Water on the Rocks
Many forms of
thirst
How much fresh
water would we need?
Why the poles?
Some Practical
Problems
Tote that Berg!
Let's think bigger…
What is so special
about towing?
What Sort of Vessel
Suits Such Payloads?
Why ice?
Ice harvesting,
limited supplies, and Carbon Dioxide
Ice as fuel
Ice types and
harvesting strategies
The big lumps
Deliver ice or
water?
Why icebergs at
all?
Why not make ice
instead of collecting it?
Chill as fuel
Why not pipe ice
instead of shipping it?
Brack, schmack!
Ecological impacts of
ice harvesting
And when there is
no more ice?
Ice,
Infrastructure, and Commitment
You should not see the desert simply as
some faraway place of little rain.
There are many forms of thirst.
William Langewiesche, Sahara Unveiled
Many an
old idea originally seen as impossible, unpractical, or stupidly cranky, has
become first possible, then obvious, then vitally, routinely, necessary. This
has happened repeatedly throughout history and a good deal of prehistory, but
as a trend it became especially obvious roughly at the time of the so-called
industrial revolution. Significantly, the drive variously to ballyhoo or
dismiss, disparage, and destroy novel advances remains as compulsive as ever.
Nearly
every genuine advance, whether based on old ideas or new, encounters greater
difficulties than expected, but also becomes more valuable in more contexts
than expected.
And
some are more vital than expected.
The
idea of exploiting the planet's largest resources of fresh water, namely our
great ice sheets, has been bruited and mocked for perhaps a century, but though
it repeatedly has been dismissed as stupidly unrealistic, the simple fact is
that it is unavoidable. We will be doing it, like it or lump it, on a scale
hardly imagined by either proponent or opponent. People will make and lose
fortunes, people will die of it, and people will make livings from it as
routinely as sailors sail and technicians build and tend wind turbines and
high-tension lines.
The
question is whether we will establish an effective industry before we suffer
serious global harm. History does not forbid us to hope, but it offers little
positive reassurance.
For
practical purposes this discussion ignores the harvesting of sea ice and
glacial ice for the sake of luxury, fashion, science, or whim. It deals with the older, more prosaic, more
visionary, idea of harvesting utility or irrigation water in bulk from sub-polar
masses such as sea ice and icebergs. It emphatically does not suggest, I find it necessary to repeat at intervals,
the towing of icebergs to where fresh water is needed. The idea of towing
icebergs is so rooted in public fancy, that there is a tendency for readers to
assume that it is necessarily the only option. That idea however, is grossly
unpractical, for reasons that I wearily mention at several points, and
that I reject accordingly.
As a
serious suggestion the idea of iceberg corralling and towing dates back to at
least the first half of the 20th century, and it has met with
understandable derision ever since. It
certainly is no part of what I propose in this essay.
However, my main reasons for rejection of the idea have to do with the nature
of current needs for fresh water, and realities concerning its accessibility,
its collection, its transport, and its processing. In part, the original
reasons for rejection were firstly, that the bulk requirement for water in
those days was smaller and less globally urgent, particularly among populations
that had the resources and skills to contemplate such giant projects. And most
nations had nothing of the type.
The
very ideas that visionaries espoused for towing icebergs, genuinely were
non-viable.
Also,
until recently the very idea of a major city running dry seemed ludicrous and
therefore could be ignored; parched third-world villages were irrelevant,
largely because of their impotence. They
still look irrelevant, and still largely because of their impotence. The poor
in their local drought-stricken valleys or villages we have had with us always
and we see no prospect of their disappearing.
What is
more, before the last twenty years or so of the 20th century the
necessary technology for marine ice collection was not at a level that encouraged
private enterprise to harvest ice for water; our shortcomings in the
undeveloped technology for such purposes still are something of a challenge.
Another
reason has been, and still is, our lack of any currently adequate
infrastructure; one does not go out on a whim to collect billions of tonnes of
water and transport them thousands of kilometres, simply relying on the
principle of: "what could possibly go wrong?"
Well,
what could?
Scale
for one thing: whenever one tackles new technology on such a scale, we simply know
that plenty can go wrong, and probably will, and what goes wrong worst generally
will not be the parts that we had predicted.
And in
this case, the sheer scale of any viable project of that type beggars the
imagination of Joe Average and Percy Politician, and so does the variety of
obstacles to overcome; if so much as the thought is to be worth while we
must think in terms of delivering, not millions, but billions of tonnes, not
annually, but pretty nearly daily.
Still,
the times they are a-changin' and by now it is a matter of religious conviction
that climate is a-changin' with them; and climate stable or climate unstable,
human populations are growing and water resources are shrinking.
It no
longer is too early to think once more of harvesting ocean water and ice. Few
people realise how unstable climate really is, even without modern human
culpability. Before our "industrial revolution" of the last three
centuries or so, at least a dozen "civilisations", or at any rate
established urban communities, were ruined or dispersed by droughts that lasted
for decades or centuries.
Collapses
of that type have happened on every major land mass where cities of any sort
existed. The biblical seven lean years were altogether believable as a very
mild instance. The very Sahara as we know it,
ancient and dreadful as it seems to us, is a relatively young desert, largely
having been savanna just a few thousand years ago. It was so recent a
development that apparently a few immemorial Atlas cedars still survive where
rare underground water sources happen to have sustained them.
Nowadays
the idea of letting a large modern city die of thirst is practically
inconceivable, so it is pretty certain that some drastic modern technological
and infrastructural advance must be developed to supply the water they need, no
matter how ridiculous such measures seemed in quite recent past. Certainly desalination with even greater
sophistication and efficiency than what we can manage at the moment will be one
of our necessary objectives. Just a few decades ago our current desalination
technology would have seemed miraculous. Improved reticulation and
redistribution of fresh water already is a must. Gathering and recycling fresh
water from as yet unexploited sources will be vitally necessary. Greater efficiency in agricultural irrigation is long overdue, as agriculture in Israel has demonstrated dramatically.
Various
possibilities often complement each other, for instance desalination works best
when the input water is at most slightly impure, brackish, such as one might be
able to gather from estuaries or from sea ice, rather than unacceptably saline.
One way or another though, we need to explore and develop as many
sources of sufficiently fresh water as we can, if only because different solutions are necessary for different purposes in different circumstances and different regions.
And we
have the thirsty with us always.
Discussion
of the potential technologies that I propose here were inspired by a drastic
drought where I live in South Africa, though it is far too late for immediate
application of this idea to that drought, and it probably is too early to take
the ideas seriously at the time of writing. Anyway, we have had droughts
before.
But
never droughts that so threatened modern cities, and with every prospect of more and worse threats in future, anthropogenic
global warming or no anthropogenic global warming.
And one
must start somewhere.
How
much fresh water would we need?
Think of a number…
We
consume a lot of water already, domestic, industrial, and agricultural. No one
knows just how much, but it definitely is beyond the untrained imagination; in
fact I suspect that even the trained imagination manages only on the principle
of "shut up and calculate". People in the know cannot afford to
let themselves be distracted by the boggling of their minds in the face of
realities. To begin now would be none too soon for rationality, though far too
soon for the politicians and business powers that be.
A rough
guesstimate at current global human consumption might be four teratonnes: four
million million tonnes of fresh water — per year.
That
alone is nearly as much as the entire flow of the Amazon
River. It amounts to a few thousand cubic kilometres, and our rate
of consumption is not decreasing; in fact many millions of people, from pole to
equator, remain frantic for fresh
water all their lives, and their demands for entitlement grow hoarser
with anguish as the ages roll, and their desperation and rage grow similarly.
In our
calculation or planning in this discussion we may ignore those desperate
people; they cannot afford to do much about their situation, so a more
practical beginning would be to provide a few billion extra tonnes of water per
year for the typical large, affluent metropolitan region. A billion tonnes of water occupy about one
cubic kilometre, just one large drop in the global bucket.
However even that drop
is beyond the imagination of most people, and what is more important, the necessary
scale of the engineering is far beyond the imagination of Jane or Joe
Average, who seem to think that all you need to do to get all the water you
want, is to install a tap.
Or,
more likely, hope someone else will install it.
It
would be funny if it were not so infuriatingly tragic: even more tragic than
thirst.
Unless
you happen to be really, urgently, thirsty.
Bulk
water engineering and the design of new bulk water handling technology are not
for amateurs; we already get water from many sources that Joe Average hardly
dreams of. And if he did dream of it, he would be grateful to forget the dream
on awakening. Most of us don't even realise that we get a lot of our water from
underground, let alone from sewage — when there is enough sewage, which there
generally is not. Not many people realise that many of our underground water
sources are limited; using them amounts to mining of water that in many places
has accumulated over thousands of years or many times longer, and replacing it
with salt water.
Such
supplies eventually peter out when the water mine is exhausted, or is ruined by
damage to geological formations that hold it. Or it may get polluted, in which
case it may be very, very hard to clean it.
Many
people also don't realise that much underground water is unusably salty, often
saltier than seawater, and that when rainwater percolates through to such salty
groundwater, it commonly becomes unusably salty in turn.
So
don't look to underground water for indefinite supplies, unless you happen to
live in a blessed region where rainfall comfortably replenishes your clean
water mine indefinitely and you can hope that it will continue to do so.
And
dammed water, say from giant schemes like the Three Gorges dams, not only is in
itself a limited resource at any given time, but is wanted for more than
relieving drought; apart from producing potable water, it has to produce power
and support transport. Such applications are not fully compatible; and they
compete more and more severely as the water reserves run lower.
Not to
mention that dams too, have ecological impacts, not all of them favourable.
So
don't get too optimistic. We already have seen the mighty Colorado River
reduced to a polluted trickle; the Nile is
threatened by each of the many countries it passes through...
Watch
this space; even the Amazon and Congo
are not infinite...
Why
the poles?
We must always remember with
gratitude and admiration the first sailors
who steered their vessels through storms and mists,
and increased our knowledge of the lands of ice in the South.
Roald Amundsen
In the
sea we have more water than we can use, though not more than we can pollute;
and our planet-wide problem is not a shortage of water as water, but how to
separate the water from the salt. The sun provides the planet's largest still,
purifiers, and condensers, but only a fraction of the usable water goes to
where we want it on land, in rivers, and in lakes. Even less ends up where we
can use it for domestic and industrial purposes.
To add
injury to insult, the condensed water often arrives in the form of floods,
always wasteful, commonly harmful, and often deadly.
And
most of what we do receive on land soon flows uselessly back into the ocean,
where it once again is lost, carrying valuable soil and nutrients with it. And
pollutants.
What
drives that cycle is the fact that the sun heats the water, evaporating it.
Sooner or later the vapour cools till it condenses or freezes. To use the water, we must intercept it at
suitable stages between salt and salt. Not to mention other pollutants. Some of
this interception is easy — waiting for
rain for example, but by ignoring some of the more difficult options, we lose a
great deal of water that otherwise could have been useful.
