Another type of energy from waste? MSW is food for bacteria-driven batteries

A battery that runs on scraps of food could fuel a battery providing electricity to top up your home’s supply, say UK researchers.





New Scientist reports that although such “microbial fuel cells” (MFCs) have been developed in the past, they have always proved extremely inefficient and expensive. Now Chris Melhuish and technologists at the University of the West of England (UWE) in Bristol have come up with a simplified MFC that costs as little as £10 to make.





Right now, their fuel cell runs only on sugar cubes, since these produce almost no waste when broken down, but they aim to move on to carrot power. “It has to be able to use raw materials, rather than giving it a refined fuel,” says Melhuish. Inside the Walkman-sized battery, a colony of E. coli bacteria produce enzymes that break down carbohydrates, releasing hydrogen atoms. The cell also contains chemicals that drive a series of redox, or reduction and oxidation reactions, stripping electrons from the hydrogen atoms and delivering them steadily to the fuel cell’s anode. This creates a voltage that can be used to power a circuit.





To prove the MFC works, the researchers are using it to power a small light-sensitive robot. And when a number of the cells are connected in series, they could power domestic appliances, running a 40-watt bulb for eight hours on about 50 grams of sugar.





Earlier MFCs were inefficient because they relied on energy-hungry filters and pumps. By experimenting with different anode materials, the UWE team have figured out how to make their system work: they dump the bacteria and redox chemicals directly into the cell.





In its current form, the UWE team says its organic battery can produce eight times as much power as any previous MFC. But Melhuish wants to improve this, both by scaling it up and finding a better mix of redox chemicals.