Don't the Yanks use large, thick paper bags for their groceries? That's what I've seen on the films anyway.
They would biodegrade quickly and therefore would be free!
Of course, I'm assuming the EU mandarins are equipped with common sense.
Trouble is they aqua degrade in the uk before you can get to your cat. Bio-degradable "plastic" bags have been around for ages.
Erm...did you mean car or do you use your moggy as a pack mule??