The group has devised a catalytic recycling process that breaks apart the chains of some of the more commonly used plastics — polyethylene and polypropylene — in such a way that the building blocks of those plastics can be used again. In some cases, with more than 90% efficiency.

The catalysts required for the reaction — sodium or tungsten — are readily available and inexpensive, they say, and early tests show the process probably is scalable at industrial levels. It uses no water and has fewer energy requirements than other recycling methods — and is even more efficient than manufacturing new, or so-called virgin, plastics, the researchers say.

“So by making one product or two products in very high yield and at much lower temperatures, we are using some energy, but significantly less energy than any other process that’s breaking down polyolefins or taking the petroleum resources and turning them into the monomers for polyolefins in the first place,” said John Hartwig, a UC Berkeley chemist who was a co-author of the study published recently in the journal Science.

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Hartwig said there are some caveats to the work. For instance, the plastic has to be sorted before the process can be applied. If the products are contaminated with other plastics, such as PVC or polystyrene, the outcome isn’t good.