Boyan Slat and the Great Pacific Garbage Patch: A comprehensive critique

Boyan Slat appeared on my radar recently. I watched two programmes on Boyan Slat, one dating from May 2017 (a presentation, 30:08 minutes), and the other from October 2018 (a documentary, 44:55 minutes). And I have some reservations.

Firstly, though, I’m not saying that we shouldn’t clean up the garbage in the oceans, especially plastic garbage. Our problem as a species is that we tend to think that out of sight is out of mind, and anything that can save us from our own myopia is to be lauded. It is with this frame of mind that I approached Slat’s 2017 presentation but, unfortunately, it was by watching a video on something I supported that the doubts arose.

[Note: From here on, the Great Pacific Garbage Patch will be abbreviated to “GPGP”. The primary source for this article is the video “Boyan Slat: How we will rid the oceans of plastic (May 2017)”, with a secondary source of “The ocean plastic cleanup of Boyan Slat – Docu – 2018” (October 2018). Both are available to view on YouTube.]

Let’s roll.

Concentration of plastic in the ocean

At minute 1:18, Slat shows us the concentration of, well, what exactly? He says it’s “plastic”, but the graph says “microplastic”. Whichever he means, I think the graph’s bogus for the simple reason that, in recent years, there has been a huge awareness of the dangers of plastic. Many cities have instituted plastic bag bans. Yet the concentration of plastic, according to Slat’s team’s projections, keeps rising. It’s a smooth, linear increase, too, which doesn’t correlate with the second factor: an incredible increase in Chinese ocean dumping. It reminds me of the charts of BAC (Blood Alcohol Concentration) in a car driver’s blood vs likelihood of having a crash. You’ve seen those graphs. In fact, they aren’t true. Studies have shown that somewhere between concentrations of 0.00 and 0.08 (I forget exactly where) the cognitive functions of a driver sharpen. One theory for this is that, as the driver becomes aware of the first wash of alcoholic “buzz” in their head, they become more focused in an effort to dispel the effect. The problem is, a BAC vs road accident graph that shows a dipbefore the inevitable increase doesn’t paint the kind of picture that governments want…so we see a smooth ever-rising slope in all the government brochures.

In the same way, with Slat’s chart, there is no dip (or jump) that mirrors either our increasing awareness and disdain for plastic or the introduction of the world’s largest manufacturing economy into the mix.

Debris allegedly plucked from the ocean

At around minute 2:20, Slat begins an exhibition of pieces his team have taken from the ocean. At minute 3:35, we see a plastic crate from 1977. And my, isn’t it clean for an item more than 40 years old? Yet, in the (late 2018) documentary, a member of Slat’s team illustrates how old a piece of nylon fishing net from the GPGP is by how much coral has grown around the green strands! In fact, the amount of coral dwarfs the strands of nylon. Doesn’t this contradict the state of debris from the earlier programme? What’s more, one of The Ocean Cleanup team (oceanographer, Laurent Lebreton) in the documentary (minute 7:24) admits that half of the GPGP’s mass is made up, not of game cartridges or plastic buckets, but of commercial fishing nets! Hmmm, I wonder if there’s anything we can do about that?

As a sidenote on Slat’s presentation of debris, let’s not forget John deCaires Taylor’s Maldives installation, “Coralarium”, which began to be colonised by sea life within monthsafter the sculptures were put in place. (It has been destroyed by the government by now, but images exist of marine growth. And there are many other artists who’ve installed similar “works of art”. Go look it up.) Yet Slat would have us believe that a 40+ year-old plastic crate, existing in similar conditions in another ocean remains pristine. Look at the interior. Not even a vestige of marine fungus of the type that can be found growing on anything in the sea, from metal to rock to fibreglass, from shallow to tidal to inter-tidal zones. I ask that you look at the items Slat’s team took out of the ocean “only last year” (i.e. 2016), and reassess them in light of what you’ve hopefully just discovered for yourself. If you ask me, ignorant shipbuilders have been needlessly wasting money on antifouling when they could just have easily have put a sheet of plastic over their hulls and called it quits!

