Techno-economic assessment of a plant for the upgrading of MSW biogas to synthetic natural gas by thermocatalytic methanation

This study evaluates the techno-economic feasibility of a plant designed to produce synthetic natural gas (SNG) from biogas through direct catalytic methanation. The proposed facility is simulated with Aspen Plus (R) v14, using a comprehensive approach that covers the entire process, from biogas pretreatment to the production of the final product. The installation aims to contribute to the development of Power-to-Gas (Power-to-Methane) strategy for decarbonization. The plant, to be located in northeastern Spain, operates at an industrial scale with a production capacity of approximately 1100 Nm3/h of SNG, obtained from a 1425 Nm3/h biogas plant. The process includes five main stages to meet Spanish gas quality standards for grid injection: desulfurization, using amines for sulfur removal; electrolysis, for the generation of renewable hydrogen; thermocatalytic methanation, which combines CO2 from the biogas with hydrogen to enrich the methane content; dehydration, to meet SNG moisture specifications; and cogeneration, intended for the joint production of electricity and steam to meet the plant's energy demands. A detailed analysis of investment costs (CAPEX) and operational expenses (OPEX) is conducted, identifying the key factors influencing the project's profitability. The economic assessment indicates a total capital investment of 21.83 M<euro> and operational expenses nearly 8 M<euro> annually. The profitability threshold for the base scenario is estimated at 91.75 <euro>/MWh, exceeding the 2023 natural gas market average in the Iberic peninsula (39.11 <euro>/MWh), highlighting the current economic challenges of SNG production.