New integrated CCS and CCU schemes with small-scale biogas-fired combined-cycle power plant: A Comparative techno-economic assessment

This study presents a unified techno-economic assessment of conventional and membrane-enabled carbon capture and storage (CCS) and carbon capture and utilization (CCU) integrated into small-scale biogas-fired combined-cycle power plants. A novel contribution is the first side-by-side evaluation of a fully membrane-based post-combustion CO2 capture system for CCS and a membrane reactor-assisted CCU configuration within a consistent Aspen HYSYS framework under identical system boundaries. Membrane integration significantly enhanced energy performance, eliminating hot-utility demand and reducing specific energy consumption by 43% in CCS. In CCU, the membrane reactor achieved higher hydrocarbon selectivity at residence times 62% shorter than in conventional reactors, implying proportional reductions in reactor size and capital expenditure. Capital costs decreased by 12% for CCS and up to 24% for CCU. Despite higher utility demand, membrane-assisted CCU increased value-added fuel production by 31.3%. Sensitivity analysis identified membrane cost, lifetime, and utility prices as key levelised cost of electricity (LCOE) drivers. A 300% increase in natural gas prices raised LCOE from −96 to 584 USD/MWh, while hydrogen prices above 3000 USD/t rendered several CCU pathways unviable. Overall, membrane-enabled systems show strong potential, contingent on optimised membrane performance and hydrogen costs.