ABSTRACT
Anaerobic biodegradation of banana leaves by cellulolytic fungus (yeast) was conducted at optimum operational conditions of concentration, temperature and pH for biogas and bioliquid production. Proximate analysis of both the fermented and unfermented substrates was carried out. Effects of nutritive additives on biogas and bioliquid production were investigated. The bioliquid generated was extracted by soxhlet extraction and, its components were separated into maltenes (soluble component) and asphaltenes (insoluble component) by precipitation. The maltenes contents of both the fermented and unfermented substrates were separated into fractions by column chromatography. Gas-chromatographic identification of organic component of the biogas generated was carried out using flame ionization detector (FID) while the heavier hydrocarbons in the bioliquid were analysed using gc-mass spectrometer. The analyses carried out revealed that, all the physio-chemical prametres employed, enhanced the production of biogas and bioliquid; the quantity of bioliquid generated from the fermented substrate was smaller than the quantity of the bioliquid generated from the unfermented substrate while the maltenes contents of the fermented substrate were higher than those in the unfermented substrate; the fractions of maltenes of the fermented substrate were in the order: saturates> polyaromatics > monoaromatics> diaromatics> resins and polars while the fractions of maltenes of the unfermented substrate were in the order: polyaromatics > monoaromatics >diaromatics >resins and polars> saturates; and the organic gas identified in the biogas was methane (CH4) while the heavier hydrocarbons detected in the bioliquid were n-alkanes, iso-alkanes and cyclo-alkanes.
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TABLE OF CONTENTS
TITLE PAGE ………………………………………………………………………….…………..i
DECLARATION ……………………………………………………………………………………ii
CERTIFICATION………………………………………………………..………………… …..iii
ACKNOWLEDGEMENT ……………………………………………………..………… …….iv
DEDICATION ……………………………………………………………………………… …..vi
TABLE OF CONTENTS……………………………………………………………………….vii
LIST OF TABLES ……………………………………………………………………………..xiv
LIST OF FIGURES …………………………………………………….……………………..xvi
Abstract……………………………………………………………………………………….…xx
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND TO THE STUDY ……………………………………………….1
1.1.1 Alternative Sources of Energy…………………………………………………..2
1.2 STATEMENT OF RESEARCH PROBLEMS ……………………………………8
1.3 AIMS AND OBJECTIVES OF THE RESEARCH ………………………………9
1.4 SIGNIFICANCE OF THE RESEARCH …………………………..…………….10
1.5 SOPE AND LIMITATIONS OF THE RESEARCH ……………………………11
CHAPTER TWO
LITERATURE REVIEW
2.1 APPROACHES TO THE DEVELOPMENT OF BIOGAS
TECHNOLOGY ………………………………………………..…………………………. 13
2.2 SOURCES OF BIOGAS AND BIOLIQUID………………….……………. ………..…17
2.3 BIOMASS ……………………………………………………………… …………….18
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2.3.1 Composition and Structure of Biomass ……………………….…………..18
2.3.2 Biomass Conversion Processes ………………………………………………..20
2.4 BIOGAS AND BIOLIQUID …………………………………..…….……………..22
2.4.1 Biogas, Composition and Properties ………………………….….………….22
2.4.2 Bioliquid, Composition and Properties ……………….………….……..……24
2.4.3 Maltenes (Deasphaltened Oils) …………………………….…………………..24
2.4.4 Asphaltenes ……………………………………………..……………………………25
2.4.5 Properties of Maltenes and Asphaltenes ……………………………..………25
2.4.6 Structure of Maltenes and Asphaltenes ……………………………….…… 26
2.4.7 Classification of Biogas and Bioliquid …………………………. ……….…… 27
2.5 CHEMISTRY OF BIOGAS AND BIOLIQUID PRODUCTION……..…………..28
2.6 THEORY OF METHANOGENESIS …………………….………………. …………..30
