Transactions of the ASABE Vol. 54(3): 1137-1148 E 2011 American Society of Agricultural and Biological Engineers ISSN 2151-0032 1137 RADIOACTIVE 85 KR AND CO 2 BALANCE FOR VENTILATION RATE MEASUREMENTS AND GASEOUS EMISSIONS QUANTIFICATION THROUGH NATURALLY VENTILATED BARNS M. Samer, W. Berg, H.‐J. Müller, M. Fiedler, M. Gläser, C. Ammon, P. Sanftleben, R. Brunsch ABSTRACT. Animal housing is a major source of gaseous emissions, such as ammonia (NH 3 ), methane (CH 4 ), nitrous oxide (N 2 O), and carbon dioxide (CO 2 ). Ammonia is an atmospheric pollutant and responsible for eutrophication and soil acidification, while CO 2 , CH 4 , and N 2 O are greenhouse gases (GHG) that contribute to global warming. The quantification of gaseous emissions from livestock buildings with natural ventilation systems is a particularly difficult task and is associated with uncertainties that are largely unknown. One key issue is to measure the ventilation rate and then to quantify the gaseous emissions. Therefore, in this study, the ventilation rate was determined by three different methods simultaneously. Field experiments were carried out to study the ventilation rate in a naturally ventilated dairy barn located in northern Germany during the summer seasons from 2006 to 2010. The air exchange rates (AER) as well as the ventilation rates were determined by the decay of the radioactive tracer krypton‐85, the carbon dioxide (CO 2 ) balance, which was used as the reference method in this study, and the combined effects of wind pressure and temperature difference forces (WT method). Subsequently, the results were compared with each other by carrying out Pearson correlation analysis and developing a regression model. During each field experiment, continuous measurements of gas concentrations (NH 3 , CO 2 , CH 4 , and N 2 O) inside and outside the building and 85 Kr tracer gas experiments were carried out. Meanwhile, the temperature was measured and recorded inside and outside the barn. Furthermore, the wind velocity was measured. Although the WT method showed minor overestimation by about 1.11 (p < 0.05) times the reference method, it is not reliable because it showed no linear correlation (0.05; p = 0.88) with the reference method. This was due to large fluctuations in the wind velocity (direction and speed), which negatively affected the WT method, which is basically dependent on wind velocity. In contrast, the 85 Kr tracer gas technique showed a good linear correlation (0.82; p < 0.05) with the reference method, which accentuates that the 85 Kr tracer gas technique is a promising method. However, this technique overestimated the air exchange rate by about 2.05 (p < 0.05) times the reference method. Therefore, the 85 Kr tracer gas technique should be further developed to produce values consistent with those estimated by the reference method. The emissions factors, subject to the reference method, were 32, 157.7, 13736, and 7.9 kg year ‐1 AU ‐1 for NH 3 , CH 4 , CO 2 , and N 2 O, respectively. Keywords. Aerodynamics, Air exchange rate, CO 2 balance, Dairy barns, Gaseous emissions, Natural ventilation, Radioactive isotope 85 Kr, Tracer gas technique, Ventilation rate. missions from agriculture have great environmen‐ tal impact and relevant political importance, and animal husbandry is a major source of atmospheric pollutants, e.g., ammonia, and greenhouse gases, Submitted for review in January 2011 as manuscript number SE 9029; approved for publication by the Structures & Environment Division of ASABE in April 2011. The authors are Mohamed Samer, ASABE Member, Research Scientist, Leibniz Institute for Agricultural Engineering Potsdam‐Bornim (ATB), Department of Engineering for Livestock Management, Potsdam, Germany; and Assistant Professor, Department of Agricultural Engineering, Faculty of Agriculture, Cairo University, Giza, Egypt; Werner Berg, Provisional Department Head, Hans‐Joachim Müller, Research Scientist (retired), Merike Fiedler (Schultz), Research Scientist, Manfred Gläser, Nuclear Physicist (retired), and Christian Ammon, Technician, Leibniz Institute for Agricultural Engineering Potsdam‐ Bornim (ATB), Department of Engineering for Livestock Management, Potsdam, Germany; Peter Sanftleben, Director, State Institute for Agriculture and Fishery MV, Institute of Animal Production, Dummerstorf, Germany; and Reiner Brunsch, Scientific Director, Leibniz Institute for Agricultural Engineering Potsdam‐Bornim (ATB), Potsdam, Germany. Corresponding author: Mohamed Samer, Leibniz Institute for Agricultural Engineering Potsdam‐Bornim (ATB), Department of Engineering for Livestock Management, Max‐Eyth‐Allee 100, 14469 Potsdam, Germany; phone: +49‐0‐331‐5699‐518; fax: +49‐0‐331‐5699‐ 849 e‐mails: msamer@atb‐potsdam.de; samer@cu.edu.eg. e.g., methane, nitrous oxide, and carbon dioxide. Ammonia is responsible for eutrophication and soil acidification. In Germany, 95% of ammonia emissions are from agricultural production and 75% are from animal housing (Reinhardt‐ Hanisch, 2008). In addition, 50% to 70% of methane and ni‐ trous oxide emissions are from agricultural production, contributing 13% and 5%, respectively, to global warming (Häussermann et al., 2006). Therefore, reducing emissions is critical. One key issue is to quantify gaseous emissions from livestock buildings. Regarding mechanically ventilated ani‐ mal buildings (forced ventilation); harmful gases are ex‐ hausted through chimneys or extractor fans, where the discharged emission mass flow can be easily determined by measuring the gas concentration and the ventilation rate. Nevertheless, natural ventilation systems are commonly used in animal buildings. Natural ventilation of buildings is gener‐ ated by two distinct sources. Buoyancy or gravity effects are present, and in large part these are due to temperature differ‐ ences between the outside and inside air. The second source is wind blowing over a building, generating pressures and suctions at different points, which can force air in and out of the building (Sallvik, 1999). Unfortunately, quantification of gaseous emissions from naturally ventilated animal houses is complicated and shows E