94. Mzumbe
Production Of Methane Gas
Mnubi Simba, Andrew Mselem and Godfrey Sembayi
Introduction:Currently there has been high rate of population growth. This population growth has been clearly proved by statistical
data; population was 30 million people in 2002 while current population estimates to be 40 million people. This population growth goes
simultaneously with high demands of food, social services and energy. Furthermore most of the Tanzanian population is situated in
rural areas where the most common source of energy is fire wood and charcoal. This in turn accelerates the rate of deforestation in
rural areas leading to environmental degradation. Also in urban areas the source of energy are mainly charcoal and electricity which
are currently very cost full. To combat the problem an alternative source of energy is needed and the suggested source is biogas.
Biogas originated in Assyria earlier before 10th century BC where it was used for heating bath water and in Persia in 16th century AD.
Later in the early 19th century Sir Humphrey Davy found that biogas (methane) was present in the gases formed by anaerobic
digestion of manure (cow dung). It was then used in lightening the Exeter streets in England in the year 1895. And from then it has
been used to meet different purposes.
For the clear demonstration of the presence of biogas (methane) in cow dung, the sample plant is fed with the mixture of water and
cow dung. The cow dung is acted upon by anaerobic bacteria to yield biogas (methane).
Methods:
Activity
1Two polythene tanks are taken and cut on the top parts in such a way that one can be
fitted into the other.
2A hole of about 5 cm is made on the lower part of the lower tank; also another hole of
about 1.5 cm is made on the upper part of the upper tank.
3An elbow is fixed in the hole of the lower tank while a pipe is fixed in the upper tank
hole
Note: Neither gas nor water should leak from the fixations made.
4Now the upper tank is fixed into the lower and pressed downwards to remove gaseous
impurities.
5A mixture of cow dung and water in the ratio of 1:2 or 1:3 is made on made on the
container and fed to the digester through the feeder to about 4/5 the volume of the lower
tank.
6The gas is collected in the upper tank (gas collector) after 5 to 7 days then be tested by
lightening the Bunsen burner refer fig 1.
Results:
As stated earlier in the introduction that production of biogas (methane) is brought about by anaerobic digestion of food remains/manure acted upon by bacteria.
There are basically four types of these bacteria which are as follows;
Firstly, the Hydrolysis bacteria convert organic polymers such as carbohydrates into forms available for other bacteria.
Secondly, the Acidogenic bacteria convert sugars and amino acids into carbon dioxide, hydrogen, ammonia and organic acids.
Thirdly, the Acetogenic bacteria convert organic acids into acetic acids with additional ammonia, hydrogen and carbon dioxide.
Finally, the Methanogens convert acetic acids, ammonia, hydrogen and carbon dioxide into methane and carbon dioxide.
About 3 kg of cow dung and water where fed in the digester (lower tank) through the feeder and covered with upper tank (gas collector).
The gas plant was left for 7 days, and then gas was produced and tested by lightning up fire.
Estimation of amount of gas produced by 1 kg is 30 liters. This amount of gas can produce 0.14 KWH electrical energy.
Therefore Biogas is an alternative source of energy since; it is environmentally friendly, it can be obtained cheaply, easily produced and it has high energy value.
Conclusions:
Statistical analysis to address the hypothesis
Statistics show that 3 kg of cow dung yield 100 liters of biogas.
This amount of gas is equivalent to 1 kg of charcoal or 10 kg of fire
wood in terms of energy
But cow dung is obtained as waste product (cost less) while bag of
charcoal is sold about 25000 T shs. This means that large amount
of money has been saved.
Also per one charcoal bag 2 trees are cut, this brings about huge
deforestation hence led to environmental degradation.
REFERENCES
ARTI COMPACT Biogas System (Azania Secondary School)
Caritas Tabora
Taylor D.J. (1997) 3rd Ed. Biological Science, Cambridge University
press, India.
Http: //www.appropodia.org/Home -biogas- system
Further information:
Download at: www.youngscientists.co.tz/posters
Acknowledgements:
Special thanks to the Almighty God for giving us ability, time and resources to
accomplish this project work.
The material of this project is a devoted contributions and diligent work of many
hands and minds. Sincere appreciation to all including those whose names will
not appear here due to our human elements.
Special thanks should go to Madam Joyce Masika- Head of Biology Department
at Mzumbe Secondary School for encouragement, advice and editing our project
work.
We are also grateful to Mr. Simon Rwegayura of Sokoine University of
Agriculture for his valuable advice and encouragement about the project .And we
thank Mrs Malamsha for allowing us to use her cow shade as a site of our
project.
Many thanks to the following for their marked and vital contributions to the
marking of this work.
Mr. Fixon Mteles - Second master at Mzumbe Secondary School
Madam Mbilinyi – Biology Department at Mzumbe Secondary School
Azania Secondary School – ARTI COMPACT BIOGAS SYSTEM
We also thank our fellow students for critical questions and suggestions that led
us to improve our project work. We welcome more ideas and we encourage also
other students to participate in a number of project works, reaches so that they
can widen their knowledge.