Will Using Green Cement End Global Warming?
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What can be done to combat climate change?
Most scientists believe that the earth’s climate is warming, because automobiles and various smokestack industries are pumping more carbon into the atmosphere than the planet’s ecosystem can absorb, potentially leading to the calamities of climate change about which folks have been hearing for many years. Most of the change appears to be in the Arctic and Antarctic, where ice is melting at an alarming rate. For those who don’t believe the earth’s climate is warming, look there!
Fortunately many people, countries and companies throughout the world are trying to reduce carbon emissions. One major way to accomplish this task is to produce “green” cement. Please read further and find out how using green cement could greatly reduce humankind’s “carbon footprint” and perhaps help save the planet in the process.
What Is Cement?
The Romans invented concrete and built their marvelous empire with it, using a mixture of lime, volcanic ash and chunks of stone to construct immense buildings such as the Pantheon and Colosseum. These days, the primary ingredient in concrete is cement, commonly known as Portland cement, which is produced by burning limestone, mostly calcium carbonate and loaded with CO2, to which clay is added, and then water, sand and aggregate to produce concrete, which is inexpensive, pourable and dries as hard as a rock. Concrete is essentially artificial stone.
According to the article “Green Cement” in the December 2011 issue of Smithsonian magazine, in 2010 the world produced about 3.6 billion tons of cement, and that amount could increase by a billion tons before 2050. Interestingly, the only substance the world uses more than concrete, in total volume, is water!
Why Is Cement Dirty?
As useful and cheap as cement is, it has environmental drawbacks. Fossil fuels are used to burn the limestone at 2,600 degrees Fahrenheit, and this process releases large amounts of CO2 into the atmosphere. Cement production accounts for five percent of the world’s human-produced carbon dioxide emissions; only automobiles and smokestack industries used to make electricity and steel release more greenhouse gases in the United States and China, the world’s largest producers of cement.
Per an article entitled “Cement from CO2: A Concrete Cure for Global Warming?” in the August 2008 issue of Scientific American, making a ton of cement results in the emission of roughly one ton of CO2.
What is Green Cement?
The Smithsonian story mentioned above stated that since 2004 companies throughout the world have been trying to make Portland cement more environmentally friendly. Producers have added steel byproducts, such as slag; coal residues, such as fly ash and other materials to try to bulk up concrete, thereby requiring less Portland cement in the mixture. They’ve also used mineral additives, trying to reduce the temperature needed to prepare the materials, thus reducing the CO2 spewed when heating the limestone. Unfortunately, compounding the problem, nobody understands exactly how Portland cement works!
A potential breakthrough came when researchers at a company named Novacem, located in the United Kingdom, began using magnesium oxide instead of limestone to produce the primary ingredient in cement. Magnesium oxide can be prepared for cement by heating it to 1,300 degrees Fahrenheit, half of what is required for limestone. But something else had to be added to the magnesium oxide to make the cement harden, so magnesium silicates have been put in. These carbon-free compounds are made from talc, serpentine, olivine and other minerals, all of which are quite plentiful and found throughout the world. Otherwise, Novacem’s process is kept a secret.
Of some importance, Novacem’s cement is pure white, rather than gray like Portland cement. White cement can be colored, enhancing its possibilities, particularly when used to make houses and office buildings.
Available on the Internet, the company overview for Novacem claims that for every ton of Portland cement replaced by Novacem’s, emissions will be reduced by 850 kilograms. But the jury is still out on whether Novacem’s cement will be as strong as Portland cement. If it isn’t, few construction companies will use it.
Recycling CO2 to Make Green Cement
Calera, a company in California, has an innovative procedure, perhaps the dream of recyclers. It uses CO2 emitted from a power plant and mixes it with seawater to create carbonates used to make cement. These carbonates can be added to Portland cement to replace some or all of the limestone. Using similar technology, the Chinese plan to build a cement plant next to a coal mine in Inner Mongolia, where they hope to use the carbon emissions to produce cement.
Researchers at Louisiana Tech University are doing away with limestone entirely, using instead a paste called geopolymer, which is made of fly ash, sodium hydroxide and potassium hydroxide.
Calix, an Australian company, makes cement by using superheated steam, which modifies the cement particles and make them purer and more chemically reactive. The process also makes it easier to separate the carbon dioxide and keep it from escaping into the atmosphere.
The stakes are high to produce green cement, for cement production is a $170 billion-dollar per year industry. Make it, and many construction companies will come. Naturally the stakes are also very high for the planet to significantly reduce its output of greenhouse gases. It appears the technology is emerging. It will simply take time to find the best “green” cement.
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