Municipal Solid Waste Characterization for Waste-to-Energy Management in Harare Metropolitan Province, Zimbabwe

Abstract

Waste-to-Energy (WtE) has gained popularity world over as a tool for assisting municipalities to reach waste management goals. The availability of data on the physical and chemical characteristics of municipal solid waste (MSW) as a potential feedstock for WtE recovery is critically important for planning purposes. In the current study, for the first time the MSW in Harare metropolitan province is examined in view of its potential as a fuel for WtE conversion. The study comprehensively focusses on selecting the most sustainable Wte technology to apply in the context of Harare. First, the metropolitan area's waste management system is evaluated through material flow analysis (MFA) and concluded to be weak and highly ineffective. Secondly, the MSW is sampled and analysed onsite for physical composition and bulk density. Samples are collected for further preparation and laboratory analyses. Scenario modelling is then applied in order to assist in WtE technology selection from five alternatives. The model is built and evaluated using multi-criteria decision analysis (MCDA) software which gives the final ranking of options. Energy content analysis showed that the MSW has a lower heating value of 10.1 MJ/kg making it ideal for thermochemical processing with minimal pre-treatment. The moisture content ranged from 30 to 36% with the mean for the province being 34%. The elemental composition of the waste is given as 47% C, 4.9% H, 33% O, 2.2% N, 0.8% S and 0.6% Cl. The study showed that the MSW can be treated by thermochemical or biochemical means without requiring supplementary fuel. Techno-economic, environmental and social sustainability considerations made through scenario modelling conclude that landfill gas to electricity can bring optimal benefits to Harare Province's waste management system. Therefore, this study provides critical data essential for waste management planning.