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An Approach for Measuring Methane Emissions from Whole Farms
Author(s) -
McGinn S. M.,
Flesch T. K.,
Harper L. A.,
Beauchemin K. A.
Publication year - 2006
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2005.0250
Subject(s) - barn , environmental science , methane , methane emissions , tracer , atmospheric sciences , sulfur hexafluoride , atmospheric dispersion modeling , hydrology (agriculture) , environmental engineering , air pollution , chemistry , ecology , biology , geography , engineering , physics , geotechnical engineering , archaeology , organic chemistry , nuclear physics
Estimates of enteric methane (CH 4 ) emissions from ruminants are typically measured by confining animals in large chambers, using head hoods or masks, or by a ratiometric technique involving sampling respired air of the animal. These techniques are not appropriate to evaluate large‐scale farm emissions and the variability between farms that may be partly attributed to different farm management. This study describes the application of an inverse‐dispersion technique to calculate farm emissions in a controlled tracer‐release experiment. Our study was conducted at a commercial dairy farm in southern Alberta, Canada (total of 321 cattle, including 152 lactating dairy cows). Sulfur hexafluoride (SF 6 ) and CH 4 were released from 10 outlet locations (barn and open pens) using mass‐flow controllers. A Lagrangian stochastic (LS) dispersion model was then used to infer farm emissions from downwind gas concentrations. Concentrations of SF 6 and CH 4 were measured by gas chromatography analysis and open path lasers, respectively. Wind statistics were measured with a three‐dimensional sonic anemometer. Comparing the inferred emissions with the known release rate showed we recovered 86% of the released CH 4 and 100% of the released SF 6 The location of the concentration observations downwind of the farm was critically important to the success of this technique.