JANUARY, 2013 THE FABRICATION OF BIOGAS DIGESTER AND PRODUCTION OF BIOGAS FROM COW DUNG AND RUMEN FLUID BY ODETUNDE, Ibrahim Omoniyi (070264), OLAWUYI, Iretioluwa (062135), JEGEDE, Olanrewaju John (072157), AGBOOLA, Olanike Elizabeth (072702). BEING A PROJECT WORK SUBMITTED TO THE DEPARTMENT OF MECHANICAL ENGINEERING FACULTY OF ENGINEERING AND TECHNOLOGY LADOKE AKINTOLA UNIVERSITY OF TECHNOLOGY (LAUTECH) OGBOMOSO, OYO STATE, NIGERIA. IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF BACHELOR OF TECHNOLOGY (B.TECH) DEGREE IN MECHANICAL ENGINEERING.
A Project work on Fabrication of Biogas Digester and co-digestion of cow dung and rumen fluid substrate
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JANUARY, 2013
THE FABRICATION OF BIOGAS DIGESTER AND
PRODUCTION OF BIOGAS FROM COW DUNG AND RUMEN
FLUID
BY
ODETUNDE, Ibrahim Omoniyi (070264),
OLAWUYI, Iretioluwa (062135),
JEGEDE, Olanrewaju John (072157),
AGBOOLA, Olanike Elizabeth (072702).
BEING A PROJECT WORK SUBMITTED TO THE
DEPARTMENT OF MECHANICAL ENGINEERING
FACULTY OF ENGINEERING AND TECHNOLOGY
LADOKE AKINTOLA UNIVERSITY OF TECHNOLOGY (LAUTECH)
OGBOMOSO,
OYO STATE, NIGERIA.
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF
BACHELOR OF TECHNOLOGY (B.TECH) DEGREE
IN
MECHANICAL ENGINEERING.
ii
CERTIFICATION
This is to certify that this project work was duly carried out by ODETUNDE,
Ibrahim Omoniyi (070264), OLAWUYI, Iretioluwa (062135), JEGEDE,
Olanrewaju John (072157) and AGBOOLA, Olanike Elizabeth (072702) of the
department of Mechanical Engineering, Faculty of Engineering and Technology,
Ladoke Akintola University of Technology, Ogbomoso.
_______________________ ____________________
Dr. Oladeji, J.T. Date
Supervisor
________________________ ____________________
Dr. Durowoju, M.O. Date
Head of Department
iii
DEDICATION
This project work is dedicated to Almighty God for making this project work realistic
and sparing our lives till this moment.
iv
ACKNOWLEDGEMENTS
We will like to make use of this medium to thank The Almighty God for enabling us
to carry out this project work successfully. We will also like to express our
appreciation to our lovely parents, who know and cherish the value of education in a
man‟s upbringing.
We really appreciate the effort of our supervisor in person of Dr. Oladeji. J.T. for his
fatherly love and supervision in making this project work a huge success. We also like
to appreciate the effort of Dr. Adebayo A., of Agricultural Engineering Department,
for his support, and contributions to the success of this project work.
Grateful acknowledgement is also made to our colleagues in the department for their
assistance and encouragement. God bless you all greatly.
v
ABSTRACT
The utilization of energy is of paramount importance and cannot be over
emphasized ranging from domestic purposes, industrial use and transportation
purposes which are dependent on fuel. It unarguably is the cornerstone of economic
and social development. However, there is energy shortage worldwide including
Nigeria and this necessitates producing energy from other sources, especially from
biomass. Therefore, this project work is focused on fabrication of a bio-digester and
generation of biogas using cow dung and rumen fluid as substrate.
A biogas digester with a capacity of 105litres was designed and fabricated.
