Scope 1 Aluminium Smelting PFC Calculator (Prebake / Søderberg / CWPB / PFPB)
Compute the Tier 1 process CO2e from primary aluminium smelting — perfluorocarbon emissions (CF4 and C2F6) from anode effects plus process CO2 from anode consumption, by cell technology, on the IPCC 2019 Refinement or 2006 default factors.
Perfluorocarbons, not smelter power. This calculator covers the Scope 1 process emissions of primary aluminium smelting — the perfluorocarbons (CF4 and C2F6) released during anode effects, and the process CO2 from consuming the carbon anode — under IPCC 2006 Guidelines Volume 3, Chapter 4 and the 2019 Refinement. It does not cover the electricity that drives the smelter, which is Scope 2 and, for most smelters, far the larger figure. The process side reported here is the part that lives inside the smelter’s own boundary.
Production times a technology-default factor. You pick your cell technology, enter primary-aluminium production, and the engine multiplies by the default emission factor for that technology — kilograms of CF4 and C2F6 per tonne of aluminium — then converts each gas to CO2e by its global-warming potential. The process CO2 from anode consumption is added on the same production basis. This is the IPCC Tier 1 method.
Two methodologies, by toggle. The 2019 Refinement is the default and the more representative method for modern point-feed cells; the original 2006 factors remain selectable for continuity with older inventories. The two can differ by an order of magnitude for the same cell — modern point-feed prebake emits a fraction of what the 2006 centre-worked factor assumes — so the methodology you report on is stated, not silent.
Tier 1, and stated as such. Every factor is a technology default. The IPCC Tier 2 slope method — which scales emissions to a smelter’s measured anode-effect minutes — and Tier 3 continuous monitoring are out of scope here; they need plant-level anode-effect data this tool does not take. A Tier 1 figure is screening-grade: a defensible first number that a smelter with its own anode-effect record will refine.
Tier 1 default factors per IPCC Vol 3 Ch 4.4 Table 4.15 (PFC) / Table 4.10 (CO₂) — choose 2019 Refinement (default) or 2006 above. Primary aluminium only. Production in tonnes, kilotonnes, or megatonnes.
2019 Refinement: PFPB cells + HVAE/LVAE. 2006: CWPB/SWPB/VSS/HSS.
CF₄: AR5 6,630 / AR6 7,380 · C₂F₆: AR5 11,100 / AR6 12,400.
PFCs (CF₄ + C₂F₆) typically dominate the total.
Annualised: result × (12 ÷ period months).
Audit mode exposes the full per-potline factor chain.
Add a potline above to calculate
Results appear instantly. The CO₂/CF₄/C₂F₆ split, a same-output technology comparison, IPCC uncertainty bands, and the full audit trail appear after calculation.
Results are indicative Scope 1 process-emission estimates for primary aluminium smelting using IPCC Vol 3 Ch 4.4 Tier 1 technology-default factors (selectable IPCC 2019 Refinement — default — or 2006). Tier 1 PFC defaults carry wide IPCC uncertainty bands and will differ from measured anode-effect (Tier 2/3) data — modern point-fed prebake (PFPB) smelters in particular emit far less than the Tier-1 prebake default. The result covers direct process emissions only (anode-effect CF₄/C₂F₆ and, in full mode, anode/paste CO₂); it excludes Scope 2 smelter electricity, which is the majority of primary aluminium’s carbon footprint, as well as alumina refining, anode-plant fuel, and Scope 3 upstream. This tool covers primary smelting only (secondary/recycled aluminium has no PFCs). Confirm cell technology and production data against your own records and, where material, proceed to third-party verification under ISO 14064-3 with measured anode-effect data.
A smelter can leak two hundred kilograms of a gas in a year and have it land on the inventory like two thousand tonnes of carbon dioxide. That is what a global-warming potential in the thousands does: a trace of perfluorocarbon, weighed in CO2e, becomes a line you cannot ignore.
Aluminium’s process footprint is not about how much metal you make — it is about how often the cell misbehaves, and which technology you run.
The aluminium PFC calculator multiplies primary-aluminium production by IPCC technology-default factors for CF4 and C2F6, converts each to CO2e at its high global warming potential, and adds process CO2 from anode consumption.
What the aluminium PFC calculator does
This calculator computes the Tier 1 Scope 1 process emissions of primary aluminium smelting: the perfluorocarbons CF4 and C2F6 released during anode effects, plus the process CO2 from consuming the carbon anode. You pick your cell technology, enter primary-aluminium production, and the engine multiplies by the IPCC default factor for that technology and converts each gas to CO2e — under the 2019 Refinement by default, or the original 2006 factors if you choose.
