This methodology represents carbon dioxide (CO2) emissions associated with the calcination of carbonate minerals. The data and calculation methodology is sourced from the IPCC, as published in Volume 3, Chapter 2 - Mineral Industry Emissions of their 2006 IPCC Guidelines for National Greenhouse Gas Inventories. IPCC tier 1 and tier 2 approaches are represented by this methodology.
Limestone (CaCO3) and dolomite (CaMg(CO3)2) are basic raw materials having commercial applications in a number of industries. The heating of carbonate minerals to high temperatures ('calcining') produces metallic oxides as well as CO2 emissions. This methodology calculates CO2 emissions from the general consumption (through calcination) of carbonate minerals.
The methodology represents a simplified mass-balance approach, assuming (1) that all carbon (C) which enters the calcination process as a component of carbonate minerals is eventually emitted as CO2; and (2) that carbonate consumption is based entirely on mixtures of limestone and dolomite (more varied composition can be handled using the tier 3 approach - see below).
Quantities of CO2 are calculated by using conversion factors which represent the stoichiometry of the chemical processes, i.e. the known molecular mass ratio of the reactant carbonate material and the product CO2.
A default composition of 85% limestone and 15% dolomite is provided for cases where specific quantities are not known. In this case this methodology represents the IPCC tier 1 approach. Where individual quantities of limestone and dolomite are provided as additional activity data, the calculation represents the tier 2 approach.
CO2 conversion factors (stoichiometric ratios) for limestone and dolomite are sourced from the IPCC and can be found here.
As well as stoichiometric considerations, CO2 emissions associated with the calcining of carbonate minerals are also related to the purity of the carbonate. Four calculation scenarios are provided with this methodology representing different levels of carbonate purity for the limestone/dolomite mix:
- pure: 100% carbonate
- rock: 95% carbonate
- clay: 10% carbonate
- other: 100% carbonate
Activity data required
Greenhouse gas emissions are directly proportionate to the quantity (i.e. mass) of carbonate consumed, which therefore must be specified in order to make a calculation. In addition, values for the proportions of limestone and dolomite and the overall mixture purity can be specified optionally, if data are available.
Calculation and results
CO2 emissions are calculated by converting the bulk quantity into a quantity for pure carbonate (via the purity value), from which the respective quantities of limestone and dolomite are calculated (via their fractional concentrations). These quantities are finally converted into a quantity of CO2 emissions on the basis of their respective CO2 conversion factors
This emissions calculated by this methodology represent those attributable to the specified quantity of carbonate calcined.
Several other IPCC methodologies are available which represent carbonate calcination. These include the IPCC tier 3 methodology which corresponds to this methodology, as well as methodologies specific to soda ash consumption, as well as glass and cement production.