Many years ago, Dutchman Boyan Slat set out with his project The Ocean Cleanup (TOC) to solve the problem of marine litter. At just 20 years old, he made a name for himself, which—in addition to the very ambitious plan—contributed to his project receiving a lot of media attention. Slat’s big goal then was to completely eliminate the Great Pacific Garbage Patch.
The Great Pacific Garbage Patch is the largest known rubbish patch in the ocean. It is located in the central North Pacific and covers an area of around 1.6 million square kilometres. Around 45,000 to 129,000 tonnes of plastic marine litter float on the surface of the water here; from plastic bags and packaging to bottles and fishing nets.
Since its first announcement 10 years ago, The Ocean Cleanup has made an announcement every few years about its major successes or failures. In autumn 2024, Boyan Slat announced that his technology could clean up the entire waste vortex in the Pacific within a decade, at a cost of just 7.5 billion dollars. But if things went well, it could be cheaper, said Slat.
An “ocean hoover” against marine litter
The technology behind Slat’s project is simple. The so-called “System 03” consists of a 2.2-kilometre-long barrier towed between two slow-moving ships. The marine litter caught in the barrier is floated into a net. When it’s full, it’s pulled out of the water and the waste is dumped on the ships. Monitoring data and AI modelling show the way to particularly dense plastic carpets. The system claims to be so effective that it can clean the area of a football pitch every five seconds.
This picture shows the barrier with the safety net in the centre. It is tempting to believe that this is the solution to marine litter. “Wouldn’t it be great to have such a simple solution?” asks Ewoud Lauwerier, plastics policy expert at OceanCare. The cleaning projects certainly seem attractive to the general public and the industry, which shows the popularity of TOC. But is the whole thing really realistic? Can our oceans be cleaned up so easily? And will we actually end up with one less problem—or will we create new ones?
Technically, “rubbish catching” is not a problem
The Ocean Cleanup has already proven several times that the technology works and that large quantities of plastic can be captured. In itself, however, this is not rocket science, as Mark Lenz, a marine researcher at GEOMAR, explains in an interview with RESET. “In principle, Boyan Slat has only further developed the concept of oil booms. He scaled up the idea of trapping drifting material at a barrier and then collecting it for plastic waste.”
The plastic waste is unloaded onto the ships in the TOC project and then transported ashore. However, environmental organisations and researchers have doubts as to how sensible the endeavour is. A report published in October 2023 by the Environmental Investigation Agency (EIA) and OceanCare emphasises the harmful effects of “quick-fire technologies” to clean up the oceans. Other studies also show that TOC and similar technologies are ineffective and capital-intensive. They often even become a threat to the very species and ecosystems they are intended to help.
Such an intervention would not be possible on land
Marine biologist Mark Lenz supervises and coordinates a research and training programme for Master’s students at GEOMAR and has done a lot of research on plastic. Lenz explains that waste collection campaigns on the open sea are extremely time-consuming. “You have to use ships to collect the material and transport it away.” And it’s a long way because the rubbish swirls are on the open sea. As marine diesel is particularly harmful to the environment, the cleaning operations generate high CO2 emissions. Studies have shown that 200 ship-based cleaning devices would not clean the world’s oceans even if they were operated continuously for more than 100 years, but would have a significant impact on the climate.
And, of course, not all litter can be collected. Small pieces of plastic in particular, known as microplastics, pass through the nets with ease.
Mikroplastic: Life in plastic – it’s… not fantastic!
Society’s over-reliance on plastics is affecting almost everything on this planet. The plastics industry is the fastest growing source of industrial greenhouse gas emissions in the world, but that’s not all.
Plastic is now almost everywhere in the environment. The list of possible and impossible places where scientists have found microplastics is long. On the highest mountain, in the deepest ocean, in human blood – and even in the breath of dolphins.
What’s more, large-scale clean-up campaigns such as TOC are massive interventions in a fragile ecosystem. It is precisely where currents collect the marine litter that small creatures are driven to. In Hawaii, for example, plastics were found in seven out of eight fish families in the surface slicks of Hawai‘i. These areas of ocean, where currents converge by the water’s surface, are vital nurseries for young fish and larvae, many of whom are caught and used for commercial purposes.
“Many plankton organisms do not have a solid exoskeleton to protect them from external influences, and the same applies to jellyfish, larvae and fish eggs. If you deploy a solid barrier in the open ocean, they are pressed against it and injured. It’s like insects hitting a windscreen. They are probably also crushed between the pieces of rubbish,” says Mark Lenz. And we don’t yet know exactly what happens when clean-up operations with fixed barriers take place across large areas. “If you wanted to do something like this on land, environmental impact assessments would have to be carried out first. This is not necessary in the open ocean because there are hardly any corresponding international laws,” says Lenz.
It is not only small marine animals, but also larger fish that end up in the net. During TOC’s deep-sea clean-up operations in 2020, the organisation reported sea turtles (including endangered species), sharks, various fish species and cephalopods as bycatch.
The TOC team is working on using cameras and image recognition to identify unwanted bycatch so that it can then be released. However, it’ll probably not be possible to avoid this completely.
