Thermodynamic and economic evaluation of a novel waste-to-energy design incorporating anaerobic digestion and incineration

To synergistically exploit organic waste and municipal solid waste, a novel design combining anaerobic digestion and incineration for waste-to-energy has been developed. In the proposed scheme, organic waste and municipal solid waste are processed by anaerobic digestion and incineration respectively. The biogas harvested from anaerobic digestion is utilized by a gas turbine, and then the hot exhaust of the gas turbine is taken to enhance the steam cycle of the incineration plant via steam superheating, steam reheating, feedwater heating, and air preheating. Thus, high-efficiency waste-to-energy using two kinds of waste can be achieved with fewer costs. A case study was conducted to examine the feasibility of the hybrid system, and its parameters were determined by modeling and simulation. From the aspects of thermodynamics and economics, the performance of the proposed system was evaluated under various conditions and the efficiency-boosting mechanism was investigated as well. Through the system integration, the biogas-to-electricity efficiency can reach up to 48.49% with 29.42 MW net power generated from biogas at the design point, while the net power generated from municipal solid waste remains as 6.22 MW. The dynamic payback period of the biogas-based power project is only 3.49 years, and the net present value attains 125,188.54 k$. Besides, the hybrid system performs well when the biogas feed rate changes. Therefore, the suggested design is extremely suitable and promising.