Geopolymer Institute

Up to 90% reduction of CO₂ Greenhouse Gas emission during cement manufacture

Professor J. Davidovits started working on CO₂ emissions mitigation as earlier as 1990, at PennState Materials Research Laboratory, USA. American Agencies (DOE and EPA) stated that this was not an important issue and both institutions declined to support research proposals.
In this section we develop:
a) Rock-based Geopolymer cements;
b) Fly ash-based Geopolymer cements

Ordinary cement, often called by its formal name of Portland cement, is a serious atmospheric pollutant. Studies have shown that one ton of carbon dioxide gas is released into the atmosphere for every ton of Portland cement which is made anywhere in the world. The only exceptions are so-called ‘blended cements’, using such ingredients as coal fly ash, where the CO₂ emissions are slightly suppressed, by a maximum of 10%-15%. There is no known technology to reduce carbon dioxide emissions of Portland cement any further.

European cement manufacturers are confronted with the EC CO₂ eco-tax proposal and are lobbying Brussel’s Administration. They claim that the eco-tax would have a negative effect on the competitiveness of the European cement industry. The planned CO₂ eco-tax on energy is likely to induce industries to move abroad. The representative of one of the world leading cement experts argues that ”(…) if Europe is the only one to adopt it [the eco-tax], it will be more profitable to install our factories in Algiers [North Africa], rather than in Marseille [France]. Freight costs would be equivalent to the increase in manufacturing costs (…)”. This statement does not reflect the true scope of the issue, which was addressed by J. Davidovits at the 5th GLOBAL WARMING International Conference (see «Global Warming Impact On the Cement and Aggregates Industries», in World Resource Review Vol. 6, N°2, 263-278, 1994) (see in LIBRARY the paper #5 Global Warming ). The burden would be shifted towards third world countries and international cement production would continue to grow.

Cement, (Portland cement), results from the calcination of limestone (calcium carbonate) at very high temperatures of approximately 1450-1500°C, and silico-aluminous material according to the reaction

5CaCO₃ + 2SiO₂ —> (3CaO,SiO₂) + (2CaO,SiO₂) + 5CO₂

this means that the manufacture of 1 metric tonne of cement generates 1 metric tonne of CO₂ greenhouse gas.

As time passes by, Portland cement manufacture increases CO₂ emissions, and, therefore, the predicted BaU (Business as Usual) values for future atmospheric CO₂ concentration should be corrected accordingly.

Assuming a 5% yearly increase, in year 2015 world cement CO₂ emissions could equal the 3,500 millions tonnes presently emitted by European (E.U.) industrial activities (industry + energy + transportation), or 65% of the present total U.S. CO₂ emissions . This illustrates the need for new technologies to be adapted to the economy of developing countries.

Estimated World Cement CO₂, Million Metric Tonnes (MT),
in year 1988, 2000 and 2015, after J. Davidovits (1990).
In 2015 World Cement CO₂ = total Europe or 67% of total USA