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• Biogas is a mixture of methane and carbon dioxideproduced by the bacterial decomposition of organicwastes and where methane is used a cooking fuel.

• The organic wastes that can be included in biogas plantsare:

Cow dung waste3

Biogas plants

Conventional

Domed shape

Floating type

Modern

Nisargrunabiogas

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• In conventional biogas plant, biogas is producedby anaerobic digestion with anaerobic bacteriaor fermentation of biodegradable materials such as manure,sewage, municipal waste, green waste, plant material, andcrops.

• Gas produced is primarily methane (CH4) and carbondioxide (CO2) and may have small amounts of hydrogensulphide (H2S), moisture and siloxanes.

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There are two types of conventional biogas plant :

• Fixed dome biogas plant

• Floating drum biogas plant

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• A fixed-dome plant comprises of a closed, dome-shapeddigester with an immovable, rigid gas-holder and adisplacement pit, also named 'compensation tank'.

• When gas production starts, the slurry is displaced intothe compensation tank.

• Gas pressure increases with the volume of gas stored.

• If there is little gas in the gas-holder, the gas pressure islow.

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• Relatively low construction costs.• The absence of moving parts and rusting steel parts.• If well constructed, fixed dome plants have a long lifespan.• The underground construction saves space and protects thedigester from temperature changes.• The construction provides opportunities for skilled localemployment.

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• Fluctuating gas pressure complicates gas utilization.

• Amount of gas produced is not immediately visible.

• Fixed dome plants need exact planning of levels.

• Excavation can be difficult and expensive in bedrock.

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

• The gas-holder floats either directly in the fermentingslurry or in a separate water jacket.

• The drum in which the biogas collects has an internaland/or external guide frame that provides stability andkeeps the drum upright.

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

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• Floating-drum plants are easy to understand and operate.• They provide gas at a constant pressure.• The stored gas-volume is immediately recognizable by theposition of the drum.• Gas-tightness is no problem, provided the gasholder is de-rusted and painted regularly.

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• The steel drum is relatively expensive and maintenance-intensive.

• Removing rust and painting has to be carried out regularly.

• The life-time of the drum is short (up to 15 years; intropical coastal regions about five years).

• If fibrous substrates are used, the gas-holder shows atendency to get "stuck" in the resultant floating scum.

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Nestle:

• At around 28 plants of nestle there exist biogasunits. They use cow manure to generate biogas and bio-fertilizers in order to reduce the environmental impact.environment

Biogas plant installed in nestle, Mexico 15

• KhanKhel Dairy Farm:

• Biogas-generated electricity from a dairy manure digester in Punjab (Pakistan) is being used for water pumping at a dairy farm.

Biogas generated is being used to generate electricity 16

• Biogas plant at Pepsico Pune:

• 18MT of waste per day

• 2500 M3 of biogas per day

• Saving 140MT of LPG and approximately cost of $140 million per annum.

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Nisargruna technology honoured with Padma Shri Award 2013

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A combination of Aerobic + Anerobic Digestion

The main steps of Nisargruna (biogas) production :

1. Hydrolysis

2. Acidification

3. Methane formation

Plant setup comprises :

• Receiving Platform

• Segregating Platform

• Mixer

• Pre-digester tank

• Main Tank (Secondary Digester)

• Manure

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Nisargruna Biogas Plant Conventional Biogas Plant

Higher costing Lower costing

Broader scope of raw materials Mainly based on cow dung

Mixers are used for betterhomogenization

No homogenization

High rate of bio-methanation process Low rate of bio-methanation process

Pre-digestion in aerobic chamber No set-up for pre-digestion

Removal of scum forming protein materials

No set-up to remove scum forming material

Improved structure for better flow, entrapment and enrichment of biogas

Conventional dome structure

Nisargruna Biogas Plant Conventional Biogas Plant

Settling tank for water recycling No water recycling

Biogas has a better fuel value Biogas has low fuel value

Lower CO2 and higher methane levels in biogas

Higher CO2 levels in biogas

More hygienic and less smell Less hygienic and more smell

Higher plant life (40 years) Normal plant life

Manure has high organic content and is weed free

Manure is generally of not very high quality

Comparison with Conventional Plant

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• Renewable source of energy

• Non polluting.

• Reduces landfills

• Cheaper in cost

• No problem to warm the water in

Nisargruna technology as in includes

Solar panel.

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• Need for regular and optimum feeding in the digester.

• Egg shell, bones cannot be included as the reduces the efficiency of the plant.

• Regular addition of warm water in winters to maintain the optimum temperature for bacteria.

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Cost of LPG (Commercial 19 KG cylinder)= ₹ 88.52/kg

Nisargruna biogas plant of 0.5 MT

Plant construction cost: ₹ 15Lakhs (without subsidy)

Plant construction cost : ₹ 9 Lakhs (with subsidy)

Total gas production =25 Kg/day (equivalent to LPG)

Total cost of biogas = 25X88.52X365(days)= ₹ 8.07 Lakhs

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Profit from sale of manure =50(kg) X 5 X 365= ₹ 0.91 lakhs/-

Total profit generated = ₹ 8.98/-

Payback period = 15/8.98

=1.67 years (without subsidy)Payback period = 9/8.98

= 1.002 years (with subsidy)

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