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Improvements in the Technology for Using Conventional Sources of Energy

Anaerobic degradation is a fermentation process, which takes place in the absence of oxygen. In this process animal and plant wastes are easily degraded by anaerobic bacteria (microorganisms) in the presence of water. These bacteria decompose (more appropriately, degrade) the carbon compounds present in the wastes and, in this process, gases such as methane, carbon dioxide, hydrogen, and hydrogen sulphide are liberated. The mixture of gases so liberated is called biogas which is an excellent fuel as it contains about 65 % methane which is combustible. Biogas can be burnt in gas stoves at homes. The residue left is rich in nitrogen and phosphorous and is used as manure.
Animal Dung as Fuel
In many villages in India, dried animal dung (in the form of cakes) is still being used as fuel for domestic purposes. However it is unwise to burn animal dung directly to obtain heat because of the following three reasons
  1. Animal dung contains compounds of nitrogen and phosphorus which are vital nutrients for plant growth. If the dung is burnt as such, these nutrients are destroyed and hence cannot be returned to the soil.
  2. As the dung cakes burn, a lot of smoke is produced which causes air pollution.
  3. Since dung cakes burn inefficiently, their use leads to a considerable wastage of fuel.
Therefore instead of burning animal dung directly, the dung should first be processed, so that the vital nutrients are retrieved before it is burnt. In fact, it is possible to convert animal dung into a clean fuel called biogas and the residue in which the vital nutrients remain intact can be used as manure in agriculture. The process by which this is achieved is called anaerobic degradation.

Biogas Plants

Two types of biogas plants are being used in our country; they are
  1. The fixed-dome type
  2. The floating gas-holder type
the main raw material used in these plants is animal dung (cow-dung, dung of horse, elephant, goat, etc). Plant wastes like vegetable skins, fruit pulp and human excreta may be added to the animal dung.
Biogas Plants
  1. Fixed-Dome Type Biogas Plant
    The plant consists of a dome shaped underground tank D called digester which is made with bricks and cement. A gas outlet G is provided near the ceiling of the dome. On one side of the digester is inlet chamber I, used for introducing the slurry (which is a mixture of animal dung and water). An outlet chamber O is provided on the other side of the digester. The outlet chamber is connected to the overflow tank F.
    Slurry is prepared in the mixing tank M by mixing animal dung and water. The slurry is introduced into the digester through the inlet chamber I. It is allowed to ferment for 50 to 60 days in the digester. During this period, the anaerobic bacteria present in the dung carries out the degradation, as a result of which biogas is evolved. This biogas begins to collect in the dome. As the gas keeps collecting in the dome, its pressure keeps on increasing. Due to increased pressure, the used slurry in the digester is forced out through the outlet chamber O into the overflow tank F. This slurry is taken out of the plant. It is rich in nitrogen and phosphorous compounds and is excellent manure. The gas outlet G is connected by a pipe to a stove or a burner. When the gas pressure falls, fresh slurry is added to the digester to produce more gas. Thus a continuous supply of gas is maintained.
  2. Floating Gas-Holder Type Biogas Plant
    This plant consists of an underground tank D called digester made of bricks and cement. A drum-shaped gas holder G floats over the slurry in the digester. The drum is made of steel and it floats in an inverted position, so that gas can collect in it. A gas outlet is provided at the top of the drum.
    The digester has a partition wall, which divides it into two chambers I and O. The inlet chamber I is connected to a mixing tank M and the outlet chamber O is connected to an overflow tank F.
    Slurry is prepared in the mixing tank M by mixing animal dung and water. The slurry is introduced in the digester through the inlet chamber I. For about 50 - 60 days, the slurry undergoes anaerobic degradation and biogas is evolved. The gas collects in the drum G. As more gas collects in the drum, its pressure increases, as a result of which the used slurry is forced into the overflow tank F through the outlet chamber O. This slurry is taken out of the plant and is used as manure. The gas outlet at the top of the drum is connected by a pipe to a gas stove.

Advantages of Biogas as a Fuel

  1. Biogas burns without smoke and hence does not pollute the air.
  2. Biogas has a high calorific value.
  3. The raw material (cow-dung) required for the production of biogas is inexpensive and easily available in villages.
  4. The residue leftover in a biogas plant is excellent manure.
However there is one limitation. The biogas plant has high initial cost, which is beyond the reach of an average rural Indian. To overcome this problem, the Khadi and Village Industries Commission and other agencies actively promise the construction of big biogas plants called community plants, designed to supply biogas and manure to a number of families in a community. The government gives loans and subsidies to farmers for this purpose. More than 70% of the energy requirement in rural India can be met by these plants. Biogas plants are indeed a big boon to the farmers.
Wind Energy
Moving air is called wind. Wind has energy. It can pick up things and send them flying; it can lift heaps of sand and pile them into sand dunes; it can blow against huge trees and send them crashing. This shows that the wind has a lot of energy to smash and destroy. But man is intelligent enough to put this wind energy to constructive use. The energy possessed by the wind is due to its high speed, that is, the wind possesses kinetic energy and it is this kinetic energy of wind, which is utilized for doing work.
In the earlier days, the energy of wind was utilized by man in winnowing to remove husk from grains; in propelling sail boats in rivers and seas for transport purpose and in windmills to pump out water from the ground and grind grain to obtain flour. Engineless aeroplanes called gliders depend totally on wind energy for their flight. These days, however, the energy of wind is being used to produce electricity.


A windmill is a machine, which works with the energy of wind. Two types of windmills have been used in the past. One, to run the water-pumps for drawing water from the ground and the other for grinding grains to produce flour. We will discuss both types of windmills one by one.

The windmill used for running a water-pump is shown in the above figure. This windmill consists of big blades B to catch the wind. These windmill blades can rotate over the top of a pole P. The centre of the windmill blades is connected to one end of a device called crank C. (The crank is a long rod having a U-shaped bend, which can convert the rotary motion into up-and-down motion and vice-versa.) The U-shaped bend of the crank is connected to the piston rod R of the water-pump as shown in the figure. Let us see how this windmill works to draw water from the ground.
The kinetic energy of wind rotates the windmill blades continuously. When the blades rotate, the crank rotates. This causes its U-shaped bend to lift the pump rod up and down. The rod works the pump that lifts the water from the ground. Thus, the wind blowing above the ground can be used to pump from a great depth.
There is also another type of windmill, which uses the energy of wind to do another hard job that is of grinding grains like wheat or corn to make flour. The windmill, which works like a flour-mill is shown in the below figure.
This windmill consists of the windmill blades B located on the top of a pole P. The blades are connected to a big wheel C having teeth by means of rod R. There is another big wheel D having teeth, which is arranged in such a way that it pushes against the teeth of wheel C. The wheel D has a long rod E in the downward direction. A stone-wheel F called mill-stone is fixed to the lower end of rod E. The mill-stone F is placed on another similar mill-stone G, which is fixed to the ground. Thus, the lower mill-stone is fixed and stands still whereas the upper mill-stone is turned by the long rod E.


Working of the Windmill to Grind Grain
The blowing wind rotates the blades of the windmill continuously. When the blades rotate, the rod R turns and rotates the wheel C attached to it. When the wheel C turns, it makes the wheel D turn. The wheel D, in turn, rotates the rod E. Since the upper mill-stone is fixed to rod E, the upper mill-stone F starts revolving over the fixed mill-stone G. Grains like wheat or corn are placed in the hole in the centre of the upper mill-stone through a hopper H. The wheat is crushed between the two mill-stones and is converted into flour, which falls through the edges of the mill-stones.

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