Techno-economic and life cycle analysis of synthetic natural gas production from low-carbon H2 and point-source or atmospheric CO2 in the United States

Synthetic natural gas (SNG) is of great interest in reducing fossil energy consumption while maintaining compatibility with existing NG infrastructure and end-use applications equipment. SNG can be produced using clean H₂ generated from renewable or nuclear energy and CO₂ captured from stationary sources or the atmosphere. In this study, we develop an engineering process model of SNG production using Aspen Plus® and production scales reported by the industry. We examine the levelized cost and life cycle greenhouse gas (GHG) emissions of SNG production under various CO₂ supply scenarios. Considering the higher cost of H₂ transportation compared with CO₂ transportation, we assume that CO₂ feedstock is transported via pipeline to the H₂ production location, which is collocated with the SNG plant. We also evaluate the cost of CO₂ captured from the atmosphere, assuming the direct air capture process can occur near the SNG facility. Depending on the CO₂ supply chain, the levelized cost of SNG is estimated to be in the range of $45–76 per million British thermal units (MMBtu) on a higher heating value (HHV) basis. The SNG production cost may be reduced to $27–57/MMBtu-HHV by applying a tax credit available in the United States for low-carbon H₂ production (45 V). With a lower electricity price of 3ȼ/kWh for water electrolysis and accounting for a 45 V tax credit, the SNG cost reaches parity with the cost of fossil NG. Depending on the CO₂ supply chain, SNG can reduce life cycle GHG emissions by 52–88 % compared with fossil NG.