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2011-05-11 18:52:02

wednedays lecture
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  1. What is the strongest green house gas?
    • Methane
    • - increasing CO2 emissions
  2. Where does methane mostly come from?
    • Enteric Fermentation
    • - releasing methane into the atmosphere increases global warming and wastes useful energy
  3. What is Biogas (Utilizing waste)?
    conversion of organic matter directly to a gas, usually a mixture of methane and CO2 w/ small quantities of other gases such as Hydrogen sulfide
  4. What are 2 ways to produce Biogas?
    • 1) Aerobic Conversion = commercial composting and activated sludge wastewater; higher rxn rate; don't produce useful fuel gas (CO2, water)
    • 2) Anaerobic Digestion = wastewater treatment and decomposition of food wastes and landfill biomass ; bacterial fermation process; produces biogas (CH4, CO2)
  5. What are the 4 steps of Anaerobic Digestion?
    • 1) Hydrolysis
    • 2) Acidogenesis
    • 3) Acetogenesis
    • 4) Methanogenesis

    complex polymers --> monomers & oligomers--> (release acetate & CO2, hydrogen) --> volatile fatty acids --> methane/ CO2
  6. What are some impt factors/ results in Methanogenesis Reaction?
    Acetoclastic Rxn and the Reduction of CO2
  7. What are some impt Operational Parameters?
    • -factors that affect rate of digestion and biogas production (MOST impt to LEAST impt)
    • 1) TEMPERATURE- higher temp is better
    • - mesophillic 95F 15-30 days
    • - thermophilic 130F 12-14 days
    • 2) pH: 5.5 - 8.5
    • 3) Carbon to Nitrogen ratio of 20-30:1
    • 4) organic loading rate needs to be optimized
  8. What is impt to know about the sustainable cyle of anerobic digestion ?
    cannot acheieve significant energy production from algae w/o recylcling most of phosphate and potassium
  9. What about agricultural Biogas plant?
    - wet digestion?
    - mixing to maintain what?
    • - wet digestion dominates agricultural sector
    • - mixing is impt to maintain a homogenous digestate/ fermatation broth
  10. T/F: Biogas yields depend on SUBSTRATE.
    - how much methane do most agricultural raw materials product?
    • TRUE; most from non-agricultural wastes; least from agricultural waste
    • 52-56%
  11. What about Biogas production from landfills?
    exploitation of landfill gas is economically feasible after 2 years
  12. What are some environmental Impacts of Biogas?
    • - has a dual GHG benefit
    • - reduction of emissions of methane
    • - reduction of the release of CO2 from fossil fuels
  13. What is Boiled Gut Biogas?
    • swedish method for biogas production
    • instestines, udders, blood, and parts of kidneys and liver
    • heated to get rid of impurities
    • digested for 1 month
    • --> resulted in Amanda= worlds first train to run on only biogas
  14. Where does 95% of global hydrogen production come from?
    Fossil Fuel Sources!
  15. What are some Biohydrogen Production Pathways?
    • 1) Direct Photolysis
    • can produce H2 directly from water and sunlight
    • 2) Indirect Photolysis
    • can produce H2 from water and fixes nitrogen
    • 3) Dark Fermenttation
    • can produce H2 w/o light and uses lots of carbon sources
    • 4) Photo Fermentation
    • uses wide spectrum of light energy and different waste materials
  16. Dark Fermentation Hydrogen Production: majority of microbial hydrogen productions comes from anaerobic metabolism of pyruvate during catabolism of substrates
    most carbon source from glucose > sucrose > xylan >>> cellulose
  17. What is differnet about Biogas formation process and biohydrogen fermentation process?
    in biohydrogen, last step of methanogenesis must be inhibited!!!!
  18. What is Photo-fermentation? What are the 2 stages?
    • photosynthetic bacteria (Rhodopseudomonas & non-sulfur bacteria) can produce hydrogen
    • 1) Dark fermentation (facultative anaerobes)
    • 2) Photofermentation (photosynthetic bacteria) --> hydrogen gas and CO2
  19. What is Nitrogenase Dependent Hydrogen production?
    • has 1) nitrogen fixation and 2) H2 production activity
    • stimulated by light and strongly inhibited by oxygen, ammonium, and nitrogen gas