Just when you thought the news about plastics couldn’t get worse, another study comes along to show that it already has. Here at Forester, we’ve published a number of posts about the problems with plastic; here’s a recent one from MSW Management editor Arturo Santiago about the growing movement to ban single-use plastic items like straws, and another, more optimistic one about a potential use for plastic that was once considered unrecyclable. A few months ago I even discussed an article from the Economist that argues plastic pollution isn’t really as bad as we think it is.
But now, new research is focusing on a previously overlooked risk of plastic in the oceans. Not only is it breaking down into smaller and smaller pieces, which are more easily ingested by fish, birds, and other organisms—which might allow it to work its way up the food chain to, eventually, us—but it might not be as inert as we thought it was, or as the Economist article claims.
The discovery came about this way, explains Sarah-Jeanne Royer, a researcher working in Hawaii who is publishing details of her recent study on plastics. She and other researchers wanted to measure the amount of methane—a greenhouse gas—coming from organisms that live in the ocean. To do so, they collected samples in high-density polyethylene (HDPE) bottles. The methane concentrations were much higher than they’d anticipated, and eventually they realized that most of the gas was coming not from the organic matter they were studying but from the bottles themselves.
Further experimentation revealed that when certain plastics are exposed to sun and seawater, they give off large amounts of methane and ethylene. The type of plastic commonly employed to make single-use plastic shopping bags is one of the worst culprits. As this BBC article explains, “At the end of the study, after 212 days in the sun, this plastic emitted 176 times more methane than at the start of the experiment.”
As the article notes, “Up to now, the link between plastics and climate change was mainly focused on the use of fossil fuels like oil and gas in the manufacture of plastic items.” However, as these new studies show, plastics like low-density polyethylene and others emit carbon dioxide, ethylene, methane, and propane as they degrade. The more they break down, the more of the plastics’ surface area is exposed, and the faster they emit the gases. “If we look at all the plastic produced since 1950, it’s pretty much all still on the planet, and it’s just degrading into smaller and smaller pieces,” says Royer. “We know the industry is booming and in the next 30 years more and more greenhouse gases will be produced—that’s a big thing.”
The research has not yet quantified the amount of greenhouse gas plastics are adding to the atmosphere—we don’t even know with any certainty the amount of plastic in the ocean—but the researchers say it’s worth a further look.