Chemical Optimisation and Microbial Analysis of Biogas Production Process Parameters

This study characterised and adjusted certain production process parameters (pH, C/N ratio and temperature) critical to increasing the process efficiency, stability and sustainability to optimise biogas yield. The optimised setup was a 20L biodigester filled with 4.46kg of cow manure, 4.46kg of cassava water, and 4.46kg of cow rumen as inoculum in a ratio 1:1:1 respectively. Microbial analysis was also performed using standard procedures on the substrate and digestates of the optimised set-up. Physical and chemical pre-treatments were done on the substrates to ensure favourable conditions for anaerobic digestion. After a retention period of 19 days, a cumulative volume of 0.03913m³ (39.13L) of biogas was obtained. The microbial analysis on the substrates allowed the following microorganisms to be isolated; Bacillus sp Escherichia coli, Pseudomonas sp Proteus sp., Klebsiella sp., Lactobacillus sp Staphylococcus aureus. Microbial analysis from the substrate (Cow rumen and Cassava water) revealed no presence of Lactic acid bacteria while digestate (Cow dung with Cow rumen and cassava water) showed the presence of lactic acid bacteria. Isolates from both digestates were glucose fermenters with the production of carbon dioxide. The presence of these microorganisms indicated possible anaerobic activities in the generation of biogas.