CO2 valorization through direct methanation of flue gas and renewable hydrogen: A technical and economic assessment

Under the scenario of an increasing sharing of renewable energy, Power to Gas technology may offer an effective and valuable solution for surplus energy management, accounting for a large and long-term chemical storage. In the present study an innovative Power to Synthetic Natural Gas (SNG) process has been described and investigated from a techno-economic and environmental point of view. The configuration is based on a methanation process, directly applied on flue gas stream thus acting both as a CO2 capture and sequestration technology and as renewable energy storage mechanism. Reacting hydrogen is produced via water electrolysis powered by surplus of renewable energy, normally low-priced otherwise wasted. With a reference capacity factor around 4000 h/y, the resulting SNG cost is 0.34 €/Nm3 based on a carbon tax equal to 30 €/t CO2. The obtained results are attractive and consistent with the fact that future investment cost for water electrolysis is decreasing accordingly.