Atmospheric Ammonia Emissions From Operational Areas of a Dairy

Ammonia gas is important in aerosol formation, soil acidification, aquatic eutrophication, acid rain and can damage human and animal respiratory systems. Anthropogenic emissions are approximately two-thirds of the global emissions of NH3 and agriculture is the dominant anthropogenic source. We are studying NH3 emissions from the WSU dairy located near Pullman, WA to provide a detailed emission inventory. The dairy has approximately 200 milking cows and 200 replacement heifers. The cows are housed in open air barns and the liquid waste is stored in four open air lagoons until it is applied to grass fields in the late summer. Agricultural emissions of NH3 have been measured in Europe but very few measurements have been made in the United States. Differences in feed and waste management practices between Europe and the U.S. could have a significant effect on NH3 emissions. Since NH3 is an aerosol precursor knowing emission levels is also important for the new U.S. EPA PM2.5 standard. NH3 was measured using an open short-path spectroscopic absorption near 200 nm. The instrument has a time resolution of about a second and a limiting sensitivity of a few ppb. The open path method has the benefit that it is fast, self-calibrating and does not have errors associated with NH3 adherance to inlet walls. As part of a detailed emission inventory, NH3 fluxes were determined from the milking cow stalls and of the main slurry lagoon using a SF6 tracer technique. Emissions from various parts of the dairy will be discussed.