Fish and Ships

The supply chain for fish could be a lot greener. I’m not going to go into the politics of quotas, territorial waters or anything like that; simply looking at what happens after the fish are caught is complicated enough. The rate at which fish spoils is alarming, so they have to be gutted and packed in ice flake as quickly as possible. As soon as the fish come ashore, they’re boxed up and sent to a fish market. It’s the boxes that are of interest here.

At best, you’ll see fish boxes being backhauled, empty, while elsewhere you find disposable polystyrene boxes lying abandoned at the back of a fishmonger’s or restaurant. Can’t we do better?

For years, this has been the choice: reusable or disposable fish boxes. As with all reusable packaging, there’s the danger that it doesn’t get returned and reused, and the investment in packaging is wasted. If you’re doing regular business with the same people, a reusable solution is the obvious choice; if you don’t know your customer, a disposable fish box is going to be needed.

The manufacturers of expanded polystyrene fish boxes will tell you that theirs is the ideal solution. It’s lightweight, a great insulator and “mostly air” so it saves materials. So what if it only gets used once: if burned for energy recovery polystyrene is twice as effective (by weight) as coal. So what’s not to love?

expanded polystyrene fish box

End-of-life expanded polystyrene fish box

It’s weak. Boxes made from expanded polystyrene need to be thick-walled, and that’s a bind because it means you can’t nest them together. You don’t get many expanded polystyrene fish boxes on a truck… and that makes them expensive: not to manufacture but to deliver. Then you fill your polystyrene box with fish and crushed ice, and send it on its way. Once it reaches its destination, you’re left with a fishy-smelling and none-too hygienic polystyrene mess. Flies love them – and of course, the waste is light enough to blow all over the place, and it floats on water. Waste polystyrene is not at all pretty, and when you consider that the UK fishing industry gets through 14,000 tonnes of the stuff per year, the light weight is no longer a virtue: it indicates an awfully large volume of waste. When I noticed that the mountain of waste polystyrene at Grimsby fish docks was visible on Google Earth, I decided that something had to be done.

So what do you do?

The normal industry solution is to invest in a machine that crushes expanded polystyrene fish boxes (with or without the application of heat: the hot version achieves better compaction) and then send the material for “recycling”. This is disingenuous as the fishy smell normally relegates fish boxes to the energy recovery route (it gets incinerated). Still its calorific value is high, so waste-to-power seems like a win… but I wanted to try a new material for fish boxes.


If you’re going to all the trouble of keeping your fish and ice flakes cool anyway… why not keep the fish box cool as well, and create a container that literally melts away when you’re done with it?

Except that ice isn’t strong enough. Give a box made of ice a little bump, and it will shatter into a million pieces… right?

Not necessarily.

Not if you’ve heard of Geoffrey Pyke.

Geoffrey Pyke, 1893–1948

Geoffrey Pyke, 1893–1948

Pyke was a loon. Let’s be clear about this: when you think about the archetypal mad inventor… you’re thinking of Pyke. The man was dangerously unconventional… and that was his job. During the Second World War he was charged with coming up with crazy things that the enemy wouldn’t anticipate (and some of them were very crazy indeed, but that’s another story).

The ‘big story’, where Geoffrey Pyke is concerned, was his proposal to win the Battle of the Atlantic with a new kind of ship.

Unsinkable, and made of ice. Codename Habbakuk: a vast ‘bergship’ that would sit in the Atlantic, acting as a base for aircraft that would attack enemy U-boats, all the while shrugging off their puny torpedoes. That the construction of his bergship (and more importantly, its built-in refrigeration units) would have required more materials than a whole fleet of conventional aircraft carriers doesn’t appear to have deterred Pyke one little bit.


A blueprint for Habbakuk, the aircraft carrier made entirely from ice.

There was method in Pyke’s madness… just about. It wasn’t to be made from ordinary ice, but from a kind that was so strong it could absorb bullets – and Pyke knew just how to make it. Back in the 1930s Herman Mark and Walter Holenstein of the Polytechnic Institute of Brooklyn had described how ice could be made much stronger if the water was mixed with cotton wool fibres before freezing. In fact, all kinds of fibres worked, and produced a material at least three times as strong as concrete. Despite the Brooklyn connection, to this day the material carries the name of its most enthusiastic advocate, as Pykrete. Add something fibrous to water; say wood pulp of the kind used in paper-making (about 14% by weight is as much as you can squeeze in) and let the whole lot freeze. Not only do the fibres act like rebar does in concrete (vastly improving its tensile strength) but when melting exposes the fibres, this outer layer acts as an insulator, slowing any further melting.

For Geoffrey Pyke, this meant that cheap and plentiful materials found in Canada could be used to create the biggest ship that the world had ever seen. There are stories (possibly exaggerated, or made up entirely) that a block of Pykrete was demonstrated most satisfactorily in Winston Churchill’s bathtub, while in another demonstration a revolver was discharged at a bucket of water ice, and a bucket of Pykrete. The ice shattered; the Pykrete caused a ricochet and an American officer was hit in the leg.

