Ocean Debris Cleanup Project Makes Progress, Battles Critics

By Greg Leatherman, ECO Editor

In 2013, a 20-year old Dutch man named Boyan Slat founded an ambitious effort to clean up plastic debris floating in the Pacific. The Ocean Cleanup has deployed a proof-of-concept, published a feasibility study and just completed a key reconnaissance effort. Slat, who has been the subject of much praise and criticism, is confident that it can all be done in a decade.

The project is preparing for full-scale deployment by 2020. Meanwhile, they’re focused on the project’s first operational pilot array, 2000 m long, in coastal waters halfway between South-Korea and Japan. Even at just 2% of the length of the full-scale technology, it will be the longest floating structure ever deployed on the oceans.

Critics say the project could do more harm than good. Slat says he is solving a global crisis that demands answers on a grand scale. Who is right?

The Passive Collection Approach
For the full-scale Ocean Cleanup Project, 50 enormous floating V-shaped barriers, anchored by floating booms, would be placed in the water to capture plastic at the infamous North Pacific Subtropical Gyre. The full length of the scalable array would reach 100 km. Attached to the seabed, the array is designed for large-magnitude deployment, covering millions of square kilometers without moving a centimeter. Because no nets are used, Slat believes the cleanup should be relatively harmless to the marine ecosystem, while also being more efficient than nets at catching smaller particles. Once gathered, the plastic could be converted to energy, oil, or other new materials, drastically reducing costs of the effort. Slat estimates it will take 5 years to reduce the debris there to a negligible amount.

Reconnaissance in Polluted Pacific
The Ocean Cleanup Project successfully concluded its Mega Expedition in August 2015. Volunteer crews on 30 boats have been measuring the size and mapping the location of tons of plastic waste floating between the West Coast and Hawaii. The month-long voyage through the Great Pacific Garbage Patch has been in preparation for the large-scale cleanup of the area set to begin in 2020.


Artist’s impression of the Mega Expedition. Photo credit: Erwin Zwart / The Ocean Cleanup

“I’ve studied plastic in all the world’s oceans, but never seen any area as polluted as the Great Pacific Garbage Patch,” said Dr. Julia Reisser, Lead Oceanographer at The Ocean Cleanup. “With every trawl we completed, thousands of miles from land, we just found lots and lots of plastic.”

The Mega Expedition’s primary goal has been to accurately determine how much plastic is floating in the Great Pacific Garbage Patch by executing the largest ocean research expedition in history. This was also the first time large pieces of plastic, such as ghost nets and Japanese tsunami debris, have been quantified. Although the samples collected during the expedition still have to be analyzed, preliminary findings indicate a higher-than-expected volume of large plastic objects floating in the ocean.

This underscores the urgency of The Ocean Cleanup’s mission to clean it up, according to CEO and founder Boyan Slat. “The vast majority of the plastic in the garbage patch is currently locked up in large pieces of debris, but UV light is breaking it down into much more dangerous microplastics, vastly increasing the amount of microplastics over the next few decades if we don’t clean it up. It really is a ticking time bomb.”

Slat said the group will publish a report of its findings by mid-2016. After that, comes the pilot-test, with the ultimate goal being construction of a 60-mi barrier in the middle of the Pacific, which Slat says could ultimately remove 7,250,000 tons of plastic waste from the world’s oceans.

The Ocean Cleanup was able to conduct the Mega Expedition thanks to major financial contributions from entrepreneur-philanthropists, including Salesforce chairman, CEO, and founder Marc Benioff. He says, “Protecting the oceans should be a priority for all of Earth's citizens. The Ocean Cleanup is taking an innovative approach to preserving one of our most critical resources and raising visibility of this global challenge.”

So, Why Did No One Think of This Before?
That’s easy, say Slat’s critics. People have thought of trying this before, and it won’t work.

In a 2013 article published at inhabitat.com, Stiv Wilson (at the time the policy director of 5Gyres.org), put it this way, “The problem is that the barriers to gyre cleanup are so massive that the vast majority of the scientific and advocacy community believe it’s a fool’s errand—the ocean is big, the plastic harvested is near worthless, and sea life would be harmed.”

