Life cycle assessment of CO2 emission reduction potential of carbon capture and utilization for liquid fuel and power cogeneration

Underground and ocean CO2 storage is facing a series of hazard like leakages, earth movement and seismic activity, which has attracted more international attention on CO2 utilization. It can potentially not only reduce the anthropogenic carbon emissions which is the main cause of climate change, but produce valuable fuels and chemicals through synthesis. This paper explored the environmental benefits of CO2 utilization through the reverse water gas shift into syngas for the production of liquid fuel and power. CO2 source is an ideal three-stage hydrogen production unit based on the Fe-based chemical looping combustion, which can capture carbon with nearly zero-energy-consumption. The life cycle emission was calculated as 129.98 kg CO2-eq/MW h, and the proportion of carbon emissions that correspond to the production of liquid fuel is 60% (taking exergy allocation as an example). Compared with the conventional NGCC and GTL standalone production system with carbon capture at same outputs, this system could achieve an energy savings of 18.19% and a life-cycle carbon emission reduction rate of 46.87%. Carbon emissions mainly came from natural gas mining and transportation, and the CO2 recompression process, which accounts for 74.54% and 15.12% of life cycle emissions, respectively. In addition, the effects of key parameters, such as CCU/CCS, solid inventory and lifetime of oxygen carrier, and different allocation methods, on these LCA results were discussed in detail to further reveal the system carbon emission reduction potential.