Assessing Livestock Greenhouse Gas Emissions with Comet-Farm.

COMET-Farm is an integrated web-based decision support tool developed to aid farmers, agricultural producers, land managers and conservationists in making on-farm decisions regarding greenhouse gas emissions and carbon sequestration. COMET-Farm provides total farm greenhouse gas accounting including cropland, pasture, range, agroforestry, livestock and on-farm energy use modules. It is well known that agricultural practices involving livestock management contribute a significant amount of greenhouse gas emissions in the agricultural sector. With the use of COMET-Farm, livestock producers can input their current management practices as well as future potential management scenarios to accurately estimate their current emissions and how applying more efficient conservation practices can reduce the emissions associated with their current practices. Users may also assess various conservation scenarios to determine the relative greenhouse gas balances of each.  Methane from enteric fermentation and methane and nitrous oxide emissions from housing and manure management are estimated using the methods set forth in the USDA document, Quantifying Greenhouse Gas Fluxes in Agriculture and Forestry: Methods for Entity-Scale Inventory using detailed animal and feed characteristics. To showcase the tools capabilities, real-world livestock production systems are assessed showing how on-farm practices influence the greenhouse gas flux from livestock production systems. The results from various livestock production systems throughout the US will be presented.