2.7 METHANE-PRODUCING MICROBES ……………..………………………….……31
2.8 NON METHANE -PRODUCING MICROBES ……….……………………………..32
2.9 PHYSIOLOGY OF MICROBES (FUNGI) ……………………………….……….…33
2.10 FACTORS REQUIRED FOR MAXIMUM BIOGAS AND BIOLIQUID
PRODUCTION …………………………………………………………………………..35
2.11 BIOGAS AND BIOLIQUID TECHNOLOGY ……………………… …..…………43
2.11.1 Large Scale Continuous Process…………………..…………… ………………43
2.11.2 Small Scale Type ………………………………………………….………………. .48
2.11.3 Management of Biogas Pit ……………………………………………………. .49
2.11.4 Factors to be Considered while Selecting of a Model ………..………..50
2.11.5 Basic Components of a Biogas and Bioliquid Pit ……………….…….….52
2.11.6 Plant Operation, Maintenance and Precautions …………………….…….57
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2.12 STORAGE OF BIOGAS AND BIOLIQUID …………………………….…………..65
2.13 BENEFITS OF BIOGAS AND BIOLIQUID TECHNOLOGY ……………..……. 65
CHAPTER THREE
MATERIALS AND METHODS
3.1 MATERIALS …………………………………….………………………………….….…..…..70
3.2 CHEMICALS / REAGENTS …………………….……………………………………….. .70
3.3 APPARATUS / INSTRUMENTS ………………………………………………………….73
3.4 SAMPLE COLLECTION AND PREPARATION ……………….…………..………….75
3.5 PREPARATION OF REAGENTS AND SOLUTIONS …..……………………….. ..75
3.6 CONSTRUCTION OF REACTOR (OR DIGESTER) …………….. …………………76
3.7 DETERMINATION OF MOISTURE CONTENT OF THE SUBSTRATES ……….77
3.8 DETERMINATION OF ASH CONTENT OF THE SUBSTRATES …………….…77
3.9 DETERMINATION OF ORGANIC MATTER CONTENT OF THE
SUBSTRATES ………………………………………….………..…. ………………….…..78
3.10 DETERMINATION OF CARBON CONTENT OF THE SUBSTRATES
BY WALKLEY – BLACK METHOD ………………………….…..………………………79
3.11 DETERMINATION OF NITROGEN CONTENT OF THE
SUBSTRATES BY KJELDAHL METHOD ………………………..….……..….. ..80
3.12 DETERMINATION OF CARBON TO NITROGEN RATIO OF
THE SUBSTRATES ………………………………………………………………………..82
3.13 DETERMINATION OF CRUDE PROTEIN CONTENT
OF UNFERMENTED AND FERMENTED SUBSTRATES …………..…………. 82
3.14 DETERMINATION OF LIGNIN CONTENT OF THE UNFERMENTED
AND FERMENTED SUBSTRATES …………………………………………….……. 82
3.15 DETERMINATION OF CRUDE FIBRE CONTENT OF UNFERMENTED
AND FERMENTED SUBSTRATES ………………………………………..…………. 83
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3.16 DETERMINATION OF CRUDE FAT OF UNFERMENTED AND
FERMENTED SUBSTRATES …………………………………………….………….. 84
3.17 DETERMINATION OF TOTAL CARBOHYDRATE OF SUBSTRATES
BY L-CYSTEIN TETRAOXOSULPHATE (VI) ACID METHOD …………….. 85
3.18 DETERMINATION OF REDUCING SUGAR OF SUBSTRATE BY
NELSON’S METHOD ……………………………………….…………………………..86
3.19 PREPARATION OF SLURRY ……………………………………………………….. 88
3.2.0 DETERMINATION OF OPTIMUM SLURRY CONCENTRATION
FORMAXIMUM BIOGAS PRODUCTION. ………………………………………. 90
3.21 DETERMINATION OF OPTIMUM YEAST CONCENTRATION
FOR MAXIMUM BIOGAS PRODUCTION ………………………………………. ..91
3.22 VERIFICATION OF OPTIMUM TEMPERATURE CONDITION
SELECTED FOR MAXIMUM BIOGAS PRODUCTION ……………………….. .92
3.23 EFFECT OF SLURRY MASS CHANGE ON BIOGAS PRODUCTION
AT FIXED CONCENTRATION OF YEAST …………………………………………92
3.24 EFFECT OF SLURRY MASS CHANGE ON BIOGAS PRODUCTION
AT VARYING CONCENTRATION OF YEAST.……………. …………………….93
3.25 EFFECT OF BUFFERING ON BIOGAS PRODUCTION USING
BUFFER SOLUTION …………………………………………………………..………. 93
3.26 EFFECT OF PH OF THE SLURRY ON BIOGAS PRODUCTION …………….94
3.27 EFFECT OF UREA ON BIOGAS PRODUCTION …………………………………95
3.28 COMBINED EFFECT OF BUFFERING AND UREA
ON BIOGAS GENERATION ………………………………………………………….95
3.29 BIOGAS GENERATION AND COMPOSITIONAL ANALYSIS………………….96
3.30 EFFECT OF BUFFERING ON THE COMPOSITION OF BIOGAS ………….101
3.31 EFFECT OF ADDITION OF UREA ON BIOGAS COMPOSITION …………102
3.32 COMBINED EFFECT OF BUFFERING AND UREA ON BIOGAS
COMPOSITION ……………………………………………………………………102
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3.33 EFFECT OF LIPIDS (OIL) ON BIOGAS PRO DUCTION …………………….102
3.34 EFFECT OF SUGAR ON BIOGAS PRODUCTION ………………….…….….103
3.35 COMBINED EFFECT OF OIL AND SUGAR ON
BIOGAS PRODUCTION ……………………………………………………………….103
3.36 EFFECT OF PROTEIN ON BIOGAS PRODUCTION ……………………..……104
3.37 EFFECT OF CARBOXYLIC ACID ON BIOGAS PRODUCTION ………….…..104
3.38 EFFECT OF ADDITION OF YEAST ON BIOGAS PRODUCTION
POTENTIAL OF FERMENTED SLURRY ………………………….…………..…..105
3.39 BIOGAS PRODUCTION POTENTIAL OF EXTRACTED SUBSTRATE …….105
3.40 COMPARISON OF BIOGAS GENERATION OF BANANA LEAVES,
MAIZE COB, MAIZE STALK, WATER HYACINTH, ELEPHANT
GRASS AND COW DUNG …………………………………………………………..….105
3.41 PRODUCTION AND COLLECTION OF BIOLIQUID (MALTENES
AND ASPHALTENES) FROM FERMENTED AND
UNFERMENTED SLURRIES …………………………………………………….….…106
3.42 PRECIPITATION OF ASPHALTENES ……………………………………………….106
3.43 COLUMN CHROMATOGRAPHIC SEPARATION OF MALTENES
(DEASPHALTENED OILS) OF FERMENTED
AND UNFERMENTED SLURRIES ………………………………………..…………..107
3.44 UREA ADDUCTION OF N-ALKANES FROM THE SATURATES
FRACTION OF FERMENTED BIOLIQUID ……………………………………….…109
3.45 THIOUREA ADDUCTOION OF CYCLICS (CYCLO-ALKANES)
AND THE SUBSEQUENT SEPARATION OF ISO-ALKANES……………….….109
3.46 GAS CHROMATOGRAPHIC IDENTIFICATION OF GASEOUS
DEGRADATION PRODUCT (BIOGAS) USING FLAME
IONIZATION DETECTOR (FID)………………………………………………………110
3.47 GC-MASS SPECTROMETRIC ANALYSIS OF THE HEAVIER
HYDROCARBONS IN THE LIQUID DEGRADATION PRODUCT……………110
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CHAPTER FOUR
RESULTS
4.1 DESCRIPTION OF TABLES OF RESULTS ………………………….……..… .112
4.2 PRESENTATION OF FIGURES OBTAINED FROM GC AND
GC–MASS SPECTROMETRIC ANALYSES………………………………….…….152
CHAPTER FIVE
DISCUSSION, SUMMARY AND RECOMMENDATIONS
5.1 DISCUSSION……………………………………………………………………………….204
5.1.1 Moisture, Ash and Volatile Solids Contents of the Substrates ……….… 204
5.1.2 Carbon to Nitrogen Ratio (C/N) of the Substrates ……………… ……….….205
5.1.3 Chemical Composition of the Substrates …………………………………….… 206
5.1.4 Optimum Operational Conditions for Maximum Biogas and
Bioliquid Generation …………………………………………………………………… 208
5.1.5 Compositional Analysis of Biogas Generated …………………………………. 213
5.1.6 Effect of Buffering and Urea on the Composition of Biogas ……………. 213
5.1.7 Effect of Oil, Sugar, Mixture of Oil and Sugar, Protein and
Carboxylic Acid on Biogas Production …………………………………………. .214
5.1.8 Effect of Addition of Yeast on Biogas Production Potential of
Fermented Slurry ……………………………………………………………………… 216
5.1.9 Biogas Production Potential of Extracted Substrates …………..………. . 217
5.1.10 Comparison of Biogas Generation of Banana Leaves, Maize
Cob, Maize Stalk, Water Hyacinth, Elephant Grass and Cow Dung .… 218
5.1.11 Production and Collection of Bioliquid ……………………………………..….. 220
5.1.12 Precipitation of Asphaltenes ………………………………………………………….220
5.1.13 Analysis of Maltenes ……………………………………………………………….…….221
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5.1.14 Percentages of Fungal Degradation Products
of 40.0g Banana Leaves ………………………………………………………….. 222
5.1.15 Urea and Thiourea Adduction for the Separation of N-alkanes,
Iso-alkanes and Cyclics from 38.00mg Saturates Fractions
Fermented Biollquid……………………………………………………………………223
5.1.16 Gas-Chromatographic Analysis of the Gaseous Degradation
Product (biogas)…………………………………………………………………………223
5.1.17 GC-Mass Spectrometric Analysis of the Liquid Degradation
Product (Bioliquid)……………………………………………………………..……….224
5.2 SUMMARY…………………………………………………………………………..…… 231
5.3 CONCLUSION …………………………………………………………………..….. ….232
5.4 RECOMMENDATIONS………………………….……………………………..…….…232