Moving along, the fact that Slat misidentifies small pieces of plastic as “microplastics” could just be due to his lack of formal education, but is troubling for someone who has supposedly spent the last six years “researching” the issue as an “engineer”. He says that the plastic items his team discovered are still large and will degrade into microplastic over the next few decades, yet this is a complete misreading of the debris sources. Primary microplastics are microbeads, smaller than grains of couscous, that are now a common part of exfoliation products, blasting technologies and drug delivery mechanisms. They don’t need to “degrade” over “decades”. They already exist in the oceans as tiny pieces of plastic entering our food chain.

Here, then, was a compelling and ready-made argument for Slat and yet he doesn’t use it. We could stop the production of primary microplastics quite quickly by mandating only natural and/or biodegradable products (e.g. pumice, oatmeal, ground fibre) be used in industry, so the omission is puzzling, to say the least.

The science

Slat suggests that the idea of using the movements of nature in order to do work is a novel one. Wow, who would have thought? Let’s discard the invention of the hot air balloon, kites, and the theory of flight! Why, none of those use the characteristics of nature in order to do work, do they? Does a nuclear bomb use the movements of nature to produce energy? Does hydroelectricity use the movements of nature to produce work? What about wind turbines? Sea turbines? I could go on and on. So the idea that one can use the ocean’s currents to concentrate the collection of garbage at sea level isn’t revolutionary (it’s how your bathroom sink works, after all) and I’m positive others have thought of it before; it’s just that they don’t have Slat’s formidable PR team.

At around minute 8:20, Slat talks about how he initiated the largest survey of the GPGP ever done, and he even presents a graphic on the routes his 30 ships took (see above).

This is a major problem because, according to the LA Times, this exact same survey looked more like this:

Random or a straight sweep? Why should it matter, you ask. So what if the LA Times has a different interpretation of how the survey was organised? It matters, dear reader, because both interpretations come from the same source: Slat’s own The Ocean Cleanup. Shouldn’t his own organisation know which one they executed? Watch the video at the LA Times and they even go into a little bit of detail on how they organised the straight sweep, so it isn’t a matter of mere simplification of method.

To what depth does the ocean need to be cleaned? “To just a few metres,” says Slat at minute 8:14. Yet, according to National Geographic:

“ Oceanographers and ecologists recently discovered that about 70% of marine debris actually sinks to the bottom of the ocean.”

Which is it?

At minute 8:50, the GPGP is crossed again with an airplane and, as Slat says, “this was actually the first time anyone conducted an aerial survey of, of an ocean garbage patch” (minute 9:00). Except, the original discoverer of the GPGP, Charles Moore, did this in 2014 through the auspices of his Algalita Marine Research Foundation using drones. (Interestingly, Moore’s date of discovery of the GPGP is also not certain. Moore says it was 1999 in an article he wrote for Natural History magazine, yet National Geographic Encyclopedia says it was 1997. Surely Moore’s own ship logs would have cleared up the misconception in short order, so why does a discrepancy remain?)

Furthermore, the GPGP is actually a zone of debris joining two vortices, one between the United States’ western seaboard and Hawaii, and the other south-west of Japan in the northern Pacific. Yet Slat, who has been intensively studying this problem for years, does not even mention the Subtropical Convergence Zone or the North Pacific Subtropical Gyre. I suppose all those technical terms were just too much for him to memorise.

But that’s not all. What about all those satellites whizzing around our heads, notoriously able to identify a bubble gum wrapper on a street in New York? Could none of them, operational for decades, survey the GPGP? In fact, wouldn’t it have been cheaper for The Ocean Cleanup to have hired a couple of minutes from an appropriately positioned, say, energy company’s satellite than to send out a cargo propellor plane “using the world’s most advanced sensors”? Just think of the fuel, equipment, outfitting and maintenance costs required to fly all the way out to the midpoint between the United States and Hawaii? Not cheap. A few satellite images would probably have been more economical.

At minute 9:59, Slat presents a “breakthrough” in how to anchor his screens to the ocean floor. In a nutshell, it discards the idea of anchoring the garbage collectors to the ocean floor in favour of floating heavy anchors in slower moving currents. It seems that, in modelling the ocean currents, Slat’s team found that at “only a few hundred metres” below sea level, the speed of ocean currents decreases dramatically.

