Deep-Sea Sediments Could Safely Store Man-Made Carbon Dioxide

Terra Daily ^ | August 17, 2006 | Staff Writers

[cogitator]

An innovative solution for the man-made carbon dioxide fouling our skies could rest far beneath the surface of the ocean, say scientists at Harvard University.

They've found that deep-sea sediments could provide a virtually unlimited and permanent reservoir for this gas that has been a primary driver of global climate change in recent decades, and estimate that seafloor sediments within U.S. territory are vast enough to store the nation's carbon dioxide emissions for thousands of years to come.

Harvard's Kurt Zenz House and Daniel P. Schrag, along with colleagues at the Massachusetts Institute of Technology and Columbia University, detail the advantages of sequestering excess carbon dioxide thousands of meters beneath the ocean's surface in this week's issue of the Proceedings of the National Academy of Sciences.

"Supplying the energy demanded by world economic growth without affecting the Earth's climate is one of the most pressing technical and economic challenges of our time," says Schrag, professor of earth and planetary sciences in Harvard's Faculty of Arts and Sciences and director of Harvard's Center for the Environment.

"Since fossil fuels -- particularly coal -- are likely to remain the dominant energy source of the twenty-first century, stabilizing the concentration of atmospheric carbon dioxide will require permanent storage of enormous quantities of captured carbon dioxide safely away from the atmosphere."

Schrag and his colleagues say an ideal storage method could be the injection of carbon dioxide into ocean sediments hundreds of meters thick. The combination of low temperature and high pressure at ocean depths of 3,000 meters turns carbon dioxide into a liquid denser than the surrounding water, removing the possibility of escape and ensuring virtually permanent storage.

Injecting carbon dioxide into seafloor sediments rather than squirting it directly into the ocean traps the gas, minimizing damage to marine life while ensuring that the gas will not eventually escape to the atmosphere via the mixing action of ocean currents.

At sufficiently extreme deep-sea temperatures and pressures, carbon dioxide moves beyond its liquid phase to form solid and immobile hydrate crystals, further boosting the system's stability. The scientists say that thus stored, the gas would be secure enough to withstand even the most severe earthquakes or other geomechanical upheaval.

Other researchers have proposed storing carbon dioxide in geologic formations such as natural gas fields, but terrestrial reservoirs run a risk of leakage.

"Deep sea sediments represent an enormous storage reservoir," says House, a graduate student in Harvard's Department of Earth and Planetary Sciences. "Some 22 percent, or 1.3 million square kilometers, of the seafloor within the United States' exclusive economic zone is more than 3,000 meters deep. Since we estimate that the annual U.S. emission of carbon dioxide could be stored in sediments beneath just 80 square kilometers, the seafloor within U.S. territory could store our nation's excess carbon dioxide for thousands of years to come."

Outside the United States' 200-mile economic zone, the scientists write, the total carbon dioxide storage capacity in deep-sea sediments is essentially unlimited.

The scientists note that thin or impermeable sediments are inappropriate for carbon dioxide storage, as are areas beneath steep deep-sea slopes, where landslides could free the gas. They add that further assessment of the mechanical feasibility of delivering carbon dioxide to the seafloor, as well as study of possible effects on sea levels, is needed.

[cogitator]

And if we are in danger of running out of CO2 for soft drinks, we can always put in a pipeline to the seafloor to get the stored CO2.

I have to note that saying CO2 "fouls our skies" is a bit over-the-top. Soot and smoke foul the skies; CO2 just alters the atmosphere. Now, if they'd said "souring our skies" instead, that would have been very clever!

[kinoxi]

Deep sea is a long way down.

[NonValueAdded]

newsflash, 2015 ... the SS Minnow was discovered by a UN Coast guard vessel with all aboard dead by suffocation ... the dreaded ocean phart is suspected once again in the area known as the Gore Triangle.

