Assessment of Municipal Solid Waste to Energy Conversion Pathways: A Case Study of Nsalaga Dumpsite, Mbeya City, Tanzania

Abstract

Growing urban populations and increasing energy demand in Tanzania have increased the urgency to develop sustainable waste management strategies that also contribute to renewable energy generation. A comprehensive characterization of the waste stream at Nsalaga dump site in Mbeya was carried out to evaluate its physical and chemical properties, as well as calorific value determination, to establish its potential as a feedstock for waste-to-energy (WTE) technologies. Quantification of waste inflows revealed that approximately 34,244 tones are delivered to the dumpsite annually, with organics dominating the waste stream at 76.8% and exhibiting a high moisture content of 54%. Conversely, plastics and nylon displayed superior energy qualities with high calorific values ranging between 39 and 40 MJ/kg, highlighting their suitability for thermal conversion routes. The gross energy potential of the entire waste stream was estimated at 239.7 TJ, equivalent to about 66.6 GWh per year, which corresponds to 16.6 GWh of electricity when converted at an assumed efficiency of 25%. To optimize technology selection, a multicriteria decision analysis (MCDA) framework was applied, incorporating technical, economic, environmental, and social indicators. The analysis indicated that anaerobic digestion is the most appropriate pathway for high moisture organic waste, while thermal technologies such as incineration and gasification are better suited for dry, high calorific fractions. study concludes that an integrated WTE system, combining anaerobic digestion for organics and thermal routes for plastics, textiles, and other combustibles, is the most sustainable solution for Mbeya City. Such an approach would mitigate environmental and health risks associated with unmanaged dumping, reduce greenhouse gas emissions, and contribute significantly to the city’s electricity supply, thereby supporting broader goals of energy diversification and sustainable waste management.