Garbage in, garbage out

A big test for an innovative approach to remove plastic trash from the ocean

Mon Nov 02 2015

Science and technology

Engineers and scientists will take on one of the world’s ugliest problems in 2016 as they test an ambitious method of cleaning the ocean of its tens of thousands of tonnes of floating plastic rubbish. The project is thoroughly unconventional. It was started by Boyan Slat, a teenage Dutch student, funded via Indiegogo, a crowdsourcing site, rather than by government grants—and at first criticised as impossible.

But in 2016 the Ocean Cleanup project is on track to build a 2km-long (1.2-mile) floating boom, claimed to be the longest structure the seas have ever seen, off the island of Tsushima in Japan. If it can remove floating junk cost-effectively, then planning will begin for a 100km structure capable of tackling the ocean’s most junk-ridden spots. Those include the notorious “great Pacific garbage patch” between California and Hawaii.

Out at sea, you are never out of sight of plastic waste which has been thrown from ships, washed down sewers and rivers, or blown from dumps. Retrieving that junk has always seemed impractical. It is spread over huge areas, and proposed solutions (such as towing giant nets behind ships) use enormous amounts of energy and endanger wildlife. It took a teenager to think differently.

Boyan Slat was 16 when he encountered seas full of garbage on a diving holiday. He came up with the idea of mooring a pair of long, floating barriers out at sea, facing into the prevailing current in a shallow arc. As the sea brought junk up to the barrier it would bob along the arms and towards the centre, where it would build up until it could be hauled out of the water in bulk. The moving water does the work of concentrating the rubbish and living creatures pass safely under the boom.

After his 2012 talk at a TEDx conference went viral, Mr Slat attracted engineers, oceanographers and donors. Tests of 40-metre-long booms provided proof of the concept, and a 535-page technical review written by over 100 scientists, engineers and companies muted objections that the technology could not be scaled up. The big test will come in 2016, when Mr Slat turns 22 years old, with the 2km boom being readied for Tsushima, an island which sees some 12,000 cubic metres of junk washed onto its beaches each year.

The project is already intensifying the debate over ocean garbage. Some believe that all effort should go into preventing plastic from getting into the oceans in the first place, not cleaning it up later. But long-standing regulations intended to prevent the dumping of plastic at sea have proved hard to enforce. Could effective rules really be agreed upon speedily?

The longer action is delayed, the more ocean plastic slips beyond the reach of even a project as ambitious as Ocean Cleanup. Recently scientists have discovered to their horror that floating plastic rapidly breaks up into ever smaller bits of “microplastic”. A survey in 2014 est­imated that at least 5.25 trillion pieces of plastic were floating in the sea and around 4.8 trillion of them were between 0.33mm and 4.75mm in diameter. Even so, the amount of plastic was far less than expected, suggesting much of it has broken into even smaller bits that were too tiny to have been sampled. These may have been eaten, or colonised by minuscule creatures and sunk into the depths.

What lies beneath

Visible littering of the ocean surface may thus be being replaced by an invisible poisoning, for microplastics both contain chemicals harmful to life and concentrate them from the surrounding water. Already scientists know that plastic particles are turning up in mussels and oysters harvested commercially. There is now a rush to find where the plastic is going and what the risks are. Landlubbers might wish to think that the sea is taking care of that vanishing rubbish for them, but they may be in for an unpleasant surprise.

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