Ammonia and hydrogen sulfide emissions from swine production facilities in North America: A meta-analysis

Literature on NH₃ and H₂S emissions from swine production facilities in North America was reviewed, and a meta-analysis was conducted on measured emissions data from swine houses and manure storage facilities as well as concentration data in the vicinity of swine production facilities. Results from more than 80 studies were compiled with results from the 11 swine sites in the National Air Emissions Monitoring Study (NAEMS). Data across studies were analyzed statistically using the MIXED procedures of SAS. The median emission rates from swine houses across various production stages and manure handling systems were 2.78 and 0.09 kg/yr per pig for NH₃ and H₂S, respectively. The median emission rates from swine storage facilities were 2.08 and 0.20 kg/yr per pig for NH₃ and H₂S, respectively. The size of swine farm that may trigger the need to report NH₃ emissions under the Emergency Planning and Community Right-to-Know Act (EPCRA) is 3,410 pigs on the basis of the median NH₃ emission rate (4.86 kg/yr per pig), but the threshold can be as low as 992 pigs on the basis of the 90th-percentile emission rates (16.71 kg/yr per pig). Swine hoop houses had significantly higher NH₃ emission rate (14.80 kg/yr per pig) than other manure-handling systems (P < 0.01), whereas deep-pit houses had the highest H₂S emission rate (16.03 kg/yr per pig, P = 0.03). Farrowing houses had the highest H₂S emission rate (2.50 kg/yr per pig), followed by gestation houses, and finishing houses had the lowest H₂S emission rate (P < 0.01). Regression models for NH₃ and H₂S emission rates were developed for finishing houses with deep pits, recharge pits, and lagoons. The NH₃ emission rates increased with increasing air temperature, but effects of air temperature on H₂S emission rates were not significant. The recharge interval of manure pits significantly affected H₂S but not NH₃ emission rates. The H₂S emission rates were also influenced by the size of the operation. Although NH₃ and H₂S concentrations at the edge of swine houses or lagoons were often higher than corresponding acute or intermediate minimum risk levels (MRL), they decreased quickly to less than corresponding chronic or intermediate MRL as distances from emission sources increased. At the distances 30 to 1,185 m from emission sources, the average ambient concentrations for NH₃ and H₂S were 46 ± 46 μg/m³ and 4.3 ± 8.6 μg/m³ respectively.