INTRODUCTION*Biogas is a mixture of gases produced by the breakdown of organic matter in the absence of oxygen.

*It is a renewable energy source.

*It is produced by anaerobic digestion of biodegradable materials such as manure, sewage, municipal waste, green waste, plant material, and crops.

*It is primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulphide (H2S), and moisture.

*Combustion of these gases produces energy.

PROPERTIES*Ignition temperature is between 650 and

750C.

*Calorific value is 18.7 to 26 MJ/m3

* Explosion limit: 5 to 14 % in air.

*Air to Methane ratio for complete

combustion is 10 to 1 by volume.

*One cubic meter of biogas is equivalent to

1.613 liter of kerosene or 2.309 kg of LPG or

0.213 kW of electricity.

PRODUCTION*Biogas is produced in a

biogas plant.

*A biogas plant is an anaerobic digester that treats farm wastes or energy crops.

*These plants can be fed with energy crops such as maize silage or biodegradable wastes including sewage sludge and food waste.

*During the process (anaerobic digestion), an air-tight tank transforms biomass waste into methane.

BIOGAS PLANT

Biogas energy production potential by source

FORMATION

CompositionTypical composition of biogas

Compound Molecular formula  %

MethaneCH4 50–75

Carbon dioxideCO2 25–50

NitrogenN2 0–10

HydrogenH2 0–1

Hydrogen sulphideH2S 0–3

OxygenO2 0–0

APPLICATION

Heating• No pre-treatment required• Easiest way to use biogas

Power generation• Both electricity and heat can be produced in the composition of 35% and 65% respectively

Vehicle fuel•Requires considerable processing•Water, impurities and particles must be removed

•Great environmental factors

Gas network• Natural gas being used for gas cookers, heaters, baking ovens, water heaters etc.

Industries• Used for heating premises, district heating power production, heating ovens etc.

ADVANTAGES*Provides a non-polluting and renewable source of energy.

*Efficient way of energy conversion (saves fuel wood).

*Saves women and children from drudgery of collection and carrying of firewood.

*Produces enriched organic manure.

*Leads to improvement in the environment, and sanitation and hygiene.

*Provides a source for decentralized power generation.

*Leads to employment generation in the rural areas.

Cont..

*Household wastes and bio-wastes can be disposed of usefully and in a healthy manner.

*The technology is cheaper and much simpler than those for other bio-fuels, and it is ideal for small scale application.

*Any biodegradable matter can be used as substrate.

*Anaerobic digestion inactivates pathogens and parasites, and is quite effective in reducing the incidence of water borne diseases.

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

DISADVANTAGES*The process is not very attractive economically (as compared to other biofuels) on a large industrial scale.

*It is very difficult to enhance the efficiency of biogas systems.

*Biogas contains some gases as impurities, which are corrosive to the metal parts of internal combustion engines.

*Not feasible to locate at all the locations.

Conclusion*Biogas is a renewable

source of energy.

*It is produced by anaerobic digestion in a biogas plant by bacteria present in the slurry.

*It mainly consist of methane and carbon dioxide gases, which can be used in various heat and power generating processes.

*It is economically and environmentally beneficial.