Since Wilson’s criticism was published, Boyan Slat has published a feasibility study that called for a series of up-scaling tests working towards a large-scale operational pilot and concluded that “The Ocean Cleanup Array is likely a feasible and viable method for large-scale, passive and efficient removal of floating plastic from the North Pacific Garbage Patch. However, for this project to be successful in reducing the amount of plastics in the Great Pacific Garbage Patch, it is essential for the influx of new plastic pollution into the oceans to be radically reduced.”

Critics Assemble, Slat Responds
However, since the feasibility study was published, a new array of critics have chimed in. Dr. Andrew David Thaler of Southern Fried Science wrote, “As the project has progressed, many in the ocean science and conservation community have not only grown more skeptical of its effectiveness, but are increasingly wary of the potential this project has to cause significant environmental harm.”

Dr. Kim Martini and Dr. Miriam Goldstein have been specific in their criticism. The two are highly-qualified to comment. Dr. Martini is a physical oceanographer who has been involved in the deployment of a variety of deep-sea oceanographic moorings. Dr. Goldstein is a biological oceanographer who has studied the ecological impacts of plastic pollution in the North Pacific Subtropical Gyre.

In an analysis published by Deep Sea News in July, 2014, Martini and Goldstein wrote, “We believe that the popular momentum behind the Ocean Cleanup could lead to real change provided it is channeled into a workable solution.”

However, in reviewing the project’s feasibility study, they found that, “The most fundamental problem is that there is an overarching use of average rather than extreme current speeds to estimate operational limits in the design process. This is a faulty assumption on which to base engineering specifications, one which propagates through many of the modeling studies used to assess both the technical and economic feasibility of this project. Another fundamental problem that has not been adequately considered is biofouling—the inevitable growth of marine life on the structure—which will change the hydrodynamics and may add considerable load to the structure. As currently designed, the moored array is under-engineered and likely to fail.”

“In addition,” say the two, “many of our original comments have not been fully addressed. While the feasibility study includes chapters on boom design, environmental impacts, bycatch, and high seas law, they are largely reviews and do not provide a framework for how the Ocean Cleanup will address these fundamental issues.”

During an interactive panel discussion on utility and feasibility for the project hosted by MarineDebris.info, Slat responded to Martini and Goldstein, but stated that while some of their points are valid, he did not believe the two could possibly be expert in all of the fields necessary to address every aspect of his project. He explained that while his team made a mistake in calculating average rather than extreme current speeds, his project remains feasible because its design will in fact stand up to those extremes.


In August 2015, nearly 30 vessels crossed the Great Pacific Garbage patch. Sailing from Hawaii to Los Angeles, California the expedition collected more plastic measurements in three weeks than have been collected in the past 40 years combined.


Mega Expedition volunteer vessel Relentless deploying its ‘manta trawl’ in the Great Pacific Garbage Patch, August 2015. Photo credit: Crew aboard Relentless.

Concerning biofouling, Slat says that floating barriers would be decommissioned and replaced by new ones before biofouling becomes a problem. Asked whether biofouling would impact the device’s performance, he points out that it would require many meters of biofouling before weigh specifications were exceeded, a prospect he finds highly unlikely. Furthermore, concerning the vertical distribution of gathered plastic, he states that his team continues to perfect the fluid-dynamics of the design, but tests lead him to believe the design remains feasible. As far as concerns that his device could snare living ocean creatures, Slat admits he’s not an ecologist and that he consults with a team of oceanographers on all such questions, but he says that “since almost all organisms in the north Pacific subtropical gyre are neutrally buoyant, they will likely get taken away by the ocean current, and hence, do not accumulate, while the plastic, which is positively buoyant, does.”

Slat also stressed that one of the benefits of his project has been that it raises awareness and discussion about the problem of plastic in the oceans, including efforts to ban plastic microbeads.

Markus Eriksen, co-founder and Research Director for the 5 Gyres Institute (5gyres.org), which conducts research worldwide on plastic pollution in the five subtropical gyres and coastal hotspots, believes that chasing plastics in the ocean is the wrong approach—because, for the most part, micro plastics are not on the surface.


