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What is the strongest green house gas?
- - increasing CO2 emissions
Where does methane mostly come from?
- Enteric Fermentation
- - releasing methane into the atmosphere increases global warming and wastes useful energy
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
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)
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
What are some impt factors/ results in Methanogenesis Reaction?
Acetoclastic Rxn and the Reduction of CO2
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
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
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
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
What about Biogas production from landfills?
exploitation of landfill gas is economically feasible after 2 years
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
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
Where does 95% of global hydrogen production come from?
Fossil Fuel Sources!
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
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
What is differnet about Biogas formation process and biohydrogen fermentation process?
in biohydrogen, last step of methanogenesis must be inhibited!!!!
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
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
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