The analysis performed until this point only includes the technical performance of the system. To incorporate the economic evaluation of the system and to determine the final cost of H2 and electricity to the final users, the investigation is continued considering a specific case study. As the electricity input profile selected corresponds to the PV electricity availability around Zurich, the CO2 input source investigated is the biogas plant of Werdhölzli, where biogas is produced from organic waste and wastewater treatment. The plant is equipped with a biogas upgrading unit, which produces CO2 as a waste stream with a total average flow of 700 Nm 3 /h. In the case study, it is envisioned that the entire CO2 stream is utilised as a platform for energy storage, enabling possible negative CO2 emissions by transporting CO2 in the form of fuel and by capturing it at the final utilisation point. To ensure the utilisation of the entire CO2 stream, a CO2 storage unit in liquefied form is envisaged. The economic analysis includes the installation cost of the PV plant to convert the entire CO2 production, the electrolysis unit to produce H2, the synthesis unit (methane or methanol production), the CO2 storage and the fraction of the cost for the reforming or electrification of the product in a centralised unit. Additionally, the cost for carbon capture at the utilisation point of the product is included. The results of the calculations are reported in figure . For clarity, the results are also reported in tabular form in the appendix. The total cost of the plant depends strongly on the storage molecule selected, as more electricity (and hence H2) is required to convert CO2 in methane than methanol. This is visible in figure , as methanol plants have a size between 12 and 13 MW, while the methanation plants need to handle between 15 and 16 MW of H2. The investment costs for the delivery of electricity to the customers is higher than the corresponding cost for H2 production, due to the lower electricity-to-electricity efficiency, as already explained in the previous sections. reforming. In particular, the reforming of methanol covers only 3 % of the total cost, as the reforming unit is simple (operation at low temperature) and the amount of methanol to reform is the minimum among the cases considered. In the most expensive case, methanol reforming to electricity, the electrification unit covers 13% of the total costs. The nature of the final product influences also the cost of the carbon capture unit, where the precombustion unit connected to the reformer is relatively cheap, accounting for 2-3% of the total costs for both methane and methanol. The post-combustion capture after electrification is instead more expensive, requiring 7-8% of the total CAPEX for this unit. This is in line with the estimations normally accepted in literature .