ABSTRACT
This study was aimed at determining the microorganisms associated with biogas produced from cassava peels and cow rumen fluid. The study adopted the use of two (2) substrates combination namely Cassava Peels (CP) and Cow Rumen Fluid (CRF). 1kg of cassava peels were collected from a grating centre in Umuahia North while about 2 litres of cow rumen fluid was collected from Ubakala Abbatoir Market which were taken to Microbiology Laboratory for analysis within 24 hours of sample collection. These samples were anaerobically digested and used in 1:1 ratio. Standard microbiological methods were used to screen the isolates and the wastes substrate for biogas production. The study isolated eight (8) bacteria species from the biodigested cassava peel and cow rumen fluid blend. The mean anaerobic count ranged from 1.13 x 106cfu/ml to 7.10 x 106cfu/ml. There was a considerable difference in the concentrations of different parameters in the daily slurry sample, observed mean chemical oxygen demand (COD) and biological oxygen demand (BOD) values at the 28th day of digestion was 1016 mg/L and 207mg/L, pH range 7.1-8.8, mean gas volume produced from cassava peel/cow rumen fluid blend was 2.09Ld-1. The findings of the study concluded that anaerobic co-digestion process has synergistic effects to increases biogas yield from the substrate. The study recommended need for more studies in organic blends in biogas production and cautions approach to handling biodigesters as pathogenic organisms proliferate there.
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgements iv
Table of Contents v
List of Tables vii
List of figures viii
Abstract ix
CHAPTER ONE
1.0 INTRODUCTION 1
1.1.1 Aim of the Study 5
1.1.2 Objectives of the Study 5
CHAPTER TWO
LITERATURE REVIEW
2.1 Renewable Energy 6
2.1.1 Solar Energy 6
2.1.2 Wind Energy 7
2.1.3 Biomass Energy 8
2.1.4
Tidal
Power 9
2.1.5
Geothermal
Energy 9
2.2 Biogas 10
2.2.1 Overview of biogas
production 12
2.2.2 Biogas Development in Africa 15
2.2.3 Biogas Development in Nigeria 15
2.3 Anaerobic Digestion (AD) 16
2.3.1 Classification of Anaerobic Digestion (AD)
System 17
2.3.2 Accelerants/Additives for AD 17
2.3.2.1 Green Biomass 18
2.3.2.2 Biological Additives 18
2.3.2.3 Chemical Additives 19
2.3.3 Stages of anaerobic degradation of organic wastes 22
2.3.3.1 Hydrolysis 22
2.3.3.2 Acidogenesis (Acidification Phase) 23
2.3.3.3 Acetogenesis 24
2.3.3.4 Methanogenesis 24
2.4 Anaerobic co-digestion 25
2.5 Anaerobic digesters 25
2.5.1 Capacity of Anaerobic Digesters 26
2.5.2 Basic considerations for digester
construction 26
2.5.3 Types of Digesters 27
2.5.3.1 Continuous and Batch Digesters 27
2.5.4 Siting of Biogas Digester 32
2.6 Cassava Peels 32
2.6.1 Biogas Production from
Cassava Peel 32
2.7 Cow Rumen Fluid 34
CHAPTER THREE
MATERIALS AND METHODS
3.1 Study area 36
3.2 Sample collection 36
3.3 Sample preparation 37
3.4 Media
preparation 37
3.5 Analysis
of samples 37
3.5.1 Determination
of Physicochemical Characteristics 37
3.5.1.1 Determination
of Temperature 37
3.5.1.2 Determination of pH 37
3.5.1.3 Determination
of Dissolved Oxygen (D.O) 38
3.5.1.4 Determination
of Biological Oxygen Demand (BOD) 39
3.5.1.5 Determination
of Chemical Oxygen Demand 39
3.5.2 Microbial
Composition and Mean Count 40
3.5.2.1 Fungi Identifications 40
3.5.2.2 Bacteria Identification 40
CHAPTER 4
RESULTS AND
DISCUSSION
4.1 Results 42
4.2 Discussion
46
CHAPTER 5
CONCLUSION AND RECOMMENDATION
5.1 Conclusion 49
5.2 Recommendations 49
REFERENCES
APPENDIX
LIST
OF TABLES
Table
Title Page
4.1: The
Microbial Composition and Mean Count 43
4.2: Daily
Physicochemical Characteristics Of Slurry For 30 Days 44
4.3: Mean
Volume of the Biogas Produced in litres per day 45
LIST
OF FIGURES
Figure Title Page
