African microbes charge up fuel cells

A young company out of Cambridge, Massachusetts, is rolling out its off-grid energy system across regions of Tanzania and Namibia. With its microbial fuel cells, which harness the natural reactions in micro-organisms that convert chemical energy into electrical energy, Lebônê Solutions has developed a small-scale portable energy system that can power an LED to provide up to five hours of light or can charge small electronics or appliances, such as cell phones or radios. MIT’s Technology Review reports that the fuel cells are easier to produce and cheaper to install than solar panels or small-scale wind turbines.

A microbial fuel cell works by collecting the protons and electrons that are released during anaerobic respiration in a micro-organism. The fuel cell’s circuitry taps into the electron transport chains within the microbes’ cells and deposits the charge on an electrode. In this case, the fuel cell consists of a sealed, oxygen-free chamber with two electrodes—the anode, a negatively charged compartment that houses the bacteria, and a positively charged compartment, the cathode. A membrane dividing the two compartments allows ions to move between the two sides. The bacteria can be fed almost any organic material, and here the company used acetic acid, the key ingredient in vinegar, and cellulose. As they munch, the bacteria release carbon dioxide and protons and electrons, which separate and attach to their similarly charged electrodes. When planted in a bucket with microbe-rich mud, manure, or other natural waste, the fuel cell has enough feedstock to generate small—but sufficient, for small applications—quantities of electricity.

Lebônê plans to produce and test 100 of its fuel cells this fall, with the intention of breaking into the emerging market of durable and simple technologies for hard-to-reach parts of the world. We recently covered another company with similar ambitions, VNL, which hopes to roll out solar-powered base stations for telephone networks in rural regions. In general, fuel cells don’t generate much power, so it may be hard to find grander applications, but for now, this preliminary launch of a long-speculative energy harvesting method is a good proof-of-concept for a very earthy technology.