Gas Emissions from Manure Management: Measurements vs Estimates

Data on GHGs emissions obtained through experimental results conducted in Italian dairy farms were compared with emissions from manure management estimated using the IPCC Tier 2. CH4 and N2O concentrations were seasonally measured in three dairy cattle buildings, characterized by different manure management systems, using a photoacoustic gas monitor according to the “dynamic chamber method”. Measurements were acquired during two years from different shed components. Meanwhile, the farm owners filled a questionnaire useful for the IPCC Tier 2 implementation. The IPCC approach does not distinguish between emissions originating from the building and from the storage. Differently, field studies are more frequently focused on a particular aspect of the whole manure management system, giving partial emission factors. For CH4, the choice of the proper Methane Conversion Factor (MCF) is crucial for the representativeness of the final result, due to their broad variation also within the same climatic zone. However, MCFs cannot reflect the variety of possible solutions for manure treatment and are grouped in generic categories poorly defined. In the case of direct N2O emissions, the IPCC equation reflects the amount of N excreted by the animal category corrected for an emission factor (named EF3). The EF3 is equal to zero for uncovered anaerobic lagoons, but our data do not support this assumption. Experimental results underline the relevance of the manure removal strategy in the determination of emissions and highlight the need of more precise and flexible emission factors in order to make estimations closer to the actual level of emissions.