CATHOMIX explores the harnessing of living, free and renewable electroactive microbial catalysts as mixed biofilms on biocompatible cathodes efficiently delivering electrons directly or in the form of H2 to a N2 fixing metabolism (the biological reduction of N2 to ammonia NH3). The ultimate objective of the project is to characterize and demonstrate in the laboratory the generation of ammonium (NH4+) at a microbial cathode powered with renewable electricity while using the microbial catalysed oxidation of waste at the anode of the device. At the cathode, the reduction of H2O to H2 is catalyzed by designed inorganic or biomimetic electrocatalysts based on non-noble metals. The cathode will be colonized with a mixed biofilm selected and enriched to target the fixation of N2 by the direct use of electrons or indirectly through electrogenerated dihydrogen. CATHOMIX will cross TRL 1-2 to TRL 3-4. The intermittence of power on energy efficiency and microbial ecology will be studied, quantified, modelled and managed.