Steve September 17, 2020

Since the widespread manufacture of plastics began in earnest in the early 1950s, plastic pollution in the environment has become a major global problem. Nowhere is this more evident than the Great Pacific Garbage Patch. A large ocean gyre that has become a swirling vortex full of slowly decaying plastic trash, it has become a primary target for ocean cleanup campaigns in recent years.

However, plastic just doesn’t magically appear in the middle of the ocean by magic. The vast majority of plastic in the ocean first passes through river systems around the globe. Thanks to new research, efforts are now beginning to turn to tackling the issue of plastic pollution before it gets out to the broader ocean, where it can be even harder to clean up.

Why Rivers?

The Great Pacific Garbage Patch is the most well-known area of ocean pollution, though four other similar gyres exist worldwide where ocean currents cause plastic pollution to gather. Image credit: The Ocean Cleanup

Recent studies have shown that river outflows are primarily responsible for the huge amounts of plastic entering the ocean each year. This is largely due to plastic being discarded on land, which then finds its way into waterways via storm drains and other routes. Rivers and stormwater systems serve to collect huge swathes of litter in this way, and then deliver them directly to the ocean.

In comparison, the direct dumping of garbage into the ocean pales in comparison to these sources. Estimates suggest that 1,000 rivers worldwide are collectively responsible for 80% of the plastic reaching the world’s oceans.

On top of this, there are efficiency gains to be had by carefully choosing the methods in which the problem is tackled. A recent study explored the impact of several different potential projects on plastic pollution levels. Existing ocean clean-up devices were shown to have an almost-negligible impact, whether deployed singularly or in numbers up to 200.

Graph showing the predicted effects of different mitigation strategies on plastic pollution. The greatest results are from a combination of river barriers and ocean collection devices. Image credit: ScienceDirect

Worse, such a deployment would have huge budgetary and labor requirements to run and maintain, for little real-world benefit. With long term modelling, the deployment of 200 ocean cleanup devices would result in roughly 816,000,000 kg of floating plastic remaining in the ocean by 2150.

However, the comparatively tractable solution of installing river barrier systems to collect plastics would have a much larger  impact. The team’s modelling showed that this would leave a much smaller amount of floating plastic in the ocean – just 398,000,000 kg – by the same milestone. Obviously, this does nothing about the plastic already in the ocean, but the research paper notes that a combined approach would net the greatest gains.

Putting Good Ideas Into Practice

Interceptor 002 in operation in the Klang river, Malaysia. The eventual goal of The Ocean Cleanup is to deploy similar systems in 1,000 rivers worldwide. Image credit: The Ocean Cleanup

With the numbers so decisively in favor of tackling the problem at the river level rather than out on the open seas, cleanup efforts have gotten down to work. The Ocean Cleanup have begun deploying their autonomous Interceptor craft to oceans around the world, and begun the long, ongoing task of reducing plastic outflows closer to the source. Built with a catamaran design, natural river currents guide waste plastic into the craft’s collection apparatus. There, the plastic is scraped from the surface of the water, and stored in dumpsters on board until ready for collection by local authorities. The entire craft is solar powered, and aims to collect waste with as minimal additional environmental impact as possible. Already, the team have delivered their fourth Interceptor, now undertaking operations in the Rio Ozama in the Dominican Republic.

The benefit of tackling plastic pollution at this level is that it no longer becomes a problem to be solved far from land, well beyond national borders, over thousands of miles of ocean. Instead, it’s a problem that can treated as something to be solved by local governments, where what are essentially point-sources of ocean pollution can be dealt with individually. In this way, it can almost be considered that the river is aiding in the collection of waste plastic such that it can be more effectively captured and disposed of properly.

No Silver Bullets

This river in Bandung, Indonesia, became clogged with plastic in 2018. Trucks were unavailable to haul the plastic away, so construction equipment was used to push the mass downstream. Much of this plastic likely entered the ocean. Image credit: David Shukman/BBC

Despite the positives of finding a better, more effective way to tackle ocean pollution, the problem is still far from solved. There are many more rivers that still need to stem the flow of garbage, and the plastic already in the ocean isn’t going anywhere.

We also need better techniques for dealing with the plastic that is captured.  Recycling efforts are ongoing in a multitude of ways, but fundamentally, mixed garbage that has been floating at sea generally doesn’t serve as a great feedstock for making raw quality materials for future use. While burning plastics may feel wrong, it’s not actually as bad as it sounds, and will serve as a better option than landfill in the medium-term until better solutions come along.

Ultimately, one of the best solutions to the problem is going all the way to the top, and stemming consumption in the first place. Initiatives to reduce the amount of single-use plastics in use are ongoing, and will have a significant role to play in solving the problem. Plastic that isn’t made can’t be thrown away, after all. Efforts in developing improved biodegradable plastics and less-wasteful packaging will continue to net gains, as well.

In the end, the solution to the plastic problem will require work in many diffuse areas. Only by reducing consumption and waste, stemming garbage outflows, and cleaning up what’s already out there, will we see a pristine ocean once again on Earth.

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