SIMPLE ESTIMATION METHODOLOGY OF LEAKAGE FROM OCEAN STORAGE OF CO_2 FOR POLICY MAKERS

摘要

The technology for CO_2 capture and storage(CCS) into ocean reservoir is to reduce the impact of CO_2 emission to the atmosphere, by artificially accelerating CO_2 absorption of the ocean. Because CO_2 keeps traversing between atmosphere and ocean, a part of CO_2 stored in the ocean gets back in the atmosphere over many generations. One of crucial issue on taking ocean storage of CO_2 into account as a climate change mitigation option is to estimate and account long-term leakage. The objective of this paper is to develop a simple methodology to estimate amount of long-term leakage, which can be utilized by those who do not have sufficient simulation resources, in order to create a basis for CCS accounting. We first assume that the location and depth of injection are main key factors which control the long-term leakage. Then we calculate the storage curves of the injected CO_2 into ocean at each condition. For calculation of the storage curve, we apply "DONGRI", a global ocean system model developed with the purpose of understanding the physical and biochemical process within ocean system and predicting the effect of ocean storage of CO_2. Based on the simulated storage curves of injected amount of CO_2, we develop a simple formulation for accounting the amount of CO_2 stored in ocean using leakage coefficients. The methodology enables to add up the amount of leakage into national inventories and would be of assistance to examine the feasibility of some CO_2 ocean storage projects for project planners and policy makers. This study is intended to contribute to accounting rules for CCS proposed by our research project.