page_title: Microbial fuel cell
section_title: Mediator-free
hierarchical_section_title: Microbial fuel cell / Types / Mediator-free
caption_attribution_description: English: A schematic of a plant microbial fuel cell. The schematic was based on the images at http://www.ete.wur.nl/UK/Research/Renewable+Energy/Green+electricity+production+by+living+plants+in+a+microbial+fuel+cell/ , http://www.plantpower.eu/index.php?option=com_content&amp;view=article&amp;id=3&amp;Itemid=4 , and http://www.microbialfuelcell.org/Publications/WUR/Strik_et%20al_2008.pdf . Unlike most microbial fuel cells, Plant microbial fuel cells allow the generation of electricity from living plant matter. 1= leaves take up CO2, and release O2 2= plant roots generate rhizodeposits (C3H2O6) 3= microorganisms take up rhizodeposits, and generate 3a, 3b, 3c 3a= CO2 3b= electrons 3c= H 3d= O2 3e= H2O 4a= cathode material (graphite granules + graphite felt) connected to wire 4b= anode material (graphite felt) connected to wire 5= cation exchange membrane; connects to 6 via wire 6= energy store (ie electrochemical battery, ...) 7= electricity See File:Plant Microbial Fuel Cell setup.JPG for a more detailed schematic.
context_page_description: A microbial fuel cell is a bio-electrochemical system that drives an electric current by using bacteria and a high-energy oxidant such as O₂, mimicking bacterial interactions found in nature. MFCs can be grouped into two general categories: mediated and unmediated. The first MFCs, demonstrated in the early 20ᵗʰ century, used a mediator: a chemical that transfers electrons from the bacteria in the cell to the anode. Unmediated MFCs emerged in the 1970s; in this type of MFC the bacteria typically have electrochemically active redox proteins such as cytochromes on their outer membrane that can transfer electrons directly to the anode. In the 21ˢᵗ century MFCs have started to find commercial use in wastewater treatment.
context_section_description: Mediator-free microbial fuel cells use electrochemically active bacteria to transfer electrons to the electrode (electrons are carried directly from the bacterial respiratory enzyme to the electrode). Among the electrochemically active bacteria are Shewanella putrefaciens, Aeromonas hydrophila and others. Some bacteria are able to transfer their electron production via the pili on their external membrane. Mediator-free MFCs are less well characterized, such as the strain of bacteria used in the system, type of ion-exchange membrane and system conditions (temperature, pH, etc.)
  Mediator-free microbial fuel cells can run on wastewater and derive energy directly from certain plants and O₂. This configuration is known as a plant microbial fuel cell. Possible plants include reed sweetgrass, cordgrass, rice, tomatoes, lupines and algae. Given that the power is derived from living plants (in situ-energy production), this variant can provide ecological advantages.
caption: A plant microbial fuel cell (PMFC)
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