Nanofibrilar cellulose membranes in microbial fuel cells: material development for sustainable, high value-added applications

Wastewater treatment has been regarded as a big energy drain. Recent data (2020) shows that, on average, 360 km3/year of municipal wastewater is generated worldwide. On the other hand, the recoverable energy potential in municipal wastewater is estimated at 805 billion kWh of electricity per year. Direct energy recovery from municipal wastewater is possible through microbial fuel cells (MFCs), which are recognized as a key technology in the global effort to achieve a clean energy industry and a clean environment of the future. MFCs can extract electricity, hydrogen, chemicals, and metals from wastewater while efficiently cleaning it. Proton exchange membranes (PEMs) are among the critical components that significantly impact MFC performance and capital cost. The current ""gold standard"" among PEMs is Nafion - a fully synthetic, expensive (40% of MFC costs), biofouling-prone and environmentally unsustainable membrane. The proposed project aims to demonstrate novel scientific and technological concepts and efficient solutions for MFC development, focusing on PEM membranes. The project will develop advanced antifouling, proton-conductive, and environmentally benign nanofibrilar membranes based on cellulose and introduce them into a pilot concept for the scale-up of entirely new and high-performance Microbial Fuel Cells. Nanofibrillated cellulose is the focus of the materials segment as a sustainable, low-cost material with essential properties for the domain of MFCs, i.e., low H2 permeability, good mechanical properties, and the inherent large length-to-diameter ratio to support directional long-range proton conduction along surfaces. The introduction of fixed charges or combination with ion-conducting phases is expected to transform them into excellent ionic conductors, the latter including graphene oxide nanoparticles with demonstrated ability to accelerate proton transport. This complementary project between Slovenian and Swiss research teams will explore the potential of the partners' latest discoveries. Indeed, the Slovenian partners (FS-UM and FKKT-UL) are already involved in the development of biopolymer/graphene membranes for ethanol fuel cells, while the project partner of HES -SO Valais-Wallis University from Applied Sciences Switzerland, Prof. Fabian Fischer's and his team have already developed the world's longest microbial fuel cell. The project consortium partners have devised a systematic work plan of R&D activities covering the development process of the novel microbial fuel cell from design to actual prototype fabrication. To obtain an innovative and efficient product at the end of the project period, the work plan has been constructed around the current technical obstacles that limit the full implementation of microbial fuel cells at the commercial scale; by directly addressing these limitations with specified tasks, we will be able to carry out the research work in a targeted manner towards the final goal. Another important topic that will be systematically investigated is microbial fuel cell assemblies and their validation, and finally, a pilot concept for scale-up. Implementing such energy and water purification systems in one is expected to solve the burden of overexploitation of nature's non-renewable resources, reduce the current status quo of harmful impacts on the environment by the traditional energy sector, and enable economic water treatment. This aligns with European policy: to achieve climate neutrality in Europe, it is necessary to promote disruptive materials science that provides industrial-scale solutions and supports the decarbonization of energy and the materials needs of European industry.