"Concrete is the most ubiquitous man-made building material on the planet, but making it generates massive amounts of CO2 emissions. Companies are experimenting with ways to green the process, from slashing the use of limestone to capturing the carbon generated when it’s burned."
"Bernd Soboll’s favorite spot at his workplace — a cement plant 30 miles north of Hamburg — is an open-air platform almost 300 feet high. From here, the construction manager can see all the steps that go into making the material that has made the modern world possible — its roads, bridges, airports, houses, and skyscrapers.
Near the horizon, a bucket wheel excavator churns through a limestone quarry. From there, chalk is transported to a drying plant, then mixed and ground into a fine powder. This so-called “raw meal” is then pumped up the large tower that holds the viewing platform. While falling back down in large pipes, the chalk is heated until it enters a rotating kiln that reaches 1,500 degrees Celsius.
Cement — a gray powder that acts as a glue when mixed with sand, gravel, and water — is the key ingredient for concrete, the world’s most widely used man-made material. It’s also one of its most problematic, climate-wise. Since the early days of the industrial revolution, coal and other fossil fuels have been used to heat cement kilns to 1,500 degrees. And when limestone is incinerated to form clinker, the precursor to cement, it releases carbon dioxide into the atmosphere. Thousands of plants around the world produce some 4 billion tons of cement a year, generating between 5 and 8 percent of global greenhouse gas emissions, a share larger than that of the entire aviation industry."
Christian Schwägerl reports for Yale Environment 360 October 29, 2024.
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