Life Cycle Assessment of CCS Scenarios in Biogas-Fueled Combined Cycle Power plants: A Pathway to Low-Carbon Power

Biogas-fuelled power generation is conventionally treated as carbon-neutral. However, by applying CCS into this biogas-to-electricity chain, net-negative CO₂ emissions can be achieved. This study evaluates the life-cycle environmental performance of such integration for a combined cycle power plant, assuming a baseline 98% CO₂ capture rate. The system boundary encompasses biogas supply, upgrading, power generation, and downstream CO₂ handling. Three configurations were assessed based on a functional unit of 1 kWh of net electricity: conventional amine-based (C-CCS), carbon molecular sieve membrane-based (MB-CCS), and a non-capture reference (C-NoCCS). The implementation of CCS imposes severe parasitic loads. Compared to the C-NoCCS net output of 5771 kW, net electricity generation drops by 33% in C-CCS (3835 kW) due to thermal and solvent demands, and by 45% in MB-CCS (3141 kW) driven by high compression requirements. These energy penalties dictate the Life Cycle Assessment (LCA) results. Because of its simpler configuration, C-NoCCS performs best in 11 of 18 non-climate indicators. The capture burdens in the C-CCS scenario outweigh the storage credit, increasing Global Warming Potential (GWP) by 77% compared to the reference system. The MB-CCS configuration avoids solvent regeneration, yielding a net-negative climate impact of -2.60 × 10⁻³ kg CO₂-eq./kWh. This net-negative performance strictly depends on specific operational thresholds. A reduction in membrane lifetime from 10 to 2.5 years shifts the MB-CCS system to a net emitter (+5.10 × 10⁻³ kg CO₂-eq./kWh). An increase in CO₂ transport distance crosses the net-zero GWP threshold at approximately 26 km. The viability of biogas-CCS systems requires minimizing energy penalties, ensuring membrane durability, and mitigating transport logistics.