On this
planet some of the largest and most dramatic regions of accumulation of fresh
water are sub-polar. That is where warm air from temperate and tropical regions
meets cold air, and dumps its water burden as ice in various forms. More
importantly, sub-polar regions also are where seawater freezes.
As it
freezes it more or less abruptly extrudes brine from between crystals of pure
ice.
These
regions are remote from where most people live and work, and in those regions
ice in large masses is largely in unfriendly forms. Accordingly we have paid
them little attention as sources of fresh water.
But
that must change.
Just as
we have been grubbing for oil in ever more incredibly difficult circumstances
in recent decades, so we shall need to look at sourcing water from the more
challenging, but more rewarding, less ecologically harmful, sources.
Almost
amusingly, we can reflect that within remote living memory, before
refrigerators were standard household appliances of the affluent, the seasonal
harvesting of ice was a major industry in regions such as much of North America
and parts of Europe; entrepreneurs would cut
blocks from frozen lakes or the like. They would warehouse those blocks, and
during summer they would transport the ice to major cities such as New York. For decades in
such cities the iceman was as familiar a figure of the everyday infrastructure,
as the milkman. Domestic ice boxes were designed to hold standard-sized blocks,
and a suitably insulated block might keep food fresh for perhaps a week or
more.
Extravagant
people even made ice cream, producing the necessary sub-zero refrigeration by
adding salt to crushed ice. The ice pick was such a standard household utensil
that it figured in many murder mysteries. In real life even Leon Trotsky was
reported murdered with one, though technically in his case it was an ice axe,
and Trotsky himself never was reported to have insisted on the distinction.
Anyway,
the sub-polar regions are textbook examples of where there is plenty of fresh
ice at all seasons. It just happens to be regrettably inconvenient to collect
and transport the permanent ice and convert it into usable form where it would
be most welcome.
Oil and
gold they say, are where you find them, and the places where you find ice in
paying quantities, quantities large enough to slake the thirsts and cool the
fevers of cities and nations, are places where you find cold.
For
example in sub-polar regions.
Nor is
that all; cold is not only where you can find
ice, it is where you can make ice.
Surprise.
So what
are you waiting for? Fetch!
But the
question of what to do with your ice once you have found it or made it, leaves
you with whole ranges of problems. As I shall point out, the fact that there
might be problems does not prove that ice is not worth finding, but it
certainly means that we cannot expect half-baked ideas to solve all those
problems. We shall have to work hard to
learn what to do with what we gain.
Some
Practical Problems
The secret fountains to follow up, waters
withdrawn to restore to the mouth,
And gather the floods as in a cup, and pour them again at a city's drouth
Rudyard Kipling, The Sons of Martha
Among all the practical problems we consider, we might as well start
with the sheer scale of the need and the supply. Just moving the equivalent of
a supertanker of fresh water is no joke. Let’s suppose it carries half a
million tonnes — nothing special when one is carrying only water; convenient
dimensions for a full load might be something like 420m long, 60m wide by 20m
high. Nothing special, as I said: barely six stories high; you could hardly get
four football fields on top of it and you could walk round it in less than 15
minutes.
Now, if you really think that is nothing special, try lifting or
dragging a single cubic metre of ice. Try freezing or melting it. If you use a
crane, see what it does if you drop the block or bash it accidentally. Tonne
masses are big and unwieldy, but million-tonne masses of ice are unbelievably
worse. Try standing by a twenty-metre ice cliff (which would be very modest;
Antarctic ice shelves rise some 50m above the sea surface, and extend about 450
below). Then try to imagine how you should go about loading that into your
tanker or dracone. (If you need to know about dracones, look up "dracone barge" on
Wikipedia at https://en.wikipedia.org/wiki/Dracone_Barge
.)
Simple to load? Just scoop out the ice with mechanised giant ice cream
scoops?
Not really so simple.
Cold ice is quite a strong material, and the rate at which you would
have to scoop it would be mind-numbing if you were to stop to think how much
you would have to move to make it worth while; remember that to be worth
collecting, water must be cheap and plentiful, and we need to think in terms of
at least hundreds of thousands of tonnes per load, not single tonnes.
Millions would be more like it. And even "warm" ice — ice that is almost
warm enough to melt — is a lot harder
than ice cream.
And ice cliffs tens of metres high are shockingly treacherous,
especially when warm. You can't just park next to them with your bulk carrier
and start loading; you and your ship could be kilometres under the sea,
crushed, your bones being picked over by hagfish shortly after the first
unexpected calving dumps a hundred thousand tonnes of ice on you.
And if you think that towing a cargo of realistic size is a doddle once
you have it loaded on a barge or in a dracone, forget it. Ocean-going tug work
is some of the toughest and most hazardous on the water. It also is expensive.
And slow. For towing any mass of the order of a large cargo vessel the hawsers
are huge and may be kilometres long, deliberately being dragged through the
water to prevent disastrous consequences if one breaks, which even giant
hawsers quite easily do if there is a sudden change in tension.
Well then, instead of towing, why not load up ice into your tanker and
speed directly up to the customer city?
Also not as easy as it sounds. What do you do with your ice when you
arrive? Unloading will need to be fast if you don't want to go bankrupt with
your ship in port, and you will need to park your payload somewhere practical
as you unload it. If you want to melt it, that will take huge energy, and even
if it had melted en route you would need pumping machinery of huge capacity to
deliver it to your reservoirs. And reservoirs cost money too. And not just any
harbour can accommodate large bulk carriers.
Might as well give up. Just sit in the corner and cry about how unfair
it all is.
Actually all these problems have solutions, some more promising than
others. I shall discuss some of them, but all will need proper engineering and
proper economic consideration before they deliver anything.
And they won't be cheap either. We will have to learn to live with water
that doesn't grow in the pipes, water that costs money — more money than we
have been used to paying.
Tote
that Berg!
And one who licks his lips for thirst with
fevered eyes shall face in fear
The palms that wave, the streams that burst, his last mirage, Caravan !
And one — the bird-voiced Singing-man — shall fall behind thee. Caravan !
And God shall meet him in the night, and he shall sing as best he can.
James Elroy Flecker Song of the East
Gate Warden
The traditional scheme for farming ice, was to cut slabs out of
surface-frozen lakes, and some of that still gets done, but it is not an approach
of much interest to our topic. It has nothing to do with transporting water to
places that need it in quantities that could quench the thirst of cities and
agriculture. Its very objective is not the same; those people who used cut ice
to sell, sold it as ice, not as water.
The needs they met were real needs, and they met them respectably, but
they are not the needs that we are confronting here and now.
We really want to deal with sources that could in principle produce
billions of tonnes annually, sustainably and without serious harm to the
environment; preferably even helping to conserve the environment. And we might
be more interested in water than ice as such. As a matter of fact, that
distinction is open to consideration, as we shall see, but we must bear it in
mind.
The earliest proposals for exploiting sea ice were to tow icebergs to
places like Arabia. It was the obvious option,
but hopelessly unpractical. Only small icebergs are towable, and they have
inconvenient shapes and their behaviour under tow is very, very bad: they
topple and yaw and split and all that. Also, they cannot be towed quickly, and
not only do they melt continuously en route anyway, but moving them through the
water really melts them quickly. To
get some idea of how quickly, treat
yourself to a soda containing a few sizable ice cubes. Select a well-behaved
cube, push it under the surface with a drinking straw and gently suck up the
liquid so that it must pass over the ice on the way into the straw. Within just
a few seconds you will erode a hollow, and in less than a minute you can melt a
hollow so deep that the cube can't slip away and you can drink freely. Pretty
soon you can become adept enough to drill holes through more than one cube per
glass of soda.
Now imagine what liquid seawater would do to any mass of ice passing
through it day after day and week after week, such as would be necessary to
deliver the ice for thousands of kilometres.
This is not my personal fancy, please note; people have experimented.
The idea is a non-starter.
In summary, most regions in need of water, let alone in need of ice, are
hopelessly too far from any realistic route to be served by towing icebergs.
But that was the good news. Even if you could arrive off Rabat or Beirut or Kuwait with
your modest little million-tonne ice cube, a hundred metres high and wide, what
now? Could you pipe it ashore before it all melted? Even if you could lift it
out of the water and dump it on land, how would that get it into the water
supply?Such practical problems are unending. Not that they aren't soluble in
principle, but in practice many of them simply are not worth solving.
Especially because, as I explained, a million tonnes of water is just a
sip; you would have to keep the sips coming pretty fast if the infrastructure
is at all to be worth developing.
Let's
think bigger…
Ocean-going tugboats are built for two purposes: to tow huge inanimate
objects across the ocean at a snail's pace or to slam ahead at full speed into
the teeth of a gale to come to the assistance of a vessel in distress. Of the
two, it is hard to say which is the most exciting. Personally, I found the long
slow trips towing a dry-dock, a dredger or even a whole factory in the shape of
a tin-dredger, a more exacting experience than the salvage business. For,
during the long trips, the officer of the watch develops a tendency to gaze
astern instead of ahead, which he will find a difficult habit to lose. When,
later, he is on watch on any other ship's bridge, pacing up and down at the
comfortable walking speed that is the secret of relaxation, he will often
experience a sinking feeling in the pit of his stomach on seeing the empty
wake.
Jan de Hartog A Sailor's Life
The water from a billion-tonne iceberg would represent a significant
addition to the water supply of even the largest city, but in every way would
represent a challenge, both at the source and at the point of delivery...
Now, there are other approaches to towing icebergs, really large ones, in
particular tabular bergs from the Antarctic, but all of them present problems
of their own. The process would be difficult and so slow that precious little
of the payload would get anywhere useful. It has been suggested that by
sticking to cold currents such as the Benguela, that move from sub-polar to
sub-tropical seas, we could improve the parameters.
True.
We certainly would be fools not to take advantage of such natural aids,
but all the same, that is not nearly sufficient on its own. Even the coldest
currents would not be cold enough to prevent ice from melting, especially when
it is being towed through salt water, and as it approaches regions where the
water is wanted, the air temperature would rise dramatically, causing faster
melting above water level.
The natural lifespan of a large tabular berg in sub-polar water, if it
has a mean diameter of some kilometres, is a few years. That is too short for
towing even if towing were practical, and what is more, if we put everything we
had into towing it, its lifespan generally would drop to less than a year. We
would be putting all that effort into re-dissolving nearly all that lovely
fresh water back into the sea instead of delivering it to a thirsty land.
Not attractive.
We could improve the balance sheet dramatically by coating the underside
of the berg with sheets of plastic, using automated, remote control underwater
craft, but the sheer scale of the effort would be sobering. For a comfortably
sized chunk of floating shelf, say some ten kilometres across, we would need
over 100 square kilometres of plastic material.
