Scope 1 Glass & Ceramics Process Emissions Calculator (Float / Container / Fibre / Ceramic — IPCC Vol 3 Ch 2)
Compute the Tier 1 process CO2 from melting glass and firing ceramics — production tonnage times the IPCC 2006 default factor, with a cullet credit that lowers the glass figure for every tonne of recycled content in the batch.
Process CO2, from carbonates. The Scope 1 process emissions of glass and ceramics come from one chemistry: carbonate decomposition. When limestone, dolomite, and soda ash are heated in a glass furnace, or the carbonates in clay are fired, they release CO2. That is the emission this calculator computes — production tonnage multiplied by the IPCC 2006 default factor for the product, as set out in Volume 3, Chapter 2. The fuel burned to heat the furnace is a separate, and usually larger, line in your combustion inventory.
Cullet is the lever for glass. Recycled glass — cullet — has already been through calcination once, so it carries no further process CO2. The more cullet in the batch, the lower the carbonate-derived emissions, in direct proportion. The calculator applies a cullet ratio to the glass factor so the headline reflects the recycled content you actually run.
Glass has IPCC defaults; ceramics is composed. The glass factors here are published IPCC Tier 1 defaults. IPCC publishes no single default for ceramics, so the calculator composes one from the carbonate content of the clay, a loss factor, and a blended carbonate ratio — and says so, rather than implying an authority the standard does not grant.
Tier 1, and stated as such. Every factor is a published default that assumes complete calcination. A plant running a raw-material carbon balance on its actual batch recipe — the IPCC Tier 3 method — will get a different, site-specific number. This tool is screening-grade by design.
Tier 1 default factors per IPCC 2006 Vol 3 Ch 2 (§2.4 glass / §2.5 ceramics). Glass production is tonnes melted; ceramics is clay input or product output (set the basis below). Tonnes, kilotonnes, or megatonnes.
Annualised: result × (12 ÷ period months).
Audit mode exposes the full per-line factor derivation chain.
Add a product line above to calculate
Results appear instantly. The Glass/Ceramics split, a cullet-sensitivity comparison, IPCC uncertainty bands, and the full audit trail appear after calculation. Furnace fuel combustion is excluded — process CO₂ only.
Results are indicative Scope 1 process-emission estimates for glass and ceramics manufacture using IPCC 2006 Vol 3 Ch 2 (§2.4 glass / §2.5 ceramics) Tier 1 default factors. The result covers melting / firing process CO₂ only (calcination of batch and clay carbonates, net of glass cullet); it excludes furnace fuel combustion — natural gas and oil — which is a separate Scope 1 stationary-combustion line and typically a larger share of an energy-intensive glass or ceramics plant’s direct emissions. It also excludes Scope 2 electricity (electric-boost furnaces), and Scope 3 batch- material and product transport. Glass Tier 1 carries wide IPCC uncertainty (≈±60% EF + cullet combined; ±10% for the Table 2.6 per-type factors). Ceramics has no published IPCC emission factor — it is composed from a default clay carbonate content (10%; EU-BREF range 0–>30%), so confirm your clay assay. Validate product, production data, cullet ratio, and clay composition against your own records and, where material, proceed to third-party verification under ISO 14064-3.
Two container-glass furnaces run the same batch and melt the same tonnage. One charges 60% recycled glass, the other 20%. Their process carbon differs by half — and not a gram of it is about how hot the furnace runs.
For glass, the recycled content in the batch is the emission factor.
The glass & ceramics process calculator multiplies production tonnage by IPCC 2006 default factors — around 0.21 t CO2/t for float and container glass — to give Tier 1 Scope 1 process CO2 from carbonate decomposition, reduced in proportion to the cullet (recycled glass) in the batch.
What the glass & ceramics process calculator does
This calculator computes the Tier 1 Scope 1 process emissions of glass melting and ceramic firing: the CO2 released when the carbonates in the raw batch or the clay decompose under heat. You enter the tonnage produced on each line, select the glass type or the ceramics basis, and the engine multiplies by the IPCC 2006 default factor — reducing the glass figure by the cullet ratio you set — and sums the lines into one process total.
