Does the name Boyan Slat ring a bell? There is a good chance it does. The now 22-years old engineer from the Netherlands decided to tackle the huge plastic waste problem in our oceans, after encountering more bags than fish in a scuba diving trip in Greece when he was 16. He came up with an invention to clean up the ocean’s garbage patches, an idea that soon would capture the attention of many after a video of his TedX talk in 2012 went viral. What the young inventor proposed is, by all means, ambitious – and in the eye of some oceanographers straight away insane. Nonetheless, in 2013 Boyan Slat founded a company to realise his idea: the Ocean Cleanup was born. After he revealed some major design changes and an updated timeline during an announcement event Delft, the Netherlands, earlier this month, it’s time to have a closer look at how this young fella thinks he will make it happen.

Boyan Slat at the announcement event on May 11th, in Delft (photo: Pierre AUGIER for The Ocean Cleanup)

A new design for the Ocean Cleanup system

The Ocean Cleanup proposes a fleet of floating structures that will be deployed in the so-called Pacific garbage patch. This is a gyre of plastic debris in the North-Pacific, between California and Hawai. Each structure consists of a U-shaped floating barrier, with a solid shield beneath it reaching 3 meters deep into the water. This screen captures plastic floating on the surface and the upper layer of the ocean. The arms drive the debris to the centre of the system, where it is collected and stored to be picked up by a collection vessel. The whole structure is connected to an anchor that floats 600 meters deeper. There, the current is about 20% slower than at the surface, hence slowing the system down. Since the debris is moving faster than the barrier, it will catch up with the barrier and be trapped inside. At the same time, the system drifts and positions itself according to the currents of the Pacific gyre.

Computer rendering of the floating system. The U-shaped arms drive the garbage to its belly, where it will be collected (photo: the Ocean Cleanup)

The fact that the waste collectors will be floating instead of fixed was one of the big announcements at the event earlier this month.  The new design follows the philosophy that ‘to catch the plastic, act like the plastic’. With other words, float along with it through the Pacific gyre. A floating solution addresses at least one of the major point of critique on the original bottom-fixed design. The ocean reaches depths of 4.5 kilometres where Boyan Slat wants to hold his big cleanup. Engineers from around the world (including me) were very very sceptical how he was ever going to connect his system to the seabed.

The Ocean Cleanup team seems to have settled on the new design: Boyan Slat revealed that some components are already being manufactured, showing off a couple of anchors at the event site. By the end of this year, a pilot project will be deployed and roll-out of the clean-up should start in 2018, two years earlier than originally intended.

The anchor is drifting 600 meters below the water surface, slowing down the drifting barrier (photo: The Ocean Cleanup)

The new and smaller design of the floating collector is ‘better, faster, and cheaper’. Working with a fleet of several smaller units instead of a few very big ones undoubtedly makes the installation easier and allows a phased roll-out with lower upfront investment. Slat claims that the new design leads to improved efficiency of garbage collection and thinks he can clean-up 50% of the garbage patch in 5-years, based on their in-house simulations. 50% of the problem solved in 5 years. No wonder people cheer for this guy and donated more than 30 billion USD so far. I have serious doubts, but more about that later.

Mapping out the Pacific garbage patch

In the early stages of the idea, several people, under which die-hard sailors and oceanographers like Dr. Goldstein, Dr. Martini and Stiv Wilson, pointed out that Boyan Slat was missing the point completely with his invention. The Ocean cleanup system cannot pick up the smallest plastic particles known as microplastics. But, it turns out that these very small and brittle parts of plastic are the most harmful ones. They can easily be ingested by fish and end up in the food chain. Yes, potentially in your stomach!

But it has to be said that there was relatively little scientific research mapping out the Pacific garbage patch. Scientists had been modelling the plastic soup in our oceans, and there were records taken by fishers and sailors of the amounts of plastic floating around in the ocean. Estimates on the number of particles varied widely and typically only looked at particles smaller than 20 centimetres. The full picture was missing. Therefore, the Ocean Cleanup set out to take measure first hand in a couple of ambitious scientific expeditions.

Garbage capturing rig for the vertical analysis, investigating the amount of plastic debris as function of the water depth (photo: the Ocean Cleanup)

First, they undertook six ‘vertical analysis’ trips, where they investigated the number of particles as a function of the water depth. They found that with increasing depth, the number of particles rapidly decreases. They only measured up to 5 meters depth though, while previous researchers claimed that some particles float at higher depths and some even reside at the seafloor.

In August 2015, the Ocean Cleanup started the so-called Mega Expedition, in which they surveyed 3.5 million square kilometres with no less than 30 vessels. They took measure of the number of larger pieces of debris as well, which were mainly neglected by previous research undertakings. In the end, they gathered more data on the garbage patch than all research in the 40 years before. Or that’s at least what they claim. To map out the largest pieces of junk, disregarded ghost fishing nets, Ocean Cleanup launched an aerial expedition in fall 2016 to complete their survey of the Pacific garbage patch.