Process gases, not smelter electricity
The defining boundary is the same one that governs every industrial-process calculator: this is the chemistry, not the energy. The perfluorocarbons form when the alumina feed runs low and the cell voltage spikes — the anode effect — and the process CO2 comes from the carbon anode oxidising as the cell reduces alumina to aluminium. Both occur inside the smelter’s own boundary and are Scope 1. The electricity that powers electrolysis — the dominant part of aluminium’s footprint — is Scope 2 and is computed from consumption and a grid factor, not here. Reporting the process side cleanly is what lets the electricity side be seen for what it is.
Tier 1 — production times a default factor
The method is production-based: tonnes of primary aluminium times a technology-default emission factor, in kilograms of gas per tonne of metal. That is IPCC Tier 1. It does not scale to your smelter’s measured anode-effect frequency or duration — that is the Tier 2 slope method, which needs plant data this tool does not take. What Tier 1 gives is a standardised first figure, computed identically for any smelter on the same technology, which is exactly what a screening estimate or a cross-check against a monitored inventory needs.
This is a process-emissions tool. The CO2e here is perfluorocarbons from anode effects plus CO2 from anode consumption — the smelter’s direct Scope 1. The electricity driving electrolysis, typically the largest single part of an aluminium footprint, is Scope 2 and sits entirely outside this boundary. A small process figure does not mean a small smelter.
Why PFCs dominate aluminium’s process gases
Perfluorocarbons are the reason aluminium has a process-gas problem at all. They are emitted in tiny masses — fractions of a kilogram per tonne of metal — but each carries a global-warming potential in the thousands, so a trace of gas converts to a substantial CO2e line. Understanding where they come from, and how heavily they weigh, is the whole basis of the calculation.
CF4 and C2F6 — small mass, enormous warming potential
The two perfluorocarbons from smelting are tetrafluoromethane (CF4) and hexafluoroethane (C2F6). Their global-warming potentials are among the highest of any greenhouse gas in routine industrial emission: on the AR5 100-year basis, 6,630 for CF4 and 11,100 for C2F6; on AR6, 7,380 and 12,400. A single kilogram of C2F6 therefore behaves like more than eleven tonnes of CO2. That multiplier is why a smelter emitting a few hundred kilograms of perfluorocarbon a year reports tens of thousands of tonnes of CO2e from it.
| Gas | AR5 GWP-100 | AR6 GWP-100 | One kilogram weighs as |
|---|---|---|---|
| CF4 (tetrafluoromethane) | 6,630 | 7,380 | ≈ 6.6–7.4 t CO2e |
| C2F6 (hexafluoroethane) | 11,100 | 12,400 | ≈ 11.1–12.4 t CO2e |
The anode effect — where the perfluorocarbons come from
Perfluorocarbons are not produced in normal operation. They form during an anode effect: when the dissolved alumina in the electrolytic bath runs too low, the cell can no longer carry its current through the usual reaction, the voltage spikes, and the carbon anode begins to react with the fluoride bath to release CF4 and C2F6. The more frequent and the longer these anode effects, the more perfluorocarbon a cell emits. That is why the headline driver of aluminium’s process gases is cell behaviour — how well alumina feeding is controlled — and why a technology that feeds alumina precisely and often emits far less than one that does not.
Perfluorocarbons scale with the anode effect, not with metal output as such. Two smelters making the same tonnage can emit very different amounts depending on how often their cells starve of alumina. The Tier 1 default factors here encode the typical anode-effect behaviour of each cell technology; a smelter with its own measured anode-effect record would use the Tier 2 slope method to reflect its actual performance.
The number is not set by how much aluminium you make. It is set by how often the cell misbehaves — and the cell technology you chose decides how often that is.
The cell technologies — prebake, point-feed, and Søderberg
Cell technology is the single largest driver of a smelter’s perfluorocarbon factor, because each design controls alumina feeding — and therefore anode effects — differently. The calculator carries the full IPCC set, from modern point-feed prebake cells with the lowest factors to the legacy Søderberg designs with the highest.
Point-feed prebake (PFPB)
Pre-baked carbon anodes with automated point feeders that dose alumina precisely and often. The modern variant (PFPBM) carries the lowest PFC factors in the set — 0.029 kg CF4/t on the 2019 Refinement — because tight feed control keeps anode effects rare and short.