Process CO2 from carbonate decomposition, not combustion
The defining boundary of this tool is process versus energy. Process emissions come from the chemistry — carbonates such as limestone, dolomite, and soda ash giving up their CO2 as they decompose in the heat. They occur because of the raw materials, not because of the fuel. The emissions from burning gas or oil to melt the glass or fire the kiln are energy emissions, and they belong in a stationary-combustion inventory, not here. IPCC 2006 Volume 3, Chapter 2 governs the process side; the combustion side sits under Volume 2 (Energy). For glass and ceramics, that combustion side is usually the larger number — a point the boundary section below returns to.
How glass and ceramics differ in this tool
The two materials are handled differently because the science is different. Glass has published IPCC Tier 1 emission factors by product type, and a cullet credit applies. Ceramics has no published IPCC factor at all, so the calculator composes one from the carbonate content of the clay. Glass is entered as tonnes melted; ceramics as clay input or product output. Keeping the two on their own terms is what makes each figure defensible.
This is a process-emissions tool. The CO2 here is from carbonate decomposition under IPCC Vol 3 Ch 2 — not from the fuel burned to heat the furnace, which is a separate combustion line under Vol 2. For glass and ceramics the process figure is typically the smaller part of the site’s Scope 1; the melting or firing energy is usually larger and sits outside this boundary.
The cullet credit — why recycled glass cuts process CO2
For glass, no other input moves the result like the cullet ratio. Cullet is recycled glass charged into the furnace alongside virgin raw materials. Because it has already been melted once, its carbonates have already given up their CO2 — so the cullet fraction of the batch emits no further process carbon. Every tonne of cullet displaces a tonne of virgin batch and the calcination CO2 that batch would have released.
A linear lever — the effective factor falls with cullet
The mechanic is straightforward: the effective factor is the base factor multiplied by one minus the cullet ratio. A float-glass factor of 0.21 t CO2 per tonne becomes 0.105 at 50% cullet, and 0.021 at 90%. The relationship is linear, so a furnace running 90% cullet emits 90% less process CO2 than the same furnace running none. The chart below shows the effect on a 300,000-tonne container line at the base factor of 0.21.
Process CO2 of a 300,000-tonne container-glass line at increasing cullet ratios, base factor 0.21 t CO2/t (IPCC 2006 Vol 3 Ch 2). Bar widths proportional to each result. The relationship is linear: the effective factor is 0.21 × (1 − cullet). Values reconcile vs MasterBrain v2026.203; the engine’s default cullet ratio is 50%.
Cullet is the single largest lever on glass process emissions. Because recycled glass is already calcined, its fraction of the batch emits no process CO2 — so the effective factor falls in direct proportion to cullet content. Set the cullet ratio to your actual recycled content; the engine default of 50% is a placeholder, not your plant’s number.
For glass, the carbon left the stone long ago. Cullet is batch that has already paid its calcination CO2 — charge more of it, and the process emission falls tonne for tonne, before the furnace is even lit.
The cullet ratio is applied as a single global figure across every glass line in the ledger. If your furnaces run materially different cullet rates — a container line at 70% and a float line at 20%, say — a single blended ratio will misstate both. Run furnaces with materially different recycled content as separate calculations, each with its own cullet ratio.
Glass — the plant-type default factors
Glass carries published IPCC Tier 1 factors by product type, in tonnes of CO2 per tonne of glass melted. The factor reflects the carbonate content of a typical batch for that product; you select the type, enter the tonnage melted, and the cullet credit then scales the result. The four groups below cover the bulk of industrial glass.
Float glass
Flat glass for windows and façades, made on a molten-tin bath. Factor 0.21 t CO2/t melted. Typically lower cullet than container glass, so the effective factor often stays near the base.
Container glass
Bottles and jars, flint or amber/green. Factor 0.21 t CO2/t melted for both colours. The highest-cullet sector — recycled content often 50% or more — so the effective factor is frequently well below the base.
Fibre glass
E-glass reinforcement at 0.19 t CO2/t and glass-wool insulation at 0.25. Insulation carries the higher factor of the two, reflecting a more carbonate-rich batch.
