Ready for some more bad news from the plastic crisis? New research from the University of Hawai'i at Manoa School of Ocean and Earth Science and Technology (SOEST) suggests that, in addition to all the other problems they cause, plastics are also emitting greenhouse gases as they degrade. That’s just great, right?
Published in PLOS ONE, the new study explains how most common plastics produce methane and ethylene when they are exposed to sunlight. The team of researchers on the case looked at a wide variety of plastics, from polycarbonate, acrylic, polypropylene, and polyethylene terephthalate, to polystyrene, high-density polyethylene and low-density polyethylene (LDPE). Polyethylene, the devil we find in single-use plastic bags that takes the prize for being the most-produced and discarded plastic out there, turns out to release the most of both greenhouse gases – not a good sign, considering how many of those plastic bags end up in the ocean and streets, just soaking up sunlight.
Watch the video series below to learn more about the different types of plastics.
"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 David Karl, senior author on the study. "This source is not yet budgeted for when assessing global methane and ethylene cycles, and may be significant." In other words, there is an incredibly huge amount of plastic degrading out there, and therefore a whole lot of greenhouse gas emissions that aren’t currently included in climate change models and projections.
Put succinctly, the authors write: “Our results show that plastics represent a heretofore unrecognized source of climate-relevant trace gases that are expected to increase as more plastic is produced and accumulated in the environment.”
Another concerning finding from the study suggests that not only do the emission rate of the greenhouse gases increases as certain plastics (like virgin pellets) become more and more degraded, but also plastics once-exposed to sunlight, will continue to emit gases even in the dark.
"We attribute the increased emission of greenhouse gases with time from the virgin pellets to photo-degradation of the plastic, as well as the formation of a surface layer marked with fractures, micro-cracks and pits," said lead author Sarah-Jeanne Royer. "With time, these defects increase the surface area available for further photo-chemical degradation and therefore contribute to an acceleration of the rate of gas production."
Nevertheless, more research is needed in order to determine the actual impact that degrading plastics will have on greenhouse gas emissions. Currently, the team of scientists is focused on developing “estimates of the amount of plastic exposed to the environment in oceanic and terrestrial regions, globally, in order to constrain the overall greenhouse gas emissions from plastics,” writes Science Daily.