Degrading plastics emit greenhouse gases

TAMPA: Need another reason to hate plastics piling up in the environment? A study in the journal PLOS ONE on Thursday found that degrading plastics emit powerful greenhouse gases like methane and ethylene, and are a previously unaccounted-for source of these heat-trapping pollutants.

Plastic water bottles, shopping bags, industrial plastics and food containers were all tested as part of the study. The "most prolific emitter" was polyethylene, which is used in shopping bags and is the most produced and discarded synthetic polymer in the world, said the report.

Researchers have not yet calculated the level of harmful greenhouse gases emitted by plastics in the environment. But with more than eight billion tons of plastic littering the planet -- the lion’s share of which is not recyclable -- and plastic production expected to double in the next two decades, they need to find out, said David Karl, the study’s senior author.

"Plastic represents a source of climate-relevant trace gases that is expected to increase as more plastic is produced and accumulated in the environment," said Karl, a professor at the University of Hawaii at Manoa School of Ocean and Earth Science and Technology.

"This source is not yet budgeted for when assessing global methane and ethylene cycles, and may be significant."

Plastic is already known to release harmful chemicals into the water and soil. And greenhouse gases have risen to all-time highs, causing the Earth to heat up and oceans to mount, threatening coastal communities worldwide.

"Considering the amounts of plastic washing ashore on our coastlines and the amount of plastic exposed to ambient conditions, our finding provides further evidence that we need to stop plastic production at the source, especially single use plastic," said lead author Sarah-Jeanne Royer, a postdoctoral research fellow at UH’s International Pacific Research Centre.