DairyGEM

The Dairy Gas Emissions Model (DairyGEM) is a tool for estimating ammonia, hydrogen sulfide, and greenhouse gas (GHG) emissions of dairy production systems as influenced by climate and farm management.

A dairy production system generally represents the processes used on a given farm, but the full system may extend beyond the farm boundaries. A production system is defined to include emissions during the production of all feeds whether produced on the given farm or elsewhere. It also includes GHG emissions that occur during the production of resources used on the farm such as machinery, fuel, electricity, and fertilizer. Manure is assumed to be applied to cropland producing feed, but any portion of the manure produced can be exported to other uses external to the system.

DairyGEM uses process level simulation to predict ammonia and hydrogen sulfide emissions from manure in the housing facility, during long term storage, following field application and during grazing. Process-based relationships and emission factors are used to predict the primary GHG emissions from the production system. Primary sources include the net emission of carbon dioxide plus all emissions of methane and nitrous oxide. All emissions are predicted through a daily simulation of feed use and manure handling. Daily emission values of each gas are summed to obtain annual values.