Case Study: Mopping Up A Sea Of Plastic

Boyan Slat – The Dutch Man Mopping Up a Sea of Plastic

Boyan Slat is a 23-year-old on a mission – to rid the world’s oceans of floating plastic.  He has dedicated his life since his teenage years to finding a way of collecting it.  But can the system really work – and is there any point when so much new plastic waste is still flowing into the sea every day?

An idea came to him at the age of 16, in the summer of 2011, when diving in Greece.  “I saw more plastic bags than fish,” says Slat.  He was shocked and even more shocked that there was no apparent solution.  “Everyone said to me: ‘Oh there’s nothing you can do about plastic once it gets into the oceans,” and I wondered whether that was true.

Over the last 30 to 40 years, millions of tonnes of plastic has entered the oceans.  Global production of plastic now stands at 288 million tonnes per year, of which 10% ends up in the ocean in time.  Most of that – 80% – comes from land-based sources.  Litter gets swept into drains, and ends up in rivers – so that plastic straw or cup lid you dropped, the cigarette butt you threw on the road… they could all end up in the sea.

The plastic is carried by currents and congregates in five revolving water systems, called gyres, in the major oceans, the most infamous being the huge Pacific Garbage Patch, half way between Hawaii and California.

Although the concentration of plastic in these areas is high – it’s sometimes described as a plastic soup – it’s still spread out over an area twice the size of Texas.  What’s more, the plastic doesn’t stay in one spot’ it rotates.  These factors make a clean-up incredibly challenging.

“Most people have this image of an island of trash that you can almost walk on, but that’s not what it’s like,” says Slat.  “It stretches for millions of square kilometres.  If you went there to try and clean up by ship it would take thousands of years.”  Not only that, it would be very costly in terms of both money and energy, and fish would be accidentally caught in the nets.

 Slat had always enjoyed working out solutions to puzzles, and while pondering this one, it came to him – rather than chase plastic, why not harness the currents and wait for it to come to you?

At school, Slat developed his idea further as part of a science project.  An array of floating barriers, anchored to the sea bed, would first catch and concentrate the floating debris.  The plastic would move along the barriers towards a platform, where it could then be efficiently extracted.  The ocean current would pass underneath the barriers, taking all buoyant sea life with it.  There would be no emissions, and no nets for marine life to get entangled in.  The collected ocean plastic would be recycled and made into products – or oil.

The high school science project was awarded Best Technical Design at Delft University of Technology.  For most teenagers, it would probably have ended there, but Slat was different.  He had been interested in engineering from a very young age.  “First I built tree houses, then zip-wires, then it evolved towards bigger things,” he says.  “By the time I was 13, I was very interested in rocketry.”  This led him to set a Guinness World Record for the most water rockets launched at the same time: 213, from a sports field in his native Delft.  “The experience taught me how to get people crazy enough to do things you want, and how to approach sponsors.”  Useful skills, as it turned out.

When Slat began studying aerospace engineering at Delft University, the idea of cleaning up the oceans just wouldn’t let him go – he says it niggled at him like “an asymmetrically positioned label” on a pair of boxer shorts.  He set up a foundation, The Ocean Cleanup, and explained his concept in a TedX Talk: How the Oceans can Clean Themselves.  Then, six months into his course, he made the decision to pause both university and social life to try make it a reality.

His entire budget consisted of 200 euros (£160) of saved-up pocket money, so he spent a few desolate months trying to get sponsorship.  “It was so disheartening, because no-one was interested,” he says.  “I remember one day contacting 300 companies for sponsorship – only one replied, and that too resulted in a dead end.” 

But then something happened.  On 26 March 2013, months after it had gone online, Slat’s TedX talk went viral.  “It was unbelievable,” he says.  “Suddenly we got hundreds of thousands of people clicking on our site every day.  I received about 1,500 emails per day in my personal mailbox from people volunteering to help.”  He set up a crowd-funding platform that made $80,000 in 15 days.

Turtles tend to be the victims of plastic bags, which when immersed in water look just like jellyfish. E volutionary adaptations make it impossible for turtles to reject bags once they’ve started to eat.  Because jellyfish are so slippery, turtles have a system in their throat that stops their prey from slipping out, so even if they find out it’s a plastic bag, it has to go in all the way.

