Bioconversion of CO2 and Biomass processes

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Bioconversion of CO2 and Biomass processes

• ??
• Hsin Chu
• Professor
• Dept. of Environmental Engineering
• National Cheng Kung University

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• Bacterial methanogens
• Nonphotosynthetic pathways for carbon dioxide
  fixation
• Algae photosynthesis
• Plants photosynthesis

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• Methanogenic and Acetogenic Bacteria
• Methanogenic archaebacteria
• Obligate anaerobes grow in freshwater and
  marine sediments, peats, swamps and wetlands,
  rice paddies, landfills, sewage sludge, manure
  piles, and the gut of animals
• Major cause of the natural methane release
• More than half 0.4 109 tons/yr
• Optimal condition
• 2095?
• Use either COH2 or CO2H2 as their only sources
  of carbon and energy (carbon monoxide
  dehydrogenase/acetyl-CoA synthase)

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• 1.1 Thermophilic Methanogens
• Waste gases from blast furnaces CO H2 CO2
• Low caloric value 755 kcal/m3
• A column bioreactor 55? and pH 7.4
• A mixture of cultures of three bacteria
• Among them, the photosynthetic bacterium
  Rhodospirillum rubrum carries out the water
  gas-shift reaction
• CO H2O ? H2 CO2
• A mixture of two methanogens
• Methanobacterium formicicum provides a high rate
  of hydrogen uptake but is inhibited by
  COMethanosarcina barkeri has a smaller rate of
  hydrogen uptake but is more tolerant of CO
• 4H2 CO2 ? CH4 2H2O
• High caloric value ? 6420 kcal/m3
• The methane yield was about 83, compared to the
  nonbiological catalytic methods 300700? and
  320 atm

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• 1.2 Extremely Thermophilic Methanogens
• 80110?
• Using CO2 as their sole carbon source and
  molecular hydrogen or reduced sulfur compounds as
  electron donors
• May be the earliest and most primitive forms of
  life that still exist
• Methanothermas fervidus
• Found at shallow depth from a volcanic spring in
  Iceland
• Methanococcus jannaschij Found from a deep-sea
  hydrothermal vent

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• 1.3 Bio Conversion of Methane to Methanol (Car
  Fuel)
• Methylosinus trichosporium
• Has methane monooxygenase
• Methylobacterium organophylum
• Has methane oxygenaye

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• 1.4 Thermophilic Homoacetogens
• Homoacetogenic bacteria
• strictly anaerobic
• Thermoanaerobacter kivui
• 4 H2 2 CO 2 ? CH3COOH 2H2O
• The carboxy group is derived from CO, which is
  formed from CO2 by the nickle enzyme carbon
  monoxide dehydrogenase.
• The methyl group is formed by the reduction of
  CO2 in sequence first by formate dehydrogenase,
  followed by a series of enzymatic reactions on
  reduced C1 intermediates bound to
  tetrahydrofolate.
• Acetyl-CoA is then produced from the methyl group
  and CO in a reaction catalyzed by carbon monoxide
  dehydrogenase.
• Acetogenesis was suggested to be involved in
  recycling of 10 to 20 of the carbon on earth.

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• 2. Algae Photosynthesis
• Natural photosynthesis in plants and
  microorganisms
• About 1011 tons CO2/yr
• However, the efficiency of solar energy
  conversion in plant production under optimal
  growth conditions is only 5 to 6.
• Under field conditions, only 12 for sugarcane,
  0.15 for forests
• Photosynthesis is much more efficient in
  microalgae than in terrestrial C3 and C4 plants.
• Algae can utilize the high concentrations of
  nitrate and phosphate nutrients contained in
  municipal and agricultural effluents for the
  fixation of CO2 emitted from power stations or
  steel plants.

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• Ribulose-1, 5-biphosphate carboxylase/oxygenase
  (RuBisCO)
• The most abundant protein on earth
• (1) Acting as monooxygenase when O2 is the
  substrate
• (2) Acting as carboxylase when CO2 is the
  substrate
• Aquatic cyanobacteria and microalgae In the form
  of HCO3-

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• 2.1 Microalgae
• Marine green alga Tetraselmis suecica
• The photosynthetic efficiency is 910 (optimal)
  or 4.65.1 (field). The CO2 utilization
  efficiency is close to 100.
• Good for ambient air (0.035 CO2), pure CO2, and
  stack gases (15 CO2).Max. growth rate ? 0.61
  d-1.33
• Maximal growth rate with 20 CO2 in a mineral
  nutrient medium at an NaCl conc. of 1.5
• Growth rate is still 50 of the maximal even at
  9 NaCl.
• Hot spring alga chlorella sp. UK 001
• Optimal growth temp. in the ranges 35 to 40?
• Max. growth rate gtgt 0.32 h-1.39
• 2.2 Macroalgae
• Marie macroalgae Gracilaria sp. and Gracilaria
  chilensis also work

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• 3. Biomass Process
• Plants carbohydrate, cellulose
• Microorganisms algae, bacteria
• Next slide (Tale 6.1)
• The composition of plants is remarkably
  constant.
• Stoichiometric composition of wood CH1.44O0.66
• Photosynthesis reaction
• CO2 0.72H2O ? CH1.44O0.66 1.03O2
• Second slide (Table 6.2)
• Biomass can be burned as fuel
• Third slide (Table 6.3)
• Rapid rotational crops energy farms

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