Free Methane Emissions calculator with clear step-by-step results.
Methane cannot be reported as raw mass if you want to compare it with carbon dioxide, because a kilogram of it traps far more heat. The chain is: activity × emission factor gives kilograms of CH₄, capture or flaring removes part of that, and the remainder is multiplied by the global warming potential — 28 over a 100-year horizon in IPCC AR5, or about 84 over 20 years — to express it as CO₂ equivalent.
Methane released
CH₄ released = activity × emission factor × (1 − captured share)
CO₂ equivalent
CO₂e = CH₄ released × GWP100
Emission factors and GWP values are prescribed by the inventory methodology you report under, and differ between IPCC assessment reports and national guidance. Regulatory reporting requires the applicable official factors.
It depends on the assessment report your inventory follows: 25 in AR4, 28 in AR5, and around 29.8 for fossil methane in AR6. Use whichever your reporting standard specifies and state it, because the choice changes the answer by up to 20%.
Methane has an atmospheric lifetime of roughly 12 years, so most of its warming happens early. Over 20 years its GWP is about 84; averaged over 100 years the same pulse looks weaker. Short-horizon figures are the relevant ones for near-term temperature targets.
No, but it helps considerably. Combustion converts CH₄ to CO₂, which has roughly a twenty-eighth of the warming effect per molecule of methane destroyed. Real flares are not perfectly efficient, so some methane still escapes.