A floating system of booms built to slowly but surely eradicate plastic waste from the Pacific Ocean has been redeployed after spending four months in the shop.

The second deployment was a quieter affair than the first, when the much-lauded cleanup system began trolling the Great Pacific Garbage Patch to collect plastic waste, but it was forced to return to port in Hawaii much earlier than planned. Just a few months after being launched, the passive floating system was catching plastic, but it wasn't necessarily retaining it and an 18-meter end section had broken away from the main frame.

The team behind the Ocean Cleanup — undeterred by their critics — says it's all part of the process.

The basic principle behind the iterative design process is to test, learn, and repeat until you have a proven concept. We do not know with certainty that these proposed options will solve the issues we have encountered. In fact, there may still be further unknowns, as is the nature when doing something that has never been done before. What we do know, is that every day we are not yet operational the plastic pollution problem is not getting better.

Ocean Cleanup is a Netherlands-based group that's the brainchild of Dutch scientist and entrepreneur Boyan Slat. Dubbed 001/B or Wilson, it consists of a 2,000-foot (600 meter) U-shaped boom with an attached woven skirt. It acts like a floating artificial coastline. The boom prevents plastic from flowing over it, while the skirt stops debris from escaping underneath it.

The offshore crew noticed on Dec. 29 that the section was detached and after some debate, determined that the boom must return to port because both end sections contained sensors and satellite communication had been compromised.

Late last year, the boom was struggling in places to hold on to plastic that it gathered.

"It has been four weeks since we deployed System 001 in the Great Pacific Garbage Patch (GPGP). In this time, we have observed that plastic is exiting the system once it is collected, so we are currently working on causes and solutions to remedy this," Slat wrote on the group's website in late November. "Because this is our beta system, and this is the first deployment of any ocean cleanup system, we have been preparing ourselves for surprises."

In the video below, Arjen Tjallema, the group's technology manager, explained the problem in more detail.

"Although we are not harvesting plastic yet, based on the current results, we are positive we are close to making it work," Slat said at the time.

A question of speed

In early October, the group finished several weeks of testing System 001 and confirmed its "general behavior and seaworthiness."

One reason the system didn't work as hoped has to do with speed. In order to catch the plastic, the system typically has to move faster — or in some cases, slower — than the plastic it's hoping to catch, Slat points out. The fix ensures that the the system will not travel at the same speed as the plastic.

The group is testing two theories with System 101B, both of which take a hint from sailing. The first is a series of giant inflatable buoys powered by wind that will essentially tow the system, and the second is a parachute-style anchor that will turn the system around and, in theory, maintain a slower speed than the plastic.

In either scenario, the team says they are ready to make faster changes on the fly.

Editor's note: This article has been updated since it was originally published in December 2018.

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.

Boyan Slat's Ocean Cleanup project relaunches
After 4 months at shore, plastic cleanup system of booms redeploys in the Great Pacific Garbage Patch.