Production of Electricity Geobacter surf


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Electricity Production by Microbial fuel cell Samuel Raj. B Madurai Kamaraj University PhD Principle investigator Dr.SRD Jebakumar


INTRODUCTION Energy generation and waste disposal are two key challenges in the quest for sustainable societies. Microbial fuel cells provide an elegant solution by linking both tasks Microbial fuel cell (MFC) technology represents a new form of renewable energy by generating electricity from what would others considered as waste. INTRODUCTION

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GENERAL PRINCIPLES OF MICROBIAL FUEL CELLS A microbial fuel cell (MFC) converts chemical energy, available in a bio-convertible substrate, directly into electricity. To achieve this, microorganism are used as a catalyst to convert substrate into electrons. A MFC consists of an anode, a cathode, a proton or cation exchange membrane and an electrical circuit. A MFC is usually made up of two chambers one anaerobic and one aerobic.

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Pseudomonas Shewanella putrefaciens Geobacter metallireducens Rhodoferax ferrireducens These bacteria will directly transfer an electron to any type of conductive material (Cathode) ELECTRICIGENS

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Exoelectrogens Transfer electrons exocellularly in three ways Self-produced mediators Membrane bound electron carriers Nanowires (Conductive appendages) Anode is used instead of the normal terminal electron acceptors Common species Geobacter and Shewanella MFC Microbiology

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PURE MIXED CULTURE CULUTRE VS Produce lower level of electricity Grow slower Produce higher level of electricity Grow much quicker Work as community

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How Does it Work?

How do electrons reach the electrode? : 

How do electrons reach the electrode? Early evidence was that bacteria produced their own mediators Pseudomonas spp. Produce mediators such as pyocyanin (Rabaey et al. 2004) Recent data suggests that Shewanella spp. use other methods… Carrier (oxidized) Carrier (reduced) Bacterium Fe (III) Mediators produced by Pseudomonas spp. have distinct colors. (Photo provided by Korneel Rabaey, Ghent University, Belgium; 2005).

New finding: bacteria use “nano-wires” : 

New finding: bacteria use “nano-wires” Other bacteria can transfer electrons directly to the electrode Pesudomonas sp. Alteromonas sp. Shewanella spp. Bacterium Electrode Yuri Goby (2005). “Composition, reactivity and regulation of extracellular metal-reducing structures produced by dissimilatory metal-reducing bacteria.” Pres. DOE NABIR meeting, April 20, 8:10 am, Warrenton, VA. e- e- e-

Electricity Production in an Cathode Microbial Fuel Cell : 

Electricity Production in an Cathode Microbial Fuel Cell Proton Exchange membrane load Anode Cathode bacteria Oxidation products (CO2) Fuel (wastes) e- e- O2 H2O H+ Source: Liu et al., Environ. Sci. Technol., (2004)

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- Increase power with air-cathode (oxygen does not need to be dissolved in water Remove proton exchange membrane (PEM) load Anode Cathode bacteria Oxidation products (CO2) Fuel (wastes) e- Oxidant (O2) Reduced oxidant (H2O) H+ e- MFC- Air cathode systems

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Mechanism of Electricity production Bacteria (Anode) (Substrate) (Wastes water) Convert Electron transport chain protons & electrons Electron transport through cell membrane using OmcB, OmcS, OmcF

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Protein electron carriers cytochrome C- type Anode (electrons) Proton Cathode Electrical circuit with a load or resistor to the Cathode The potential difference (Volt) between the anode and the cathode, together with the flow of electrons (Ampere) results in the generation of electrical power (Watt).

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Future out look MFC designs need improvements before a marketable product will be possible. Issues of the scale-up of the process remain critical issues. While full-scale, highly effective MFCs are not yet within our grasp, the technology holds considerable promise, and major hurdles will undoubtedly be overcome by engineers and scientists. The growing pressure on our environment, and the call for renewable energy sources will further stimulate development of this technology, leading soon to its successful implementation.

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