Microbial fuel cells as a sustainable nexus of wastewater treatment and bioelectricity generation: Advances, challenges, and future directions in a circular bioeconomy

Microbial Fuel Cells (MFCs) have emerged as a promising technology for wastewater treatment and bioelectricity generation, offering a sustainable solution to energy and environmental challenges. Recent advancements in MFC systems, particularly in material design and microbial optimization, have significantly improved power densities and efficiency. MFCs have demonstrated chemical oxygen demand (COD) removal efficiencies of up to 97%, with power densities ranging from 0.1 W/m 2 to 23 W/m 2 , depending on substrate type and system configuration. Despite these advances, challenges such as high capital costs and limited energy recovery efficiency hinder large-scale adoption. The integration of Internet of Things (IoT) and machine learning for system optimization, alongside hybrid MFC systems combining solar and wind energy, has enhanced operational efficiency by up to 20% in some cases. This review presents a comprehensive overview of these breakthroughs, highlighting the environmental, economic, and policy considerations crucial for scaling MFC technology. It also identifies key areas for future research, including improvements in electrode material durability and microbial community stability, which are vital for achieving long-term operational reliability and economic viability in real-world applications.