Dynamic Model for Methane Emission from Manure Storage

Abstract

The methane emissions from liquid manure are an important source of greenhouse gases from agriculture. Methanogenic bacteria produce methane when manure decomposes in an anaerobic environment. Manure management practice is a dominant factor that determines methane emissions. Emissions of methane from agricultural sources should be calculated in accordance to the IPCC Reference Guide (IPCC, 1996) and Good Practice Guidance (IPCC, 2001). Emission factors are based on the volatile solids content; the biodegradability and methane conversion factor (MCF), which differ per management system; and climate region. IPCC models do not include dynamic factors of storage systems, like storage time, loading and unloading rates and temperature. A new dynamic model for methane emissions from liquid manure storage has been developed to facilitate the inclusion of these factors. The dynamic model is used to adapt the MCF in manure management systems typically used in the Netherlands. Resulting methane emissions will be compared with emissions based on default values of MCF. 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.