Specialty glass
The widest spread of any group — laboratory and pharmaceutical glass at 0.03, tableware at 0.10, television funnel and panel glass at 0.13 and 0.18, lighting at 0.20. Pick the closest match to the product.
| Glass type | Factor | Unit | Note |
|---|---|---|---|
| Generic glass (Tier 1 default) | 0.20 | t CO2 / t melted | Use where product type is unknown |
| Float | 0.21 | t CO2 / t melted | Flat glass |
| Container — flint | 0.21 | t CO2 / t melted | Clear container glass |
| Container — amber / green | 0.21 | t CO2 / t melted | Coloured container glass |
| Fibreglass — E-glass | 0.19 | t CO2 / t melted | Reinforcement fibre |
| Fibreglass — insulation | 0.25 | t CO2 / t melted | Glass-wool insulation |
| Specialty — lab / pharma | 0.03 | t CO2 / t melted | Borosilicate, low-carbonate batch |
| Specialty — tableware | 0.10 | t CO2 / t melted | Domestic glassware |
| Specialty — TV funnel | 0.13 | t CO2 / t melted | Legacy CRT glass |
| Specialty — TV panel | 0.18 | t CO2 / t melted | Legacy CRT glass |
| Specialty — lighting | 0.20 | t CO2 / t melted | Lamp and tube glass |
The basis throughout is tonnes of glass melted, not packed or sold — pack-to-melt losses are a downstream yield question, not a process-emission one. Every factor assumes complete calcination of the batch carbonates, which is the Tier 1 convention. The cullet credit then applies on top, uniformly across the glass lines in the ledger.
Ceramics — a composed factor, because IPCC publishes none
Ceramics is the part of this calculator where the standard runs out of published numbers. IPCC Vol 3 Ch 2 gives no single default emission factor for ceramic ware — no per-product figure for brick, tile, pipe, or refractory. Where there is no published factor, the honest move is to say so and show exactly how a defensible figure is composed, rather than presenting an invented number as an IPCC default.
How the ceramics factor is composed
The calculator builds the ceramics factor from three IPCC parameters: the carbonate content of the clay (a default of 0.10 tonnes of carbonate per tonne of clay), a loss factor of 1.1 that converts a product-output basis back to the clay input it came from, and a blended carbonate CO2 ratio of 0.44535 tonnes of CO2 per tonne of carbonate — an 85/15 limestone/dolomite mix from IPCC Equation 2.14. On a product-output basis the composed factor is 1.1 × 0.10 × 0.44535, or about 0.049 t CO2 per tonne of product.
There is no IPCC default emission factor for ceramics. The calculator composes one from clay carbonate content (0.10 t/t), a loss factor (1.1), and a blended limestone/dolomite carbonate ratio (0.44535) — roughly 0.049 t CO2 per tonne of product. It is a defensible composition of published parameters, not a published factor, and is treated as such: a screening estimate, not an authority.
One product, set by clay carbonate content
Because the driver is the carbonate content of the clay rather than the product shape, ceramics is treated as a single product covering brick, tile, pipe, and refractory alike. The variable that matters is how carbonate-rich the clay is, not whether it becomes a roof tile or a sewer pipe. A clay with materially different carbonate content from the 0.10 default should carry a site-specific value — a Tier 2 refinement — rather than the default.
The ceramics basis matters. Entering tonnes of finished product applies the 1.1 loss factor to recover the clay input; entering tonnes of clay input does not. Choose the basis that matches your data and do not mix the two in one line — a product tonnage costed as clay input understates the carbonate, and clay input costed as product overstates it.
How the calculation works
Each line follows the same short path: pick the product, enter the tonnage, and the engine reads the default factor live, applies the cullet credit for glass, and adds the line to the total. You build a ledger of as many lines as your site runs, and the engine sums them into one process figure.
What you enter, what the engine derives
You enter production tonnages and select the type — the glass product, or the ceramics basis — and you set one cullet ratio for the glass lines. The engine derives everything else: the effective glass factor after the cullet credit, the composed ceramics factor, the per-line CO2, and the summed total. The calcination fraction is fixed at the Tier 1 convention of complete calcination and is not yours to adjust at this tier.
The one operation — tonnage times effective factor
For a glass line the calculation is tonnes melted times the base factor times one minus the cullet ratio. For a ceramics line it is tonnage times the composed factor, with the loss factor applied if the basis is product output. There is no gas conversion: glass and ceramics process emissions are CO2 only, carried at a global-warming potential of one, so the figure is already in tonnes of CO2e. That single-gas simplicity is why this calculator has no AR5-versus-AR6 choice — there is no high-warming gas to reweight.
Get the basis right before reading the result. Glass is tonnes melted — use the furnace pull, not the packed tonnage. Ceramics is clay input or product output, and the choice changes whether the 1.1 loss factor applies. And set the cullet ratio to your real recycled content rather than leaving the 50% default, since on a high-cullet container line that default could overstate or understate the result by a wide margin.
