Great Pacific Garbage Patch cleanup system destroyed by waves

SAN FRANCISCO — It’s back to the drawing board for engineers at the ambitious Ocean Cleanup, a Dutch non-profit that in October launched a plastic cleanup system meant to rid the world’s oceans of plastic pollution. They say they hope to have it back up and running by early summer.

The system failed in late December when a 60-foot length of the device deployed in the Great Pacific Garbage Patch between Hawaii and California broke off. That necessitated towing the entire 2,000-foot device back to Hawaii for testing and inspection. 

Several weeks of analysis found that material fatigue caused a piece of three-inch thick high-density polyethylene pipe to crack and break, spokesman Alan Dunton said Thursday. 

“The team hasn’t determined the exact fix yet,” he said.

They believe the action of the waves causing the device to rise and fall in the water resulted in over 1.5 million load cycles on the material. Each load cycle is a time when the plastic flexed. That, combined with a local stress concentration from a weld, caused the pipe to fracture, they believe.

“The team is considering moving its work upgrading the system back in California. The root cause analysis will be complete and reported in a few weeks. We expect to be able to return to the patch in early summer,” he told USA TODAY. 

The Ocean Cleanup is a passive system involving a 2,000-foot floating series of connected four-foot diameter pipes that make up a boom, which forms a giant horseshoe on the surface of the ocean.

Below that hangs a nine-foot skirt that corrals the tiny pieces of plastic trash that float in the water. The action of the currents and waves is meant to push trash into the system’s center while the micro-plastic, as it is called, gets captured by the hanging barrier.

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The break in the system was discovered Dec. 29 during a routine inspection by the cleanup system’s crew. It was floating several dozen yards from the main system.

The 60-foot long piece of pipe couldn’t have gotten lost because it has GPS sensors on it. It’s also buoyant and contains air chambers, so it couldn’t sink, said The Ocean Cleanup’s CEO Boyan Slat.

Even the tiniest defect in a material can start a crack, said Francisco Presuel-Moreno, a professor of Ocean and Mechanical Engineering at Florida Atlantic University in Boca Raton, Florida.

“Either defects that are present from the beginning, or in this case they had some sort of weld, those are locations that might be prone to a crack initiating,” he said.

The ocean is a harsh environment because of the salt water, exposure to UV radiation and the constant movement of the waves causing tension and compression on the material, he said.

Critics have suggested that The Ocean Cleanup has taken up money and energy that might have better gone towards more traditional efforts aimed at keeping plastic pollution out of the world’s waterways and oceans, especially given that it is a new design which failed within three months of first being deployed.

The organization is undeterred. In a post to its Facebook group on Thursday, it said that discovering and resolving issues is an essential part of achieving success.

“We are using materials and we are in an environment that has hardly been modeled, so there are a lot of things that you just have to try out for the first time and simply see what happens,” said Fedde Poppenk, a mechanical engineer with the organization. 

 

 

 

 

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