Reshaping the plastic life cycle into a circle

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In 1950, 2 million tons (2.2 million tons) of new plastic were produced worldwide. In 2018 the world produced 360 million tons (397 million tons) of plastic. Because of their low cost, durability, and versatility, plastics can be found everywhere – including the environment – and only 9 percent of the plastic ever made has been recycled. The vast majority ends up in landfills, where it accumulates due to its slow degradation, while ubiquitous microplastics have been found everywhere from the interior of living bodies to the sea floor.

“With our current plastic waste generation rate, increasing waste management capacity alone will not be enough to meet plastic pollution goals,” said Vikas Khanna, associate professor of civil and environmental engineering at the University of Pittsburgh’s Swanson School of Engineering. “There is an urgent need for measures such as limiting the global production of new plastic from fossil fuels and developing products and packaging for recyclability.”

New research under the direction of Khanna gives a bird’s eye view of the extent of global plastic production, showing where it is produced, where it ends and what impact it has on the environment.

The researchers found the greenhouse gas emissions associated with plastic production in 2018 shockingly high: 170 million tons (187 million tons) of primary plastics were traded worldwide in 2018, with the associated greenhouse gas emissions accounting for 350 million tons (386 million tons) of CO2 Equivalent – roughly the same amount that nations like Italy and France produce in a year.

“And if anything, our assessment is at the lower end. Converting primary plastic resins into end products will lead to additional greenhouse gases and other emissions, ”warned Khanna.

The work was recently published in the journal ACS Sustainable Chemistry and Engineering.

“We know plastics are a problem, and we know keeping materials in a circular economy instead of the usual take-make-waste model is a great solution,” said Khanna. “But if we don’t understand the current state of the system, it’s difficult to come up with numbers and understand the order of magnitude. We wanted to understand how plastics are mobilized across geographical boundaries. “

Because international trade plays such a crucial role in the supply of tangible goods, including plastics, researchers applied network theory to data from the UN Comtrade database to explore the role of individual countries, trade relations between countries, and structural features that determine these interactions to understand. The Global Primary Plastic Trade Network (GPPTN) they created referred to each country as a “node” in the network and a trade relationship between two countries as the “edge” so they could determine the critical actors (countries) and manufacturers with the greatest impact.

The researchers examined 11 primary thermoplastic resins that make up the majority of plastic products. They found that the majority of the model’s most influential hubs exported more plastics than they imported: Saudi Arabia is the leading exporter, followed by the US, South Korea, Germany and Belgium. The five largest importers of primary plastics are China, Germany, the USA, Italy and India.

In addition to greenhouse gas emissions, energy consumption in the GPPTN is estimated at 1.5 trillion barrels of crude oil, 230 billion cubic meters of natural gas, or 407 tons (448 tons). of coal. The carbon embedded in the model is estimated to be the carbon equivalent of 118 million tons (130 million tons) of natural gas or 109 million tons (120 million tons) of petroleum.

“The results are particularly important and timely, especially given the recent discussions at the Conference of the Parties (COP26) in Glasgow and the importance of understanding where emissions are coming from in key sectors,” said co-author Melissa Bilec, co-director of Mascaro Center for Sustainable Innovation and William Kepler Whiteford Professor of Civil and Environmental Engineering. “The collaboration with Dr. Khanna and his lab enables us to learn new system-level modeling techniques as we approach understanding solutions to our complex challenges. ”

This paper, titled Quantifying Energy and Greenhouse Gas Emissions Embodied in Global Primary Plastic Trade Network, is supported by the NSF Circular Economy Convergence Research Project led by Bilec.

Using more recycled plastics instead of making new resins that eventually end up in landfills would be far better for the environment; However, both financial and behavioral barriers need to be overcome before a true circular economy for plastics can become a reality.

“While emerging chemical recycling techniques promise to reclaim more material in an economical and environmentally sound way, we need to make sure that using recycled materials is as cost effective as using virgin plastic resins,” said Khanna. “Our next step is to understand the interaction between the GPPTN and the plastic waste trading network to identify the ways in which investments could drive a circular economy for plastics.”

– This press release was originally published on the University of Pittsburgh website


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