Green Cement - Tackling an Environmental Culprit
Cement is the most consumed material on the planet after water. Every year 2.5 billion tons are produced and global production is expected to reach 5 billion tons by 2050. China alone makes and uses 45 percent of global output. Ukraine’s production doubles every four years.
But the cement industry accounts for 5 percent of the world’s man-made carbon dioxide emissions, third in line behind fossil fuel combustion and deforestation. Most of these emissions take place when the raw material that makes up cement, limestone, clay and sand, is heated to about 1,480 C in huge cylindrical steel rotary kilns lined with firebrick. Not only does a chemical reaction drive out carbon dioxide during the heating process, but the greenhouse gas is also released when fossil fuels are burned to heat up the kilns themselves.
With this in mind, a number of companies are building more efficient cement-producing facilities. Some, for instance, are heating their kilns with carbon-neutral fuels instead of coal. Ten percent of the fuel used by Lafarge, the world’s second largest cement manufacturer by mass, is biomass and alternative fuels. The company has reduced its emissions from 347 kilograms of CO2 per ton of cement in 1990 to 297 in 2006, according to the International Herald Tribune.
Between 1990 and 2006, Canada’s cement manufacturers have improved the energy efficiency of their production operations by 11 % per ton of cement, and have reduced greenhouse gas emissions intensity of its production by 6.4%, according to the Cement Association of Canada’s 2008 Sustainability Report.
The Vancouver-based EcoSmart Foundation, a one time initiative of the GLOBE Foundation, has developed a cement product that significantly reduces greenhouse gas emissions. EcoSmart Concrete replaces up to 80 percent of cement with supplementary materials, such as fly-ash from coal burning power stations.
The result, according to EcoSmart, is material able to resist salt corrosion in extreme marine environments. Today construction crews are using fly ash in the concrete mix of what will be the world’s tallest building, the Burj Dubai, set to be completed in the United Arab Emirates in 2009.
There are also geopolymer materials which, according to their manufacturers, spew out less than half of the emissions achieved by the most efficient producers. One such company, Zeobond, started the commercialization of a geopolymer concrete called E-Crete. The material has the same starting materials as regular cement but the chemical activation steps of geopolymerisation changes the nature of the final product.
This concrete is being used in 18 local councils and private individuals in Victoria, Australia, in small, non-safety-critical projects, such as paving, driveways and barriers. The company hopes to test its E-Crete panels in one-storey buildings this year.
Zeobond’s products are up to 15 percent more expensive than regular cement. One reason is that limestone is cheap and readily available around the world. Another is a question of scale - everyone has been using cement since it was developed in England during the 19th century, and the validation process for new construction material is not as rigorous in Australia as it is in say, Europe, where it takes a long time to gain regulatory approval.
Governments want to make sure that if they’re going to spend millions of dollars on a bridge or a dam, the projects have to last at least 100 years. A product coming out on the market today cannot prove its long-term durability.
And then there is Halifax-based Carbon Sense Solutions. Typically a factory makes a reusable mold to form the walls, panels or beams of a building which is then shipped to a construction site. The environmental consulting firm says it has found a way to pump the carbon dioxide gases emitted by the factory during this production stage into the concrete itself. A pilot program is under way in rural Nova Scotia.
Cement producers are also getting together to find common solutions. Several of them are working on sustainable development through an environmental program called the Cement Sustainability Initiative (CSI), sponsored in part by the World Business Council on Sustainable Development. One CSI project suggests that concrete should be mixed with less cement to reduce emissions. Another that better insulation should be installed in cement buildings to increase energy efficiency. These conventional methods were found, among others, to yield possible reductions of 30 percent in carbon dioxide by 2020.
In other words, reducing carbon dioxide emissions to produce ’green cement’ is possible but will be done essentially through energy improvements and the use of alternative materials or fuels. Any new product launched on the market to replace or change the cement used to make concrete faces harsh scrutiny from industry players who want a flawless product that doesn’t break the bank.
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