Side-worked prebake (SWPB)
Pre-baked anodes but with crust broken along the sides to feed alumina, a coarser control than point feeding. Higher anode-effect activity gives a markedly higher factor — 0.364 kg CF4/t on the 2019 Refinement — than the point-feed designs.
Søderberg (VSS / HSS)
Self-baking anodes formed in place, vertical-stud (VSS) or horizontal-stud (HSS). Legacy designs with the highest factors — HSS reaches 0.503 kg CF4/t on the 2019 Refinement — and the technology most aluminium decarbonisation aims to retire.
Why point-feed cells emit least
The pattern across the table below is consistent: the more precisely a cell feeds alumina, the fewer anode effects it suffers, and the lower its perfluorocarbon factor. Modern point-feed prebake cells, dosing small amounts of alumina many times an hour, hold the bath concentration steady and rarely starve. Side-worked and Søderberg cells, feeding in larger and less frequent batches, swing closer to the anode-effect threshold and cross it more often. The factor difference between the best and worst technology spans roughly seventeen-fold on CF4 — which is why retrofitting feed control, or replacing Søderberg lines entirely, is the central lever in primary-aluminium process decarbonisation.
If you do not know your exact cell variant, the technology family is enough to get the order of magnitude right — prebake point-feed cells sit low, side-worked and Søderberg cells sit high. But pick the closest specific variant where you can: the gap between modern and legacy point-feed prebake, or between the two Søderberg designs, is large enough to matter for the reported figure.
How the calculation works — production times factor
Each potline is one line in the ledger. You pick its cell technology and enter its primary-aluminium production; the engine reads the technology-default factors live, multiplies, converts each gas to CO2e, adds the process CO2, and sums the lines into a smelter total. A multi-line ledger handles a smelter running more than one technology across its potrooms.
What you enter, what the engine derives
You enter primary-aluminium production per potline, in tonnes, kilotonnes, or megatonnes, and select the cell technology. The engine derives the rest: the CF4 and C2F6 masses from the technology factors, each converted to CO2e at the selected GWP basis, the process CO2 from the anode-type factor, and the line and portfolio totals. The methodology toggle (2019 Refinement or 2006) and the GWP basis (AR5 or AR6) set which factors and multipliers apply.
The three operations per line
For each potline the engine computes three quantities and adds them. The CF4 contribution is production times the CF4 factor in kilograms per tonne, times the CF4 GWP, divided to tonnes. The C2F6 contribution is the same with its own factor and GWP — C2F6 is a separate emission factor, not a fixed ratio of CF4. The process CO2 is production times the anode-type CO2 factor. The line total is the sum of the three; the smelter total is the sum of the lines.
C2F6 is computed from its own factor, not derived as a ratio of CF4 at run time. Each technology has a distinct C2F6 factor in the IPCC tables, and the calculator reads it directly. On the 2019 Refinement the CF4 factor is itself the sum of two components — a high-voltage and a low-voltage anode-effect contribution — added before the GWP is applied. Do not reconstruct C2F6 by scaling CF4; the two gases track different cell behaviours.
Two methodologies — IPCC 2006 and the 2019 Refinement
The calculator offers both the original IPCC 2006 default factors and the 2019 Refinement update, selected by a toggle. They are not interchangeable: the 2019 Refinement re-measured anode-effect behaviour across the cell fleet and, for modern point-feed cells, produced factors an order of magnitude lower than the 2006 values. The default here is the 2019 Refinement, as the more representative method for the cells in service today.
| Technology | 2019 Refinement CF4 (kg/t) | 2019 Refinement C2F6 (kg/t) | 2006 CF4 (kg/t) | 2006 C2F6 (kg/t) |
|---|---|---|---|---|
| PFPBM — point-feed prebake, modern | 0.029 | 0.001 | 0.4 ‡ | 0.04 ‡ |
| PFPBL — point-feed prebake, legacy | 0.025 | 0.001 | 0.4 ‡ | 0.04 ‡ |
| SWPB — side-worked prebake | 0.364 | 0.093 | 1.6 | 0.4 |
| VSS — vertical-stud Søderberg | 0.160 | 0.009 | 0.8 | 0.04 |
| HSS — horizontal-stud Søderberg | 0.503 | 0.033 | 0.4 | 0.03 |
‡ The 2006 Guidelines use a single centre-worked prebake (CWPB) factor of 0.4 / 0.04 kg/t for point-feed designs rather than separate modern and legacy variants; the 2019 Refinement split these into PFPBM and PFPBL with much lower values. The 2019 set also adds a point-feed “worked” variant (PFPBMW: 0.161 / 0.013 kg/t) not shown above. On the 2019 Refinement each CF4 factor is the sum of a high-voltage and a low-voltage anode-effect component. Factor values via MasterBrain v2026.203, IPCC 2006 Vol 3 Ch 4 and 2019 Refinement.
