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May 27, 2015

A deceptively simple way to clean up the world's oceans

By Barbara Speed

A year or so ago, a campaigner from the World Wildlife Federation told me that the Next Big Thing in environmental campaigning would be a push to rescue the planet’s oceans. 

“Seas aren’t under anybody’s jurisdiction,” she said. “Oceans need international effforts to protect the species that live there. And, that, for the most part, isn’t happening.” Combine this with oceans’ enormous size, and you end up with 70 per cent of the planet covered in what is basically an unregulated dumping ground with no designated caretakers.

It’s not surprising, then, that The Ocean Cleanup, a nonprofit with a new system designed to clear rubbish out of oceans, is able to claim its invention as the “world’s first” ocean cleaning system. The idea was bashed out by 100 volunteer scientists, and the subsequent stages of design and development have been totally crowdfunded. 

So how do you clear out swathes of the ocean on little money and no governmental support? Not easily. Take the “Great Pacific Garbage Patch” (also, excitingly, known as the “Pacific garbage vortex”): the Ocean Cleanup team calculated that, using nets and boats, it would take up to 80,000 years and billions of dollars to completely clear the rubbish out. The process would also generate lots of CO, which rather cancels out the benefits. 

These figures are almost mind-bogglingly depressing. But then, as they describe on their website, the Ocean Cleanup team had an idea which might just let them circumvent them: “Why move through the oceans, if the oceans can move through you?” The ocean is constantly moving the rubbish around of its own accord: could some kind of static sieving mechanism capture the rubbish as it passes without expending any energy?

The project’s current design uses a long, floating barrier tethered to a cable on the ocean floor. Because most plastic rubbish is lighter than water, the barrier is able to trap it without catching any sealife. When the team tried out a 40m length of the barrier as proof of concept, they saw that rubbish was indeed trapped, while even tiny sealife like plankton were not: 

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A 2,000m long prototype is due to be tested in coastal waters in 2016, but in the mean time the team have crunched some numbers to demonstrate how quickly their invention could clear up the oceans.They estimate that a 100km length of cleanup system, deployed for 10 years, would clear up over 70m kg of rubbish – the equivalent of 42 per cent of the “Great Pacific Garbage Patch”.This would cost an estimated €4.53 per kilogram of rubbish collected. 

Based on viability testing, the scientists reckon that the barrier would catch about 80 per cent of the detritus it comes into contact with, whiile its chevron-like shape would force it to condense at the barrier’s point, like so:

From there, the rubbish could be collected and recycled. 

The project’s still about five years from large-scale deployment, but if the science holds, it looks like it could pose a real solution. Now we just need to find that  €320m.

Images: The Ocean Cleanup. 

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