Composition-Tunable Power-to-Syngas: Techno-Economic and Sustainability Assessment

This study investigates a composition-tunable power-to-syngas platform in which a natural-gas-fired Allam–Fetvedt (AF) supercritical CO2 (sCO2) power cycle is coupled with three electrolysis architectures for converting internally available CO2 and H2O into synthesis gas. Because the AF power block is fueled by natural gas, the integrated system is treated here as a low-carbon process-integration concept rather than as a fully renewable energy pathway. Three Aspen HYSYS configurations are evaluated on the same 437 MW-net AF power basis: (i) separate PEM water electrolysis and AEM CO2 electrolysis followed by H2/CO blending, (ii) AEM co-electrolysis, and (iii) high-temperature solid-oxide co-electrolysis. The H2/CO molar ratio is varied from 0.25 to 2.0. Increasing H2/CO lowers the mass of syngas produced per unit electrical input while increasing stoichiometric water demand and oxygen generation; lower H2/CO ratios require greater CO2 conversion. The 5.07 × 106 kg h−1 CO2 value used in the process model represents the internal circulating sCO2 inventory rather than net carbon generation. On the common AF basis, only a controlled fraction of the net CO2-rich product stream is routed to syngas synthesis, while the remainder is retained for recycling or export/storage. The electrolysis section requires approximately 8.9–35% of the recovered AF process-water stream on a stoichiometric basis, and the oxygen co-product is equivalent to approximately 22.9–26% of the AF oxygen requirement. These resource-integration quantities are reported without crediting additional electrical power to the electrolyzers. The sustainability results are relative process-level screening scores and do not constitute a cradle-to-gate life-cycle assessment. Under the adopted economic assumptions, positive returns are concentrated mainly at H2/CO ≈ 1.5–2.0 for low-temperature configurations, whereas the solid-oxide route remains strongly constrained by current capital and replacement costs. Overall, the preferred operating region depends jointly on electrolysis architecture, syngas composition, and the economic boundary used for valuation.