Greenhouse gas emissions from storage of untreated pig slurry, digestate and the corresponding liquid fractions after solid-liquid separation

The effect of slurry separation on CH₄ and N₂O emissions was investigated in two pilot-scale storage experiments during summer (123 days) and winter (159 days). Pig slurry, anaerobically digested slurry and their corresponding liquid fractions after separation were stored in triplicate. The Anaerobic Biodegradation Model was used to interpret the results of pig slurry. The separated liquid fractions had a higher conversion of initial volatile solids content and different explanations are discussed. There was no clear difference in annual emission between separated and unseparated slurry, although variability was high. The conditions in the field experiment were used for the modelled emissions, and the results demonstrated that the initial microbial community, pH, volatile solids content, and slurry temperature can change the results dramatically. These factors should always be reported, to be able to compare literature values and for future modelling work.