Gallium and germanium: Comparing demand and supply with consideration of electronic waste as a secondary source

Gallium and germanium are scarce elements in the earth's crust, typically occurring at very low concentrations below 19 ppm. The escalating demand for next-generation electronic and optoelectronic devices has intensified concerns regarding the depletion of natural reserves and emphasized the need to exploit alternative secondary sources, such as electronic waste (e-waste). Since the early 2000s, considerable progress has been made in developing selective materials and techniques for gallium and germanium recovery from e-waste, with a resurgence of research interest following the rapid expansion of artificial intelligence technologies after 2021. This review provides a critical analysis of e-waste, encompassing its generation, composition, collection, and recycling rates, with a particular focus on recent advancements in the recovery of gallium and germanium. It highlights current methodologies, process efficiencies, and material innovations. Furthermore, it discusses the key challenges in achieving reproducible and environmentally sustainable recovery processes and evaluates the associated economic and ecological implications. This work provides a comprehensive assessment of the potential of e-waste as a viable and strategic source of gallium and germanium for future research and large-scale industrial applications.