Scope 1 Coal Mine Methane Calculator (Surface + Underground — IPCC 2019 Refinement Vol 2 Ch 4)
Compute the Tier 1 fugitive methane CO2e from coal mining — run-of-mine tonnage times the IPCC 2019 Refinement default factor for the mine type, across a per-line ledger that separates surface from underground and adds the post-mining tail.
One gas, two mine types, two stages. Coal mine methane is a fugitive methane emission released as the coal seam is broken and the gas held in it escapes. Unlike a process emission, there is no combustion and no product chemistry — the driver is how much gas the seam holds and how deep it sits. The calculator splits the estimate by the only two things that move it at Tier 1: whether the mine is surface or underground, and whether you add the post-mining tail from handling, transport, and storage of the freshly cut coal.
Depth is the lever, and it swings by an order of magnitude. Underground mining works deeper, gassier seams; surface mining works shallow coal that has already lost much of its gas to the atmosphere over geological time. The IPCC default for underground mining is roughly fifteen times the surface default on the same tonne of coal. Selecting the wrong mine type is the largest single error you can make on a line.
Tier 1, and stated as such. Every factor is an IPCC 2019 Refinement default, read live from MasterBrain. A mine running a gas-content measurement campaign or seam-specific monitoring will get a different number. This tool is screening-grade by design: a defensible first figure that names where a site-specific method would diverge.
Recovery is a mass balance, not a discount. Where a mine captures and destroys methane — drainage gas flared or used — you enter the quantity recovered as a single global figure, and the engine deducts it from the gross, floored at zero. The default is no recovery, so an unconfigured calculation errs high rather than low. A mine without a capture system is never silently handed a reduced figure.
Tier-1 global-average factors per IPCC 2019 Refinement Vol 2 Ch 4. Enter run-of-mine coal extracted (not saleable/clean coal). Output in tonnes, kilotonnes, or megatonnes.
Adds post-mining outgassing (UG +46.9 / surface +1.876 kg CO₂e/t) to the extraction factor.
AR5 CH₄ = 28 (DEFRA-aligned); AR6 CH₄ = 29.8 (GHG Protocol / CSRD).
Tier 3 reveals measured-intensity inputs for the mine types in your ledger.
Reweights the CH₄ volumetric within the published IPCC depth band.
Captured and destroyed (flared/utilised) only — vented methane is not deductible.
m³ converted at 0.67 kg/m³ (IPCC).
Annualised: result × (12 ÷ period months).
Audit mode exposes the full per-line factor rebuild chain.
Add a mine and enter coal output above to calculate
Results appear instantly. The Surface/Underground split, a same-output comparison, IPCC depth-sensitivity bands, recovery netting, and the full audit trail appear after calculation. Coal combustion is excluded — fugitive methane only.
Results are indicative Scope 1 fugitive coal-mine-methane estimates using IPCC 2019 Refinement Vol 2 Ch 4 Tier-1 global-average emission factors (or your Tier-3 measured gas intensity). The result covers fugitive seam gas only — CH₄ (with minor CO₂) liberated during mining and post-mining handling; it excludes coal combustion CO₂/CH₄/N₂O, which is a separate Scope 1 stationary-combustion line. It also excludes abandoned / closed mine methane (AMM) — a distinct IPCC category not covered here — Scope 2 electricity, and Scope 3 transport and well-to-tank emissions. Methane recovery is credited only for gas that is captured and destroyed (flared or utilised); the CO₂ produced by flaring is not added. Tier-1 factors are global averages: an individual mine’s methane liberation can deviate by 3–10× with seam gassiness and depth, so for verification-grade figures use measured ventilation-air-methane and drainage data (Tier 3). Confirm mine type, run-of-mine output, and recovery data against your own records and, where material, proceed to third-party verification under ISO 14064-3.
Two coal mines sit in the same basin. One is an open pit moving three million tonnes a year; the other is an underground operation a third its size. The pit dominates the region’s coal output. Yet nearly nine-tenths of the basin’s mining methane comes from the smaller underground mine.
In coal accounting, the tonnage on the conveyor is not the story. The depth of the seam is.
