Cement Stories: from Cambridge to Heidelberg

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    Saving the planet is a titanic task indeed, as we’ve learned through a steady flow of highly educational Hollywood epics featuring valiant superheroes. There is no lack of monsters to be defeated nor battles to be won. Luckily, the nifty and tenacious heroes are often able to come up with clever solutions even to seemingly impossible challenges.

    Marking yet another heroic triumph of human ingenuity, researchers from the University of Cambridge, Department of Engineering announced last week that they had invented the world’s first-ever zero-emissions cement. Construction being a notoriously dirty and resource-intensive business[1], any attempt to change the deplorable state of (building) affairs is more than welcome. The patent filed by Dr Cyrille Dunant, Dr Pippa Horton, and Professor Julian Allwood is, therefore, truly significant.

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    Let me refresh your cement-manufacturing knowledge, just in case. You start with a rock called limestone that you mine in a quarry. The rock is then crushed and heated up (or ‘sintered’) to about 1480°C. Some chemical and physical transformations later, what comes out of the furnace are large, glassy, red-hot cinders called ‘clinker’. Once you cool and grind the clinker, your cement powder is ready to mix into concrete. And here is a spoiler: a massive amount of CO2 is released throughout the process.

    Enter Cambridge Electric Cement, a virtuous recycling loop that not only eliminates the emissions of cement production but also saves raw materials. Starting with concrete waste from demolishing old buildings, the process isolates the old cement powder and uses it in steel recycling. As it turns out, the slag that floats on the melted steel, once cooled and ground up into powder, is virtually identical to the so desirable clinker.

    Magic, right? Even the scientists that discovered it seem baffled. Not to worry, they have now been rewarded with a new research grant of GBP 1.7m to try and figure out the underlying science behind the new process.

    It all sounds very encouraging, not least for us Swedish environmentalists who have been following the evolving cement drama on the beautiful island of Gotland closely.

    Perhaps not as revolutionary, yet just as uplifting is the path that HeidelbergCement (and its subsidiary Cementa) have chosen towards cleaning up the image of cement manufacturing. This week, the company announced that it had come one step closer to establishing a climate-positive cement plant in Sweden. Presenting the results of a pre-feasibility study for a CCS plant on Gotland, Cementa claims that this could potentially become one of Sweden’s most significant green industrial transformation projects.

    Is there any chance that the Cambridge invention could render Cementa’s costly and long-term plans obsolete then? Not according to Karin Comstedt Webb, Senior Vice President HeidelbergCement Sweden. “We see them as complementary solutions,” she says (in Swedish). “We are also working extensively on using, for example, slag from SSAB as a raw material. You can make concrete without cement for niche applications, but for large-scale construction, you will need limestone-based cement for a very long time,” she adds.

    It would appear that we need all these heroes, from Cambridge to Heidelberg and beyond, if we are to solve the cement puzzle and save the planet.

    [1] Worldwide, buildings are responsible for around 40 % of carbon emissions, 50 % of all extracted materials, 33 % of water consumption and 35 % of waste generated, according to IEA’s Global Status Report.

    Image courtesy of TK on Unsplash
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