2.1: A Single Stage Process Conventional Digester 27
2.2: A Double Stage Process Conventional Digester 28
2.3: A Floating Gas Holder Digester 30
2.4: The
Fixed Dome Digester 30
CHAPTER ONE
1.0 INTRODUCTION
Interest in biogas
technology is increasing around the world due to the requirements for renewable
energy production, reuse of materials such as cassava peels and animal waste of
various categories and reduction of harmful emissions. Biogas technology offers
versatile and case-specific options for tackling renewable energy and reuse of
waste materials with simultaneous controlled treatment of various organic
materials (Lehtomäki, 2006; Amon et al.,
2007; Seppälä et al., 2009). It
produces methane-rich biogas which can be utilized as renewable energy in
various ways (Mata-Alvarez, 2003). The residual material, digestate, contains
all the nutrients of the original raw materials and offers a way to recycle
them. Along the process steps, also emissions directly from the raw materials
(storage, use, and disposal) or from the replaced products (fossil fuels,
inorganic fertilizers) can be reduced. Biogas technology is currently the most
sustainable way to utilize the energy content of manure w
hile also recycling
the nutrients and minimizing the emissions (Mata-Alvarez, 2003).
Biogas production
from crop residues and animal manure by anaerobic digestion is a sustainable
approach for waste reduction and energy recovery. Hydrolysis is considered as
the rate-limiting step during the anaerobic digestion of these waste streams
due to their high content of lignocellulosic materials. Consequently, numerous
studies have focused on the development of feedstock pretreatment methods and
inoculation strategies in order to improve the hydrolytic efficiency and
consequently enhance the rates of acidogenesis and methanogenesis (Emine et al., 2018).
Biogas is also called
swamp gas, sewer gas, marsh gas, gobar gas and digester gas ‘will O the wisp
gas, natural gas, landfill gas and sewage gas (Asikong et al., 2017). Biogas is a mixture of gasses consisting of methane
50 – 70%, carbon dioxide 30 – 40%, Hydrogen 5 – 10%, Nitrogen 1 – 2%, water
vapour 0 – 3%, and traces of Hydrogen sulphide. It is colourless, relatively
odourless and flammable; it is also stable and non-toxic. Biogas formation can
occur naturally in swamps, marine sediments, and water logged soils, rice
fields, deep bodies of water, sanitary landfills and even in the digestive
system of ruminants; and termites. It can also be recovered from lagoons used
for waste treatment. It burns with a blue flame and has a calorific value of
4500 – 6000 kcal/m3 when its methane content ranges from 60 – 70% (Igoni
et al., 2008; Adeyanju, 2008).
Generally, four
different stages have been recognized in the production of biogas with several
other intermediate products. These include; hydrolysis, acidogenesis,
acetogenesis and methanogenesis. The
efficiency, effectiveness and stability of anaerobic digestion and consequently
biogas generation can vary significantly based on various operational factors
such as; type of waste streams, digester design, temperature, moisture content,
retention time, pH, agitation or mixing, bacterial species and organic loading
rate. Presence of toxicants can also influence biogas production. Positive
implications of biogas include; the reduction in environmental pollution, odour
(Budiyono et al., 2010; Lund et al., 2010), and in the destruction of
most pathogenic organisms, worms, ova, etc. Biogas can also serve as a clean
alternative to fuel energy source to oil, electricity and wood. The negative
implications of biogas technology include; concentration of toxic compounds
such as pesticides and heavy metals in plants and ground water contamination (Prescott
et al., 2005).
