7.4.2.2 Magnesium

Magnesium, produced in low volumes, is very energy intensive. Its growth rate has been high due to increasing use of this lightweight metal in the transport industry. SF₆ is quite commonly used as cover gas for casting the primary metal into ingots and for die casting magnesium. Estimates of global SF₆ emissions from these sources in 2000 range from about 9 MtCO₂-eq (2.4 MtC-eq) (US EPA, 2006a), to about 20 MtCO₂-eq (5.5 MtC-eq) (EDGAR, 2005). The later value is about equal to energy related emissions from the production of magnesium. Harnisch and Schwarz (2003) found that the majority of these emissions can be abated for <1.2 US$/tCO₂-eq (<4.4 US$/tC-eq) by using SO₂, the traditional cover gas, which is toxic and corrosive, or using more advanced fluorinated cover gases with low GWPs. US EPA (2006a) report similar results. Significant parts of the global magnesium industry located in Russia and China still use SO₂ as a cover gas. The International Magnesium Association, which represented about half of global magnesium production in 2002, has committed its member companies to phasing out SF₆ use by 2011 (US EPA, 2006a).

7.4.2.3 Total emissions and reduction potentials

Table 7.7 gives the lower bounds for key emission sources in the non-ferrous metal industry. Total annual GHG gas emissions from the non-ferrous metal industry were at least 500 MtCO₂-eq (140 MtC-eq) in 2000. The GHG abatement options for the production of non-ferrous metals other than aluminium are still fairly uncertain. In the past, these industries have been considered too small or too complex regarding raw materials, production technologies and product qualities, to be systematically assessed for reduction options.

Table 7.7: Greenhouse-gas emission from production of various non-ferrous metals