Carbon on the half shell

A lighthearted look at biosequestration

Posted by Erik Hoffner (Guest Contributor) at 10:49 AM on 21 Feb 2008

Read more about: oceans | fishing | aquaculture | climate | carbon sequestration

A semi-recent issue of High Country News carried a feature on the deep-rock carbon sequestration potential in the northwestern U.S.: it's maybe possible to inject CO2 captured from power plants into the basalt that underlies the region, producing inert calcium carbonate. If so, there's apparently enough basalt to capture centuries of the region's carbon emissions.

It's safe to say the research has its doubters. And carbon sequestration in general deserves the hairy eyeball: even if proven both ecologically and geologically viable and economically feasible, if it leads to the continued destruction of Appalachia and vast tracts of the West for coal, count me out.

Elsewhere, a study's findings added to the body of evidence that shellfish, like clams, oysters, and mussels (oh, and plankton, crustaceans, and corals), will start growing more slowly or dissolving altogether due to anthropogenic ocean acidication (from all of the excess CO2 we produce that goes into oceanic solution), which would dissolve their shells. Fewer/smaller/weaker shellfish would have economic effects, but also much greater impacts on marine life: they're an important food source for everything from fish to whales and birds.

My point? These critters fix carbon ("biosequestration") in their shells, so we could start losing an important piece of the ocean's ability to maintain its natural alkalinity, plus its tendency to sequester carbon, just when they're most needed.

My disinterested and clear-eyed proposal, then, is increased aquaculture of mollusks in bays, sounds, estuaries, sloughs, etc. We're already growing tens of millions of pounds of clams alone each year in the U.S., and unlike most other forms of aquaculture, you don't get the massive energetic losses like with the feeding of fish meal to top-of-the-food-chain finfish.

Clams and company subsist on the soup of microscopic life that paddles by (and in coastal zones near metro areas or fertilizer-laden river mouths rich with an excess of "nutritious effluent," they'd clean the water of the frequent plankton blooms that can cause dead zones).

And if they're going to start growing more slowly in an acidic ocean, why, then we're going to have to start creating a lot more of them if we're going to witness the survival of such cultural rituals as the clambake.

Once harvested, the shells could be used to create additional ocean bottom substrate for those shellfish-like oysters that need hard surfaces to colonize. Even those folks opposed to eating the critters could understand growing them for ecosystem services alone, and their culture would also result in greater wild stocks of shellfish, due to the natural reproduction and subsequent reseeding of adjacent areas that commonly occurs near the farms.

Whether humanity can grow enough shellfish to slow climate destabilization is certainly a goofball question, but what could be more picturesque, or, um, tasty?

For story: Carbon on the half shell
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carbon in a half shell

Hello Erik

Not such a crazy idea. There is current research underway in parts of europe - Sweden is leading the way - on just this idea (carbon sequestration) and also on the ability of mussels (in the main as they are the easiest to grow) to act as bioremediators for excess nitrates and phosphates. There are limits of course - physical - as to where bivalves can be grown as there is indeed with everything but the idea is sound. If you want some references I can pass these on.
ta

by welsh heretic at 5:28 AM on 22 Feb 2008

spat

Here's a program that I ought to have mentioned in the original post: the Southold Program on Aquaculture Technology (SPAT) is training volunteers to culture oysters, scallops, and clams and grow them in floating racks in Peconic Bay on Long Island in NY...to help reseed the bay with mollusks.

http://www.spatcornell.org/

Hundreds of volunteer culturists have come thru the program at this point and some have started their own shellfish farms elsewhere in the Bay. Very cool.

Erik

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by Erik Hoffner at 4:49 PM on 24 Feb 2008

more info

Someone in the business of growing shellfish emailed me the following additional data which I edited down a bit - gives some interesting figures on the carbon sequestration abilities of shellfish:

Shellfish are very good at sequestering carbon - shell is about 13% carbon by weight and is resistant to decay unless exposed to strong acid.
...to sequester all of the excess CO2 being produced at todays rates...(it'd take) something like 14 trillion oysters. (we are growing about 53 billion on the east and gulf coasts today)
...not including wild (oysters) or (oysters grown in) canada or clams and came up with 53,321 metric tons of carbon being sequestered annually.
...shellfish aquaculture can be one of many solutions we need to incorporate in the process of fixing the (climate) problem.

And this is a hopeful note on ocean acidification:

As to whether the declining pH is going to be an issue.... I pray not. But as an oceanography grad student we were taught that the ocean's pH was one of those invariate numbers (except in small coastal pockets). The system was too large and had too much buffering capacity to ever move more than a fraction of a pH point. Like so much else I learned in school I am finding that these types of "truths" need to be reexamined in a fresh light. I expect that we are already seeing an impact on larvae in coastal waters. Their thin translucent shells are fragile and the ability of a microscopic larvae to fight a pH issue among all the other challenges they face may be one of the reasons why sets are on the decline in many areas.
If the fears are right and we start to impact the ability of shellfish (and more importantly microscopic foraminifera which are the basis for the chalk in the cliffs of Dover and elsewhere around the world) then I see a positive feedback loop where the failure of the environment to be able to naturally sequester tons of CO2 into shell actually accelerates the production of excess CO2 with disastrous impact. I just hope we run out of oil and coal before that happens.

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by Erik Hoffner at 9:27 AM on 06 Mar 2008

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