Twenty plastic-busting inventions to clean our rivers and seas

From plastic-devouring machines to watchful drones, these technologies are helping tackle plastic pollution in the ocean

Emma Bryce May 10, 2021

There’s an incomprehensible amount of plastic in the ocean – estimates put the known total at 5 trillion individual pieces, or around 150 million tonnes. An additional 8 million tonnes finds its way into the ocean every year. That’s only increased thanks to Covid-19 and the resulting surge in single-use items like masks and gloves.

Most plastic enters the ocean via rivers, which carry vast amounts of waste from inland sources. Once in the ocean, plastic is broken down by the sun’s rays and by wind and waves, eventually transforming into smaller fragments called microplastics. But the hardy nature of the material means that this process can take hundreds of years. In the meantime, plastic – both macro and micro – wreaks havoc on marine life. It brings the risk of entanglement, and starvation (as species mistake plastics for food). As it enters the food chain, it also potentially leaches toxins into animals’ bodies – with as-yet largely unknown effects on these creatures, and the humans who consume them.

Around the world, inventors, scientists and entrepreneurs are trying to innovate us out of this predicament. With everything from plastic-munching machines, to watchful drones and microplastic-dissolving technologies, they’re finding clever ways to remove plastics from the ocean – or to stop it reaching there in the first place. The majority of these inventions target pollution in rivers, down which most waste travels before reaching the seas. Some, however, venture much further out to tackle the gargantuan task of scooping plastic directly out of the open ocean.

The Interceptor barge is one innovation helping to clear rivers of plastic waste before it enters the sea (Image: The Ocean Cleanup)

But can technology really solve the plastics crisis? Arguably, the only real solution is to stop making so much plastic available to infiltrate the environment in the first place. That not only means reusing and recycling more, but also drastically reducing the production of single-use plastics, which are used for a day but can persist in the environment for centuries. And, ultimately, it means closing the tap on all non-essential production of this material. Combined action from governments, companies and consumers is the only way to move the dial on this ultimate goal.

Even if we do all of this, however, these changes will be gradual – taking years, if not decades, to unfold. And in the interim, tonnes of plastic will continue entering rivers and flowing into the seas. So while we figure out how to break up with plastic, the 20 inventions below can play a role in reducing its impact, and perhaps unpicking some of the damage that’s already been done.

Rehabilitating rivers

The barge-like Interceptor can detain thousands of tonnes of plastic before it reaches the ocean. Invented by Dutch NGO The Ocean Cleanup, the main structure is attached to a barrier stretching at an angle across a river, which directs drifting plastic into the barge. Once there, it goes along a conveyor belt and into the Interceptor’s belly, where it’s sorted and readied for recycling. The structure is solar-powered, and can remove 50 tonnes or more of plastic waste a day. Currently, it’s being put to work in three waterways – in Malaysia, Indonesia and the Dominican Republic – but the inventors have a more ambitious goal: ultimately, they want to deploy Interceptors on the world’s 1,000 most polluted rivers, where they could collectively rake up millions of tonnes of plastic before it flows into the sea.

This idea is not unlike Mr. Trash Wheel , a smaller-scale, plastic-gathering invention that’s been in Baltimore City’s harbour since 2014. The solar- and hydro-powered machine, fitted with comical googly eyes, slurps up plastic river trash that’s funnelled by a containment boom towards its mouth. Since 2014, two other charismatic plastic-munching machines have been added to the Trash Wheel “family”. They’ve collectively gathered almost 1,500 tonnes of plastic waste and debris from Baltimore’s rivers.

Another invention takes a more abstract approach to the problem of plastic pollution. The Netherlands-based Great Bubble Barrier intercepts waste with the help of a pipe, fitted with holes, and laid across riverbeds.

The Great Bubble Barrier (Graphic: Jing Zhang / China Dialogue Ocean)

When the pipe is pumped full of air, it releases a dense stream of bubbles that, for plastic, creates an almost impassable wall across the river. Waste gets diverted towards the riverbank, where it’s gathered and recycled.

The Great Bubble Barrier (Graphic: Jing Zhang / China Dialogue Ocean)

In early trials in the Netherland’s River IJssel the bubble screen stopped 86% of waste. It also increased oxygen levels in rivers, supporting aquatic life. Now a permanent Bubble Barrier has been installed in one of Amsterdam’s canals, where it stops plastic entering the IJssel, the North Sea and ultimately the global ocean.

