SciTech

Ocean Cleanup system gears up to take down the garbage patch

Halfway between California and Hawaii, ocean currents come together to create a gyre. This vortex of waves concentrates floating debris to form what is known as the Great Pacific Garbage Patch, a collection of water-borne trash big enough to be an independent country.

Can anyone get rid of it?

The garbage patch, first described in a paper by the US National Oceanic and Atmospheric Administration in 1988, is estimated to cover anywhere from 700,000 square kilometers (about the size of Texas) to 15 million (roughly equivalent to Russia).

One reason it is so difficult to nail down the extent of the Garbage Patch is because it depends on the cutoff: when is the concentration of plastics high enough to count as being part of the patch? Scientists estimate concentrations of 10 kilograms per square kilometer in its outer regions, and up to 100 kilograms per square kilometers in the center. In total, that comes out to be about 80,000 metric tons of plastic, and 1.8 trillion pieces.

But this plastic doesn’t remain in the same state in which it was dumped. Plastic will break down with sunlight, a process called "photodegradation." The pieces become smaller and smaller, but remain polymers. In some areas, the concentration of plastics is seven times greater than that of zooplankton. This adds another layer of difficulty in defining the extent of the Patch: the plastic concentrations have to be determined through manual sampling. After sufficient photodegradation, the plastic is too small to be seen; most of the small pieces of plastic exist just under the surface, so satellite images cannot capture the necessary information. Eventually, the plastic pieces become small enough to be ingested by aquatic animals. As smaller animals are eaten by bigger ones, these microplastics become concentrated in the food chain.

The World Economic Forum estimates that the ocean will contain more plastics than fish by 2050. "The primary source of marine debris is the improper waste disposal or management of trash and manufacturing products” says a 2011 EPA report, “including plastics (e.g., littering, illegal dumping) ... Debris is generated on land at marinas, ports, rivers, harbors, docks, and storm drains. Debris is generated at sea from fishing vessels, stationary platforms, and cargo ships."

Enter The Ocean Cleanup, a company founded by Dutch inventor Boyan Slat when he was only 18. They sent out a beta test of their floating garbage collector technology on Sept 8th. The 600m (apx. 2000ft) System 001 nicknamed “Wilson,” five years in the making, cost about $24.6 million (including design, development, production, assembly, and monitoring during the first year). It has solar-powered lights and anti-collision systems, and it actively transmits its position at all times. Wilson will gather 5 tons of trash per month and will carry instruments to monitor wear and tear, and collect climate and wave data from Great Pacific Garbage Patch, more than 1000 nautical miles away from its launch point in California.

Wilson’s job is to take advantage of wind, wave, and current to corral dispersed plastic and allow for more efficient collection. Most of the plastic mass is in larger pieces of debris, which are easier to collect than the microplastics they will eventually become.

The device has two main parts. The first is buoyant, and it sits on the surface of the water. Below, an apx. 3m (10ft) skirt is attached. Because the ocean currents move the system and plastic alike, it automatically drifts to areas of highest plastic concentrations. Unlike the current, the waves only move the floater, which is partly above the surface, while the plastic that is usually just beneath the surface is unaffected. The skirt is longer in the middle, which creates more area for the current to apply force. This differential pressure causes the flexible system to assume a u-shape. The floating part keeps the system buoyant and keeps debris from washing over the system, while the skirt catches what flows underneath. Every 4-6 weeks, a boat comes out to gather concentrated plastic and transport it back to land.

Proceeds from recycling and creating products from the collected plastic will help fund operations in the future. The Ocean Cleanup’s eventual goal is to take the lessons they learn from Wilson’s beta test and deploy a fleet of 60 improved units in a year and a half. Additional funding will come from corporations, which will be able to sponsor cleanup systems in the future. Sponsors will be able to use an app to follow the unit’s course and monitor how much plastic is collected.

The Ocean Cleanup set an ambitious target of cleaning up 50 percent of the Great Pacific Garbage Patch in five years, and 90 percent by 2040. Of course, this is treating the symptoms, but not the disease. The existing ocean garbage does need to be cleaned up, but we should also find ways to prevent it from getting there in the first place.