Backyard play sets, car components, windblown shopping bags and giant patches of ocean trash are all silently releasing greenhouse gases into the air, according to a new study of plastics left out in the sun.
Researchers at the University of Hawaii at Manoa have identified a wide range of plastics that silently leach methane and ethylene gases as they degrade through exposure to the sun. Both gases have previously been identified as contributors to climate change.
“It’s a sad discovery,” said Sarah-Jeanne Royer, a Montreal-born post-doctoral research fellow at U of H’s School of Ocean and Earth Science and Technology.
Royer says a few of her colleagues first noticed the issue while studying seawater samples that had been collected in plastic containers. The seawater contained unusually high levels of methane, leading the team to suspect that it might have leached out of the plastic when exposed to the sun.
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Royer says plastics may have a much greater influence on climate change than previously believed, although the exact impact of plastic emissions will require further study. Royer suggested it might be a “very high amount” in a phone interview with Global News.
Acadia University pollution researcher Jennifer Provencher, who was not involved in the study, said the discovery is “another piece of evidence suggesting that losing plastic to the environment is not good.”
Jonathan Nichols, an associate professor of earth sciences at Colombia University, said the finding was “definitely important.”
“You can’t solve the greenhouse gas problem until you’ve defined every part of it,” he told Reuters.
Environmental sciences professor Tony Walker, who studies pollution and its impact on the environment at Dalhousie University, said the findings are “not surprising.”
“Plastics are derived from petroleum – the same fossil fuel that, when combusted, releases greenhouse gases into the atmosphere,” Walker told Global News.
He added that he’s been concerned about the issue “for some time.”
Royer and her team tested a wide range of commonly-used plastics for their study, which is published in the August edition of the peer-reviewed journal PLOS ONE.
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Every type of plastic in the test was found to release the invisible pollutants. However, the highest polluter was low-density polyethylene, one of the most widely-used plastics on the planet. The material is used to make plastic bags, shampoo bottles, food storage containers and a wide range of textiles and construction components.
Even brand-new chunks of this low-density plastic were found to release greenhouse gases after 212 days of exposure to sunlight.
“This is the most produced plastic in the world, and also the most discarded plastic that we find on the beaches and in the ocean,” Royer said.
Royer and her team found that the plastic emissions appear to be based on exposed surface area, and that the emissions will continue even after plastic is taken out of the sun. They also found that more gas was released as the plastic aged.
“We have all kinds of plastic constantly exposed to solar radiation which is being degraded [at this moment],” Royer said.
Scientists estimated last year that 8.3 billion metric tonnes of plastic have been produced since the 1950s, and that 12,000 metric tonnes of plastic waste will enter landfills and the environment by 2050.
“Plastics represent a source of climate-relevant trace gases that is expected to increase as more plastic is produced and accumulated in the environment,” David Karl, the senior author on the study, said in a news release.
He added that it’s not clear how much these traces gases are contributing to the global methane and ethylene cycles, but it “may be significant.”
Royer says her findings highlight the need to drastically curb the production of plastic waste, which winds up sitting out in the sun for decades in giant garbage patches on the world’s oceans and beaches. These plastics never fully disappear, but are instead broken down into microscopic bits that can wind up inside fish and water supplies.
“With time and with this exponential increase in plastic production and consumption, we know that more will be found in the environment,” Royer said.
Lawmakers around the world have started to push for a reduction in single-use plastic waste, through such initiatives as banning straws and taxing plastic bags.
However, much of the Western world remains mired in a plastic waste crisis triggered by China, which closed its doors to all recyclables in January. The country was previously the world’s top buyer of recyclable plastics, and its reversal has left many municipal governments scrambling to find another way to dispose of their tough-to-recycle materials.
Royer says the next step in her research will be to study the full scope of greenhouse gas emissions from plastic.
“It’s a really tricky question to try and estimate,” she said.
“If we look at all the plastic produced since 1950, we know that it’s all being degraded.”
—With files from Reuters