What role does sensing play in detecting and analyzing garbage in the world’s oceans?

If you were not previously aware of the Great Pacific Garbage Patch (GPGP), viewing “Under Paris,” when it streamed on Netflix in the summer of 2024, provided painful awareness of a serious and growing problem — even though the movie was fantasy. “Under Paris” garnered over 69.6 million views in its premiere in June, making the Netflix movie the site’s fifth most popular non-English language movie, so many people became aware of the GPGP. However, there have been a few documentaries that have increased awareness and addressed the problem as well.

Located halfway between Hawaii and California, the GPGP is the largest of five offshore plastic accumulation zones — large faux plastic islands — in the world’s oceans caused by systems of currents known as gyres that coral floating plastic. With an estimated surface area of 1.6 million square kilometers — twice the size of Texas — the GPGP is an ecological nightmare worthy of the mutated shark in “Under Paris.”

Sensing aspects

Several different sensing technologies detect and monitor the oceans’ plastic accumulation zones. While densely distributed within a zone, the plastic materials are scattered and do not form a solid mass or trash island. With their long degradation rate, plastic materials accumulate and disintegrate slowly (due to sunlight, temperature, and other factors) into microplastics (particles smaller than 5 mm) and nanoplastics (particles usually less than 200 nm). Consequently, in addition to the more easily recognized macroplastics, these much smaller aspects require unique sensing approaches.

As part of one study, an aircraft conducted GPGP Aerial Expedition employed three types of sensors: LiDAR (light detection and ranging), a short-wave infrared (SWIR) imager to detect ocean plastic, and an RGB (red/green/blue) camera. These sensor measurements provided a baseline for identifying the GPGP plastics.

Today, synthetic aperture radar (SAR) remote sensing is being pursued as a more promising technology than optical remote sensing, which is currently used to detect microplastics in oceans.

Real islands have garbage problems, too

Caribbean islands like Puerto Rico also have problems with garbage (including plastics). Unlike hard-to-find, unoccupied locations in the middle of an ocean, these islands’ problems can easily be visually and olfactorily observed by residents and visitors, providing an instant basis for disgust and concern. Specifically, Puerto Rico’s trash problem has been growing for decades. The island’s inhabitants and tourists generate about 3.7 million tons of waste yearly, and its landfills are full.

Landfill gas is monitored by measuring carbon dioxide (CO₂₎ and methane (CH₄) gases. With data acquired from visible/near-infrared (IR), thermal infrared, and SAR sensors, researchers report that data fusion can provide an effective instrument to fully support the monitoring of landfills, including plastics, and their effect on the surrounding area.

So what?

With sensors providing critical information and increasing awareness of the oceans’ and islands’ garbage problems, what can be done to solve them?

Started in 2013, Ocean Cleanup is a non-profit organization that aims to clean up 90% of floating ocean plastic pollution by 2040. To increase awareness and solve the plastic problem, they need donations, partners, innovative team members, and social media promotions. This is one effort, but there are several others.

Unlike offshore plastic accumulation zones, islands are the responsibility of countries. Specifically, the Commonwealth of Puerto Rico is an unincorporated territory of the United States. In this case, the island’s inhabitants, its government, and the US government need to work together to solve the garbage problem.