I have seen plastic 2 X 4's at Home Despot that I was told were made from shredded and melted milk and water bottles. Even if they were only 3/4ths recycled, it sounded like a good idea.
I believe this shows that it really works, but I am skeptical about the cost-effectiveness, even at $150/Bl for newly drilled oil.
Polymers (plastics) can be dissolved and catalyzed into smaller bits in a way that results in a liquid, but the weight won't change. Plastics float because they are "fluffy" and less dense than the petro-liquids they are made from.
How many plastic bags and shredded milk/water bottles would it take to equal the weight of one 55-gallon barrel of oil?
Water is about 8 lbs/gallon (yes?) and since oil floats it weighs less, so 7-ish lbs/gallon? 7 X 55 = ~385 lbs? Thats a truckload of plastic to get one drum.
That being said, I'm all for recycling, so if somebody wants to treat plastic and re-use it, I say why not.