Sweeping Plastic out of the Oceans

Cleaning up oceanic garbage is a laudable enterprise, but not as easy as it looks.

In a culture that reveres young entrepreneurs who seem wise beyond their years, Boyan Slat, a 19-year-old Dutch aeronautical engineering student, has become a darling of the TED Talk circuit and environmental movement. Celebrities, journalists, and United Nations officials have showered him with praise for his proposal to construct an offshore floating structure that will sit in the middle of ocean currents and sweep up floating plastic debris. However this is not just a theoretical presentation at a science fair, Slat is taking steps to make it happen. The first seven days of his crowd funding campaign raised nearly $200,000 in contributions from over 3,300 backers, and so far it has raised over half of its $2 million goal.

Often described as garbage “patches” that give the misleading impression that the waste is concentrated into large clumps—it is actually scattered and very diffuse—plastic pollution in the oceans is a major environmental problem. Marine animals, incapable of distinguishing between food and floating trash, ingest the deadly litter often resulting in death by choking, intestinal blockage and starvation. Plastics do not degrade like organic matter, but they do eventually break into smaller and smaller pieces, causing other problems. Smaller plastic particles can be ingested by marine life without necessarily choking, but chemical compounds in the materials poison the food chain, which eventually have a knock-on effect on humans. Because of the robust properties of plastics, this is a one-way problem that ratchets upwards as more and more garbage makes its way into the seas, 80 percent of it originating on land and some of it washing up on shore where it causes more problems.

Traditional solutions take the form of ships moving through the water trailing large booms that gather up the rubbish like a minesweeper or trawler. Slat’s proposal is to save energy by letting the garbage come to the collector rather than the other way around. A large v-shaped floating boom structure would be moored offshore in a known path of plastic pollution, catch floating garbage as it flows along the gyre, and funnel it to a collection platform in the center where it is periodically emptied by a visiting ship. Marine life can pass safely underneath the boom. Smaller plastic particles can be separated from the water, without destroying plankton, using a centrifugal process. Slat maintains that the system can be automated, powered by renewable sources, and the sale of retrieved plastic can make the operation profitable.

A pressing problem, an attractive solution proposed by a young visionary, no apparent financial downside, and attractive renderings depicting the array sitting in calm waters beneath a blue sky have made this a prime candidate for social media sharing by well-intentioned people.

It has drawn the attention of Deep Sea News (DSN), a blog maintained by a group of scientists and PhD candidates. DSN has given a technical review of the proposal and subject it to scientific scrutiny. While lauding the drive and the vision of Slat, there are a number of issues with his proposal. Some sections of the feasibility study are said to be “incomplete and/or inaccurate”, and conclusions presented in the executive summary bear no relation to conclusions in individual sections. Design decisions have been made based on average ocean current speeds rather than extreme conditions that the structure is likely to face, and such an underestimation of forces could result in it being not robust enough to withstand the pounding of the ocean. The growth of marine life on the structure would have a considerable effect on its performance, and apparently this has not been adequately addressed. Structural deformation and mechanical loads on the moorings have not been calculated using a system that could have been used. The pilot study to investigate the depth at which plastic floats was deemed inadequate for determining the depth of plastic pollution in the ocean currents where this structure is expected to operate.

DSN diplomatically praises the enthusiasm for the project and speaks highly of its potential, but it also addresses an important point about how the project has been funded. Since Slat has gone down the crowd funding route, this is outside the normal grant-making process in which scientific peer-review is a prerequisite for funding. As a result, well-meaning members of the public may find themselves donating to a project the feasibility of which has not been adequately tested. The scientists at DSN have therefore provided a valuable service to Slat and his team who have responded positively to the feedback and agreed to take the constructive criticism on board.

If the public nature of such honest peer review creates a feedback loop that results in a revised design and a successful project, it could prove to be a model for how future projects could be developed. The benefits of crowd funding can be enjoyed, but also the benefits of qualified peer review can ensure that projects are subject to rigorous evaluation so that financial contributors can make a more informed decision.