The "MeTEmSiS" project aims to develop and test methods that allow to offer fattening pigs an outdoor run in order to promote animal welfare while at the same time it should minimize ammonia emissions. The aim is to reduce the specific trade-off between animal welfare and environmental protection. It is planned to give the animals access to an outdoor run via computer-controlled sluices. The pigs should learn that they can only move between the inside of the barn and the outdoor run if they are noticed of this by acoustic and/or visual signals. Thus, when the "signal sluices" are closed, conventional negative pressure ventilation can be maintained inside the barn and air filtering for emission reduction is possible. At the same time, the signal locks are expected to provide cognitive environmental enrichment for the pigs. A further reduction of emissions is to be achieved by optimizing the soiling areas in the outdoor run which should limit the emission-active surface. In addition, low-maintenance and robust technical procedures will be developed and tested to achieve faeces-urine separation in the soiling areas and thus a reduction in the formation of ammonia.