Energy of the future

Biogas is a mixture of gases produced by the breakdown of organic matter in the absence of oxygen. Biogas is produced by anaerobic digestion with anaerobic bacteria or fermentation of biodegradable materials such as manure, sewage, municipal waste, green waste, plant material, and crops.

COMPONENTS PERCENTAGE

Methane (CH4) 50-75

Carbon Dioxide (CO2) 20-50

Nitrogen (N2) 0-10

Hydrogen (H2) 0-1

Hydrogen Sulphide (H2S) 0-3

Fixed dome type

Floating drum type

ARTI type

Nisargruna (BARC) type

Advantages:

◦ easy to operate

◦ Provide gas at

constant pressure

Disadvantages:

◦ Expensive

◦ Rusting

◦ Requires regular

maintenance

Advantages:◦ Easy to construct

◦ Inexpensive

Disadvantages:◦ Its volume is fixed.

So the gas pressure increases inside

◦ Plant must be gas-tight (no leakage)

This model is developed by Dr. Anand karve (President of ARTI) in 2003

It uses starchy or sugary (kitchen waste, leftover food, green leaves)feedstock instead of low calories influent like cattle dung (or conventional feed stock).

2 kg of such feedstock is able to generate 500gm of methane.

Around 10,000 such plants are operational in Maharashtra and few plants are also installed I other parts of India as well.

It is 20 time as efficient as conventional biogas plant.

Effluent is watery so easy to handle.

This design have won Adshen award for sustainable energy in 2006.

Conventional Biogas system

ARTI Biogas system

Amount of feedstock required 40kg +40lit water 1-1.5kg +15 lit water

Nature of required feed stock Dung Any starchymaterial

Reaction time 40 Days 48-72 hours

Standard size of household 4000 lit 1-1.5 kL

Capital investment per unit including stove

INR 20,000 INR 10,000

Amount and nature of slurry to be disposed

80 lit sludge 15 lit watery

Running expense per meal INR 25 0 to INR 5

Influent get choked in inlet pipe, so influent should be chopped properly before mixing in water.

Leakage of gas occurs due to its design which causes 10-20% loss of biogas.

Developed by Dr. S. P. Kale (Scientist BARC) around 2005

It uses biodegradable kitchen waste, paper waste, green grass, leaf litter, animal remains in abattoirs, hospital waste, green plant waste, cow dung, crop residues, sugarcane, baggase, water hyacinth, etc.

Major focus of this plant is to manage municipal solid waste.

The waste is first segregated carefully to remove non-biodegradable material and then homogenized to make a slurry. It is then processed in a sequential manner first by aerobic and then by anaerobic process

About 70% of Water can be recycled at the end of the process.

based on thermophilic microorganisms and microbial processes develop the design of the biogas plant. The plant is completely gravity based.

1. Mixer 5. Main digester tank

2. Pre- mix tanks 6. Dome

3. Solar heating system 7. waste water tank

4. Pre digester tank

Mixing stage: The waste that enters the Nisargruna Bio-digesters has to be properly segregated as some materials may detrimentally affect the efficiency of the plant and may spoil the mixer blades as well as interfere with the microbial activities in both the aerobic and anaerobic digesters;

Pre-treatment Stage:

The introduction of the high temperature water in the aerobic digester is essential for the breakdown of the sulphurus and other toxic products that may be present in the waste. To maintain aerobic condition air compressor is used.

Anaerobic Digestion Stage:

The two stage digestion helps in improving the purity of the methane gas, of up to 90%, thereby increasing its fuel efficiency when burned. However, this purity is dependent on how effectively the pre-digester temperatures are maintained and the amount/ quality of the waste that enters the system.

Gas produced from Nisargruna plant has

o Methane: 70-75%

o Carbon Dioxide: 10-15%

o Water vapors : 5-10%

Gas produced from nisargruna biogas plant has high methane content.

Infrastructure RequiredThe following infrastructures required for set-up a 1 tonne/day capacity Bio gas plant:

Space : ~ 300 m2

Manpower : Two unskilled persons for operation

Power supply : 3 phase AC

Water Supply : 1.2 kL for one tonne plant

Sr.NO.

ORGANIC WASTES ESTIMATED QUANTITY

1 Municipal Solid Waste 30million tons/year

2 Municipal liquid Waste 1200 million lt./day

3 Distillery (243 units) 8057 kilolitres/day

4 Press mud 9 million tons/year

5 Food & fruit processing wastes 4.5 million tons/year

6 Willow dust 30000 tons/year

7 Dairy industry waste 50-60 million lt./day

8 Paper & pulp industry waste (300mills) 1600 m3/day

9 Tannery (2000 units) 52500 m3waste water/day

Sr.No.

Raw Materials Biogas production inlts/kg

Methane content in Biogas (%)

1 Cattle Dung 40 60.0

2 Green Leaves & Twigs 100 65.0

3 Food waste 160 62.0

4 Bamboo Dust 53 71.5

5 Fruit Waste 91 49.2

6 Bagasse 330 56.9

7 Dry Leaves 118 59.2

8 Non E 242 67.5

Cooking: Biogas can be used in a specially designed burner for cooking purpose. A biogas plant of 2 cubic metres capacity is sufficient for providing cooking fuel needs of a family of about five persons.

Lighting: Biogas is used in silk mantle lamps for lighting purpose. The requirement of gas for powering a 100 candle lamp (60 W) is 0.13 cubic meter per hour.

Power Generation: Bio Biogas can be used to operate a dual fuel engine to replace up to 80 % of diesel-oil. Diesel engines have been modified to run100 per cent on biogas. Petrol and CNG engines can also be modified easily to use biogas.

Transport Fuel: After removal of CO2 H2S and water vapour, biogas can Be converted to natural gas quality for use in vehicles.

Purification is carried out to enrich biogas by scrubbing off the unwanted components i.e. carbon dioxide (CO2) and hydrogen sulfide (H2S).

It is essential to have more energy per unit volume of compressed biogas and to get rid of the corrosive effect of H2S.

Various purification processes include absorption into water, absorption by chemical, pressure swing adsorption and membrane separation.

One of the simple and cheap method is the use of pressurized water as an absorbent liquid.

Water is good solvent for CO2 and it is most suitable method for rural areas.

The solubility of CO2 in water is governed by variation in pressures and temperatures

Biogas is an important renewable energy resource for rural areas in India.

It is an environment friendly, clean, cheap and versatile fuel.

Average calorific value of biogas is 20 MJ/m3(4713 kcal/m3).

Biogas like Liquefied Petroleum Gas (LPG) cannot be liquefied under normal temperature and pressure.

An estimate indicates that India has a potential of generating 6.38 X 1010 m3 of biogas from 980 million tones of cattle dung produced annually .

The heat value of this gas amounts to 1.3 X 1012 MJ . In addition, 350 million tones of manure would also produce along with biogas.

To make biogas suitable for automobile application, the enriched biogas was compressed up to 20.0MPa after moisture removal and filled in special high pressure seamless steel cylinders (as used in CNG filling)

MNES Report (2001) Renewable Energy in India and business opportunities. MNES (Ministry of Non-conventional Energy Sources), Government of India, New Delhi.

http://www.barc.gov.in/technologies/kitchen/Kitchen.html

http://www.barc.gov.in/akruti-tp/atp_nisar.html

MIT Co Lab, Sustainable management of organic wet waste in developing cities.

The 2nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)” C-003 (O) 21-23 November 2006, Bangkok, Thailand