Energy Recovery from Organic Wastes Using Microbial Fuel Cells: Traditional and Nonconventional Organic Substrates

Microbial fuel cells (MFCs) are environmentally friendly energy converters that use electrochemically active bacteria (EAB) as catalysts to break down organic matter while producing bioelectricity. Traditionally, MFC research has relied on simple organic substrates, such as acetate, glucose, sucrose, butyrate, and glutamate, the production of which involves energy-intensive, CO2-dependent processes and chemically aggressive methods. In contrast, nonconventional waste streams offer a more sustainable alternative as feedstocks, aligning with zero-waste and regenerative agricultural principles. This review highlights the potential of nonconventional organic wastes, such as fruit and vegetable wastes, raw human and livestock urine, and farm manure, as globally available and low-cost substrates for MFCs, particularly in household and farming applications at small-scale waste levels. Furthermore, complex waste sources, including hydrocarbon-contaminated effluents and lignin-rich industrial wood waste, which present unique challenges and opportunities for their integration into MFC systems, were examined in depth. The findings of this review reveal that MFCs utilizing nonconventional substrates can achieve power outputs comparable to traditional substrates (e.g., 8314 mW m−2–25,195 mW m−2 for crude sugarcane effluent and raw distillery effluent, respectively) and even superior to them, reaching up to 88,990 mW m−2 in MFCs utilizing vegetable waste. Additionally, MFCs utilizing hydrocarbon-containing petroleum sediment achieved one of the highest reported maximum power densities of 50,570 mW m−2. By integrating diverse organic waste streams, MFCs can contribute to carbon-neutral energy generation and sustainable waste management practices.