NRT Sorting Systems Capable of Segregating NatureWorks PLA

NRT, based in Nashville, Tenn., has studied the sorting of polylactide (PLA) bottles using its proven system for sorting other plastics from PET at industrial feed-rates.

"Because the NatureWorks PLA will likely be in the same stream as common items like salad dressing bottles, vegetable oil bottles, mouthwash and other plastics like PVC, we anticipate that existing NRT infrared machines will not need to be modified to separate PLA from the PET stream," John Thomsen, engineering manager at NRT, says. "We also think that the PLA can be distinguished from PVC and other non-PET polymers, but further validation isn't warranted until larger post-consumer quantities of PLA bottles are available."

Derived 100 percent from annually renewable resources, NatureWorks PLA is an alternative to traditional, petroleum-based plastic materials manufactured by Cargill Dow. With increasing commercialization of bottles made from NatureWorks PLA, Cargill Dow says it continues to work with appropriate recycling stakeholders to ensure the successful integration of PLA into the U.S. recycling stream.

The NRT data are consistent with other studies using infrared technology to sort NatureWorks PLA from the PET stream, according to Cargill Dow. Testing in December 2002 by Nashville-based MSS using its high-capacity Aladdin System found that NatureWorks PLA has a unique signature in the near-infrared (NIR) spectrum, allowing the polymer to be distinguished from PET and other plastics.

In May 2004, TiTech VisionSort in Borken, Germany, also evaluated the separation of PLA from PET by request of Recycle America Alliance, a subsidiary of Waste Management Inc., Houston. It also found that PLA has a very unique IR scan and its Auto Sort equipment was able to separate NatureWorks PLA bottles and fragments from a stream that included PP, PET, PETG, PC, PS, EPS and ABS at standard efficiency rates, according to the statement from Cargill Dow.

"We are pleased to be getting validation from the recycling industry's leading sort system manufacturers that NatureWorks PLA can be separated from the post-consumer PET stream, and can likely be separated into its own stream when post-consumer amounts warrant such a move," Brian Glasbrenner, business development manager, PLA bottles, for Cargill Dow, says. "We will continue to work with the appropriate associations and industry experts to evaluate the disposal impact of PLA in all waste management systems."

In addition to its fit with the recycling stream, PLA has been successfully composted in applications where that disposal method is desired and commercial composting infrastructure is in place, and it has been reviewed by the Biodegradable Products Institute (BPI) and is listed as positive for compostable materials.

The multiple disposal alternatives of PLA mean that it can play a key role in landfill diversion. In addition to its ability to be mechanically recycled and composted, it has shown favorable properties for use where incineration is the preferred waste disposal method. In addition, PLA may offer the potential landfill diversion option of being chemically recycled, Cargill Dow says.