One of the most disheartening things about
the response to those scientific second thoughts is a common public
response along the lines of "at least Slat is doing something about the
problem, unlike these scientists who can't do anything but tear down his
good idea instead of helping." That's being said about people who have,
in some cases, been sounding the alarm about plastic pollution since
before Slat was born. Some groups critical of Slat's idea, such as the
organization 5 Gyres (about whom more in a moment), have been working
feverishly to come up with workable solutions to the ocean plastics
problem. Many of the critics have lauded Slat's enthusiasm, merely
suggesting that it be tempered by a bit of real-world thinking.
That's not to say that big ideas might not be perfectly appropriate
tools with which to tackle the problem of plastics pollution in the
ocean. It's a big problem. There are five distinct "garbage patches" in
the world's oceans, where discarded plastic has accumulated as a result
of finding relatively stable spots between oceans' currents. The largest
known of these, dubbed the "Great Pacific Garbage Patch," is usually
compared in area to the state of Texas.
And that's a problem, because that plastic doesn't just sit there and
float around. It gets eaten by marine life, and can cause them serious
health problems -- including starvation from having a belly full of
indigestible plastic. It leaches chemicals into the ocean water, and can
disrupt the normal ecological functions of the open ocean, blocking
sunlight that plankton depend on for photosynthesis, among other things.
In order to remedy this, Slat and his crew say they want to place as
many as 24 floating booms about 1,000 kilometers long (621 miles) at
strategic spots in the ocean. The booms would be designed to funnel
pieces of floating plastic into collectors, from which it would be
hauled elsewhere for recycling.
Slat says that his boom designs could rid the world's oceans of
plastic garbage in five years, while posing minimal risk to the oceans'
wildlife.
That's got a lot of people who may not have much experience with
actual conditions on the open ocean pretty excited. Marine biologists,
oceanographers, and engineers with experience with offshore
infrastructure aren't jumping on the bandwagon quite as
enthusiastically. It's great to chase bold visions, but the devil, as
they say, is in the details.
Here are some of those details.
1. Ocean plastic doesn't behave the way the project's backers say it does.
Technical details of The Ocean Cleanup's design are sparse, but it
looks as though the group plans to funnel plastic into collectors using
long baffles that extend three meters below the ocean surface. Their
contention is that the majority of plastic debris will be floating in
the top three meters of ocean.
The Ocean Cleanup conducted a
study
of the water column in an area in the Atlantic that they say backs up
this contention. That study found that the amount of plastic dropped off
"exponentially" deeper than three meters below the surface.
But as oceanographers Kim Martini and Miriam Goldstein
pointed out in their review of that study,
The Ocean Cleanup's team did no sampling deeper than five meters below
the surface. That despite the fact that winds have been proven to mix
surface ocean waters as deep as 100 meters, with plastic documented at
least that deep.
Martini and Goldstein also point out that the project's June 2014
feasibility study mentions that the array won't be able to collect
pieces of plastic smaller than two centimeters across. If your
impression of the oceans' plastic contamination is that it's all intact
grocery bags and water bottles, that may not seem like a big deal. But
the vast majority of plastic in the ocean is made up of particles one
centimeter and smaller, remnants of larger pieces broken up by
ultraviolet light, the corrosive effects of seawater, and physical abuse
from wave action and marine creatures.
In fact, as the ocean pollution activist group 5 Gyres Institute
suggests, The Ocean Cleanup's plans seems to be based on a notion of
ocean plastic that just isn't true. As the group's Anna Cummins wrote in
January:
The idea that there are "patches" of trash in the oceans is a
myth created 15 years ago that should be abandoned in favor of "clouds"
of microplastics that emanate out of the 5 subtropical gyres. Our recent publication in the journal Plos One
estimates 269,000 tons of plastic from 5.25 trillion particles, but
more alarming than that is it's mostly microplastic (>92 percent in
our study) and most of the plastic in the ocean is likely not on the sea
surface. Recent research has shown microplastics in ice cores, across
the seafloor, vertically throughout the ocean, and on every beach
worldwide. The little stuff is everywhere.