The size of the gap is the point. A modern point-feed prebake cell carries a 2019 CF4 factor of 0.029 kg/t against the 2006 centre-worked value of 0.4 — roughly fourteen times lower. Reporting a modern smelter on the 2006 factor would overstate its perfluorocarbons by more than a factor of ten. The methodology you select is therefore a material disclosure, not a formatting choice, and the calculator stamps which one produced the figure.
Do not compare a 2019-Refinement total against a 2006 total as if they were the same measurement. For modern point-feed cells the 2019 factors are roughly an order of magnitude lower, reflecting better-characterised anode-effect behaviour. Mixing the two vintages across an inventory — some lines on 2006, some on 2019 — produces a figure on no single basis. Pick one methodology for the inventory and state it.
Worked example — a modern PFPB smelter
A worked smelter shows the method end to end: the two perfluorocarbons converted at their high GWPs, the process CO2 from anode consumption, and the share each contributes. The smelter below produces 200,000 tonnes of primary aluminium a year on modern point-feed prebake cells, computed on the 2019 Refinement, AR5 basis, in full mode. The factor values are live MasterBrain figures; the production tonnage is an illustrative input.
The emission lines
| Line | Production × factor × GWP | Result |
|---|---|---|
| CF4 | 200,000 t × 0.029 kg/t = 5,800 kg × 6,630 ÷ 1000 | 38,454 t CO2e |
| C2F6 | 200,000 t × 0.001 kg/t = 200 kg × 11,100 ÷ 1000 | 2,220 t CO2e |
| Process CO2 (prebake anode) | 200,000 t × 1.6 t CO2/t | 320,000 t CO2e |
| Smelter total | 38,454 + 2,220 + 320,000 | 360,674 t CO2e |
CF4 and C2F6 factors from the 2019 Refinement point-feed-prebake-modern rows; process CO2 factor (1.6 t CO2/t Al) is the prebake anode value, shared by both methodologies. GWPs on AR5 (CF4 6,630; C2F6 11,100). Factor values via MasterBrain v2026.203. Every figure reconciles as production × factor × GWP ÷ 1000; only the production tonnage is illustrative.
On AR6 (CF4 7,380; C2F6 12,400) the perfluorocarbon lines rise to 42,804 and 2,480 t CO2e, lifting the total to ≈365,284 t — a ≈1.3% move, since the perfluorocarbons are ≈11% of the inventory. The process CO2 is unchanged by GWP basis. The perfluorocarbon share is modest here because the cells are modern point-feed; on a legacy Søderberg or side-worked cell the same production would push the perfluorocarbon share well above the process CO2.
The legacy-cell contrast
Run the same 200,000 tonnes on the 2006 centre-worked prebake factor of 0.4 kg CF4/t and 0.04 kg C2F6/t, and the perfluorocarbon lines alone come to roughly 619,000 t CO2e — about fifteen times the modern point-feed figure, and on their own larger than this smelter’s entire 2019-Refinement inventory. That gap is the combined effect of methodology vintage and cell technology, and it is the clearest illustration of why both the method and the cell type are material disclosures rather than defaults to accept silently.
For this modern smelter the process CO2 dominates and the perfluorocarbons are a tenth of the total. That balance flips on older cells: a Søderberg or side-worked smelter at the same production reports perfluorocarbons that swamp its process CO2, because the anode-effect factors are an order of magnitude higher. Read the perfluorocarbon share as a signal of cell-technology age, not a fixed feature of aluminium.
Reading the result — CF4, C2F6, and process CO2
The most useful view of the result is the contribution split: how much of the CO2e is process CO2 from the anode against how much is perfluorocarbon, and within the perfluorocarbons, how CF4 and C2F6 divide. For the worked modern smelter the process CO2 is the large block and the perfluorocarbons a thin band; the chart below shows that split.
Process contribution split of the worked PFPB smelter (360,674 t CO2e, 2019 Refinement, AR5). Bar widths are proportional to each line’s share. This is one modern smelter’s inventory, not a sector benchmark — a Søderberg or side-worked smelter would show the perfluorocarbon bands overtaking the process CO2. Figures are engine output, reconciled vs MasterBrain v2026.203.
