ENERGY-AGRO-FOOD STAKEHOLDERS WORKSHOP
ENERGY_AGRO-FOOD Energy_Agro-food Synergies in Africa:
New Models for African Universities
Biogas From Animal By-product (Cow dung)
Institutional Case Study:
College of Agriculture and Veterinary
Sciences,
University of Nairobi
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Eng. Prof. Ayub N. Gitau
University of Nairobi
BACKGROUND
Livestock waste / by-product is a potential source of domestic and
institutional energy, a major contributor to greenhouse gas emissions and
pollution of surface and ground water resources.
To reduce production of greenhouse gas and pollution from livestock by-
product, biogas production from this by-product is a better solution.
Biogas production from livestock by-product is on the rise in Kenya as a
way of improving access to power as well as reduction of power cost.
The College in partnership with the Ministry of Energy and Petroleum
(MoEP) are promoting use of green energy through the implementation of
a 120m3 biogas pilot project that utilizes cow-dung that is readily
available in the College.
Note: In Kenya we have; individual, communal and Institutional biogas
plants. Currently up to 2 MW plants are available and fed to the
National grid. Hence Bio-fuels production and utilization is on the rise.
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PLANT LOCATION
The plant is located at the University of Nairobi, Upper Kabete Campus which is 15 km West of Nairobi, Kenya.
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Gas Line 1.3 Km Proposed extension to
Milk Processing plant
The cost of the plant is
KShs 7.5 million (USD
75,000)
Serves approx. 500
students in the college
The unit houses 100 heads
of cattle.
The animals are fed on
Napier grass
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Zero Grazing Unit
• The mixing chamber is fed with about 240 kilograms of dung on a daily basis at a ratio of 1:1
Loading
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Inlet
• The digester has a capacity of 120 m3
Underground Digester
Water trap
Gas flow Metre
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Gas flow Metre
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Gas flow Piping
• The gas flows in a
50 mm PVC
underground pipe.
• The distance
between the
digester and the
consumer unit is 1.3
km
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Gas flow Piping • Due to Variation in terrain within the
piping system, the line is installed with seven water traps at the lowest points of depressions with the inclination maintained at less than 1%.
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• Variation in terrain
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Suction Pump
• The suction pump pumps the gas into the Biogas bag
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Compressor and the desulfurizer ensures the purification is done before storage so that gas usage can continue even during power outages
Plastic Gas Holder Friday, 26 February 2016
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The gas holder has a capacity of 20m3
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Biogas Cooking Stoves Friday, 26 February 2016
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50-litre cookpot
Biogas Burner
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Biogas Cooking Stoves
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Effluent Storage
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FINANCIAL ANALYSIS
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Assumptions:
i. Dung production = 10kg/head/day
ii. Total O&M costs = 0.3% of the total
investment cost
iii. Other benefits (C) = KShs 20,000/month
iv. Discounting rate = 12%
DIRECT BENEFITS FROM THE PROJECT
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1. Biogas: Number of cattle – 100 heads
Dung produced per day – 1000Kgs
Cost of lpg saved per day = KShs 4,445
Benefits from Biogas (A) = KShs 4,445
Per month KShs. 4,445x30 = KShs. 133, 350
2. BIO-SLURRY (ORGANIC FERTILIZER)
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Volume of slurry produced in a day =
(1,000X2) kg = 2,000
Price of artificial/chemical fertilizer = KShs
80/ kg.
Total savings on fertilizer cost assuming 50%
conversion efficiency = (0.5X2,000X80)=
KShs. 80,000.
Benefits from Bio-slurry (B) = KShs. 80,000
Benefits per Month:
30 x 80,000 = KShs. 2, 400, 000
TOTAL BENEFITS
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Total financial benefits = A + B + C
= KShs 133, 350 + 2, 400,000 +20,000
= KShs 2, 553, 350/month
Investment cost = KShs 7.5 million
SUMMARY OF FINANCIAL ANALYSIS RESULTS
(WITH PROJECT BASIS)
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Year
Total
Investment
Cost
(KShs)
Total
Benefits
(KShs)
Annual
Variable
Costs
(KShs)
Total Costs
(KShs)
Cash Flows
(KShs)
NPV
Coeffi
cient NPV
0 7,500,000 0 0 7,500,000 (7,500,000) 1 (7,500,000)
1 0 3,280,200 18,750 18750 3,261,450 0.9 2,912,009
2 0 3,280,200 18,750 18750 3,261,450 0.8 2,600,008
3 0 3,280,200 18,750 18750 3,261,450 0.7 2,321,436
7,500,000 9,840,600 7,556,250 333,453
FINANCIAL & ECONOMIC INDICATORS
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I. Net Present Value = KShs 333,453
II. Benefit Cost Ratio = 1.30
III. Internal Rate of Return = 15%
IV. Pay Back Period = Three (3) Years
CONCLUSION
Renewable energy potentials in Eastern African
are enormous in form of Biomass; Wind; Hydro;
Solar and Geothermal.
The potential are not highly exploited
Expansion and scaling up should be embraced
The pilot project shows that such sources of
energy are economically viable and should be
embraced.
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