Comparing NH3 emissions under different cattle housing conditions in cold regions in China with an inverse dispersion technique

Abstract

Accurately assessing ammonia (NH3) emissions from animal farms is necessary for determining the effectiveness of various mitigation practices to minimize related environmental risks and maximize the potential of recycling nitrogen from manure. This study attempted to validate a hypothesis formulated using a mass-flow inventory model, which suggested that "Barn only" housing facilities without open lots might have a lower NH3 loss potential than "Barn+Lot" facilities with both dairy barns and open lots. NH3 emissions from two "Barn+Lot" dairy farms and one "Barn only" dairy farm were measured using a combination of an inverse dispersion modeling technique and an open-path laser in summer and winter. It was found that the uncertainty of emission estimates owing to the spatial variation of animal densities in the three dairy farms was 8–12%, and the total uncertainty of the NH3 emission estimates owing to spatial variation in animal densities, distortion of wind flow by animal buildings, and the inverse dispersion calculation was estimated to be less than 30%. The NH3 emission rates obtained from the "Barn only" farm (28–43 g head−1d − 1) were lower than the rates from the conventional "Barn+Lot" farms (93–184 g head−1d − 1), indicating emission mitigation of 71–76%. In comparison with the conventional dairy farms, the "Barn only" dairy farm had a lower NH3 loss potential, most likely due to the greater animal density, frequent manure removal, and lower crude protein feed. However, more field measurements of such comparisons are necessary to provide robust suggestions for mitigating environmental risks.