The substrate (cow dung and rumen fluid) was mixed in the ratio 3:2 and water to
substrate ratio of 2:1 was used. The digester was stirred thrice daily to avoid scum
formation in the digester and to allow for easy escape of the gas produced. The
retention time used for this experiment was 42 days during which the daily internal
temperature reading was taken in order to determine temperature variation and also to
determine the effect of sunlight on the production rate. A rubber hose was connected
to the digester gas outlet located at the top of the digester and the other end of the
rubber hose was connected to a tyre tube provided for storing the gas generated,
which was further taken to the laboratory for analysis.
The biogas yielded consists of 57.99% of methane (CH4), 39.99% of carbon
dioxide (CO2), 2.00% of oxygen (O2), 0.01% of hydrogen sulphide (H2S) and 0.01%
of water vapour. The methane has the highest percentage which represents the main
source of energy and oxygen having 2.00% which shows that the process was purely
carried out under anaerobic condition.
Result of this study showed that methane has the highest percentage and
generally cow dung with rumen fluid easily subjected them to anaerobic digestion.
vi
TABLE OF CONTENTS
CERTIFICATION ii
DEDICATION iii
ACKNOWLEDGEMENTS iv
ABSTRACT v
TABLE OF CONTENTS vi
LIST OF FIGURES x
LIST OF PLATE xi
LIST OF TABLES xii
CHAPTER ONE 1
1.0 INTRODUCTION 1
1.1 Background to the Study 1
1.2 Problem Statement 2
1.3 Aim and Objectives 3
1.4 Justification for the Research 3
1.5 Scope of the Study 4
CHAPTER TWO 5
2.0 LITERATURE REVIEW 5
2.1 What is Biogas? 5
2.2 History of Biogas 5
2.3 The Renewable Source for Obtaining Biogas 8
vii
2.3.1 Solid Bio-energy Sources 9
2.3.2 Liquid Bio-energy Sources 10
2.4 Biogas Plant 10
2.5 Biogas Plants in Developing Countries. 11
2.5.1 Fixed Dome Digester 12
2.5.1a Characteristics & Functions Fixed Dome Digester 13
2.5.1b Advantages of Fixed Dome Digester 13
2.5.1c Disadvantages of Fixed Dome Digester 14
2.5.2 Floating Dome Digester 14
2.5.2a Characteristics 15
2.5.2b Advantages of Floating Dome Digester 15
2.5.2c Disadvantages of Floating Drum Digester 16
2.5.3 Bag Digester/ Balloon plants 16
2.5.3a Advantages of Bag Digester/ Balloon plants 17
2.5.3b Disadvantages of Bag Digester/ Balloon plants 17
2.5.4 Maintenance of Biogas Plants 17
2.6 Biogas Production with Substrate 18
2.7 Composition of Biogas 18
2.8 Uses of Product of Biogas 18
2.8.1 Methane 19
2.8.2 Carbon-dioxide 20
viii
2.8.3 Liquid 21
2.9 The Benefits of Biogas Technology 22
2.10 Conversion Processes in Anaerobic System 22
2.10.1 Hydrolysis 23
2.10.2 Acidification 23
2.10.3 Methane Formation 23
2.11 Factors Affecting Biogas Production 24
2.11.1 Temperature range of anaerobic fermentation 25
2.11.1a Minimal Average Temperature 25
2.11.1b Changes in Temperature 25
2.11.2 Available Nutrient 26
2.11.3 pH Value 26
2.11.4 Retention Time 27
2.12 Review of Previous Work 27
CHAPTER THREE 37
3.0 MATERIALS AND METHODS 37
3.1 Choice of Feedstock 37
3.2 Material Procurement 37
3.3 Material Preparation 37
3.4 Materials and their Uses 38
3.5 The following are the component parts of the digester 39
ix
3.6 Design of Biogas Digester 39
3.7 Fabrication Process of the Digester 43
3.8 The Experimental Procedures 43
3.9 Characterization of the wastes 44
3.10 Biogas Purification 45
3.11 Cost Analysis 45
CHAPTER FOUR 47
4.0 RESULTS AND DISCUSSIONS 47
4.2: Discussion of Results 50
CHAPTER FIVE 52
5.0 CONCLUSION AND RECOMMENDATION 52
5.1 Conclusions 52
5.2 Recommendations 52
REFERENCES 54
x
LIST OF FIGURES
Fig.2.1: Fixed Dome Plant 12
Fig.2.2: Cross- section of a floating dome digester 14
Fig. 2.3: Bag digester in Bolivia 16
