Techno-economic assessment of a negative-emission energy storage concept: compressed oxygen energy storage with oxy-fuel biogas combustion

• Compressed oxygen energy storage (COES) enables negative-emission energy storage. • Oxy-fuel biogas combustion with CCS integrated into the COES system. • Biogas-driven COES achieves a round-trip efficiency of 40.3% • Minimum selling price of discharge electricity estimated at 163.4 $/MWh. • Biogenic CO 2 subsidy of 100 $/MWh cuts the minimum selling price of electricity by 77% Energy storage is essential for balancing power systems with high shares of intermittent renewables, yet conventional compressed air energy storage systems rely on fossil fuels during discharge and thus retain a carbon footprint. This study addresses the challenge of developing a dispatchable storage system that simultaneously provides grid balancing and permanent carbon removal. Integrating oxy-fuel biogas combustion and carbon capture and storage into a compressed oxygen energy storage configuration can enable electricity dispatch while achieving net-negative emissions. A thermodynamic process model was developed to simulate the integrated charging-discharging cycle. The designed system operates with charging and discharging capacities of 11 and 25 MW, respectively, purchasing 22.9 MWh during a 2-hour charging period and delivering 100.6 MWh during a 4-hour discharge, while capturing 72.3 tCO 2 per cycle; the round-trip efficiency is 40.3%. Under assumed biogas and electricity prices of 36 and 20 $/MWh, the minimum selling price of electricity is estimated to be 163.4 $/MWh during discharge, which decreases by 77% if a 100 $/t subsidy for biogenic CO 2 capture is applied. Results suggest that the proposed concept could serve as a dispatchable energy storage technology that simultaneously enables permanent removal of biogenic CO 2 .