In a prior blog I commented on ignorance and how easy it is to jump to incorrect solutions. In that blog I made reference to Boyan Slat and his Ted Talk as an example of an incredibly awful Ted lecture.
In his lecture Boyan Slat proposes a method for removing plastic trash from oceans. The lecture is presented by an enthusiastic young man in front of a basically ignorant audience. With universal approval he makes a moving appeal for doing something we all want to do: Save our environment.
A friend sent me link to this lecture knowing that I am one of those seaweed hugging engineers and hoping that I would enjoy this young man’s resolve. Instead I was horrified.
First allow me to provide a disclaimer and position statement. I love young people, and I support them in any crazy idea they have as long as they do no harm. I do not say this lightly, I want young people to think big and many postings on our website support this notion. On the other hand, big thinking by young people should not allow them to ignore nature and the world as it exists. That means that water does not flow uphill, and, no matter how much a young person wants it to flow uphill, it will not flow uphill. If a young person’s ideas hit a physical wall, it should be pointed out and they should be pointed to more productive endeavors. Nobody, young or old is allowed to sell flim flam, no matter how charming their story.
So let’s get back to Mr. Slat.
Mr. Slat heard about ocean plastic islands and became worried about the impact of the plastic and so am I. Plastic does not belong in the oceans and I have been on salvage projects on deserted islands where the plastic at the tide line was 4 feet high and 12 feet wide for the entire length of the beach. Meanwhile, while I have seen the plastic on the beach, nobody has seen the plastic island, since it does not exist. However, plastic packaging is a pox on our world and (since water flows downhill) any bit of plastic that is not picked up ashore will have the tendency to drift into our oceans.
Apparently Mr. Slat did some dreaming and proposed to make huge 100 mile long nets and booms that will capture ocean plastic debris behind the nets. Then the plastic would migrate along the nets and end up at floating collecting stations where it can be recycled. If he would have talked to me, or any other person who has any experience with ocean technical systems, I could have discussed his idea and I would have cautioned him about the realities that I will outline later in this blog.
This did not happen, and somehow Mr. Slat was allowed to make his Ted presentation, which was nothing more than the verbalization of a hallucination to wide acclaim among the ignorati.
This resulted in a crowd source fundraiser of multiple million dollars and eventually a Nor-Shipping 2015 Young Entrepreneur Award. A Marine Technology News article about Mr. Slat and the award reports on his plans, but does not analyze his technical approach for removing plastic from the oceans. The author of the article tries to elicit some responses from industry insiders, but fails to get any strong responses. That sort of makes sense; why would anybody want to step on a young man’s dream of caring of the ocean environment?
Well, there is one good reason. If his dreams make no technical sense, why should he be allowed to foul the discussion on this subject, waste real money, and be rewarded for a deeply flawed invention?
At this stage this may sound like old man envy. But let me provide a few technical considerations about Mr. Slat’s approach:
1. Mr. Slat published a 500 page feasibility study on his website. The problem is that it is not a feasibility study; it is an endless listing of loose ideas, none of which make it to the bottom line. A feasibility study requires a technical risk assessment. The study fails to make a risk assessment and, if the assessment were made, it would show that the chance of success is very, very small.
2. Mr. Slat wants to remove plastic from the ocean using moored collecting booms. These booms are little different from oil booms. Anybody who has tried to collect oil with booms in any type of seaway knows that there is a lot of movement and very little oil collecting. Instead of attacking an oil slick, Mr. Slat’s booms need to collect plastic. Ocean plastic consists of a few large pieces, and tremendous amounts of small pieces down to microscopic size. Even in the Pacific gyre, where the term “plastic island” provides an image of an actual island, one will not see more than one or two pieces of floating plastic at a time. Assuming that my field of vision is a mile, I would need a one mile long boom to collect two pieces of plastic at any one time. One can assume that the boom will continually catch plastic, so if I assume a current of one mile per hour, in 24 hours one mile of boom could catch about 50 pieces of plastic. These pieces of plastic then would have to migrate to a collection station. But what if the plastic does not have sufficient bouyancy and the current drives the piece of plastic beneath the boom? And, if I design a boom to prevent the plastic from slipping underneath the boom, how will it migrate to the collection station which will have to be many miles away?
3. Collecting large pieces of plastic is nice, but large plastic is not the problem. The environmental problem relates to microparticles. Mr. Slat’s system does nothing about collecting microparticles. Instead it collects only a fraction of all plastic in the water.
4. Mr. Slat assumes that all plastic is near the surface, and even makes mention of field tests in his feasibility report. However, his method is flawed, and relates to simple buoyancy principles. Large plastic either floats or sinks. Only tiny particles remain suspended in the column, but he is not dealing with tiny particles and therefore can quickly state that his system will capture most of the plastic that he could find and that would be near the surface.
5. So how does this boom stay in place? It needs to be in a continuous current, otherwise it will not hold the trash (due to backwashing from a reversing current) and then will never transport the trash to the collection station. It should be anchored. How will it be anchored? One can anchor a boom in shallow water, but, if a boom is anchored in a current, it needs to have a certain amount of rigidity and buoyancy to prevent it from submerging at the unanchored points. This is a wicked complex problem in shallow water moors, but Mr. Slat wants to do it in very deep water and open ocean.
6. Moored systems both have weight and drag. In theory it is possible to use zero buoyancy or even floating mooring lines, but it is not possible to use zero drag lines. Even a one knot current on a very long line results in tremendous drag and this drag needs to be compensated for in the buoyancy of the boom. In other words, the greater the depth, the greater the boom diameter and the greater the cost and drag of the boom. Mr. Slat talks about scalability, but actually this system is not scalable from shallow to deep water, or even scalable from a short boom to a very long boom.
7. And then we have a storm. Will this system be able to contain the occasional piece of plastic that has been collected over an extended period of time or will the boom tear apart and release the plastic? How will it be repaired if it breaks away from its moorings? Will Mr. Slat’s broken booms and their mooring lines also be added to the plastic trash that floats around in the oceans?
8. Oh, and have we discussed biofouling, or corrosion or UV damage?
9. And how long will these booms be again? One break in the boom, whether from a failed mooring line, or a sunken section, will result in the release of all the plastic caught in the upstream section over many days.
I have previously stated that nothing takes more time to debunk than really bad and long “expert” reports. To actually go through the pile of technical debris that Mr. Slat and his associates have collected will take an order of magnitude more time than it took for them to throw it together, and I hope that the above comments suffice to show the foolishness of the invention.
Take it from someone who still dreams big dreams and likes nothing better than to be enthralled by youthful enthusiasm, the time has come to shut Mr. Slat’s dream down. It has gone on too long and if it is not shut down forcefully by the world technical community today, it will become another corn ethanol story, another cold fusion story, another electromagnetic ship propulsion story, another red scare or another 1950’s Blue Ribband commercial delusion.
Cleaning up the environment takes courage Mr. Slat. if you want to clean up the environment, you have to have the personal courage to face the technical music and stop wasting the world’s resources on something that cannot work. Shift your enthusiasm and salesman skills to less wasteful endeavors.
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