Image from D G Brown
A new study published in the Proceedings of the National Academy of Sciences makes the case that 208-250 billion tons of carbon dioxide -- roughly equivalent to a century's worth of future emissions (122-147 years, to be exact) -- could be safely stored within the Juan de Fuca plate, reports The Guardian's Alok Jha.
The tectonic plate, which arises from the Juan de Fuca Ridge, encompasses an area of the seafloor several hundred kilometers from the coasts of Washington and Oregon. David Goldberg, a geologist at Columbia University's Lamont-Doherty Earth Observatory, believes its basalt layers could be suitable for a carbon capture and storage (CCS) project.
Image from USGS
Physical vs. geochemical trapping
In their study, Goldberg and his colleagues describe two methods by which CO2 could be stored for the long-term: physical trapping (the gas is buried under layers that have zero to low permeability) and geochemical/mineral trapping (the gas reacts with the underlying rocks to form carbonate -- a stable, solid mineral).
The team chose the Juan de Fuca site because it matched several of their ideal criteria for CCS: They are under at least 2,700 meters of water and are covered by over 200 meters of sediment. At such a depth, CO2 becomes denser than seawater and liquefies -- which means that, even if a leak were to occur, it shouldn't be able to rise up to the surface.
The risks of ocean storage
A series of difficulties could complicate the enterprise, however. According to Andy Chadwick, a CCS expert from the British Geological Survey, Goldberg and his colleagues would first need to find a suitable number of fractures in the basalt into which they could pump the CO2. These fractures, which he says will be very difficult to locate, could be connected to the seafloor or surface -- which would provide leakage pathways for the gas.
Couple that with the sheer costs and infrastructure needed to mount such an effort -- not to mention the many unknowns -- and you're left with a risky, potentially unappealing carbon-mitigation option.
Via ::The Guardian: Ocean floor could store century of US carbon emissions (news website)
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