Dynamic model for methane emission from manure storage

Methane emissions from agricultural sources should be calculated in accordance with the IPCC good practice guidelines, based on emission factors and activity data. Emission factors are based on the volatile solids content, biodegradability and methane conversion factor (MCF), which differ per management system and climate region. Not included in the IPCC models are dynamic factors of storage systems, like storage time, loading and unloading rates and temperature. A new dynamic model has been developed to include these factors. A slurry pit is an accumulation system. Experimental results of Zeeman (1991) showed that emission velocity (m(3)/day) increases linearly with filling time, i.e. the relation between emission (m(3)) and filling time is quadratic. The model is used to derive values for the MCF, depending on filling time and temperature. The dynamic model has been applied to a typical dairy and pig farm, with a large effect on the emission figures. The proposed model can be used to improve calculations of national emissions.