Worked example — container versus float, the cullet contrast
The cleanest way to show the method is two glass lines that share a base factor but differ in cullet. Both furnaces below carry the same 0.21 base factor; the only difference is recycled content — and that difference more than halves one furnace’s per-tonne process CO2. The factor values are live MasterBrain figures; the production tonnages and cullet ratios are illustrative inputs.
The process ledger
| Line | Melted (t) | Cullet | Effective factor | Process CO2 |
|---|---|---|---|---|
| Container glass (flint) | 300,000 | 60% | 0.21 × (1 − 0.60) = 0.084 | 25,200 t CO2 |
| Float glass | 500,000 | 20% | 0.21 × (1 − 0.20) = 0.168 | 84,000 t CO2 |
Each figure reconciles as melted tonnage × base factor × (1 − cullet); only the tonnages and cullet ratios are illustrative. The two lines are shown as separate runs because the cullet ratio is a single global input — a plant with this split would run each furnace on its own cullet rather than a blended figure. Factor values via MasterBrain v2026.203, IPCC 2006 Vol 3 Ch 2.
Same 0.21 base factor, different cullet. The container line melts less glass than the float line, but its higher recycled content cuts its effective factor to half the float line’s — so the gap in process CO2 is wider than the gap in tonnage. This is the recycled-content lever in a single comparison. Figures are engine output, reconciled vs MasterBrain v2026.203.
Why cullet, not tonnage, sets the gap
The float line melts two-thirds more glass than the container line, yet emits more than three times the process CO2. The difference is not scale — it is recycled content. At 60% cullet the container line’s effective factor is half the float line’s at 20%, so its per-tonne process emission is half as large before any tonnage is counted. For glass, reading the cullet ratio tells you more about the process footprint than reading the tonnage does.
Reading the result — process is the smaller number
For glass and ceramics, the process figure this calculator produces is usually the smaller part of the site’s Scope 1. The carbonate CO2 is real and reportable, but the energy to melt the glass or fire the kiln typically emits more — often substantially more. Reading the process number in isolation, without the combustion number beside it, gives a misleadingly small picture of the site’s total direct emissions.
The process CO2 is not the furnace’s footprint — it is the carbonate slice of it. The fuel burned to reach melting or firing temperature is a separate, usually larger, combustion line under IPCC Vol 2. Report both: the process figure from here, the energy figure from a stationary-combustion inventory. Presenting the process number alone understates the site’s Scope 1.
Read intensity, not just the total. Tonnes of CO2 per tonne of glass melted is the number that compares furnaces and tracks the cullet lever year to year. For container glass especially, a falling process intensity usually means rising recycled content — the cleanest single signal of decarbonisation on the process side.
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 the higher tiers are exactly where the carbonate-batch detail this tool does not ask for would come in.
| Tier | Method | When it applies |
|---|---|---|
| Tier 1 (this calculator) | Production tonnage × published default factor, with a cullet credit for glass | Screening estimates, first inventories, cross-checks, sites without a batch carbon balance |
| Tier 2 | Country- or plant-specific factors, or a site-specific clay carbonate content | Where some plant data exists but a full raw-material balance does not |
| Tier 3 | Carbonate raw-material input method — mass of each carbonate × stoichiometric ratio × calcination fraction | Regulated facilities, verified inventories, ETS reporting where the batch recipe is metered |
The Tier 3 method is the rigorous one: it takes the actual mass of limestone, dolomite, soda ash, and other carbonates charged, multiplies each by its stoichiometric CO2 ratio, and applies the real calcination fraction rather than assuming complete decomposition. That method needs the batch recipe, which this Tier 1 tool does not ask for. A Tier 1 default and a Tier 3 carbon balance for the same furnace will differ — the default is a standardised proxy, the balance is the plant’s actual chemistry.
Tier 1 is screening-grade by design. It gives a defensible, comparable first figure from published defaults and the cullet ratio, and it tells you where a batch-specific method would diverge. For a regulated inventory under an emissions-trading scheme, the Tier 3 carbonate raw-material method is usually required — this tool is the cross-check against that work, not a substitute for it.
Process versus energy emissions — the boundary that trips audits
The boundary that trips glass and ceramics audits is the line between process CO2 and energy CO2 — and the particular trap here is the reverse of the steel case. A steel inventory fails by under-counting process emissions. A glass or ceramics inventory more often fails by treating the whole furnace as an energy problem and omitting the carbonate CO2 altogether, because the energy number is so much larger that the process number is easy to overlook.
