Shellfish shell is
permanently solidified carbon dioxide
About half the mass of shellfish is shell, and shellfish-shell is solidified carbon dioxide. So far, just like wood. But, and here’s the advantage, shellfish shell is permanently solidified carbon dioxide. The carbon dioxide comes from the atmosphere and stays out of the atmosphere.
Intact shellfish shells
are excavated regularly from the middens associated with coastal
Palaeolithic communities (old Stone Age; from around 12,000 years ago).
Intact shellfish shells abound in deep-water cores of ancient coastal
sediments of hundreds of thousands of years ago. And remember the fossils
from deep geological time: brachiopods (550 million years ago), trilobites
(520 million years ago) and ammonites (240 to 65 million years ago).
Certainly, these fossil shells are changed considerably in chemistry by now,
but the shells did survive over geological time in order to be fossilised;
and in vast numbers. How much more permanent, do you want permanent to be?
What is aquaculture?
The Food and Agriculture
Organization of the United Nations Fisheries & Aquaculture Department
maintains a database of Global Aquaculture Production that contains
statistics on production volume. In this respect ‘Aquaculture’ is understood
to mean the farming of aquatic organisms including molluscs
and crustaceans. Farming implies some form of intervention in the rearing
process to enhance production, such as regular stocking, feeding, protection
from predators, etc. Farming also implies individual or corporate ownership
of the stock being cultivated. For statistical purposes aquatic organisms
which are exploitable by the public as a common property resource, with or
without appropriate licences, are the harvest of fisheries, not
aquaculture.
Data from FAO Fisheries and
Aquaculture Information and Statistics Branch (as of 25 May 2019) show that
over the years 2010 to 2017 aquaculture harvests across the globe totalled
53,512,850 metric tonnes of crustaceans and 122,527,372 metric tonnes
of molluscs (a combined total of 176,040,222 metric tonnes in 8
years.
If we assume that the shell
represents 50% of the animal’s mass, then the total shellfish-shell produced
was 88 million tonnes over 8 years; which is an
average of
11 million tonnes of shell per year.
Further assume that the shell is made from CaCO3; on a
molar mass basis, carbon represents 12% of the mass of calcium carbonate.
So, 11 million tonnes of shell per year is equivalent to
1.32 million tonnes of carbon
per year being captured from the atmosphere by current aquaculture
activities.
Could that be done?
If we doubled aquaculture
production of crustaceans and molluscs each year then in the 14th year we
could be removing 10.7 billion tonnes of carbon from the atmosphere each
year. Annual doubling may not be realistic; but this simple arithmetic
enables us to calculate that with determined effort to increase aquaculture
we could be permanently extracting significant amounts of carbon annually
from the atmosphere within the timescale envisaged for carbon capture by
trees.
If we’re willing to contemplate
planting a billion hectares of new forest trees, we should surely be willing
to create a few more mussel farms [imagine a mussel farm on every offshore
wind turbine, every oil and gas rig, every pier, wharf and jetty, every
breakwater or harbour wall].
The carbon balance of the
growth phase of the animals is not important. Nor do we need to harvest
them, though the animals within the shells could be a valuable source of
animal protein (with the profits from their sale providing ongoing finance
for further expansion). The most relevant fact though, is that when the
animal dies (either in the aquaculture farm or in your kitchen) it leaves
behind a shell made of insoluble carbonates constructed using CO2
(now permanently) removed from the atmosphere. The same considerations apply
to crabs and lobsters, freshwater shellfish, and land snails, though,
obviously, the cultivation techniques have to be tailored to each animal.
A realistic atmospheric
remediation programme might feature three prime targets
1. Fund a development
foundation that will invest cash immediately in every existing aquaculture
enterprise with the aim of doubling their production each season for the
next three seasons.
2. Fund research programmes to
study:
·
existing aquaculture farming methods to adapt
them to wider ranges of sites and locations;
·
new aquaculture farming methods to establish
new organisms and new methods to enhance incorporation of atmospheric carbon
into shells.
3. Fund developmental research
into high-technology programmes. Could we grow coccolithophore algae in
giant illuminated fermenters (maybe using the Quorn™ fermenters as a model)?
These marine algae make calcium carbonate wall plates. Perhaps we could
harvest from these fermenters a sludge of insoluble plates of calcium
carbonate from which we could build our own ‘white cliffs of Dover’. Using
this calcium carbonate as a feedstock for cement production would replace
the fossil limestone that is currently used to make quicklime (in 2014,
cement production accounted for 6% of the fossil CO2 emissions
from industrial sources).
We need a lot of funding and
the determination to do it. So, if there’s anyone out there with the odd
billion dollars to spare just let me know and I’ll get the programme rolling
… Now, then; would anyone like
another bowl of moules marinière; or maybe a crab salad?
[1]
Intergovernmental Panel on Climate Change (IPCC) 2018 Special Report
on the Impacts of Global Warming of 1.5
°C above Pre-Industrial Levels and Related Global Greenhouse Gas Emission
Pathways (https://www.ipcc.ch/sr15/).
[2]
Bastin, J.-F., Finegold, Y., Garcia, C., Mollicone, D., Rezende, M., Routh,
D., Zohner, C.M. & Crowther, T.W. (2019). The global tree restoration
potential. Science, 365: 76-79. DOI:
https://doi.org/10.1126/science.aax0848.
[3] Watling, R. & Harper, D.B. (1998). Chloromethane
production by wood-rotting fungi and an estimate of the global flux to the
atmosphere. Mycological Research, 102: 769-787.
DOI:
https://doi.org/10.1017/S0953756298006157.
[4]
Rinne-Garmston (Rinne), K.T., Peltoniemi, K.,
Chen, J., Peltoniemi, M., Fritze, H., Peltoniemi, M. & Mäkipää, R. (2019).
Carbon flux from decomposing wood and its dependency on temperature, wood N2
fixation rate, moisture and fungal composition in a Norway spruce forest.
Global Change Biology, 25: 1852-1867.
DOI:
https://doi.org/10.1111/gcb.14594.
I think we need to get
this idea registered in the consciousness of those involved in controlling
climate change. It deserves, at least, to be considered alongside plans to
expand tree planting on scarce agricultural land. About 71% of the Earth's
surface is covered with water. We should exploit that.
I’ve tried sending this
note to the scientific media, but none even replied. I’ve sent it to
academic journals and though they did reply (and one even described it as
‘intriguing’), none agreed to publish.
If you think this is an
idea worth pursuing, you could download a PDF version of this page and send
it to those you think might be interested; your MP, Congressman,
representative, conservation group or even your local multi-millionaire.
Tell them you found it on
David Moore’s World of Fungi website <http://www.davidmoore.org.uk/>
CLICK HERE TO DOWNLOAD A PDF-version OF THIS NOTE
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