Emission of ammonia from swine production facilities is of a major
concern from an ecological viewpoint due to deposition and a potential health effect
due to formation of 2.5 micron (μm) particles. One of the critical factors in ammonia
emission is the variation in the emission rate from swine production facilities
throughout a production cycle and the variation in the ammonia concentrations at
various distances from a building. This study was conducted to measure ammonia
concentrations in the air surrounding a 3,600 head grow-finish unit throughout a
production cycle. Measurements were made at 16 m (50 ft) and 33 m (100 ft)
downwind of the buildings at a height of 1 m (3 ft), 6 m (18 ft), and 12 m (36 ft) at 33
m (100 ft) from the buildings with a ion mobility spectrometer with an accuracy of 5
ppbv. An additional study was conducted to measure ammonia concentrations during
application of manure and anhydrous ammonia.
Ammonia concentrations varied during the production cycle with the
concentrations near 1000 ppbv at 50 feet and rapidly decreasing to less than 200
ppbv at 100 feet from the buildings. This decrease in concentration was typical
throughout the complete production cycle. There was a decrease in ammonia
concentrations with height above the surface. The variation among days during a
week was large and it was not uncommon to observe variations within a day from 50
to 1000 ppbv. This magnitude of variation decreased with distance because of the
lower maximum values. The large variation with time was due to the extreme
turbulent regime observed within close proximity of production buildings. This
degree of variation has prohibited the use of traditional micrometeorological methods
to estimate emission rates from buildings. Ammonia concentrations at 1 m above
the surface during manure application reached a maximum of 400 ppbv within six
hours following application and remained at 100 ppbv for the next 24 hours. In
contrast, ammonia concentrations at 1 m above the surface reached 250 ppbv within
2 hours and then rapidly decreased to less than 10 ppbv within 4 hours after
application. The patterns of ammonia emission following application of manure were
caused by manure being deposited on the surface compared to the ammonia being
injected into the soil. Understanding variations in ammonia concentrations around
swine production units provides increased confidence in evaluating management
practices that reduce ammonia emissions.