The carbonate is decomposed by calcination or heating (burning) of minerals containing calcium and magnesium. The decomposition products are water, calcium oxide and the escaping carbon dioxide (CO₂). The calcination processes for magnesite and other metal oxides are analogous.

The process plays a central role in the production of cement and magnesium. Rotary kilns are mainly used in this process; a very special application of MgO production takes place in a fluidised bed kiln. (STYROMAG AG, Project Report)

The main challenge of the process is to reduce the very high primary energy consumption. The VWE approach to reduction includes burner and combustion chamber optimisation as well as support in fuel switching. Due to the use of substitute fuels, emissions of CO, NO_x, etc. also represent an important aspect, and CO₂emissions per se are also a key factor from the operator’s economic point of view.