Fig. 2.4: The Conversion Processes in Anaerobic System 24
Fig. 2.5: Schematic diagram for methanogenic activity test and reactor setup 33
Fig 3.1: Cross-section of a digester 42
Fig.4.1 Graph showing temperature (oC) against HRT (weeks) 49
xi
LIST OF PLATE
Plate 3.1 A cylindrical drum digester 41
xii
LIST OF TABLES
Tables 2.1: General Characteristics for the Biomass Batches 28
Table 2.2: Major Elements for the Biomass Batches 28
Table2.3: Physical Characteristics of 5-L and 20-L Working Volume Digesters 35
Table 3.1: Materials and Uses 38
Table 3.2: Cost Analysis of Materials Used for Construction 46
Table 4.1: Chemical composition of the substrate 47
Table 4.2: Average Weekly Temperature Readings for Biogas Production 48
Table 4.3: Percentage Composition of Biogas 49
1
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the Study
Energy is one of the most important factors to global prosperity in which its
importance cannot be over emphasized ranging from domestic purposes (heat energy
for cooking food and heating water), for industrial use (for heating furnaces and
running electric motors) and for transport purposes which run on fuel. It is also
important because it is the cornerstone of economic and social development (El-
saeidy, 2004).
There is energy shortage worldwide including Nigeria, which is as a result of
less potential energy to harness, making hydropower a less desirable energy
source(Okoye, 2007). The projected refining capacity only supports 445,000 barrels a
day, and the actual output of these refineries is far below capacity (Rilwanua, 2003).
Additionally, the refineries do not capture the gas that is given off in the refining
process and it is instead burned as flares. There is a trend of deforestation in Nigeria
at 300,000 hectares per year (Girod and Jacques, 1998).
Fossil fuel is one of the principal sources of energy. 86% of all the energy
consumed comes from fossil fuels (Kaliyan and Morey, 2009). There are many
problems associated with fossil fuels, which include high costs and fluctuation of
prices, increase in demand, disruption in supply, and environmental pollution which is
a major problem of fossil fuels. This is because they give off carbon dioxide when
burned thereby causing a greenhouse effect. This is also the main contributory factor
to the global warming experienced by the earth today.
2
Agricultural residues and Animal wastes are increasingly being diverted for
use as domestic fuel to displace fossils fuel and reduce environmental pollution and
reduce emission of greenhouse gases. Cassava solid wastes, amongst other plant
wastes have been widely used (Kozo et al., 1996). Agricultural residues in their
natural forms will not bring a desired result because they are mostly loose and of low
density materials in addition to the fact that their combustion cannot be effectively
controlled (Oladeji, 2009). Agricultural residues and even animal wastes are used in
production of biogas.
Biogas is a mixture of methane and carbon dioxide, produced by the
breakdown of organic waste by bacteria without oxygen (anaerobic digestion). It
contains methane and carbon (IV) oxide with traces of hydrogen sulphide and water
vapour. It burns with pale blue flame and has a calorific value of between 25.9-30J/m3
depending on the percentage of methane in the gas. Biogas production is a profitable
means of reducing or even eliminating the menace and nuisance of urban wastes in
many cities in Nigeria (Akinbami et al., 2001).
Consequently, biogas can be utilized in all energy consuming applications designed
for natural gas.
1.2 Problem Statement
There is energy scarcity all over the world and fluctuation in prices of energy.
