Emission Factors and Global Warming Potentials (GWPs)

EcoVision
Nov 9
1 min read

Emission factors express the warming potential of greenhouse gases (GHGs) relative to carbon dioxide (CO₂), usually known as Global Warming Potentials (GWPs) over a 100‑year period (GWP₁₀₀).

The most recently adopted authoritative values come from the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6, 2021) — which many international and regional regulators (including the  EU ETS,  UK DEFRA, and  ISO 14064‑1:2018 updates) have begun using or referencing.

🌍 Updated 100‑year Global Warming Potentials (GWP100) — IPCC AR6 (2021)

Gas	Chemical Formula	GWP₁₀₀ (without climate‑carbon feedbacks)	GWP₁₀₀ (with feedbacks)*	Notes
Carbon dioxide	CO₂	1	1	Baseline gas
Methane	CH₄	27.9	29.8	Updated from AR5 value of 28 / 34
Nitrous oxide	N₂O	273	273	Similar to AR5 (≈ 265–298 range)
Hydrofluorocarbons (HFCs)	—	Varies ~ 150 – 14 000	—	Depends on compound (see below)
Perfluorocarbons (PFCs)	—	~ 6 500 – 11 100	—	Extremely long‑lived gases
Sulphur hexafluoride	SF₆	≈ 25 200	≈ 23 500 – 25 200	Very high GWP, long atmospheric life
Nitrogen trifluoride	NF₃	≈ 17 400	—	Used in electronics manufacturing

(*) “With feedbacks” includes climate‑carbon cycle interactions; many reporting standards still use “without feedbacks” unless otherwise specified.

🧮 Practical Example (CO₂‑e conversions)

If a process emits  1  ton  CH₄:→ CO₂‑equivalent =  1  ton  CH₄ × 27.9  = 27.9 t CO₂‑e

If a process emits  1  kg  SF₆:→  CO₂‑equivalent = 1 kg  SF₆ × 25 200  =  25.2 t CO₂‑e

✅ Summary

Gas	Updated  GWP₁₀₀  (AR6 2021)
CO₂	1
CH₄	27.9 – 29.8
N₂O	273
SF₆	25 200 (approx.)
NF₃	17 400
HFCs	150 – 14 000 (varies)
PFCs	6 500 – 11 100 (varies)