Seven European gas transmission system operators, including Gas Networks Ireland (GNI), have signed a joint declaration proclaiming the aim to establish a 100% CO2-neutral gas supply by 2050. The production of bio-SNG through a nationwide gasification and methanation system can constitute the basis of renewable gas production from indigenous biomass. Previous studies showed the potential of biomass in the Republic of Ireland but the low energy content and scattered distribution of the resources require smart design to abate costs and emissions. This work presents a geographical information system (GIS) based optimization model for the design of bio-SNG production system. The model includes a thermodynamic model and a techno-economic assessment which provide detailed mass and energy balances and capital and operational expenditures cost curves of the conversion process. The GIS-model performs a network analysis, analyses the economic performance and provides the near-optimal configuration which minimize the levelized cost of the energy produced. Four scenarios in which the economic performances of four possible configurations of pretreatments and number of main bio-SNG production plants are compared.