What belongs here, and what belongs in the combustion inventory
Process emissions — the carbonate CO2 from melting glass or firing clay — belong in this calculator. The combustion of natural gas, oil, or other fuel to heat the furnace or kiln belongs in a stationary-combustion inventory under IPCC Volume 2. The two are separate sources at the same furnace: one from the raw materials, one from the fuel. Both are Scope 1, both must be reported, and neither substitutes for the other.
| Belongs in this calculator (process) | Belongs in the combustion calculator (energy) |
|---|---|
| Carbonate CO2 from the glass batch decomposing | Natural gas and oil burned to reach melting temperature |
| Carbonate CO2 from the carbonates in fired clay | Kiln and furnace fuel for ceramic firing |
| The cullet-adjusted process figure for glass | On-site power generation and electric-boost electricity (the latter via Scope 2) |
| Composed ceramics process CO2 | Any coal or petcoke fired for heat |
The audit failures to pre-empt
01 — Process CO2 omitted entirely
Treating the furnace as purely an energy source and reporting only fuel combustion. The carbonate CO2 is a distinct source that energy accounting misses — small next to the fuel, but real and reportable.
02 — Cullet credit overstated
A cullet ratio higher than the furnace actually runs, or a single global ratio applied to furnaces with very different recycled content. Both understate the process figure. Use real, furnace-specific cullet.
03 — Packed tonnage used for melted
Entering packed or sold tonnage instead of glass melted. Pack-to-melt losses make these different numbers; the process factor is per tonne melted, at the furnace.
04 — Ceramics basis mismatched
Mixing product output and clay input on the ceramics line, or applying the 1.1 loss factor to a clay-input figure. Decide the basis and keep it consistent.
05 — Tier 1 default presented as measured
A screening-grade default reported as the plant’s verified figure. State the tier. A regulated inventory needs the Tier 3 carbonate balance, and the default will differ from it.
06 — Composed ceramics factor cited as IPCC
Presenting the composed ceramics number as a published IPCC default. It is a composition of IPCC parameters, not a published factor — say so when it carries into a disclosure.
Reporting context — EU ETS, CBAM, IPCC inventories, SBTi
Glass and ceramics process emissions feed 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 glass & ceramics process emissions | Tier expected |
|---|---|---|
| IPCC 2006 Guidelines, Vol 3 (IPPU) | The source of the method and the glass default factors. Chapter 2 defines the mineral-industry process boundary this calculator computes. | Tier 1–3 framework |
| GHG Protocol Corporate Standard | Places process emissions in Scope 1. The consolidated corporate total rolls process, energy, and indirect emissions together. | Method-agnostic |
| EU ETS | Regulated cap-and-trade covering glass and ceramics installations above capacity thresholds. Requires monitored, verified emissions — typically the Tier 3 carbonate balance, not an IPCC default. | Tier 3 / measured |
| EU CBAM | Carbon border levy. Its current product scope is iron and steel, aluminium, cement, fertilisers, hydrogen, and electricity — glass and ceramics are not in scope (see warning below). | Not in current scope |
| SBTi Corporate Net-Zero | Target-setting against a base-year inventory. The process figure feeds the Scope 1 base year; for glass, rising cullet is a visible near-term lever. | Inventory-grade |
Glass and ceramics are not currently in CBAM scope. The EU’s Carbon Border Adjustment Mechanism covers iron and steel, aluminium, cement, fertilisers, hydrogen, and electricity — not glass or ceramic products. Do not use this calculator, or any CBAM tool, to produce a CBAM declaration for glass or ceramics; there is no CBAM obligation for these products under the current regulation. Use this tool for a Scope 1 inventory or a screening estimate.
For the corporate roll-up that consolidates this process figure with energy and indirect emissions into one organisational total, the process line carries into the GHG inventory aggregator as a Scope 1 entry. For the regulated reporting that glass and ceramics installations face, the EU ETS allowance calculator works from verified installation emissions rather than this Tier 1 default.
