Computer model shows many paths to cutting plastic pollution

Enacting a combination of four policies could reduce mismanaged plastic waste by 91% and greenhouse gas (GHG) emissions by about 37% third by 2050, according to a model created by scientists at the University of California, Berkeley, and the University of California, Santa Barbara (Science 2024, DOI: 10.1126/science.adr3837).

If world leaders leave global plastic use and waste policies as is, annual plastics-related GHG emissions will swell from the current level of about 2.75 billion metric tons to 3.35 billion metric tons of CO₂ equivalent by 2050, according to the model. The amount of mismanaged plastic waste—waste that doesn’t end up in a landfill, get burned in a regulated incinerator, or get recycled—will almost double, to around 121 million metric tons (t) per year.

The researchers created this machine learning model in response to ongoing negotiation of the United Nations Environment Programme treaty to end plastic pollution. Policymakers, scientists, and treaty negotiators have suggested many plans for controlling plastic waste but lacked a tool to determine which of these policies would best lower GHG emissions and mismanaged plastic waste.

“As part of our paper, we released an interactive tool online that allows policymakers to see how different combinations of policies can have an influence overall,” says Sam Pottinger, a data scientist at UC Berkeley and one of the authors of the paper.

Policymakers can look at the effect of up to eight potential policies. The researchers identified four—a packaging tax, a mandate setting a minimum amount of recycled content, a cap on virgin plastic production, and investment in waste management infrastructure—that reduce mismanaged plastic waste and plastic GHG emissions the most, Pottinger says.

“Everything that you see in the tool is something that’s been discussed or mentioned as being of interest by a [plastic treaty] delegation,” he says. But the researchers found that there’s not one silver bullet that would lead to an effective plastics treaty. “There’s a suite of options that we have available,” Pottinger says. Varying combinations of the eight modeled policies can potentially achieve the treaty’s goals, he says.

In treaty negotiations so far, the idea of capping virgin plastic production has been particularly contentious. According to the model, enacting such a cap would cause a big drop in both GHG emissions and mismanaged plastic waste. “But if, for some reason, negotiators were to decide that it wasn’t feasible to include in the treaty, we demonstrate that there’s other options as well,” Pottinger says.

This research is important and includes ideas that other models haven’t explored much, such as some financial regulatory policies, says Ed Cook, a research fellow on waste plastics at the University of Leeds. “They imply that a $10 [per metric ton] tax on plastic production worldwide could reduce uncontrolled management of waste by 40% if the proceeds were invested in waste management infrastructure,” Cook says. “This seems like an achievable goal with little real-world negative impact.”

“Policymakers have options,” Pottinger says. “This is going to be hard, but it’s worth it, and we just really encourage our global leaders to come to the next round of negotiations with high ambition.”

The final meeting to negotiate the plastics treaty will be held from Nov. 25 to Dec. 1 in Busan, South Korea.