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  2. 2. 03/13/13
  3. 3. 03/13/13
  4. 4. Mystery unveiled…. Alessandro volta03/13/13
  5. 5. BIOGAS• Mixture of gases.• Produced by anaerobic digestion of organic matter.• Consist of CH4 ,CO2 ,traces of H2 & other gases.03/13/13
  6. 6. Composition of Biogas03/13/13
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  8. 8. BENEFITS FROM BIOGAS PLANTS• Used mainly for cooking & lighting purposes.• Used in internal combustion engines to power water pumps & electric generators.03/13/13
  9. 9. • Used as fuel in fuel type refridgerators.• Sludge - fertilizer.• ↓ envt. pollution03/13/13
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  11. 11. SUBSTRATE• Plant & animal biomass.• Plant biomass –• Animal biomass – cattle dung,manure from poultry,goats & sheep slaughter house & fishery wastes.• Agricultural wastes also used03/13/13
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  13. 13. Parts of biogas plant• Digester• Gas holder• Inlet• Outlet03/13/13
  14. 14. Inlet chamber• To supply cow dung to the digester• It is made at the ground level so that the cow dung can be poured easily.• made up of bricks, cement and sand.• The outlet wall of the inlet chamber is made inclined so that the cow dung easily flows to the digester.03/13/13
  15. 15. Digester• Most important part of biogas plant• Fermentation takes place - fermentation tank.• Built underground – insulated,airtight• Made up of bricks, sand and cement.03/13/13
  16. 16. • Almost at the middle of the height of digester, two openings are provided on the opposite sides for inflow of fresh cow dung and outflow of used cow dung.03/13/13
  17. 17. Gas holder• Cylindrical container• Above digester• Collect gas• The gas pipe carries the biogas to the place where it is consumed.03/13/13
  18. 18. Outlet Chamber• Digested slurry from which the biogas has been generated is removed from the biogas plant.• The outlet chamber is also at the ground level.03/13/13
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  20. 20. Types• GAS HOLDER• Fixed dome type• Floating drum type FREQUENCY OF FILLING SUBSTRATE Batch type Continuous type03/13/13
  21. 21. Fixed dome type• A fixed-dome plant consists of a digester with a fixed, non-movable gas holder, which sits on top of the digester.03/13/13
  22. 22. Floating-drum type• Consist of an underground digester and a moving gas-holder.• Gas-holder floats either directly on the fermentation slurry or in a separate water jacket.• The gas is collected in the gas drum, which rises or moves down, according to the amount of gas stored03/13/13
  23. 23. Floating-drum type03/13/13
  24. 24. • Batch type• Filled once,sealed.• Emptied when raw materials stop producing gas.• Continuous type• Fed with a definite quantity of wastes at regular intervals• Gas production continuous & regular03/13/13
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  26. 26. MICROBIOLOGY OF BIOGAS•4 steps•Hydrolysis•Acidogenesis•Acetogenesis•Methanogenesis03/13/13
  27. 27. Hydrolysis• Biomass is made up of large organic polymers• Complex polymers hydrolysed to monomers• complex organic molecules → simple sugars, amino acids, and fatty acids.• Done by hydrolytic fermentative bacteria03/13/13
  28. 28. Acidogenesis• Results in further breakdown of the remaining components by acidogenic bacteria.• Ammonia, H2, CO2, H2S, shorter volatile fatty acids, carbonic acids, alcohols, as well as trace amounts of other byproducts produced03/13/13
  29. 29. Acetogenesis• Simple molecules created through the acidogenesis phase further digested to acetic acid, carbon dioxide and hydrogen.• Acetogenic bacteria03/13/13
  30. 30. Methanogenesis• The terminal stage• Intermediate products of the preceding stages converted to methane, carbon dioxide, and water.• These components make up the majority of the biogas emitted from the system.• Methanogenic bacteria03/13/13
  31. 31. MICRO ORGANISMS• Hydrolytic & fermentative bacteria.• Acidogenic bacteria.• Acetogenic bacteria.• Methanogenic bacteria.03/13/13
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  33. 33. Methanogenic bacteria.• Create methane from the final products of acetogenesis as well as from some of the intermediate products from hydrolysis and acidogenesis .• Archaebacteria03/13/13
  35. 35. • Cocci• Spirilli• Bacilli Cocci forming colonies in cubical packets of• sarcina eight or more are called sarcina03/13/13
  36. 36. • Methanogens are a diverse group of organisms that can live in a wide range of environments.• They have been found in a range of salinity from freshwater to hypersaline.03/13/13
  37. 37. • Biogas plant – Methanosarcina barkeri, Methanobacterium omelianskii03/13/13
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  39. 39. Factors affecting methane formation.• pH• Temperature• Nitrogen concentration• C:N ratio• Creation of anaerobic conditions03/13/13
  40. 40. pH• 6-8• Acidic medium lowers methane formation. • Temperature• Fluctuation ↓ methane formation – inhibit growth of methanogens.• 30-40oC03/13/13
  41. 41. Nitrogen concentration• ↑ N2 - ↓ growth of bacteria - ↓ CH4 C:N ratio• Micro organisms in a biogas plant needs both N nitrogen and C carbon.• Research has shown that the methanogenic bacteria work best with a C/N ratio 30:1.03/13/13
  42. 42. Creation of anaerobic conditions• CH4 production takeplace in strictly anaerobic condition.• Digesters – airtight, burried under soil.03/13/13
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