The use of carbon capture leads to two effects on the 500 MW NGCC plants: lowering the emissions but shrinking the net electricity output. As shown in Table , PSA has fewer emissions than MEA; 20% electricity loss is seen for the deployment of MEA, while 16% electricity loss for PSA. Hence, PSA has an advantage over MEA regarding GHG emissions reduction and energy saving. However, this advantage is negligible when referring to GHG emissions in the whole CCU system because more emissions are caused by the utilization paths than the capture paths (Figure ). The optimal operating conditions are listed in Table . To maximize the GHG reduction, the requirements for sub-systems are as follows: