How close should a ceramic unit's default estimate and its carbonate-by-carbonate estimate be under the Intergovernmental Panel on Climate Change guide?

The Intergovernmental Panel on Climate Change (IPCC) says estimates from different tiers can be compared and, with the same fraction calcined, will likely be similar in magnitude. It gives no tolerance. A big gap in carbon dioxide (CO2) usually means the default 10 percent carbonate in clay is not your clay.

What the guide says

In its quality checks for other process uses of carbonates, the guide says estimates from any tier can be compared with the other tiers, even though Tier 3 may count extra carbonate species. It adds: "Assuming that the same fraction of calcination achieved is used for all Tiers, the emissions estimated using the respective approaches will likely be similar in magnitude, considering that limestone and dolomite likely contribute the greatest percentage of emissions for these sources." It does not state a percentage band.

How to run the comparison

1. Default route: product tonnes x 1.1 (the guide's loss factor) gives clay tonnes; x 10 percent carbonate; x 0.44535, the 85 and 15 limestone and dolomite blend.
2. Carbonate route: assay or supplier analysis of the clay by carbonate species, plus any carbonate you add, each x its Table 2.1 factor.
3. Use the same fraction calcined in both, as the guide says. Compare the totals.

Reading a gap

• This is my reading; the guide's check is written for national tiers and gives no tolerance.
• Default much higher: your clay probably holds less than 10 percent carbonate. The assay will bring the figure down.
• Carbonate route higher: species or additives the default does not see. The guide says the default assumes only limestone and dolomite, so check the assay lists every species, such as magnesite or siderite.
• Close: the default may fit your clay. Keep the assay on file to show it.

600 tonnes of fired product, one clay, no additives

• Default: 600 x 1.1 = 660 tonnes of clay; x 10% = 66 tonnes of carbonate; x 0.44535 = 29.39 tonnes of CO2
• Assay says 4% calcite: 660 x 4% = 26.4 tonnes; x 0.43971 = 11.61 tonnes of CO2
• Ratio: 29.39 / 11.61 = 2.53. Most of the gap is the carbonate share, 10 against 4 percent.

Output tonnes and the 4% assay are example numbers.

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 clay assays or product weights into a process estimate, so both routes are worked from your own records.

• Process CO2 for clay products without an assay
• How uncertain ceramic process emissions are
• Clay carbonates beyond limestone and dolomite
• Known limestone and dolomite split

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.