Data sources, model, and factor basis
The model — source and structure
The calculator reads its glass factors from the minerals.glass.* keyspace in MasterBrain, sourced from IPCC 2006 Guidelines Volume 3, Chapter 2 (Mineral Industry Emissions), Table 2.6 and the generic Equation 2.13. The ceramics factor is composed from the ceramics.* parameters and a blended carbonate ratio under carbonate_other.tier1_blend_default, per Equation 2.14. Every row is a Scope 1 process factor — the emissions occur at the producing facility — and resolves 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, and no GWP at all
The process 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. Because glass and ceramics process emissions are CO2 only, the engine reads no global-warming-potential rows at all: there is no high-warming gas to reweight, so there is no AR5/AR6 selector and no GWP constant to hardcode. Every value this calculator uses is a live MasterBrain read with no floor beneath it.
A missing factor shows an em-dash, never a guess. The process factors have no fallback floor by design, and because the calculator is CO2-only it carries no GWP constants either — there is no gas to reweight. The canonical values are exactly those in the glass factor table and the composed ceramics figure above, rendered live.
Why there is no GWP basis here
Unlike the chemicals or aluminium process calculators, this tool has no AR5-versus-AR6 choice. Glass and ceramics process emissions are carbonate-decomposition CO2, which carries a global-warming potential of one on every basis. There is no methane, nitrous oxide, or fluorinated gas in the IPCC Chapter 2 Tier 1 method for these products, so the reweighting question that matters elsewhere simply does not arise. The carbonate raw-material method that a future version will add stays CO2-only for the same reason.
A dedicated glass and ceramics carbonate methodology page sets out the IPCC tier structure, the carbonate raw-material input method, and the cullet treatment in full; it is a roadmap page and will be linked here when it publishes.
Related process calculators
This calculator sits in the industrial-process fleet alongside the other Scope 1 emitter tools. The process figure it produces is a Scope 1 line that consolidates into a full corporate inventory, and it sits beside the regulated-reporting tools that work from monitored figures.
The closest neighbour is the Scope 1 cement & lime process calculator, which computes the same carbonate-decomposition chemistry for clinker and lime — the natural companion to this page. For other industrial processes, the iron & steel process calculator covers ironmaking and steelmaking CO2, the aluminium smelting PFC calculator covers perfluorocarbon emissions, and the chemicals process calculator covers nitric, adipic, and the petrochemical families. For the organisational roll-up, the GHG inventory aggregator consolidates Scope 1, 2, and 3 into one boundary total, and the EU ETS allowance calculator handles regulated installation reporting. The semiconductor etch-gases calculator covers CF4, C2F6, NF3, and SF6 from etch and chamber-clean, the coal mine methane calculator covers fugitive mine CH4, and the F-gas inventory aggregator rolls up HFC, PFC, SF6, and NF3 emissions.
Frequently asked questions
It measures the Tier 1 Scope 1 process emissions of glass melting and ceramic firing — the CO2 released when the carbonates in the batch or clay decompose under heat, under IPCC 2006 Guidelines Volume 3, Chapter 2. You enter production tonnage and a glass type or ceramics basis, and the engine multiplies by the default factor, reducing the glass figure by the cullet ratio. It does not measure the fuel burned to heat the furnace — that is an energy emission that belongs in a combustion inventory.
Cullet is recycled glass that has already been melted once, so its carbonates have already released their CO2. The cullet fraction of the batch therefore emits no further process carbon. The effective factor is the base factor times one minus the cullet ratio — a linear relationship, so a furnace at 90% cullet emits 90% less process CO2 than the same furnace at zero. It is the single largest lever on glass process emissions.
Both float glass and container glass — flint or amber/green — carry an IPCC 2006 default of 0.21 t CO2 per tonne of glass melted, before the cullet credit. Fibreglass is 0.19 for E-glass reinforcement and 0.25 for glass-wool insulation; specialty glasses range from 0.03 for laboratory and pharmaceutical glass up to 0.20 for lighting glass. The effective factor falls below these once cullet is applied.
IPCC Vol 3 Ch 2 publishes no single default emission factor for ceramic ware. The calculator composes one from the carbonate content of the clay (a default of 0.10 t carbonate per tonne of clay), a loss factor of 1.1, and a blended limestone/dolomite carbonate ratio of 0.44535 — about 0.049 t CO2 per tonne of product. It is a defensible composition of published IPCC parameters, not a published factor, and should be described that way in any disclosure.
Process emissions only — the carbonate CO2 from melting glass or firing clay, under IPCC Volume 3. The fuel burned to heat the furnace or kiln is an energy emission under IPCC Volume 2 and belongs in a stationary-combustion inventory. For glass and ceramics the energy figure is usually the larger of the two, so reporting only the process number understates the site’s Scope 1 — report both.
