Does adding lime or ground limestone to make masonry cement, or grinding imported clinker, add process carbon dioxide under the IPCC?

No. The Intergovernmental Panel on Climate Change (IPCC) says masonry cement adds no process carbon dioxide (CO2) at the cement plant: the guide says lime emissions should already sit under lime production, and ground limestone adds none. A plant grinding only imported clinker may be considered to have zero process CO2 of its own.

What the guide says

• There are no additional emissions associated with the production of masonry cement.
• Where masonry cement is made by adding lime to portland cement or its clinker, the emissions of the lime should already be accounted for under lime production.
• Adding ground limestone to portland cement or its clinker does not lead to additional emissions.
• Cement made entirely from imported clinker means the cement facility may be considered to have zero process related CO2 emissions.

Where the CO2 went

The guide says emissions from imported clinker are left out of the importing country's estimate because they were accounted for elsewhere, and clinker that is exported is counted where it was made. Table 2.2 gives masonry cement as two thirds portland cement, 64 percent clinker, and notes that this varies considerably.

My reading for one company: the process CO2 sits with the clinker maker. For a grinding unit it shows up as bought clinker in Scope 3, not as process CO2 in its own Scope 1. The unit's own Scope 1 and 2 are drying fuel and mill power. The Batangas page covers the imported clinker side.

What this does not say

It does not make bought lime or limestone free of emissions for the buyer. The guide only says the plant adds no further process CO2. Quarrying, grinding and transport of those inputs are separate lines, and the lime maker's kiln CO2 belongs in its own accounts.

A unit that grinds 50,000 tonnes of bought clinker

• Process CO2 at the unit from calcination: 0
• At the IPCC Tier 1 clinker factor, 50,000 x 0.52 = 26,000 tonnes of CO2 sit with the clinker bought
• Ask the supplier for its own figure per tonne of clinker, which replaces 0.52 if it is measured

Tonnes are an example. 0.52 is the guide's Tier 1 default for clinker, used only as a stand-in until the supplier gives a plant figure.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so kiln fuel and mill power are on file for each month. Clinker chemistry and cement type records stay with your plant laboratory and production log.

• Grinding unit CO2 per tonne
• Imported clinker in Scope 3, Batangas
• IPCC default factors for lime
• Free calculators

Sources: IPCC, 2006 Guidelines for National Greenhouse Gas Inventories, Volume 3, Chapter 2: Mineral Industry Emissions

Last reviewed 2026-11-05. Figures are from the 2006 IPCC Guidelines. Check whether your buyer or reporting scheme asks for a different edition of the IPCC guidance, and use your own plant measurements where you have them.