I asked 15 ocean plastic pollution experts about the Ocean Cleanup project, and they have concerns

The online ocean science community has been vocally skeptical about the Ocean Cleanup, a device that aims to physically remove plastic pollution from the ocean. Drs. Kim Martini and Miriam Goldstein published a technical review of its feasibility over at Deep Sea News, and Andrew asked some important questions that have yet to be answered. Also, be sure to read environmental journalist Chris Clarke’s thorough overview of these concerns.

Overall concerns include a lack of understanding of the problem (including but not limited to the fact that much of the harmful ocean plastic is small and well-dispersed), insufficient structural integrity for a large object that will be deployed in the open ocean (which would result in the object breaking and creating even more ocean garbage), and the fact that this device is designed to aggregate objects of a certain size to remove them from the water but cannot distinguish between plastic and living things.

Mainstream media coverage has been noticeably less critical of the Ocean Cleanup, often presenting the idea as revolutionary and it’s creator as a genius.

Artist’s conception of the Ocean Cleanup, from TheOceanCleanup.com

I am not an expert in ocean plastic pollution. However, the uncritical tone of most mainstream media coverage of the Ocean Cleanup does not seem to correspond with my impression of expert opinion on this matter from speaking with expert colleagues who study this.

Through professional contacts, I developed a list of 51 ocean plastic pollution experts who work in academia, government, and the environmental non-profit sector, and I sent them some questions about the Ocean Cleanup. 15 (4 in academia, 5 each in government and the non-profit sector, and 1 in industry) agreed to participate in an anonymous survey. While this is not (and not intended to be) an exhaustive survey of the entire field of ocean plastic pollution, the broad agreement among a diverse group of experts is telling. Below, please see what they had to say through some representative quotes. Some respondents chose to provide an on-the-record quote, while many chose to remain anonymous out of concerns about reprisal.

I also asked Lonneke Holierhoek, COO of the Ocean Cleanup, to respond to these concerns. Her comments are included in each section.

Not one surveyed expert unreservedly supports the Ocean Cleanup. 

A majority of surveyed experts had major concerns about the Ocean Cleanup overall, and more than 1/4 believed that the entire concept is “a bad idea with little or no redeeming value.”

“It is frustrating that so much money is being poured into this, though, when every marine debris expert I know says the design is flawed. Those millions of dollars could be spent more productively somewhere else.”

“I think that the education value of using it as a teaching tool can be useful. But in terms of addressing the actual problem of marine plastic pollution and its effects on marine ecosystems it has very little merit.”

“Unfortunately, plastic pollution is a much more complicated problem than the Ocean Cleanup makes it out to be, and solving it will require more than just a device to collect plastic in the Pacific gyre.”

“The first question I usually get after giving a talk on my research on ocean plastics is, “What are we doing to clean up these gyres?” The Ocean Cleanup Project is going to provide some valuable information. If it succeeds even for a month, it may help us gain a better understanding of the quantity of debris floating on the ocean surface. If it fails, we can answer the question by saying, we tried by throwing millions of dollars into technology but the ocean wasn’t having it.” – Bonnie Monteleone, Ocean Plastics Researcher at UNC-Wilmington and Executive Director of the Plastic Ocean Project.

“To make the claim, as the Ocean Cleanup Project is, that they will “clean the oceans” by 2040 or whenever, is disingenuous and misleading, when it will, at best, clean a very small percentage of what’s found on the surface.” – Eben Schwartz, Marine Debris Program Manager, California Coastal Commission

In response, Lonneke Holierhoek said “we’ve heard some of these concerns from the community before. We know people have concerns, and we are trying our damndest to do this right and address them. With all this publicity we have a lot of responsibility to do the right thing. We are passionate about improving the oceans. We’re doing exciting stuff that has never been done before and we want to do it responsibly.”

Similarly, while Lonneke Holierhoek stressed several times to me that the Ocean Cleanup is in the process of performing a voluntary Environmental Impact Assessment, the experts I spoke to were concerned and shocked that they waited until years into the project to do this important step that usually occurs before a project even starts.

