HR: 1340h
AN: U43C-1381    [Abstracts]
TI: In-situ Carbonation of Magnesium Silicates: an Experimental Investigation of the Sequestration Potential of Oceanic Crust
AU: * Carpenter, T M
EM: tomcarp@u.washington.edu
AF: Los Alamos National Laboratory, Hydrogeology, Geochemistry, and Geology (EES-6) Earth and Environmental Sciences Division Mail Stop J514, Los Alamos, NM 87545, United States
AU: * Carpenter, T M
EM: tomcarp@u.washington.edu
AF: University of Washington, Johnson Hall 070 Box 351310 4000 15th Avenue NE, Seattle, Wa 98195-1310, United States
AU: Kaszuba, J P
EM: jkaszuba@lanl.gov
AF: Los Alamos National Laboratory, Hydrogeology, Geochemistry, and Geology (EES-6) Earth and Environmental Sciences Division Mail Stop J514, Los Alamos, NM 87545, United States
AB: A promising solution to the problem of anthropogenic greenhouse carbon is through carbonation of ultramafic minerals. Investigations of the carbonation potential of magnesium silicate minerals in industrial settings have been conducted, but the process is energy intensive and expensive. Direct injection of carbon dioxide into seafloor hydrothermal systems that are rich in magnesium silicate minerals may provide an alternate, viable pathway for sequestering carbon dioxide. Experiments were conducted on seawater-oceanic crust-carbon dioxide systems to simulate injection of carbon dioxide into a seafloor hydrothermal system and determine the extent of fluid-rock reaction. The solid reactant was comprised of 71.4% olivine, 18.4% diopside, and 10.2% enstatite. This proxy for oceanic crust was reacted at 300 C and 500 bar in a synthetic seawater solution to approach steady state, then injected with supercritical carbon dioxide and reacted for 550 hours. Three mole percent of carbon dioxide relative to water was injected into the experimental system. The experimental pressure decreased 17 bars in three hours following carbon dioxide injection due to initial dissolution and mineralization of carbon dioxide. The pressure decreased an additional 20 bars due to mineralization during the remainder of the experiment. Approximately 20% of injected carbon dioxide was mineralized, and the remainder was dissolved into the aqueous fluid. Brine-rock reaction decreased pH from 7.4 to 5. Aqueous calcium was consumed following carbon dioxide injection, whereas magnesium and silica concentrations increased due to increased brine acidity. Mineral reactants dissolved, as indicated by surface pits and etching on mineral fragments and the increase of aqueous magnesium and silica concentration. Mineral reactants were serpentinized, and then reacted to talc and magnesite following carbon dioxide injection. Magnesite comprised approximately 30 weight % of the reaction products. Carbon dioxide dissolution and attendant magnesite precipitation indicates that direct injection of carbon dioxide into oceanic crust may be a viable means of sequestering anthropogenic carbon.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 4806 Carbon cycling (0428)
DE: 6304 Benefit-cost analysis
DE: 6309 Decision making under uncertainty
SC: Union [U]
MN: 2007 Fall Meeting