Biofuels in Perspective

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11 Biological Hydrogen Production by Anaerobic Microorganisms Servé W.M. Kengen, Heleen P. Goorissen, Marcel Verhaart and Alfons J.M. Stams Laboratory of Microbiology, Wageningen University and Research Center Ed W.J. van Niel Laboratory of Applied Microbiology, University of Lund, Sweden Pieternel A.M. Claassen Agrotechnology and Food Sciences Group, Wageningen University and Research Center, Wageningen, The Netherlands Abbreviations Ca Caldicellulosiruptor Cl Clostridium E. Escherichia Eb Enterobacter ED Entner-Doudoroff EM Embden-Meyerhof P. Pyrococcus P(H2) Hydrogen partial pressure PP Pentose phosphate Ta Thermoanaerobacter Tt Thermotoga Biofuels. Edited by Wim Soetaert, Erick J. Vandamme. © 2009 John Wiley & Sons Ltd. ISBN: 978-0-470-02674-8
198 Biofuels 11.1 Introduction Hydrogen gas has great potential as a future fuel, as during its combustion the greenhouse gas CO2 is not produced. However, hydrogen is only a true ‘green’ fuel if it is produced from renewable sources like wind, sunlight, geothermal energy or biomass. A wide variety of microorganisms is able to form hydrogen in light-dependent and in light-independent processes, such as dark fermentations. Hydrogen can be formed in the fermentation of complex biomass, but for large-scale production thus far only hydrogen formation from polysaccharides is feasible. The various types of microorganisms that can play a role in hydrogen formation by dark fermentations will be discussed here, with special emphasis on the thermophilic hydrogen-producing microorganisms. At elevated temperatures hydrogen formation is thermodynamically more feasible, and less undesired side-products are produced. The current knowledge on the key enzymes (hydrogenases, oxidoreductases) of the various hydrogen producing microorganisms is highlighted, making use of the genome information that is available now for several of the hydrogen producing species. The availability of the complete genome sequences also offers the possibility to apply genetic tools to optimize hydrogen formation. Acetate is an obligate end product of dark fermentations, which limits the hydrogen yield. Options to deal with the acetate problem are discussed. The application of electricity-mediated electrolysis would broaden the range of compounds that can be used for hydrogen formation. 11.2 Hydrogen Formation in Natural Ecosystems In methanogenic environments hydrogen is a key intermediate in the anaerobic decomposition of organic matter to methane and carbon dioxide. 1 At low temperatures (up to about 45 ◦ C) about 1/3 of the methane is formed by reduction of carbon dioxide with hydrogen as electron donor: 4H2 + HCO3 − + H + → CH4 + 2H2O �G 0′ =−135.6 kJ/mol methane while 2/3 of the methane is formed by acetate cleavage: (acetate − + H2O → HCO3 − + CH4 �G 0′ =−31 kJ/mol methane As methanogens cannot metabolize complex organic carbon compounds (polysaccharides, proteins, lipids, nucleic acids, etc), fermentative bacteria are required to funnel the degradation of complex organic compounds to the methanogenic substrates hydrogen and acetate. Irrespective the type of microorganisms that are involved and irrespective the nature of organic compounds, in methanogenic environments methane and carbon dioxide are the final carbon end products. At moderately high temperatures (50–80 ◦C), even all methane is formed from the reduction of carbon dioxide by hydrogen. This is because at these conditions, acetate is first degraded by bacteria to form hydrogen and carbon dioxide: acetate − → 2HCO3 − + H + + 4H2 �G 0′ =+104.6 kJ/mol acetate the hydrogen being used by methanogens to reduce carbon dioxide to methane. 2 At first glance it may seem that at high temperatures all organic carbon can be converted into carbon dioxide and hydrogen, provided that methanogens are inhibited. This indeed
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Biofuels Biofuels. Edited by Wim So
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Biofuels Edited by WIM SOETAERT Ghe
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Contents Series Preface ix Preface
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Contents vii 6.3 Biomass Gasificati
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Series Preface Renewable resources,
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Preface This volume on Biofuels fit
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Editors List of Contributors Wim So
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1 Biofuels in Perspective W. Soetae
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Table 1.1 Approximate average world
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Table 1.3 Energy yields of bio-ener
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Biofuels in Perspective 7 is burnt
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2 Sustainable Production of Cellulo
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Sustainable Production of Cellulosi
