It has been a rocky start to life for The Ocean Cleanup’s U-shaped barriers, which it hopes will sweep through the Great Pacific Garbage Patch collecting plastic waste that can be hauled back to shore and recycled. The team is now reporting to have overcome a significant stumbling block, using a novel parachute-anchor mechanism to correct speed-related troubles plaguing its earlier approach to ocean-going garbage collection.
The Great Ocean Cleanup team envisions fleets of its U-shaped barrier drifting through the Great Pacific Garbage Patch eating up plastic waste like a giant Pac-Man. The basic premise is that the plastic on the surface of the ocean is propelled by the current and will travel at a different speed to the system which is powered by the combination of currents, surface waves and wind.
And this speed differential is key, because the challenge isn’t just to gather plastic waste within the giant barrier, but hold it there for long periods without human intervention. That’s because the garbage patch is located great distances from shore, around five times as far as the International Space Station is from land.
The first system the team deployed endured some fractures after some time in the ocean, owing to the rough conditions of the open sea. But more concerning for the team was the inability to maintain a regular speed. For the trash to gather within the barrier and stay there, consistency across the water is key.
So the team hauled it in and made some modifications, taking a modular approach to the redesign that would enable them to test out a number of solutions without hauling it back to shore each time. Among these alterations was the attachment of a huge parachute, designed to act as an anchor and slow down the barrier so the faster-moving plastic can then drift into its opening.
After testing out a number of options, the team has declared the parachute system the winner and will be moving forward with the design. It says this approach produced no negative speed differential at all, and that the plastic successfully drifted into the barrier and remained there.
But it’s not all sunshine and rainbows, at least not yet. Following this redesign, the team has encountered another problem, albeit one it says will be easier to solve. Some of the gathered plastic has a tendency to spill over the cork line used at the surface to hold the screen in place. It will now test out a modified system that expands the diameter of these cork lines from 15 cm (0.5 ft) to around half a meter (1.6 ft), in order to better contain the mess.