That is not in itself an unrealistic investment in material, but as an
engineering feat it would be astounding. Designing the jacket to survive the
trip long enough would be a serious challenge in itself; wave erosion and
impact are shockingly powerful forces. Recovering the material afterwards, or
ensuring that it would recycle harmlessly into the ocean in the form of
innocuous fish food, would also be demanding.
Amylose film rather than non-biodegradable plastic jacketing might do
the trick, but I am not sure that any realistic plastic jacketing would last
well enough on the business leg of the trip. At present amylose certainly would
be too costly, though one never knows...
Still, it does open tempting lines of thought. We might return...
...
And returning, I find that I forgot about Pykrete. (If that is an
unfamiliar term, read the description at: https://en.wikipedia.org/wiki/Pykrete
). In short, Pykrete is a form of ice of increased structural strength and
resistance to melting, imparted by incorporating small percentages of wood pulp
or similar fibre. Pykrete can be created at sea by spraying doped water under
freezing conditions. A freshwater iceberg, or a sufficiently large slab or
cylinder of ice could be protected by Pycrete, though the technical problems of
achieving even coverage might prove to be prohibitive.
Alternatively, fresh water ice, stored and handled as Pykrete, or jacketed
with it, might be stronger, safer, and more durable to handle, sufficiently so
to justify its use.
Please note that in this topic, I am strictly handwaving. I not only
lack detailed proposals for the practicality of Pykrete projects, but even lack
clear applications. But wherever, in sub-polar regions, one is thinking of
coating objects with foreign materials such as plastic, it might be worth
pausing to consider Pykrete as an option.
On melting at the point of use of the delivered ice, the fibre would be
simple to filter out and recycle for preparation and retrieval of the next
load.
What
is so special about towing?
We need to quit arguing about
whether the glass is half full or half empty — and instead
acknowledge that there's not quite
enough water to go around.
Kate Brown
When you come down to it, the idea of towing icebergs is naïve. Towing
them certainly does save all sorts of complications and ships, with no problems
other than the loss of practically all your payload and the need for special
facilities at the delivery end.
With problems like that, who needs droughts and disasters?
Well then, that doesn't sound encouraging, but do we have alternatives?
Yes.
To begin with, two forms of alternatives at least.
Firstly we could collect the water at the source (meaning mainly ice
shelves in Antarctica, and glacier calving areas in the Arctic),
and leave the floating bergs to the suckers.
Alternatively we could let a berg drift as it pleases, but begin by selecting
masses suitably situated for currents and winds to deliver them efficiently; we
then could proceed to parasitise them while they travel, benefiting from the
distance that they drifted spontaneously. To do that we could accompany them
with ships and equipment with which we could carve them up or speed up their
melting.
What would that achieve?
To begin with, any payload that we could get on board a suitably
designed ship or barge, no matter how slow and cheap that ship might be, we
could move much faster and more efficiently than would be possible by towing
the berg, and the ship could be far less dependent on wind or current. Once ice
or water were loaded aboard, it could be delivered almost loss-free, without
any specially urgent race against melting into the sea.
We also would need no more infrastructure at the discharge end than
pumping and storage facilities. No magic iceberg-handling would be necessary.
If the payload were conveyed by dracone, it wouldn't matter whether much of the
ice had remained unmelted or not; the towing vessel simply could deliver the
dracone as temporary storage along with the water it contained. After
delivering the dracone, the ship could prepare for the next voyage and leave
with empty dracones as soon as refuelling etc were complete, generally even
before unloading the payload had begun.
In short, no towing of any iceberg would offer any attraction unless
there were reason for positioning or rotating a berg. For example, a berg in a
region of water too cold to encourage melting as required, might be towed, or
at least nudged, towards warmer water, or if selective freezing were required,
to colder.
What
Sort of Vessel Suits Such Payloads?
We forget that the water cycle
and the life cycle are one.
Jacques Yves Cousteau
Especially in the early days of gaining experience with polar water
transport, we could experiment with second-hand tankers or tugs, but as
experience accumulated, we might consider designing dedicated vessels for any
of at least three options, all of them on a very large scale.
Buoyancy should not be a serious problem, because fresh water floats on
seawater, and so does ice. Nor does fresh water in trivial quantities such as a
few trillion tonnes pose any significant pollution risk even if spilt
wholesale. So, laden or not, neither sinking nor pollution should pose any
special risk.
Dracones, giant sausage-like balloons containing thousands to hundreds
of thousands of tonnes of fresh water or ice, have certain attractions. The
filled dracones could be connected in chains many kilometres long, and towed by
tugs. This is no novelty; dracones have been used in similar ways for other
types of cargo for many years, though on smaller scales. They have many
advantages in flexibility and low overheads. This approach could solve the
storage problem at the port of delivery, and also problems of necessary delays
for melting residual ice so that it could be pumped ashore after docking; once
delivered and secured, a dracone could be left behind for as long as desired,
while the towing vessel immediately proceeded with its next task.
All the same, towing of any gigantic load of liquid in any form probably
would be slower and more costly in energy than conveying the same load in a
rigid vessel. It is not clear for example, whether large fluid-carrying
dracones should contain internal baffles to control resonant internal sloshing,
or whether they should have exterior contours or appendages to improve control
and attitude in the water. Possibly some sort of resonantly contracting design
of concertina-like dracone would be specially efficiently towable through
water, but that remains to be demonstrated, and the dynamics almost certainly
would be complex. The practicalities and economics would have to be assessed in
each context.
There would be a need to shuttle empty dracones, and to design a dracone
that is manageable both when very full and nearly empty might prove to be a
non-trivial problem. Especially if it needs to be loadable either with mainly
ice, or mainly water, or slurry. There are options for concertina designs or
smooth, for example, and designs with various forms of symmetry. They have
implications for working life, scale, streamlining, tendency to capsize or
twist, or whether the difficulties with loading, unloading, dragging line
astern or in bunches are acceptable.
Considerations of that type need not be insuperable, but nor can the
design implications be dismissed as trivial.
The design of tankers for carrying massive cargoes of fresh water and
ice should be simpler than the design of dracones, but they still open several
lines of approach. They could differ from any previous designs of supertankers
in several ways. Unlike the largest of oil supertankers, they would demand little
precaution against pollution, because only the ship's fuel would be a serious
hazard, not the cargo. A few million tonnes of fresh water spilt into the open
sea would be a major monetary loss, but no more of an ecological disaster than
a heavy rainstorm at sea. Accordingly, double-walled construction and similar
precautions regarded as necessary for an oil tanker, need not be considered
unless it were thought worth the extra expense and weight to reduce the risk of
loss of the vessel.
Again, the size of the ship need not be limited by anything other than
the available facilities at the designated ports of delivery and the hazards at
the points of collection. In contrast to oil tankers, freshwater tankers or
tanker barges, carrying volumes exceeding a million tonnes, could be routine.
In fact they would have to be routine; we need water in vastly greater volumes
than we use oil. And we use oil in staggering quantities. The very nature of
the cargo and market would rapidly dictate new designs of vessels to accommodate
water cargo, whether liquid or ice.
Any baffles, separated tanks, cargo containers, and leakage protection
within ships designed for carrying water or ice would be matters of detailed
design, rather than basic problems.
Whether they would be considered practical at all would be open to
question, especially if their cargoes were mainly solid ice. Such vessels might
be very efficient in transport and collection, but they might take months to
unload, so they would be major liabilities in harbour.
Accordingly a third option would be comparatively attractive: giant
barges. In essence they would amount to the equivalent of the tankers,
except that they would largely be unpowered except possibly for manoeuvring,
pumping, and crew accommodation. They variously might be manned or unmanned.
Depending on their design they might or might not be connected in strings or in
parallel for towing, and they might be used for storage as well as transport.
If intended to store ice rather than water, they might be insulated, but
independently of such considerations, they ideally should be very, very large,
much like the powered tankers, only probably even larger. Maybe tens of
millions of tonnes deadweight rather than hundreds of thousands of tonnes.
The advantages of each option would depend on the nature of the
collection mechanism. For example, parking a quarter-million-tonne ship or
barge anywhere near an iceberg or ice cliff, or even aggressive sea ice, might
be suicidal. It might prove more practical to collect the ice or water with
fleets of small foraging and loading vessels that capture it and process it
before passing it on to the transport vessels.
Another factor is the cost of parking a vessel for months while it is
being unloaded or waiting its turn to be unloaded. Proportionately, parking a
special-function multi-million-tonne barge or dracone should demand a lot less
overhead than parking a fully functional, smaller vessel.
People say that if you find
water rising up to your ankle,
that's the time to do something about it,
not when it's around your neck.
Chinua Achebe
Ice has all sorts of disadvantages compared to water — harder to load,
less dense, further to fetch, needing heat to make it usable, dangerous in
large masses, melts inconveniently, can't be piped or pumped — the list goes
on.
But some of those just can't be helped; if fresh water simply were
available in any desired quantity wherever wanted we certainly would not
consider prospecting for it in the form of far-off ice. As fresh water is
increasingly at a premium however, or simply is unavailable in many places, we
must go out of our way to get more, or we might as well stop moaning.
And from a different perspective some of the supply problems look more
like opportunities.
Harder to load? Well, in some circumstances ice certainly is not easy to
load; it is harder than efficient pumping of liquid water. All the same, as we
shall discuss, suitable preparation and equipment can be developed for
collecting sea ice, crushed ice, and slabs of ice. We still shall have to
develop a lot of infrastructure and technology, but developing infrastructure
and technology is necessary for exploiting any large-scale new opportunity.
And once properly loaded, ice can't slosh about and endanger the tanker;
sloshing can be quite a problem with liquid cargoes. Sloshing is a deadly — and
costly — problem with giant ore carriers for example, in which either slurries,
or even powders, slosh about and capsize the vessel. It is not exactly an
everyday problem, but not rare either; world-wide, as far as I can make out,
there is roughly one such event annually.
Dangerous in large masses? Too true; ice certainly is terrifyingly dangerous, and dangerous in various ways too, but
liquid water in large masses is no less terrifyingly dangerous — and dangerous
in various ways too. Each needs its own techniques and precautions — there is
no value to whingeing about it; buckle down and earn your winnings.
Less dense? Meaning that your ship can't hold so much? But that also
means greater buoyancy, which means that the larger storage or transport ship
or barge may cost no more to build than a ship designed to carry the same mass
of water. And the stiffness of a mass of ice can be exploited to reinforce a
suitably designed ship rather than decreasing its stability the way that
sloshing liquid or slush would.
And the lower density means that it can burst pipes when it freezes? True, but
that is more of a problem in buildings on land than ice freighters at sea.
Routine problems like that are easily dealt with after the first few sinkings
have taught us the first few lessons.
Further to fetch? How sad. But that only is true when nearby fresh
liquid is available. Where none is available even distant ice can be worth
fetching, and not especially distant either, in comparison to distant fresh
water.
All these simply are realities to be approached intelligently and
positively in context. That is what engineering is for.
