Estimating Whole-Farm Greenhouse Gas and Energy Footprints.

The COMET-Farm system is a web-based, full greenhouse gas accounting system designed for comprehensive farm-level analyses.  The system has a fully spatial user interface to specify individual field boundaries and management systems.  The interface uses Web Soil Survey to overlay soil maps and delineate soil×topographic postition× management subunits to estimate soil CO₂ and N₂O emissions and removals using the DayCent biogeochemical process model.  The prototype system incorporates EVI (Enhanced Vegetation Index) values from MODIS (250 m) to support site-specific estimates of NPP and residue inputs.  Emissions from livestock (enteric CH₄) and manure management (CH₄ and N₂O) are estimated using empirical functions derived from 2006 IPCC methods. Livestock emissions estimates include options for enhanced characterizations based on user supplied feed and livestock attributes designed for CH4 emission abatement.  The system also provides for monitoring energy use, fossil-derived CO2 emissions and on-farm energy production.  Example applications of the model and case study examples of farm-level GHG footprints for baseline and GHG mitigation options are discussed.