My steel or sugar mill burns its own lime: do I count that kiln, and can I subtract the carbon dioxide the lime takes back up?

Count it. The Intergovernmental Panel on Climate Change (IPCC) says all lime production counts, sold or not, including lime a steel or sugar mill burns for its own use. Carbon dioxide (CO2) the lime later takes back may be reported only where proven, as a separate removal in the year it happens.

What counts

The IPCC says all lime production is reported as lime production, whether it is a marketed product or a non-marketed reagent. It names metallurgy, pulp and paper, sugar refining, precipitated calcium carbonate and water softeners as places to look, and says many plants making steel, soda ash, calcium carbide, magnesia and magnesium metal, plus copper smelters and sugar mills, make lime and may not report it. Leaving it out can understate national lime by a factor of two or more.

In a company inventory the same kiln's CO2 is process emissions from making a material, which the Greenhouse Gas (GHG) Protocol Corporate Standard puts in Scope 1, together with the fuel the kiln burns.

Taking CO2 back is a separate line

• Hydrated lime used for water softening re-forms calcium carbonate, so the CO2 is taken back. Precipitated calcium carbonate for paper is made by reacting hydrated lime with CO2. In sugar refining, excess lime is removed by carbonation.
• The IPCC allows such recarbonation to be reported only where proven and validated methods are used, under Other.
• Report the emissions and the removals separately. Reporting only the net figure is not good practice, and a removal is reported only in the year it happens.
• For sugar mills, lime-making emissions go under lime production and the removals under food and beverages.

Lime mortar is left out

Lime mortars in buildings slowly absorb CO2 over months to decades. The IPCC says that is too uncertain to count and is not good practice to include.

What to keep

• Limestone or dolomite fed, with the lab assay, and fuel bought for the kiln.
• Tonnes of lime made, whether it all stays inside the plant or not.
• For any recarbonation claim, the method, the tonnes of CO2 taken back and the year.

A sugar mill kiln making 3,000 tonnes of lime a year

• Process CO2 at the IPCC default of 0.75: 3,000 x 0.75 = 2,250 tonnes
• If the mill can prove 600 tonnes taken back in carbonation, report emissions of 2,250 and a removal of 600
• Not a single net figure of 1,650

The 3,000 tonnes and the 600 tonnes are example numbers. Fuel for the kiln is added separately.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so the kiln's fuel is on file. Lime tonnes, the lab assay and any recarbonation figures are yours to keep beside them.

• Carbon calculators
• Quicklime kiln: CO2 per tonne
• Which limestone uses release carbon dioxide
• Process CO2 from limestone calcination

Sources: IPCC, 2006 Guidelines for National Greenhouse Gas Inventories, Volume 3, Chapter 2: Mineral Industry Emissions, GHG Protocol, Corporate Accounting and Reporting Standard

Last reviewed 2026-11-04. The 2006 Guidelines are written for national inventories. A plant's own lab assay, production log and fuel invoices replace these defaults wherever you have them.