The problem with consumer plastic is that there is little profit in taking back waste.  It doesn’t cost us anything to throw it away.  But the cost to us could be very high, in the long term.  Plastics can act as a sponge and soak up chemicals in the water.   There are a lot of pollutants in the oceans now, such as DDT used in pesticides.  Those chemicals adsorb on to the plastic and and birds and fish the plastic.  This then raises the question of how that transfers up the food chain and what is the impact.

It is a grave situation – so when Slat came along with a seemingly simple solution, he began making headlines across the world.  Could a teenager save the world’s oceans?  His enthusiasm fired up millions of people, but along with the offers of help and donations, came criticism.  It wouldn’t work, some said.  Others argued that it would be better to collect litter from beaches, where it gets deposited by waves.

“It’s in my nature that when people say something is impossible I like to prove them wrong,” Slat says.  Having caught the world’s attention, the first thing he did was to disappear from sight.  He needed scientific evidence to back up his theory and answer his critics.

He assembled a team of 100 people, mostly volunteers, who were spread out across the world.  “To manage so many people at such a young age was “interesting”, says Slat.   During the feasibility study, Slat visited the gyre, known as the North Atlantic Garbage Patch, where his platform was destined to be built.  “I was pretty seasick for the first three days.  There were winds of 25-30 knots and waves 3m high.  It was quite an experience,” he says.

In June 2015, a month before his 20th birthday, Slat re-emerged with a 530-page feasibility report, the cover of which was made out of recycled ocean plastic.  The report, based on extensive testing and computer simulations and authored by 70 scientists and engineers, answered many of the questions which had been levelled at him by his critics.  It was followed by another crowd-funding campaign which swiftly reached its target of $2m.  This would fund a larger pilot the following year and Slat hoped his North Atlantic platform could be a reality in 2020.

But if Slat expected all experts in the field of ocean plastics to welcome his concept this time, he was wrong.  One problem is that plastic isn’t just floating on the surface, but found throughout the water column, even in sediment at the bottom of the ocean in its deepest parts. 

Another issue is the potential effect on wildlife with some experts believing that fish eggs will be mopped up with the plastics.   Aside from the question whether the Ocean Cleanup technology could work, there is also the question whether it should be a priority.  Many experts believe that funding should be channelled into approaches to stop the plastic from entering the oceans in the first place.  There’s no point mopping up the bathroom floor if you leave the bath running.

The mop analogy is one that Slat has heard often, and it really gets him fired up.  “First of all, the ‘mop’ hasn’t been invented yet so it certainly can’t do any harm to try,” he says.  As for focusing solely on prevention, he feels it is an “uninspiring and demotivating message to say ‘The best we can do is not make it worse’.  “He adds: “Of course it shouldn’t be an excuse to pollute, but I think it’s a motivating message that it’s not a hole that’s too deep for us to climb out of.”

Several other companies are now emerging with clean-up technology designed to capture plastic in rivers and streams, like the Plastic Visser (‘plastic fisher’) which is being trialled in the Netherlands, or the Trash Wheel – a solar-and water-powered barrier being used in Baltimore harbour.

Slat, too, is looking to develop spin-off technologies for use in rivers.  “It is difficult to adapt something that works in rivers to the sea, whereas it’s actually quite easy to adapt something that was developed for the worst conditions in the world – the sea – to work in rivers,” he says.  “That is why we’re approaching it in this order.”

Slat doesn’t think his youth has held him back, if anything it may have been an advantage:  “Not only does it make the story more appealing, but I think I’m very enthusiastic about my concept and that really helped,” he says.

Besides, he had everything to play for.  “I had nothing to lose except my study income, so it was not a worry,” he says.  “If you want to do something, do it as soon as possible.”  A rallying cry to teenage inventors everywhere.

Cleaning up the Great Pacific Garbage Patch using conventional methods – vessels and nets – would take thousands of years and tens of billions of dollars to complete.  Boyan Slat’s passive systems are estimated to remove half the Great Pacific Garbage Patch in 5 years, at a fraction of the cost.  The first cleanup system is set to be deployed mid-2018.

For more information, visit the Big Ocean Cleanup website at

This case study was written by Vibeke Venema for the BBC World Service and is displayed on the BBC News website at