POTENTIALS FOR ANAEROBIC DIGESTION OF SEWAGE FOR ENERGY PRODUCTION AND ENVIRONMENTAL PROTECTION IN SECONDARY SCHOOLS OF KAKAMEGA COUNTY, KENYA

Abstract

Sewage biogas is one of the renewable green energy that is being developed in many countries of the world using anaerobic digestion. However, its utilisation in Kenya may be facing various challenges such as socio-economic, cultural and religious believes. It is strongly believed that secondary schools can generate energy from sewage to supplement biomass energy while protecting the environment. Sewage poses health risks due to poor disposal methods. It is against this background that this study assessed potentials for anaerobic digestion of sewage for energy production and environmental protection in secondary schools of Kakamega County, Kenya. The study was guided by four objectives: determine the quantity of sewage generated in secondary schools for potential energy generation in Kakamega County, Kenya; examine the potential environmental impact of chemical and microbial characteristics of the sewage generated; determine the economic and environmental benefits of anaerobic digestion of sewage for energy generation and evaluate the enhancement strategies in secondary schools for anaerobic digestion of sewage for energy generation and environmental protection. The study adopted four research designs: cross-section survey, experimental, correlational and evaluative to achieve its objectives. Focused Group Discussions, Key informants, interviews, questionnairesand observation check lists were used to collect data. Data were analyzed both descriptively and inferentially by using Graph Pad Prism 5, Excel and SAS and subjecting them to Chi-square and t-test, cross tabulation and evaluation. It was established that secondary schools in Kakamega County generate 17,662.3 tons of human waste per school academic year of 273 days with an energy equivalent of 43,273.6gj. The chemical characteristics in the sewage generated are: Total Kjeldal Nitrogen (TKN) 8.30 mg/l with a Standard Error (SE) of 0.45; pH 5.75 with SE of 0.13; Total Phosphate (P2O5)1.15mg/l with SE of 0.46; Cd 0.0249 mg/l; Pb 0.0046 mg/l; Dry Matter(DM) 13.80% with SE of 0.66. The microbial characteristics in the sewage generated are: E.coli 390 MPN/100mls and faecal coliforms 450 MPN/100 mls. The anaerobically digested effluent increased its concentration of TKN and P2O5 by 8.2% and 1.7% respectively. Its pH also increased by 26.1%. However, the DM, E.coli and faecal coliforms reduced by 61.8%, 74.4% and 88.89% respectively. The traceable quantities of heavy metals remained unchanged in the effluent after the Anaerobic Digestion (AD) process. The infrastructure, concerted efforts of all stakeholders and socio-economic factors are of paramount importance in realizing the anaerobic digestion of sewage in secondary schools for bioenergy production. Key players in this respect were the school sponsors. Majority of these sponsors accepted the use of sewage for energy generation in their schools. The students who are the direct beneficiaries of sewage energy generation are also in support of the idea. The study established that there is a substantial quantity of sewage generated in secondary schools of Kakamega County for sewage energy generation. If everything is held constant 21% ofwood fuel would be replaced by sewage energy. The microbial characteristics of the sewage generated in secondary schools impact negatively on the environment by causing pollution of the soils and water. Economically, AD of sewage will supplement the wood fuel used by schools for their cooking and heating needs. Environmentally, the process reduces the E.coli and faecal coliforms concentrations in the effluent to harmless trace levels. The decrease in DM means that less space will be required hence reduced rate of refilling. A decrease in E. coli and faecal coliforms meant that some important biological process was going on in the environment. The increase in P2O5 and TKN is beneficial to soils as bio nutrients. Generally, the use of sewage bioenergy will help reduce the effect of methane on the biosphere. There is adequate support from the stakeholders for the use of sewage in secondary schools to generate energy.