If you follow the life of plastic in the oceans, as we have done for
50,000 miles since 2009, you find the large items leaving coastlines in
droves, then it rapidly shreds as it migrates toward the calmer waters
of the subtropical gyres where sunlight, waves and nibbling fish rip it
to micro-size particles smaller than a grain of rice. Microplastic then
flow [s] through the bodies of billions of organisms, making their way
out of the gyres to deeper currents, and ultimately the seafloor.
That's the end-life of plastic.
Included in the burgeoning world of microplastic:
microbeads,
an arguably useless gimmick included in personal care products now
entering the world's oceans in alarming amounts. KCET's "SoCal
Connected" looked at microbeads
in a segment earlier this year. 5 Gyres and others are
working to ban microbeads jurisdictions worldwide.
In other words, if 98 percent of the problem plastics in our oceans
are the size of grains of rice or smaller, building a plastic collector
that takes only pieces larger than 2 centimeters from the top three
meters of the ocean would seem a fairly useless exercise.
2. The collectors will break really, really quickly.
It's hard to imagine a better description of actual conditions in the oceans' gyres than this one,
written by veteran ocean conservation activist Stiv Wilson, Policy Director for 5 Gyres Institute, in 2013:
So far, we've taken one gyre cleanup advocate across the
South Atlantic, from Brazil to South Africa. We had 22 days of storms
with seas in excess of 30 feet at times. By the time we got to the other
side, some 30-plus days later, he'd abandoned his hope of cleaning the
gyres once he realized how big a "place" we're talking about... the sea
is one giant corrosive force. Even on just a month-long sail across The
South Atlantic, we tore our sails twice, broke some rigging, and utterly
destroyed a wind-powered generator -- all due to the force of nature.
Any blue water sailor will tell you about how destructive the sea is to
anything with moving parts. That's why sailors say, "a boat is a hole
you fill with money." Heck, outer space is less corrosive to machines
than the ocean is.
Promotional photos offered by the Ocean Cleanup folks show the booms
floating on a nearly flat, glassy sea, where it's easy to imagine them
remaining intact for months on end. In 30-foot seas, how long would
those booms last before breaking apart? Martini and Goldstein, in their
review
of the project's June 2004 feasibility study, express serious doubts
whether the structures would withstand bluewater stresses for very long.
In that review, Martini and Goldstein pointed out that the study
"severely underestimated" the stresses to which the booms would be
subject under typical ocean storm conditions. The designers modeled
their study on average ocean currents rather than likely peak currents,
raising the possibility that the booms would be exposed to tougher
currents than they could handle as much as half the time. (It's the
extremes, not the averages, that break equipment.)
In order to keep the booms stably placed within the currents they're
intended to clean, they'd need to be securely moored. Slat and company
say that some of the booms would be deployed in water as much as 4,000
meters deep. That's twice the current maximum depth at which ships or
other structures have ever been moored.
And when the currents in which the booms are moored shift, point out
Martini and Goldstein, the booms could deform, seriously reducing their
ability to collect plastic -- or even spilling collected plastics back
into the ocean.
And then there's the issue of "biofouling," the term of art used to
mean "marine critters using your expensive equipment as a place to
live." Place a rigid object in the ocean and within 24 hours, bacteria
and diatoms will have attached to it, creating a "biofilm" that then
provides habitat for algae and protozoans. That in turn provides a place
for larger organisms like tunicates, sponges, mollusks, and crustaceans
-- barnacles being the most familiar example of the latter.
And that adds weight to the structure. The Ocean Cleanup's
feasibility study itself says that biofouling could add tens to hundreds
of kilograms of extra weight per square meter of submerged surface.
That
could sink the booms. It
would change the way
currents flow along that three-meter-deep skirt beneath the booms,
altering the efficiency with which the booms funnel plastic into the
collection area.
There's also potential for damage from a very specific kind of
biofouling: larger fish "vandalizing" the structures. "Fish bite" damage
to submerged equipment, from sensors to mooring lines, is a
real thing.
