Microbial characterization and biogas production from palm oil mill wastes

Chan, Christy Sien Wei (2016) Microbial characterization and biogas production from palm oil mill wastes. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Palm Oil Mill Effluent (POME) of palm oil industry is currently being studied extensively due to its high potential in biogas production. Bioconversion of POME to methane via anaerobic digestion involves a consortium of microbes which are responsible in several steps of the biodegradation process. In this study, the microbial community from selected POME was characterized via molecular techniques as well as through culture-based plating in order to determine their composition, and subsequently understand their functions in the anaerobic community. Genomic DNA of the microbial community was extracted using direct extraction technique, followed by PCR targe ting the 16S rDNA region. Distinct fragments of approximately 1,100 bp in sizes were successfully amplified using PCR and cloned onto Escherichia coli XL-1 Blue. Upon sequencing of the fragments, BLAST queries identified the bacteria as Thermoanaerobacterium sp. In addition, two other bacterial species which were successfully isolated from the POME by culturing on DVS agar belonged to the Bacillus genus. The ability of the isolates in utilizing different substrates suggested that anaerobic digestion of mixture of POME sludge and solid cud taken from the first compartment of cow’s stomach (1:2 and 2:1 ratio) as co-mixture was applicable. Thus, the co-mixture was incubated at 50 °C in a 2 L vessel with initial starter of 400 ml and sampling was conducted every four weeks interval during 12 weeks of incubation. For specific detection of methanogens, 16S rRNA-cloning analysis was carried out. Methanobrevibacter sp. and Methanosaeta sp. were confirmed to be present within the 2:1 ratio of co-mixture while only Methanobrevibacter sp. was found in 1:2 ratio of comixture on both Week 0 and Week 4. Duration of anaerobic digestion was reduced to 4 weeks as no methanogens were detected from both co-mixtures on Week 8 and Week 12. By understanding the bacterial community present, improvement of the anaerobic x digestion process to enhance the production of biogas can be carried out. Biogas production from mono- and co-digestion of POME sludge and solid cud from ruminant stomach on Empty Fruit Bunch (EFB) were also investigated at different ratio of POME sludge and solid cud (1:1, 1:2 and 2:1). All digestions were operated at thermophilic condition (50 ˚C) for 4 weeks. Biogas productions from the co-digestion samples were generally higher compared to the mono-digestion experiments. POME sludge to solid cud ratio of 1:2 generated the highest biogas yield with a total of 3,754 cm 3 after 4 weeks of incubation. Biogas production of POME sludge to solid cud ratio was 42.87% and 70.91% higher than single digestion of POME sludge and solid cud, respectively. Although at 1:1 and 2:1 POME sludge to solid cud ratio produced less biogas compare to 1:2 ratio, both codigestion mixtures generated 33.97% and 41.25% more gas than mono- treatment using only solid cud, which only produced 1,092 cm 3 of biogass after 4 weeks of incubation

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