By,N Venkata Srinath,1st Year MS Power Systems.

Bio-GasBiogas typically refers to a gas produced by

the biological breakdown of organic matter in the absence of oxygen.

This is produced by anaerobic decomposition of bio-mass.

How Bio-gas is alternative/renewableThe increased consumption of energy all over

the world has led to a drastic increase to the rates of all carbon based fuels.

A finite(Non renewable) sources that will not be able to meet the increasing fuel needs in the world.

 Fossil fuels emitting excessive carbon dioxide and other gases, they increase the global warming in the world……….

One of the alternative as well as renewable source of energy is Bio-Gas.

Evaluation

1630-Von Helmont first observed about an inflammable gas emanating from decaying organic matter.

But, major exposure was from the World War II when people faced scarcity of fossil fuel.

Block diagram of Bio-gas Production

Input Digester

Methane(40-70)%

Slurry

CO2 (30-60),

H2- 1%, N2 -

0.5%, CO- 1%,

O2- 1%, H2S- 1%

InputBio-Mass

Animal-waste Agro-waste Night soil

Dung Crop Residue Slaughterhouse Vegetable Waste Poultry-Casting Catering Waste Dead Bodies Food processing Waste

The above inputs either sole or in combination are mixed with water and fed into a digester.

Digester: A biogas digester, also known as a methane digester, is an equipment which can turn organic waste into usable fuel.

The biogas digester relies on bacterial decomposition of biomass.

Digester TypesFixed-dome plantsFloating-drum plantsBalloon plantsHorizontal plantsEarth-pit plantsFerro cement plants

Fixed-dome plants

Characteristics The costs of a fixed-dome biogas plant are relatively

low.

It is simple as no moving parts exist.

Here are also no rusting steel parts and hence a long life of the plant (20 years or more) can be expected.

The plant is constructed underground, protecting it from physical damage and saving space.

There wont be much external temperature effect.

Floating-drum plants

A floating-drum plant consists of a cylindrical or dome-shaped digester and a moving, floating gas-holder, or drum

If biogas is produced, the drum moves up, if gas is consumed, the gas-holder sinks back.

Digestion ProcessBio-Chemical process.Anaerobic decomposition.

Digestion ProcessBio-Chemical process: Here, micro

organisms are involved in the chemical reaction.

Digestion ProcessBio-Chemical process: Here, micro organisms

are involved in the chemical reaction.Anaerobic decomposition: A process in which

organic matter is broke down into simple compounds in the absence of oxygen.

Anaerobic decomposition

AcidificationMethanogenesis

Acidification: In this, acidic bacteria dismantle the complex organic molecules into peptides, glycerol, alcohol and the simpler sugars.

Methanogenesis: In this process, methane producing bacteria gets activated and produce methane gas by utilizing the products obtained from acidification.

Anaerobic digestion will occur best within a pH range of 6.8 to 8.0. and temperature range of 32-350C

More acidic or basic mixtures will ferment at a lower speed.

The introduction of raw material will often lower the pH (make the mixture more acidic).

Digestion will stop or slow dramatically until the bacteria have absorbed the acids.

A high pH(Basic in nature) will encourage the production of acidic carbon dioxide to neutralize the mixture again.

OutputMethane(40-70)% CO2 (30-60)%

O2- - 1%CO - 1%H2S -1%

N2 -0.5%

By- product: Slurry( N-1.4%,P-1%,K-0.8%.)

ApplicationsPower Generation: Biogas can be used to

operate a dual fuel engine and can replace up to 80% of   diesel.

Biogas can be used for cooking.

Gas lamps can be fueled by biogas.

Advantages Eco friendly energy production.Smaller biogas production units can support

lightning and cooking.Visible improvement in rural hygiene.Environmental benefits on a global scale:

Biogas plants significantly lower the greenhouse effects on the earth's atmosphere.

 Protects the earth's natural resources. Conversion of natural organic waste into Bio-

fertilizer.

DisadvantagesThe main disadvantage is the loss of the organic

waste for compost or fertilizer. 

Very limited in the quantity of electricity it can produce on the global scale .

There is little or no control on the rate of gas production, although the gas can, to some extent be stored and used as required. 

Technical DetailsSize of plant Quantity of

cattle dung required daily

No. of cattle heads

required

Estimated cost

1 cubic meters 25 kg 2-3 Rs.7,000/-

2 cubic meters*

50 kg 4-6 Rs.9,000/-

3 cubic meters 75 kg 7-9 Rs.10,500/-

4 cubic meters 100 kg 10-12 Rs.12,500/-

6 cubic meters 150 kg 14-16 Rs. 15,000/-

*A biogas plant of 2 cum capacity is sufficient for providing cooking fuel to a family of 4 members.

Indian Scenario In India its experimentation started in 1940.

The importance of energy was brought into sharp focus since the 1970’s oil shortage which escalated the prices of conventional energy. Since then attention has shifted to alternative sources of energy.

The Central Sector Scheme on National Biogas Program, which mainly caters to setting up of family type biogas plants, has been under implementation since 1981-82.

The Municipal Corporation of Delhi is planning to install a 1-MW bio-gas power plant on a public-private partnership basis at the Ghogha Dairy complex in North Delhi

Central Subsidy :

Capacity of the Biogas plant

(Cum)

General (Rs.) SC/ST/Small farmers (Rs.)

Additional for attaching toilet

(Rs.)1 2100 2800 500

2 to 6 2700 3500 500