Introduction

The Ocean Cleanup, brainchild of Dutch inventor Boyan Slat, was in the news again this past week after announcing that in addition to the fact that their system is unable to collect plastic as intended, it suffered a mechanical failure. “Wilson” is currently being towed to Hawaii, where it will undergo repairs and upgrades, presumably to be towed back out to the garbage patch for a second trial.

I am not a mechanical engineer, so I don’t intend to comment on the details of their mechanical failure. I am, however, a sea-going oceanographer. Which means that I am used to the sorts of situations with scientific research equipment that was so succinctly paraphrased by Dr. Miriam Goldstein:

Designing for physics

But beyond the engineering, there are the questions of what the *physics* are that TOC are relying on for their system to be successful. Some of you may recall that the original design was to moor (i.e. *anchor*) their device in 6000m (20000 feet) of water, and let existing ocean currents sweep garbage into the U-shaped structure. Thankfully, they realized the challenges associated with deep-ocean moorings, and abandoned that idea.

The latest design iteration (misleadingly called “System 001”, as though they haven’t built and tested any other previous to it), is to have a freely-drifting system, avoiding the use of anchors. TOC claim that under the influence of current, wind, and waves, their design will drift *faster* than the plastic — causing it to accumulate in the U, making for easy pickup. They summarize the concept with a little explainer video on their website, with a representative screen shot below:

Based on a quick Twitter rant that I had after thinking about all this for a few minutes (see here), I wanted to explain out the various points that have either a) been missed by TOC design team, or b) deliberately excluded from their rosy assessment of how they expect their system to actually collect garbage. What follows is a “first stab” at a physical oceanographic assessment of the basic idea behind “System001”, and what TOC would need to address to convince the community (i.e. scientists, conservationists, etc) that their system is actually worth the millions of dollars going into development and testing.

The premise

As outlined in the video, the premise of System001 as a garbage collection system is that through the combined action of wind, waves, and currents, the U-shaped boom will travel faster through the water than the floating plastic, thereby collecting and concentrating it for eventual removal. This appears to be based on the idea that while both the boom and the plastic will drift with the current, because the boom protrudes from the water (like a sail), it will actually move faster than the surface water by catching wind.

There are some issues with this premise. Or, at least, there are some real aspects of oceanography that have either been ignored or missed in thinking that such a system will behave in the predictable way described by TOC. I’ll try and outline them here.

Stokes drift

Any of you who may have had an introduction to ocean waves may have heard that during the passage of a wave, the water particles move in little circles (often called wave orbital motion). While not a bad “first-order” description, it turns out that for real ocean waves there is also some drift in the direction of wave propagation. This drift is named after Gabriel Stokes, who first described it mathematically in 1847 (see wikipedia article here).

The amount of drift depends nonlinearly on both the amplitude and the wavelength of the wave. For example, for a 0.5m amplitude wave with a wavelength of 10m and period of 10s (something like typical ocean swell), the drift velocity is about 10 cm/s right at the surface.

Of course, the Stokes’ solution describes the motion of the water parcels being moved by the wave. For those water parcels to then have an effect on anything in the water, one would need to consider the various components of force/impulse/momentum (i.e. our buddy Sir Isaac Newton). Needless to say, it seems obvious that a smallish piece of neutrally buoyant plastic will respond to the Stokes drift much more readily than a 600m long floating cylinder with a large mass (and therefore large inertia).

This alone could be enough to quash the idea of a passive propagating collection system. Mr Slat?

Ekman currents

While we’re talking about long-dead European fluid mechanics pioneers, any study of the effect of winds and currents wouldn’t be complete without a foray into the theories proposed by Swedish oceanographer Vagn Walfrid Ekman in 1905. What Ekman found was that when the wind blew over the surface of the ocean, the resulting current (forced by friction between the air and the water) didn’t actually move in the same direction as the wind. The reason for this is because of the so-called “Coriolis effect”, whereby objects moving on the surface of the Earth experience an “acceleration” orthogonal to their direction of motion that appears to make them follow a curved path (for those who want to go down the rabbit hole, the Coriolis acceleration is essentially a “fix” for the fact that the surface of the Earth is non-inertial reference frame, and therefore doesn’t satisfy the conditions for Newton’s laws to apply without modification).