The coal mine methane calculator multiplies run-of-mine tonnage by IPCC 2019 Refinement defaults to give Tier 1 Scope 1 fugitive emissions — about 349 kg CO2e per tonne underground against 23 for surface — with captured methane deducted.
What the coal mine methane calculator does
This calculator computes the Tier 1 Scope 1 fugitive methane emissions of a coal mine: you enter the tonnage of run-of-mine coal produced on each line, select whether the line is surface or underground, and the engine multiplies by the IPCC 2019 Refinement default factor for that mine type — converting the methane to CO2e at its global-warming potential — and sums the lines into one fugitive total. A global toggle adds the post-mining stage; a global control deducts any methane you capture and destroy.
One gas, released — not burned
Coal mine methane is not a combustion emission and not a process emission. It is gas physically held in and around the coal seam — adsorbed onto the coal and trapped in surrounding strata — that escapes when mining breaks the rock and relieves the pressure holding it in place. Because it is methane, a gas with roughly twenty-eight times the warming potential of CO2 on the AR5 100-year basis, even a modest mass per tonne of coal becomes a large CO2e figure. The factor also carries a small CO2 component from the carbon dioxide co-emitted with the seam gas, but methane is almost the entire result.
Tier 1 — production times a default factor
The arithmetic is the IPCC Tier 1 method: tonnes of run-of-mine coal produced on a line, multiplied by the default emission factor for the selected mine type. The factor is expressed in kilograms of CO2e per tonne of coal, having already converted the underlying cubic metres of methane per tonne to mass and then to CO2e at the methane global-warming potential. It does not model your specific seam gas content, mining depth, or basin geology — those are the Tier 2 and Tier 3 refinements that require site measurement the default method does not carry.
This is a fugitive-emissions tool, not a combustion one. It reports the methane released by breaking the coal seam — underground or surface, with an optional post-mining tail — and converts it to CO2e. The fuel burned to run the mine’s draglines, conveyors, and ventilation fans is a separate stationary- and mobile-combustion inventory and must not be folded into this figure.
Underground versus surface — the order-of-magnitude gap
Before any tonnage is entered, the mine type decides the magnitude of the estimate. The same tonne of coal carries a wildly different fugitive figure depending on whether it came from underground or from a surface pit, because the two methods work coal of fundamentally different gas content. Getting the type right is the first correctness check, and it matters more here than almost anywhere in fugitive accounting.
Underground mining
Works deeper seams under pressure, where methane has been retained over geological time. Gas content is high, and breaking the seam releases most of it. The IPCC 2019 Refinement default is roughly 349 kg CO2e per tonne of coal mined — the dominant source at almost any underground operation.
Surface mining
Works shallow coal in open pits or strip mines, where much of the original seam gas has already migrated out and dissipated to the atmosphere over geological time. Gas content is low, so the mining-stage default is around 23 kg CO2e per tonne — about one-fifteenth of the underground figure.
| Mine type | Seam worked | Gas content | Mining-stage factor (kg CO2e/t) |
|---|---|---|---|
| Underground | Deep, pressurised | High — retained over geological time | 348.54 |
| Surface | Shallow, open pit | Low — much already dissipated | 23.32 |
In coal accounting the depth decides the factor. A tonne of underground coal and a tonne of surface coal are the same on the conveyor and an order of magnitude apart in the inventory. Pick the mine type before you read the number — nothing else on the line moves it as far.
The post-mining stage — the tail you cannot omit
The mining-stage factor is not the whole emission. Coal continues to release methane after it leaves the face — during handling, crushing, transport, and storage — as the gas still held in the freshly cut coal works its way out. This post-mining stage is a distinct emission factor, smaller than the mining stage but far from negligible, and it is the source most often left out of a coal inventory because it happens away from the working face.
Why post-mining is easy to miss
Mining-stage methane vents at the shaft or the pit, where it is visible and metered. Post-mining methane leaks slowly from coal sitting on stockpiles, moving on conveyors, and riding in rail cars — diffuse, untracked, and often outside the mine boundary the inventory was scoped around. The IPCC method assigns it a default factor precisely because it is real and consistently present, even though no single point source captures it.
