Environmental Impact of Cement

Environmental Impact

Cement is a fine gray powder used in the production of concrete and mortar. A total of 12 billion tons of concrete,1 or approximately 3 billion tons of cement,2 are used around the world each year. With each person consuming about 3 tons of cement annually, it is the second most used material on Earth after water.3 Cement is an essential component in basic infrastructural construction and is one of the most widely used building materials in the world. It is the world’s second largest growing economy led by China, which alone produced over 1.87 billion tons of cement in 2010 and is predicted to reach 2.1 billion tons in 2011,4 followed by India and the U.S.

The cement production process begins with the calcination of about 65% limestone (calcium carbonate – CaCO3), 22% silica oxide (SiO2), 6% aluminum oxide (Al2O3), and 3% iron oxide (Fe2O3) at a temperature of 1450°C. The heating process, which takes place in a large kiln, can be fueled by various materials, including fossil fuels like coal or industrial wastes like tires and liquid or solid waste oils. It makes up about 90% of the cement industry’s energy consumption. During this heating process, large amounts of CO2 are released as calcium carbonate is turned into calcium oxide, resulting in a hard material known as “clinker.” The clinker is ground into powder, and when mixed with water, sand, gravel, and other aggregates, the calcium silicate in the cement acts as a binder, fixing the ingredients together to form a hardened material. With the addition of gypsum, the clinker forms what we commonly know as Ordinary Portland Cement (OPC).

The most taxing process in cement production is the calcining process during which clinker is made. Cement production consumes a large amount of energy, requiring 60 to 130 kg of fuel and 110kWh of electricity to produce a single ton of cement.5 This accounts for nearly 2% of the world’s primary energy consumption, which is about 5% of the world’s industrial energy consumption.6

Cement production also produces a high amount of CO2, accounting for almost 5% of the world’s anthropogenic CO2 emissions.7 Approximately 337 billion tons of carbon have been emitted through cement production and the burning of fossil fuels since 1751.8 The amount of carbon released from cement production has more than doubled since the 1970s.9 A single ton of cement produces about 0.9 to 1.0 tons of CO2, with 50-55% derived from the chemical reaction during the calcination of limestone and 45-50% emitted by the combustion of fossil fuels and other materials during the calcining process.

Global Carbon Emissions Graph

Source: Boden, T.A., G. Marland, and R.J. Andres. 2010. Global, Regional, and National Fossil-Fuel CO2 Emissions. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi 10.3334/CDIAC/00001_V2010

1 “Greening Cement Production has a Big Role to Play in Reducing Greenhouse Gas Emissions.” 2010. United Nations Environment Programme, Global Resource Information Database, Sioux Falls, USA.

2 “Cement Statistics.” 2010. U.S. Geological Survey, Mineral Resources Program, USA.

3 Curry, Andrew. “New Chemistry, Less Energy Could Yield Greener Cement.” 2010. National Geographic News, USA.

4 “China Cement Association Predicts 12% Growth in 2011 for Cement Industry.” 2010. China Cement Net, China.

5 “Greening Cement Production has a Big Role to Play in Reducing Greenhouse Gas Emissions.” 2010. United Nations Environment Programme, Global Resource Information Database, Sioux Falls, USA.

6 Hendricks, C.A., Worrell, E., de Jager, D., Blok, K., and Riemer, P. “Emission Reduction of Greenhouse Gases from the Cement Industry.” 2004. IEA Greenhouse Gas R&D Programme, Netherlands.

7 “Greening Cement Production has a Big Role to Play in Reducing Greenhouse Gas Emissions.” 2010. United Nations Environment Programme, Global Resource Information Database, Sioux Falls, USA.

8 Boden, T.A., G. Marland, and R.J. Andres. “Global Fossil-Fuel CO2 Emissions.” 2010. Global, Regional, and National Fossil-Fuel CO2 Emissions. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi 10.3334/CDIAC/00001_V2010.

9 Boden, T.A., G. Marland, and R.J. Andres. “Global Fossil-Fuel CO2 Emissions.” 2010. Global, Regional, and National Fossil-Fuel CO2 Emissions. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi 10.3334/CDIAC/00001_V2010.