Tonnes melted, at the furnace — not packed or sold tonnage. Pack-to-melt losses make these different numbers, and the process factor is defined per tonne of glass melted because that is where the carbonates decompose. Using packed or sold tonnage understates the process emission by the yield loss.
Because glass and ceramics process emissions are CO2 only. Carbon dioxide carries a global-warming potential of one on every basis, so there is nothing to reweight — no methane, nitrous oxide, or fluorinated gas in the IPCC Chapter 2 Tier 1 method for these products. The AR5-versus-AR6 choice that matters on the chemicals or aluminium calculators simply does not arise here.
It is Tier 1 — production tonnage times a published default factor, with a cullet credit. That is screening-grade: defensible and standardised, but not your furnace’s measured batch chemistry. The EU ETS generally requires the Tier 3 carbonate raw-material method from metered inputs, which will differ from the default. Use this tool for a first inventory, a screening estimate, or a cross-check — not as the reported number for a regulated installation.
No — and not because of a method mismatch, but because glass and ceramics are not in CBAM scope. The EU’s Carbon Border Adjustment Mechanism covers iron and steel, aluminium, cement, fertilisers, hydrogen, and electricity. Glass and ceramic products carry no CBAM obligation under the current regulation, so there is no CBAM declaration to produce. Use this tool for a Scope 1 inventory or a screening estimate.
The calculator shows an em-dash and skips that line with a banner rather than a fabricated value. The 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. Because the calculator is CO2-only it carries no GWP constants either. 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 process emissions of glass melting and ceramic firing — the carbonate-decomposition CO2 — under IPCC 2006 Guidelines Volume 3, Chapter 2. It is a process-emissions tool: it does not compute the energy emissions from the fuel burned to heat the furnace or kiln, which belong in a separate stationary-combustion inventory under IPCC Volume 2 and are typically the larger figure.
Method — production times default factor. Glass is production tonnage (tonnes melted) multiplied by the IPCC default factor for the product type, then multiplied by one minus the cullet ratio. Ceramics is tonnage multiplied by a composed factor — clay carbonate content (0.10 t/t default) times a loss factor (1.1) times a blended carbonate ratio (0.44535), per Equation 2.14 — with the loss factor applied on a product-output basis. The calcination fraction is fixed at the Tier 1 convention of complete calcination. This is the Tier 1 method throughout.
The cullet credit. Cullet is recycled glass that is already calcined, so its fraction of the batch emits no process CO2; the effective glass factor is the base factor times one minus the cullet ratio. The cullet ratio is a single global input applied uniformly to all glass lines, defaulting to 50%. Ceramics lines are unaffected by cullet. Furnaces with materially different recycled content should be run as separate calculations, each with its own cullet ratio.
Ceramics is a composed factor. IPCC publishes no default emission factor for ceramics. The calculator composes one from published parameters and treats it as a screening estimate, not a published factor. There are no per-product ceramic factors — brick, tile, pipe, and refractory are treated as one product whose variable is the clay carbonate content. A site with a materially different clay carbonate content should use a site-specific value as a Tier 2 refinement.
CO2-only — no GWP basis. Glass and ceramics process emissions are carbonate-decomposition CO2, which carries a global-warming potential of one. There is no methane, nitrous oxide, or fluorinated gas in the IPCC Chapter 2 Tier 1 method for these products, so the calculator has no AR5/AR6 selector and reads no GWP rows.
Tier boundary. The calculator is Tier 1 only. The carbonate raw-material input method — the actual mass of each carbonate times its stoichiometric ratio times the real calcination fraction — is the Tier 3 method and is not modelled in this version. A Tier 1 default will differ, sometimes materially, from a plant’s batch-specific Tier 3 figure; the output is a screening estimate and a cross-check, not a measured inventory.
Factor basis and live reads. Glass factors resolve live from the minerals.glass.* MasterBrain keyspace and the ceramics parameters from ceramics.* and carbonate_other.* (source IPCC 2006 Vol 3 Ch 2) at calculation time, and the MasterBrain version is stamped on the output for restatement work. The process factors carry no hardcoded fallback floor: a failed read renders an em-dash and skips the line. Because the calculator is CO2-only, it carries no hardcoded GWP constants.
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 3 carbonate balance is generally required. Glass and ceramics are not in EU CBAM scope, so no CBAM declaration arises for these products. Review by a qualified practitioner is required before use in any regulated filing.