The GHG emissions are evaluated based on the life cycle assessment (LCA) with a cradle-togate boundary. We seek to compare the overall emissions from the reference process (described in Section 2: Problem statement) to emissions of the system with CCU. For a meaningful comparison (Fig. ), we evaluate multiple process configurations where both the reference process and the CCU system yield exactly the same amount of electricity and fuels (defined as the system expansion strategy ). A more detailed information for the system boundary and the system expansion strategy can be referred to Section S4.1 -S4.2 (SI). Based on the mass and energy balances derived from process models and lifecycle GHG emission factors (SI, Table ), the GHG reduction is calculated in Eq 1-Eq 3 (further details are given in Section S4 in SI).