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Biomass Fuel Cells

Biomass Fuel Cells. Sergey K aly uzhnyi. Department of Chemical Enzymology, Chemistry Faculty Moscow State University, 119992, Moscow, Russia. Content. Basic principles of fuel cell. Limitations of chemical fuel cell. Enzymatic fuel cell. Biomass fuel cell:. how it works?.

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Biomass Fuel Cells

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  1. Biomass Fuel Cells Sergey Kalyuzhnyi Department of Chemical Enzymology, Chemistry Faculty Moscow State University, 119992, Moscow, Russia

  2. Content • Basic principles of fuel cell • Limitations of chemical fuel cell • Enzymatic fuel cell • Biomass fuel cell: • how it works? • performance • problems • perspectives

  3. ® + - 2H 4H + 4e Anode: 2 Cathode: - + ® 4e + 4H + O 2H O 2 2 Basic principles of fuel cell (FC) • Related to battery: both convert chemical energy into electricity • Battery: the chemical energy has to be stored beforehand • FC only operates when it is supplied from external sources • Fundamental mechanism: inverse water hydrolysis reaction Net reaction: 2H2 + O2 2H2O

  4. Fuel cell technologies

  5. Hydrogen-oxygen PEFC(data ofUS Department of Energy )

  6. Limitations of large chemical FC • Cost is the major hurdle • The most widely marketed FC - 4,500 $/kW • Diesel generators – 800-1,500 $/kW • Natural gas turbines - even less! • The goal of US DOE – to cut costs for FC to 400 $/kW by 2010

  7. 50 kW(<$ 10 000) Limitations of small chemical FC • Cost as well $10,000 – only engine! • Pt-based: • poisoning with CO, H2S etc. • low fuel versatility (H2, CH3OH) • cost & shortage of Pt

  8. Dynamic of Pt cost & its availability Annualproduction: 180 tons In 2000: 57.5 mln.cars 5750 tons Pt 50 kWengines

  9. Reforming gas (H2): 12.5 % of CO under 0.1% CO activity irreversibly decreases 100 times after 10 min Pt electrodes: Poisoning by fuel impurities Hydrogenase el-ds: -not sensitive up to 1% of CO; -reversibly restore activity after inhibition; - catalystis renewable

  10. Electric current Solid polymer electrolyte O2 Н2 Immobilised hydrogenase Immobilised oxydase (laccase) Enzymatic fuel cell (indirect bioFC) Power density – till 40 W/m2 Specific power - till 6 kW/l Theoretical specific power - till 20 kW/l

  11. Problems of enzymatic fuel cells • No any full scale implementation • Cost (pure enzymes are expensive) • Stability of enzymes (inactivation, inhibition) • Low fuel versatility (enzymes are too specific) • Strong need in further R&D: • Genetic engineering for improvement of enzyme properties & development of stable large-scale source of enzymes • Improvement of electrode compartments (mass-transfer, new methods of enzyme immobilization)

  12. V Anode Solid electrolyte Cathode Organics Electron transport chain of cell Mred H2O Electron O2 Mox H+ Microbial fuel cell (MFC) CO2 • MFC – mimic of biological system in which bacteria do not directly transfer their produced electrons to their characteristic acceptors • MFC could be mediator–less (e.g., external cytochromes like in Shewanella putrefaciens or Geobacter sulfurreducens)

  13. History & current developments of MFC • Pioneering research: Potter (1912), Cohen (1931), Allen (1972) - inefficient • The first viable MFC – Bennetto et al., 1984 • Yeast-driven MFC (Reed & Nagodawithana, 1991) Current interest on the following types of prokaryotes: • Heterotrophs (Delaney et al., 1984) • Photoheterotrophs (Tsujimura et al., 2001) • Sediment (Tender et al., 2002)

  14. Electricity from anaerobic digestion Indirect (via biogas) • Gas-generators (additionally - heat production) • Reforming (conversion to H2) + H2-O2 fuel cell Direct (without biogas) • Mediator MFC • Sulphate reducing fuel cell (sulphide is mediator) • Mediator-less MFC (direct transfer of electrons from cells)

  15. V Anode Solid electrolyte Cathode Organics SRB cells S2- H2O Electron O2 SO42- CO2 H+ Biological reaction: SO42- + 2CH2O S2- + 2CO2 + 2H2O Anode reaction: S2- + 4H2O SO42- + 8H+ + 8e Cathode reaction: 2O2 + 8H+ + 8e 4H2O Sulphate reducing fuel cell

  16. Performance of MFC

  17. Problems of Microbial FC • Anode efficiency (harmonization of biological & anode reactions) • Inhibition of biological activity (pH, products) • Biofilm formation on electrode (hardly controlled) • Mass transfer limitations • Good mediators are toxic, stable binding to the electrode surface is difficult to achieve • Cathode efficiency: overpotential, H2O2 production (the same as for chemical FC), biocathodes are possible • Proton transport (membranes are costly – 100$/m2)

  18. Perspectives of MFC • No any full scale implementation • Due broad fuel versatility - not only energy production but waste(water) treatment too! *Calculations of Bert Hamelers (Wageningen University)

  19. Gastrorobot • Literally: robot with a stomach (food powered machine) • Goal – to create bioelectrochemical machine that derives all the operational power by tapping the energy of real food digestion, using microorganisms as biocatalysts The challenges of gastrorobotics: • Foraging (food location & identification) • Harvesting (food gathering) • Mastication (chewing) • Ingestion (swallowing) • Digestion (energy extraction) - MFC • Defecation (waste removal)

  20. “Gastronome”: a prototype MFC powered robot Wilkinson (2000), University of South Florida

  21. Thank you!

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