Germanium (Ge) is chemically similar to its group neighbors Tin and Silicon. Like Silicon, Ge naturally reacts and forms complexes with Oxygen in nature. Unlike Silicon (ca. 270 ppm), Ge (ca 1.8 ppm) is much scarcer in the earth crust. Therefore, the market price of Ge is usually two orders of magnitude higher than that of Silicon, as shown in the following figure:
Figure: upper: Germanium price evolution from 2013 to 2015 around 1800 $ per kg (data extracted from U.S. Geological Survey, Mineral Commodity Summaries), and on the lower side the polysilicon spot price of around 13 $ per kg in the last two years.
Compared to Silicon, the production volume of Ge worldwide is relatively smaller. In 2011, about 118 tons of Ge were produced worldwide, which is about 3 orders of magnitude of the Silicon produced in the same year, mostly in China, Russia and United States. Ge is mainly recovered as a by-product from sphalerite zinc, or in Silver, lead, and copper ores, or even sometimes from fly ash of coal power plants. Total Germanium on the market is about 165 tons a year, 15% for PV wafering applications, (REF Roberts DOI: 10.1007/s11837-014-1267-6). Germanium has been classified as “critical material” by the European Union (https://ec.europa.eu/growth/sectors/raw-materials/specific-interest/critical_en) due to its supply risk as well as its economical importance. As well as ensuring a securer supply, Germanium recycling has environmental benefits. A lifecycle assessment has found that secondary Germanium production from PV production scrapes has 95% lower environmental impact compared with primary production. (Robertz, B., Verhelle, J. & Schurmans, M. JOM (2015) 67: 412. doi:10.1007/s11837-014-1267-6). In order to produce Ge wafers for high end solar cells (see later) in a cost-effective way, Ge has to be recycled from all relevant waste streams. Even aside from the cost benefits, the increasing EH&S (Environment, Health and Safety) awareness of the materials processing industry further consists on a strong driver for recycling waste streams and minimizing emissions to the environment.