How uncertain is a ceramic unit's process carbon dioxide figure under the Intergovernmental Panel on Climate Change guide, and what drives it?

Small if you measure, large if you assume. The Intergovernmental Panel on Climate Change (IPCC) puts weighing carbonates at 1 to 3 percent uncertainty, their chemical analysis at 1 to 3 percent, and a purity assumption at plus or minus 1 to 5 percent. A European reference quoted by the guide puts clay carbonate at 0 to over 30 percent.

The guide's numbers

• Emission factor: negligible uncertainty, if the activity data are collected correctly and the right factor is used, because it is a fixed chemical ratio.
• Weighing or proportioning the carbonates for an industry: 1 to 3 percent, if the carbonate is allocated to the right industry.
• Chemical analysis of carbonate content and identity: 1 to 3 percent.
• Assuming a purity where only carbonate rock data exist: plus or minus 1 to 5 percent.
• Using the Tier 1 or 2 default of 85 percent limestone and 15 percent dolomite: the guide says it varies with country circumstances, and gives no number.

Where the big uncertainty sits

The note to the 10 percent clay carbonate default says a European reference reports clay carbonate contents from 0 to over 30 percent. Against 1 to 3 percent for weighing, a guessed clay carbonate share swamps everything else. So the first record to improve is an assay of your own clay, not a finer weighbridge. That ordering is my reading.

Adding the errors

The guide does not combine these for a single unit. As a worst case, if weighing and analysis both sit 3 percent high, the carbonate tonnes are off by about 6 percent. That sum is mine; the guide's Volume 1 has its own way of combining uncertainties, which I did not check.

The unspecified line

The guide warns that national statistics with an other unspecified uses line raise uncertainty. The same warning fits a purchase ledger line such as limestone, miscellaneous. Keep carbonate bought for the kiln apart from carbonate bought for anything else. This is my reading.

Ten tonnes of limestone, three ways to be wrong

• Base: 10.0 x 0.43971 = 4.397 tonnes of carbon dioxide (CO2)
• Weighing 3% high: 4.397 x 1.03 = 4.529 tonnes
• Weighing and analysis both 3% high: 4.397 x 1.03 x 1.03 = 4.665 tonnes, 6.1% above base
• Purity assumed at 95% when the rock is 92%: 9.5 against 9.2 tonnes of carbonate, 3.3% too high

Quantities and the 92% purity 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 run clay assays or weigh carbonates; those records and their error bands are yours.

• Process CO2 for clay products without an assay
• Default against carbonate-by-carbonate check
• Is my lab CO2 factor within the IPCC range
• Fuel activity data uncertainty

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.