The world produces about 2.1 billion metric tons of cement every year and is the second most widely used substance on the planet after water. The amount of cement produced yearly weighs more than 5 times the cumulative weight of the entire living human population on the planet.
Cement starts out as limestone and clay which is pulverized and heated (usually via coal combustion) in kilns to 1,500 degrees Celsius. This process alone is responsible for 5% of global carbon dioxide emissions. It is estimated that total global carbon dioxide emissions are approaching 27 billion metric tons per year. Therefore, cement production is responsible for approximately 1.35 billion metric tons yearly. Moreover, that means that each metric ton of cement produced emits approximately 640 kilograms of carbon dioxide.
China’s consumption of concrete accounts for nearly 45% of the world’s total consumption. Roughly 14% of the world’s carbon dioxide emissions come from China. And due to China’s use of cheap, outdated kilns, the country’s cement plants are responsible for up to 8% of its total carbon dioxide output. In addition, cement production facilities in China are responsible for over 40% of the country’s total industrial particulate emissions.
Recycling concrete from demolition sites by pulverizing it and adding it to new cement can save transportation costs for removal by as much as 25 cents per ton per mile and landfill disposal costs as high as $100 per ton.
There was 1.3 billion metric tons of crude steel produced in 2007. That is more than 3 times the cumulative weight of the entire living human population on the planet. World steel production results in about 5% (1.35 billion metric tons) of the world’s yearly carbon dioxide emissions. That means that each ton of steel produced is responsible for over 1 ton of carbon dioxide.
China is responsible for about 34% of the world’s crude steel production and 47% of pig iron (raw iron) production.
About 75% of production energy is saved by recycling steel rather than refining from iron ore. Moreover, recycling one metric ton of steel saves about 1,100 kilograms of iron ore, 630 kilograms of coal, and 55 kilograms of limestone. Steel has long been the most recycled material on the planet, and in fact, nearly 95% of structural steel is of recycled origin.
Rainforest depletion accounts for 20 percent of the world's total carbon dioxide emissions. This is because 5.4 billion metric tons of carbon dioxide would have been photosynthesized into oxygen if those forests still existed.
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Recycling Concrete. Concrete Network. March, 2007.
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So Hard to See the Wood for the Trees. The Economist. December 22, 2007. Pp. 98.
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