May 09, 2009
Simplest Ocean Iron Fertilization Disappoints On Carbon Sequestration

The late oceanographer John Martin of the Moss Landing Marine Laboratories proposed over 20 years ago using iron fertilization of oceans to pull carbon dioxide out of the atmosphere to cool the planet. Lawrence Berkeley Lab oceanographers find the simplest iron fertilization approach disappoints by not permanently sequestering much carbon.

BERKELEY, CA – Oceanographers Jim Bishop and Todd Wood of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory have measured the fate of carbon particles originating in plankton blooms in the Southern Ocean, using data that deep-diving Carbon Explorer floats collected around the clock for well over a year. Their study reveals that most of the carbon from lush plankton blooms never reaches the deep ocean.

The surprising discovery deals a blow to the simplest version of the Iron Hypothesis, whose adherents believe global warming can be slowed or even reversed by fertilizing plankton with iron in regions that are iron-poor but rich in other nutrients like nitrogen, silicon, and phosphorus. The Southern Ocean is one of the most important such regions.

The scientists used floating autonomous sensor pods called Carbon Explorers that can take themselves down a few thousand feet and do continuous measurements for months. These pods collected the data that made this analysis possible. Deployment of a much larger number of Carbon Explorers would enable the scientists to develop a much more complex model of the ecosystem of phytoplankton and the zooplankton that feed on them.

The scientists aren't entirely dismissing the idea of using iron to pull carbon dioxide out of the atmosphere. But they think finding a way to do this requires development of a much more complex understanding of how to optimize phytoplankton growth.

The Iron Hypothesis isn’t wrong, but it’s much more subtle than usually stated. Achieving optimum carbon sedimentation from plankton growth may require the right “recipe” of iron and other trace nutrients to grow the right kind of phytoplankton. Says Bishop, “You can grow a lot of Brussels sprouts, but kids won’t eat it. The same appears to be the case with diatom phytoplankton and zooplankton. It’s the zooplankton community that determines carbon sedimentation.”

Share |      Randall Parker, 2009 May 09 07:42 AM  Climate Engineering

James Bowery said at May 9, 2009 8:52 AM:

I've been asking the same question for 15 years of these characters and never get an answer:

Why not just park your iron salt tankers in HNLC currents doing a continuous release and then aquaculture the resulting ecosystem over time into a fishery? You don't have to worry about trophic losses that much given how cost effective your bioreactor is per unit area.

For crying out loud, you quite possibly could make MONEY doing carbon capture without so much as a single carbon credit.

Randall Parker said at May 9, 2009 9:22 AM:

James, Yes, aquaculture is an attractive reason to do ocean fertilization. I wonder how the economics work out. The fertilization operation would want to get the bulk of the resulting harvested fish in order to pay for the fertilization costs.

Beelzebub said at May 10, 2009 9:55 AM:

Hmmm A non-solution for a non-problem! Makes sense to me. Let's spend trillions of newly printed money. If things get better, claim credit. If not, think of something else. Obviously we're not trying hard enough.

James Bowery said at May 10, 2009 5:01 PM:

Its pretty hard to question the economics:

You get something like a 25000 multiplier of iron salts to biomass. How expensive are iron salts? How expensive is fish?

James Bowery said at May 10, 2009 5:06 PM:

Actually, I may have understated the multiplier:

Recent research has expanded this constant to "106 C: 16 N: 1 P: .001 Fe" signifying that in iron deficient conditions each atom of iron can fix 106,000 atoms of carbon,[28] or on a mass basis, each kilogram of iron can fix 83,000 kg of carbon dioxide. The 2004 EIFEX experiment reported a carbon dioxide to iron fixation ratio of nearly 300,000 to 1. Assuming that data is on a mass basis, then the normalized atomic ratio would be approximately: "380,000 C: 58,000 N: 3,600 P: 1 Fe".

(I can hear the brain-dead now: "But but... what if the biomass sinks?!)

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