Hey guys. And good lovers of this page. I welcome you to my blog. This article was supposed to be uploaded yesterday but I mistakenly pressed "discard button" and the article erased before my eyes. It was really maddening, and I have never felt so bad. Thanks goodness I am back now, and here we go again.
Governments all over the world are shifting focus to renewable sustainable and pollution-free fuels because fossilized fuels, like petroleum and its likes, are exhaustible and contribute to the worsening environmental pollution. Even governments of oil producing countries are realizing that crude oil is not a strategic economic resource. It is exhaustible and therefore makes no economic sense for government to continue to depend on it as a viable means of earning foreign exchange.
Due to the health hazards posed to humans by fossilized fuels, their limited supply and being no strategic means of foreign exchange, a lot of funds are being expended on researches that are tailored at discovering worthy alternatives, which have led to some noteworthy achievements. I have written articles here, here and here on some recently discovered worthy alternatives that are being perfected as replacements to fossilized fuels. The theme of today's article will be on another source of alternative energy, and I don't intend to stop here; I will reveal some more sources in my future articles.
That being said, most of us know that we can harvest renewable energy from sun (solar energy), wind, water (hydropower), or earth (geothermal energy). But do you know that we can generate electricity and, at the same time, convert harmful organic wastes to harmless by-products via bacteria action in devices known as **Microbial Fuel cells (MFCs)? Yes we can; how this is possible forms the basis of this article.
By using MFCs with appropriate isolates of bacteria species, we can harvest electricity while ridding our environment of harmful organic wastes including PCBs (Polychlorinated biphenyls), sewage, mud, and other toxic chemical pollutants. Although the technology is still evolving, however, when this system is perfected, we will have the capacity to generate electricity at low cost while also transforming domestic, industrial and farm toxic pollution into harmless end products all via bacteria action! Nothing can be so beneficial! Ain't it?
Now, we have known that it is possible to generate electricity and transform harmful organic substrates using bacteria in MFCs. However, the question is how does this happen? In other words, where does the electrical current come from and how was the electrons transfered and captured in order to generate the said electricity? These bring us to the concepts of breathing metal and bacterial "wires" which I will be explaining in the subsequent paragraphs.
The concepts of breathing metal and bacterial "wires" — the secrets behind MFCs
Some species of Bacteria have been found to have natural ability to produce electricity under anaerobic conditions. This, according to some studies, is due to their ability to breathe solid lumps of iron in the soil. These group of bacteria occur naturally in places with limited sources of oxygen such as sewage, mud, wastewater. And use the said process during which they generate electricity to actually breath in the absence of oxygen. This electricity can be harvested using MFCs.
To successfully harvest this electricity using an MFC, then there is a need to have a mechanism that transports electrons between the anode and cathode electrodes. And this is where the concept of bacterial wires enters. In a simple MFC, there is no intermediate mechanism to effect this electron transfer other than bacteria. Bacteria have to reach out and touch the anode for electrons to flow and generate electrical current. To do this, according to the work of Professor Derek Lovley and his team of researchers at University of Massachusetts at Amherst, bacteria have to produce some unique filamentous (or pili) structures that have the capacity to transfer electrons in the same way a metallic conductor does. This biological filaments or pili that can act like metal is known as nanowires because, in fact, they are tiny wires.
These nanowires are capable of joining together to form a conductive biofilms when billions of bacteria are grown together. Conductive biofilms can transfer electrons across a long distance, making them the most suitable material for growing organic and self-repairing electrical conductors in the future. Such conductors have potential to be used in biocomputers.
Sample Microbial Fuel cell (MFC) and how it works
Basically, MFC comes in different types but for the purpose of this article, we will be using just one type to represent the working mechanism of a typical MFC.
An MFC comprises two electrodes — anode and cathode. While anodic chamber, which contains the bacteria, is sealed off to enable anaerobic condition, cathodic side is exposed to the air. A solution that's consisting of organic matter and microbes is used as fuel. In the course of their normal metabolic activities, bacteria breath out electrons onto anode. The released electrons travel via an external circuit to produce electricity. This system as it is, is known as electrochemically inactive microbial fuel cell. This means that the electrons from microbes are not readily carried to anode, making the system to work at a very low efficiency.
Organic compounds called exogenous mediators including thionine, neutral red, humid acid, methyl blue, and methyl viologen can be added to act as shuttles for electrons, delivering electrons to anode and diffusing back to bacteria. And hence increasing the efficiency of the system. However, these mediators are expensive and can be toxic too, and thus engendering the need for alternate solution.
This is provided with the discovery of certain bacteria that produce electrically conductive appendages. Commonly used in MFC are Shewanella oneidensis and Geobacter sulfurreducens. Their nanowires readily facilitate the transfer of electrons to anode and greatly increased the efficiency of the MFC. It is noted that the efficiency is increased by six times in when solution of other microbes are added (i.e in a mixed culture).
Conclusion
Even as revolutionary as MFC may be with its characteristics ability to render harmful organic wastes harmless while generating electricity at the same time, it will take some time before the technology will be commercialized for public use. Presently, wide scale applications are limited by low power output and high cost of production. However, man has always strive to innovate. When MFC is perfected and mass produced for public use, it would help the world resolve energy crisis and pollution problems. Thanks for reading.
References for further reading
- Microbial wires, an electronic dream
- Microbial Fuel Cell
- Meet the electric life forms that live on pure energy
- Bacteria eating pollution and generating energy
- Double bonus: bacteria eat pollution, generate electricity
- Mud power: how bacteria can turn wastes into electricity
- Microbes to generate electricity
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