Post-mining, underground coal
Coal from deep gassy seams carries more residual gas off the face, so its post-mining factor is the larger of the two — around 47 kg CO2e per tonne, roughly an eighth of the underground mining-stage figure on top of it.
Post-mining, surface coal
Surface coal has little gas left to release after extraction, so its post-mining factor is small — around 1.9 kg CO2e per tonne. Small, but it is the correct figure, and omitting it understates a surface inventory.
Post-mining is a separate emission factor, not a rounding allowance inside the mining figure. For underground coal it adds roughly 47 kg CO2e per tonne — about a thirteen-percent uplift on the mining stage — and leaving it out understates the inventory by that margin. The calculator applies it through a single global toggle so it is added consistently across every line, surface and underground, or omitted from all of them deliberately.
The emission factors by mine type and stage
Every factor below is an IPCC 2019 Refinement default for Vol 2 Chapter 4 fugitive emissions, read live from MasterBrain at calculation time. There are four: a mining-stage and a post-mining factor for each of the two mine types. All are expressed in kilograms of CO2e per tonne of run-of-mine coal, on the AR5 100-year methane basis the calculator defaults to.
| Mine type | Stage | Factor (AR5) | Factor (AR6) | Unit |
|---|---|---|---|---|
| Underground | Mining | 348.54 | 370.24 | kg CO2e / t coal |
| Post-mining | 46.9 | 49.92 | kg CO2e / t coal | |
| Surface | Mining | 23.32 | 24.77 | kg CO2e / t coal |
| Post-mining | 1.876 | 1.997 | kg CO2e / t coal |
AR5 factors render live from MasterBrain via [gc_factor key=”fugitive_coal_methane.cmm.<type>_<stage>”]; the AR6 alternates are quoted from the same MasterBrain rows as static figures (they sit in the row’s alternate basis, which the value shortcode does not surface). Underlying volumetrics in cubic metres of methane per tonne are carried by the engine and not shown here. IPCC 2019 Refinement Vol 2 Ch 4, MasterBrain v2026.203.
One gas drives the whole figure
The factors are almost entirely methane. Each carries a tiny co-emitted CO2 component, but the methane share is so dominant that the choice of methane GWP basis moves the whole result. Methane converts to CO2e at 28 on the AR5 100-year basis the calculator defaults to, or 29.8 on AR6 — and because the footprint is essentially all methane, switching basis lifts every factor by about six percent. That is a larger basis sensitivity than on a CO2-dominated page, where most of the result carries a GWP of 1 and never moves. For the underlying values, see the IPCC AR6 GWP values reference.
Methane recovery — the mass-balance deduction
Some mines do not let all their methane escape. Underground operations in particular drain gas ahead of mining and either flare it or pipe it to use — power generation, boiler fuel, or pipeline injection. Methane that is captured and destroyed is methane that does not reach the atmosphere, and the calculator credits it. But it does so as a mass balance against the gross emission, not as a percentage discount on the factor.
One global figure, deducted from the gross
You enter the quantity of methane recovered and destroyed as a single site-wide figure — in cubic metres or tonnes of methane — and the engine converts it to mass at the IPCC gas density and subtracts it from the gross total of all your lines. The net is floored at zero: a recovery figure larger than the gross cannot produce a negative inventory. There is no per-line recovery field and no percentage input; recovery is one operation applied to the whole mine, because that is how a drainage system is metered in practice.
Flaring credits the methane, not the carbon dioxide
When recovered methane is flared, combustion converts it to CO2 — a gas with a GWP of 1 instead of 28. The calculator credits the avoided methane in full at its GWP, which is where almost all the benefit lies. It does not then add back the small quantity of CO2 the flare produces: that stream is treated as de minimis and is stated as excluded in the scope notice rather than estimated from an unsourced figure. The headline effect is the same either way — captured methane, whether used or flared, comes off the inventory.
Recovery is a single global mass-balance deduction from the gross fugitive total, floored at zero — illustrative proportions, not a fixed recovery rate. The default is no recovery, so an unconfigured calculation reports the gross.
