Evaluation of carbon dioxide sequestration in Japan with a mathematical model

Cost effectiveness of CO2 sequestration, especially into aquifers, strongly depends on the sequestration capacities and the routes to connect CO2 sequestration sites and recovery sites. This site dependency of CO2 sequestration makes its evaluation difficult. In order to evaluate the cost effectiveness of CO2 sequestration in parallel with other carbon mitigation options in Japan, a new mathematical model of optimization type has been developed. The energy systems and the processes of CO2 recovery, transportation and sequestration are modeled in the bottom-up fashion. To pay due consideration to the site dependency, the land area of Japan is divided into 20 regions and the offshore area also into 20 regions. The land regions have various kinds of energy supply-side facilities and CO2 recovery and transportation facilities. The final energy demand is grouped into four types of energy: solid fuel, gaseous fuel, liquid fuel and electricity. On the other hand, the offshore regions have aquifers for CO2 sequestration. In addition, CO2 sequestration into ocean is taken into account. These model regions are inter-linked with each other, and inter-regional CO2 transportation and energy transportation are considered. The total cost of energy systems and CO2 sequestration in Japan between the years 2000 and 2050 is minimized in this model. This paper describes the structure of this new model for evaluation of CO2 sequestration in Japan, and presents model-based optimization solutions as to when, where and how much CO2 sequestration and other carbon mitigation options should be implemented under assumed carbon mitigation policy options.