To draw down carbon and cool off the planet, ocean fertilization gets another look
Geoeng Info
To draw down carbon and cool off the planet, ocean fertilization gets another look
Warren Cornwall
In January 2009, a German research ship set out for the Southern Ocean carrying 6 tons of iron and a boatload of controversy. The iron was meant to trigger a massive phytoplankton bloom that would suck carbon dioxide (CO2) from the air, but environmentalists objected, viewing the trial as a reckless form of geoengineering. The German government briefly suspended the work, before letting it go ahead. It would be the last iron fertilization experiment for more than a decade.
But that could soon change, after a panel of leading ocean scientists last week said such experiments were a priority and called for the United States to spend up to $290 million on even larger ones that would spread 100 tons of iron across 1000 square kilometers of ocean. Already, researchers next year plan to pour iron across a patch of the Arabian Sea.
Rigorous tests of the strategy are critical, says Ken Buesseler, a biogeochemist at the Woods Hole Oceanographic Institution and a co-author of the National Academies of Sciences, Engineering, and Medicine (NASEM) panel report. “I think it is going to happen with or without the science,” Buesseler says. “My fear is we see this commercialized before we know some of the fundamentals about the ocean response.”
Even if nations make steep cuts to greenhouse gas emissions, many scientists believe that to prevent severe climate change, the world also needs to pursue “negative emissions technologies” that would pull CO2 and other warming gases from the air. Billions of dollars have gone into land-based schemes that, for instance, promote reforestation or agricultural practices that store more carbon in the soil. But Scott Doney, a University of Virginia oceanographer who chaired the NASEM report, says when it comes to carbon sequestration research, “The ocean is a relatively new space.”
The ocean has already absorbed nearly one-third of the carbon emissions from human activities, and scientists hope it can shoulder even more of the burden. Besides iron fertilization, the panel looked at rehabilitating coastal ecosystems; growing vast plantations of seaweed; and spurring plankton production by forcing nutrients up from deep in the ocean. Higher cost options included using electricity to strip CO2 from seawater and inject it underground; and spreading pulverized rocks across the ocean to make it more alkaline, increasing the amount of CO2 it can absorb.
Iron fertilization is among the cheapest options. Photosynthetic plankton act like tropical rainforests, sucking CO2 from the atmosphere. Their populations are often limited by a scarcity of iron, which sifts into the ocean in windblown dust from deserts, in volcanic ash, and even from underwater hydrothermal vents. Extra iron would stimulate a bloom, the thinking goes, causing plankton to take up extra carbon. The carbon would sink into the depths in the form of dead plankton, or the feces or bodies of organisms that eat them. In theory, the carbon would be entombed for centuries.
Tests have shown the iron does stimulate plankton growth. But key questions remain, says Dave Siegel, a marine scientist at the University of California, Santa Barbara, who served on the NASEM panel. How much of the absorbed carbon makes it to the deep ocean is uncertain, he says: Other organisms might consume the sinking material and re-emit the carbon as CO2. Another question on Siegel’s mind: How would companies or governments track these carbon flows well enough to claim they are countering greenhouse gas pollution?
Buesseler is encouraged by recent computer modeling, published by Doney, Siegel, and colleagues in Environmental Research Letters, showing nearly one-third of the carbon captured near the ocean surface by events such as plankton blooms should sink to the deep ocean. Ocean-fertilization strategies could be viable “if we can get even 10% down deep enough,” he says.
But skeptics note that a recent survey of 13 past fertilization experiments found only one that increased carbon levels deep in the ocean. That track record is one reason why making iron fertilization a research priority is “barking mad,” says Wil Burns, an ocean law expert at Northwestern University.
Stephanie Henson, a marine biogeochemist at the United Kingdom’s National Oceanography Centre, also worries about surprise consequences of the approach, likening it to the catastrophic introduction of rabbits to Australia ecology. “You could just imagine something like that happening in the oceans completely by accident.” But Buesseler thinks gauging the potential risks is one reason to go ahead with the research.
David King, head of the Centre for Climate Repair at the University of Cambridge, is ready to test these politically charged waters. Next summer, working with scientists at India’s Institute of Maritime Studies in Goa, he plans to spread iron-coated rice husks across a swath of the Arabian Sea, to learn whether suspending the nutrient for longer can spark a bloom with less iron.
To head off environmental concerns, King plans to confine the work within a giant plastic bag running from the surface to the sea floor several kilometers below. “There’s an enormous amount of naysaying going on,” King says. “There are many, many people saying let’s leave the oceans alone, as if we haven’t already interfered with them.”
Ronal Larson
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Wil Burns
Dear Ron,
I think that there’s a need for a lot more experimentation to determine if harvesting for biomass is a viable approach, but it assuredly has a lot more “legs” in my mind than OIF. I did not find the NAS chapter on OIF to be comprehensive nor balanced in terms of the science, including risks.
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WIL BURNS Visiting Professor Environmental Policy & Culture Program Northwestern University
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Eelco Rohling
Prof. Eelco J. Rohling
(Ocean & Climate Change)
- 2012 Australian Laureate Fellow
- editor, Reviews of Geophysics
Research School of Earth Sciences
The Australian National University
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Australia
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Ronal Larson
On Jan 9, 2022, at 3:50 PM, Eelco Rohling <eelco....@anu.edu.au> wrote:Typically, Iron fertilisation needs to be don in High Nutrient Low Chlorophyll (HNLC) zones because that’s where there is evidence of limitation of phytoplankton growth by another (micro-)nutrient as there is plenty of N and P (hence, the High Nutrient part of the the name).Where are the HNLCs? Here: https://en.wikipedia.org/wiki/High-nutrient,_low-chlorophyll_regions
Note that the Arabian Sea receives plenty iron in different valences via windblown dust, and is not an HNLC. Instead, productivity is rather high already.
