Figure – 4 Floating gas holder type biogas plant. [7]
The spent slurry is now forced into the outlet chamber
from the top of the inlet chamber. When the outlet
chamber gets filled with the spent slurry, the excess is
forced out through the outlet pipe into the overflow
tank. This is later used as manure for plants. The gas
valve of the gas outlet is opened to get a supply of
biogas. Once the production of biogas begins, a
continuous supply of gas can be ensured by regular
removal of spent slurry and introduction of fresh
slurry. [7]
Disadvantages of floating gas holder type biogas plant
are (a) Expensive (b) Steel drum may rust and (c)
Requires maintenance.