Key points
Microbial electrochemical technologies (METs) hold strong promise for resource-efficient waste management while advancing environmental sustainability.
Electrode–membrane–microbe synergy must be enhanced to increase energy and product recovery in METs.
Circular economy-driven integrated configurations can advance wastewater treatment for water reuse applications and resource recovery.
Introduction
Building on the Frontiers in Science lead article by Schröder et al. (1), this viewpoint highlights selected engineering and systems-level challenges and opportunities that will determine whether microbial electrochemical technologies (METs) can transition from promising concepts to scalable, real-world wastewater treatment solutions. While the merits of METs are well established, materials- and product-related techno-economic barriers continue to limit full-scale deployment. These challenges can be overcome by enhancing energy and product recovery through innovative system design for optimized electron flow, developing circular economy-driven integrated configurations, and expanding the role of METs through a nexus-based approach to environmental sustainability (2).
Energy resilience through system engineering
Synergy of materials and microbes
MET operation relies on the synergy between electrodes, membranes, and most critically, microbial biofilms. Advances in electrode materials have shifted preference from metal-based to carbon-based electrodes because of their biocompatibility and cost-effectiveness, albeit often at the expense of electrical conductivity. Likewise, membrane separators, such as ion-exchange membranes, are used to separate anode and cathode compartments but can induce localized pH imbalances, pore clogging, and increased internal resistance. Together, these components and biofilm dynamics strongly influence MET performance. Addressing electrode or membrane limitation in isolation is insufficient; a conducive environment for microbial enrichment and efficient electron transfer kinetics is essential.
To reduce oxygen intrusion and substrate diffusion barriers while enhancing electron transfer kinetics and cathodic reaction potential, the electrode–membrane–biofilm interface must be optimized (3). Dynamic membrane separators have shown promise in addressing interface limitations in METs. Conductive dynamic membranes that combine permeability enhancement, oxygen suppression, and electron transfer functions offer improved oxygen reduction kinetics, enhanced mass transport, and potential-driven microbial enrichment (4). Synthetic biology combined with materials engineering may further enhance electron transfer (5). For example, incorporating conductive materials on electrodes or within biofilms can significantly increase current density. Introducing conductive materials into individual microbes via in situ nanoparticle synthesis may further improve microbe–electrode electron transfer, although the feasibility of such approaches in practical applications requires further investigation.
System design and pilot-scale optimization
System design directly affects power density and the production of value-added outputs. Internal resistance is the primary bottleneck, while electrode selection and sizing also influence performance. Increasing electrode surface in large-scale reactors has led to increased internal resistance and decreased power outputs in microbial fuel cells (MFCs). Electrode spacing similarly affects electron transfer efficiency. Optimizing electrode packing density per reactor volume may help address limitations associated with electrode size and spacing (6). Larger reactors are frequently configured as stacked cells, leading to challenges related to flow distribution, electrode pairing, mass transport, and substrate utilization. Anode–cathode interconnections and material combinations further complicate system performance, and trade-offs persist between electricity generation and economic feasibility as reactor size increases.
Air cathodes are commonly used in MFCs to enable passive oxygen transport, with oxygen serving as the preferred terminal electron acceptor. Aerated biocathodes may facilitate faster and more effective cathodic reduction reactions. The energy required for aeration can be minimized through intermittent aeration cycles that improve oxygen utilization efficiency.
Biocathodes can also mitigate the trade-off between electricity generation and chemical oxygen demand (COD) removal by enabling additional COD reduction and nutrient (nitrogen and phosphorus) recovery, supporting more efficient treatment pathways for water reuse. In aerated biocathode MFCs, oxygen supply and utilization become key process variables that must be systematically evaluated at scale. Biocathodes can also mitigate the trade-off of METs operating at low COD removal rates for higher electricity generation by providing a comprehensive approach for further COD removal and/or recovery of nutrients (nitrogen and phosphorus) from wastewater, leading to more efficient treatment alternatives for water reuse. There are many biological cathodes that could be considered for this purpose. In aerated biocathode MFCs, oxygen supply and utilization efficiencies become additional process variables impacting energy performance, which must be studied systematically for large-scale reactors.
Pilot-scale demonstrations remain limited despite extensive laboratory research. Recent studies have begun to address unanswered questions regarding energy recovery and treatment feasibility at larger scales, yet cost–performance uncertainty persists due to variable results. Reported power densities and treatment efficiencies span a wide range across wastewater types, including artificial wastewaters. Cathode material and reaction mechanisms play a significant role, with air cathodes generally yielding lower power densities in reactors exceeding 100 L. Experience with biocathodes is sparse, although one study reported a promising performance for a 1500 L reactor (7). More long-term, in situ pilot-scale studies using real wastewaters are needed to generate reliable performance benchmarks. System design and optimization may also benefit from artificial intelligence, including machine learning and deep learning approaches, to develop predictive models that improve efficiency and reduce costs, provided data quality and consistency are adequately addressed.
