In August 2015, around 30 vessels crossed the Great Pacific Garbage Patch in parallel, creating the largest ocean research expedition ever. Sailing between Hawaii and California, the expedition mapped an area measuring 3.5 million square kilometers and collected more data on oceanic plastic than has been collected in the past 40 years combined.
If you work on solving a problem, it is important to thoroughly understand the problem as well. Around the time The Ocean Cleanup was founded, estimates on the amount of plastic in the Great Pacific Garbage Patch still ranged from tens of thousands of tons to tens of millions of tons. Furthermore, only a small part of the size spectrum (pieces in the millimeter – centimeter range) had actually been measured, so there was no real understanding on the size distribution of plastic in the oceans.
Not only are these physical properties of the ocean plastic key design constraints for the cleanup system, but it also the number one metric when it comes to the economics of a cleanup operation. If there is more or less plastic than expected, the cleanup cost per ton will subsequently fall or rise.
To solve this problem limiting the cleanup technology development, we decided to launch the Mega Expedition, aiming to produce the first high-resolution map of the area. Next to scale, it was also the first time large debris (in the decimetre – meter range) has been measured.
Although the samples are still being analysed, initial findings indicate the concentration of plastic had been heavily underestimated, finding that most mass can be found attributed to the (previously unquantified) large debris.
HOW WE MEASURED THE PATCH
A compact surface trawl was dragged behind each vessel to catch smaller plastic particles. The device, known as a Manta Trawl, is standard scientific equipment used for measuring concentrations of microplastics.
The 171 foot-long Ocean Starr served as the fleet's mothership. It was fitted with two very wide nets designed to capture high volumes of all sizes of plastic debris.
THE OCEAN CLEANUP APP
A custom-made smartphone app enabled crews to easily count and characterize the large plastic objects floating by, adding another layer of data to the Mega Expedition.
The Ocean Cleanup Survey App is available for anyone to use at sea, and can be downloaded for both iOS and Android devices.
After the expedition our lab started analysing the catch, focussing on size, weight and debris type. In May of 2016 over one million pieces of plastic had already been analysed - by hand.
An interactive version of the expedition map is available here.