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Plastic causes climate change

Plastic is a petro-based and thus artificially created raw material, for which approximately 16 % of crude oil and natural gas are currently consumed worldwide every day. The Heinrich Böll Foundation estimates that carbon dioxide (CO₂) caused emissions of 1,781 million tonnes in 2015 alone. Global plastic production accounts for 10-13 % of the total CO₂ budget that may be consumed as a maximum to limit man-made global warming to 1.5 degrees.

CO₂ and the ocean

Around 400 million tonnes of plastic of various compositions are produced worldwide every year. According to estimates, about one third of this is disposed of in the environment. A large part ends up in the ocean, forming 5 large plastic whirlpools of 1.6 square kilometres in diameter (as of 2018)

It is assumed that the increasing amount of Microplastics in the oceans, created by the decay of plastic, disrupt biological processeswith the help of which plankton at the sea surface binds CO2 through photosynthesis. This process, called the biological carbon pump, is of central importance for the role of the ocean as a so-called carbon sink and contributes significantly to a stable Earth climate.

Through natural death processes, the plankton secretes the CO2 again when it sinks to the seabed. The partly highly toxic effect of microplastics leads to the increased dieback of the plankton and thus to an increased release of CO2 into the atmosphere.

Currently, more than half of the CO2 produced annually by humans is stored in the ocean. Statements about the amount and how storage could change in the future are the subject of research.

Decomposition of plastic causes methane

According to an August 2018 study by the University of Hawaii UV light promotes the decomposition of plastic in the environment, releasing methane and ethylene. Methane (CH4) is one of the most important greenhouse gases and is 21 times more effective than CO₂.

The studies on different types of plastics showed that most of the methane is released by plastic particles of Low density polyethylene (LDPE), a variant of the Polyethylene (PE), was produced. Methane emissions increased the longer the plastic particles were irradiated by UV light. UV light apparently acts as a catalyst, as methane production, once triggered, no longer requires UV light to continue.

LDPE and PE is the most commonly produced material in the world and is used in dispenser bottles, wash bottles, tubing, plastic bags, work surfaces and plastic sheeting, among other things.

Recycling and reduction of plastic production represent an important goal worldwide for saving emissions of the anthropogenic greenhouse gases CO₂ and methane.

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© Dr. med. Dipl. Biol. Susanne Saha 05/2021

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