5.5 CONTRIBUTION TO KNOWLEDGE …………………………………………..…..233
5.6 SUGGESTION ON THE AREAS FOR FURTHER WORK …………..…..….…234
REFERENCES …………………………… ………………………………………..……. 235
APPENDICES …………………………………………………………………………….. 244
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CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND TO THE STUDY
The cost and scarcity of improved petroleum products used for agricultural, industrial and domestic fuels are drastically increasing. This makes it very difficult for most people to rise beyond subsistence level especially in developing countries like Nigeria. There is the problem of environmental pollution due to the release of by-products such as SO2, PbO, CO2, etc. when petroleum products are used in internal combustion engines. The use of firewood as fuel for domestic energy supply also causes environmental pollution as well as desertification, erosion and reduced biodiversity due to the frequent indiscriminate felling of trees. There is also the problem of tremendous amount of biodegradable wastes produced everyday due to increase in population, which of course constitutes nuisance to the environment and reduces the aesthetic (beautiful) value of the environment.
If the subsistence and the developmental needs of such developing countries are to be met as well as reduce environmental hazards, there is therefore the need to think about alternative energy sources, which are cheap, abundant and environmentally friendly.
Biogas technology appears to have promise as an alternative way of getting energy and at the same time, could alleviate environmental problems and enhance agricultural production.
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1.1.1 Alternative Sources of Energy
The major alternative sources of energy are broadly divided into two (2) categories. They are: renewable and non-renewable.
Renewable energy is the energy obtained from the continuing or repetitive currents of energy occurring in the natural environment (Twindell & Anthony, 1990). The following are the major alternative sources of renewable energy: hydroelectric power; wind power; geothermal power, solar power and the power obtained from waste (Dangoggo, 1984).
Hydroelectric power is obtained from oceans and stream currents and it is limited by the number of rivers and water waves that can be utilized to drive generators. The total exploitation of hydropower potential of Nigeria was estimated at over 10,000MV and it is capable of generating 36,000 GWh of electricity annually (Sambo, 1992). However, only one-fifth of this power is being exploited as reported by Ahmad (2000).
Wind energy is obtained as a result of seasonal changes, it is used for sailing ships, windmills are used for pumping of water and milling as reported by Dangoggo (1984).
Geothermal energy is released from the interior of the earth core by conduction and heat convection from hot springs and volcanoes. However, the use of this form of energy is restricted because volcanoes and hot springs are not found everywhere (Dangoggo, 1984).
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Solar energy is the most reliable because it is available everywhere, it cannot be depleted and it can be used in its original form or after conversion. Nigeria lies within a high sunshine belt and within the country solar radiation is fairly well distributed. The annual average total solar radiation varies from about 3.5 KWh/m2/day in the coastal latitudes to about 7.0KWh/m2/day in the far north. Solar radiation intensities are diluted when compared to the volumetric concentration of energy in fossil fuels (Sambo, 1992).
