In the ongoing search for renewable energy, scientists have found an unlikely ally — microbes. Hidden in soil, sewage, and sediment are bacteria capable of doing something extraordinary: generating electricity. These living power sources form the foundation of microbial fuel cells (MFCs) — bio-electrochemical systems that convert organic matter directly into usable electrical energy.

The concept emerged in the early 20th century, but it wasn’t until the late 1990s that MFCs gained serious attention. Researchers discovered a special class of microorganisms known as electrogenic bacteria, such as Geobacter sulfurreducens and Shewanella oneidensis, that can transfer electrons outside their cells to solid surfaces — a process called extracellular electron transfer (EET). In a microbial fuel cell, these bacteria form biofilms on an electrode and, as they consume organic “fuel,” they release electrons and protons.

Here’s how it works: organic material — often wastewater, plant residue, or even food scraps — flows into the anode chamber, where microbes break it down. The released electrons travel through an external circuit to the cathode, generating an electric current, while the protons migrate through a membrane and combine with oxygen to form water. The result is a self-sustaining system that simultaneously cleans waste and produces electricity.

Unlike chemical batteries, MFCs don’t rely on toxic metals or synthetic electrolytes. Their energy source is renewable, and their byproducts are often harmless. Though the voltage produced per cell is small, the system’s beauty lies in its duality of purpose — energy recovery and waste treatment in one process. In a world seeking sustainable cycles rather than linear consumption, microbial fuel cells embody biology’s quiet efficiency.