Well meant is not always well done
With these significant impacts on living organisms, it is difficult to assess the actual benefits of clean-up operations. Many researchers would rather leave the rubbish to its own devices. “The floating materials are often already part of the ecosystem. Many invertebrates colonise it and fish like to hide under the flotsam,” reports Lenz. If the rubbish disappears, their habitat is lost. Plastic waste in the open ocean is therefore not exclusively bad for marine life. This makes it almost a philosophical discussion as to whether the rubbish should be collected or not, Lenz points out. And gives another example:
“In the 1980s, the coast of Alaska was polluted by oil and a great deal of effort was made to clean up the coast. Back then, water jetting systems and chemicals were used to remove oil residues. Looking back, there are ecologists who say that the clean-up ultimately had worse ecological consequences, at least for the coast, than the actual pollution.”
So are TOC and similar projects causing more damage than the marine litter itself? The final answer is still pending. What is certain, however, is that litter clean-ups in the open sea start far too late.
Collecting rubbish in the open sea is too late
“Collecting the waste at the very end of the journey, just before the parts sink into the deep sea, does not address the causes,” says Lenz. Rather, such clean-up projects serve the industry above all to divert attention from the real problem. Of course, TOC and other media-effective projects can be credited with drawing attention to the issue in the first place. At the same time, however, they suggest to the public that there is a simple solution to the problem.
This is particularly problematic if it means that other, much more sensible initiatives are neglected and problems that could be solved on land are lost sight of.
How can the 7.5 billion euros be put to good use?
“Much more can be achieved with the seven and a half billion euros if the money is used differently,” Mark Lenz is convinced.
Instead of collecting rubbish in the open sea under the most adverse conditions, the main aim is to stop the flow of plastic before it even reaches the natural environment. The very first step is to produce less waste. Then it’s about dealing with waste more responsibly. “This can only be achieved through better management. But in many countries, the technical possibilities are simply not there because there is not enough money. That’s exactly where we need to start.”
Even if immediate and consistent measures were introduced, the plastic waste entering the environment cannot be stopped immediately. “In this respect, you can certainly think about collecting the waste again,” says Lenz. However, it makes more sense to start earlier. Namely, where the waste is concentrated and large and has not yet become part of the ecosystem. “This could be river estuaries, for example. You also have bycatch there, but it may be in better proportion to the amount of plastic that can be removed.”
Cleaning up rivers, harbours and beaches
One of The Ocean Cleanup’s solutions for catching plastic waste in rivers. With its “Interceptor Solutions”, The Ocean Cleanup is also working on high-tech to low-tech solutions to intercept plastic from rivers. The Amsterdam-based company Great Bubble Barrier has also developed a technology that uses air bubbles to trap plastic in rivers. However, here too, the negative effects on ecosystems must be balanced out by the positive effects. The collection technologies in rivers not only collect plastic particles, but also organisms, wood and other natural flotsam. Researchers at the Alfred Wegner Institute therefore emphasise rainwater catchment basins as a more environmentally friendly alternative. Here, large pieces of plastic are retained closer to the point of release and do not end up in streams and rivers in the first place.
Many harbours around the world use plastic separation technologies such as Seabins, which skim floating debris from the sea surface by pumping water into a collection device. However, a scientific evaluation showed that they only collect small amounts of plastic (0.0059 kilos per day), but significant amounts of seaweed. Floating rubbish bins in harbours therefore appear to be a pointless endeavour from the outset.
Beaches also need quiet zones
The same applies to beach clean-ups. If heavy equipment is used here, sensitive ecosystems are destroyed. Even if plastic waste disturbs the image of a perfect beach, animals and plants often live better with it than with invasive cleaning operations.
Manual maintenance, a lower maintenance frequency and the designation of quiet zones, on the other hand, reduce the pressure on ecosystems, as a study by the Alfred Wegener Institute recommends.
A large proportion of plastic waste is washed ashore and all measures implemented on land help to reduce this proportion.
Another part is fishing nets and other fishing legacies. A much more targeted approach could be taken here. One example of this is the WWF’s ghost nets project. “We have been working on this project in Germany since 2016 and have successfully recovered several tonnes of ghost nets in the Baltic Sea,” explains Gabriele Dederer, Ghost Nets Officer at WWF Germany.
To locate the ghost nets, the team uses side-scan sonar devices and travels to the sites by sailboat. Divers can also participate in the preparation of ghost net recovery operations by documenting and checking finds using the GhostDiver app.
The answer can be found on land
No matter how many attempts we make, with whatever technology, to rid our oceans of marine litter, we can only get to grips with the problem if we stop the proliferation of plastic on land. Avoiding plastic on an individual level is not unimportant, but it is only a small part of the solution. What is urgently needed above all is a binding, far-reaching global agreement to reduce plastic production that holds companies and industry to account.
Initial negotiations are underway with the UN agreement against plastic waste. However, there are no real results yet. For these talks to be successful, governments need to feel more pressure from citizens and civil society.
It is also important to support countries in the Global South, which often suffer disproportionately from the effects of plastic consumption worldwide, in waste management. Technologies can have their place here, if they are used in the right places.
Ghana, for example, is demonstrating how citizen science can become a bridge between citizens and policymakers in order to tackle the problem of plastic waste together. In this African country, existing citizen science data and networks are being used to close data gaps at the national level and thus contribute to global SDG monitoring and reporting. More about the project: Ghana relies on citizen science to combat plastic waste
