Which Intergovernmental Panel on Climate Change (IPCC) methane factor fits my coal supplier's mine depth: low, average or high?
IPCC 2006 Tier 1 says use the low factor for underground mines shallower than 200 metres (10 cubic metres of methane per tonne), the high one beyond 400 metres (25), and the average of 18 in between. Opencast: low 0.3 under 25 metres of overburden, high 2.0 over 50 metres, else 1.2.
The depth rule
- Underground mining, Tier 1: low 10, average 18, high 25 cubic metres of methane per tonne of raw coal. The IPCC says to choose the low end for average mining depths under 200 metres, the high value for depths over 400 metres, and average values for intermediate depths.
- Surface (opencast) mining, Tier 1: low 0.3, average 1.2, high 2.0. Use the low end for average overburden under 25 metres and the high end over 50 metres; between those use the average. Where overburden thickness is not known, the Guidelines say it is good practice to use the average, 1.2 cubic metres per tonne.
- Post-mining, added on top: underground 0.9, 2.5 and 4.0; surface 0, 0.1 and 0.2. The depth sentence in the Guidelines sits only under mining; they give no depth rule for choosing the low, average or high underground post-mining value, so we use the average (our choice, not source text). For surface post-mining the Guidelines say the average should be used unless there is country-specific evidence for the low or high.
How wrong can Tier 1 be
The Guidelines give likely uncertainties as expert judgement: underground mining "factor of 2 greater or smaller" and post-mining "factor of 3 greater or smaller"; surface mining and post-mining both a factor of 3. So 18 cubic metres could in practice be anywhere from 9 to 36 (our arithmetic on the factor of 2). Ask the supplier for basin-specific figures (Tier 2) or, for underground mines, mine-specific measurements (Tier 3), and use Tier 1 only as the fallback. For surface mines the Guidelines say mine-specific Tier 3 measurement is "not yet feasible".
Where your coal comes from
Ask the supplier whether the coal is underground or opencast and the mine depth or overburden. A supplier who sells from several mines needs a weighted figure by tonnes. Our other coal pages give the 18 and 1.2 averages; this page adds the depth rule that picks the low or high end. The IPCC counts these as sector emissions at the mine and does not use Scopes; treating them as your upstream Scope 3 is our reading, as on our other coal pages.
1,000 tonnes of coal from a 450 metre underground mine
- Depth over 400 metres, so the high mining factor of 25; the Guidelines give no depth rule for underground post-mining, so we use the average 2.5, added: 25 + 2.5 = 27.5 cubic metres of methane per raw tonne
- 1,000 x 27.5 = 27,500 cubic metres, and 27,500 x 0.67 kilograms per cubic metre = 18,425 kilograms of methane
- At the average factors instead: 18 + 2.5 = 20.5 cubic metres, 20,500 x 0.67 = 13,735 kilograms of methane
- The depth rule raises the figure by 18,425 / 13,735 = 1.34 times
- Multiply kilograms of methane by the methane global warming potential in your chosen report
The 450 metres and 1,000 tonnes are examples. The Guidelines use 0.67 kilograms of methane per cubic metre at 20 degrees Celsius and 1 atmosphere. The factors apply to raw coal; see our washed coal page.
What Senseible does here
Senseible reads fuel invoices and electricity bills into dated records, so the tonnes of coal bought each month are on file. It does not know your supplier's mine depth, so ask the supplier and keep the reply with the invoices.
- Coking coal mine methane in Scope 3
- Opencast coal mine methane and diesel
- Coal methane factor: raw or washed coal
Last reviewed 2026-11-05. Tier 1 values are from the 2006 Guidelines. Replace them with supplier or basin figures when you can get them.