Ammonia emissions from a U.S. broiler house--comparison of concurrent measurements using three different technologies

There is a need for robust and accurate techniques for the measurement of ammonia (NH3) and other atmospheric pollutant emissions from poultry production facilities. Reasonable estimates of NH3 emission rate (ER) from poultry facilities are needed to guide discussions about the industry's impact on local and regional air quality. The design of these facilities features numerous emission points and results in emission characteristics of relatively low concentrations and exhaust flow rates that vary diurnally, seasonally, and with bird age over a considerable range. These factors combine to render conventional emissions monitoring approaches difficult to apply. Access to these facilities is also often restricted for biosecurity reasons. The three objectives of this study were (1) to compare three methods for measuring exhaust NH3 concentrations and thus ERs, (2) to compare ventilation rates using in situ measured fan characteristics versus using manufacturer sourced fan curves, and (3) to examine limitations of the alternative measurement technologies. In this study, two open-path monitoring systems operating outside of the buildings were compared with a portable monitoring system sampling upstream of a primary exhaust fan. The position of the open-path systems relative to the exhaust fans, measurement strategy adopted, and weather conditions significantly influenced the quality of data collected when compared with the internally located, portable monitoring system. Calculation of exhaust airflow from the facility had a large effect on calculated emissions and assuming that the installed fans performed as per published performance characteristics potentially overestimated emissions by 13.6-26.8%. The open-path measurement systems showed promise for being able to obtain ER measurements with minimal access to the house, although the availability of individual fan characteristics markedly improved the calculated ER accuracy. However, substantial operator skill and experience and favorable weather conditions were required to obtain good quality results.