carbon dioxide concentration measurements for Barn R, but there was a significant interaction of these factors for Barn F and H NH3 and CO2 concentrations. There was a larger variation in the gas concentrations over the manure surface by season than for gas measurements elsewhere in the barn, and this is attributed to temperature and manure characteristic changes between seasons. The ammonia concentration over the manure surface ranged from 14 to 61 ppm for Barn F over the three seasons, and 1 to 9 ppm for Barns H and R. However, at nose and floor level, average ammonia concentration levels were less than 9 ppm for all three barns and seasons. There was also a significant interaction of pen and season for NH3 at Barn H. This may relate to pen position over the two manure storage pits. The interaction of pen and season for CO2 concentrations was significant for Barns F and R. This difference may be related to differences in manure characteristics, but also stocking density. This information demonstrates the variability between production-scale barns, and informs the design of future concentration and emission modeling efforts.