From Biogas to Propulsion and Power: A Life Cycle Perspective on Fuel Synthesis and CHP Integration

Anaerobic digestion of organic waste offers a promising pathway for energy production and sustainable waste management. Within this framework, five pathways for biogas energy utilization were evaluated, and their environmental performance was compared, focusing on marine transportation and combined heat and power (CHP) production. In Scenarios 1 and 2, biogas is upgraded to biomethane, while the captured CO₂ is used to synthesize additional methane (Scenario 1) or methanol (Scenario 2). The upgraded methane is used to produce CHP, while the synthesized fuels are used for marine transportation. In Scenarios 3 and 4, the upgraded methane is liquefied and used in marine transportation. Finally, in Scenario 5, the direct use of biogas for CHP, without further upgrading or fuel synthesis, was evaluated. A Life Cycle Assessment (LCA) was performed using OpenLCA software, Ecoinvent database, and the Environmental Footprint method. Regarding Global Warming Potential, Scenario 1 causes the lowest impact, while Scenario 5 causes the highest. In the scenarios where CO2 is utilized to produce methanol instead of methane, the impact is higher by 3.3-3.4%. These results suggest that additional criteria, such as fuel handling and life cycle cost, should also be considered in future decision-making.