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Photoacoustic Spectroscopy in Livestock Buildings: Interference Effects on Ammonia, Nitrous Oxide and Methane Concentrations

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2012 IX International Livestock Environment Symposium (ILES IX)  ILES12-1158.(doi:10.13031/2013.41554)
Authors:   Mélynda Hassouna, Paul ROBIN, Alicia Charpiot, Nadège Edouard, Bertrand Méda
Keywords:   Emissions, livestock house, infrared photoacoustic spectroscopy, interference, uncertainty

Most countries where the livestock sector has an important social and economical place would like to reduce their emissions of ammonia and greenhouse gases. However emission estimates per building and per year are usually observed or measured with uncertainties higher than the reduction targets. Therefore mitigation strategies and public fund efficiency should benefit from progress in measurement and modeling of emissions from livestock houses. The quantification of livestock house emissions requires accurate measurements of gas concentration gradients. Infrared photoacoustic is used since decades because of selectivity, reduced drift in calibration, existence of industrialized analyzers. But even if the infrared bands selected by optical filters are narrow, unexpected interferences between gases and cascade effect can induce overestimation or underestimation of gas concentration. In livestock houses, molecules emitted by animals, the feed, the manure, the heating or motor-driven equipments can interfere with measurements of CH4, N2O, NH3 and CO2 as it is not possible to compensate all the interferences. The aim of this study is to show how unexpected interferences in livestock houses can lead to either over/underestimation of NH3, N2O or CH4 concentration (e.g. for NH3, 12 instead of 2 mg/m3, and N2O, 3 instead of 1 mg/m3) and to discuss how to detect unexpected interferences and cascade effects and to decrease the uncertainty on concentration measurements.

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