October 21st, 2009:
Bacteria are one of the most abundant organisms on the planet and also one of the most studied. Today, scientists use bacteria for genetics research, antibiotics, and yes! Even biofuels. Recent technological advances have made a battery running on bacteria a reality. Known as microbial fuels cells or MFCs, batteries running on bacteria and other microbes have been keenly researched by scientist for decades.
How bacteria powered batteries work
Contrary to popular belief, bacteria do not directly produce electricity in a MFC. Bacteria powered batteries use the chemical energy generated by bacteria, and convert it into electrical energy using a relatively simple mechanism. Like most batteries, a bacteria powered battery has an anode (the negative end) and a cathode (the positive end). In addition to the anode and cathode, a bacteria powered battery also has a membrane capable of filtering electrons (anions) and protons (cations) produced during the chemical breakdown of substances by bacteria.
Once the bacterial breakdown starts producing ions, the anions are transferred from the cathode compartment via an external circuit and the protons are sent to the cathode from the anode. In a nutshell, the chemical energy generated by bacterial activity is converted to electrical energy.
Unfortunately, not all bacteria are electrochemically active and require a substance known as a ‘mediator’ to facilitate the flow of ions. Substances like thionine, methyl viologen, methyl blue, humic acid and neutral red were used as mediators but their toxicity was a major concern for scientists. A few years back scientists engineered electrochemically active bacteria, and the science of bacteria powered batteries took a huge leap forward. Mediator less MFCs can run on everything from waste water to a simple saline solution and are truly environment friendly batteries.
Recent developments
Harvard scientists working under the Lebone banner have created a bacteria powered battery that uses bacteria found in African soil. What is truly remarkable about the MFC created by Lebone is that the battery uses a layer of sand as the ionic membrane, mud with manure as the bacterial substrate, and a graphite cloth as the anode.
Like most eco-friendly and renewable solutions, the MFC created by Harvard scientists uses substances readily available throughout Africa and is expected to provide electricity in remote parts of Africa. In fact, the only non-biodegradable substance used in the bacteria powered battery created by Lebone scientists is probably the 5 pound plastic bucket used to case the battery. Although the amount of energy produced by the bacteria powered battery is far from amazing, it can produce enough power to run a few LED lights and small electronics.
The future of bacteria powered batteries
Organizations like Lebone are one of the many organizations that are investing time and money in creating truly eco-friendly renewable energy options. The quest for a truly eco-friendly energy source may not have ended with bacteria powered batteries, but MFCs are a step forward in the right direction. With regular batteries clogging waste grounds the world over, recyclable energy sources like bacteria powered batteries are necessity.
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