Design and performance evaluation of hybrid waste-to-energy plants for valorization of municipal solid waste and landfill gas.

Abstract

The low electrical efficiency and high investment costs remain major barriers to the implementation of waste to energy (WTE) plants, especially in regions with insufficient government support. As shown by several authors, it is possible to overcome these challenges by means of integrating their steam bottoming cycles with gas topping cycles fed by natural gas (NG). The main drawback is the high fossil fuel consumption, which makes some systems unfeasible from economic and environmental perspectives. The present work proposes two hybrid systems based on a novel integration of Rankine and Brayton cycles. A numerical model was developed to simulate each design option, fed by municipal solid waste (MSW) and landfill gas (LFG), with capacity to produce 20MWe over 8,000 h/year, and calculate energy, economic, and environmental indicators. Unlike reported hybrid systems, the proposed plants operate with a reduced gas share (below 20%) and electrical efficiencies above 24.6%, representing a 13% improvement over the 21.8% baseline of the reference WTE plant. Parametric analysis confirmed economic viability, with an internal rate of return above 31%, even under variability in investment and operating costs. In the absence of LFG, equivalent NG consumption allows continuous operation, maintaining the carbon footprint in scope 1 below 748.4 kgCO2eq/MWhe, which is lower than that of the reference WTE plant (829 kgCO2eq/MWhe). Therefore, the proposed systems can deliver stable electricity to the grid, offering a cost-effective solution with low tipping fee requirements (24.0 USD/tonneMSW), thus contributing to the energy transition and the development of the waste sector.