Techno-economic comparison of Power-to-Gas systems using solid oxide and anion exchange membrane carbon dioxide/water electrolysers

• Power-to-Gas systems based on carbon capture, co-electrolysis and methanation. • Anion exchange membrane electrolysers are compared with solid oxide electrolysers. • Higher SNG flow rate (455 kg/h) and energy efficiency (47 %) in the high-temperature plant. • Thermal duty for stripping is almost fully covered in the high temperature configuration. • Levelized cost of SNG of 304 €/MWh for SOEC wrt 375.6 €/MWh for AEMEC. Carbon dioxide (CO 2 ) electro-reduction is an alternative pathway to synthesize low-carbon fuels and chemicals from renewable electricity. However, comprehensive techno-economic evaluations on this technology are still relatively few in the scientific literature. In this work, novel Power-to-Gas systems have been structured into three main subsequent process steps: (1) CO 2 separation by absorption with aqueous monoethanolamine from a waste incinerator flue gases; (2) co-electrolysis of CO 2 and steam (H 2 O) to produce a syngas; (3) catalytic methanation to generate substitute natural gas (SNG) with a methane (CH 4 ) purity exceeding 92 %. Two different electrolysis configurations have been analysed, involving: (1) two anion exchange membrane electrolysers in parallel performing CO 2 and H 2 O electrolysis (1.8 and 7.5 MW el , respectively); a solid oxide electrolyser splitting CO 2 /H 2 O coupled with one anion exchange membrane H 2 O electrolyser (3.6 and 7.4 MW el , respectively) for additional hydrogen (H 2 ) production. Because of the CO 2 crossover of the anion exchange membrane electrolyser to the anode side and its lower energy efficiency (34 %) with respect to the SOEC, the combination of Solid Oxide and Anion Exchange Membrane Electrolysers achieves higher natural gas production rate (296 vs 455 kg SNG /h), higher global energy efficiency of SNG production (37 % vs 47 %), and lower specific energy consumption per captured CO 2 (39 MJ/kg CO2 vs 50 MJ/kg CO2 ). Additionally, the high-temperature configuration provides a levelized cost of substitute natural gas of around 304 €/MWh with respect to 376 €/MWh of the low-temperature scenario assuming 80 % capacity factor and electricity cost of around 52 €/MWh. To achieve economic competitiveness with natural gas and biomethane, both systems will benefit from efficiency optimization, cost reductions by technological learning rate and scaling-up to hundreds of MW el , as well as incentives on renewable fuels production. The proposed configurations are easily adaptable to the production of other key chemical products, such as methanol and Fischer–Tropsch products.