Fortunately, Nigeria is an agricultural country that can use these agricultural residues
and animal wastes in biogas production. There is need to generate energy from other
sources, especially from agricultural residues, which are generated in large quantities
from farming activities. The large quantities of agricultural residues produced in
3
Nigeria can play a significant role in meeting her energy demand. Cassava and yam
are ones of the most important agricultural products in Nigeria, especially in southern
and western parts of the country. Residues in form of peels are generated from
processing of these crops. Initial digestion studies carried out on cassava peels
showed that the peels are poor producers of biogas probably as a result of their
content of toxic cyanogenic glycosides (Okafor, 1998). This work is therefore on one
of the techniques involved in production of biogas from cow dung and rumen fluid.
1.3 Aim and Objectives
The broad aim of this project was to produce biogas from cow dung and rumen
fluid. To achieve this, the project had the following specific objectives:
i. To prepare sample of cow dung and rumen fluid.
ii. To design and fabricate a digester that will facilitate conversion of cow dung
and rumen fluid into biogas.
iii. To produce biogas from cow dung and rumen fluid.
1.4 Justification for the Research
Biogas is a form of energy produced when organic materials such as animal
excrement or products that are left over from agriculture are fermented easily and at
low cost. The advantage of biogas is that it replaces other energy sources for example
charcoal, firewood, electricity, liquid petroleum gas and oil. After animal excrement
had been fermented in the gas plant it becomes a good quality and odourless substrate,
which is better than fresh manure in improving the soil for the agriculture. As an
4
energy source, it prevents deforestation and animal excrement from causing pollution,
smell, flies and water pollution in the community.
Also the problem of agricultural waste disposal is posing challenge to the
farmers and to the general public as this waste constitutes a nuisance to the
environment as well as an eyesore to the public. Therefore if these wastes could be
used to generate energy, it would be a welcomed solution to the problem of waste
pollution, disposal and control (Enweremadu et al., 2004a).
Nowadays the use of bio-gas has spread from small farms to big animal farms.
It is expected that biogas will be a significant source of energy in the future to
preserve the environment, solve the pollution problem and to promote better health to
agriculture and community.
1.5 Scope of the Study
The study covered the production of biogas from cow dung and rumen fluid.
5
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 What is Biogas?
Biogas is a renewable fuel provided by anaerobic digestion of organic material
as substrate for biomethanation. The gas is flammable, which is obtained through the
action of methanogenic bacteria, which work in the absence of oxygen through a
process of anaerobic digestion (Quaak et al., 2001).
It contains 50-75% methane, carbon dioxide, hydrogen sulphide and hydrogen.
It can be used as fuel in boilers and dual fuel engines. It is made by fermenting
organic wastes in biogas digesters.
The wastes are fed into the digesters via the inlet pipe and undergo digestion
in the digestion chamber.
The temperature of the process is quite important because methane producing
bacteria do their work best at temperatures between 30-40 o
C and 50-60oC. It takes 2-
8 weeks to digest a load of wastes.
2.2 History of Biogas
Ancient Persians observed that rotting vegetables produce flammable gas. In
1859 Indians built the first sewage plant in Bombay. Marco Polo has mentioned the
use of covered sewage tanks in China. This is believed to go back to 2,000–3,000
years ago in ancient China.
6
This idea for the manufacturing of gas was brought to the UK in 1895 by
producing wood gas from wood and later coal. The resulting biogas was used for gas
lighting in street lamps and homes (Ioana and Cioabla, 2010).
Biogas typically refers to a gas produced by the biological breakdown of
organic matter in the absence of oxygen. Biogas originates from biogenic material and
is a type of bio-fuel. One type of biogas is produced by anaerobic digestion or
fermentation of biodegradable materials such as biomass, manure, sewage, municipal
waste, green waste, plant material and energy crops. This type of biogas comprises
primarily methane and carbon dioxide. The other principal type of biogas is wood gas
which is created by gasification of wood or other biomass. This type of biogas is
comprised primarily of nitrogen, hydrogen, and carbon monoxide, with trace amounts
of methane.
