Synthetic hydrocarbons can be produced sustainably with power-to-gas processes, resulting in a net reduction of greenhouse gas emissions due to the substitution of conventional natural gas and other fossil fuels with carbon neutral alternatives. Acquisition of the CO2 for the synthetic fuel production can be implemented in multiple ways. This work introduces a node-based model to assess different implementation strategies of CO2 utilization systems, taking into account temporal effects, regional variation, and economies of scale for CO2 capture. Intermediate storage volumes, capture costs, transport quantities, and other relevant infrastructural aspects of the CCU system can be estimated with the model. Finland is used as a case study, focusing specifically on the national and regional scale. CO2 capture costs are significant, being nearly four times larger than the cost of storage in the baseline scenario (354 ME, 85 ME). CO2 sources with smaller annual emissions increases capture costs by 14% compared to baseline. This increase in cost is comparable to the cost of transporting over a quarter of all captured CO2 to off-site processing (varying distance, 100-400 km). Seasonal storage of CO2 is found to be beneficial for the cost-efficient production of synthetic fuels, owing to the temporal disparity between CO2 emissions and utilization, as well as the overall cost structure of the components. Five key decision categories are proposed for a carbon utilization system: scale, type, units, location, and technological decisions. These may be applied to describe any carbon utilization system, helping to form a more comprehensive picture of a future energy system, where carbon is widely used as a raw material.