Sustainability analyses of CO2 sequestration and CO2 utilization as competing options for mitigating CO2 emissions

CO2 capture and sequestration (CCS) and CO2 capture and utilization (CCU) are potential alternatives to mitigate CO2 emissions. There have been concerns regarding long-term geological impact of CCS and CCU requires co-reactant(s) for converting CO2 into value-added products. In this work, sustainability of CCS and CCU are assessed by simulating three processes. Each of these processes used post-combustion amine technique to capture CO2 from flue gas stream coming out of natural gas-based power plant. In the first process (CCS), captured CO2 undergoes sequestration whereas in the other two processes (CCU) CO2 reacts with hydrogen to produce methanol and dimethyl ether. Based on our technoeconomic assessment, total annualized cost of CCS process is 7.57% and 6.55% lower than CCU-methanol and CCU-DME processes, respectively. Thus, CCS is economically favourable over CCU. DME is found to be a favourable CCU-product owing to its higher market price as compared to methanol. Our analysis suggests that hydrogen price significantly impacts the technoeconomics of CCU processes. We have also demonstrated that at current market prices of methanol and DME, CCU process can be economical compared to CCS provided hydrogen price reduces to $778.5/t and $942.6/t for CCU-methanol and CCU-DME processes, respectively.