Cattle manure is
frequently used as an inoculum for the start-up of agricultural biogas plants
or as a co-substrate in the anaerobic digestion of lignocellulosic feedstock.
Ruminal microbiota are considered to be effective plant fiber degraders, but the
microbes contained in manure do not necessarily reflect the rumen microbiome
(Emine et al., 2018).
However, in
contemporary times, cassava is being recognized as an important source of
biofuel. Adelekan (2012), Cassava (Manihot
esculenta Cranz) is a very important crop grown for food and industrial
purposes in several parts of the tropics. Adelekan and Bamgboye (2009a)
investigated biogas productivity of cassava peels, mixed with poultry, piggery
and cattle waste types in ratios 1:1, 2:1, 3:1 and 4:1 by mass, using a
retention period of 30 days and within the mesophilic temperature range.
Cassava peels have high value of organic carbon and low value of total
nitrogen, and this result in a particularly high C/N ratio. According to Karki et al. (1994) high C/N ratio is
indicative of the fact that the material is not good for biogas production and
will not appreciably yield biogas. However, the work points out that such a
material could be mixed with another with a much lower C/N ratio to stabilize
the ratio to an optimal value between 22 and 30. Biogas yield was significantly
(P ≤ 0.05) influenced by cassava peels used. The cumulative average biogas
yield from digested cassava peels was 0.6 l/kg- TS. Since cassava peel is a
material with a high C/N ratio, it will not yield much biogas. Several researchers
have recently reported improvements in biofuel production from various
agricultural materials including biogas from mixtures of cassava peels and
livestock wastes (Adelekan and Bamgboye, 2009a), biogas from pretreated water
hyacinth (Ofuefule et al., 2009),
methanol from cow dung (Ajayi, 2009) fuel from indigenous biomass wastes
(Saptoadi et al., 2009), ethanol from
non-edible plant parts (Inderlwildi and King, 2009), as well as biogas from
various livestock wastes (Adelekan and Bamgboye, 2009b). Adelekan (2012) showed
that cassava, an often neglected but sturdy crop is a potent energy crop for
the production of methane and ethanol, and presented production estimates for
these biofuels based on cassava yield from the tropical countries. It has been
discovered that, under aerobic conditions, living plants also produce methane.
Cattle rumen fluid is
a suitable substrate for anaerobic digesters, its recalcitrant fiber structure
and high water content results in a low methane yield in mono-digestion. The
combination of different substrates with manure facilitates the digestion by
increasing the easily degradable fraction and thus enhancing the methane yield
(Lund et al., 2010). Cattle manure is
commonly considered as an inoculum well-suited for the start-up of anaerobic
digesters, since it contains a diverse microbial community that can easily adapt
to changing operational conditions (Janke et
al., 2016; Goberna et al., 2015).
Most studies on the rumen environment focused on microbial community dynamics depending
on the dietary differentiation of animals (Zened et al., 2013; Kong et al.,
2010; Kittelmann and Janssen, 2011).
However, these
products make up a tangible net weight
and contain toxic cyanogenic glycosides. As a result of these reasonable large
quantities in homes engaged in farming activities and industrial areas where
commercial quantities are produced, these peels waste products become a
nuisance and create waste disposal problem. Also, in contemporary times, a
great deal of interest has been generated worldwide regarding the use of
biofuels namely biogas, bioethanol and biodiesel for energy supply since there
availability is rampant. It is on this basis that this study is carried out to ascertain the
microbial diversity of biogas produced from cassava peels and cow rumen fluid.
1.2
Aim and Objective of the Study
1.2.1 Aim of the
Study
The aim of the study
is to determine the microorganisms associated with biogas
produced from cassava peels and cow rumen fluid.
1.2.2 Objectives of the Study
The objectives of
this study include:
i)
determine the potentials of biogas energy generation from cassava peels
and cow dung fluid
ii)
to identify the key microorganisms of use for efficient lignocellulose
degradation.
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