The Ocean Cleanup. The newest of the new plans to remove marine plastic.

UPDATE: The Ocean Cleanup released a feasibility study in June 2014 that attempted to address many of the concerns we had below. You can read our updated technical review here.

I’m just going to come out and say it, any project that touts itself as the “World’s first realistic Ocean Clean-up Concept” is just asking to be torn apart.

“The Ocean Cleanup” is the brainchild of a 19-year old Boyan Slat. He proposes using the oceans themselves to clean up plastic. By setting up a line of giant sifting booms across the major ocean gyres, ocean currents will push plastic into these giant traps to be collected and reused for profit.  He plans to set up an array of 24 of these sifters and calculates they will clean the ocean in 5 years.

The Ocean Cleanup’s proposed plastic sifting boom.

Before I add my two cents, here’s what Miriam had to say about the idea at the Marine Debris Listserv:

Dear all,

I’ve tried to stop fact-checking to every cleanup scheme, but I guess it’s an addiction at this point. Also, I feel that as a community we cannot move forward with practical solutions to marine debris until we lay some of these common misconceptions to rest. These points respond Boyan Slat’s TEDx talk, but you can also see photos of his proposal here: and

  • Most zooplankton don’t survive being caught in a standard manta net, never mind being spun in a centrifuge. They might still be twitching, but they have lost a lot of their important parts, like antennae and feeding apparatus. When we want to capture live zooplankton, we use special live-collection nets and are very, very careful. For gelatinous zooplankton like salps, the only way to bring them up in good condition is to individually capture them in glass jars on SCUBA. I am highly skeptical that any significant proportion of zooplankton are viable after caught in a net and spun at 50 RPM. (though I realize that he’s not proposing to do this on a large scale.) 
  • Mooring fixed “ships” in the open ocean (avg depth 4000 meters) is highly improbable for a lot of reasons. Just to pick one: I could not find data on the absolute deepest mooring in the world, but this implies that it is approximately 2,000 meters. So these ships would have to be moored at twice the depth of one of the deepest moorings that existed ~2007. 
  • Having seen no data, I can’t really speak to the efficacy of floating booms in removing microplastic. However, Giora Proskurowski & colleagues have shown that microplastic get mixed down below the surface in fairly moderate winds. These booms would be unlikely to function in any significant wind and wave action. And the mixed layer in the open ocean can get quite deep, around 100-150 meters in the winter with storms. 
  • Speaking of wind and wave actions, ships on fixed moorings and thousands of miles of booms (because the scale of this is also improbable) have the potential to create a lot more marine debris, and seem particularly hazardous to entanglement-prone marine life. 
  • This isn’t even getting into issues of scale (the California Current alone is ~300 miles across), maintenance and fouling…

I realize that Mr. Slat is a student, and have no doubt that he, and the inventors of countless other plastic cleanup schemes, have only the best of intentions. I am hoping we can work together as marine debris professionals to channel their energies into more productive directions.


Miriam Goldstein

While I can’t speak to what these booms will and will not pick up, I completely agree with her I am highly skeptical whether the design is even feasible from an ocean engineering standpoint. Here are some of the major unanswered technical questions:

1) How does the sifter work?  To be honest, I am not completely sure. The website and TED talk are completely devoid of technical details. But from what I can gather from the concept art and the talk, I think the booms have large nets underneath them that gather plastic into what I think is a oversized swimming pool leaf trap shaped like a manta ray. UPDATE: I misinterpreted the images on the website. The design as it stands now has no nets, only the initial tests had nets. Now I have to ask, what is that sheet hanging down from the booms?

2) The booms.  The claim is that only 24 sifters are need to clean the ocean and span the gyre radius, which means the booms have to be huge. Possibly 100’s of kilometer wide. Are they rigid or flexible? Are they the manta rays? How will they be kept in formation?