‘Codends’ filled with plastic particles after trawling the Great Pacific Garbage Patch for one hour. Photo credit: Crew aboard ExtremeH20.

When it comes to macroplastics, he says, “Having done 15 expeditions around the world, I’ve been to a bunch of islands. Every island in the gyre is collecting macro plastics on its windward side. What we’re finding is that the debris is washing ashore in huge quantities. Islands are the best nets. I mean, you are not going to invent any contraption, any device, that’s more efficient at collecting macroplastics than the islands in the gyres. And the best part is that they’re free. If you do a beach cleanup on these islands, you’ll get more macro plastics than you can carry.”


Mega Expedition crew members Mario Merkus and Serena Cunsolo on mothership R/V Ocean Starr with the results of trawling with one 6 meter-wide net for one hour, 2 August 2015. Photo credit: The Ocean Cleanup.

Eriksen’s preferred approach is to focus on preventing plastic from entering the ocean. He believes that the gyre cleanup ideas out there, of which Slat’s is but one, are more hype than prototype, that they have had very little sea time, that people underestimate both the costs and ecological impacts, and that they send a mixed message of remediation rather than prevention.

“I haven’t seen one proven prototype that works,” he says.

Eriksen says that while the focus from the 70s onward has been on people causing the problem and on stopping individuals from littering, the focus now has to be on designing smarter products. Insofar as gyre cleanup, Eriksen believes it would be more efficient to clean plastic from waterways before they reach the ocean. The reason: if plastic stops entering the ocean, then the ocean can clean itself by depositing a great deal of the existing plastic on beaches.

“Focus on upstream solutions, focus on product design, and focus on the message of prevention over cleanup,” he says. “That’s where I think the focus ought to be.”

Nicholas Mallos of the Ocean Conservancy agrees, “Cleanups are a Band-Aid to this disease, and what we really need is a cure. And when we take that cleanup from the beach out into the ocean, we’re talking about an even more unfeasible solution. Cleaning up on land prevents debris from entering the ocean in the first place, whereas the Ocean Cleanup is looking to address this issue at the very, very end of this long ocean plastic pollution vector. And addressing this issue at the end of the pipe is not addressing the source.”


Artist’s impression of what the 2000 m-long Coastal Pilot will approximately look like in front of Tsushima Island, Japan. Photo credit: The Ocean Cleanup.

In response, Slat says, “I don’t think there’s any reason to believe that the Ocean Cleanup would act as some sort of a distraction. I think the exposure can assist with these preventative measures.”

Slat agrees with Achem Steiner, Executive Director of the United Nations Environmental Program, who says that the attention the Ocean Cleanup generates may prevent more tons of plastic from reaching into the ocean than it eventually cleans up. However, Slat points out that oceanographic models predicting the paths of plastic pollution show that the gyre appears to be a sink where plastic is trapped for a long while. It makes sense then to clean up what we can.

Mallos says that if plastic trash production continues at is current rate, “We could very well see an ocean with one pound of plastic for every two pounds of fish by mid-century.” Even if the Ocean Cleanup Project successfully rids the north-Pacific gyre of all plastics, Mallo says, “What we’re talking about is solving essentially one ten thousandth of our ocean plastic problem.”

Still, Boyan Slat believes it is worth trying because he does not believe that his cleanup is in any way competing against other methods of reducing plastic pollution or cleaning up the accumulated plastic already out there. He says his computational models show that his project can clean up over 40% of the surface plastic in the entire north Pacific subtropical gyre. “I wouldn’t call it insignificant,” he concludes.

For more information on Boyan Slat’s vision, visit www.theoceancleanup.com.

Technical critiques by Drs. Martini and Goldstein are available at www.deepseanews.com/2014/07/the-ocean-cleanup-part-2-technical-review-of-the-feasibility-study/.

A video from Marinedebis.info featuring Marcus Eriksen (5 Gyres), Boyan Slat (The Ocean Cleanup), and Nick Mallos (Ocean Conservancy) debating Slat’s cleanup array approach can be viewed at www.youtube.com/watch?v=lrDqe_Qp6XM.

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