Notorious plastic bags and containers can finally be upcycled, thanks to a new technique for recycling polyethylene bags and food packaging into valuable starter materials for high-value plastics and chemicals.

Polyethylene plastics are used to make plastic bags, shampoo bottles, and many products that are extremely difficult to recycle. In fact, only 14 percent of all polyethylene plastic are currently able to be recycled—and, then, only for certain products such as garden furniture.

They make up about one-third of the entire plastics market worldwide—all manufactured using massive amounts of fossil fuels.

But this may be changing thanks to scientists at the University of California, Berkeley in the Lawrence Berkeley National Laboratory.

They have found a way to break the sturdy polymers into the three-carbon molecule called propylene—a valuable molecule that can then be used to make new plastics, including polypropylene, which is used in ropes, twine, tape, carpets, upholstery, clothing, and camping equipment.

Not only that, the discovery will allow them to do it with very minimal fossil fuels.

"You can't take a plastic bag and then make another plastic bag out of it with the same properties," said John Hartwig, UC Berkeley Chair in Organic Chemistry. "But if you can take that polymer bag back to its monomers, break it down into small pieces and repolymerize it, then instead of pulling more carbon out of the ground, you use that as your carbon source to make other things — for example, polypropylene."