Effects of mechanical separation on GHG and ammonia emissions from cattle slurry under winter conditions

Effects of cattle slurry mechanical separation on CO2, CH4, N2O and NH3 emissions during slurry management under winter conditions were investigated in a laboratory study. Greenhouse gas (GHG) emissions during storage and soil application of raw cattle slurry by broadcasting of its liquid and solid fractions were assessed. Carbon dioxide was the predominant emission source during storage and soil application of manure on a CO2-eq basis, but CH4 was the predominant GHG emission from stored slurries. During storage, NH3 fluxes from liquid fractions were higher than from the solid fraction, but the solid fraction was the main source of NH3 emissions after land application and ∼70% of total ammoniacal N applied to soil was lost. Combining losses during storage and after soil application of both liquid and solid fractions, CO2-eq emissions of combined fractions were 11% higher than from raw cattle slurry. Results suggest that mechanical separation of cattle slurry should not be used by farmers unless other GHG emission reduction measures are adopted.