The 27-country European Union requires single-use plastic bottles to contain at least 25 percent of recycled plastic -- with the share set to increase to 30 percent by 2030.

Up to now only plastic recycled through mechanical techniques, which involve washing, shredding and remelting the stuff, could be used towards the quota.

The European Commission on Tuesday officially extended the same benefit to chemically recycled plastics, as part of a push to support a sector struggling against competition from China and other parts of Asia.

"Europe's plastic recycling sector faces mounting pressures. The new rules on chemical recycling are part of the answer to that challenge," said the EU's environment chief, Jessika Roswall.

Chemical recycling involves heating plastics to high temperatures to break down the material in smaller molecules, a process environmental groups say is energy intensive and more polluting than mechanical techniques.

But the commission counters it is more effective for some types of otherwise hard-to-recycle plastics, such as waste with food residues, additives and mixed materials.

"In these cases, chemical recycling can complement mechanical recycling," it said.