Simplified method developed for estimating the on-farm EF GHG and NH3 – presentation & results

Estimating the greenhouse gas (GHG) and ammonia (NH3) emission factors (EF) of cattle farming is challenging in open barn production systems since ventilation rates are very difficult to do in such situations. To overcome this difficulty, we developed a method based on: (1) indoor/outdoor CO2, CH4, N2O and NH3 concentration measurements; and (2) a farm questionnaire estimating the carbon mass balance at the building scale. This ‘Simplified Method’ has been applied in an international study including eight European countries totalizing over 50 dairy farms with seasonal repetitions and the results of the questionnaire were also used to characterize the farm diversity. The dairy population in the barn where the air samplings were done ranged from 8 to 979 cows. The feeding quantity was between 14 and 31 kg DM/animal/day and the milk production between 18 and 50 kg milk/animal/day. Most of them had concrete or slatted floors (40 and 35% respectively) and one fourth were separated urine and faeces. The ‘Simplified Method’ will be shortly described and examples of the results per countries, farms and seasons will be presented.