Industrial and urban wastes represent a growing fraction of the waste produced worldwide. These wastes can be either organic (such as wastewater sludge or compost) or inorganic (such as electronic waste). Both types represent a non-negligible source of valuable, yet non-renewable resources, such as phosphorous or precious metals. At present-day, the recycling of these compounds is still in its infancy. Only about 20 metals are currently recycled, with a recovery rate of around 50% for elements such as gold. Besides this, there are other valuable metals that are not or only very poorly recycled, such as rare earth elements (REEs) and lithium for instance. Current methods in metal recycling consist in relatively polluting approaches (pyro- and hydrometallurgy). Regarding phosphorous, enormous amounts are lost via the incineration of wastewater sludge. As a result, the field of urban waste recycling (urban-mining) is a timely issue that requires the development of innovative and sustainable approaches. Many industrial and urban wastes typically consist of a heterogeneous matrix of materials and thus a parallel can be drawn to other complex systems such as soils. In soils, microbial interactions are essential to maintain biogeochemical cycles. In this project, using digested sewage sludge and e-waste as model urban waste, we explore the possibility to take advantage of both bacterial and fungal biogeochemical capabilities towards metals, along with the synergistic effect of bacterial-fungal interactions, in order to recover metals in minute concentrations from heterogeneous matrices. Our experimental approach includes the isolation and selection of metal-resistant bacterial-fungal consortia and the assessment of their capabilities towards the mobilization and immobilization of valuable compounds such as metals and phosphorous. By using microorganisms as miniaturized chemical reactors in urban mining we aim at proposing an innovative and sustainable answer to metal mining from the environment, accumulation of e-waste in landfills, and pollution of metal recycling during pyro- and hydrometallurgical processing, which are all major environmental issues linked to the use of metals in our daily lives.

• Funding: Fondation Pierre Mercier pour la Science
• People: Saskia Bindschedler (PI), Isha Hashmi (Post-doc), Matteo Buffi (PhD student), MSc students (past: Geremia Losa, Kasimir Ruegg, Iuliana Lungu; present: Arnaud Guggisberg, Hendrick Vermeulen, Patrick Hilpisch, Arthur Schneither) and interns (Anant Jain – ThinkSwiss fellow, Raimundo Pizzaro)
• Collaborations: EPFL – Soft Transducers Laboratory (Dr Danick Briand), STEP de la Chaux-de-Fonds, Unil - IDYST (Prof. Eric Verrecchia)