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

2011 ASABE Annual Meeting

M. Samer, W. Berg, M. Fiedler, H.-J. Müller, M. Gläser, C. Ammon, C. Loebsin, O. Tober, P. Sanftleben, R. Brunsch

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Introduction

Investigation of emissions from livestock buildings is important as these pollutants affect the health of farmers and the surrounding environment

Emission monitoring enables judgments on the effectiveness of mitigation strategies and controls on emission targets

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

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Methodology

The ventilation rates were determined by two methods: tracer gas technique and CO2-balance

Fifteen field experiments were carried out to study the ventilation rate in a naturally ventilated dairy barn located in North Germany during 3 consecutive winter seasons

During each field experiment, continuous measurements of gaseous concentrations (NH3, CO2, CH4, and N2O) were carried out

Microclimatic and climatic conditions were measured and recorded

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The investigated dairy barn

Plan view of the investigated barn

Side view of the investigated barn

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Methodology

The following factors were tested: 85Kr line release source vs. 85Kr point release source,

average α-values vs. sum impulses, selected radiation counters vs. all radiation counters

The results were compared with each other by developing a linear regression model and carrying out Pearson correlation analysis

The differences between the reference method and the eight factor combinations were tested using the ANOVA model

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Results

The results showed that the best factor combinations were:

Line release source considering the impulses recorded by selected radiation counters and implementing the sum method of all impulses, where high R2 value of 0.82 and reliable parameter estimate of 1.00±0.19 were found

Point release source considering the impulses recorded by all radiation counters and implementing the sum method of all impulses, where high R2 value of 0.91 and reliable parameter estimate of 1.19±0.15 were found

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Factor Combinations

Diff

eren

ce to

Ref

eren

ce (

h-1)

a1b1c2 a1b1c1 a2b1c2 a2b1c1 a1b2c2 a1b2c1 a2b2c2 a2b2c1

a185Kr line release source

b1 Average α-valuesc1 Selected radiation counters

Differences of air exchange rates of the

eight factor combinations to the reference method

a285Kr point release source

b2 Sum impulsesc2 All radiation counters

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Results

The average hourly 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 average daily gaseous emissions were 70, 347, 42853, and 37.5 g d-1 AU-1 for NH3, CH4, CO2, and N2O, respectively

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Conclusions

Sum of impulses lead to better results than the average α-values

Considering all readings of the radiation counters is more representative for air movement

Point release source shows better results than the line release source during winter measurements

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