Power from waste is principally derived from biomass resources such as wood, forage-grasses and shrubs, animal wastes arising from forestry, agricultural, municipal and industrial activities as well as aquatic biomass. It has been reported by Garba (1998) that the biomass resources of the nation have been estimated at about 8 x 102 MJ.
Non-renewable energy is the energy obtained from static store of energy that remains bound unless released by human interaction (Twindell & Anthony, 1990). Petroleum (Crude oil), coal, natural gas and plants are the examples of non-renewable energy resources available in Nigeria.
(a) Liquid petroleum (Crude oil) is a complex mixture of organic compounds, principally hydrocarbons. Of these hydrocarbons, straight chain alkanes predominate, cycloalkanes (ring or cyclic alkanes), such as cyclopentane, cyclohexane, and their derivatives, are present in lesser
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proportions, and there are even smaller amount of aromatic hydrocarbons. Traces of sulphur, nitrogen and oxygen compounds are also present in petroleum as contaminants. The predominance of alkanes (i.e. saturated hydrocarbons) in petroleum, and the absence of alkenes (i.e. unsaturated hydrocarbons), indicate that fats and possibly proteins were the likely starting points for petroleum formation (Hill & Holman, 1982).
Petroleum which means rock oil in Latin occurs as a dark viscous liquid in huge subterranean deposits, in many part of the world. It is a mixture of gaseous, liquid and solid alkanes (containing about one to forty carbon atoms per molecule), cycloalkanes, aromatic hydrocarbons, and others. It is generally believed to have been formed from the remains of microscopic plants and animals which lived in the warm inland seas millions of years ago. The chemical effects of pressure, heat and bacteria have converted these remains into petroleum (Ababio, 1985).
The actual proportions of the petroleum constituents depends on the source of the oil, but alkanes and cycloalkanes form the larger majority, with aromatics making only about 10% of the total hydrocarbons (Hill & Holman, 1982).
Petroleum has no significant use in its raw form (i.e. in crude form). To provide useful products, it components must be partly separated and, if necessary, modified. Petroleum has been a source of energy for heating, lighting and locomotion and, in particular, it provides
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the most convenient of all fuels for the internal combustion engines. In fact, practically, all the petroleum processed up to about 1920 was used as fuel. It was only after 1920 that petroleum emerged as an important source of raw materials for industrial uses in
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the chemical industry; and its importance in this field has had a phenomenal growth ever since as reported by Bamkole and Ogunkoya (1997).
Other sources of petroleum includes bituminous (tar) sands and shale oil (kerogen).
Bituminous sands – petroleum is some times found impregnated into sand or clay relatively near the earth surface. The exact mode of formation of such “sand” is not clear, but they are believed to be similar to conventional crude oil formation. The proportions of oil and water vary from 12 – 16% oil and 3 – 15% water. The separation of the oil from finely divided solids is a difficult matter, but considerable amount of experiments have been carried out which indicate that a practical method can be found (Mailabari, 1983).
Oil samples separated during exploration work showed considerable variation of properties, but all the oils are of the asphaltic type, with specific gravity ranging from 1.002 – 1.027 and 4 – 5% of Sulphur as reported by Mailabari (1983).
Shale oil (kerogen) – The reserves of shale in the world are considerable, amounting in oil equivalent to 20,000 million tons, but in view of the greater availability of petroleum, its utilization at present is comparatively negligible. Workable deposits are widely distributed in many parts of the world. In Britain, the production of shale oil was formerly an important source of fuel oil as reported by Mailabari (1983).
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Just like in the formation of petroleum, similar conditions led to the formation of natural gas that is often found associated with petroleum as well as in deposits on its own as reported by Hill and Holman (1982). Natural gas is a convenient raw material for producing hydrocarbons with a low relative molecular mass. The major part of natural gas is methane (82-98%), the remainder being ethane, propane and buthane (Oganesian, 1989). Besides the use of natural gas as domestic and industrial fuel, Oganesian also reported that large amount of carbon black is obtained from natural gas, which is used in making Vehicle tires. He also reported that numerous organic substances such as some acids and alcohols are produced from the hydrocarbons contained in the natural gas.
