Life cycle and techno-economic analyses of biofuels production via anaerobic digestion and amine scrubbing CO2 capture

Abstract

The global energy landscape highlights the importance of the hydrogen economy, emphasizing its critical role in worldwide energy policies. This study explores a system designed for producing biomethanol and biomethane by integrating anaerobic digestion, biogas upgrading, and high-temperature electrolysis. The system builds on real-scale industrial data from an existing anaerobic digestion plant, which has been expanded to include biogas upgrading, an oxy-fuel gas turbine, a Solid Oxide Electrolysis Cell (SOEC), and a methanol production unit. Hydrogen, generated through electrolysis, synthesizes biomethanol by reacting with CO2. Additionally, the system produces biomethane through biogas upgrading. The system incorporates thermal energy integration with an oxy-fuel gas turbine. Life cycle assessment (LCA) results demonstrate the system’s environmental potential, achieved negative CO2 emissions of −0.0075 kgCO2eq/kgBiomass in case of photovoltaic panels and −0.0096 kgCO2eq/kgBiomass in case of wind turbines as electricity sources, attributed to efficient conversion of sewage sludge into valuable biofuels. Thermodynamic modeling in Aspen Plus shows an energy efficiency of 58.09 %, with outputs of 188 kg/h of biomethane and 269 kg/h of biomethanol. The techno-economic analysis reveals a payback period of 6.11 years and a levelized cost of biomethanol of 294.37 € per ton, indicating the system’s economic viability. The LCA further underscores the system’s sustainability, supporting its environmental benefits. This comprehensive analysis provides valuable insights into the viability and environmental impact of the proposed biofuel production system.