The bergship idea was taken seriously, for a while. Ultimately, improvements in the rage of aircraft, and the realisation that building Pyke’s invention would strip an awful lot of Canada of its trees meant that the project came to and end… but not before a remarkably successful technology demonstrator was constructed in secret, and sailed on Lake Patricia in Canada, one hot summer.

After coming up with a few more incredibly off-the-wall inventions, none of them adopted, Geoffrey Pyke committed suicide in 1948. From time to time, somebody proposes that Pkyrete should be used to construct seasonal features in ski resorts, or Antarctic base facilities… but nobody ever actually did anything much with Pykrete. You might have seen when ‘Mythbusters’ demonstrated the viability of a Pykrete boat, made from water and newspapers (with judicious use of a CO2 fire extinguisher for freezing when it started to delaminate). You might have seen when ‘Bang Goes the Theory’ did something similar a few years later… but nobody has ever done anything particularly significant with Pykrete.

The BBC consulted me, when they attempted to recreate Pyke’s idea on ‘Bang Goes the Theory’...

The BBC consulted me when they attempted to recreate Pyke’s idea on ‘Bang Goes the Theory’. (Photo: Solent News & Photo Agency)

I wasn’t in the shipbuilding business, but I was interested in shipping fish. My fish boxes would be heavier than the polystyrene kind, but I reasoned that this would be OK as they would only be making a one-way trip, having been made on-site where the fish were landed and processed. (Who wants to transport a truckload of empty polystyrene boxes to each fish dock, anyway?) Once the fish box had been finished with, it could be left to disappear in its own time, being 86% fresh water. The 14% pulp was biodegradable by definition, and if present in quantity it could be rotted down for use as a soil improver, or pressed into fuel pellets.

During my programme of experiments I discovered some interesting things. You don’t actually need a big, wet mass of sawdust or wood pulp: a ‘sandwich’ of corrugated card with a more absorbent layer of paper on either side will create a material that’s as strong as plywood, once wetted and frozen. I found that a broken or melted Pkyrete sample would ‘self heal’ if returned to the freezer. A collection of fibres that were merely damp were almost as good as a much more saturated mixture in terms of impact resistance, although the thermal mass of the saturated material was better. One of the big problems was ‘freezer burn’: water leaving the Pykrete by sublimation, and condensing elsewhere within the freezer. This is what eventually ruins food that isn’t stored in an airtight container, and an exposed Pykrete sample was seen to lose a lot of its strength over the course of six weeks or so.

Pykrete versus hammer

This lightweight sample, made from damp strips of cardboard, was strong enough to withstand repeated hammer blows.

I had some fun recreating the ‘Mountbatten Experiment’: shooting at samples of water ice and various recipes for Pykrete. I can confirm that Pykrete resists impacts splendidly.

And yes, I had some fun recreating the ‘Mountbatten Experiment’: shooting at samples of water ice and various recipes for Pykrete.

Water ice shatters at the first strike. Not a bad shot, if I say so myself…

Pykrete target

Pykrete simply doesn’t shatter the way water ice does. This sample has absorbed several bullets.

I knew the Pykrete fish box wouldn’t be perfect for all applications. It’s out of the running for transport of fish by air, for example, since meltwater is not permitted with airfreight (dry ice is employed in such applications). Even so, I thought somebody would appreciate the idea of being able to make their own single-use fish boxes.

I designed a ‘flat pack fish box’ made from my papery plywood substitute, plus a means of sputtering a Pykrete mixture onto a cold, collapsible former that meant one could cast a Pykrete fish box in minutes.

Pykrete fish box

Conceptual design for a fish box, cast in Pykrete.

Pykrete fish box

Design for a flatpack Pykrete box: just assemble, spray with water, and leave in the cold store.

The fishing industry hated the idea of a reinforced ice fish box. Nobody I spoke to would touch it. Were they wedded to their recent investment in machines that crushed up end-of-life polystyrene boxes? Maybe. Were there food hygiene rules that I didn’t know about? That seemed unlikely, given the perfunctory (in some cases non-existent) washing practices that I saw employed with reusable fish boxes. I began to suspect that those in the cold chain for fish don’t actually refrigerate it as well as we might hope. If the product isn’t kept reliably and consistently below zero throughout its time in the supply network, that would be a powerful argument against trusting to a fish box that might turn to mush due to poor refrigeration. (Was this the reason that a frozen fish box was a non-starter? I think… maybe.)

life cycle diagrams

I still think I was on to something, though.

The biggest nail in the coffin of the Pykrete fish box came when I lost control of the intellectual property. An administrator who was creating web pages for all our research projects decided that she needed some text on the project, and dipped into an internal report to obtain it. When you’re going after a patent (or several) the one thing that is guaranteed to destroy your chances is disclosure: a previous revelation of the features or methods that you were seeking to protect.

With the publishing of several key ideas on innovative features for Pykrete fish box manufacture on-demand, there was no possibility of any commercial return on the project, so it came to an end.

And the administrator who leaked my secrets? I think she’s still in the freezer.


2 thoughts on “Fish and Ships

  1. Pingback: A Gap in the Market | Capacify

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