Algal bloom carbon sequestration plot is kicked around once more, despite glaring flaws
It's been over 50 years since the U.S. has experienced as severe a drought as the one plaguing the nation this summer. Heat levels have set records. Unsurprisingly, global warming researchers have come out of the woodwork crying doomsday, as they hunt for research grants to fund speculative studies on what "might" happen in a "worst case" warming scenario.
Comments Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research in Boulder, Colo., "[Manmade global warming] means more energy that has to go somewhere. In dry conditions it amplifies drying and goes into heating, creating heat waves. It is small on a day-to-day basis, but is always in one direction and it creates stronger, more intense, and longer-lasting drought. No doubt about it."
I. The Return of the Anti-Warming Algae Bloom Plot
A new study by Professor Victor Smetacek of the Alfred Wegener Institute and 29 other authors has some calling for the revival of a head-scratching "carbon sequestration" scheme to fund.
The research community is generally unsure exactly how "hot" the Earth will get before compensatory factors like the water cycle and plant growth "put on the brakes". And many researchers argue that trying to halt manmade warning is a lost cause and a waste of money. Last, but not least, some argue that warming's effects on mankind may not be entirely bad, increasing crop yields in some regions and opening up new resources.
Still, that hasn't stopped researchers from coming up with Mouse Trap-style schemes looking to pour money into, in hopes of somehow tipping the balance away from a warming climate.
The study examines such a strategy, which involves dumping iron sulfate into the ocean in hopes of triggering a massive algal bloom, which the team hopes will "mostly" sink to the bottom of the ocean, sequestering the captured carbon.
A new study examines/revives the idea of using algal blooms to sink carbon into the sea.
[Image Source: Duke University]
According to the authors, the five-week study in the Indian Ocean was a success. They conclude "at least half the bloom biomass sank far below a depth of 1,000 metres and that a substantial portion is likely to have reached the sea floor."
However, they admit, "[B]ecause the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncertain."
Still they venture a guess that the bloom sequestered 13,000 carbon atoms -- at least for a while -- per ever iron atom.
II. Numbers Look Okay at First Glance...
Given that estimate, it's relatively easy to calculate some basic economics for the scheme.
Iron sulfate (ferrous sulfate) is composed of a single iron (Fe) cation, bonded to a sulfate (SO4) anion. As a monohydrate, it weighs 151.908 g/mol, versus 44.01 g/mol for CO2. Thus a ton of carbon (in theory) could be captured with about 240.6 grams of the fertilizer.
Ferrous sulfate would be used to fuel the algal bloom. [Image Source: ByTrade]
Assuming a bulk price of about $1.00 USD/lb. [Source; PDF], that would place the theoretical costs of capturing the carbon at $0.53 USD/ton. In 2011 there were 34 billion tons of emitted carbon [source], so that would put the sticker price of "halting" carbon increases at about $18B USD per year.
III. ...But the Devil is in the Details
That doesn't sound too bad, but the big issue, is that 35 billion metric tons of carbon would have a deadly effect on ocean life. Even mid-sized algal blooms can kill fish for miles. Thus an industrial carbon sequestration scheme, instituted over multiple years could have a crippling effect on the fishing industries, costing the world $225-240B USD per year [source], causing far worse environmental damage than the warming itself caused.
(To be clear, not all algal blooms are harmful, but so called harmful-algal blooms (HABs) would be impossible to screen as it would likely be the luck of the draw of what algae happened to be in the area of the fertilizer dump.)
That's not to mention that nobody is quite sure how long the carbon would stay in the ocean, or what effect sinking billions of tons of carbon into the ocean's carbonic acid cycle could have ocean currents.
Often algal blooms can prove deadly, killing fish. [Image Source: USGS]
And there are past studies that have suggested that algae sequestration is not even as effective as the current scheme suggests [1][2]. One potential problem -- in one past study, a swarm of shrimp ate the growing algal bloom, preventing it from fully capturing as much carbon as it could have unhindered.
All of these factors have lead to a UN moratorium on the controversial tactic.
So why is such a large team of researchers spending so much money to look into this potentially "killer cure"? That is not immediately clear, but the answer likely lies with the fact that current sequestration efforts have generally been so unaffordable and far-fetched that even the outlandish of ideas are receiving serious research consideration.
Sources: Nature, UN [via Nature]
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