Energetic, exergetic, economic and environmental (4E) assessment of power cycles integrated with anaerobic digester

As the world struggles with climate change, biogas produced via anaerobic digestion (AD) offers a promising sustainable energy solution. While numerous studies have explored integrating AD with heat-to-power generation systems, a key gap remains in understanding how biomass affects overall system performance. In particular, through comprehensive energy, exergy, economy, and environmental (4E) assessments which are essential for a more accurate system modelling, and system optimization. To address this gap, this research evaluated five biogas-powered configurations: gas turbine cycle (GT), organic Rankine cycle (ORC), ORC with an internal regenerator (ORC-IG), supercritical carbon dioxide (SCO 2 ), and SCO 2 with a recuperator (SCO 2 -R). These systems were assessed and compared based on energy and exergy efficiency, total annual cost, CO 2 emissions, and CO 2 equivalent emission. Among them, the GT-SCO 2 -R system delivered the best overall performance, achieving the highest thermal and exergy efficiencies (44.33% and 43.0%, respectively), maximum net power output (11,078 kW), the shortest payback period (1.72 years), and the greatest CO 2 emissions reduction (13,515 tCO 2 /year). It also compares alternative waste management methods and outlines critical factors for policymakers. The analysis also revealed that the digestion plant caused the highest exergy destruction, indicating the need for technological improvements at this stage. This study contributes to a deeper understanding of biogas system performance and provides valuable insights into design optimisation. It also compares alternative waste management methods and outlines critical factors for policymakers. The findings support the strategic advancement of biogas as a viable path toward sustainable energy production. • Undertaking a comparative study on integrating WHRs with AD. • Conducting a comprehensive analysis covering energy, exergy, economic, and environmental performance. • Carrying out a detailed sensitivity analysis to assess the impact of key parameters. • GT-SCO 2 -R demonstrated the highest thermal efficiency and lowest CO 2 emissions. • Achieved maximum thermal and exergy efficiencies of 44.33%, and 43.0%, respectively.