There are already quite substantial emissions when turning oil into plastics and other products. Steam crackers are among the biggest industrial carbon sources.

There are already quite substantial emissions when turning oil into plastics and other products. Steam crackers are among the biggest industrial carbon sources. But that's not all: The common end of life processing of most plastics these days is waste incineration (causes CO2) or landfils (may cause methane, which is worse than CO2). Sooner or later most carbon embedded in the oil used for products will end up in the atmosphere.