- Written by Dr Peter Edwards, Global Cement Magazine
Ordinary Portland Cement (OPC) is by far the most commonly produced type of cement, the world's second most consumed commodity after water. OPC production emits vast amounts of CO2 and meeting the world's current needs for OPC causes billions of tons of the gas to be emitted to the atmosphere every year. With rising environmental concerns about the effects of CO2 on the world's climate, cement manufacturers have made efforts to decrease fuel use, make efficiency savings and re-use 'waste' materials in the production of cement.
Ahead of the inaugural Future Cement Conference, which will be held in London, UK on 8 February 2011, Global Cement Magazine looks at the current proposals and solutions for reducing the CO2 output of the calcination step itself or eliminating it altogether.
Since being patented in 1824 by James Aspdin, OPC (CEMI)has become the world standard in cement production. The basic raw materials needed to produce OPC; limestone, sand and a fuel source, are available on every continent and as a result OPC is readily produced by manufacturers across the globe in an ever-increasing number of countries. The Global Cement Directory 2010 lists 1997 integrated cement plants in 137 countries, with a total combined cement capacity of 3132Mt/yr. Most of these produce OPC and economies of scale and the popularity of OPC have side-lined other types of cement into niche markets.
OPC is far from an ideal product in environmental terms, however. Not only does the production of OPC clinker require vast quantities of (often fossil) fuel in order to fire the kiln, but the chemical process of decarbonation carried out in the kiln emits almost 1t of CO2 for 1t of clinker produced. This means that cement production is a massive contributor to CO2 emissions. It is readily agreed by the industry that cement production accounts for 5-6% of all world CO2.
It is remarkable, given the high CO2 emissions and the intense pressure put on other industries to lower their CO2 emissions, that cement production is not considered in the same light either by national governments or the general public. Nonetheless, the industry is looking at ways to reduce CO2 emissions and there are many emerging processes that may offer significant gains.