His idea is to use the “braking” action of the screen anchors at, say, half a kilometre below the surface, to thus slow down the speed of the screens at surface level so that the plastic at surface level will effectively run into the screens, thus making collection more efficient.

I have one major issue with this hypothesis and Slat’s use of the word “speed” initially clued me in to this. You see, speed is a scalar; that is, it describes quantity but not direction. If you want to use a directional component, you use the word “velocity”. That’s standard O-level (junior high school) physics, which even Slat should have completed.

Go outside for a couple of hours, lie down on your back and watch the clouds. Like water, air too has currents. But if you cloud-gaze, as I do but not as often as I’d like, you’ll notice that different layers of clouds behave in different ways. In fact, it’s particularly entertaining when a higher layer of cirrus, for example, moves in the opposite direction to a lower layer of cumulus. Additionally, air has warm currents (low-pressure areas) and cool currents (high-pressure areas) that produce convection patterns within a localised area. That’s a very simple description of a very complex model, which is why meteorology isn’t yet an exact science.

Yet, the same kind of dynamics are also at play in the ocean. Marine currents have layers, and convection is also a major factor of current behaviour. In other words, just because an upper layer of water moves at a particular speed in a particular direction does not automatically mean that the lower layers move more slowly in the same direction. We know even less about water currents than air currents, so jumping to conclusions about this (and his idea of “drift” at 700m below sea level being identical in direction to the surface water) is simply bad science. And I’m not even mentioning the pressure differential which, I wouldn’t be surprised, may also have effects on current modelling, not to mention the effect of wind on surface level water movement.

Another point is the braking mechanism itself. I personally don’t see the need for these almost kilometre long heavy tethers just to stop the screens moving as fast as the debris. Here we move into the field of fluid dynamics, of which I know a little, but I would think that a modelling of planned turbulence vectors (yes! speed and direction!) around the screens would be able to produce a similar effect without those long-arsed anchors. Now, if he’d mentioned “stability” as a factor for those anchors, I may have understood it more, but that’s not how his team appears to be using them. In fact, I can easily imagine a storm hitting the middle of the ocean and all those floating pipes and skirts tumbling about and somersaulting, as nothing is keeping them stable.

Slat flubs it at minute 16:24 when he describes a “kedratic” equation. There is no such thing as a “kedratic equation”. I think what he’d like to say is a “quadratic equation”, but even that makes little sense because what he goes on to describe (a decrease in speed of one-fifth leads to a decrease in force of one-twenty-fifth) is “inverse proportionality”, a concept that is widely used when describing other forces such as gravity and luminosity.

A garden variety quadratic equation looks like this:

y = ax^2 + bx +c,

but in Slat’s illustration, we see no “bx + c” component. It’s a straight inverse proportionality. Thus bx +c must equal zero (i.e. y = ax^2), which makes the use of a “quadratic equation” to describe what he’s explaining—okay, I’ll say it—stupid. And remember, I’m only drawing on O-level maths here.

The fleet of smaller systems he mentions at minute 18:38 is one that actually makes sense as the screens can be leveraged to exploit localised conditions. However, Slat’s estimate of an incredibly large “several hundred million dollars” for the cleanup is actually, forgive the pun, a drop in the ocean compared to a lot of government programs. The “water tax” planned for hapless Californians, for example, (US$0.95 per Californian per month) is proposed to bring in US$2 billion over the next 15 years, in which case, what would be needed to bring in mere “hundreds of millions”?

Our global population currently stands at 7.7 billion. If the combined populations of the three most industrialised continents—North America, Asia and Europe (5.75 billion people)—contributed US$0.20 each, that would total almost US$2 billion, enough to get rid of allthe garbage patches throughout the world. Isn’t this what bodies such as the United Nations are supposed to be concentrating on?

If Slat flubbed it at minute 16+, he goes completely off the rails at around minute 22:07, when he says that “the more you slow down the system, the more plastic you would collect, right? But actually, the opposite is the case.”

But actually, I don’t know what he’s talking about. What system? His collection screens/skirts? The plastic? The currents? I’ve replayed this segment several times and still don’t know what he’s on about.

