Cement, the Unheralded Polluter


It is time again for the Green Building Festival in Toronto, and like last year, it is sponsored by St. Lawrence Cement. We did a rant last year at this time about why concrete isn't green and won't repeat it; instead we will note a column by David Adam in the Guardian.

"There were no climate change protesters waiting to jeer as the chief executives and other senior figures of one of the world's biggest industries gathered on Wednesday. Yet they represented a business that produces more than 5% of mankind's carbon dioxide emissions. And they were in Brussels to discuss climate change.

These chief executives deal in a more down-to-earth commodity: cement. It is the key ingredient in concrete, and one that is rapidly emerging as a major obstacle on the world's path to a low-carbon economy.

No company will make carbon-neutral cement any time soon. The manufacturing process depends on burning vast amounts of cheap coal to heat kilns to more than 1,500C. It also relies on the decomposition of limestone, a chemical change which frees carbon dioxide as a byproduct. So as demand for cement grows, for sewers, schools and hospitals as well as for luxury hotels and car parks, so will greenhouse gas emissions. Cement plants and factories across the world are projected to churn out almost 5bn tonnes of carbon dioxide annually by 2050 - 20 times as much as the government has pledged the entire UK will produce by that time."


Dimitri Papalexopoulos, managing director of Titan Cement, Athens, who attended the meeting, said: "No matter what you do, cement production will always release carbon dioxide. You can't change the chemistry, so we can't achieve spectacular cuts in emissions.

"Cement is needed to satisfy basic human needs, and there is no obvious substitute, so there is a trade-off between development and sustainability."

Concrete is the second most used product on the planet, after water, and almost half of it is produced in China. The booming Chinese economy has created such a demand for building materials that cement production there last year released 540m tonnes of carbon dioxide - just short of Britain's total output from all sources. Cement's weight and low value mean it is almost always made close to where it is needed, and China's demand helped it to overtake the US as the world's leading polluter last year.

Like the aviation industry, the expected rapid growth in cement production is at severe odds with calls to cut carbon emissions to tackle global warming. " ::Guardian

Treehugger has noted lots of ways of making eco-cement, Pollution eating concrete, and nano-engineering. But as the man said, "You can't change the chemistry" -we need concrete for a lot of things that can't be built with anything else, we should keep working to improve it, but we can't call it green.

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