(a) What is biogas? Name the major component of biogas.
(b) What are the raw materials used for making biogas?
(c) Describe the construction and working of a biogas plant with the help of a labelled diagram.
(d) Write any two uses of biogas.
(e) Write any two advantages of using biogas.
(a) Biogas is a mixture of gases produced by anaerobic degradation of biomass in the presence of water but in the absence of oxygen. Methane is the major component of biogas.
(b) Cow-dung and water.
(c) Construction and working of biogas plant:
A biogas plant consists of a wall-shaped, underground tank called digester, which is made of bricks, and has a dome shaped roof D. The dome acts as a gas-holder. There is a gas outlet S at the top of the dome having a valve V. There is a sloping inlet chamber I connected to a mixing tank M and a rectangular outlet chamber O connected to the overflow tank F.
Cow dung and water are mixed in equal proportions in the mixing tank M to prepare the slurry. This slurry is fed into the digester tank through the inlet chamber I to fill the tank upto the cylindrical level. Then, the cow-dung undergoes anaerobic degradation with the evolution of biogas which collects in the dome. The pressure of biogas on the slurry forces the spent slurry to go into the overflow tank F through outlet chamber O, from where it is removed.
(d) Two uses of bio gas:
(i) For cooking purpose
(ii) For lightning purpose
(e) Two advantages of biogas:
(i) Smoke-free cooking
(ii) High calorific value