Satellites used to identify plastics floating in ocean

Satellites can be used to successfully identify plastics floating on the surface of the sea, a study has found, with the potential to help ocean clean-ups.

Data from the European Space Agency’s Sentinel-2 satellites was used to develop the method, which allows aggregations of plastic pieces and items such as bottles and carrier bags to be spotted and identified from space.

The study led by scientists at Plymouth Marine Laboratory used high-resolution data of coastal waters from the satellites, which “see” across the visible light spectrum and into infrared light waves.

The data was put through an algorithm tuned to highlighting objects floating on the surface of the ocean, which reflect near-infrared light while water absorbs it, to create a “floating debris index”.

They then used information on how the satellites “see” collections of plastics deployed in the sea by the University of the Aegean for their new study into plastic litter, to establish an optical “signature” of floating plastic.

The team also used data of plastic debris detected after severe flooding in Durban, South Africa, to help the system identify floating plastic.

The researchers carried out the same process to distinguish natural debris, such as driftwood, seaweed and sea foam, which is likely to be mixed in with patches of plastic litter.

Then the researchers tested out their method on plastic “in the wild”, focusing on debris collections in four locations based on previous studies and social media posts, off the coasts of Scotland, Canada, Ghana and Vietnam.

They used the satellite data to identify suspected plastic debris floating on the surface of the ocean, and trained an algorithm to automatically analyse it, which successfully identified it as plastics with an overall accuracy of 86%.

The researchers said the work, primarily funded by the Natural Environment Research Council (Nerc), is the first step towards developing an operational method of detecting floating plastic patches in waters all over the world.

Dr Lauren Biermann, Earth observation scientist at Plymouth Marine Laboratory and lead author, said: “Plastic pollution is a global issue.

“This method will hopefully provide a stepping stone for satellites and drones to be used to tackle the marine plastics problem at the end of the product life cycle.

“However, we will only ever make meaningful progress if we also tackle the source and reduce the amount of plastics produced.”

The study was published in the journal Scientific Reports.