There is an old American saying 'He who lives in a
glass house
should not try to kill two birds with one stone.'
Vladimir Nabokov Pnin
Mining or farming sub-polar ice, drift ice in particular, also offers
vital advantages over exploiting seriously inadequate freshwater resources in
temperate or torrid regions. The ice is plentiful and is continually renewed
seasonally, whether we love the fact or loathe it, both in the Arctic and Antarctic, and it offers hopes of dealing with
increasingly ominous threats of global warming.
For example, removing sea ice cover increases the rate at which cold air
can produce ice, and accordingly also increases the production of surface brine
that contributes to the natural cycle of cold water that conveys carbon dioxide
to the depths.
Such capture of carbon dioxide is regarded as very, very important,
fresh water or no fresh water. Whether the effect would be significant on a
global scale is another matter, but it might very well remove more carbon
dioxide than the operation produces. This would in particular be true if the
major vessels involved were nuclear powered or hydrogen powered.
Or ice-powered, as I discuss later.
Now, eventually, ice harvesting might well become one of the planet's
largest-scale industries. It might strip millions of square kilometres of
sea-surface per year. As such it would be far more promising than some of the
more harebrained schemes for carbon sequestration that enthusiasts popularly
tout.
There is a positive feedback aspect to this concept: the greater the area
of sea ice that gets removed, the more water gets frozen in winter, because
surface ice insulates the surface from atmospheric freezing conditions, and
removing the protective duvet of floating sea ice during winter, freezes water
that otherwise would have remained unfrozen that year. Surface ice also
prevents the solution of carbon dioxide in seawater, so, notionally, removing
it could double the carbon sequestration in the harvested areas.
Some concern has been raised about the effect of carbon dioxide in
acidifying the sea water and dissolving the shells of sea life, but I am
inclined to discount that effect, because for one thing, the effect is gradual,
and there would be strong selection, and even localised selection, for animals
that could manage lower pH levels. In combination with that concern, there is
no shortage of dissolved calcium and magnesium in sea water, so the
sequestration would depend on no more than energy-consuming proton pumps in
acid adapted organisms.
We do a good deal of that in our own stomachs.
And if disposal of more carbon dioxide in the sea becomes a problem,
then the solution lies in reducing carbon dioxide output, not ice output.
Developing and maintaining a sense of perspective in system design is
not an optional extra.
Another question is whether there is enough ice. Well, for convenience
in meeting the purposes of this essay I am assuming that we might want to
harvest ice to meet our total needs of fresh water. That is totally
unrealistic, but the assumption is convenient for calculating notional
feasibility.
We have two major sources of ice on any interesting scale: the Northern
(Arctic) Ocean and the Southern (Antarctic)
ocean. One might wish to neglect the Northern, because of its receding
volume in recent years, and in fact I will ignore it for this essay. However,
let us not permit ourselves to be stampeded into futility by facile
assumptions. What matters is not how much ice there is, but how much its volume
oscillates by season, and what happens to unharvested ice. As things stand we
still have millions, if not billions, of tonnes of new ice forming on the
Arctic circumpolar water every year, and as long as that remains true, the
difference between winter and summer ice levels is roughly what we might
reasonably harvest, because we know that it melts every year anyway. And the
ice that melts seasonally is of little ecological value anyway, being too thin
or too mushy for large animals to rely on it for support. So, properly
harvested, even the Arctic seasonal freeze should be valuable, even adequate,
for the needs of say, the pacific Northwest.
In passing, another source of fresh water that deserves attention,
though it could not compete with sub-polar ice, is the fresh water that flows
into the sea from major rivers, most notoriously from the Amazon, though the
likes of the Congo, the
Ganges, Orinoco, Niger,
and Nile also could be exploited. Wherever
such large outflows occur, the fresh water floats on the surface in such
quantities that it is a lot more profitable to collect some of it than to waste
it on sea fishes. Famously, ships in distress from lack of fresh water, out of
sight of land, have been rescued by friendly advice to collect bucketfuls of
water from the sea surface. The locals were aware that they were in the outflow
of the Amazon.
Of course, we need not expect such water from all great rivers to be
usable as is, but as I point out in another section, brack water is almost as
valuable as fresh, when desalination is practical, or when it is possible to cultivate or breed salt-tolerant crops. If one can collect water
containing say, 1% salt, which is hardly drinkable or usable, then by
desalinating it till the residue is at the same concentration as the
surrounding sea, one can shed the waste back into the sea without any pollution problems, and two
thirds of the output will be pure, potable water. What is more, if it could be
shed in suitable places, its content of soluble nutrients could support
commercially valuable marine communities.
A more serious problem is that fresh ice is a lot more valuable than
fresh water, but thirsty beggars make thirsty choosers. Brack water is better
than no water.
The major source of ice for our purposes is from the Antarctic
ocean. What the future holds we cannot say, but at present the
seasonal range of coverage of sea ice averages from roughly 2 million square
kilometres at minimum, to roughly 20 million at maximum. It would not be
practical to harvest the entire area, but even if it were, and it were done
early in the season, most of the surface would be frozen that same season,
though hardly worth harvesting in less than a year or maybe three.
If (which is not plausible in the immediately foreseeable future) say 10
million square kilometres of sea ice could be recovered from the Antarctic ocean per year, that would be equivalent to
rather more than the outflow of the Amazon, and more than human total
freshwater requirements, without serious ecological penalties.
Now, I re-emphasise: these figures are not only rough, but quite
artificial for the foreseeable future. All they are intended for is to
illustrate that the scope for an adequate supply of fresh water will in
principle suffice till long after most of the world's major rivers have
suffered the fate of the Colorado river, not to mention the Nile
and others in their turn.
And as I now shall point out: at an energetic profit.
Some say the world will end in
fire,
Some say in ice.
From what I've tasted of desire,
I hold with those who favor fire.
But if it had to perish twice
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice.
Robert Frost
One
major concern in all such harvesting and transport initiatives is energy. There
is no room to argue against the value of ice delivered in usable form to places
where it is wanted; but if we have to go thousands of kilometres to fetch it
and spend months on the trips both ways, then the question of cost necessarily
is very worrying.
Expensive
water amounts to no water, except perhaps on a spacecraft.
And the
most important cost in this connection is energy. It is not a cost we can
dodge; arguably the most implacable constraints in our world are those of
thermodynamics, paraphrased wryly as:
Do as we please to improve efficiency, we cannot do better than 100%.
We cannot achieve 100% except at a temperature of absolute zero.
We cannot reach absolute zero.
So one
thing is certain: we can't get our water free of cost.
Well,
we all know there is no such thing as a free lunch.
Still,
that is not the issue. The question is how far we can reduce the cost, and
whether the resultant profit would be attractive. We don't want fresh water to
be an expensive luxury, but a profitable staple. If we can manage to make the
cost of major dams look like economic and ecological suicide, that would be
really gratifying.
So
whether the proposals in this essay stand any chance of being practical,
depends on how we can cost our options profitably.
And
there turns out to be more to the equation than is obvious at first sight. We
need to be alert, not only for the primary objective, but for subsidiary items
that can make the difference between failure and a handsome success.
Meaning
profit.
I
suggest, not that we can beat the laws of thermodynamics, but that we need to
examine their fine print more carefully, looking for options that we can
exploit to achieve an actual, or extra, profit.
And one
of them is that what matters in exploiting energy is not how much energy we have (there is plenty of energy all about
us, more than we ever could use). What matters is the exergy, which depends not on the energy in the system, so much as
the difference in energy levels between one part of the system and
another.
Let us
call the high energy level the heat
source, and the low energy level the heat
sink. For example, a flame at a temperature of say 1000 degrees in a
chamber at a temperature of 200 degrees notionally performs no better as a
source of power than a flame at 800 degrees in a chamber at zero degrees. The
heat source in both cases is 800 degrees hotter than the heat sink. For more
coherent detail consult the article at https://en.wikipedia.org/wiki/Exergy
together with its links.
But
here the important point is that one can improve the energy efficiency of a
suitably designed system just as much by reducing
the temperature of the sink, or at least preventing its temperature from
rising, as by increasing the temperature
of the source. In fact, by decreasing the temperature of the heat sink, one
achieves somewhat greater efficiency than by raising the temperature of the
source. For an explanation of that effect, consult the article at https://en.wikipedia.org/wiki/Carnot_cycle.
Now,
for most of this essay we regard the problem of importing ice as implying a
need to melt it at the reception installation. And that is reasonable; there is
not much we can use the water for before it melts. And melting requires heat.
And not only does it take huge amounts of fuel to drag it through megametres of
ocean, but it also takes even more energy to melt billions of tonnes of ice.
And
yet, a million tonnes of ice at a few degrees below freezing point, used
constructively as a heat sink, offers the equivalent of something like 334
joules per gram, which works out at 334 billion kilojoules, ignoring the
scope for a few billion extra kilojoules to bring it to typical ambient
temperatures. Those 334 billion kilojoules are roughly equivalent to the energy
output of 30000 tonnes of coal or similar fuel.
And no
ash, no air pollution, no wasted fossil fuels or chemical feedstocks.
It also
depends on the form in which we use that energy, but that is a question of
engineering, not a matter for us to pursue here. I do mention elsewhere the
value of exposing the ice to air, which condenses any water vapour, adding
clean water to our yield from melting the ice, and at the same time produces
large volumes of cold, clean air, which is valuable in various industrial
applications, such as air conditioning.
If you
do not believe me, ask them in parts of Canada
(in Canada
of all places!), where they recently had heat waves of over 50 degrees
centigrade. They could have used a lot of cold air just then...
But
those are details.
The
important point remains, that we can extract more energy from the melting of
the ice, than it takes to ship ice from the points of collection to the point
of consumption. One almost is tempted to argue in favour of doing it all for
the energy yield alone. Any water we then can extract at the point of
consumption would be a mere bonus.
But one
thing that does matter, is the influence of such factors on the engineering
strategy. One strategy is to melt the ice and ship the water, but we thereby
would reduce the profit in imported exergy by a factor of several hundred.
We
have a strong incentive to import our water in the form of ice, in low-cost
passive vessels such as barges or dracones that can be parked for months at the
point of collection or delivery, with as little melting and as much freezing as
possible until we desire to extract the water and apply the exergy to achieve
desirable objectives.
A
temperature difference of say twenty- to thirty degrees centigrade might not
seem very exciting to a power engineer, given that each degree of difference
offers only about four joules per gram, but the latent heat of melting of the
ice amounts to nearly eighty times as much, so that a shipping a million tonnes
of ice to a hot climate begins to make things look a lot more attractive than
shipping huge quantities of fuel pole-wards to melt it, even if the power
engineering challenges of exploiting such a small temperature gradient seem
unattractive compared to the many hundreds of degrees available from flame or
nuclear sources.
Remember
too, that the way one uses energy makes a big difference.
