What fraction of the carbonate should a ceramic or glass unit assume is calcined if it has not measured it?

You can assume all of it. The Intergovernmental Panel on Climate Change (IPCC) says that where the fraction of calcination achieved is not known, it can be assumed equal to 1.00, in both its glass and its ceramics equations. For glass it puts the uncertainty of assuming 100 percent at 1 percent.

The equation and the default

Tier 3 for glass (Equation 2.12) and for other process uses of carbonates, which include ceramics (Equation 2.16), is carbon dioxide (CO2) equals the sum over carbonates of Mi x EFi x Fi.

Mi is tonnes of carbonate i used, EFi its Table 2.1 factor in tonnes of CO2 per tonne, and Fi the fraction calcination achieved. The guide says that where it is not known, it can be assumed that the fraction calcination is equal to 1.00.

What that assumption does

Fi cannot exceed 1.00, so assuming 1.00 can only raise the figure or leave it unchanged. A measured Fi below 1.00 lowers it. For glass the guide puts the uncertainty of assuming 100 percent calcination at 1 percent. That the default cannot understate is my reading.

Where the default does not apply

• Tier 1 for other uses of carbonates (Equation 2.14) has no calcination term: carbon dioxide equals carbonate tonnes x (0.85 x the limestone factor + 0.15 x the dolomite factor).
• Calcined magnesia is not fully calcined. The guide says typically 96 to 98 percent of the contained CO2 is released in calcined magnesia, and nearly 100 percent for dead burned and fused magnesia. Applying that as Fi is my reading. See the magnesia page linked below.
• The guide says the Tier 3 method for other uses should only be applied at plant level.

If you do have a measurement

A lab test of the fired body or glass for leftover carbonate would let you set Fi yourself. The guide does not prescribe a test. Keep the report with the month's carbonate records.

Limestone and dolomite in one month

• Limestone: 12.0 tonnes x 0.43971 = 5.2765 tonnes of CO2
• Dolomite: 3.0 tonnes x 0.47732 = 1.4320 tonnes
• At Fi = 1.00: 5.2765 + 1.4320 = 6.7085 tonnes, reported as 6.7
• If a test showed Fi = 0.95 for both: 6.7085 x 0.95 = 6.3731 tonnes, reported as 6.4

Quantities are example numbers, taken as pure carbonate. The 0.95 is an example, not a default.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so the fuel and power lines of a furnace or kiln are on file. In the self-serve product it does not read carbonate purchases or lab tests, so Fi and the carbonate tonnes stay in your own records.

• Process CO2 for clay products without an assay
• Share of CO2 released in magnesia
• IPCC glass factors and cullet ratios
• How many digits process CO2 can carry

Sources: IPCC, 2006 Guidelines, Volume 3, Chapter 2: Mineral Industry Emissions

Last reviewed 2026-11-06. Quotes and figures are from the 2006 IPCC Guidelines, Volume 3, Chapter 2. The 2019 Refinement was not checked for this page; check it if a buyer names it.