Analysis and optimization of carbon supply chains integrated to a power to gas process in Italy

The mathematical model for carbon capture, utilization and storage supply chains is developed for Italian regions. This model is used to design supply chains minimizing total costs and reducing significantly carbon dioxide emissions. Carbon dioxide can be stored or utilized to produce methane through a power to gas system, where hydrogen is obtained by the electrolysis of water using renewable power while methane is fed to the gas grid. The Mixed Integer Linear Program model is applied to design carbon systems developed for ten regions with major carbon dioxide emissions, while different saline aquifers are proposed as storage sites. Results show that the Adriatic sea is the most appropriate offshore storage site in the supply chain. This leads to a lower net methane production cost and to the lowest level of economic incentives as compared to other cases. The total costs of this supply chain are 7.34·104 million €/year (953 €/tonCO2 captured), and 16.1 Mton/year of methane are produced. The supply chain does not result economically favorable without substantial financial incentives (80 €/tonCO2 for carbon tax and 260 €/MWh economic incentive for methane production). Comparing supply chains that include simultaneous utilization and storage of carbon dioxide with a carbon capture and utilization supply chain (without storage) shows that the latter is economically less favorable. In addition to mitigation of carbon environmental impact for the whole Country, the large scale supply chain proposed here meets 35% of Italy’s methane demand as a whole, a significant contribution to a global economic perspective, widely discussed nowadays, which should include self-sustainment elements at regional level.