Plastic pollution treaty would be 'failure' without tackling emissions

Delegates from nearly every country gathered in Canada this week to hammer out the details of a global treaty to address ballooning plastic pollution. One source of division at the summit, which concluded on 29 April, was how to address the greenhouse gas emissions generated by producing and using plastic, a growing and under-recognised driver of climate change.

“When people think about plastic, they think about what they see visually,” says Alice Zhu at the University of Toronto. But extracting and processing the fossil fuels and other chemicals used to make plastic produces substantial greenhouse gas emissions, as does generating the energy required to make plastic products. Plastic now accounts for around 10 per cent of total demand for oil and natural gas; coal is also increasingly used to power plastic production.

Incinerating plastic waste is another source of greenhouse gas emissions. As it degrades, plastic in the environment can also produce carbon dioxide and methane emissions. Plastic may even reduce how much carbon ecosystems can store, although these effects are poorly quantified, says Zhu.

The numbers on emissions from producing plastic are clearer. In a study published this month, Nihan Karali at Lawrence Berkeley National Laboratory in California and her colleagues estimated that plastic production in 2019 generated the equivalent of 2.24 gigatonnes of CO2, or about 5 per cent of global greenhouse gas emissions. That is roughly four times as much as was produced by aviation that year.

Assuming no changes to how plastic is produced, they found these emissions could triple by 2050 with increases in plastic production. Since most of the emissions are associated with extracting and processing the fossil fuels and other chemicals used to make plastics, they also found decarbonising the power grid has only a small effect on projected emissions.

The global plastic treaty under debate could offer a “historic” chance to limit those emissions, the researchers wrote. In 2022, more than 175 countries agreed to join a legally binding treaty that would address plastic pollution across the full life cycle of the material, with final details to be agreed by the end of this year.

However, a group of petroleum-producing countries, including China and Russia, argued during negotiations that the treaty should only address plastic waste through clean-up and recycling, and not limit or change production, which is the main source of greenhouse gas emissions from plastic. A group of countries including the UK and EU have argued the treaty should include provisions to reduce production to keep emissions in line with global climate targets.

“There are so many things on the table, and climate is certainly not being discussed too much,” says Neil Nathan at the University of California, Santa Barbara, who attended the meeting to advocate for an ambitious treaty.

Based on modelling he and his colleagues have done, he says a strong treaty that limits production and takes other steps, like mandating that plastic products contain a high proportion of recycled material, could keep emissions at their current levels. He says the plastics treaty would be “a failure” if it didn’t address production.

Sarah-Jeanne Royer at the University of California, San Diego, says reducing the use of new plastic through recycling or switching to more sustainable materials to make plastic, such as bioplastics or captured CO2, would also reduce greenhouse gas emissions, even if the treaty didn’t address them explicitly.

However, Paul Stegmann at TNO, a research organisation in the Netherlands, cautions that some alternatives to plastic, such as steel, may generate more emissions, depending on how they are reused and recycled. “In the end, we need policies that ensure that we do not just shift the problem elsewhere but that reduce the system-wide impact of our society,” he says.