Plastic causes climate change
Plastic is a petroleum-based raw material; approximately 16% of the world's oil and natural gas is currently consumed every day in producing this artificial material. The Heinrich-Böll Foundation estimates that carbon dioxide (CO2) caused emissions of 1781 million tonnes in 2015 alone. Global plastic production accounts for 10-13% of the total maximum CO2 budget that can be consumed in order to limit man-made global warming to 1.5 degrees.
CO2 and the oceans
Around 400 million tonnes of plastic of various compositions are produced worldwide every year. According to estimates, approximately one third of this is disposed of in the environment. A large part ends up in the ocean and forms five large plastic whirlpools with a diameter of 1.6 square kilometres (as of 2018).
It is assumed that the increasing amount of microplastics in the oceans, which is produced by the breakdown of plastic, disrupts biological processes; these processes are a key component in the process, by which plankton at the sea surface binds CO2 through photosynthesis. Known as the biological carbon pump, this process is central to the ocean's role as a carbon sink and contributes significantly to a stable Earth climate.
As a result of natural death processes, the plankton secretes the CO2 again when it sinks to the sea floor. The sometimes highly toxic effect of microplastics results in a higher death rate 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. Current research is addressing questions about the amount and how storage could change in the future.
Decomposition of plastic produces methane
According to a study by the University of Hawaii in August 2018, UV light promotes the decomposition of plastic in the environment, releasing methane and ethylene. Methane (CH4) is one of the most significant greenhouse gases and is 21 times more potent than CO2.
Investigations into various types of plastic have shown that the majority of methane was produced by plastic particles of low density polyethylene (LDPE), a variant of polyethylene (PE). Methane emissions increased the longer the plastic particles were irradiated by UV light. UV light evidently acts as a catalyst, as methane production, once triggered, no longer requires UV light to continue.
LDPE and PE are the most commonly produced materials in the world and are used in dispenser bottles, wash bottles, hoses, plastic bags, worktops and plastic sheeting, among other products.
Recycling and reduction of plastic production represent important goals worldwide for reducing emissions of the anthropogenic greenhouse gases CO2 and methane.
© Dr. med. Dipl. Biol. Susanne Saha 05/2021
Update November 2021: