Gas emissions from welfare-friendly pig housing systems with outdoor runs

With the emerging of welfare-friendly pig farms with outdoor runs, more attention is paid to the environmental impact of these farms in the Netherlands. To quantify gaseous emissions, it is important to select reliable methods. However, current methods for intensive farms are not applicable due to the open-air structure, where the ventilation rate is almost impossible to measure. In addition, outdoor climate conditions are more variable, and pigs may show different elimination behaviours due to lower stocking density and larger excretion areas. In this project, a process-based was optimized depending on the climate conditions in the outdoor environment on the urine puddle level. A local approach combined process-based modelling with on-site measurements simulated the ammonia emissions on the pen level and manure pit under the floor to show the contribution of different ammonia emitting source. In addition, a farm-level approach using micrometeorological methods (bLS model) verified by tracer gas ratio method estimates total emissions of both ammonia and methane. The research objectives are: (1) to explore the effect of temperature and air velocity on ammonia release rate (puddle level); (2) to quantify ammonia emissions based on pig elimination behaviour and emitting area (pen level); (3) to determine ammonia emissions from manure under the floor; (4) to estimate farm-level ammonia emissions using process-based modelling; (5) to quantify the ammonia and methane emissions using bLS modelling verified with tracer gas ratio method.