Cost and Economical

Viability of Biogas

Technology

Faizan AhmadE11-CE-01

M.Kazim SialE11-CE-39

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What is Biogas

A gas obtained due to anaerobic decomposition of organic matter (cattle dung)

It is a mixture of methane, carbon dioxide, hydrogen sulphide, water vapor, oxygen, nitrogen and hydrogen.

Biogas has been known as swamp gas, sewer gas, fuel gas, marsh gas etc.

In Pakistan, it is more commonly known as ‘gobar’ gas.

The digester in which the decomposition takes place is known as BIOGAS PLANT

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Composition of Biogas

Methane 50-70%

Carbon dioxide 30-45%

Hydrogen 0-1%

Nitrogen 0-1%

Water 0.1%

Hydrogen sulphide 0-1%

Oxygen 0-1%

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Common Uses of biogas

Cooking

Lighting

Power generation

Engine running

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Energy Equivalence of biogas

Use of 1m3 of biogas as fuel can save other sources of energy as:

0.52 litre of diesel

0.62 litre of kerosene oil

3.40 kg of wood

12.30 kg of cow dung cakes

0.43 kg of LPG

1.46 kg of coal

4.70 KW of electricity

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Commonly used organic matter

used for generation of biogas

Cattle dung

Kitchen and dining hall waste

Vegetable market waste

Poultry dropping

Crop residue

Pig and horse excreta

Aquatic weeds such as water hyacinth

Agro industrial waste

Sewage Sludge

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Comparative Biogas Production of

Different Feed Stocks

S No Type of feed stock Gas Yield per

Kg ( m3 )

Normal Feed availability per

animal per day (Kg)

1 Cattle dung 0.036 10 to 15

2 Human excreta 0.07 0.5

3 Horse dung 0.045 10

4 Sheep dropping 0.042 1

5 Camel droppings 0.056 6

6 Piggery waste 0.08 2.25

7 Poultry droppings 0.062 0.18

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Overall scheme for anaerobic digestion of

organic matter

1st Phase- hydrolysis of complex organic materials, i.e.,carbohydrates,fats,proteins, nitrogen compounds,salts etc. into soluble organic compounds, i.e., sugars,fatty acids,amino acids etc.

2nd Phase- soluble organic compounds are reduced to simpler compounds, i.e., organic acids (acetic acid, propionic acid etc.) , simpler alcohols and acetone.

3rd Phase- Organic acids ,mainly acetic acid and certain other oxidised compounds are converted to methane and carbon dioxide by methanogenic bacteria.

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Role of Biogas plants in saving of environment Direct and immediate impact :

Save other fuels and hence less stress on other fuels

Using biogas as a kitchen fuel can prevent deforestation and hence soil erosion

Change of environment in the house as biogas is a clean fuel. Other fuels being commonly used creates pollution by generating smoke.

The use of biogas prevents chances of eye diseases and respiratory diseases. Hence healthy life of rural woman.

Clean kitchen and utensils and hence saving in the time of women

Clean House and hence less expenditure for maintenance of house

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Costs of a Biogas Plant

Categories of costsAs far as costs are concerned there are three major categories:

Manufacturing or acquisition costs (production costs)

Operation and maintenance costs (running costs)

Capital costs

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Production Costs

The production costs of biogas plants are determined by the

following factors:

Purchasing costs or opportunity costs for land which is needed

for the biogas plant and slurry storage

Model of the biogas plant

Size and dimensioning of the biogas unit

Amount and prices of material

Labor input and wages

Degree of participation of the future biogas user and his

opportunity costs for labor

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Running Costs

The operation and maintenance costs consist of wage and

material cost for:

Acquisition (purchase, collection and transportation) of the

substrate

Water supply for cleaning the stable and mixing the substrate

Feeding and operating of the plant

Supervision, maintenance and repair of the plant

Storage and disposal of the slurry

Gas distribution and utilization

Administration

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Capital Costs

Capital costs consist of redemption and

interest for the capital taken up to finance the

construction costs. For dynamic cost

comparison the capital fixed in the plant is

converted into equal annual amounts.

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Economic Viability

The Economic viability of projects points out the financial

feasibility of investment alternatives. Three types of questions

need to be answered.

Which project is the least expensive among an array of

options that produce the same output (least cost analysis)

Which project shows the highest net benefit (benefit minus

cost) among an array of options (cost benefit analysis)

Is a project a financially viable solution to the problem on

hand? (absolute viability)

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Investment Criteria

The dynamic approach deals with a consideration of

benefits and costs over several years.

Investment criteria are, as follows:

A. Net Present Value(NPV)

B. Internal Rate of Return(IRR)

C. Dynamic Unit cost criterion

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Net Present Value

The most common investment criteria is the NPV and

is defined as follows. Where

PV - Net Present Value

Ct - Costs in year

Bt - Benefits in year t

k - discount rate

t - number of years from the present

n - total number of the years of the analysis period

Please refer to example given below

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Internal Rate of Return

A further criterion which can be applied for the

purpose of viability calculation is the internal rate of

return (IRR). It is the discount rate at which the

present value of cost is equal to the present value of

the benefits. In other words, it is the discount rate at

which the net present value is zero:

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Dynamic Unit Cost

Criterion

To gain additional transparency, the Dynamic Unit

Cost criterion (Cdyn) stands for the calculation of the

financial analysis performed on a per unit basis (if Ct > Bt):

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As the Population is increasing; so is the

demand for energy is increasing, we

can use the Bio-gas as an alternative

fuel to cope-up with the growing

demands

Thank-You

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