Dairy farm methane emissions using a dispersion model
Th ere is a need to know whole-farm methane (CH 4) emissions since confi ned animal facilities such as beef cattle feedlots and dairy farms are emission "hot spots" in the landscape. However, measurements of whole-farm CH 4 emissions can diff er between farms because of diff erences in contributing sources such as manure handling, number of lactating and nonlactating cows, and diet. Such differences may limit the usefulness of whole-farm emissions for national inventories and mitigation purposes unless the variance between farms is taken into account or a large number of farms can be examined. Our study describes the application of a dispersion model used in conjunction with fi eld measurements of CH 4 concentration and stability of the air to calculate wholefarm emissions of CH 4 from three dairy farms in Alberta, Canada, during three sequential campaigns conducted in November 2004 and May and July 2005. Th e dairy farms ranged in herd size from 208 to 351 cows (102 to 196 lactating cows) and had different manure handling operations. Th e results indicate that the average CH 4 emission per cow (mixture of lactating and nonlactating) from the three dairy farms was 336 g d -1, which was reduced to 271 g d -1 when the emission (estimated) from the manure storage was removed. Further separation of source strength yielded an average CH 4 (enteric) emission of 363 g d -1 for a lactating cow. Th e estimated CH 4 emission intensities were approximately 15 g CH 4 kg -1 dry matter intake and 16.7 L CH 4 L -1 of milk produced. Th e approach of understanding the farm-to-farm differences in CH 4 emissions as affected by diet, animal type, and manure management is essential when utilizing whole-farm emission measurements for mitigation and inventory applications. © 2012 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.
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