Abstract

This study was aimed at investigating microorganisms associated with biogas production using cassava peel as substrates. Cassava peels obtained after peeling cassava roots were anaerobically digested using a 5 litre capacity fermentor. The peels were blended and mixed with water, in the ratio of 1:2. Standard microbiological methods and anaerobic biodigester were used to screen the isolates and the wastes substrate for biogas production. The mean flammable biogas yield of the cassava peels was 13.7Litre/total mass of slurry. Analysis revealed that the temperature of raw substrates ranged between 26°C and 30°C while the pH varied between 4.04 and 6.86 during digestion. The results of the total heterotrophic and anaerobic microbial counts during the digestion period showed a steady variation in the anaerobic bacteria and fungal counts as fermentation progressed. The load obtained for the total heterotrophic bacteria and anaerobic bacteria were within 2.9x104cfu/ml to 9.4x104cfu/ml and 1.8x103cfu/ml to 6.9x103cfu/ml respectively. Similarly the fungal count obtained through the digestion period ranged from 1.1x10cfu/ml to 3.9x10cfu/ml. The bacterial isolates were identified as Pseudomonas sp, Escherichia coli, Bacillus sp, Clostridium sp, and Methanococcus sp, while fungi isolated were identified as Saccharomyces cerevicae, Aspergillus sp and Penicillium sp.

TABLE OF CONTENT

Title page i

Certification ii

Declaration iii

Dedication iv

Acknowledgement v

Table of content vi

List of Table vii

List of Figures viii

Abstract ix

CHAPTER 1:

INTRODUCTION

1.1     Introduction 1

1.2    Aim and Objectives 4

CHAPTER 2:

LITERATURE REVIEW

2.0      Literature Review 5

2.1. Biogas 5

2.2 Biogas Composition 5

2.3 Chemical Characteristics of Biogas 6

2.4 Physical Characteristics of Biogas 6

2.5 Methane as a Component of Biogas 6

2.6 Collection of Biogas 7

2.7 Types of Biogas bioreactor 7

2.8 Substrate  (Cassava Peels ) 7

2.9 Microbial Floral Present in Production of Biogas 8

2.10 Microbiology and Biochemistry of Biogas Production 8

2.10.1 Hydrolysis 10

2.10.2 Acidification/Acetogenesis 10

2.10.3 Methane Formation 10

2.11 Interactions between the Various Microbial Groups 11

2.12 Factors Influencing Biogas Production. 11

2.12.1 Temperature 11

2.12.2 pH (Hydrogen Concentration) 12

2.12.3 Substrate Quality and Characterization 13

2.12.4 Loading Rate 13

2.12.5   Bioreactor  Design 14

2.13 Benefit of Biogas Technology 14

2.14 Domestic and Industrial Uses        15

2.15    Other Uses of Biogas 15

CHAPTER 3:

3.0 MATERIALS AND METHODS 

3.1 Construction of Anaerobic Digester 16

3.2 Sample Collection 16

3.3 Pretreatment of Cassava Peels 16

3.4 Charging of the Digester 16

3.5 Determination of Quantity of Biogas Produced 16

3.6 Determination of Physiochemical Analysis of the Slurry in the Bioreactor. 17

3.6.1 Hydrogen Ion Concentration (pH) 17

3.6.2 Temperature 17

3.6.3 Dissolved Oxygen (DO) 17

3.7 Determination of Biogas Flammability 17

3.9   Collection of Sample for Isolation 17

3.9 Media Preparation 18

3.10 Isolation Of Microorganisms (Fungi And Bacteria) 18

3.13  Isolation And Identification Of Bacterial Isolates 19

3.14  Gram Staining 19

3.14  Biochemical Identification of the Isolates 19

3.14.1 Catalase test 20

3.14.2  Coagulase Test 20

3.14.3  Oxidase Test 20

3.14.4   Indole Test 20

3.14.5 Citrate Utilization Test 21

3.14.6 Urease Test 21

3.14.7 Methyl Red Test 21

3.14.8 Voges- Proskauer Test 21

3.14.9 Sugar Fermentation Test 21

CHAPTER 4:

RESULTS

4.0    Results of Biogas Produced and microbial isolates 23

4.1    Results 23

CHAPTER 5:

 DISCUSSION, CONCLUSION AND RECOMMENDATION

5.1    Discussion 29

5.2    Conclusion 31

5.3    Recommendations 32

REFERENCES 47