A group of scientists has used deep ocean-floor drilling and experiments to show that volcanic rocks off the West Coast and elsewhere might be used to securely imprison huge amounts of globe-warming carbon dioxide captured from power plants or other sources. In particular, they say that natural chemical reactions under 30,000 square miles of ocean floor off California, Oregon, Washington and British Columbia could lock in as much as 150 years of U.S. CO2 production. The findings are published in theProceedings of the National Academy of Sciences .
in so-called carbon sequestration is growing worldwide. However, no large-scale
projects are yet off the ground, and other geological settings could be
problematic. For instance, the petroleum industry has been pumping CO2 into
voids left by old oil wells on a small scale, but some fear that these might
eventually leak, putting gas back into the air and possibly endangering people
author David Goldberg, a geophysicist at Columbia University's Lamont-Doherty Earth
Observatory, called the study, "the first good evidence that this kind of
carbon burial is feasible."
are convinced that the sub-ocean floor is a significant part of the solution to
the global climate problem," says Goldberg. "Basalt reservoirs are
understudied. They are immense, accessible and well sealed – a huge prize in
the search for viable options." One of the main advantages, he explains,
is a chemical process between basalt and pumped-in CO2 that would convert the
carbon into a solid mineral.
their paper, Goldberg and his colleagues Taro Takahashi and Angela Slagle used
previous deep-ocean drilling studies of the Juan de Fuca plate, some 100 miles
off the Pacific coast, to chart a vast basalt formation that they say could be
suitable for such pumping. Basalt, the basic stuff of the ocean floors, is
hardened lava erupted from undersea fissures and volcanoes. In this region,
much of it lies under some 8,850 feet of water, and 650 feet or more of
overlying fine-grained sediment. Drilling by the Integrated Ocean Drilling
Program has shown the rock is honeycombed with watery channels and pores that
would provide room for pressurized CO2. The scientists have mapped out specific
areas that they say are isolated from earthquakes, hydrothermal vents or other
factors that might upset the system.
experiments by Lamont scientists on land have shown that when CO2 is combined
with basalt, the gas and components of the rock naturally react to create a
solid carbonate – basically, chalk. Later this year, a separate team headed by
Lamont geochemist Juerg Matter will begin pumping CO2 into a landbound basalt
formation at a power plant near Reykjavik, Iceland – the first such
large-scale demonstration. Basalts lie at or near the surfaces of other land
areas, including the northeast United States, the Caribbean, northern and southern Africa, and southeast Asia.
says that undersea basalts, which are widespread, may be bigger, and better,
than ones on land. At the depths studied, any CO2 that does not react with the
rock will be heavier than seawater, and thus unable to rise. And in places like
the Juan de Fuca, even if some did escape the rock, it would hit the overlying
impermeable cap of clayey sediment.
Skeptics point out
that getting the CO2 to such sites could be expensive and tricky. But Goldberg
says the West Coast formations should be close enough to the land for delivery
by pipelines or tankers. He called on government to study the details of how
the idea might work, and whether it would be economically feasible. The United States currently spends about $40
million a year studying carbon sequestration, but nearly all of that goes to
land-based research. "Forty million is about the opening-day box office
forFinding Nemo," says Goldberg. “We need policy change now, to energize
research beyond our coastlines."
Undersea Volcanic Rocks May Offer Vast Repository for Greenhouse Gas
August 14, 2008