A microbial fuel cell (MFC) is a bioelectrochemical device in which microorganisms oxidize organic substrates and transfer electrons to an anode, generating a flow of electricity. The process converts chemical energy stored in compounds such as sugars and waste products into electrical energy.
Working Principle and Components
An MFC typically consists of an anode chamber, a cathode chamber and a separator. In the anode chamber, anaerobic bacteria metabolize organic matter and release electrons and protons. Exoelectrogenic microbes such as Geobacter sulfurreducens and Shewanella oneidensis can transfer electrons directly to the anode via conductive pili, outer membrane cytochromes or soluble redox mediators. Electrons flow through an external circuit from the anode to the cathode, producing an electrical current, while protons diffuse through a proton exchange membrane to the cathode. At the cathode, a terminal electron acceptor, often dissolved oxygen, combines with electrons and protons to form water. MFC performance depends on factors such as electrode material and surface area, internal resistance, substrate concentration, pH and temperature. Designs range from two‑chamber systems with separate anode and cathode compartments to single‑chamber air‑cathode configurations, with materials such as graphite felt or carbon cloth used for electrodes and catalysts such as platinum or biofilms enhancing cathodic reactions.
Applications and Examples
Microbial fuel cells are investigated for sustainable energy generation and wastewater treatment because they can simultaneously remove organic pollutants and produce electricity. Laboratory prototypes have used domestic wastewater, brewery effluent and agricultural waste as substrates, achieving power outputs sufficient to operate small electronic sensors. Plant‑MFC systems harvest electrons from rhizosphere microbes in rice paddy soils to provide continuous low‑level power for monitoring devices. Microbial electrolysis cells, a related technology, apply an external voltage to generate hydrogen gas from the anodic oxidation of organics. While current MFCs deliver low power densities compared with conventional fuel cells, ongoing research aims to improve electrode materials, enhance electron transfer pathways and develop scalable reactors for practical applications. Microbial fuel cells illustrate the potential of harnessing microbial metabolism to generate electricity from renewable resources. Further developments in materials science and microbiology may enhance their efficiency and enable wider adoption. Related Terms: Bioelectrochemical system, Exoelectrogen, Geobacter, Anode, Cathode