Why does this matter? Ocean plastic proliferation is only set to get worse without action, with annual plastic leakage set to treble to reach 29 million tonnes annually by 2040 and the ocean plastic stock set to quadruple by this date – rising to 646 mt. This could help push species towards extinction, with evidence also emerging that ocean microplastic can cause sea creatures to develop abnormally.
To tackle the issue, efforts are being focused on a number of fronts, including on devices to collect plastic already in the oceans. The above highlighted new study, however, describes the projected impact of ocean clean up devices as “very modest”. The forecasted impact remained limited even when the researchers’ model calculated the effect of 200 clean-up devices across the ocean working continuously for 120 years.
The Ocean Cleanup’s Matthias Egger disputes the findings, stating the study underestimates the device and, if it is deployed at areas of high plastic concentration such as the Great Pacific garbage patch, it will be more effective.
Submerged plastic, however, is substantially more difficult to remove than plastic floating at the top of the ocean. Separate reports indicate around 99% of ocean plastic ultimately ends up in the deep sea, with around 35 times more plastic currently in all levels of the ocean than the amount located at its surface.
While clean up devices may play a small role, it’s much more important to stop plastic entering the marine environment in the first place. In a piece arguing ocean clean-up devices are an uneconomic “dangerous distraction”, Systemiq’s Yoni Shiran likens the issue to a flooded house – you should first turn off the tap before you start mopping the floor.
Global rivers and waterways are a significant source of ocean plastic, with analysis indicating up to 34 mt of plastic emissions enter these each year. Collecting this before it reaches the ocean is one solution. Ocean Cleanup is also developing solar powered river-based devices, such as its Interceptor, which can trap and collect plastic before it reaches the sea.
Elsewhere, bubble barriers are being tested to push plastic to waterway surfaces for collection. Mapping the problem can also help – in Japan, researchers have developed a high-resolution plastic emissions map of the country to enable waterway problem areas to be targeted for reduction efforts.
Of course, better still would be to stop plastic even entering waterways, where it still impacts water-based species. Indonesia is embarking on a strategy to reduce the amount of plastic entering its waters by 70% by 2025 through doubling plastic waste collection and recycling, redesigning plastic products and expanding waste disposal facilities. Alongside corporate pledges to reduce virgin plastic use, recycling and circular economic principles and technologies can help, with plastic able to be repurposed into hydrocarbon feedstocks for new plastic, chemical products, low-sulphur oil or even hydrogen.
Science of the Total Environment