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Biogas energy
1. Jordan University of Science and Technology
Mechanical Engineering Department
RENEWABLE ENERGY SYSTEMS (ME 720)
Students:
Mutaz Al-Deiry
Tareq Al-Anbar
Hussam Al-Omri
Mohammed Al-Sbahen
Instructor:
Professor Ghassan M. Tashtoush
2. Outlines
Definition
Components of a waste treatment biogas plant
The Biogas process
Process parameter for biogas plant
The major applications of biogas plant
Design digester of biogas plant
Case study
Conclusion
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3. History
First determined in 17th century that
flammable gases could evolve from decaying
organic matter.
The first digestion plant was built at a leper
colony in Bombay, India in 1859.
In the 1930s, studying and researches was to
identify anaerobic bacteria and the conditions
that promote methane production.
4. Definition
Biogas is a renewable energy source.
Biogas is the mixture of gases produced by
the breakdown of organic matter in the
absence of oxygen, usually consisting of
certain quantities of methane and other
constituents.
Biogas can be produced from raw materials
such as agricultural waste, manure, municipal
waste, plant material, sewage, green
waste or food waste.
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5. Biogas is a combustible mixture of gases. It consists mainly of methane (CH4) and
carbon dioxide (CO2) and is formed from the anaerobic bacterial decomposition
of organic compounds, i.e. without oxygen.
Table (1): Composition of biogas
Definition1 1
7. Components of waste treatment biogas plant
Feedstock
Air collection system
Bio filters
Digester
Gas tight storage
Gas cleaning
system
Separate storage
Stora
ge
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8. The biogas process
Biogas production is obtained by anaerobic decomposition (absence of
oxygen) of biomass in the presence of bacteria. The bacterial decomposition of
biomass takes place in three phases, namely hydrolysis phase, acid phase and
methane phase.
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10. Process parameters for a biogas plant
1) Temperature:
Temperature is one of the most crucial factors in
biogas generation. The rate of biochemical
processes generally increases with temperature.
2) Anaerobic environment:
The methanogens need an oxygen-free
environment – they are obligate anaerobic.
3) Acidity (pH):
The optimum environment is a pH of between
6.5 and 8, and the preferred level is 7.2.
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11. The major applications of biogas plant
Lighting
Fig.(3): Major application
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Cooking power generation
12. Design Digester of Biogas plant
Biogas digester is any structure that converts
organic material (waste) into energy in the
absence of oxygen.
Various materials and geometric
configuration have been used for the design
of biogas digester system.
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14. Biogas Digester Sizing
The volumes of the digesters were
calculated from the following equations:
𝑉𝑑 = 𝑆 𝑑 ∗ 𝑅𝑡
Where:
𝑉𝑑= volume of the digester in cubic meters
𝑆 𝑑: amount of substrate in kilograms
𝑅𝑡= retention time in days
6.2 6.2
15. Biogas production was calculated using
equation:
G = Vs x Gy
Where:
Vs = weight of feedstock available per
day in kilograms
Gy = Gas yield in cubic meters
G = biogas production in cubic meters
Biogas Digester Sizing6.2 6.2
16. Gas production rate was calculated using
equation:
Gp = G/Vd
Where:
G 𝑃 = gas production rate in cubic meters
per day.
G = biogas production in cubic meters.
Vd = digester volume in cubic meters.
Biogas Digester Sizing6.2 6.2
17. Biomass is the major source of domestic
energy for both rural and urban areas in
Uganda . This translates to million tones
of round wood for firewood and charcoal
per year.
About 92% of ugandas energy demands
are satisfied by wood and charcoal which
caused loss of 27 % of the total forest
and tree cover in the last 15 years.
Case study7 7
18. The energy obtained from waste materials like plants , animals and humans is
what is referred to as biomass energy .
Here we have the composition of the biogas.
19. The calorific value of biogas is approximately 20MJ/m^3.
Methane is responsible for the energy obtained from the biogas depending on
the biological process and type of biomaterial.
An average dairy caw produces about 55 Kg of solid waste per day, which adds
to 20 metric tons of dung per annum, around 3 kwh of electricity could be
generated daily from the dung and urine of just one caw.
Unmanaged livestock waste can create negative environmental impact ( air
pollution and ground water contamination).
The methane created through anaerobic digestion of manure has proven to be
21 times more damaging than carbon dioxide, aggravating to climate change.
20. The ideal temperature for methane producing bacteria is about 35 C.
Low temperature reduces gas production and nearly stops at 10 C.
Plants built underground tend to have stable temperatures within daily allowable
fluctuations of 1 C and in our site the minimum is 17 C.
The time required for the organic matter to be digested in the digester is called the
retention time and its temperature dependent, the higher the temperature the
faster the bacteria use the food in the slurry and the sooner it needs replacement.
Suitable solid content ( dry matter concentration ) is 7-9 %.
25. At a cost of 2000$ and 4-6 herds of a cattle , a family of 5-8 people can acquire
a biogas plant to meet their daily cooking and lighting energy for between 20 to
30 years, the average of 10 cows is adequate.
The fixed dome type biogas plant was chosen because of low cost and cheap
technology.
The size of the plant digester volume was determined to be 6 m^3.
The major economic activity of the rural populace in this study area is cattle
keeping and subsistence farming which provide disposal system for the by-
product of biogas plant in form of fertilizer.
The situation on the ground warrants the implementation of a biogas energy
initiative as the major domestic energy for cooking and lighting.
Conclusion8 8