Integrated configurations for the circular economy
METs are not yet viable as standalone wastewater treatment systems but can perform effectively within integrated settings that meet regulatory requirements. Advanced treatment coupled with resource recovery represents a practical pathway toward circular economy-driven MET deployment. Integrated configurations such as MFC–microbial electrolysis cell (MEC) systems can provide synergistic benefits, with MFCs serving as pre-treatment steps and MECs functioning as secondary treatment processes that capitalize on shared inputs and outputs. In such systems, MFCs treat wastewater while generating electricity and carbon dioxide (CO2), which can support hydrogen production in MECs. Additional integrated configurations, including combinations with constructed wetlands, hydroponics, electrochemical systems, and membrane bioreactors, have demonstrated encouraging technology readiness levels (8), with some showing feasibility in under-resourced settings (1). These systems require further evaluation to establish circular economy-based treatment strategies that enhance overall process resilience. Integrating METs with anaerobic digestion (AD) to enhance carbon and energy recovery is a particularly promising approach. AD generates biogas and nutrient-rich digestate suitable for agricultural reuse, while thermochemical conversion of sludge to biochar can yield low-cost electrode materials or conductive amendments for METs, further reinforcing circularity (9). At present, AD is typically operated as a standalone unit in linear economy designs, and this paradigm must evolve. Ultimately, MET circularity will depend on the ability to deliver diverse, value-added products cost-effectively. Cooperative multispecies biofilms or granule-based processes may enable breakdown of recalcitrant molecules into simpler molecules, which could be further converted into useful products through synergistic microbial interactions.
Nexus approach for environmental sustainability
The application of METs extends beyond wastewater treatment and Sustainable Development Goal (SDG) 6. METs are well-suited to complex environmental nexus scenarios, including the food–energy–water, water–carbon–energy, water–energy–materials, and water–energy–land nexuses. Their application can be expanded to groundwater and soil remediation and to the conversion of atmospheric CO2 into valuable products. An underexplored opportunity lies in mitigating gaseous emissions from industrial, hazardous, and municipal waste management processes, where METs could capture and convert pollutants into useful products. At scale, MET deployment could contribute to multiple SDGs (2, 3, 7, 9, 12, 13, and 15) at the global level.
Within the food–energy–water nexus, integrated MET systems have been used to treat concentrated agricultural and food-processing wastewaters, offering insights transferable to municipal wastewater treatment. AD-MET configurations with biochar amendments showcase the water–carbon–energy nexus. The water–energy–materials nexus is particularly relevant given the growing importance of recovering critical raw materials such as nitrogen, phosphorus, and precious metals. These elements can be selectively recovered from wastewater via cathodic reduction, with cathode potential enabling targeted metal recovery (10).
Next steps
Future MET development must adopt a holistic perspective that supports scale-up of critical components while preserving microbial biofilm efficiency and system resilience. Recent advances have transformed miniature laboratory-scale METs into pilot-scale operations, strengthening links between microbial electrochemistry and environmental sustainability. Rather than confining METs to waste management, circular economy-enabled approaches should be prioritized to meet cost and performance objectives. Integration-oriented, nexus-based process development will be crucial for accelerating MET implementation and establishing circular economy-driven waste infrastructure. With this approach, METs can evolve into robust waste-to-value platforms aligned with future energy, environmental, and regulatory landscapes.
Statements
Author contributions
VG: Conceptualization, Formal Analysis, Investigation, Methodology, Resources, Writing – original draft, Writing – review & editing.
Funding
The author declared that financial support was not received for this work and/or its publication. While the author is the recipient of grants from the National Science Foundation and United States Department of Agriculture to conduct research discussed in this article, none of these funds were expended for the creation of this manuscript.
Conflict of interest
The author declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The author declared that they were an editorial board member of Frontiers at the time of submission. This had no impact on the peer review process and the final decision.
Generative AI statement
The author declared that generative AI was not used in the creation of this manuscript.
Publisher’s note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
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Summary
Keywords
biofilm, circular economy, electrode, membrane, microbial fuel cells, energy recovery, sustainability
Citation
Gude VG (2026) Advancing microbial electrochemical technologies for the circular economy, energy resilience, and environmental sustainability. Front Sci 4:1808328. doi: 10.3389/fsci.2026.1808328
Received
10 February 2026
Accepted
27 February 2026
Published
18 March 2026
Volume
4 - 2026
Edited and reviewed by
Nicolas Bernet, Institut National de recherche pour l’agriculture, l’alimentation et l’environnement (INRAE), France
Updates
Copyright
© 2026 Gude.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Veera Gnaneswar Gude, vgude@purdue.edu
Disclaimer
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.