Enter recovery only for methane you actually capture and destroy, and only the quantity your drainage system meters. The default — blank, no recovery — gives the conservative gross figure. If you are unsure how much your flare or utilisation plant destroyed over the period, leaving recovery blank overstates rather than understates, which is the safe direction for a screening estimate.
How the calculation works
Each line follows the same short path: pick the mine type, enter the run-of-mine tonnage, and the engine reads the matching default factor live, adds the post-mining factor if the global stage toggle is on, applies the methane conversion, and adds the line to the gross total. Recovery is then deducted once, globally, and the net is reported with a mine-type split.
What you enter, what the engine derives
You enter the run-of-mine production tonnage and select surface or underground per line. Everything else is global: whether post-mining is included, the GWP basis, the tier, and the quantity of methane recovered across the whole mine. The engine derives the per-line CO2e, the gross total, the recovery deduction, the net, and the split between surface and underground tonnage — which is where the depth story becomes visible, because a small underground line can outweigh a much larger surface one.
The conversion
For each line the engine computes tonnes of coal times the kilograms of CO2e per tonne for the selected mine type and stage, dividing by 1,000 to reach tonnes of CO2e. Because the published factor already bundles the methane-to-CO2e conversion, the line arithmetic is a single multiplication. The engine rebuilds the factor internally from cubic metres of methane per tonne, so its audit trail differs from hand-arithmetic on the rounded published factor by a fraction of a percent — immaterial, and the published factor is the citable figure.
Enter run-of-mine output, not saleable or washed tonnage. The IPCC factors are calibrated to the coal as mined, before preparation losses, and entering a lower saleable figure understates the methane. If your line reads as saleable rather than run-of-mine, the calculator nudges you to check — the factor assumes the gross extracted tonnage.
Worked example — an underground mine beside a surface operation
A two-line inventory shows the method and the depth-dominance effect together. The basin below runs an underground mine producing 1,500,000 tonnes of run-of-mine coal a year and a surface operation producing 3,000,000 tonnes. The post-mining stage is included; no methane recovery is entered. The factor values are live MasterBrain figures; the production tonnages are illustrative inputs. The basis is AR5.
The fugitive ledger
| Line | Stage factor (kg/t) | Production × factor | Result |
|---|---|---|---|
| Underground · mining + post-mining | 348.54 + 46.90 = 395.44 | 395.44 kg/t × 1,500,000 t ÷ 1,000 | 593,160 t CO2e |
| Surface · mining + post-mining | 23.32 + 1.876 = 25.196 | 25.196 kg/t × 3,000,000 t ÷ 1,000 | 75,588 t CO2e |
| Gross total (no recovery) | — | 593,160 + 75,588 | 668,748 t CO2e |
Every figure reconciles as production × factor ÷ 1,000. Post-mining is included, so each line uses the summed mining-plus-post-mining factor; no methane recovery is deducted, so the net equals the gross. Factor values via MasterBrain v2026.203, IPCC 2019 Refinement Vol 2 Ch 4; the live engine rebuilds from volumetrics and so differs from this hand-arithmetic by about a thousandth of a percent.
The underground mine produces a third of the basin’s coal yet contributes nearly nine-tenths of its mining methane. On AR6 (methane 29.8) the total rises to roughly 711 ktCO2e — about six percent, driven entirely by the methane reweight, since the footprint is almost all methane.
Why the smaller mine dominates
The underground mine works coal carrying far more methane per tonne than the surface pit. Even at half the tonnage, its much higher factor produces the larger emission — and the gap is wide enough that the surface operation, despite moving twice the coal, is a minority share of the total. This is the defining feature of coal fugitive accounting: the result tracks the gas content of the seam, not the throughput of the mine, and a deep gassy operation can outweigh a far larger shallow one. Reading the mine-type split, not just the total, is what makes the inventory interpretable.