Energy
is energy, no
matter what you do to it, but when one wants to increase the efficiency of a
machine by increasing the exergy, the difference between the source and the
sink, that can be more rewarding than using two sources of low-grade energy
separately.
Or one
could use the cold to produce cold dry air that would have taken a great deal
of fuel to produce by refrigeration, but would take effectively no fuel when
using warm, moist air to melt the ice. Then the fuel saved could be used
instead to drive the vessels and equipment in collecting ice from the sea.
If you don’t think too good, don’t think too much.
Yogi Berra
Not all sub-polar ice is the same. In this topic the main categories
from our point of view are firstly drift ice, ranging from perhaps 10 cm thick
up to say three hundred centimetres thick.
More particularly, we might be interested in pack ice, that is to say
drift ice that covers a good three quarters of the local sea surface. Such
sheets could be harvested more efficiently than chasing after individual
flakes.
Secondly there are ice shelves and glacier calvings that float out to
sea as they lose contact with land.
Thirdly there are the large, irregular icebergs typical of those in the Arctic; they too are from glaciers, but under
circumstances different from those in the Antarctic.
Instead of mass ice, drift ice several years old could be precious,
being easier to harvest.
Preferably we would look for sheets a metre or two thick, or fairly
undistorted floes. Sheets of mature drift ice could in fact be so precious that
prospecting for them by satellite should be rewarding as well as convenient and
cheap. Such ice is fairly salt-free and could be collected by fleets of
harvester vessels.
The design of the drift ice harvesters could be based on modifications
of ice-breaker principles: unlike the traditional icebreaker, that breaks
through floating ice by riding up on it till it falls through under its own
weight, a harvester might invert the process by sliding beneath the crust and
raising the ice in strips a few tens of metres wide and stacking them on board
till the load reached capacity. It then could return the booty to the mother
ship or the dispatching facility for loading into the barges or dracones.
While the load is being processed the harvester returns to its floe
nibbling.
One cannot always expect ice to break neatly and obligingly according to
our desires, so other, cheaper utility shuttle vessels could scavenge
free-floating blocks small enough to fish out of the water, in lumps massing a
few tonnes or tens of tonnes at a bite.
Because old ice is so much more valuable than young, it probably would
be worth maintaining satellite surveillance of young ice fields as well as mature
fields, until they were ripe and had thickened and shed their brine, rather
than attack them while still salty.
Harvesting such well-formed sheets of ice should be relatively safe and
profitable. A fairly small field, say a hundred kilometres square and with a
mean thickness of about 1 metre, could yield about ten billion tonnes of
relatively pure ice in manageable form. Of course, that would take some
thousands of ships or barges to collect all the harvest and deliver it to the
client countries and cities. The clients in turn would need facilities to
handle the imports, but those need not be any more demanding than damming and
treating the water of major rivers. It also would be a good deal less costly,
especially if the water were collected and delivered in the form of ice that at
local temperatures could be used as a power source.
Young sea ice, one or two years old, generally would be less valuable,
because it is saltier, but it still is much less salty than seawater. So where
there is no conveniently pure ice, it still could be worth harvesting young
ice.
There always is scope for more design, so I do not go into detail here
and now, but for example, polar storms at sea can be very severe, so it might
turn out to be worth designing some of the ice harvesting and management craft
as submarines, preferably nuclear submarines. Whether they did most of their
work on the surface or not, they could ride out the worst storms in deep water,
when submerged a few tens of metres.
A sea setting us upon the ice
has brought us close to danger.
Henry Hudson
Calving glaciers and irregular icebergs might well prove too dangerous
to be worth harvesting, but their substance is tempting, being large masses of
practically pure water. Practically all the major bergs originate on land, from
snow and other precipitation, so they don't contain forbidding amounts of
brine. Even those that originate from collisions of exceptional masses of drift
ice generally are old enough to have lost most of their brine.
So if we could find efficient and effective ways of cleaving them into
harvestable slabs, that should be rewarding. I have no firm suggestions as yet,
but explosives or injection of compressed gases or seawater might be used to
smash bulk ice into harvestable sizes or to induce calving. ANFO probably would
be the cheapest and safest explosive, but liquid oxygen or hydrogen peroxide
mixed with fuels such as propane or hydrogen might have advantages of speed and
cleanness. One would not want to use highly brisant explosives, because it
would be more efficient to load large slabs of ice than crushed fragments, and
would entail less salt pollution.
Instead of drilling into mass ice, we might find that light artillery
specially designed for shooting charges into dangerous ice masses, might work
rapidly and efficiently enough to be valuable. After all, they would never need
to work at ranges of more than a couple of hundred metres. The propellant could
be a gas/air system such as propane. A suitable gun based on such a principle
would not need any propellant cartridge; Diesel-type compression could render
ignition unnecessary.
Ice shelves attached to land might best be avoided for reasons of safety
and possibly ecological considerations, but detached or detaching floating shelves
of pure drift ice that simply would melt uselessly as they floated towards the
equator, should be worth intercepting in time for harvesting. A fairly
realistic tabular iceberg with a harvestable thickness of 100 metres and an
area of 250000 square metres (say 5 km square) should yield about 25 million
tonnes of fresh water. How to harvest it is a more complicated matter, because
one cannot simply skim it like cream or like sea ice.
Really large floating ice shelves, such as those of the order of 10 billion
square metres would be very valuable in principle, but it hardly seems possible
to harvest more than a fraction of such a shelf before it broke up. All in all,
sea ice seems to be the most promising large scale routine resource, but though
northern hemisphere icebergs might be hard to handle, Antarctic floating
shelves, whether free or still attached to land, do suggest special value. It
should be possible to develop special quarrying techniques to blast vertical
slabs from the sea faces of such shelves. Slabs of 1000 to 100000 tonnes,
roughly one to ten metres thick, could come to float safely, flat and shallow
in the water, after being cleaved off the seaward face of a shelf. They then
could be loaded directly into suitable craft, if necessary after further
cleaving to fit the equipment. It might not be as safe or easy as handling
dominoes, but then nothing is as easy as it looks, especially not as easy as it
looks to the amateur watching a professional at work.
But 1000-tonne floating chunks of ice in cold water should be
attractively profitable items for quick loading onto a million-tonne deadweight
barge, leaving room to be filled in with crushed ice or skimmed fragments.
So in general, it might be possible to harvest enough shelf ice to be
worth while, especially in very high latitudes, where freezing winter cold alternates
with summer temperatures above freezing. As we shall see, cleaving and
quarrying are not the only options; such alternation could be exploited in
various ways.
As already noted, explosive nibbling designed to detach harvestable
chunks in huge quantities should be practical. It might be particularly
valuable where warm ice is weak and starting to melt faster in warmer water.
It might even be worth exploring options for tethering major ice shelves
that threaten to separate and drift wastefully away. Nowadays we usually have
several years of warning of the separation of huge shelves. If we could slow
down their separation enough to match the maximal rate of nibbling at the
seaward margin and melting from beneath, that would pay for quite costly tethering.
But, tethered or free, where the shelf still is cold enough, thick
enough, and stable enough, it might be worth installing our equivalent of
ice-cream scoops, though the resemblance to your familiar retail ice cream
scoops would be remote. Devices like the leviathans used in open cast mining of
coal could strip huge areas of ice onto transport facilities for loading onto
barges or into dracones. As the upper surface was stripped from a shelf of say,
100 to 500 metres thick, the ice sheet would float progressively higher till
the shelf in the mined region became too thin for stability. Then the equipment
could up sticks and move on to thicker ice, leaving the residue for collection along with ordinary sea ice. The final residual layer could
be broken up into suitably sized blocks for direct loading – after retrieving
the valuable equipment for the next sheet of course.
It is not clear that this strip-mining approach would compete
successfully with collection of thin drift ice or nibbling at the edges of
shelves with explosives, especially in the early years of the industry, but
exploration of the options we may leave for future generations.
The fact that ice shelves are melting from beneath and from above
suggests other approaches. In the warmer sub-polar regions in summer, suitable
pigments on ice shelves could collect sunlight to create ice lakes kilometres
across and many metres deep, well worth pumping directly into barges and
dracones. No ice breaking involved. Just spray your pigments, such as carbon or
dark clay or soluble dyes and wait till next season to start pumping.
Irregular bergs probably could not be scooped easily enough to justify
the installation of equipment in the same way as big shelves, but they might
well reward explosive carving or smashing into blocks for loading, as I already
have described. Similarly, the edges of tabular bergs could be cleaved
vertically or nibbled into loadable blocks. For example, if submarine craft
became established for sub-polar ice prospecting, it should be fairly practical
in deep water to cleave floating bergs without explosives, using drilling from
below plus hydraulic pressure to force calving.
The fact that fresh water floats on salt has other promising
implications. Barriers of biodegradable polymer foam could be extruded by robot
underwater craft, forming fences beneath ice shelves in suitably chosen
locations where the water is still and there is little relative current causing
water exchange. The barriers' buoyancy could hold them against the underwater
ice ceiling. Any molten fresh water would remain against the underside of the
shelf by its buoyancy. Alternatively, the craft could carve hollows beneath the
ceiling by directing seawater jets upwards. In either case, holes drilled from
above down to the underwater domes could enable freshwater melt to float
upwards for collection.
Because of contact with the seawater, much of such molten ice would be
brack, but as noted elsewhere in this article, even brack water is valuable.
Depending on which options would be most profitable, it either could be
delivered to market directly, or pumped into ponds on the shelf surface to
freeze into plates of usable purified ice in winter.
Diarrhea, 90 percent of which
is caused by food and water
contaminated by excrement, kills a child every fifteen seconds.
That's more than AIDS, malaria, or measles, combined.
Human feces are an impressive weapon of mass destruction.
Rose George
Delivery of either ice or water has its attractions and each presents
its own problems. Water is easy to pump aboard in loading the harvest, and to
pump ashore in delivering the water. Water also is compact, either in itself or
if we use it to fill the gaps between ice blocks in storage vessels' holds. But
it also needs special precautions to handle at sea and it cannot be stacked
like solid ice blocks. Also, its capacity for storing cold is small, compared
to the latent heat of melting of ice. In industry concentrated cold can be just
as valuable as concentrated heat. That is why we who remain ashore spend money
on freezers, heat pumps, air conditioning and the like.
Accordingly, as described, massive ice delivered to warm regions where
suitable infrastructure is established, could be valuable, for instance in
cooling and drying air, and in the process it could collect a fair amount of
condensed water from the warm, humid incoming air. The cold also could be used
in heat pumps to freeze seawater or brack water to produce ice from which to
collect pure water.
Again, at the delivery end, seawater warmed by solar power or heat pumps
could be used to humidify air taken in to melt the ice, or to or carve mass ice while
yielding an extra profit in desalinated water.
Air that had been cooled and dried in such ways could be used for air
conditioning, much as one can use waste heat from power stations for combined
heat-and-power schemes.
