Measurement and mitigation of reactive nitrogen species from swine and poultry production facilities

Abstract Text: Reactive nitrogen (Nr) species include oxides of nitrogen (nitric oxide, nitrogen dioxide and nitrous oxide (N₂O)), anions (nitrate and nitrite) and amine derivatives (ammonia (NH₃), ammonium salts and urea). Of the different Nr species, air emissions from swine and poultry facilities are dominantly NH₃ followed by N₂O. Excreta emissions are NH₃, ammonium ions, and urea with trace amounts of nitrate and nitrite. Farm systems and practices that handle manure as a wet product without pH modification favor almost exclusive NH₃ production while systems and practices associated with dry manure handling and bedded systems emit more NH₃ and result in greater N₂O production than that produced in wet systems. Results from a turkey grow-out study estimated that just under 1% of consumed nitrogen was emitted as N₂O from housing, compared to just under 11% emitted as NH₃. Despite generally lower N₂O emissions from animal housing compared to crop field emissions, N₂O emissions from housing are greater than often estimated. Lagoon systems emit more N₂O than either slurry or deep pit swine systems. Deep pit swine buildings emit as much as two thirds less N₂O than deep bedded swine systems and laying hen, broiler chicken and turkey buildings emit over 4 times as much N₂O as swine housing, on an animal unit basis. Critical control points for mitigation center on 1) reducing the amount of nitrogen excreted and therefore excreted nitrogen available for loss to air or water during housing, manure storage or following land application of manures, 2) capturing excreted nitrogen to prevent release of nitrogen-containing compounds to air, water or soil resources or 3) conversion/treatment of nitrogen-containing compounds to non-reactive nitrogen gas.

Keywords: Air emissions, poultry, swine