Where livestock methane comes from
Ruminant and non-ruminant livestock produce methane (CH4) mainly through enteric fermentation — the microbial digestion of feed in the animal’s gut, which is then belched out. Methane is a potent greenhouse gas, and livestock enteric fermentation is one of the largest sources of agricultural methane worldwide.
How this calculator works
This calculator applies the IPCC (Intergovernmental Panel on Climate Change) Tier 1 default emission factors for enteric fermentation, expressed in kilograms of CH4 per head per year, and scales them by the number of animals and the number of days in your chosen period: Total CH4 = Emission Factor × Number of Animals × (Days ÷ 365). The result is also converted to CO2-equivalent using a methane global warming potential (GWP100) of 27, a commonly used non-fossil methane value from the IPCC’s Sixth Assessment Report.
Tier 1 factors are global or regional averages and vary in reality with breed, feed quality, body weight, and management practices — actual farm-level emissions can differ substantially. This tool is intended for general educational and planning estimates, not for regulatory greenhouse gas inventories or certification.