Doctoral

Permanent URI for this collection

https://repository.futo.edu.ng/handle/20.500.14562/1260

Browse

Browsing Doctoral by Subject "ACEFUELS"

Now showing 1 - 1 of 1
  • Thumbnail Image
    ItemOpen Access
    Exploitation of potentials of micro-organisms with volatile fatty acid degrading genes in biogas production
    (Federal University of Technology, Owerri, 2024-10) Kemka, Ugochi Nneka
    Anaerobic digestion of cow rumen waste and human fecal slurry was carried out to evaluate the cumulative bigas yield over a 60-day retention, to isolate and identify bacterial species with volatile fatty degrading genes with molecular characterization. Microbial analysis, biochemical tests, isolation, characterization and physicochemical analysis were carried out. The total aerobic and anaerobic bacterial counts were 3.5 x 107 cfu/ml and 1.6 x 107 cfu/ml respectively. Bacterial and fungal isolates were identified as Paenibacillus lautus, Moellerella wisconsensis, Providencia alcalifaciens, Shimwellia blattae, Micrococcus yunnanensis, Bacillus barbaricus, Proteus vulgaris, Paenibacillus septentrionalis, Paenibacillus curdlanolyticus, Budvicia aquatica, Azotobacter beijerinekii and Acinetobacter iwoffii. Fungal isolates were identified as Aspergillus niger, Aspergillus flavus and Trichophyton rubrum. Most of the organisms were facultative anaerobes. Temperature was maintained at mesophilic rate. pH and total viable count were recorded over the period. Biogas yield for cow rumen waste increased steadily from the 6th day (31.403ml) to the 42nd day (247.039ml) arriving its peak generation of 251.226ml at the 45th day. The biogas yield of the substrate began to decline steadily from the 48th day till the 60th day showing reduced volumes of 215.636ml to 167.016ml. Biogas yiel for human fecal slurry substrate increased steadily from the 6th day (27.216ml) to the 45th day (221.916ml) arriving its peak generation of 226.103ml at the 48thday. A decline occurred steadily on the 51st day till the 60th day showing reduced volumes of 200.981ml to 125.613ml. Analysis of response surface methodology for cow rumen waste showed a mean optimal biogas production of 162.245ml can be achieved at a pH of 6.36, retention time of 10.5 days and microbial count of 1.03 x 109 cfu/ml. A mean optimal biogas production of 145.711ml can occur using human fecal slurry at a pH of 7.45, retention time of 10.5 days and microbial count of 5.9 x 108cfu/ml. GC-MS analysis showed methane contents of 57.99% and 50.39% and carbon dioxide contents of 17.12% and 19.21% for human fecal slurry and cow rumen waste respectively. GC-FID results of VFA production at three intervals of 20 days each within the 60-day retention time showed the presence of acetic, isobutyric, valeric, isovaleric and caproic acids amongst others. The cumulative volumes of the VFAs reduced steadily for cow rumen waste in the ranking order of 745.797ppm >372.539ppm > 86.366ppm while that of human fecal slurry ranked 509.405ppm > 133.627ppm > 71.318ppm. GC-FID results of LCFA production showed presence of saturated fatty acids such as palmitic, stearic acids and unsaturated acids such as linoleic, cervonic acids amongst others. A reduction in LCFA content was also observed. At the 20th and 60th day, LCFA fell from 108.216 to 60.499 ppm, and from 113.195 to 44.94ppm for cow rumen waste and human fecal slurry respectively. Polymerase chain reaction results identified 4 potential VFA degrading bacteria. The reductions in VFA concentrations demonstrated the influence of VFA degrading bacteria on the VFA and LCFA content within the digesters. More so, presence of high volumes of unsaturated acids in cow rumen waste led the lower levels of methane in cow rumen waste since presence of unsaturated acids are toxic to methane generation. It is therefore concluded that these microbial isolates possess ample capacity to degrade VFA and LCFA in these substrates and could be excellent inoculum for bioaugmentation purposes in enhancing biogas production.