Anyway — the consequence is that in an ideal ocean, with a steady wind blowing over the surface, the surface currents actually move at an angle of 45 degrees to the wind direction! Whether it’s to the left or right of the wind depends on which hemisphere you are in — I’ll leave it as an exercise to determine which is which. And what’s cooler, is that the surface current then acts like a frictional layer to the water just below it, causing it to move at an angle, and so on, with the effect being that the wind-forced flow actually makes a SPIRAL that gets smaller with depth. This is known as the Ekman spiral.

The actual depth that the spiral penetrates to depends on a mysterious ocean parameter called Az, which describes the vertical mixing of momentum between the layers — kind of like the friction between them. What is clear though, is that a small particle of plastic floating close to the surface and a 3m deep floating structure will likely not experience the same wind-forced current, and therefore won’t move in the same direction. Hmmm … that’s going to make it hard to pick up pieces of plastic.

What is a “Gyre” anyway?

The final point I wanted to make in this article (I have more, which I’ll summarize at the end for a possible future article), is to try and give a sense of what currents in the ocean (including in the “gyre” or in the region often referred to as the “Great Pacific Garbage Patch”) actually look like. The conception that there is a great swirling current 1000’s of km across is true only when the currents are averaged for a very long time. At any given instant, however, the ocean current field is a mess of flows at various space and time scales. An appropriate term for describing typical ocean flow fields is “turbulent”, as in an oft-viewed video made by NASA from satellite ocean current data.

To illustrate this, I took some screenshots of current conditions from the wonderful atmosphere/ocean visualization tool at earth.nullschool.net showing: ocean currents, surface waves, and wind.

These images illustrate the potential problem with TOC idea, by highlighting the fact that the wind, wave, and current fields of the ocean (including even in the “quiet” garbage patch) are highly variable spatially and temporally, and are almost never aligned at the same period in time. What’s more, is that the currents and waves at a given time and location are not always a result of the wind at that location. Eddies in the ocean are generated through all kinds of different processes, and can propagate across ocean basins before finally dissipating.

Similarly, surface waves have been measured to cross oceans (i.e. the famous “Waves across the Pacific” study pioneered by the transformative oceanographer Walter Munk).

Other issues

Following the “rule of three”, I tried to hit what I consider to be the biggest concerns with TOC system design and principle, from my perspective as a physical oceanographer. However, there are other issues that should be addressed, if the system as designed is really believed by the TOC team to be capable of doing what they say. And really, it seems like a crazy waste of time on behalf of everyone involved to have spent this much time on something if they aren’t sure it will even work theoretically … not to mention the money spent thus far. So, part of me *has* to believe that all the dozens of people involved care deeply about making something that might actually work, and they have studied and considered all the effects and potential issues I (and others) have raised.

Anyway, the other issues are:

• What is the actual response of the system to a rapid change in wind/wave direction? Wind can change direction pretty quickly, especially compared to ocean currents. What’s to prevent a bunch of accumulated plastic getting blown out the open end of the U after a 180 degree shift in wind but before the system can re-orient?
• What about wave reflection from the boom structure itself? It is a well-known fact that objects (even floating ones) can reflect and “scatter” waves (scattering is when the reflected waves have a shorter wavelength than the original ones), and it seems like this could create a wave field in the U that might actually causes drift *out* of the system.
• The idea that all wildlife can just “swim under” the skirt (because it’s impermeable) is not supported by anything that I consider to be rigorous fluid mechanics, aside from the fact that much of what actually lives in the open ocean are non-motile or “planktonic” species. There are a lot of communities in the open ocean that float and drift at the surface, and I see no way that if the System collects floating plastic as it is designed that it won’t just sweep up all those species too. The latest EIA brushed off the effect of the System on planktonic organisms by stating that they “are ubiquitous in the world’s oceans and any deaths that occur as a result of the plastic extraction process will not have any population level effects”. But that doesn’t take into account that the stated mission is to deploy 60 such systems, which are estimated to clean the garbage patch of surface material at a rate of 50% reduction every 5 years. It stands to reason that they would also clean the Pacific of its planktonic communities by the same amount.

The post The (ocean) physics of The Ocean Cleanup’s System 001 first appeared on Deep Sea News.

boon·dog·gle
/ˈbo͞onˌdäɡəl/

noun:  work or activity that is wasteful or pointless but gives the appearance of having value.

verb: waste money or time on unnecessary or questionable projects.