Tier 1 versus Tier 2/3 — accuracy and when each applies
The IPCC framework offers three tiers of increasing accuracy and data demand. This calculator is Tier 1 throughout, and saying so plainly is part of using it correctly. A Tier 1 number is a standardised default keyed only to mine type; a Tier 2 or Tier 3 number is your basin’s or your mine’s measured gas content.
| Tier | Method | When it applies |
|---|---|---|
| Tier 1 (this calculator) | Run-of-mine tonnage × IPCC global-average default factor for the mine type | Screening estimates, first inventories, cross-checks, mines without a gas-content measurement programme |
| Tier 2 | Country- or basin-specific factors reflecting local coal rank, depth, and gas content | Where representative basin gas-content data exists but continuous mine measurement does not |
| Tier 3 | Mine-specific measured emissions — ventilation and drainage gas flow monitoring, or direct seam gas-content sampling | Regulated facilities, verified inventories, emissions-trading reporting where measured emissions are mandated |
The Tier 1 gap is wider for coal than for many process emissions because gas content varies enormously between basins and even between seams in one mine. A global-average underground factor is a reasonable screening proxy, but a specific gassy mine can sit well above it and a low-gas mine well below. The default is a defensible starting estimate, not a substitute for a measurement programme where one is required.
Tier 1 is screening-grade by design. The default factor is a global average keyed only to surface versus underground — it does not know your basin’s coal rank, your mining depth, or your seam gas content, all of which a Tier 2 or Tier 3 method would capture. A regulated coal-mine methane inventory under an emissions-trading scheme generally needs measured Tier 3 figures; this tool is the cross-check against that work, not a replacement for it.
Fugitive versus combustion — the double-count boundary
The boundary that trips a coal-mine inventory is the line between gas that escapes and gas that is burned. Fugitive methane released from the seam is one account; the fuel combusted to run the mine — and any recovered methane used as fuel — is another. Mixing the two either double-counts a stream or misses it entirely.
What belongs where
This calculator reports the methane that escapes from the coal — the fugitive emission. It does not report the diesel burned in the haul trucks and draglines, the gas or electricity that powers the ventilation fans and coal-preparation plant, or the methane you capture and then combust on site. Those are stationary- and mobile-combustion emissions, accounted separately. Recovered methane is the subtle case: as a fugitive stream it is deducted here when captured and destroyed, but if it is then burned to raise steam or generate power, that combustion is a combustion-inventory line — the deduction here and the combustion line there describe two different events for the same gas, and both are correct.
| Fugitive — belongs in this calculator | Combustion — belongs in a separate inventory |
|---|---|
| Methane released from the seam at the working face | Diesel burned in haul trucks, draglines, and mobile plant |
| Post-mining methane from handling, transport, and storage | Gas or electricity powering ventilation fans and the prep plant |
| Drainage methane vented to atmosphere unused | Recovered methane combusted on site for power or heat |
| Recovered methane destroyed by flaring (credited as a deduction) | The CO2 from that combustion, where it is separately accounted |
The audit failures to pre-empt
01 — Mine type wrong
A surface line entered as underground, or the reverse. This swings the result roughly fifteen-fold on the same tonnage — the single most consequential error on a coal line. Confirm surface versus underground before reading the number.
02 — Post-mining omitted
The mining-stage factor used alone, with no post-mining tail. This understates an underground inventory by around an eighth and a surface one by a smaller margin. Decide once whether the stage toggle is on, for the whole inventory.
03 — Saleable tonnage entered as run-of-mine
Washed or saleable coal entered where the factor expects gross extracted tonnage. This understates the methane in proportion to preparation losses. Enter run-of-mine output.
04 — Recovery claimed but not metered
A capture deduction entered larger than the drainage system actually destroyed. This understates the net. Deduct only metered, destroyed methane — and flooring at zero will not save an over-claim on a single mine.
05 — Combustion folded into fugitive
The fuel burned to run the mine added into this fugitive figure, or recovered methane used as fuel counted only here and not in the combustion inventory. Keep the two accounts separate.
06 — Tier 1 default presented as measured
A global-average screening default reported as the mine’s verified figure. State the tier. A regulated coal-mine methane inventory needs measured Tier 3 emissions, and the default will differ — sometimes substantially — from a gassy or a low-gas mine.