Ice delivered in such masses rather than in loadable blocks would be
difficult to get off large ships and therefore would be something of a
liability if it took months to unload. This would be a good reason for using
low-value dracones or barges for transport. Such ice-laden vessels would serve
as storage buffers while the load thawed and got pumped ashore as required.
Meanwhile the tugs could have returned polewards, taking previously
emptied vessels with them. Possibly they might have fetched a few more full
loads on successive journeys by the time their previous load had been consumed.
Brackish ice might be expected to produce more saline water from its
lower levels as it melted, the upper levels being effectively pure water, while
the brack material could be desalinated and the brine dumped. Some brine would
remain after desalination of brackish water until it became too concentrated to
be worth further desalination. In contrast to the residue from desalination of
seawater, the volume of brine from brackish water might be too small to be
worth attention, so there would be advantages to desalinating it to no higher
concentrations than the local seawater could accept without special treatment.
As mentioned before, such salt water is likely to contain nutrients that would
favour the growth of valuable organisms, including photosynthetic life forms
that consume atmospheric carbon dioxide.
For one thing, such conservative desalination would remove the problem
of disposal, because the brine then could be dumped anywhere into the sea
without special precautions. The problem of disposing of brine after
desalination to concentrations greater than that of local seawater has turned
out to be a serious concern in practice.
The technology of managing such processes economically could become
quite sophisticated.
Why icebergs at all?
We buy a bottle of water in
the city, where clean water comes out in its taps.
You know, back in 1965, if someone said to the average person, 'You know
in thirty years you are going to buy water in plastic bottles and pay more for
that water than for gasoline?' Everybody would look at you like you're
completely out of your mind.
Paul Watson
Icebergs, especially large tabular icebergs, are very concentrated
sources of water, and in suitable circumstances are less seasonal than drift
ice. They also tend to be very low in salinity. This suggests that it should take less energy to collect
them than it would take harvester craft to retrieve drift ice.
It also might be easier and cheaper to deliver potable water from
icebergs than from thawed young drift ice that might be expected to be more
saline. Accordingly it might be worth breaking large bergs into manageable
blocks with explosives, as already suggested, after which the blocks could be
loaded or broken up mechanically into loadable sizes.
Why
not make ice instead of collecting it?
The society which scorns
excellence in plumbing as a humble activity and tolerates
shoddiness in philosophy because it is an exalted activity will have neither
good
plumbing nor good philosophy: neither its pipes nor its theories will hold
water.
John W. Gardner
The primary objective is to deliver water to the thirsty clients, and
for them to receive it exactly when required and pump it to where it is
required is the obvious option. However, the entire operation is costly in
energy, infrastructure, and human resources; the source is largely seasonal,
and to consider every material saving and gain is in the enlightened interest
of all parties.
Polar ice is in many ways valuable, but Nature does not present it on a
tray, ready for consumption. The most plentiful and accessible forms of drift
ice tend to contain more salt than we would like, though not nearly as much as
seawater does. Even if we cannot get pure water, sufficient reduction in salt
content is of value; we might well ship brackish water to willing clients who
could process it further according to their needs. That at least would be
cheaper than desalinating seawater, especially on a huge scale. In short, where
local circumstances are suitable, we might have better uses for large
quantities of brackish water than dumping it at sea.
Again, brack water, say 0.1% to 1% salt, compared to seawater's 3% to 4%
or so, also could be processed at the site of collection in subpolar regions,
by freezing in polar winter instead of shipping it to be desalinated on delivery;
that could work better than freezing seawater, and produce ice much less salty
than frozen seawater. To begin with, seawater is rarely still, so a lot of
things that seem simple to the landsman, become terribly complicated in real
life at sea. For instance, the turbulence causes mixing of surface waters, and
mixing makes it difficult to discard the salt. So finding ways to keep water
still can be very valuable.
For example, imagine a giant tabular ice sheet near Antarctica,
either still landfast, moored, or not yet about to fragment or proceed rapidly
north. Imagine that we had excavated a large, deep quarry into it, probably by
solar melting, pumping out the fresh water to our tankers for freezing during
the following winter before shipping it to the client ports.
During summer we could dump our marginal harvest of brack water into
that hollow, where it would melt high quality, low salinity ice, increasing the
volume of brack water while decreasing its salinity. The hollow might be
excavated by adding traces of carbon black or organic pigments such as
chlorophyll or other porphyrins to promote solar-powered melting. The surface
of the water in the hollow would be relatively still compared to the
turbulence of the sea. Because of its stillness and low salt content it would
freeze more easily than sea water and would form sheets of ice rather than
porous mats of crystals. During the sub-polar winter such water should freeze
thick, say 30 cm to 1 metre or so, and the ice in such a situation should be of
high purity and undiluted by seawater: Nature's free desalination service — or
nearly free anyway. Come the harvest season in spring, or even during the polar
night if that proves practical, such effectively pure ice on a stable surface
could be collected and loaded onto transport craft. The process could be
promoted by spraying the fresh or slightly brack water into the cold air,
collecting the solids directly into the transport vessels with most of the
desirable freezing already accomplished.
Such preprocessing should at least be easier than collecting clean ice
from a restless sea surface. For one thing, to freeze seawater on open sea is
neither as fast nor as easy as it sounds, because water that contains about as
much salt as seawater does, does not expand as much as fresh water does when it
approaches its freezing point, so it does not float as well, and it takes
longer to freeze over deep water; and it tends to sink a few times before it
freezes.
Once the ice harvesting industry had matured, there should be large
numbers of dracones or barges continually available, but not yet fully loaded.
Or, if loaded, their water might be brack. Such craft could be left with their
holds open for the winter or the shedding of their heat content into the cold
atmosphere could be accelerated by spraying, stirring or other dynamic
exposure. The diluted saltwater, very likely nucleated with fresh ice, would
freeze from the surface down. The deeper layers would concentrate the salinity
while their upper layers would improve in quality. Come springtime each vessel
could be assessed, either discarding the brine, preparing it for appropriate
further treatment, or using it to freeze fresh water.
Meanwhile the harvesters could fill up the vacated ice quarry with good
water pooled from other sources. Each craft would be dispatched to the home
port when it filled.
If ice harvesting vessels could chase sufficiently cold weather and
sufficiently cold seas, freezing could be induced by pumping seawater over cold
surfaces that prevent convection over deep water. The ice could be sieved off,
leaving the brine to go overboard. Such ice would contain salt, but probably
less salt than 1-year-old sea ice, and collecting it would require no
assistance from ice-breakers. The product could join the brackwater-processing
stream.
Possibly, in water covered with enough ice to suppress troublesome swell
action, large belts of suitably textured plastic netting could be drawn over
the sea surface at a rate controlled to bring in a coat of freezing ice that
gets shed into the hold as it passes over. The belt then passes below the
incoming mat to freeze again on the way back in.
Or it might be better to design ice-making craft equipped with large
areas on board, onto which water is pumped to freeze, the ice being skimmed off
as the brine returns to the sea; it is futile to discuss details when the
implementation still is so far from practical design.
When conditions are favourable it could be better to utilise ambient
cold to process and reprocess brack water or liquid fresh water on board
instead of shipping brack water to the client ports. The more usably pure ice
that can be delivered ready for final processing on land, the greater the
profit.
One of the problems with using young sea ice is that freezing seawater
collects in fluffy or spongy mats of crystals, and such mats contain a lot of
brine. Possibly crushing such ice would usefully reduce its brine content, but
I have no idea how practical that would be. However, the complications of
handling briny ice sponge could be circumvented by providing suitable surfaces
to nucleate the formation of compact freshwater ice ready for harvesting. Such
surfaces could be provided by heat pipes cooling the seawater by shedding its
latent heat of freezing into the subpolar winter air. If the pipes were covered
in silicone or suitable plastics, the resulting solid ice could easily be
harvested.
Alternatively, freshwater ice itself should be perfect for nucleation;
relatively small amounts of fresh water could be sprayed over sea just
approaching the stage of freezing, and the fresh water would freeze solidly,
not like blotting paper full of brine. Or snow harvested from the polar surface
could be used for the purpose. Or coarsely crushed brack ice could be scattered
over the water surface for similar nucleation. Then the relatively clean new
ice could be harvested more cheaply and profitably than by processing it at the
point of delivery.
In effect, subpolar conditions could be used in various ways to
accomplish direct desalination by freezing. Desalination by freezing was
attempted in the mid-twentieth century, but it never was energetically
profitable -- however, it might become profitable in subpolar winter conditions
on scales of millions of tonnes.
Ironically, if we were to import ice to thirsty countries, the value of
ice as a heat sink might resurrect desalination of sea water as a viable
technology. We might not get two-for-the-price-of-one, but one-and-a-half
for the price of one still can be an attractive prospect. And ice or cold water
can yield a bit extra by condensing humidity from the air, as I mention
elsewhere.
It all is very speculative, but that reflects the scale and the variety
of the potential, rather than the unpracticality of the suggestions. The field
will reward the engineers who develop it, not the scoffers who rage at their
own inability to conceive the opportunities.
Don't find fault, find a remedy;
anybody can complain.
Henry Ford
It seems likely that, given winter temperatures of well below -20C near the
Antarctic coast, it should be practical to exploit that cold as a source of
power. We already have contemplated using the cold air to produce ice in
various roles, but really, that seems to be a narrow view of important
opportunities.
Understand that, though the ambient temperatures near the Antarctic coast
are not nearly low enough to liquefy gases such as O2, N2,
or even CO2, they are low enough to reduce the costs of producing,
storing, and working with, such gases. Furthermore, Antarctica
is a source of significant renewable solar and wind power — wind at all
seasons, and solar photovoltaic power for nearly half the year, including a lot of midnight sun
during high summer. If it were to support a large industry of clean power accumulation,
that resource could be enormously valuable once the scale of operation grew large enough, and we could exploit it without importing expensive, polluting, non-renewable fossil fuels.
Various renewable power units could be used at all seasons for accumulating
compressed gases and possibly even for separating some of them. In particular, they could be
used for condensing CO2 as a liquid under pressure at winter
temperatures, and for cooling air or even O2, and N2 if desired, for storage either as gases under
pressure or as liquids in cryogenic storage.
"What on Earth for?" I hear the engineers cry! Understandably,
because there is not much market for such products so far down south, and though compressed
gases are valuable in industrial countries, it would be out of the question to
produce them for commercial export thousands of kilometres to the north.
Yes, but compressed or condensed gas can be
used for driving engines. In fact it is rather a good medium for storing power for such functions. And it is a very good medium for storing cold, because one need not store one's cold at such low temperatures; extremely low temperatures are harder to maintain than moderately low temperatures — and as the comfortably cold gas expands and the pressure drops, it cools accordingly. The thermodynamics present tempting opportunities for sophisticated designers.
