Plastic waste pollution in the ocean: technology at the tipping point
Image credit: Getty Images
A change in public attitudes is helping to turn the tide on how we deal with plastic waste.
A whale found washed up on a beach in Spain earlier this year had 29kg of large pieces of plastic in its digestive system – including rubbish bags, ropes, pieces of net and a drum. While such cases make good photo opportunities, there is growing concern about damage to sea life caused by a far less visible problem – the ‘smog’ of tiny broken-up pieces of plastic on the ocean surface that pass through marine ecosystems before settling on the seafloor.
In 2015, an international research team led by Erik van Sebille at Imperial College London estimated that between 15 and 51 trillion plastic particles (nominally sized below 200mm, but with most concentrated between 0.33mm and 5mm) are floating in the world’s oceans. Their combined weight is between 93,000 and 236,000 tonnes.
The highest particle counts of ‘plastic smog’ are in the Mediterranean and North Pacific. Why? Because the Med is like a bowl (so the plastic cannot escape), while the North Pacific contains a huge mass of rubbish spilling out from the most polluted rivers in the world.
Each year, between 1.2 and 2.4 million tonnes of plastic enters the oceans from rivers, according to a paper published last year in Nature Communications by Laurent Lebreton of The Ocean Cleanup (TOC) and colleagues. They calculated that two-thirds of this comes from just 20 rivers, mostly in Asia. That the most polluted sea areas are next to the most polluting rivers can be seen clearly by the map produced by Win Cowger from the University of California, Riverside, on behalf of the 5Gyres Institute.
Such findings are beginning to change public and industry perceptions. The idea that you might scoop up thousands of tonnes of ‘plastic smog’ in the oceans with trawlers, nets or clever plastic-collecting booms (as proposed by TOC) seems optimistic to say the least. TOC is reengineering its prototype booms because they get destroyed in the sea by the same forces that cause plastic trash to break up into tiny pieces.
“We need to think of plastic pollution like the hole in the ozone layer or air pollution over a city,” says Marcus Eriksen, co-founder of 5Gyres, the first organisation to research plastic in all five main subtropical ocean gyres. “We didn’t try to make a huge vacuum cleaner and suck up the CFCs or smog particles; we banned CFCs and tried to reduce air pollution. Plastics are the same – our efforts need to be about prevention.
“People are waking up to the idea that it’s unrealistic to expect consumers to carry the burden and pay for waste management, and to subsidise the negative consequences of poorly designed products,” he says.
Plastic: changing it up
If we are going to benefit from new materials, clear labelling will be essential. Bio-PET, for instance, is a plastic made from renewable feedstocks like the leftover pulp from harvesting sugarcane. Coca Cola’s bio-PET Plant bottle is made like this, but bio-PET behaves like oil-based PET (used for plastic bottles) and is recyclable, but not compostable.
There may yet be hope for biodegradable PET following the discovery of an enzyme dubbed ‘PETase’, produced by a bacterium called Ideonella sakaiensis 201-F6 that was found in the soil of a Japanese PET bottle recycling plant. Researchers at the US Department of Energy’s National Renewable Energy Laboratory (NREL) and University of Portsmouth announced recently they had developed a faster working variant of the enzyme this year that can break down PET bottles more quickly.
Over the last 12 months, public pressure has begun to turn the tide. Unilever and Starbucks are two of the global companies that have pledged to get rid of single-use plastics after being named and shamed by the Break Free From Plastics movement. Starbucks’ crime was failing to deliver a fully recyclable cup after promising one eight years ago. Unilever products, along with those of Proctor & Gamble and Nestlé, were among the biggest contributors to beach litter in a week-long clean up by Greenpeace and Break Free From Plastics in the Philippines, one of the biggest ocean-polluting countries.
A mobile app called Litterati is raising the stakes by making it easy for individuals to document and geotag corporate logos and names found on polluting plastics.
In the UK, a campaign by 38 Degrees for teabags free of polypropylene (a sealant used across the industry) has prompted many well-known brands including PG Tips, Clipper, Twinings, Tetley, Yorkshire Tea and the Co-op to take action and work on fully biodegradable alternatives.
Governments are taking action too. Indonesia, which is responsible for two of the world’s ten most polluted rivers, has announced a national programme to tackle land-based waste over four years with up to $1bn to reduce plastic pollution. The EU wants all plastic packaging to be recyclable or reusable by the end of the next decade. The UK’s more relaxed aim is to eliminate all ‘avoidable’ plastic waste within 25 years.
‘We need to think of plastic pollution like the hole in the ozone layer or air pollution over a city.’
What materials can companies use instead? 5Gyres has recently published the BAN 2.0 List (Better Alternatives Now) to show how new generations of bio-materials perform in the environment.
It tested a range of bags, baby wipes, straws, cups and cutlery made from new biodegradable biopolymers based on natural substances such as chitin or cellulose, or polylactic acid (PLA) made from plants, or the polymer polyhydroxyalkanoate (PHA) produced by bacteria. These materials are generally compostable in high-temperature (over 50°C) industrial facilities. When they’re left to biodegrade in the sea and on land, the story is mixed.
Of the PLA-based disposable cups, straws and cutlery tested, none broke down in the sea or on land, even after two years. Products included Eco Products’ PLA cups, Planet coffee cups (lined with Ingeo – a brand of PLA made by Natureworks), World Centric PLA straws, Eco Products’ PLA Rossetto cutlery, and Eco Products’ cutlery made from plant starch materials. The only products that disintegrated fully were paper straws.
Baby wipes performed better. Eco-Me, Huggies, Jackson Reece and Earth Friendly completely disintegrated after 12 months on both land and in the ocean in all time frames. Element Naturals baby wipes, made from Ingeo, did not degrade on land, but were completely degraded in the ocean. Only one of the four brands, Jackson Reece, identifies the polymer, describing it as a cellulose fibre from plant material.
A beach toy and a Paper Mate pen made from PHA also passed the biodegradability test. The pen’s PHA components began to fragment after two years in the ocean. The PHA beach toy completely decomposed in the sea with no visible fragments. On land, the test item remained whole after two years – though it was cracked and pitted and a plant grew out of it.
Encouragingly, a biopolymer plastic bag called Bio Bag, made from a material called Mater-Bi (developed out of starches, cellulose, and vegetable oils, by the firm Novamont) disintegrated on land in six months and in the ocean after two years.
The ideal packaging material would be like fruit skins – biodegradable in all environments (compost facilities, on land, and in water) – but we are not there yet. Meanwhile, Eriksen says, it makes sense to follow the waste hierarchy: reduce (eliminate use in first place), opt for reusables, and, as a last resort, recycle and compost.
Most plastic-polluting rivers in the world
1. Yangtze, China
2. Ganges India, Bangladesh
3. Xi, China
4. Huangpu, China
5. Cross Nigeria, Cameroon
6. Branta,s Indonesia
7. Amazon, Brazil, Peru, Columbia, Ecuador
8. Pasig, Philippines
9. Irrawaddy, Myanmar
10. Solo, Indonesia
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