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BIOMAN 2011 WORKSHOP MiraCosta College Instructor: Elmar Schmid, Ph.D. “Biofuels Production & Analysis” Session #1 – Biohydrogen.

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Presentation on theme: "BIOMAN 2011 WORKSHOP MiraCosta College Instructor: Elmar Schmid, Ph.D. “Biofuels Production & Analysis” Session #1 – Biohydrogen."— Presentation transcript:

1 BIOMAN 2011 WORKSHOP MiraCosta College Instructor: Elmar Schmid, Ph.D. “Biofuels Production & Analysis” Session #1 – Biohydrogen

2 Hydrogen  Biohydrogen is hydrogen gas (H 2 ) produced with the help of biological life forms from renewable biomass materials.  Hydrogen is the single most abundant chemical element in the universe; it is abundantly present on earth in form of water and stored in biomass.  H 2 is - with a molecular weight of 2 g/mol - the lightest known gas.  H 2 has a very low solubility in water. - only 1.93 ml of hydrogen gas dissolves in 100 ml of water at STP  With 143 MJ/kg, H 2 has the highest gravimetric energy density (or heating value) of any known fuel.  H 2 can be converted into usable heat and electricity with high conversion efficiency and without carbon emissions, e.g. CO 2 or soot, using fuel cell (FC) technology. Bio

3 Type of FuelOriginMolecularStandardHeating FormulaEnthalpy ΔH o Value (kJ/mol)(MJ/kg) Crude Oilfossilmixturen.a.-44.3 GasolinefossilC 5-12 H 12-26 -6,130-47.3 Kerosenefossilmixturen.a.-46.2 Coal*fossilC 135 H 96 O 9 NS-55,210-30.5 Methane/NGfossil & bioCH 4 -890.4-55.6 EthanolbioC 2 H 5 OH-1,368-29.7 MethanolbioCH 3 OH-727.5-22.7 Petroleum DieselfossilC 15-18 H 32-38 n.a.-44.8 BiodieselbioC 9 H 20 -5,520-43 HydrogenbioH2H2 -286-143 GlucosebioC 6 H 12 O 6 -2,803-15.57 Wood**biomixturen.a.-12.1 Comparative standard enthalpies and heat values of fuels

4 2 H + + 4 e - → H 2 H2H2 Industrial Production of Hydrogen Natural Gas Coal Crude Oil Fossil Fuels

5 Production of Biohydrogen  from renewable biomass Pre- Processor + Enzymes Fermenter (Bacteria) H2H2 Cellulosics Hemicellulosics Starch Glucose/ Sucrose Sun Photo- Bioreactor (Algae) CO 2 H 2 O Figure©E.Schmid-2010

6 Trapped gas (H 2 + CO 2 ) Gas-producing Bacterium (Glucose broth) Non-gas-producing Bacterium (Glucose broth) Gas producing microbes

7 ProcessType of microorganism AdvantagesDisadvantages Direct biophotolysis Green algae H 2 directly from cheap water and free sunlight. High solar conversion efficiency Requires high light intensities. Low H 2 production rate (HPR). Indirect photolysis Cyanobacteria H 2 from cheap water with the help of nitrogenase enzyme. Ability to generate ammonium at same time. Degradation of H 2 via uptake hydrogenases lowers HPR and H 2 yield. About 30% O 2 in gas mixture has inhibitory effect on nitrogenase. Photofermentation Photosynthetic bacteria Utilization of wide spectrum of light. H 2 production from different waste materials, e.g. distillery effluents. Light conversion efficiency is with about 1-5% very low. O 2 is strong inhibitor of hydrogenase. Dark fermentation Fermentative bacteria (Enterobacter, Clostridia, Thermotoga, Klebsiella) Continuous H 2 production in the absence of light. High HPR from diverse biomass-derived carbon feedstock. Simultaneous production of other value products, such as butyric acid, lactic acid, ethanol, etc. Relatively low H 2 yields with expensive carbon feedstock, e.g. glucose. Product gas mixture contains CO 2 and may contain other noxious gases, i.e. H 2 S which have to be separated. The toxic gas H 2 S is also “poisoning” fuel cells. Comparison of important biological hydrogen production processes