Watch the perfluorocarbon share, not just the total. A rising CF4 band is the signature of worsening anode-effect control — more frequent or longer effects — and it is the part of the inventory a smelter can move without changing its electricity. For the process CO2, which tracks anode consumption per tonne, the lever is anode efficiency and inert-anode technology, not feed control.
Tier 1 versus the slope method — accuracy and scope
The IPCC framework offers three tiers for aluminium PFCs, and this calculator is Tier 1. Saying so plainly matters, because the higher tiers answer a different question — they reflect a specific smelter’s measured anode-effect performance rather than the typical behaviour of its technology class.
| Tier | Method | When it applies |
|---|---|---|
| Tier 1 (this calculator) | Production × technology-default factor (2006 or 2019 Refinement) | Screening estimates, first inventories, cross-checks, smelters without anode-effect monitoring data |
| Tier 2 | Slope method — emissions scaled to measured anode-effect minutes or overvoltage per cell | Smelters with routine anode-effect monitoring; the standard for regulated and verified inventories |
| Tier 3 | Continuous direct measurement of PFC emissions | Facilities with continuous PFC monitoring instrumentation |
The slope method, Tier 2, is how most regulated aluminium smelters actually report: it multiplies a measured anode-effect quantity — minutes per cell-day, or overvoltage — by a smelter-specific slope coefficient, so the figure tracks real cell performance rather than a class average. Those slope coefficients and the anode-effect inputs are not part of this calculator. A Tier 1 figure and a Tier 2 figure for the same smelter can differ substantially, in either direction, depending on whether the smelter runs better or worse than its technology’s typical anode-effect behaviour.
Tier 1 is screening-grade by design, and the right tool when you do not have anode-effect monitoring data. A smelter that records anode-effect minutes or overvoltage should report on the Tier 2 slope method, which reflects its actual cell performance. Use this calculator for a first estimate, a sanity check on monitored figures, or a smelter without that instrumentation — not as the reported number for a regulated installation that has slope data.
The electricity boundary — why Scope 2 dwarfs process PFC
PFCs are only the process slice of aluminium’s footprint. For the full cradle-to-gate embodied carbon of steel and aluminium — dominated by smelting electricity and recycled-content choices — see the embodied-carbon methodology.
The boundary that most often confuses an aluminium footprint is the one between this process calculator and the smelter’s electricity. Aluminium smelting is among the most electricity-intensive industrial processes there is, and for a smelter on a fossil grid the electricity emissions typically dwarf everything computed here.
What belongs here, and what belongs in Scope 2
The perfluorocarbons and the anode process CO2 are Scope 1 and belong in this calculator. The electricity drawn for electrolysis — typically thirteen to fifteen megawatt-hours per tonne of aluminium — is Scope 2, computed from consumption and a grid emission factor, and reported there. On a coal-heavy grid that electricity can contribute well over ten tonnes of CO2e per tonne of aluminium, several times the process intensity computed here; on a hydro or renewable grid it can be near zero. The process figure is the same either way, which is precisely why it must be read alongside the electricity, not instead of it.
| Belongs in this calculator (Scope 1 process) | Belongs in Scope 2 electricity accounting |
|---|---|
| CF4 and C2F6 from anode effects | Electricity for electrolysis (≈13–15 MWh per tonne of aluminium) |
| Process CO2 from carbon-anode consumption | Grid emission factor — location-based and market-based |
| The smelter’s direct, in-boundary process gases | The indirect emissions of the power the smelter buys |
The audit failures to pre-empt
01 — Process figure read as the footprint
Reporting the Scope 1 process total as the smelter’s emissions and omitting the electricity. For a fossil-grid smelter the Scope 2 electricity is usually the larger figure by far; the process number is only part of the picture.
02 — Methodologies mixed across lines
Some potlines on 2006 factors, others on the 2019 Refinement. The vintages differ by an order of magnitude for modern cells; an inventory on no single basis cannot be reconciled. Pick one methodology.
03 — Wrong cell technology selected
A modern point-feed smelter reported on a Søderberg or centre-worked factor, or the reverse. The factor spans seventeen-fold across technologies; the cell type is the largest single input to get right.
04 — C2F6 derived from CF4
Reconstructing C2F6 as a fixed fraction of CF4. Each has its own technology factor; the ratio varies by cell type. Read both factors directly rather than scaling one from the other.
