Waste to energy bio-digester selection and design model for the organic fraction of municipal solid waste

In this study, a feasibility study was carried out in terms of quantification-characterization of waste, biomethane potential from organic biomass and bio-digester selection and designing. From waste quantification, 38% was found to be an organic fraction of the municipal solid waste (OFMSW) of the 1.4 million tonnes per year. The composition of the waste was investigated using a laboratory batch anaerobic digester for biochemical methane potential (BMP) and the waste to energy bio-digester selection and design for the anaerobic co-digestion of different OFMSW originating from the City of Johannesburg landfills. The carbon to nitrogen (C/N) ratio of OFMSW was found to be below 13. Through co-digestion, the C/N ratio settled at 15. Laboratory experimental data from 500 ml batch anaerobic digester operating at a mesophilic temperature of 37 °C and pH of 6.9 had a good productivity of methane of average 59% recommended in the literature and was used to derive the volume of digester and surface area. The artificial intelligence (AI) technique was applied to select the most preferred digester model. Using the application of the simple multi-attribute rating (SMART) technique of multiple-criteria decision analysis (MCDA) as a decision support tool, the most preferred option of a bio-digester model was selected from a list of potential alternatives available in the market. The continuous stirred tank reactor (CSTR) scored highest with 79% and was selected as the most preferred digester for the OFMSW digestion. The geometry of the biodigester parameters was found to be comparable and economically feasible with the process parameters, energy generation from the BMP and scale up model for the independent power producer (IPP).