The end of 2018 was tough for the Ocean Cleanup and its founder, inventor, and CEO Boyan Slat.   In September, the 2000 foot-boom and supposed plastic collection device, was first deployed about 240 nautical miles offshore of San Francisco where it was tested for two weeks.  The boom was then towed an additional 1,400 miles off the West Coast, about halfway between California and Hawaii, to begin collecting plastic in the Great Pacific Garbage Patch.  This was supposed to be the first real-world proof of concept and trials of the device in the Pacific Garbage Patch.

Note that the previous prototype in the North Sea also failed at a shallower depth in calm seas. Of course, the next step is to build a bigger one and place it in rougher and deeper seas.

But in November, Ocean Cleanup stated the system was not holding plastic it collected.  This lack of plastic collection arose from the system moving too slowly at times to hold plastic within the U-shaped collection area.  The system is supposed to work by currents pushing plastics into the booms and nets.  Yet slow and complex currents in this region of the Pacific allowed plastics to float out of the device again.

In late December, 60-feet of boom had detached due to material fatigue.  Slat then indicated that this likely occurred due to wave action placing stress on the boom. The fracture was caused by material fatigue, he wrote. That’s likely because of the intense action of the waves that puts tremendous stress on objects in the water.

So to recap, the Ocean Cleanup system cannot either collect plastic or withstand the Pacific Ocean.

 In a September interview with NPR, he said the device averages about four inches per second, which his team has now concluded is too slow. The break in the barrier was due to an issue with the material used to build it.

However, both of these issues could have easily been avoided by more appropriate simulations, analyses, and information prior to construction and deployment.

When the material failure occurred, it wasn’t due to the result of a major Pacific storm. It was just normal wear and tear, Slat said

Understanding material stresses is a key component of an engineering project and one that is well understood before construction.   Note as well that the system is not something actually new, but is a modification of RO-BOOMS used in oil spill clean up since 1988.  I am confident the specifications for use and the ocean states the booms can operate in are well known by the manufacturer and previous users alike. [UPDATE: The booms used ar eno longer the RO-BOOMS.  It is a completely different design, a recent internal iteration which may explain the failure.]

And while currents are complex, a whole field of physical oceanography exists and provides readily the information to know the current regime in the area.  If more detailed temporal or spatial resolution is needed, the Ocean Cleanup team should have conducted more field studies to gain the data on the currents beforehand.    The Ocean Cleanup has always seemed poorly developed and executed, ignorant of the best science and data available, blatantly dismissive of critique, and far too hurried.

This rush to place the device in the ocean for both good publicity and for the feeling of accomplishing something is unproductive at best and dangerous at the worst.  And it clear that Slat is committed to an overly ambitious timeline no matter the consequences.

Founder & CEO Boyan Slat announced the news in a December 31 blog post, saying “setbacks like this are inevitable when pioneering new technology at a rapid pace”, and maintaining that ” these teething troubles are solvable, and the cleanup of the Great Pacific Garbage Patch will be operational in 2019″.
Read more at http://www.mysailing.com.au/latest/ocean-cleanup-s-20-million-plastic-catcher-breaks#1R7mecWOPU9tLbJl.99

I get no pleasure in saying I told you so but…

As noted in a recent article featuring Dr. Goldstein,

But a critic who has followed Slat’s project since he unveiled it more than five years ago said the failure was predictable and that systems deployed closer to shore stand a greater chance of slowing the deluge of plastics spilling into the world’s oceans.

“I certainly hope they will be able to get it to work, but this is a very difficult environment where equipment breaks, which is why you normally do things closer to shore, where things are easier to repair,” said [Dr.] Miriam Goldstein, director of ocean policy at the Center for American Progress

In 2014, Drs. Kim Martini and Drs. Miriam Goldstein, a physical and biological oceanographer, provided a detailed technical review of the feasibility study here at DSN. Note the two of them pointed nearly 4 years ago about these issues.

….The modeling studies severely underestimate potential loads and tensions on the moored array and boom. Therefore, they are insufficient to properly design a mooring concept and estimate potential costs…

Since the authors had access to ORCAFLEX, a professional software package to design offshore marine structures, a full-scale mooring array could have been modeled to estimate loads and tensions on the moored array, but was not.

Structural deformation of the array and loss of functionality by ocean currents are not addressed…

Yeah. So these exact failures were predicted four years ago.

As this article clearly lays out, we should focus our funding and time, on more promising solutions to the ocean trash problem.

The post The Continued Boondoggle of the Ocean Cleanup first appeared on Deep Sea News.

They deployed a 100-m long prototype

that is really 30-year old RO-BOOM technology

with some new fancy hardware.

