Farm-Scale Full GHG Accounting With COMET-Farm.

The COMET-Farm system is an integrated web-based platform, designed for quantification and assessment of whole farm greenhouse gas emissions, that uses state-of-the-art computation methods but in an environment that enables farmers (as well as ag consultants and land management agency personnel) to manage their data and produce high-quality estimates and reports of their emissions. COMET-Farm includes three estimation modules: soil and biomass related (field-based) emissions, livestock emissions and energy use.  For field-based emissions, the system includes a full spatial interface that allows management to be specified for individual fields and pastures (and subdivided by within-field soil type using Web Soil Survey).  Biomass CO₂ and soil CO₂ and N₂O emissions/removals are calculated dynamically using the DayCent simulation model, with optional empirical models for biomass stocks in agroforestry systems.  Livestock emissions, for enteric CH₄ and CH₄ and N₂O emissions from manure management are estimated from empirical models using basic livestock characteristics or with more detailed information on feeding regimes.   Other emission source categories, including biomass burning, liming and urea applications are included in the system. Energy use from off-site sources and on-farm energy production and use can be tracked and greenhouse gas emissions, along with embodied emissions from agricultural inputs.  Scenarios for different farm-types and management systems are presented and emission estimates are compared to results from relevant field experiments and alternative accounting protocols.