Gobar Gas Plant construction Class IX

Bio gas for village… Bio gas is a clean unpolluted and cheap source of energy in rural areas.  It consists of 55-70% methane  which is inflammable. Bio gas is produced from cattle dung in a bio gas plant commonly known as gobar gas plant through a process called digestion. 

Objectives 1. To provide fuel for cooking purposes and organic manure to rural house holds through family type Bio Gas Plants. 2. To mitigate drudgery of rural women, reduce pressure on forests and accentuate social benefits.  3. To improve sanitation in villages by linking sanitary toilets with bio gas plants.

Construction Technique – Need to keep in Mind Site Selection Digging of the pit Foundation laying  Machinery construction work Laying of pipeline and accessories Precautions in lying pipelines.

A lay out Model of Gobar gas plant

Components required for Bio gas plant Mixing tank and inlet  Digester Gas holder or gas storage dome Outlet and compost pits and  Gas main outlet and valve, pipeline, water fittings, gas stoves, lamp and similar appliances run on bio gas.

Feeder (Raw materials) from the Villages Cow dung Human waste (link latrine to the Gas plant) Animal waste livestock and poultry wastes, night soil, crop residues, food-processing and paper wastes, and materials such as aquatic weeds, water hyacinth, filamentous algae, and seaweed.

Construction Process… First a pit is dug, perhaps ten feet deep. Then a water-tight cement cylinder (with brick or gravel) is constructed. Next, a wall is built across the middle, extending up from the bottom, not quite to the top. Intake and outgo pipes are installed. The whole unit is water-tight.

The manure is mixed with water in the Intake basin to make a slurry, which then goes down the pipe to the bottom of the left side. This side of the cylinder gradually fills and overflows to the right side. Meanwhile, the whole mass bubbles methane up to the top. It collects under the large metal bell-like cover. The gas builds pressure, and can be taken off through a rubber tube to a gas stove in a kitchen.

Model of Gas plant

When both sides of the cylinder are full, the effluent flows out from the bottom of the right side each time more raw manure is added to the left. What comes out on the right is of more value as fertilizer than the raw manure. So the methane is an added byproduct literally "something for nothing," once the capital expense of the construction is paid.

Cost estimate… Sl. no. Capacity of plant retention period Unit cost 1 1 cu. m 40 days 4700/- 2 2 cu. m 6500/- 3 3 cu. m 7600/- 4 4 cu. m 8700/-

Subsidy available to Villages Size of Plant (in cu. m)  Central subsidy for SF, MF AL SC ST Hilly areas Central subsidy for others State subsidy under Anila Yojane SF MF AL SC ST Hilly areas State subsidy for Hilly areas not approved from central government Total 1 2300 1800 1500 2000 3800 2 3500 4000 5800 3 4

Advantages (a) Large cattle population in the countryside ensuring steady source of supply of the raw material required for running the gas plant. (b) Helps in reducing the deforestation as it arrests for cutting of trees for firewood. (c) Helps in maintaining ecological balance. (d) Helps in rural sanitation (e) Lower capital cost and almost cost free maintenance. (f) Removes drudgery of women.

Uses of Gobar Gas… Generally the uses of the gas can be as under 1) cooking 2) lighting 3) Motive Power a) run pump set b) chalf-cutter 4) can produce electricity.  Motive Power can be produced by linking the Gobar Gas to a duel fuel engine, specially designed for Gobar Gas.

Courtesy http://www.unu.edu/unupress/unupbooks/80434e/80434E0k.htm