Plastic bags are releasing greenhouse gases

There may be a hidden source of greenhouse gases that we have not considered.

The University of Hawaii in Manoa found in a new study that when plastics come into contact with light, they release a gas that absorbs heat and causes the climate to heat up. Light not only breaks down the plastic, it also releases methane and ethylene from the plastic – this It is the two most troublesome greenhouse gases. Although the gases released during plastic degradation may only account for a very small portion of global emissions, their proportion may increase.

In order to study what kind of gas the plastic releases, the research team collected the most common consumer plastic samples – all newly produced and freshly harvested from the sea – and then monitored the targets as floating in the sea. Medium or gas generated when exposed to air. All samples emit methane and ethylene, but low density polyethylene (LDPE) exposed to air releases more gas than any other material-environment combination. LDPE is a thin material used to make plastic wrap films and supermarket plastic bags. LDPE is one of the most important plastic products and the most frequently discarded plastic products. The first author of this paper is from the University of Hawaii. Marine biologist Sarah-Jeanne Royer said.

The researchers said in a new research paper that the longer LDPE is exposed to sunlight, the more methane and ethylene it releases. The paper was published in the August 1 issue of PLOS ONE.

Royer and her team said that the gas was released because the ultraviolet light slowly decomposed the plastic material. As the plastic ages, it breaks apart, which is why the plastic fragments floating in the sea are so large. Royer explains Speaking of smaller plastic fragments means that a larger area will be exposed to light. So her team evaluated the gas emissions of different sizes of LDPE chips. They found that the LDPE powder emitted methane was LDPE tablets. 500 times.

If the total amount of gas emitted by plastics is still small, the surface area of ​​the degraded plastics can explain why this problem may only be worse, Royer said. 'We are worried because the plastic we have been manufacturing since 1950 is still Stay on Earth, and as we talk about they are degrading, so they will release more and more methane.

Chris Ellison, a professor of chemical engineering and materials science at the University of Minnesota, who did not participate in the current study, agreed with the paper that light caused plastics to release greenhouse gases.

'Lighting speeds up all kinds of reactions, whether or not the reaction requires light,' Ellison told Live Science in the mail. He said he was also very curious about the percentage of global methane levels at the source of this new discovery, but It is well known that this is a difficult question to answer. Ellison pointed out that the good news is that most of the plastic is buried in the soil and is not exposed to light when it is broken down.

Whether the plastics in the real world will be as difficult to say as the plastics in Royer's lab. This team analyzes the pure samples of each type of plastic, but the purity of the ocean and the buried plastic is not so high. Plastics manufacturers will Adding tough additives in pure plastic, and the formula is trade secret. Royer contacted the manufacturer to get the exact ingredients, but she said that all manufacturers refused to provide relevant information.

Even though the study couldn't perfectly replicate the reality, it was a starting point, Royer said. The next step is to figure out how much of the world's methane comes from plastic, and which plastic is the worst culprits.