Coupling PEM Electrolysis and Catalytic Methanation of Biogenic CO2 in Southern Spain: A Techno-Economic Feasibility Study

Synthetic natural gas (SNG) from renewable hydrogen and captured CO2 has reached the commercial stage; it is more expensive than fossil gas but may be justified as a renewable fuel for hard-to-decarbonize industry, and its cost depends strongly on how renewable generation, storage and grid electricity are combined. This work reports an hourly techno-economic assessment of a 10 MWe PEM electrolysis and catalytic methanation plant fed with biogenic CO2 in the Huelva chemical cluster (southwest Spain), built on a rigorous AVEVA Process Simulation model with Xu–Froment kinetics. At design conditions, a two-reactor train converts 98.2% of the CO2 into 322 kg/h of gas at 95.3 mol% CH4. Over a year, the base case produces 2140 t of SNG, with 50.8% of the available electricity (LHV) converted into SNG,and a levelized cost of 217.4 €/MWh (2.88 €/kg). Sizing the electrolyzer to the reactor and supplying it with firm grid power lowers the cost to 160.4 €/MWh, or to 178.4 €/MWh with the contract held at 5 MW. These are production costs; whether the plant is profitable depends on the price and support that renewable methane can obtain.