Manfred Gläser

Implementation of Radioactive 85Kr for Ventilation Rate Measurements in Dairy Barns

Quantifying gaseous emissions from naturally ventilated animal buildings is a particularly difficult task and associated with large uncertainties. One aspect is to measure the ventilation rate and then to quantify the gaseous emissions. Therefore, the ventilation rate was determined by two methods, simultaneously. Fifteen field experiments were carried out to study the ventilation rate in a naturally ventilated dairy barn located in Northern Germany during three consecutive winter seasons. The air exchange rates and then the ventilation rates were determined by the decay of the radioactive tracer Krypton-85, and the carbon dioxide (CO2) balance which is the reference method. Afterwards, the results were compared with each other by developing a linear regression model and carrying out Pearson correlation analysis. During each field experiment, continuous measurements of gas concentrations (NH3, CO2, CH4, and N2O) inside and outside the building and 85Kr tracer gas experiments were carried out. Meanwhile, the microclimatic and climatic conditions were measured and recorded. The tracer gas technique was further developed for better application through winter measurements. Where, eight combination factors were tested which are: 85Kr line release source vs. 85Kr point release source, average a-values vs. sum impulses, selected radiation counters vs. all radiation counters. The differences between the reference method and the eight factor combinations were tested using the ANOVA model. The results showed that the best factor combinations were: (1) line release source considering the impulses recorded by selected radiation counters and implementing the sum method of all impulses where high R-square value of 0.82 and reliable parameter estimate of 1.00±0.19 were found for this combination, and (2) point release source considering the impulses recorded by all radiation counters and implementing the sum method of all impulses where high R-square value of 0.91 and reliable parameter estimate of 1.19±0.15 were found for this combination. The average gaseous emissions through the different winter seasons, subject to the reference method, were 2.9, 14.5, 1785, and 1.6 g h-1 AU-1 for NH3, CH4, CO2, and N2O respectively.

The Influence of Building Equipment and Operation on the Air Exchange Rates throughout a Naturally Ventilated Dairy Barn

Naturally ventilated barns have gained wide acceptance worldwide, due to the easy design and the low energy consumption. The inside climate and the air exchange rate (AER) of such buildings is mainly affected by the outside conditions. The AER has a great influence on emission fluxes. There is no reference method for AER estimation in naturally ventilated barns but several methods with different pros and cons and each with uncertainties have been used. The aim of this study is to evaluate the influence of side curtains of a naturally ventilated barn on AER as well as the reliability of tracer gas technique in AER quantification throughout these kinds of barns. The AER and the emission fluxes were measured in a naturally ventilated dairy barn in north Germany. The AER was estimated using two methods. The first one is the concentration decay of radioactive isotope tracer-gas Krypton (85Kr-M) with two different evaluation procedures: (1) AER obtained from the sum of impulses for all 85Kr-detectors (sum-85Kr-M), and (2) AER obtained from the arithmetic average of the single 85Kr-detectors (average-85Kr-M). The second method is the CO2-mass balance model (CO2-M). The meteorological parameters were recorded inside and outside the barn, as well as the concentrations of ammonia (NH3), carbon dioxide (CO2) and methane (CH4). Pearson correlation analysis was performed and linear regression models were fitted. On this basis, the influence of the side curtains on AER was investigated and evaluated. The AERs, derived from CO2-M, were 35.3±14.6 h-1 and 22.0±7.1 h-1 for opened and closed side curtains, respectively. The 85Kr-M resulted in higher AERs values compared to CO2-M by 0.15±0.13 for sum-85Kr- M and by 3.66±1.17 for average-85Kr- M. The emission fluxes according to CO2-M were during the summer seasons 124, 538 and 45,600 g d-1AU-1 for NH3, CH4, and CO2, respectively. During winter seasons they were 64, 348 and 42,700 g d-1AU-1.

Quantification of Air Exchange Rates and Gaseous Emissions throughout Naturally Ventilated Dairy Barns

Animal husbandry is a major source of atmospheric emissions, e.g., ammonia, and methane. The quantification of emission flow has gained special attention in the recent years. But, in naturally-ventilated barns this quantification is still a difficult task. A main issue is to estimate the air exchange rate (AER) of the barn, and then to quantify the emission flow. This study consisted of several trials conducted during mild and cold periods of the year in two naturally-ventilated dairy cattle barns located in northeast Germany. During the experiments, the concentrations of (NH3, CH4 and CO2) as well as the temperature were measured outside and inside the barns. The wind speed and the wind direction outside the barns were recorded as well as the air speed through the openings of the barns. The AERs were estimated according to three methods: concentration decay of radioactive isotope tracer-gas Krypton85 (85Kr-M), the air speed through the inlet openings (AS-M), and the CO2 mass balance model (CO2-M). The comparison was done by performing the Pearson correlation analysis and by developing a linear regression model.

Quantitative Erfassung von Raumluftströmungen in frei gelüfteten Ställen

Houses can either be acclimated through forced or natural ventilation. Natural ventilation means energy saving and noise reduction, but is also dependent on the reliable functioning of the ventilation principle through the design of the construction cover, as well as the incoming and the outgoing air openings. Sufficient data on the emission and the immission characteristics of naturally ventilated livestock buildings is lacking. For designing animal houses with natural ventilation, as well as for making an eco-relevant assessment of these systems, knowledge about the through-flow in such buildings is necessary. More ideas are given in this contribution.