Reporting context — IPCC inventories, EU ETS, the Methane Pledge, SBTi
Coal mine methane feeds several reporting and regulatory regimes, and the tier and boundary that satisfy each one differ. A Tier 1 screening figure is a starting point for all of them and a sufficient figure for none of the regulated ones.
| Framework | Role for coal mine methane | Tier expected |
|---|---|---|
| IPCC 2019 Refinement | The source of the method and the default factors. Vol 2 Chapter 4 defines the fugitive coal-mining boundary this calculator computes and updates the earlier 2006 factor set. | Tier 1–3 framework |
| GHG Protocol (Scope 1) | Places fugitive mine methane in Scope 1 as a direct emission. The consolidated corporate total rolls fugitive, combustion, and indirect emissions together. | Method-agnostic |
| EU ETS | Coal-mine methane is being brought into scope under tightening EU methane rules for the energy sector. Where covered, monitored and verified emissions are required — typically Tier 3, not an IPCC default. | Tier 3 / measured |
| Global Methane Pledge | The international commitment to cut methane across sectors. Coal mine methane is a priority abatement target; a screening inventory establishes the baseline against which cuts are measured. | Inventory-grade |
| SBTi Corporate Net-Zero | Target-setting against a base-year inventory. The fugitive methane figure feeds the Scope 1 base year; methane capture and drainage are major near-term levers for coal producers. | Inventory-grade |
Methane pledges and some regulatory regimes cite a 20-year global-warming potential, on which methane’s figure is far higher than the 100-year value this calculator uses. The tool reports on the AR5 or AR6 100-year basis only; it does not offer a 20-year mode. If your reporting obligation is stated on a 20-year basis, this screening figure will understate it substantially, and you should convert using the appropriate 20-year potential rather than reading this result directly.
For the corporate roll-up that consolidates this fugitive figure with combustion and indirect emissions into one organisational total, the fugitive line carries into the GHG inventory aggregator as a Scope 1 entry. The fuel burned to run the mine belongs in a separate combustion account — the Scope 1 stationary combustion calculator and the mobile combustion calculator handle the prep plant and the haul fleet respectively, and the coal combustion methodology covers the case where the coal is later burned rather than sold.
Data sources, model, and factor basis
The model — source and structure
The calculator reads its factors from the fugitive_coal_methane keyspace in MasterBrain, sourced from the IPCC 2019 Refinement to the 2006 Guidelines, Volume 2 (Energy), Chapter 4 (Fugitive Emissions). There are four rows — a mining and a post-mining factor for each of surface and underground — and every row is a Scope 1 fugitive factor, because the emission occurs at the mine. The factors resolve live by key at calculation time, so a figure computed today and the same figure recomputed after a data-layer release are distinguishable by the MasterBrain version stamped on the output.
No fallback floor — em-dash on miss
The coal methane factors carry no hardcoded fallback value. This is deliberate. If a factor cannot be read from MasterBrain, the calculator renders an em-dash and skips that line with a banner rather than a stale or invented number — the house rule across GreenCalculus value lookups. The only hardcoded constants in the engine are the methane global-warming potentials (28 on AR5, 29.8 on AR6) and the IPCC gas densities used to convert recovered volumes to mass, and even those prefer the live MasterBrain read and exist only defensively. So the canonical values are exactly those in the factor table above, rendered live; there is no second set of floor values to reconcile against.
GWP basis — why methane basis matters most here
The footprint is almost entirely methane, so the methane GWP basis moves the whole result. Methane converts at 28 on the AR5 100-year basis the calculator defaults to, or 29.8 on AR6 — a roughly six-percent lift across the board, larger than the basis sensitivity on a CO2-dominated inventory because there is almost no GWP-1 carbon to dilute it. The small co-emitted CO2 component in each factor carries a GWP of 1 and is never reweighted. Set one basis for the whole inventory; an inconsistent basis across lines shifts the total materially when every line is methane.
A missing factor shows an em-dash, never a guess. The coal methane factors have no fallback floor by design — the tool would rather show nothing than a fabricated number. The only hardcoded values are the methane GWPs and the gas densities used to convert recovered methane to mass, and even those defer to the live MasterBrain read.
