That's a nice thought, but unfortunately the environmental cost of "storing" all of this material - i.e. all the billions of tonnes of plastic pollution already

That's a nice thought, but unfortunately the environmental cost of "storing" all of this material - i.e. all the billions of tonnes of plastic pollution already out there, and in there (inside you in the form of microplastics) - doesn't come for free. It's a current problem, and we don't seem to have the technology or even the political will to solve it currently.