The
following proposals are not to be taken seriously for early phases of
development, but within a few decades of experience and expansion, they could become downright attractive, both
commercially and ecologically. As an analogous example, not too many years ago, wind and solar power did not look at all promising, but already both are goring many of the sacred cows of the traditional power industries.
Such cold could be welcome as an aid to stripping greenhouse gases such as CO2 and H2O from the atmosphere directly, either for industrial use as a by-product, or simply for disposal
wherever it might be suitable. That objective is not of direct interest to this project,
but collecting CO2 might render subpolar freshwater extraction industry
carbon-neutral or better.
More directly, condensed or compressed atmospheric gases could be used
on site or loaded onto transport vessels as fuel to be consumed at warmer latitudes. O2 or oxygen-enriched air might be used in
combustion engines as a means of supercharging, but I prefer the idea of using
the gases as they are, to drive the ships' turbines without using fossil fuels. For that we do not want the
gases to be cold; in fact it would be good to heat them up, and the hotter the
better. Reducing the pressure on the gases as they are used for propulsion could require the harvesting of heat from the environment; delivery pipes exposed to the air, or even to sea water at
temperatures above freezing, could create ice or condense water to add
to the payload on the way home. In doing so, the waste heat would warm the gas to drive the vessel.
In this discussion it would be premature to propose details of how to manage the thermodynamics of allocating energies
and materials most profitably; for one thing, such processes would only
be worth while on a very large scale, after a lot of smaller-scale development
had matured. But the scope for establishing a clean industry of global
importance should not be ignored. Again, we should reflect on the explosive growth of the wind and solar power technology and industry in recent years, when just a few decades ago they looked derisory.
Why
not pipe ice instead of shipping it?
I love the sounds and the
power of pounding water,
whether it is the waves or a waterfall.
Mike May
This obviously sounds unattractive for clients near the equator, and
there is no question of anything of the kind in the short term, but the need
for fresh water world-wide, shows no prospect of easing. Meanwhile the
population is increasing. There certainly will be an increasing need for global
water reticulation. The necessary infrastructure will be far too huge to pop
into existence suddenly. One of the early forms will very likely be large,
long-distance ducts for shipping ice and slurry from the sub-polar regions to
consumer regions.
Transoceanic ducts could be collapsible modular submarine pipelines of
suitable tough plastic, each say a few kilometres long, with control and
communication modules at one end or both, designed to control their buoyancy at
each unit’s appropriate depth. They could very likely be used for
communications and power transmission too, and maybe for certain types of
material transport as well, very likely containerised.
The water ducts could be say a few metres in internal diameter, at least
partly driven by wave power. Modules would serve simultaneously as ducts,
processing units, and buffer storage. A duct unit with an internal cross
sectional area of ten square metres and a length of one kilometre, would have a
capacity of 10000 tonnes of water. A 1000 km pipeline could act as a buffer
store for holding ten million tonnes. Not huge, but enough to matter.
If a portion of the capacity were reserved for air to be fed into the
warm end, it could be used partly as a source of water of condensation, and
partly to melt or at least warm ice at the cold end. Where it is released at
the cold end its excess pressure could be used as a source of power. For instance it could contribute to ice
breaking and loading.
Brack,
schmack!
Seeing that our thirst was
increasing and the water was killing us, while
the storm did not abate, we agreed to trust to God, Our Lord, and rather
risk the perils of the sea than wait there for certain death from thirst.
Alvar N. C. de Vaca
As already mentioned, one thing we cannot expect is to get pure water
from sea ice. Old sea ice generally has shed most of its brine, and ice shelf
and glacier ice are largely old snow deposits, so such classes of ice generally
have very low salinity, but in practice we must expect pollution from contact
with seawater; for example shelf ice may soak up a lot of seawater because it
is porous, and some of our most easily harvested ice will be just a year or two
old — it still contains too much brine anyway. To shed much of that brine would
take another year or two of warming and cooling by the seasons and of massaging
by storms and swells.And such delays are unwelcome to industrial engineers.
Some old ice might be drinkable when melted, but not really up to
standard for heavy irrigation and commercial potability. Really young sea ice
is barely drinkable in times of desperation if at all: it might contain say 1%
or so of salt. Seawater usually is somewhere between 3% and 4% salt, and
realistic desalination is practical for salt solutions of up to roughly twice
that concentration.
However, the cheapest, fastest, and most sustainable desalination is the
purification of large volumes of slightly brack or otherwise impure water. It
certainly is better and cheaper than trying to desalinate seawater.
Firstly, one does not simply chuck weak brine into the machine and get
out pure water plus concentrated brine. Different strengths of brine require
different treatments with different membranes and pressures and energy
consumption, and ecologically acceptable disposal of concentrated brines is
more difficult than disposal of weak brine.
Accordingly, if one cannot provide the client with pure water, he might
well be willing to pay for say 0.3% brine, about ten times weaker than
seawater, so that he only discards about 10% of the output at 3% concentration
instead of discarding 50% of the input brack water. He can do so without
precautions against pollution, because at that rate the discarded brine is
pretty close to the concentration of raw seawater. For most commercial purposes
a solution about fifty to one hundred times weaker than seawater is usable as
is, with no more discarded output than from processing most kinds of fresh
water.
Mind you, do not take these figures too seriously; the
intention is mo more than to give some idea of the major principles. In practice desalination is
not as simple as it sounds; cleaning, backwashing and so on make for some waste
as well.
Again, where sea water is used for industrial cooling, such as for power stations, the waste heat, which is what the water is used to carry away, could be manipulated, using heat pumps or similar tricks, to evaporate as much of the brine as practical, and that evaporation incidentally is the most effective consumer of the waste heat, and the vapour could be condensed into water pure enough for immediate use.
"Well then, why has that never been done?" I hear you cry?
That is not as simple as it sounds; it already might be standard in some applications for all I know, but certainly at the time of writing it is not common practice, and not long ago it would have been regarded as ridiculous; even now it would require special justification and special circumstances to be practically profitable, but the same could have been said of solar power or wind power, just a very few decades ago.
As for how to apply the heat from the condensation of the water; it could be especially valuable for melting deliveries of polar ice, as I already have mentioned.
Whether harvesting high-value chemicals from desalination or ice
harvesting waste could be worth while, is a point for chemical engineers to
consider. I suspect that there is room for such projects, but I am not able to develop the idea any further at this point.
The upshot in any case is that ice harvesters need not insist on pure-water ice,
but would need to assess every major item they attacked or brought on board.
They would not mix relatively strong brines with more or less potable water,
and they would price the water according to its intended purpose and the amount
and nature of purification or dilution it would need. No doubt such things as
dates of delivery, contracts, and special circumstances would affect prices
too.
Future markets in water promise to be a very interesting field of study
and practice.
When elephants
fight, it is the grass that suffers
Attributed to an African proverb
Everything anyone can choose to do, including avoiding doing anything at all,
entails consequences. If it did not, it would be pointless doing it — including doing
nothing. As a rule, the larger the scale and relevance of the action or
inaction, the greater the consequences.
Ecology in particular is affected by almost any change on a large scale,
including the growing effect of a static condition or trend, and there is a tendency
to regard every such change as pernicious. Such disapproval commonly is
justified, but often the outcome is no worse than reasonable alternative
actions would be in the long term.
Consider for example the stripping of ice cover from large areas of sub-polar
seas. It sounds like vandalism, but suppose that as an alternative to
stripping, I were to propose covering a million square km of sea surface with
ice ranging in thickness from 10 cm to 40000 cm, with all the associated
implications for heat exchange, gas exchange, ionic migration and exclusion,
exclusion of light, and exclusion of large classes of both animals and plants.
That would be at least as harmful as stripping. Right?
And yet, that would be the precise equivalent of leaving the current sea ice unharvested,
without human intervention, on a scale beyond anything proposed in this essay,
and without any clear improvement to human, plant, animal, or climatic
situations. And in nature the cycle continues practically annually
throughout major regions, global warming or no global warming.
Furthermore, if ice collection were to become established as an
industry, then harvesting, especially in the early days, would largely be
confined to free sea ice, whether continuous or fragmented, simply because it
is safer, faster, and easier to collect than floe ice or iceberg ice. In fact,
it is not yet clear to what extent ice that could most profitably be collected
would be free-floating pancakes or fragments of ice sheets broken by wave
action.
In the natural course of events huge areas of sea ice melt annually in
summer and reform to a thickness of about 10 cm to 1 metre each winter, largely
in the Antarctic. To harvest such ice towards the start of the melting season
could seldom be harmful at all. In fact, there is at the time of writing,
growing alarm at the rate of fresh water entering the Southern Ocean from
melting ice, especially from the glaciers.
Fresh water floats on the surface instead of sinking, so such a floating
layer will prevent the turnover of surface water to the depths. In contrast,
cold and salty surface water is dense, and inclined to sink, especially when
stirred by wind. It then carries soluble gases down to the depths, and the most
important soluble gases in that region are oxygen and carbon dioxide.
We want to send down plenty of oxygen, because the marine life in the
depths needs it. The last thing we want is to create a dead zone down there; it
would be a disaster beyond calculation; certainly of planetary
proportions.
We also want to send down as much carbon dioxide as we can; the deep sea
is one of our most important carbon sinks.
So the more fresh water we can strip from the southern ocean surface in
the form of ice, and the colder we can leave the salt water by exposing it to
the winter air when the ice is gone, the better for our planet.
Two forms of free-floating drift ice and pack ice could be worth
harvesting: three years old or more; and young ice, less than three years old,
sometimes only months old. Areas of either type might be large enough for
harvesting in a given region and season.
Unfortunately, young ice tends to be unattractively salty, but as I point out
elsewhere, even brack water is valuable because it can be desalinated more
cheaply than water from the open sea, and the waste brine, if not to be used
for other purposes, can be limited to harmless salt concentrations that may
be dumped safely.
The implication is that profitable harvesting need not be limited to
effectively salt-free ice. For example, if a product of 0.1% salt is
acceptable, and the brack water salt content is 1% , then about 70% of the
brack water could be extracted, harmlessly discarding less than 30% of the
input at the concentration of sea water. If the input brack water contained
0.35% salt, the yield would be more like 90%, and the desalination would be
easier, faster, and cheaper than desalination of sea water.
Initial desalination might be done at the site of delivery, or various
techniques could permit most of the processing to be done at the site of
collection to produce low-salt ice instead of shipping briny ice immediately on
collection. Shipping water instead of ice would generally be less desirable; I
discuss several considerations elsewhere in this essay.
The details of the state of the input ice would depend very much on the
ice sources locally available. Sea ice quality varies according to the region
and the conditions under which the ice forms. Old icebergs tend to be very pure
ice, while young drift ice, such as nilas, that formed from grease ice, shuga, and frazil (fine
crystals of ice growing on cold seawater) may contain more like 0.1% to nearly 1% salt. The
sheer variety of ice forms and their names is too great to deal with in this
essay.