Deployed in only 30 m of water

during a calm summer

the prototype failed after 2 months.

Because shackles.

It cost $2 million euros

and collected ZERO pieces of plastic.

If you, like me, are concerned about plastic in the ocean consider helping groups like The Ocean Conservancy who collected more than 18 million pounds of trash during the 2015 Coastal Ocean Cleanup or Mr. Trash Wheel and Professor Trash Wheel who has collected 1,050,540 lbs. of trash from Baltimore’s Inner Harbor since May 9, 2014. The problem of ocean plastic isn’t solved yet.

The post What did the Boyan Slat and the Ocean Cleanup do last summer? first appeared on Deep Sea News.

Why are they using RO-BOOM oil booms?

Andrew Thaler over at Southern Fried Science pointed this out. RO-BOOMS are commercially available oil containment spill booms that have been around at least since 1988. I would assume that something is known about their durability?

Yup, definitely a RO-BOOM.

Excuse my language, BUT WHY THE F** ARE THEY BLACK?

You just spent all this money to add a custom paint job to a floating advertisement potential maritime hazard and it’s one of the least visible colors at sea. I CAN’T EVEN.

Where are the booms?

There’s gotta be a notice to mariner’s out there somewhere. In case you don’t know what this is, it’s a public announcement that you have to put out when ever you deploy anything at sea. So people don’t run over it or anything cause it’s camouflaged.

Are these the booms the 1 km deployment planned for Japan will use?

ARE THEY? I NEEDS TO KNOW. They look a lot different from the booms that were tested at the Marin Facility. 

which also seems to be different than what was tested at the Deltares facility.

Do the maybe intended booms actually collect plastic?

No seriously, there seems to have been a lot of effort to test the structural stability, but no testing whether they actually collect plastic and debris. I would have liked to see them drag the barrier around a bit just to see before deploying a big and expensive mooring if it is indeed the one they are going to use. As the Feasibility study indicated, sometimes the barriers can’t collect plastic so it would be useful to know when this is.

How did they get funding EUR 0.5 Million from the Dutch Government?

Is there a public proposal? It would be great to see, especially since this is now a publicly funded project and it would be great resource for reporters interested in the project (instead of them asking Miriam and I to constantly peer review it…grumble grumble).

That’s all I got for now. Any more questions you can ask Andrew Thaler at Southern Fried Science who also has questions.

The post The Ocean Cleanup deployed a prototype and I honestly have A LOT of questions first appeared on Deep Sea News.

1. The Whirlbird:  The design relies upon driving winds through massive propellors on top of the ship to turn macrocentrifuge devices underneath the hull.  These devices the spin microplastics out of the top layers of ocean.

2. The Beach Scrubber.  The concept is a series of 37 feet tall robots that are interlocked.  The robots, stretching nearly two miles, move in unison down the coasts.  During this time, individual robots uptake beach sand, remove the plastics, and pump fresh sand back on the beach.

2. The Coastal Scrubber.  By the same design outfit the Coastal Scrubber is a similar design except focuses on near shore waters.  Given the force of wave action, Coastal Scrubbers work individually but are guided by daily satellite link ups.

3. The Plastic Wedge: Using repurposed U.S. Naval technology and ships, this concept moves a large open wedge, attached to the front of a vessel, at fast speeds through plastic islands.

4. Center Pivot Collector: This unique concept actually features a bridging arm design that rotates on a central base similar to a center pivot irrigation system.   Floats on both sides of the arm hold nets that funnel plastics to central immersed collectors.

5. The Plastic Hunter: The most futuristic of the lot is this modern design for a submersible.  Not all plastics will occur at the ocean surface and this design proposes to seek out and find large plastic falls on the ocean bottom.  The genius of this plan is that the sub has a gas chromotography mass spectrometer set it its nose cone to detect plastic plumes in the currents.

6. Submerged Plastics Array: A series of individual collectors will use propellers to move plastics into vertical tubes.  When these tubes fill with plastics, individual collectors will indicate by turning a mounted light from red to green.  A collection ship will then dock with the collectors and empty them.

7. Underwater Vacuum Pipe Network: A series of pipes will be laid on the ocean floor focused first on oceanic gyres.  The pipes will terminate into a device using a set of high powered gears that will vacuum plastics back to shore for processing.

8. The Plastic City: In a more low tech design, one firm proposes to place cities at sea stocked with workers who make daily ventures into the plastic islands with small nets and boats for collections.  Collected plastics would be used for building and fueling the city.

