In the nitrogen balance all nitrogen sources have to be considered and included to have a better appreciation of the animal concentration and impact in an area. The nitrogen flow in a pig facility was investigated using the input/output relation in different stages: – feed consumption and liveweight produce; – slurry sampling (in the manure pit inside the building); – slurry storage; – slurry separation; – aeration of the liquid slurry phase; – long term storage of the treated slurry in a lagoon.