About the Work
Class: A Research Project
Field: Applied Microbiology
Author: Abasiama Akpan
Number of Pages: 71
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ABSTRACT
Oryza sativa husks and peels of Musa paradisiaca were pretreated by hydrothermal and acid fermentation using cassava mill effluent, and co-digested in a laboratory scale reactor maintained at 45 ± 2 ⁰C for 42 days. Five digesters were used for the experiment and each digester contained Oryza sativa husks and Musa paradisiaca in the ratio of 1:1 with cow dung as inoculum. Substrate in Digester X (Control) was not pretreated, Digester A (Oryza sativa husks pretreated hydrothermally), B (Oryza sativa husks pretreated with cassava mill effluent), C (Substrates pretreated hydrothermally + acid fermentation with cassava mill effluent), whereas D contained Musa paradisiaca peels and Oryza sativa husks mixture subjected to combined pretreatment. During the digestion period, Digester X (control) generated the lowest cumulative biogas of 68mL gVS-1 while Digester C produced the highest biogas yield of 209mL gVS-1. Digestate obtained from the Digester C contained microbial load of 6.31Log10CFU g-1 while the control contained lowest microbial load of 5.23Log10CFU g-1. Methanogens of genera Methanosarcina, Methanocorpusculum, Methanobacterium, Methanobrevibacter and Methanothrix were isolated from the digestates. The Substrates contained total solids of 7.88, 7.49, 6.53, 6.87 and 6.02mg kg⁻¹; and volatile solids of 7.07, 7.02, 6.36, 6.61 and 5.28mg kg⁻¹, respectively. After digestion, digestates analyzed contained total solids of 5.21, 4.94, 5.01, 5.04, 5.2604mg kg⁻¹; and volatile solids of 5.15, 4.81, 4.91, 4.49 and 5.12mg kg⁻¹ for Digester X, A, B, C, and D respectively.. Therefore this experiment has proved that Oryza sativa husks and peels of Musa paradisiaca are potential substrates for biogas production.
TABLE OF CONTENTS
TITLE PAGE
Inner page - - - - - - - - - i
Certification - - - - - - - - - ii
Dedication - - - - - - - - - iii
Acknowledgements - - - - - - - - iv
Table of contents - - - - - - - - v-vi
List of figures - - - - - - - - - ii
List of tables - - - - - - - - - viii
Abstract - - - - - - - - - ix
CHAPTER ONE
1.1 Introduction - - - - - - - - 1-4
1.2 Objective of study - - - - - - - 5
CHAPTER TWO: LITERATURE REVIEW
2.1 Types of feedstock / substrates for biogas production - - 6-7
2.1.1 Agricultural wastes with manure co-digestion - - - 8-10
2.1.2 Energy crops with manure as substrate - - - - 10-11
2.1.3 Food wastes with manure as substrate - - - - 11
2.1.4 Industrial wastes and by-products as substrates - - - 11-12
2.1.5 Manure as substrates for biogas production - - - - 12
2.2 Processes of anaerobic digestion and microorganisms involved - 12-13
2.2.1 Hydrolysis - - - - - - - - 13
2.2.2 Acidogenesis - - - - - - - - 14
2.2.3 Acetogenesis - - - - - - - - 14-15
2.2.4 Methanogenesis - - - - - - 15-16
2.2.5 Types of anaerobic digestion - - - - - - 18
2.2.6 Advantages of anaerobic digestion - - - - 19
2.3 Factors affecting anaerobic digestion for biogas production - - 19
2.3.1 Nature or type of substrate/ sub-layer composition - - - 19-21
2.3.2 Digester temperature - - - - - - - 21
2.3.3 Hydraulic retention time (HRT) - - - - - 22
2.3.4 pH - - - - - - - - - 22-23
2.3.5 Working pressure in the fermenter - - - - - 23-24
2.3.6 Digester design - - - - - - - - 24
2.4 Methods of improving biogas production - - - - 25
2.4.1 Pretreatment - - - - - - - - 25-30
2.4.2 Co-digestion - - - - - - - - 31-32
2.4.3 Microbial bioaugmentation - - - - - - 32
2.4.4 Agitation of the reaction system - - - - - 32-33
2.5 Composition and utilization of biogas - - - - 33-34
2.6 Sources of the substrates and their chemical composition - - - 34-37
CHAPTER THREE: MATERIALS AND METHODS
3.0 Equipment and supplies - - - - - - - 38
3.1 Aseptic techniques and sterilization procedure - - - - 38
3.2 Sample collection and processing - - - - - - 39
3.3 Experimental design - - - - - - - - 39-41
3.3.1 Digestion of substrate - - - - - - - - 41
3.3.2 Measurement of biogas - - - - - - - 41-43
3.4 Determination of total and volatile solids (TS and VS) - - - 44
3.5 Microbial analysis - - - - - - - - 44
3.5.1 Media preparation - - - - - - - - 44
3.5.2 Isolation of anaerobic bacteria - - - - - - 45
3.5.3 Characterization and identification of bacteria isolates - - - 45-48
CHAPTER FOUR: RESULT
4.0 Results - - - - - - - - - - 49-54
CHAPTER FIVE: DISCUSSION AND CONCLUSION
5.1 Discussionand conclusion - - - - - - - -55-56
5.2 Conclusion - - - - - - - - - 56
REFERENCES - - - - - - - - - 57-65
LIST OF FIGURES
Figure Title Page
2.1 Stages of anaerobic digestion and associated microbial groups - - 17
3.1 Diagram of the experimental design - - - - - - - 43
4.1 Cumulative biogas yield - - - - - - - - - - 51
4.2 Total solid content of the substrates and digestates - - - - - 52
4.3 Total Volatile solid content of the substrates and digestates - - - 52
4.4 Counts of anaerobic microorganisms associated with the biogas production in the digestate - - - - - - - - - 53
LIST OF TABLES
Table Title Page
2.1 Some constituents of selected lignocellulosic materials - - - - 8
2.2 Comparison between dry and wet digestion - - - - - - - 18
2.3 Methods of pretreatment of lignocellulosic materials - - - - - 30
2.4 Percentage composition of biogas - - - - - - - - - - 34
3.1 Composition of basal medium used for selective enrichment and growth of some methanogenic species isolated from the substrates - - - - 48
4.1 Morphological and biochemical characteristics of methanogenic bacteria species
Isolated from the digestate - - - - - - - - 54
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