Slat's test next year will deploy a boom that's one five-hundredth
the length of the proposed booms that are his ultimate goals. It remains
to be seen how well that far shorter model holds up in the relatively
protected waters of the Korea Strait. As currently described, it seems
likely that the larger versions would, after the first winter storm,
become part of the floating ocean plastic problem -- 600 miles of
plastic per boom.
3. The project will harm wildlife.
Slat's team says in its feasibility study that they don't have a
workable solution to the biofouling issue, saying that mechanical
cleaning of 24,000 kilometers of boom floating in the open ocean would
be too expensive. Martini and Goldstein point out that the only other approach that's even close to workable would be for The
Ocean Cleanup to use so-called anti-biofouling coatings on their
equipment, to slow down the rate at which the structures are colonized
by marine life.
Though research is being done into new surfaces that are resistant to
biofouling, using nanomaterials technology, the standard
anti-biofouling coatings in use these days are chemical treatments that
contain "biocides." Biocides are pretty much what they sound like:
substances that kill living things. The idea is that biocides
incorporated into the coatings will deter organisms from forming that
biofilm that starts the biofouling process.
The problem is, anti-biofouling coatings have a finite effective
lifespan. And that's in part because the biocides leach out of the
coatings.
Imagine 24,000 kilometers of boom coated with anti-biofouling
coatings leaching biocides into the ocean -- from a project intended to
benefit marine life.
The most effective biocidal coatings, and the most widely used, are compounds in the
tributyltin
family, which are known to leach into seawater and pose documented
risks to microorganisms and larger marine life. Some governments have
moved to phase out tributyltin, but there aren't many economical
alternatives.
The booms pose physical threats to marine life as well. The designers
claim that neutrally buoyant microorganisms such as plankton will
merely flow beneath the three-meter skirts. That may be true for some
species, but marine biologists point out that the North Pacific gyre
(for instance) has planktonic organisms that don't stray from the highly
oxygenated waters found right at the surface of the ocean, and that
such species would likely be swept up in large numbers. Any plankton
that's swept up into the collectors will be separated out by centrifuge,
the effects of which Miriam Goldstein described thusly in a marine
scientists' email list server conversation:
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.
As for larger organisms, the feasibility study itself says this:
Highly migratory species will be highly affected by this
project. Swordfish, marlin, sailfish, sharks, tuna-like species are all
highly susceptible to being caught in the holding tanks, and possibility
diverted by the booms into the platform.
The Ocean Cleanup makes much of the fact that their booms are
unlikely to directly ensnare large wildlife due to the skirt's smooth
surfaces. Due to biofouling, those smooth surfaces may not last long.
Among the pieces of plastic floating in the ocean are "ghost nets,"
discarded pieces of fishing net sometimes hundreds of meters long. With
24 1,000-kilometer booms scattered across the oceans, the possibility
that such ghost nets would get hung up on patches of barnacles growing
on the skirts is significant. And since the boom would be moored and the
ghost nets would suddenly stop moving with the current, animals that
do move with the current would face greater threats from those nets.
As mentioned above, the public image of plastic pollution in the
oceans differs greatly from reality: only a tiny percentage of discarded
plastic is found in large floating pieces that would be easily swept up
by Slat's booms. Ironically, such floating plastic is highly likely to
have itself been "biofouled," adopted as a home by marine organisms that
would be injured or killed during the collection process.
In 2014, Charles Moore -- original discoverer of the "Great Pacific
Garbage Patch" -- found a floating island in the North Pacific thought
to mainly consist of trash washed out to sea by the 2011 Japanese
tsunami. The 50-foot island was home to an apparently permanent
population of sea anemones, algae, clams, and mussels. That's just an
indication of how readily wildlife will colonize every available surface
in the ocean -- including floating plastic. And that means that the
plastic Slat's design can collect is the plastic most likely to have
wildlife stowaways.
One wonders just how much help from The Ocean Cleanup the oceanic wildlife of the world can withstand.