Collected waste during the Mega Expedition (photo: the Ocean Cleanup)

In fall 2016, an areal survey was undertaken to map out ghost nets (photo: The Ocean Cleanup)

Doubts, doubts, doubts

The fact that Boyan Slat and his team now know the area they want to clean up so much better can only be applauded. It makes their case much stronger, and their scientific contribution is admirable. It seems that the bigger parts of plastic are more numerous than previously thought, and in terms of weight they have a big contribution to the total plastic soup. Nonetheless, it seems that their undertakings have not influenced the basic idea behind the cleanup system: it’s still a U-shaped barrier floating at the water surface, just like in the early days. And the many other concerns uttered by scientists and engineers in the early stages of the project, have still not been addressed properly. A non-exhaustive list of doubts (please don’t hate me for this!).

One thing you might have been wondering about since the beginning of this article is how the hack Slat hopes to avoid collisions between ships and their fleet of waste collectors happily drifting around in the Pacific. That question also popped up on facebook soon after the event earlier this month, to which Ocean cleanup responded: “The moving systems will be equipped with Automatic Identification System (AIS), which is a maritime anti-collision norm, that will allow them to be noticed by ships and the other systems. They will also be equipped with reflectors to make them show up on radar.” I still want to see if they get all the regulation sorted out to even put the systems out there, but let’s assume they can get an expert on legislation on their side.

More problematic is the impact on marine life. The premise of the whole project is to get debris out of the ocean before it ends up in the stomach of a fish, turtle, bird or, eventually, human. But a structure like this, in an area with quite some migration of sea animals, will undoubtedly interfere with sea life. In fact, it will attract all kinds of shells and mussels that will feel very at home on the floating barrier. They in return will attract small fish, who attract bigger fish, which attract birds, and… before you know you have created a small ecosystem. But this is not what we want, because, if the collector works as it is supposed to, the concentration of debris at the collector is way higher than elsewhere in the ocean and hence aggravates the damage on the sea-life. Not to think about the damaging effect a tonne of mussels could have on the structural integrity of the system.

According to simulations, it would be far more effective to place garbage collection systems close to the biggest pollutors, shown by the circles in the image (source:

Even putting aside the argument that seems to come up every time – shouldn’t we address the issue at the source and just avoid plastic from getting into the ocean in the first place? – it has been shown that it would be much more efficient to capture waste more upstream before it ends up in Pacific garbage patch. As some scientists found in a simulation,  it turns out you better cast your nets right off the coasts of the world’s largest polluters. And it has been shown that about half of what ends up in the garbage gyre, is eventually spewed out again and ends up on a beach somewhere. So yes, it seems that the way more effective -but boring- way to clean-up the oceans is by waiting for the ocean to spew it back to us and clean it up there. Yes, I know, manually collecting garbage on the beach is by far not as cool as Boyan Slat’s fleet of Ocean cleaners.

Where is the business plan, sir?

What I find most striking though, is that four years after the Ocean Cleanup was founded, there still seems to be no proper business plan for the idea. Okay, the Ocean Cleanup is a non-profit, I get it. But eventually, the system should pay for itself right? The stream of enthusiastic donors is going to end at one point or another. It is loosely mentioned that the collected waste will be recycled and reused for production of all kinds of products. Even if we neglect the fact that it will be hard to compete with recycled plastic on land with respect to collection cost, there is still the huge issue of the quality of the plastic. It has been out in the ocean for many years, deteriorated by sunlight and the salty chemical soup our oceans are. The question is if the quality will be high enough to be accepted as raw material again. And anyways, typically some biological life has formed on the debris, which needs to be washed off before the plastic can be recycled.

Final thoughts

Look, I really don’t like that I have to write so many negative things about Boyan Slat’s grand idea to clean up the oceans. It’s a noble cause from a guy that has the same age as me. I can only feel respect and awe for the fact that he taken up this challenge. His announcement – or should I call it show? – a couple of weeks back had the allure of a Silicon Valley pitch. And yes, one should dare to dream big if one wants to solve such big problems.

But by stubbornly sticking to the initial idea of a floating barrier that is going to scoop the debris from the oceans, I think the Ocean Cleanup is making things more complicated (and expensive) than necessary. I wish they had done the effort to analyse a broader range of solutions first, rather than working out the original concept straight away. But, as an engineering student with entrepreneurial ambitions myself, I know how damn tempting it is to not challenge your own invention, knowing that you might as well find out someone else’s is better.


This article is mainly based on the information available on the Ocean Cleanup’s website, the announcement event on May 11th in the Netherlands, scientific reviews of the project by oceanographers Dr. Kim Martini and Dr. Miriam Goldstein in 2014 and 2016, and an opinion piece by policy director of the ocean conservation nonprofit Stiv Wilson