05 — GWP basis unstated
A perfluorocarbon total with no AR5-or-AR6 label. The GWPs differ — CF4 6,630 against 7,380 — so the basis must be recorded, matching the rest of the inventory.
06 — Tier 1 default presented as measured
A technology-default figure reported as the smelter’s verified emissions. A regulated smelter with anode-effect monitoring should report on the Tier 2 slope method; the default will differ from it.
Reporting context — EU ETS, CBAM, SBTi, IPCC inventories
Aluminium process emissions feed several reporting and regulatory regimes, and the tier each expects differs. A Tier 1 screening figure is a starting point for all of them and a sufficient figure for none of the regulated ones — the table sets out which is which.
| Framework | Role for aluminium process emissions | Tier expected |
|---|---|---|
| IPCC 2006 Guidelines | The source of the original method and default factors. Volume 3, Chapter 4 defines the aluminium PFC and process-CO2 boundary. | Tier 1–3 framework |
| IPCC 2019 Refinement | Updates the aluminium PFC factors for the modern cell fleet, splitting point-feed prebake into modern and legacy variants. The default methodology here. | Tier 1–3 framework |
| GHG Protocol Corporate Standard | Places the perfluorocarbons and anode CO2 in Scope 1; the smelter electricity in Scope 2. Consolidates both into the corporate total. | Method-agnostic |
| EU ETS | Regulated cap-and-trade covering aluminium installations, including PFCs. Requires monitored, verified emissions — the Tier 2 slope method, not an IPCC default. | Tier 2 / measured |
| EU CBAM | Carbon border levy covering aluminium. Uses its own Annex I default factors per country and product code — a separate regulatory dataset, not this IPCC method (see warning below). | CBAM default or verified |
| SBTi Corporate Net-Zero | Target-setting against a base-year inventory. Aluminium has a sector pathway; the process figure feeds the Scope 1 base year alongside the Scope 2 electricity. | Inventory-grade |
This calculator is not a CBAM tool. CBAM declarations for aluminium use the EU’s own Annex I default emission factors, set per origin country and product code, which differ from the IPCC process factors here and are expressed per tonne of finished good. Use this tool for a Scope 1 inventory or a screening estimate; for a CBAM import declaration, use the dedicated CBAM factors and reporting workflow. The two datasets are not interchangeable.
For the corporate roll-up that consolidates this process figure with the smelter’s electricity and value-chain emissions, the process line carries into the GHG inventory aggregator as a Scope 1 entry. For the regulated reporting downstream, the EU ETS allowance calculator and the EU CBAM calculator work from monitored or regulatory-default figures rather than this Tier 1 default. The same process-versus-energy boundary governs the iron & steel process calculator, the sibling tool for the other major primary-metals emitter.
Data sources, model, and GWP basis
The complete underlying reference — every factor in this section, versioned with full source provenance and downloadable as CSV with a citable Zenodo DOI — is published as the IPCC industrial-process (IPPU) emission factors dataset.
The model — source and structure
The calculator reads its factors from two MasterBrain keyspaces: the IPCC 2006 aluminium factors under metals.aluminium.* and the 2019 Refinement factors under industrial_processes_refinement.aluminium_pfc.*, both sourced from IPCC Volume 3, Chapter 4. Every row is a Scope 1 process factor — the emissions occur at the smelter. The perfluorocarbon factors are stored as native gas mass, kilograms of CF4 or C2F6 per tonne of aluminium, with the global-warming potential applied by the engine at calculation time rather than baked into the stored value. Each carries a structured IPCC uncertainty band, surfaced in the tool as a confidence indicator.
No fallback floor — em-dash on miss
Like the other industrial-process factors, the aluminium factors carry no hardcoded fallback value. If a factor cannot be read from MasterBrain, the calculator renders an em-dash rather than a stale or invented number — the house rule across GreenCalculus value lookups. The only hardcoded constants in the engine are the four perfluorocarbon global-warming potentials (CF4 and C2F6 on AR5 and AR6), which mirror the canonical GWP rows. So the canonical factor values are exactly those in the methodology table above, rendered live; there is no second set of floor values to reconcile against.
A missing factor shows an em-dash, never a guess. The aluminium process factors have no fallback floor by design — the tool would rather show nothing than a fabricated number. The single set of hardcoded values is the four perfluorocarbon GWPs, and they exist only to convert the gas masses to CO2e.