3) Anchoring something that large.  I am going to assume that the booms need to stay relatively taut to retain their shape and the most obvious way to do this will be with multiple anchor lines. The water depths are deep (>3000 m), horizontal surface motions needs to be small and then there is all that water pushing on what is essentially a giant paddle. That means a fairly sophisticated plan for anchoring the array will have to be developed. Having seen how large anchors are for low-tension subsurface moorings (>1000 kg), I can’t even begin to imagine what they are going to use or how that is going to be set up.

4) Biofouling. I forsee two major biofouling issues. The first is biological growth, which can be particularly bad because all the major mechanical parts are near the surface. There is going to be growth on the mesh, on the booms, on everything submerged which can make the booms and nets heavy, dragging them underwater. The second is fishbite. Did you know that fish attack underwater moorings like crazed rabid zombie munchers?  Now I don’t know if fish would actually chew on the mesh, but previous experience indicates they are not picky about what pieces of underwater line they snack on. So what will happen if fish gnaw holes through the collection nets?

5) The assumption of low current speeds. This is a bad assumption. While the array may not be placed in the most energetic current regime, storms and eddies can briefly induce large currents which could place a lot of stress and shear on such a large array.

6) Zero bycatch by net avoidance .  Sorry, I couldn’t resist.

Swim free zooplankton!

The Ocean Cleanup project is still in the planning stage, so all these problems have the potential to be solved. But I think it is highly unlikely that an array of this size and magnitude will ever be feasible.

UPDATE: Another good roundup by Micheal Cote of potential issues with the Ocean Cleanup design can be found here.

UPDATE 2:  Some more critiques brought to my attention in the comments

Those Crazy Plastic Cleaning Machines


38 Replies to “The Ocean Cleanup. The newest of the new plans to remove marine plastic.”

  1. I’d been noodling a post on this, and now don’t have to. It’s been said far better than I could’ve said it!

    I appreciate anyone who’s actively trying to come up with solutions to the ocean plastics problem. But the answer will never lie in cleaning up the mess after the fact. The ocean is too big & strong & cruel, the mixing goes too deep, the intermingling with delicate life too thorough. The solution comes before it gets to the ocean. After it’s there, it’s too late.

  2. Although we all will never agree on the perfect way of doing things, I feel that picking apart someone elses ideas is nonproductive. The problems will come up, this we all know. What this young man needs is ideas on how to fix the problems that may come up. I am no way an expert on this matter but I think that if we keep moving forward and stop picking apart the ideas, maybe we might be able to clean the Ocean sooner than later.

  3. Is there some way we could grow large amounts of plankton?

    I’m afraid there simply is no answer at all. Making significant inroads on the amount of plastics dumped in the oceans would require dictatorial powers on the part of any governments involved. There are way too many human beings who are too lazy, too stupid, too selfish to accept any “green” measures that would require them to change their habits.

    And of course lots of people will scream about the economics. Look at Carnival Cruise Lines. Right now they deal with trash by simply dumping it. Preventing them from fouling the oceans would mean they would have to rebuild their ships to include waste storage space and warehousing their trash until they return to port, and offload it there. The only way they could have enough waste storage space would be to reduce their passenger load per ship to half what it is now. And of course the work of offloading the trash on land would add to their turnaround time and the cost of maintenance, and there would be fees for hauling the garbage to a dump, etc…They would spend more money lobbying Congress for laws that let them avoid that kind of restructuring than it would cost them to rebuild the ships.

  4. I think it’s reasonable for the community to offer honest opinion about ideas, especially ones that have years & years of study behind them. Every couple of months the next big ‘Great Plan’ comes out to solve all the ocean’s problems without us having to lift a finger or change how we do things. It’s a smokescreen. It saps energy away from taking a hard look at ourselves and making the changes that we know actually do work & do matter. It kicks the can down the road another 3 months or year. And then when we wake up and realize that ‘Great Plan’ #47 has no legs just like all the others, and we’re a year further down the rabbit hole.

  5. Part of fixing the problems inherent with any new idea is to point them out, which is what was done in this post. These are technical issues that have to be addressed in order for this project to succeed regardless of whether I support it or not. Criticism, while it may sting at times, is productive and when taken into consideration will lead to a better solution.

