Performance assessment of an urban solid waste-fired boiler with flue gas heat recovery in some locations in Nigeria

Rapid industrialization and urban growth have intensified waste management and energy supply challenges in developing nations like Nigeria. This study presents the design, characterization, and performance evaluation of an urban solid waste (USW)-fired steam boiler system integrated with a waste-conditioning unit for moisture control. The system aims to enhance combustion efficiency, reduce fuel consumption, and contribute to sustainable waste-to-energy (WtE) conversion. Representative waste samples—including paper, plastics, textiles, and wood residues—were collected from four Nigerian cities (Aba, Akure, Kaduna, and Makurdi) and analysed for proximate, ultimate, and calorific properties following ASTM standards. The results showed significant variations (p < 0.05) among waste types, with plastics exhibiting the highest fixed carbon (21.30%) and calorific value, while paper recorded the highest ash content (13.79%). Combustion analysis revealed that lower moisture content and optimized excess air ratios improved furnace temperature, flue gas exergy, and overall boiler efficiency. The integration of the waste-conditioning unit effectively reduced moisture-induced energy losses, enhancing steady-state combustion. Correlation models established between higher heating value (HHV) and fuel parameters such as fixed carbon, ash, and oxygen contents (R² > 0.95) demonstrated reliable predictive capacity for energy estimation. The findings affirm the feasibility of utilizing heterogeneous urban solid wastes as renewable fuel sources for small- to medium-scale steam generation. This work contributes to advancing circular economy goals and supports the United Nations Sustainable Development Goals 7 and 13 through clean energy generation and climate action.