Biogas-integrated liquid air energy storage system enabling negative carbon emissions and high energy efficiency

As global energy demand rises, renewable energy is becoming vital to achieving carbon neutrality by 2050. Liquid air energy storage (LAES) has emerged as a promising large-scale solution. This study proposes an advanced LAES system powered by biomethane to enhance energy efficiency and significantly reduce indirect carbon emissions. By integrating biogas upgrading, oxy-fuel combustion, and carbon capture, the system overcomes key limitations of conventional LAES, including low round-trip efficiency and carbon intensity. The use of thermal energy at both high and cryogenic temperatures across subsystems significantly enhances overall efficiency. The system was comprehensively evaluated in terms of energy, environmental, and economic performance. Thermodynamic analysis revealed a round-trip efficiency (overall energy output divided by electricity and fuel input) of 112.32 % and an exergy efficiency of 68.16 %. Environmental analysis revealed that 99.989 % of CO₂ emissions were effectively captured, resulting in negative carbon emissions of –7.85 t/h. Economically, the system achieved a net present value of $50.37 million and an internal rate of return of 15.93 %, confirming its financial viability. Overall, the proposed biogas-LAES system is highly efficient, environmentally sustainable, and contributes substantially to carbon reduction beyond neutrality, thus supporting a cleaner energy transition.