There is certainly enough lava. The eruption that occurred in 2018 in my home town produced 1 billion cubic yards or 914402.757839 cubic kilometers.

https://volcanoes.usgs.gov/vsc/file_mngr/file-224/OVERVIEW_K...

I imaging the outgassing of the plastic would be pretty terrible but the volcanic gas is pretty damaging too. But yes, I imagine there are a hundred different reasons this wouldn't really work out.