PROFILING AND EVALUATION OF BACTERIAL CONSORTIA FOR EFFICIENT BIOGAS PRODUCTION IN SMALL SCALE BIODIGESTERS WITHIN UASIN-GISHU COUNTY

Abstract

Anaerobic digestion is a sequential biological activity that accepts the efficient capture of methane for energy production. The dependence on fossil and wood fuels as a primary energy source has led to multitudes of problems such as global warming, environmental degradation and human respiratory health complications. The aim of this research was to characterize the anaerobic bacterial present in small scale bio-digesters within Uasin Gishu County. The specific objective of the study is to profile and evaluate anaerobic bacterial consortia for their efficiency in biogas production in a small-scale bio-digesters within Uasin Gishu County. Six study sites namely Opande, Radar, Energy station, Langas, Nettos and Beta farm were selected within Uasin Gishu county, they varied in both volume and biogas production volume. The cow dung which had been fed into bio-digesters were collected aseptically in 250ml sterile flask and transported to the laboratory. Bacteria were isolated in Microbiology laboratory, University of Eldoret by spread plate method on methanogenic media and incubated under anaerobic conditions in a Gas-pak jar at a mesophilic temperature of 35oC for seven days. Isolates were coded as per their study sites. Pure isolates were obtained using streak plate method and evaluation of physicochemical parameters was done in situ. Identification of isolates was done using cultural, morphological and biochemical characteristics. Laboratory scale set up of anaerobic digester for biogas production was done to evaluate the anaerobe efficiency in biogas production. Three, 500ml erlernymer flask were half filled with cow dung and inoculated with Methanococcus and Methanosaeta sp separately and in consortia of both. This was done in triplicate with different inoculum ratios at 10:500, 20:500 and 30:500ml respectively and a control experiment with cow dung only was allowed to run for 31 days. Gas generated was collected by volume displacement of water and measured at an interval of 0:10, 11:21 and 21:31 days in ml. The temperature and the pH were regulated and monitored regularly. Shannon Weiner diversity test and Chi-square test was used to analyze the morphological and diversity of the anaerobes in each study sites. Duncan Multiple Range Test was used to determine the physico-chemical parameters while the Analysis of variance and linear regression was used to analyze the quantity of biogas produced in the three set- ups. Study identified 7 different anaerobic bacteria genera as Methanococcus, Sulfolobus, Methanosaeta, Methanospirillium, Methanosarcina, Methanomicrobium and Methanothrix. The most predominant methanogenic bacterial genera, which occurred in at least 5 digesters were Methanococcus and Methanosaeta genera which also produced the highest volume of gas with maximum production being observed in 21-31 days at a ratio of 30:500. Methanococcus and Methanosaeta synergistic activity yield the highest gas production of 74.23 ml versus 22.50ml in control. The study on the 6 bio digesters showed that physico-chemical parameters play a paramount role in biogas production and should be maintained at an optimum range. Predominant methanogens Methanococcus and Methanosaeta genera when inoculated in the digesters increased the quantity of biogas produced. Research recommends that biogas technique is an effective way of providing solution to the increasing waste management and disposal problems apart from the liberation of fuel or energy from recyclable energy sources, promotes the use of organic fertilizer as compared to chemical based fertilizers Further research work should be done on methanogenic bacteria involved in the production of biogas, the anaerobes should be isolated, recognized, and characterized at the species and strain levels before being utilized to produce biogas.