Card Set Information
What is the strongest green house gas?
- increasing CO2 emissions
Where does methane mostly come from?
- 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?
Aerobic Conversion =
commercial composting and activated sludge wastewater; higher rxn rate; don't produce useful fuel gas (CO2, water)
= 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?
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
: 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