GWP basis and completeness
The perfluorocarbons convert at their global-warming potentials: CF4 at 6,630 (AR5) or 7,380 (AR6), C2F6 at 11,100 (AR5) or 12,400 (AR6), selectable to match the rest of your inventory. The process CO2 carries a GWP of 1 and is never reweighted. Because the perfluorocarbons are a substantial share of the total — around a tenth for a modern smelter, more for a legacy one — the AR5-versus-AR6 choice moves the figure more here than it does for a category whose gases are nearly all CO2. There is no nitrous oxide for aluminium smelting in IPCC Vol 3 Ch 4 — a genuine completeness fact, recorded so a reviewer knows N2O was considered and is not applicable. For the underlying perfluorocarbon GWP values, see the IPCC AR6 GWP values reference.
A dedicated aluminium smelting PFC methodology page sets out the IPCC tier structure, the slope method for Tier 2, and the anode-effect mechanism in full; it is a roadmap page and will be linked here when it publishes.
Related process calculators
This calculator is one of the industrial-process tools and the primary-aluminium entry point. The process figure it produces is a Scope 1 line that consolidates into a full corporate inventory, and it sits alongside the iron & steel process tool and the regulated-reporting calculators that work from monitored or border-adjustment figures.
For the organisational roll-up that brings this process total together with the smelter’s electricity and value-chain emissions, the GHG inventory aggregator consolidates Scope 1, 2, and 3 into one boundary total. The iron & steel process calculator is the closest sibling — the same process-versus-energy boundary and Tier 1 production-based method for the other major primary-metals emitter. For the regulated reporting aluminium installations face, the EU ETS allowance calculator works from verified installation emissions and the EU CBAM calculator handles import declarations on the EU border-adjustment factors. Companion industrial-process calculators cover the cement & lime process calculator, the chemicals process calculator, the glass & ceramics process calculator, and the semiconductor etch-gases calculator. For other Scope 1 fugitive and fluorinated sources, the coal mine methane calculator handles mine CH4, and the F-gas inventory aggregator consolidates HFC, PFC, SF6, and NF3 lines.
Quick converters: turn a single PFC mass into CO₂e — CF₄ (PFC-14) and C₂F₆ (PFC-116), the two perfluorocarbons released by aluminium anode effects.
Frequently asked questions
It measures the Tier 1 Scope 1 process emissions of primary aluminium smelting — the perfluorocarbons CF4 and C2F6 released during anode effects, plus the process CO2 from consuming the carbon anode — under IPCC 2006 Guidelines Volume 3, Chapter 4 and the 2019 Refinement. You pick your cell technology, enter primary-aluminium production, and the engine multiplies by the technology-default factor and converts each gas to CO2e. It does not measure the smelter’s electricity, which is Scope 2.
Perfluorocarbons — CF4 and C2F6 — are released during the anode effect, when the alumina in the electrolytic bath runs low and the carbon anode reacts with the fluoride bath. They are emitted in small masses but carry very high global-warming potentials: 6,630 and 11,100 on AR5, 7,380 and 12,400 on AR6. A single kilogram of C2F6 weighs more than eleven tonnes of CO2e, so even a few hundred kilograms a year becomes a substantial inventory line.
Because perfluorocarbons scale with anode effects, and modern point-feed prebake cells control alumina feeding precisely enough to make anode effects rare and short. The 2019 Refinement gives modern point-feed prebake a CF4 factor of 0.029 kg/t against the 2006 centre-worked value of 0.4 — about fourteen times lower. Side-worked and Søderberg cells, with coarser feed control, sit far higher. The cell technology is the single largest input to the figure.
The 2019 Refinement is the default and the more representative method for cells in service today, especially modern point-feed prebake, for which the 2006 factors substantially overstate perfluorocarbons. The 2006 factors remain selectable for continuity with older inventories. Whichever you choose, use it for the whole inventory — do not mix vintages across potlines, because the two differ by an order of magnitude for modern cells and the result would be on no single basis.
No. This calculator covers only the Scope 1 process emissions — perfluorocarbons and anode CO2. The electricity that drives electrolysis is Scope 2, typically thirteen to fifteen megawatt-hours per tonne of aluminium, and is computed separately from consumption and a grid emission factor. For most smelters the electricity is the larger figure by far — far larger on a fossil grid — so the process total here should always be read alongside the Scope 2 electricity, never as the whole footprint.
