Carbon Sequestration in Coal Seams in Japan and Biogeochemical Carbon Cycle in Tertiary Sedimentary Basins

Abstract

A new research and development project, “CO2 sequestration in coal seams” began in Japan in 2002 to develop new type of “coal mines” for CO2-enhanced coal gas recovery. Coal seams are promising for CO2 storage and as sources of hydrocarbon gas. Researches are being devoted to a deeper understanding of CO2-coal interaction, to monitoring of CO2 behavior in coal seams, and to prospecting of untapped deep coal seams. Supercritical CO2-enhanced coal seam gas recovery (ECGR) and in situ fire-free microbial gasification of coal can produce sufficient amounts of methane for the CO2 emission-free closed-circuit power plant and new type of "coal mines" without underground works, even in gas-poor coalfields. Deep, untapped coal seams as well as remaining coal in old mines provide huge potential CO2 reservoirs and sources of hydrocarbon gas. CO2 sequestration into coal seams with recovery of coalbed methane can realize the CO2 emission-free closed-circuit system of electric power generation. The last two major mines—Taiheiyou mine and Ikeshima mine—were undersea mines. However, offshore extensions of many coal seams were out of survey. Underground biogeochemical carbon recycling makes zero-emission closed-circuit power and heat generation possible, while coal seams and saline aquifers are capacious enough to accommodate large volume of CO2 from fossil fuel and refuse-derived fuel (RDF). Tertiary sedimentary basins are suitable as CO2 stores, hydrocarbon gas reservoirs, and, possibly, CO2-CH4 converters. Subsurface biogeochemical carbon recycling can realize greenhouse gas control with restoration of energy resources.