title: Biological CO2 conversion to acetate in subsurface coal-sand formation using a high-pressure reactor system.
abstract: Geological CO2 sequestration in unmineable subsurface oil/gas fields and coal formations has been proposed as a means of reducing anthropogenic greenhouse gasses in the atmosphere. However, the feasibility of injecting CO2 into subsurface depends upon a variety of geological and economic conditions, and the ecological consequences are largely unpredictable. In this study, we developed a new flow-through-type reactor system to examine potential geophysical, geochemical and microbiological impacts associated with CO2 injection by simulating in-situ pressure (0-100 MPa) and temperature (0-70°C) conditions. Using the reactor system, anaerobic artificial fluid and CO2 (flow rate: 0.002 and 0.00001 ml/min, respectively) were continuously supplemented into a column comprised of bituminous coal and sand under a pore pressure of 40 MPa (confined pressure: 41 MPa) at 40°C for 56 days. 16S rRNA gene analysis of the bacterial components showed distinct spatial separation of the predominant taxa in the coal and sand over the course of the experiment. Cultivation experiments using sub-sampled fluids revealed that some microbes survived, or were metabolically active, under CO2-rich conditions. However, no methanogens were activated during the experiment, even though hydrogenotrophic and methylotrophic methanogens were obtained from conventional batch-type cultivation at 20°C. During the reactor experiment, the acetate and methanol concentration in the fluids increased while the δ(13)Cacetate, H2 and CO2 concentrations decreased, indicating the occurrence of homo-acetogenesis. 16S rRNA genes of homo-acetogenic spore-forming bacteria related to the genus Sporomusa were consistently detected from the sandstone after the reactor experiment. Our results suggest that the injection of CO2 into a natural coal-sand formation preferentially stimulates homo-acetogenesis rather than methanogenesis, and that this process is accompanied by biogenic CO2 conversion to acetate.
authors.affiliation: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ohtomo
authors.affiliation: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan ; Submarine Resources Research Project, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Ijiri
authors.affiliation: Submarine Resources Research Project, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan ; Civil Engineering Research Laboratory, Central Research Institute of Electric Power Industry Chiba, Japan.
authors.forename: Yojiro
authors.initials: Y
authors.lastname: Ikegawa
authors.affiliation: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan.
authors.forename: Masazumi
authors.initials: M
authors.lastname: Tsutsumi
authors.affiliation: Submarine Resources Research Project, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan ; Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Yokosuka, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Imachi
authors.affiliation: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan ; Submarine Resources Research Project, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan.
authors.forename: Go-Ichiro
authors.initials: G
authors.lastname: Uramoto
authors.affiliation: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan ; Submarine Resources Research Project, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan.
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Hoshino
authors.affiliation: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan ; Submarine Resources Research Project, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Morono
authors.affiliation: Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Yokosuka, Japan.
authors.forename: Sanae
authors.initials: S
authors.lastname: Sakai
authors.affiliation: Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Yokosuka, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Saito
authors.affiliation: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan ; Submarine Resources Research Project, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Tanikawa
authors.affiliation: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan ; Submarine Resources Research Project, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Hirose
authors.affiliation: Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan ; Submarine Resources Research Project, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Kochi, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Inagaki
keywords: bituminous coal; coal-bed methane; geobio-reactor system; geological CO2 sequestration; homo-acetogenesis; methanogen