The gases methane, hydrogen and carbon monoxide can be combusted or
oxidized with oxygen. Air contains 21% oxygen. This energy release allows biogas to
be used as a fuel. Biogas can be used as a low-cost fuel in any country for any heating
purpose, such as cooking, etc. It can also be used in modern waste management
facilities where it can be used to run any type of heat engine, to generate either
mechanical or electrical power. Biogas can be compressed, much like natural gas, and
used to power different energy chains. It is a renewable fuel, so it qualifies for
renewable energy subsidies in some parts of the world.
Biogas typically refers to a gas produced by the biological breakdown of
organic matter, in absence of oxygen. Biogas originates from biogenic material and is
a type of bio-fuel (Cioablă, 2009). Biogas arises from decomposition of organic
substance, by means of bacteria, in anaerobic or aerobic fermentation processes
(Bejan and Rusu, 2007). Organic matter consists mainly of water, albumin, fat,
7
carbohydrates and minerals and together with bacteria; they decompose the original
components, carbon dioxide, minerals and water. Thus a mixture of gas, called
biogas, arises as a metabolic product. Flammable methane (CH4) is the main
component of biogas, with a percentage of 50-85 % by volume, and thus represents
the main source of energy.
This natural process of decomposition occurs only in anaerobic environment, i.e. only
when oxygen is absent. The decomposition process is called decay in this case and is
naturally occurring in swamps, lakes, etc. In case of oxygen presence, decomposition
is carried out by other bacteria; the term for this process is rotting or composting.
Microorganisms that generate methane production are called methanogen
microorganisms, of liquid and acidogene origin. The energy released in the anaerobic
decomposition process is transferred as energy heat in the form of composting, and it
is used by bacteria to form methanogen flammable methane molecules. Collected and
stored in the biogas, the energy is of renewable nature, being derived from organic
matter of the green plants. More and more, the fossil energy will be less used and
replaced, alternatives are becoming necessary and the use of biogas is becoming
increasingly important.
The use of waste water and so-called renewable resources for energy supply is
not a novelty, with evidence of such practices even before Christ‟s birth. Even around
3000 BC, Sumerians practiced anaerobic waste cleaning (Deublein and Steinhauser,
2008). Old Roman scholar Plinius described around 50 years BC lights that glittered
phenomena, in the ponds area.
By 1776, Alessandro Volta personally collected gas from the atmosphere over
the Lake Como, in order to analyse it. His research showed that the formation of gas
depends on a fermentation process and can even form an explosive mixture with air.
8
English physicist Faraday made experiments with swamp gas and identified a type of
hydrocarbon in its composition. Later, around 1800, Dalton, Henry Davy described
the first chemical structure of methane. The final chemical formula was elucidated by
Avogadro in 1821.
In the second half of 19th
century, in France, a systematic and scientific
research for a better understanding of the process of anaerobic fermentation started.
The objective was to remove bad odour emanating from waste water. During
investigations, the researchers have detected typical microorganisms that are retested
nowadays as essential for the fermentation process. Bechamp identified by 1868 that a
mixed population of microorganisms is necessary to convert ethanol to methane, since
more final products were formed by the fermentation process; the whole process
depends on the substrate used.
By 1876, Herter reported the presence of acetate in the waste water, forming
methane and carbon dioxide in stoichiometric amounts. Louis Pasteur tried by 1884 to
produce biogas from horse droppings, collected from the streets of Paris. Together
with his students he managed to produce 100 m3 of methane from a fermentation
process, developed at 35 °C. Pasteur explained that the rate of production is sufficient
to cover energy needs for street lightening in Paris. Practically, this is considered the
starting point of larger application of renewable energy.
