Bioelectrochemical systems: Difference between revisions

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[[Category:Technologies & Solutions]]

[[Bioelectrochemical systems]] (BESs) are integrated systems combining wastewater treatment with energy production and resource recovery. They utilize microorganisms to biochemically catalyse complex substrates into useful energy products, in which the catalytic reactions take place on electrodes<ref>[https://www.sciencedirect.com/science/article/pii/B9780128111574000073 Sustainable Waste-to-Energy Technologies: Bioelectrochemical Systems]</ref>.

[[Bioelectrochemical systems]] (BESs) are integrated systems combining wastewater [[treatment]] with energy production and resource [[recovery]]. They utilize microorganisms to biochemically catalyse complex substrates into useful energy products, in which the catalytic reactions take place on electrodes<ref>[https://www.sciencedirect.com/science/article/pii/B9780128111574000073 Sustainable Waste-to-Energy Technologies: Bioelectrochemical Systems]</ref>.

BESs have boomed over the past decade for their contribution as an emerging sustainable technology for concurrent electricity production and wastewater treatment. In addition, BESs also offer unique possibilities for clean and efficient production of fuels and high-value chemicals using microorganisms. Applications of BESs include: microbial desalination cells (MDCs), sediment/plant microbial fuel cells (MFCs), microbial electrosynthesis (MES) converts ~~CO2~~ or organic molecules to higher value organic molecules, they are efficient bioreactors for the treatment of pollutants and toxic wastewater (process known as bioelectrochemical treatment (BET)/microbial electroremediation (MER)).

BESs have boomed over the past decade for their contribution as an emerging sustainable technology for concurrent electricity production and wastewater [[treatment]]. In addition, BESs also offer unique possibilities for clean and efficient production of fuels and high-value chemicals using microorganisms. Applications of BESs include: microbial desalination cells (MDCs), sediment/plant microbial fuel cells (MFCs), microbial electrosynthesis (MES) converts CO2 or organic molecules to higher value organic molecules, they are efficient bioreactors for the treatment of pollutants and toxic wastewater (process known as bioelectrochemical treatment (BET)/microbial electroremediation (MER)).

In these electrochemical systems, the redox potentials of an oxidation reaction at the anode and a reduction reaction at the cathode create a potential difference which is the driving force for electrons to flow from a low potential to high potential. This flow of electrons through an external circuit is measured as electric current. Whenever, microbes or enzymes are involved in the oxidation or reduction or both reactions, the system is termed as a bioeclectrocehmical system (BES) or microbial electrochemical system (MXC)<ref name="ref1">[https://www.sciencedirect.com/science/article/pii/S0960148116301860 Bioelectrochemical Systems (BESs)]</ref>.

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==== 1. Microbial fuel cells (MCFs) ====

MFCs harness electrical current from the microbial oxidation of organic matter using a solid electrode as an electron acceptor. The anode surface facilitates microbial attachment and oxidation of organics, therefore generating electrons which are then simultaneously transferred to the cathode compartment through an external circuit containing an external load. Electroneutrality is warranted by ions transport through an ion-permeable medium or a membrane while electricity is produced in the process.

MFCs harness electrical current from the microbial oxidation of [[Organic Waste|organic matter]] using a solid electrode as an electron acceptor. The anode surface facilitates microbial attachment and oxidation of organics, therefore generating electrons which are then simultaneously transferred to the cathode compartment through an external circuit containing an external load. Electroneutrality is warranted by ions transport through an ion-permeable medium or a membrane while electricity is produced in the process.

A number of bacterial species have been identified with the ability to produce electric current. The Shewanella and Geobacter species were earlier found as the electron-transferring microbes and so are well-studied. The presence of Geobacteraceae in the bioanode community often showed high power densities registered in MFCs.

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MECs utilize the property of bacteria to convert chemical energy to electrical energy and allow electrolysis of water. External power applied onto the electrical circuit of BES drives electrons from anode to the cathode. This also supports the hydrogen production at the cathode which operates under anaerobic conditions. However the anoxic environment in MECs, along with high concentrations of hydrogen production, can also promote methane production once ~~CO2~~ and methanogens are available. Methods to mitigate toxic build up includes the aeration of the cathode chamber between batches, lowering of the pH, operation at short retention times, giving a heat shock to the inoculum and adding chemicals that inhibit the growth of methanogens.

