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The Ocean Cleanup: the next phase in capturing plastic

There is so much plastic in the ocean, there is no way to clean it all up. The best thing we can do is not making it worse. Right? Not according to the Dutch foundation The Ocean Cleanup. Yesterday (11 May), the foundation announced the next step in their project to rid the ocean of plastic. The new device they launched gathers plastic by following the currents, and allows for half of the Great Pacific Garbage Patch to be cleaned up in just 5 years.

Most of the plastic in the ocean is found at the surface. The material floats around, following the currents. These currents cause the material to gather in certain places in the ocean, forming so called garbage patches. There are five main places where the plastic gathers, the largest of which is the Great Pacific Garbage Patch. This garbage patch will have the size of California by 2030 if we continue with our plastic consumption as we are.

While the majority of the plastic still consists of larger pieces, when plastic becomes older, it turns brittle. Small pieces, microplastics, break off, which are ingested by animals that mistake it for food.

The Ocean Cleanup was set up in 2013 with as goal to clean the oceans by getting rid of the plastic, their main aim being to clean up the Great Pacific Garbage Patch. Instead of going after the plastic with vessels and nets, they are developing a network of long floating U-shaped barriers with screen attached to them that act as an artificial coastline. These barriers work with nature, using the ocean currents to their advantage to catch plastic.

Last year, the foundation took 1.5 million pieces of plastic out of the ocean thanks to their technology. Because the screens they use are closed, there is no bycatch of fishes, only plastic.

On 11 May, the CEO of The Ocean Cleanup, Boyan Slat, announced the new and improved design of their clean up device. Using the slogan, “To catch the plastic, act like the plastic”, they made a clean up device that drifts, rather than one that is fastened in one place.

The currents are still doing the work. The U-shaped screens channel floating plastic to a central point. Because theses screens are free to float about, they follow the plastic. To make sure they catch the plastic, four sea anchors are fastened to a screen, so that they are slowed down. These anchors, each 12 metres (40 feet) long, hang at 600 metres deep, where the ocean currents are much slower than at the surface.

Aside from being more efficient in capturing plastic, the drifting barriers have another advantage over fastened ones. The fastened ones had to be anchored with thick, strong ropes to withstand the forces of nature, for instance during a storm. The drifting barriers, however, follow the water where it goes, so much less material is needed.

The floaters of the new barriers will be a continuous hard-walled pipe made from high density polyethylene (HDPE), an extremely durable and recyclable material. The pipe, with a length of 1-2 kilometres (0.6-1.2 miles), is flexible enough to follow the wave and rigid enough to keep its U-shape.

Rather than one massive barrier, the improved clean up system consists of a fleet of screens. Because of this, the project can be scaled up, instead of making one large investment at once.

Once the buffer of the cleanup system is full, a support system empties it using pumps and belts, before shipping the plastic back to land. So what to do with all the caught plastic? In addition to catching the plastic, The Ocean Cleanup also designs processes to turn recovered ocean plastic into valuable raw materials.

The aim with the old barriers was to clean up 42 per cent of the Great Pacific Garbage Patch in 10 years. Now, the goal, which has been simulated by computer models, is to clean up 50 per cent in only 5 years.

A 100-metre (328-feet) prototype of the plastic catching device was tested in the North Sea in June 2016. The new system will be tested at the west coast of the US at the end of 2017. With the first deployment in the Great Pacific Garbage Patch in the first half of 2018, The Ocean Cleanup will start its mission two years ahead of schedule.

To see yesterday’s announcement, click here.

Renderings: The Ocean Cleanup

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