Design of a Community-Based Anaerobic Digester for Sustainable Solid Waste Management in Ile-Oluji Ondo State Nigeria

Abstract

Aim: A Community-Based Anaerobic Digester was designed in this study for sustainable solid waste management in Ile-Oluji, Ondo state Nigeria. Methodology: Waste samples were collected from selected households for a period of one month and the components and percentage composition were determined. Afterwards, the physico-chemical characteristics of the substrate was investigated and the result used to design a community-based anaerobic digester. Results: The quantity, components and characteristics of waste generated was determined. The rate of waste generation was found to be 0.2kg/capita/day while the organic fraction of the total waste generated was found to be 55.7%. Physico-chemical characterization of the substrate was also investigated.  The pH was found to be 6.36 ± 0.18, while the alkalinity 692.81 ± 78.62.  The moisture content was found to be in the range of 71.20 ± 4.63%. Total solid was in the range 38.91 ± 5.25 while volatile solid was found to be 26.44 ± 2.83. carbon oxygen demand was found to be 834.33 ± 12.61, total phosphorus was in the range 4.20 ± 0.33. The Carbon on a dry weight basis was found to be in the range 60.41 ± 2.38, while nitrogen was found to be 4.79 ± 1.03. The C/N ration was found to be 21.61. The biogas yield ranged from 0 – 320 cm3 and 0 – 380cm3 per litre of substrate for biodegradable-only samples and biodegradable-cow dung samples respectively, for a forty days period of retention. The cylindrical dome type biogas digester was chosen for this study because of its simplicity in design and maintenance coupled with lower set up cost. The optimum volume of hydraulic chamber and gas storage chamber were designed to be the same as 850m3. Volume of fermentation chamber and sludge layer were calculated to be 2014m3 and 246m3 respectively, while the height and diameter of the fermentation chamber were 7m and 17m respectively. Conclusion: Anaerobic digestion of the biodegradable fraction of solid waste is a viable alternative that government and non-government organizations can key into for the improvement of public health especially in developing countries. The standardization of digester design parameters may pose challenges because of varying climatic conditions and complex socio-economic factors across different geographical contexts. Solutions may have to be adapted and localized to achieve a sustainable world.