Around the Water Cooler: Perpetual Plastics

By Dustin Renwick

Image courtesy State of Hawaii

Hawaii has become synonymous with tropical sunsets and legendary surfing. And trash. Ocean currents annually deliver 20 tons of refuse, much of it plastics, to the Big Island from the swirling mess called the Great Pacific Garbage Patch. Now, scientists expect added debris from Japan’s 2011 tsunami.

I wish I could have learned about this firsthand, maybe when surfing, but instead, I watched a video as I ate dinner 5,000 miles from the 5oth state.

We rely on plastics for diverse products such as packaging, pipes and car parts. These strong, all-purpose materials are designed as stable substances – you don’t want your water bottle to disintegrate.

Because they’re so durable, plastics can outlive their creators.

EPA scientist Richard Zepp is working on this problem as part of the Pathfinder Innovation Projects that I’ve blogged about previously. He’s researching ways to shorten the material lifecycle of common plastic items.

Water, sunlight, and microbes dissolve a newspaper or a discarded banana peel, but plastics, such as polyethylene, have tightly packed molecule chains that are nearly impervious to forces that might return them to the natural ecosystem.

“We don’t know how long polyethylene will last in the environment,” Zepp said. “They use polyethylene as liners in landfills” because it’s so tough.

In his research, Zepp incorporates an additive, something called a pro-oxidant, that helps natural forces disrupt the molecule chains so a plastic will break down more quickly. Parts of the UV spectrum of sunlight interact with the pro-oxidants and “put a chink in the armor of the plastic,” he said, “even with polyethylene.”

This plastic then becomes brittle and more susceptible to natural abrasion.

“If you’re out in the environment, that’s a key to the breakdown of plastic – it becomes more readily attacked by bacteria, which will degrade it completely.”

Researching the whole lifecycle for plastics means we’re thinking about the reality that all garbage isn’t created (or destroyed) equally.

About the author: Dustin Renwick works as part of the innovation team in the EPA Office of Research and Development.