(b) Coal: It is believed that about 350 million years ago there existed flat swamps and forest of huge trees in many parts of the earth. This period was known as carboniferous period (Bajah, Tebo, Onwu & Obikwere, 1988).
Coal originates from the vegetation of carboniferous era which was protected from complete decay by overlaying water-washed earth deposits. Decomposition occurred gradually under pressure and in the absence of air. Carbon IV oxide, methane and water were liberated, leaving behind a material that contained a very high percentage of carbon. During this process of carbonization, the vegetative materials were converted in stages into peat, lignite (or brown coal), bituminous (or
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soft coal) and finally the anthracite (known as hard coal), which is about 95% pure carbon with some nitrogen content in it,
sulphur and phosphorus as impurities (Ababio, 1985). Carbon with naturally occurring hydrocarbons and other compounds are also found in coal (Bajah & Godman, 1975). Coal is widely used for domestic heating and power stations for generating electricity. Enormous quantities of coal are made into gas and coke for use in various furnace as pointed out by Bajah et al (1988). Besides the fact that coal is sued as fuel, it also provides valuable raw materials for the chemical industries.
The usefulness of coal is achieved after its destructive distillation; i.e. the industrial distillation in which it is heated to a very high temperature (1,200oC) in the absence of air to give four main products, namely coal gas, coal tar, ammonical liquor and coke. The volatile products are collected at different temperatures. The composition and the uses of the industrial distillation products of coal as pointed out by Bajah et al (1988) are as follows:
Coal gas – consists of a mixture of gases such as hydrogen, methane, carbon II oxide, ethane and minute impurities such as sulphur IV oxide and hydrogen sulphide. Coal gas is used as fuel in industries. Coke, the residue from the destructive distillation of coal, is light and porous, but chemically similar to hard coal. It contains about 90% amorphous carbon. Coke is extensively used as both industrial and domestic fuel. It is also
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used as reducing agent in the extraction of metals from their ores and in the manufacture of carbide. Gasification of coke gives rise to producer gas and water gas, which are also used as fuel.
Coal tar -This is a thick, brownish black liquid. It is a mixture of many organic chemicals, among which are benzene, toluene, phenol, nepthalene and anthracene. Coal tar is used to produce a host of useful chemicals, such as disinfectants, explosives for blasting rocks, pain killing drugs, etc., it is also used in making roads’ surface.
Ammonical liquour – contains mainly ammonia. It is used in the preparation of ammonium tetraoxosulphate VI which is used as fertilizer.
(C) Plants (Vegetative biomass)-Plants (the total dry mass accumulated excluding the moisture) obtained from aquatic plants, natural vegetation and agricultural crops, which are used for domestic fuel for most rural populace and some urban dwellers. The use of plants for fuel is achieved by direct burning of the plants for immediate heat. Dry homogenous input is preferred for efficient energy production and effective heating. In addition to fuel benefit, some plants are used for making of shelter and other construction purposes.
1.2 CONCEPT
Scientific researches are conducted in order to come up with the new idea (s) that could greatly help in solving problems and /or uplifting the standard of living as well as lowering the cost of living. The current
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fuel scarcity in Nigeria, and the environmental hazards associated with the use of petroleum products and fire – wood as fuel as well as the use of plants as ources of organic compounds could possibly be alleviated through the use of biogas and bioliquid as alternative sources of fuel and organic compounds respectively. This could only be possible when the necessary information needed about biogas and bioliquid technology are carefully studied and obtained.
1.3 GENERAL OBJECTIVE OF THE RESEARCH
The general objective of this research is to produce biogas and bioliquid from banana leaves by fungal degradation at optimum operational conditions.
