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The New Iron Age

In our first radio show, Phil brought up an idea for combating the greenhouse gas CO2 that I hadn't heard before - seeding the oceans with iron. The August edition of Popular Science details several different methods for dealing with Global Warming, but the "iron-the-oceans" idea looks like the most promising. For the record, the other methods discussed are:

  • Store CO2 Underground (which is already being done in small amounts).

  • Filter CO2 From The Air.

  • Turn CO2 To Limestone.

  • Enhancing Cloud Cover.

  • Deflect Sunlight With A Space Mirror.

According to the article, the average American puts 25 tons of CO2 into the atmosphere annually. One-half pound of iron strategically seeded in the right part of the ocean could encourage the growth of sufficient plankton to sequester the typical American's annual output.

At a lecture more than a decade ago, [oceanographer John Martin] declared: “Give me a half-tanker of iron, and I will give you an ice age.” He was alluding to the fact that the Southern Ocean is packed with minerals and nutrients but strangely devoid of sea life. Martin had concluded that the ocean was anemic—containing very little iron, an essential nutrient for plankton growth. Adding iron, Martin believed, would cool the planet by triggering blooms of CO2-consuming plankton.

This idea has now been tested.

On January 5, 2002, Revelle, a research vessel operated by the Scripps Institution of Oceanography, left New Zealand for the Southern Ocean—a belt of frigid, stormy seas that separates Antarctica from the rest of the world. There the scientists dumped almost 6,000 pounds of iron powder overboard and unleashed an armada of instruments to gauge the results.

The experiment proved that small amounts of iron can encourage the growth of huge plankton blooms.

Some scientists are concerned that cultivating plankton blooms in the South Seas could devour nutrients essential to life in other parts of the ocean. We'd have a nice cool planet with a dead ocean.

Probably every method that Popular Science discussed for reducing atmospheric CO2 has the potential for dangerous unintended consequences. Our planet is such a complicated system, that it may be impossible to know with 100% certainty all effects that any method for reducing CO2 could have.

To prevent unintented consequences on a massive scale, plankton cultivation should be incrementally implemented. If at any point the practice begins to cause a problem, the amount of plankton cultivated could be reduced. And, before beginning, I'm sure the scientific community would want to do extensive modeling with Japan's Earth Simulator.

Of all the solutions for global warming discussed in the article, only the "iron-the-ocean" solution harnesses life to do the work for us. All the other solutions would require the expenditure of massive amounts of energy - often by burning fossil fuels. But here, we would be using the energy of the sun (via photosynthesis) to cool the planet. This solution to global warming is simply too feasible to be ignored.

“Even if the process is only 1 percent efficient, you just sequestered half a ton of carbon for a dime.”


Old growth forests are unable to absorb as much Co2 as young trees. Clearcutting and planting new growth trees is the answer. ;^)


"Slash and Burn! 'Cause it's the right thing to do."


More seriously... burning releases the carbon.

Slash and, er, make furniture?

And replant...maybe with plants genetically modified to absorb more carbon.

There's a couple unanswered questions here:

  1. What else do the algae do to the chemistry of the water?
  2. How long will the carbon actually remain out of circulation?

If the answers to these questions aren't satisfactory, we can take biomass (including biomass-derived refuse), use it as process material for a solar-thermochemical energy system, and then bury the CO2 product; the net result is energy is produced and carbon removed from the atmosphere.  I called this Going negative.


Your comment is related to an idea I'm working on for a follow-up post.

The answer to your first question "what else does this do to change the chemistry of the water." Well, and this is a guess, it may lower the acidity. Something that needs to be done.

Here's the email I sent Phil this morning:

Subject: Atmospheric CO2 and the ocean acid problem


Okay, I'm out of my depth on an ocean problem (heh). I wrote about the "iron the oceans" solution to global warming yesterday.


CO2 is absorbed and "sequestered" (the word the article used) by plankton that is fertilized by iron in the iron-poor South Sea.

Another great environmental problem we're facing is rising acid in the oceans. The more acidic the oceans, the less coral reefs can grow, and this forms the base of the food chain - of the entire world. Something that we obviously shouldn't mess with.


The acid in the oceans is carbonic acid. This acid is the byproduct of the chemical reaction of CO2 (which is rising everywhere) and water.


It's been suggested that one solution to the acidic oceans is to dump limestone - an alkaline material.


The problem is the expense of mining limestone and transporting it to the ocean. Also, you might burn a little fossil fuel in the process of doing that. :-)

Reading this I was reminded that one of the suggestions for dealing with CO2 was to turn it into limestone. That's from the Popular Science article.


Putting those two ideas together it would seem to
suggests that there might be a single solution to both problems - atmospheric CO2 and ocean acidity.

What if turning CO2 to limestone was a ocean-based operation? Once the CO2 is stored in limestone, it could be dumped into the ocean and help turn it more alkaline.

What if, instead of some factory, this was handled by plankton? I guess I need to know how the plankton "sequesters" the CO2. If it's
sequestered into an alkaline substance like limestone, does that help the ocean's pH? Would the CO2 stay sequestered if the substance its
sequestered into is also busy neutralizing carbonic acid?


IF plankton sequesters CO2 in an alkaline form (or could be genetically modified to do so)


IF that alkaline substance was made in sufficient quantities to help the entire ocean's pH


IF CO2 stays sequestered while also neutralizing carbonic acid


we've got a pretty awesome twofer here - all powered by the sun.

Calcium carbonate is only stable in seawater down to a certain depth; as pressure increases, it dissolves more and more easily.  There are diatoms which build their shells out of calcium carbonate, but as they fall toward the bottom after dying their shells dissolve and go back into the water.

The fate of the rest of the biomass is another question.  There are large food chains at the ocean bottom driven by the rain of dead organisms from above.  If you add enough carbon to this to offset human fossil fuel consumption, will you have enough oxygen in the deep waters for the aerobic organisms?  Will the deep ocean floor go anoxic and become one huge dead zone?  I'd want to know before pushing this scheme further.

If we were going to bury CO2 at the ocean bottom, the best scheme might be to drop hundred-ton dry-ice torpedoes and let them bury themselves deep in the bottom sediments where the CO2 would be locked up as gas hydrate for the next ten millennia.

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