8 Fermentation Principle Organic substrates are metabolized without the involvement of an exogenous (external) oxidizing molecule, e.g. O 2. Fermentation is typically (but not necessarily) anaerobic. Substrate Oxidized product(s) Reduced products NAD+ NADH +H + Internal intermediates e.g. Pyr 2e - + 2 H + e.g. H 2, CO 2 Acetate Lactate 2,3 Butanediol Bacterium e.g. Glucose Xylose

9 Pyruvate + HS-CoA + 2 Fd → Acetyl-CoA + 2 FdH + CO 2 1. Clostridia bacteria 2 FdH → 2 Fd + H2H2 PFOR Hyd Bacterial Biohydrogen Production - Strictly anaerobic bacteria

10 Pyruvate + HS-CoA → Acetyl-CoA + Formate (HCOOH) PFL HCOOH + X → CO 2 + XH 2 XH 2 → X + FHL Ni, Se Mg Hyd H2H2 2. Enterobacteriaceae-type - Facultative anaerobic bacteria

11  Key enzymes used by different hydrogen producing microbes which produce molecular hydrogen (H 2 )  Most hydrogenases are nickel-iron-selenium [NiFeSe]- of nickel- iron [NiFe]-containing enzymes  [NiFe]-dependent uptake hydrogenases catalyze the reversible heterolytic cleavage of molecular hydrogen (H 2 ↔ 2 H + + 2 e - )  Hydrogenases are extremely oxygen-sensitive enzymes and become rapidly inactivated in the presence of molecular oxygen (O 2 ) - anaerobic conditions are required in biohydrogen fermenters Bacterial Hydrogenases

12 Visible H 2 production by a hydrogen producing microbe

13  In the presence of oxygen, H 2 can be converted into usable heat and electricity with the help of combustion or via electrochemical processes, i.e. fuel cells.  Hydrogen conversion happens without carbon-based emissions, i.e. the green house gas CO 2 or soot.  Conversion of hydrogen gas in a fuel cell generates DC electricity and only water and some heat are released as waste products. Hydrogen conversion into usable energy 2 H 2 (g) + O 2 (g) 2 H 2 O (l) - 286 kJ/mol

14 H2H2 4e - 2 H + O2O2 H2OH2O + 4e - 1 FC stack H 2 Source VmVm + Cathode - Anode Pt or Pd Nafion Membrane Fuel Cell Working Principle


16 5-stack PEM Hydrogen Fuel Cell Power per cell: 200 mW Power (5 cells): 1 W ( H2H2 H2OH2O O2O2 - + Cathode Anode

17 37 o C N2N2 Heater/Stirrer plate Solid bed Bacterial Culture (500 ml) Spinner flask Valve 4 Cartridge (filled with soda lime) Glass beaker 20% NaOH Inverted graduated cylinder (500 ml) Silicone tubing 1 W Fuel cell Voltmeter Lab Set-Up Graphic©E.Schmid-2010 2 ml shaped Plastic pipette Water bath Valve 1 Valve 2 Valve 3 Fan

18 1. Hydrogen production rate -Amount of hydrogen gas generated per time per volume -Unit usually given in: ml H 2 / h / l or mmol H 2 / h / l (mM / h) 2.Hydrogen yield - Amount of hydrogen gas generated per amount of feedstock - Units given in: mol H 2 per mol glucose Lab Objectives In this lab session you will measure the amount of hydrogen gas produced by a batch culture of a hydrogen-producing bacterium and perform following calculations: For glucose (C 6 H 12 O 6 ) the theoretical (achievable) microbial hydrogen yield is 4 mol H 2 / mol glucose


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