ETH Zürich, Institut für Agrarwissenschaften, 8092 Zürich

Effect of season and feeding on methane emission from Swiss dairy cow slurry

Due to the lack of country-specific data, the so-called IPCC default values are often taken for calculating greenhouse gas budgets. The default value to be applied for Switzerland for the ultimate methane (CH4) production capacity (B0) of slurry amounts to 240 l CH4/kg volatile solids (VS). In the present study, slurry from 64 dairy farms representing all major Swiss milk producing Cantons was collected. Sampling took place both in winter and summer on farms feeding either silage or no silage (two major Swiss dairy cattle feeding systems). Farms were further classified by their annual milk yield. B0 was determined by incubating the slurry at 35 °C for 14 weeks. Winter slurry resulted in a B0 ranging between 241 and 314 l CH4/kg VS, summer slurry B0 ranged between 35 and 62 l CH4/kg VS. This low B0 could have resulted from previous fermentation in the slurry ponds or strong dilution through precipitation. Annual milk yield and feeding system did not influence B0, even though nutrient composition of diets and VS differed significantly. The results indicate that further differences in feeding and slurry management have to be considered in developing countryspecific data.

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