Plastic waste emits greenhouse gases when exposed to sunlight

Published by Shamim Malekmian on

August 13th, 2018

The plastic used in everyday items such as plastic bags emit greenhouse gases when exposed to sunlight, a new study has found.

Researchers from the University of Hawaii discovered that our everyday plastic rubbish on land and in the oceans releases a variety of potent chemicals during degradation.

The most commonly used plastics use for the likes of food storage and construction materials produce methane and ethylene when exposed to ambient solar radiation, according to the study in the Journal PLOS ONE.

Polyethylene used in shopping bags – the most produced and discarded synthetic polymer globally – was found by the researchers from the University of Hawaii to be the most prolific emitter of both gases.

Discarded plastics on shores, coastlines and open green spaces had the highest rate of emissions due to their direct exposure to sunlight. Researchers found, however, that chemicals activated by sun radiation continue to pollute the environment during the night.

Methane emissions

Emissions from degrading plastics are not currently included in global methane budgets. Until now, methane emissions have been associated with the burning of fossil fuels in industry, landfill gases, and emissions from livestock farming systems.

“We found that as plastic decomposes, it is producing a new source of greenhouse gas pollution not included in climate models,” Sarah-Jeanne Royer, the study’s lead researcher told Greenpeace.

“Our research shows that as the plastic breaks down in the ocean, the greenhouse emissions increase dramatically, up to 488 times more than in pellet form.”

Single-use plastic cup on beach Photo: Øyvind Holmstad

Single-use plastic cup on beach Photo: Øyvind Holmstad

While the study found that plastics are currently an “insignificant component” of the global methane budget, the increasing rate of plastic production will see more plastic waste ending up in marine systems and a subsequent rise in methane emissions into the future.

Humans have produced nine billion tonnes of plastic since the 1950s, with the bulk of it discarded in landfills or the environment, previous research has found.

“Plastic represents a source of climate-relevant trace gases that are expected to increase as more plastic is produced and accumulated in the environment,” said David Karl, a senior author of the study.

Ms Royer is now working to estimate the amount of plastic exposed to the environment in oceanic and terrestrial regions in order to determine the overall greenhouse gas emissions from plastics.

The Pacific Ocean holds the world’s most extensive collection of floating plastic debris, known as the Pacific garbage patch, with a total of 1.8 trillion pieces of plastic found floating among the ocean’s marine species.

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Shamim Malekmian

Shamim is a Senior Reporter at The Green News and a contributing writer to the Irish Examiner, Cork Evening Echo and the Dublin Inquirer.