LAUSR

Abstract The present work assesses the feasibility of a circular approach towards a carbon-neutral process that leads to the production of 500 ktn/yr of synthetic natural gas (SNG). Overall, three main systems were sized, simulated and heat/energy coupled under a realistic scenario that ensures an autonomous and economically feasible operation: a) cement-based CO2 capture with amines, b) H2 production through combined solar/wind powered water electrolysis and c) CO2 catalytic hydrogenation. The economic analysis revealed a min-to-max break-even price of 500–1550 €/tn of SNG, taking also into account the potential sales of the high-purity O2 (from water electrolysis) and the excess electricity produced via renewable energy sources (RES). The ranges for the SNG prices correspond to the screening of CO2 penalty fees (25–100 €/tn) along with the option to subsidy the RES-H2 system up to 36 %. Two further critical issues were also revealed: a highly feasible operating circular scheme is achieved only when SNG is recycled to the cement industry (to satisfy heat/energy requirements), whereas RES-powered H2 is more competitive than electricity grid, as long as electricity prices are higher than 0.02 €/kWh. The proposed process proves that a combination of novel technologies and renewables can lead in a circular approach towards added-value products.