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BIOGAS FOR MARGINAL

INCOME GROUPS

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WHY ONLY BIOGAS The enormous potential of biogas, estimated at

17,000 MW

Biogas technology is a particularly useful system inthe Indian rural economy, and can fulfill several enduses.

The gas is useful as a fuel substitute for firewood,

dung, agricultural residues, petrol, diesel, andelectricity, depending on the nature of the task, andlocal supply conditions and constraints, thussupplying energy for cooking and lighting.

Biogas systems also provide a residue organicwaste, after anaerobic digestion, that has superiornutrient qualities over the usual organic fertilizer,cattle dung, as it is in the form of ammonia .

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Why biogas is used for marginal

income?

Biogas is a clean ,non-polluting and low-costfuel.

It contains about 55-75% methane, which isinflammable.

Biogas can be produced from cattle dung,human waste and other organic matter by aprocess called anaerobic digestion in a bio

gas plant. The digested material, which comes out of the

plant is an enriched manure.

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WHAT IS BIOGAS TECHNOLOGY?Biogas technology is a two phase process.

In the first phase, the acid-forming bacteriahydrolyse and ferment the organic compounds(such as carbohydrates, lipids, proteins, etc.) toform organic acids, alcohols and gases of carbon

dioxide, nitrogen and traces of hydrogen sulphide.The environment in which the above activity occursis "acidic" with pH ranging from 5.1 to 6.8 .

In the second phase, a "consortium of bacteria or

(group of bacteria) work upon the organic acidsproduced during the earlier phase to producemethane gas This group of bacteria is relativelyslow performing and gives optimum performance .

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CHARACTERISTICS OF GOOD

Community-size biogas plant

(CBP) A good biogas plant must optimize the following

four functions:

i) gas production rateii) methane gas concentration in the biogas

produced

iii) stability of the processiv) lower overall cost of production of biogas

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Parts of a biogas plants1. a digester( where the slurry is anaerobically

fermented)2. an inlet tank (where dung and water are mixed)

3. a gas holder /dome (into which the generated

gas is collected)

4. An outlet tank ( to remove the digested slurry)

5. a manure pit (for digested slurry storage)

6. distribution pipeline (to take the biogas to utility

points)

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The evolution of biogas technology Biogas plants in India were experimentally

introduced in the 1930's, The early plants

developed were very expensive and were notcost effective in terms of the gas output, indeedthe early models were not producing enough gasto supply a small family . Some of the earlymodels were also prone to burst, so overall, thetechnology was not viable for dissemination.

In 1961 the Khadi and Village IndustryCommission chose to promote Patel's design,which, although more costly than other models,

was more productive, had a longer life, andrequired minimal maintenance.

Anaerobic digester design has continued toevolve over the years, but systems are generally

variations around the theme of the floating-domeand the fixed-dome design. (KVIC, 1993).

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Different types of biogas plant

recognized by MNES (Ministry of Non-

Conventional Energy Sources ) Floating-drum plant with a cylinder digester (KVICmodel).

Fixed-dome plant with a brick reinforced, moulded dome(Janata model).

Floating-drum plant with a hemisphere digester (Pragatimodel).

Fixed-dome plant with a hemisphere digester(Deenbandhu model).

Floating-drum plant made of angular steel and plastic foil

(Ganesh model). Floating-drum plant made of pre-fabricated reinforced

concrete compound units.

Floating-drum plant made of fibreglass reinforcedpolyester.

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Factors hindering spread of biogas Technically, problems have arisen from installing too

large a capacity plant . Economically, biogas systems have been shown to be

cost-effective .

Despite the positive cost-benefit of biogas technology,the 'macro-environment', may discriminate against the

uptake of biogas.

The system of grants and loans may hinder the correct

choice of plant for different users, such as theineligibility of community size systems, due to their

size.

Th Mi i f N C i l

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The Ministry of Non ConventionalEnergy Sources has taken up following

programmes for development and

harnessing of biogas potential in the

country National Project on Biogas Development (NPBD) {for

setting up of family type biogas plants} [35 lakh plantsup to 31 March 2003 against 120 lakh]

Community, Institutional and Night Soil based BiogasPlants (CBP/IBP/NBP) Programme

[3,902 plants up to 31 march 2002.] Research& Development on Biogas {Production &

Utilization Technology}