Greenhouse Gas Emission from Stored Livestock Slurry

Abstract Animal manure contributes about 40% of the total methane (CH 4 ) and 20% of the total nitrous oxide (N 2 O) emissions in Denmark. We measured the CH 4 and N 2 O emissions from stored cattle slurry and fermented slurry during fall 1996 and summer 1997 and evaluated the effect of surface covers consisting of straw, floating leca pebbles, or a natural surface crust on the patterns of these emissions. No emission of N 2 O was measured during periods with more rain than evaporation from the slurry stores and no emission was measured from uncovered slurry, irrespective of climatic conditions. During the summer storage with drying conditions, N 2 O emissions of up to 25 mg N m −2 h −1 were recorded from slurry with surface covers. Total N 2 O emission was highest from digested slurry. The emission of CH 4 from stored fermented slurry and cattle slurry varied between <0.01 and 1.4 or 0.7 g CH 4 —C m −3 h −1 , respectively. The log‐transformed emissions were linearly related to the inverse temperature. Emission of CH 4 was reduced, on average, by 38% with surface covers. The reduction was probably due to CH 4 oxidation in the surface covers or in the interface between the cover and liquid in the store. Fermentation did not reduce CH 4 emissions during storage of the slurry.