4. Recyclers don't want the plastic.
Slat and his colleagues say that the end destination of the collected
plastic is land-based plastics recyclers. This is unlikely to turn out
to be the case. Unlike glass and aluminum and high-quality paper, which
can be recycled a number of times into products similar to the original.
But when you put your plastic water bottle in the recycling bin, you
won't be getting a recycled plastic water bottle at the other end of the
process. Plastics' polymer chains break down too readily when melted,
meaning that your water bottle becomes a lower-grade plastic product,
and usually not a disposable one.
That means that plastics recycling is actually better called
"downcycling," and it's not a solution to the problem of disposable
plastics. And
that's assuming that plastics recyclers have
access to a supply of clean, sorted, high-quality discarded plastic,
such as you might find in a residential or office recycling bin.
Slat's machines, on the other hand, will be collecting plastic that's
been drifting in the ocean for who knows how long, its polymer chains
under attack from dissolved salts and ultraviolet light, and absorbing
environmental contaminants from random industrial harbors. Instead of
being readily sortable bottles and bags, much of the collected plastic
will be in small pieces, and that means recyclers would need to use
spectrographs to determine whether the salvaged plastic is polyethylene,
polyproplylene, polystyrene, or something else altogether.
Plastic recycling is a completely marginal industry, with supply of scrap plastic far outstripping demand. It's only a
de facto
subsidy by recycling collection programs, which provide a mostly clean,
mostly sorted source of scrap plastic at low cost, that makes plastic
recycling even slightly feasible. Offer to truck hundreds of tons of
contaminated mixed plastic to those recycling facilities, and it's
doubtful you'd get a polite response.
5. There's a far more effective way to clean large plastic pieces from the ocean's gyres.
It's called "beach cleanup." Current thinking (no pun intended) has
it that as much as half the plastic in a gyre is jettisoned in each
rotation, where it then follows ocean currents wherever they lead. often
enough, those currents lead to beaches, where the plastic can be
removed by volunteer labor with minimal harm to wildlife. If it's not
picked up off the beach, the next storm can wash it back out to sea,
where it may eventually rejoin a gyre.
That makes our beaches a very accessible part of the ocean plastic
garbage cycle, and it just makes sense to focus our ocean plastic
cleanup efforts on that low-hanging fruit.
In 2014 on one Beach Cleanup Day in California alone, 66,292
volunteers collected 564 tons of trash, some 80 percent of which was
single-use disposable plastic items. That's 564 tons of trash that won't
be joining the Garbage Patch.
You can find the next beach cleanup event near you at
The Ocean Conservancy's website.
6. It's far more efficient, cheaper, and safer to keep the plastic out of the ocean in the first place.
In a way, it's ironic that supporters of Slat's project in social
media have been accusing critics of not contributing to solutions to the
issue of plastic pollution, because the net effect of The Ocean Cleanup
may well be to persuade regular folks that the problem has been solved,
and they don't need to take action to limit the amount of plastic that
goes into the world's waterways.
There are initiatives already taking place that promise to
significantly reduce the amount of plastic trash making its way into our
oceans. More and more places are enacting bans on disposable plastic
grocery bags, a major component of plastic pollution. Single-use plastic
water bottles are another bit of low-hanging fruit just asking to be
banned, a move some national parks have already taken.
As mentioned
above, bills to ban plastic microbeads are advancing, including Assembly
Bill 888, which passed the California Assembly in May and is now being
considered by the California State Senate.
We're not discounting the importance of clever technological
approaches; they just don't belong on the ocean. Some municipalities
have had good results from putting screens on strom drains and
collecting the accumulated plastic. Baltimore operates a
"Water Wheel"
where the river Jones Falls flows into the city's Inner Harbor. In the
last year, that device has filled dumpsters with almost 200 tons of
trash that would have flowed into Chesapeake Bay.
But the ultimate solution to the problem of ocean plastics is to stop
using so much single-use, disposable plastic in the first place,
whether as packaging or in single use items such as
drinking straws.
Once that plastic gets to the ocean, there's no technological quick
fix, no matter how much we might want there to be one. We've got to stop
counting on some bright young inventor to save the planet and start
doing it ourselves.