Not one surveyed expert believed that the Ocean Cleanup will be able to remove plastic from the ocean without killing marine life.

A majority felt that it will definitely kill marine life, and nearly as many had major concerns.

“Since the device is passive, it won’t be able to discriminate between plastic and marine life.”

“I am concerned that the project does not seem to acknowledge or account for potential impacts on migratory marine species (especially air-breathing mammals and sea turtles)”

“It will certainly remove habitat and marine organisms living on and around debris. The cost-benefits of this approach on pelagic communities should be modeled and predicted.”

In response to these concerns, Lonneke Holierhoek said “We have designed our system not to harm marine life by entanglement or other means. It’s designed to minimize negative impacts, and we’re putting a lot of emphasis on that.”

She also sent me a technical document produced by the Ocean Cleanup team focusing on bycatch mitigation. It notes that there will be a nearby vessel monitoring interactions the device has with marine life, an effort focused on monitoring mammals and turtles through the use of observers, acoustic sensors, and camera equipment. It also notes that the device will be brightly colored so animals can see it, designed with materials that minimize biofouling, move slowly so that animals won’t be struck by it, and will include a flow system that passively moves animals out of the way of the plastic collector. They anticipate that the device will not act as a FAD (fish aggregating device) and have claimed that while it may harm some marine life, the net benefits outweigh the net negatives. (The experts that I asked about these presented solutions remain skeptical and deeply concerned.)

A large majority of surveyed experts feel that Ocean Cleanup creator Boyan Slat has major misunderstandings about key issues related to ocean plastics, and not one would unreservedly call him an expert on ocean plastic. 

“I think the biggest misconception that he is perpetuating is that the majority of plastic in the ocean is in the gyres. In fact, only 3% of the plastic in the ocean is floating on the surface and would be recoverable by the Ocean Cleanup’s device.”

“He either misunderstands how the global movement to solve the issue works, or he understands it and chooses to work against it.”

“He may be very experienced in his field of engineering, but has much to learn about ocean life, and how human made structures in the oceans have been shown to impact marine life.”

A large majority of surveyed experts believe that even if the Ocean Cleanup works as advertised, it isn’t focusing on the larger problem with ocean plastics, which are plastic pieces smaller than what this device can target.

“While removing pieces of plastics larger than 1 cm may help minimize the plastic entanglement issue for marine species, the impacts from plastic ingestion will not be addressed for most birds and fish as these groups ingest and accumulated pieces that are often smaller than 1 cm.”

“While clean-up efforts are a valuable tool in reducing plastics in our lives and the oceans, efforts such as the Ocean Cleanup are likely to have a minimum effect on reducing the plastics that are affecting seabirds and other marine organisms. Seabirds are particularly vulnerable to small plastic pieces smaller than 1 cm, which are highly abundant in the ocean, and the Ocean Cleanup does not address. Thus stopping plastics from entering the oceans are a much larger priority in terms of actions and innovation needed.” – Dr. Jennifer Provencher, Weston Fellow in Northern Research at Acadia University and Liber Ero Fellow.

In response, Lonneke Holierhoek shared a study with me that showed that in the top few meters of the Pacific gyre, 92% of plastic by mass is bigger than 1 cm. (Experts that I shared this response with say that it totally misses the point, since most of the plastic isn’t in the top few meters of the water column at all, and note that this study was funded by the Ocean Cleanup and includes Ocean Cleanup staff as coauthors).

A slight majority of surveyed experts believe that stopping plastic from entering the ocean is a better solution than trying to remove plastic once it’s in the ocean already. 

Not one surveyed expert believed that the Ocean Cleanup’s approach (attempting to remove plastic once it’s already in the ocean) is the best solution.

“The project takes focus from the real problem of preventing plastic pollution at the source and holding manufacturers of plastic products responsible for their products.”

