Greenhouse gas (GHG) emissions from two naturally-ventilated dairy freestall barns measured for a total of 21d, one week each in May, July, and September 2009, are presented in this article. The holding capacity of Barn 1 (B1) was 400 Holstein cows, while that for Barn 2 (B2) was 850 cows. Air samples were taken from inlets and outlets of the barns via a custom made multiplexer gas sampling system for measurement of gas concentrations using a photoacoustic infrared multigas analyzer. Barn ventilation rates were based on air velocity measured with arrays of 3-D ultrasonic anemometers at inlets and outlets. Gas concentrations (10min means) in the barns ranged from: 443-789ppm for CO2, 0.0-39.4ppm for CH4, and 0.25-0.39ppm for N2O; with mean concentrations ranging from 6 to 20%, 0 to 4%, and 26 to 180% above the average background concentrations for CO2, N2O, and CH4, respectively. The correlations between CO2 and CH4 enhanced concentrations were relatively stronger (R of 0.67-0.74) than between CO2 and N2O enhanced concentrations (R of 0.10-0.20). Environmental conditions did not significantly (p=0.46) impact the enhanced concentrations of N2O in the barns. All three parameters (T, RH, and v) had significant (p<0.01) influences on CO2 enhanced concentrations; while only T (p<0.01) and v (p<0.01) had significant influences on CH4 enhanced concentrations. Enhanced concentrations of CO2 and CH4 correlated negatively with all three parameters. The influence of the temperature-humidity index (THI) on CO2 enhanced concentrations was higher than that of v; while the effect v had on CH4 enhanced concentrations was slightly higher than that of the temperature-humidity index. The average emissions, based on hourly means, ranged from 5.3 to 10.7kgd-1AU-1 for CO2; 0.3 to 2.5gd-1AU-1 for N2O; and between 67 and 252gd-1AU-1 for CH4. Nitrous oxide emissions from the smaller barn, B1 (0.4-2.5gd-1AU-1), were significantly higher than from the larger barn, B2 (0.3-0.5gd-1AU-1) most probably because 50% of B1 was open (no stalls) loose dirt floor.
Bibliographical noteFunding Information:
The authors acknowledge the financial support of the Agricultural Air Research Council (AARC), the National Dairy Board , and the Dairy Research Institute for funding and administration of this research, and the cooperation and assistance of the producer.
© 2014 Elsevier Ltd.
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- Enhanced concentrations
- Environmental factors
- Freestall barns
- Greenhouse gases