It is Tier 1 — production times a technology-default factor. That is screening-grade, not your smelter’s measured performance. The EU ETS generally requires the Tier 2 slope method, which scales emissions to monitored anode-effect minutes or overvoltage per cell, and will differ from the default. Use this tool for a first inventory, a screening estimate, or a cross-check — not as the reported figure for a regulated installation that has anode-effect monitoring data.
No. C2F6 has its own technology-default emission factor in the IPCC tables, and the calculator reads it directly rather than scaling it from CF4. The ratio between the two gases varies by cell technology, so deriving one from the other would introduce error. On the 2019 Refinement the CF4 factor is itself the sum of a high-voltage and a low-voltage anode-effect component, added before the GWP is applied.
Yes, in full mode. As well as the perfluorocarbons, the calculator adds the process CO2 from carbon-anode consumption — 1.6 tonnes of CO2 per tonne of aluminium for prebake cells, 1.7 for Søderberg — on the same production basis. For a modern smelter this anode CO2 is the larger part of the process total, with the perfluorocarbons around a tenth; for a legacy smelter the perfluorocarbons can exceed it.
No. CBAM declarations for aluminium use the EU’s own Annex I default emission factors, set per origin country and product code, which are a separate dataset from the IPCC process factors this calculator uses. This tool is for a Scope 1 inventory or a screening estimate. For a CBAM import declaration, use the dedicated CBAM factors and quarterly reporting workflow — the two datasets are not interchangeable.
The calculator shows an em-dash rather than a fabricated value. The aluminium process 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 four perfluorocarbon global-warming potentials used to convert the gas masses to CO2e. An em-dash on a result 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 process emissions of primary aluminium smelting — perfluorocarbons (CF4, C2F6) from anode effects, plus process CO2 from carbon-anode consumption — under IPCC 2006 Guidelines Volume 3, Chapter 4 and the 2019 Refinement. It is a process-emissions tool: it does not compute the smelter’s electricity emissions, which are Scope 2 and typically the dominant part of an aluminium footprint.
Method — production times default factor. Each potline is production tonnage multiplied by a technology-default factor. Perfluorocarbons are stored as native gas mass (kilograms of CF4 or C2F6 per tonne of aluminium) and converted to CO2e by their GWP at calculation time; on the 2019 Refinement the CF4 factor is the sum of a high-voltage and a low-voltage anode-effect component. Process CO2 is production times the anode-type factor (1.6 prebake, 1.7 Søderberg). C2F6 is read from its own factor, not derived from CF4. This is the Tier 1 method throughout.
Two methodologies. The 2019 Refinement (default) and the 2006 Guidelines are selectable by toggle. They differ by up to an order of magnitude for modern point-feed cells; an inventory should use one methodology throughout, and the calculator stamps which one produced the figure. The cell technology selected — point-feed prebake (modern or legacy), side-worked prebake, or Søderberg (vertical- or horizontal-stud) — is the largest single input to the result.
Tier boundary. The calculator is Tier 1 only. The Tier 2 slope method — emissions scaled to measured anode-effect minutes or overvoltage — and Tier 3 continuous monitoring are out of scope and require plant-level anode-effect data this tool does not take. A Tier 1 default will differ from a smelter’s slope-method figure, in either direction, depending on its actual anode-effect performance; the output is a screening estimate and a cross-check, not a measured inventory.
GWP basis and completeness. Perfluorocarbons convert at CF4 6,630 / C2F6 11,100 (AR5, default) or 7,380 / 12,400 (AR6, selectable). Process CO2 carries a GWP of 1. The C2F6 GWP is read from the canonical perfluorocarbon GWP row. There is no nitrous oxide factor for aluminium smelting in IPCC Vol 3 Ch 4 — a completeness fact, recorded as considered and not applicable. Each perfluorocarbon factor carries a structured IPCC uncertainty band, surfaced as a confidence indicator.
Factor basis and live reads. Factors resolve live from the metals.aluminium.* (2006) and industrial_processes_refinement.aluminium_pfc.* (2019 Refinement) MasterBrain keyspaces at calculation time, and the MasterBrain version is stamped on the output for restatement work. The aluminium factors carry no hardcoded fallback floor: a failed read renders an em-dash, never a fabricated value. The only hardcoded constants are the four perfluorocarbon GWPs.
No regulatory substitution. Results are Tier 1 estimates and do not constitute a verified inventory or an assurance opinion. For EU ETS installations the Tier 2 slope method is generally required; for CBAM declarations the EU Annex I default factors apply, not these IPCC factors. Review by a qualified practitioner is required before use in any regulated filing.
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