[P-40]

Be a good thing to keep that CO2 away from the plants. Might make them sick... :)

[keithtoo]

It is amazing how CO2 is described as a pollutant is most articles. No mention about how, without CO2, life would cease to exist. Jeez.

[theBuckwheat]

Ocean sediments already store an enormous amount of methane in the form of methane hydrates.

[Solamente]

I must be retarded.

Can't we solve this by planting more vegetation, which uses CO2 to create oxygen?

[theBuckwheat]

I am sure that it is just an inadvertent omission, but the carbon dioxide that everyone is expressing concern for came from the atmosphere. We are just being warned that it is dangerous to release it back to its natural point of origin.

[hawkaw]

Question

I think in the making of cement, CO2 is released when the limestone (calcium carbonate) bedrock is mixed with the other materials.

Am I wrong?

[nomorelurker]

I saw at least one proposal to take crop or other carbon type residues encase them in glass and drop them in the deep ocean as one solution.

[Bones75]

Also, where, pray tell, is the energy to pump millions of cubic meters of CO2 miles down into the deep sea floor going to come from?

Power plants? ..which burn fuel and release CO2 which will then also have to be pumped miles down into the deep sea floor?

[kinoxi]

Vegetation creates methane plumes over the Amazon rain forest which is supposedly more insulating than CO2. There is no way out of this leftist pseudo scientific mess.

[muawiyah]

We already have massive ocean currents that pull warm surface water down to the seafloor and pump it toward the other pole.

Best way to make use of them is to allow the surface water to absorb CO2. Once the currents drag the highly carbonated water to the seafloor, they will then be absorbed.

[Yo-Yo]

Water Vapor Rules the Greenhouse System

Just how much of the "Greenhouse Effect" is caused by human activity?

It is about 0.28%, if water vapor is taken into account-- about 5.53%, if not.

This point is so crucial to the debate over global warming that how water vapor is or isn't factored into an analysis of Earth's greenhouse gases makes the difference between describing a significant human contribution to the greenhouse effect, or a negligible one.

Water vapor constitutes Earth's most significant greenhouse gas, accounting for about 95% of Earth's greenhouse effect (4). Interestingly, many "facts and figures' regarding global warming completely ignore the powerful effects of water vapor in the greenhouse system, carelessly (perhaps, deliberately) overstating human impacts as much as 20-fold.

[Dan(9698)]

I think in the making of cement, CO2 is released when the limestone (calcium carbonate) bedrock is mixed with the other materials.

When limestone is burned, it turns to synthetic trona. That is calcium carbonate as it is used in glass manufacture.

If volcanoes didn't melt and spew gasses from the bedrock, there would soon be no atmosphere. They recycle the Carbon in the form of CO2, and also Oxygen in the CO2.

That is where the martian atmosphere went. It is bound up in the rocks because there are no more volcanoes to recycle it.

[Mike Darancette]

Injecting carbon dioxide into seafloor sediments rather than squirting it directly into the ocean traps the gas, minimizing damage to marine life while ensuring that the gas will not eventually escape to the atmosphere via the mixing action of ocean currents.

Are sea floors permanent? I thought that the sea floors eventually subducted under the continental plates? When that liquid CO2 in the seafloor sediments is heated then what? Geologically speaking very little is permanent.

[sox_the_cat]

It's lovely theory to sequester CO2 below the ocean, but it's already been mentioned the energy and cost to create a transport system to get it there must be extraordinary. Also, capturing CO2 can be done pretty well, but the daily volume output of CO2 from a single power plant is huge. The task of transporting that seems quite daunting.

[Larry Lucido]

Actually, I think earth's atmosphere can safely store "man made" carbon dioxide.

[Uncledave]

Renewable Energy Ping

Please Freep Mail me if you'd like on/off

[cogitator]

Can't we solve this by planting more vegetation, which uses CO2 to create oxygen?

There's a limit to the arable land that could provide a place for the vegetation and the amount that the vegetation could absorb.