  6. The way I understood the plan is that there are no nets at all—only booms (check out the third picture here: It’s like a large funnel essentially-the booms funnel the plastic into the manta ray. The plan makes the (spurious) assumption that all plastic floats to the surface and the plankton will not (as per the website “Although this hypothesis still has to be tested, even the planktonic species – due to their density being close to that of the sea water – may move under the booms along with the water flow.”).

  7. What about typhoons, tsunamis and other storm weather ripping these devices into tiny pieces as has been documented in localities that are hit by hurricanes, tornadoes and tidal waves.

    What about interference with ocean going pleasure or touring craft, ocean going cargo container vessels and commercial trawlers on GPS guided systems. It’s not like there isn’t commercial traffic moving across the ocean that may have to divert their routes.

    Next what about anything that is part of this built filtering environment causing damage to property or ocean traffic when ships anchors give way or booms break loose and engage with vessels and their drives or ballast systems.

    I’m sure there are more issues than these three alone. You know lawyers will have a field day

  8. If only the originator of this had simply suggested that a kickstarter programme be launched to pick beach debris off the shoreline of remote locations I think this would be more practical, would achieve more and would actually be a really nice thing to fund. Especially if it could direct some funds into remote communities with limited access to outside cash resources.

  9. So the concept is a great idea, and with any idea there are issues to be addressed. Dr. Martini and Mr. Denny have pointed this out very well. However, here is the problem I have with most of the other posts.

    Life in the cheap seats must be really nice. To sit back and criticize an idea is everyone’s right, but don’t sit back with your expertise of the oceans and do nothing but complain. Be apart of the solution. This young man came up with an idea based upon knowledge he obtained. His knowledge of information about sea life and currents may be limited. Don’t just point out an issue and do nothing, propose an idea of improving the design to address the issue. Offer your expertise to this young man to make his concept work better.

    Coming from an engineering and design world, I see this quite a bit. A good idea comes out and the experts pick it apart with issues and hurdles, but do not present ideas to correct them. Why is this? In my area, it’s ego’s and I see it everyday. The engineers criticize the idea because it was not their idea to make them look good. They will never admit this, but it’s true. Some time later when the project is forgotten by the masses, they will re-present it as their idea with a majority of the improvements implemented.

    All of you presented pertinent issues but did not present possible solutions. In some cases, I think your issues were the start of other conceptual ideas to address those issues. The basis of bringing any idea to reality is to recruit the knowledge experts applicable to the idea. You have the knowledge and the information he may need, offer it to him.

  10. @Jan

    are you for real? you think there’s going to be a lot of touring and pleasure craft or transport vessels that are upset by efforts undertaken in the great pacific garbage patch?

    since that’s a nonstarter, we can skip your “next” problems entirely

  11. But the knowledge experts, the ones who have studied this for years, -are- giving their knowledge & information. Freely & willingly. The answer just happens to be one that’s hard to hear.

    Since the beginning of the 20th Century we’ve increasingly fallen into this trap. This idea that if we’ve messed something up, there’s science/tech out there that can fix it. That can keep us from having to make the hard choices about our lifestyle. In this case, there isn’t. It is not possible to clean the oceans up of their debris. Not without breaking the bank of every nation on earth and scooping out and killing all the life in its first 100 feet of depth.

    That’s what we have done to our planet in just a couple generations. That’s plastic’s legacy. We cannot actively go out and clean it up in any meaningful way

    What we -can- do is to change consumption behavior, change materials, improve waste management — do the things that stop persistent plastic from getting into the ocean in the first place. Any effort geared toward that has at least a chance of making a difference. Anything else is just kicking the can down to the road so it’s even more of a disaster for my daughter & her generation once she grows up.

  12. Wow. Nice list. I would like to learn more about the plankton comment.

    I jusssssst posted my own list of issues here, if you’re interested.

