Merike Fiedler

Seasonal and diel variations of ammonia and methane emissions from a naturally ventilated dairy building and the associated factors influencing emissions

Understanding seasonal and diel variations of ammonia (NH3) and methane (CH4) emissions from a naturally ventilated dairy (NVD) building may lead to develop successful control strategies for reducing emissions throughout the year. The main objective of this study was to quantify seasonal and diel variations of NH3 and CH4 emissions together with associated factors influencing emissions. Measurements were carried out with identical experimental set-up to cover three winter, spring and summer seasons, and two autumn seasons in the years 2010, 2011, and 2012. The data from 2010 and 2011 were used for developing emission prediction models and the data from 2012 were used for model validation. The results showed that NH3 emission varied seasonally following outside temperature whereas CH4 emission did not show clear seasonal trend. Diel variation of CH4 emission was less pronounced than NH3. The average NH3 and CH4 emissions between 6a.m. and 6p.m. were 66% and 33% higher than the average NH3 and CH4 emissions between 6p.m. and 6a.m., respectively for all seasons. The significant relationships (P<0.0001) between NH3 and influencing factors were found including outside temperature, humidity, wind speed and direction, hour of the day and day of the year. The significant effect (P<0.0001) of climate factors, hours of the day and days of the year on CH4 emission might be directly related to activities of the cows.

Measurement of ventilation rate in livestock buildings with radioactive tracer gas technique: Theory and methodology

Natural ventilation systems are commonly used in livestock buildings, where the natural ventilation is a more energy efficient approach to provide effective ventilation. The foremost predicament of natural ventilation is the lack of precise, continuous and direct measuring techniques for ventilation rates, which is critical for monitoring gaseous emissions in livestock buildings for controlling the indoor air quality. Several ventilation rate measurement methods have been reported in the literature. However, these methods have some limitations and errors. The objectives of this study are to investigate the different tracer gas techniques (TGTs) especially using a radioactive tracer gas, to elucidate the applied methodology and instrumentation required and to investigate the methods of data analysis with results using radioactive TGT. The paper presents the technique of radioactive tracer gas preparation in the isotopes laboratory, tools used, the release methods, and locations, and calculations. This study has initiated a development of a radioactive TGT for an accurate determination of ventilation rates in naturally ventilated animal buildings. The radioactive TGT can be applied to other larger naturally ventilated buildings, such as warehouses, aircraft hangers and depositories, as well as to smaller rooms such as offices, class rooms and store.

A comparative study among H2O-balance, heat balance, CO2-balance and radioactive tracer gas technique for airflow rates measurement in naturally ventilated dairy barns

The major problem of natural ventilation is the lack of accurate measurement methods for air exchange rates (AER) which is crucial for emissions quantification. This paper aims at comparing four methods and to recommend thereof one method for further developments. Thirty six experiments were performed to study the AERs in a naturally ventilated dairy barn through four summer seasons and three winter seasons. AERs were determined using moisture (H2O) balance, heat balance (HB), CO2-balance and radioactive tracer gas technique (TGT). The statistical analyses were correlation analysis, regression model, ANOVA and t-test. Continuous measurements of CO2 concentrations, temperature and relative humidity inside and outside the barn were performed. H2O-balance showed reliable results through winter and slightly acceptable results through summer. HB showed slightly acceptable results through summer and unsatisfactory results through winter. CO2-balance showed unexpected high differences to the other methods in some cases. TGT showed reliable results compared to all methods and is independent on physiological parameters. Therefore, TGT should be further developed. The airflow rates (AFRs), subject to TGT, were 0.12 m3 s-1 m-2, 1.15 m3 s-1 cow-1, 0.88 m3 s-1 LU-1 (LU is livestock unit of 500 kg), 395 m3 s-1 and 470 kg air s-1 through summer, and 0.08 m3 s-1 m-2, 0.83 m3 s-1 cow-1, 0.64 m3 s-1 LU-1, 275 m3 s-1 and 328 kg air s-1 through winter. AERs were 37, 81, 63 and 62 h-1 through summer, and 40, 143, 61 and 39 h-1 through winter subject to H2O-balance, HB, CO2-balance and TGT, respectively.

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.

Windkanaluntersuchungen an einem frei gelüfteten Milchviehstall

The air exchange rate regulating the climate inside of natural ventilated livestock buildings is hard to determine in the field due to the variability of time and space of the dominant processes. Experiments in a wind tunnel laboratory can produce sound statistical and representative data obtained under controlled boundary conditions to complete data sets from the field. In this study, measurements of the horizontal wind components within a model of a natural ventilated barn were performed in the wind tunnel. The approach flow was chosen with low turbulence in order to gain knowledge on the influence of the installed equipment on the air flow. In fact, the measured profiles were influenced by the installed equipment and the feeding alley.

Spatial variability of ambient ammonia in the vicinity of a broiler farm.

Ammonia (NH3) emissions from agricultural sources affect the air quality in negative manner. The objective of this study was to quantify NH3 emissions from a commercial broiler farm by measuring weekly averages of atmospheric NH3 at different locations at the same time during two growing cycles. Thus, it was possible to analyze the spatial occurrence of NH3 in air and assess the environmental impact of the farm. For detecting NH3 in air, passive sampling was used at five locations in the immediate vicinity of the farm. The inside NH3 concentrations and the performance of the air volumetric flow rate were measured continuously during the growing cycles inside one broiler barn. In addition, the wind direction was detected.

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.