future view

Plastics in rivers may be a bigger problem than 'plastic soup'

29 July 2019 • 3 min reading time

The accumulation of plastic waste in the environment is a major and urgent global problem. To help find a solution, TNO is carrying out various studies into the transport mechanisms of plastics in aquatic ecosystems and advises governments and businesses based on its findings. A recently published article reveals that plastic waste in rivers may be a bigger problem than the ‘plastic soup’ in the ocean. TNO wants to accelerate the transition to circular plastics, which will result in less plastic waste, less CO2 and less use of fossil raw materials.

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There is a lot of information about ‘plastic soup’ in the media and online. But what about the rivers? And where exactly do different kinds of plastics end up? "We carry out life cycle analyses, which involves analysing the environmental impact of products. A lot about plastics is still unknown and we see opportunities to improve our analyses," says Anna Schwarz, who works for TNO Circular Economy as a junior scientist.

"Because we knew too little about where plastic waste accumulates, we analysed how different types of plastic waste are dispersed across various parts of a river, such as the banks, beaches and river bed. We then compared studies of plastic waste in different aquatic ecosystems to produce a global picture of how plastics are transported and how they accumulate in water. We hope the research will contribute to more effective policies for reducing and disposing of plastic."

PLASTICS remain in rivers

The research revealed that the vast majority of plastic waste in rivers does not reach the sea, but instead ends up in river sediment or on riverbanks. Only 1% of all plastic waste is found floating in the oceans. The problem is thus much bigger than the plastic soup.

"This 1% is at odds with what you read online: that 80% of plastic waste is carried to the ocean by rivers. So we have our doubts about that figure," says Gerard van der Laan, programme manager and senior scientist with TNO’s Circular Plastics group.

Plastic packaging and plastic consumer products are most often found floating in rivers. The plastic floating in the sea mainly originates from the fishing industry and fish farms. "We may be focussing too much on plastic in the sea at present; we also need to clean up the plastic waste in the rivers and prevent more from ending up there. Obviously it would also be a good idea to prevent plastic from fishing vessels and fish farms from ending up in the sea," adds Schwarz.

What ends up where?

The highest diversity of polymers – the building blocks of plastics – is found in sediments in both fresh and saltwater. Most sediments (or deposits) are found on river bottoms and ocean floors. "Based on our research, we have concluded that only thicker and larger plastics made from low-density polymers (i.e. the plastics that remain afloat) are actually transported over long distances, such as from a river to a sea. The vast majority of plastics is deposited on riverbanks, beaches and in river sediments. This is because plastic foil and heavy plastics sink, while plastic bottles are typically blown up onto riverbanks," explains Schwarz.

reduce, recycle and reuse plastics

The Netherlands has an efficient waste collection system, and only a small proportion (some 2%) ends up in the environment, but there is still room for improvement. Much of this plastic is incinerated, but it is even better to reduce, recycle or reuse it.

TNO is studying ways to chemically recycle plastic, for example, whereby plastic waste is purified and chemically separated into new, pure chemical building blocks which can be used to manufacture new plastics. TNO also conducts independent research for the government and industry into sustainable plastics and develops and demonstrates innovative recycling technologies and redesigned plastic products. 



Plastic has a bad image, but that is not entirely justified, think Schwarz and Van der Laan. ‘Plastic is a fantastic and useful material, and often much more durable than other materials such as cardboard, glass, bamboo or wood… provided it is recycled properly,’ says Van der Laan. ‘Plastic could be valued more highly around the world through the implementation of good policies, which is also the message of the World Wildlife Fund for Nature. It is clear that something has to be done to prevent plastics from polluting the environment and it is important to accelerate the transition to circular plastics. TNO wants to help achieve this.’ Schwarz worked with The Ocean Cleanup and saw how bad things are at sea. ‘But now I can also see the subtleties of the problem. Our goal is simply to present the objective facts,’ says Schwarz.

Would you like to know more about TNO’s research into plastics?

Please contact Gerard van der Laan


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