Global warming impact of the magnesium produced in China using the Pidgeon process

摘要

China is the largest producer of magnesium in the world, and supplies currently 40-50% of the world demand for magnesium. The current growth in the demand for magnesium is primarily driven by automotive industry for light weighting automobiles to reduce emissions. Magnesium production in China is based on a thermal process, known as the Pidgeon process that was originally invented in Canada in the 1940s. The raw material used is dolomite, which is initially calcined, and the calcined dolomite is reduced using the Pidgeon process by supplying ferrosilicon and thermal energy to produce pure magnesium crowns. The magnesium crowns are then melted and cast as pure magnesium ingots, which are then exported from China to meet the growing world demand. With a focus on the global warming impact, a cradle-to-gate life cycle study is conducted using averaged data for magnesium production in China. Calculations show that the cradle-to-gate global warming impact of Chinese magnesium ingots is 42 kg CO_2 eq/kg Mg ingot, within an uncertain range of 37-47 kg CO_2 eq/kg Mg ingot. The value of impact for the magnesium produced in China is ～60% higher than the global warming impact of aluminium, a competing material that is also produced in China in abundance. The calculated impact for magnesium is discussed in the context of the future magnesium products value chain that may have a strong dependence on the magnesium produced in China.