CO2e emissions implications of methanol production from cement-derived CO2 under transitional energy system constraints

Carbon capture and utilization pathways are increasingly proposed to reduce emissions from hard-to-abate industrial sectors, yet their mitigation potential depends strongly on upstream energy system conditions. For cement-derived CO2 utilization (CeCU) to methanol systems, it remains unclear whether emissions reductions can be achieved under near- to mid-term deployment conditions characterized by constrained hydrogen availability and partially decarbonized electricity supply. This study evaluates methanol production from captured cement process CO2 across hydrogen supply pathways (electrolysis, SMR, SMR with CCS, and industrial by-product hydrogen), electricity carbon-intensity (CIelec) scenarios, and siting configurations, relative to a business-as-usual (BAU) clinker and methanol reference. Emissions are assessed using an expanded-boundary, methanol-normalized emissions framework. Results indicate that hydrogen supply pathway is the dominant determinant of system-level emissions performance, with CIelec acting as a decisive modifier for electrolytic pathways. Conventional SMR-based hydrogen consistently increases emissions relative to BAU, while SMR with CCS enables emissions reductions under current and transitional electricity systems. Electrolytic hydrogen only delivers emissions reductions once CIelec falls below 160-195 g CO2e/kWh, depending on system configuration. Process co-location integration provides measurable but secondary benefits that do not alter pathway ranking. CO2e avoidance-cost analysis indicates that emissions-reducing CeCU-to-methanol pathways are primarily constrained by hydrogen economics, with near-zero avoidance costs achievable only at hydrogen prices of approximately 1 AUD/kg or under substantial carbon crediting. Overall, CeCU-to-methanol emerges as a conditional emissions mitigation pathway whose near-term deployment outcomes are governed more by hydrogen system evolution and electricity decarbonization than by CO2 availability or process integration alone.