Moving Towards Sustainable Germanium Sourcing Evaluated by Means of Life Cycle Assessment

Abstract

A 2015 Life Cycle Assessment (LCA) study on germanium included the sourcing from fly ashes from coal combustion and its recycling from photovoltaic production scrap. Germanium is also produced as a byproduct from zinc production, typically present at levels above 75 ppm in zinc ores, and this is the second globally most important primary source for germanium. This life cycle assessment study evaluates primary germanium from three zinc ore production systems. In total 15 life cycle indicators were calculated and economic allocation applying a 25% cut-off value is used as the baseline scenario. This allocation scenario is selected as it best fits the economic reality of germanium as byproduct from zinc production. A representative mix of the three germanium production systems as byproduct from zinc is created. Its global warming value is 852 kg CO2-eq/kg germanium crystals. This value is in the mid to lower range from other germanium sources, i.e., 5771 kg CO2-eq/kg germanium crystals for germanium sourced from coal and 280 kg CO2-eq/kg germanium crystals for germanium sourced from recycling. Mineral and fossil non-renewable resources depletion might be seen as a relevant indicator for germanium, given it is on the US and EU list of critical materials. However, resource depletion results differ by 6 orders of magnitude for different depletion indicator methods. All LCAs on germanium were critically reviewed per ISO standard 14040/44 and the reviewers concluded that results from the studies can be compared.