Is it true that open ocean clean-up is an effective way to tackle plastic pollution
It’s uncertain whether cleaning up the open oceans is a good idea or not. The pros and cons for each technology and location need to be carefully evaluated on a case by case basis. Clean-up could have benefits. Removing larger pieces of plastic from the ocean before they degrade into microplastics or nanoplastics reduces the risk to marine life and can help monitor plastic pollution and inform policy. But ocean clean-up technologies might also cause their own problems. They might harm ecosystems, contribute to climate change, or remove only a small fraction of the pollution at a very high cost. Technical solutions can also displace other solutions because the public and policy makers assume the problem is solved so we do not need to modify our plastic consumption or reduce plastic production. With careful consideration, clean-ups could have benefits in some locations. But, when new plastic enters the ocean every day, clean-ups won't end pollution on a global scale.
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It is estimated that several million tons of new plastic waste enters the ocean each year. Since plastics are very persistent and don’t easily biodegrade, the total amount of plastics in the ocean is growing. According to a 2024 report by the British Royal Society, “cleaning up plastic from the environment will never be as efficient as taking preventative measures to tackle plastic pollution at source”.
But environmental clean-up can also be beneficial in some instances, especially when it’s done closer to the source of plastic pollution, closer to or on land, at river mouths or sewage outlet pipes. Clean-up of the open ocean, however, is much more challenging, as plastic pollution disperses over vast areas and into the depths and ecosystems of the oceans.
In the past two decades, several organizations and entrepreneurs have designed devices including drones, platforms and ships to remove plastics from the ocean. The most well known is the Ocean Cleanup (TOC), a Dutch non-profit organization. TOC deploys booms dragged by ships to scoop up plastic waste from the surface of the open ocean. They operate in The Great Pacific Garbage Patch, an area located in the North Pacific Gyre between Hawaii and California.
The North Pacific Gyre is one of five great ocean gyres. These are large areas of rotating ocean currents in the Pacific, Atlantic and Indian Ocean. Gyres form because of the rotation of the Earth, the Coriolis effect. When plastic trash reaches these currents, it can get trapped there and circulate for many years. Eventually, currents might take some of the plastics away into other ocean areas, or to a beach.
Although these areas are most infamous for plastic pollution, it is estimated that just 2% of marine plastic floats on the surface of the open ocean surface. Most plastic (88%) is thought to stay closer to shore, sink deeper down the water column, or get deposited on the seabed. Some of the plastics also circulate through the food-chain, because they get eaten or incorporated into the bodies of marine animals and organisms. This means that clean-up technologies that operate on the surface of the high seas can catch a very small amount of the total ocean plastic. On the other hand, the surface of the ocean is an important place for many marine organisms to feed, float and breathe. So in places where the surface plastics strongly endanger them, there could be benefits to carefully removing this waste.
To understand the harms and benefits of clean-up, we also need to consider the climate impacts and costs. Most operations on the open ocean are expensive and energy intensive, and the oceans are vast in size. Plastic pieces are spread thinly over wide areas of the ocean like a “plastic soup”. There are no plastic islands you can just go to and start easily removing.
The Ocean Cleanup (TOC)’s approach is to create an “artificial coastline” at the surface where plastic gets stuck and can then be collected and removed. They use a long tube with a net attached. The original idea, presented by founder Boyan Slat in 2012, was to take advantage of the rotating currents of the gyre to capture the trash floating in the patch, not follow the plastic items actively with ships or drones. TOC wanted to avoid spending a lot of fuel, which would cause greenhouse gas emissions. But the idea wasn’t feasible, and TOC later reverted to using ships to drag the device while purchasing carbon offsets.
Scientists also worry that the side-effects of placing such barriers in the ocean might cause harm to the ecosystem. This may occur when wildlife gets stuck in the nets as bycatch, or when organic matter needed in the ecosystem, like algae, is being removed together with the waste. The neuston, a community of small organisms that floats on the ocean surface and is crucial to ocean health, is thought to be especially vulnerable. These organisms float with the wind and cannot actively swim around or underneath a barrier. The Ocean Cleanup has installed a marine animal safety hatch to avoid such bycatch.
Data from over 1500 waste-collection events in 84 countries suggest that the more plastics a company produces, the more pollution it causes in the environment. The need to reduce plastic production is also supported by studies that calculate future scenarios for tackling plastic pollution. Therefore it is crucial to close the “plastic tap”.
Imagine you leave a bath tap running water, and it is overflowing. You can mop the floor as much as you want, but you will never be done unless you turn off the tap. This analogy is used frequently to explain why cleaning up the oceans will not be sufficient to solve the plastic problem. Unless we turn off the “plastic tap” by reducing and stopping the flow of plastics into the oceans, clean-ups will be a never ending, sysiphean task.
While closing the tap is the most impactful step, there might be cases where clean-up is justified and brings a net benefit. The British Royal Society report notes that in “carefully considered” cases and locations, removing plastic from the environment could be beneficial - for example, when it protects habitats for rare and endangered species, ensures food security for the local population, or when the damage by pollution is very high. This needs to be weighed against the feasibility, effectiveness and risk of negative consequences of the clean-up technology.
The Royal Society notes that clean-up closer to the source of the pollution, such as in rivers or on coastlines, will likely be more effective than trying to clean up once plastic has dispersed thinly over vast areas of the open ocean. This is already being done in a number of places. For example, the city of Baltimore in the United States installed a “Trash Wheel” in the harbor in 2008. At the outflow of a river, this moored platform rakes trash onto a conveyor belt, powered by a water wheel and solar cells, and collects it in a container. A small number of similar interceptors have been installed around Baltimore since.
The project illustrates the co-benefits of cleanup for public conscience and policy. A clever and fun communication campaign inspires people to follow “Mr. Trash Wheel” on- and offline, inspiring people to tackle plastic waste and pollution. The Trash Wheel also collects data. It showed the large amount of Styrofoam foodware in their capture device. This informed a ban on this material in 2020. After the ban, the amount of styofoam in trash wheels has dropped significantly. This shows the benefits of monitoring to inform solutions and their effectiveness.
The Ocean Cleanup has scaled up the idea of river collection. Since 2019, TOC has installed over a dozen “Interceptors” in different locations in Asia, South America and the United States. There are many other projects, that are less publicized, such as the “WasteSharks” aquadrones in Toronto, or the “Litta Traps”, catchpit inserts that can be installed on roadsides to filter stormwater runoff. These are just a few examples of the many inventions and solutions people have come up with around the world. This also includes low-tech and local community solutions.
However, catchment devices in harbors, rivers and along the coasts can also have environmental impacts that will need to be carefully weighed against the benefits. The Royal Society calls for a regulation of clean-up technologies to ensure their benefits are greater than their harm. This includes conducting environmental impact assessments, life-cycle analysis, documentation of efficiency, bycatch and the management of the recovered waste.
Expert check
Thanks to Chelsea Rochman of the University of Toronto for scientific fact-checking.
Updated on: October 14, 2024