A dedicated coal mine methane methodology page sets out the IPCC tier structure, the volumetric-to-mass conversion, and the recovery mass balance in full; it is a roadmap page and will be linked here when it publishes.
Related process and fugitive calculators
This calculator sits in the industrial-process and fugitive-emissions fleet alongside the other Scope 1 emitter tools. The fugitive figure it produces is a Scope 1 line that consolidates into a full corporate inventory, and it sits beside the process-emission calculators for the heavy industries.
For the other Scope 1 process emitters, the iron & steel process calculator covers ironmaking and steelmaking CO2, the aluminium smelting PFC calculator covers perfluorocarbon emissions, the cement & lime process calculator covers clinker calcination, and the chemicals process calculator covers nitric, adipic, and the petrochemical families. For the organisational roll-up that brings this fugitive total together with combustion and value-chain emissions, the GHG inventory aggregator consolidates Scope 1, 2, and 3 into one boundary total. Companion fugitive-emissions calculators for the wider F-gas inventory follow in the same phase and will be linked here as they publish.
Frequently asked questions
It measures the Tier 1 Scope 1 fugitive methane emissions of a coal mine under the IPCC 2019 Refinement, Volume 2, Chapter 4. You enter run-of-mine coal tonnage and select surface or underground per line, and the engine multiplies by the IPCC default factor for that mine type — around 349 kg CO2e per tonne underground against 23 surface — optionally adds a post-mining tail, deducts any methane you capture, and reports the net in tonnes of CO2e.
Because underground mining works deeper, gassier seams. Coal at depth has retained the methane held in it over geological time; shallow surface coal has already lost much of its gas to the atmosphere. So the same tonne of coal carries roughly fifteen times the fugitive methane underground as it does at the surface — about 349 kg CO2e per tonne against 23. Selecting the right mine type is the single largest correctness check on a coal line.
Post-mining methane is the gas that continues to escape from coal after it leaves the working face — during handling, crushing, transport, and storage. It is a separate IPCC default factor, around 47 kg CO2e per tonne for underground coal and 1.9 for surface, applied through a global toggle. Include it for a complete inventory; omitting it understates an underground figure by roughly an eighth. It is the source most often missed because it happens away from the mine itself.
You enter the quantity of methane recovered and destroyed as a single site-wide figure in cubic metres or tonnes, and the engine deducts it from the gross total as a mass balance, floored at zero. There is no per-line recovery percentage. For flared methane, the calculator credits the avoided methane at its full GWP and does not add back the small CO2 the flare produces — that stream is treated as de minimis and stated as excluded. The default is no recovery, which gives the conservative gross figure.
Run-of-mine — the coal as extracted, before washing or preparation. The IPCC factors are calibrated to gross mined tonnage, so entering a lower saleable or washed figure understates the methane in proportion to your preparation losses. If a line reads as saleable rather than run-of-mine, the calculator nudges you to confirm, because the factor assumes the gross extracted tonnage.
No. This calculator reports only the fugitive methane that escapes from the coal seam. The diesel burned in haul trucks and draglines, and the gas or electricity that powers ventilation fans and the coal-preparation plant, are combustion emissions accounted in a separate stationary- and mobile-combustion inventory. Folding that fuel into this fugitive figure double-counts. Recovered methane that you then burn on site is also a combustion line, separate from the fugitive deduction made here.
It defaults to AR5 (methane 28 on the 100-year basis) and offers AR6 (29.8), selectable to match the rest of your inventory. Because the footprint is almost entirely methane, switching basis lifts the whole result by about six percent — a larger sensitivity than on a CO2-dominated page. The calculator does not offer a 20-year potential; if your reporting obligation is stated on a 20-year basis, this 100-year figure will understate it. Set one basis across the whole inventory.
It is Tier 1 — run-of-mine tonnage times an IPCC global-average default factor keyed only to mine type. That is screening-grade: defensible and standardised, but it does not know your basin’s coal rank, mining depth, or seam gas content. A regulated coal-mine methane inventory, including under tightening EU methane rules, generally requires measured Tier 3 emissions from ventilation and drainage monitoring. Use this tool for a first inventory, a screening estimate, or a cross-check — not as the reported figure for a regulated mine.
