Which is basically HDPE (plastic) foil with limestone filler. And a whole website full of marketing that somehow never mentions that 20% of the material is non-renewable (made from petroleum products) and not biodegradable.
Yes, they say its HDPE, but then conveniently in all their talk about sustainability, they somehow forget to talk about where HDPE actually comes from. Just that it being composed of carbon and hydrogen somehow makes it "clean". Which, I guess, is something you could also say about things like gasoline. Plastic shopping bags are also made of polyethylene. So are they sustainable as well?
Sure it is. But it's also nowhere near cost competitive and so no one does. They also don't even claim they're using anything else than "normal" HDPE made from ethylene distilled from crude oil.
They don't use "normal" HDPE, they use recycled HDPE which means they don't know what's inside their feedstock and it definitively means you can't get rid of the paper by burning it, because you're also burning whatever mystery chemicals remain inside.