The GHG emissions of sub-systems are presented in Figure . Under a random (initial) system configuration, CCU deployment results in more life cycle GHG emissions than the reference system, used to generate the same amount of electricity and products. This is because, within the initially evaluated process configuration, CO2-based reforming requires extensive energy input, which can lead to more emissions if no proper operating conditions are set. For example, emissions from [Reforming + FT] is almost triple of that from the refinery in the reference system (Figure ). Under the optimal operating condition, GA selects to produce more methanol instead of gasoline (thus, emissions from [Reforming + FT] become negligible). This is probably because CO2 cannot be converted in the FT path, 39, 40 while CO2 can be well utilized in MS. emissions for the configuration determined as optimal, where methanol production is favored.