Evaluation of Economic and Environmental Impacts of Green H ₂ Integration in Raw Syngas Methanation

Optimizing the integration of (green) H2 into methanation is a way to improve the economic viability and the environmental performance of this process. Herein we simulated different integration alternatives to convert raw syngas into BioSNG, adjusting and allocating H2 across the different methanation stages. We systematically screened a broad solution space, varying the stoichiometric number and H2 distribution across methanation stages, and performed a comprehensive system-level techno-economic analysis and life cycle assessment. Results indicate that adjusting the stoichiometric number between 2.7 to 3.2 while distributing between 67 to 100% of additional H2 to the first methanation stage and the remainder mainly to the second stage achieves the lowest break-even prices. A large-scale combinatorial sensitivity analysis of the economic parameters with ∼ 106 scenarios show that reductions in electricity price, biomass cost and gasification CAPEX are the key economic parameters to enhance the competitiveness of this technology. Life cycle assessment revealed electrolysis as the main environmental impact contributor, with BioSNG reducing global warming potential, ozone depletion, and fossil depletion compared to fossil natural gas, though increasing impacts in other categories due to a shift of environmental impacts from the fuel-use stage to upstream life cycle stages related to electricity consumption in electrolysis, biomass supply and facility construction materials. These findings can guide the industrial-scale implementation of BioSNG production systems in renewable energy supply chains.