Meanwhile, a company called Ichthion has developed an invention called Azure , designed to intercept waste in two major Ecuadorian rivers, before it is carried out on ocean currents to the famously biodiverse Galapagos Islands. This invention also uses a barrier to direct waste onto conveyor belts, which run along the riverbank, and deposit it into receptacles. But Azure’s conveyor belt system is also equipped with cameras that snap images of the waste, and then use algorithms to identify the plastic by type. That will help authorities understand how best to reduce waste at source. Azure is currently at pilot scale, but once up and running, it’s expected to capture 80 tonnes of waste per day.

Surveillance schemes

Along the Jiulong River in the Chinese port city of Xiamen, researchers have installed three cameras: their job is to track the slow passage of plastic pollution as it wends its way towards the ocean. This project, run by Xiamen University , is using the vast repository of visual data collected by the cameras to identify patterns in the movement of waste downriver; that enables the researchers to make daily forecasts about where plastic pollution is likely to flow the next day. The information is then shared with the city, so authorities can collect it efficiently, before it reaches the sea. This predictive camera-surveillance approach is just one part of a wider plan Xiamen has in place to identify sources of waste entering rivers.

The concept of plastic surveillance is spreading to other cities, too. On the River Thames in London, the Buriganga River in Dhaka, and along stormwater channels in Hobart, surveillance cameras sporadically snap photographs of river waste floating by. These are part of an international project pioneered by Australia’s Commonwealth Scientific and Industrial Research Organisation, which has so far amassed over 6,000 photos from water bodies in these three cities. Using artificial intelligence, it’s training computers to automatically identify plastic pollution in the photos, and to place it into one of 30 categories. That’s already revealed that some of the most common forms of waste are food packaging and plastic bottles, helping cities make more informed decisions about how to tackle it at source.

In other places, drones have become a critical plastic-tracking tool. In the Philippines, a partnership between researchers from both that country and Germany has led to the lift-off of a drone fleet that’s mapping plastic pollution in rivers flowing into the highly-polluted Manila Bay. The researchers have applied machine-learning to analyse the resulting video footage, which is combined with footage from cameras positioned on river bridges to detect waste flowing into the bay. So far, the project, which is funded by the World Bank, has pinpointed several hotspots where the majority of plastic pollution congregates before entering the bay. It’s hoped that, alongside further field surveys, the drone’s mapping efforts will inform government interventions to stem the waste.

Visual surveillance technologies can only detect waste on the surface of rivers, lakes and oceans – not the plastic sunk beneath – which means they’re only revealing part of the picture. But they are, nevertheless, providing the best estimates we can get on the scale of the challenge. The Ellipsis Earth project, for one, has an ambitiously global focus: Ellipsis crowd-sources global footage produced by drones, satellites, submarines and even CCTV, and augments it with imagery from their own drones. The result is a vast visual repository that they can rake through to identify plastic waste across the planet. Their programmes can now identify plastic with 93% accuracy, and they’re using their findings to create a worldwide heat map of global pollution – information they’re sharing with governments, NGOs and educational institutions to encourage action on plastic waste.

Meanwhile, the European Space Agency (ESA) is zooming out on the challenge, putting its satellites to the test. In recent research , they showed they were able to train satellites, using machine learning, to identify the unique optical signatures that plastic pollution creates when viewed from above. Their satellites can now do this with 86% accuracy, distinguishing plastic from other types of earthly debris. That’s enabled the ESA to track plastic waste from thousands of kilometres above – generating a truly global perspective on the problem. While the technology is still in its early stages, as it’s streamlined the goal is to chart a global map of plastic waste, so we can get a handle on the challenge and identify where to focus our efforts.

Small solutions

Smaller clean-up efforts can also be a surprisingly big part of the solution. Take the Seabin Project which began small-scale in Australia. The idea is to distribute plastic-catching “garbage bins” to harbours, marinas and ports. These bins move with the tides, filtering seawater and capturing any floating waste within. It’s a simple but effective solution, which has grown and grown. So far there are over 800 Seabins in more than 50 countries . Each one can capture 1.4 tonnes of waste a year .

From the Dutch company RanMarine, there’s the WasteShark , an autonomous water drone, about the size of a canoe, that skims the calm waters of ports, harbours and marinas and gulps up any floating trash and polluting oils in its path. The device can collect half a tonne of waste a day, which is returned to land to be repurposed. The WasteShark is also equipped to measure water quality as it putts around. Similarly, an early prototype floating robot called FRED , being developed by San Diego-based non-profit Clear Blue Sea, is designed to scoop up plastic waste offshore. Modelled roughly on a catamaran, it uses conveyor belts to winch waste up out of the sea, and can take in items ranging from 10 millimetres to 1 metre long.

