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| (source: The Ocean Cleanup) |
So far we have looked into the problems associated with
marine plastics right up the food chain. But now we will investigate the
current methods tackling the issue.
The first method is one I have been following for a while, The Ocean Cleanup (TOC). This project was founded by Dutch inventor,
Boyan Slat in 2013. It aims to reduce the amount of floating plastic in the
North Pacific Garbage Patch (NPGP) by 50% in 5 years. The team will do this by
placing long floating screens (below) which drop down into in the ocean and collect the
plastic, transported by ocean currents, as it floats into the arms.
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| (source: The Ocean Cleanup) |
The plastic
would then gather in the middle of the arms where it would be collected by
boats every 45 days. Once back on land, it would be recycled or converted to
oil. They estimate that this method of collection will be 7,900 times quicker than
conventional methods. The project has been in development for almost 5 years
and the team hope to fully launch the project by mid-2018. See the video below
for a brief history and full explanation of TOC.
One of the innovative aspects of this design is that instead
of being anchored to the seabed, it is instead anchored to deeper, slower
moving water (relative to the surface) which allows it to be much more flexible.
But there are some concerns:
- Environmental
Impact? The project stated in their 2015 annual report that
an environmental impact report will be conducted by an independent institute in
the pilot stage of the project and this was released in May last year. One
environmental risk is that marine life will be exposed to high concentrations
of plastic, thus seeing this as a potential source of food. For example, when
organisms biofoul (accumulate on wetted surfaces) they produce dimethyl sulphide
(DMS) which has an attracting odour for seabirds who think it’s food.
- The
feasibility study. This study was conducted in 2014 and a lot has changed
since then (for example the swap between using a stationary anchored system to
a drifting system), but it was met with heavy criticism by Martini and Goldstein (2014) concluding that, at the time, it was not feasible. One of the
major issues they found with the report included the fact that TOC had not suggested a solution to the
biofouling issue However an antifouling
system is currently being tested on the prototype in the North Sea, the results
of which will be known in March 2018.
- Will it
disrupt shipping? The simple answer, no. It will be positioned away from
shipping lanes, be fitted with detection equipment and their locations will be
mapped.
- It cannot catch all plastic sizes. The design can only capture microplastics down to
the size of 1 cm. Particles smaller than this will escape collection. Although
these larger plastics will eventually break down into much smaller sizes, so
one could argue that it isn’t too bad if it can’t collect the sub 1 cm pieces.
- Will it
be in the optimal locations? Authors like Dugdale (2016) suggest it would
be better positioned in coastal areas. A
study by Sherman and van Sebille (2016) modelled where the best locations would
be for the marine collection of microplastics by using buoys tracked by
satellites and microplastic observational data. They found that the ideal
location would be off the coasts of China and Indonesia. They estimate that by
2025, collection points off these coasts would remove 14% more microplastic
mass than the same number of collectors in the NPGP. There is also very little life in the NPGP and so would reducing the waste here be the
best way to reduce the harm on marine life?
But like any other problem, there is not just a single fix, there must be
several different approaches to solve the issue. By concentrating on the coastal
regions, the NPGP and the garbage patches in the other subtropical gyres will still be present. The
best approach is to tackle these high concentrations of plastic but to also
tackle the problem in coastal regions.
Both
the scientific community and the media have raised this geographical aspect as an issue, saying that more effort and
resources should be put into trapping the plastic at the source (i.e. coastal
areas/rivers). But TOC have not neglected this issue and have in fact
carried out a study on the influx of plastics from rivers into the
oceans in which they estimate that between 1.15 and 2.41 million tonnes of
plastic waste makes its way to the oceans via rivers, with the highest months
from May to October. Like Sherman and van Sebille (2016), they acknowledge Asia
as a major source of plastic influx from rivers. So they have shown that they
are not only concentrating all their efforts on the open ocean, but are taking
into account the sources of the problem as well.
 |
| (source: The Ocean Cleanup) |
TOC looks promising and I’m excited to see how well it will work. It is clear that there are several hurdles they must
overcome, but many of these have already been tackled. Though the most
important thing to remember is that this is one of many solutions out there and
it is these solutions working in parallel that will best combat the issue of
marine plastic pollution.
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