9: The Tube: Large hollow structures over 3000 feet all would be placed in the oceans.  Wind currents over the top of the stack would generate centrifugal counter currents within the stack drawing light weight objects, like plastic, out of the water.

10: Bioengineered Plastic Super Sharks: Genetically modified sharks would be bioengineered to large sizes and to filter feed on plastics.  Human trainers and jockeys would guide these sharks through the plastic patches.

In case you have not already figured it out this is satire. None of the above are real just like all the proposed massive engineering solutions proposed to deal with plastics in the oceans. All the images are random illustrations and photographs I found on Shutterstock. A decade ago we saw a multitude of ocean geosequesteration schemes that were going to taken carbon dioxide from the atmosphere and place into the deep oceans.  A decade later and none of the plans are realized, and carbon dioxide and global warming our on a runaway course.  I feel like history is repeating itself lately.

The media seems more transfixed on pretty artwork and pie-in-the-sky designs than with actual solutions to address the ocean’s health.  Want to actually fix the ocean plastic problem?  Here is how!

The post The Top 10 Engineering Designs to Clean Up Plastics In the Oceans: You Won't Believe What We Found! first appeared on Deep Sea News.

This is the first of two-part post. This installment is written by Kim, who will present alternatives to the Ocean Cleanup project to help curb the problem of plastic pollution in the oceans. The second installment is a technical review of the Ocean Cleanup feasibility study and is a collaboration between Kim and Miriam .

Last year, Deep Sea News reviewed the Ocean Cleanup project. The brain child of Boyan Slat, he claimed that his design could clean the ocean of plastic in 10 years. At the time the project was just a concept. It was a concept that we found had serious potential problems. As is explained in the technical review, we still think it has a lot of problems.

We can all agree here, we WANT to see plastic in the ocean cleaned up. But it isn’t an easy job and right now there isn’t a catch-all solution. Therefore, I’ve assembled a list of organizations that are actively trying to reduce ocean plastic, and suggestions on how you can help facilitate positive change. Because ocean plastic is a big problem that needs a big solution, and we need to work together on multiple fronts to solve it.

ORGANIZATIONS THAT ARE HELPING REDUCE OCEAN PLASTIC

5 GYRES, BEAT THE MICROBEAD, and THE NORTH SEA FOUNDATION

These organizations have waged an awesome and successful war against ocean plastic and in particular the terrible microbead. Microbeads are the little pieces of plastic that cosmetic companies put in their products for some extra scrubbiness. But once you wash your face, these microbeads go straight into waterways because they can’t be removed from wastewater*. Working together, 5 Gyres, Beat the Microbead (part of the Plastic Soup Foundation) and The North Sea Foundation has successfully convinced Unilever, The Body Shop, L’Oreal, Colgate-Palmolive, and Johnson & Johnson to all stop using microbeads in their products. These organizations are also working with lawmakers to enact microplastic bans in the US, Canada and Europe. Keep up the good work you banishers of microplastics!

You can also stop using cosmetics with plastic microbeads, but make sure you dispose of them properly.

OCEAN CONSERVANCY

Sometimes you got to use a little muscle to clean the ocean. And that’s just what the ocean conservancy does, each year they organize the International Coastal Cleanup. The next one is September 20. Volunteering is good for your soul and the beach.

SURFRIDER FOUNDATION – RISE ABOVE OCEAN PLASTICS

They surf, they shred, they care about the ocean. The Surfrider foundation is on it with their Rise above Plastics campaign, working at the local and state level to get plastic bags banned and help pass other plastic reducing initiatives.

BALTIMORE’S INNER HARBOR WATER WHEEL

Writer at Southern Fried Science and friend of Deep Sea News Andrew Thaler just alerted us to this really neat trash collecting water wheel. In development since 2008, its collecting plastic before it enters the ocean RIGHT NOW.

THINGS YOU CAN DO TO CURB OCEAN PLASTIC

GET INVOLVED LOCALLY

Does your town/city/state recycle? Do they have a plastic bag ban? Is there a ban on microbeads? No? Then get on it people! You can find ways to help make these plastic reducing initiatives a reality in your area and in your country. Congressman Frank Pallone has just introduced legislation to ban microbeads nationwide. But for reals, Seattle started making everyone pay 5 cents per plastic bag and I can see the change when almost everyone brings reusable bags to grocery shop!

