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The emissions start with mining raw materials such as limestone and crushing it to prepare for a process called calcination.

It happens at room temperature, without the need for fossil fuels or calcination - two of the main sources of the cement industry's CO2 emissions.

MFI nanosheets on Si wafer were then rubbed by cotton fabric to detach the seeds, followed by additional calcination under identical conditions to remove any organic contamination.

Therefore, said Black, it is possible to recover the whole of the chalk originally present before calcination, by adding a fixed alkali to the calcined chalk or quicklime.

The calcination, or roasting, is conducted at a low temperature in some form of reverberatory furnace.