“While there is need to identify novel ways to come up with solutions to remove or address the plastic that is already in the ocean, it’s not as simple as putting a giant floating plastic capturing device in the middle of the ocean – mainly because it’s a soup rather than an ‘island’ as portrayed by the project.”

“The propaganda is dishonest. While everyone is working upstream, they are manipulating public awareness to perpetuate downstream clean up”

“What concerns me most is that this project gives the public the sense that the problem can just be cleaned up – feeding into the ‘don’t worry, someone else will deal with it’ mentality, it fails to address the root cause of the problem.”

“Like smog over our cities and the hole in the ozone layer, the solution is 100% prevention.”

“Let’s hope they can get this project over with, so they may join the rest of the global movement of 1000’s of organizations working to prevent plastic from entering the ocean in the first place.”

“Cleaning it up will help individual animals (assuming the technology exists to clean it up without hurting them), but the problem is going to continue until people understand their impact on the ocean and shift away from disposable plastics. Without a human respect for and appreciation for the ocean, the need for cleanups will continue.” – Jen Kennedy, Executive Director, Blue Ocean Society for Marine Conservation

” Let’s hope they can get this project over with, so they may join the rest of the global movement of 1000’s of organizations working to prevent plastic from entering the ocean in the first place.”  Marcus Eriksen, Research Director, 5 Gyres

In response to this concern, Lonneke Holierhoek said “we agree that plastic must be prevented from flowing into our oceans. However, even if the flow stops today, a large amount of harmful plastic has accumulated in the gyres, which we believe should be cleaned up. It is not an either/or choice, we need to do both.”

Surveyed experts are not pleased with the factual accuracy of mainstream media coverage of the Ocean Cleanup. 

“They don’t seem to ask the hard questions about this device.”

“The media are great at sensationalizing things as silver bullet solutions to major environmental problems (e.g. climate change) to get ratings but take little responsibility in accurately providing the full picture, which can make our lives as scientists challenging – especially when we become the negative Nancy’s. Plastic pollution is a major environmental catastrophe, we need the media to help disseminate accurate information to promote behavior change, not single solutions that absolve us from unsustainable lifestyles.”

“Mainstream media (and Boyan/Ocean Cleanup) have been valuable in raising awareness about the broader issue. The flip side is that the messaging has distilled the solution into a silver bullet that has yet to be proven effective at removing trash and/or withstanding real life ocean conditions.”

“The overall coverage has been far too cavalier with the facts and has not been well researched to illuminate the fact that ocean plastics are distributed throughout the water column, on the sea floor, on coastlines, etc, and that the ocean cleanup project, even if wildly successful, will only scratch the surface of this issue.”

In response to this concern, Lonneke Holierhoek said that “I’ve never read anywhere in our communication that we claim to be the solution for the entire problem of ocean plastic. But I understand that since we get such overwhelming coverage that this may sometimes seem to be the case.”


It is clear from their public statements and from my interview with Lonneke Holierhoek that the Ocean Cleanup team is composed of passionate people who are earnestly trying to help. However, trying to help is not the same thing as helping.

The Ocean Cleanup device will be one of the largest, if not the largest, human-made structures ever placed into the oceans. One would hope that a project like this would be based on the best available science and enjoy the enthusiastic support of most relevant experts, but concerns from the experts I spoke to suggest that this is not the case.

The ocean plastic pollution experts that I spoke to are concerned that this unproven technology is based on an incorrect understanding of the problem, is likely to do a lot of harm to marine life, and diverts attention and resources from solutions that we know work. At best, they believe that this project will do little to solve the ocean plastic pollution problem, and at worst it will take resources and attention away from solutions that really can help. Uncritical media coverage of this controversial project has done a real disservice to the oceans.

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Author’s note: While many surveyed experts expressed concerns about the structural integrity of the Ocean Cleanup device itself, they stressed that they are not engineering experts, and therefore it isn’t appropriate to focus on this issue in an expert survey.