Design and Calibration of Chambers for Measuring Ammonia Emissions from Tie-stall Dairy Barns

Dairy barns are thought to emit large amounts of ammonia, which can have detrimental effects on human health and natural ecosystems. In the U.S., relatively little is known about the processes that affect the rate and magnitude of ammonia emissions from dairy barns. The end of a conventional tie-stall dairy barn was remodeled into four chambers (four animals per chamber) to initially evaluate dairy diet and bedding impacts on ammonia production and loss. This article describes the technical aspects of the chamber design, operation, and calibration. The chamber walls consisted of drop-down curtains of polyvinyl material, with Velcro seals at the edges and weighted at the bottom to minimize air loss other than through the exhaust ducts. The curtains were attached to automatic roll-up, roll-down mechanisms fixed to the ceiling. Intake air, which was drawn from outside the barn, provided information on background ammonia levels. Two types of chamber calibrations were performed: (1) release and capture of known amounts of ammonia gas, and (2) total nitrogen (N) balances for growing heifers, or the percentage difference between N outputs (manure, ammonia, and livestock weight gain) and N inputs (feed and bedding). On average, 102% (range 88% to 131%) of released ammonia was captured using the ammonia release-capture calibration method, and 99% (range 94% to 104%) of input N was accounted for by output N. Calibration results indicate that chambers should provide precise data on ammonia emitted from tie-stall dairy barns under the prevailing management and environmental conditions.