1.4 SPECIFIC OBJECTIVES OF THE RESEARCH
The specific objectives of this research work are to:
(i) assess the potentiality of banana leaves as a substrate for biogas and bioliquid generation;
(ii) determine the effect of physio-chemical parameters – concentration, temperature and pH on biogas and bioliquid generation;
(iii) determine the influence of nutritive additives such as: urea, blood meal as source of protein), sugar, lipid (oil) and ethanoic acid on biogas and bioliquid generation;
(iv) assess the combined effect of buffering and addition of urea on biogas production and its composition;
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(v) determine the moisture, ash (inorganic), volatile solids (organic), carbon and nitrogen contents as well as carbon to nitrogen ratio of the fermented and unfermented substrates (banana leaves);
(vi) determine the lignin, crude fibre, crude fat, crude protein, total carbohydrates and reducing sugar contents of the fermented ad unfermented banana leaves;
(vii) assess the maltenes (deasphaltened oils) and asphaltenes contents of the biolioquid extracted from fermented and unfermented banana leaves;
(viii) analyse the maltenes contents of both the fermented and unfermented banana leaves in terms of saturates, mono-aromatics, di-aromatics, poly-aromatics, and resins and polars contents by column chromatographic method;
(ix) identify by gas-chromatographic method the organic component of the gaseous degradation products (biogas) using flame ionization detector (FID), and the inorganic component (CO2) using thermal conductivity detector (TCD); and
(x) identify the heavier hydrocarbons in the liquid biodegradation products (bioliquid) by G-C mass spectrometric analysis.
1.5 SCOPE AND LIMITATIONS OF THE RESEARCH
This research will consist of the laboratory analyses and assessment of the feasibility of generating biogas and bioliquid from banana leaves, and their potentials as sources of energy and other useful
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organic products like saturates, aromatics and resins. The study will also assess the effect(s) of some physio-chemical parameters and the effect(s) nutritive additives on the biogas generating rate and yield as well as the influence of these
physio-chemical parameters on the composition of biogas produced. Percentage fungal degradation of the substrates, percentage gaseous degradation product (biogas) and percentage liquid degradation product (bioliquid) will be treated. Compositional analysis of the substrates (fermented and unfermented), column chromatographic separation of maltenes, gas-chromatographic analysis of biogas and G-C mass spectrometric analysis of bioliquid will also be treated.
The major limitation of this research was electricity power fluctuation, which if not supplemented with boiled water, could have rendered the microbes less active at temperatures below 330C and impair degradation. The problem of electricity power fluctuation was overcome by using boiled water and maintained the temperature of the water bath within which the digesters were immersed at 330C.
1.6 RESEARCH PROBLEM
There is the problem of over-reliance on petroleum products, which are scarce and expensive for domestic and industrial fuels as well as the ecological problems associated with the use of petroleum products, indiscriminate felling of trees for fire-wood and improper ways of disposing agricultural wastes (banana leaves inclusive) by our local
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farmers. In order toreduce/minimize environmental pollution and nuisance in our environment the practice of biogas and bioliquid production from wastes would greatly be of paramount importance.
1.7 SIGNIFICANCE OF THE RESEARCH
Banana leaves are among the abundant crops residues (as agricultural wastes) in most gardens and in some farms, and most farmers dump it on the swampy farmlands to decay aerobically to be used as green manure. Some farmers also burn them to ash, to supplement fertilizer. The practice of dumping banana leaves leads to the generation of large quantity of CO2 by aerobic fermentation; through hydrolysis followed by oxidation, which causes environmental pollution like “green-house effect” and ozone layer depletion. The burning of banana leaves is a wasteful process, which also generates gaseous pollutants in the atmosphere, and also causes the destruction of some useful micro-organisms in the soil. In addition, dumping of organic substrates (banana leaves inclusive) under favourable anaerobic fermentation condition leads to the generation of methane gas in the atmosphere without control. This also causes a serious environmental hazard because methane gas is a greenhouse gas that remains in the atmosphere for considerable length of time as reported by EPA(1986); EPA (2005). It was also reported by Ayodele and Emmanuel (2007) that methane gas is more effective in trapping heat than carbon (iv) oxide.
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The scientific perception of the problems associated with the dumping and burning of agricultural wastes of any kind (banana leaves inclusive) coupled with the high energy demands for crops processing in modern farming system nowadays, made it necessary to think about an appropriate and effective way of dealing with such wastes on farmlands and gardens, as well as to think about an environmentally friendly and cheaper sources of energy for crops processing and other energy demanding processes. The production of biogas and bioliquid is of course one of the ways through which biodegradable wastes of any kind can be converted into useful products (i.e. fuel and biofertilizer); the rate of felling trees for firewood could drastically be reduced, which would in turn save the environment from erosion and desert encroachment; and would also minimize the utilization of petroleum products and natural gas, whose combustion also cause total environmental pollution (i.e. air, land and water pollution) via the formation of some solid and gaseous by-products.
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