ETH Researchers Demonstrate CO2 Removal by Cement Plants

(CONNECT) In a study, ETH researchers have demonstrated how cement production can be used to remove CO2 from the atmosphere. According to a press release, the study by Vittoria Bolongaro and the group led by André Bardow, professor of energy and process systems engineering, demonstrates that cement production can be combined with calcium looping DAC. In calcium looping, the furnace used for calcination is powered by electricity rather than fossil fuels. At the same time, the CO2 produced during calcination can be captured directly, since it is not mixed with combustion exhaust gases, according to the press release.

The process can also capture CO2 from the ambient air (Direct Air Capture/DAC). When water is added, quicklime turns into slaked lime, which once again absorbs CO2 from the atmosphere and reverts to limestone. Through repeated cycles, additional CO2 can be removed from the atmosphere. The captured CO2 is then compressed and permanently stored underground.

"We were able to show that the technology's carbon footprint is net negative—in other words, that commercial calcium-looping DAC plants with CO2 storage remove more CO2 than they emit over their entire lifecycle," Bolongaro is quoted as saying.

To integrate DAC into existing cement plants, additional contact points are needed above all to capture CO2 from the ambient air. In addition, the calcining furnace must be powered by low-carbon or carbon-free energy.

The study's calculations are based on future scenarios through 2050 and assume significant progress in decarbonizing the electricity supply. In addition, key components—particularly indirectly heated electric calcining furnaces—are not yet in widespread industrial use. It therefore remains to be seen whether the process can be operated profitably. ETH researchers believe it is possible to reduce CO2 emissions from cement production by up to 78 percent by 2050. The results thus demonstrate, above all, the climate benefits of combining cement production with direct air capture. ce/ja