How do you accurately price externalities without resolving them? If you spend a billion a year cleaning up plastic it's pretty simple math to spread that out over the cost of plastic products. On the other hand if you don't actually do anything to resolve it you are just guessing on what that costs and could be way over or under.
This seems like "I want UBI" with a flimsy environmental justification.
You don’t need to accurately price them. You just gradually keep increasing the price year over year until the companies spin up R&D departments to switch to biodegradable sustainable alternatives, or their competitors do.
You have to hit those corps in their pocketbook and affect their bottom line before they act. It’s the only thing they understand.
As far as cleanup - forget it. We may be able to clean up the Great Pacific Garbage Patch, but we won’t be able to remove microplastics around the world. It is urgent we stop creating MORE though. That means also mandating drainage systems that filter and trap these particles before they escape. We already mandate that for many forms of grease!
That's not really taxing externalities. Biodegradable solutions likely have externalities of their own at scale. In less words this solution is "tax corporations that make plastic a lot and distribute the funds to the citizens leaving the mess behind for future generations". It isn't as noble when put that way.
It you on the other hand took those funds and used them for environmental clean up, recycling programs, etc I'd be on board. Consumers should pay for the disposal of what they consumed.
This seems like "I want UBI" with a flimsy environmental justification.