Prospect of Geological Sequestration of CO sub(2) for Greenhouse Gas Mitigation and Natural Gas Recovery

The annual 70 million tons' CO sub(2) injection separated from flue gas of fossil fueled power plants into aquifer may reduce Japan's artificial carbon dioxide emission as much as 6% with annual cost of 420 billion yens that match 1, 200 yens/c carbon tax. Geological sequestration of CO sub(2) is a technically and economically feasible option for mitigation of greenhouse gas emission. Carbon dioxide injection under gas-hydrate-filled layers or under permafrost layers can realize the greenhouse gas mitigation and recovery of unused natural gas. Autogenous sealing of CO sub(2) in deep and cool aquifers assures virtually complete and practically unlimited subsurface containment of CO sub(2). Chemoautotrophs fix carbon dioxide in deep aquifers even without sun light. Methanogens can convert CO sub(2) into methane in deep anoxic aquifers. Biogenetic restoration of subsurface hydrocarbon deposits is expected in CO sub(2)injected aquifers after tens or hundreds of years. Microbiological recycling of CO sub(2) in aquifers is an attractive future technology for energy-short countries such as Japan. Important key for underground CO sub(2) recycling is hydrogen supplies owing to microbial decomposition of organic matter and from geochemical water-rock interaction in deep rock formations.