Nitrogen-Focused S creening L ife C ycle A ssessment of C ommercial P ig P roduction from F eed to S laughterhouse G ate

Pig production is a source of animal protein but generates nitrogen losses that contribute to acidification, eutrophication, and climate change. This study quantifies N flows in a commercial pig production system from feed intake to the slaughterhouse gate, using a functional unit of 1 kg carcass weight. A mass balance model was constructed using literature-based parameters, including N efficiency, carcass yield, and emission factors for manure storage. Feed N intake was estimated at 5.43 kg per pig, with a carcass weight of 66.0 kg. Results show that 30.8% of feed N is retained in the carcass, 18.2% in offal, 11.6% is lost as NH₃, and 0.015% as N₂O, while 39.4% remains in manure after 42 days of storage. Manure storage is identified as the primary N hotspot, holding both the largest residual N pool and the dominant gaseous loss. The NH₃ loss per pig corresponds to an acidification potential of 1.44 kg SO₂ eq per pig and a eutrophication potential of 0.895 kg N eq per pig. Sensitivity analysis shows that NH₃ loss is most responsive to the NH₃ emission factor, followed by feed intake, manure N content, and N efficiency, whereas carcass yield and N₂O emission factor have no effect.