Use of industrial waste to produce carbon neutral alternatives

Cement production weighs heavily on our climate: about 8% of global annual carbon dioxide emissions can be attributed to this process. However, the demand for cement continues to increase. A team of geoscientists from the Martin Luther University Halle-Wittenberg (MLU) has found a way to produce alternatives that are more environmentally friendly and sustainable. In the newspaper Construction and construction materials they describe how industrial residues can be used to produce high-quality, climate-friendly materials.

The basic raw material for cement is limestone, which is converted into cement clinker in large furnaces. The impact of this process on the environment is disastrous: "One tonne of carbon dioxide is emitted during the production of cement for every tonne of limestone. Most of this is emitted by the limestone itself, "says Professor Herbert Pöllmann, a geoscientist at MLU. Replacing limestone in cement production would generate enormous savings potential, adds the researcher. However, the material produced should have the same beneficial properties as traditional cement.

In their search for alternative raw materials, Halle researchers discovered two types of industrial waste: the residual materials from the production of kaolin and aluminum. "I do not really like the term industrial waste, it's actually industrial waste that can still be used very efficiently, for example to produce alternative forms of cement," Pöllmann says. For the new study, his team tested different mixing ratios and analyzed the physical properties of the newly produced cements. The study showed that both industrial residues can be used to produce cements with the same properties as conventional mixtures.

The advantage of the two residual materials that MLU mineralogists have investigated is that they do not contain carbon dioxide that can be released during further processing. "And you can use them to produce large quantities of cement that has great properties," says Pöllmann. In the new study, he and his team also describe in detail the mixing ratios and production steps of more environmentally friendly cements. According to the researcher, producers could either switch to more climate-friendly materials or produce cement mixes that use lower limescale content and are therefore more climate friendly.

However, the process has its limitations: "There is not enough industrial waste to cover global demand for cement," Pöllmann said. Therefore, his team is also looking for suitable natural products, such as volcanic ash or various mineral resources that have not yet been used industrially and do not emit carbon dioxide, for example various types of clays.

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Martin Luther University Halle-Wittenberg