“The less you slow down,” he says; i.e. the less you decelerate, “the more you act like the plastic, the more these clean-up systems will gravitate towards those high-density zones and therefore catch more plastic.”

So is he now saying that he wants the clean-up systems to move faster, contradicting his “action” experiment where Bruno Sainte-Rose (Lead Computational Modeler [sic]) showed how the clean-up system moving slower captured the plastic? At this point, “How much more plastic?” is the least of my questions; my thoughts are more along the lines of, “Make sense, why don’t you?”

Just like Musk when he tries to explain, well, anything, Slat quickly drops that subject like a hot potato and goes to a completely different topic, the size of the GPGP.

At minute 23:30, he says, “we can now clean up 50% of the Patch in five years’ time”, but I hope you’ll take that with as much a grain of salt as his other pronouncements. There’s no basis, no methodology, no strategy, no explanation as to how he can do this. Just trust the dropout and everything will work out just fine.

At minute 27:02, a lovely graphic is shown of the “SEA ANCHOR”: “? SPEED: 20%”. The triangular symbol means “delta”, which is another way of saying “difference”. A “delta” only makes sense when comparing two elements of the same type. You can’t have a “delta” just sitting out there in a field by itself; it is defined as the difference between two other things that use the same scale. So if the temperature inside your house is 20 degrees Celsius and the temperature outside your house is 5 degrees Celsius, the delta—or difference—is 15 degrees Celsius.

Here, the delta between the speed of the sea anchor and the speed of the screen/skirt at the surface (because, really, that’s the only comparison that makes sense) is shown as “20%”, but this is clearly incorrect, as an earlier graphic (see one of the screenshots above) shows that the “speed” of the current at 600 metres’ depth is four to five times less than the speed at the surface. According to him. So the “delta” speed is actually more like 80% at a depth of 600m, assuming identical direction of movement of both components which, as I’ve said before, is a bit of an assumption. In other words, the graphic from Slat’s own organisation is, once again, wrong.

At minute 28:12, Slat talks about the manufacturing of the “first part of the floating pipe, the barrier”. Okay, so I don’t know the specifics of the floating pipe, but I assume that the “floating pipe” will, er, float on the surface of the water. TIME magazine helped me out on this by telling me that the tube will sit above a “10ft deep ‘skirt’”, which will trap the plastic. No, it won’t. Slat doesn’t like nets (sea creatures become ensnared) but that’s exactly what makes fishing nets so efficient. The holes are there to maximise throughput of water while catching as many fish as possible. If you doubt this, go cast a net using a bedsheet and let me know how it goes.

This comes back to fluid dynamics. Air is less dense than water and yet insect screens, which are by no means solid “skirts”, can still stop a substantial amount of air from moving through it. The solid skirt will collect some plastic debris but, due to the action of turbulence in (here I go again) fluid dynamics, the time will very quickly come when the skirt fills up, “under”flows, overflows or “side”flows the barrier, at which point the mechanism becomes—shall we say—suboptimal. I noticed that Slat didn’t go through any specifics of how and how often the debris will be collected. It’ll all just be beamed up into space or something, I suppose, at no extra cost.

If you think that’s the end of my criticism, unfortunately you’re wrong. And if you think I’m enjoying putting together such a long-arsed article that I know most people won’t read, you’d also be wrong. It’s just that Slat and his model have such gaping holes in their logic, that I can’t help but write to this length.

The audience stands

Why is the audience standing? The answer is, because they’re not sitting. You see, you can absorb more information when you sit, especially if there’s a lot of it headed your way. I have a standing desk and it has taken a bit of adjustment to get used to, and that is already with me absorbing information from the screen at a rate I set.

In Slat’s presentation, the information is being relayed to the standing audience at a rate that Slat sets. Not only does he move around a lot, causing people to shift their bodies to follow him, his presentation is also conflicting with people’s physiological level of comfort. We modern urbanites aren’t used to standing for any length of time. We shift, we look down, we fidget, we take note of how our feet feel, whether our heels are aching, why the person next to us is moving, adjusting to their movements, and so on. In other words, being part of a standing-room only audience, cognitively speaking, means that people will not be focusing all of their attention on what Slat has to say. That is why people who conduct standing briefings keep the points short and repeat them.