2.3 The Renewable Source for Obtaining Biogas
Biomass is the only renewable energy source that can be transformed into gas,
liquid or solid fuel by special conversion technologies. This universal renewable
energy carrier can be used in a wide range of applications, in the energy sector, for
9
small scale but also larger applications. Presently it is possible to provide this
renewable resource for the whole range of applications that require energy input,
starting from heating stations until providing electricity to mobile applications for
transport. On average, the industrialized countries contribute to the total biomass
energy sources used in a proportion of 9- 13 %, while in developing countries it
contributes in a percentage ranging from 5 % to 30 % ( Faaij, 2006). Typically, after
the biomass was treated, it is transformed into one of the major energy forms: (i)
Electricity or (ii) Heat. Range of application and disposal of biomass form the two,
very important advantages of biomass. Another major argument for using the energy
resources originated in bio – resources is the possibility of protecting the environment
and climate. When stored in biomass energy use, greenhouse gases like carbon
dioxide are emitted, but this amount is not a supplementary generated product, as it is
result from a natural decay processes. Thus bio-energy carriers can be considered
neutral in terms of climate damage, particular CO2 emission.
2.3.1 Solid Bio-energy Sources
The largest group of solid bio-energy sources includes products made from
wood. They are derived from industrial processing of wood waste. In many areas of
agricultural by-products such as straw, are also used to generate energy from biomass.
On one hectare of straw cereals is approximately equivalent to 200 litres of oil (Ioana
and Cioabla, 2010). However, straw and other products in this category have different
combustion characteristics from those of woody fuels. Point transformation in ash and
emission behaviour of biomass type straw means that different technical approaches
are needed.
10
Another important category of waste, which is not necessarily part of the old
wood sector, represents the wood residues from environmental management. These
occurred during maintenance work on roads and canals, parks and care. Wood
residues from environmental management are usually a mixture of wood, leaves and
straw type products. Only very rarely it is possible to consider these mixtures for a
new final product, thus utilization of its energy content is a very good strategy.
2.3.2 Liquid Bio-energy Sources
Mobility is essential in industrialized society. With few exceptions, passenger
transport and freight are based on liquid fuel. Today, there are few alternative bio-
fuels for these tasks. Ethanol, the alcoholic fermentation and methanol produced from
cellulose can be considered as having a biomass origin.
2.4 Biogas Plant
In many countries worldwide, biogas plants are in operation, producing biogas
from the digestion of manure or other biomass (GTZ, 2007). In addition, with success
small scale biogas plants are utilized to displace woody fuels and dung in many
developing countries. For example, the Dutch Development Organization, SNV,
implemented with success in Nepal and Vietnam over 220,000 household on site
biogas plants (FMO, 2007). Moreover, in China and India, millions of plants are in
operation. In conclusion, biogas plants have proven to be an effective and attractive
technology for many households in developing countries.
Under the right conditions a biogas plant will yield several benefits for the end-
users, the main benefits are (GTZ, 2007):
11
i. Production of energy for lighting, heat, electricity
ii. Improved sanitation (reduction of pathogens, worm eggs and flies)
iii. Reduction of workload (less firewood collecting) and biogas stoves has a
better cooking performance
iv. Environmental benefits (fertilizers substitution, less greenhouse gas emission)
v. Improved indoor air quality (less smoke and harmful particle emission of a
biogas stove compared to wood or dung fuels).
vi. Economic benefits (substitution of spending on expensive fuels and fertilizer)
The problems experienced by the biogas production include the following:
(a) Design faults
(b) Construction faults
(c) Difficulty of financing
(d) Operational problems due to incorrect feeding or poor maintenance and
(e) Organizational problems arising from the differences of approaches and lack of
coordination.
All these aspects need to be taken into account. In addition, back up services are
important, i.e. monitoring of the performance by experts.
2.5 Biogas Plants in Developing Countries.
In developing countries, there are several digesters in operation; the most
familiar is the fixed dome digester. In addition, the floating dome digester and bag
digester are found in many developing countries. These types of digesters are
respectively explained below:
12
2.5.1 Fixed Dome Digester
The fixed dome digester is the most popular digester; its archetype was
developed in China. This is CSTR type digester. The digester comes in various types,
notably the Chinese fixed dome, Janata model and Janata II model.