AMMONIA EMISSIONS FROM U.S. LAYING HEN HOUSES IN IOWA AND PENNSYLVANIA

摘要

Ammonia (NH{sub}3) emission rates (ER) of ten commercial layer houses (six high-rise or HR houses and four manure-belt or MB houses) with different manure handling or dietary schemes were monitored for one year in Iowa (IA) and Pennsylvania (PA). Gaseous (NH{sub}3 and CO{sub}2) concentrations of incoming and exhaust air streams were measured using custom-designed portable monitoring units that shared similar performance to EPA-approved measurement apparatus. Building ventilation rates were determined by calibrated CO{sub}2 mass balance using the latest metabolic rate data for modern laying hens. The field monitoring involved a total of 386 and 164 house-day measurements or 18,528 and 7,872 30-min emission data points for the HR houses and the MB houses, respectively. The ER showed considerable diurnal and seasonal variations. The annual mean ERs (g NH{sub}3 hen{sup}(-1) d{sup}(-1)) and standard errors were 0.90 ±0.027 for IA-HR houses with standard diet, 0.81 ±0.02 for IA-HR houses with a nutritionally balanced 1% lower crude protein diet, 0.83 ±0.070 for PA-HR houses with standard diet, 0.054 ±0.0035 for IA-MB houses with daily manure removal, and 0.094 ±0.006 for PA-MB houses with twice a week manure removal. Mass balance of nitrogen (N) intake and output performed for IA-HR houses revealed a total N intake recovery of 94% to 101%, further verifying the certainty of the NH{sub}3 ER measurements. Results of the study contribute to the U.S. national inventory on NH{sub}3 emissions from animal feeding operations, particularly laying hen facilities as affected by housing type, manure handling scheme, crude protein content of the diet, and geographical location.