A comparison of the greenhouse impacts of magnesium produced by electrolytic and pidgeon processes

With a focus on the global warming impact, this paper deals with the cradle-to-gate life cycle study of the following two practical production systems for producing magnesium ingots: (i) Magnesite ore is processed using the Australian Magnesium process to produce anhydrous magnesium chloride, which is then electrolysed to produce magnesium; and (ii) Dolomite ore is calcined to produce magnesium oxide, which is then thermally reduced with ferrosilicon using the Pidgeon process, based on the current practice used in China for magnesium production. The global warming impact of the ingots produced by the Australian Magnesium process is similar to 24.3 kg CO2-eq/kg of Mg ingot, assuming to HFC-134a is used as the blanketing gas, and electricity and steam are co-generated using Australian black coal. The impact of the magnesium ingots produced in China using the Pidgeon process is similar to 42 kg CO2-eq/kg Mg ingot. This value is based on the current usage of sulphur powder for blanketing molten magnesium while casting. The values of GHG impact for the two systems are discussed in light of energy consumption and process contributions.