Scientists at Lawrence Berkeley National Laboratory analysed the emissions from producing the world's primary plastics, covering fossil-fuel extraction, refining, polymer manufacturing and the energy used at each step.
They found that primary plastic production emitted 2.24 billion tonnes of greenhouse gases in 2019, measured as the amount of carbon dioxide (CO2) that would have the same warming effect. This was equal to 5.3% of global greenhouse-gas emissions excluding agriculture and land use, and more than the entire aviation sector. If production grows at 2.5% a year, emissions reach 4.75 billion tonnes by 2050, consuming 21–26% of the remaining carbon budget for 1.5 °C (the carbon dioxide the world can still emit while keeping warming to 1.5 °C); at 4% growth, 6.78 billion tonnes and 25–31% of the budget.
The report matters because it quantifies the climate case for capping plastic production, showing that plastics are a major and rapidly growing source of emissions in their own right.
It covers production only, not use or disposal, and was funded by Bloomberg Philanthropies' Beyond Petrochemicals campaign; the '600 coal plants' comparison comes from secondary coverage.