Why not CO2 Sequestration?
CO2, as the world's politicians are now learning, is a
GreenHouse Gas (GHG) that is now warming the world. Mostly, this is because we
are burning a lot of fossil fuels, which Gaia (or early life), locked up into
coals and oils, largely to keep the earth cool by taking the CO2 from the
For life to survive, at least life as we have come
to know it, we have to reduce the volumes of CO2 we release. Already, we
have increased the concentration of CO2 in our air from about 245 parts per
million to around 320 ppm, and all predictions suggest that, unless we do
something serious about it very soon it will reach 500ppm or much more within
the next century or so. As well as making the earth hotter - indeed, there are
fears that it could trigger a runaway effect that could make the earth as hot
and inert as Venus - this may well have an impact on us and on the life with whom we share the planet. We live our whole lives immersed
in the only atmosphere we have, and it has changed a lot from what our
ancestors (even perhaps our grandparents) were used to.
This is what Kyoto is about. Building a set of international laws that help
us all, fairly and honestly, limit the CO2 we form and release.
We can, of course, try and capture CO2 and lock
it up where it does no harm to the atmosphere - the sequestration route. And
there are ways of doing this:
Trees, or other biomass. Of course, this idea is not new, as
Gaia did a lot of this during Carboniferous times. And growing trees is
undoubtedly a Good Thing. But we do not yet know how to convert trees into
the dense solid, material we recognise as
coal that can be safely locked away for the many millennia it has already
existed. So it is undoubtedly better not to destroy coal, rather than to
burn coal and try to make it again from growing trees.
CO2 itself. The
general principle is that we take the coal (or oil or gas), burn it and
extract the energy (probably in a most fantastically inefficient way),
remove the CO2 from the combustion products, and put this CO2
back where it came from.
The trouble is that nobody has found a way of
doing this safely. The establishment (scientific, political, industrial)
seems to believe this can be done safely, by pumping the CO2, at very
high pressures, back into the reservoirs from which we have extracted oil.
Indeed, there are various projects, to try this out, and there are many
reservoirs which do this to push more of the oil out of the reservoir, so
called Enhanced Oil Recovery, or EOR. So there are old oil reservoirs which
hold many millions of tons of CO2, and have done so for several years, even decades.
The Air Pollution and Climate Secretariat (www.airclim.org)
has done a more thorough job of documenting the Carbon Capture and Storage
(CCS) than I can, and an excellent report is available from them (Last
gasp of the coal industry).
Let us have a little thought experiment: What
happens when this CO2 escapes. For us in the UK it is perhaps most helpful to think if this as happening
under the North Sea.
CO2 might escape slowly. So it will leak out, perhaps through some complex
and slow route of porous rocks. So long as there is no life that gets
suffocated on this route from reservoir to atmosphere, no great harm is
done, although, of course, there is no benefit to the atmosphere, which
ends up with the CO2 we tried to hide.
CO2 may escape fast, in some sort of catastrophic release lasting,
perhaps, a few days. Given the huge pressures under which it would be
stored, and the likely rapid corrosion of any leakage hole, this seems
more plausible. An earthquake would be very good at opening such holes.
Before going into further detail of this scenario,
let us review some things known about CO2:
suffocates us. Too much CO2 in our air prevents us benefiting from
breathing, and kills us quite quickly. It also kills all animal life.
is heavier than air. Brewers learn early in their careers (or not at all)
not to lean too far into a vat of fermenting brew, or it could suffocate
these two together, and what happened around Lake Enyos
is one of the first warning we have had (at least that we know about). This
incident killed some 1700 people, but there have been others since.
Now let us consider the North Sea:
rumour of dead fish floating is the sea,
but a fishing boat heading that way falls mysteriously silent.
Sea Rescue Helicopter approaches the vessel, reports some sea foam, but
also falls silent and crashes. Remember that virtually all our power
sources depend on combustion that will be suffocated by high
concentrations of CO2.
ship approaching a patch of foamy water sinks. Bubbles in the water lower
its density, so less can float in it. So a ship would suddenly find it was
floating on air, and would sink.
CO2 will, of course, be cold from expansion, enhancing
its natural tendency to spread at low level. With luck, it might freeze a
patch of sea for a while. At this point, there is virtually nothing that
anybody can do except estimate what will happen. No planes can fly close.
How quickly will the small leak grow, considering the huge pressures
involved? Which way will the wind send the cloud? How much CO2
will escape? We could be in the position of the designer of the Titanic,
able to calculate only how long we have left?
the cloud headed for London, there is no possibility of evacuating the population
in time. It could take less than 12 hours to reach the capital. But it
might head for Norway or Scotland.
One of the most disturbing aspects of this
scenario is that it never goes away. Unlike radiation, the CO2 stored
underground has no half life. It does not become less risky as time passes. It
is there until it escapes.
So I do not find this an
attractive way to obtain our energy, and wish to see these risks (or future
recognised by those contemplating the actions
that lead to them. Hence
this collection of information, and its release to the Web.
Fortunately, we do have time before this becomes
commercially attractive. Unfortunately this is because the price of CO2 is
ridiculously low, at about €20 per ton, and the costs of putting the CO2 back are
far higher than that. So let us use this opportunity to prevent this ever
Here are some links to relevant resources.
On Enhanced Oil Recovery
Updated 26th December 2008
Page Version 0.6,
First released draft. 8th November 2002