Mi-Hy is a circular hydroponic-bioelectrical system (BES) designed for urban agriculture. It integrates carbon and nitrogen metabolism in plants to optimize their transformation into animal feed and other valuable products. This system combines BES technology, which uses electrons from biochemical reactions, with hydroponics, a method of growing plants without soil. The goal of TFNS joining the consortium is to valorise wastestreams from Mi-Hy by developing complementary bioprocess and biomaterial solutions that enhance the circularity and sustainability of the Mi-Hy system. This includes valorizing by-products from waste stream feedstock, such as urban wastewater (WW) sludge, sludge dewatering effluent (EF), hydroponics waste solution, and hydroponics sludge. These by-products still contain significant amounts of carbon and nitrogen after processing, which can be further used. Valorization routes include developing microbially-mediated processes and “green” building materials (GBMs). Two major pathways are defined as specific objectives (SO): SO1 aims to create biofertilizing products (BFP), including biostimulants, blends of biostimulants and organic fertilizers. SO2 focuses on developing novel GBMs using sludge effluents (EFs) combined with other industrial waste materials to create new ceramic blends and microbially induced calcite precipitation (MICP)-based biobricks. The proposed methodology integrates bio-based principles to use renewable bioresources and nutrients, addressing environmental issues in agriculture (hydroponics, chemical fertilizers) and green building applications (e.g., high embodied energy materials like fired bricks, steel, and glass). These sectors currently rely on fossil fuels and material extraction. The valorised Mi-Hy waste streams, have potential applications in organic agriculture and the green building sector. Including TFNS, a Western Balkans (WB) institution will support the specific objective (SO3) related to the WIDERA topic.

For the first time, Mi-Hy brings together Microbial Fuel Cell (MFC) technology and hydroponics, thereby introducing a prosthetic rhizosphere (an extended rhizosphere community) to the typically “soil-less” configuration of hydroponics systems. The Mi-Hy system will modulate nitrogen forms, plant root microbiomes optimise nitrogen uptake, and mobilise phosphorous, averting the need for chemical fertilisers. This circular, sustainable platform turns carbon into biomass and reclaims nitrogen from wastewater streams. Linked through shared microbiomes, the bioelectricity generating Bioelectrochemical System (BES) Microbial Fuel Cell (MFC) platform is: i) optimised to generate electricity from wastewater at 1mW/1mL feedstock (setting a new benchmark for MFCs); ii) driving wavelength-specific LEDs to optimize photosynthesis; iii) capable of recovering useful biomolecules using adjacent MFCs to modulate the redox potential of a workhorse Microbial Electrolysis Cell (MEC) performing microbial electro synthesis (MES). This novel development brings together MFCs & MECs. Since these share common microbial constituents, they can be technologically combined without the need for external, (fossil-fuel based) energy sources. To achieve this goal, Mi-Hy aims to design biofilms using metabolic engineering in wild type symbiotic strains. This next-generation hydroponics system has near-future applications in agriculture and in the urban environment. It delivers a smart, decentralized, low power digital infrastructure with sustainable organic solutions, which are in line with the ambitions of the Missions Cities & Climate adaptation (urban agriculture, precision gardening, wastewater treatments, energy generation, synthesis of high value compounds e.g., vitamins). Mi-Hy will also invite designers and stakeholders from various sectors to co-create future applications. Ultimately, it anticipates and facilitates a healthier, sustainable, nature-based urban landscape.