By 2050, cement factories are expected to emit five billion tons of carbon dioxide annually, according to The Guardian.
As high pollution emitters, transportation vehicles have traditionally drawn ire from environmentalists. But cement? A little known fact, cement is considered to be one of the biggest contributors of carbon emissions in the world. How so?
The manufacturing of conventional cement is a highly energy intensive process. Cement is manufactured by heating limestone with clay and then pulverizing it into a fine mixture. The procedure not only depends upon the decomposition of limestone, but involves burning huge amounts of coal to heat kilns to more than 1,500 degrees centigrade, both steps that release a significant amount of carbon into the air. Currently, cement factories are the world’s second largest emitters of carbon dioxide, behind oil refineries and power plants. The most commonly used variety across the world is Portland cement, so named for its origins in Portland in Dorset, England, where it was first made in the 19th century. Around 2.5 billion tons of Portland cement is produced annually and it is responsible for 5% of global emissions.
Enter green cement. The concept of green cement evolved with the discovery of geopolymer cement in the 1950s by Ukrainian scientist Victor Glukhovsky. Geopolymer cement is made using alumino-silicates instead of the more harmful calcium oxide used in Portland cement. These silicates are also sourced from industrial waste materials like fly ash, which makes it a viable green resource.
In recent times, various companies have been experimenting with the composition of cement in order to make it more eco-friendly. One of the earliest companies to develop green cement for the mass market, California-based Calera, is perfecting a different kind of cement that is made from waste carbon dioxide. Calera scientists capture the smoky air from areas populated by coal-fired industrial plants. The carbon dioxide molecules are separated and mixed with briny water to create a blend similar to limestone, but crucially, without the use of high heat. “For every ton of cement we make, we are sequestering half a ton of CO2,” Calera founder Brent Constantz explains to the Scientific American.
Wired magazine selected Calera’s product as the number
one green technology breakthrough in 2008.
Calera is not alone. A Georgia-based firm, Sriya Green Materials, claims that its manufacturing processes slashes the time taken for production from 40 minutes to 40 seconds. Sriya employs heating at much lower temperatures and uses simple materials that also reduce equipment costs.
Yet, as with all new green technologies, there are practicalities that must be sorted out. Despite all its advantages, the traditional cement market is not exactly embracing the concept of green cement. Regulations, which are based on conventional silicon-based cement, must be adjusted. Large cement companies are worried about low profit margins and the financial risks. The primary fear factor is that green cement typically costs 62% more per cubic meter than Portland cement.
However, there are signs of change in the air, pointing to an increased awareness of the problem. In early 2003, the cement industry promised a 10% carbon emission reduction per ton of cement and a 60% cutback of cement kiln dust disposed in the air by 2020. Last year, The Cement Sustainability Initiative, a coalition that represents 18 members of the cement industry who account for 30% of the world’s cement, agreed to aim for a 25% emission reduction. Recently, the Environmental Protection Agency (EPA) imposed new regulations on cement manufacturing companies in the U.S. to slash mercury emissions by 92% and sulphur dioxide by 78%.
Hopefully, changing standards such as these will enable the idea of green cement to gain traction. With rapidly expanding markets like China and India requiring more and more cement, there is a need to promote a more eco-friendly building material. Now, just as we have green cars and factories, we can cement a green future as well.