Daniel Wüthrich

Fossil fuel dependency accelerates climate change, leading to more extreme weather events and consequently causing food insecurity, economic instability, and geopolitical conflicts. Currently, renewable energy sources have the potential to replace fossil fuels, thus reducing global warming impacts. However, this transition is threatened by the reliance on imported critical raw materials; these are extracted through unsustainable and environmentally harmful methods, and are themselves nonrenewable. The European Commission recognized this issue by adopting the EU Critical Raw Material Act in 2024 to ensure secure and sustainable access to critical raw materials across the EU. Untapped sources of critical raw materials can be found in electrical waste (e-waste) such as printed circuit boards (PCBs)—rich in metals like iron, copper, manganese, and rare earth elements. Microbes can be used to selectively bioleach these metals through oxidative or reductive pathways (i.e., remove metals from e-wastes). We hypothesize that microbial reduction of core metals, such as Fe(III) and Cu(II), leads to the co-release of associated rare earth elements from e-waste. Preliminary results from batch incubations of microbial iron-reducing cultures supplemented with PCBs showed that Geobacter metallireducens has considerable bioleaching potential for iron and manganese, and could help mobilize associated critical metals. Further research on G. metallireducens will be carried out to optimize conditions for metal mobilization rates from e-waste by supplementing additional electron donors and acceptors. Bioleached metals will be followed over time with ICP-MS/OES, and total metal content will be determined through acid digestion. Additionally, strains of other metal reducers (e.g., Shewanella oneidensis and Geobacter sulfurreducens) will also be assessed for their capacity to release metals from e-waste. This research project is expected to yield more insights into the potential of metal-utilizing microbes to reclaim metals from e-waste.