I think this is something that would be awesome. However, I'm not sure any of these major companies are all that excited about spending their R&D money on trying to figure out how to print using trash. These companies make money off of selling Filament, thus if you could print with plastic bottles they wouldn't be making as much money.

In actuality, companies could probably allow plastic (garbage) to be fed into a machine based on the Plastic Recycle codes on the item.

You have all seen these. They look like this:


This tells recycling companies what type of plastic it is.

The 3d Printers could allow for certain size feets (for example 3X6 sheets) to be fed into the printer, as long as they are of the correct plastic (recycling code). I don't see why this wouldn't work, and perhaps someone will come up with the idea soon.

As for other garbage, I wouldn't be surprised to see this utilized in the future. Perhaps even molecular breakdown.