Would you prefer they shit diamonds? Being serious here, but you do know that polystyrene foam is made from refined oil, yes? Once the oil is extracted, you can either A) leave it in a tank. B: make it into something and bury it into the ground. C) Covert it back into CO2 via burning or organic methods.
What would you prefer is done with the existing polystyrene foam out there?
The obvious answer is leave it buried in the ground. Anthropogenic global warming is caused by us taking carbons that have been locked away underground in the form of fossil fuels and releasing them into the atmosphere. If we use those fossil fuels but keep the carbon locked up or re-entered into the ground instead of the atmosphere, we wouldn't have nearly as much trouble with all the greenhouse effects. We'd have another problem in the form of mountains of waste we don't know what to do with, but that's a different discussion.