Researchers have developed fluorescent coating that could allow for fast, automated sorting of food-contact PET from non-food-contact PET in mixed recycling streams.

The Polymark project released preliminary results in the effort to create beverage container identifiers that are safe for food packaging and are removable after sortation.

Bottle-to-bottle recycling is allowed in the European Union, but legislation prohibits non-food-application plastic from being recycled into food-contact packaging unless there is a barrier and only virgin plastic contacts the food, according to the project.

Polymark, a three-year project funded by the EU government and multiple industry groups, aims to help facilities easily separate those food-contact plastics that can be used for bottle-to-bottle recycling.

“Our research partners have successfully developed a complete technology package,” Patrick Peuch of trade group Petcore Europe announced in a press release. Petcore Europe, short for PET Container Recycling Europe, is the project coordinator.

The project developed flexible, spray-on bottle coatings that effectively mark PET bottles by giving them a distinct “fingerprint.” Researchers used commercially available, near-UV-excitable markers “with strong fluorescence in the visible region of the electromagnetic spectrum,” according to the preliminary results report. The fluorescence was distinguishable from the background fluorescence of PET, the report states.

Researchers also demonstrated the marker can be removed under alkaline wash conditions already in use in recycling facilities. That way a food-contact plastic with a marker isn’t recycled into a non-food-contact product that is later mistakenly identified as food-contact plastic during recycling.

The coating approach also allows for additional dispersible marker pigments to be used in combination, allowing for the development of a coding system in the future, the report states. The technology could also be used on other polymer types, including PP.

In the U.S., plastic with non-food-grade additives can’t be recycled into food-contact packaging, but those additives are not used in PET anyway, said Dave Cornell, technical consultant for the Association of Plastic Recyclers (formerly the Association of Postconsumer Plastic Recyclers).

“With regard to the source of recycled PET, the FDA has limits on what material history is acceptable for food contact of recyclable PET and, so far, no problems have developed that justify the creation of a marker system,” Cornell said.

Non-food-grade additives are used in some HDPE and PP household chemical bottles, however, making separation of food grade and non-food grade bottles an issue for those resins, he said.

For the Polymark project, the next phase involves working on the detection and sorting equipment. The coating-based marker system will be tested using prototype detection/sorting equipment currently under development, according to the report.

Polymark launched in 2014. Two-thirds of its funding comes from an EU grant.