    My main crits are on impacts to protected species and how the owners would (could) navigate countless marine laws across 6 oceans/seas. Second, there’s Moral Hazard, which is basically a false hope of “technology will save us.”

  13. Harry I’m afraid your right, it seems freshwater and arable land keeping pace.I’d hate to look at your ‘flotsam diaries’ in 10 years.

    Thank-you for your addiction Miriam I hope more people get hooked.

  14. Moral hazard, an aspect I didn’t even know existed! You definitely hit on some other important points, I’ll post the link above.

  15. Those Crazy Plastic Cleaning Machines
    Posted by Manuel Maqueda on Mar 27, 2013 in News, Plastic Pollution

    If I had a dime for each brilliant idea to “clean up the “Garbage Patch” that has been forwarded to me over the last few years I would be a millionaire.

    These gyre cleanup machines, devices and foundations that emerge periodically are not going to happen. However they are likely to get lots of media attention –and distract from the real solutions.

    These more or less sophisticated delusions and fantasies of massive offshore cleanups testify to how misunderstood our plastic pollution problem is, and how disconnected we are from nature in general, and from our oceans in particular.

    What about stopping plastic pollution at the source? Wouldn’t that be a better use of our ingenuity, time and money? It also happens to be quite doable too

    The plastic industry loves distractions like the cleaning machines, because they put the focus on “cleaning up”, not on how their business of making disposable plastics is destroying the planet

    We live inside of an entropic culture addicted to process: doing, manufacturing, selling… However, many of our planetary problems call for quite the opposite: not doing, stopping, preventing, protecting, designing better, etc. Protective actions that are so simple to be noticed and valued by our culture.

  16. I would love to support an enterprise that will effectively clean up our oceans. Can anyone give me that one? I also agree that we need to stop the damage at source, BEFORE this killer plastic reaches our seas.

  17. There seems to be some expectation that the booms are going to make the plastic accumulate at the intake, but I don’t see how that would be the case. All they can do is feed the input with a continuous supply of water containing roughly the same distribution of plastic as all the water around it. The current can feed the intake with exactly the same water, so the booms are completely pointless. Agreed?

  18. I will admit that I have not studied this plan n depth, but most of the obvious problems I see pointed out should have been addressed in the original proposal.

    My gut feeling is that this is a lot of fuss and bother over an idea rather than a plan, and that the fuss is primarily the result of the ‘5 years to clean’ statements which seem unsupported by any sort of cost estimates, allowances for design requirements changes or even the construction time and costs.

    My own idea to reduce the temperature of the Caribbean to reduce the effects of climate change are still very rough after 5 years, but I at least know where the questions that need to be answered lie, and have answers for most of the likely problems of design and construction…and that idea (Tras-Panama Pipe,) could retard, halt or reverse the climate changes beginning after 7 years of construction (at an estimated cost of US$7-10 billion)–and unlike other geo-engineering ideas, the operation is easily halted or canceled if it proves more damaging than helpful. It also uses only known engineering techniques.

    The ‘5 years’ is also misleading since none of the headlines regarding the idea mention that it only cleans up floating plastic & debris in the gyres, which is of course the concentration, but the majority of the damage is caused before the material gets that far to sea…the plan does nothing about the areas of the ocean that are most affected because they have the highest marine life concentrations.

    I’m glad that people are thinking of things, but the idea stage is far too early to get extremely excited about any single plan.

    Issues mentioned which are readily solvable are positioning of the machinery (jets and gps) and to a degree biofouling (using special coatings and such.) These add costs, but are not insolvable engineering problems. Transfer of materials to be remove to shore, storage and eventual destruction/recycling of the materials also raise questions, which are probably solvable, but may hold hidden problems which are not as easily solved.

    Recycling ought to be fairly easy, we have several research projects which have reached pilot plant stage directed at restructuring organic and plastic materials into products similar to heavy oils used as feedstock in refining plants.

    Such large permanent structures will, as the gyres themselves have, produce new ecosystems.

