Effects of environmental and housing system factors on ammonia and greenhouse gas emissions from cattle barns: A meta-analysis of a global data collation

This study provides a meta-analysis on the relationships between cattle barn CH₄, NH₃ and N₂O emission rates and their key drivers (i.e., housing type, floor type, environmental conditions). Understanding these relationships is essential to reduce uncertainties in emission inventories and suggest targeted mitigation measures. The total number of daily emission rates included in the analysis was 139 for CH₄, 293 for NH₃ and 100 for N₂O emissions. Emission rates in the database showed a large variation with 45–803.5 g/LU d⁻¹ for CH₄, 0.036–146.7 gN LU⁻¹ d⁻¹ for NH₃, and 0.002–18 gN LU⁻¹ d⁻¹ for N₂O emissions. Despite the high emission variability, significant effects were identified·NH₃ showed positive correlation with air temperature; NH₃ emissions differed between housing types but not between floor types·NH₃ emissions from tied stalls were lower than the ones from cubicle housing regardless of the floor type. Additionally, NH₃ emissions from loose housings were lower than the ones from cubicle housing·NH₃ and N₂O emission rates from temperate wet zones were lower than the ones from temperate dry zones. CH₄ emission rates were affected by environmental factors only and not by housing and floor type, showing negative correlation with air temperature and humidity. The factors investigated can be suggested as ancillary variables and descriptors when cattle barn emissions are measured, in order to make best use of emission data. Country-specific data of these key drivers can be included into national inventories to adapt them to different agroecosystems and support targeted policies.