Cement Plants

Cement is the most abundant manufactured material in the world and used in concrete as one of the world's most commonly used building materials. Globally, over 150 countries produce cement, or "clinker", the primary input to cement. In 2005, the United States used 124 million metric tons (MMt). Of that total 93 million tons of Portland cement and about 5 million tons of masonry cement were produced at 113 plants in 37 States. About 5 billion cubic yards of concrete are used each year; annual production is about two tons per person on the planet. Concrete consists of cement, water, and aggregates--gravel, sand, crushed stone, or other materials. It is used to form the foundation of virtually every building in addition to being used for sidewalks, curbs, building blocks, mortar for masonry, and numerous other construction components.

Significant quantities of carbon dioxide (CO₂) are released through the combustion of fuels in the kiln, and during the production of cement (clinker). Primary combustion fuels used in North America are coal (67%) and petroleum coke (14%). However, many kilns also use waste materials as additional fuel sources (15%). In a kiln, calcium carbonate (CaCO3) is heated to 1200-1450°C to induce a series of chemical reactions and partial melting (calcination and sintering) that results in the conversion of carbonates to oxides and production of clinker. CO₂ is released as a by-product of the chemical reactions. CO₂ emitted from the chemical process of cement production represents one of the largest sources of industrial CO₂ emissions in the United States.

In 2004, CO₂ emissions from calcination during cement production were estimated to be 45.6 TgCO₂ (45.6 million metric tons) (EPA, 2006). Using the reported combustion related emissions of 36 TgCO₂ in 2001 from U.S. cement industry (computed in Hanle et al. 2006) and the increase in domestic clinker production from 2001 to 2004, the combustion related emission in 2004 is roughly estimated at approximately 40 TgCO₂. In 2004, total emissions of CO₂ from U.S. would total approximately 85-86 TgCO₂. In 2004, the total estimated CO₂ emissions from all U.S. cement kilns inventoried in NatCarb totals 87.6 million metric tons. The difference in the top down and individual kiln computations is probably due to inability to account for facility specific and secondary fuel sources used in individual kilns. Adding the estimated emission from cement kilns in Canada, the total estimated CO₂ emissions from both combustion and non-combustion sources inventoried in NatCarb is 104.8 million metric tons (104.8 TgCO₂)

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Explanation of our methodology

Additional Sources on Cement Production and Greenhouse Gas Emissions

California Climate Action Registry , Cement Report Protocol, 17 p.

Environment Canada, 2004, A guidance manual for estimating greenhouse gas emissions from fuel combustion and process-related sources for cement production, 82 p.

Hanle, L. J., K. R. Jayaraman, and J. S. Smith, 2006, CO2 Emissions Profile of the U.S. Cement Industry: U.S. Environmental Protection Agency, 05-03-2006, 14 p.

Portland Cement Association

US Environmental Protection Agency, 2006, US Emissions Inventory 2006, Inventory of U.S. Greenhouse Gas Emissions and Sinks : 1990-2004 (April 2006), USEPA #430-R-06-002, 459 p.

U.S. Geological Survey, 2006, Cement Statistics and Information

van Oss, H. G., 2005, Background Facts and Issues Concerning Cement and Cement Data: U.S. Geological Survey, Open-File Report 2005-1152, 88 p.

The Cement CO2 Protocol: CO2 Accounting and Reporting Standard for the Cement Industry, Version 2.0, June 2005, The Cement Sustainability Initiative, World Business Council for Sustainable Development, 62 p.