    You can NEVER do ‘just one thing’ any action you take has multiple effects, many of which are difficult or even impossible to predict…save only that they will exist for certain.

  19. It’s crazy that shark finning gets so much publicity in comparison to this. Shark finning is terrible, dont get me wrong, but this I see as a much bigger issue that needs to have a lot of money invested in finding a solution right away

  20. Are those booms… plastic?

    (Really though I think enough has been said here. I commend the guy and encourage him to continue his quest, but it appears this isn’t the right solution. Yet.)

  21. i agree with dr martini -only after very intense analyzation of equipment and real time use evaluation along with economic research pertaining to construction and life of equipment —

  22. Just a thought. If it could be made to work, even with nets, would the loss of any sea life be less then if we left the plastic there to carry on doing harm?
    Could it be the least worst option? Obviously you need to address the reasons why it got there in the first place so you don’t have to come back again.

  23. Keith – I don’t understand this. If the cruise lines have a place to store supplies that haven’t been used yet, couldn’t these be used to store trash as well? I get it that the spaces would need to be redesigned for this purpose, and that trash would ideally need to be sorted, washed, etc., but it doesn’t seem like they would NEED to take up cabin space.

  24. i know very little about environmental issues, probably less about sea life, and frankly, it is not my focus in life…maybe i’m reading the wrong section of the internet, and i expect armed hippies will keyboard attack me for that… sorry…

    i dont know whether this idea is feasible. Im sure that stopping the problem at source is the most effective way at stopping the problem, but really… the (seemingly) intelligent people stating “It is not possible to clean the oceans up of their debris. Not without breaking the bank of every nation on earth and scooping out and killing all the life in its first 100 feet of depth.” and other such comments.

    Hmmm… so technology will never be able to do this. Interesting. i wonder what you would have thought when plato theorised that the world was round. Lets not go that far back… what would you have thought 30 years ago if someone told you that one day you would carry a little device in your pocket, and at the touch of a button, could speak to anyone just about anywhere in the world, from just about anywhere in the world… never mind that, you could send them letters too… that they receive instantly… not only that, you could keep all the information you ever wanted to store about just about anything on that same device… not only that, you could take pictures, send them, find out where the nearest plastic manufacturer is etc etc etc… you get my point.

    anyone that says to me “this cannot be done, ever” gets written of as an ignorant fool. technology has, and will continue to create, and solve, the worlds problems. this is the human legacy.

    and if i told you that we will send a human to mars one day?

  25. Anything is possible in principle; but since we have no idea when, or if, someone will solve the problem of how to remove junk from the oceans, our only ethical choice is to do everything we can to limit the amount of junk that gets there in the first place. This is a formidable task. People’s thinking and behaviour will need to change, all over the world. We need to start thinking of the Earth as a small closed system, not a big empty place where we can dump our garbage and it will disappear forever. But there are relatively simple ways to change behaviour. One is to charge a significant deposit on all plastic goods, which is refunded when people return them to a collection depot. This doesn’t work when it’s a 10-cent deposit on a three-dollar bottle of water. But what if it were a one-dollar deposit? And what if everything plastic came with a deposit, not just bottles? That would make a difference. If the environmental cost of products were factored into the sticker price, there would be real opportunities for people to design products that last longer and/or biodegrade faster. With enough popular support in the rich nations, we can experiment with regulations, taxes, ethical investing, and education. This, I believe, will be the way forward.

  26. While most of the issues I’ve seen raised about this are valid and I don’t believe it’s too early to voice these thoughts, it’s important to note the following:

    “The last couple of months several (spontaneous) articles have been published, claiming The Ocean Cleanup Array is a ‘feasible method’ of extracting plastic from the gyres. This is an incorrect statement; we are currently only at about halfway our feasibility study. Only after finishing that study, we believe such statements should be made. Although the preliminary results look promising, and our team of about 50 engineers, modellers, external experts and students is making good progress, we had and have no intention of presenting a concept as a feasible solution while still being in investigative phase.”
    -copied from

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