The only way I could absorb what was going on in Slat’s presentation was by (a) sitting, (b) watching the entire video several times over, and (c) frequently pausing and replaying certain sections. Slat’s audience had none of these advantages.

There is a reason why students sit when in lectures or at written exams. It has to do with physical comfort and concentration, two factors that are intertwined. If you’ve been standing for half-an-hour, I guarantee that unless you’re leaning against something, the only things you’ll be thinking about by minute 20 will be how much longer you have to stand and when will you be able to leave while still being polite. Thoughts like that don’t make for a very critical audience, but they do make for a very good uncritical cheering squad. Especially near the end.

Boyan Slat the dropout

For some reason, we keep getting sold on the idea that only dropouts are capable of great science. This riffs off Peter Thiel’s doomed “drop out grant” from 2014. Remember how well that worked out? Not. Boyan Slat, too, is supposedly part of Peter Thiel’s “I’m not going to get educated but I’m smarter than anybody else on this planet” group. Allegedly, he dropped out of aerospace engineering so he could research the ocean’s garbage patches, this “inventor since birth”. He also says that “everybody” told him that cleaning up the GPGP was “impossible”. Quite frankly, this is an insult to all engineers.

I know engineers. I have worked with them. I have engineers in my family. There’s nothing an engineer likes more than solving problems. Nothing. Engineers don’t see problems as “impossible”; they see them as puzzles to be unlocked. The very fact that there’s a difficult problem in the world is, to an engineer, akin to a red rag to a bull, so Slat’s assertions that he was told that “nothing could be done” about the GPGP, and that the problem was “impossible to solve” till he came along, is plain nonsense.

In fact, there’s an entire field of science called “marine engineering” dating back to the 1700s (if not to antiquity), yet it took an 18 year-old dropout to “solve” the problem of the ocean’s garbage? Please.

Boyan Slat the speaker

Boyan Slat is smooth. Boyan Slat is too smooth. He presents his case like a snake-oil salesman. Don’t get me wrong, he’s better than that stammering airhead, Elon Musk, but there’s the same aura of flim-flam around both men. I don’t see any passion, any emotion when I watch Slat; instead, I wonder how long it took him to memorise his lines.

As a public speaker myself, I can tell you that it takes time to present yourself well in front of an audience. My children are okay speakers, but it required years of coaching on my part to get them to a stage I still consider barely adequate. So where did Slat get his mad skillz from because, believe me, it doesn’t come without a lot of practice.

The GPGP itself

At minute 9:04 of the first video, we see the view from Boyan’s first ever aerial survey of the GPGP. Except we don’t. All we see is clear blue water. Which, again, seems like a huge misstep. If you want to guilt people into funding you, why not show the GPGP? Wouldn’t that be a powerful argument, pictures being worth a thousand words and video being worth a novel or two? After all, remember all those stark images and clips from Gore’s An Inconvenient Truth? Why don’t we see that here?

With that in mind, I went looking for images of the GPGP, just to help ole Boyan out. And, wouldn’t you know it, I couldn’t find any. I saw diagrams. I saw animations. I saw beaches strewn with rubbish. (We’re supposed to be in the middle of the Pacific Ocean, remember?) I saw tightly-focused photos of broken plastic. I saw floating debris with obvious landforms in the background (beaches, mountains, hills). But the GPGP itself? Nope.


I believe we should clean up after ourselves. I believe we should leave the kind of world that won’t turn around and bite our children and grandchildren after we’re gone. But I also believe in science. Real science. And what Boyan Slat is peddling ain’t it.

What is Boyan Slat after, then? I don’t know. Money, maybe. Fame. Power. Influence. Lots of girl/boyfriends. Who knows? But there’s enough deception in what he’s saying to make me not trust him. Any one of the points I have detailed above isn’t enough to damn him, but I believe that all of them together, are.

This isn’t science. This is a circus.

I’ll be keeping a close eye on The Ocean Cleanup and just hope that not too many people get duped before it all falls to pieces.

PS Maybe, at some point in the future, I may analyse Slat’s controlling, micromanagement style but, for the time being, I’m done. Thanks for reading this far.

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