CO2 Emissions From Cement Production
Cement is an important construction ingredient produced in virtually all countries. Carbon dioxide (CO2) is a by-
product of a chemical conversion process used in the production of clinker, a component of cement, in which
limestone (CaCO3) is converted to lime (CaO). CO2 is also emitted during cement production by fossil fuel
combustion and is accounted for elsewhere. However, the CO2 from fossil fuels is accounted for elsewhere in
emission estimates for fossil fuels. The Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories
(IPCC Guidelines) provide a general approach to estimate CO2 emissions from clinker production, in which the
amount of clinker produced is multiplied by the clinker emission factor.
The IPCC Guidelines recommend two possible methods for calculating the clinker emission factor. The first
method is to use the IPCC default value for the fraction of lime in clinker. The second method is to calculate the
average lime concentration in clinker by collecting data on clinker production and lime fraction by type. The
IPCC Guidelines state that the difference between the default value and a value based on collected data is
expected to be small. If clinker production data are not available, it is recommended that countries back-calculate
clinker production from the cement data while applying a correction factor for clinker imports/exports. Once an
estimate has been derived, emissions can be estimated by means of the clinker emission factor.
The IPCC recommends using clinker data, rather than cement data, to estimate CO2 emissions because CO2 is
emitted during clinker production and not during cement production. If clinker is traded internationally, using
cement production data results in a biased emissions estimate because the cement could potentially be produced
from clinker that was made in another country. Although clinker data are the preferred data source, cement data
may be more readily available in some countries. In this case, the recommended approach is to estimate the
fraction of clinker in the cement and back-calculate clinker production.
Quality assurance and quality control activities should be implemented at several stages in the emission
estimation process. At the plant level, key activities include internal quality control on production data and
emission factors, as well as documenting data and methods for reviewers. The inventory agency must ensure the
accuracy of plant submissions as well as the compiled inventory. It is also responsible for providing
documentation and sufficient information to the United Nations Framework Convention on Climate Change
(UNFCCC). One or more types of external review may also be appropriate.