Synthetic natural gas (SNG) production with higher carbon recovery from biomass: Techno-economic assessment

Due to the growth in the share of renewable energy sources (RES) in the power generation sector worldwide and their intermittency, storage of surplus electricity is needed. The technology known as Power to X (PtX) facilitates the extended storage of excess electricity by converting it into gaseous or liquid fuels such as hydrogen, methane, ammonia, or methanol. This study examines the potential of synthetic natural gas (SNG) technology as a viable energy storage solution. The paper introduces three distinct SNG production systems, all of which are based on the processes of biomass gasification and methanation. Case 1 assumes further CO2 capture from generated SNG, and Cases 2 and 3 additionally assume hydrogen production and almost complete CO2 utilization by syngas hydrogenation via the methanation process. The methanation process converts syngas and hydrogen into SNG with a high methane content (>90 vol% dry), that can be injected into the natural gas grid. The thermodynamic and economic potential of SNG production systems is presented in this work. The simulations were conducted using the AspenONE software. The methanation process was analyzed for various design conditions such as methanation temperature and pressure, and different H-2:CO, and H-2:CO2 ratios. The estimated cold gas efficiency of proposed SNG production systems varies from 63.27% to 77.10% and can be increased up to about 69.10-75.58% when the recovery of heat from methanation is considered. A sensitivity analysis was conducted to determine the break-even price of SNG, considering different scenarios for the costs of feedstock, specifically biomass and electricity. The results indicate that under the most optimistic conditions, the break-even price of SNG is estimated to be 115 /MWh(SNG), 58 /MWh(SNG) and 67 /MWh(SNG) for Cases 1, 2, and 3, respectively.