Techno-economic analysis of an integrated system of anaerobic digestion and pyrolysis reactors with Kalina power cycle

Waste management challenges have intensified in recent decades due to population growth and industrialisation. Among the various waste management strategies, waste-to-energy technologies have shown considerable potential; however, each method presents limitations when implemented individually. In this context, the integration of multiple technologies can significantly enhance overall system performance. The integration of anaerobic digestion (AD) with pyrolysis (PY) has recently attracted increasing attention and has been investigated primarily through experimental studies. This study aimed to develop a comprehensive numerical model of this integrated system to improve process understanding and identify potential operational challenges. The system was further coupled with a Kalina cycle to enhance energy recovery and enable cogeneration. Following detailed modelling, the system was evaluated through energy, exergy, economic, and environmental (4E) analyses. The results indicated that the energy efficiency increased from 12.16% to 19.59% after integration with the Kalina cycle. The exergy efficiency of the integrated system was calculated to be 38.15% and increased further to 40.1% with the addition of a cooling subsystem. From an economic perspective, the fully integrated system demonstrated a payback period of 2.51 years. Environmentally, the system achieved specific CO₂ emissions of 0.3861 kg CO₂/kWh. These findings, supported by the 4E assessment, contribute to the advancement of sustainable waste management and energy production, particularly in developing countries.