MECs utilize the property of bacteria to convert chemical energy to electrical energy and allow electrolysis of water. External power applied onto the electrical circuit of BES drives electrons from anode to the cathode. This also supports the hydrogen production at the cathode which operates under [[Anaerobic Digestion|anaerobic]] conditions. However the anoxic environment in MECs, along with high concentrations of hydrogen production, can also promote methane production once CO2 and methanogens are available. Methods to mitigate toxic build up includes the aeration of the cathode chamber between batches, lowering of the pH, operation at short retention times, giving a heat shock to the inoculum and adding chemicals that inhibit the growth of methanogens.

In an MEC with bioanode and biocathode, expensive metals such as platinum are not required as catalyst and the enrichment of microbes on the carbon cathode decreases the start-up time and produces comparable current densities to those of bioanode. Also the hydrogen synthesized in MECs can also drive the biochemical production of other chemicals<ref name="ref1" />.

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==== 3. Microbial electrosynthesis (MES) ====

MES (also known as bioelectrosynthesis) uses the reducing power generated from the anodic oxidation to produce value added products at the cathode. Cathodic biocatalysts (with attached cathodic biofilms) reduce the available terminal electron acceptor to produce value added products. Biocathodes are the key components of microbial electrosynthesis, where the electrode oxidizing microorganisms are involved in the formation of reduced value-added product such as acetate, ethanol, butyrate. MES includes the production of chemical compounds in an electrochemical cell by electricity-driven ~~CO2~~ reduction as well as reduction/oxidation of other organic feedstocks using microbes as biocatalyst<ref name="ref1" />.

MES (also known as bioelectrosynthesis) uses the reducing power generated from the anodic oxidation to produce value added products at the cathode. Cathodic biocatalysts (with attached cathodic biofilms) reduce the available terminal electron acceptor to produce value added products. Biocathodes are the key components of microbial electrosynthesis, where the electrode oxidizing microorganisms are involved in the formation of reduced value-added product such as acetate, ethanol, butyrate. MES includes the production of chemical compounds in an electrochemical cell by electricity-driven CO2 reduction as well as reduction/oxidation of other [[Organic Waste|organic feedstocks]] using microbes as biocatalyst<ref name="ref1" />.

