Deep-sea disposal of fossil-fuel CO2:
First ocean observations
EMBARGOED FOR RELEASE:
Thursday, 6 May 1999 at 15:00 U.S. Eastern Time
MOSS LANDING, CaliforniaThe unexpected results from novel in situ
experiments on the behavior of liquid carbon dioxide in the deep ocean will be published
in the May 7 issue of the journal Science.
The burning of fossil fuels to create the energy that our society depends on releases
excess carbon dioxide into the atmosphere where it, and other so-called "greenhouse
gases," contribute to global warming. Since the oceans naturally absorb carbon
dioxide, one possibility for disposing the human-generated excess is to directly put it
into the deep ocean, bypassing the atmosphere. Ocean chemist Peter Brewer and his
colleagues at the Monterey Bay Aquarium Research Institute (MBARI) and Stanford University
designed and executed some of the first experiments to test theoretical predictions about
the behavior of liquid CO2, the form that would be used for
direct disposal, in the cold, extremely high-pressure environment of the deep sea.
Under cool temperatures and high pressures, carbon dioxide and other greenhouse gases
react with water to form a solid ice-like compound called clathrate hydrate. At shallow
depths liquid carbon dioxide will rise to the surface. But based on laboratory experiments
with CO2 hydrates, researchers imagined that liquid carbon
dioxide put deep in the ocean would form a stable layer on the seafloor with a skin of
solid hydrate as a boundary, like a pond covered by ice in winter.
Brewer and his colleagues took such experiments out of the lab and into the ocean.
Using special instruments on the institutes remotely operated vehicle
the researchers generated CO2 hydrate from gas and liquid at
depths ranging from 350 meters to 1000 meters in Monterey Bay. At these shallow depths,
liquid CO2 with a skin of hydrate is indeed less dense than
seawater and will rise toward the surface and dissolve at shallow depths.
Brewers most recent work, conducted last summer, concentrated on the behavior of
liquid carbon dioxide at much greater depths where it is denser than seawater. In these
experiments, MBARI researchers used the institutes ROV Tiburon to inject
several liters of liquid CO2 into a glass beaker at a depth of
3600 meters. Tiburons video camera relayed surprising information back to the
researchersthe liquid CO2 was highly reactive with the
surrounding seawater, significantly increasing in volume within the first hour of the
experiment. As water
molecules combined with CO2 molecules, gas hydrate formed and
accumulated at the bottom of the beaker. The expanding volume of hydrate plus remaining
liquid CO2 caused globules of liquid CO2
to spill over the top of the beaker, where they bounced to the seafloor and were carried
easily away by the currents. "Nothing like this was predicted," Brewer
Brewer and colleagues will conduct subsequent experiments this summer to test new
hypotheses generated from previous results. They also have begun collaborations with MBARI
ecologists to study the possible effects of liquid CO2 on
Ocean disposal for excess atmospheric carbon dioxide is gaining interest
internationally with the recent adoption of the 1997 Kyoto Protocols to the United Nations
Framework Convention on Climate Change. The enormous natural carbon buffering system of
the ocean suggests that the deep ocean could absorb the amount of carbon that would cause
a doubling in atmospheric concentrations and change its concentration by only two percent.
Brewer is optimistic that ocean disposal, while expensive, is a safe and viable option
for deterring the harmful buildup of atmospheric carbon dioxide. Says Brewer,
"Its imperative to conduct research that will help us understand the
fundamental science, the risks, and the opportunities."
Research article: Brewer,
P.G., G.E. Friederich, E.T. Peltzer, and F.M. Orr, Jr. Direct Experiments on the Ocean Disposal of
Fossil Fuel CO2. Science, May 7, 1999, 284: 943-945.
For more information about this research, visit the MBARI greenhouse gas website.
Debbie Meyer, 831-775-1807, email@example.com