Codigestion of Oryza sativa Husks and Musa paradisiaca Peels for the Production of Biogas

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 equal proportion of Oryza sativa husks and Musa paradisiaca in the ratio of 1:1; and cow dung (the inoculum) was added across. Substrate in Digester X (Control) was not pretreated. Digester A contained Oryza sativa husks pretreated hydrothermally; Oryza sativa husks in Digester B was pretreated with cassava mill effluent only, that of Digester C was pretreated hydrothermally before cassava mill effluent was used; while Digester D contained Musa paradisiaca peels and Oryza sativa husks mixed together before the combined pretreatment was applied. Digester X (control) generated cumulative biogas of 68mL gVS-1 while Digester C produced the biogas of 209mL gVS-1. Substrates in Digester C contained microbial load of 6.31Log10CFU g-1 while the control contained load of 5.23Log10CFU g-1. Methanogens of genera Methanosarcina, Methanocorpusculum, Methanobacterium, Methanobrevibacter and Methanothrix were isolated from the digestates with Methanosarcina sp. as a predominant methanogen. Substrate C contained total solids of 6.87 mg kg⁻¹ and volatile solid of 6.12 mg kg⁻¹ while the digester C digestate contained a total solid of 5.04mg kg⁻¹ and volatile solid of 4.49mg kg ⁻¹ on average. Therefore this experiment has proven that Oryza sativa husks and peels of Musa paradisiaca are potential substrates for biogas production.

TABLEOFCONTENTS

TITLEPAGE

Certification- - - - - - - - - - i

Dedication - - - - - - - - - - ii

Acknowledgements- - - - - - - - - iii

Tableofcontents - - - - - - - - - iv

Abstract - - - - - - - - - - v

CHAPTERONE

1.1Introduction - - - - - - - - - -

1.2Objectiveofstudy - - - - - - - - -

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CHAPTERTWO(LITERATUREREVIEW)

2.1Typesoffeedstock/substratesforbiogasproduction - - - -

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2.1.1Agriculturalwasteswithmanureco-digestion - - - - -

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2.1.2Energycropswithmanureassubstrate - - - - - -

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2.1.3Foodwasteswithmanureassubstrate - - - - - -

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2.1.4Industrialwastesandby-productsassubstrates- - - - -

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2.1.5Manureassubstratesforbiogasproduction - - - - -

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2.2Processesofanaerobicdigestionandmicroorganismsinvolved- - -

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2.2.1Hydrolysis - - - - - - - - - -

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2.2.2Acidogenesis- - - - - - - - - -

2.2.3Acetogenesis- - - - - - - - - -

2.2.4Methanogenesis - - - - - - - - -

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2.2.5Typesofanaerobicdigestion - - - - - - -

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2.2.6Advantagesofanaerobicdigestion- - - - - - -

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2.3Factorsaffectinganaerobicdigestionforbiogasproduction - - -

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2.3.1Natureortypeofsubstrate/sub-layercomposition - - - -

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2.3.2Digestertemperature- - - - - - - - -

2.3.3Hydraulicretentiontime(HRT) - - - - - - -

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2.3.4pH - - - - - - - - - - -

2.3.5Workingpressureinthefermenter- - - - - - -

2.3.6 Digesterdesign- - - - - - - - - -

2.4Methodsofimprovingbiogasproduction - - - - - -

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2.4.1Pretreatment- - - - - - - - - -

2.4.2Co-digestion - - - - - - - - - -

2.4.3Microbialbioaugmentation - - - - - - - -

2.4.4Agitationofthereactionsystem - - - - - - -

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2.5Compositionandutilisationofbiogas - - - - - -

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2.6Sourcesofthesubstratesandtheirchemicalcomposition - - -

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CHAPTERTHREE(MATERIALSANDMETHODS)

3.0Equipmentandsupplies - - - - - - - -

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3.1Aseptictechniquesandsterilizationprocedure - - - - -

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3.2Samplecollectionandprocessing - - - - - - -

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3.3Experimentaldesign - - - - - - - - -

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3.3.1Digestionofsubstrate - - - - - - - -

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3.3.2Measurementofbiogas - - - - - - - -

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3.4Proximateandmineralanalysis - - - - - - -

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3.5Microbialanalysis - - - - - - - - -

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3.5.1Mediapreparation - - - - - - - - -

3.5.2Isolationofanaerobicbacteria - - - - - - -

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3.5.3Characterizationandidentificationofbacteriaisolates- - - -

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CHAPTERFOUR

4.0Results

CHAPTERFIVE

DISCUSSIONANDCONCLUSION

5.0Discussionandconclusion - - - - - - - -

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5.1Conclusion - - - - - - - - - -

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REFERENCES

LISTOFFIGURESANDTABLES

Figure1Stagesofanaerobicdigestion - - - - - - -

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Figure2Dailybiogasproductionpatternofthedifferentsamples - - -

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Figure3Quantitativecomparisonofthemicrobialloadoftheisolate - -

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Figure4Totalsolidofthesamples- - - - - - - -

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Figure5Volatilesolids - - - - - - - - -

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Table1Chemicalconstituentofsomelignocellulosicmaterials - - -

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Table2Comparisonbetweenwetanddrydigestion - - - - -

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Table3Methodsofpretreatmentoflignocellulosicmaterials- - - -

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Table4Percentagecompositionofbiogas - - - - - -

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Table5Morphologicalandbiochemicalcharacteristicsofbacteriaspeciesisolated

fromthesamples afteranaerobicdigestion-- - - - - -

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Table6Cumulativebiogasyieldofsamples - - - - - -

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Table7Culturalcharacteristicsoftheisolate - - - - -