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Figure 2.9 2004 US adoption rates o
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3 Bio-Ethanol Development in the US
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Bio-Ethanol Development in the USA
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Biorefineries in Production (115) B
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Cost of Cellulosic Ethanol, $ per g
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4 Bio-Ethanol Development(s) in Bra
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Bio-Ethanol Development(s) in Brazi
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Share of energy consumption 100% 90
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Table 4.2 Main technological improv
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4.7.4 Use of Fertilizers and Pestic
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78 Biofuels Table 5.1 Biodiesel pro
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80 Biofuels CH 2 O CH O COR R1 + 3
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82 Biofuels short reaction times. 9
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84 Biofuels Table 5.4 Overview on h
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86 Biofuels Table 5.5 Critical cond
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88 Biofuels methoxide as catalyst u
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90 Biofuels KOH Methano Oil/Fat Aci
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92 Biofuels 16. J. Graille, P. Loza
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6 Bio-based Fischer-Tropsch Diesel
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6.2.1.2 Catalysts Bio-based Fischer
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Bio-based Fischer-Tropsch Diesel Pr
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7 Plant Oil Biofuel: Rationale, Pro
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Table 7.1 Market milestones for pla
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Water CO 2 Figure 7.1 Closed CO 2 l
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Plant Oil Biofuel: Rationale, Produ
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130 Biofuels Among the attractive f
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132 Biofuels Table 8.1 Enzymatic tr
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134 Biofuels conversion was maintai
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136 Biofuels (diglycerides) decreas
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138 Biofuels ME content (wt.%) Reac
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140 Biofuels Ratio of initial react
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142 Biofuels (a) 34 kDa 31 kDa 34 k
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144 Biofuels preparation of whole-c
Page 161 and 162: ability to reduce flocculation (% o
Page 163 and 164: 148 Biofuels 5. R. C. Strayer, J. A
Page 165 and 166: 150 Biofuels 46. H. Fukuda, Immobil
Page 168 and 169: 9 Production of Biodiesel from Wast
Page 170 and 171: Production of Biodiesel from Waste
Page 174 and 175: 9.3.2 Processing of Crude and Waste
Page 176 and 177: Heavy layer from alkaline neutralis
Page 182 and 183: CPO I 1 1 Heating 60°C Reaction st
Page 184 and 185: References Production of Biodiesel
Page 186 and 187: 10 Biomass Digestion to Methane in
Page 188 and 189: Cow manure Pig manure Yard manure B
Page 190 and 191: Number of plants 3000 2500 2000 150
Page 192 and 193: Biomass Digestion to Methane in Agr
Page 196 and 197: Table 10.4 Alternative forms of ene
Page 200 and 201: Wet fermentation 3 - 10% TS applica
Page 202 and 203: Rel. Frequency [%] 35 30 25 20 15 1
Page 204 and 205: Steam 2 1 Energy crops (& manure) D
Page 210: Biomass Digestion to Methane in Agr
Page 215 and 216: 200 Biofuels lactate 6 glucose 1 GA
Page 217 and 218: Table 11.2 Continued Organism Domai
Page 219 and 220: 204 Biofuels NADH is that the react
Page 221 and 222: 206 Biofuels Clostridium thermocell
Page 223 and 224: 208 Biofuels in particular in Cl. p
Page 225 and 226: 210 Biofuels ferredoxin-dependent m
Page 227 and 228: 212 Biofuels Concentration (mM) 45
Page 229 and 230: 214 Biofuels genes of the glycolysi
Page 231 and 232: 216 Biofuels 11. S. Tanisho and Y.
Page 233 and 234: 218 Biofuels 49. M. J. Axley, D. A.
Page 235 and 236: 220 Biofuels 83. P. J. Silva, E. C.
Page 238 and 239: 12 Improving Sustainability of the
Page 240 and 241: Table 12.1 Corn ethanol dry mill: e
Page 242 and 243: Table 12.2 Atmospheric CO2 (equival
Page 244 and 245: Table 12.3 Incremental CO2 equivale
Page 246 and 247: Improving Sustainability of the Cor
Page 248 and 249: Improving Sustainability of the Cor
Page 250 and 251: Index italic entries indicate refer
Page 252 and 253: iorefineries 3, 10, 11, 41 and corn
Page 254 and 255: policy (official) 59-61 production
Page 256 and 257: NADH 200-6, 207, 210 natural gas 1
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