REDUCE, REUSE, RECYCLE

I have a confession to make to you all. I may love all my new-fangled science gadgets, but I am a big earth loving hippie at heart. I try my best to make my footprint on this earth as small as I can. And you should too.

Before you run away screaming from what you imagine to be my patchouli stink, I just want to clarify that I’m not here to tell you to go all Ed Begley Jr. tomorrow because the ocean is filled with plastic. Instead I just want you to think about making one small change. One small change that you try and abide by regularly to reduce the amount of plastic you use.

Put a reusable bag in your car so you always have a bag at the grocery store. Use tupperware instead of a plastic baggies. Buy something you really want used instead of new (and save money…SCORE!). Bring a reusable water bottle/coffee mug. Cloth diapers if you dare. Cloth wipes if you double dare. Pick up a piece of trash and put it in a waste basket. Use a razor with replaceable blades. Even better, look badass and use a straight razor. Buy laundry detergent in cardboard boxes. Switch out your plastic microbead face wash for one with a natural biodegradable exfoliant like apricot seeds. Use paper disposable plates and compostable dinnerware. Reuse a ziploc bag or get compostable ones. Throw your cigarette butt in the trash instead of the street. Hold onto that bottle until you find an appropriate recycling bin.

Once you get the hang of this one change, add another. It might take a while to make the change a habit, but stick with it. Because I seriously do believe that a little change by everyone is much more effective than one person changing everything. And we all need a little less plastic in this world.

AND FINALLY AN IDEA I LIKE…A LOT.

STORM WATER DEBRIS NETS

I’ll admit, I am particularly enamored with this idea and I REALLY want it to work. By adding nets to the outlets of storm drains, a lot of plastic can be captured before it potentially gets to the ocean (which is also why Baltimore’s water wheel is SO awesome!). But this solution also has its problems, as the nets need to be emptied and maintained. That costs manpower and money. Money many municipalities don’t have right now. I really wish they did. And even if the array doesn’t work, it would be wonderful if the plastic collection technology that results from ocean cleanup project could be adapted to filter plastics from stormwater runoff.

Have any other solutions to reduce ocean plastic? Please list them in the comments below!

*The Ocean Cleanup array can’t collect microplastics, so even if you think the plan will work, STOP USING MICROBEADS NOW.

The post The Ocean Cleanup, Part 1: Alternatives to reduce ocean plastic first appeared on Deep Sea News.

To join in on all the fun I stumbled upon this little video floating around on the internetz. Let the cuteness overwhelm you.

Also, if you have yet to read Chelsea’s and Miriam’s recent plastic posts. Do it now. Soooooo goooood.

The post The Majestic Plastic Bag first appeared on Deep Sea News.

Deepling emeritus, Miriam Goldstein, is a science rock star.  My science crush on her only deepens after watching her completely explode TeX Oslo.  Miriam is all like BAM SCIENCE!   In case you don’t know, Miriam is a marine biologist and science communicator currently spending a year as a Sea Grant Fellow in the United States Congress.  She was one of the original DSN crew and holds  a Ph.D. from the Harvard of Oceanography, Scripps Institution of Oceanography in San Diego California. She is a leading expert on the ecological impacts of plastic debris in the North Pacific Subtropical Gyre.

The post How I Learned to Stop Worrying and Love the Garbage Patch first appeared on Deep Sea News.

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.

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: http://www.boyanslat.com/plastic5/ and http://www.boyanslat.com/in-depth/.

• 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. http://www.offshore-technology.com/projects/atlantisplatform/. 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.

Regards,

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.

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. http://climateadaptation.tumblr.com/post/46515698066/this-invention-keeps-popping-up-in-my-daily

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

Those Crazy Plastic Cleaning Machines

http://inhabitat.com/the-fallacy-of-cleaning-the-gyres-of-plastic-with-a-floating-ocean-cleanup-array/

The post The Ocean Cleanup. The newest of the new plans to remove marine plastic. first appeared on Deep Sea News.

Recently, my friend Michael Barton went to check out the Washed Ashore Exhibit, currently at Portland Community College, and was gracious enough to share some his images of it on flickr for us! It is all made from washed up beach debris and arranged to create stories of how plastic and trash in the ocean affects sea life. He also pointed me to this great video of the exhibit which does a great job of describing the scale of it. You can follow the exhibit on twitter @WashedAshoreArt.

The post Washed Ashore first appeared on Deep Sea News.