Then there’s Hoola One , a Canadian invention to tackle the huge problem of microplastics embedded in beach sand. This hoover-like contraption sucks up sand, then uses a tank of water to separate floating microplastics from sinking natural material, which is returned to the beach. Meanwhile, the microplastics (the machine can capture fragments as small as 0.05 millimetres) are siphoned off and contained. So far, Hoola One has been tested on Kamilo Beach in Hawaii, one of the most polluted shores in the world. Trials showed it could clean three gallons of sand a minute, and gobble up 48 kilograms of microplastics in just a few hours.

The Hoola One (Graphics: Jing Zhang / China Dialogue Ocean)

Boom it

In 2019, a 600-metre-long crescent-shaped boom was deployed in the Pacific Ocean to scoop up plastic from the Great Pacific Garbage Patch – the biggest of the world’s five enormous waste-accumulating gyres (circulating ocean currents). Built by The Ocean Cleanup, this boom was one in a line of prototypes designed to remove some of the several million tonnes of plastic that have made their fateful path into the ocean, and which mostly circulate in those gyres. The NGO’s prototypes are made up of a containment boom attached to a floating anchor, which counterbalances the boom against strong ocean currents, waves and wind. That ensures the boom is always moving slower than the surrounding sea, enabling it to capture the waste that drifts into it. With their invention, The Ocean Cleanup has essentially created an artificial “coastline” in the middle of the Pacific, against which floating plastic gathers, and is later collected by boats that service the area.

The technology has been in development since 2012, but after several technical hiccups, only in 2019 did the boom finally gather its first batch of ocean plastic. Now the team is building on that success with a new version of the boom, currently being trialled in the North Sea. They hope to scale up and ultimately distribute several of their waste-snaring booms across the ocean’s five gyres. By 2040, they believe their invention could extract 90% of the ocean’s plastic waste.

Developed by The Ocean Cleanup, this prototype boom was tested in 2019, successfully removing waste from the Great Pacific Garbage Patch (Image: The Ocean Cleanup)

Using boom technology in the oceans is an ambitious undertaking, but it’s already having a measurable impact in rivers around the world, where it’s much easier to apply. For instance, at the mouth of Greece’s Kissifos River, a containment boom called the Tactical Recovery System Hellas (TRASH ) directs floating waste into cages waiting at the surface, capturing it just before it flows into the open ocean. The cages are mechanised and remotely operated. When they’re full, they’re brought to the surface to disgorge their waste onto land. As part of this European Union-funded project, the plastic is then converted into a combustible gas used to power ships and various activities at ports.

In South Africa, an initiative called The Litterboom Project has deployed simple booms made of piping across 20 of the country’s rivers, which are managed by teams onshore who routinely haul in the waste to sort and recycle it. So far, these Litterbooms have intercepted 120,000 kilograms of plastic on their usual path to the sea. And even very low-tech approaches are making a difference: in Guatemala, floating booms made from lines of empty plastic bottles strung across rivers – named “ biofences ” by their inventors – have successfully reduced the passage of plastic downstream by 60%.

On the horizon

Other inventions haven’t quite yet reached water, but are on their way. For instance, one team of Chinese and Australian scientists sees the potential of nanotechnology to one day vanquish microplastics in the ocean. Their invention is a microscopic magnetic carbon coil , the width of a human hair, that’s coated in nitrogen and manganese. Combined, the three ingredients create high levels of reactive oxygen in water, which degrades microplastics into less harmful components: a benign mix of salt compounds, carbon dioxide and water. When the scientists added these coils to water samples containing microplastic fragments, within a few hours, half of the microplastics had disappeared. Because the coils are magnetic, they could then be removed from the water, and reused in other samples. The scientists think their invention could be applied in wastewater treatment plants, where it could annihilate microplastics before they flow out into rivers and the sea.

Also targeting microplastics is a team of Swedish and Lebanese researchers developing a nano-coating for plastic . It is made of ingredients that react to sunlight in a way that weakens the plastic, causing it to crack and break apart. When they applied it to microplastics, the scientists discovered it reduced the volume of microplastic particles by 65% after a couple of weeks of light exposure. If these nano-coatings were combined with a dose of sunlight, or even simulated sunlight, in wastewater treatment plants, this could eradicate microplastics, whittling them down to nothing, before they reach the ocean.

Source: China Dialogue Ocean

Taxonomy

• plastic pollution
• plastic debris
• microplastics
• Plastic waste