• Making cement results in high levels of CO2 output.
• Cement production is the third ranking producer of anthropogenic (man-made) CO2 in the world after transport and energy generation.
• 4 - 5% of the worldwide total of CO2 emissions is caused by cement production.
• CO2 is produced at two points during cement production :
- the first is as a byproduct of burning of fossil fuels, primarily coal, to generate the heat necessary to drive the cement-making process
- the second from the thermal decomposition of calcium carbonate in the process of producing cement clinker.
CaCO3 (limestone) + heat -> CaO (lime) + CO2
• Production of one tonne of cement results in 780 kg of CO2
• Of the total CO2 output, 30% derives from the use of energy and 70% results from decarbonation
• Important to realise is that although 5% of the worldwide generation of CO2 is due to cement production, that level of output also reflects the unique and universal importance of concrete throughout the construction industry.