Wouldn’t be my first choice. I guess that go there because there is a major Oxygen minimum zone in the subsurface, which would favour Corg preservation at depth.
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Prof. Eelco J. Rohling
(Ocean & Climate Change)
- 2012 Australian Laureate Fellow
- editor, Reviews of Geophysics
Research School of Earth Sciences
The Australian National University
Canberra, ACT 2601
Australia
Mobile: (+61) 434 667441
Tel. Office: (+61) 2 612 53857
e-mail: eelco....@anu.edu.au
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Tom Goreau
Almost all inhabited coastal habitats are smothered with harmful benthic algae blooms caused by our failure to recycle anthropogenic nutrients from sewage, fertilizer, and biomass destruction. Their biomass makes wonderful balanced fertilizer for plants because they are rich in carbon, nitrogen, and phosphorus, and elevated in all the trace metals that can be deficient in soils and limit plant productivity. Using them removes dangerous excess nutrients killing coastal ecosystems and recycles them back on the land, where we most need them to enhance soil productivity without having to buy costly and energetically expensive chemical fertilizers. Chemical fertilizers are largely incomplete and unbalanced in their nutrient spectrum, which limits plant uptake and causes most to be wasted polluting rivers, lakes, and coastal zones and causing expanding dead zones. As a boy I swam in coral reefs inside the Kingston Harbour, Jamaica but it became one of the first dead zones in the 1960s. Jamaican marine biologist Barry Wade saw all the marine life on the bottom vanish from one year to the next as the whole water column turned anoxic from sewage.
Dry or wet algae first need to have the sodium and chloride simply rinsed out with a little fresh water (easier when they are dry), as these salts cause soil salinization that kills plants (even coconuts and mangroves die in hypersaline soils). Once you do that, the dried algae are a fast-release, rapidly decomposing organic fertilizer. As it lacks lignins and is full of carbohydrates and proteins, it decomposes rapidly and needs to be renewed annually. Dry seaweed is very bulky and light, so it costs a lot to transport it, and is only economically viable if you live near the sea. In Woods Hole I would stuff my car full of dry seaweed on the beach, and leach it in rain before using it my garden. These practices are traditional in many coastal cultures around the world.
Even better is to turn it into biochar. Conventional biochar kilns need dry material otherwise the heat is wasted drying out wet material, but hydrothermal pyrolysis seems to be a great solution that needs to implemented on a large scale. Once again, because of lack of lignins, the resulting biochar is high in nutrients but low in black carbon, so it is a medium rapid release fertilizer, and won’t help much to sequester long-lived black carbon in soil, which you get from hardwood biochars. I don’t know of any measurements of hydrothermal algae biochar lifetime in soils compared to lignin biochars and dry seaweed mulch (perhaps Stephen Joseph can help?). Performance in soil will vary by species because some algae are much richer in nitrogen or phosphorus or certain trace metals.
Many groups around the Caribbean now turning the Sargassum piling up on our beaches and killing coastal life from anoxia and hydrogen sulfide and converting it into fertilizer, chemicals, and even building materials. There is an urgent need to expand their efforts as well as research to optimize putting the nutrients back on the land and out of the sea.
Failure of the National Academy of Sciences Expert Report to consider recycling marine algae carbon on land, to save the sea, the land, and the air, is a major omission.
Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance
Chief Scientist, Blue Regeneration SL
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Books:
Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase
http://www.crcpress.com/product/isbn/9781466595392
Innovative Methods of Marine Ecosystem Restoration
http://www.crcpress.com/product/isbn/9781466557734
No one can change the past, everybody can change the future
It’s much later than we think, especially if we don’t think
Those with their heads in the sand will see the light when global warming and sea level rise wash the beach away
Geotherapy: Regenerating ecosystem services to reverse climate change
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David Brown
The pro-research argument I've heard goes something like this:
(1) There are better ways to apply the Fe. Previous experiments used FeS. The paleo-oceanographic record suggests that other minerals like Fe-Si were responsible for sequestration in the past. It's reasonable to think these would work better as FeS is fast-release and these would release slower.
(2) There are benefits of scale and pulsing the Fe applications, which will lead to a higher conversion efficiency from carbon fixation to carbon sequestration. Also there are benefits of siting this on ocean Eddies for increasing the sink rate.
(3) various measurement technologies are much better today, so the experimentation will get more efficient.
The flip-side of only 1 out of 13 experiments showing deep ocean carbon enhancements is: can the reasons the single experiment worked be determined and then systematically replicated? From my standpoint working in sustainable agriculture product development, it's possible to go from a 7% success rate (not a product) to a 70% success rate (a blockbuster product) in managed biogeochemical systems.
The above computes for me as a reasonable research hypothesis to me. That said, I am assuredly not an expert on oceans science.
Thank you for your time and consideration,
David Brown
Wil Burns
Dear Dave,
My primary concerns about OIF, which weren’t really captured by the interviewer, aren’t on the effectiveness side, though I am extremely skeptical in this context also, but rather on the risk side of the equation. This include potential proliferation of phytoplankton species that may prove unpalatable to zooplankton, the potential for this approach to rob nutrients from downstream ecosystems, and toxic algae blooms. I also think that the signal to noise ratio is such that you would have to conduct field experiments of such a size that you could have extremely serious negative impacts on ocean ecosystems even in the experimental phase. wil
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