Reducing Global Carbon Dioxide Emissions

Cement Manufacture and CO2 Emissions

The construction sector is a major contributor to global carbon dioxide emissions. Though this is well known, it appears difficult to reduce the scale of construction activities, especially as it is a established route to bring about more equitable conditions in developing countries like India as against developed countries.

In the manufacture of Portland cement, limestone and  key inputs like clay are heated together in huge kilns to very high temperatures (approx. 1,450 degrees C), so that the components fuse without melting to give cement clinker. This part of the process releases the most amount of CO2. The carbon dioxide comes both from the burning of the fuel needed to create that temperature and also due to the breakdown of limestone into calcium oxide and carbon dioxide. The former process accounts for 40% of CO2 emissions while, the latter part accounts for 60% of the CO2 emissions in manufacture of cement. The best thing to do would be to substitute CO2-intensive clinker with one of less CO2 emissions.

Currently in India, fly ash which is a waste bye-product in the burning of coal for producing energy, is used in the manufacture of blended cement or Portland pozzolana cement. However, this is used in lower proportions and only where available so, is ineffective in reducing emissions to a more reasonable level.

One method of effectively reducing global carbon dioxide emissions is the use of Limestone Calcined Clay Cement or the LC3 technology. A research collaboration between India and Switzerland on a new cement material that can reduce carbon dioxide emissions in the manufacturing process is set to take off into implementation.