|DREWRY, JESSICA - University Of Wisconsin
|CHOI, CHRISTOPHER - University Of Wisconsin
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2017
Publication Date: 7/1/2017
Citation: Drewry, J.L., Powell, J.M., Choi, C.Y. 2017. Design and calibration of chambers for the measurement of housed dairy cow gaseous emissions. Transactions of the ASABE. 60:1291-1300.
Interpretive Summary: Accurate measurement of gas emissions from dairy cows is essential to assess how to maximize milk production while reducing environmental impact. We describe methods and procedures to instrument, calibrate, and assess the uncertainty of gas emissions from cows housed in chambers that simulate dairy production settings. These methods and procedures can be used to enhance the accuracy of gas emissions measurements from various gas mitigation technologies.
Technical Abstract: The increased global demand for milk and other dairy products over the past decade has heightened concerns about potential for increased environmental impacts. Accurate measurement of gas emissions from dairy cows is essential to assess the effect of cow diets and other management practices on both the composition and rate of gas emissions. We describe methodologies to instrument, calibrate, and assess the uncertainty of gas emissions by cows housed in chambers that simulate production settings. The inlet and outlet of each chamber were equipped with pitot tubes, temperature and relative humidity probes, and gas samplers to monitor airflow rates, gas compositions and gas emission rates. A fourier transform infrared spectroscopy (FTIR) instrument was used to monitor gas concentrations in the gas samples on a semi-continuous basis. The measurement uncertainty in calculating the rate of gaseous emission from the chambers was quantified, and gas concentration and differential pressure, as measured by the pitot tubes, were identified as the primary parameters contributing to gas emission uncertainties. The recovery of methane was within 10% for the mass recovery tests, which was within the measurement uncertainty. We experimentally determined fan operating curves to identify optimum differential chamber pressures to minimize gas leakage from chambers. A computational fluid dynamics model was developed to assess mixing air patterns and define steady state conditions. The computational fluid dynamics model was validated with experimental data of air velocity within each chamber. These procedures will facilitate accurate measurement of gas emissions from housed dairy cows and provide a laboratory to test various gas mitigation treatments.