There is plenty of discussion of the topic online, for example in
various Wikis. Whether it would be practical to begin the processing of
brine-rich ice by squeezing it during collection, I do not know, but such
options could be worth study in regions where young ice is the major harvest.
Anyway, in regions where ice would have melted annually, it would be
beneficial to remove it strip-wise before melting begins. Such harvesting would
have little ecological effect in any but very shallow water. On the other
hand, if we removed ice at the height of the freezing season, the surface
would be covered again within days, and that would be too fast for most
organisms to be much affected, whether they were plant or animal, such as krill
in the process of propagation. After stripping ice from freezing waters would
be a good time to spray traces of soluble nutrients such as iron and zinc onto
the open sea surface. Quite a slight concentration below the newly formed ice
should dramatically increase the harvest of the algae that feed the krill when
the sunlight returns.
New annual ice would be left for most of the season, whereas harvesting
more valuable older sea ice would be delayed for say, 3 years at least after
each harvest.
Studies should demonstrate whether it would be worth confining
harvesting to local strips, in deep water, so that no organisms, whether algae
or crustacea, are far separated from intact surface ice, and so that there are
no significant coherent effects on the sea bed and its communities: no
brinicles for example. I doubt that strip harvesting would be worth it, because
the ice should cover the surface again within days or weeks, especially in the
cold seasons. But either way, it could be a realistic option. Where harvesting
has created strips of open water or thin ice, it might for example save the
lives of many a marine mammal or diving bird.
One might wonder about my being so optimistic about the recovery of
surface ice after harvesting, in the face of Arctic ice recession, but to
harvest receding ice would be pointless; no one with any sense would undertake
any such project, climate change or no climate change, except where sea ice is
plentiful and preferably forming actively and surviving unmelted for at least
three seasons. Nor would it necessary to create any local disturbance to assess
the promising areas, because prospecting would generally be done by satellite
rather than by ship – simply for reasons of speed, broad perspective, and
economy.
It might seem perverse to the point of insanity to propose harvesting
sea ice during polar winters, but I submit that the incentives of extra cold,
and the associated ease of harvesting, stowage, and refining, should make it
rewarding to design the equipment and to plan the operations to exploit just
such profitable insanity. That it also would be beneficial from the ecological
viewpoint would be welcome, though incidental, so there should be little need
to police the operations for good practice.
All this of course, refers mainly to sea ice and pack ice sheets. Ice
floes and icebergs would have their own considerations, including the fact that
for the same volumes of ice they involve tens to hundreds of times smaller
areas than floating sheet ice. Harvesting such masses, if practical at all,
would have correspondingly smaller effects on the ecology beneath. Floating ice
islands such as those of the Antarctic are another matter: they are so episodic
that it is hard to take them seriously as long-term ecological concerns anyway.
On the other hand, there accordingly is no reason to spare them from
exploitation. Besides, mass for mass, they too would cover smaller areas than
ordinary sea ice.
If instead, a good case could be made for conserving the ice islands,
the logical response would be to tether sufficiently large islands to the
mainland ice sheet to conserve them for seasons, perhaps indefinitely. Then
they would be spared from harvesting. Such tethering even might cause them to
re-attach to the land-bound ice shelf.
Should tethering not strike anyone as attractive, then the floating
shelf should certainly be harvested as expeditiously as possible; the valueless
melting of an ice island is in the words of a great thinker: “a pernicious
interference with the laws of Nature”; it would affect larger areas than ice
harvesting would cover for years. The process of uncontrolled melting would
kill all sorts of organisms where the island drifted and melted, marooning
polar organisms in lower latitudes where they would die. And that happens every
few years, when new ice islands break off and drift northwards.
Far rather harvest the ice as soon and as completely as possible, before
it got into hot water, where it would leave its passengers to their fates. And
much the same could be said of icebergs.
Another real-world aspect that is emerging as I write, is that melting of large areas of ice sheets is causing a great deal of concern in some circles —informed circles in particular. As the sheets melt on land or slide into the ocean, they raise the ocean level accordingly. No surprise: this has happened in the past, with ocean levels fluctuating by hundreds of metres over geological periods. And the changes of ocean level that we calculate at present are slight: of the order of a few metres — say five or ten.
The catch is that the number of people whose lives and livelihoods are within say, ten metres of mean sea level, is huge. Not only are there may inhabited islands that would disappear entirely, but entire countries could vanish. Even some states, like Florida and Louisiana could become history, leaving the likes of the United States with an internal refugee problem of the order of many millions; we could yet see Mexico refusing to take refugees from the United States.
Now, that particular topic is huge and complicated and of great intrinsic interest in its own right, but does not primarily have much to do with fresh water supplies, so I shall not discuss it here, but one immediate point is that every bit of ice shelf that we remove as it approaches the sea, whether from Greenland or Antarctica, will tend to a net improvement of the situation, rather than aggravation.
So at the very worst, that concern does not militate against the harvesting of polar fresh water.
A
king ordered his wisest man to prove his wisdom by teaching a horse to talk.
The man acceded, but said it would take
at least five years.
Privately he explained to despairing friends:
"If I had
refused he certainly would have killed me at once.
As it is,
I have five years in which anything may happen.
The horse might die. The king
might die.
I might die.
And besides, who knows?
I never have tried any such thing;
perhaps in five years I can teach
the horse to talk."
Traditional parable
Some
people object that to harvest ice would be futile in the long term:
Anthropogenic Global Warming will soon eliminate sea ice and eliminate ice from
Greenland and the Antarctic. That is as may
be, but even Anthropogenic Global Warming will not change the inclination of
the Earth's axis by much, and it follows that winter will not be abolished. In
fact, even if sea ice eventually melts disastrously and completely in each subpolar region every
summer, which is by no means certain, and even if no form of engineering could
mitigate the effects, which is positively unlikely, there should be large
quantities of rain, snow, and sea ice within each polar circle every winter.
Young
sea ice to be sure, but we already have contemplated means for exploiting it.
For one
thing, the hotter the summers, the greater the humidity will be, and somewhere
there must be matching precipitation in the cooler regions. Where the
precipitation would occur is a different question, and all sorts of engineering
schemes might be necessary for capturing rain and snow by other means than
exploiting sea ice, but as long as there is precipitation and freezing wherever
there is a polar night over polar seas, we can be confident of finding or
making fresh or brackish ice. In fact,
if suitable quantities of suitable quality do not form spontaneously, we could
have ice harvesters and factories covering square kilometres of ocean in
strips, collecting the ice for much of the year, and refining it for the rest
of the year.
And in
such conditions the value of ice deliveries, rather than water deliveries,
would be all the greater.
Anthropogenic
Global Warming would be seen as disastrous in most contexts, but to prevent it
or at least mitigate it, and ultimately to exploit it, would be in the finest
traditions of the achievements of human hubris.
If you’re achieving all your
goals, you’re not setting them aggressively enough.
Laszlo Bock
We have
known for generations that, short of a pandemic causing a few billion deaths,
the need for fresh water can only grow. Certainly in our traditional
consumption of fresh water there is scope for water savings, for avoiding and
ameliorating pollution and water loss, for using water more intelligently, and
equally certainly we need to improve our practice accordingly, but that scope
is limited. Besides, if you look into the real prospects and the requirements
for those necessary measures, you find that on any major scale they are neither
easier nor cheaper than anything so far discussed in this essay. Furthermore,
water is needed for so many things, power, irrigation, industry, as well as
domestic supply, that we cannot simply go out and collect whatever we want for
any particular use: almost any water we divert to alleviate one need aggravates
some other need or interferes with some other function or increases some other
cost.
Our
immediate problem is not to find more water; the planet has plenty for our next
few centuries. What we do need is to find the largest immediate uncommitted
source that we can afford to exploit without harming other interests. Salt
water is plentiful, but expensive to purify, even though we have made massive
improvements in desalination. Anything we can do to decrease the energy cost of
obtaining fresh water is worth looking into.
Now,
natural processes continuously desalinate water in quantities greater than we
yet have any need for, and they even store a lot of it for us in the form of
ice and dispense that ice in quantities greater than we need at any particular
time. Pack ice drifts till it melts, and glaciers dribble gradually into the
ocean or down rivers.
Rain
and snow in temperate regions are another matter, but they already are largely
claimed by various legal parties, except when they present threats of floods or
mudflows. Even when we do not use them all, we cannot simply take more, or we
conflict with downstream users in one way or another. For instance, some rivers
simply get used (even re-used) completely. Examples include the Colorado river. Others get too polluted to be of use to
downstream users. Damming of the Nile has practically destroyed the
Mediterranean sardine fishing industry off the Nile delta, and it prevents the
annual Nile silting. And worse is in store:
with more damming, as is currently underway, the Nile
as we know it might yet cease to exist within our children's lifetime.
Trouble
is brewing around our major rivers and lakes. If you dam water you cover land.
If you fail to dam water, and you decrease flood control options. Use
accumulated water for power and you limit its scope for irrigation, industrial,
and domestic use. And whenever you empty dams you create other problems.
In
short we need fresh water from elsewhere. We know where most of our surface
fresh water is. We know that it is frozen, and generally the frozen water is
far from where we want it. Proposals for using it have so far been pathetically
naïve, for instance dragging icebergs over the ocean. Fair enough, ideas have
to start from somewhere, but such non-starters have given the feasibility of
exploiting sub-polar ice a bad name.
This
essay has argued that there is scope for taking the harvesting of sub-polar ice
seriously as a source of water, and in fact, that such an industry is
inevitable and could be developed within a matter of years.
The
obstacles are:
- It does not sound possible
(much as undersea oil drilling was dismissed when the idea was proposed)
- It will not be as easy as its
proponents make it sound
- It will take heavy
investment, and in particular it will be costly to start up as an industry
- On anything but a huge scale
it never will be worth while, let alone economical
- Harvesting and transporting
the ice, whether solid or molten, will be only part of the problem;
dealing with it at the point of delivery is no trivial matter either
- Design of the harvesting,
transport, delivery and application technology involves whole ranges of
different problems; we cannot simply think up a bright idea and expect it
to work economically first time, quite apart from the problem of producing
trained staff to run the industry
In
short, humanity needs to generate start-up capital and infrastructure, and
possibly the development of
international legal standards as well. National commitments might be
necessary to encourage development. People rarely understand the scope and
importance of infrastructure, so pioneers tend to come up with half-baked ideas
that crash ignominiously.
Conversely,
other people stand abashed at the scale of start-up challenges, and proclaim
every form of new development impossible.
It is a
shame and an indictment that some of the most spectacular of our
multi-billionaires, who squander huge sums on space tourism and similar
gambles, cannot instead spend much less on a far more profitable and beneficial
new industry.
But it
is worth repeating: our exploitation of natural ice as a source of water is not
a matter of whether, but of when and how. It is high time to think it over at
levels of authority sufficient to invest resources in the development of
pioneering plans and equipment.
