OpinionFlourishing Oceans21 Feb 2019

How a global river clean-up strategy could help us reduce ocean plastic pollution

Plastic is filling our waterways. We explain five of the most promising technologies hoping to intercept the flow of waste from rivers to the ocean.

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Waste on a river bank. Photo Credit: The Ocean Cleanup.

Each year, around 15 million tonnes of plastic ends up in our oceans. That’s enough to fill about 85,000 road trains. No surprise then that this plastic harms wildlife and affects human health, natural ecosystems and economies at a terrible scale.

The most significant contributor to plastic in oceans is the lack of functioning waste collection systems in many low to middle-income countries. With no alternative, plastic ends up in river systems and then flows out to the ocean. To address this we need to improve these waste management systems while simultaneously stemming the production of fossil fuel-based plastics. In 2016 alone, we produced a staggering 242 million tonnes of plastic waste.

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Mass of river plastic flowing into oceans per year. River contribution estimates derived from statistical model using waste management, population density and hydrological data. Photo Credit: Nature Communications.

Changing human behaviour, businesses and policies takes time. But we don’t have time to waste. We believe a multinational river clean-up program would help create a ‘quick fix’ to begin addressing the problem, while work continues on an ongoing global solution.

The top 20 polluting rivers, predominantly located in Asia, are responsible for over two-thirds of the plastic entering oceans from river systems. If temporary solutions to intercept this flow of plastic were implemented, waste emissions would decrease by up to 70 per cent.

By creating a global network of standardised river clean-up operations, we would also be able to create a powerful network of pollution monitoring stations feeding data into a ‘pollution map’ online. These platforms would help us monitor the efficiency of core solutions such as educational programs, enhanced recycling and policy implementation. They would also enhance waste literacy in consumers, producers and governments.

Minderoo Foundation’s Flourishing Oceans initiative is working to ensure our oceans contain more fish than plastic by 2050. We have reviewed the most promising existing river clean-up operations working to reduce the flow of plastic into our precious oceans.

Trash Skimmer Boats 
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The Trash Cat has removed billions of tons of debris from New York to Dubai to Malaysia. Photo Credit: Mud Cat Dredges.

Trash skimmer boats are ‘underwater lawn mowers’ that scoop floating plastic, rubbish and aquatic weeds out of rivers and store the debris aboard until the vessel can be emptied. The TrashCat (pictured above) uses a pickup conveyor belt that extends into the water and catches floating rubbish. These boats can store up to 5,500 kilograms of debris at a time, including wooden logs and other large items. They are designed to be super manoeuvrable, easily getting into areas where waste accumulates to maximise efficiency.    

The WasteShark
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The WasteShark autonomous waste-eating aquadrone was modelled on the whale shark. Photo Credit: RanMarine Technology.

The WasteShark is an autonomous robot designed to tackle plastic pollution in rivers. This floating drone has a wide open “mouth” at the front to collect floating plastic in rivers and harbours and can work constantly without needing an operator. Utilising high-tech sensors and ultrasound technology to prevent collisions with unsuspecting wildlife, the system also collects water quality information such as pH, dissolved oxygen and salinity. Designed in Cape Town and operating in Dubai and the Port of Rotterdam, the WasteShark learns about its environment over time and becomes more efficient at picking up rubbish. Each shark can pick up approximately 160 kilograms of rubbish before returning to its base for emptying.

Mr Trash Wheel
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The googly eyed, trash eating superhero Mr Trash Wheel is a local tourist attraction. Photo Credit: Waterfront Partnership of Baltimore.

The Baltimore Inner Harbour Water Wheel, known as ‘Mr Trash Wheel’ to locals, is the trash-munching, googly-eyed star of river plastic removal. Mr Trash Wheel has 18,000 followers on Twitter, who track his garbage-eating adventures and trash-themed jokes (they are very good). The system is powered by currents and solar panels that turn rotating forks to pick up floating debris and place it on a conveyer belt. The belt then empties into a dumpster which is towed away by barge to allow the garbage to be later incinerated for power production. Invented by a local resident and launched in 2014, the trash interceptor and his subsequent accomplices ‘Captain Trash Wheel’ and ‘Professor Trash Wheel’ have since collected over 999 tonnes of rubbish, significantly improving plastic levels in the harbour.

Seabins
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The Seabins are currently removing microplastic particles in the size range from 2 mm to 5 mm, as well as larger debris. Photo Credit: The Seabin Project.

The local heroes who created Seabin Project cleverly combine plastic clean up with education programs. The project is the brain child of two Perth surfers who, sick of seeing rubbish in the ocean, quit their jobs and crowdfunded the production of their invention. The units are similar to garbage bins and are capable of collecting 20 kilograms of rubbish at a time. They are most often stationed at marinas, ports and yacht clubs. Requiring a small amount of power to run, the Seabin pump sucks in rubbish, while pushing water back out. While the inventors recognise the Seabins are small compared to the size of the global problem, their focus is also on education, research and advocacy work

The Great Bubble Barrier
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The Great Bubble Barrier pilot calculated that the system captures ~70-80% of top-surface floating plastic and 50% of plastic underwater. Photo Credit: The Great Bubble Barrier.

Developed by three Dutch women the Great Bubble Barrier is the newest innovation on this list and although still in it’s early stages, it is winning awards all over the world. Based on established technology used in the oil and dredging industry the project utilises a pipe placed diagonally across the path of the river. The pipe expels a wall of bubbles to intercept debris, forcing plastic in the water to the surface for manual removal. With their laboratory testing, full scale pilot project and crowdfunding campaign now successfully completed, we look forward to the first permanent bubble barrier being installed this year.

Inaction is not an option

As a global community, our ultimate goal must be to reduce virgin plastic production while increasing the use of recycled content. To do that, we need to change human behaviour, implement effective policies and work with global businesses and start-ups.

We recognise this takes time, but inaction in the interim is not an option. We believe a multinational river clean-up program is urgently needed to begin to address this problem, while we rally together to orchestrate positive and lasting change.

Julia Reisser
Asha McNeill
by Julia Reisser & Asha McNeill
Julia, our lead plastic researcher, has extensive experience in setting up, managing and leading research projects and has led many scientific missions in the Atlantic, Pacific, Indian, and Antarctic oceans. Julia’s research has received many scientific citations (1700+) and there has been media coverage of the 20+ peer-reviewed publications she has co-authored.
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