The 2019 Refinement to the 2006 Guidelines, Volume 2, Chapter 4. The Refinement updated the fugitive coal-mining factor set, and this calculator uses those updated defaults rather than the original 2006 values. The method structure — Tier 1 production times a default factor, by surface or underground mine type — is unchanged; the factor values reflect the 2019 update.
The calculator shows an em-dash and skips that line with a banner rather than a fabricated value. The coal methane factors carry no hardcoded fallback floor by design — if MasterBrain cannot supply the factor, the tool renders nothing for that line rather than a stale or guessed number. The only hardcoded constants are the methane GWPs and the gas densities used to convert recovered methane to mass. An em-dash is a signal to check the data layer, not a number to report.
Methodology notes and limitations
Scope and purpose. This calculator computes the Tier 1 Scope 1 fugitive methane emissions of a coal mine under the IPCC 2019 Refinement, Volume 2, Chapter 4. It covers two mine types (surface and underground) across two stages (mining and an optional post-mining tail). It does not compute the combustion emissions of the fuel burned to run the mine, which belong in a separate stationary- and mobile-combustion inventory, nor the downstream emissions from burning the coal once sold.
Method — production times default factor. Each line is run-of-mine tonnage multiplied by the IPCC default factor for the selected mine type, plus the post-mining factor where the global stage toggle is on. The factor already bundles the conversion of cubic metres of methane per tonne to CO2e at the methane GWP (28 on AR5, the default; 29.8 on AR6). The engine sums the lines into a gross total, deducts any globally entered recovery as a mass balance floored at zero, and reports the net with a mine-type split. This is the Tier 1 method throughout.
Recovery as a mass balance. Methane captured and destroyed — flared or used — is entered as one global quantity and deducted from the gross, not applied as a per-line percentage. Flaring is credited only for the avoided methane; the CO2 produced by the flare is treated as de minimis and excluded, since MasterBrain carries no sourced figure for it. The default is no recovery, so an unconfigured calculation reports the conservative gross.
The conservative default. Mine type defaults are not auto-abated and recovery is never assumed. The calculator reports gross fugitive methane unless you enter a metered recovery quantity, so an unconfigured inventory errs high rather than low. A mine without a drainage and capture system is never silently handed a reduced figure.
Tier boundary and what Tier 1 omits. The calculator is Tier 1 only. Basin- and mine-specific gas-content factors are Tier 2 and Tier 3 refinements and are not modelled. The IPCC method at this tier does not separately resolve drainage gas, ventilation air methane, or abandoned-mine emissions as distinct streams — they are subsumed into the single mining-stage default. Ventilation air methane in particular, the dilute methane carried out in a mine’s airflow, is a large real-world source at gassy underground mines and the hardest to abate, but it is not a separately computed line in this Tier 1 model; a mine quantifying it requires Tier 3 measurement. A Tier 1 default will differ — sometimes materially — from a mine’s site-specific figure, and the output is a screening estimate and a cross-check, not a measured inventory.
Factor basis and live reads. The four variant factors resolve live from the fugitive_coal_methane MasterBrain keyspace (source IPCC 2019 Refinement Vol 2 Ch 4) at calculation time, and the MasterBrain version is stamped on the output for restatement work. The coal methane factors carry no hardcoded fallback floor: a failed read renders an em-dash and skips the line. The only hardcoded constants are the methane GWPs and the IPCC gas densities. Hand-arithmetic in this article uses the published rounded factors; the live engine rebuilds from the underlying volumetrics and so differs by about a thousandth of a percent — negligible, and the published factor value is the citable figure.
No regulatory substitution. Results are Tier 1 estimates and do not constitute a verified inventory or an assurance opinion. Regulated coal-mine methane reporting, including under tightening EU methane rules for the energy sector, generally requires measured Tier 3 emissions. Reporting obligations stated on a 20-year global-warming-potential basis are not served by this 100-year tool. Review by a qualified practitioner is required before use in any regulated filing.