Production of Biogas - Fixed Dome Type Biogas Plant

Production of Biogas - Fixed Dome Type Biogas Plant

 

 Raw Materials Required

Forms of biomass listed below may be used along with water:

• Animal dung
• Poultry wastes
• Plant wastes ( Husk, grass, weeds etc.)
• Human excreta
• Industrial wastes(Saw dust, wastes from food processing industries)
• Domestic wastes (Vegetable peels, waste food materials)

Principle

Biogas is produced as a result of anaerobic fermentation of biomass in the presence of water.

Construction

The biogas plant is a brick and cement structure having the following five sections:

• Mixing tank present above the ground level
  
• Inlet chamber: The mixing tank opens underground into a sloping inlet chamber
  
• Digester: The inlet chamber opens from below into the digester which is a huge tank with a dome like ceiling. The ceiling of the digester has an outlet with a valve for the supply of biogas
  
• Outlet chamber: The digester opens from below into an outlet chamber
  
• Overflow tank: The outlet chamber opens from the top into a small over flow tank

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Working

• The various forms of biomass are mixed with an equal quantity of water in the mixing tank. This forms the slurry
  
• The slurry is fed into the digester through the inlet chamber. The temperature of the slurry must be maintained around 35 ^oC. Any drop in temperature will reduce the anaerobic activity and hence the yield of biogas
  
• When the digester is partially filled with the slurry, the introduction of slurry is stopped and the plant is left unused for about two months
  
• During these two months, anaerobic bacteria present in the slurry decompose or ferment the biomass in the presence of water
  
• As a result of anaerobic fermentation, biogas is formed, which starts collecting in the dome of the digester
  
• As more and more biogas starts collecting, the pressure exerted by the biogas forces the spent slurry into the outlet chamber
  
• From the outlet chamber, the spent slurry overflows into the overflow tank
  
• The spent slurry is manually removed from the overflow tank and used as manure for plants
  
• The gas valve connected to a system of pipelines is opened when a supply of biogas is required
  
• To obtain a continuous supply of biogas, a functioning plant can be fed continuously with the prepared slurry
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Advantages of Fixed Dome Type of Biogas Plant

• Requires only locally and easily available materials for construction
• Inexpensive
• Easy to construct
• Due to the above reasons, this plant is also called the Janata Gobar gas plant.

Advantages of Biogas as a Fuel

• As domestic fuel
• For street lighting
• For generation of electricity

• High calorific value
• Clean and excellent fuel containing upto 75% methane
• No residue produced
• No smoke produced
• Non - polluting
• The slurry is periodically removed and used as excellent manure which is rich in nitrogen and phosphorous
• Economical
• Can be supplied through pipe lines
• Burns readily - has a convenient ignition temperature Uses of Biogas
  
  • Biogas is used