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 [[Category:Technologies & Solutions]]
-[[Bioelectrochemical systems]] (BESs) are integrated systems combining wastewater treatment with energy production and resource recovery. They utilize microorganisms to biochemically catalyse complex substrates into useful energy products, in which the catalytic reactions take place on electrodes<ref>[https://www.sciencedirect.com/science/article/pii/B9780128111574000073 Sustainable Waste-to-Energy Technologies: Bioelectrochemical Systems]</ref>.
+[[Bioelectrochemical systems]] (BESs) are integrated systems combining wastewater [[treatment]] with energy production and resource [[recovery]]. They utilize microorganisms to biochemically catalyse complex substrates into useful energy products, in which the catalytic reactions take place on electrodes<ref>[https://www.sciencedirect.com/science/article/pii/B9780128111574000073 Sustainable Waste-to-Energy Technologies: Bioelectrochemical Systems]</ref>.
-BESs have boomed over the past decade for their contribution as an emerging sustainable technology for concurrent electricity production and wastewater treatment. In addition, BESs also offer unique possibilities for clean and efficient production of fuels and high-value chemicals using microorganisms. Applications of BESs include: microbial desalination cells (MDCs), sediment/plant microbial fuel cells (MFCs), microbial electrosynthesis (MES) converts CO2 or organic molecules to higher value organic molecules, they are efficient bioreactors for the treatment of pollutants and toxic wastewater (process known as bioelectrochemical treatment (BET)/microbial electroremediation (MER)).
+BESs have boomed over the past decade for their contribution as an emerging sustainable technology for concurrent electricity production and wastewater [[treatment]]. In addition, BESs also offer unique possibilities for clean and efficient production of fuels and high-value chemicals using microorganisms. Applications of BESs include: microbial desalination cells (MDCs), sediment/plant microbial fuel cells (MFCs), microbial electrosynthesis (MES) converts CO<sub>2</sub> or organic molecules to higher value organic molecules, they are efficient bioreactors for the treatment of pollutants and toxic wastewater (process known as bioelectrochemical treatment (BET)/microbial electroremediation (MER)).
 In these electrochemical systems, the redox potentials of an oxidation reaction at the anode and a reduction reaction at the cathode create a potential difference which is the driving force for electrons to flow from a low potential to high potential. This flow of electrons through an external circuit is measured as electric current. Whenever, microbes or enzymes are involved in the oxidation or reduction or both reactions, the system is termed as a bioeclectrocehmical system (BES) or microbial electrochemical system (MXC)<ref name="ref1">[https://www.sciencedirect.com/science/article/pii/S0960148116301860 Bioelectrochemical Systems (BESs)]</ref>.
@@ Line 19: / Line 19: @@
 ==== 1. Microbial fuel cells (MCFs) ====
 [[File:MFC Diagram.png|right|MFC Diagram. All Rights Reserved.]]
-MFCs harness electrical current from the microbial oxidation of organic matter using a solid electrode as an electron acceptor. The anode surface facilitates microbial attachment and oxidation of organics, therefore generating electrons which are then simultaneously transferred to the cathode compartment through an external circuit containing an external load. Electroneutrality is warranted by ions transport through an ion-permeable medium or a membrane while electricity is produced in the process.
+MFCs harness electrical current from the microbial oxidation of [[Organic Waste|organic matter]] using a solid electrode as an electron acceptor. The anode surface facilitates microbial attachment and oxidation of organics, therefore generating electrons which are then simultaneously transferred to the cathode compartment through an external circuit containing an external load. Electroneutrality is warranted by ions transport through an ion-permeable medium or a membrane while electricity is produced in the process.
 A number of bacterial species have been identified with the ability to produce electric current. The Shewanella and Geobacter species were earlier found as the electron-transferring microbes and so are well-studied. The presence of Geobacteraceae in the bioanode community often showed high power densities registered in MFCs.
@@ Line 30: / Line 30: @@
 [[File:MEC Diagram.png|right|MEC Diagram. All Rights Reserved.]]
-MECs utilize the property of bacteria to convert chemical energy to electrical energy and allow electrolysis of water. External power applied onto the electrical circuit of BES drives electrons from anode to the cathode. This also supports the hydrogen production at the cathode which operates under anaerobic conditions. However the anoxic environment in MECs, along with high concentrations of hydrogen production, can also promote methane production once CO2 and methanogens are available. Methods to mitigate toxic build up includes the aeration of the cathode chamber between batches, lowering of the pH, operation at short retention times, giving a heat shock to the inoculum and adding chemicals that inhibit the growth of methanogens.
+MECs utilize the property of bacteria to convert chemical energy to electrical energy and allow electrolysis of water. External power applied onto the electrical circuit of BES drives electrons from anode to the cathode. This also supports the hydrogen production at the cathode which operates under [[Anaerobic Digestion|anaerobic]] conditions. However the anoxic environment in MECs, along with high concentrations of hydrogen production, can also promote methane production once CO<sub>2</sub> and methanogens are available. Methods to mitigate toxic build up includes the aeration of the cathode chamber between batches, lowering of the pH, operation at short retention times, giving a heat shock to the inoculum and adding chemicals that inhibit the growth of methanogens.
 In an MEC with bioanode and biocathode, expensive metals such as platinum are not required as catalyst and the enrichment of microbes on the carbon cathode decreases the start-up time and produces comparable current densities to those of bioanode. Also the hydrogen synthesized in MECs can also drive the biochemical production of other chemicals<ref name="ref1" />.
@@ Line 39: / Line 39: @@
 ==== 3. Microbial electrosynthesis (MES) ====
 [[File:MES Diagram.png|right|MES Diagram. All Rights Reserved.]]
-MES (also known as bioelectrosynthesis) uses the reducing power generated from the anodic oxidation to produce value added products at the cathode. Cathodic biocatalysts (with attached cathodic biofilms) reduce the available terminal electron acceptor to produce value added products. Biocathodes are the key components of microbial electrosynthesis, where the electrode oxidizing microorganisms are involved in the formation of reduced value-added product such as acetate, ethanol, butyrate. MES includes the production of chemical compounds in an electrochemical cell by electricity-driven CO2 reduction as well as reduction/oxidation of other organic feedstocks using microbes as biocatalyst<ref name="ref1" />.
+MES (also known as bioelectrosynthesis) uses the reducing power generated from the anodic oxidation to produce value added products at the cathode. Cathodic biocatalysts (with attached cathodic biofilms) reduce the available terminal electron acceptor to produce value added products. Biocathodes are the key components of microbial electrosynthesis, where the electrode oxidizing microorganisms are involved in the formation of reduced value-added product such as acetate, ethanol, butyrate. MES includes the production of chemical compounds in an electrochemical cell by electricity-driven CO<sub>2</sub> reduction as well as reduction/oxidation of other [[Organic Waste|organic feedstocks]] using microbes as biocatalyst<ref name="ref1" />.
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