# What default carbon dioxide factor does the Intergovernmental Panel on Climate Change give for lime, and does it change with the type of lime?

Canonical: https://senseible.earth/answers/ipcc-lime-default-emission-factors-by-lime-type

The Intergovernmental Panel on Climate Change (IPCC) 2006 Guidelines give 0.75 tonnes of carbon dioxide (CO2) per tonne of lime as the Tier 1 default, from an assumed 85% high-calcium and 15% dolomitic mix. By type: high-calcium 0.75, dolomitic 0.86 or 0.77, hydraulic 0.59.

## The three lime types in the table

- High-calcium lime: 0.785 tonnes of CO2 per tonne of calcium oxide (CaO), times a default CaO content of 0.95 (range 93 to 98%), gives 0.75.
- Dolomitic lime: 0.913 per tonne of calcium magnesium oxide, times 0.95 or 0.85, gives 0.86 or 0.77. The guide suggests the higher value for developed countries and the lower for developing ones.
- Hydraulic lime: 0.785 times a default 0.75 CaO content (range 65 to 92%, counting CaO in silicate phases) gives 0.59.

## Where the single 0.75 comes from

With no data on lime types, assume 85% high-calcium and 15% dolomitic: 0.85 x 0.75 + 0.15 x 0.77 = 0.6375 + 0.1155 = 0.75 tonnes of CO2 per tonne of lime. Hydraulic lime is assumed zero unless you know otherwise.

## Two corrections in the guide

- Hydrated lime: multiply production by 1 minus (share hydrated x water content). The defaults are 0.10 and 0.28, which gives 0.97. With no data at Tier 1, assume no hydrated lime.
- Lime kiln dust: Tier 1 needs no correction; Tier 2 and Tier 3 do. See the page on lime kiln dust for rotary and shaft kilns.

## Use your own assay instead of the default

At Tier 2 the factor is 0.785 times the CaO content of your lime from a lab assay, so a lime at 88% CaO is 0.69, not 0.75. The factor covers only the CO2 released from the stone. Kiln fuel is a separate line, added from your fuel invoices.

## A kiln making 5,000 tonnes of high-calcium lime a year

- Tier 1 default: 5,000 x 0.75 = 3,750 tonnes of CO2
- With a lab assay of 88% CaO: 5,000 x 0.785 x 0.88 = 3,454 tonnes
- The default overstates this kiln by about 296 tonnes

Production and the 88% assay are example numbers. Use your own production log and lab report.

## What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so the kiln's fuel and power are on file. Process CO2 from the stone comes from your lab assay and production log, which you keep beside them.

- [Carbon calculators](https://senseible.earth/calculators)
- [Quicklime kiln: CO2 per tonne](https://senseible.earth/answers/quicklime-kiln-co2-per-tonne)
- [Process CO2 from limestone calcination](https://senseible.earth/answers/process-co2-from-limestone-calcination)
- [Jodhpur lime kilns and petcoke](https://senseible.earth/answers/jodhpur-lime-kiln-units-petcoke-carbon)

Sources: [IPCC, 2006 Guidelines for National Greenhouse Gas Inventories, Volume 3, Chapter 2: Mineral Industry Emissions](https://www.ipcc-nggip.iges.or.jp/public/2006gl/pdf/3_Volume3/V3_2_Ch2_Mineral_Industry.pdf)

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.