Plastics aren’t just polluting our oceans — they’re releasing greenhouse gases

by Sarah-Jeanne Royer

Researchers from the University of Hawaii, Manoa have discovered startling new evidence that the plastics on land and in the ocean release greenhouse gases as they break down. In this article, scientist Sarah-Jeanne Royer tells us about what she found in the field and why it’s now even more important to break free from plastic. © Sarah-Jeanne Royer

I’m a French-Canadian postdoctoral scholar at the University of Hawaii, Manoa and part of the School of Ocean and Earth Science & Technology (SOEST). As part of our team’s research, we found that, as plastic decomposes, it is producing a new source of greenhouse gas pollution not included in previous climate models. These emissions are only expected to increase — especially as more plastic is produced and accumulated in the environment and degrades over time.  
Greenhouse gases have a direct impact on climate change — affecting sea level rise, global temperatures, ecosystem health on land and in the ocean, and storms, increasing flooding, drought, and erosion. Most plastic is created from natural gases, so the release of greenhouse gases from plastic waste might not seem surprising. Even so, the University of Hawaii is actually the first group publishing data about the link between greenhouse gases and plastic in the environment.
Of particular concern is a type of plastic called low-density polyethylene, which is the highest emitter of climate-wrecking greenhouse gases. It’s commonly found in the most produced, used, and discarded single-use plastics making their way into our oceans and waterways today. Our research shows that as this plastic breaks down in the ocean, the greenhouse emissions increase dramatically — up to 488 times more than in pellet form, the term used to describe ‘raw’ plastic before it’s been made into an end product like a bag or water bottle. 
Unfortunately, that’s not all. Plastics exposed directly to sunlight in the air — like on land at beaches, coastlines, fields, and playgrounds — make an even greater contribution to greenhouse gas emissions. So while we urgently need to keep plastics out of the ocean to stop the negative impacts of pollution on marine life and coastal communities, that’s not enough. On land, discarded plastics still release greenhouse gases and contribute to climate change even while no one is watching.
This research has big implications for waste management as well as potential climate change impacts. Plastic pollution is already reaching crisis levels, and this new information only makes the problem more urgent to address — and fast. Considering the amounts of plastic washing ashore on our coastlines, along with the amount of plastic exposed to environmental conditions, to protect our planet against climate change, we need to stop plastic production at the source.

Plastic straws collected during a beach cleanup and brand audit activity on Freedom Island, Philippines in 2017. © Daniel Müller / Greenpeace

Sarah-Jeanne Royer is a French-Canadian postdoctoral scholar at the University of Hawaii, Manoa and part of the School of Ocean and Earth Science & Technology (SOEST). To learn more about her research on plastics and greenhouse gas emissions, read the full published report here.