Several greenhouse gases are emitted as common plastics degrade in the environment, according to researchers from the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology (SOEST).

Mass production of plastics started nearly 70 years ago, and the production rate is expected to double over the next two decades. While serving many applications because of their durability, stability and low cost, plastics have a negative impact on the environment. Plastic is known to release a variety of chemicals during degradation, some of which negatively affect organisms and ecosystems.

The study, published in PLOS One, reports the unexpected discovery of the universal production of greenhouse gases methane and ethylene by the most common plastics when exposed to sunlight. The SOEST team tested polycarbonate, acrylic, polypropylene, polyethylene terephthalate, polystyrene, high-density polyethylene and low-density polyethylene (LDPE)—materials used to make food storage, textiles, construction materials and various plastic goods. Polyethylene, used in shopping bags, is the most produced and discarded synthetic polymer globally, and was found to be the most prolific emitter of both gases.

The team found that the emission rate of the gases from virgin pellets of LDPE increased during a 212-day experiment, and that LDPE debris found in the ocean also emitted greenhouse gases when exposed to sunlight. Once exposed to solar radiation, the emission of these gases continued in the dark.

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