|Review of Emission Factors and Methodologies to Estimate Ammonia Emissions From Animal Waste Handling (EPA/600/R-02/017) April 2002
Currently, about 80 percent of ammonia (NH3) emissions in the United States originate from livestock waste. This report summarizes and discusses recent U.S. and European information on NH3 emissions from swine farms and assesses the applicability for general use in the U.S. and, in particular, North Carolina. Limited information on NH3 emissions from other farm animals is also included, as well as some information on methane emissions from anaerobic animal waste lagoons and nitrous oxide emissions from swine waste spray fields. The report discusses a comprehensive mass balance approach that may be used to estimate emissions for certain livestock and poultry operations.
The emission rates for the pig houses, calculated by various methods, show good agreement and suggest that the houses are a more significant source than previously thought. It is believed that there is enough of a basis to recommend a general emission factor for houses of 3.7 ± 1.0 kilograms (kg) NH3 per finisher pig per year (kg NH3/pig/year) or 59 ± 10 grams (g) NH3 per kg live weight per year. This value is supported by the 4.3 kg NH3/pig/year reported for several pull-plug houses that were tested in the summer of 2000.
For lagoons, it was found that there is good similarity between the field test results and the number calculated by a mass balance method. The suggested annual NH3 emission factor, based on field tests at one swine farm lagoon in North Carolina, is 2.4 kg NH3/pig/year. The emission factor for lagoons is based on field tests at only one lagoon and is considered to be less accurate than the emission factor for houses. Emission rates from spray fields were estimated using a total mass balance approach, while subtracting the house and lagoon emissions.
The total emission rates for finishing pigs at the test farm compared well to the total rate established by a mass balance approach based on nitrogen intake and volatilization. Therefore, it was concluded that a mass balance approach can be helpful in estimating NH3 emissions from swine farms. Assuming that the swine population at the test farm was a self-sustaining population, similar to the average swine population in North Carolina, a general emission factor of 7 kg NH3/pig/year was developed. This emission factor is comparable to three general European emission factors, which varied from 5 to 6 kg NH3/pig/year.
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