Microbial Fuel Cell
Basic principles of Microbial Fuel Cell :
Microbial Fuel Cell (MFC) technology has been emerging as one of the popular wastewater treatment-based technology to provide clean water and green energy production . MFCs are bio-electrochemical devices where organic wastes degrade to smaller molecules, releasing electrons and protons, thereby generating electricity. MFCs can directly convert chemical energy into electrical energy through bio-electrochemical reactions utilizing microorganism or enzymatic catalysis. MFCs have several advantages as compared to the traditional fuel cells and enzymatic fuel cells. It is possible to utilize a wide range of organic or inorganic matter such as organic wastes, soil sediments as a source of fuel generation. High conversion efficiency can be achieved with such devices due to the direct or a single step conversion of substrate energy to electricity. Unlike a conventional fuel cell, MFCs can run at ambient temperature and atmospheric pressure.
MFC is a bioelectrochemical system comprised of an anaerobic anode chamber and an aerobic cathode chamber physically separated by an ion exchange membrane. In a typical MFC, microbes are utilized for oxidation of substrate inanode chamber; subsequently the electron released from the microorganism goesto cathode via external wire. The anode chamber consists of microorganism (catalyst) and an electrode (anode) and it can be fed with growth media or wastewaternamed as anolyte and redox mediator (not required in case of mediator-less MFC). The necessary protons and electrons extracted during bacterial substrate catabolism combine with oxygen to form water on cathode.
Usually, electrons flow tothe cathode via a conductive material having an external resistance. The protonswhich migrate through membrane are reduced by accepting these electrons. Terminal electron acceptors (e.g. O2 to water) at the cathode are similar to chemical fuel cell . Separator plays an important role in MFC. It physically divides anode chamber and cathode but ionically and electronically conjugated. In a dual chambered MFC, separator facilitates in developing both anodic and cathodic half-cell potential by splitting anolyte at the anode chamber to cathode. The electrons producing through bacterial metabolic activity pass via an external circuit while the proton migrates via a separator, separating the anode chamber from the one in which the cathode is immersed . Use of separator has several advantages in MFC like transport of anolyte or substrate from anode to cathode. MFCs have several operational advantages over the technologies that have currently used for producing energy from organic sources . First, the direct transformation of substrate energy to electricity enables high conversion efficiency. Second, MFCs operate efficiently at ambient, and even at low, temperatures distinguishing them from all current bio-energy processes. Third, the MFC does not require gas treatment because the off-gases of MFCs are enriched in carbon dioxide and normally have no useful energy content. Fourth, MFCs do not need energy input for aeration provided the cathode is passively aerated. Fifth, MFCs have potential for widespread applications in location lacking electrical infrastructures and also to expand the diversity of fuels, we use to satisfy our energy requirements.
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